Photochemical charge separation in zeolites: Electron transfer dynamics, nanocrystals and zeolitic membranes. Final technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, Prabir K.

2001-09-30

Aluminosilicate zeolites provide an excellent host for photochemical charge separation. Because of the constraints provided by the zeolite, the back electron transfer from the reduced acceptor to the oxidized sensitizer is slowed down. This provides the opportunity to separate the charge and use it in a subsequent reaction for water oxidation and reduction. Zeolite-based ruthenium oxide catalysts have been found to be efficient for the water splitting process. This project has demonstrated the usefulness of zeolite hosts for photolytic splitting of water.

Charge Transfer from n-Doped Nanocrystals: Mimicking Intermediate Events in Multielectron Photocatalysis.

PubMed

Wang, Junhui; Ding, Tao; Wu, Kaifeng

2018-06-12

In multielectron photocatalytic reactions, an absorbed photon triggers charge transfer from the light-harvester to the attached catalyst, leaving behind a charge of the opposite sign in the light-harvester. If this charge is not scavenged before the absorption of the following photons, photoexcitation generates not neutral but charged excitons from which the extraction of charges should become more difficult. This is potentially an efficiency-limiting intermediate event in multielectron photocatalysis. To study the charge dynamics in this event, we doped CdS nanocrystal quantum dots (QDs) with an extra electron and measured hole transfer from n-doped QDs to attached acceptors. We find that the Auger decay of charged excitons lowers the charge separation yield to 68.6% from 98.4% for neutral excitons. In addition, the hole transfer rate in the presence of two electrons (1290 ps) is slower than that in the presence one electron (776 ps), and the recombination rate of charge separated states is about 2 times faster in the former case. This model study provides important insights into possible efficiency-limiting intermediate events involved in photocatalysis.

Efficient charge-carrier extraction from Ag₂S quantum dots prepared by the SILAR method for utilization of multiple exciton generation.

PubMed

Zhang, Xiaoliang; Liu, Jianhua; Johansson, Erik M J

2015-01-28

The utilization of electron-hole pairs (EHPs) generated from multiple excitons in quantum dots (QDs) is of great interest toward efficient photovoltaic devices and other optoelectronic devices; however, extraction of charge carriers remains difficult. Herein, we extract photocharges from Ag2S QDs and investigate the dependence of the electric field on the extraction of charges from multiple exciton generation (MEG). Low toxic Ag2S QDs are directly grown on TiO2 mesoporous substrates by employing the successive ionic layer adsorption and reaction (SILAR) method. The contact between QDs is important for the initial charge separation after MEG and for the carrier transport, and the space between neighbor QDs decreases with more SILAR cycles, resulting in better charge extraction. At the optimal electric field for extraction of photocharges, the results suggest that the threshold energy (hνth) for MEG is 2.41Eg. The results reveal that Ag2S QD is a promising material for efficient extraction of charges from MEG and that QDs prepared by SILAR have an advantageous electrical contact facilitating charge separation and extraction.

Double heterojunction nanowire photocatalysts for hydrogen generation.

PubMed

Tongying, P; Vietmeyer, F; Aleksiuk, D; Ferraudi, G J; Krylova, G; Kuno, M

2014-04-21

Charge separation and charge transfer across interfaces are key aspects in the design of efficient photocatalysts for solar energy conversion. In this study, we investigate the hydrogen generating capabilities and underlying photophysics of nanostructured photocatalysts based on CdSe nanowires (NWs). Systems studied include CdSe, CdSe/CdS core/shell nanowires and their Pt nanoparticle-decorated counterparts. Femtosecond transient differential absorption measurements reveal how semiconductor/semiconductor and metal/semiconductor heterojunctions affect the charge separation and hydrogen generation efficiencies of these hybrid photocatalysts. In turn, we unravel the role of surface passivation, charge separation at semiconductor interfaces and charge transfer to metal co-catalysts in determining photocatalytic H2 generation efficiencies. This allows us to rationalize why Pt nanoparticle decorated CdSe/CdS NWs, a double heterojunction system, performs best with H2 generation rates of ∼434.29 ± 27.40 μmol h(-1) g(-1) under UV/Visible irradiation. In particular, we conclude that the CdS shell of this double heterojunction system serves two purposes. The first is to passivate CdSe NW surface defects, leading to long-lived charges at the CdSe/CdS interface capable of carrying out reduction chemistries. Upon photoexcitation, we also find that CdS selectively injects charges into Pt NPs, enabling simultaneous reduction chemistries at the Pt NP/solvent interface. Pt nanoparticle decorated CdSe/CdS NWs thus enable reduction chemistries at not one, but rather two interfaces, taking advantage of each junction's optimal catalytic activities.

A multi-pathway model for photosynthetic reaction center

NASA Astrophysics Data System (ADS)

Qin, M.; Shen, H. Z.; Yi, X. X.

2016-03-01

Charge separation occurs in a pair of tightly coupled chlorophylls at the heart of photosynthetic reaction centers of both plants and bacteria. Recently it has been shown that quantum coherence can, in principle, enhance the efficiency of a solar cell, working like a quantum heat engine. Here, we propose a biological quantum heat engine (BQHE) motivated by Photosystem II reaction center (PSII RC) to describe the charge separation. Our model mainly considers two charge-separation pathways which is more than that typically considered in the published literature. We explore how these cross-couplings increase the current and power of the charge separation and discuss the effects of multiple pathways in terms of current and power. The robustness of the BQHE against the charge recombination in natural PSII RC and dephasing induced by environments is also explored, and extension from two pathways to multiple pathways is made. These results suggest that noise-induced quantum coherence helps to suppress the influence of acceptor-to-donor charge recombination, and besides, nature-mimicking architectures with engineered multiple pathways for charge separations might be better for artificial solar energy devices considering the influence of environments.

Photoinduced charge separation at polymer-fullerene interfaces of BHJ solar cells (Conference Presentation)

NASA Astrophysics Data System (ADS)

Poluektov, Oleg G.; Niklas, Jens; Mardis, Kristy

2016-09-01

While photovoltaic cells are highly promising man-made devices for direct solar energy utilization, a number of fundamental questions about how the organic bulk heterojunction cell enables efficient long-lived and long-range charge separation remain unanswered. These questions were address by employing an advanced suite of EPR spectroscopy in combination with DFT calculations to study mechanism of charge separation at the polymer-fullerene interfaces of photo-active BHJ. Observed charge delocalization in BHJ upon photoinduced ET is analogous to that in organic donor-acceptor material. This is an efficient mechanism of charge stabilization in photosynthetic assemblies. Time-resolved EPR spectra show a strong polarization pattern for all polymer-fullerene blends under study, which is caused by non-Boltzmann population of the electron spin energy levels in the radical pairs. The first observation of this phenomenon was reported in natural and artificial photosynthetic assemblies, and comparison with these systems allows us to better understand charge separation processes in OPVs. The spectral analysis presented here, in combination with DFT calculations, shows that CS processes in OPV materials are similar to that in organic photosynthetic systems. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, under Contract DE-AC02-06CH11357 at Argonne National Laboratory.

Hot kinetic model as a guide to improve organic photovoltaic materials.

PubMed

Sosorev, Andrey Yu; Godovsky, Dmitry Yu; Paraschuk, Dmitry Yu

2018-01-31

The modeling of organic solar cells (OSCs) can provide a roadmap for their further improvement. Many OSC models have been proposed in recent years; however, the impact of the key intermediates from photons to electricity-hot charge-transfer (CT) states-on the OSC efficiency is highly ambiguous. In this study, we suggest an analytical kinetic model for OSC that considers a two-step charge generation via hot CT states. This hot kinetic model allowed us to evaluate the impact of different material parameters on the OSC performance: the driving force for charge separation, optical bandgap, charge mobility, geminate recombination rate, thermalization rate, average electron-hole separation distance in the CT state, dielectric permittivity, reorganization energy and charge delocalization. In contrast to a widespread trend of lowering the material bandgap, the model predicts that this approach is only efficient along with improvement of the other material properties. The most promising ways to increase the OSC performance are decreasing the reorganization energy, i.e., an energy change accompanying CT from the donor molecule to the acceptor, increasing the dielectric permittivity and charge delocalization. The model suggests that there are no fundamental limitations that can prevent achieving the OSC efficiency above 20%.

Ewald Electrostatics for Mixtures of Point and Continuous Line Charges.

PubMed

Antila, Hanne S; Tassel, Paul R Van; Sammalkorpi, Maria

2015-10-15

Many charged macro- or supramolecular systems, such as DNA, are approximately rod-shaped and, to the lowest order, may be treated as continuous line charges. However, the standard method used to calculate electrostatics in molecular simulation, the Ewald summation, is designed to treat systems of point charges. We extend the Ewald concept to a hybrid system containing both point charges and continuous line charges. We find the calculated force between a point charge and (i) a continuous line charge and (ii) a discrete line charge consisting of uniformly spaced point charges to be numerically equivalent when the separation greatly exceeds the discretization length. At shorter separations, discretization induces deviations in the force and energy, and point charge-point charge correlation effects. Because significant computational savings are also possible, the continuous line charge Ewald method presented here offers the possibility of accurate and efficient electrostatic calculations.

What Controls the Rate of Ultrafast Charge Transfer and Charge Separation Efficiency in Organic Photovoltaic Blends.

PubMed

Jakowetz, Andreas C; Böhm, Marcus L; Zhang, Jiangbin; Sadhanala, Aditya; Huettner, Sven; Bakulin, Artem A; Rao, Akshay; Friend, Richard H

2016-09-14

In solar energy harvesting devices based on molecular semiconductors, such as organic photovoltaics (OPVs) and artificial photosynthetic systems, Frenkel excitons must be dissociated via charge transfer at heterojunctions to yield free charges. What controls the rate and efficiency of charge transfer and charge separation is an important question, as it determines the overall power conversion efficiency (PCE) of these systems. In bulk heterojunctions between polymer donor and fullerene acceptors, which provide a model system to understand the fundamental dynamics of electron transfer in molecular systems, it has been established that the first step of photoinduced electron transfer can be fast, of order 100 fs. But here we report the first study which correlates differences in the electron transfer rate with electronic structure and morphology, achieved with sub-20 fs time resolution pump-probe spectroscopy. We vary both the fullerene substitution and donor/fullerene ratio which allow us to control both aggregate size and the energetic driving force for charge transfer. We observe a range of electron transfer times from polymer to fullerene, from 240 fs to as short as 37 fs. Using ultrafast electro-optical pump-push-photocurrent spectroscopy, we find the yield of free versus bound charges to be weakly dependent on the energetic driving force, but to be very strongly dependent on fullerene aggregate size and packing. Our results point toward the importance of state accessibility and charge delocalization and suggest that energetic offsets between donor and acceptor levels are not an important criterion for efficient charge generation. This provides design rules for next-generation materials to minimize losses related to driving energy and boost PCE.

Foam separation of Rhodamine-G and Evans Blue using a simple separatory bottle system.

PubMed

Dasarathy, Dhweeja; Ito, Yoichiro

2017-09-29

A simple separatory glass bottle was used to improve separation effectiveness and cost efficiency while simultaneously creating a simpler system for separating biological compounds. Additionally, it was important to develop a scalable separation method so this would be applicable to both analytical and preparative separations. Compared to conventional foam separation methods, this method easily forms stable dry foam which ensures high purity of yielded fractions. A negatively charged surfactant, sodium dodecyl sulfate (SDS), was used as the ligand to carry a positively charged Rhodamine-G, leaving a negatively charged Evans Blue in the bottle. The performance of the separatory bottle was tested for separating Rhodamine-G from Evans Blue with sample sizes ranged from 1 to 12mg in preparative separations and 1-20μg in analytical separations under optimum conditions. These conditions including N 2 gas pressure, spinning speed of contents with a magnetic stirrer, concentration of the ligand, volume of the solvent, and concentration of the sample, were all modified and optimized. Based on the calculations at their peak absorbances, Rhodamine-G and Evans Blue were efficiently separated in times ranging from 1h to 3h, depending on sample volume. Optimal conditions were found to be 60psi N 2 pressure and 2mM SDS for the affinity ligand. This novel separation method will allow for rapid separation of biological compounds while simultaneously being scalable and cost effective. Published by Elsevier B.V.

Explicit symplectic algorithms based on generating functions for charged particle dynamics.

PubMed

Zhang, Ruili; Qin, Hong; Tang, Yifa; Liu, Jian; He, Yang; Xiao, Jianyuan

2016-07-01

Dynamics of a charged particle in the canonical coordinates is a Hamiltonian system, and the well-known symplectic algorithm has been regarded as the de facto method for numerical integration of Hamiltonian systems due to its long-term accuracy and fidelity. For long-term simulations with high efficiency, explicit symplectic algorithms are desirable. However, it is generally believed that explicit symplectic algorithms are only available for sum-separable Hamiltonians, and this restriction limits the application of explicit symplectic algorithms to charged particle dynamics. To overcome this difficulty, we combine the familiar sum-split method and a generating function method to construct second- and third-order explicit symplectic algorithms for dynamics of charged particle. The generating function method is designed to generate explicit symplectic algorithms for product-separable Hamiltonian with form of H(x,p)=p_{i}f(x) or H(x,p)=x_{i}g(p). Applied to the simulations of charged particle dynamics, the explicit symplectic algorithms based on generating functions demonstrate superiorities in conservation and efficiency.

Explicit symplectic algorithms based on generating functions for charged particle dynamics

NASA Astrophysics Data System (ADS)

Zhang, Ruili; Qin, Hong; Tang, Yifa; Liu, Jian; He, Yang; Xiao, Jianyuan

2016-07-01

Dynamics of a charged particle in the canonical coordinates is a Hamiltonian system, and the well-known symplectic algorithm has been regarded as the de facto method for numerical integration of Hamiltonian systems due to its long-term accuracy and fidelity. For long-term simulations with high efficiency, explicit symplectic algorithms are desirable. However, it is generally believed that explicit symplectic algorithms are only available for sum-separable Hamiltonians, and this restriction limits the application of explicit symplectic algorithms to charged particle dynamics. To overcome this difficulty, we combine the familiar sum-split method and a generating function method to construct second- and third-order explicit symplectic algorithms for dynamics of charged particle. The generating function method is designed to generate explicit symplectic algorithms for product-separable Hamiltonian with form of H (x ,p ) =pif (x ) or H (x ,p ) =xig (p ) . Applied to the simulations of charged particle dynamics, the explicit symplectic algorithms based on generating functions demonstrate superiorities in conservation and efficiency.

Basic statistical analyses of candidate nickel-hydrogen cells for the Space Station Freedom

NASA Technical Reports Server (NTRS)

Maloney, Thomas M.; Frate, David T.

1993-01-01

Nickel-Hydrogen (Ni/H2) secondary batteries will be implemented as a power source for the Space Station Freedom as well as for other NASA missions. Consequently, characterization tests of Ni/H2 cells from Eagle-Picher, Whittaker-Yardney, and Hughes were completed at the NASA Lewis Research Center. Watt-hour efficiencies of each Ni/H2 cell were measured for regulated charge and discharge cycles as a function of temperature, charge rate, discharge rate, and state of charge. Temperatures ranged from -5 C to 30 C, charge rates ranged from C/10 to 1C, discharge rates ranged from C/10 to 2C, and states of charge ranged from 20 percent to 100 percent. Results from regression analyses and analyses of mean watt-hour efficiencies demonstrated that overall performance was best at temperatures between 10 C and 20 C while the discharge rate correlated most strongly with watt-hour efficiency. In general, the cell with back-to-back electrode arrangement, single stack, 26 percent KOH, and serrated zircar separator and the cell with a recirculating electrode arrangement, unit stack, 31 percent KOH, zircar separators performed best.

Directional Charge Separation in Isolated Organic Semiconductor Crystalline Nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Michael; Labastide, Joelle; Bond-Thompson, Hilary

2017-03-01

In the conventional view of organic photovoltaics (OPV), localized electronic excitations (excitons) formed in the active layer are transported by random 3D diffusion to an interface where charge separation and extraction take place. Because radiative de-excitation is usually strongly allowed in organic semiconductors, efficient charge separation requires high exciton mobility, with much of the diffusive motion ‘wasted’ in directions that don’t result in an interface encounter. Our research efforts are focused on ways to enforce a preferred directionality in energy and/or charge transport using ordered crystalline nanowires in which the intermolecular interactions that facilitate transport along, for example, the pi-stackingmore » axis, can be made several orders of magnitude stronger than those in a transverse direction. The results presented in our recent work (Nature Communications) is a first step towards realizing the goal of directional control of both energy transport and charge separation, where excitons shared between adjacent molecules dissociate exclusively along the pi-stacking direction.« less

Separation efficiency of the MASHA facility for short-lived mercury isotopes

NASA Astrophysics Data System (ADS)

Rodin, A. M.; Belozerov, A. V.; Chernysheva, E. V.; Dmitriev, S. N.; Gulyaev, A. V.; Gulyaeva, A. V.; Itkis, M. G.; Kliman, J.; Kondratiev, N. A.; Krupa, L.; Novoselov, A. S.; Oganessian, Yu. Ts.; Podshibyakin, A. V.; Salamatin, V. S.; Siváček, I.; Stepantsov, S. V.; Vanin, D. V.; Vedeneev, V. Yu.; Yukhimchuk, S. A.; Granja, C.; Pospisil, S.

2014-06-01

The mass-separator MASHA built to identify Super Heavy Elements by their mass-to-charge ratios is described. The results of the off- and on-line measurements of its separation efficiency are presented. In the former case four calibrated leaks of noble gases were used. In the latter the efficiency was measured via 284 MeV Ar beam and with using the hot catcher. The ECR ion source was used in both cases. The -radioactive isotopes of mercury produced in the complete fusion reaction Ar+SmHg+xn were detected at the mass-separator focal plane. The half-lives and the separation efficiency for the short-lived mercury isotopes were measured. Potentialities of the MEDIPIX detector system have been demonstrated for future use at the mass-separator MASHA.

Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

NASA Astrophysics Data System (ADS)

Abramavicius, V.; Pranculis, V.; Melianas, A.; Inganäs, O.; Gulbinas, V.; Abramavicius, D.

2016-09-01

Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

Describing long-range charge-separation processes with subsystem density-functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solovyeva, Alisa; Neugebauer, Johannes, E-mail: j.neugebauer@uni-muenster.de; Pavanello, Michele, E-mail: m.pavanello@rutgers.edu

2014-04-28

Long-range charge-transfer processes in extended systems are difficult to describe with quantum chemical methods. In particular, cost-effective (non-hybrid) approximations within time-dependent density functional theory (DFT) are not applicable unless special precautions are taken. Here, we show that the efficient subsystem DFT can be employed as a constrained DFT variant to describe the energetics of long-range charge-separation processes. A formal analysis of the energy components in subsystem DFT for such excitation energies is presented, which demonstrates that both the distance dependence and the long-range limit are correctly described. In addition, electronic couplings for these processes as needed for rate constants inmore » Marcus theory can be obtained from this method. It is shown that the electronic structure of charge-separated states constructed by a positively charged subsystem interacting with a negatively charged one is difficult to converge — charge leaking from the negative subsystem to the positive one can occur. This problem is related to the delocalization error in DFT and can be overcome with asymptotically correct exchange–correlation (XC) potentials or XC potentials including a sufficiently large amount of exact exchange. We also outline an approximate way to obtain charge-transfer couplings between locally excited and charge-separated states.« less

Apparatus for molecular weight separation

DOEpatents

Smith, Richard D.; Liu, Chuanliang

2001-01-01

The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, (4) conducting a two-stage separation or (5) any combination of (1), (2), (3) and (4).

Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niklas, Jens; Beaupré, Serge; Leclerc, Mario

2015-06-18

Understanding charge separation and charge transport is crucial for improving the efficiency of organic solar cells. Their active media are based on organic molecules and polymers, serving as both light-absorbing and transport layers. The charge-transfer (CT) states play an important role, being intermediate for free carrier generation and charge recombination. Here, we use light-induced electron paramagnetic resonance spectroscopy to study the CT dynamics in blends of the polymers P3HT, PCDTBT, and PTB7 with the fullerene derivative C-60-PCBM. Time-resolved EPR measurements show strong spin-polarization patterns for all polymer-fullerene blends, confirming predominant generation of singlet CT states and partial orientation ordering nearmore » the donor-acceptor interface. These observations allow a comparison with charge separation processes in molecular donor-acceptor systems and in natural and artificial photosynthetic assemblies, and thus the elucidation of the initial steps of sequential CT in organic photovoltaic materials.« less

Revealing the Double-Edged Sword Role of Graphene on Boosted Charge Transfer versus Active Site Control in TiO2 Nanotube Arrays@RGO/MoS2 Heterostructure.

PubMed

Quan, Quan; Xie, Shunji; Weng, Bo; Wang, Ye; Xu, Yi-Jun

2018-05-01

Charge separation/transfer is generally believed to be the most key factor affecting the efficiency of photocatalysis, which however will be counteracted if not taking the active site engineering into account for a specific photoredox reaction. Here, a 3D heterostructure composite is designed consisting of MoS 2 nanoplatelets decorated on reduced graphene oxide-wrapped TiO 2 nanotube arrays (TNTAs@RGO/MoS 2 ). Such a cascade configuration renders a directional migration of charge carriers and controlled immobilization of active sites, thereby showing much higher photoactivity for water splitting to H 2 than binary TNTAs@RGO and TNTAs/MoS 2 . The photoactivity comparison and mechanistic analysis reveal the double-edged sword role of RGO on boosted charge separation/transfer versus active site control in this composite system. The as-observed inconsistency between boosted charge transfer and lowered photoactivity over TNTAs@RGO is attributed to the decrease of active sites for H 2 evolution, which is significantly different from the previous reports in literature. The findings of the intrinsic relationship of balanced benefits from charge separation/transfer and active site control could promote the rational optimization of photocatalyst design by cooperatively manipulating charge flow and active site control, thereby improving the efficiency of photocatalysis for target photoredox processes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced charge separation of rutile TiO2 nanorods by trapping holes and transferring electrons for efficient cocatalyst-free photocatalytic conversion of CO2 to fuels.

PubMed

Wu, Jing; Lu, Hongwei; Zhang, Xuliang; Raziq, Fazal; Qu, Yang; Jing, Liqiang

2016-04-11

Modification with chloride and phosphate anions, and coupling with carbon nanotubes could effectively trap holes and transfer the electrons of rutile nanorods, respectively, so as to greatly promote photogenerated charge separation, leading to an obviously-improved cocatalyst-free photocatalytic conversion of CO2 to CH4 and CO, along with the positive effects of constructed phosphate bridges.

Charge-based separation of particles and cells with similar sizes via the wall-induced electrical lift.

PubMed

Thomas, Cory; Lu, Xinyu; Todd, Andrew; Raval, Yash; Tzeng, Tzuen-Rong; Song, Yongxin; Wang, Junsheng; Li, Dongqing; Xuan, Xiangchun

2017-01-01

The separation of particles and cells in a uniform mixture has been extensively studied as a necessity in many chemical and biomedical engineering and research fields. This work demonstrates a continuous charge-based separation of fluorescent and plain spherical polystyrene particles with comparable sizes in a ψ-shaped microchannel via the wall-induced electrical lift. The effects of both the direct current electric field in the main-branch and the electric field ratio in between the inlet branches for sheath fluid and particle mixture are investigated on this electrokinetic particle separation. A Lagrangian tracking method based theoretical model is also developed to understand the particle transport in the microchannel and simulate the parametric effects on particle separation. Moreover, the demonstrated charge-based separation is applied to a mixture of yeast cells and polystyrene particles with similar sizes. Good separation efficiency and purity are achieved for both the cells and the particles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the role of local charge carrier mobility in the charge separation mechanism of organic photovoltaics.

PubMed

Yoshikawa, Saya; Saeki, Akinori; Saito, Masahiko; Osaka, Itaru; Seki, Shu

2015-07-21

Although the charge separation (CS) and transport processes that compete with geminate and non-geminate recombination are commonly regarded as the governing factors of organic photovoltaic (OPV) efficiency, the details of the CS mechanism remain largely unexplored. Here we provide a systematic investigation on the role of local charge carrier mobility in bulk heterojunction films of ten different low-bandgap polymers and polythiophene analogues blended with methanofullerene (PCBM). By correlating with the OPV performances, we demonstrated that the local mobility of the blend measured by time-resolved microwave conductivity is more important for the OPV output than those of the pure polymers. Furthermore, the results revealed two separate trends for crystalline and semi-crystalline polymers. This work offers guidance in the design of high-performance organic solar cells.

Highly-Efficient Charge Separation and Polaron Delocalization in Polymer-Fullerene Bulk-Heterojunctions: A Comparative Multi-Frequency EPR & DFT Study

PubMed Central

Niklas, Jens; Mardis, Kristy L.; Banks, Brian P.; Grooms, Gregory M.; Sperlich, Andreas; Dyakonov, Vladimir; Beaupré, Serge; Leclerc, Mario; Xu, Tao; Yu, Luping; Poluektov, Oleg G.

2016-01-01

The ongoing depletion of fossil fuels has led to an intensive search for additional renewable energy sources. Solar-based technologies could provide sufficient energy to satisfy the global economic demands in the near future. Photovoltaic (PV) cells are the most promising man-made devices for direct solar energy utilization. Understanding the charge separation and charge transport in PV materials at a molecular level is crucial for improving the efficiency of the solar cells. Here, we use light-induced EPR spectroscopy combined with DFT calculations to study the electronic structure of charge separated states in blends of polymers (P3HT, PCDTBT, and PTB7) and fullerene derivatives (C60-PCBM and C70-PCBM). Solar cells made with the same composites as active layers show power conversion efficiencies of 3.3% (P3HT), 6.1% (PCDTBT), and 7.3% (PTB7), respectively. Under illumination of these composites, two paramagnetic species are formed due to photo-induced electron transfer between the conjugated polymer and the fullerene. They are the positive, P+, and negative, P-, polarons on the polymer backbone and fullerene cage, respectively, and correspond to radical cations and radical anions. Using the high spectral resolution of high-frequency EPR (130 GHz), the EPR spectra of these species were resolved and principal components of the g-tensors were assigned. Light-induced pulsed ENDOR spectroscopy allowed the determination of 1H hyperfine coupling constants of photogenerated positive and negative polarons. The experimental results obtained for the different polymer-fullerene composites have been compared with DFT calculations, revealing that in all three systems the positive polaron is distributed over distances of 40 - 60 Å on the polymer chain. This corresponds to about 15 thiophene units for P3HT, approximately three units PCDTBT, and about three to four units for PTB7. No spin density delocalization between neighboring fullerene molecules was detected by EPR. Strong delocalization of the positive polaron on the polymer donor is an important reason for the efficient charge separation in bulk heterojunction systems as it minimizes the wasteful process of charge recombination. The combination of advanced EPR spectroscopy and DFT is a powerful approach for investigation of light-induced charge dynamics in organic photovoltaic materials. PMID:23670645

Charge recombination in organic photovoltaic devices with high open-circuit voltages.

PubMed

Westenhoff, Sebastian; Howard, Ian A; Hodgkiss, Justin M; Kirov, Kiril R; Bronstein, Hugo A; Williams, Charlotte K; Greenham, Neil C; Friend, Richard H

2008-10-15

A detailed charge recombination mechanism is presented for organic photovoltaic devices with a high open-circuit voltage. In a binary blend comprised of polyfluorene copolymers, the performance-limiting process is found to be the efficient recombination of tightly bound charge pairs into neutral triplet excitons. We arrive at this conclusion using optical transient absorption (TA) spectroscopy with visible and IR probes and over seven decades of time resolution. By resolving the polarization of the TA signal, we track the movement of polaronic states generated at the heterojunction not only in time but also in space. It is found that the photogenerated charge pairs are remarkably immobile at the heterojunction during their lifetime. The charge pairs are shown to be subject to efficient intersystem crossing and terminally recombine into F8BT triplet excitons within approximately 40 ns. Long-range charge separation competes rather unfavorably with intersystem crossing--75% of all charge pairs decay into triplet excitons. Triplet exciton states are thermodynamically accessible in polymer solar cells with high open circuit voltage, and we therefore suggest this loss mechanism to be general. We discuss guidelines for the design of the next generation of organic photovoltaic materials where separating the metastable interfacial charge pairs within approximately 40 ns is paramount.

Highly efficient tandem organic light-emitting devices employing an easily fabricated charge generation unit

NASA Astrophysics Data System (ADS)

Yang, Huishan; Yu, Yaoyao; Wu, Lishuang; Qu, Biao; Lin, Wenyan; Yu, Ye; Wu, Zhijun; Xie, Wenfa

2018-02-01

We have realized highly efficient tandem organic light-emitting devices (OLEDs) employing an easily fabricated charge generation unit (CGU) combining 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile with ultrathin bilayers of CsN3 and Al. The charge generation and separation processes of the CGU have been demonstrated by studying the differences in the current density-voltage characteristics of external-carrier-excluding devices. At high luminances of 1000 and 10000 cd/m2, the current efficiencies of the phosphorescent tandem device are about 2.2- and 2.3-fold those of the corresponding single-unit device, respectively. Simultaneously, an efficient tandem white OLED exhibiting high color stability and warm white emission has also been fabricated.

Phonon-Assisted Ultrafast Charge Transfer at van der Waals Heterostructure Interface.

PubMed

Zheng, Qijing; Saidi, Wissam A; Xie, Yu; Lan, Zhenggang; Prezhdo, Oleg V; Petek, Hrvoje; Zhao, Jin

2017-10-11

The van der Waals (vdW) interfaces of two-dimensional (2D) semiconductor are central to new device concepts and emerging technologies in light-electricity transduction where the efficient charge separation is a key factor. Contrary to general expectation, efficient electron-hole separation can occur in vertically stacked transition-metal dichalcogenide heterostructure bilayers through ultrafast charge transfer between the neighboring layers despite their weak vdW bonding. In this report, we show by ab initio nonadiabatic molecular dynamics calculations, that instead of direct tunneling, the ultrafast interlayer hole transfer is strongly promoted by an adiabatic mechanism through phonon excitation occurring on 20 fs, which is in good agreement with the experiment. The atomic level picture of the phonon-assisted ultrafast mechanism revealed in our study is valuable both for the fundamental understanding of ultrafast charge carrier dynamics at vdW heterointerfaces as well as for the design of novel quasi-2D devices for optoelectronic and photovoltaic applications.

Simultaneously promoting charge separation and photoabsorption of BiOX (X = Cl, Br) for efficient visible-light photocatalysis and photosensitization by compositing low-cost biochar

NASA Astrophysics Data System (ADS)

Li, Min; Huang, Hongwei; Yu, Shixin; Tian, Na; Dong, Fan; Du, Xin; Zhang, Yihe

2016-11-01

Exploration of novel and efficient composite photocatalysts is of great significance for advancing the practical application of photocatalysis. BiOX (X = Cl, Br) is a kind of promising photocatalysts, but the charge separation efficiency and photoabsorption need to be ameliorated. In this work, we first employ a low-cost and easily accessable carbon material biochar to modify BiOX (X = Cl, Br) and develop biochar/BiOX (X = Cl, Br) composite photocatalysts via a facile in-situ deposition method. The as-prepared composites are detailedly characterized by SEM, SEM-mapping, TEM, XRD and XPS, and DRS result demonstrates that the visible-light absorption of BiOX (X = Cl, Br) catalysts can be exceedingly enhanced by biochar. The biochar/BiOX (X = Cl, Br) composites are found to unfold remarkably enhanced visible-light-driven photocatalytic activity toward degradation of MO and photocurrent generation. The strengthened photocatalytic performance mainly stems from the profoundly improved charge separation and delivery efficiency, as evidenced by the electrochemical impedance spectra (EIS), photoluminescence (PL), and time-resolved PL decay spectra. Additionally, the biochar exerts importance in enhancing the two different types of photochemical reactions of BiOBr and BiOCl, in which the photocatalytic mechanisms are found to be photocatalysis and photosensitization process, respectively. The present work may open up a new avenue for framing economic and efficient photocatalytic materials and new composite materials for photoelectric application.

Design and Synthesis of Novel Block Copolymers for Efficient Opto-Electronic Applications

NASA Technical Reports Server (NTRS)

Sun, Sam-Shajing; Fan, Zhen; Wang, Yiqing; Taft, Charles; Haliburton, James; Maaref, Shahin

2002-01-01

It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks may facilitate the charge carrier separation and migration in organic photovoltaic devices due to improved morphology in comparison to polymer blend system. This paper presents preliminary data describing the design and synthesis of a novel Donor-Bridge-Acceptor (D-B-A) block copolymer system for potential high efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene (PPV), the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene (PPV), and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes and facilitates the transport of the holes, the acceptor block stabilizes and facilitates the transport of the electrons, the bridge block is designed to hinder the probability of electron-hole recombination. Thus, improved charge separation and stability are expected with this system. In addition, charge migration toward electrodes may also be facilitated due to the potential nano-phase separated and highly ordered block copolymer ultra-structure.

Separation of photoactive conformers based on hindered diarylethenes: efficient modulation in photocyclization quantum yields.

PubMed

Li, Wenlong; Jiao, Changhong; Li, Xin; Xie, Yongshu; Nakatani, Keitaro; Tian, He; Zhu, Weihong

2014-04-25

Endowing both solvent independency and excellent thermal bistability, the benzobis(thiadiazole)-bridged diarylethene system provides an efficient approach to realize extremely high photocyclization quantum yields (Φo-c , up to 90.6 %) by both separating completely pure anti-parallel conformer and suppressing intramolecular charge transfer (ICT). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A singly charged ion source for radioactive {sup 11}C ion acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katagiri, K.; Noda, A.; Nagatsu, K.

2016-02-15

A new singly charged ion source using electron impact ionization has been developed to realize an isotope separation on-line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive {sup 11}C ion beams. Low-energy electron beams are used in the electron impact ion source to produce singly charged ions. Ionization efficiency was calculated in order to decide the geometric parameters of the ion source and to determine the required electron emission current for obtaining high ionization efficiency. Based on these considerations, the singly charged ion source was designed and fabricated. In testing, the fabricated ion source wasmore » found to have favorable performance as a singly charged ion source.« less

Capillary electrophoresis electrospray ionization mass spectrometry interface

DOEpatents

Smith, Richard D.; Severs, Joanne C.

1999-01-01

The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

Breaking the barriers of all-polymer solar cells: Solving electron transporter and morphology problems

NASA Astrophysics Data System (ADS)

Gavvalapalli, Nagarjuna

All-polymer solar cells (APSC) are a class of organic solar cells in which hole and electron transporting phases are made of conjugated polymers. Unlike polymer/fullerene solar cell, photoactive material of APSC can be designed to have hole and electron transporting polymers with complementary absorption range and proper frontier energy level offset. However, the highest reported PCE of APSC is 5 times less than that of polymer/fullerene solar cell. The low PCE of APSC is mainly due to: i) low charge separation efficiency; and ii) lack of optimal morphology to facilitate charge transfer and transport; and iii) lack of control over the exciton and charge transport in each phase. My research work is focused towards addressing these issues. The charge separation efficiency of APSC can be enhanced by designing novel electron transporting polymers with: i) broad absorption range; ii) high electron mobility; and iii) high dielectric constant. In addition to with the above parameters chemical and electronic structure of the repeating unit of conjugated polymer also plays a role in charge separation efficiency. So far only three classes of electron transporting polymers, CN substituted PPV, 2,1,3-benzothiadiazole derived polymers and rylene diimide derived polymers, are used in APSC. Thus to enhance the charge separation efficiency new classes of electron transporting polymers with the above characteristics need to be synthesized. I have developed a new straightforward synthetic strategy to rapidly generate new classes of electron transporting polymers with different chemical and electronic structure, broad absorption range, and high electron mobility from readily available electron deficient monomers. In APSCs due to low entropy of mixing, polymers tend to micro-phase segregate rather than forming the more useful nano-phase segregation. Optimizing the polymer blend morphology to obtain nano-phase segregation is specific to the system under study, time consuming, and not trivial. Thus to avoid micro-phase segregation, nanoparticles of hole and electron transporters are synthesized and blended. But the PCE of nanoparticle blends are far less than those of polymer blends. This is mainly due to the: i) lack of optimal assembly of nanoparticles to facilitate charge transfer and transport processes; and ii) lack of control over the exciton and charge transport properties within the nanoparticles. Polymer packing within the nanoparticle controls the optoelectronic and charge transport properties of the nanoparticle. In this work I have shown that the solvent used to synthesize nanoparticles plays a crucial role in determining the assembly of polymer chains inside the nanoparticle there by affecting its exciton and charge transport processes. To obtain the optimal morphology for better charge transfer and transport, we have also synthesized nanoparticles of different radius with surfactants of opposite charge. We propose that depending on the radius and/or Coulombic interactions these nanoparticles can be assembled into mineral structure-types that are useful for photovoltaic devices.

Spontaneous Charge Separation and Sublimation Processes are Ubiquitous in Nature and in Ionization Processes in Mass Spectrometry

NASA Astrophysics Data System (ADS)

Trimpin, Sarah; Lu, I.-Chung; Rauschenbach, Stephan; Hoang, Khoa; Wang, Beixi; Chubatyi, Nicholas D.; Zhang, Wen-Jing; Inutan, Ellen D.; Pophristic, Milan; Sidorenko, Alexander; McEwen, Charles N.

2018-02-01

Ionization processes have been discovered by which small and large as well as volatile and nonvolatile compounds are converted to gas-phase ions when associated with a matrix and exposed to sub-atmospheric pressure. Here, we discuss experiments further defining these simple and unexpected processes. Charge separation is found to be a common process for small molecule chemicals, solids and liquids, passed through an inlet tube from a higher to a lower pressure region, with and without heat applied. This charge separation process produces positively- and negatively-charged particles with widely different efficiencies depending on the compound and its physical state. Circumstantial evidence is presented suggesting that in the new ionization process, charged particles carry analyte into the gas phase, and desolvation of these particles produce the bare ions similar to electrospray ionization, except that solid particles appear likely to be involved. This mechanistic proposition is in agreement with previous theoretical work related to ion emission from ice.

Understanding the free energy barrier and multiple timescale dynamics of charge separation in organic photovoltaic cells.

PubMed

Yan, Yaming; Song, Linze; Shi, Qiang

2018-02-28

By employing several lattice model systems, we investigate the free energy barrier and real-time dynamics of charge separation in organic photovoltaic (OPV) cells. It is found that the combined effects of the external electric field, entropy, and charge delocalization reduce the free energy barrier significantly. The dynamic disorder reduces charge carrier delocalization and results in the increased charge separation barrier, while the effect of static disorder is more complicated. Simulation of the real-time dynamics indicates that the free charge generation process involves multiple time scales, including an ultrafast component within hundreds of femtoseconds, an intermediate component related to the relaxation of the hot charge transfer (CT) state, and a slow component on the time scale of tens of picoseconds from the thermally equilibrated CT state. Effects of hot exciton dissociation as well as its dependence on the energy offset between the Frenkel exciton and the CT state are also analyzed. The current results indicate that only a small energy offset between the band gap and the lowest energy CT state is needed to achieve efficient free charge generation in OPV devices, which agrees with recent experimental findings.

Understanding the free energy barrier and multiple timescale dynamics of charge separation in organic photovoltaic cells

NASA Astrophysics Data System (ADS)

Yan, Yaming; Song, Linze; Shi, Qiang

2018-02-01

By employing several lattice model systems, we investigate the free energy barrier and real-time dynamics of charge separation in organic photovoltaic (OPV) cells. It is found that the combined effects of the external electric field, entropy, and charge delocalization reduce the free energy barrier significantly. The dynamic disorder reduces charge carrier delocalization and results in the increased charge separation barrier, while the effect of static disorder is more complicated. Simulation of the real-time dynamics indicates that the free charge generation process involves multiple time scales, including an ultrafast component within hundreds of femtoseconds, an intermediate component related to the relaxation of the hot charge transfer (CT) state, and a slow component on the time scale of tens of picoseconds from the thermally equilibrated CT state. Effects of hot exciton dissociation as well as its dependence on the energy offset between the Frenkel exciton and the CT state are also analyzed. The current results indicate that only a small energy offset between the band gap and the lowest energy CT state is needed to achieve efficient free charge generation in OPV devices, which agrees with recent experimental findings.

Double heterojunction nanowire photocatalysts for hydrogen generation

NASA Astrophysics Data System (ADS)

Tongying, P.; Vietmeyer, F.; Aleksiuk, D.; Ferraudi, G. J.; Krylova, G.; Kuno, M.

2014-03-01

Charge separation and charge transfer across interfaces are key aspects in the design of efficient photocatalysts for solar energy conversion. In this study, we investigate the hydrogen generating capabilities and underlying photophysics of nanostructured photocatalysts based on CdSe nanowires (NWs). Systems studied include CdSe, CdSe/CdS core/shell nanowires and their Pt nanoparticle-decorated counterparts. Femtosecond transient differential absorption measurements reveal how semiconductor/semiconductor and metal/semiconductor heterojunctions affect the charge separation and hydrogen generation efficiencies of these hybrid photocatalysts. In turn, we unravel the role of surface passivation, charge separation at semiconductor interfaces and charge transfer to metal co-catalysts in determining photocatalytic H2 generation efficiencies. This allows us to rationalize why Pt nanoparticle decorated CdSe/CdS NWs, a double heterojunction system, performs best with H2 generation rates of ~434.29 +/- 27.40 μmol h-1 g-1 under UV/Visible irradiation. In particular, we conclude that the CdS shell of this double heterojunction system serves two purposes. The first is to passivate CdSe NW surface defects, leading to long-lived charges at the CdSe/CdS interface capable of carrying out reduction chemistries. Upon photoexcitation, we also find that CdS selectively injects charges into Pt NPs, enabling simultaneous reduction chemistries at the Pt NP/solvent interface. Pt nanoparticle decorated CdSe/CdS NWs thus enable reduction chemistries at not one, but rather two interfaces, taking advantage of each junction's optimal catalytic activities.Charge separation and charge transfer across interfaces are key aspects in the design of efficient photocatalysts for solar energy conversion. In this study, we investigate the hydrogen generating capabilities and underlying photophysics of nanostructured photocatalysts based on CdSe nanowires (NWs). Systems studied include CdSe, CdSe/CdS core/shell nanowires and their Pt nanoparticle-decorated counterparts. Femtosecond transient differential absorption measurements reveal how semiconductor/semiconductor and metal/semiconductor heterojunctions affect the charge separation and hydrogen generation efficiencies of these hybrid photocatalysts. In turn, we unravel the role of surface passivation, charge separation at semiconductor interfaces and charge transfer to metal co-catalysts in determining photocatalytic H2 generation efficiencies. This allows us to rationalize why Pt nanoparticle decorated CdSe/CdS NWs, a double heterojunction system, performs best with H2 generation rates of ~434.29 +/- 27.40 μmol h-1 g-1 under UV/Visible irradiation. In particular, we conclude that the CdS shell of this double heterojunction system serves two purposes. The first is to passivate CdSe NW surface defects, leading to long-lived charges at the CdSe/CdS interface capable of carrying out reduction chemistries. Upon photoexcitation, we also find that CdS selectively injects charges into Pt NPs, enabling simultaneous reduction chemistries at the Pt NP/solvent interface. Pt nanoparticle decorated CdSe/CdS NWs thus enable reduction chemistries at not one, but rather two interfaces, taking advantage of each junction's optimal catalytic activities. Electronic supplementary information (ESI) available: Details of NW syntheses, processing and characterization. Additional TEM images of CdS, CdSe and CdSe/CdS core/shell NWs. NW concentration and cross section estimates. Details of the Pt NP decoration. Additional TEM images of Pt NP decorated CdS, CdSe and CdSe/CdS core/shell NWs. Size distribution of Pt NPs for CdSe/Pt NP and CdSe/CdS/Pt NP NWs. Xe arc lamp spectrum. Details of H2 generation experiments. Estimated photon absorption rate. Details of TDA measurements. TDA spectra and kinetics of CdS and CdS/Pt NP NWs. Plot illustrating CdSe NW band edge bleach kinetics. Comparison of CdSe band edge bleach kinetics in CdSe/CdS core/shell NWs when excited at λexc = 387 nm and λexc = 560 nm. Comparison of CdSe band edge bleach kinetics in CdSe/Pt NP NWs when excited at λexc = 387 nm and λexc = 560 nm. Bar graph showing H2 generation efficiencies of CdS and CdS/Pt NP NWs. Bleach kinetics of CdSe/CdS/Pt NP NWs at λexc = 387 nm and λexc = 560 nm. Comparison of CdS band edge bleach kinetics in CdS/Pt NP, and CdSe/CdS core/shell NWs when excited at λexc = 387 nm. See DOI: 10.1039/c4nr00298a

A predictive theory of charge separation in organic photovoltaics interfaces

NASA Astrophysics Data System (ADS)

Troisi, Alessandro; Liu, Tao; Caruso, Domenico; Cheung, David L.; McMahon, David P.

2012-09-01

The key process in organic photovoltaics cells is the separation of an exciton, close to the donor/acceptor interface into a free hole (in the donor) and a free electron (in the acceptor). In an efficient solar cell, the majority of absorbed photons generate such hole-electron pairs but it is not clear why such a charge separation process is so efficient in some blends (for example in the blend formed by poly(3- hexylthiophene) (P3HT) and a C60 derivative (PCBM)) and how can one design better OPV materials. The electronic and geometric structure of the prototypical polymer:fullerene interface (P3HT:PCBM) is investigated theoretically using a combination of classical and quantum simulation methods. It is shown that the electronic structure of P3HT in contact with PCBM is significantly altered compared to bulk P3HT. Due to the additional free volume of the interface, P3HT chains close to PCBM are more disordered and, consequently, they are characterized by an increased band gap. Excitons and holes are therefore repelled by the interface. This provides a possible explanation of the low recombination efficiency and supports the direct formation of "quasi-free" charge separated species at the interface. This idea is further explored here by using a more general system-independent model Hamiltonian. The long range exciton dissociation rate is computed as a function of the exciton distance from the interface and the average dissociation distance is evaluated by comparing this rate with the exciton migration rate with a kinetic model. The phenomenological model shows that also in a generic interface the direct formation if quasi-free charges is extremely likely.

Incorporating an Electrode Modification Layer with a Vertical Phase Separated Photoactive Layer for Efficient and Stable Inverted Nonfullerene Polymer Solar Cells.

PubMed

Shi, Zhenzhen; Liu, Hao; Wang, Yaping; Li, Jinyan; Bai, Yiming; Wang, Fuzhi; Bian, Xingming; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2017-12-20

For bulk heterojunction polymer solar cells (PSCs), the donors and acceptors featuring specific phase separation and concentration distribution within the electron donor/acceptor blends crucially affect the exciton dissociation and charge transportation. Herein, efficient and stable nonfullerene inverted PSCs incorporating a phase separated photoactive layer and a titanium chelate electrode modification layer are demonstrated. Water contact angle (WCA), scanning kelvin probe microscopy (SKPM), and atomic force microscopy (AFM) techniques are implemented to characterize the morphology of photoactive layers. Compared with the control conventional device, the short-circuit current density (J sc ) is enhanced from 14.74 to 17.45 mAcm -2 . The power conversion efficiency (PCE) for the inverted PSCs with a titanium (diisopropoxide)-bis-(2,4-pentanedionate) (TIPD) layer increases from 9.67% to 11.69% benefiting from the declined exciton recombination and fairly enhanced charge transportation. Furthermore, the nonencapsulated inverted device with a TIPD layer demonstrates the best long-term stability, 85% of initial PCE remaining and an almost undecayed open-circuit voltage (V oc ) after 1440 h. Our results reveal that the titanium chelate is an excellent electrode modification layer to incorporate with a vertical phase separated photoactive layer for producing high-efficiency and high-stability inverted nonfullerene PSCs.

Effects of Magnetic Nanoparticles and External Magnetostatic Field on the Bulk Heterojunction Polymer Solar Cells

DOE PAGES

Wang, Kai; Yi, Chao; Liu, Chang; ...

2015-03-18

The price of energy to separate tightly bound electron-hole pair (or charge-transfer state) and extract freely movable charges from low-mobility materials represents fundamental losses for many low-cost photovoltaic devices. In bulk heterojunction (BHJ) polymer solar cells (PSCs), approximately 50% of the total efficiency lost among all energy loss pathways is due to the photogenerated charge carrier recombination within PSCs and low charge carrier mobility of disordered organic materials. To address these issues, we introduce magnetic nanoparticles (MNPs) and orientate these MNPS within BHJ composite by an external magnetostatic field. Over 50% enhanced efficiency was observed from BHJ PSCs incorporated withmore » MNPs and an external magnetostatic field alignment when compared to the control BHJ PSCs. The optimization of BHJ thin film morphology, suppression of charge carrier recombination, and enhancement in charge carrier collection result in a greatly increased short-circuit current density and fill factor, as a result, enhanced power conversion efficiency.« less

Electrostatic Separator for Beneficiation of Lunar Soil

NASA Technical Reports Server (NTRS)

Quinn, Jacqueline; Arens, Ellen; Trigwell, Steve; Captain, James

2010-01-01

A charge separator has been constructed for use in a lunar environment that will allow for separation of minerals from lunar soil. In the present experiments, whole lunar dust as received was used. The approach taken here was that beneficiation of ores into an industrial feedstock grade may be more efficient. Refinement or enrichment of specific minerals in the soil before it is chemically processed may be more desirable as it would reduce the size and energy requirements necessary to produce the virgin material, and it may significantly reduce the process complexity. The principle is that minerals of different composition and work function will charge differently when tribocharged against different materials, and hence be separated in an electric field.

Role of charge separation mechanism and local disorder at hybrid solar cell interfaces

NASA Astrophysics Data System (ADS)

Ehrenreich, Philipp; Pfadler, Thomas; Paquin, Francis; Dion-Bertrand, Laura-Isabelle; Paré-Labrosse, Olivier; Silva, Carlos; Weickert, Jonas; Schmidt-Mende, Lukas

2015-01-01

Dye-sensitized metal oxide polymer hybrid solar cells deliver a promising basis in organic solar cell development due to many conceptual advantages. Since the power conversion efficiency is still in a noncompetitive state, it has to be understood how the photocurrent contribution can be maximized (i.e., which dye-polymer properties are most beneficial for efficient charge generation in hybrid solar cells). By the comparison of three model systems for hybrid solar cells with Ti O2 -dye-polymer interfaces, this paper was aimed at elucidating the role of the exact mechanism of charge generation. In the exciton dissociation (ED) case, an exciton that is generated in the polymer is split at the dye-polymer interface. Alternatively, this exciton can be transferred to the dye via an energy transfer (ET), upon which charge separation occurs between dye and Ti O2 . For comparison, the third case is included in which the high lowest unoccupied molecular orbital of the dye does not allow exciton separation or ET from the dye to the polymer, so that the dye only is responsible for charge generation. To separate effects owing to differences in energy levels of the involved materials from the impact of local order and disorder in the polymer close to the interface, this paper further comprises a detailed analysis of the polymer crystallinity based on the H-aggregate model. While the massive impact of the poly(3-hexylthiophene) crystallinity on device function has been outlined for bare metal oxide-polymer interfaces, it has not been considered for hybrid solar cells with dye-sensitized Ti O2 . The results presented here indicate that all dye molecules in general influence the polymer morphology, which has to be taken into account for future optimization of hybrid solar cells. Apart from that, it can be suggested that ED on the polymer needs an additional driving force to work efficiently; thus, energy transfer seems to be currently the most promising strategy to increase the polymer photocurrent contribution.

Stacked white OLED having separate red, green and blue sub-elements

DOEpatents

Forrest, Stephen; Qi, Xiangfei; Slootsky, Michael

2014-07-01

The present invention relates to efficient organic light emitting devices (OLEDs). The devices employ three emissive sub-elements, typically emitting red, green and blue, to sufficiently cover the visible spectrum. Thus, the devices may be white-emitting OLEDs, or WOLEDs. Each sub-element comprises at least one organic layer which is an emissive layer--i.e., the layer is capable of emitting light when a voltage is applied across the stacked device. The sub-elements are vertically stacked and are separated by charge generating layers. The charge-generating layers are layers that inject charge carriers into the adjacent layer(s) but do not have a direct external connection.

"Double-Cable" Conjugated Polymers with Linear Backbone toward High Quantum Efficiencies in Single-Component Polymer Solar Cells.

PubMed

Feng, Guitao; Li, Junyu; Colberts, Fallon J M; Li, Mengmeng; Zhang, Jianqi; Yang, Fan; Jin, Yingzhi; Zhang, Fengling; Janssen, René A J; Li, Cheng; Li, Weiwei

2017-12-27

A series of "double-cable" conjugated polymers were developed for application in efficient single-component polymer solar cells, in which high quantum efficiencies could be achieved due to the optimized nanophase separation between donor and acceptor parts. The new double-cable polymers contain electron-donating poly(benzodithiophene) (BDT) as linear conjugated backbone for hole transport and pendant electron-deficient perylene bisimide (PBI) units for electron transport, connected via a dodecyl linker. Sulfur and fluorine substituents were introduced to tune the energy levels and crystallinity of the conjugated polymers. The double-cable polymers adopt a "face-on" orientation in which the conjugated BDT backbone and the pendant PBI units have a preferential π-π stacking direction perpendicular to the substrate, favorable for interchain charge transport normal to the plane. The linear conjugated backbone acts as a scaffold for the crystallization of the PBI groups, to provide a double-cable nanophase separation of donor and acceptor phases. The optimized nanophase separation enables efficient exciton dissociation as well as charge transport as evidenced from the high-up to 80%-internal quantum efficiency for photon-to-electron conversion. In single-component organic solar cells, the double-cable polymers provide power conversion efficiency up to 4.18%. This is one of the highest performances in single-component organic solar cells. The nanophase-separated design can likely be used to achieve high-performance single-component organic solar cells.

Facile Synthesis of Ultrafine Hematite Nanowire Arrays in Mixed Water-Ethanol-Acetic Acid Solution for Enhanced Charge Transport and Separation.

PubMed

Wang, Jian; Wang, Menglong; Zhang, Tao; Wang, Zhiqiang; Guo, Penghui; Su, Jinzhan; Guo, Liejin

2018-04-18

Nanostructure engineering is of great significance for semiconductor electrode to achieve high photoelectrochemical performance. Herein, we report a novel strategy to fabricate ultrafine hematite (α-Fe 2 O 3 ) nanowire arrays in a mixed water-ethanol-acetic acid (WEA) solvent. To the best of our knowledge, this is the first report on direct growth of ultrafine (∼10 nm) α-Fe 2 O 3 nanowire arrays on fluorine-doped tin oxide substrates through solution-based fabrication process. The effect of WEA ratio on the morphology of nanowires has been systematically studied to understand the formation mechanism. Photoelectrochemical measurements were conducted on both Ti-treated α-Fe 2 O 3 nanowire and nanorod photoelectrodes. It reveals that α-Fe 2 O 3 nanowire electrode has higher photocurrent and charge separation efficiencies than nanorod electrode if the carrier concentration and space-charge carrier width are in the same order of magnitude. Normalized by electrochemically active surface area, the Ti-treated α-Fe 2 O 3 nanowire electrode obtains 6.4 times higher specific photocurrent density than nanorod electrode. This superiority of nanowires arises from the higher bulk and surface charge separation efficiencies, which could be partly attributed to reduced distance that holes must transfer to reach the semiconductor-liquid junction.

Hexahedron Prism-Anchored Octahedronal CeO2: Crystal Facet-Based Homojunction Promoting Efficient Solar Fuel Synthesis.

PubMed

Li, Ping; Zhou, Yong; Zhao, Zongyan; Xu, Qinfeng; Wang, Xiaoyong; Xiao, Min; Zou, Zhigang

2015-08-05

An unprecedented, crystal facet-based CeO2 homojunction consisting of hexahedron prism-anchored octahedron with exposed prism surface of {100} facets and octahedron surface of {111} facets was fabricated through solution-based crystallographic-oriented epitaxial growth. The photocatalysis experiment reveals that growth of the prism arm on octahedron allows to activate inert CeO2 octahedron for an increase in phototocatalytic reduction of CO2 into methane. The pronounced photocatalytic performance is attributed to a synergistic effect of the following three factors: (1) band alignment of the {100} and {111} drives electrons and holes to octahedron and prism surfaces, respectively, aiming to reach the most stable energy configuration and leading to a spatial charge separation for long duration; (2) crystallographic-oriented epitaxial growth of the CeO2 hexahedron prism arm on the octahedron verified by the interfacial lattice fringe provides convenient and fast channels for the photogenerated carrier transportation between two units of homojuntion; (3) different effective mass of electrons and holes on {100} and {111} faces leads to high charge carrier mobility, more facilitating the charge separation. The proposed facet-based homojunction in this work may provide a new concept for the efficient separation and fast transfer of photoinduced charge carriers and enhancement of the photocatalytic performance.

Femtosecond Visible Transient Absorption Spectroscopy of Chlorophyll f-Containing Photosystem I.

PubMed

Kaucikas, Marius; Nürnberg, Dennis; Dorlhiac, Gabriel; Rutherford, A William; van Thor, Jasper J

2017-01-24

Photosystem I (PSI) from Chroococcidiopsis thermalis PCC 7203 grown under far-red light (FRL; >725 nm) contains both chlorophyll a and a small proportion of chlorophyll f. Here, we investigated excitation energy transfer and charge separation using this FRL-grown form of PSI (FRL-PSI). We compared femtosecond transient visible absorption changes of normal, white-light (WL)-grown PSI (WL-PSI) with those of FRL-PSI using excitation at 670 nm, 700 nm, and (in the case of FRL-PSI) 740 nm. The possibility that chlorophyll f participates in energy transfer or charge separation is discussed on the basis of spectral assignments. With selective pumping of chlorophyll f at 740 nm, we observe a final ∼150 ps decay assigned to trapping by charge separation, and the amplitude of the resulting P700 +• A 1 -• charge-separated state indicates that the yield is directly comparable to that of WL-PSI. The kinetics shows a rapid 2 ps time constant for almost complete transfer to chlorophyll f if chlorophyll a is pumped with a wavelength of 670 nm or 700 nm. Although the physical role of chlorophyll f is best supported as a low-energy radiative trap, the physical location should be close to or potentially within the charge-separating pigments to allow efficient transfer for charge separation on the 150 ps timescale. Target models can be developed that include a branching in the formation of the charge separation for either WL-PSI or FRL-PSI. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Microdialysis unit for molecular weight separation

DOEpatents

Smith, Richard D.; Liu, Chuanliang

1999-01-01

The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, or (4) any combination of (1), (2), and (3).

Greatly Increasing Trapped Ion Populations for Mobility Separations Using Traveling Waves in Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Ibrahim, Yehia M.; Garimella, Sandilya V. B.

The initial use of traveling waves (TW) for ion mobility (IM) separations using a structures for lossless ion manipulations (SLIM) employed an ion funnel trap (IFT) to accumulate ions from a continuous electrospray ionization source, and limited to injected ion populations of ~106 charges due to the onset of space charge effects in the trapping region. Additional limitations arise due to the loss of resolution for the injection of ions over longer periods (e.g. in extended pulses). In this work a new SLIM ‘flat funnel’ (FF) module has been developed and demonstrated to enable the accumulation of much larger ionmore » populations and their injection for IM separations. Ion current measurements indicate a capacity of ~3.2×108 charges for the extended trapping volume, over an order of magnitude greater than the IFT. The orthogonal ion injection into a funnel shaped separation region can greatly reduce space charge effects during the initial IM separation stage, and the gradually reduced width of the path allows the ion packet to be increasingly compressed in the lateral dimension as the separation progresses, allowing e.g. efficient transmission through conductance limits or compatibility with subsequent ion manipulations. This work examined the TW, RF, and DC confining field SLIM parameters involved in ion accumulation, injection, transmission and separation in the FF IM module using both direct ion current and MS measurements. Wide m/z range ion transmission is demonstrated, along with significant increases in signal to noise (S/N) ratios due to the larger ion populations injected. Additionally, we observed a reduction in the chemical background, which was attributed to more efficient desolvation of solvent related clusters over the extended ion accumulation periods. The TW SLIM FF IM module is anticipated to be especially effective as a front end for long path SLIM IM separation modules.« less

First-principles studies of interfacial charge separation in nano-materials photovoltaic heterojunction

NASA Astrophysics Data System (ADS)

Kanai, Yosuke

2009-03-01

Charge separation is a crucial process that must be understood in order to make substantial improvements in nano-materials based PV cells. In our work, first principles quantum mechanical calculations are employed to shed light on this process for some important nano-material heterojunctions. I will first present our work on the interfacial charge separation in Fullerene/P3HT and CNT/P3HT heterojunctions. Our findings indicate that in the fullerene system a two-step process is operative, involving an adiabatic electron transfer and an exciton dissociation via quasi-degenerate states localized on the fullerene. For the nanotubes, on the other hand, while such a two-step process is not necessary for efficient charge separation, the presence of metallic nanotubes lead to undesirable charge traps. Secondly, I will discuss how we are addressing the difficulty in employing standard DFT approaches for investigating inorganic-organic PV interfaces, which are composed of two distinct materials with very different electronic environments. I will discuss a QMC scheme for obtaining many-body corrections to the Kohn-Sham level alignments and its application to a CdSe/Oligothiophene hybrid PV interface, with the aim of tailoring its behavior by controlling the conjugation length.

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI(3-x)Cl(x) perovskite solar cells.

PubMed

Edri, Eran; Kirmayer, Saar; Mukhopadhyay, Sabyasachi; Gartsman, Konstantin; Hodes, Gary; Cahen, David

2014-03-11

Developments in organic-inorganic lead halide-based perovskite solar cells have been meteoric over the last 2 years, with small-area efficiencies surpassing 15%. We address the fundamental issue of how these cells work by applying a scanning electron microscopy-based technique to cell cross-sections. By mapping the variation in efficiency of charge separation and collection in the cross-sections, we show the presence of two prime high efficiency locations, one at/near the absorber/hole-blocking-layer, and the second at/near the absorber/electron-blocking-layer interfaces, with the former more pronounced. This 'twin-peaks' profile is characteristic of a p-i-n solar cell, with a layer of low-doped, high electronic quality semiconductor, between a p- and an n-layer. If the electron blocker is replaced by a gold contact, only a heterojunction at the absorber/hole-blocking interface remains.

Strategies for Efficient Charge Separation and Transfer in Artificial Photosynthesis of Solar Fuels.

PubMed

Xu, Yuxing; Li, Ailong; Yao, Tingting; Ma, Changtong; Zhang, Xianwen; Shah, Jafar Hussain; Han, Hongxian

2017-11-23

Converting sunlight to solar fuels by artificial photosynthesis is an innovative science and technology for renewable energy. Light harvesting, photogenerated charge separation and transfer (CST), and catalytic reactions are the three primary steps in the processes involved in the conversion of solar energy to chemical energy (SE-CE). Among the processes, CST is the key "energy pump and delivery" step in determining the overall solar-energy conversion efficiency. Efficient CST is always high priority in designing and assembling artificial photosynthesis systems for solar-fuel production. This Review not only introduces the fundamental strategies for CST but also the combinatory application of these strategies to five types of the most-investigated semiconductor-based artificial photosynthesis systems: particulate, Z-scheme, hybrid, photoelectrochemical, and photovoltaics-assisted systems. We show that artificial photosynthesis systems with high SE-CE efficiency can be rationally designed and constructed through combinatory application of these strategies, setting a promising blueprint for the future of solar fuels. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular approaches to solar energy conversion: the energetic cost of charge separation from molecular-excited states.

PubMed

Durrant, James R

2013-08-13

This review starts with a brief overview of the technological potential of molecular-based solar cell technologies. It then goes on to focus on the core scientific challenge associated with using molecular light-absorbing materials for solar energy conversion, namely the separation of short-lived, molecular-excited states into sufficiently long-lived, energetic, separated charges capable of generating an external photocurrent. Comparisons are made between different molecular-based solar cell technologies, with particular focus on the function of dye-sensitized photoelectrochemical solar cells as well as parallels with the function of photosynthetic reaction centres. The core theme of this review is that generating charge carriers with sufficient lifetime and a high quantum yield from molecular-excited states comes at a significant energetic cost-such that the energy stored in these charge-separated states is typically substantially less than the energy of the initially generated excited state. The role of this energetic loss in limiting the efficiency of solar energy conversion by such devices is emphasized, and strategies to minimize this energy loss are compared and contrasted.

Core/shell colloidal quantum dot exciplex states for the development of highly efficient quantum-dot-sensitized solar cells.

PubMed

Wang, Jin; Mora-Seró, Iván; Pan, Zhenxiao; Zhao, Ke; Zhang, Hua; Feng, Yaoyu; Yang, Guang; Zhong, Xinhua; Bisquert, Juan

2013-10-23

Searching suitable panchromatic QD sensitizers for expanding the light-harvesting range, accelerating charge separation, and retarding charge recombination is an effective way to improve power conversion efficiency (PCE) of quantum-dot-sensitized solar cells (QDSCs). One possible way to obtain a wide absorption range is to use the exciplex state of a type-II core/shell-structured QDs. In addition, this system could also provide a fast charge separation and low charge-recombination rate. Herein, we report on using a CdTe/CdSe type-II core/shell QD sensitizer with an absorption range extending into the infrared region because of its exciplex state, which is covalently linked to TiO2 mesoporous electrodes by dropping a bifunctional linker molecule mercaptopropionic acid (MPA)-capped QD aqueous solution onto the film electrode. High loading and a uniform distribution of QD sensitizer throughout the film electrode thickness have been confirmed by energy dispersive X-ray (EDX) elemental mapping. The accelerated electron injection and retarded charge-recombination pathway in the built CdTe/CdSe QD cells in comparison with reference CdSe QD-based cells have been confirmed by impedance spectroscopy, fluorescence decay, and intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) analysis. With the combination of the high QD loading and intrinsically superior optoelectronic properties of type-II core/shell QD (wide absorption range, fast charge separation, and slow charge recombination), the resulting CdTe/CdSe QD-based regenerative sandwich solar cells exhibit a record PCE of 6.76% (J(sc) = 19.59 mA cm(-2), V(oc) = 0.606 V, and FF = 0.569) with a mask around the active film under a full 1 sun illumination (simulated AM 1.5), which is the highest reported to date for liquid-junction QDSCs.

Improved charge breeding efficiency of light ions with an electron cyclotron resonance ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vondrasek, R.; Delahaye, P.; Kutsaev, Sergey

2012-11-01

The Californium Rare Isotope Breeder Upgrade is a new radioactive beam facility for the Argonne Tandem Linac Accelerator System (ATLAS). The facility utilizes a 252Cf fission source coupled with an electron cyclotron resonance ion source to provide radioactive beam species for the ATLAS experimental program. The californium fission fragment distribution provides nuclei in the mid-mass range which are difficult to extract from production targets using the isotope separation on line technique and are not well populated by low-energy fission of uranium. To date the charge breeding program has focused on optimizing these mid-mass beams, achieving high charge breeding efficiencies ofmore » both gaseous and solid species including 14.7% for the radioactive species 143Ba27+. In an effort to better understand the charge breeding mechanism, we have recently focused on the low-mass species sodium and potassium which up to present have been difficult to charge breed efficiently. Unprecedented charge breeding efficiencies of 10.1% for 23Na7+ and 17.9% for 39K10+ were obtained injecting stable Na+ and K+ beams from a surface ionization source.« less

Vertical phase separation in bulk heterojunction solar cells formed by in situ polymerization of fulleride

PubMed Central

Zhang, Lipei; Xing, Xing; Zheng, Lingling; Chen, Zhijian; Xiao, Lixin; Qu, Bo; Gong, Qihuang

2014-01-01

Vertical phase separation of the donor and the acceptor in organic bulk heterojunction solar cells is crucial to improve the exciton dissociation and charge transport efficiencies. This is because whilst the exciton diffusion length is limited, the organic film must be thick enough to absorb sufficient light. However, it is still a challenge to control the phase separation of a binary blend in a bulk heterojunction device architecture. Here we report the realization of vertical phase separation induced by in situ photo-polymerization of the acrylate-based fulleride. The power conversion efficiency of the devices with vertical phase separation increased by 20%. By optimising the device architecture, the power conversion efficiency of the single junction device reached 8.47%. We believe that in situ photo-polymerization of acrylate-based fulleride is a universal and controllable way to realise vertical phase separation in organic blends. PMID:24861168

Concentration specific and tunable photoresponse of bismuth vanadate functionalized hexagonal ZnO nanocrystals based photoanodes for photoelectrochemical application

NASA Astrophysics Data System (ADS)

Singh, Sonal; Ruhela, Aakansha; Rani, Sanju; Khanuja, Manika; Sharma, Rishabh

2018-02-01

In the present work, dual layer BiVO4/ZnO photoanode is instigated for photo-electrochemical (PEC) water splitting applications. Two different photocatalytic layers ZnO and BiVO4, reduces charge carrier recombination and charge transfer resistance at photoanode/electrolyte junction. The concentration-specific, tunable and without 'spike and overshoot' features, photocurrent density response is originated by varying BiVO4 concentration in the BiVO4/ZnO photoanode. The crystal structure of ZnO (hexagonal wurtzite structure) and BiVO4 (monoclinic scheelite structure) is confirmed by X-ray diffraction studies. The band gap of BiVO4/ZnO was estimated to be ca. 2.42 eV through Kubler-Munk function F(R∞) using diffuse reflectance spectroscopy. Electrochemical behavior of samples was analyzed with photocurrent measurements, electrochemical impedance, Mott-Schottky plots, bulk separation efficiency and surface transfer efficiency. The maximum photocurrent density of BiVO4/ZnO photoanode was found to be 2.3 times higher than pristine ZnO sample.0.038 M BiVO4/ZnO exhibited the highest separation efficiency of 72% and surface transfer efficiency of 64.7% at +1.23 V vs. RHE. Mott-Schottky study revealed the maximum charge carrier density in the same sample.

Enhancement in Organic Photovoltaic Efficiency through the Synergistic Interplay of Molecular Donor Hydrogen Bonding and -Stacking

DOE PAGES

Shewmon, Nathan; Watkins, Davita; Galindo, Johan; ...

2015-07-20

For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom-up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H-bonding) interactions between π-conjugated electron donor molecules encourage formation of vertically aligned donor π-stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groupsmore » that are either capable or incapable of self-complementary H-bonding. When applied to OPVs, the H-bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H-bond promoted assembly results in redshifted absorption (in neat films and donor:C 60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X-ray scattering reveals a synergistic interplay of lateral H-bonding interactions and vertical π-stacking for directing the favorable morphology of the BHJ.« less

Microchip Electrophoresis at Elevated Temperatures and High Separation Field Strengths

PubMed Central

Mitra, Indranil; Marczak, Steven P.; Jacobson, Stephen C.

2014-01-01

We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11-cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45 °C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths can be used to offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45 °C with separation field strengths ≥500 V/cm. PMID:24114979

Dissecting protein function: an efficient protocol for identifying separation-of-function mutations that encode structurally stable proteins.

PubMed

Lubin, Johnathan W; Rao, Timsi; Mandell, Edward K; Wuttke, Deborah S; Lundblad, Victoria

2013-03-01

Mutations that confer the loss of a single biochemical property (separation-of-function mutations) can often uncover a previously unknown role for a protein in a particular biological process. However, most mutations are identified based on loss-of-function phenotypes, which cannot differentiate between separation-of-function alleles vs. mutations that encode unstable/unfolded proteins. An alternative approach is to use overexpression dominant-negative (ODN) phenotypes to identify mutant proteins that disrupt function in an otherwise wild-type strain when overexpressed. This is based on the assumption that such mutant proteins retain an overall structure that is comparable to that of the wild-type protein and are able to compete with the endogenous protein (Herskowitz 1987). To test this, the in vivo phenotypes of mutations in the Est3 telomerase subunit from Saccharomyces cerevisiae were compared with the in vitro secondary structure of these mutant proteins as analyzed by circular-dichroism spectroscopy, which demonstrates that ODN is a more sensitive assessment of protein stability than the commonly used method of monitoring protein levels from extracts. Reverse mutagenesis of EST3, which targeted different categories of amino acids, also showed that mutating highly conserved charged residues to the oppositely charged amino acid had an increased likelihood of generating a severely defective est3(-) mutation, which nevertheless encoded a structurally stable protein. These results suggest that charge-swap mutagenesis directed at a limited subset of highly conserved charged residues, combined with ODN screening to eliminate partially unfolded proteins, may provide a widely applicable and efficient strategy for generating separation-of-function mutations.

Separation efficiency of free-solution conjugated electrophoresis with drag-tags incorporating a synthetic amino acid.

PubMed

Seo, Kyung-Ho; Chu, Hun-Su; Yoo, Tae Hyeon; Lee, Sun-Gu; Won, Jong-In

2016-03-01

DNA sequencing or separation by conventional capillary electrophoresis with a polymer matrix has some inherent drawbacks, such as the expense of polymer matrix and limitations in sequencing read length. As DNA fragments have a linear charge-to-friction ratio in free solution, DNA fragments cannot be separated by size. However, size-based separation of DNA is possible in free-solution conjugate electrophoresis (FSCE) if a "drag-tag" is attached to DNA fragments because the tag breaks the linear charge-to-friction scaling. Although several previous studies have demonstrated the feasibility of DNA separation by free-solution conjugated electrophoresis, generation of a monodisperse drag-tag and identification of a strong, site-specific conjugation method between a DNA fragment and a drag-tag are challenges that still remain. In this study, we demonstrate an efficient FSCE method by conjugating a biologically synthesized elastin-like polypeptide (ELP) and green fluorescent protein (GFP) to DNA fragments. In addition, to produce strong and site-specific conjugation, a methionine residue in drag-tags is replaced with homopropargylglycine (Hpg), which can be conjugated specifically to a DNA fragment with an azide site. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective separation of trivalent f-ions using 1,10-phenanthroline-2,9-dicarboxamide ligands in ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dehaudt, Jeremy; Williams, Neil J.; Shkrob, Ilya A.

1,10-Phenanthroline-2,9-dicarboxamide complexants decorated with alkyl chains and imidazolium cations have been studied for extraction of trivalent f-ions into imidazolium ionic liquids. The dicationic complexants are shown to extract Am over Eu with separation factors > 50 and high extraction efficiencies. Lastly, the different size selectivities for lanthanide ions were observed for these two types of the complexants, highlighting the importance of the positive charge in controlling both extraction efficiencies and extraction selectivities.

Selective separation of trivalent f-ions using 1,10-phenanthroline-2,9-dicarboxamide ligands in ionic liquids

DOE PAGES

Dehaudt, Jeremy; Williams, Neil J.; Shkrob, Ilya A.; ...

2016-06-13

1,10-Phenanthroline-2,9-dicarboxamide complexants decorated with alkyl chains and imidazolium cations have been studied for extraction of trivalent f-ions into imidazolium ionic liquids. The dicationic complexants are shown to extract Am over Eu with separation factors > 50 and high extraction efficiencies. Lastly, the different size selectivities for lanthanide ions were observed for these two types of the complexants, highlighting the importance of the positive charge in controlling both extraction efficiencies and extraction selectivities.

A rational approach towards enhancing solar water splitting: a case study of Au-RGO/N-RGO-TiO2.

PubMed

Bharad, Pradnya A; Sivaranjani, Kumarsrinivasan; Gopinath, Chinnakonda S

2015-07-07

A rational approach was employed to enhance the solar water splitting (SWS) efficiency by systematically combining various important factors that helps to increase the photocatalytic activity. The rational approach includes four important parameters, namely, charge generation through simulated sunlight absorption, charge separation and diffusion, charge utilization through redox reaction, and the electronic integration of all of the above three factors. The complexity of the TiO2 based catalyst and its SWS activity was increased systematically by adding reduced graphene oxide (RGO) or N-doped RGO and/or nanogold. Au-N-RGO-TiO2 shows the maximum apparent quantum yield (AQY) of 2.46% with a H2 yield (525 μmol g(-1) h(-1)) from aqueous methanol, and overall water splitting activity (22 μmol g(-1) h(-1); AQY = 0.1%) without any sacrificial agent under one sun conditions. This exercise helps to understand the factors which help to enhance the SWS activity. Activity enhancement was observed when there is synergy among the components, especially the simulated sunlight absorption (or one sun conditions), charge separation/conduction and charge utilization. Electronic integration among the components provides the synergy for efficient solar light harvesting. In our opinion, the above synergy helps to increase the overall utilization of charge carriers towards the higher activity.

Enhanced Charge Separation in Ternary P3HT/PCBM/CuInS2 Nanocrystals Hybrid Solar Cells

PubMed Central

Lefrançois, Aurélie; Luszczynska, Beata; Pepin-Donat, Brigitte; Lombard, Christian; Bouthinon, Benjamin; Verilhac, Jean-Marie; Gromova, Marina; Faure-Vincent, Jérôme; Pouget, Stéphanie; Chandezon, Frédéric; Sadki, Saïd; Reiss, Peter

2015-01-01

Geminate recombination of bound polaron pairs at the donor/acceptor interface is one of the major loss mechanisms in organic bulk heterojunction solar cells. One way to overcome Coulomb attraction between opposite charge carriers and to achieve their full dissociation is the introduction of high dielectric permittivity materials such as nanoparticles of narrow band gap semiconductors. We selected CuInS2 nanocrystals of 7.4 nm size, which present intermediate energy levels with respect to poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM). Efficient charge transfer from P3HT to nanocrystals takes place as evidenced by light-induced electron spin resonance. Charge transfer between nanocrystals and PCBM only occurs after replacing bulky dodecanethiol (DDT) surface ligands with shorter 1,2-ethylhexanethiol (EHT) ligands. Solar cells containing in the active layer a ternary blend of P3HT:PCBM:CuInS2-EHT nanocrystals in 1:1:0.5 mass ratio show strongly improved short circuit current density and a higher fill factor with respect to the P3HT:PCBM reference device. Complementary measurements of the absorption properties, external quantum efficiency and charge carrier mobility indicate that enhanced charge separation in the ternary blend is at the origin of the observed behavior. The same trend is observed for blends using the glassy polymer poly(triarylamine) (PTAA). PMID:25588811

Fabrication of Heterogeneous-Phase Solid-Solution Promoting Band Structure and Charge Separation for Enhancing Photocatalytic CO2 Reduction: A Case of ZnXCa1-XIn2S4.

PubMed

Zeng, Chao; Huang, Hongwei; Zhang, Tierui; Dong, Fan; Zhang, Yihe; Hu, Yingmo

2017-08-23

Photocatalytic CO 2 reduction into solar fuels illustrates huge charm for simultaneously settling energy and environmental issues. The photoreduction ability of a semiconductor is closely correlated to its conduction band (CB) position. A homogeneous-phase solid-solution with the same crystal system always has a monotonously changed CB position, and the high CB level has to be sacrificed to achieve a benign photoabsorption. Herein, we report the fabrication of heterogeneous-phase solid-solution Zn X Ca 1-X In 2 S 4 between trigonal ZnIn 2 S 4 and cubic CaIn 2 S 4 . The Zn X Ca 1-X In 2 S 4 solid solutions with orderly tuned photoresponsive range from 540 to 640 nm present a more negative CB level and highly enhanced charge-separation efficiency. Profiting from these merits, all of these Zn X Ca 1-X In 2 S 4 solid solutions exhibit remarkably strengthened photocatalytic CO 2 reduction performance under visible light (λ > 420 nm) irradiation. Zn 0.4 Ca 0.6 In 2 S 4 , bearing the most negative CB position and highest charge-separation efficiency, casts the optimal photocatalytic CH 4 and CO evolution rates, which reach 16.7 and 6.8 times higher than that of ZnIn 2 S 4 and 7.2 and 3.9 times higher than that of CaIn 2 S 4 , respectively. To verify the crucial role of the heterogeneous-phase solid solution in promoting the band structure and photocatalytic performance, another heterogeneous-phase solid-solution Zn X Cd 1-X In 2 S 4 has been synthesized. It also displays an upshifted CB level and promoted charge separation. This work may provide a new perspective into the development of an efficient visible-light driven photocatalyst for CO 2 reduction and other photoreduction reactions.

Evolved phase separation toward balanced charge transport and high efficiency in polymer solar cells.

PubMed

Fan, Haijun; Zhang, Maojie; Guo, Xia; Li, Yongfang; Zhan, Xiaowei

2011-09-01

Understanding effect of morphology on charge carrier transport within polymer/fullerene bulk heterojunction is necessary to develop high-performance polymer solar cells. In this work, we synthesized a new benzodithiophene-based polymer with good self-organization behavior as well as favorable morphology evolution of its blend films with PC(71)BM under improved processing conditions. Charge carrier transport behavior of blend films was characterized by space charge limited current method. Evolved blend film morphology by controlling blend composition and additive content gradually reaches an optimized state, featured with nanoscale fibrilla polymer phase in moderate size and balanced mobility ratio close to 1:1 for hole and electron. This optimized morphology toward more balanced charge carrier transport accounts for the best power conversion efficiency of 3.2%, measured under simulated AM 1.5 solar irradiation 100 mW/cm(2), through enhancing short circuit current and reducing geminate recombination loss.

Design and engineering of water-soluble light-harvesting protein maquettes

DOE PAGES

Kodali, Goutham; Mancini, Joshua A.; Solomon, Lee A.; ...

2017-01-01

Design of nanometer scale artificial light harvesting and charge separating proteins enables reengineering to overcome the limitations of natural selection for efficient systems that better meet human energetic needs.

Design and engineering of water-soluble light-harvesting protein maquettes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kodali, Goutham; Mancini, Joshua A.; Solomon, Lee A.

Design of nanometer scale artificial light harvesting and charge separating proteins enables reengineering to overcome the limitations of natural selection for efficient systems that better meet human energetic needs.

Quantum design of photosynthesis for bio-inspired solar-energy conversion.

PubMed

Romero, Elisabet; Novoderezhkin, Vladimir I; van Grondelle, Rienk

2017-03-15

Photosynthesis is the natural process that converts solar photons into energy-rich products that are needed to drive the biochemistry of life. Two ultrafast processes form the basis of photosynthesis: excitation energy transfer and charge separation. Under optimal conditions, every photon that is absorbed is used by the photosynthetic organism. Fundamental quantum mechanics phenomena, including delocalization, underlie the speed, efficiency and directionality of the charge-separation process. At least four design principles are active in natural photosynthesis, and these can be applied practically to stimulate the development of bio-inspired, human-made energy conversion systems.

Efficient Solar-Induced Photoelectrochemical Response Using Coupling Semiconductor TiO2-ZnO Nanorod Film

PubMed Central

Abd Samad, Nur Azimah; Lai, Chin Wei; Lau, Kung Shiuh; Abd Hamid, Sharifah Bee

2016-01-01

Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod with an average 500 nm in length and average diameter of about 75 nm was successfully formed via electrodeposition method in 0.05 mM ZnCl2 and 0.1 M KCl electrolyte at 1 V for 60 min under 70 °C condition. Continuous efforts have been exerted to further improve the solar driven PEC response by incorporating an optimum content of TiO2 into ZnO nanorod using dip-coating technique. It was found that 0.25 at % of TiO2 loaded on ZnO nanorod film demonstrated a maximum photocurrent density of 19.78 mA/cm2 (with V vs. Ag/AgCl) under UV illumination and 14.75 mA/cm2 (with V vs. Ag/AgCl) under solar illumination with photoconversion efficiency ~2.9% (UV illumination) and ~4.3% (solar illumination). This performance was approximately 3–4 times higher than ZnO film itself. An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO2-ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers. Besides, phenomenon of charge-separation effect at type-II band alignment of Zn and Ti could further enhance the charge carrier transportation during illumination. PMID:28774068

Stacked white OLED having separate red, green and blue sub-elements

DOEpatents

Forrest, Stephen; Qi, Xiangfei; Slootsky, Michael

2015-06-23

The present invention relates to efficient organic light emitting devices (OLEDs). More specifically, the present invention relates to white-emitting OLEDs, or WOLEDs. The devices of the present invention employ three emissive sub-elements, typically emitting red, green and blue, to sufficiently cover the visible spectrum. The sub-elements are separated by charge generating layers.

Stacked white OLED having separate red, green and blue sub-elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forrest, Stephen; Qi, Xiangfei; Slootsky, Michael

The present invention relates to efficient organic light emitting devices (OLEDs). More specifically, the present invention relates to white-emitting OLEDs, or WOLEDs. The devices of the present invention employ three emissive sub-elements, typically emitting red, green and blue, to sufficiently cover the visible spectrum. The sub-elements are separated by charge generating layers.

Synthesis of Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} through a reactive flux method and its visible-light photocatalytic performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Xianglin; Wang, Zeyan, E-mail: wangzeyan@sdu.edu.cn, E-mail: bbhuang@sdu.edu.cn; Huang, Baibiao, E-mail: wangzeyan@sdu.edu.cn, E-mail: bbhuang@sdu.edu.cn

2015-10-01

Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} was prepared by a reactive flux method. The structures, morphologies, and light absorption properties were investigated. Owing to the polar crystal structure, an internal electric field can be formed inside the material, which can facilitate the photogenerated charge separation during the photocatalytic process. Based on both the wide light absorption spectra and high charge separation efficiency originated from the polarized internal electric field, Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} exhibit higher efficiency over Ag{sub 3}PO{sub 4} during the degradation of organic dyes under visible light irradiation, which is expected to be a potential material for solarmore » energy harvest and conversion.« less

Self-Assembled Heteroepitaxial Oxide Nanocomposite for Photoelectrochemical Solar Water Oxidation

PubMed Central

2016-01-01

We report on spontaneously phase ordered heteroepitaxial SrTiO3 (STO):ZnFe2O4 (ZFO) nanocomposite films that give rise to strongly enhanced photoelectrochemical solar water oxidation, consistent with enhanced photoinduced charge separation. The STO:ZFO nanocomposite yielded an enhanced photocurrent density of 0.188 mA/cm2 at 1.23 V vs a reversible hydrogen electrode, which was 7.9- and 2.6-fold higher than that of the plain STO film and ZFO film cases under 1-sun illumination, respectively. The photoelectrode also produced stable photocurrent and Faradaic efficiencies of H2 and O2 formation that were more than 90%. Incident-photon-to-current-conversion efficiency measurements, Tauc plots, Mott–Schottky plots, and electrochemical impedance spectroscopy measurements proved that the strongly enhanced photogenerated charge separation resulted from vertically aligned pseudosingle crystalline components, epitaxial heterojunctions, and a staggered band alignment of the components of the nanocomposite films. This study presents a completely new avenue for efficient solar energy conversion applications. PMID:27212792

Substituent effects on photosensitized splitting of thymine cyclobutane dimer by an attached indole.

PubMed

Tang, Wenjian; Zhou, Hongmei; Wang, Jing; Pan, Chunxiao; Shi, Jingbo; Song, Qinhua

2012-12-21

In chromophore-containing cyclobutane pyrimidine dimer (CPD) model systems, solvent effects on the splitting efficiency may depend on the length of the linker, the molecular conformation, and the oxidation potential of the donor. To further explore the relationship between chromophore structure and splitting efficiency, we prepared a series of substituted indole-T< >T model compounds 2 a-2 g and measured their splitting quantum yields in various solvents. Two reverse solvent effects were observed: an increase in splitting efficiency in solvents of lower polarity for models 2 a-2 d with an electron-donating group (EDG), and vice versa for models 2 e-2 g with an electron-withdrawing group (EWG). According to the Hammett equation, the negative value of the slope of the Hammett plot indicates that the indole moiety during the T< >T-splitting reaction loses negative charge, and the larger negative value implies that the repair reaction is more sensitive to substituent effects in low-polarity solvents. The EDGs of the models 2 a-2 d can delocalize the charge-separated state, and low-polarity solvents make it more stable, which leads to higher splitting efficiency in low-polarity solvents. Conversely, the EWGs of models 2 e-2 g favor destabilization of the charge-separated state, and high-polarity solvents decrease the destabilization and hence lead to more efficient splitting in high-polarity solvents. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved charge breeding efficiency of light ions with an electron cyclotron resonance ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vondrasek, R.; Kutsaev, Sergey; Delahaye, P.

2012-11-15

The Californium Rare Isotope Breeder Upgrade is a new radioactive beam facility for the Argonne Tandem Linac Accelerator System (ATLAS). The facility utilizes a {sup 252}Cf fission source coupled with an electron cyclotron resonance ion source to provide radioactive beam species for the ATLAS experimental program. The californium fission fragment distribution provides nuclei in the mid-mass range which are difficult to extract from production targets using the isotope separation on line technique and are not well populated by low-energy fission of uranium. To date the charge breeding program has focused on optimizing these mid-mass beams, achieving high charge breeding efficienciesmore » of both gaseous and solid species including 14.7% for the radioactive species {sup 143}Ba{sup 27+}. In an effort to better understand the charge breeding mechanism, we have recently focused on the low-mass species sodium and potassium which up to present have been difficult to charge breed efficiently. Unprecedented charge breeding efficiencies of 10.1% for {sup 23}Na{sup 7+} and 17.9% for {sup 39}K{sup 10+} were obtained injecting stable Na{sup +} and K{sup +} beams from a surface ionization source.« less

Direct evidence of charge separation in a metal-organic framework: efficient and selective photocatalytic oxidative coupling of amines via charge and energy transfer.

PubMed

Xu, Caiyun; Liu, Hang; Li, Dandan; Su, Ji-Hu; Jiang, Hai-Long

2018-03-28

The selective aerobic oxidative coupling of amines under mild conditions is an important laboratory and commercial procedure yet a great challenge. In this work, a porphyrinic metal-organic framework, PCN-222, was employed to catalyze the reaction. Upon visible light irradiation, the semiconductor-like behavior of PCN-222 initiates charge separation, evidently generating oxygen-centered active sites in Zr-oxo clusters indicated by enhanced porphyrin π-cation radical signals. The photogenerated electrons and holes further activate oxygen and amines, respectively, to give the corresponding redox products, both of which have been detected for the first time. The porphyrin motifs generate singlet oxygen based on energy transfer to further promote the reaction. As a result, PCN-222 exhibits excellent photocatalytic activity, selectivity and recyclability, far superior to its organic counterpart, for the reaction under ambient conditions via combined energy and charge transfer.

Graphene-based supercapacitors in the parallel-plate electrode configuration: ionic liquids versus organic electrolytes.

PubMed

Shim, Youngseon; Kim, Hyung J; Jung, Younjoon

2012-01-01

Supercapacitors with two single-sheet graphene electrodes in the parallel plate geometry are studied via molecular dynamics (MD) computer simulations. Pure 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI+BF4-) and a 1.1 M solution of EMI+BF4- in acetonitrile are considered as prototypes of room-temperature ionic liquids (RTILs) and organic electrolytes. Electrolyte structure, charge density and associated electric potential are investigated by varying the charges and separation of the two electrodes. Multiple charge layers formed in the electrolytes in the vicinity of the electrodes are found to screen the electrode surface charge almost completely. As a result, the supercapacitors show nearly an ideal electric double layer behavior, i.e., the electric potential exhibits essentially a plateau behavior in the entire electrolyte region except for sharp changes in screening zones very close to the electrodes. Due to its small size and large charge separation, BF4- is considerably more efficient in shielding electrode charges than EMI+. In the case of the acetonitrile solution, acetonitrile also plays an important role by aligning its dipoles near the electrodes; however, the overall screening mainly arises from ions. Because of the disparity of shielding efficiency between cations and anions, the capacitance of the positively-charged anode is significantly larger than that of the negatively-charged cathode. Therefore, the total cell capacitance in the parallel plate configuration is primarily governed by the cathode. Ion conductivity obtained via the Green-Kubo (GK) method is found to be largely independent of the electrode surface charge. Interestingly, EMI+BF4- shows higher GK ion conductivity than the 1.1 M acetonitrile solution between two parallel plate electrodes.

Intermolecular interaction approach for TADF (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wong, Ken-Tsung

2016-09-01

Materials with thermally activated delayed fluorescence (TADF) have recently emerged as new fluorescent emitters for highly efficient organic light-emitting diodes (OLEDs). Molecule with TADF behavior needs to have a small singlet-triplet energy difference (ΔES-T) that allows the up-conversion from nonradiative triplet state (T1) to radiative singlet state (S1) via reverse intersystem crossing (RISC) process. Generally, molecules with small ΔES-T can be obtained via carefully manipulate the degree of "intramolecular" charge transfer (ICT) between electron-donating and -accepting components, such that the electron exchange energy that contributes to ΔES-T, can be minimized. Alternatively, excited state with small ΔES-T can be feasibly realized via "intermolecular" charge transfer occurring at the interface between spatially separating donor (D) and acceptor (A) molecules. Because the exchange energy decreases as the HOMO-LUMO separation distance increases, theoretically, the intermolecular D/A charge transfer state (or exciplex) should have rather small ΔES-T, leading to efficient TADF. However, it is still a challenge to access highly efficient exciplex systems. This is mainly because exciplex formation is commonly accompanied with a large red shift of emission spectra and long radiative lifetime, which tend to diminish photoluminescence quantum yield (PLQY) as well as electroluminescence (EL) performance. Until now, exciplex-based OLEDs with external quantum efficiency (EQE) above 10% are still limited. By judicious selection of donor and acceptor, the formation of efficient exciplex can be feasibly achieved. In this conference, our recent efforts on highly efficient exciplexes using C3-symmetry triazine acceptors and various donors, and their device characteristics will be presented.

High-potential perfluorinated phthalocyanine-fullerene dyads for generation of high-energy charge-separated states: formation and photoinduced electron-transfer studies.

PubMed

Das, Sushanta K; Mahler, Andrew; Wilson, Angela K; D'Souza, Francis

2014-08-25

High oxidation potential perfluorinated zinc phthalocyanines (ZnF(n)Pcs) are synthesised and their spectroscopic, redox, and light-induced electron-transfer properties investigated systematically by forming donor-acceptor dyads through metal-ligand axial coordination of fullerene (C60) derivatives. Absorption and fluorescence spectral studies reveal efficient binding of the pyridine- (Py) and phenylimidazole-functionalised fullerene (C60Im) derivatives to the zinc centre of the F(n)Pcs. The determined binding constants, K, in o-dichlorobenzene for the 1:1 complexes are in the order of 10(4) to 10(5) M(-1); nearly an order of magnitude higher than that observed for the dyad formed from zinc phthalocyanine (ZnPc) lacking fluorine substituents. The geometry and electronic structure of the dyads are determined by using the B3LYP/6-31G* method. The HOMO and LUMO levels are located on the Pc and C60 entities, respectively; this suggests the formation of ZnF(n)Pc(.+)-C60Im(.-) and ZnF(n)Pc(.+)-C60Py(.-) (n=0, 8 or 16) intra-supramolecular charge-separated states during electron transfer. Electrochemical studies on the ZnPc-C60 dyads enable accurate determination of their oxidation and reduction potentials and the energy of the charge-separated states. The energy of the charge-separated state for dyads composed of ZnF(n)Pc is higher than that of normal ZnPc-C60 dyads and reveals their significance in harvesting higher amounts of light energy. Evidence for charge separation in the dyads is secured from femtosecond transient absorption studies in nonpolar toluene. Kinetic evaluation of the cation and anion radical ion peaks reveals ultrafast charge separation and charge recombination in dyads composed of perfluorinated phthalocyanine and fullerene; this implies their significance in solar-energy harvesting and optoelectronic device building applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced Solar Cell Conversion Efficiency of InGaN/GaN Multiple Quantum Wells by Piezo-Phototronic Effect.

PubMed

Jiang, Chunyan; Jing, Liang; Huang, Xin; Liu, Mengmeng; Du, Chunhua; Liu, Ting; Pu, Xiong; Hu, Weiguo; Wang, Zhong Lin

2017-09-26

The piezo-phototronic effect is the tuning of piezoelectric polarization charges at the interface to largely enhance the efficiency of optoelectronic processes related to carrier separation or recombination. Here, we demonstrated the enhanced short-circuit current density and the conversion efficiency of InGaN/GaN multiple quantum well solar cells with an external stress applied on the device. The external-stress-induced piezoelectric charges generated at the interfaces of InGaN and GaN compensate the piezoelectric charges induced by lattice mismatch stress in the InGaN wells. The energy band realignment is calculated with a self-consistent numerical model to clarify the enhancement mechanism of optical-generated carriers. This research not only theoretically and experimentally proves the piezo-phototronic effect modulated the quantum photovoltaic device but also provides a great promise to maximize the use of solar energy in the current energy revolution.

Insights into collaborative separation process of photogenerated charges and superior performance of solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xiangyang, E-mail: lxy081276@126.com; Wang, Shun; Zheng, Haiwu

2016-07-25

ZnO nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} (ZnO/CBS) and ZnO nanowires/CBS-graphene nanoplates (ZnO/CBS-GNs), as well as two types of solar cells were prepared. The photovoltaic responses of CBS-GNs and ZnO/CBS-GNs can be improved with incorporation of GNs. The transient surface photovoltage (TPV) can provide detailed information on the separation and transport of photogenerated carriers. The multichannel separation process from the TPVs indicates that the macro-photoelectric signals can be attributed to the photogenerated charges separated at the interface of CBS/GNs, rather than CBS/ZnO. The multi-interfacial recombination is the major carrier loss, and the hole selective p-V{sub 2}O{sub 5} can efficiently accelerate the chargemore » extraction to the external circuit. The ZnO/CBS-GNs cell exhibits the superior performance, and the highest efficiency is 10.9%. With the adequate interfaces of CBS/GNs, GNs conductive network, energy level matching, etc., the excitons can easily diffuse to the interface of CBS/GNs, and the separated electrons and holes can be collected quickly, inducing the high photoelectric properties. Here, a facile strategy for solid state solar cells with superior performance presents a potential application.« less

Highly Efficient Organic Photovoltaic Cells from Polymer-Aligned Carbon Nanotube Dispersed Heterojunctions

DTIC Science & Technology

2009-09-01

semiconducting VA-SWNTs, and muiltcomponent micropatterns of VA- CNTs . We also designed and synthesized several classes of novel low bandgap...photovoltaic active polymers, and polymer-/TiO2–coated VA- CNTs , critical to developing high efficient polymer photovoltaic cells and dye-sensitized solar...an efficient solar absorption and charge separation/collection. Besides, novel N-doped CNT fuel cells, polymer/quantum dot light-emitting diodes, and

Large impact of reorganization energy on photovoltaic conversion due to interfacial charge-transfer transitions.

PubMed

Fujisawa, Jun-ichi

2015-05-14

Interfacial charge-transfer (ICT) transitions are expected to be a novel charge-separation mechanism for efficient photovoltaic conversion featuring one-step charge separation without energy loss. Photovoltaic conversion due to ICT transitions has been investigated using several TiO2-organic hybrid materials that show organic-to-inorganic ICT transitions in the visible region. In applications of ICT transitions to photovoltaic conversion, there is a significant problem that rapid carrier recombination is caused by organic-inorganic electronic coupling that is necessary for the ICT transitions. In order to solve this problem, in this work, I have theoretically studied light-to-current conversions due to the ICT transitions on the basis of the Marcus theory with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. An apparent correlation between the reported incident photon-to-current conversion efficiencies (IPCE) and calculated reorganization energies was clearly found, in which the IPCE increases with decreasing the reorganization energy consistent with the Marcus theory in the inverted region. This activation-energy dependence was systematically explained by the equation formulated by the Marcus theory based on a simple excited-state kinetic scheme. This result indicates that the reduction of the reorganization energy can suppress the carrier recombination and enhance the IPCE. The reorganization energy is predominantly governed by the structural change in the chemical-adsorption moiety between the ground and ICT excited states. This work provides crucial knowledge for efficient photovoltaic conversion due to ICT transitions.

Investigations on the charge transfer mechanism at donor/acceptor interfaces in the quest for descriptors of organic solar cell performance.

PubMed

Muraoka, Azusa; Fujii, Mikiya; Mishima, Kenji; Matsunaga, Hiroki; Benten, Hiroaki; Ohkita, Hideo; Ito, Shinzaburo; Yamashita, Koichi

2018-05-07

Herein, we theoretically and experimentally investigated the mechanisms of charge separation processes of organic thin-film solar cells. PTB7, PTB1, and PTBF2 have been chosen as donors and PC 71 BM has been chosen as an acceptor considering that effective charge generation depends on the difference between the material combinations. Experimental results of transient absorption spectroscopy show that the hot process is a key step for determining external quantum efficiency (EQE) in these systems. From the quantum chemistry calculations, it has been found that EQE tends to increase as the transferred charge, charge transfer distance, and variation of dipole moments between the ground and excited states of the donor/acceptor complexes increase; this indicates that these physical quantities are a good descriptor to assess the donor-acceptor charge transfer quality contributing to the solar cell performance. We propose that designing donor/acceptor interfaces with large values of charge transfer distance and variation of dipole moments of the donor/acceptor complexes is a prerequisite for developing high-efficiency polymer/PCBM solar cells.

Non-Faradaic Li + Migration and Chemical Coordination across Solid-State Battery Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gittleson, Forrest S.; El Gabaly, Farid

Efficient and reversible charge transfer is essential to realizing high-performance solid-state batteries. Efforts to enhance charge transfer at critical electrode–electrolyte interfaces have proven successful, yet interfacial chemistry and its impact on cell function remains poorly understood. Using X-ray photoelectron spectroscopy combined with electrochemical techniques, we elucidate chemical coordination near the LiCoO 2–LIPON interface, providing experimental validation of space-charge separation. Space-charge layers, defined by local enrichment and depletion of charges, have previously been theorized and modeled, but the unique chemistry of solid-state battery interfaces is now revealed. Here we highlight the non-Faradaic migration of Li+ ions from the electrode to themore » electrolyte, which reduces reversible cathodic capacity by ~15%. Inserting a thin, ion-conducting LiNbO 3 interlayer between the electrode and electrolyte, however, can reduce space-charge separation, mitigate the loss of Li+ from LiCoO 2, and return cathodic capacity to its theoretical value. This work illustrates the importance of interfacial chemistry in understanding and improving solid-state batteries.« less

BiVO4/WO3/SnO2 Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell.

PubMed

Baek, Ji Hyun; Kim, Byeong Jo; Han, Gill Sang; Hwang, Sung Won; Kim, Dong Rip; Cho, In Sun; Jung, Hyun Suk

2017-01-18

Coupling dissimilar oxides in heterostructures allows the engineering of interfacial, optical, charge separation/transport and transfer properties of photoanodes for photoelectrochemical (PEC) water splitting. Here, we demonstrate a double-heterojunction concept based on a BiVO 4 /WO 3 /SnO 2 triple-layer planar heterojunction (TPH) photoanode, which shows simultaneous improvements in the charge transport (∼93% at 1.23 V vs RHE) and transmittance at longer wavelengths (>500 nm). The TPH photoanode was prepared by a facile solution method: a porous SnO 2 film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO 3 deposition, leading to the formation of a double layer of dense WO 3 and a WO 3 /SnO 2 mixture at the bottom. Subsequently, a BiVO 4 nanoparticle film was deposited by spin coating. Importantly, the WO 3 /(WO 3 +SnO 2 ) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO 4 /WO 3 heterojunction layer improves light absorption and charge separation. The resultant TPH photoanode shows greatly improved internal quantum efficiency (∼80%) and PEC water oxidation performance (∼3.1 mA/cm 2 at 1.23 V vs RHE) compared to the previously reported BiVO 4 /WO 3 photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoO x electrocatalyst deposition. Finally, we demonstrated a bias-free and stable solar water-splitting by constructing a tandem PEC device with a perovskite solar cell (STH ∼3.5%).

Charge Separation and Triplet Exciton Formation Pathways in Small-Molecule Solar Cells as Studied by Time-Resolved EPR Spectroscopy

DOE PAGES

Thomson, Stuart A. J.; Niklas, Jens; Mardis, Kristy L.; ...

2017-09-13

Organic solar cells are a promising renewable energy technology, offering the advantages of mechanical flexibility and solution processability. An understanding of the electronic excited states and charge separation pathways in these systems is crucial if efficiencies are to be further improved. Here we use light induced electron paramagnetic resonance (LEPR) spectroscopy and density functional theory calculations (DFT) to study the electronic excited states, charge transfer (CT) dynamics and triplet exciton formation pathways in blends of the small molecule donors (DTS(FBTTh 2) 2, DTS(F2BTTh 2) 2, DTS(PTTh 2) 2, DTG(FBTTh 2) 2 and DTG(F2BTTh 2) 2) with the fullerene derivative PCmore » 61BM. Using high frequency EPR the g-tensor of the positive polaron on the donor molecules was determined. The experimental results are compared with DFT calculations which reveal that the spin density of the polaron is distributed over a dimer or trimer. Time-resolved EPR (TR-EPR) spectra attributed to singlet CT states were identified and the polarization patterns revealed similar charge separation dynamics in the four fluorobenzothiadiazole donors, while charge separation in the DTS(PTTh 2) 2 blend is slower. Using TR-EPR we also investigated the triplet exciton formation pathways in the blend. The polarization patterns reveal that the excitons originate from both intersystem crossing (ISC) and back electron transfer (BET) processes. The DTS(PTTh 2) 2 blend was found to contain substantially more triplet excitons formed by BET than the fluorobenzothiadiazole blends. As a result, the higher BET triplet exciton population in the DTS(PTTh 2) 2 blend is in accordance with the slower charge separation dynamics observed in this blend.« less

Charge Separation and Triplet Exciton Formation Pathways in Small Molecule Solar Cells as Studied by Time-resolved EPR Spectroscopy.

PubMed

Thomson, Stuart A J; Niklas, Jens; Mardis, Kristy L; Mallares, Christopher; Samuel, Ifor D W; Poluektov, Oleg G

2017-10-19

Organic solar cells are a promising renewable energy technology, offering the advantages of mechanical flexibility and solution processability. An understanding of the electronic excited states and charge separation pathways in these systems is crucial if efficiencies are to be further improved. Here we use light induced electron paramagnetic resonance (LEPR) spectroscopy and density functional theory calculations (DFT) to study the electronic excited states, charge transfer (CT) dynamics and triplet exciton formation pathways in blends of the small molecule donors (DTS(FBTTh 2 ) 2 , DTS(F 2 BTTh 2 ) 2 , DTS(PTTh 2 ) 2 , DTG(FBTTh 2 ) 2 and DTG(F 2 BTTh 2 ) 2 ) with the fullerene derivative PC 61 BM. Using high frequency EPR the g-tensor of the positive polaron on the donor molecules was determined. The experimental results are compared with DFT calculations which reveal that the spin density of the polaron is distributed over a dimer or trimer. Time-resolved EPR (TR-EPR) spectra attributed to singlet CT states were identified and the polarization patterns revealed similar charge separation dynamics in the four fluorobenzothiadiazole donors, while charge separation in the DTS(PTTh 2 ) 2 blend is slower. Using TR-EPR we also investigated the triplet exciton formation pathways in the blend. The polarization patterns reveal that the excitons originate from both intersystem crossing (ISC) and back electron transfer (BET) processes. The DTS(PTTh 2 ) 2 blend was found to contain substantially more triplet excitons formed by BET than the fluorobenzothiadiazole blends. The higher BET triplet exciton population in the DTS(PTTh 2 ) 2 blend is in accordance with the slower charge separation dynamics observed in this blend.

Charge Separation and Triplet Exciton Formation Pathways in Small-Molecule Solar Cells as Studied by Time-Resolved EPR Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomson, Stuart A. J.; Niklas, Jens; Mardis, Kristy L.

Organic solar cells are a promising renewable energy technology, offering the advantages of mechanical flexibility and solution processability. An understanding of the electronic excited states and charge separation pathways in these systems is crucial if efficiencies are to be further improved. Here we use light induced electron paramagnetic resonance (LEPR) spectroscopy and density functional theory calculations (DFT) to study the electronic excited states, charge transfer (CT) dynamics and triplet exciton formation pathways in blends of the small molecule donors (DTS(FBTTh 2) 2, DTS(F2BTTh 2) 2, DTS(PTTh 2) 2, DTG(FBTTh 2) 2 and DTG(F2BTTh 2) 2) with the fullerene derivative PCmore » 61BM. Using high frequency EPR the g-tensor of the positive polaron on the donor molecules was determined. The experimental results are compared with DFT calculations which reveal that the spin density of the polaron is distributed over a dimer or trimer. Time-resolved EPR (TR-EPR) spectra attributed to singlet CT states were identified and the polarization patterns revealed similar charge separation dynamics in the four fluorobenzothiadiazole donors, while charge separation in the DTS(PTTh 2) 2 blend is slower. Using TR-EPR we also investigated the triplet exciton formation pathways in the blend. The polarization patterns reveal that the excitons originate from both intersystem crossing (ISC) and back electron transfer (BET) processes. The DTS(PTTh 2) 2 blend was found to contain substantially more triplet excitons formed by BET than the fluorobenzothiadiazole blends. As a result, the higher BET triplet exciton population in the DTS(PTTh 2) 2 blend is in accordance with the slower charge separation dynamics observed in this blend.« less

Electrospun nylon 6/zinc doped hydroxyapatite membrane for protein separation: Mechanism of fouling and blocking model.

PubMed

Esfahani, Hamid; Prabhakaran, Molamma P; Salahi, Esmaeil; Tayebifard, Ali; Rahimipour, Mohamad Reza; Keyanpour-Rad, Mansour; Ramakrishna, Seeram

2016-02-01

Development of composite nanofibrous membrane via electrospinning a polymer with ceramic nanoparticles (NPs) for application in protein separation systems is explored during this study. Positively charged zinc doped hydroxyapatite (xZH) NPs were prepared in three different compositions via chemical precipitation method. Herein, we created a positively charged surface containing nanoparticles on electrospun Nylon-6 nanofibers (NFs) to improve the separation and selectivity properties for adsorption of negatively charged protein, namely bovine serum albumin (BSA). The decline in permeate flux was analyzed using the framework of classical blocking models and fitting, demonstrated that the transition of fouling mechanisms was dominated during the filtration process. The standard blocking model provided the best fit of the experimental results during the mid-filtration period. The membrane decorated by NPs containing 4at.% zinc cations not only provided maximum BSA separation but also capable of separating higher amounts of BSA molecules (even after 1h filtration) than the pure Nylon membrane. Protein separation was achieved through this membrane with the incorporation of NPs that had high zeta potential (+5.9±0.2mV) and lower particle area (22,155nm(2)). The developed membrane has great potential to act as a high efficiency membrane for capturing BSA. Copyright © 2015 Elsevier B.V. All rights reserved.

Charge separation and carrier dynamics in donor-acceptor heterojunction photovoltaic systems.

PubMed

Teuscher, Joël; Brauer, Jan C; Stepanov, Andrey; Solano, Alicia; Boziki, Ariadni; Chergui, Majed; Wolf, Jean-Pierre; Rothlisberger, Ursula; Banerji, Natalie; Moser, Jacques-E

2017-11-01

Electron transfer and subsequent charge separation across donor-acceptor heterojunctions remain the most important areas of study in the field of third-generation photovoltaics. In this context, it is particularly important to unravel the dynamics of individual ultrafast processes (such as photoinduced electron transfer, carrier trapping and association, and energy transfer and relaxation), which prevail in materials and at their interfaces. In the frame of the National Center of Competence in Research "Molecular Ultrafast Science and Technology," a research instrument of the Swiss National Science Foundation, several groups active in the field of ultrafast science in Switzerland have applied a number of complementary experimental techniques and computational simulation tools to scrutinize these critical photophysical phenomena. Structural, electronic, and transport properties of the materials and the detailed mechanisms of photoinduced charge separation in dye-sensitized solar cells, conjugated polymer- and small molecule-based organic photovoltaics, and high-efficiency lead halide perovskite solar energy converters have been scrutinized. Results yielded more than thirty research articles, an overview of which is provided here.

Separation of biogenic materials by electrophoresis under zero gravity (L-3)

NASA Technical Reports Server (NTRS)

Kuroda, Masao

1993-01-01

Electrophoresis separates electrically charged materials by imposing a voltage between electrodes. Though free-flow electrophoresis is used without carriers such as colloids to separate and purify biogenic materials including biogenic cells and proteins in blood, its resolving power and separation efficiency is very low on Earth due to sedimentation, flotation, and thermal convection caused by the specific gravity differences between separated materials and buffer solutions. The objective of this experiment is to make a comparative study of various electrophoresis conditions on the ground and in zero-gravity in order to ultimately develop a method for separating various important 'vial' components which are difficult to separate on the ground.

RADIOMETRIC EQUIPMENT ON SECOND SPACESHIP-SATELLITE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papkov, S.F.; Pisarenko, N.F.; Savenko, I.A.

1961-01-01

Equipment installed on the second Soviet spaceshipsatellite to measure radiation and determine dose absorption is described. A scintillation counter recorded charged particles penetrating the skin of the spaceship and gamma quanta with energies exceeding 25 kev. Two CTC-5 gas-discharge counters also recorded charged particles, and, as the efficiency of gamma recording was low (below 10/sup -2/), a comparison of readings made it possible to evaluate the contribution of the charged particles and the gamma quanta, respectively, to the absorbed dose. A separate scintillation counter measured the energy flow of relatively soft charged particles. Electronic equipment was supplied with energy frommore » a 6( plus or minus 1)-v battery with power not over 0.5 w. A thorough check of the spaceship after its return to earth demonstrated that all the counters and electronie devices had retained their efficiency. A block diagram of the equipment is given. (OTS)« less

Enhanced Photocarrier Separation in Hierarchical Graphitic-C3N4-Supported CuInS2 for Noble-Metal-Free Z-Scheme Photocatalytic Water Splitting.

PubMed

Li, Xiaoxue; Xie, Keyu; Song, Long; Zhao, Mengjia; Zhang, Zhipan

2017-07-26

The effective separation of photogenerated electrons and holes in photocatalysts is a prerequisite for efficient photocatalytic water splitting. CuInS 2 (CIS) is a widely used light absorber that works properly in photovoltaics but only shows limited performance in solar-driven hydrogen evolution due to its intrinsically severe charge recombination. Here, we prepare hierarchical graphitic C 3 N 4 -supported CuInS 2 (denoted as GsC) by an in situ growth of CIS directly on exfoliated thin graphitic C 3 N 4 nanosheets (g-C 3 N 4 NS) and demonstrate efficient separation of photoinduced charge carriers in the GsC by forming the Z-scheme system for the first time in CIS-catalyzed water splitting. Under visible light illumination, the GsC features an enhanced hydrogen evolution rate up to 1290 μmol g -1 h -1 , which is 3.3 and 6.1 times higher than that of g-C 3 N 4 NS and bare-CIS, respectively, thus setting a new performance benchmark for CIS-based water-splitting photocatalysts.

Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering.

PubMed

Lukman, Steven; Chen, Kai; Hodgkiss, Justin M; Turban, David H P; Hine, Nicholas D M; Dong, Shaoqiang; Wu, Jishan; Greenham, Neil C; Musser, Andrew J

2016-12-07

Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics.

Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering

PubMed Central

Lukman, Steven; Chen, Kai; Hodgkiss, Justin M.; Turban, David H. P.; Hine, Nicholas D. M.; Dong, Shaoqiang; Wu, Jishan; Greenham, Neil C.; Musser, Andrew J.

2016-01-01

Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics. PMID:27924819

Composite tin and zinc oxide nanocrystalline particles for enhanced charge separation in sensitized degradation of dyes.

PubMed

Bandara, J; Tennakone, K; Jayatilaka, P P B

2002-10-01

Composite ZnO/SnO2 catalyst has been studied for the sensitized degradation of dyes e.g. Eosin Y (2', 4', 5', 7'-tetrabromofluorescein disodium salt) in relation to efficient charge separation properties of the catalyst. Improved photocatalytic activity was observed in the case of ZnO/SnO2 composite catalyst compared to the catalytic activity of ZnO, SnO2 or TiO2 powder. The suppression of charge recombination in the composite ZnO/SnO2 catalyst led to higher catalytic activity for the degradation of Eosin Y. Degradation of Eosin follows concomitant formation of CO2 and formation of CO2 followed a pseudo-first-order rate. Photoelectrochemical cells constructed using SnO2, ZnO, ZnO/SnO2 sensitized with Eosin Y showed V(oc) of 175, 306, 512 mV/cm2 and I(sc) of 50, 70, 200 microA/cm2 respectively. A higher irreversible degradation of Eosin Y and higher V(oc) observed on composite ZnO/SnO2 than ZnO and SnO2 separately can be considered as a proof of enhanced charge separation of ZnO/SnO2 catalyst. Eosin Y showed a higher emission decreases on ZnO/SnO2 composite than on individual ZnO, SnO2 or TiO2 indicating dominance of the charge injection process. Photoinjected electrons are tunneled from ZnO to SnO2 particles accumulating injected electrons in the conduction bands allowing wider separation of excited carriers.

Modular Homogeneous Chromophore–Catalyst Assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mulfort, Karen L.; Utschig, Lisa M.

2016-05-17

Photosynthetic reaction center (RC) proteins convert incident solar energy to chemical energy through a network of molecular cofactors which have been evolutionarily tuned to couple efficient light-harvesting, directional electron transfer, and long-lived charge separation with secondary reaction sequences. These molecular cofactors are embedded within a complex protein environment which precisely positions each cofactor in optimal geometries along efficient electron transfer pathways with localized protein environments facilitating sequential and accumulative charge transfer. By contrast, it is difficult to approach a similar level of structural complexity in synthetic architectures for solar energy conversion. However, by using appropriate self-assembly strategies, we anticipate thatmore » molecular modules, which are independently synthesized and optimized for either light-harvesting or redox catalysis, can be organized into spatial arrangements that functionally mimic natural photosynthesis. In this Account, we describe a modular approach to new structural designs for artificial photosynthesis which is largely inspired by photosynthetic RC proteins. We focus on recent work from our lab which uses molecular modules for light-harvesting or proton reduction catalysis in different coordination geometries and different platforms, spanning from discrete supramolecular assemblies to molecule–nanoparticle hybrids to protein-based biohybrids. Molecular modules are particularly amenable to high-resolution characterization of the ground and excited state of each module using a variety of physical techniques; such spectroscopic interrogation helps our understanding of primary artificial photosynthetic mechanisms. In particular, we discuss the use of transient optical spectroscopy, EPR, and X-ray scattering techniques to elucidate dynamic structural behavior and light-induced kinetics and the impact on photocatalytic mechanism. Two different coordination geometries of supramolecular photocatalyst based on the [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) light-harvesting module with cobaloxime-based catalyst module are compared, with progress in stabilizing photoinduced charge separation identified. These same modules embedded in the small electron transfer protein ferredoxin exhibit much longer charge-separation, enabled by stepwise electron transfer through the native [2Fe-2S] cofactor. We anticipate that the use of interchangeable, molecular modules which can interact in different coordination geometries or within entirely different structural platforms will provide important fundamental insights into the effect of environment on parameters such as electron transfer and charge separation, and ultimately drive more efficient designs for artificial photosynthesis.« less

Ultrafast exciton dynamics and light-driven H2 evolution in colloidal semiconductor nanorods and Pt-tipped nanorods.

PubMed

Wu, Kaifeng; Zhu, Haiming; Lian, Tianquan

2015-03-17

Colloidal quantum confined one-dimensional (1D) semiconductor nanorods (NRs) and related semiconductor-metal heterostructures are promising new materials for efficient solar-to-fuel conversion because of their unique physical and chemical properties. NRs can simultaneously exhibit quantum confinement effects in the radial direction and bulk like carrier transport in the axial direction. The former implies that concepts well-established in zero-dimensional quantum dots, such as size-tunable energetics and wave function engineering through band alignment in heterostructures, can also be applied to NRs; while the latter endows NRs with fast carrier transport to achieve long distance charge separation. Selective growth of catalytic metallic nanoparticles, such as Pt, at the tips of NRs provides convenient routes to multicomponent heterostructures with photocatalytic capabilities and controllable charge separation distances. The design and optimization of such materials for efficient solar-to-fuel conversion require the understanding of exciton and charge carrier dynamics. In this Account, we summarize our recent studies of ultrafast charge separation and recombination kinetics and their effects on steady-state photocatalytic efficiencies of colloidal CdS and CdSe/CdS NRs and related NR-Pt heterostructures. After a brief introduction of their electronic structure, we discuss exciton dynamics of CdS NRs. By transient absorption and time-resolved photoluminescence decay, it is shown that although the conduction band electrons are long-lived, photogenerated holes in CdS NRs are trapped on an ultrafast time scale (∼0.7 ps), which forms localized excitons due to strong Coulomb interaction in 1D NRs. In quasi-type II CdSe/CdS dot-in-rod NRs, a large valence band offset drives the ultrafast localization of holes to the CdSe core, and the competition between this process and ultrafast hole trapping on a CdS rod leads to three types of exciton species with distinct spatial distributions. The effect of the exciton dynamics on photoreduction reactions is illustrated using methyl viologen (MV(2+)) as a model electron acceptor. The steady-state MV(2+) photoreduction quantum yield of CdSe/CdS dot-in-rod NRs approaches unity under rod excitation, much larger than CdSe QDs and CdSe/CdS core/shell QDs. Detailed time-resolved studies show that in quasi-type II CdSe/CdS NRs and type II ZnSe/CdS NRs strong quantum confinement in the radial direction facilitates fast electron transfer and hole removal, whereas the fast carrier mobility along the axial direction enables long distance charge separation and slow charge recombination, which is essential for efficient MV(2+) photoreduction. The NR/MV(2+) relay system can be coupled to Pt nanoparticles in solution for light-driven H2 generation. Alternatively, Pt-tipped CdS and CdSe/CdS NRs provide fully integrated all inorganic systems for light-driven H2 generation. In CdS-Pt and CdSe/CdS-Pt hetero-NRs, ultrafast hole trapping on the CdS rod surface or in CdSe core enables efficient electron transfer from NRs to Pt tips by suppressing hole and energy transfer. It is shown that the quantum yields of photodriven H2 generation using these heterostructures correlate well with measured hole transfer rates from NRs to sacrificial donors, revealing that hole removal is the key efficiency-limiting step. These findings provide important insights for designing more efficient quantum confined NR and NR-Pt based systems for solar-to-fuel conversion.

Highly-efficient capillary photoelectrochemical water splitting using cellulose nanofiber-templated TiO 2 photoanodes

Treesearch

Zhaodong Li; Chunhua Yao; Yanhao Yu; Zhiyong Cai; Xudong Wang

2014-01-01

Among current endeavors to explore renewable energy technologies, photoelectrochemical (PEC) water splitting holds great promise for conversion of solar energy to chemical energy. [ 1–4 ] Light absorption, charge separation, and appropriate interfacial redox reactions are three key aspects that lead to highly efficient solar energy conversion. [ 5–10 ] Therefore,...

Boosting the efficiency of quantum dot sensitized solar cells through modulation of interfacial charge transfer.

PubMed

Kamat, Prashant V

2012-11-20

The demand for clean energy will require the design of nanostructure-based light-harvesting assemblies for the conversion of solar energy into chemical energy (solar fuels) and electrical energy (solar cells). Semiconductor nanocrystals serve as the building blocks for designing next generation solar cells, and metal chalcogenides (e.g., CdS, CdSe, PbS, and PbSe) are particularly useful for harnessing size-dependent optical and electronic properties in these nanostructures. This Account focuses on photoinduced electron transfer processes in quantum dot sensitized solar cells (QDSCs) and discusses strategies to overcome the limitations of various interfacial electron transfer processes. The heterojunction of two semiconductor nanocrystals with matched band energies (e.g., TiO(2) and CdSe) facilitates charge separation. The rate at which these separated charge carriers are driven toward opposing electrodes is a major factor that dictates the overall photocurrent generation efficiency. The hole transfer at the semiconductor remains a major bottleneck in QDSCs. For example, the rate constant for hole transfer is 2-3 orders of magnitude lower than the electron injection from excited CdSe into oxide (e.g., TiO(2)) semiconductor. Disparity between the electron and hole scavenging rate leads to further accumulation of holes within the CdSe QD and increases the rate of electron-hole recombination. To overcome the losses due to charge recombination processes at the interface, researchers need to accelerate electron and hole transport. The power conversion efficiency for liquid junction and solid state quantum dot solar cells, which is in the range of 5-6%, represents a significant advance toward effective utilization of nanomaterials for solar cells. The design of new semiconductor architectures could address many of the issues related to modulation of various charge transfer steps. With the resolution of those problems, the efficiencies of QDSCs could approach those of dye sensitized solar cells (DSSC) and organic photovoltaics.

Comparing Positively and Negatively Charged Distonic Radical Ions in Phenylperoxyl Forming Reactions.

PubMed

Williams, Peggy E; Marshall, David L; Poad, Berwyck L J; Narreddula, Venkateswara R; Kirk, Benjamin B; Trevitt, Adam J; Blanksby, Stephen J

2018-06-04

In the gas phase, arylperoxyl forming reactions play a significant role in low-temperature combustion and atmospheric processing of volatile organic compounds. We have previously demonstrated the application of charge-tagged phenyl radicals to explore the outcomes of these reactions using ion trap mass spectrometry. Here, we present a side-by-side comparison of rates and product distributions from the reaction of positively and negatively charge tagged phenyl radicals with dioxygen. The negatively charged distonic radical ions are found to react with significantly greater efficiency than their positively charged analogues. The product distributions of the anion reactions favor products of phenylperoxyl radical decomposition (e.g., phenoxyl radicals and cyclopentadienone), while the comparable fixed-charge cations yield the stabilized phenylperoxyl radical. Electronic structure calculations rationalize these differences as arising from the influence of the charged moiety on the energetics of rate-determining transition states and reaction intermediates within the phenylperoxyl reaction manifold and predict that this influence could extend to intra-molecular charge-radical separations of up to 14.5 Å. Experimental observations of reactions of the novel 4-(1-carboxylatoadamantyl)phenyl radical anion confirm that the influence of the charge on both rate and product distribution can be modulated by increasing the rigidly imposed separation between charge and radical sites. These findings provide a generalizable framework for predicting the influence of charged groups on polarizable radicals in gas phase distonic radical ions. Graphical Abstract.

Comparing Positively and Negatively Charged Distonic Radical Ions in Phenylperoxyl Forming Reactions

NASA Astrophysics Data System (ADS)

Williams, Peggy E.; Marshall, David L.; Poad, Berwyck L. J.; Narreddula, Venkateswara R.; Kirk, Benjamin B.; Trevitt, Adam J.; Blanksby, Stephen J.

2018-06-01

In the gas phase, arylperoxyl forming reactions play a significant role in low-temperature combustion and atmospheric processing of volatile organic compounds. We have previously demonstrated the application of charge-tagged phenyl radicals to explore the outcomes of these reactions using ion trap mass spectrometry. Here, we present a side-by-side comparison of rates and product distributions from the reaction of positively and negatively charge tagged phenyl radicals with dioxygen. The negatively charged distonic radical ions are found to react with significantly greater efficiency than their positively charged analogues. The product distributions of the anion reactions favor products of phenylperoxyl radical decomposition (e.g., phenoxyl radicals and cyclopentadienone), while the comparable fixed-charge cations yield the stabilized phenylperoxyl radical. Electronic structure calculations rationalize these differences as arising from the influence of the charged moiety on the energetics of rate-determining transition states and reaction intermediates within the phenylperoxyl reaction manifold and predict that this influence could extend to intra-molecular charge-radical separations of up to 14.5 Å. Experimental observations of reactions of the novel 4-(1-carboxylatoadamantyl)phenyl radical anion confirm that the influence of the charge on both rate and product distribution can be modulated by increasing the rigidly imposed separation between charge and radical sites. These findings provide a generalizable framework for predicting the influence of charged groups on polarizable radicals in gas phase distonic radical ions.

High Throughput Engineering to Revitalize a Vestigial Electron Transfer Pathway in Bacterial Photosynthetic Reaction Centers*

PubMed Central

Faries, Kaitlyn M.; Kressel, Lucas L.; Wander, Marc J.; Holten, Dewey; Laible, Philip D.; Kirmaier, Christine; Hanson, Deborah K.

2012-01-01

Photosynthetic reaction centers convert light energy into chemical energy in a series of transmembrane electron transfer reactions, each with near 100% yield. The structures of reaction centers reveal two symmetry-related branches of cofactors (denoted A and B) that are functionally asymmetric; purple bacterial reaction centers use the A pathway exclusively. Previously, site-specific mutagenesis has yielded reaction centers capable of transmembrane charge separation solely via the B branch cofactors, but the best overall electron transfer yields are still low. In an attempt to better realize the architectural and energetic factors that underlie the directionality and yields of electron transfer, sites within the protein-cofactor complex were targeted in a directed molecular evolution strategy that implements streamlined mutagenesis and high throughput spectroscopic screening. The polycistronic approach enables efficient construction and expression of a large number of variants of a heteroligomeric complex that has two intimately regulated subunits with high sequence similarity, common features of many prokaryotic and eukaryotic transmembrane protein assemblies. The strategy has succeeded in the discovery of several mutant reaction centers with increased efficiency of the B pathway; they carry multiple substitutions that have not been explored or linked using traditional approaches. This work expands our understanding of the structure-function relationships that dictate the efficiency of biological energy-conversion reactions, concepts that will aid the design of bio-inspired assemblies capable of both efficient charge separation and charge stabilization. PMID:22247556

Dual initiation strip charge apparatus and methods for making and implementing the same

DOEpatents

Jakaboski, Juan-Carlos [Albuquerque, NM; Todd,; Steven, N [Rio Rancho, NM; Polisar, Stephen [Albuquerque, NM; Hughs, Chance [Tijeras, NM

2011-03-22

A Dual Initiation Strip Charge (DISC) apparatus is initiated by a single initiation source and detonates a strip of explosive charge at two separate contacts. The reflection of explosively induced stresses meet and create a fracture and breach a target along a generally single fracture contour and produce generally fragment-free scattering and no spallation. Methods for making and implementing a DISC apparatus provide numerous advantages over previous methods of creating explosive charges by utilizing steps for rapid prototyping; by implementing efficient steps and designs for metering consistent, repeatable, and controlled amount of high explosive; and by utilizing readily available materials.

Construction of RGO/CdIn2S4/g-C3N4 ternary hybrid with enhanced photocatalytic activity for the degradation of tetracycline hydrochloride

NASA Astrophysics Data System (ADS)

Xiao, Peng; Jiang, Deli; Ju, Lixin; Jing, Junjie; Chen, Min

2018-03-01

Although RGO shows great advantage in promoting charge separation and transfer of semiconductor, construction of an efficient RGO-incorporated photocatalyst is still challenging. Herein, RGO was employed to construct novel RGO/CdIn2S4/g-C3N4 (donated as RGO/CIS/CN) ternary photocatalyst by a facile hydrothermal method for the degradation of tetracycline hydrochloride (TC). The RGO/CIS/CN ternary photocatalyst showed significantly enhanced photocatalytic activity towards the degradation of TC as compared to the binary CIS/CN, CIS/CN, and CN/RGO. The photoluminescence and photocurrent response results indicate that this enhanced photocatalytic activity can be mainly ascribed to the improved charge separation and transfer efficiency. Based on the radical trapping and electron spin resonance results, the superoxide radicals and holes are proposed to play an important role in the degradation of TC over RGO/CIS/CN ternary photocatalyst. This work paves new opportunities for the synthesis of RGO-incorporated ternary photocatalyst as an efficient photocatalyst for the degradation of organic contaminant.

Hybrid morphology dependence of CdTe:CdSe bulk-heterojunction solar cells

PubMed Central

2014-01-01

A nanocrystal thin-film solar cell operating on an exciton splitting pattern requires a highly efficient separation of electron-hole pairs and transportation of separated charges. A hybrid bulk-heterojunction (HBH) nanostructure providing a large contact area and interpenetrated charge channels is favorable to an inorganic nanocrystal solar cell with high performance. For this freshly appeared structure, here in this work, we have firstly explored the influence of hybrid morphology on the photovoltaic performance of CdTe:CdSe bulk-heterojunction solar cells with variation in CdSe nanoparticle morphology. Quantum dot (QD) or nanotetrapod (NT)-shaped CdSe nanocrystals have been employed together with CdTe NTs to construct different hybrid structures. The solar cells with the two different hybrid active layers show obvious difference in photovoltaic performance. The hybrid structure with densely packed and continuously interpenetrated two phases generates superior morphological and electrical properties for more efficient inorganic bulk-heterojunction solar cells, which could be readily realized in the NTs:QDs hybrid. This proved strategy is applicable and promising in designing other highly efficient inorganic hybrid solar cells. PMID:25386107

Hybrid morphology dependence of CdTe:CdSe bulk-heterojunction solar cells.

PubMed

Tan, Furui; Qu, Shengchun; Zhang, Weifeng; Wang, Zhanguo

2014-01-01

A nanocrystal thin-film solar cell operating on an exciton splitting pattern requires a highly efficient separation of electron-hole pairs and transportation of separated charges. A hybrid bulk-heterojunction (HBH) nanostructure providing a large contact area and interpenetrated charge channels is favorable to an inorganic nanocrystal solar cell with high performance. For this freshly appeared structure, here in this work, we have firstly explored the influence of hybrid morphology on the photovoltaic performance of CdTe:CdSe bulk-heterojunction solar cells with variation in CdSe nanoparticle morphology. Quantum dot (QD) or nanotetrapod (NT)-shaped CdSe nanocrystals have been employed together with CdTe NTs to construct different hybrid structures. The solar cells with the two different hybrid active layers show obvious difference in photovoltaic performance. The hybrid structure with densely packed and continuously interpenetrated two phases generates superior morphological and electrical properties for more efficient inorganic bulk-heterojunction solar cells, which could be readily realized in the NTs:QDs hybrid. This proved strategy is applicable and promising in designing other highly efficient inorganic hybrid solar cells.

The Role of FRET in Non-Fullerene Organic Solar Cells: Implications for Molecular Design.

PubMed

Gautam, Bhoj R; Younts, Robert; Carpenter, Joshua; Ade, Harald; Gundogdu, Kenan

2018-04-19

Non-fullerene acceptors (NFAs) have been demonstrated to be promising candidates for highly efficient organic photovoltaic (OPV) devices. The tunability of absorption characteristics of NFAs can be used to make OPVs with complementary donor-acceptor absorption to cover a broad range of the solar spectrum. However, both charge transfer from donor to acceptor moieties and energy (energy) transfer from high-bandgap to low-bandgap materials are possible in such structures. Here, we show that when charge transfer and exciton transfer processes are both present, the coexistence of excitons in both domains can cause a loss mechanism. Charge separation of excitons in a low-bandgap material is hindered due to exciton population in the larger bandgap acceptor domains. Our results further show that excitons in low-bandgap material should have a relatively long lifetime compared to the transfer time of excitons from higher bandgap material in order to contribute to the charge separation. These observations provide significant guidance for design and development of new materials in OPV applications.

Position-dependent effects of polylysine on Sec protein transport.

PubMed

Liang, Fu-Cheng; Bageshwar, Umesh K; Musser, Siegfried M

2012-04-13

The bacterial Sec protein translocation system catalyzes the transport of unfolded precursor proteins across the cytoplasmic membrane. Using a recently developed real time fluorescence-based transport assay, the effects of the number and distribution of positive charges on the transport time and transport efficiency of proOmpA were examined. As expected, an increase in the number of lysine residues generally increased transport time and decreased transport efficiency. However, the observed effects were highly dependent on the polylysine position in the mature domain. In addition, a string of consecutive positive charges generally had a more significant effect on transport time and efficiency than separating the charges into two or more charged segments. Thirty positive charges distributed throughout the mature domain resulted in effects similar to 10 consecutive charges near the N terminus of the mature domain. These data support a model in which the local effects of positive charge on the translocation kinetics dominate over total thermodynamic constraints. The rapid translocation kinetics of some highly charged proOmpA mutants suggest that the charge is partially shielded from the electric field gradient during transport, possibly by the co-migration of counter ions. The transport times of precursors with multiple positively charged sequences, or "pause sites," were fairly well predicted by a local effect model. However, the kinetic profile predicted by this local effect model was not observed. Instead, the transport kinetics observed for precursors with multiple polylysine segments support a model in which translocation through the SecYEG pore is not the rate-limiting step of transport.

Position-dependent Effects of Polylysine on Sec Protein Transport*

PubMed Central

Liang, Fu-Cheng; Bageshwar, Umesh K.; Musser, Siegfried M.

2012-01-01

The bacterial Sec protein translocation system catalyzes the transport of unfolded precursor proteins across the cytoplasmic membrane. Using a recently developed real time fluorescence-based transport assay, the effects of the number and distribution of positive charges on the transport time and transport efficiency of proOmpA were examined. As expected, an increase in the number of lysine residues generally increased transport time and decreased transport efficiency. However, the observed effects were highly dependent on the polylysine position in the mature domain. In addition, a string of consecutive positive charges generally had a more significant effect on transport time and efficiency than separating the charges into two or more charged segments. Thirty positive charges distributed throughout the mature domain resulted in effects similar to 10 consecutive charges near the N terminus of the mature domain. These data support a model in which the local effects of positive charge on the translocation kinetics dominate over total thermodynamic constraints. The rapid translocation kinetics of some highly charged proOmpA mutants suggest that the charge is partially shielded from the electric field gradient during transport, possibly by the co-migration of counter ions. The transport times of precursors with multiple positively charged sequences, or “pause sites,” were fairly well predicted by a local effect model. However, the kinetic profile predicted by this local effect model was not observed. Instead, the transport kinetics observed for precursors with multiple polylysine segments support a model in which translocation through the SecYEG pore is not the rate-limiting step of transport. PMID:22367204

Effect of solvent and subsequent thermal annealing on the performance of phenylenevinylene copolymer: PCBM solar cells.

PubMed

Sharma, G D; Suresh, P; Sharma, S S; Vijay, Y K; Mikroyannidis, John A

2010-02-01

The morphology of the photoactive layer used in the bulk heterojunction photovoltaic devices is crucial for efficient charge generation and their collection at the electrodes. We investigated the solvent vapor annealing and thermal annealing effect of an alternating phenylenevinylene copolymer P:PCBM blend on its morphology and optical properties. The UV-visible absorption spectroscopy shows that both solvent and thermal annealing can result in self-assembling of copolymer P to form an ordered structure, leading to enhanced absorption in the red region and hole transport enhancement. By combining the solvent and thermal annealing of the devices, the power conversion efficiency is improved. This feature was attributed to the fact that the PCBM molecules begin to diffuse into aggregates and together with the ordered copolymer P phase form bicontinuous pathways in the entire layer for efficient charge separation and transport. Furthermore, the measured photocurrent also suggests that the space charges no longer limit the values of the short circuit current (J(sc)) and fill factor (FF) for solvent-treated and thermally annealed devices. These results indicate that the higher J(sc) and PCE for the solvent-treated and thermally annealed devices can be attributed to the phase separation of active layers, which leads to a balanced carrier mobility. The overall PCE of the device based on the combination of solvent annealing and thermal annealing is about 3.7 %.

Theoretical investigation of the electron transfer dynamics and photodegradation pathways in a hydrogen-evolving ruthenium-palladium photocatalyst.

PubMed

Staniszewska, Magdalena; Kupfer, Stephan; Guthmuller, Julien

2018-05-16

Time-dependent density functional theory calculations combined with the Marcus theory of electron transfer (ET) were applied on the molecular photocatalyst [(tbbpy)2Ru(tpphz)PdCl2]2+ in order to elucidate the light-induced relaxation pathways populated upon excitation in the longer wavelength range of its absorption spectrum. The computational results show that after the initial excitation, metal (Ru) to ligand (tpphz) charge transfer (MLCT) triplet states are energetically accessible, but that an ET toward the catalytic center (PdCl2) from these states is a slow process, with estimated time constants above 1 ns. Instead, the calculations predict that low-lying Pd-centered states are efficiently populated - associated to an energy transfer toward the catalytic center. Thus, it is postulated that these states lead to the dissociation of a Cl- and are consequently responsible for the experimentally observed degradation of the catalytic center. Following dissociation, it is shown that the ET rates from the MLCT states to the charge separated states are significantly increased (i.e. 10^5-10^6 times larger). This demonstrates that alteration of the catalytic center generates efficient charge separation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonuniform Effect of Carrier Separation Efficiency and Light Absorption in Type-II Perovskite Nanowire Solar Cells

NASA Astrophysics Data System (ADS)

Wang, Weiping; He, Jialun; Cao, Yiyan; Kong, Lijing; Zheng, Xuanli; Wu, Yaping; Chen, Xiaohong; Li, Shuping; Wu, Zhiming; Kang, Junyong

2017-03-01

Coaxial structures exhibit great potential for the application of high-efficiency solar cells due to the novel mechanism of radial charge separation. Here, we intensively investigate the nonuniform effect of carrier separation efficiency (CSE) and light absorption in perovskite-based type-II coaxial nanowire solar cells (ZnO/CH3NH3PbI3). Results show that the CSE rapidly decreases along the radial direction in the shell, and the value at the outer side becomes extremely low for the thick shell. Besides, the position of the main light absorption gradually moves to the outer side with the increase of the shell thickness. As a result, the external quantum efficiency shows a positional dependence with a maximal value close to the border of the nanowire. Eventually, in our case, it is found that the maximal power conversion efficiency of the solar cells reduces from 19.5 to 17.9% under the effect of the nonuniformity of CSE and light absorption. This work provides a basis for the design of high-efficiency solar cells, especially type-II nanowire solar cells.

Nonuniform Effect of Carrier Separation Efficiency and Light Absorption in Type-II Perovskite Nanowire Solar Cells.

PubMed

Wang, Weiping; He, Jialun; Cao, Yiyan; Kong, Lijing; Zheng, Xuanli; Wu, Yaping; Chen, Xiaohong; Li, Shuping; Wu, Zhiming; Kang, Junyong

2017-12-01

Coaxial structures exhibit great potential for the application of high-efficiency solar cells due to the novel mechanism of radial charge separation. Here, we intensively investigate the nonuniform effect of carrier separation efficiency (CSE) and light absorption in perovskite-based type-II coaxial nanowire solar cells (ZnO/CH 3 NH 3 PbI 3 ). Results show that the CSE rapidly decreases along the radial direction in the shell, and the value at the outer side becomes extremely low for the thick shell. Besides, the position of the main light absorption gradually moves to the outer side with the increase of the shell thickness. As a result, the external quantum efficiency shows a positional dependence with a maximal value close to the border of the nanowire. Eventually, in our case, it is found that the maximal power conversion efficiency of the solar cells reduces from 19.5 to 17.9% under the effect of the nonuniformity of CSE and light absorption. This work provides a basis for the design of high-efficiency solar cells, especially type-II nanowire solar cells.

Separation and Purification of Mineral Salts from Spacecraft Wastewater Processing via Electrostatic Beneficiation

NASA Technical Reports Server (NTRS)

Miles, John D., II; Lunn, Griffin

2013-01-01

Electrostatic separation is a class of material processing technologies commonly used for the sorting of coarse mixtures by means of electrical forces acting on charged or polarized particles. Most if not all of the existing tribo-electrostatic separators had been initially developed for mineral ores beneficiation. It is a well-known process that has been successfully used to separate coal from minerals. Potash (potassium) enrichment where underground salt mines containing large amounts of sodium is another use of this techno logy. Through modification this technology can be used for spacecraft wastewater brine beneficiation. This will add in closing the gap beeen traveling around Earth's Gravity well and long-term space explorations. Food has been brought on all man missions, which is why plant growth for food crops continues to be of interest to NASA. For long-term mission considerations food productions is one of the top priorities. Nutrient recovery is essential for surviving in or past low earth orbit. In our advance bio-regenerative process instead of nitrogen gas produced; soluble nitrate salts that can be recovered for plant fertilizer would be produced instead. The only part missing is the beneficiation of brine to separate the potassium from the sodium. The use of electrostatic beneficiation in this experiment utilizes the electrical charge differences between aluminum and dried brine by surface contact. The helixes within the aluminum tribocharger allows for more surface contact when being agitated. When two materials are in contact, the material with the highest affinity for electrons becomes negatively charged, while the other becomes positively charged. This contact exchange of charge may cause the particles to agglomerate depending on their residence time within the tribocharger, compromising the efficiency of separation. The aim of this experiment is to further the development in electrostatic beneficiation by optimizing the separation of ersatz and possibly real wastewater brine residues. In doing so, ideally it will yield a high potassium enrichment for use in spacecraft plant systems.

Hole-Accepting-Ligand-Modified CdSe QDs for Dramatic Enhancement of Photocatalytic and Photoelectrochemical Hydrogen Evolution by Solar Energy.

PubMed

Li, Xu-Bing; Liu, Bin; Wen, Min; Gao, Yu-Ji; Wu, Hao-Lin; Huang, Mao-Yong; Li, Zhi-Jun; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

2016-04-01

Solar H 2 evolution of CdSe QDs can be significantly enhanced simply by introducing a suitable hole-accepting-ligand for achieving efficient hole extraction and transfer at the nanoscale interfaces, which opens an effective pathway for dissociation of excitons to generate long-lived charge separation, thus improving the solar-to-fuel conversion efficiency.

Monodispersed Zinc Oxide Nanoparticle-Dye Dyads and Triads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gladfelter, Wayne L.; Blank, David A.; Mann, Kent R.

The overall energy conversion efficiency of photovoltaic cells depends on the combined efficiencies of light absorption, charge separation and charge transport. Dye-sensitized solar cells are photovoltaic devices in which a molecular dye absorbs light and uses this energy to initiate charge separation. The most efficient dye-sensitized solar cells (DSSCs) use nanocrystal titanium dioxide films to which are attached ruthenium complexes. Numerous studies have provided valuable insight into the dynamics of these and analogous photosystems, but the lack of site homogeneity in binding dye molecules to metal oxide films and nanocrystals (NCs) is a significant impediment to extracting fundamental details aboutmore » the electron transfer across the interface. Although zinc oxide is emerging as a potential semiconducting component in DSSCs, there is less known about the factors controlling charge separation across the dye/ZnO interface. Zinc oxide crystallizes in the wurtzite lattice and has a band gap of 3.37 eV. One of the features that makes ZnO especially attractive is the remarkable ability to control the morphology of the films. Using solution deposition processes, one can prepare NCs, nanorods and nanowires having a variety of shapes and dimensions. This project solved problems associated with film heterogeneity through the use of dispersible sensitizer/ZnO NC ensembles. The overarching goal of this research was to study the relationship between structure, energetics and dynamics in a set of synthetically controlled donor-acceptor dyads and triads. These studies provided access to unprecedented understanding of the light absorption and charge transfer steps that lie at the heart of DSSCs, thus enabling significant future advances in cell efficiencies. The approach began with the construction of well-defined dye-NC dyads that were sufficiently dispersible to allow the use of state of the art pulsed laser spectroscopic and kinetic methods to understand the charge transfer events at a fundamental level. This was combined with the synthesis of a broad range of sensitizers that provide systematic variation of the energetics, excited state dynamics, structure and interfacial bonding. The key is that the monodisperse nature and high dispersibility of the ZnO NCs made these experiments reproducible; in essence, the measurements were on discrete molecular species rather than on the complicated mixtures that resulted from the typical fabrication of functional photovoltaic cells. The monodispersed nature of the NCs also allowed the use of quantum confinement to investigate the role of donor/acceptor energetic alignment in chemically identical systems. The results added significantly to our basic understanding of energy and charge transfer events at molecule-semiconductor interfaces and will help the R&D community realize zinc oxide's full potential in solar cell applications.« less

Local Time-Dependent Charging in a Perovskite Solar Cell.

PubMed

Bergmann, Victor W; Guo, Yunlong; Tanaka, Hideyuki; Hermes, Ilka M; Li, Dan; Klasen, Alexander; Bretschneider, Simon A; Nakamura, Eiichi; Berger, Rüdiger; Weber, Stefan A L

2016-08-03

Efficient charge extraction within solar cells explicitly depends on the optimization of the internal interfaces. Potential barriers, unbalanced charge extraction, and interfacial trap states can prevent cells from reaching high power conversion efficiencies. In the case of perovskite solar cells, slow processes happening on time scales of seconds cause hysteresis in the current-voltage characteristics. In this work, we localized and investigated these slow processes using frequency-modulation Kelvin probe force microscopy (FM-KPFM) on cross sections of planar methylammonium lead iodide (MAPI) perovskite solar cells. FM-KPFM can map the charge density distribution and its dynamics at internal interfaces. Upon illumination, space charge layers formed at the interfaces of the selective contacts with the MAPI layer within several seconds. We observed distinct differences in the charging dynamics at the interfaces of MAPI with adjacent layers. Our results indicate that more than one process is involved in hysteresis. This finding is in agreement with recent simulation studies claiming that a combination of ion migration and interfacial trap states causes the hysteresis in perovskite solar cells. Such differences in the charging rates at different interfaces cannot be separated by conventional device measurements.

Relative optically stimulated luminescence and thermoluminescence efficiencies of Al2O3:C dosimeters to heavy charged particles with energies relevant to space and radiotherapy dosimetry

NASA Astrophysics Data System (ADS)

Sawakuchi, G. O.; Yukihara, E. G.; McKeever, S. W. S.; Benton, E. R.; Gaza, R.; Uchihori, Y.; Yasuda, N.; Kitamura, H.

2008-12-01

This article presents a comprehensive characterization of the thermoluminescence (TL) and optically stimulated luminescence (OSL) relative luminescence efficiencies of carbon-doped aluminum (Al2O3:C) for heavy charged particles (HCPs) with atomic numbers ranging from 1 (proton) to 54 (xenon) and energies ranging from 7 to 1000 MeV/u, and investigates the dependence of the Al2O3:C response on experimental conditions. Relative luminescence efficiency values are presented for 19 primary charge/energy combinations, plus 31 additional charge/energy combinations obtained by introducing absorbers in the primary beam. Our results show that for energies of hundreds of MeV/u the data can be described by a single curve of relative luminescence efficiency versus linear energy transfer (LET). This information is needed to compensate for the reduced OSL efficiency to high-LET particles in such applications as space dosimetry. For lower energies, the relative luminescence efficiency as function of LET cannot be described by a single curve; instead, it separates into different components corresponding to different particles. We also present data on the low-LET dose response of Al2O3:C, measured under the same experimental conditions in which the relative luminescence efficiencies to HCPs were obtained, providing information relevant to future theoretical investigations of HCP energy deposition and luminescence production in Al2O3:C.

Modulating interactions between ligand-coated nanoparticles and phase-separated lipid bilayers by varying the ligand density and the surface charge.

PubMed

Chen, Xiaojie; Tieleman, D Peter; Liang, Qing

2018-02-01

The interactions between nanoparticles and lipid bilayers are critical in applications of nanoparticles in nanomedicine, cell imaging, toxicology, and elsewhere. Here, we investigate the interactions between nanoparticles coated with neutral and/or charged ligands and phase-separated lipid bilayers using coarse-grained molecular dynamics simulation. Both penetration and adsorption processes as well as the final distribution of the nanoparticles can be readily modulated by varying the ligand density and the surface charge of the nanoparticles. Completely hydrophobic (neutral) nanoparticles with larger size initially preferentially penetrate into the liquid-disordered region of the lipid bilayer and finally transfer into the liquid-ordered region; partially hydrophilic nanoparticles with low or moderate surface charge tend to either distribute in the liquid-disordered region or be adsorbed on the surface of the lipid bilayer, while strongly hydrophilic nanoparticles with high surface charge always reside on the surface of the lipid bilayer. Interactions of the nanoparticles with the lipid bilayers are affected by the surface charge of nanoparticles, hydrophobic mismatch, bending of the ligands, and the packing state of the lipids. Insight in these factors can be used to improve the efficiency of designing nanoparticles for specific applications.

One-dimension modeling on the parallel-plate ion extraction process based on a non-electron-equilibrium fluid model

NASA Astrophysics Data System (ADS)

Li, He-Ping; Chen, Jian; Guo, Heng; Jiang, Dong-Jun; Zhou, Ming-Sheng; Department of Engineering Physics Team

2017-10-01

Ion extraction from a plasma under an externally applied electric field involve multi-particle and multi-field interactions, and has wide applications in the fields of materials processing, etching, chemical analysis, etc. In order to develop the high-efficiency ion extraction methods, it is indispensable to establish a feasible model to understand the non-equilibrium transportation processes of the charged particles and the evolutions of the space charge sheath during the extraction process. Most of the previous studies on the ion extraction process are mainly based on the electron-equilibrium fluid model, which assumed that the electrons are in the thermodynamic equilibrium state. However, it may lead to some confusions with neglecting the electron movement during the sheath formation process. In this study, a non-electron-equilibrium model is established to describe the transportation of the charged particles in a parallel-plate ion extraction process. The numerical results show that the formation of the Child-Langmuir sheath is mainly caused by the charge separation. And thus, the sheath shielding effect will be significantly weakened if the charge separation is suppressed during the extraction process of the charged particles.

Novel High Efficient Organic Photovoltaic Materials

NASA Technical Reports Server (NTRS)

Sun, Sam; Haliburton, James; Fan, Zben; Taft, Charles; Wang, Yi-Qing; Maaref, Shahin; Mackey, Willie R. (Technical Monitor)

2001-01-01

In man's mission to the outer space or a remote site, the most abundant, renewable, nonpolluting, and unlimited external energy source is light. Photovoltaic (PV) materials can convert light into electrical power. In order to generate appreciable electrical power in space or on the Earth, it is necessary to collect sunlight from large areas due to the low density of sunlight, and this would be very costly using current commercially available inorganic solar cells. Future organic or polymer based solar cells seemed very attractive due to several reasons. These include lightweight, flexible shape, ultra-fast optoelectronic response time (this also makes organic PV materials attractive for developing ultra-fast photo detectors), tunability of energy band-gaps via molecular design, versatile materials synthesis and device fabrication schemes, and much lower cost on large-scale industrial production. It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks will facilitate the charge separation and migration due to improved electronic ultrastructure and morphology in comparison to current polymer composite photovoltaic system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel donor-bridge-acceptor block copolymer system for potential high-efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene, the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene, and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes the holes, the acceptor block stabilizes the electrons. The bridge block is designed to hinder the electron-hole recombination. Thus, improved charge separation is expected. In addition, charge migration will also be facilitated due to the expected nano-phase separated and highly ordered block copolymer ultrastructural. The combination of all these factors will result in significant overall enhancement of photovoltaic power conversion efficiency.

Blue Thermally Activated Delayed Fluorescence Polymers with Nonconjugated Backbone and Through-Space Charge Transfer Effect.

PubMed

Shao, Shiyang; Hu, Jun; Wang, Xingdong; Wang, Lixiang; Jing, Xiabin; Wang, Fosong

2017-12-13

We demonstrate novel molecular design for thermally activated delayed fluorescence (TADF) polymers based on a nonconjugated polyethylene backbone with through-space charge transfer effect between pendant electron donor (D) and acceptor (A) units. Different from conventional conjugated D-A polymers with through-bond charge transfer effect, the nonconjugated architecture avoids direct conjugation between D and A units, enabling blue emission. Meanwhile, spatial π-π interaction between the physically separated D and A units results in both small singlet-triplet energy splitting (0.019 eV) and high photoluminescence quantum yield (up to 60% in film state). The resulting polymer with 5 mol % acceptor unit gives efficient blue electroluminescence with Commission Internationale de l'Eclairage coordinates of (0.176, 0.269), together with a high external quantum efficiency of 12.1% and low efficiency roll-off of 4.9% (at 1000 cd m -2 ), which represents the first example of blue TADF nonconjugated polymer.

Multiple exciton dissociation in CdSe quantum dots by ultrafast electron transfer to adsorbed methylene blue.

PubMed

Huang, Jier; Huang, Zhuangqun; Yang, Ye; Zhu, Haiming; Lian, Tianquan

2010-04-07

Multiexciton generation in quantum dots (QDs) may provide a new approach for improving the solar-to-electric power conversion efficiency in QD-based solar cells. However, it remains unclear how to extract these excitons before the ultrafast exciton-exciton annihilation process. In this study we investigate multiexciton dissociation dynamics in CdSe QDs adsorbed with methylene blue (MB(+)) molecules by transient absorption spectroscopy. We show that excitons in QDs dissociate by ultrafast electron transfer to MB(+) with an average time constant of approximately 2 ps. The charge separated state is long-lived (>1 ns), and the charge recombination rate increases with the number of dissociated excitons. Up to three MB(+) molecules per QD can be reduced by exciton dissociation. Our result demonstrates that ultrafast interfacial charge separation can effectively compete with exciton-exciton annihilation, providing a viable approach for utilizing short-lived multiple excitons in QDs.

Robust nonfullerene solar cells approaching unity external quantum efficiency enabled by suppression of geminate recombination.

PubMed

Baran, Derya; Gasparini, Nicola; Wadsworth, Andrew; Tan, Ching Hong; Wehbe, Nimer; Song, Xin; Hamid, Zeinab; Zhang, Weimin; Neophytou, Marios; Kirchartz, Thomas; Brabec, Christoph J; Durrant, James R; McCulloch, Iain

2018-05-25

Nonfullerene solar cells have increased their efficiencies up to 13%, yet quantum efficiencies are still limited to 80%. Here we report efficient nonfullerene solar cells with quantum efficiencies approaching unity. This is achieved with overlapping absorption bands of donor and acceptor that increases the photon absorption strength in the range from about 570 to 700 nm, thus, almost all incident photons are absorbed in the active layer. The charges generated are found to dissociate with negligible geminate recombination losses resulting in a short-circuit current density of 20 mA cm -2 along with open-circuit voltages >1 V, which is remarkable for a 1.6 eV bandgap system. Most importantly, the unique nano-morphology of the donor:acceptor blend results in a substantially improved stability under illumination. Understanding the efficient charge separation in nonfullerene acceptors can pave the way to robust and recombination-free organic solar cells.

Significant efficiency enhancement of hybrid solar cells using core-shell nanowire geometry for energy harvesting.

PubMed

Tsai, Shin-Hung; Chang, Hung-Chih; Wang, Hsin-Hua; Chen, Szu-Ying; Lin, Chin-An; Chen, Show-An; Chueh, Yu-Lun; He, Jr-Hau

2011-12-27

A novel strategy employing core-shell nanowire arrays (NWAs) consisting of Si/regioregular poly(3-hexylthiophene) (P3HT) was demonstrated to facilitate efficient light harvesting and exciton dissociation/charge collection for hybrid solar cells (HSCs). We experimentally demonstrate broadband and omnidirectional light-harvesting characteristics of core-shell NWA HSCs due to their subwavelength features, further supported by the simulation based on finite-difference time domain analysis. Meanwhile, core-shell geometry of NWA HSCs guarantees efficient charge separation since the thickness of the P3HT shells is comparable to the exciton diffusion length. Consequently, core-shell HSCs exhibit a 61% improvement of short-circuit current for a conversion efficiency (η) enhancement of 31.1% as compared to the P3HT-infiltrated Si NWA HSCs with layers forming a flat air/polymer cell interface. The improvement of crystal quality of P3HT shells due to the formation of ordering structure at Si interfaces after air mass 1.5 global (AM 1.5G) illumination was confirmed by transmission electron microscopy and Raman spectroscopy. The core-shell geometry with the interfacial improvement by AM 1.5G illumination promotes more efficient exciton dissociation and charge separation, leading to η improvement (∼140.6%) due to the considerable increase in V(oc) from 257 to 346 mV, J(sc) from 11.7 to 18.9 mA/cm(2), and FF from 32.2 to 35.2%, which is not observed in conventional P3HT-infiltrated Si NWA HSCs. The stability of the Si/P3HT core-shell NWA HSCs in air ambient was carefully examined. The core-shell geometry should be applicable to many other material systems of solar cells and thus holds high potential in third-generation solar cells.

Construction of g-C3N4/CeO2/ZnO ternary photocatalysts with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Yuan, Yuan; Huang, Gui-Fang; Hu, Wang-Yu; Xiong, Dan-Ni; Zhou, Bing-Xin; Chang, Shengli; Huang, Wei-Qing

2017-07-01

Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis. In this work, binary g-C3N4/CeO2 nanosheets are first prepared by pyrolysis and subsequent exfoliation method, then decorated with ZnO nanoparticles to construct g-C3N4/CeO2/ZnO ternary nanocomposites with multi-heterointerfaces. Notably, the type-II staggered band alignments existing between any two of the constituents, as well as the efficient three-level transfer of electron-holes in unique g-C3N4/CeO2/ZnO ternary composites, leads to the robust separation of photoexcited charge carriers, as verified by its photocurrent increased by 8 times under visible light irradiation. The resulting g-C3N4/CeO2/ZnO ternary nanocomposites unveil appreciably increased photocatalytic activity, faster than that of pure g-C3N4, ZnO and g-C3N4/CeO2 by a factor of 11, 4.6 and 3.7, respectively, and good stability toward methylene blue (MB) degradation. The remarkably enhanced photocatalytic activity of g-C3N4/CeO2/ZnO ternary heterostructures can be interpreted in terms of lots of active sites of nanosheet shapes and the efficient charge separation owing to the resulting type-II band alignment with more than one heterointerface and the efficient three-level electron-hole transfer. A plausible mechanism is also elucidated via active species trapping experiments with various scavengers, which indicating that the photogenerated holes and •OH radicals play a crucial role in photodegradation reaction under visible light irradiation. This work suggest that the rational design and construction of type II multi-heterostructures is powerful for developing highly efficient and reusable visible-light photocatalysts for environmental purification and energy conversion.

Charge separation and carrier dynamics in donor-acceptor heterojunction photovoltaic systems

PubMed Central

Teuscher, Joël; Brauer, Jan C.; Stepanov, Andrey; Solano, Alicia; Boziki, Ariadni; Chergui, Majed; Wolf, Jean-Pierre; Rothlisberger, Ursula; Banerji, Natalie; Moser, Jacques-E.

2017-01-01

Electron transfer and subsequent charge separation across donor-acceptor heterojunctions remain the most important areas of study in the field of third-generation photovoltaics. In this context, it is particularly important to unravel the dynamics of individual ultrafast processes (such as photoinduced electron transfer, carrier trapping and association, and energy transfer and relaxation), which prevail in materials and at their interfaces. In the frame of the National Center of Competence in Research “Molecular Ultrafast Science and Technology,” a research instrument of the Swiss National Science Foundation, several groups active in the field of ultrafast science in Switzerland have applied a number of complementary experimental techniques and computational simulation tools to scrutinize these critical photophysical phenomena. Structural, electronic, and transport properties of the materials and the detailed mechanisms of photoinduced charge separation in dye-sensitized solar cells, conjugated polymer- and small molecule-based organic photovoltaics, and high-efficiency lead halide perovskite solar energy converters have been scrutinized. Results yielded more than thirty research articles, an overview of which is provided here. PMID:29308415

Steady-state and time-resolved studies on the photophysical properties of fullerene-pyropheophorbide a complexes in polar and nonpolar solvents

NASA Astrophysics Data System (ADS)

Ermilov, E. A.; Al-Omari, S.; Helmreich, M.; Jux, N.; Hirsch, A.; Röder, B.

2004-04-01

A novel monofullerene-bis(pyropheophorbide a) dyad has been photophysically characterized by steady-state as well as time-resolved techniques. It was revealed that in this complex strong and fast quenching of the first excited singlet state of the pyropheophorbide a (pyroPheo) molecule occurs by efficient photoinduced electron transfer to the fullerene moiety in both polar (DMF) and nonpolar (toluene) solvents. In DMF the energy of the charge-separated state is 0.94 eV and it undergoes directly transition to the ground state resulting in a very low value of photosensitized singlet oxygen generation. In contrast to the situation in a polar solvent, in toluene the charge-separated state lies above the exited triplet state of pyroPheo as well as that of C 60. It has been shown that in a nonpolar solvent a sufficient amount of singlet oxygen was generated by energy transfer from the excited triplet state of pyroPheo which has been populated via relaxation of the charge-separated state.

Organic solar cells: understanding the role of Förster resonance energy transfer.

PubMed

Feron, Krishna; Belcher, Warwick J; Fell, Christopher J; Dastoor, Paul C

2012-12-12

Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by F¨orster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of F¨orster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells.

Fine-Tuning the Quasi-3D Geometry: Enabling Efficient Nonfullerene Organic Solar Cells Based on Perylene Diimides.

PubMed

Liu, Zhitian; Zhang, Linhua; Shao, Ming; Wu, Yao; Zeng, Di; Cai, Xiang; Duan, Jiashun; Zhang, Xiaolu; Gao, Xiang

2018-01-10

The geometries of acceptors based on perylene diimides (PDIs) are important for improving the phase separation and charge transport in organic solar cells. To fine-tune the geometry, biphenyl, spiro-bifluorene, and benzene were used as the core moiety to construct quasi-three-dimensional nonfullerene acceptors based on PDI building blocks. The molecular geometries, energy levels, optical properties, photovoltaic properties, and exciton kinetics were systematically studied. The structure-performance relationship was discussed as well. Owing to the finest phase separation, the highest charge mobility and smallest nongeminate recombination, the power conversion efficiency of nonfullerene solar cells using PDI derivatives with biphenyl core (BP-PDI 4 ) as acceptor reached 7.3% when high-performance wide band gap donor material poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] was blended.

Facile fabrication of BiVO4 nanofilms with controlled pore size and their photoelectrochemical performances

NASA Astrophysics Data System (ADS)

Feng, Chenchen; Jiao, Zhengbo; Li, Shaopeng; Zhang, Yan; Bi, Yingpu

2015-12-01

We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures.We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06584d

Enhanced photocatalytic activity of BiOCl by C70 modification and mechanism insight

NASA Astrophysics Data System (ADS)

Ma, Dongmei; Zhong, Junbo; Li, Jianzhang; Wang, Li; Peng, Rufang

2018-06-01

As an excellent photocatalyst which can compete with TiO2, BiOCl has triggered increasing attention. However, the practical application of BiOCl has been significantly limited by the fast recombination of the photoinduced electron-hole charge pairs. In this study, to further enhance the separation efficiency of photoinduced electron-hole charge pairs of BiOCl, a series of efficient BiOCl photocatalysts were prepared by C70 surface modification. The trapping experiments reveal that the main active species were determined to be superoxide radicals (O2rad -) and holes (h+) under simulated sunlight irradiation. The surface photovoltage spectroscopy (SPS) demonstrates that separation of the photoinduced electron-hole pairs has been significantly promoted, forming more radOH, proven by terephthalic acid photoluminescence probing technique. The photocatalytic evaluation results display that the C70/BiOCl photocatalysts exhibit much higher photocatalytic activity in decolorization of rhodamine B (RhB) than that of the bare BiOCl under the simulated sunlight irradiation. The excellent electron acceptability of C70 is conducive to the separation of the photogenerated carriers and results in efficient formation of O2rad -, proven by the results of SPS and electron spin-resonance (ESR), therefore the photocatalytic performance of C70/BiOCl has been greatly improved. Based on all these observations, an enhancement mechanism in photocatalytic performance of C70/BiOCl was proposed.

Fluorination-enabled optimal morphology leads to over 11% efficiency for inverted small-molecule organic solar cells

PubMed Central

Deng, Dan; Zhang, Yajie; Zhang, Jianqi; Wang, Zaiyu; Zhu, Lingyun; Fang, Jin; Xia, Benzheng; Wang, Zhen; Lu, Kun; Ma, Wei; Wei, Zhixiang

2016-01-01

Solution-processable small molecules for organic solar cells have attracted intense attention for their advantages of definite molecular structures compared with their polymer counterparts. However, the device efficiencies based on small molecules are still lower than those of polymers, especially for inverted devices, the highest efficiency of which is <9%. Here we report three novel solution-processable small molecules, which contain π-bridges with gradient-decreased electron density and end acceptors substituted with various fluorine atoms (0F, 1F and 2F, respectively). Fluorination leads to an optimal active layer morphology, including an enhanced domain purity, the formation of hierarchical domain size and a directional vertical phase gradation. The optimal morphology balances charge separation and transfer, and facilitates charge collection. As a consequence, fluorinated molecules exhibit excellent inverted device performance, and an average power conversion efficiency of 11.08% is achieved for a two-fluorine atom substituted molecule. PMID:27991486

Charging YOYO-1 on Capillary Wall for Online DNA Intercalation and Integrating This Approach with Multiplex PCR and Bare Narrow Capillary–Hydrodynamic Chromatography for Online DNA Analysis

PubMed Central

2016-01-01

Multiplex polymerase chain reaction (PCR) has been widely utilized for high-throughput pathogen identification. Often, a dye is used to intercalate the amplified DNA fragments, and identifications of the pathogens are carried out by DNA melting curve analysis or gel electrophoresis. Integrating DNA amplification and identification is a logic path toward maximizing the benefit of multiplex PCR. Although PCR and gel electrophoresis have been integrated, replenishing the gels after each run is tedious and time-consuming. In this technical note, we develop an approach to address this issue. We perform multiplex PCR inside a capillary, transfer the amplified fragments to a bare narrow capillary, and measure their lengths online using bare narrow capillary–hydrodynamic chromatography (BaNC-HDC), a new technique recently developed in our laboratory for free-solution DNA separation. To intercalate the DNA with YOYO-1 (a fluorescent dye) for BaNC-HDC, we flush the capillary column with a YOYO-1 solution; positively charged YOYO-1 is adsorbed (or charged) onto the negatively charged capillary wall. As DNA molecules are driven down the column for separation, they react with the YOYO-1 stored on the capillary wall and are online-intercalated with the dye. With a single YOYO-1 charging, the column can be used for more than 40 runs, although the fluorescence signal intensities of the DNA peaks decrease gradually. Although the dye-DNA intercalation occurs during the separation, it does not affect the retention times, separation efficiencies, or resolutions. PMID:25555111

Enhanced Charge Separation and FRET at Heterojunctions between Semiconductor Nanoparticles and Conducting Polymer Nanofibers for Efficient Solar Light Harvesting

PubMed Central

Sardar, Samim; Kar, Prasenjit; Remita, Hynd; Liu, Bo; Lemmens, Peter; Kumar Pal, Samir; Ghosh, Srabanti

2015-01-01

Energy harvesting from solar light employing nanostructured materials offer an economic way to resolve energy and environmental issues. We have developed an efficient light harvesting heterostructure based on poly(diphenylbutadiyne) (PDPB) nanofibers and ZnO nanoparticles (NPs) via a solution phase synthetic route. ZnO NPs (~20 nm) were homogeneously loaded onto the PDPB nanofibers as evident from several analytical and spectroscopic techniques. The photoinduced electron transfer from PDPB nanofibers to ZnO NPs has been confirmed by steady state and picosecond-resolved photoluminescence studies. The co-sensitization for multiple photon harvesting (with different energies) at the heterojunction has been achieved via a systematic extension of conjugation from monomeric to polymeric diphenyl butadiyne moiety in the proximity of the ZnO NPs. On the other hand, energy transfer from the surface defects of ZnO NPs (~5 nm) to PDPB nanofibers through Förster Resonance Energy Transfer (FRET) confirms the close proximity with molecular resolution. The manifestation of efficient charge separation has been realized with ~5 fold increase in photocatalytic degradation of organic pollutants in comparison to polymer nanofibers counterpart under visible light irradiation. Our results provide a novel approach for the development of nanoheterojunctions for efficient light harvesting which will be helpful in designing future solar devices. PMID:26611253

Spatial Electron-hole Separation in a One Dimensional Hybrid Organic-Inorganic Lead Iodide

NASA Astrophysics Data System (ADS)

Savory, Christopher N.; Palgrave, Robert G.; Bronstein, Hugo; Scanlon, David O.

2016-02-01

The increasing efficiency of the inorganic-organic hybrid halides has revolutionised photovoltaic research. Despite this rapid progress, the significant issues of poor stability and toxicity have yet to be suitably overcome. In this article, we use Density Functional Theory to examine (Pb2I6) · (H2DPNDI) · (H2O) · (NMP), an alternative lead-based hybrid inorganic-organic solar absorber based on a photoactive organic cation. Our results demonstrate that optical properties suitable for photovoltaic applications, in addition to spatial electron-hole separation, are possible but efficient charge transport may be a limiting factor.

Spatial Electron-hole Separation in a One Dimensional Hybrid Organic–Inorganic Lead Iodide

PubMed Central

Savory, Christopher N.; Palgrave, Robert G.; Bronstein, Hugo; Scanlon, David O.

2016-01-01

The increasing efficiency of the inorganic-organic hybrid halides has revolutionised photovoltaic research. Despite this rapid progress, the significant issues of poor stability and toxicity have yet to be suitably overcome. In this article, we use Density Functional Theory to examine (Pb2I6) · (H2DPNDI) · (H2O) · (NMP), an alternative lead-based hybrid inorganic-organic solar absorber based on a photoactive organic cation. Our results demonstrate that optical properties suitable for photovoltaic applications, in addition to spatial electron-hole separation, are possible but efficient charge transport may be a limiting factor. PMID:26858147

Complex coacervation of supercharged proteins with polyelectrolytes.

PubMed

Obermeyer, Allie C; Mills, Carolyn E; Dong, Xue-Hui; Flores, Romeo J; Olsen, Bradley D

2016-04-21

Complexation of proteins with polyelectrolytes or block copolymers can lead to phase separation to generate a coacervate phase or self-assembly of coacervate core micelles. However, many proteins do not coacervate at conditions near neutral pH and physiological ionic strength. Here, protein supercharging is used to systematically explore the effect of protein charge on the complex coacervation with polycations. Four model proteins were anionically supercharged to varying degrees as quantified by mass spectrometry. Proteins phase separated with strong polycations when the ratio of negatively charged residues to positively charged residues on the protein (α) was greater than 1.1-1.2. Efficient partitioning of the protein into the coacervate phase required larger α (1.5-2.0). The preferred charge ratio for coacervation was shifted away from charge symmetry for three of the four model proteins and indicated an excess of positive charge in the coacervate phase. The composition of protein and polymer in the coacervate phase was determined using fluorescently labeled components, revealing that several of the coacervates likely have both induced charging and a macromolecular charge imbalance. The model proteins were also encapsulated in complex coacervate core micelles and micelles formed when the protein charge ratio α was greater than 1.3-1.4. Small angle neutron scattering and transmission electron microscopy showed that the micelles were spherical. The stability of the coacervate phase in both the bulk and micelles improved to increased ionic strength as the net charge on the protein increased. The micelles were also stable to dehydration and elevated temperatures.

Harvesting solar energy by means of charge-separating nanocrystals and their solids.

PubMed

Diederich, Geoffrey; O'Connor, Timothy; Moroz, Pavel; Kinder, Erich; Kohn, Elena; Perera, Dimuthu; Lorek, Ryan; Lambright, Scott; Imboden, Martene; Zamkov, Mikhail

2012-08-23

Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials offering a superior control over the spatial distribution of charge carriers across material interfaces. As this study demonstrates, a combination of donor-acceptor nanocrystal (NC) domains in a single nanoparticle can lead to the realization of efficient photocatalytic materials, while a layered assembly of donor- and acceptor-like nanocrystals films gives rise to photovoltaic materials. Initially the paper focuses on the synthesis of composite inorganic nanocrystals, comprising linearly stacked ZnSe, CdS, and Pt domains, which jointly promote photoinduced charge separation. These structures are used in aqueous solutions for the photocatalysis of water under solar radiation, resulting in the production of H2 gas. To enhance the photoinduced separation of charges, a nanorod morphology with a linear gradient originating from an intrinsic electric field is used. The inter-domain energetics are then optimized to drive photogenerated electrons toward the Pt catalytic site while expelling the holes to the surface of ZnSe domains for sacrificial regeneration (via methanol). Here we show that the only efficient way to produce hydrogen is to use electron-donating ligands to passivate the surface states by tuning the energy level alignment at the semiconductor-ligand interface. Stable and efficient reduction of water is allowed by these ligands due to the fact that they fill vacancies in the valence band of the semiconductor domain, preventing energetic holes from degrading it. Specifically, we show that the energy of the hole is transferred to the ligand moiety, leaving the semiconductor domain functional. This enables us to return the entire nanocrystal-ligand system to a functional state, when the ligands are degraded, by simply adding fresh ligands to the system. To promote a photovoltaic charge separation, we use a composite two-layer solid of PbS and TiO2 films. In this configuration, photoinduced electrons are injected into TiO2 and are subsequently picked up by an FTO electrode, while holes are channeled to a Au electrode via PbS layer. To develop the latter we introduce a Semiconductor Matrix Encapsulated Nanocrystal Arrays (SMENA) strategy, which allows bonding PbS NCs into the surrounding matrix of CdS semiconductor. As a result, fabricated solids exhibit excellent thermal stability, attributed to the heteroepitaxial structure of nanocrystal-matrix interfaces, and show compelling light-harvesting performance in prototype solar cells.

Light-induced charge separation across bio-inorganic interface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimitrijevic, N. M.; Rajh, T.; De La Garza, L.

Rational design of hybrid biomolecule - nanoparticulate semiconductor conjugates enables coupling of functionality of biomolecules with the capability of semiconductors for solar energy capture, that can have potential application in energy conversion, sensing and catalysis. The particular challenge is to obtain efficient charge separation analogous to the natural photosynthesis process. The synthesis of axially anisotropic TiO{sub 2} nano-objects such as tubes, rods and bricks, as well as spherical and faceted nanoparticles has been developed in our laboratory. Depending on their size and shape, these nanostructures exhibit different domains of crystallinity, surface areas and aspect ratios. Moreover, in order to accommodatemore » for high curvature in nanoscale regime, the surfaces of TiO{sub 2} nano-objects reconstructs resulting in changes in the coordination of surface Ti atoms from octahedral (D{sub 2d}) to square pyramidal structures (C{sub 4v}). The formation of these coordinatively unsaturated Ti atoms, thus depends strongly on the size and shape of nanocrystallites and affects trapping and reactivity of photogenerated charges. We have exploited these coordinatively unsaturated Ti atoms to coupe electron-donating (such as dopamine) and electron-accepting (pyrroloquinoline quinone) conductive linkers that allow wiring of biomolecules and proteins resulting in enhanced charge separation which increases the yield of ensuing chemical transformations.« less

Superior visible light hydrogen evolution of Janus bilayer junctions via atomic-level charge flow steering

NASA Astrophysics Data System (ADS)

Li, Jie; Zhan, Guangming; Yu, Ying; Zhang, Lizhi

2016-05-01

Although photocatalytic hydrogen evolution (PHE) is ideal for solar-to-fuel conversion, it remains challenging to construct a highly efficient PHE system by steering the charge flow in a precise manner. Here we tackle this challenge by assembling 1T MoS2 monolayers selectively and chemically onto (Bi12O17) end-faces of Bi12O17Cl2 monolayers to craft two-dimensional (2D) Janus (Cl2)-(Bi12O17)-(MoS2) bilayer junctions, a new 2D motif different from van der Waals heterostructure. Electrons and holes from visible light-irradiated Bi12O17Cl2 are directionally separated by the internal electric field to (Bi12O17) and (Cl2) end-faces, respectively. The separated electrons can further migrate to MoS2 via Bi-S bonds formed between (Bi12O17) and MoS2 monolayers. This atomic-level directional charge separation endows the Janus bilayers with ultralong carrier lifetime of 3,446 ns and hence a superior visible-light PHE rate of 33 mmol h-1 g-1. Our delineated Janus bilayer junctions on the basis of the oriented assembly of monolayers presents a new design concept to effectively steer the charge flow for PHE.

Application of ion mobility-mass spectrometry to microRNA analysis.

PubMed

Takebayashi, Kosuke; Hirose, Kenji; Izumi, Yoshihiro; Bamba, Takeshi; Fukusaki, Eiichiro

2013-03-01

Liquid chromatography/mass spectrometry is widely used for studying sequence determination and modification analysis of small RNAs. However, the efficiency of liquid chromatography-based separation of intact small RNA species is insufficient, since the physiochemical properties among small RNAs are very similar. In this study, we focused on ion mobility-mass spectrometry (IM-MS), which is a gas-phase separation technique coupled with mass spectrometry; we have evaluated the utility of IM-MS for microRNA (miRNA) analysis. A multiply charged deprotonated ion derived from an 18-24-nt-long miRNA was formed by electrospray ionization, and then the time, called the "drift time", taken by each ion to migrate through a buffer gas was measured. Each multivalent ion was temporally separated on the basis of the charge state and structural formation; 3 types of unique mass-mobility correlation patterns (i.e., chainlike-form, hairpin-form, and dimer-form) were present on the two-dimensional mobility-mass spectrum. Moreover, we found that the ion size (sequence length) and the secondary structures of the small RNAs strongly contributed to the IM-MS-based separation, although solvent conditions such as pH had no effect. Therefore, sequence isomers could also be discerned by the selection of each specific charged ion, i.e., the 6(-) charged ion reflected a majority among chainlike-, hairpin-, and other structures. We concluded that the IM-MS provides additional capability for separation; thus, this analytical method will be a powerful tool for comprehensive small RNA analysis. Copyright © 2012. Published by Elsevier B.V.

A quantitative structure–function relationship for the Photosystem II reaction center: Supermolecular behavior in natural photosynthesis

PubMed Central

Barter, Laura M. C.; Durrant, James R.; Klug, David R.

2003-01-01

Light-induced charge separation is the primary photochemical event of photosynthesis. Efficient charge separation in photosynthetic reaction centers requires the balancing of electron and excitation energy transfer processes, and in Photosystem II (PSII), these processes are particularly closely entangled. Calculations that treat the cofactors of the PSII reaction center as a supermolecular complex allow energy and electron transfer reactions to be described in a unified way. This calculational approach is shown to be in good agreement with experimentally observed energy and electron transfer dynamics. This supermolecular view also correctly predicts the effect of changing the redox potentials of cofactors by site-directed mutagenesis, thus providing a unified and quantitative structure–function relationship for the PSII reaction center. PMID:12538865

Enhanced charge efficiency and reduced energy use in capacitive deionization by increasing the discharge voltage.

PubMed

Kim, T; Dykstra, J E; Porada, S; van der Wal, A; Yoon, J; Biesheuvel, P M

2015-05-15

Capacitive deionization (CDI) is an electrochemical method for water desalination using porous carbon electrodes. A key parameter in CDI is the charge efficiency, Λ, which is the ratio of salt adsorption over charge in a CDI-cycle. Values for Λ in CDI are typically around 0.5-0.8, significantly less than the theoretical maximum of unity, due to the fact that not only counterions are adsorbed into the pores of the carbon electrodes, but at the same time coions are released. To enhance Λ, ion-exchange membranes (IEMs) can be implemented. With membranes, Λ can be close to unity because the membranes only allow passage for the counterions. Enhancing the value of Λ is advantageous as this implies a lower electrical current and (at a fixed charging voltage) a reduced energy use. We demonstrate how, without the need to include IEMs, the charge efficiency can be increased to values close to the theoretical maximum of unity, by increasing the cell voltage during discharge, with only a small loss of salt adsorption capacity per cycle. In separate constant-current CDI experiments, where after some time the effluent salt concentration reaches a stable value, this value is reached earlier with increased discharge voltage. We compare the experimental results with predictions of porous electrode theory which includes an equilibrium Donnan electrical double layer model for salt adsorption in carbon micropores. Our results highlight the potential of modified operational schemes in CDI to increase charge efficiency and reduce energy use of water desalination. Copyright © 2014 Elsevier Inc. All rights reserved.

Organic solar cells based on high dielectric constant materials: An approach to increase efficiency

NASA Astrophysics Data System (ADS)

Hamam, Khalil Jumah Tawfiq

The efficiency of organic solar cells still lags behind inorganic solar cells due to their low dielectric constant which results in a weakly screened columbic attraction between the photogenerated electron-hole system, therefore the probability of charge separating is low. Having an organic material with a high dielectric constant could be the solution to get separated charges or at least weakly bounded electron-hole pairs. Therefore, high dielectric constant materials have been investigated and studied by measuring modified metal-phthalocyanine (MePc) and polyaniline in pellets and thin films. The dielectric constant was investigated as a function of temperature and frequency in the range of 20Hz to1MHz. For MePc we found that the high dielectric constant was an extrinsic property due to water absorption and the formation of hydronuim ion allowed by the ionization of the functional groups such as sulphonated and carboxylic groups. The dielectric constant was high at low frequencies and decreasing as the frequency increase. Investigated materials were applied in fabricated bilayer heterojunction organic solar cells. The application of these materials in an organic solar cells show a significant stability under room conditions rather than improvement in their efficiency.

Impact of charge transport on current–voltage characteristics and power-conversion efficiency of organic solar cells

PubMed Central

Würfel, Uli; Neher, Dieter; Spies, Annika; Albrecht, Steve

2015-01-01

This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current–voltage curves of organic solar cells under illumination with the Shockley equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells. PMID:25907581

Efficient Yttrium(III) Chloride-Treated TiO2 Electron Transfer Layers for Performance-Improved and Hysteresis-Less Perovskite Solar Cells.

PubMed

Li, Minghua; Huan, Yahuan; Yan, Xiaoqin; Kang, Zhuo; Guo, Yan; Li, Yong; Liao, Xinqin; Zhang, Ruxiao; Zhang, Yue

2018-01-10

Hybrid organic-inorganic metal halide perovskite solar cells have attracted widespread attention, owing to their high performance, and have undergone rapid development. In perovskite solar cells, the charge transfer layer plays an important role for separating and transferring photogenerated carriers. In this work, an efficient YCl 3 -treated TiO 2 electron transfer layer (ETL) is used to fabricate perovskite solar cells with enhanced photovoltaic performance and less hysteresis. The YCl 3 -treated TiO 2 layers bring about an upward shift of the conduction band minimum (E CBM ), which results in a better energy level alignment for photogenerated electron transfer and extraction from the perovskite into the TiO 2 layer. After optimization, perovskite solar cells based on the YCl 3 -treated TiO 2 layers achieve a maximum power conversion efficiency of about 19.99 % (19.29 % at forward scan) and a steady-state power output of about 19.6 %. Steady-state and time-resolved photoluminescence measurements and impedance spectroscopy are carried out to investigate the charge transfer and recombination dynamics between the perovskite and the TiO 2 electron transfer layer interface. The improved perovskite/TiO 2 ETL interface with YCl 3 treatment is found to separate and extract photogenerated charge rapidly and suppress recombination effectively, which leads to the improved performance. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Z-schematic water splitting by the synergistic effect of a type-II heterostructure and a highly efficient oxygen evolution catalyst

NASA Astrophysics Data System (ADS)

Li, Xiaoyun; Hu, Haihua; Xu, Lingbo; Cui, Can; Qian, Degui; Li, Shuang; Zhu, Wenzhe; Wang, Peng; Lin, Ping; Pan, Jiaqi; Li, Chaorong

2018-05-01

Artificial Z-scheme system inspired by the natural photosynthesis in green plants has attracted extensive attention owing to its advantages such as simultaneously wide range light absorption, highly efficient charge separation and strong redox ability. In this paper, we report the synthesis of a novel all-solid-state direct Z-scheme photocatalyst of Ag3PO4/CeO2/TiO2 by depositing Ag3PO4 nanoparticles (NPs) on CeO2/TiO2 hierarchical branched nanowires (BNWs), where the CeO2/TiO2 BNWs act as a novel substrate for the well dispersed nano-size Ag3PO4. The Ag3PO4/CeO2/TiO2 photocatalyst exhibits excellent ability of photocatalytic oxygen evolution from pure water splitting. It is suggested that the Z-scheme charge transfer route between CeO2/TiO2 and Ag3PO4 improves the redox ability. On the other hand, the cascade energy level alignment in CeO2/TiO2 BNWs expedites the spatial charge separation, and hence suppresses photocatalytic backward reaction. However, it is difficult to realize a perfect excitation balance in Ag3PO4/CeO2/TiO2 and the composite still surfers photo-corrosion in photocatalysis reaction. Nevertheless, our results provide an innovative strategy of constructing a Z-scheme system from a type-II heterostructure and a highly efficient oxygen evolution catalyst.

Improvement of charge separation in TiO{sub 2} by its modification with different tungsten compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tryba, B., E-mail: beata.tryba@zut.edu.pl; Tygielska, M.; Grzeskowiak, M.

2016-04-15

Highlights: • Ammonium m-tungstate doped to TiO{sub 2} highly improved charge separation in TiO{sub 2}. • Negative electrokinetic potential of TiO{sub 2} facilitates holes migration to its surface. • Fast migration of holes to TiO{sub 2} surfaces increased yield of OH radicals formation. • Adsorption of dyes on photocatalyst increased its decomposition under visible light. - Abstract: Three different tungsten precursors were used for TiO{sub 2} modification: H{sub 2}WO{sub 4}, WO{sub 2}, and ammonium m-tungstate. It was proved that modification of TiO{sub 2} with tungsten compounds enhanced its photocatalytic activity through the improvement of charge separation. This effect was obtainedmore » by coating of TiO{sub 2} particles with tungsten compound, which changed their surficial electrokinetical potential from positive onto negative. The most efficient tungsten compound, which caused enhanced separation of free carriers was ammonium m-tungstate (AMT). Two dyes with different ionic potential were used for the photocatalytic decomposition. It appeared that cationic dye—Methylene Blue was highly adsorbed on the negatively charged surface of TiO{sub 2} modified by AMT and decomposed, however this photocatalyst was quickly deactivated whereas anionic dye—acid red was better adsorbed on the less acidic surface of TiO{sub 2} and was rapidly decomposed with almost the same rate in the five following cycles.« less

Removal of oil droplets from water using carbonized rice husk: enhancement by surface modification using polyethylenimine.

PubMed

Lin, Kun-Yi Andrew; Yang, Hongta; Petit, Camille; Chen, Shen-Yi

2015-06-01

Carbonized rice husk (CRH) is a promising material to separate oil from water owing to its abundance, low-cost, and environmentally benign characteristics. However, CRH's performance is somewhat limited by its similar surface charge to that of oil, leading to repulsive interactions. To improve the separation efficiency of CRH, CRH was modified via impregnation with a cationic biocompatible polymer, polyethlyenimine (PEI) to form PEI-CRH. The modified sample exhibits a remarkably higher (10-50 times) oil/water (O/W) separation efficiency than that of the unmodified one. Small PEI-CRH particles (about 64 μm) are found to adsorb oil droplets faster and larger quantities than bigger particles (about 113 and 288 μm). PEI-CRH exhibits higher separation efficiency at high temperatures owing to the destabilization of the emulsion. It is also found that the oil adsorption mechanism involves a chemical interaction between PEI-CRH and oil droplets. The addition of NaCl considerably improves the separation efficiency, while the addition of a cationic surfactant has the opposite effect. In acidic emulsions, PEI-CRH adsorbs more oil than in neutral or basic conditions owing to favorable attractive forces between oil droplets and the surface of PEI-CRH. PEI-CRH can be easily regenerated by washing with ethanol. These promising features of PEI-CRH indicate that PEI-CRH could be an efficient and low-cost adsorbent for the O/W separation applications.

Solution deposited and modified iron oxide for enhanced solar water splitting

NASA Astrophysics Data System (ADS)

Abel, Anthony J.

Growing worldwide energy demand coupled with an increasing awareness of anthropogenic climate change has driven research into carbon-neutral and solar-derived energy sources. One attractive strategy is the storage of solar energy in the bonds of H2 formed by photoelectrochemical (PEC) water splitting. Hematite, an iron oxide, has been widely investigated as a candidate material for PEC water splitting due to its stability, non-toxicity, earth abundance and consequent low cost, and a theoretical 15% solar-to-hydrogen conversion efficiency. However, poor electrical properties and slow rates of the water oxidation reaction have limited its potential as an economical water splitting catalyst. Additionally, the most efficient hematite-based devices are fabricated via expensive, vacuum-phase techniques, limiting scalability to broad integration into the energy supply. In this thesis, I develop a new, solution-based deposition method for high quality, planar hematite thin films using successive ionic layer adsorption and reaction (SILAR). The constant geometry and tight control over layer thickness possible with SILAR makes these films ideal model systems to understand the two key steps of PEC water oxidation: charge separation and interfacial hole transfer. In Chapter 3, I report on facile annealing treatments to dope hematite with Ti and Sn, and I show that these impurity atoms at the hematite/electrolyte interface increase hole transfer efficiency from nearly 0 to above 60%. However, charge separation remains below 15% with these dopants incorporated via solid state diffusion, mainly due to low hole mobility. To overcome this associated small transport length, extremely thin hematite coatings were deposited on Sb:SnO2 monolayer inverse opal scaffolds. With this modified substrate, photocurrent increased proportionately to the surface area of the scaffold. While Chapter 3 discusses incorporation of dopants via solid state diffusion, Chapter 4 examines methods to incorporate Ti via modified SILAR solutions. With this method, hematite films with well-controlled, uniform doping profiles were successfully fabricated. An optimal Ti concentration of 4.2% in the film enabled a charge separation efficiency of >20%, and I show that holes generated within 3 nm of the depletion region are separated with unity efficiency. With the addition of an ultrathin FeOOH overlayer, hole transfer efficiency is increased to 100% as a result of an increased concentration of reactive holes at the hematite/electrolyte interface. These combined effects lead to photocurrents >0.85 mAcm-2 at 1.23 VRHE, which is competitive with champion planar films regardless of fabrication method. Importantly, the methods of fabrication and analysis described in this thesis are applicable to a wide range of materials for a variety of applications. The SILAR method can be applied to many compounds, provided their constituent atoms are soluble in liquid solvents. Additionally, the facile optical and electrochemical measurements used to analyze hematite in Chapters 3 and 4 can be readily adapted to other semiconductor materials with the aim of understanding their charge transport properties.

Cationic flocculants carrying hydrophobic functionalities: applications for solid/liquid separation.

PubMed

Schwarz, S; Jaeger, W; Paulke, B-R; Bratskaya, S; Smolka, N; Bohrisch, J

2007-07-26

The flocculation behaviors of three series of polycations with narrow molecular weight distributions carrying hydrophobic substituents on their backbones [poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride), poly(N-vinylbenzyl-N,N-dimethyl-N-butylammonium chloride), and poly(N-vinylbenzylpyridinium chloride)] were investigated in dispersions of monodisperse polystyrene latexes and kaolin. Apparently, the charge density of the polycations decreases with increasing substituent hydrophobicity and increasing molecular weight of the polyelectrolytes. The necessary amount of flocculant for phase separation in dispersions with high substrate surface charge densities increases with increasing hydrophobicity of the polyelectrolyte. Nevertheless, the introduction of hydrophobic functionalities is beneficial, resulting in a substantial broadening of the range between the minimum and maximum amounts of flocculant necessary for efficient flocculation (flocculation window). An increase in ionic strength supports this effect. When the substrate has a low charge density, the hydrophobic interactions play a much more significant role in the flocculation process. Here, the minimum efficient doses remained the same for all three polyelectrolytes investigated, but the width of the flocculation window increased as the polycation hydrophobicity and the molecular weight increased. The necessary amount of flocculant increased with an increase in particle size at constant solid content of the dispersion, as well as with a decreasing number of particles at a constant particle size.

Hierarchical FeTiO3-TiO2 hollow spheres for efficient simulated sunlight-driven water oxidation.

PubMed

Han, Taoran; Chen, Yajie; Tian, Guohui; Wang, Jian-Qiang; Ren, Zhiyu; Zhou, Wei; Fu, Honggang

2015-10-14

Oxygen generation is the key step for the photocatalytic overall water splitting and considered to be kinetically more challenging than hydrogen generation. Here, an effective water oxidation catalyst of hierarchical FeTiO3-TiO2 hollow spheres are prepared via a two-step sequential solvothermal processes and followed by thermal treatment. The existence of an effective heterointerface and built-in electric field in the surface space charge region in FeTiO3-TiO2 hollow spheres plays a positive role in promoting the separation of photoinduced electron-hole pairs. Surface photovoltage, transient-state photovoltage, fluorescence and electrochemical characterization are used to investigate the transfer process of photoinduced charge carriers. The photogenerated charge carriers in the hierarchical FeTiO3-TiO2 hollow spheres with a proper molar ratio display much higher separation efficiency and longer lifetime than those in the FeTiO3 alone. Moreover, it is suggested that the hierarchical porous hollow structure can contribute to the enhancement of light utilization, surface active sites and material transportation through the framework walls. This specific synergy significantly contributes to the remarkable improvement of the photocatalytic water oxidation activity of the hierarchical FeTiO3-TiO2 hollow spheres under simulated sunlight (AM1.5).

A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes

PubMed Central

Hwang, Ee Taek; Sheikh, Khizar; Orchard, Katherine L; Hojo, Daisuke; Radu, Valentin; Lee, Chong-Yong; Ainsworth, Emma; Lockwood, Colin; Gross, Manuela A; Adschiri, Tadafumi; Reisner, Erwin; Butt, Julea N; Jeuken, Lars J C

2015-01-01

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems. PMID:26180522

C@SiNW/TiO2 Core-Shell Nanoarrays with Sandwiched Carbon Passivation Layer as High Efficiency Photoelectrode for Water Splitting

PubMed Central

Devarapalli, Rami Reddy; Debgupta, Joyashish; Pillai, Vijayamohanan K.; Shelke, Manjusha V.

2014-01-01

One-dimensional heterostructure nanoarrays are efficiently promising as high performance electrodes for photo electrochemical (PEC) water splitting applications, wherein it is highly desirable for the electrode to have a broad light absorption, efficient charge separation and redox properties as well as defect free surface with high area suitable for fast interfacial charge transfer. We present highly active and unique photoelectrode for solar H2 production, consisting of silicon nanowires (SiNWs)/TiO2 core-shell structures. SiNWs are passivated to reduce defect sites and protected against oxidation in air or water by forming very thin carbon layer sandwiched between SiNW and TiO2 surfaces. This carbon layer decreases recombination rates and also enhances the interfacial charge transfer between the silicon and TiO2. A systematic investigation of the role of SiNW length and TiO2 thickness on photocurrent reveals enhanced photocurrent density up to 5.97 mA/cm2 at 1.0 V vs.NHE by using C@SiNW/TiO2 nanoarrays with photo electrochemical efficiency of 1.17%. PMID:24810865

Organic Solar Cells: Understanding the Role of Förster Resonance Energy Transfer

PubMed Central

Feron, Krishna; Belcher, Warwick J.; Fell, Christopher J.; Dastoor, Paul C.

2012-01-01

Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by Förster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of Förster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells. PMID:23235328

Energetics of bacterial photosynthesis.

PubMed

Lebard, David N; Matyushov, Dmitry V

2009-09-10

We report the results of extensive numerical simulations and theoretical calculations of electronic transitions in the reaction center of Rhodobacter sphaeroides photosynthetic bacterium. The energetics and kinetics of five electronic transitions related to the kinetic scheme of primary charge separation have been analyzed and compared to experimental observations. Nonergodic formulation of the reaction kinetics is required for the calculation of the rates due to a severe breakdown of the system ergodicity on the time scale of primary charge separation, with the consequent inapplicability of the standard canonical prescription to calculate the activation barrier. Common to all reactions studied is a significant excess of the charge-transfer reorganization energy from the width of the energy gap fluctuations over that from the Stokes shift of the transition. This property of the hydrated proteins, breaking the linear response of the thermal bath, allows the reaction center to significantly reduce the reaction free energy of near-activationless electron hops and thus raise the overall energetic efficiency of the biological charge-transfer chain. The increase of the rate of primary charge separation with cooling is explained in terms of the temperature variation of induction solvation, which dominates the average donor-acceptor energy gap for all electronic transitions in the reaction center. It is also suggested that the experimentally observed break in the Arrhenius slope of the primary recombination rate, occurring near the temperature of the dynamical transition in proteins, can be traced back to a significant drop of the solvent reorganization energy close to that temperature.

Toward Eco-Friendly and Highly Efficient Solar Water Splitting Using In2S3/Anatase/Rutile TiO2 Dual-Staggered-Heterojunction Nanodendrite Array Photoanode.

PubMed

Yang, Jih-Sheng; Wu, Jih-Jen

2018-01-31

The TiO 2 -based heterojunction nanodendrite (ND) array composed of anatase nanoparticles (ANPs) on the surface of the rutile ND (RND) array is selected as the model photoanode to demonstrate the strategies toward eco-friendly and efficient solar water splitting using neutral electrolyte and seawater. Compared with the performances in alkaline electrolyte, a non-negligible potential drop across the electrolyte as well as impeded charge injection and charge separation is monitored in the ANP/RND array photoanode with neutral electrolyte, which are, respectively, ascribed to the series resistance of neutral electrolyte, the fundamentally pH-dependent water oxidation mechanism on TiO 2 surface, as well as the less band bending at the interface of TiO 2 and neutral electrolyte. Accordingly, a TiO 2 -based dual-staggered heterojunction ND array photoanode is further designed in this work to overcome the issue of less band bending with the neutral electrolyte. The improvement of charge separation efficiency is realized by the deposition of a transparent In 2 S 3 layer on the ANP/RND array photoanode for constructing additional staggered heterojunction. Under illumination of AM 1.5G (100 mW cm -2 ), the improved photocurrent densities acquired both in neutral electrolyte and seawater at 1.23 V vs reversible hydrogen electrode (RHE), which approach the theoretical value for rutile TiO 2 , are demonstrated in the dual-staggered-heterojunction ND array photoanode. Faradaic efficiencies of ∼95 and ∼32% for solar water oxidation in neutral electrolyte and solar seawater oxidation for 2 h are acquired at 1.23 V vs RHE, respectively.

Enhancing the Efficiency of Silicon-Based Solar Cells by the Piezo-Phototronic Effect.

PubMed

Zhu, Laipan; Wang, Longfei; Pan, Caofeng; Chen, Libo; Xue, Fei; Chen, Baodong; Yang, Leijing; Su, Li; Wang, Zhong Lin

2017-02-28

Although there are numerous approaches for fabricating solar cells, the silicon-based photovoltaics are still the most widely used in industry and around the world. A small increase in the efficiency of silicon-based solar cells has a huge economic impact and practical importance. We fabricate a silicon-based nanoheterostructure (p + -Si/p-Si/n + -Si (and n-Si)/n-ZnO nanowire (NW) array) photovoltaic device and demonstrate the enhanced device performance through significantly enhanced light absorption by NW array and effective charge carrier separation by the piezo-phototronic effect. The strain-induced piezoelectric polarization charges created at n-doped Si-ZnO interfaces can effectively modulate the corresponding band structure and electron gas trapped in the n + -Si/n-ZnO NW nanoheterostructure and thus enhance the transport process of local charge carriers. The efficiency of the solar cell was improved from 8.97% to 9.51% by simply applying a static compress strain. This study indicates that the piezo-phototronic effect can enhance the performance of a large-scale silicon-based solar cell, with great potential for industrial applications.

Nanoimprinting-induced nanomorphological transition in polymer solar cells: enhanced electrical and optical performance.

PubMed

Jeong, Seonju; Cho, Changsoon; Kang, Hyunbum; Kim, Ki-Hyun; Yuk, Youngji; Park, Jeong Young; Kim, Bumjoon J; Lee, Jung-Yong

2015-03-24

We have investigated the effects of a directly nanopatterned active layer on the electrical and optical properties of inverted polymer solar cells (i-PSCs). The capillary force in confined molds plays a critical role in polymer crystallization and phase separation of the film. The nanoimprinting process induced improved crystallization and multidimensional chain alignment of polymers for more effective charge transfer and a fine phase-separation between polymers and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) to favor exciton dissociation and increase the generation rate of charge transfer excitons. Consequently, the power conversion efficiency with a periodic nanostructure was enhanced from 7.40% to 8.50% and 7.17% to 9.15% in PTB7 and PTB7-Th based i-PSCs, respectively.

Plasmon-induced charge separation: chemistry and wide applications.

PubMed

Tatsuma, Tetsu; Nishi, Hiroyasu; Ishida, Takuya

2017-05-01

Recent development of nanoplasmonics has stimulated chemists to utilize plasmonic nanomaterials for efficient and distinctive photochemical applications, and physicists to boldly go inside the "wet" chemistry world. The discovery of plasmon-induced charge separation (PICS) has even accelerated these trends. On the other hand, some confusion is found in discussions about PICS. In this perspective, we focus on differences between PICS and some other phenomena such as co-catalysis effect and plasmonic nanoantenna effect. In addition, materials and nanostructures suitable for PICS are shown, and characteristics and features unique to PICS are documented. Although it is well known that PICS has been applied to photovoltaics and photocatalysis, here light is shed on other applications that take better advantage of PICS, such as chemical sensing and biosensing, various photochromisms, photoswitchable functionalities and nanoscale photofabrication.

Preparation of ionic membranes for zinc/bromine storage batteries

NASA Astrophysics Data System (ADS)

Assink, R. A.; Arnold, C., Jr.

Zinc/bromine flow batteries are being developed for vehicular and utility load leveling applications. During charge, an aqueous zinc bromide salt is electrolyzed to zinc metal and molecular bromine. During discharge, the zinc and bromine react to again form the zinc bromide salt. One serious disadvantage of the microporous separators presently used in the zinc/bromine battery is that modest amounts of bromine and negatively charged bromine moieties permeate through these materials and react with the zinc anode. This results in partial self-discharge of the battery and low coulombic efficiencies. Our approach to this problem is to impregnate the microporous separators with a soluble cationic polyelectrolyte. In laboratory screening tests a sulfonated polysulfone resin and fully fluorinated sulfonic acid polymer substantially reduced bromine permeation with only modest increases in the area resistance.

Unified superresolution experiments and stochastic theory provide mechanistic insight into protein ion-exchange adsorptive separations

PubMed Central

Kisley, Lydia; Chen, Jixin; Mansur, Andrea P.; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Chen, Wen-Hsiang; Dhamane, Sagar; Willson, Richard C.; Landes, Christy F.

2014-01-01

Chromatographic protein separations, immunoassays, and biosensing all typically involve the adsorption of proteins to surfaces decorated with charged, hydrophobic, or affinity ligands. Despite increasingly widespread use throughout the pharmaceutical industry, mechanistic detail about the interactions of proteins with individual chromatographic adsorbent sites is available only via inference from ensemble measurements such as binding isotherms, calorimetry, and chromatography. In this work, we present the direct superresolution mapping and kinetic characterization of functional sites on ion-exchange ligands based on agarose, a support matrix routinely used in protein chromatography. By quantifying the interactions of single proteins with individual charged ligands, we demonstrate that clusters of charges are necessary to create detectable adsorption sites and that even chemically identical ligands create adsorption sites of varying kinetic properties that depend on steric availability at the interface. Additionally, we relate experimental results to the stochastic theory of chromatography. Simulated elution profiles calculated from the molecular-scale data suggest that, if it were possible to engineer uniform optimal interactions into ion-exchange systems, separation efficiencies could be improved by as much as a factor of five by deliberately exploiting clustered interactions that currently dominate the ion-exchange process only accidentally. PMID:24459184

Unified superresolution experiments and stochastic theory provide mechanistic insight into protein ion-exchange adsorptive separations.

PubMed

Kisley, Lydia; Chen, Jixin; Mansur, Andrea P; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Chen, Wen-Hsiang; Dhamane, Sagar; Willson, Richard C; Landes, Christy F

2014-02-11

Chromatographic protein separations, immunoassays, and biosensing all typically involve the adsorption of proteins to surfaces decorated with charged, hydrophobic, or affinity ligands. Despite increasingly widespread use throughout the pharmaceutical industry, mechanistic detail about the interactions of proteins with individual chromatographic adsorbent sites is available only via inference from ensemble measurements such as binding isotherms, calorimetry, and chromatography. In this work, we present the direct superresolution mapping and kinetic characterization of functional sites on ion-exchange ligands based on agarose, a support matrix routinely used in protein chromatography. By quantifying the interactions of single proteins with individual charged ligands, we demonstrate that clusters of charges are necessary to create detectable adsorption sites and that even chemically identical ligands create adsorption sites of varying kinetic properties that depend on steric availability at the interface. Additionally, we relate experimental results to the stochastic theory of chromatography. Simulated elution profiles calculated from the molecular-scale data suggest that, if it were possible to engineer uniform optimal interactions into ion-exchange systems, separation efficiencies could be improved by as much as a factor of five by deliberately exploiting clustered interactions that currently dominate the ion-exchange process only accidentally.

Observation of Internal Photoinduced Electron and Hole Separation in Hybrid Two-Dimentional Perovskite Films.

PubMed

Liu, Junxue; Leng, Jing; Wu, Kaifeng; Zhang, Jun; Jin, Shengye

2017-02-01

Two-dimensional (2D) organolead halide perovskites are promising for various optoelectronic applications. Here we report a unique spontaneous charge (electron/hole) separation property in multilayered (BA) 2 (MA) n-1 Pb n I 3n+1 (BA = CH 3 (CH 2 ) 3 NH 3 + , MA = CH 3 NH 3 + ) 2D perovskite films by studying the charge carrier dynamics using ultrafast transient absorption and photoluminescence spectroscopy. Surprisingly, the 2D perovskite films, although nominally prepared as "n = 4", are found to be mixture of multiple perovskite phases, with n = 2, 3, 4 and ≈ ∞, that naturally align in the order of n along the direction perpendicular to the substrate. Driven by the band alignment between 2D perovskites phases, we observe consecutive photoinduced electron transfer from small-n to large-n phases and hole transfer in the opposite direction on hundreds of picoseconds inside the 2D film of ∼358 nm thickness. This internal charge transfer efficiently separates electrons and holes to the upper and bottom surfaces of the films, which is a unique property beneficial for applications in photovoltaics and other optoelectronics devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cadiz, Fabian, E-mail: cadiz@insa-toulouse.fr; Tricard, Simon; Gay, Maxime

Developments in optoelectronics and spin-optronics based on transition metal dichalcogenide monolayers (MLs) need materials with efficient optical emission and well-defined transition energies. In as-exfoliated MoS{sub 2} MLs, the photoluminescence (PL) spectra even at low temperature consist typically of broad, overlapping contributions from neutral, charged excitons (trions) and localized states. Here, we show that in superacid treated MoS{sub 2} MLs, the PL intensity increases by up to 60 times at room temperature. The neutral and charged exciton transitions are spectrally well separated in PL and reflectivity at T = 4 K, with linewidth for the neutral exciton of 15 meV, but both transitions have similarmore » intensities compared to the ones in as-exfoliated MLs at the same temperature. Time resolved experiments uncover picoseconds recombination dynamics analyzed separately for charged and neutral exciton emissions. Using the chiral interband selection rules, we demonstrate optically induced valley polarization for both complexes and valley coherence for only the neutral exciton.« less

Inner-shell excitation and ionic fragmentation of molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hitchcock, A.P.; Tyliszczak, T.; Cavell, R.G.

1997-04-01

Inner-shell excitation and associated decay spectroscopies are site specific probes of electronic and geometrical structure and photoionization dynamics. X-ray absorption probes the geometric and electronic structure, while time-of-flight mass spectrometry with multi-coincidence detection provides information on the photofragmentation dynamics of the initially produced inner-shell state. Auger decay of inner-shell excited and ionised states is an efficient source of multiply charged ions. The charge separation and fragmentation of these species, studied by photoelectron-photoion-photoion coincidence (also called charge separation mass spectrometry) gives insights into bonding and electronic structure. In molecules, the dependence of the fragmentation process on the X-ray energy can revealmore » cases of site and/or state selective fragmentation. At the ALS the authors have examined the soft X-ray spectroscopy and ionic fragmentation of a number of molecules, including carboranes, silylenes, phosphorus halides, SF{sub 6} and CO{sub 2}. Their work is illustrated using results from the carborane and PF{sub 3} studies.« less

Direct Observation of Photoinduced Charge Separation in Ruthenium Complex/Ni(OH) 2 Nanoparticle Hybrid

DOE PAGES

Tang, Yu; Pattengale, Brian A.; Ludwig, John M.; ...

2015-12-17

We report that Ni(OH) 2 have emerged as important functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen and oxygen evolution reactions. However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions remain unexplored. In this paper, we investigate the CS dynamics of a newly designed hybrid catalyst by integrating a Ru complex with Ni(OH) 2 nanoparticles (NPs). Using time resolved X-ray absorption spectroscopy (XTA), we directly observed the formation of the reduced Ni metal site (~60 ps), unambiguously demonstrating CS process in the hybrid through ultrafast electron transfer frommore » Ru complex to Ni(OH) 2 NPs. Compared to the ultrafast CS process, the charge recombination in the hybrid is ultraslow (>>50 ns). These results not only suggest the possibility of developing Ni(OH) 2 as solar fuel catalysts, but also represent the first time direct observation of efficient CS in a hybrid catalyst using XTA.« less

Band alignment and charge transfer predictions of ZnO/ZnX (X = S, Se or Te) interfaces applied to solar cells: a PBE+U theoretical study.

PubMed

Flores, Efracio Mamani; Gouvea, Rogério Almeida; Piotrowski, Maurício Jeomar; Moreira, Mário Lucio

2018-02-14

The engineering of semiconductor materials for the development of solar cells is of great importance today. Two topics are considered to be of critical importance for the efficiency of Grätzel-type solar cells, the efficiency of charge separation and the efficiency of charge carrier transfer. Thus, one research focus is the combination of semiconductor materials with the aim of reducing charge recombination, which occurs by spatial charge separation. From an experimental point of view, the combining of materials can be achieved by decorating a core with a shell of another material resulting in a core-shell system, which allows control of the desired photoelectronic properties. In this context, a computational simulation is mandatory for the atomistic understanding of possible semiconductor combinations and for the prediction of their properties. Considering the construction of ZnO/ZnX (X = S, Se or Te) interfaces, we seek to investigate the electronic influence of the shell (ZnX) on the core (ZnO) and, consequently, find out which of the interfaces would present the appropriate properties for (Grätzel-type) solar cell applications. To perform this study, we have employed density functional theory (DFT) calculations, considering the Perdew-Burke-Ernzerhof (PBE) functional. However, it is well-known that plain DFT fails to describe strong electronic correlated materials where, in general, an underestimation of the band gap is obtained. Thus, to obtain the correct description of the electronic properties, a Hubbard correction was employed, i.e. PBE+U calculations. The PBE+U methodology provided the correct electronic structure properties for bulk ZnO in good agreement with experimental values (99.4%). The ZnO/ZnX interfaces were built and were composed of six ZnO layers and two ZnX layers, which represents the decoration process. The core-shell band gap was 2.2 eV for ZnO/ZnS, ∼1.71 eV for ZnO/ZnSe and ∼0.95 eV for ZnO/ZnTe, which also exhibited a type-II band alignment. Bader charge analysis showed an accumulation of charges in the 6th layer of ZnO for the three ZnO/ZnX interfaces. On the basis of these results, we have proposed that ZnO/ZnS and ZnO/ZnSe core-shell structures can be applied as good candidates (with better efficiency) for photovoltaic devices.

An insight into the mechanism of charge-transfer of hybrid polymer:ternary/quaternary chalcopyrite colloidal nanocrystals.

PubMed

Chawla, Parul; Singh, Son; Sharma, Shailesh Narain

2014-01-01

In this work, we have demonstrated the structural and optoelectronic properties of the surface of ternary/quaternary (CISe/CIGSe/CZTSe) chalcopyrite nanocrystallites passivated by tri-n-octylphosphine-oxide (TOPO) and tri-n-octylphosphine (TOP) and compared their charge transfer characteristics in the respective polymer: chalcopyrite nanocomposites by dispersing them in poly(3-hexylthiophene) polymer. It has been found that CZTSe nanocrystallites due to their high crystallinity and well-ordered 3-dimensional network in its pristine form exhibit a higher steric- and photo-stability, resistance against coagulation and homogeneity compared to the CISe and CIGSe counterparts. Moreover, CZTSe nanocrystallites display efficient photoluminescence quenching as evident from the high value of the Stern-Volmer quenching constant (K SV) and eventually higher charge transfer efficiency in their respective polymer P3HT:CZTSe composites. We modelled the dependency of the charge transfer from the donor and the charge separation mechanism across the donor-acceptor interface from the extent of crystallinity of the chalcopyrite semiconductors (CISe/CIGSe/CZTSe). Quaternary CZTSe chalcopyrites with their high crystallinity and controlled morphology in conjunction with regioregular P3HT polymer is an attractive candidate for hybrid solar cells applications.

Novel High Efficient Organic Photovoltaic Materials

NASA Technical Reports Server (NTRS)

Sun, Sam; Haliburton, James; Wang, Yi-Qing; Fan, Zhen; Taft, Charles; Maaref, Shahin; Bailey, Sheila (Technical Monitor)

2003-01-01

Solar energy is a renewable, nonpolluting, and most abundant energy source for human exploration of a remote site or outer space. In order to generate appreciable electrical power in space or on the earth, it is necessary to collect sunlight from large areas and with high efficiency due to the low density of sunlight. Future organic or polymer (plastic) solar cells appear very attractive due to their unique features such as light weight, flexible shape, tunability of energy band-gaps via versatile molecular or supramolecular design, synthesis, processing and device fabrication schemes, and much lower cost on large scale industrial production. It has been predicted that supramolecular and nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks may facilitate the charge carrier separation and migration due to improved electronic ultrastructure and morphology in comparison to polymer composite system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel block copolymer system containing donor and acceptor blocks covalently attached. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene (RO-PPV), the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene (SF-PPV). The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block has a strong PL emission at around 560 nm, and acceptor block has a strong PL emission at around 520 nm, the PL emissions of final block copolymers are severely quenched. This verifies the expected electron transfer and charge separation due to interfaces of donor and acceptor nano phase separated blocks. The system therefore has potential for variety light harvesting applications, including high efficient photovoltaic applications.

A semiempirical study for the ground and excited states of free-base and zinc porphyrin-fullerene dyads

NASA Technical Reports Server (NTRS)

Parusel, A. B.

2000-01-01

The ground and excited states of a covalently linked porphyrin-fullerene dyad in both its free-base and zinc forms (D. Kuciauskas et al., J. Phys. Chem. 100 (1996) 15926) have been investigated by semiempirical methods. The excited-state properties are discussed by investigation of the character of the molecular orbitals. All frontier MOs are mainly localized on either the donor or the acceptor subunit. Thus, the absorption spectra of both systems are best described as the sum of the spectra of the single components. The experimentally observed spectra are well reproduced by the theoretical computations. Both molecules undergo efficient electron transfer in polar but not in apolar solvents. This experimental finding is explained theoretically by explicitly considering solvent effects. The tenth excited state in the gas phase is of charge-separated character where an electron is transferred from the porphyrin donor to the fullerene acceptor subunit. This state is stabilized in energy in polar solvents due to its large formal dipole moment. The stabilization energy for an apolar environment such as benzene is not sufficient to lower this state to become the first excited singlet state. Thus, no electron transfer is observed, in agreement with experiment. In a polar environment such as acetonitrile, the charge-separated state becomes the S, state and electron transfer takes place, as observed experimentally. The flexible single bond connecting both the donor and acceptor subunits allows free rotation by ca. +/- 30 degrees about the optimized ground-state conformation. For the charge-separated state this optimized geometry has a maximum dipole moment. The geometry of the charge-separated state thus does not change relatively to the ground-state conformation. The electron-donating properties of porphyrin are enhanced in the zinc derivative due to a reduced porphyrin HOMO-LUMO energy gap. This yields a lower energy for the charge-separated state compared to the free-base dyad.

Physical aspects of ferroelectric semiconductors for photovoltaic solar energy conversion

NASA Astrophysics Data System (ADS)

Lopez-Varo, Pilar; Bertoluzzi, Luca; Bisquert, Juan; Alexe, Marin; Coll, Mariona; Huang, Jinsong; Jimenez-Tejada, Juan Antonio; Kirchartz, Thomas; Nechache, Riad; Rosei, Federico; Yuan, Yongbo

2016-10-01

Solar energy conversion using semiconductors to fabricate photovoltaic devices relies on efficient light absorption, charge separation of electron-hole pair carriers or excitons, and fast transport and charge extraction to counter recombination processes. Ferroelectric materials are able to host a permanent electrical polarization which provides control over electrical field distribution in bulk and interfacial regions. In this review, we provide a critical overview of the physical principles and mechanisms of solar energy conversion using ferroelectric semiconductors and contact layers, as well as the main achievements reported so far. In a ferroelectric semiconductor film with ideal contacts, the polarization charge would be totally screened by the metal layers and no charge collection field would exist. However, real materials show a depolarization field, smooth termination of polarization, and interfacial energy barriers that do provide the control of interface and bulk electric field by switchable spontaneous polarization. We explore different phenomena as the polarization-modulated Schottky-like barriers at metal/ferroelectric interfaces, depolarization fields, vacancy migration, and the switchable rectifying behavior of ferroelectric thin films. Using a basic physical model of a solar cell, our analysis provides a general picture of the influence of ferroelectric effects on the actual power conversion efficiency of the solar cell device, and we are able to assess whether these effects or their combinations are beneficial or counterproductive. We describe in detail the bulk photovoltaic effect and the contact layers that modify the built-in field and the charge injection and separation in bulk heterojunction organic cells as well as in photocatalytic and water splitting devices. We also review the dominant families of ferroelectric materials that have been most extensively investigated and have provided the best photovoltaic performance.

Self-Assembly Strategies for Integrating Light Harvesting and Charge Separation in Artificial Photosynthetic Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wasielewski, Michael R.

In natural photosynthesis, organisms optimize solar energy conversion through organized assemblies of photofunctional chromophores and catalysts within proteins that provide specifically tailored environments for chemical reactions. As with their natural counterparts, artificial photosynthetic systems for practical solar fuels production must collect light energy, separate charge, and transport charge to catalytic sites where multielectron redox processes will occur. While encouraging progress has been made on each aspect of this complex problem, researchers have not yet developed self-ordering and self-assembling components and the tailored environments necessary to realize a fully-functional artificial system. Previously researchers have used complex, covalent molecular systems comprised ofmore » chromophores, electron donors, and electron acceptors to mimic both the light-harvesting and the charge separation functions of photosynthetic proteins. These systems allow for study of the dependencies of electron transfer rate constants on donor?acceptor distance and orientation, electronic interaction, and the free energy of the reaction. The most useful and informative systems are those in which structural constraints control both the distance and the orientation between the electron donors and acceptors. Self-assembly provides a facile means for organizing large numbers of molecules into supramolecular structures that can bridge length scales from nanometers to macroscopic dimensions. The resulting structures must provide pathways for migration of light excitation energy among antenna chromophores, and from antennas to reaction centers. They also must incorporate charge conduits, that is, molecular 'wires' that can efficiently move electrons and holes between reaction centers and catalytic sites. The central scientific challenge is to develop small, functional building blocks with a minimum number of covalent linkages, which also have the appropriate molecular recognition properties to facilitate self-assembly of complete, functional artificial photosynthetic systems. In this Account, we explore how self-assembly strategies involving ?-stacking can be used to integrate light harvesting with charge separation and transport.« less

Separation analysis of macrolide antibiotics with good performance on a positively charged C18HCE column.

PubMed

Wei, Jie; Shen, Aijin; Yan, Jingyu; Jin, Gaowa; Yang, Bingcheng; Guo, Zhimou; Zhang, Feifang; Liang, Xinmiao

2016-03-01

The separation of basic macrolide antibiotics suffers from peak tailing and poor efficiency on traditional silica-based reversed-phase liquid chromatography columns. In this work, a C18HCE column with positively charged surface was applied to the separation of macrolides. Compared with an Acquity BEH C18 column, the C18HCE column exhibited superior performance in the aspect of peak shape and separation efficiency. The screening of mobile phase additives including formic acid, acetic acid and ammonium formate indicated that formic acid was preferable for providing symmetrical peak shapes. Moreover, the influence of formic acid content was investigated. Analysis speed and mass spectrometry compatibility were also taken into account when optimizing the separation conditions for liquid chromatography coupled with tandem mass spectrometry. The developed method was successfully utilized for the determination of macrolide residues in a honey sample. Azithromycin was chosen as the internal standard for the quantitation of spiramycin and tilmicosin, while roxithromycin was used for erythromycin, tylosin, clarithromycin, josamycin and acetylisovaleryltylosin. Good correlation coefficients (r(2) > 0.9938) for all macrolides were obtained. The intra-day and inter-day recoveries were 73.7-134.7% and 80.7-119.7% with relative standard deviations of 2.5-8.0% and 3.9-16.1%, respectively. Outstanding sensitivity with limits of quantitation (S/N ≥ 10) of 0.02-1 μg/kg and limits of detection (S/N ≥ 3) of 0.01-0.5 μg/kg were achieved. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Monte Carlo (N,V,T) study of the stability of charged interfaces: A simulation on a hypersphere

NASA Astrophysics Data System (ADS)

Delville, A.; Pellenq, R. J.-M.; Caillol, J. M.

1997-05-01

We have used an exact expression of the Coulombic interactions derived on a hypersphere of an Euclidian space of dimension four to determine the swelling behavior of two infinite charged plates neutralized by exchangeable counterions. Monte Carlo simulations in the (N,V,T) ensemble allows for a derivation of short-ranged hard core repulsions and long-ranged electrostatic forces, which are the two components of the interionic forces in the context of the primitive model. Comparison with numerical results obtained by a classical Euclidian method illustrates the efficiency of the hyperspherical approach, especially at strong coupling between the charged particles, i.e., for divalent counterions and small plate separation.

Factors that influence the efficiency of a fluidized-bed-type tribo-electrostatic separator for mixed granular plastics

NASA Astrophysics Data System (ADS)

Dascalescu, L.; Fati, O.; Bilici, M.; Rahou, F.; Dragan, C.; Samuila, A.; Iuga, A.

2011-06-01

Fluidized bed devices have already been used as tribochargers for various industrial electrostatic separation processes. In the present paper, the authors investigate the behaviour of polyamide - polycarbonate granular plastic mixtures in a parallelepiped bed, the height of which is roughly 2 times its length or width, so that the collisions between granules become the prevailing tribocharging mechanism. Two of the opposite walls of the tribocharging chamber consist of metallic plates connected to two DC high-voltage supplies of opposite polarities, so that the charged particles are attracted to the electrodes and separated while still in the fluidized state. The collecting hoppers are designed as Faraday cups connected to two electrometers, thus allowing the instantaneous measurement of the charge carried by the separated particles. Experimental design methodology was employed for the optimization of the tribo-aero-electrostatic separation process, the input variables being the high-voltage applied to the electrodes and the duration of the tribocharging. Higher voltages applied to the electrode system do not necessarily lead to larger quantities of collected products but improve the purity of the concentrates. The composition of the mixture influences the outcome of the process.

Energy transfer in light-adapted photosynthetic membranes: from active to saturated photosynthesis.

PubMed

Fassioli, Francesca; Olaya-Castro, Alexandra; Scheuring, Simon; Sturgis, James N; Johnson, Neil F

2009-11-04

In bacterial photosynthesis light-harvesting complexes, LH2 and LH1 absorb sunlight energy and deliver it to reaction centers (RCs) with extraordinarily high efficiency. Submolecular resolution images have revealed that both the LH2:LH1 ratio, and the architecture of the photosynthetic membrane itself, adapt to light intensity. We investigate the functional implications of structural adaptations in the energy transfer performance in natural in vivo low- and high-light-adapted membrane architectures of Rhodospirillum photometricum. A model is presented to describe excitation migration across the full range of light intensities that cover states from active photosynthesis, where all RCs are available for charge separation, to saturated photosynthesis where all RCs are unavailable. Our study outlines three key findings. First, there is a critical light-energy density, below which the low-light adapted membrane is more efficient at absorbing photons and generating a charge separation at RCs, than the high-light-adapted membrane. Second, connectivity of core complexes is similar in both membranes, suggesting that, despite different growth conditions, a preferred transfer pathway is through core-core contacts. Third, there may be minimal subareas on the membrane which, containing the same LH2:LH1 ratio, behave as minimal functional units as far as excitation transfer efficiency is concerned.

Charge-Transfer Processes in Warm Dense Matter: Selective Spectral Filtering for Laser-Accelerated Ion Beams

NASA Astrophysics Data System (ADS)

Braenzel, J.; Barriga-Carrasco, M. D.; Morales, R.; Schnürer, M.

2018-05-01

We investigate, both experimentally and theoretically, how the spectral distribution of laser accelerated carbon ions can be filtered by charge exchange processes in a double foil target setup. Carbon ions at multiple charge states with an initially wide kinetic energy spectrum, from 0.1 to 18 MeV, were detected with a remarkably narrow spectral bandwidth after they had passed through an ultrathin and partially ionized foil. With our theoretical calculations, we demonstrate that this process is a consequence of the evolution of the carbon ion charge states in the second foil. We calculated the resulting spectral distribution separately for each ion species by solving the rate equations for electron loss and capture processes within a collisional radiative model. We determine how the efficiency of charge transfer processes can be manipulated by controlling the ionization degree of the transfer matter.

Functional Two-Dimensional Coordination Polymeric Layer as a Charge Barrier in Li-S Batteries.

PubMed

Huang, Jing-Kai; Li, Mengliu; Wan, Yi; Dey, Sukumar; Ostwal, Mayur; Zhang, Daliang; Yang, Chih-Wen; Su, Chun-Jen; Jeng, U-Ser; Ming, Jun; Amassian, Aram; Lai, Zhiping; Han, Yu; Li, Sean; Li, Lain-Jong

2018-01-23

Ultrathin two-dimensional (2D) polymeric layers are capable of separating gases and molecules based on the reported size exclusion mechanism. What is equally important but missing today is an exploration of the 2D layers with charge functionality, which enables applications using the charge exclusion principle. This work demonstrates a simple and scalable method of synthesizing a free-standing 2D coordination polymer Zn 2 (benzimidazolate) 2 (OH) 2 at the air-water interface. The hydroxyl (-OH) groups are stoichiometrically coordinated and implement electrostatic charges in the 2D structures, providing powerful functionality as a charge barrier. Electrochemical performance of the Li-S battery shows that the Zn 2 (benzimidazolate) 2 (OH) 2 coordination polymer layers efficiently mitigate the polysulfide shuttling effects and largely enhance the battery capacity and cycle performance. The synthesis of the proposed coordination polymeric layers is simple, scalable, cost saving, and promising for practical use in batteries.

A Nonfullerene Small Molecule Acceptor with 3D Interlocking Geometry Enabling Efficient Organic Solar Cells.

PubMed

Lee, Jaewon; Singh, Ranbir; Sin, Dong Hun; Kim, Heung Gyu; Song, Kyu Chan; Cho, Kilwon

2016-01-06

A new 3D nonfullerene small-molecule acceptor is reported. The 3D interlocking geometry of the small-molecule acceptor enables uniform molecular conformation and strong intermolecular connectivity, facilitating favorable nanoscale phase separation and electron charge transfer. By employing both a novel polymer donor and a nonfullerene small-molecule acceptor in the solution-processed organic solar cells, a high-power conversion efficiency of close to 6% is demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Molecular Stresses on Energy Transfer Pathways in Opto- and Electro-Excited Conjugated Polymers for High-Efficiency Optoelectronic Devices

DTIC Science & Technology

2014-10-20

unless it hops, and lead to obstructed recombination for PL or charge separation for solar cells and the reduced quantum efficiencies of the...excitons (Fig. 1a and 1b). For the free-moving delocalized states of the Wannier-Mott excitons, the binding energy in silicon , for example, is around...typically encompass many unit cells and typically exist in materials of small bandgap and large dielectric constant. In converse, the the tightly

Adsorptive removal and separation of chemicals with metal-organic frameworks: Contribution of π-complexation.

PubMed

Khan, Nazmul Abedin; Jhung, Sung Hwa

2017-03-05

Efficient removal and separation of chemicals from the environment has become a vital issue from a biological and environmental point of view. Currently, adsorptive removal/separation is one of the most promising approaches for cleaning purposes. Selective adsorption/removal of various sulfur- and nitrogen-containing compounds, olefins, and π-electron-rich gases via π-complex formation between an adsorbent and adsorbate molecules is very competitive. Porous metal-organic framework (MOF) materials are very promising in the adsorption/separation of various liquids and gases owing to their distinct characteristics. This review summarizes the literature on the adsorptive removal/separation of various π-electron-rich compounds mainly from fuel and gases using MOF materials containing metal ions that are active for π-complexation. Details of the π-complexation, including mechanism, pros/cons, applications, and efficient ways to form the complex, are discussed systematically. For in-depth understanding, molecular orbital calculations regarding charge transfer between the π-complexing species are also explained in a separate section. From this review, readers will gain an understanding of π-complexation for adsorption and separation, especially with MOFs, to develop new insight for future research. Copyright © 2016 Elsevier B.V. All rights reserved.

Interfacial charge separation and photovoltaic efficiency in Fe(ii)-carbene sensitized solar cells.

PubMed

Pastore, Mariachiara; Duchanois, Thibaut; Liu, Li; Monari, Antonio; Assfeld, Xavier; Haacke, Stefan; Gros, Philippe C

2016-10-12

The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(ii)-carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(ii)-NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(ii)-carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications.

Multimodal charge-induction chromatography for antibody purification.

PubMed

Tong, Hong-Fei; Lin, Dong-Qiang; Chu, Wen-Ning; Zhang, Qi-Lei; Gao, Dong; Wang, Rong-Zhu; Yao, Shan-Jing

2016-01-15

Hydrophobic charge-induction chromatography (HCIC) has advantages of high capacity, salt-tolerance and convenient pH-controlled elution. However, the binding specificity might be improved with multimodal molecular interactions. New ligand W-ABI that combining tryptophan and 5-amino-benzimidazole was designed with the concept of mutimodal charge-induction chromatography (MCIC). The indole and benzimidazole groups of the ligand could provide orientated mutimodal binding to target IgG under neutral pH, while the imidazole groups could induce the electrostatic repulsion forces for efficient elution under acidic pH. W-ABI ligand was coupled successfully onto agarose gel, and IgG adsorption behaviors were investigated. High affinity to IgG was found with the saturated adsorption capacity of 70.4 mg/ml at pH 7, and the flow rate of mobile phase showed little impact on the dynamic binding capacity. In addition, efficient elution could be achieved at mild acidic pH with high recovery. Two separation cases (IgG separation from albumin containing feedstock and monoclonal antibody purification from cell culture supernatant) were verified with high purity and recovery. In general, MCIC with the specially-designed ligand is an expanding of HCIC with improved adsorption selectivity, which would be a potential alternative to Protein A-based capture for the cost-effective purification of antibodies. Copyright © 2015 Elsevier B.V. All rights reserved.

Staggered Mesh Ewald: An extension of the Smooth Particle-Mesh Ewald method adding great versatility

PubMed Central

Cerutti, David S.; Duke, Robert E.; Darden, Thomas A.; Lybrand, Terry P.

2009-01-01

We draw on an old technique for improving the accuracy of mesh-based field calculations to extend the popular Smooth Particle Mesh Ewald (SPME) algorithm as the Staggered Mesh Ewald (StME) algorithm. StME improves the accuracy of computed forces by up to 1.2 orders of magnitude and also reduces the drift in system momentum inherent in the SPME method by averaging the results of two separate reciprocal space calculations. StME can use charge mesh spacings roughly 1.5× larger than SPME to obtain comparable levels of accuracy; the one mesh in an SPME calculation can therefore be replaced with two separate meshes, each less than one third of the original size. Coarsening the charge mesh can be balanced with reductions in the direct space cutoff to optimize performance: the efficiency of StME rivals or exceeds that of SPME calculations with similarly optimized parameters. StME may also offer advantages for parallel molecular dynamics simulations because it permits the use of coarser meshes without requiring higher orders of charge interpolation and also because the two reciprocal space calculations can be run independently if that is most suitable for the machine architecture. We are planning other improvements to the standard SPME algorithm, and anticipate that StME will work synergistically will all of them to dramatically improve the efficiency and parallel scaling of molecular simulations. PMID:20174456

Color-selective photodetection from intermediate colloidal quantum dots buried in amorphous-oxide semiconductors.

PubMed

Cho, Kyung-Sang; Heo, Keun; Baik, Chan-Wook; Choi, Jun Young; Jeong, Heejeong; Hwang, Sungwoo; Lee, Sang Yeol

2017-10-10

We report color-selective photodetection from intermediate, monolayered, quantum dots buried in between amorphous-oxide semiconductors. The proposed active channel in phototransistors is a hybrid configuration of oxide-quantum dot-oxide layers, where the gate-tunable electrical property of silicon-doped, indium-zinc-oxide layers is incorporated with the color-selective properties of quantum dots. A remarkably high detectivity (8.1 × 10 13 Jones) is obtained, along with three major findings: fast charge separation in monolayered quantum dots; efficient charge transport through high-mobility oxide layers (20 cm 2  V -1  s -1 ); and gate-tunable drain-current modulation. Particularly, the fast charge separation rate of 3.3 ns -1 measured with time-resolved photoluminescence is attributed to the intermediate quantum dots buried in oxide layers. These results facilitate the realization of efficient color-selective detection exhibiting a photoconductive gain of 10 7 , obtained using a room-temperature deposition of oxide layers and a solution process of quantum dots. This work offers promising opportunities in emerging applications for color detection with sensitivity, transparency, and flexibility.The development of highly sensitive photodetectors is important for image sensing and optical communication applications. Cho et al., report ultra-sensitive photodetectors based on monolayered quantum dots buried in between amorphous-oxide semiconductors and demonstrate color-detecting logic gates.

Integration of Semiconducting Sulfides for Full-Spectrum Solar Energy Absorption and Efficient Charge Separation.

PubMed

Zhuang, Tao-Tao; Liu, Yan; Li, Yi; Zhao, Yuan; Wu, Liang; Jiang, Jun; Yu, Shu-Hong

2016-05-23

The full harvest of solar energy by semiconductors requires a material that simultaneously absorbs across the whole solar spectrum and collects photogenerated electrons and holes separately. The stepwise integration of three semiconducting sulfides, namely ZnS, CdS, and Cu2-x S, into a single nanocrystal, led to a unique ternary multi-node sheath ZnS-CdS-Cu2-x S heteronanorod for full-spectrum solar energy absorption. Localized surface plasmon resonance (LSPR) in the nonstoichiometric copper sulfide nanostructures enables effective NIR absorption. More significantly, the construction of pn heterojunctions between Cu2-x S and CdS leads to staggered gaps, as confirmed by first-principles simulations. This band alignment causes effective electron-hole separation in the ternary system and hence enables efficient solar energy conversion. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasmonic Landau damping in active environments

NASA Astrophysics Data System (ADS)

Thakkar, Niket; Montoni, Nicholas P.; Cherqui, Charles; Masiello, David J.

2018-03-01

Optical manipulation of charge on the nanoscale is of fundamental importance to an array of proposed technologies from selective photocatalysis to nanophotonics. Open plasmonic systems where collective electron oscillations release energy and charge to their environments offer a potential means to this end as plasmons can rapidly decay into energetic electron-hole pairs; however, isolating this decay from other plasmon-environment interactions remains a challenge. Here we present an analytic theory of noble-metal nanoparticles that quantitatively models plasmon decay into electron-hole pairs, demonstrates that this decay depends significantly on the nanoparticle's dielectric environment, and disentangles this effect from competing decay pathways. Using our approach to incorporate embedding material and substrate effects on plasmon-electron interaction, we show that predictions from the model agree with four separate experiments. Finally, examination of coupled nanoparticle-emitter systems further shows that the hybridized in-phase mode more efficiently decays to photons whereas the out-of-phase mode more efficiently decays to electron-hole pairs, offering a strategy to tailor open plasmonic systems for charge manipulation.

Simulations of Coulomb systems with slab geometry using an efficient 3D Ewald summation method

NASA Astrophysics Data System (ADS)

dos Santos, Alexandre P.; Girotto, Matheus; Levin, Yan

2016-04-01

We present a new approach to efficiently simulate electrolytes confined between infinite charged walls using a 3d Ewald summation method. The optimal performance is achieved by separating the electrostatic potential produced by the charged walls from the electrostatic potential of electrolyte. The electric field produced by the 3d periodic images of the walls is constant inside the simulation cell, with the field produced by the transverse images of the charged plates canceling out. The non-neutral confined electrolyte in an external potential can be simulated using 3d Ewald summation with a suitable renormalization of the electrostatic energy, to remove a divergence, and a correction that accounts for the conditional convergence of the resulting lattice sum. The new algorithm is at least an order of magnitude more rapid than the usual simulation methods for the slab geometry and can be further sped up by adopting a particle-particle particle-mesh approach.

Upconversion-Triggered Charge Separation in Polymer Semiconductors.

PubMed

Jang, Yu Jin; Kim, Eunah; Ahn, Seonghyeon; Chung, Kyungwha; Kim, Jihyeon; Kim, Heejun; Wang, Huan; Lee, Jiseok; Kim, Dong-Wook; Kim, Dong Ha

2017-01-19

Upconversion is a unique optical property that is driven by a sequential photon pumping and generation of higher energy photons in a consecutive manner. The efficiency improvement in photovoltaic devices can be achieved when upconverters are integrated since upconverters contribute to the generation of extra photons. Despite numerous experimental studies confirming the relationship, fundamental explanations for a real contribution of upconversion to photovoltaic efficiency are still in demand. In this respect, we suggest a new approach to visualize the upconversion event in terms of surface photovoltage (SPV) by virtue of Kelvin probe force microscopy (KPFM). One of the most conventional polymer semiconductors, poly(3-hexyl thiophene) (P3HT), is employed as a sensitizer to generate charge carriers by upconverted light. KPFM measurements reveal that the light upconversion enabled the formation of charge carriers in P3HT, resulting in large SPV of -54.9 mV. It confirms that the energy transfer from upconverters to P3HT can positively impact the device performance in organic solar cells (OSCs).

Cooling of trapped ions by resonant charge exchange

NASA Astrophysics Data System (ADS)

Dutta, Sourav; Rangwala, S. A.

2018-04-01

The two most widely used ion cooling methods are laser cooling and sympathetic cooling by elastic collisions (ECs). Here, we demonstrate another method of cooling ions that is based on resonant charge exchange (RCE) between the trapped ion and the ultracold parent atom. Specifically, trapped C s+ ions are cooled by collisions with cotrapped, ultracold Cs atoms and, separately, by collisions with cotrapped, ultracold Rb atoms. We observe that the cooling of C s+ ions by Cs atoms is more efficient than the cooling of C s+ ions by Rb atoms. This signals the presence of a cooling mechanism apart from the elastic ion-atom collision channel for the Cs-C s+ case, which is cooling by RCE. The efficiency of cooling by RCE is experimentally determined and the per-collision cooling is found to be two orders of magnitude higher than cooling by EC. The result provides the experimental basis for future studies on charge transport by electron hopping in atom-ion hybrid systems.

Plasmon-induced charge separation: chemistry and wide applications

PubMed Central

Nishi, Hiroyasu; Ishida, Takuya

2017-01-01

Recent development of nanoplasmonics has stimulated chemists to utilize plasmonic nanomaterials for efficient and distinctive photochemical applications, and physicists to boldly go inside the “wet” chemistry world. The discovery of plasmon-induced charge separation (PICS) has even accelerated these trends. On the other hand, some confusion is found in discussions about PICS. In this perspective, we focus on differences between PICS and some other phenomena such as co-catalysis effect and plasmonic nanoantenna effect. In addition, materials and nanostructures suitable for PICS are shown, and characteristics and features unique to PICS are documented. Although it is well known that PICS has been applied to photovoltaics and photocatalysis, here light is shed on other applications that take better advantage of PICS, such as chemical sensing and biosensing, various photochromisms, photoswitchable functionalities and nanoscale photofabrication. PMID:28507702

Ion-exchange chromatography purification of extracellular vesicles.

PubMed

Kosanović, Maja; Milutinović, Bojana; Goč, Sanja; Mitić, Ninoslav; Janković, Miroslava

2017-08-01

Despite numerous studies, isolating pure preparations of extracellular vesicles (EVs) has proven challenging. Here, we compared ion-exchange chromatography (IEC) to the widely used sucrose density gradient (SDG) centrifugation method for the purification of EVs. EVs in bulk were isolated from pooled normal human amniotic fluid (AF) by differential centrifugation followed by IEC or sucrose density gradient separation. The purity of the isolated EVs was evaluated by electrophoresis and lectin blotting/immuno blotting to monitor the distribution of total proteins, different EVs markers, and selected N-glycans. Our data showed efficient separation of negatively charged EVs from other differently charged molecules, while comparative profiling of EVs using SDG centrifugation confirmed anion-exchange chromatography is advantageous for EV purification. Finally, although this IEC-based method was validated using AF, the approach should be readily applicable to isolation of EVs from other sources as well.

Role of Amines in Thermal-Runaway-Mitigating Lithium-Ion Battery.

PubMed

Shi, Yang; Noelle, Daniel J; Wang, Meng; Le, Anh V; Yoon, Hyojung; Zhang, Minghao; Meng, Ying Shirley; Qiao, Yu

2016-11-16

Benzylamine (BA), dibenzylamine (DBA), and trihexylamine (THA) are investigated as thermal-runaway retardants (TRR) for lithium-ion batteries (LIBs). In a LIB, TRR is packaged separately and released when internal shorting happens, so as to suppress exothermic reactions and slow down temperature increase. THA is identified as the most efficient TRR. Upon nail penetration, 4 wt % THA can reduce the peak temperature by nearly 50%. The working mechanisms of the three amines are different: THA is highly wettable to the separator and immiscible with the electrolyte, and therefore, it blocks lithium-ion (Li + ) transport. BA and DBA decrease the ionic conductivity of electrolyte and increase the charge transfer resistance. All three amines react with charged electrodes; the reactions of DBA and THA do not have much influence on the overall heat generation, while the reaction of BA cannot be ignored.

Nanotechnologies for efficient solar and wind energy harvesting and storage

NASA Astrophysics Data System (ADS)

Eldada, Louay A.

2010-08-01

We describe nanotechnologies used to improve the efficient harvest of energy from the Sun and the wind, and the efficient storage of energy in secondary batteries and ultracapacitors, for use in a variety of applications including smart grids, electric vehicles, and portable electronics. We demonstrate high-quality nanostructured copper indium gallium selenide (CIGS) thin films for photovoltaic (PV) applications. The self-assembly of nanoscale p-n junction networks creates n-type networks that act as preferential electron pathways, and p-type networks that act as preferential hole pathways, allowing positive and negative charges to travel to the contacts in physically separated paths, reducing charge recombination. We also describe PV nanotechnologies used to enhance light trapping, photon absorption, charge generation, charge transport, and current collection. Furthermore, we describe nanotechnologies used to improve the efficiency of power-generating wind turbines. These technologies include nanoparticle-containing lubricants that reduce the friction generated from the rotation of the turbines, nanocoatings for de-icing and self-cleaning technologies, and advanced nanocomposites that provide lighter and stronger wind blades. Finally, we describe nanotechnologies used in advanced secondary batteries and ultracapacitors. Nanostructured powder-based and carbon-nanotube-based cathodes and anodes with ultra-high surface areas boost the energy and power densities in secondary batteries, including lithium-ion and sodium-sulfur batteries. Nanostructured carbon materials are also controlled on a molecular level to offer large surface areas for the electrodes of ultracapacitors, allowing to store and supply large bursts of energy needed in some applications.

Colloidal aspects and packing behaviour of charged microparticulates in high efficiency ion chromatography.

PubMed

Wahab, M Farooq; Pohl, Christopher A; Lucy, Charles A

2012-12-28

The development of small particles in ion chromatography (IC) is a recent phenomenon. Very few studies are available on packing polymeric particles bearing ionizable functional groups. This study explores the colloidal and rheological properties that govern slurry packing to form high efficiency IC columns. The polymeric substrate used was non-porous 4.4 μm sulfonated ethylvinylbenzene–divinylbenzene (1.4 mequiv. SO(3)H/g resin) with 55% crosslink. We developed simple tests optical microscopy and sedimentation tests for predicting the quality of packed columns. The negatively charged particles (zeta potential: −52 mV in water) behave like colloids. The influence of counter-ion charge (Al(3+), Mg(2+), Na(+)) and ionic strength on column efficiency followed the Schulze–Hardy rule. Highly flocculating slurries give poorly packed columns with N ~ 900 whereas under non-agglomerating slurry conditions efficiencies up to N > 10,000 can be achieved. A non-agglomerating slurry also shows non-Newtonian behaviour, specifically shear thickening. Packing at lower flow rate (<1 mL/min) or higher temperature (>50 °C) reduces the shear thickening and produces higher efficiency columns. The packed sulfonated resin column is coated with 72 nm quaternary ammonium bearing latex (AS4A) and used in the separation of F(−), Cl(−), NO(2)(−), Br(−), and NO(3)(−) yielding a reduced plate height of 1.9 under optimum conditions.

Spin dynamics of light-induced charge separation in composites of semiconducting polymers and PC60BM revealed using Q-band pulse EPR.

PubMed

Lukina, E A; Suturina, E; Reijerse, E; Lubitz, W; Kulik, L V

2017-08-23

Light-induced processes in composites of semiconducting polymers and fullerene derivatives have been widely studied due to their usage as active layers of organic solar cells. However the process of charge separation under light illumination - the key process of an organic solar cell is not well understood yet. Here we report a Q-band pulse electron paramagnetic resonance study of composites of the fullerene derivative PC 60 BM ([6,6]-phenyl-C 61 -butyric acid methyl ester) with different p-type semiconducting polymers regioregular and regiorandom P3HT (poly(3-hexylthiophene-2,5-diyl), MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]), PCDTBT (poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]), PTB7 (poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}))), resulting in a detailed description of the in-phase laser flash-induced electron spin echo (ESE) signal. We found that in organic donor-acceptor composites the laser flash simultaneously induces species of two types: a polymer˙ + /fullerene˙ - spin-correlated polaron pair (SCPP) with an initial singlet spin state and (nearly) free polymer˙ + and fullerene˙ - species with non-equilibrium spin polarization. Species of the first type (SCPP) are well-known for polymer/fullerene blends and are usually associated with a charge-separated state. Also, spin polarization of long-living free species (polarons in deep traps) is affected by the laser flash, which is the third contribution to the flash-induced ESE signal. A protocol for extracting the in-phase ESE signal of the SCPP based on the dependence of the microwave nutation frequency on the strength of the spin coupling within the polaron pair was developed. Nutation experiments revealed an unusual pattern of the SCPP in RR-P3HT/PC 60 BM composites, from which the strength of the exchange interaction between the polymer˙ + and fullerene˙ - was extracted. In composites with low-efficient polymers the contribution of the SCPP to the in-phase ESE signal is high, while in composites with high-efficient polymers it is low. This finding can be used as a selection criterion of charge separation efficiency in the polymer/fullerene composites.

High-Efficiency Selective Electron Tunnelling in a Heterostructure Photovoltaic Diode.

PubMed

Jia, Chuancheng; Ma, Wei; Gu, Chunhui; Chen, Hongliang; Yu, Haomiao; Li, Xinxi; Zhang, Fan; Gu, Lin; Xia, Andong; Hou, Xiaoyuan; Meng, Sheng; Guo, Xuefeng

2016-06-08

A heterostructure photovoltaic diode featuring an all-solid-state TiO2/graphene/dye ternary interface with high-efficiency photogenerated charge separation/transport is described here. Light absorption is accomplished by dye molecules deposited on the outside surface of graphene as photoreceptors to produce photoexcited electron-hole pairs. Unlike conventional photovoltaic conversion, in this heterostructure both photoexcited electrons and holes tunnel along the same direction into graphene, but only electrons display efficient ballistic transport toward the TiO2 transport layer, thus leading to effective photon-to-electricity conversion. On the basis of this ipsilateral selective electron tunnelling (ISET) mechanism, a model monolayer photovoltaic device (PVD) possessing a TiO2/graphene/acridine orange ternary interface showed ∼86.8% interfacial separation/collection efficiency, which guaranteed an ultrahigh absorbed photon-to-current efficiency (APCE, ∼80%). Such an ISET-based PVD may become a fundamental device architecture for photovoltaic solar cells, photoelectric detectors, and other novel optoelectronic applications with obvious advantages, such as high efficiency, easy fabrication, scalability, and universal availability of cost-effective materials.

Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells

NASA Astrophysics Data System (ADS)

Edley, Michael

Photovoltaic energy is a clean and renewable source of electricity; however, it faces resistance to widespread use due to cost. Nanostructuring decouples constraints related to light absorption and charge separation, potentially reducing cost by allowing a wider variety of processing techniques and materials to be used. However, the large interfacial areas also cause an increased dark current which negatively affects cell efficiency. This work focuses on extremely thin absorber (ETA) solar cells that used a ZnO nanowire array as a scaffold for an extremely thin CdSe absorber layer. Photoexcited electrons generated in the CdSe absorber are transferred to the ZnO layer, while photogenerated holes are transferred to the liquid electrolyte. The transfer of photoexcited carriers to their transport layer competes with bulk recombination in the absorber layer. After charge separation, transport of charge carriers to their respective contacts must occur faster than interfacial recombination for efficient collection. Charge separation and collection depend sensitively on the dimensions of the materials as well as their interfaces. We demonstrated that an optimal absorber thickness can balance light absorption and charge separation. By treating the ZnO/CdSe interface with a CdS buffer layer, we were able to improve the Voc and fill factor, increasing the ETA cell's efficiency from 0.53% to 1.34%, which is higher than that achievable using planar films of the same material. We have gained additional insight into designing ETA cells through the use of dynamic measurements. Ultrafast transient absorption spectroscopy revealed that characteristic times for electron injection from CdSe to ZnO are less than 1 ps. Electron injection is rapid compared to the 2 ns bulk lifetime in CdSe. Optoelectronic measurements such as transient photocurrent/photovoltage and electrochemical impedance spectroscopy were applied to study the processes of charge transport and interfacial recombination. With these techniques, the extension of the depletion layer from CdSe into ZnO was determined to be vital to suppression of interfacial recombination. However, depletion of the ZnO also restricted the effective diffusion core for electrons and slowed their transport. Thus, materials and geometries should be chosen to allow for a depletion layer that suppresses interfacial recombination without impeding electron transport to the point that it is detrimental to cell performance. Thin film solar cells are another promising technology that can reduce costs by relaxing material processing requirements. CuInxGa (1-x)Se (CIGS) is a well studied thin film solar cell material that has achieved good efficiencies of 22.6%. However, use of rare elements raise concerns over the use of CIGS for global power production. CuSbS2 shares chemistry with CuInSe2 and also presents desirable properties for thin film absorbers such as optimal band gap (1.5 eV), high absorption coefficient, and Earth-abundant and non-toxic elements. Despite the promise of CuSbS2, direct characterization of the material for solar cell application is scarce in the literature. CuSbS2 nanoplates were synthesized by a colloidal hot-injection method at 220 °C in oleylamine. The CuSbS2 platelets synthesized for 30 minutes had dimensions of 300 nm by 400 nm with a thickness of 50 nm and were capped with the insulating oleylamine synthesis ligand. The oleylamine synthesis ligand provides control over nanocrystal growth but is detrimental to intercrystal charge transport that is necessary for optoelectronic device applications. Solid-state and solution phase ligand exchange of oleylamine with S2- were used to fabricate mesoporous films of CuSbS2 nanoplates for application in solar cells. Exchange of the synthesis ligand with S2- resulted in a two order of magnitude increase in 4-point probe conductivity. Photoexcited carrier lifetimes of 1.4 ns were measured by time-resolved terahertz spectroscopy, indicating potential for CuSbS2 as a solar cell absorber material.

The Charging Events in Contact-Separation Electrification.

PubMed

Musa, Umar G; Cezan, S Doruk; Baytekin, Bilge; Baytekin, H Tarik

2018-02-06

Contact electrification (CE)-charging of surfaces that are contacted and separated, is a common phenomenon, however it is not completely understood yet. Recent studies using surface imaging techniques and chemical analysis revealed a 'spatial' bipolar distribution of charges at the nano dimension, which made a paradigm shift in the field. However, such analyses can only provide information about the charges that remained on the surface after the separation, providing limited information about the actual course of the CE event. Tapping common polymers and metal surfaces to each other and detecting the electrical potential produced on these surfaces 'in-situ' in individual events of contact and separation, we show that, charges are generated and transferred between the surfaces in both events; the measured potential is bipolar in contact and unipolar in separation. We show, the 'contact-charges' on the surfaces are indeed the net charges that results after the separation process, and a large contribution to tribocharge harvesting comes, in fact, from the electrostatic induction resulting from the generated CE charges. Our results refine the mechanism of CE providing information for rethinking the conventional ranking of materials' charging abilities, charge harvesting, and charge prevention.

Active space debris charging for contactless electrostatic disposal maneuvers

NASA Astrophysics Data System (ADS)

Schaub, Hanspeter; Sternovsky, Zoltán

2014-01-01

The remote charging of a passive object using an electron beam enables touchless re-orbiting of large space debris from geosynchronous orbit (GEO) using electrostatic forces. The advantage of this method is that it can operate with a separation distance of multiple craft radii, thus reducing the risk of collision. The charging of the tug-debris system to high potentials is achieved by active charge transfer using a directed electron beam. Optimal potential distributions using isolated- and coupled-sphere models are discussed. A simple charging model takes into account the primary electron beam current, ultra-violet radiation induced photoelectron emission, collection of plasma particles, secondary electron emission and the recapture of emitted particles. The results show that through active charging in a GEO space environment high potentials can be both achieved and maintained with about a 75% transfer efficiency. Further, the maximum electrostatic tractor force is shown to be insensitive to beam current levels. This latter later result is important when considering debris with unknown properties.

Stark tuning and electrical charge state control of single divacancies in silicon carbide

NASA Astrophysics Data System (ADS)

de las Casas, Charles F.; Christle, David J.; Ul Hassan, Jawad; Ohshima, Takeshi; Son, Nguyen T.; Awschalom, David D.

2017-12-01

Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color centers whose long coherence times and near-telecom operating wavelengths make them promising for scalable quantum communication technologies compatible with existing fiber optic networks. However, local strain inhomogeneity can randomly perturb their optical transition frequencies, which degrades the indistinguishability of photons emitted from separate defects and hinders their coupling to optical cavities. Here, we show that electric fields can be used to tune the optical transition frequencies of single neutral divacancy defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same technique can also control the charge state of the defect on microsecond timescales, which we use to stabilize unstable or non-neutral divacancies into their neutral charge state. Using fluorescence-based charge state detection, we show that both 975 nm and 1130 nm excitation can prepare their neutral charge state with near unity efficiency.

Real-space decoupling transformation for quantum many-body systems.

PubMed

Evenbly, G; Vidal, G

2014-06-06

We propose a real-space renormalization group method to explicitly decouple into independent components a many-body system that, as in the phenomenon of spin-charge separation, exhibits separation of degrees of freedom at low energies. Our approach produces a branching holographic description of such systems that opens the path to the efficient simulation of the most entangled phases of quantum matter, such as those whose ground state violates a boundary law for entanglement entropy. As in the coarse-graining transformation of Vidal [Phys. Rev. Lett. 99, 220405 (2007).

The Use of Clay-Polymer Nanocomposites in Wastewater Pretreatment

PubMed Central

Rytwo, Giora

2012-01-01

Some agricultural effluents are unsuitable for discharge into standard sewage-treatment plants: their pretreatment is necessary to avoid clogging of the filtering devices by colloidal matter. The colloidal stability of the effluents is mainly due to mutual repulsive forces that keep charged particles in suspension. Pretreatment processes are based on two separate stages: (a) neutralization of the charges (“coagulation”) and (b) bridging between several small particles to form larger aggregates that sink, leaving clarified effluent (“flocculation”). The consequent destabilization of the colloidal suspension lowers total suspended solids (TSSs), turbidity, and other environmental quality parameters, making the treatments that follow more efficient. Clay-based materials have been widely used for effluent pretreatment and pollutant removal. This study presents the use of nanocomposites, comprised of an anchoring particle and a polymer, as “coagoflocculants” for the efficient and rapid reduction of TSS and turbidity in wastewater with a high organic load. The use of such particles combines the advantages of coagulant and flocculant by neutralizing the charge of the suspended particles while bridging between them and anchoring them to a denser particle (the clay mineral), enhancing their precipitation. Very rapid and efficient pretreatment is achieved in one single treatment step. PMID:22454607

0D/2D Z-Scheme Heterojunctions of Bismuth Tantalate Quantum Dots/Ultrathin g-C3N4 Nanosheets for Highly Efficient Visible Light Photocatalytic Degradation of Antibiotics.

PubMed

Wang, Kai; Zhang, Gaoke; Li, Jun; Li, Yuan; Wu, Xiaoyong

2017-12-20

Constructing 0D/2D Z-scheme photocatalysts is a great promising path to improve photocatalytic activity by  efficiently enhancing charge separation. Herein, we fabricated a visible-light-responsive Bi 3 TaO 7 quantum dots (QDs)/g-C 3 N 4 nanosheets (NSs) 0D/2D Z-scheme composite via a facile ultrasound method, and Bi 3 TaO 7 QDs could be interspersed on the surface of g-C 3 N 4 NSs uniformly. Furthermore, the strong interaction between Bi 3 TaO 7 QDs and g-C 3 N 4 NSs disturbed the CN heterocycles by forming C═O bonds between C atoms of the N-(C) 3 group and O atoms of the Ta-O bond. The optimum composite with 20 wt % g-C 3 N 4 NSs showed the superior photocatalytic activity for degradation of ciprofloxacin (CIP) over the composites prepared by mechanical mixing and solid-state methods, the photocatalytic efficiency of which were 4 and 12.2 times higher than those of bare Bi 3 TaO 7 and g-C 3 N 4 . Photoluminescence (PL), time-resolved transient PL decay spectra, and photocurrent together verify that the photogenerated hole-electron pairs in this 0D/2D Z-scheme composite have been effectively separated. The enhanced photocatalytic activity of as-synthesized photocatalysts could be attributed to the synergistic effect of efficient Z-scheme charge separation, highly dispersed 0D Bi 3 TaO 7 nanocrystals, coordinating sites of 2D g-C 3 N 4 NSs and the strong coupling between them. This study might pave the way toward designing novel visible-light-induced 0D/2D photocatalyst systems for highly efficient degradation of antibiotics.

Early bacteriopheophytin reduction in charge separation in reaction centers of Rhodobacter sphaeroides.

PubMed

Zhu, Jingyi; van Stokkum, Ivo H M; Paparelli, Laura; Jones, Michael R; Groot, Marie Louise

2013-06-04

A question at the forefront of biophysical sciences is, to what extent do quantum effects and protein conformational changes play a role in processes such as biological sensing and energy conversion? At the heart of photosynthetic energy transduction lie processes involving ultrafast energy and electron transfers among a small number of tetrapyrrole pigments embedded in the interior of a protein. In the purple bacterial reaction center (RC), a highly efficient ultrafast charge separation takes place between a pair of bacteriochlorophylls: an accessory bacteriochlorophyll (B) and bacteriopheophytin (H). In this work, we applied ultrafast spectroscopy in the visible and near-infrared spectral region to Rhodobacter sphaeroides RCs to accurately track the timing of the electron on BA and HA via the appearance of the BA and HA anion bands. We observed an unexpectedly early rise of the HA⁻ band that challenges the accepted simple picture of stepwise electron transfer with 3 ps and 1 ps time constants. The implications for the mechanism of initial charge separation in bacterial RCs are discussed in terms of a possible adiabatic electron transfer step between BA and HA, and the effect of protein conformation on the electron transfer rate. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Highly Enhanced Photoelectrochemical Water Oxidation Efficiency Based on Triadic Quantum Dot/Layered Double Hydroxide/BiVO 4 Photoanodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Yanqun; Wang, Ruirui; Yang, Ye

2016-08-03

The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., Emore » < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is -1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.« less

Cherenkov and scintillation light separation in organic liquid scintillators

NASA Astrophysics Data System (ADS)

Caravaca, J.; Descamps, F. B.; Land, B. J.; Yeh, M.; Orebi Gann, G. D.

2017-12-01

The CHErenkov/Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2 g/L of PPO as a fluor (LAB/PPO). This is the first successful demonstration of Cherenkov light detection from the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338± 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 ± 3 % and 63± 8% for time- and charge-based separation, respectively, with scintillation contamination of 36± 5% and 38± 4%. LAB/PPO data is consistent with a rise time of τ _r=0.72± 0.33 ns.

Study of talcum charging status in parallel plate electrostatic separator based on particle trajectory analysis

NASA Astrophysics Data System (ADS)

Yunxiao, CAO; Zhiqiang, WANG; Jinjun, WANG; Guofeng, LI

2018-05-01

Electrostatic separation has been extensively used in mineral processing, and has the potential to separate gangue minerals from raw talcum ore. As for electrostatic separation, the particle charging status is one of important influence factors. To describe the talcum particle charging status in a parallel plate electrostatic separator accurately, this paper proposes a modern images processing method. Based on the actual trajectories obtained from sequence images of particle movement and the analysis of physical forces applied on a charged particle, a numerical model is built, which could calculate the charge-to-mass ratios represented as the charging status of particle and simulate the particle trajectories. The simulated trajectories agree well with the experimental results obtained by images processing. In addition, chemical composition analysis is employed to reveal the relationship between ferrum gangue mineral content and charge-to-mass ratios. Research results show that the proposed method is effective for describing the particle charging status in electrostatic separation.

Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts

NASA Astrophysics Data System (ADS)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu

2017-02-01

Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H2) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H2 evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu2MoS4 nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu2MoS4nanosheets. These layered Cu2MoS4 nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H2 production by water splitting. We have obtained superior H2 production rates by using Cu2MoS4 loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Design principle for efficient charge separation at the donor-acceptor interface for high performance organic solar cell device

NASA Astrophysics Data System (ADS)

Nie, Wanyi; Gupta, Gautam; Crone, Brian; Wang, Hsing-Lin; Mohite, Aditya; MPA-11 Material synthesis and integrated device Team; MPA-chemistry Team

2014-03-01

The performance of donor (D) /acceptor (A) structure based organic electronic devices, such as solar cell, light emitting devices etc., relays on the charge transfer process at the interface dramatically. In organic solar cell, the photo-induced electron-hole pair is tightly bonded and will form a charge transfer (CT) state at the D/A interface after dissociation. There is a large chance for them to recombine through CT state and thus is a major loss that limit the overall performance. Here, we report three different strategies that allow us to completely suppress the exciplex (or charge transfer state) recombination between any D/A system. We observe that the photocurrent increases by 300% and the power conversion efficiency increases by 4-5 times simply by inserting a spacer layer in the form of an a) insulator b) Oliogomer or using a c) heavy atom at the donor-acceptor interface in a P3HT/C60 bilayer device. By using those different functional mono layers, we successfully suppressed the exciplex recombination in evidence of increased photocurrent and open circuit voltage. Moreover, these strategies are applicable universally to any donor-acceptor interface. And we demonstrated such strategies in a bulk-heterojunction device which improved the power conversion efficiency from 3.5% up to 4.6%.

Design of a CW high charge state heavy ion RFQ for SSC-LINAC

NASA Astrophysics Data System (ADS)

Liu, G.; Lu, Y. R.; He, Y.; Wang, Z.; Xiao, C.; Gao, S. L.; Yang, Y. Q.; Zhu, K.; Yan, X. Q.; Chen, J. E.; Yuan, Y. J.; Zhao, H. W.

2013-02-01

The new linac injector SSC-LINAC has been proposed to replace the existing Separator Sector Cyclotron (SSC). This effort is to improve the beam efficiency of the Heavy Ion Research Facility of Lanzhou (HIRFL). As a key component of the linac, a continuous-wave (CW) mode high charge state heavy ion radio-frequency quadrupole (RFQ) accelerator has been designed. It accelerates ions with the ratio of mass to charge up to 7 from 3.728 keV/u to 143 keV/u. The requirements of CW mode operation and the transportation of intense beam have been considered as the greatest challenges. The design is based on 238U34+ beams, whose current is 0.5 pmA (0.5 particle mili-ampere, which is the measured 17 emA electric current divided by charge state of heavy ions). It achieves the transmission efficiency of 94% with 2508.46 mm long vanes in simulation. To improve the transmission efficiency and quality of the beams, the phase advance has been taken into account to analyze the reasons of beam loss and emittance growth. Parametric resonance and beam mismatch have been carefully avoided by adjusting the structure parameters. The parameter-sensitivity of the design is checked by transportation simulations of various input beams. To verify the applicability of machining, the effects of different vane manufacturing methods on beam dynamics are presented in this paper.

Direct observation of metal nanoparticles as heterogeneous nuclei for the condensation of supersaturated organic vapors: nucleation of size-selected aluminum nanoparticles in acetonitrile and n-hexane vapors.

PubMed

Abdelsayed, Victor; El-Shall, M Samy

2014-08-07

This work reports the direct observation and separation of size-selected aluminum nanoparticles acting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metal nanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor. Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for the heterogeneous nucleation of both acetonitrile and hexane vapors, particles are activated at significantly smaller sizes than predicted by the Kelvin equation. The activation of the Al nanoparticles occurs at nearly 40% and 65% of the onset of homogeneous nucleation of acetonitrile and hexane supersaturated vapors, respectively. The lower activation of the charged Al nanoparticles in acetonitrile vapor is due to the charge-dipole interaction which results in rapid condensation of the highly polar acetonitrile molecules on the charged Al nanoparticles. The charge-dipole interaction decreases with increasing the size of the Al nanoparticles and therefore at low supersaturations, most of the heterogeneous nucleation events are occurring on neutral nanoparticles. No sign effect has been observed for the condensation of the organic vapors on the positively and negatively charged Al nanoparticles. The present approach of generating metal nanoparticles by pulsed laser vaporization within a supersaturated organic vapor allows for efficient separation between nucleation and growth of the metal nanoparticles and, consequently controls the average particle size, particle density, and particle size distribution within the liquid droplets of the condensing vapor. Strong correlation is found between the seed nanoparticle's size and the degree of the supersaturation of the condensing vapor. This result and the agreement among the calculated Kelvin diameters and the size of the nucleating Al nanoparticles determined by transmission electron microscopy provide strong proof for the development of a new approach for the separation and characterization of heterogeneous nuclei formed in organic vapors. These processes can take place in the atmosphere by a combination of several organic species including polar compounds which could be very efficient in activating charged nanoparticles and cluster ions of atmospheric relevance.

Direct observation of metal nanoparticles as heterogeneous nuclei for the condensation of supersaturated organic vapors: Nucleation of size-selected aluminum nanoparticles in acetonitrile and n-hexane vapors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdelsayed, Victor; Samy El-Shall, M., E-mail: mselshal@vcu.edu

This work reports the direct observation and separation of size-selected aluminum nanoparticles acting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metal nanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor. Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicatesmore » that for the heterogeneous nucleation of both acetonitrile and hexane vapors, particles are activated at significantly smaller sizes than predicted by the Kelvin equation. The activation of the Al nanoparticles occurs at nearly 40% and 65% of the onset of homogeneous nucleation of acetonitrile and hexane supersaturated vapors, respectively. The lower activation of the charged Al nanoparticles in acetonitrile vapor is due to the charge-dipole interaction which results in rapid condensation of the highly polar acetonitrile molecules on the charged Al nanoparticles. The charge-dipole interaction decreases with increasing the size of the Al nanoparticles and therefore at low supersaturations, most of the heterogeneous nucleation events are occurring on neutral nanoparticles. No sign effect has been observed for the condensation of the organic vapors on the positively and negatively charged Al nanoparticles. The present approach of generating metal nanoparticles by pulsed laser vaporization within a supersaturated organic vapor allows for efficient separation between nucleation and growth of the metal nanoparticles and, consequently controls the average particle size, particle density, and particle size distribution within the liquid droplets of the condensing vapor. Strong correlation is found between the seed nanoparticle's size and the degree of the supersaturation of the condensing vapor. This result and the agreement among the calculated Kelvin diameters and the size of the nucleating Al nanoparticles determined by transmission electron microscopy provide strong proof for the development of a new approach for the separation and characterization of heterogeneous nuclei formed in organic vapors. These processes can take place in the atmosphere by a combination of several organic species including polar compounds which could be very efficient in activating charged nanoparticles and cluster ions of atmospheric relevance.« less

Study of gain and photoresponse characteristics for back-illuminated separate absorption and multiplication GaN avalanche photodiodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaodong; Pan, Ming; Hou, Liwei

2014-01-07

The gain and photoresponse characteristics have been numerically studied for back-illuminated separate absorption and multiplication (SAM) GaN avalanche photodiodes (APDs). The parameters of fundamental models are calibrated by simultaneously comparing the simulated dark and light current characteristics with the experimental results. Effects of environmental temperatures and device dimensions on gain characteristics have been investigated, and a method to achieve the optimum thickness of charge layer is obtained. The dependence of gain characteristics and breakdown voltage on the doping concentration of the charge layer is also studied in detail to get the optimal charge layer. The bias-dependent spectral responsivity and quantummore » efficiency are then presented to study the photoresponse mechanisms inside SAM GaN APDs. It is found the responsivity peak red-shifts at first due to the Franz-Keldysh effect and then blue-shifts due to the reach-through effect of the absorption layer. Finally, a new SAM GaN/AlGaN heterojunction APD structure is proposed for optimizing SAM GaN APDs.« less

Bi-continuous Multi-component Nanocrystal Superlattices for Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kagan, Cherie; Murray, Christopher; Kikkawa, James

2017-06-14

Our SISGR program studied an emerging class of nanomaterials wherein different combinations of semiconductor or semiconductor and plasmonic nanocrystals (NCs) are self-assembled into three-dimensional multi-component superlattices. The NC assemblies were designed to form bicontinuous semiconductor NC sublattices with type-II energy offsets to drive charge separation onto electron and hole transporting sublattices for collection and introduce plasmonic NCs to increase solar absorption and charge separation. Our group is expert in synthesizing and assembling an extraordinary variety of artificial systems by tailoring the NC building blocks and the superlattice unit cell geometry. Under this DOE BES Materials Chemistry program, we introduced chemicalmore » methods to control inter-particle distance and to dope NC assemblies, which enabled our demonstration of strong electronic communication between NCs and the use of NC thin films as electronic materials. We synthesized, assembled and structurally, spectroscopically, and electrically probed NC superlattices to understand and manipulate the flow of energy and charge toward discovering the design rules and optimizing these complex architectures to create materials that efficiently convert solar radiation into electricity.« less

Charge separation in photoredox reactions. Technical progress report, May 1, 1981-May 1, 1984. [N,N,N',N'-tetramethylbenzidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, L.

1984-05-01

The structural aspects controlling charge separation in molecular photoionization reactions in organized molecular assemblies involving micelles and vesicles are being studied by optical and electron magnetic resonance techniques including the time domain technique of electron spin echo modulation (ESEM). Photoionization of N,N,N',N'-tetramethylbenzidine (TMB) to give the cation radical has been carried out in both liquid and frozen micellar and vesicular solutions. Cation-water interactions have been detected by ESEM analysis and indicate that the cation is localized asymmetrically within these organized molecular assemblies. x-Doxylstearic acid spin probes have been used to determine that the neutral TMB molecule before photoionization is alsomore » localized asymmetrically within such organized molecular assemblies. Electron spin echo detection of laser photogenerated TMB cation in liquid micellar solutions gives a direct measurement of the phase memory magnetic relaxation time which gives additional structural information. The photoionization efficiency has been related to cation-water interactions measured by ESEM. The photoionization efficiency is also dependent on surface charge and is about twofold greater in cationic micelles and vesicles compared to anionic micelles and vesicles. TMB is in a less polar environment in vesicles compared to micelles consistent with ESEM results. The preferential adsorption of metal species at micellar surfaces has been detected by ESEM. Modifications in the micelle surface have been effected by added salts and varying counterions which have been related to cation-water interactions and to the TMB photoionization efficiency. Corresponding changes in the surface and internal micellar structure have been investigated by x-doxylstearic acid spin probes and specifically deuterated surfactants. The decay kinetics of TMB cations in micelles have been interpreted in terms of a time dependent rate constant.« less

Design and engineering of water-soluble light-harvesting protein maquettes

DOE PAGES

Kodali, Goutham; Mancini, Joshua A.; Solomon, Lee A.; ...

2017-01-01

Natural selection in photosynthesis has engineered tetrapyrrole based, nanometer scale, light harvesting and energy capture in light-induced charge separation. By designing and creating nanometer scale artificial light harvesting and charge separating proteins, we have the opportunity to reengineer and overcome the limitations of natural selection to extend energy capture to new wavelengths and to tailor efficient systems that better meet human as opposed to cellular energetic needs. While tetrapyrrole cofactor incorporation in natural proteins is complex and often assisted by accessory proteins for cofactor transport and insertion, artificial protein functionalization relies on a practical understanding of the basic physical chemistrymore » of protein and cofactors that drive nanometer scale self-assembly. Patterning and balancing of hydrophobic and hydrophilic tetrapyrrole substituents is critical to avoid natural or synthetic porphyrin and chlorin aggregation in aqueous media and speed cofactor partitioning into the non-polar core of a man-made water soluble protein designed according to elementary first principles of protein folding. In conclusion, this partitioning is followed by site-specific anchoring of tetrapyrroles to histidine ligands strategically placed for design control of rates and efficiencies of light energy and electron transfer while orienting at least one polar group towards the aqueous phase.« less

Design and engineering of water-soluble light-harvesting protein maquettes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kodali, Goutham; Mancini, Joshua A.; Solomon, Lee A.

Natural selection in photosynthesis has engineered tetrapyrrole based, nanometer scale, light harvesting and energy capture in light-induced charge separation. By designing and creating nanometer scale artificial light harvesting and charge separating proteins, we have the opportunity to reengineer and overcome the limitations of natural selection to extend energy capture to new wavelengths and to tailor efficient systems that better meet human as opposed to cellular energetic needs. While tetrapyrrole cofactor incorporation in natural proteins is complex and often assisted by accessory proteins for cofactor transport and insertion, artificial protein functionalization relies on a practical understanding of the basic physical chemistrymore » of protein and cofactors that drive nanometer scale self-assembly. Patterning and balancing of hydrophobic and hydrophilic tetrapyrrole substituents is critical to avoid natural or synthetic porphyrin and chlorin aggregation in aqueous media and speed cofactor partitioning into the non-polar core of a man-made water soluble protein designed according to elementary first principles of protein folding. In conclusion, this partitioning is followed by site-specific anchoring of tetrapyrroles to histidine ligands strategically placed for design control of rates and efficiencies of light energy and electron transfer while orienting at least one polar group towards the aqueous phase.« less

Charge Generation and Recombination in Organic Materials for Photovoltaics

NASA Astrophysics Data System (ADS)

Ramirez, Jessica Jacklyn

Understanding the nature of molecular exciton states is critical for the design of organic photovoltaic materials that push current device efficiencies into the next realm. This thesis describes several research projects that have sought to further our understanding of the generation and recombination of charge carriers, facilitated by such excitonic states, in organic systems. We begin with fundamental studies on the excited-state dynamics of several fullerene derivatives. We also venture away from the traditional fullerene-based electron acceptors and consider several derivatized perylene diimides as alternate electron acceptors. We then report on the observation of a broad, structureless, emission emanating from charge-generating films comprised of perfluoroalkyl fullerene derivatives dilutely dispersed in polyfluorene hosts. We have determined that this red-shifted PL signature is the result of radiative recombination from a charge-transfer state that is populated initially as a precursor to charge generation, and may be repopulated upon charge recombination. Our data offers an observable link between charge-generation and charge-transfer emission that is kinetically associated with carrier recombination, and we utilize this link to probe the influence of driving force and polymer microstructure in the fundamental processes of charge generation and decay in small molecule/polymer heterojunctions. Thereafter, we sought to develop our understanding of a novel photophysical mechanism (known as energy pooling) which would allow for the energy of multiple excitons to be 'pooled' towards a central molecular moiety, where the individual exciton energies may add together to create a single highly excited excitonic state. This upconversion-like process would facilitate more efficient photocurrent generation in devices utilizing this mode of charge separation. The primary modes of inquiry utilized in this work come from the spectroscopic techniques of absorbance, steady-state and time-resolved photoluminescence, transient absorption and time-resolved microwave conductivity. Some secondary methods employed include cyclic voltammetry, X-ray diffraction and computational tools from density functional theory. This utilization of both experimental and theoretical methodologies provides a powerful approach to furthering our understanding of both the fundamental photophysics of the systems studied, as well as the charge generation and recombination pathways occurring at organic donor-acceptor interfaces, helping to guide the design of more efficient organic photovoltaics.

Studies on graphene zinc-oxide nanocomposites photoanodes for high-efficient dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Effendi, N. A. S.; Samsi, N. S.; Zawawi, S. A.; Hassan, O. H.; Zakaria, R.; Yahya, M. Z. A.; Ali, A. M. M.

2017-09-01

A dye-sensitized solar cells (DSSCs) using a nanocomposite (NC) semiconductor film, consisting of graphene layer and ZnO nanosheets (Gr-ZnO) is fabricated by electrodeposition process. The DSSCs based on Gr-ZnO NC were determined via electrochemical impedance spectra (EIS), UV-Visible diffused reflectance spectroscopy (UV-Vis), and photovoltaic performances J-V curves to substantiate the explanations. Impedance spectra shows that a smaller charge transport time constant occurs in DSSCs based on Gr-ZnO NC comparing to ZnO. This improved the electron collecting efficiency significantly, resulting in high open circuit voltage. Moreover, Gr-ZnO NC shows an efficient photoinduced charge separation and transportation can be achieved at the interface thus exhibit excellent potential for photocurrent generation compared with sole ZnO. Gr-ZnO NC obtained a maximum photocurrent response for an open-circuit voltage and a power conversion efficiency of 0.96 V and 7.01% respectively, which is doubled from sole ZnO. The fabricated Gr-ZnO NC cells show better performances compared to conventional ZnO structure reference cell.

Plasmonic Photovoltaic Cells with Dual-Functional Gold, Silver, and Copper Half-Shell Arrays.

PubMed

Wu, Ling; Kim, Gyu Min; Nishi, Hiroyasu; Tatsuma, Tetsu

2017-09-12

Solid-state photovoltaic cells based on plasmon-induced charge separation (PICS) have attracted growing attention during the past decade. However, the power conversion efficiency (PCE) of the previously reported devices, which are generally loaded with dispersed metal nanoparticles as light absorbers, has not been sufficiently high. Here we report simpler plasmonic photovoltaic cells with interconnected Au, Ag, and Cu half-shell arrays deposited on SiO 2 @TiO 2 colloidal crystals, which serve both as a plasmonic light absorber and as a current collector. The well-controlled and easily prepared plasmonic structure allows precise comparison of the PICS efficiency between different plasmonic metal species. The cell with the Ag half-shell array has higher photovoltaic performance than the cells with Au and Cu half-shell arrays because of the high population of photogenerated energetic electrons, which gives a high electron injection efficiency and suppressed charge recombination probability, achieving the highest PCE among the solid-state PICS devices even without a hole transport layer.

Energy Level Tuning of Poly(phenylene-alt-dithienobenzothiadiazole)s for Low Photon Energy Loss Solar Cells.

PubMed

Heuvel, Ruurd; van Franeker, Jacobus J; Janssen, René A J

2017-03-01

Six poly(phenylene- alt -dithienobenzothiadiazole)-based polymers have been synthesized for application in polymer-fullerene solar cells. Hydrogen, fluorine, or nitrile substitution on benzo-thiadiazole and alkoxy or ester substitution on the phenylene moiety are investigated to reduce the energy loss per converted photon. Power conversion efficiencies (PCEs) up to 6.6% have been obtained. The best performance is found for the polymer-fullerene combination with distinct phase separation and crystalline domains. This improves the maximum external quantum efficiency for charge formation and collection to 66%. The resulting higher photocurrent compensates for the relatively large energy loss per photon ( E loss = 0.97 eV) in achieving a high PCE. By contrast, the poly-mer that provides a reduced energy loss ( E loss = 0.49 eV) gives a lower photocurrent and a reduced PCE of 1.8% because the external quantum efficiency of 17% is limited by a suboptimal morphology and a reduced driving force for charge transfer.

Hot Charge Carrier Transmission from Plasmonic Nanostructures

NASA Astrophysics Data System (ADS)

Christopher, Phillip; Moskovits, Martin

2017-05-01

Surface plasmons have recently been harnessed to carry out processes such as photovoltaic current generation, redox photochemistry, photocatalysis, and photodetection, all of which are enabled by separating energetic (hot) electrons and holes—processes that, previously, were the domain of semiconductor junctions. Currently, the power conversion efficiencies of systems using plasmon excitation are low. However, the very large electron/hole per photon quantum efficiencies observed for plasmonic devices fan the hope of future improvements through a deeper understanding of the processes involved and through better device engineering, especially of critical interfaces such as those between metallic and semiconducting nanophases (or adsorbed molecules). In this review, we focus on the physics and dynamics governing plasmon-derived hot charge carrier transfer across, and the electronic structure at, metal-semiconductor (molecule) interfaces, where we feel the barriers contributing to low efficiencies reside. We suggest some areas of opportunity that deserve early attention in the still-evolving field of hot carrier transmission from plasmonic nanostructures to neighboring phases.

Moving towards sustainable resources: Recovery and fractionation of nutrients from dairy manure digestate using membranes.

PubMed

Gerardo, Michael L; Aljohani, Nasser H M; Oatley-Radcliffe, Darren L; Lovitt, Robert W

2015-09-01

The fractionation of nitrogen (as ammonia/ammonium) and phosphorus (as phosphate ions) present in the dairy manure digestate was investigated using a nanofiltration membrane NF270. The filtration and separation efficiencies were correlated to pH across the range 3 < pH < 11. Filtration at pH 11 enabled higher permeate flux of 125-150 LMH at 20 bar, however rejection of ammonia was high at 30-36% and phosphate was 96.4-97.2%. At pH 3 and pH 7, electrostatic charge effects led to higher permeation of ammonium and thus more efficient separation of nitrogen. The rejection of phosphorus was relatively constant at any given pH and determined as 83% at pH 3, 97% at pH 7 and 95% at pH 11. The fractionation of nitrogen and phosphorus from complex aqueous solutions was demonstrated to be highly dependent on the charge of the membrane and ionic speciation. Solutions rich in nitrogen (as ammonia/ammonium) were obtained with almost no phosphorus present (<1 ppm) whilst the purification of the PO4-P was achieved by series of diafiltration (DF) operations which further separated the nitrogen. The separation of nutrients benefited from an advantageous membrane process with potential added value for a wide range of industries. The analysis of the process economics for a membrane based plant illustrates that the recovery of nutrients, particularly NH3-N, may be commercially feasible when compared to manufactured anhydrous NH3. Copyright © 2015 Elsevier Ltd. All rights reserved.

Light harvesting and charge management by Ni4S3 modified metal-organic frameworks and rGO in the process of photocatalysis.

PubMed

Liu, Duanduan; Jin, Zhiliang; Zhang, Yongke; Wang, Guorong; Ma, Bingzhen

2018-06-01

Harvesting and charge management is obtained by means of Ni 4 S 3 modified Metal-organic Frameworks (MOF) and rGO, namely, the Uio-66 (Zr)/rGO combined with Ni 4 S 3 photocatalyst was successfully prepared with the solvothermal method. The Ni 4 S 3 acted as the electron transfer agent greatly improve the electrons transmission from the excited state dye to the rGO/MOF surface for proton reduction reaction. The hydrogen production amount over EY-sensitized rGO/MOF/Ni 4 S 3 photocatalyst has reached 280 μmol for 5 h, which is about 14 times than that of the pure Ni 4 S 3 photocatalyst and 185 times than that of the pure rGO/MOF photocatalyst under visible light irradiation (λ ≥ 420 nm). In the composite, the rGO acts as electron-transfer mediator and Ni 4 S 3 serves as H 2 -evolution active site. A series of studies shown that the Ni 4 S 3 modified MOF and rGO provided more active sites and improved the efficiency of photo-generated charge separation by means of several characterizations such as SEM, XRD, XPS, Element Mapping, UV-vis DRS, BET, Photocurrent, Voltammetric Scanning, Fluorescence Spectra and FTIR. and the results of which were in good agreement with each other. The photoelectron migration rate and photogenerated charge separation efficiency of the composite can be obviously increased with graphene as a good electron acceptor and transfer medium and Ni 4 S 3 as hydrogen producing active site. Copyright © 2018 Elsevier Inc. All rights reserved.

Fluid mechanics of electroosmotic flow and its effect on band broadening in capillary electrophoresis.

PubMed

Ghosal, Sandip

2004-01-01

Electroosmotic flow (EOF) usually accompanies electrophoretic migration of charged species in capillary electrophoresis unless special precautions are taken to suppress it. The presence of the EOF provides certain advantages in separations. It is an alternative to mechanical pumps, which are inefficient and difficult to build at small scales, for transporting reagents and analytes on microfluidic chips. The downside is that any imperfection that distorts the EOF profile reduces the separation efficiency. In this paper, the basic facts about EOF are reviewed from the perspective of fluid mechanics and its effect on separations in free solution capillary zone electrophoresis is discussed in the light of recent advances.

Results of the ETV-1 breadboard tests under steady-state and transient conditions. [conducted in the NASA-LeRC Road Load Simulator

NASA Technical Reports Server (NTRS)

Sargent, N. B.; Dustin, M. O.

1981-01-01

Steady state tests were run to characterize the system and component efficiencies over the complete speed-torque capabilities of the propulsion system in both motoring and regenerative modes of operation. The steady state data were obtained using a battery simulator to separate the effects on efficiency caused by changing battery state-of-charge and component temperature. Transient tests were performed to determine the energy profiles of the propulsion system operating over the SAE J227a driving schedules.

Hybrid Organic/Inorganic Nanocomposites for Photovoltaic Cells

PubMed Central

Liu, Ruchuan

2014-01-01

Inorganic/organic hybrid solar cells have attracted a lot of interest due to their potential in combining the advantages of both components. To understand the key issues in association with photoinduced charge separation/transportation processes and to improve overall power conversion efficiency, various combinations with nanostructures of hybrid systems have been investigated. Here, we briefly review the structures of hybrid nanocomposites studied so far, and attempt to associate the power conversion efficiency with these nanostructures. Subsequently, we are then able to summarize the factors for optimizing the performance of inorganic/organic hybrid solar cells. PMID:28788591

Solids and nutrient removal from flushed swine manure using polyacrylamides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanotti, M.B.; Hunt, P.G.

1999-12-01

Most of the organic nutrients and reduced carbon (C) materials in liquid swine manure are contained in fine suspended particles that are not separated by available mechanical separators. Treatment with polyacrylamide (PAM) polymers prior to mechanical removal or gravity settling has the potential for enhancing solids-liquid separation, thus concentrating nitrogen (N), phosphorus (P), and organic C. In this work, the authors determined PAM charge and density characteristics most desirable for swine wastewater applications and established the optimum chemical requirement. Treatments were applied to flushed manure from two swine operations in North Carolina. Cationic PAMs significantly increased solids separation while performancemore » of neutral and anionic types was not different from a control. Cationic PAMs with moderate-charge density (20%) were more effective than polymers with higher charge density. Flocs were large and effectively retained with a 1-mm screen. Optimum PAM rate varied with the amount of total suspended solids (TSS) in the liquid manure; 26 and 79 mg PAM/L for samples containing 1.5 and 4.1 g TSS/L, respectively. Corresponding TSS removal efficiencies were 90 to 94%. In contrast, screening without PAM treatment captured only 5 to 14% of the suspended solids. Polymer usage rate was consistent and averaged 2.0{degree} based on weight of dry solids produced. Volatile suspended solids (VSS) were highly correlated with TSS and comprised 79.5% of TSS. Chemical oxygen demand (COD) and organic nutrient concentrations in the effluent were also significantly decreased by PAM treatment. The decrease of COD concentration, an important consideration for odor control, was linearly related with removal of suspended solids, at a rate of 2.0 g COD/g TSS and 2.6 g COD/g VSS. Removal efficiency of organic N and P followed approximately a 1:1 relationship with removal efficiency of TSS. Chemical cost to capture 90% of the suspended solids was estimated to be $0.026 per hog per day ($2.79 per finished hog). Results obtained indicate that PAM treatment is very effective for removal of manure solids, COD, and organic nutrients from flushed swine effluents. The technology provides an attractive alternative to existing liquid manure handling methods for conserving nutrients and avoiding excessive nutrient application in areas where swine production is concentrated.« less

Exploring Photoinduced Excited State Evolution in Heterobimetallic Ru(II)-Co(III) Complexes.

PubMed

Kuhar, Korina; Fredin, Lisa A; Persson, Petter

2015-06-18

Quantum chemical calculations provide detailed theoretical information concerning key aspects of photoinduced electron and excitation transfer processes in supramolecular donor-acceptor systems, which are particularly relevant to fundamental charge separation in emerging molecular approaches for solar energy conversion. Here we use density functional theory (DFT) calculations to explore the excited state landscape of heterobimetallic Ru-Co systems with varying degrees of interaction between the two metal centers, unbound, weakly bound, and tightly bound systems. The interplay between structural and electronic factors involved in various excited state relaxation processes is examined through full optimizations of multiple charge/spin states of each of the investigated systems. Low-energy relaxed heterobimetallic states of energy transfer and excitation transfer character are characterized in terms of energy, structure, and electronic properties. These findings support the notion of efficient photoinduced charge separation from a Ru(II)-Co(III) ground state, via initial optical excitation of the Ru-center, to low-energy Ru(III)-Co(II) states. The strongly coupled system has significant involvement of the conjugated bridge, qualitatively distinguishing it from the other two weakly coupled systems. Finally, by constructing potential energy surfaces for the three systems where all charge/spin state combinations are projected onto relevant reaction coordinates, excited state decay pathways are explored.

Interfacial disorder drives charge separation in molecular semiconductors

NASA Astrophysics Data System (ADS)

Willard, Adam

One of the fundamental microscopic processes in photocurrent generation is the dissociation of neutral photo-excitations (i.e., Frenkel excitons) into free charge carriers (i.e., electrons and holes). This process requires the physical separation of oppositely charged electrons and holes, which are held to together by an attractive electrostatic binding energy. In traditional inorganic-based photovoltaic (PV) materials, this binding energy is generally small and easily overcome, however, in organic-based PVs (OPVs) the exciton binding energy can significantly exceed thermal energies. The inability of bound charges to overcome this large binding energy has been implicated as a primary source of efficiency loss in OPVs. Here I present results from our recent efforts to explore the role of static molecular disorder in mediating this process. Using a simple lattice model of exciton dynamics we demonstrate that random spatial variations in the energetic landscape can mitigate the attractive Coulomb interaction between electrons and holes. We show that this effect manifests as a reduction in the free energy barrier for exciton dissociation that grows more pronounced with increasing disorder. By considering the competition between this thermodynamic effect and the disorder-induced slowing of dissociation kinetics we demonstrate that exciton dissociation yields are expected to depend non-monotonically on the degree of static disorder.

Conjugated ionomers for photovoltaic applications: electric field driven charge separation in organic photovoltaics. Final Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lonergan, Mark

Final technical report for Conjugated ionomers for photovoltaic applications, electric field driven charge separation in organic photovoltaics. The central goal of the work we completed was been to understand the photochemical and photovoltaic properties of ionically functionalized conjugated polymers (conjugated ionomers or polyelectrolytes) and energy conversion systems based on them. We primarily studied two classes of conjugated polymer interfaces that we developed based either upon undoped conjugated polymers with an asymmetry in ionic composition (the ionic junction) or doped conjugated polymers with an asymmetry in doping type (the p-n junction). The materials used for these studies have primarily been themore » polyacetylene ionomers. We completed a detailed study of p-n junctions with systematically varying dopant density, photochemical creation of doped junctions, and experimental and theoretical work on charge transport and injection in polyacetylene ionomers. We have also completed related work on the use of conjugated ionomers as interlayers that improve the efficiency or organic photovoltaic systems and studied several important aspects of the chemistry of ionically functionalized semiconductors, including mechanisms of so-called "anion-doping", the formation of charge transfer complexes with oxygen, and the synthesis of new polyfluorene polyelectrolytes. We also worked worked with the Haley group at the University of Oregon on new indenofluorene-based organic acceptors.« less

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2.

PubMed

Aaboud, M; Aad, G; Abbott, B; Abdallah, J; Abdinov, O; Abeloos, B; Abidi, S H; AbouZeid, O S; Abraham, N L; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adachi, S; Adamczyk, L; Adelman, J; Adersberger, M; Adye, T; Affolder, A A; Agatonovic-Jovin, T; Agheorghiesei, C; Aguilar-Saavedra, J A; Ahlen, S P; Ahmadov, F; Aielli, G; Akatsuka, S; Akerstedt, H; Åkesson, T P A; Akimov, A V; Alberghi, G L; Albert, J; Albicocco, P; Alconada Verzini, M J; Aleksa, M; Aleksandrov, I N; Alexa, C; Alexander, G; Alexopoulos, T; Alhroob, M; Ali, B; Aliev, M; Alimonti, G; Alison, J; Alkire, S P; Allbrooke, B M M; Allen, B W; Allport, P P; Aloisio, A; Alonso, A; Alonso, F; Alpigiani, C; Alshehri, A A; Alstaty, M; Alvarez Gonzalez, B; Álvarez Piqueras, D; Alviggi, M G; Amadio, B T; Amaral Coutinho, Y; Amelung, C; Amidei, D; Santos, S P Amor Dos; Amorim, A; Amoroso, S; Amundsen, G; Anastopoulos, C; Ancu, L S; Andari, N; Andeen, T; Anders, C F; Anders, J K; Anderson, K J; Andreazza, A; Andrei, V; Angelidakis, S; Angelozzi, I; Angerami, A; Anisenkov, A V; Anjos, N; Annovi, A; Antel, C; Antonelli, M; Antonov, A; Antrim, D J; Anulli, F; Aoki, M; Aperio Bella, L; Arabidze, G; Arai, Y; Araque, J P; Araujo Ferraz, V; Arce, A T H; Ardell, R E; Arduh, F A; Arguin, J-F; Argyropoulos, S; Arik, M; Armbruster, A J; Armitage, L J; Arnaez, O; Arnold, H; Arratia, M; Arslan, O; Artamonov, A; Artoni, G; Artz, S; Asai, S; Asbah, N; Ashkenazi, A; Asquith, L; Assamagan, K; Astalos, R; Atkinson, M; Atlay, N B; Augsten, K; Avolio, G; Axen, B; Ayoub, M K; Azuelos, G; Baas, A E; Baca, M J; Bachacou, H; Bachas, K; Backes, M; Backhaus, M; Bagnaia, P; Bahrasemani, H; Baines, J T; Bajic, M; Baker, O K; Baldin, E M; Balek, P; Balli, F; Balunas, W K; Banas, E; Banerjee, Sw; Bannoura, A A E; Barak, L; Barberio, E L; Barberis, D; Barbero, M; Barillari, T; Barisits, M-S; Barklow, T; Barlow, N; Barnes, S L; Barnett, B M; Barnett, R M; Barnovska-Blenessy, Z; Baroncelli, A; Barone, G; Barr, A J; Barranco Navarro, L; Barreiro, F; Barreiro Guimarães da Costa, J; Bartoldus, R; Barton, A E; Bartos, P; Basalaev, A; Bassalat, A; Bates, R L; Batista, S J; Batley, J R; Battaglia, M; Bauce, M; Bauer, F; Bawa, H S; Beacham, J B; Beattie, M D; Beau, T; Beauchemin, P H; Bechtle, P; Beck, H P; Becker, K; Becker, M; Beckingham, M; Becot, C; Beddall, A J; Beddall, A; Bednyakov, V A; Bedognetti, M; Bee, C P; Beermann, T A; Begalli, M; Begel, M; Behr, J K; Bell, A S; Bella, G; Bellagamba, L; Bellerive, A; Bellomo, M; Belotskiy, K; Beltramello, O; Belyaev, N L; Benary, O; Benchekroun, D; Bender, M; Bendtz, K; Benekos, N; Benhammou, Y; Benhar Noccioli, E; Benitez, J; Benjamin, D P; Benoit, M; Bensinger, J R; Bentvelsen, S; Beresford, L; Beretta, M; Berge, D; Bergeaas Kuutmann, E; Berger, N; Beringer, J; Berlendis, S; Bernard, N R; Bernardi, G; Bernius, C; Bernlochner, F U; Berry, T; Berta, P; Bertella, C; Bertoli, G; Bertolucci, F; Bertram, I A; Bertsche, C; Bertsche, D; Besjes, G J; Bessidskaia Bylund, O; Bessner, M; Besson, N; Betancourt, C; Bethani, A; Bethke, S; Bevan, A J; Beyer, J; Bianchi, R M; Biebel, O; Biedermann, D; Bielski, R; Biesuz, N V; Biglietti, M; Billoud, T R V; Bilokon, H; Bindi, M; Bingul, A; Bini, C; Biondi, S; Bisanz, T; Bittrich, C; Bjergaard, D M; Black, C W; Black, J E; Black, K M; Blair, R E; Blazek, T; Bloch, I; Blocker, C; Blue, A; Blum, W; Blumenschein, U; Blunier, S; Bobbink, G J; Bobrovnikov, V S; Bocchetta, S S; Bocci, A; Bock, C; Boehler, M; Boerner, D; Bogavac, D; Bogdanchikov, A G; Bohm, C; Boisvert, V; Bokan, P; Bold, T; Boldyrev, A S; Bolz, A E; Bomben, M; Bona, M; Boonekamp, M; Borisov, A; Borissov, G; Bortfeldt, J; Bortoletto, D; Bortolotto, V; Boscherini, D; Bosman, M; Bossio Sola, J D; Boudreau, J; Bouffard, J; Bouhova-Thacker, E V; Boumediene, D; Bourdarios, C; Boutle, S K; Boveia, A; Boyd, J; Boyko, I R; Bracinik, J; Brandt, A; Brandt, G; Brandt, O; Bratzler, U; Brau, B; Brau, J E; Breaden Madden, W D; Brendlinger, K; Brennan, A J; Brenner, L; Brenner, R; Bressler, S; Briglin, D L; Bristow, T M; Britton, D; Britzger, D; Brochu, F M; Brock, I; Brock, R; Brooijmans, G; Brooks, T; Brooks, W K; Brosamer, J; Brost, E; Broughton, J H; de Renstrom, P A Bruckman; Bruncko, D; Bruni, A; Bruni, G; Bruni, L S; Brunt, B H; Bruschi, M; Bruscino, N; Bryant, P; Bryngemark, L; Buanes, T; Buat, Q; Buchholz, P; Buckley, A G; Budagov, I A; Buehrer, F; Bugge, M K; Bulekov, O; Bullock, D; Burch, T J; Burckhart, H; Burdin, S; Burgard, C D; Burger, A M; Burghgrave, B; Burka, K; Burke, S; Burmeister, I; Burr, J T P; Busato, E; Büscher, D; Büscher, V; Bussey, P; Butler, J M; Buttar, C M; Butterworth, J M; Butti, P; Buttinger, W; Buzatu, A; Buzykaev, A R; Cabrera Urbán, S; Caforio, D; Cairo, V M; Cakir, O; Calace, N; Calafiura, P; Calandri, A; Calderini, G; Calfayan, P; Callea, G; Caloba, L P; Calvente Lopez, S; Calvet, D; Calvet, S; Calvet, T P; Camacho Toro, R; Camarda, S; Camarri, P; Cameron, D; Caminal Armadans, R; Camincher, C; Campana, S; Campanelli, M; Camplani, A; Campoverde, A; Canale, V; Cano Bret, M; Cantero, J; Cao, T; Capeans Garrido, M D M; Caprini, I; Caprini, M; Capua, M; Carbone, R M; Cardarelli, R; Cardillo, F; Carli, I; Carli, T; Carlino, G; Carlson, B T; Carminati, L; Carney, R M D; Caron, S; Carquin, E; Carrá, S; Carrillo-Montoya, G D; Carvalho, J; Casadei, D; Casado, M P; Casolino, M; Casper, D W; Castelijn, R; Castillo Gimenez, V; Castro, N F; Catinaccio, A; Catmore, J R; Cattai, A; Caudron, J; Cavaliere, V; Cavallaro, E; Cavalli, D; Cavalli-Sforza, M; Cavasinni, V; Celebi, E; Ceradini, F; Cerda Alberich, L; Cerqueira, A S; Cerri, A; Cerrito, L; Cerutti, F; Cervelli, A; Cetin, S A; Chafaq, A; Chakraborty, D; Chan, S K; Chan, W S; Chan, Y L; Chang, P; Chapman, J D; Charlton, D G; Chau, C C; Chavez Barajas, C A; Che, S; Cheatham, S; Chegwidden, A; Chekanov, S; Chekulaev, S V; Chelkov, G A; Chelstowska, M A; Chen, C; Chen, H; Chen, S; Chen, S; Chen, X; Chen, Y; Cheng, H C; Cheng, H J; Cheplakov, A; Cheremushkina, E; Cherkaoui El Moursli, R; Chernyatin, V; Cheu, E; Chevalier, L; Chiarella, V; Chiarelli, G; Chiodini, G; Chisholm, A S; Chitan, A; Chiu, Y H; Chizhov, M V; Choi, K; Chomont, A R; Chouridou, S; Christodoulou, V; Chromek-Burckhart, D; Chu, M C; Chudoba, J; Chuinard, A J; Chwastowski, J J; Chytka, L; Ciftci, A K; Cinca, D; Cindro, V; Cioara, I A; Ciocca, C; Ciocio, A; Cirotto, F; Citron, Z H; Citterio, M; Ciubancan, M; Clark, A; Clark, B L; Clark, M R; Clark, P J; Clarke, R N; Clement, C; Coadou, Y; Cobal, M; Coccaro, A; Cochran, J; Colasurdo, L; Cole, B; Colijn, A P; Collot, J; Colombo, T; Conde Muiño, P; Coniavitis, E; Connell, S H; Connelly, I A; Constantinescu, S; Conti, G; Conventi, F; Cooke, M; Cooper-Sarkar, A M; Cormier, F; Cormier, K J R; Corradi, M; Corriveau, F; Cortes-Gonzalez, A; Cortiana, G; Costa, G; Costa, M J; Costanzo, D; Cottin, G; Cowan, G; Cox, B E; Cranmer, K; Crawley, S J; Creager, R A; Cree, G; Crépé-Renaudin, S; Crescioli, F; Cribbs, W A; Cristinziani, M; Croft, V; Crosetti, G; Cueto, A; Cuhadar Donszelmann, T; Cukierman, A R; Cummings, J; Curatolo, M; Cúth, J; Czirr, H; Czodrowski, P; D'amen, G; D'Auria, S; D'eramo, L; D'Onofrio, M; Da Cunha Sargedas De Sousa, M J; Via, C Da; Dabrowski, W; Dado, T; Dai, T; Dale, O; Dallaire, F; Dallapiccola, C; Dam, M; Dandoy, J R; Daneri, M F; Dang, N P; Daniells, A C; Dann, N S; Danninger, M; Hoffmann, M Dano; Dao, V; Darbo, G; Darmora, S; Dassoulas, J; Dattagupta, A; Daubney, T; Davey, W; David, C; Davidek, T; Davies, M; Davis, D R; Davison, P; Dawe, E; Dawson, I; De, K; de Asmundis, R; De Benedetti, A; De Castro, S; De Cecco, S; De Groot, N; de Jong, P; De la Torre, H; De Lorenzi, F; De Maria, A; De Pedis, D; De Salvo, A; De Sanctis, U; De Santo, A; De Vasconcelos Corga, K; De Vivie De Regie, J B; Dearnaley, W J; Debbe, R; Debenedetti, C; Dedovich, D V; Dehghanian, N; Deigaard, I; Del Gaudio, M; Del Peso, J; Prete, T Del; Delgove, D; Deliot, F; Delitzsch, C M; Dell'Acqua, A; Dell'Asta, L; Dell'Orso, M; Della Pietra, M; Della Volpe, D; Delmastro, M; Delporte, C; Delsart, P A; DeMarco, D A; Demers, S; Demichev, M; Demilly, A; Denisov, S P; Denysiuk, D; Derendarz, D; Derkaoui, J E; Derue, F; Dervan, P; Desch, K; Deterre, C; Dette, K; Devesa, M R; Deviveiros, P O; Dewhurst, A; Dhaliwal, S; Di Bello, F A; Di Ciaccio, A; Di Ciaccio, L; Di Clemente, W K; Di Donato, C; Di Girolamo, A; Di Girolamo, B; Di Micco, B; Di Nardo, R; Di Petrillo, K F; Di Simone, A; Di Sipio, R; Di Valentino, D; Diaconu, C; Diamond, M; Dias, F A; Diaz, M A; Diehl, E B; Dietrich, J; Díez Cornell, S; Dimitrievska, A; Dingfelder, J; Dita, P; Dita, S; Dittus, F; Djama, F; Djobava, T; Djuvsland, J I; do Vale, M A B; Dobos, D; Dobre, M; Doglioni, C; Dolejsi, J; Dolezal, Z; Donadelli, M; Donati, S; Dondero, P; Donini, J; Dopke, J; Doria, A; Dova, M T; Doyle, A T; Drechsler, E; Dris, M; Du, Y; Duarte-Campderros, J; Dubreuil, A; Duchovni, E; Duckeck, G; Ducourthial, A; Ducu, O A; Duda, D; Dudarev, A; Dudder, A Chr; Duffield, E M; Duflot, L; Dührssen, M; Dumancic, M; Dumitriu, A E; Duncan, A K; Dunford, M; Duran Yildiz, H; Düren, M; Durglishvili, A; Duschinger, D; Dutta, B; Dyndal, M; Eckardt, C; Ecker, K M; Edgar, R C; Eifert, T; Eigen, G; Einsweiler, K; Ekelof, T; Kacimi, M El; Kosseifi, R El; Ellajosyula, V; Ellert, M; Elles, S; Ellinghaus, F; Elliot, A A; Ellis, N; Elmsheuser, J; Elsing, M; Emeliyanov, D; Enari, Y; Endner, O C; Ennis, J S; Erdmann, J; Ereditato, A; Ernis, G; Ernst, M; Errede, S; Escalier, M; Escobar, C; Esposito, B; Estrada Pastor, O; Etienvre, A I; Etzion, E; Evans, H; Ezhilov, A; Ezzi, M; Fabbri, F; Fabbri, L; Facini, G; Fakhrutdinov, R M; Falciano, S; Falla, R J; Faltova, J; Fang, Y; Fanti, M; Farbin, A; Farilla, A; Farina, C; Farina, E M; Farooque, T; Farrell, S; Farrington, S M; Farthouat, P; Fassi, F; Fassnacht, P; Fassouliotis, D; Faucci Giannelli, M; Favareto, A; Fawcett, W J; Fayard, L; Fedin, O L; Fedorko, W; Feigl, S; Feligioni, L; Feng, C; Feng, E J; Feng, H; Fenton, M J; Fenyuk, A B; Feremenga, L; Fernandez Martinez, P; Fernandez Perez, S; Ferrando, J; Ferrari, A; Ferrari, P; Ferrari, R; Ferreira de Lima, D E; Ferrer, A; Ferrere, D; Ferretti, C; Fiedler, F; Filipčič, A; Filipuzzi, M; Filthaut, F; Fincke-Keeler, M; Finelli, K D; Fiolhais, M C N; Fiorini, L; Fischer, A; Fischer, C; Fischer, J; Fisher, W C; Flaschel, N; Fleck, I; Fleischmann, P; Fletcher, R R M; Flick, T; Flierl, B M; Flores Castillo, L R; Flowerdew, M J; Forcolin, G T; Formica, A; Förster, F A; Forti, A; Foster, A G; Fournier, D; Fox, H; Fracchia, S; Francavilla, P; Franchini, M; Franchino, S; Francis, D; Franconi, L; Franklin, M; Frate, M; Fraternali, M; Freeborn, D; Fressard-Batraneanu, S M; Freund, B; Froidevaux, D; Frost, J A; Fukunaga, C; Fusayasu, T; Fuster, J; Gabaldon, C; Gabizon, O; Gabrielli, A; Gabrielli, A; Gach, G P; Gadatsch, S; Gadomski, S; Gagliardi, G; Gagnon, L G; Galea, C; Galhardo, B; Gallas, E J; Gallop, B J; Gallus, P; Galster, G; Gan, K K; Ganguly, S; Gao, Y; Gao, Y S; Garay Walls, F M; García, C; García Navarro, J E; Garcia-Sciveres, M; Gardner, R W; Garelli, N; Garonne, V; Gascon Bravo, A; Gasnikova, K; Gatti, C; Gaudiello, A; Gaudio, G; Gavrilenko, I L; Gay, C; Gaycken, G; Gazis, E N; Gee, C N P; Geisen, J; Geisen, M; Geisler, M P; Gellerstedt, K; Gemme, C; Genest, M H; Geng, C; Gentile, S; Gentsos, C; George, S; Gerbaudo, D; Gershon, A; Geßner, G; Ghasemi, S; Ghneimat, M; Giacobbe, B; Giagu, S; Giannetti, P; Gibson, S M; Gignac, M; Gilchriese, M; Gillberg, D; Gilles, G; Gingrich, D M; Giokaris, N; Giordani, M P; Giorgi, F M; Giraud, P F; Giromini, P; Giugni, D; Giuli, F; Giuliani, C; Giulini, M; Gjelsten, B K; Gkaitatzis, S; Gkialas, I; Gkougkousis, E L; Gkountoumis, P; Gladilin, L K; Glasman, C; Glatzer, J; Glaysher, P C F; Glazov, A; Goblirsch-Kolb, M; Godlewski, J; Goldfarb, S; Golling, T; Golubkov, D; Gomes, A; Gonçalo, R; Goncalves Gama, R; Goncalves Pinto Firmino Da Costa, J; Gonella, G; Gonella, L; Gongadze, A; González de la Hoz, S; Gonzalez-Sevilla, S; Goossens, L; Gorbounov, P A; Gordon, H A; Gorelov, I; Gorini, B; Gorini, E; Gorišek, A; Goshaw, A T; Gössling, C; Gostkin, M I; Gottardo, C A; Goudet, C R; Goujdami, D; Goussiou, A G; Govender, N; Gozani, E; Graber, L; Grabowska-Bold, I; Gradin, P O J; Gramling, J; Gramstad, E; Grancagnolo, S; Gratchev, V; Gravila, P M; Gray, C; Gray, H M; Greenwood, Z D; Grefe, C; Gregersen, K; Gregor, I M; Grenier, P; Grevtsov, K; Griffiths, J; Grillo, A A; Grimm, K; Grinstein, S; Gris, Ph; Grivaz, J-F; Groh, S; Gross, E; Grosse-Knetter, J; Grossi, G C; Grout, Z J; Grummer, A; Guan, L; Guan, W; Guenther, J; Guescini, F; Guest, D; Gueta, O; Gui, B; Guido, E; Guillemin, T; Guindon, S; Gul, U; Gumpert, C; Guo, J; Guo, W; Guo, Y; Gupta, R; Gupta, S; Gustavino, G; Gutierrez, P; Gutierrez Ortiz, N G; Gutschow, C; Guyot, C; Guzik, M P; Gwenlan, C; Gwilliam, C B; Haas, A; Haber, C; Hadavand, H K; Haddad, N; Hadef, A; Hageböck, S; Hagihara, M; Hakobyan, H; Haleem, M; Haley, J; Halladjian, G; Hallewell, G D; Hamacher, K; Hamal, P; Hamano, K; Hamilton, A; Hamity, G N; Hamnett, P G; Han, L; Han, S; Hanagaki, K; Hanawa, K; Hance, M; Haney, B; Hanke, P; Hansen, J B; Hansen, J D; Hansen, M C; Hansen, P H; Hara, K; Hard, A S; Harenberg, T; Hariri, F; Harkusha, S; Harrington, R D; Harrison, P F; Hartmann, N M; Hasegawa, M; Hasegawa, Y; Hasib, A; Hassani, S; Haug, S; Hauser, R; Hauswald, L; Havener, L B; Havranek, M; Hawkes, C M; Hawkings, R J; Hayakawa, D; Hayden, D; Hays, C P; Hays, J M; Hayward, H S; Haywood, S J; Head, S J; Heck, T; Hedberg, V; Heelan, L; Heidegger, K K; Heim, S; Heim, T; Heinemann, B; Heinrich, J J; Heinrich, L; Heinz, C; Hejbal, J; Helary, L; Held, A; Hellman, S; Helsens, C; Henderson, R C W; Heng, Y; Henkelmann, S; Henriques Correia, A M; Henrot-Versille, S; Herbert, G H; Herde, H; Herget, V; Hernández Jiménez, Y; Herr, H; Herten, G; Hertenberger, R; Hervas, L; Herwig, T C; Hesketh, G G; Hessey, N P; Hetherly, J W; Higashino, S; Higón-Rodriguez, E; Hill, E; Hill, J C; Hiller, K H; Hillier, S J; Hils, M; Hinchliffe, I; Hirose, M; Hirschbuehl, D; Hiti, B; Hladik, O; Hoad, X; Hobbs, J; Hod, N; Hodgkinson, M C; Hodgson, P; Hoecker, A; Hoeferkamp, M R; Hoenig, F; Hohn, D; Holmes, T R; Homann, M; Honda, S; Honda, T; Hong, T M; Hooberman, B H; Hopkins, W H; Horii, Y; Horton, A J; Hostachy, J-Y; Hou, S; Hoummada, A; Howarth, J; Hoya, J; Hrabovsky, M; Hrdinka, J; Hristova, I; Hrivnac, J; Hryn'ova, T; Hrynevich, A; Hsu, P J; Hsu, S-C; Hu, Q; Hu, S; Huang, Y; Hubacek, Z; Hubaut, F; Huegging, F; Huffman, T B; Hughes, E W; Hughes, G; Huhtinen, M; Huo, P; Huseynov, N; Huston, J; Huth, J; Iacobucci, G; Iakovidis, G; Ibragimov, I; Iconomidou-Fayard, L; Idrissi, Z; Iengo, P; Igonkina, O; Iizawa, T; Ikegami, Y; Ikeno, M; Ilchenko, Y; Iliadis, D; Ilic, N; Introzzi, G; Ioannou, P; Iodice, M; Iordanidou, K; Ippolito, V; Isacson, M F; Ishijima, N; Ishino, M; Ishitsuka, M; Issever, C; Istin, S; Ito, F; Iturbe Ponce, J M; Iuppa, R; Iwasaki, H; Izen, J M; Izzo, V; Jabbar, S; Jackson, P; Jacobs, R M; Jain, V; Jakobi, K B; Jakobs, K; Jakobsen, S; Jakoubek, T; Jamin, D O; Jana, D K; Jansky, R; Janssen, J; Janus, M; Janus, P A; Jarlskog, G; Javadov, N; Javůrek, T; Javurkova, M; Jeanneau, F; Jeanty, L; Jejelava, J; Jelinskas, A; Jenni, P; Jeske, C; Jézéquel, S; Ji, H; Jia, J; Jiang, H; Jiang, Y; Jiang, Z; Jiggins, S; Jimenez Pena, J; Jin, S; Jinaru, A; Jinnouchi, O; Jivan, H; Johansson, P; Johns, K A; Johnson, C A; Johnson, W J; Jon-And, K; Jones, R W L; Jones, S D; Jones, S; Jones, T J; Jongmanns, J; Jorge, P M; Jovicevic, J; Ju, X; Rozas, A Juste; Köhler, M K; Kaczmarska, A; Kado, M; Kagan, H; Kagan, M; Kahn, S J; Kaji, T; Kajomovitz, E; Kalderon, C W; Kaluza, A; Kama, S; Kamenshchikov, A; Kanaya, N; Kanjir, L; Kantserov, V A; Kanzaki, J; Kaplan, B; Kaplan, L S; Kar, D; Karakostas, K; Karastathis, N; Kareem, M J; Karentzos, E; Karpov, S N; Karpova, Z M; Karthik, K; Kartvelishvili, V; Karyukhin, A N; Kasahara, K; Kashif, L; Kass, R D; Kastanas, A; Kataoka, Y; Kato, C; Katre, A; Katzy, J; Kawade, K; Kawagoe, K; Kawamoto, T; Kawamura, G; Kay, E F; Kazanin, V F; Keeler, R; Kehoe, R; Keller, J S; Kempster, J J; Kendrick, J; Keoshkerian, H; Kepka, O; Kerševan, B P; Kersten, S; Keyes, R A; Khader, M; Khalil-Zada, F; Khanov, A; Kharlamov, A G; Kharlamova, T; Khodinov, A; Khoo, T J; Khovanskiy, V; Khramov, E; Khubua, J; Kido, S; Kilby, C R; Kim, H Y; Kim, S H; Kim, Y K; Kimura, N; Kind, O M; King, B T; Kirchmeier, D; Kirk, J; Kiryunin, A E; Kishimoto, T; Kisielewska, D; Kitali, V; Kiuchi, K; Kivernyk, O; Kladiva, E; Klapdor-Kleingrothaus, T; Klein, M H; Klein, M; Klein, U; Kleinknecht, K; Klimek, P; Klimentov, A; Klingenberg, R; Klingl, T; Klioutchnikova, T; Kluge, E-E; Kluit, P; Kluth, S; Kneringer, E; Knoops, E B F G; Knue, A; Kobayashi, A; Kobayashi, D; Kobayashi, T; Kobel, M; Kocian, M; Kodys, P; Koffas, T; Koffeman, E; Köhler, N M; Koi, T; Kolb, M; Koletsou, I; Komar, A A; Komori, Y; Kondo, T; Kondrashova, N; Köneke, K; König, A C; Kono, T; Konoplich, R; Konstantinidis, N; Kopeliansky, R; Koperny, S; Kopp, A K; Korcyl, K; Kordas, K; Korn, A; Korol, A A; Korolkov, I; Korolkova, E V; Kortner, O; Kortner, S; Kosek, T; Kostyukhin, V V; Kotwal, A; Koulouris, A; Kourkoumeli-Charalampidi, A; Kourkoumelis, C; Kourlitis, E; Kouskoura, V; Kowalewska, A B; Kowalewski, R; Kowalski, T Z; Kozakai, C; Kozanecki, W; Kozhin, A S; Kramarenko, V A; Kramberger, G; Krasnopevtsev, D; Krasny, M W; Krasznahorkay, A; Krauss, D; Kremer, J A; Kretzschmar, J; Kreutzfeldt, K; Krieger, P; Krizka, K; Kroeninger, K; Kroha, H; Kroll, J; Kroll, J; Kroseberg, J; Krstic, J; Kruchonak, U; Krüger, H; Krumnack, N; Kruse, M C; Kubota, T; Kucuk, H; Kuday, S; Kuechler, J T; Kuehn, S; Kugel, A; Kuger, F; Kuhl, T; Kukhtin, V; Kukla, R; Kulchitsky, Y; Kuleshov, S; Kulinich, Y P; Kuna, M; Kunigo, T; Kupco, A; Kupfer, T; Kuprash, O; Kurashige, H; Kurchaninov, L L; Kurochkin, Y A; Kurth, M G; Kus, V; Kuwertz, E S; Kuze, M; Kvita, J; Kwan, T; Kyriazopoulos, D; La Rosa, A; La Rosa Navarro, J L; La Rotonda, L; Lacasta, C; Lacava, F; Lacey, J; Lacker, H; Lacour, D; Ladygin, E; Lafaye, R; Laforge, B; Lagouri, T; Lai, S; Lammers, S; Lampl, W; Lançon, E; Landgraf, U; Landon, M P J; Lanfermann, M C; Lang, V S; Lange, J C; Langenberg, R J; Lankford, A J; Lanni, F; Lantzsch, K; Lanza, A; Lapertosa, A; Laplace, S; Laporte, J F; Lari, T; Manghi, F Lasagni; Lassnig, M; Laurelli, P; Lavrijsen, W; Law, A T; Laycock, P; Lazovich, T; Lazzaroni, M; Le, B; Le Dortz, O; Le Guirriec, E; Le Quilleuc, E P; LeBlanc, M; LeCompte, T; Ledroit-Guillon, F; Lee, C A; Lee, G R; Lee, S C; Lee, L; Lefebvre, B; Lefebvre, G; Lefebvre, M; Legger, F; Leggett, C; Lehan, A; Lehmann Miotto, G; Lei, X; Leight, W A; Leite, M A L; Leitner, R; Lellouch, D; Lemmer, B; Leney, K J C; Lenz, T; Lenzi, B; Leone, R; Leone, S; Leonidopoulos, C; Lerner, G; Leroy, C; Lesage, A A J; Lester, C G; Levchenko, M; Levêque, J; Levin, D; Levinson, L J; Levy, M; Lewis, D; Li, B; Li, H; Li, L; Li, Q; Li, S; Li, X; Li, Y; Liang, Z; Liberti, B; Liblong, A; Lie, K; Liebal, J; Liebig, W; Limosani, A; Lin, S C; Lin, T H; Lindquist, B E; Lionti, A E; Lipeles, E; Lipniacka, A; Lisovyi, M; Liss, T M; Lister, A; Litke, A M; Liu, B; Liu, H; Liu, H; Liu, J K K; Liu, J; Liu, J B; Liu, K; Liu, L; Liu, M; Liu, Y L; Liu, Y; Livan, M; Lleres, A; Llorente Merino, J; Lloyd, S L; Lo, C Y; Sterzo, F Lo; Lobodzinska, E M; Loch, P; Loebinger, F K; Loesle, A; Loew, K M; Loginov, A; Lohse, T; Lohwasser, K; Lokajicek, M; Long, B A; Long, J D; Long, R E; Longo, L; Looper, K A; Lopez, J A; Lopez Mateos, D; Lopez Paz, I; Solis, A Lopez; Lorenz, J; Lorenzo Martinez, N; Losada, M; Lösel, P J; Lou, X; Lounis, A; Love, J; Love, P A; Lu, H; Lu, N; Lu, Y J; Lubatti, H J; Luci, C; Lucotte, A; Luedtke, C; Luehring, F; Lukas, W; Luminari, L; Lundberg, O; Lund-Jensen, B; Luzi, P M; Lynn, D; Lysak, R; Lytken, E; Lyubushkin, V; Ma, H; Ma, L L; Ma, Y; Maccarrone, G; Macchiolo, A; Macdonald, C M; Maček, B; Machado Miguens, J; Madaffari, D; Madar, R; Mader, W F; Madsen, A; Maeda, J; Maeland, S; Maeno, T; Maevskiy, A S; Magerl, V; Mahlstedt, J; Maiani, C; Maidantchik, C; Maier, A A; Maier, T; Maio, A; Majersky, O; Majewski, S; Makida, Y; Makovec, N; Malaescu, B; Malecki, Pa; Maleev, V P; Malek, F; Mallik, U; Malon, D; Malone, C; Maltezos, S; Malyukov, S; Mamuzic, J; Mancini, G; Mandelli, L; Mandić, I; Maneira, J; Manhaes de Andrade Filho, L; Manjarres Ramos, J; Mann, A; Manousos, A; Mansoulie, B; Mansour, J D; Mantifel, R; Mantoani, M; Manzoni, S; Mapelli, L; Marceca, G; March, L; Marchese, L; Marchiori, G; Marcisovsky, M; Marjanovic, M; Marley, D E; Marroquim, F; Marsden, S P; Marshall, Z; Martensson, M U F; Marti-Garcia, S; Martin, C B; Martin, T A; Martin, V J; Martin Dit Latour, B; Martinez, M; Martinez Outschoorn, V I; Martin-Haugh, S; Martoiu, V S; Martyniuk, A C; Marzin, A; Masetti, L; Mashimo, T; Mashinistov, R; Masik, J; Maslennikov, A L; Massa, L; Mastrandrea, P; Mastroberardino, A; Masubuchi, T; Mättig, P; Maurer, J; Maxfield, S J; Maximov, D A; Mazini, R; Maznas, I; Mazza, S M; Mc Fadden, N C; Goldrick, G Mc; Mc Kee, S P; McCarn, A; McCarthy, R L; McCarthy, T G; McClymont, L I; McDonald, E F; Mcfayden, J A; Mchedlidze, G; McMahon, S J; McNamara, P C; McPherson, R A; Meehan, S; Megy, T J; Mehlhase, S; Mehta, A; Meideck, T; Meier, K; Meirose, B; Melini, D; Mellado Garcia, B R; Mellenthin, J D; Melo, M; Meloni, F; Menary, S B; Meng, L; Meng, X T; Mengarelli, A; Menke, S; Meoni, E; Mergelmeyer, S; Mermod, P; Merola, L; Meroni, C; Merritt, F S; Messina, A; Metcalfe, J; Mete, A S; Meyer, C; Meyer, J-P; Meyer, J; Meyer Zu Theenhausen, H; Miano, F; Middleton, R P; Miglioranzi, S; Mijović, L; Mikenberg, G; Mikestikova, M; Mikuž, M; Milesi, M; Milic, A; Miller, D W; Mills, C; Milov, A; Milstead, D A; Minaenko, A A; Minami, Y; Minashvili, I A; Mincer, A I; Mindur, B; Mineev, M; Minegishi, Y; Ming, Y; Mir, L M; Mistry, K P; Mitani, T; Mitrevski, J; Mitsou, V A; Miucci, A; Miyagawa, P S; Mizukami, A; Mjörnmark, J U; Mkrtchyan, T; Mlynarikova, M; Moa, T; Mochizuki, K; Mogg, P; Mohapatra, S; Molander, S; Moles-Valls, R; Monden, R; Mondragon, M C; Mönig, K; Monk, J; Monnier, E; Montalbano, A; Montejo Berlingen, J; Monticelli, F; Monzani, S; Moore, R W; Morange, N; Moreno, D; Moreno Llácer, M; Morettini, P; Morgenstern, S; Mori, D; Mori, T; Morii, M; Morinaga, M; Morisbak, V; Morley, A K; Mornacchi, G; Morris, J D; Morvaj, L; Moschovakos, P; Mosidze, M; Moss, H J; Moss, J; Motohashi, K; Mount, R; Mountricha, E; Moyse, E J W; Muanza, S; Mudd, R D; Mueller, F; Mueller, J; Mueller, R S P; Muenstermann, D; Mullen, P; Mullier, G A; Munoz Sanchez, F J; Murray, W J; Musheghyan, H; Muškinja, M; Myagkov, A G; Myska, M; Nachman, B P; Nackenhorst, O; Nagai, K; Nagai, R; Nagano, K; Nagasaka, Y; Nagata, K; Nagel, M; Nagy, E; Nairz, A M; Nakahama, Y; Nakamura, K; Nakamura, T; Nakano, I; Naranjo Garcia, R F; Narayan, R; Narrias Villar, D I; Naryshkin, I; Naumann, T; Navarro, G; Nayyar, R; Neal, H A; Nechaeva, P Yu; Neep, T J; Negri, A; Negrini, M; Nektarijevic, S; Nellist, C; Nelson, A; Nelson, M E; Nemecek, S; Nemethy, P; Nessi, M; Neubauer, M S; Neumann, M; Newman, P R; Ng, T Y; Nguyen Manh, T; Nickerson, R B; Nicolaidou, R; Nielsen, J; Nikolaenko, V; Nikolic-Audit, I; Nikolopoulos, K; Nilsen, J K; Nilsson, P; Ninomiya, Y; Nisati, A; Nishu, N; Nisius, R; Nitsche, I; Nobe, T; Noguchi, Y; Nomachi, M; Nomidis, I; Nomura, M A; Nooney, T; Nordberg, M; Norjoharuddeen, N; Novgorodova, O; Nowak, S; Nozaki, M; Nozka, L; Ntekas, K; Nurse, E; Nuti, F; O'connor, K; O'Neil, D C; O'Rourke, A A; O'Shea, V; Oakham, F G; Oberlack, H; Obermann, T; Ocariz, J; Ochi, A; Ochoa, I; Ochoa-Ricoux, J P; Oda, S; Odaka, S; Ogren, H; Oh, A; Oh, S H; Ohm, C C; Ohman, H; Oide, H; Okawa, H; Okumura, Y; Okuyama, T; Olariu, A; Oleiro Seabra, L F; Olivares Pino, S A; Oliveira Damazio, D; Olszewski, A; Olszowska, J; Onofre, A; Onogi, K; Onyisi, P U E; Oppen, H; Oreglia, M J; Oren, Y; Orestano, D; Orlando, N; Orr, R S; Osculati, B; Ospanov, R; Otero Y Garzon, G; Otono, H; Ouchrif, M; Ould-Saada, F; Ouraou, A; Oussoren, K P; Ouyang, Q; Owen, M; Owen, R E; Ozcan, V E; Ozturk, N; Pachal, K; Pacheco Pages, A; Pacheco Rodriguez, L; Padilla Aranda, C; Pagan Griso, S; Paganini, M; Paige, F; Palacino, G; Palazzo, S; Palestini, S; Palka, M; Pallin, D; Panagiotopoulou, E St; Panagoulias, I; Pandini, C E; Panduro Vazquez, J G; Pani, P; Panitkin, S; Pantea, D; Paolozzi, L; Papadopoulou, Th D; Papageorgiou, K; Paramonov, A; Paredes Hernandez, D; Parker, A J; Parker, M A; Parker, K A; Parodi, F; Parsons, J A; Parzefall, U; Pascuzzi, V R; Pasner, J M; Pasqualucci, E; Passaggio, S; Pastore, Fr; Pataraia, S; Pater, J R; Pauly, T; Pearson, B; Pedraza Lopez, S; Pedro, R; Peleganchuk, S V; Penc, O; Peng, C; Peng, H; Penwell, J; Peralva, B S; Perego, M M; Perepelitsa, D V; Perini, L; Pernegger, H; Perrella, S; Peschke, R; Peshekhonov, V D; Peters, K; Peters, R F Y; Petersen, B A; Petersen, T C; Petit, E; Petridis, A; Petridou, C; Petroff, P; Petrolo, E; Petrov, M; Petrucci, F; Pettersson, N E; Peyaud, A; Pezoa, R; Phillips, F H; Phillips, P W; Piacquadio, G; Pianori, E; Picazio, A; Piccaro, E; Pickering, M A; Piegaia, R; Pilcher, J E; Pilkington, A D; Pin, A W J; Pinamonti, M; Pinfold, J L; Pirumov, H; Pitt, M; Plazak, L; Pleier, M-A; Pleskot, V; Plotnikova, E; Pluth, D; Podberezko, P; Poettgen, R; Poggi, R; Poggioli, L; Pohl, D; Polesello, G; Poley, A; Policicchio, A; Polifka, R; Polini, A; Pollard, C S; Polychronakos, V; Pommès, K; Ponomarenko, D; Pontecorvo, L; Pope, B G; Popeneciu, G A; Poppleton, A; Pospisil, S; Potamianos, K; Potrap, I N; Potter, C J; Poulard, G; Poulsen, T; Poveda, J; Pozo Astigarraga, M E; Pralavorio, P; Pranko, A; Prell, S; Price, D; Price, L E; Primavera, M; Prince, S; Proklova, N; Prokofiev, K; Prokoshin, F; Protopopescu, S; Proudfoot, J; Przybycien, M; Puri, A; Puzo, P; Qian, J; Qin, G; Qin, Y; Quadt, A; Queitsch-Maitland, M; Quilty, D; Raddum, S; Radeka, V; Radescu, V; Radhakrishnan, S K; Radloff, P; Rados, P; Ragusa, F; Rahal, G; Raine, J A; Rajagopalan, S; Rangel-Smith, C; Rashid, T; Raspopov, S; Ratti, M G; Rauch, D M; Rauscher, F; Rave, S; Ravinovich, I; Rawling, J H; Raymond, M; Read, A L; Readioff, N P; Reale, M; Rebuzzi, D M; Redelbach, A; Redlinger, G; Reece, R; Reed, R G; Reeves, K; Rehnisch, L; Reichert, J; Reiss, A; Rembser, C; Ren, H; Rescigno, M; Resconi, S; Resseguie, E D; Rettie, S; Reynolds, E; Rezanova, O L; Reznicek, P; Rezvani, R; Richter, R; Richter, S; Richter-Was, E; Ricken, O; Ridel, M; Rieck, P; Riegel, C J; Rieger, J; Rifki, O; Rijssenbeek, M; Rimoldi, A; Rimoldi, M; Rinaldi, L; Ripellino, G; Ristić, B; Ritsch, E; Riu, I; Rizatdinova, F; Rizvi, E; Rizzi, C; Roberts, R T; Robertson, S H; Robichaud-Veronneau, A; Robinson, D; Robinson, J E M; Robson, A; Rocco, E; Roda, C; Rodina, Y; Rodriguez Bosca, S; Rodriguez Perez, A; Rodriguez Rodriguez, D; Roe, S; Rogan, C S; Røhne, O; Roloff, J; Romaniouk, A; Romano, M; Romano Saez, S M; Romero Adam, E; Rompotis, N; Ronzani, M; Roos, L; Rosati, S; Rosbach, K; Rose, P; Rosien, N-A; Rossi, E; Rossi, L P; Rosten, J H N; Rosten, R; Rotaru, M; Roth, I; Rothberg, J; Rousseau, D; Rozanov, A; Rozen, Y; Ruan, X; Rubbo, F; Rühr, F; Ruiz-Martinez, A; Rurikova, Z; Rusakovich, N A; Russell, H L; Rutherfoord, J P; Ruthmann, N; Ryabov, Y F; Rybar, M; Rybkin, G; Ryu, S; Ryzhov, A; Rzehorz, G F; Saavedra, A F; Sabato, G; Sacerdoti, S; Sadrozinski, H F-W; Sadykov, R; Safai Tehrani, F; Saha, P; Sahinsoy, M; Saimpert, M; Saito, M; Saito, T; Sakamoto, H; Sakurai, Y; Salamanna, G; Salazar Loyola, J E; Salek, D; De Bruin, P H Sales; Salihagic, D; Salnikov, A; Salt, J; Salvatore, D; Salvatore, F; Salvucci, A; Salzburger, A; Sammel, D; Sampsonidis, D; Sampsonidou, D; Sánchez, J; Sanchez Martinez, V; Sanchez Pineda, A; Sandaker, H; Sandbach, R L; Sander, C O; Sandhoff, M; Sandoval, C; Sankey, D P C; Sannino, M; Sansoni, A; Santoni, C; Santonico, R; Santos, H; Santoyo Castillo, I; Sapronov, A; Saraiva, J G; Sarrazin, B; Sasaki, O; Sato, K; Sauvan, E; Savage, G; Savard, P; Savic, N; Sawyer, C; Sawyer, L; Saxon, J; Sbarra, C; Sbrizzi, A; Scanlon, T; Scannicchio, D A; Scarcella, M; Scarfone, V; Schaarschmidt, J; Schacht, P; Schachtner, B M; Schaefer, D; Schaefer, L; Schaefer, R; Schaeffer, J; Schaepe, S; Schaetzel, S; Schäfer, U; Schaffer, A C; Schaile, D; Schamberger, R D; Scharf, V; Schegelsky, V A; Scheirich, D; Schernau, M; Schiavi, C; Schier, S; Schildgen, L K; Schillo, C; Schioppa, M; Schlenker, S; Schmidt-Sommerfeld, K R; Schmieden, K; Schmitt, C; Schmitt, S; Schmitz, S; Schnoor, U; Schoeffel, L; Schoening, A; Schoenrock, B D; Schopf, E; Schott, M; Schouwenberg, J F P; Schovancova, J; Schramm, S; Schuh, N; Schulte, A; Schultens, M J; Schultz-Coulon, H-C; Schulz, H; Schumacher, M; Schumm, B A; Schune, Ph; Schwartzman, A; Schwarz, T A; Schweiger, H; Schwemling, Ph; Schwienhorst, R; Schwindling, J; Sciandra, A; Sciolla, G; Scuri, F; Scutti, F; Searcy, J; Seema, P; Seidel, S C; Seiden, A; Seixas, J M; Sekhniaidze, G; Sekhon, K; Sekula, S J; Semprini-Cesari, N; Senkin, S; Serfon, C; Serin, L; Serkin, L; Sessa, M; Seuster, R; Severini, H; Sfiligoj, T; Sforza, F; Sfyrla, A; Shabalina, E; Shaikh, N W; Shan, L Y; Shang, R; Shank, J T; Shapiro, M; Shatalov, P B; Shaw, K; Shaw, S M; Shcherbakova, A; Shehu, C Y; Shen, Y; Sherafati, N; Sherwood, P; Shi, L; Shimizu, S; Shimmin, C O; Shimojima, M; Shipsey, I P J; Shirabe, S; Shiyakova, M; Shlomi, J; Shmeleva, A; Shoaleh Saadi, D; Shochet, M J; Shojaii, S; Shope, D R; Shrestha, S; Shulga, E; Shupe, M A; Sicho, P; Sickles, A M; Sidebo, P E; Sideras Haddad, E; Sidiropoulou, O; Sidoti, A; Siegert, F; Sijacki, Dj; Silva, J; Silverstein, S B; Simak, V; Simic, Lj; Simion, S; Simioni, E; Simmons, B; Simon, M; Sinervo, P; Sinev, N B; Sioli, M; Siragusa, G; Siral, I; Sivoklokov, S Yu; Sjölin, J; Skinner, M B; Skubic, P; Slater, M; Slavicek, T; Slawinska, M; Sliwa, K; Slovak, R; Smakhtin, V; Smart, B H; Smiesko, J; Smirnov, N; Smirnov, S Yu; Smirnov, Y; Smirnova, L N; Smirnova, O; Smith, J W; Smith, M N K; Smith, R W; Smizanska, M; Smolek, K; Snesarev, A A; Snyder, I M; Snyder, S; Sobie, R; Socher, F; Soffer, A; Søgaard, A; Soh, D A; Sokhrannyi, G; Solans Sanchez, C A; Solar, M; Soldatov, E Yu; Soldevila, U; Solodkov, A A; Soloshenko, A; Solovyanov, O V; Solovyev, V; Sommer, P; Son, H; Sopczak, A; Sosa, D; Sotiropoulou, C L; Soualah, R; Soukharev, A M; South, D; Sowden, B C; Spagnolo, S; Spalla, M; Spangenberg, M; Spanò, F; Sperlich, D; Spettel, F; Spieker, T M; Spighi, R; Spigo, G; Spiller, L A; Spousta, M; St Denis, R D; Stabile, A; Stamen, R; Stamm, S; Stanecka, E; Stanek, R W; Stanescu, C; Stanitzki, M M; Stapf, B S; Stapnes, S; Starchenko, E A; Stark, G H; Stark, J; Stark, S H; Staroba, P; Starovoitov, P; Stärz, S; Staszewski, R; Steinberg, P; Stelzer, B; Stelzer, H J; Stelzer-Chilton, O; Stenzel, H; Stewart, G A; Stockton, M C; Stoebe, M; Stoicea, G; Stolte, P; Stonjek, S; Stradling, A R; Straessner, A; Stramaglia, M E; Strandberg, J; Strandberg, S; Strauss, M; Strizenec, P; Ströhmer, R; Strom, D M; Stroynowski, R; Strubig, A; Stucci, S A; Stugu, B; Styles, N A; Su, D; Su, J; Suchek, S; Sugaya, Y; Suk, M; Sulin, V V; Sultan, Dms; Sultansoy, S; Sumida, T; Sun, S; Sun, X; Suruliz, K; Suster, C J E; Sutton, M R; Suzuki, S; Svatos, M; Swiatlowski, M; Swift, S P; Sykora, I; Sykora, T; Ta, D; Tackmann, K; Taenzer, J; Taffard, A; Tafirout, R; Tahirovic, E; Taiblum, N; Takai, H; Takashima, R; Takasugi, E H; Takeshita, T; Takubo, Y; Talby, M; Talyshev, A A; Tanaka, J; Tanaka, M; Tanaka, R; Tanaka, S; Tanioka, R; Tannenwald, B B; Tapia Araya, S; Tapprogge, S; Tarem, S; Tartarelli, G F; Tas, P; Tasevsky, M; Tashiro, T; Tassi, E; Tavares Delgado, A; Tayalati, Y; Taylor, A C; Taylor, G N; Taylor, P T E; Taylor, W; Teixeira-Dias, P; Temple, D; Ten Kate, H; Teng, P K; Teoh, J J; Tepel, F; Terada, S; Terashi, K; Terron, J; Terzo, S; Testa, M; Teuscher, R J; Theveneaux-Pelzer, T; Thomas, J P; Thomas-Wilsker, J; Thompson, P D; Thompson, A S; Thomsen, L A; Thomson, E; Tibbetts, M J; Ticse Torres, R E; Tikhomirov, V O; Tikhonov, Yu A; Timoshenko, S; Tipton, P; Tisserant, S; Todome, K; Todorova-Nova, S; Tojo, J; Tokár, S; Tokushuku, K; Tolley, E; Tomlinson, L; Tomoto, M; Tompkins, L; Toms, K; Tong, B; Tornambe, P; Torrence, E; Torres, H; Torró Pastor, E; Toth, J; Touchard, F; Tovey, D R; Treado, C J; Trefzger, T; Tresoldi, F; Tricoli, A; Trigger, I M; Trincaz-Duvoid, S; Tripiana, M F; Trischuk, W; Trocmé, B; Trofymov, A; Troncon, C; Trottier-McDonald, M; Trovatelli, M; Truong, L; Trzebinski, M; Trzupek, A; Tsang, K W; Tseng, J C-L; Tsiareshka, P V; Tsipolitis, G; Tsirintanis, N; Tsiskaridze, S; Tsiskaridze, V; Tskhadadze, E G; Tsui, K M; Tsukerman, I I; Tsulaia, V; Tsuno, S; Tsybychev, D; Tu, Y; Tudorache, A; Tudorache, V; Tulbure, T T; Tuna, A N; Tupputi, S A; Turchikhin, S; Turgeman, D; Turk Cakir, I; Turra, R; Tuts, P M; Ucchielli, G; Ueda, I; Ughetto, M; Ukegawa, F; Unal, G; Undrus, A; Unel, G; Ungaro, F C; Unno, Y; Unverdorben, C; Urban, J; Urquijo, P; Urrejola, P; Usai, G; Usui, J; Vacavant, L; Vacek, V; Vachon, B; Vadla, K O H; Vaidya, A; Valderanis, C; Valdes Santurio, E; Valente, M; Valentinetti, S; Valero, A; Valéry, L; Valkar, S; Vallier, A; Valls Ferrer, J A; Van Den Wollenberg, W; van der Graaf, H; van Gemmeren, P; Van Nieuwkoop, J; van Vulpen, I; van Woerden, M C; Vanadia, M; Vandelli, W; Vaniachine, A; Vankov, P; Vardanyan, G; Vari, R; Varnes, E W; Varni, C; Varol, T; Varouchas, D; Vartapetian, A; Varvell, K E; Vasquez, J G; Vasquez, G A; Vazeille, F; Vazquez Schroeder, T; Veatch, J; Veeraraghavan, V; Veloce, L M; Veloso, F; Veneziano, S; Ventura, A; Venturi, M; Venturi, N; Venturini, A; Vercesi, V; Verducci, M; Verkerke, W; Vermeulen, A T; Vermeulen, J C; Vetterli, M C; Viaux Maira, N; Viazlo, O; Vichou, I; Vickey, T; Vickey Boeriu, O E; Viehhauser, G H A; Viel, S; Vigani, L; Villa, M; Villaplana Perez, M; Vilucchi, E; Vincter, M G; Vinogradov, V B; Vishwakarma, A; Vittori, C; Vivarelli, I; Vlachos, S; Vlasak, M; Vogel, M; Vokac, P; Volpi, G; von der Schmitt, H; von Toerne, E; Vorobel, V; Vorobev, K; Vos, M; Voss, R; Vossebeld, J H; Vranjes, N; Vranjes Milosavljevic, M; Vrba, V; Vreeswijk, M; Vuillermet, R; Vukotic, I; Wagner, P; Wagner, W; Wagner-Kuhr, J; Wahlberg, H; Wahrmund, S; Wakabayashi, J; Walder, J; Walker, R; Walkowiak, W; Wallangen, V; Wang, C; Wang, C; Wang, F; Wang, H; Wang, H; Wang, J; Wang, J; Wang, Q; Wang, R; Wang, S M; Wang, T; Wang, W; Wang, W; Wang, Z; Wanotayaroj, C; Warburton, A; Ward, C P; Wardrope, D R; Washbrook, A; Watkins, P M; Watson, A T; Watson, M F; Watts, G; Watts, S; Waugh, B M; Webb, A F; Webb, S; Weber, M S; Weber, S W; Weber, S A; Webster, J S; Weidberg, A R; Weinert, B; Weingarten, J; Weirich, M; Weiser, C; Weits, H; Wells, P S; Wenaus, T; Wengler, T; Wenig, S; Wermes, N; Werner, M D; Werner, P; Wessels, M; Weston, T D; Whalen, K; Whallon, N L; Wharton, A M; White, A S; White, A; White, M J; White, R; Whiteson, D; Whitmore, B W; Wickens, F J; Wiedenmann, W; Wielers, M; Wiglesworth, C; Wiik-Fuchs, L A M; Wildauer, A; Wilk, F; Wilkens, H G; Williams, H H; Williams, S; Willis, C; Willocq, S; Wilson, J A; Wingerter-Seez, I; Winkels, E; Winklmeier, F; Winston, O J; Winter, B T; Wittgen, M; Wobisch, M; Wolf, T M H; Wolff, R; Wolter, M W; Wolters, H; Wong, V W S; Worm, S D; Wosiek, B K; Wotschack, J; Wozniak, K W; Wu, M; Wu, S L; Wu, X; Wu, Y; Wyatt, T R; Wynne, B M; Xella, S; Xi, Z; Xia, L; Xu, D; Xu, L; Yabsley, B; Yacoob, S; Yamaguchi, D; Yamaguchi, Y; Yamamoto, A; Yamamoto, S; Yamanaka, T; Yamatani, M; Yamauchi, K; Yamazaki, Y; Yan, Z; Yang, H; Yang, H; Yang, Y; Yang, Z; Yao, W-M; Yap, Y C; Yasu, Y; Yatsenko, E; Yau Wong, K H; Ye, J; Ye, S; Yeletskikh, I; Yigitbasi, E; Yildirim, E; Yorita, K; Yoshihara, K; Young, C; Young, C J S; Yu, J; Yu, J; Yuen, S P Y; Yusuff, I; Zabinski, B; Zacharis, G; Zaidan, R; Zaitsev, A M; Zakharchuk, N; Zalieckas, J; Zaman, A; Zambito, S; Zanzi, D; Zeitnitz, C; Zemaityte, G; Zemla, A; Zeng, J C; Zeng, Q; Zenin, O; Ženiš, T; Zerwas, D; Zhang, D; Zhang, F; Zhang, G; Zhang, H; Zhang, J; Zhang, L; Zhang, L; Zhang, M; Zhang, P; Zhang, R; Zhang, R; Zhang, X; Zhang, Y; Zhang, Z; Zhao, X; Zhao, Y; Zhao, Z; Zhemchugov, A; Zhou, B; Zhou, C; Zhou, L; Zhou, M; Zhou, M; Zhou, N; Zhu, C G; Zhu, H; Zhu, J; Zhu, Y; Zhuang, X; Zhukov, K; Zibell, A; Zieminska, D; Zimine, N I; Zimmermann, C; Zimmermann, S; Zinonos, Z; Zinser, M; Ziolkowski, M; Živković, L; Zobernig, G; Zoccoli, A; Zou, R; Zur Nedden, M; Zwalinski, L

2017-01-01

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 [Formula: see text] for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb[Formula: see text] of data collected by the ATLAS experiment and simulation of proton-proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 [Formula: see text]. The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 [Formula: see text] is quantified using a novel, data-driven, method. The method uses the energy loss, [Formula: see text], to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is [Formula: see text] and [Formula: see text] for jet transverse momenta of 200-400 [Formula: see text] and 1400-1600 [Formula: see text], respectively.

Removal of the commercial pesticides Novadim Progress, Bordeaux mixture and Karate Zeon by pullulan derivatives based flocculants.

PubMed

Ghimici, Luminita; Constantin, Marieta

2018-04-14

Cationic pullulan derivatives have been synthesized and evaluated, for the first time, as flocculants for the separation of the commercial pesticides, Novadim Progress (organophosphoric type), Bordeax mixture and Karate Zeon (pyrethroid type) from synthetic wastewater. The investigated polymer samples contained either pendent tertiary amine or quaternary ammonium salts groups. The separation efficiency was followed by UV-Vis spectroscopy, while the information regarding the mechanism involved in the separation of pesticide particles have been obtained by zeta potential. UV-Vis spectroscopy data showed strong pesticide particles/polycation interactions in case of Novadim Progress and Bordeaux mixture (maximum pesticide removal between 90% and 98%). Good separation efficiency (around 80%) of Karate Zeon emulsion was also noticed. The zeta potential measurements indicated that the charge neutralization was the common flocculation mechanism for the removal of these pesticides. In addition, the hydrogen bondings and chelation of copper ions by amide and/or tertiary amino groups of the polycations had a noteworthy contribution to the pesticide removal. Copyright © 2018 Elsevier Ltd. All rights reserved.

Separation of charge-regulated polyelectrolytes by pH-assisted diffusiophoresis.

PubMed

Hsu, Jyh-Ping; Hsu, Yen-Rei; Shang-Hung, Hsieh; Tseng, Shiojenn

2017-03-29

The potential of separating colloidal particles through simultaneous application of a salt gradient and a pH gradient, or pH-assisted diffusiophoresis, is evaluated by considering the case of spherical polyelectrolytes (PEs) having different equilibrium dissociation constants in an aqueous solution with KCl as the background salt. The simulation results gathered reveal that the dependence of the particle velocity on pH is more sensitive than that in pH-assisted electrophoresis, where an electric field and a pH gradient are applied simultaneously. This implies that the separation efficiency of pH-assisted diffusiophoresis can be better than that of pH-assisted electrophoresis. In particular, two types of PE having different equilibrium dissociation constants can be separated effectively by applying the former by enhancing/reducing their diffusiophoretic velocities.

Cherenkov and scintillation light separation in organic liquid scintillators

DOE PAGES

Caravaca, J.; Descamps, F. B.; Land, B. J.; ...

2017-11-29

The CHErenkov/Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2 g/L of PPO as a fluor (LAB/PPO). This is the first successful demonstration of Cherenkov light detection from the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338 ± 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 ± 3 % and 63 ± 8 % for time- and charge-based separation, respectively, with scintillation contamination of 36 ± 5 % andmore » 38 ± 4 %. LAB/PPO data is consistent with a rise time of τ r = 0.72 ± 0.33 ns.« less

Cherenkov and scintillation light separation in organic liquid scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caravaca, J.; Descamps, F. B.; Land, B. J.

The CHErenkov/Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2 g/L of PPO as a fluor (LAB/PPO). This is the first successful demonstration of Cherenkov light detection from the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338 ± 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 ± 3 % and 63 ± 8 % for time- and charge-based separation, respectively, with scintillation contamination of 36 ± 5 % andmore » 38 ± 4 %. LAB/PPO data is consistent with a rise time of τ r = 0.72 ± 0.33 ns.« less

Single-step electron transfer on the nanometer scale: ultra-fast charge shift in strongly coupled zinc porphyrin-gold porphyrin dyads.

PubMed

Fortage, Jérôme; Boixel, Julien; Blart, Errol; Hammarström, Leif; Becker, Hans Christian; Odobel, Fabrice

2008-01-01

The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II)-gold(III) bisporphyrin dyads (ZnP--S--AuP(+)) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert-(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45 A. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit. At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state (.+)ZnP--S--AuP(.), whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge-separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2 ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge-shifted lifetime (tau=2.3 ns) was obtained with the penta-(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge-mediated super-exchange mechanisms as electron or hole transfer. These new bis-porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long-range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnP--AuP(+) dyads linked via meso-phenyl groups to oligo-phenyleneethynylene spacers. This study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long-range charge separations.

Cationic polyelectrolyte induced separation of some inorganic contaminants and their mixture (zirconium silicate, kaolin, K-feldspar, zinc oxide) as well as of the paraffin oil from water.

PubMed

Ghimici, Luminita

2016-03-15

The flocculation efficiency of a cationic polyelectrolyte with quaternary ammonium salt groups in the backbone, namely PCA5 was evaluated on zirconium silicate (kreutzonit), kaolin, K- feldspar and zinc oxide (ZnO) suspensions prepared either with each pollutant or with their mixture. The effect of several parameters such as settling time, polymer dose and the pollutant type on the separation efficacy was evaluated and followed by optical density and zeta potential measurements. Except for ZnO, the interactions between PCA5 and suspended particles led to low residual turbidity values (around 4% for kreutzonit, 5% for kaolin and 8% for K-feldspar) as well as to the reduction of flocs settling time (from 1200 min to 30 min and 120 min in case of kaolinit and K-feldspar, respectively), that meant a high efficiency in their separation. The negative value of the zeta potential and flocs size measurements, at the optimum polymer dose, point to contribution from charge patch mechanism for the particles flocculation. A good efficiency of PCA5 in separation of paraffin oil (a minimum residual turbidity of 9.8%) has been also found. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of a temperature gradient focusing method for in situ extraterrestrial biomarker analysis.

PubMed

Danger, Grégoire; Ross, David

2008-08-01

Scanning temperature gradient focusing (TGF) is a recently described technique for the simultaneous concentration and separation of charged analytes. It allows for high analyte peak capacities and low LODs in microcolumn electrophoretic separations. In this paper, we present the application of scanning TGF for chiral separations of amino acids. Using a mixture of seven carboxyfluorescein succinimidyl ester-labeled amino acids (including five chiral amino acids) which constitute the Mars7 standard, we show that scanning TGF is a very simple and efficient method for chiral separations. The modulation of TGF separation parameters (temperature window, pressure scan rate, temperature range, and chiral selector concentration) allows optimization of peak efficiencies and analyte resolutions. The use of hydroxypropyl-beta-CD at low concentration (1-5 mmol/L) as a chiral selector, with an appropriate pressure scan rate ( -0.25 Pa/s) and with a low temperature range (3-25 degrees C over 1 cm) provided high resolution between enantiomers (Rs >1.5 for each pair of enantiomers) using a short, 4 cm long capillary. With these new results, the scanning TGF method appears to be a viable method for in situ trace biomarker analysis for future missions to Mars or other solar system bodies.

Electro-optical modeling of bulk heterojunction solar cells

NASA Astrophysics Data System (ADS)

Kirchartz, Thomas; Pieters, Bart E.; Taretto, Kurt; Rau, Uwe

2008-11-01

We introduce a model for charge separation in bulk heterojunction solar cells that combines exciton transport to the interface between donor and acceptor phases with the dissociation of the bound electron/hole pair. We implement this model into a standard semiconductor device simulator, thereby creating a convenient method to simulate the optical and electrical characteristics of a bulk heterojunction solar cell with a commercially available program. By taking into account different collection probabilities for the excitons in the polymer and the fullerene, we are able to reproduce absorptance, internal and external quantum efficiency, as well as current/voltage curves of bulk heterojunction solar cells. We further investigate the influence of mobilities of the free excitons as well as the mobilities of the free charge carriers on the performance of bulk heterojunction solar cells. We find that, in general, the highest efficiencies are achieved with the highest mobilities. However, an optimum finite mobility of free charge carriers can result from a large recombination velocity at the contacts. In contrast, Langevin-type of recombination cannot lead to finite optimum mobilities even though this mechanism has a strong dependence on the free carrier mobilities.

Simultaneous and selective decarboxylation of L-serine and deamination of L-phenylalanine in an amino acid mixture--a means of separating amino acids for synthesizing biobased chemicals.

PubMed

Teng, Yinglai; Scott, Elinor L; Witte-van Dijk, Susan C M; Sanders, Johan P M

2016-01-25

Amino acids (AAs) obtained from the hydrolysis of biomass-derived proteins are interesting feedstocks for the chemical industry. They can be prepared from the byproduct of biofuel production and agricultural wastes. They are rich in functionalities needed in petrochemicals, providing the opportunity to save energy, reagents, and process steps. However, their separation is required before they can be applied for further applications. Electrodialysis (ED) is a promising separation method, but its efficiency needs to be improved when separating AAs with similar isoelectric points. Thus, specific conversions are required to form product with different charges. Here we studied the enzymatic conversions which can be used as a means to aid the ED separation of neutral AAs. A model mixture containing L-serine, L-phenylalanine and L-methionine was used. The reactions of L-serine decarboxylase and L-phenylalanine ammonia-lyase were employed to specifically convert serine and phenylalanine into ethanolamine and trans-cinnamic acid. At the isoelectric point of methionine (pH 5.74), the charge of ethanolamine and trans-cinnamic acid are +1 and -1, therefore facilitating potential separation into three different streams by electrodialysis. Here the enzyme kinetics, specificity, inhibition and the operational stabilities were studied, showing that both enzymes can be applied simultaneously to aid the ED separation of neutral AAs. Copyright © 2015 Elsevier B.V. All rights reserved.

Visible-light-driven photoelectrochemical and photocatalytic performances of Cr-doped SrTiO3/TiO2 heterostructured nanotube arrays.

PubMed

Jiao, Zhengbo; Chen, Tao; Xiong, Jinyan; Wang, Teng; Lu, Gongxuan; Ye, Jinhua; Bi, Yingpu

2013-01-01

Well-aligned TiO2 nanotube arrays have become of increasing significance because of their unique highly ordered array structure, high specific surface area, unidirectional charge transfer and transportation features. However, their poor visible light utilization as well as the high recombination rate of photoexcited electron-hole pairs greatly limited their practical applications. Herein, we demonstrate the fabrication of visible-light-responsive heterostructured Cr-doped SrTiO3/TiO2 nanotube arrays by a simple hydrothermal method, which facilitate efficient charge separation and thus improve the photoelectrochemical as well as photocatalytic performances.

Separator Decoration with Cobalt/Nitrogen Codoped Carbon for Highly Efficient Polysulfide Confinement in Lithium-Sulfur Batteries.

PubMed

Hu, Wen; Hirota, Yuichiro; Zhu, Yexin; Yoshida, Nao; Miyamoto, Manabu; Zheng, Tao; Nishiyama, Norikazu

2017-09-22

A macro-/mesoporous Co-N-C-decorated separator is proposed to confine and reutilize migrating polysulfides. Endowed with a desirable structure and synchronous lithio- and sulfiphilic chemistry, the macro-/mesoporous Co-N-C interface manipulates large polysulfide adsorption uptake, enabling good polysulfide adsorption kinetics, reversible electrocatalysis toward redox of anchored polysulfides, and facile charge transport. It significantly boosts the performance of a simple 70 wt % S/MWCNTs (MWCNTs=multi-walled carbon nanotubes) cathode, achieving high initial capacities (e.g., 1406 mAh g -1 at 0.2C, 1203 mAh g -1 at 1C), nearly 100 % Coulombic efficiencies, and high reversible capacities after cycle tests (e.g., 828.4 mAh g -1 at 1C after 100 cycles) at both low and high current rates. These results demonstrate that decorating separator with macro-/mesoporous Co-N-C paves a feasible way for developing advanced Li-S batteries. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Progressive Design of Plasmonic Metal-Semiconductor Ensemble toward Regulated Charge Flow and Improved Vis-NIR-Driven Solar-to-Chemical Conversion.

PubMed

Han, Chuang; Quan, Quan; Chen, Hao Ming; Sun, Yugang; Xu, Yi-Jun

2017-04-01

Surface plasmon resonance (SPR)-mediated photocatalysis without the bandgap limitations of traditional semiconductor has aroused significant attention in solar-to-chemical energy conversion. However, the photocatalytic efficiency barely initiated by the SPR effects is still challenged by the low concentration and ineffective extraction of energetic hot electrons, slow charge migration rates, random charge diffusion directions, and the lack of highly active sites for redox reactions. Here, the tunable, progressive harvesting of visible-to-near infrared light (vis-NIR, λ > 570 nm) by designing plasmonic Au nanorods and metal (Au, Ag, or Pt) nanoparticle codecorated 1D CdS nanowire (1D CdS NW) ensemble is reported. The intimate integration of these metal nanostructures with 1D CdS NWs promotes the extraction and manipulated directional separation and migration of hot charge carriers in a more effective manner. Such cooperative synergy with tunable control of interfacial interaction, morphology optimization, and cocatalyst strategy results in the distinctly boosted performance for vis-NIR-driven plasmonic photocatalysis. This work highlights the significance of rationally progressive design of plasmonic metal-semiconductor-based composite system for boosting the regulated directional flow of hot charge carrier and thus the more efficient use of broad-spectrum solar energy conversion. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Peijun; Xia, Yi; Gong, Jue

Solution-processable metal-halide perovskites (MHPs) offer great promise for efficient light harvesting and emitting devices due to their long carrier lifetime and superior carrier transport characteristics. Ferroelectric effects, a hallmark of traditional oxide perovskites, was proposed to be a mechanism to suppress carrier recombination and enhance charge transport in MHPs, but the existence and influence of such polar order is still of considerable debate. Here we performed transient reflection measurements on single crystals of both inorganic and organic-inorganic (hybrid) MHPs over a range of temperatures, and demonstrate significant phonon softening in the cubic phases close to the cubic-to-tetragonal phase transition temperatures.more » Such phonon softening indicates the formation of polar domains, which grow in size upon cooling and can persist in the low-temperature tetragonal and orthorhombic phases. Our results link the extraordinary electronic properties of MHPs to the spontaneous polarizations which can contribute to more efficient charge separation and characteristics of an indirect bandgap.« less

Surface modification of TiO{sub 2} nanoparticles with carotenoids. EPR study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konovalova, T.A.; Kispert, L.D.; Konovalov, V.V.

1999-06-03

Among the semiconductors, titanium dioxide is the most suitable for many environmental applications. EPR measurements demonstrate efficient charge separation on carotenoid-modified titanium dioxide nanoparticles (7 nm). Strong complexation of carotenoids containing terminal carboxy groups ({minus}CO{sub 2}H) with the TiO{sub 2} surface leads to electron transfer from the adsorbed carotenoid molecule to the surface trapping site. For these systems, EPR signals of the carotenoid radical cations Car{sup {sm_bullet}+} and the electrons trapped on the TiO{sub 2} are observed before irradiation (77 K). Their UV-visible spectra show an absorption band with a maximum near 650 nm that is characteristic of the trappedmore » electrons. Surface modification of the TiO{sub 2} by other carotenoids results in the formation of a complex with an optical absorption band near 545 nm. These systems form charge-separated pairs [Car{sup {sm_bullet}+}{hor_ellipsis}TiO{sub 2}(e{sup {minus}}{sub tr}){sub surf}. TiO{sub 2}(e{sup {minus}}{sub tr}){sub latt}] only upon 365--600 nm illumination at 77 K. Complexation of the TiO{sub 2} colloids with carotenoids enhances spatial charge separation, shifts the absorption threshold into the visible region, and thus greatly improves the reducing ability of the semiconductor. Photoreduction of acceptor molecules such as 2,5-dichloro-1,4-benzoquinone, nitrobenzene, and oxygen is demonstrated.« less

A multimodal histamine ligand for chromatographic purification of plasmid DNA.

PubMed

Černigoj, Urh; Vidic, Urška; Barut, Miloš; Podgornik, Aleš; Peterka, Matjaž; Štrancar, Aleš

2013-03-15

To exploit different chromatographic modes for efficient plasmid DNA (pDNA) purification a novel monolithic chromatographic support bearing multimodal histamine (HISA) groups was developed and characterized. Electrostatic charge of HISA groups depends on the pH of the mobile phase, being neutral above pH 7 and becoming positively charged below. As a consequence, HISA groups exhibit predominantly ion-exchange character at low pH values, which decreases with titration of the HISA groups resulting in increased hydrophobicity. This feature enabled separation of supercoiled (sc) pDNA from other plasmid isoforms (and other process related impurities) by adjusting salt or pH gradient. The dynamic binding capacity (DBC) for a 5.1kbp large plasmid at pH 5 was 4.0 mg/ml under low salt binding conditions, remaining relatively high (3.0 mg/ml) even in the presence of 1.0 M NaCl due to the multimodal nature of HISA ligand. Only slightly lower DBC (2.7 mg/ml) was determined under preferentially hydrophobic conditions in 3.0 M (NH(4))(2)SO(4), pH 7.4. Open circular and sc pDNA isoforms were baseline separated in descending (NH(4))(2)SO(4) gradient. Furthermore, an efficient plasmid DNA separation was possible both on analytical as well as on preparative scale by applying the descending pH gradient at a constant concentration (above 3.0 M) of (NH(4))(2)SO(4). Copyright © 2013 Elsevier B.V. All rights reserved.

Organic phototransistors with nanoscale phase-separated polymer/polymer bulk heterojunction layers

NASA Astrophysics Data System (ADS)

Hwang, Hyemin; Kim, Hwajeong; Nam, Sungho; Bradley, Donal D. C.; Ha, Chang-Sik; Kim, Youngkyoo

2011-05-01

Low-cost detectors for sensing photons at a low light intensity are of crucial importance in modern science. Phototransistors can deliver better signals of low-intensity light by electrical amplification, but conventional inorganic phototransistors have a limitation owing to their high temperature processes in vacuum. In this work, we demonstrate organic phototransistors with polymer/polymer bulk heterojunction blend films (mixtures of p-type and n-type semiconducting polymers), which can be fabricated by inexpensive solution processes at room temperature. The key idea here is to effectively exploit hole charges (from p-type polymer) as major signaling carriers by employing p-type transistor geometry, while the n-type polymer helps efficient charge separation from excitons generated by incoming photons. Results showed that the present organic transistors exhibited proper functions as p-type phototransistors with ~4.3 A W-1 responsivity at a low light intensity (1 µW cm-2), which supports their encouraging potential to replace conventional cooled charge coupled devices (CCD) for low-intensity light detection applications.Low-cost detectors for sensing photons at a low light intensity are of crucial importance in modern science. Phototransistors can deliver better signals of low-intensity light by electrical amplification, but conventional inorganic phototransistors have a limitation owing to their high temperature processes in vacuum. In this work, we demonstrate organic phototransistors with polymer/polymer bulk heterojunction blend films (mixtures of p-type and n-type semiconducting polymers), which can be fabricated by inexpensive solution processes at room temperature. The key idea here is to effectively exploit hole charges (from p-type polymer) as major signaling carriers by employing p-type transistor geometry, while the n-type polymer helps efficient charge separation from excitons generated by incoming photons. Results showed that the present organic transistors exhibited proper functions as p-type phototransistors with ~4.3 A W-1 responsivity at a low light intensity (1 µW cm-2), which supports their encouraging potential to replace conventional cooled charge coupled devices (CCD) for low-intensity light detection applications. Electronic supplementary information (ESI) available: XPS spectra of P3HT:F8BT nanolayers and pristine P3HT and F8BT films, HRTEM images of P3HT:F8BT blend film detached from the substrate, and 1D GIXD profiles of P3HT:F8BT nanolayers and PI layer coated on the ITO-glass substrates. See DOI: 10.1039/c0nr00915f

Conjugated block copolymers: A building block for high-performance organic photovoltaics

NASA Astrophysics Data System (ADS)

Guo, Changhe

State-of-the-art organic photovoltaics rely on kinetically trapped, partially phase-separated structures of donor/acceptor mixtures to create a high interfacial area for exciton dissociation and networks of bicontinuous phases for charge transport. Nevertheless, intrinsic structural disorder and weak intermolecular interactions in polymer blends limit the performance and stability of organic electronic devices. We demonstrate a potential strategy to control morphology and donor/acceptor heterojunctions through conjugated block copolymer poly(3-hexylthiophene)- block-poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(thiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (P3HT-b-PFTBT). Block copolymers can self-assemble into well-ordered nanostructures ideal for photovoltaic applications. When utilized as the photovoltaic active layer, P3HT-b-PFTBT block copolymer devices demonstrate thermal stability and photoconversion efficiency of 3% well beyond devices composed of the constituent polymer blends. Resonant soft X-ray scattering (RSOXS) is used to elucidate the structural origin for efficient block copolymer photovoltaics. Energy tuning in soft X-ray ranges gives RSOXS chemical sensitivity to characterize organic thin films with compositionally similar phases or complicated multiphase systems. RSOXS reveals that the remarkable performance of P3HT-b-PFTBT devices is due to self-assembly into nanoscale in-plane lamellar morphology, which not only establishes an equilibrium microstructure amenable for exciton dissociation but also provides pathways for efficient charge transport. Furthermore, we find evidence that covalent control of donor/acceptor interfaces in block copolymers has the potential to promote charge separation and optimize the photoconversion process by limiting charge recombination. To visualize the nanostructure in organic thin films, we introduce low energy-loss energy-filtered transmission electron microscopy (EFTEM) as an important alternative approach to generate contrast from differences in optoelectronic properties and enable chemical imaging of organic materials. The widely-studied polymer/fullerene system is used as a test sample to demonstrate the application of this technique for structure characterization in the active layer of organic solar cells. In addition, well-ordered equilibrium nanostructures and covalent control of donor/acceptor interfaces make P3HT-b-PFTBT an excellent model for studying the effect of crystalline texture in the active layer on charge transport and photovoltaic performance. Solvent additives are applied to induce a drastic texture change from mainly face-on to edge-on orientations in crystalline P3HT domains of block copolymer thin films. We find that P3HT- b-PFTBT block copolymer devices demonstrate similar optimal performance, regardless of the dramatic changes in the predominant crystalline orientations adopted in P3HT domains. Our results provide further insights into the molecular organization required for efficient charge transport and device operation.

Hierarchical Inorganic Assemblies for Artificial Photosynthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Wooyul; Edri, Eran; Frei, Heinz

Artificial photosynthesis is an attractive approach for renewable fuel generation because it offers the prospect of a technology suitable for deployment on highly abundant, non-arable land. Recent leaps forward in the development of efficient and durable light absorbers and catalysts for oxygen evolution and the growing attention to catalysts for carbon dioxide activation brings into focus the tasks of hierarchically integrating the components into assemblies for closing of the photosynthetic cycle. A particular challenge is the efficient coupling of the multi-electron processes of CO 2 reduction and H 2O oxidation. Among the most important requirements for a complete integrated systemmore » are catalytic rates that match the solar flux, efficient charge transport between the various components, and scalability of the photosynthetic assembly on the unprecedented scale of terawatts in order to have impact on fuel consumption. To address these challenges, we have developed in this paper a heterogeneous inorganic materials approach with molecularly precise control of light absorption and charge transport pathways. Oxo-bridged heterobinuclear units with metal-to-metal charge-transfer transitions absorbing deep in the visible act as single photon, single charge transfer pumps for driving multi-electron catalysts. A photodeposition method has been introduced for the spatially directed assembly of nanoparticle catalysts for selective coupling to the donor or acceptor metal of the light absorber. For CO 2 reduction, a Cu oxide cluster is coupled to the Zr center of a ZrOCo light absorber, while coupling of an Ir nanoparticle catalyst for water oxidation to the Co donor affords closing of the photosynthetic cycle of CO 2 conversion by H 2O to CO and O 2. Optical, vibrational, and X-ray spectroscopy provide detailed structural knowledge of the polynuclear assemblies. Time resolved visible and rapid-scan FT-IR studies reveal charge transfer mechanisms and transient surface intermediates under photocatalytic conditions for guiding performance improvements. Separation of the water oxidation and carbon dioxide reduction half reactions by a membrane is essential for efficient photoreduction of CO 2 by H 2O to liquid fuel products. A concept of a macroscale artificial photosystem consisting of arrays of Co oxide–silica core–shell nanotubes is introduced in which each tube operates as a complete, independent photosynthetic unit with built-in membrane separation. The ultrathin amorphous silica shell with embedded molecular wires functions as a proton conducting, molecule impermeable membrane. Photoelectrochemical and transient optical measurements confirm tight control of charge transport through the membrane by the orbital energetics of the wire molecules. Finally, hierarchical arrangement of the components is accomplished by a combination of photodeposition, controlled anchoring, and atomic layer deposition methods.« less

Modeling the Electric Potential and Surface Charge Density near Charged Thunderclouds

ERIC Educational Resources Information Center

Neel, Matthew Stephen

2018-01-01

Thundercloud charge separation, or the process by which the bottom portion of a cloud gathers charge and the top portion of the cloud gathers the opposite charge, is still not thoroughly understood. Whatever the mechanism, though, a charge separation definitely exists and can lead to electrostatic discharge via cloud-to-cloud lightning and…

Effective Electrostatic Interactions Between Two Overall Neutral Surfaces with Quenched Charge Heterogeneity Over Atomic Length Scale

NASA Astrophysics Data System (ADS)

Zhou, S.

2017-12-01

Using Monte Carlo results as a reference, a classical density functional theory ( CDFT) is shown to reliably predict the forces between two heterogeneously charged surfaces immersed in an electrolyte solution, whereas the Poisson-Boltzmann ( PB) theory is demonstrated to deteriorate obviously for the same system even if the system parameters considered fall within the validity range of the PB theory in the homogeneously charged surfaces. By applying the tested CDFT, we study the effective electrostatic potential of mean force ( EPMF) between two face-face planar and hard surfaces of zero net charge on which positive and negative charges are separated and considered to present as discontinuous spots on the inside edges of the two surfaces. Main conclusions are summarized as follows: (i) strength of the EPMF in the surface charge separation case is very sensitively and positively correlated with the surface charge separation level and valency of the salt ion. Particularly, the charge separation level and the salt ion valency have a synergistic effect, which makes high limit of the EPMF strength in the surface charge separation case significantly go beyond that of the ideal homogeneously charged surface counterpart at average surface charge density similar to the average surface positive or negative charge density in the charge separation case. (ii) The surface charge distribution patterns mainly influence sign of the EPMF: symmetrical and asymmetrical patterns induce repulsive and attractive (at small distances) EPMF, respectively; but with low valency salt ions and low charge separation level the opposite may be the case. With simultaneous presence of both higher valency cation and anion, the EPMF can be repulsive at intermediate distances for asymmetrical patterns. (iii) Salt ion size has a significant impact, which makes the EPMF tend to become more and more repulsive with the ion diameter regardless of the surface charge distribution patterns and the valency of the salt ion; whereas if the 1:1 type electrolyte and the symmetrical patterns are considered, then the opposite may be the case. All of these findings can be explained self-consistently from several perspectives: an excess adsorption of the salt ions (induced by the surface charge separation) serving to raise the osmotic pressure between the plates, configuration fine-tuning in the thinner ion adsorption layer driven by the energy decrease principle, direct Coulombic interactions operating between charged objects on the two face-to-face plates involved, and net charge strength in the ion adsorption layer responsible for the net electrostatic repulsion.

Boosting Photocatalytic Hydrogen Production of a Metal-Organic Framework Decorated with Platinum Nanoparticles: The Platinum Location Matters.

PubMed

Xiao, Juan-Ding; Shang, Qichao; Xiong, Yujie; Zhang, Qun; Luo, Yi; Yu, Shu-Hong; Jiang, Hai-Long

2016-08-01

Improving the efficiency of electron-hole separation and charge-carrier utilization plays a central role in photocatalysis. Herein, Pt nanoparticles of ca. 3 nm are incorporated inside or supported on a representative metal-organic framework (MOF), UiO-66-NH2 , denoted as Pt@UiO-66-NH2 and Pt/UiO-66-NH2 , respectively, for photocatalytic hydrogen production via water splitting. Compared with the pristine MOF, both Pt-decorated MOF nanocomposites exhibit significantly improved yet distinctly different hydrogen-production activities, highlighting that the photocatalytic efficiency strongly correlates with the Pt location relative to the MOF. The Pt@UiO-66-NH2 greatly shortens the electron-transport distance, which favors the electron-hole separation and thereby yields much higher efficiency than Pt/UiO-66-NH2 . The involved mechanism has been further unveiled by means of ultrafast transient absorption and photoluminescence spectroscopy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antimicrobial membrane surfaces via efficient polyethyleneimine immobilization and cationization

NASA Astrophysics Data System (ADS)

Qiu, Wen-Ze; Zhao, Zi-Shu; Du, Yong; Hu, Meng-Xin; Xu, Zhi-Kang

2017-12-01

Biofouling control is a major task in membrane separation processes for water treatment and biomedical applications. In this work, N-alkylated polyethylenimine (PEI) is facilely and efficiently introduced onto the membrane surfaces via the co-deposition of catechol (CCh) and PEI, followed by further grafting of PEIs (600 Da, 70 kDa and 750 kDa) and cationization with methyl iodide (CH3I). The physical and chemical properties of the constructed membrane surfaces are characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential and water contact angle measurements. Antibacterial assay reveals that the optimized membrane surfaces possess around 95% antibacterial efficiency against Gram-positive Staphylococcus aureus (S. aureus) with weak adhesion of bacteria cells after 24 h of bacterial contact. Additionally, the membrane surfaces also exhibit much enhanced antifouling property during the filtration of opposite charged bovine serum albumin (BSA). These results demonstrate a useful strategy for the surface modification of separation membranes by a kind of antimicrobial and antifouling coating.

Nano-hetero functional materials for photocatalytic hydrogen generation

NASA Astrophysics Data System (ADS)

Tongying, Pornthip

This dissertation focuses on designing nanomaterials and investigating their photocatalytic response for H2 generation. Hydrogen has gained a lot of attention as a new source of sustainable energy. It can be used to directly generate power in fuel cells and to produce liquid fuels such as methanol. Water splitting is an ideal (clean) way of producing H2 because it uses water and sunlight, two renewable resources. To explore the use of nanostructures and particularly nanostructure heterojunctions for photocatalytic H2 generation, four different systems have been synthesized: (i) CdSe nanowires (NWs), (ii) CdSe/CdS core/shell NWs, (iii) CdSe NWs decorated with Au or Pt nanoparticles, and (iv) CdSe/CdS NWs decorated with Au or Pt nanoparticles. This is motivated by (a) the fact that CdSe NWs absorb light from the UV to the near infrared (b) the NW morphology simultaneously enables us to explore the role of nanoscale dimensionality in photocatalytic processes (c) a CdS coating can enhance photogenerated carrier lifetimes, and (d) metal nanoparticles are catalytically active and can also enhance charge separation efficiencies. Charge separation and charge transfer across interfaces are key aspects in the design of efficient photocatalysts for solar energy conversion. Femtosecond transient differential absorption (TDA) spectroscopy has been used as a tool to reveal how semiconductor/semiconductor and metal/semiconductor heterojunctions affect the charge separation and hydrogen generation efficiencies of these hybrid photocatalysts. The use of this technique in concert with hydrogen evolution tests also reveal how CdS, CdSe and metal NP interact within metal NP decorated CdSe and CdSe/CdS NWs during photocatalytic hydrogen generation reactions. Electron transfer events across both semiconductor/semiconductor and metal/semiconductor heterojunctions are followed to identify where H 2 is evolved and the role each heterojunction plays in determining a system's overall efficiency. To extend my study beyond 1D CdSe NWs, 2D CdSe nanosheets (NSs) have been synthesized. The use of cation exchange allows synthesizing micrometer-sized crystalline thin CdSe nanosheets (NSs), otherwise difficult to produce directly through solution-based methods. Starting from cubic-phased Cu2-xSe NSs as a template, CdSe NSs are obtained by cation exchange of copper to cadmium. This exchange reaction preserves the 2D morphology of the starting NSs and also retains the cubic crystal structure. Resulting CdSe NSs have a lateral size up to 6 mum and an average of thickness approximately 6 nm. Such large lateral dimensions are advantageous for single sheet optical measurements and for applications in optical and electronic devices.

Isotope separation by selective charge conversion and field deflection

DOEpatents

Hickman, Robert G.

1978-01-01

A deuterium-tritium separation system wherein a source beam comprised of positively ionized deuterium (D.sup.+) and tritium (T.sup.+) is converted at different charge-exchange cell sections of the system to negatively ionized deuterium (D.sup.-) and tritium (T.sup.-). First, energy is added to the beam to accelerate the D.sup.+ ions to the velocity that is optimum for conversion of the D.sup.+ ions to D.sup.- ions in a charge-exchange cell. The T.sup.+ ions are accelerated at the same time, but not to the optimum velocity since they are heavier than the D.sup.+ ions. The T.sup.+ ions are, therefore, not converted to T.sup.- ions when the D.sup.+ ions are converted to D.sup.- ions. This enables effective separation of the beam by deflection of the isotopes with an electrostatic field, the D.sup.- ions being deflected in one direction and the T.sup.+ ions being deflected in the opposite direction. Next, more energy is added to the deflected beam of T.sup.+ ions to bring the T.sup.+ ions to the optimum velocity for their conversion to T.sup.- ions. In a particular use of the invention, the beams of D.sup.- and T.sup.- ions are separately further accelerated and then converted to energetic neutral particles for injection as fuel into a thermonuclear reactor. The reactor exhaust of D.sup.+ and T.sup.+ and the D.sup.+ and T.sup.+ that was not converted in the respective sections is combined with the source beam and recycled through the system to increase the efficiency of the system.

Long-Lived Charge Separation at Heterojunctions between Semiconducting Single-Walled Carbon Nanotubes and Perylene Diimide Electron Acceptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Hyun Suk; Sisto, Thomas J.; Peurifoy, Samuel

Nonfullerene electron acceptors have facilitated a recent surge in the efficiencies of organic solar cells, although fundamental studies of the nature of exciton dissociation at interfaces with nonfullerene electron acceptors are still relatively sparse. Semiconducting single-walled carbon nanotubes (s-SWCNTs), unique one-dimensional electron donors with molecule-like absorption and highly mobile charges, provide a model system for studying interfacial exciton dissociation. Here, we investigate excited-state photodynamics at the heterojunction between (6,5) s-SWCNTs and two perylene diimide (PDI)-based electron acceptors. Each of the PDI-based acceptors, hPDI2-pyr-hPDI2 and Trip-hPDI2, is deposited onto (6,5) s-SWCNT films to form a heterojunction bilayer. Transient absorption measurements demonstratemore » that photoinduced hole/electron transfer occurs at the photoexcited bilayer interfaces, producing long-lived separated charges with lifetimes exceeding 1.0 us. Both exciton dissociation and charge recombination occur more slowly for the hPDI2-pyr-hPDI2 bilayer than for the Trip-hPDI2 bilayer. To explain such differences, we discuss the potential roles of the thermodynamic charge transfer driving force available at each interface and the different molecular structure and intermolecular interactions of PDI-based acceptors. As a result, detailed photophysical analysis of these model systems can develop the fundamental understanding of exciton dissociation between organic electron donors and nonfullerene acceptors, which has not been systematically studied.« less

Long-Lived Charge Separation at Heterojunctions between Semiconducting Single-Walled Carbon Nanotubes and Perylene Diimide Electron Acceptors

DOE PAGES

Kang, Hyun Suk; Sisto, Thomas J.; Peurifoy, Samuel; ...

2018-04-13

Nonfullerene electron acceptors have facilitated a recent surge in the efficiencies of organic solar cells, although fundamental studies of the nature of exciton dissociation at interfaces with nonfullerene electron acceptors are still relatively sparse. Semiconducting single-walled carbon nanotubes (s-SWCNTs), unique one-dimensional electron donors with molecule-like absorption and highly mobile charges, provide a model system for studying interfacial exciton dissociation. Here, we investigate excited-state photodynamics at the heterojunction between (6,5) s-SWCNTs and two perylene diimide (PDI)-based electron acceptors. Each of the PDI-based acceptors, hPDI2-pyr-hPDI2 and Trip-hPDI2, is deposited onto (6,5) s-SWCNT films to form a heterojunction bilayer. Transient absorption measurements demonstratemore » that photoinduced hole/electron transfer occurs at the photoexcited bilayer interfaces, producing long-lived separated charges with lifetimes exceeding 1.0 us. Both exciton dissociation and charge recombination occur more slowly for the hPDI2-pyr-hPDI2 bilayer than for the Trip-hPDI2 bilayer. To explain such differences, we discuss the potential roles of the thermodynamic charge transfer driving force available at each interface and the different molecular structure and intermolecular interactions of PDI-based acceptors. As a result, detailed photophysical analysis of these model systems can develop the fundamental understanding of exciton dissociation between organic electron donors and nonfullerene acceptors, which has not been systematically studied.« less

Cu2O-tipped ZnO nanorods with enhanced photoelectrochemical performance for CO2 photoreduction

NASA Astrophysics Data System (ADS)

Iqbal, Muzaffar; Wang, Yanjie; Hu, Haifeng; He, Meng; Hassan Shah, Aamir; Lin, Lin; Li, Pan; Shao, Kunjuan; Reda Woldu, Abebe; He, Tao

2018-06-01

The design of Cu2O-tipped ZnO nanorods is proposed here aiming at enhanced photoelectrochemical properties. The tip-selective deposition of Cu2O is confirmed by scanning transmission electron microscopy (STEM). The photoinduced charge behavior like charge generation, separation and transport has been thoroughly studied by UV-vis absorption analysis and different photoelectrochemical characterizations, including transient photocurrent, incident photon-to-current efficiency (IPCE), electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS), and Mott-Schottky measurements. The photoelectrochemical characterizations clearly indicate that ZnO/Cu2O structures exhibit much higher performance than pristine ZnO, due to the formation of p-n junction, as well as the tip selective growth of Cu2O on ZnO. Photocatalytic CO2 reduction in aqueous solution under UV-visible light illumination shows that CO is the main product, and with the increase of the Cu2O content in the heterostructure, the CO yield increases. This work shows that Cu2O-tipped ZnO nanorods possess improved behavior of charge generation, separation and transport, which may work as a potential candidate for photocatalytic CO2 reduction.

Long-lived charge carrier generation in ordered films of a covalent perylenediimide–diketopyrrolopyrrole–perylenediimide molecule

DOE PAGES

Hartnett, Patrick E.; Dyar, Scott M.; Margulies, Eric A.; ...

2015-07-31

The photophysics of a covalently linked perylenediimide–diketopyrrolopyrrole–perylenediimide acceptor–donor–acceptor molecule (PDI–DPP–PDI, 1) were investigated and found to be markedly different in solution versus in unannealed and solvent annealed films. Photoexcitation of 1 in toluene results in quantitative charge separation in τ = 3.1 ± 0.2 ps, with charge recombination in τ = 340 ± 10 ps, while in unannealed/disordered films of 1, charge separation occurs in τ < 250 fs, while charge recombination displays a multiexponential decay in ~6 ns. The absence of long-lived, charge separation in the disordered film suggests that few free charge carriers are generated. In contrast, uponmore » CH₂Cl₂ vapor annealing films of 1, grazing-incidence X-ray scattering shows that the molecules form a more ordered structure. Photoexcitation of the ordered films results in initial formation of a spin-correlated radical ion pair (electron–hole pair) as indicated by magnetic field effects on the formation of free charge carriers which live for ~4 μs. This result has significant implications for the design of organic solar cells based on covalent donor–acceptor systems and shows that long-lived, charge-separated states can be achieved by controlling intramolecular charge separation dynamics in well-ordered systems.« less

Mixed Metal Phosphonate- Phosphate Resins for Separation of Lanthanides from Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clearfield, Abraham

As indicated in the previous annual report the goals of this project are to develop procedures for efficient separation of lanthanides from actinides and curium from americium. These processes are required for the nuclear fuel cycle to minimize the waste and recover the valuable actinides. The basis for our study is that we have prepared a group of compounds that are porous and favor the uptake of ions with charges 3+ and 4+ over ions of lesser charge. The general formula for these materials is M(O 3PC 6H 4PO 3) 1-x/2(APO 4)x·nH 2O: where M=Zr 4+, Sn 4+, A=H, Na,more » or K and X=O, 0.5, 0.8, 1.0, 1.33 and 1.61-3. One of our tasks is to determine which members of this group of compounds are effective in carrying out the required separations. A difficulty in obtaining this required information is that the compounds are amorphous. That is they are not crystalline, therefore we need to resort to synchrotron data to obtain structural data which will be presented in detail. This information will be provided as a separate section.« less

(Charge separation in photoredox reactions). Informal annual technical progress report, October 1, 1981-October 1, 1982. [N,N,N',N'tetramethylbenzidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, L.

1982-10-21

During this period work has focused on the structural aspects of photoinduced charge separation in micellar media with initial forays into vesicular media. The primary techniques utilized are electron spin resonance and electron spin echo spectrometry. The analysis of electron spin echo modulation gives a unique handle on very weak hyperfine interactions thus providing a new structural tool for this general problem. Electron spin resonance and electron spin echo studies of the photoionization of N,N,N',N'tetramethylbenzidine (TMB) to give the cation radical have been carried out in anionic, cationic and nonionic micellar solutions frozen to 77/sup 0/K. The photoionization efficiency ofmore » TMB has also been studied in micelles with varying alkyl chain lengths of the surfactant. Stearic acid nitroxide spin probes have also been used to determine some structural aspects of the location of the neutral TMB molecule in anionic micelles before photoionization. The nitroxide work in which the nitroxide is acting as an electron acceptor also shows that a suitable electron acceptor can be located within the micellar structure. The effect of inorganic solutes on the efficiency of the photoionization of TMB in frozen micelles has also been studied. A series of electron scavenger studies have been initiated to study the effect on TMB photoionization efficiency. Electron spin echo detection of laser photogenerated TMB cation in liquid sodium dodecyl sulfate solutions at room temperature has recently been observed.« less

Trap and transfer. two-step hole injection across the Sb2S3/CuSCN interface in solid-state solar cells.

PubMed

Christians, Jeffrey A; Kamat, Prashant V

2013-09-24

In solid-state semiconductor-sensitized solar cells, commonly known as extremely thin absorber (ETA) or solid-state quantum-dot-sensitized solar cells (QDSCs), transfer of photogenerated holes from the absorber species to the p-type hole conductor plays a critical role in the charge separation process. Using Sb2S3 (absorber) and CuSCN (hole conductor), we have constructed ETA solar cells exhibiting a power conversion efficiency of 3.3%. The hole transfer from excited Sb2S3 into CuSCN, which limits the overall power conversion efficiency of these solar cells, is now independently studied using transient absorption spectroscopy. In the Sb2S3 absorber layer, photogenerated holes are rapidly localized on the sulfur atoms of the crystal lattice, forming a sulfide radical (S(-•)) species. This trapped hole is transferred from the Sb2S3 absorber to the CuSCN hole conductor with an exponential time constant of 1680 ps. This process was monitored through the spectroscopic signal seen for the S(-•) species in Sb2S3, providing direct evidence for the hole transfer dynamics in ETA solar cells. Elucidation of the hole transfer mechanism from Sb2S3 to CuSCN represents a significant step toward understanding charge separation in Sb2S3 solar cells and provides insight into the design of new architectures for higher efficiency devices.

Modeling of polymer brush grafted nanoparticles for algal harvesting

NASA Astrophysics Data System (ADS)

Goins, Jason

Microalgae derived biofuel shows great potential as a replacement to petroleum based fuels. However, industrial scale and economical production of fuel from microalgae suffer from an expensive dewatering step brought on by the organism's specific cell properties. A retrievable, paramagnetic nanoparticle polyelectrolyte brush (NPPB) has been designed as a flocculation agent to provide a low cost method in collecting algal biomass in biofuel production. In conjunction with experiment, subsequent theoretical investigations have been conducted in order to understand experimental observations and inform future design. A strategy has been implemented to provide informative descriptions for the relationship between flocculation agent parameters and dewatering efficiency. We studied the effect altering the degree of polymerization and monomer charge fraction had on the harvesting efficiency by considering flocculation as the criteria for harvesting. As the number of charges on the polymer backbone of the NPPB is increased, less NPPB concentrations are required to achieve equal harvesting efficiencies. This is a result of needing less NPPB to completely screen the effective charge on the algae surface. However, the Debye length limits the amount of charge on the algae surface one NPPB can screen. Using the free energy calculations for the complete set of pair interactions between the NPPB and the algae, we determined how many adsorbed NPPB were required in order for the force between coated algae to become attractive at some algae surface separation. This corresponded to the NPPB bridging two algae surfaces. NPPB with higher monomer charge fractions and degree of polymerizations led to a stronger bridging bond and larger bridging gap that could outweigh the algae pair repulsion. Optimized structures maximize these effects.

Bioinspired Organic PV Cells Using Photosynthetic Pigment Complex for Energy Harvesting Materials

DTIC Science & Technology

2010-05-10

ultrafast laser spectroscopy. More recently the structures of the LH2 complexes has revealed the nonameric or octameric arrangement of repeating units...Scheme 1. Compartimentalization of light harvesting and charge separation. The antenna complexes( LH2 ,LH1-RC) efficiently realize various...photosynthetic functions using cofactors (BChl a and carotenoid) assembled into the apoproteins (LH1 and LH2 ). The light-harvesting mechanisms in these

Bio-Inspired Assembly of Artificial Photosynthetic Antenna Complexes for Development of Nanobiodevices

DTIC Science & Technology

2011-06-24

extensively studied by ultrafast laser spectroscopy. More recently the structures of the LH2 complexes has revealed the nonameric and octameric arrangement of...Scheme 1). 4 Scheme 1. Compartimentalization of light harvesting and charge separation. The antenna complexes( LH2 ,LH1-RC) efficiently...realize various photosynthetic functions using cofactors (BChl a and carotenoid) assembled into the apoproteins (LH1 and LH2 ). The light-harvesting

Y-doping TiO2 nanorod arrays for efficient perovskite solar cells

NASA Astrophysics Data System (ADS)

Deng, Xinlian; Wang, Yanqing; Cui, Zhendong; Li, Long; Shi, Chengwu

2018-05-01

To improve the electron transportation in TiO2 nanorod arrays and charge separation in the interface of TiO2/perovskite, Y-doping TiO2 nanorod arrays with the length of 200 nm, diameter of 11 nm and areal density of 1050 μm-2 were successfully prepared by the hydrothermal method and the influence of Y/Ti molar ratios of 0%, 3%, 5% in the hydrothermal grown solutions on the growth of TiO2 nanorod arrays was investigated. The results revealed that the appropriate Y/Ti molar ratios can increase the areal density of the corresponding TiO2 nanorod arrays and improve the charge separation in the interface of the TiO2/perovskite. The Y-doping TiO2 nanorod array perovskite solar cells with the Y/Ti molar ratio of 3% exhibited a photoelectric conversion efficiency (PCE) of 18.11% along with an open-circuit voltage (Voc) of 1.06 V, short-circuit photocurrent density (Jsc) of 22.50 mA cm-2 and fill factor (FF) of 76.16%, while the un-doping TiO2 nanorod array perovskite solar cells gave a PCE of 16.42% along with Voc of 1.04 V, Jsc of 21.66 mA cm-2 and FF of 72.97%.

Visible Light-Driven Photocatalytic Performance of N-Doped ZnO/g-C3N4 Nanocomposites.

PubMed

Kong, Ji-Zhou; Zhai, Hai-Fa; Zhang, Wei; Wang, Shan-Shan; Zhao, Xi-Rui; Li, Min; Li, Hui; Li, Ai-Dong; Wu, Di

2017-09-06

N-doped ZnO/g-C 3 N 4 composites have been successfully prepared via a facile and cost-effective sol-gel method. The nanocomposites were systematically characterized by XRD, FE-SEM, HRTEM, FT-IR, XPS, and UV-vis DRS. The results indicated that compared with the pure N-doped ZnO, the absorption edge of binary N-doped ZnO/g-C 3 N 4 shifted to a lower energy with increasing the visible-light absorption and improving the charge separation efficiency, which would enhance its photocatalytic activity. Compared with the pure g-C 3 N 4 , ZnO, N-doped ZnO and the composite ZnO/g-C 3 N 4 , the as-prepared N-doped ZnO/g-C 3 N 4 exhibits a greatly enhanced photocatalytic degradation of methylene blue and phenol under visible-light irradiation. Meanwhile, N-doped ZnO/g-C 3 N 4 possesses a high stability. Finally, a proposed mechanism for N-doped ZnO/g-C 3 N 4 is also discussed. The improved photocatalysis can be attributed to the synergistic effect between N-doped ZnO and g-C 3 N 4 , including the energy band structure and enhanced charge separation efficiency.

Reduced graphene oxide-mediated Z-scheme BiVO4/CdS nanocomposites for boosted photocatalytic decomposition of harmful organic pollutants.

PubMed

Clament Sagaya Selvam, N; Kim, Yeong Gyeong; Kim, Dong Jin; Hong, Won-Hwa; Kim, Woong; Park, Sung Hyuk; Jo, Wan-Kuen

2018-09-01

The efficient photocatalytic degradation of harmful organic pollutants (isoniazid (ISN) and 1,4-dioxane (DX)) via the Z-scheme electron transfer mechanism was accomplished using a photostable composite photocatalyst consisting of BiVO 4 , CdS, and reduced graphene oxide (RGO). Compared to their pristine counterparts, the RGO-mediated Z-scheme CdS/BiVO 4 (CdS/RGO-BiVO 4 ) nanocomposites exhibited superior degradation activities, mainly attributed to the prolonged charge separation. RGO was found to be involved in visible-light harvesting and acted as a solid-state electron mediator at the CdS/BiVO 4 interface to realize an effective Z-scheme electron transfer pathway, avoid photocatalyst self-oxidation, and lengthen the life span of charge carriers. The results of reactive species scavenging experiments, photoluminescence measurements, and transient photocurrent measurements, as well as the calculated band potentials of the synthesized photocatalysts, supported the Z-scheme electron/hole pair separation mechanism. Additionally, the intermediates formed during the degradation of ISN and DX were identified, and a possible fragmentation pattern was proposed. This systematic work aims to develop photostable Z-scheme composites as unique photocatalytic systems for the efficient removal of harmful organic pollutants. Copyright © 2018 Elsevier B.V. All rights reserved.

Room-temperature preparation of trisilver-copper-sulfide/polymer based heterojunction thin film for solar cell application

NASA Astrophysics Data System (ADS)

Lei, Yan; Yang, Xiaogang; Gu, Longyan; Jia, Huimin; Ge, Suxiang; Xiao, Pin; Fan, Xiaoli; Zheng, Zhi

2015-04-01

Solar cells devices based on inorganic/polymer heterojunction can be a possible solution to harvest solar energy and convert to electric energy with high efficiency through a cost-effective fabrication. The solution-process method can be easily used to produce large area devices. Moreover, due to the intrinsic different charge separation, diffusion or recombination in various semiconductors, the interfaces between each component may strongly influence the inorganic/polymer heterojunction performance. Here we prepared a n-type Ag3CuS2 (Eg = 1.25 eV) nanostructured film through a room-temperature element reaction process, which was confirmed as direct bandgap semiconductor through density function theory simulation. This Ag3CuS2 film was spin-coated with an organic semiconducting poly(3-hexythiophene) (P3HT) or polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) film, which formed an inorganic/polymer heterojunction. After constructing it to a solar cell device, the power conversion efficiencies of 0.79% and 0.31% were achieved with simulated solar illumination on Ag3CuS2/P3HT and Ag3CuS2/PTB7, respectively. A possible mechanism was discussed and we showed the charge separation at interface of inorganic and polymer semiconductors played an important role.

Free-solution electrophoretic separations of DNA–drag-tag conjugates on glass microchips with no polymer network and no loss of resolution at increased electric field strength

PubMed Central

Albrecht, Jennifer Coyne; Kerby, Matthew B.; Niedringhaus, Thomas P.; Lin, Jennifer S.; Wang, Xiaoxiao; Barron, Annelise E.

2012-01-01

Here, we demonstrate the potential for high-resolution electrophoretic separations of ssDNA-protein conjugates in borosilicate glass microfluidic chips, with no sieving media and excellent repeatability. Using polynucleotides of two different lengths conjugated to moderately cationic protein polymer drag-tags, we measured separation efficiency as a function of applied electric field. In excellent agreement with prior theoretical predictions of Slater et al., resolution is found to remain constant as applied field is increased up to 700 V/cm, the highest field we were able to apply. This remarkable result illustrates the fundamentally different physical limitations of Free-Solution Conjugate Electrophoresis (FSCE)-based DNA separations relative to matrix-based DNA electrophoresis. Single-stranded DNA separations in “gels” have always shown rapidly declining resolution as the field strength is increased; this is especially true for ssDNA > 400 bases in length. FSCE’s ability to decouple DNA peak resolution from applied electric field suggests the future possibility of ultra-rapid FSCE sequencing on chips. We investigated sources of peak broadening for FSCE separations on borosilicate glass microchips, using six different protein polymer drag-tags. For drag-tags with four or more positive charges, electrostatic and adsorptive interactions with pHEA-coated microchannel walls led to appreciable band-broadening, while much sharper peaks were seen for bioconjugates with nearly charge-neutral protein drag-tags. PMID:21500207

PVC removal from mixed plastics by triboelectrostatic separation.

PubMed

Park, Chul-Hyun; Jeon, Ho-Seok; Park, Jai-Koo

2007-06-01

Ever increasing oil price and the constant growth in generation of waste plastics stimulate a research on material separation for recycling of waste plastics. At present, most waste plastics cause serious environmental problems due to the disposal by reclamation and incineration. Particularly, polyvinyl chloride (PVC) materials among waste plastics generates hazardous HCl gas, dioxins containing Cl, and so on, which lead to air pollution and shorten the life of incinerator, and it makes difficultly recycling of other plastics. Therefore, we designed a bench scale triboelectrostatic separator for PVC removal from mixed plastics (polyvinyl chloride/polyethylene terephthalate), and then carried out material separation tests. In triboelectrostatic separation, PVC and PET particles are charged negatively and positively, respectively, due to the difference of the work function of plastics in tribo charger of the fluidized-bed, and are separated by means of splitter through an opposite electric field. In this study, the charge efficiency of PVC and PET was strongly dependent on the tribo charger material (polypropylene), relative humidity (below 30%), air velocity (over 10 m/s), and mixture ratio (PET:PVC=1:1). At the optimum conditions (electrode potential of 20 kV and splitter position of -2 cm), PVC rejection and PET recovery in PET products were 99.60 and 98.10%, respectively, and the reproducibility of optimal test was very good (+/-1%). In addition, as a change of splitter position, we developed the technique to recover high purity PET (over 99.99%) although PET recovery decreases by degrees.

Coagulation of dust particles in a plasma

NASA Technical Reports Server (NTRS)

Horanyi, M.; Goertz, C. K.

1990-01-01

The electrostatic charge of small dust grains in a plasma in which the temperature varies in time is discussed, pointing out that secondary electron emission might introduce charge separation. If the sign of the charge on small grains is opposite to that on big ones, enhanced coagulation can occur which will affect the size distribution of grains in a plasma. Two scenarios where this process might be relevant are considered: a hot plasma environment with temperature fluctuations and a cold plasma environment with transient heating events. The importance of the enhanced coagulation is uncertain, because the plasma parameters in grain-producing environments such as a molecular cloud or a protoplanetary disk are not known. It is possible, however, that this process is the most efficient mechanism for the growth of grains in the size range of 0.1-500 microns.

Laser desorption vs. electrospray of polyyne-threaded rotaxanes: Preventing covalent cross-linking and promoting noncovalent aggregation

NASA Astrophysics Data System (ADS)

Neugebauer, Thomas S.; Franz, Michael; Frankenberger, Stephanie; Tykwinski, Rik R.; Drewello, Thomas

2018-02-01

Laser-induced cross-linking of polyynes is successfully hindered when the polyyne is encapsulated as part of a rotaxane and therefore protected by a surrounding macrocycle. When the rotaxane is electrosprayed, however, noncovalent aggregate ions are efficiently formed. Aggregates of considerable size (including more than 50 rotaxane molecules with masses beyond 100k Da) and charge states (up to 13 charges and beyond) have been observed. Either protons or sodium cations act as the charge carriers. These aggregates are not formed when the individual components of the rotaxane, i.e., the macrocycle or the polyyne, are separately electrosprayed. This underlines the structural importance of the rotaxane for the aggregate formation. Straightforward force field calculations indicate that the polyyne thread hinders the folding of the macrocycles, which facilitates the bonding interaction between the two components.

Charge collection and pore filling in solid-state dye-sensitized solar cells.

PubMed

Snaith, Henry J; Humphry-Baker, Robin; Chen, Peter; Cesar, Ilkay; Zakeeruddin, Shaik M; Grätzel, Michael

2008-10-22

The solar to electrical power conversion efficiency for dye-sensitized solar cells (DSCs) incorporating a solid-state organic hole-transporter can be over 5%. However, this is for devices significantly thinner than the optical depth of the active composites and by comparison to the liquid electrolyte based DSCs, which exhibit efficiencies in excess of 10%, more than doubling of this efficiency is clearly attainable if all the steps in the photovoltaic process can be optimized. Two issues are currently being addressed by the field. The first aims at enhancing the electron diffusion length by either reducing the charge recombination or enhancing the charge transport rates. This should enable a larger fraction of photogenerated charges to be collected. The second, though less actively investigated, aims to improve the physical composite formation, which in this instance is the infiltration of mesoporous TiO(2) with the organic hole-transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Here, we perform a broad experimental study to elucidate the limiting factors to the solar cell performance. We first investigate the charge transport and recombination in the solid-state dye-sensitized solar cell under realistic working conditions via small perturbation photovoltage and photocurrent decay measurements. From these measurements we deduce that the electron diffusion length near short-circuit is as long as 20 µm. However, at applied biases approaching open-circuit potential under realistic solar conditions, the diffusion length becomes comparable with the film thickness, ∼2 µm, illustrating that real losses to open-circuit voltage, fill factor and hence efficiency are occurring due to ineffective charge collection. The long diffusion length near short-circuit, on the other hand, illustrates that another process, separate from ineffective charge collection, is rendering the solar cell less than ideal. We investigate the process of TiO(2) mesopore infiltration with spiro-MeOTAD by examining the cross-sectional images of and performing photo-induced absorption spectroscopy on devices with a range of thickness, infiltrated with spiro-MeOTAD with a range of concentrations. We present our interpretation of the mechanism for material infiltration, and by improving the casting conditions demonstrate efficient charge collection through devices of over 7 µm in thickness. This investigation represents an improvement in our understanding of the limiting factors to the dye-sensitized solar cell. However, much work, focused on composite formation and improved kinetic competition, is required to realize the true potential of this concept.

Effective Charge Carrier Utilization in Photocatalytic Conversions.

PubMed

Zhang, Peng; Wang, Tuo; Chang, Xiaoxia; Gong, Jinlong

2016-05-17

Continuous efforts have been devoted to searching for sustainable energy resources to alleviate the upcoming energy crises. Among various types of new energy resources, solar energy has been considered as one of the most promising choices, since it is clean, sustainable, and safe. Moreover, solar energy is the most abundant renewable energy, with a total power of 173 000 terawatts striking Earth continuously. Conversion of solar energy into chemical energy, which could potentially provide continuous and flexible energy supplies, has been investigated extensively. However, the conversion efficiency is still relatively low since complicated physical, electrical, and chemical processes are involved. Therefore, carefully designed photocatalysts with a wide absorption range of solar illumination, a high conductivity for charge carriers, a small number of recombination centers, and fast surface reaction kinetics are required to achieve a high activity. This Account describes our recent efforts to enhance the utilization of charge carriers for semiconductor photocatalysts toward efficient solar-to-chemical energy conversion. During photocatalytic reactions, photogenerated electrons and holes are involved in complex processes to convert solar energy into chemical energy. The initial step is the generation of charge carriers in semiconductor photocatalysts, which could be enhanced by extending the light absorption range. Integration of plasmonic materials and introduction of self-dopants have been proved to be effective methods to improve the light absorption ability of photocatalysts to produce larger amounts of photogenerated charge carriers. Subsequently, the photogenerated electrons and holes migrate to the surface. Therefore, acceleration of the transport process can result in enhanced solar energy conversion efficiency. Different strategies such as morphology control and conductivity improvement have been demonstrated to achieve this goal. Fine-tuning of the morphology of nanostructured photocatalysts can reduce the migration distance of charge carriers. Improving the conductivity of photocatalysts by using graphitic materials can also improve the transport of charge carriers. Upon charge carrier migration, electrons and holes also tend to recombine. The suppression of recombination can be achieved by constructing heterojunctions that enhance charge separation in the photocatalysts. Surface states acting as recombination centers should also be removed to improve the photocatalytic efficiency. Moreover, surface reactions, which are the core chemical processes during the solar energy conversion, can be enhanced by applying cocatalysts as well as suppressing side reactions. All of these strategies have been proved to be essential for enhancing the activities of semiconductor photocatalysts. It is hoped that delicate manipulation of photogenerated charge carriers in semiconductor photocatalysts will hold the key to effective solar-to-chemical energy conversion.

Rational construction of multiple interfaces in ternary heterostructure for efficient spatial separation and transfer of photogenerated carriers in the application of photocatalytic hydrogen evolution

NASA Astrophysics Data System (ADS)

Shi, Jian-Wen; Ma, Dandan; Zou, Yajun; Fan, Zhaoyang; Shi, Jinwen; Cheng, Linhao; Ji, Xin; Niu, Chunming

2018-03-01

The design of efficient and stable photocatalyst plays a critical role in the photocatalytic hydrogen evolution from water splitting. Herein, we develop a novel ZnS/CdS/ZnO ternary heterostructure by the in-situ sulfuration of CdS/ZnO, which includes four contact interfaces: CdS-ZnS interface, ZnS-ZnO interface, CdS-ZnO interface and ZnS-CdS-ZnO ternary interface, forming three charge carrier-transfer modes (type-I, type-II and direct Z-scheme) through five carrier-transfer pathways. As a result, the separation and transfer of photoexcited electron-hole pairs are promoted significantly, resulting in a high hydrogen evolution rate of 44.70 mmol h-1 g-1, which is 2, 3.7 and 8 times higher than those of binary heterostructures, CdS/ZnO, CdS/ZnS and ZnS/ZnO, respectively, and 26.5, 280 and 298 times higher than those of single CdS, ZnO and ZnS, respectively. As a counterpart ternary heterostructure, CdS/ZnS/ZnO contains only two interfaces: CdS-ZnS interface and ZnS-ZnO interface, which form two charge carrier-transfer modes (type-I and type-II) through two carrier-transfer pathways, leading to its much lower hydrogen evolution rate (27.25 mmol h-1 g-1) than ZnS/CdS/ZnO ternary heterostructure. This work is relevant for understanding the charge-transfer pathways between multi-interfaces in multicomponent heterojunctions.

Domain Formation Induced by the Adsorption of Charged Proteins on Mixed Lipid Membranes

PubMed Central

Mbamala, Emmanuel C.; Ben-Shaul, Avinoam; May, Sylvio

2005-01-01

Peripheral proteins can trigger the formation of domains in mixed fluid-like lipid membranes. We analyze the mechanism underlying this process for proteins that bind electrostatically onto a flat two-component membrane, composed of charged and neutral lipid species. Of particular interest are membranes in which the hydrocarbon lipid tails tend to segregate owing to nonideal chain mixing, but the (protein-free) lipid membrane is nevertheless stable due to the electrostatic repulsion between the charged lipid headgroups. The adsorption of charged, say basic, proteins onto a membrane containing anionic lipids induces local lipid demixing, whereby charged lipids migrate toward (or away from) the adsorption site, so as to minimize the electrostatic binding free energy. Apart from reducing lipid headgroup repulsion, this process creates a gradient in lipid composition around the adsorption zone, and hence a line energy whose magnitude depends on the protein's size and charge and the extent of lipid chain nonideality. Above a certain critical lipid nonideality, the line energy is large enough to induce domain formation, i.e., protein aggregation and, concomitantly, macroscopic lipid phase separation. We quantitatively analyze the thermodynamic stability of the dressed membrane based on nonlinear Poisson-Boltzmann theory, accounting for both the microscopic characteristics of the proteins and lipid composition modulations at and around the adsorption zone. Spinodal surfaces and critical points of the dressed membranes are calculated for several different model proteins of spherical and disk-like shapes. Among the models studied we find the most substantial protein-induced membrane destabilization for disk-like proteins whose charges are concentrated in the membrane-facing surface. If additional charges reside on the side faces of the proteins, direct protein-protein repulsion diminishes considerably the propensity for domain formation. Generally, a highly charged flat face of a macroion appears most efficient in inducing large compositional gradients, hence a large and unfavorable line energy and consequently lateral macroion aggregation and, concomitantly, macroscopic lipid phase separation. PMID:15626713

Magnetic nanoparticles for efficient cell transduction with Semliki Forest virus.

PubMed

Kurena, Baiba; Vežāne, Aleksandra; Skrastiņa, Dace; Trofimova, Olga; Zajakina, Anna

2017-07-01

Semliki Forest virus (SFV) is a potential cancer gene therapy vector capable of providing high and transient expression of heterologous proteins in mammalian cells. However, SFV has shown suboptimal transduction levels in several cancer cell types as well as wide biodistribution of SFV has been observed after in vivo applications. Magnetic nanoparticles (MNPs) have been shown to increase cell transduction with several viral vectors in vitro under an external magnetic field and enhance magnetically guided viral vector delivery. Here, we examined a panel of MNPs for enhanced cancer cell transduction with SFV vector. Magneto-transduction using positively charged MNPs increased Semliki Forest virus transduction in TS/A mouse mammary carcinoma cells in vitro in the presence of fetal bovine serum. Positively charged MNPs efficiently captured SFV particles independently of capturing medium, and MNPs-SFV complexes were successfully separated from suspension by magnetic precipitation. These results reveal the potential application of MNPs for enhanced gene delivery by SFV vector as well as proposes magnetic precipitation for efficient concentration of SFV particles from different media. Copyright © 2017 Elsevier B.V. All rights reserved.

The role of energy losses in photosynthetic light harvesting

NASA Astrophysics Data System (ADS)

Krüger, T. P. J.; van Grondelle, R.

2017-07-01

Photosynthesis operates at the bottom of the food chain to convert the energy of light into carbohydrates at a remarkable global rate of about 130 TW. Nonetheless, the overall photosynthetic process has a conversion efficiency of a few percent at best, significantly less than bottom-up photovoltaic cells. The primary photosynthetic steps, consisting of light harvesting and charge separation, are often presented as having near-unity quantum efficiency but this holds only true under ideal conditions. In this review, we discuss the importance of energy loss mechanisms to establish robustness in photosynthetic light harvesting. Thermal energy dissipation of light-harvesting complexes (LHCs) in different environments is investigated and the relationships and contrasts between concentration quenching of high pigment concentrations, photoprotection (non-photochemical quenching), quenching due to protein aggregation, and fluorescence blinking are discussed. The role of charge-transfer states in light harvesting and energy dissipation is highlighted and the importance of controlled protein structural disorder to switch the light-harvesting antennae between effective light harvesters and efficient energy quenchers is underscored. The main LHC of plants, LHCII, is used as a prime example.

Improving the Performance of PbS Quantum Dot Solar Cells by Optimizing ZnO Window Layer

NASA Astrophysics Data System (ADS)

Yang, Xiaokun; Hu, Long; Deng, Hui; Qiao, Keke; Hu, Chao; Liu, Zhiyong; Yuan, Shengjie; Khan, Jahangeer; Li, Dengbing; Tang, Jiang; Song, Haisheng; Cheng, Chun

2017-04-01

Comparing with hot researches in absorber layer, window layer has attracted less attention in PbS quantum dot solar cells (QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on. Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V oc of 18%, J sc of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aaboud, M.; Aad, G.; Abbott, B.

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb -1 of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of charged-particle separations andmore » multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 GeV is quantified using a novel, data-driven, method. The method uses the energy loss, dE/dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is 0.061±0.006 (stat.)±0.014 (syst.) and 0.093±0.017 (stat.)±0.021 (syst.) for jet transverse momenta of 200–400 GeV and 1400–1600 GeV, respectively.« less

High yield of secondary B-side electron transfer in mutant Rhodobacter capsulatus reaction centers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kressel, Lucas; Faries, Kaitlyn M.; Wander, Marc J.

2014-08-01

From the crystal structures of reaction centers (RCs) from purple photosynthetic bacteria, two pathways for electron transfer (ET) are apparent but only one pathway (the A side) operates in the native protein-cofactor complex. Partial activation of the B-side pathway has unveiled the true inefficiencies of ET processes on that side in comparison to analogous reactions on the A side. Of significance are the relative rate constants for forward ET and the competing charge recombination reactions. On the B side, these rate constants are nearly equal for the secondary charge-separation step (ET from bacteriopheophytin to quinone), relegating the yield of thismore » process to < 50%. Herein we report efforts to optimize this step. In surveying all possible residues at position 131 in the M subunit, we discovered that when glutamic acid replaces the native valine the efficiency of the secondary ET is nearly two-fold higher than in the wild-type RC. The positive effect of M131 Glu is likely due to formation of a hydrogen bond with the ring V keto group of the B-side bacteriopheophytin leading to stabilization of the charge-separated state involving this cofactor. In conclusion, this change slows charge recombination by roughly a factor of two and affords the improved yield of the desired forward ET to the B-side quinone terminal acceptor.« less

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2

DOE PAGES

Aaboud, M.; Aad, G.; Abbott, B.; ...

2017-10-11

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb -1 of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of charged-particle separations andmore » multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 GeV is quantified using a novel, data-driven, method. The method uses the energy loss, dE/dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is 0.061±0.006 (stat.)±0.014 (syst.) and 0.093±0.017 (stat.)±0.021 (syst.) for jet transverse momenta of 200–400 GeV and 1400–1600 GeV, respectively.« less

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation

NASA Astrophysics Data System (ADS)

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-01

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H2 evolution has been studied extensively. TiO2 is a well-established semiconductor in the field of photocatalytic H2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C3N4-modified TiO2 nanobelts (TCN–Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K–g-C3N4 and the TiO2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C3N4, suggesting increased charge transfer efficiency. The H2 production efficiency of the TCN–Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H2 production activity was due to the superior charge separation and electron transfer efficiency of TCN–Kx composite materials.

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation.

PubMed

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-25

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H 2 evolution has been studied extensively. TiO 2 is a well-established semiconductor in the field of photocatalytic H 2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C 3 N 4 -modified TiO 2 nanobelts (TCN-Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K-g-C 3 N 4 and the TiO 2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C 3 N 4 , suggesting increased charge transfer efficiency. The H 2 production efficiency of the TCN-Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H 2 production activity was due to the superior charge separation and electron transfer efficiency of TCN-Kx composite materials.

A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, Alexander S.; Bryantsev, Vyacheslav S.

An accurate description of solvation effects for trivalent lanthanide ions is a main stumbling block to the qualitative prediction of selectivity trends along the lanthanide series. In this work, we propose a simple model to describe the differential effect of solvation in the competitive binding of a ligand by lanthanide ions by including weakly co-ordinated counterions in the complexes of more than a +1 charge. The success of the approach to quantitatively reproduce selectivities obtained from aqueous phase complexation studies demonstrates its potential for the design and screening of new ligands for efficient size-based separation.

A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides

DOE PAGES

Ivanov, Alexander S.; Bryantsev, Vyacheslav S.

2016-06-20

An accurate description of solvation effects for trivalent lanthanide ions is a main stumbling block to the qualitative prediction of selectivity trends along the lanthanide series. In this work, we propose a simple model to describe the differential effect of solvation in the competitive binding of a ligand by lanthanide ions by including weakly co-ordinated counterions in the complexes of more than a +1 charge. The success of the approach to quantitatively reproduce selectivities obtained from aqueous phase complexation studies demonstrates its potential for the design and screening of new ligands for efficient size-based separation.

Electronic coupling in iron oxide-modified TiO2 leads to a reduced band gap and charge separation for visible light active photocatalysis.

PubMed

Nolan, Michael

2011-10-28

In recent experiments Tada et al. have shown that TiO(2) surfaces modified with iron oxide display visible light photocatalytic activity. This paper presents first principles simulations of iron oxide clusters adsorbed at the rutile TiO(2) (110) surface to elucidate the origin of the visible light photocatalytic activity of iron oxide modified TiO(2). Small iron oxide clusters adsorb at rutile (110) surface and their presence shifts the valence band so that the band gap of the composite is narrowed towards the visible, thus confirming the origin of the visible light activity of this composite material. The presence of iron oxide at the TiO(2) surface leads to charge separation, which is the origin of enhanced photocatalytic efficiency, consistent with experimental photoluminesence and photocurrent data. Surface modification of a metal oxide is thus an interesting route in the development of visible light photocatalytic materials. This journal is © the Owner Societies 2011

Removal of unburned carbon from coal fly ash using a pneumatic triboelectrostatic separator.

PubMed

Kim, J K; Cho, H C; Kim, S C

2001-01-01

A pneumatic triboelectrostatic beneficiation system of fly ash was studied using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests were conducted to evaluate the charge density and the separation efficiency at various operating conditions. It was found that the higher charge densities were obtained at (1) the air flow rate of 1.75 m3/min. (2) the feed rate of less than 50 kg/h. and (3) the relative humidity of less than 30% with use of a stainless ejector tribocharger. With these optimum conditions, the clean ash of less than LOI 3% was recovered with a yield over 75% when operated at the diffuser slit gap of 4mm, the diffuser outlet velocity of 16.1-18.6 m/s, and the distance of 15 cm between diffuser slit and splitter. The optimum feed rate was found to be 740 kg/h per m2 of electrode surface area, which can be used as a scale-up factor of electroseparator.

Enhancement of plasmon-induced charge separation efficiency by coupling silver nanocubes with a thin gold film

NASA Astrophysics Data System (ADS)

Akiyoshi, Kazutaka; Saito, Koichiro; Tatsuma, Tetsu

2016-10-01

Plasmon-induced charge separation (PICS), in which an energetic electron is injected from a plasmonic nanoparticle (NP) to a semiconductor on contact, is often inhibited by a protecting agent adsorbed on the NP. We addressed this issue for an Ag nanocube-TiO2 system by coating it with a thin Au layer or by inserting the Au layer between the nanocubes (NCs) and TiO2. Both of the electrodes exhibit much higher photocurrents due to PICS than the electrodes without the Au film or the Ag NCs. These photocurrent enhancements can be explained in terms of PICS with accelerated electron transfer, in which electron injection from the Ag NCs or Ag@Au core-shell NCs to TiO2 is promoted by the Au film, or PICS enhanced by a nanoantenna effect, in which the electron injection from the Au film to TiO2 is enhanced by optical near field generated by the Ag NC.

Semiconducting Single-Walled Carbon Nanotubes in Solar Energy Harvesting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blackburn, Jeffrey L.

Semiconducting single-walled carbon nanotubes (s-SWCNTs) represent a tunable model one-dimensional system with exceptional optical and electronic properties. High-throughput separation and purification strategies have enabled the integration of s-SWCNTs into a number of optoelectronic applications, including photovoltaics (PVs). In this Perspective, we discuss the fundamental underpinnings of two model PV interfaces involving s-SWCNTs. We first discuss s-SWCNT-fullerene heterojunctions where exciton dissociation at the donor-acceptor interface drives solar energy conversion. Next, we discuss charge extraction at the interface between s-SWCNTs and a photoexcited perovskite active layer. In each case, the use of highly enriched semiconducting SWCNT samples enables fundamental insights into themore » thermodynamic and kinetic mechanisms that drive the efficient conversion of solar photons into long-lived separated charges. As a result, these model systems help to establish design rules for next-generation PV devices containing well-defined organic semiconductor layers and help to frame a number of important outstanding questions that can guide future studies.« less

Semiconducting Single-Walled Carbon Nanotubes in Solar Energy Harvesting

DOE PAGES

Blackburn, Jeffrey L.

2017-06-14

Semiconducting single-walled carbon nanotubes (s-SWCNTs) represent a tunable model one-dimensional system with exceptional optical and electronic properties. High-throughput separation and purification strategies have enabled the integration of s-SWCNTs into a number of optoelectronic applications, including photovoltaics (PVs). In this Perspective, we discuss the fundamental underpinnings of two model PV interfaces involving s-SWCNTs. We first discuss s-SWCNT-fullerene heterojunctions where exciton dissociation at the donor-acceptor interface drives solar energy conversion. Next, we discuss charge extraction at the interface between s-SWCNTs and a photoexcited perovskite active layer. In each case, the use of highly enriched semiconducting SWCNT samples enables fundamental insights into themore » thermodynamic and kinetic mechanisms that drive the efficient conversion of solar photons into long-lived separated charges. As a result, these model systems help to establish design rules for next-generation PV devices containing well-defined organic semiconductor layers and help to frame a number of important outstanding questions that can guide future studies.« less

A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sigaud, L., E-mail: lsigaud@if.uff.br; Jesus, V. L. B. de; Ferreira, Natalia

In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell—to study ionization of atoms and molecules by electron impact—is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements.

PubMed

Sigaud, L; de Jesus, V L B; Ferreira, Natalia; Montenegro, E C

2016-08-01

In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell-to study ionization of atoms and molecules by electron impact-is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

Future carbon beams at SPIRAL1 facility: Which method is the most efficient?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maunoury, L., E-mail: maunoury@ganil.fr; Delahaye, P.; Dubois, M.

2014-02-15

Compared to in-flight facilities, Isotope Separator On-Line ones can in principle produce significantly higher radioactive ion beam intensities. On the other hand, they have to cope with delays for the release and ionization which make the production of short-lived isotopes ion beams of reactive and refractory elements particularly difficult. Many efforts are focused on extending the capabilities of ISOL facilities to those challenging beams. In this context, the development of carbon beams is triggering interest [H. Frånberg, M. Ammann, H. W. Gäggeler, and U. Köster, Rev. Sci. Instrum. 77, 03A708 (2006); M. Kronberger, A. Gottberg, T. M. Mendonca, J. P.more » Ramos, C. Seiffert, P. Suominen, and T. Stora, in Proceedings of the EMIS 2012 [Nucl. Instrum. Methods Phys. Res. B Production of molecular sideband radioisotope beams at CERN-ISOLDE using a Helicon-type plasma ion source (to be published)]: despite its refractory nature, radioactive carbon beams can be produced from molecules (CO or CO{sub 2}), which can subsequently be broken up and multi-ionized to the required charge state in charge breeders or ECR sources. This contribution will present results of experiments conducted at LPSC with the Phoenix charge breeder and at GANIL with the Nanogan ECR ion source for the ionization of carbon beams in the frame of the ENSAR and EMILIE projects. Carbon is to date the lightest condensable element charge bred with an ECR ion source. Charge breeding efficiencies will be compared with those obtained using Nanogan ECRIS and charge breeding times will be presented as well.« less

Future carbon beams at SPIRAL1 facility: Which method is the most efficient?

NASA Astrophysics Data System (ADS)

Maunoury, L.; Delahaye, P.; Angot, J.; Dubois, M.; Dupuis, M.; Frigot, R.; Grinyer, J.; Jardin, P.; Leboucher, C.; Lamy, T.

2014-02-01

Compared to in-flight facilities, Isotope Separator On-Line ones can in principle produce significantly higher radioactive ion beam intensities. On the other hand, they have to cope with delays for the release and ionization which make the production of short-lived isotopes ion beams of reactive and refractory elements particularly difficult. Many efforts are focused on extending the capabilities of ISOL facilities to those challenging beams. In this context, the development of carbon beams is triggering interest [H. Frånberg, M. Ammann, H. W. Gäggeler, and U. Köster, Rev. Sci. Instrum. 77, 03A708 (2006); M. Kronberger, A. Gottberg, T. M. Mendonca, J. P. Ramos, C. Seiffert, P. Suominen, and T. Stora, in Proceedings of the EMIS 2012 [Nucl. Instrum. Methods Phys. Res. B Production of molecular sideband radioisotope beams at CERN-ISOLDE using a Helicon-type plasma ion source (to be published)]: despite its refractory nature, radioactive carbon beams can be produced from molecules (CO or CO2), which can subsequently be broken up and multi-ionized to the required charge state in charge breeders or ECR sources. This contribution will present results of experiments conducted at LPSC with the Phoenix charge breeder and at GANIL with the Nanogan ECR ion source for the ionization of carbon beams in the frame of the ENSAR and EMILIE projects. Carbon is to date the lightest condensable element charge bred with an ECR ion source. Charge breeding efficiencies will be compared with those obtained using Nanogan ECRIS and charge breeding times will be presented as well.

Future carbon beams at SPIRAL1 facility: which method is the most efficient?

PubMed

Maunoury, L; Delahaye, P; Angot, J; Dubois, M; Dupuis, M; Frigot, R; Grinyer, J; Jardin, P; Leboucher, C; Lamy, T

2014-02-01

Compared to in-flight facilities, Isotope Separator On-Line ones can in principle produce significantly higher radioactive ion beam intensities. On the other hand, they have to cope with delays for the release and ionization which make the production of short-lived isotopes ion beams of reactive and refractory elements particularly difficult. Many efforts are focused on extending the capabilities of ISOL facilities to those challenging beams. In this context, the development of carbon beams is triggering interest [H. Frånberg, M. Ammann, H. W. Gäggeler, and U. Köster, Rev. Sci. Instrum. 77, 03A708 (2006); M. Kronberger, A. Gottberg, T. M. Mendonca, J. P. Ramos, C. Seiffert, P. Suominen, and T. Stora, in Proceedings of the EMIS 2012 [Nucl. Instrum. Methods Phys. Res. B Production of molecular sideband radioisotope beams at CERN-ISOLDE using a Helicon-type plasma ion source (to be published)]: despite its refractory nature, radioactive carbon beams can be produced from molecules (CO or CO2), which can subsequently be broken up and multi-ionized to the required charge state in charge breeders or ECR sources. This contribution will present results of experiments conducted at LPSC with the Phoenix charge breeder and at GANIL with the Nanogan ECR ion source for the ionization of carbon beams in the frame of the ENSAR and EMILIE projects. Carbon is to date the lightest condensable element charge bred with an ECR ion source. Charge breeding efficiencies will be compared with those obtained using Nanogan ECRIS and charge breeding times will be presented as well.

Adsorbent for hydroquinone removal based on graphene oxide functionalized with magnetic cyclodextrin-chitosan.

PubMed

Li, Leilei; Fan, Lulu; Sun, Min; Qiu, Huamin; Li, Xiangjun; Duan, Huimin; Luo, Chuannan

2013-07-01

Magnetic cyclodextrin-chitosan/graphene oxide (CCGO) with high surface area was synthesized via a simple chemical bonding method. The characteristics results of FTIR, SEM, TEM and XRD showed that CCGO was prepared. The large saturation magnetization (22.35 emu/g) of the synthesized nanoparticles allows fast separation of the CCGO from liquid suspension. These composites could efficiently remove hydroquinone from simulated wastewater with a facile subsequent solid-liquid separation because of their large area, abundant hydroxyl and amino groups with handy operation, and hydrophobicity. The hydroquinone removal process was found to obey the Freundlich adsorption model and its kinetics followed pseudo-second-order rate equation. The hydroquinone removal mechanism of CCGO might be attributed to the electrostatic adsorption of hydroquinone in the form of negatively charged hydroquinone by positively charged chitosan, accompanying hydroquinone absorbed by cavities of the cyclodextrin, and forming hydrogen bonds between hydroquinone and the hydroxyl groups on the surface of CCGO. The used CCGO could be recovered with ethanol. This study provides a promising nanostructured adsorbent with easy separation property for heavy metal ions removal. Copyright © 2013 Elsevier B.V. All rights reserved.

ZnO/ZnSxSe1-x core/shell nanowire arrays as photoelectrodes with efficient visible light absorption

NASA Astrophysics Data System (ADS)

Wang, Zhenxing; Zhan, Xueying; Wang, Yajun; Safdar, Muhammad; Niu, Mutong; Zhang, Jinping; Huang, Ying; He, Jun

2012-08-01

ZnO/ZnSxSe1-x core/shell nanowires have been synthesized on n+-type silicon substrate via a two-step chemical vapor deposition method. Transmission electron microscopy reveals that ZnSxSe1-x can be deposited on the entire surface of ZnO nanowire, forming coaxial heterojunction along ZnO nanowire with very smooth shell surface and high shell thickness uniformity. The photoelectrode after deposition of the ternary alloy shell significantly improves visible light absorption efficiency. Electrochemical impedance spectroscopy results explicitly indicate that the introduction of ZnSxSe1-x shell to ZnO nanowires effectively improves the photogenerated charge separation process. Our finding opens up an efficient means for achieving high efficient energy conversion devices.

Photocarrier generation from interlayer charge-transfer transitions in WS2-graphene heterostructures

PubMed Central

Yuan, Long; Chung, Ting-Fung; Kuc, Agnieszka; Wan, Yan; Xu, Yang; Chen, Yong P.; Heine, Thomas; Huang, Libai

2018-01-01

Efficient interfacial carrier generation in van der Waals heterostructures is critical for their electronic and optoelectronic applications. We demonstrate broadband photocarrier generation in WS2-graphene heterostructures by imaging interlayer coupling–dependent charge generation using ultrafast transient absorption microscopy. Interlayer charge-transfer (CT) transitions and hot carrier injection from graphene allow carrier generation by excitation as low as 0.8 eV below the WS2 bandgap. The experimentally determined interlayer CT transition energies are consistent with those predicted from the first-principles band structure calculation. CT interactions also lead to additional carrier generation in the visible spectral range in the heterostructures compared to that in the single-layer WS2 alone. The lifetime of the charge-separated states is measured to be ~1 ps. These results suggest that interlayer interactions make graphene–two-dimensional semiconductor heterostructures very attractive for photovoltaic and photodetector applications because of the combined benefits of high carrier mobility and enhanced broadband photocarrier generation. PMID:29423439

Impacts of side chain and excess energy on the charge photogeneration dynamics of low-bandgap copolymer-fullerene blends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huo, Ming-Ming, E-mail: hithuomm@163.com; Zhang, Jian-Ping, E-mail: jpzhang@chem.ruc.edu.cn, E-mail: hjhzlz@iccas.ac.cn; Department of Chemistry, Renmin University of China, Beijing 100872

2014-02-28

Primary charge photogeneration dynamics in neat and fullerene-blended films of a pair of alternating benzo[1,2-b:4,5-b{sup ′}]dithiophene (BDT) and thieno[3,4-b]thiophene (TT) copolymers are comparatively studied by using near-infrared, time-resolved absorption (TA) spectroscopy under low excitation photon fluence. PBDTTT-E and PBDTTT-C, differed merely in the respective TT-substituents of ester (-E) and carbonyl (-C), show distinctly different charge photogeneration dynamics. The pair of neat PBDTTT films show exciton lifetimes of ∼0.1 ns and fluorescence quantum yields below 0.2%, as well as prominent excess-energy enhanced exciton dissociation. In addition, PBDTTT-C gives rise to >50% higher P{sup •+} yield than PBDTTT-E does irrespective to themore » excitation photon energy. Both PBDTTT-E:PC{sub 61}BM and PBDTTT-C:PC{sub 61}BM blends show subpicosecond exciton lifetimes and nearly unitary fluorescence quenching efficiency and, with respect to the former blend, the latter one shows substantially higher branching ratio of charge separated (CS) state over interfacial charge transfer (ICT) state, and hence more efficient exciton-to-CS conversion. For PBDTTT-C:PC{sub 61}BM, the ultrafast charge dynamics clearly show the processes of ICT-CS interconversion and P{sup •+} migration, which are possibly influenced by the ICT excess energy. However, such processes are relatively indistinctive in the case of PBDTTT-E:PC{sub 61}BM. The results strongly prove the importance of ICT dissociation in yielding free charges, and are discussed in terms of the film morphology and the precursory solution-phase macromolecular conformation.« less

Enhanced photoelectrochemical water splitting of BiVO4 photonic crystal photoanode by decorating with MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Nan, Feng; Cai, Tianyi; Ju, Sheng; Fang, Liang

2018-04-01

Bismuth vanadate (BiVO4) has been considered as one of the promising Photoelectrochemical (PEC) photoanode materials. However, the performances remain poorly rated due to inefficient carrier separation, short carrier diffusion length, and sluggish water oxidation kinetics. Herein, a photoanode consisting of MoS2 nanosheet coating on the three-dimensional ordered BiVO4 inverse opal is fabricated by a facile combination of nanosphere lithography and hydrothermal methods. By taking advantage of the photonic crystal and two-dimensional material, the optimized MoS2/BiVO4 inverse opal photoanode exhibits a 560% improvement of the photocurrent density and threefold enhancement of the incident photon-to-current efficiency than that of the pristine BiVO4 film photoanode. Systematic studies reveal that the excellent PEC activity should be attributed to enhanced light harvesting and charge separation efficiency.

Engineering titania nanostructure to tune and improve its photocatalytic activity

PubMed Central

Cargnello, Matteo; Montini, Tiziano; Smolin, Sergey Y.; Priebe, Jacqueline B.; Delgado Jaén, Juan J.; Doan-Nguyen, Vicky V. T.; McKay, Ian S.; Schwalbe, Jay A.; Pohl, Marga-Martina; Gordon, Thomas R.; Lu, Yupeng; Baxter, Jason B.; Brückner, Angelika; Murray, Christopher B.

2016-01-01

Photocatalytic pathways could prove crucial to the sustainable production of fuels and chemicals required for a carbon-neutral society. Electron−hole recombination is a critical problem that has, so far, limited the efficiency of the most promising photocatalytic materials. Here, we show the efficacy of anisotropy in improving charge separation and thereby boosting the activity of a titania (TiO2) photocatalytic system. Specifically, we show that H2 production in uniform, one-dimensional brookite titania nanorods is highly enhanced by engineering their length. By using complimentary characterization techniques to separately probe excited electrons and holes, we link the high observed reaction rates to the anisotropic structure, which favors efficient carrier utilization. Quantum yield values for hydrogen production from ethanol, glycerol, and glucose as high as 65%, 35%, and 6%, respectively, demonstrate the promise and generality of this approach for improving the photoactivity of semiconducting nanostructures for a wide range of reacting systems. PMID:27035977

Molecular Effects on Coacervate-Driven Block Copolymer Self Assembly

NASA Astrophysics Data System (ADS)

Lytle, Tyer; Radhakrishna, Mithun; Sing, Charles

Two oppositely charged polymers can undergo associative phase separation in a salt solution in a process known as \\x98complex coacervation. Recent work has used this as a motif to control the self-assembly behavior of a mixture of oppositely-charged block copolymers which form nanoscale structures. The materials formed from these complex coacervate-block copolymers (BCPs) have potential use as drug delivery systems, gels, and sensors. We have developed a hybrid Monte Carlo-Single Chain in a Mean Field (MC-SCMF) simulation method that is able to determine morphological phase diagrams for BCPs. This technique is an efficient way to calculate morphological phase diagrams and provides a clear link between molecular level features and self-assembly behaviors. Morphological phase diagrams showing the effects of polymer concentration, salt concentration, chain length, and charge-block fraction at large charge densities on self-assembly behavior have been determined. An unexpected phase transition from disorder to hexagonal packing at large salt concentrations has been observed for charge-block fractions equal to and larger than 0.5. This is attributed to the salt filling space stabilizing the morphology of the BCP.

A charge-polarized porous metal-organic framework for gas chromatographic separation of alcohols from water.

PubMed

Sun, Jian-Ke; Ji, Min; Chen, Cheng; Wang, Wu-Gen; Wang, Peng; Chen, Rui-Ping; Zhang, Jie

2013-02-25

A bipyridinium ligand with a charge separated skeleton has been introduced into a metal-organic framework to yield a porous material with charge-polarized pore space, which exhibits selective adsorption for polar guest molecules and can be further used in gas chromatography for the separation of alcohol-water mixtures.

A Charge Separation Study to Enable the Design of a Complete Muon Cooling Channel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshikawa, C.; Ankenbrandt, Charles M.; Johnson, Rolland P.

2013-12-01

The most promising designs for 6D muon cooling channels operate on a specific sign of electric charge. In particular, the Helical Cooling Channel (HCC) and Rectilinear RFOFO designs are the leading candidates to become the baseline 6D cooling channel in the Muon Accelerator Program (MAP). Time constraints prevented the design of a realistic charge separator, so a simplified study was performed to emulate the effects of charge separation on muons exiting the front end of a muon collider. The output of the study provides particle distributions that the competing designs will use as input into their cooling channels. We reportmore » here on the study of the charge separator that created the simulated particles.« less

Efficient interfacial charge transfer through plasmon sensitized Ag@Bi2O3 hierarchical photoanodes for photoelectrocatalytic degradation of chlorinated phenols.

PubMed

Eswar, Neerugatti KrishnaRao; Adhikari, Sangeeta; Ramamurthy, Praveen C; Madras, Giridhar

2018-01-31

The present work demonstrates an extremely proficient and robust study of efficient interfacial charge transfer through plasmonic Ag decorated Bi 2 O 3 hierarchical photoanodes for the photoelectrochemical treatment of chlorinated phenols. Unique 2D flake-like Bi 2 O 3 hierarchical nanostructures were grown onto a fluorine-doped tin oxide (FTO) substrate by a simple chemical bath deposition method using triethanolamine as complexing agent. The formation of Bi 2 O 3 on FTO was governed by the decomposition of a nucleated bismuth-hydroxyl complex (Bi 2 O 1-x (OH) x ) and modification to the electrode was carried out by the deposition of Ag via a chemical reduction method using hydrazine hydrate. Both the fabricated electrodes were well characterized for their photo- and electro-optical properties. Efficient charge separation was observed due to the surface plasmon resonance phenomenon of silver nanoparticles with the favorable intrinsic properties of Bi 2 O 3 under application of a small electric bias of 1 V preventing the recombination of charge carriers and thereby increasing the rate of photoelectrocatalytic degradation of the chlorinated phenols. PEC degradation using the Ag@Bi 2 O 3 photoelectrode followed the trend 4-CP < 2,4-DCP < 2,4,6-TCP < P-CP due to efficient attack at the chlorinated positions by reactive oxygen species with increasing chlorine substitution and also due to the absence of an expected chain reaction of the generated chlorine radicals (Cl˙) during the PEC reaction. The PEC activity of Ag@Bi 2 O 3 was 1.5 times higher than a Bi 2 O 3 nanoflake electrode for 4-CP over 2 h. The fabricated Ag@Bi 2 O 3 proved to be an efficient photoelectrode with synergistic solar-induced photoactivity. A detailed mechanistic study in the presence of scavengers suggests degradation by produced hydroxyl radical species. Thus, physical insights into the degradation of chlorinated phenols were obtained.

Structural dynamics of a noncovalent charge transfer complex from femtosecond stimulated Raman spectroscopy.

PubMed

Fujisawa, Tomotsumi; Creelman, Mark; Mathies, Richard A

2012-09-06

Femtosecond stimulated Raman spectroscopy is used to examine the structural dynamics of photoinduced charge transfer within a noncovalent electron acceptor/donor complex of pyromellitic dianhydride (PMDA, electron acceptor) and hexamethylbenzene (HMB, electron donor) in ethylacetate and acetonitrile. The evolution of the vibrational spectrum reveals the ultrafast structural changes that occur during the charge separation (Franck-Condon excited state complex → contact ion pair) and the subsequent charge recombination (contact ion pair → ground state complex). The Franck-Condon excited state is shown to have significant charge-separated character because its vibrational spectrum is similar to that of the ion pair. The charge separation rate (2.5 ps in ethylacetate and ∼0.5 ps in acetonitrile) is comparable to solvation dynamics and is unaffected by the perdeuteration of HMB, supporting the dominant role of solvent rearrangement in charge separation. On the other hand, the charge recombination slows by a factor of ∼1.4 when using perdeuterated HMB, indicating that methyl hydrogen motions of HMB mediate the charge recombination process. Resonance Raman enhancement of the HMB vibrations in the complex reveals that the ring stretches of HMB, and especially the C-CH(3) deformations are the primary acceptor modes promoting charge recombination.

Assembly of Photosynthetic Antenna Protein Complexes from Algae for Development of Nano-biodevice and Its Fuelization

DTIC Science & Technology

2013-05-20

More recently the structures of the LH2 complexes has revealed the nonameric and octameric arrangement of repeating units consisting of two...Compartimentalization of light -harvesting and charge separation. The antenna complexes( LH2 ,LH1-RC) efficiently realize various photosynthetic functions...using cofactors (BChl a and carotenoid) assembled into the apoproteins (LH1 and LH2 ). The light-harvesting mechanisms in these light-harvesting

Assembly of Photosynthetic Antenna Protein / Pigments Complexes from Algae and Plants for Development of Nanobiodevices

DTIC Science & Technology

2012-07-10

recently the structures of the LH2 complexes has revealed the nonameric and octameric arrangement of repeating units consisting of two apoproteins and...Compartimentalization of light -harvesting and charge separation. The antenna complexes( LH2 ,LH1-RC) efficiently realize various photosynthetic functions using...cofactors (BChl a and carotenoid) assembled into the apoproteins (LH1 and LH2 ). The light-harvesting mechanisms in these light-harvesting complexes have

Largely enhanced photocatalytic activity of Au/XS2/Au (X = Re, Mo) antenna-reactor hybrids: charge and energy transfer.

PubMed

Chen, Kai; Ding, Si-Jing; Luo, Zhi-Jun; Pan, Gui-Ming; Wang, Jia-Hong; Liu, Jia; Zhou, Li; Wang, Qu-Quan

2018-02-22

An antenna-reactor hybrid coupling plasmonic antenna with catalytic nanoparticles is a new strategy to optimize photocatalytic activity. Herein, we have rationally proposed a Au/XS 2 /Au (X = Re, Mo) antenna reactor, which has a large Au core as the antenna and small satellite Au nanoparticles as the reactor separated by an ultrathin two-dimensional transition-metal dichalcogenide XS 2 shell (∼2.6 nm). Due to efficient charge transfer across the XS 2 shell as well as energy transfer via coupling of the Au antenna and Au reactor, the photocatalytic activity has been largely enhanced: Au/ReS 2 /Au exhibits a 3.59-fold enhancement, whereas Au/MoS 2 /Au exhibits a 2.66-fold enhancement as compared to that of the sum of the three individual components. The different enhancement in the Au/ReS 2 /Au and Au/MoS 2 /Au antenna-reactor hybrid is related to the competition and cooperation of charge and energy transfer. These results indicate the great potential of the Au/XS 2 /Au antenna-reactor hybrid for the development of highly efficient plasmonic photocatalysts.

Trapping in irradiated p +-n-n - silicon sensors at fluences anticipated at the HL-LHC outer tracker

DOE PAGES

Adam, W.

2016-04-22

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200μm thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to 3 x 10 15 neq/cm 2. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulationmore » assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. Furthermore, the effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectations.« less

The selective conversion of glutamic acid in amino acid mixtures using glutamate decarboxylase--a means of separating amino acids for synthesizing biobased chemicals.

PubMed

Teng, Yinglai; Scott, Elinor L; Sanders, Johan P M

2014-01-01

Amino acids (AAs) derived from hydrolysis of protein rest streams are interesting feedstocks for the chemical industry due to their functionality. However, separation of AAs is required before they can be used for further applications. Electrodialysis may be applied to separate AAs, but its efficiency is limited when separating AAs with similar isoelectric points. To aid the separation, specific conversion of an AA to a useful product with different charge behavior to the remaining compounds is desired. Here the separation of L-aspartic acid (Asp) and L-glutamic acid (Glu) was studied. L-Glutamate α-decarboxylase (GAD, Type I, EC 4.1.1.15) was applied to specifically convert Glu into γ-aminobutyric acid (GABA). GABA has a different charge behavior from Asp therefore allowing a potential separation by electrodialysis. Competitive inhibition and reduced operational stability caused by Asp could be eliminated by maintaining a sufficiently high concentration of Glu. Immobilization of GAD does not reduce the enzyme's initial activity. However, the operational stability was slightly reduced. An initial study on the reaction operating in a continuous mode was performed using a column reactor packed with immobilized GAD. As the reaction mixture was only passed once through the reactor, the conversion of Glu was lower than expected. To complete the conversion of Glu, the stream containing Asp and unreacted Glu might be recirculated back to the reactor after GABA has been removed. Overall, the reaction by GAD is specific to Glu and can be applied to aid the electrodialysis separation of Asp and Glu. © 2014 American Institute of Chemical Engineers.

Controlling Gas-Phase Reactions for Efficient Charge Reduction Electrospray Mass Spectrometry of Intact Proteins

PubMed Central

Frey, Brian L.; Lin, Yuan; Westphall, Michael S.; Smith, Lloyd M.

2006-01-01

Charge reduction electrospray mass spectrometry (CREMS) reduces the charge states of electrospray-generated ions, which concentrates the ions from a protein into fewer peaks spread over a larger m/z range, thereby increasing peak separation and decreasing spectral congestion. An optimized design for a CREMS source is described that provides an order-of-magnitude increase in sensitivity compared to previous designs and provides control over the extent of charge reduction. Either a corona discharge or an α-particle source was employed to generate anions that abstract protons from electrosprayed protein cations. These desired ion/ion proton transfer reactions predominated, but some oxidation and ion-attachment reactions also occurred leading to new peaks or mass-shifted broader peaks while decreasing signal intensity. The species producing these deleterious side-reactions were identified, and conditions were found that prevented their formation. Spectrometer m/z biases were examined because of their effect upon the signal intensity of higher m/z charge-reduced protein ions. The utility of this atmospheric pressure CREMS was demonstrated using a cell lysate fraction from E. coli. The spectral simplification afforded by CREMS reveals more proteins than are observed without charge reduction. PMID:16198118

Photoinduced electron transfer in a molecular dyad by nanosecond pump-pump-probe spectroscopy.

PubMed

Ha-Thi, M-H; Pham, V-T; Pino, T; Maslova, V; Quaranta, A; Lefumeux, C; Leibl, W; Aukauloo, A

2018-06-01

The design of robust and inexpensive molecular photocatalysts for the conversion of abundant stable molecules like H2O and CO2 into an energetic carrier is one of the major fundamental questions for scientists nowadays. The outstanding challenge is to couple single photoinduced charge separation events with the sequential accumulation of redox equivalents at the catalytic unit for performing multielectronic catalytic reactions. Herein, double excitation by nanosecond pump-pump-probe experiments was used to interrogate the photoinduced charge transfer and charge accumulation on a molecular dyad composed of a porphyrin chromophore and a ruthenium-based catalyst in the presence of a reversible electron acceptor. An accumulative charge transfer state is unattainable because of rapid reverse electron transfer to the photosensitizer upon the second excitation and the low driving force of the forward photodriven electron transfer reaction. Such a method allows the fundamental understanding of the relaxation mechanism after two sequential photon absorptions, deciphering the undesired electron transfer reactions that limit the charge accumulation efficiency. This study is a step toward the improvement of synthetic strategies of molecular photocatalysts for light-induced charge accumulation and more generally, for solar energy conversion.

Separation of organic cations using novel background electrolytes by capillary electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steiner, S.; Fritz, J.

2008-02-12

A background electrolyte for capillary electrophoresis containing tris(-hydroxymethyl) aminomethane (THAM) and ethanesulfonic acid (ESA) gives excellent efficiency for separation of drug cations with actual theoretical plate numbers as high as 300,000. However, the analyte cations often elute too quickly and consequently offer only a narrow window for separation. The best way to correct this is to induce a reverse electroosmotic flow (EOF) that will spread out the peaks by slowing their migration rates, but this has always been difficult to accomplish in a controlled manner. A new method for producing a variable EOF is described in which a low variablemore » concentration of tributylammonium- or triethylammonium ESA is added to the BGE. The additive equilibrates with the capillary wall to give it a positive charge and thereby produce a controlled opposing EOF. Excellent separations of complex drug mixtures were obtained by this method.« less

Wide size range fast integrated mobility spectrometer

DOEpatents

Wang, Jian

2013-10-29

A mobility spectrometer to measure a nanometer particle size distribution is disclosed. The mobility spectrometer includes a conduit and a detector. The conduit is configured to receive and provide fluid communication of a fluid stream having a charged nanometer particle mixture. The conduit includes a separator section configured to generate an electrical field of two dimensions transverse to a dimension associated with the flow of the charged nanometer particle mixture through the separator section to spatially separate charged nanometer particles of the charged nanometer particle mixture in said two dimensions. The detector is disposed downstream of the conduit to detect concentration and position of the spatially-separated nanometer particles.

Charge separation and transport of the n=2 instability in C-2 FRC plasmas

NASA Astrophysics Data System (ADS)

Deng, Bihe; Sun, Xuan; Tuszewski, Michel

2012-10-01

Charge separation is critical in the positive feedback loop for gravitational type instabilities to grow [1], such as in the case of the n=2 mode in the C-2 field reversed configuration (FRC) experiment [2]. A fast time response Langmuir probe with minimum perturbation to the plasma is inserted into the edge of the C-2 plasma to measure the plasma floating potential. With the combined plasma wobble motion and spin motion, 2-D scans of the plasma floating potential are obtained, and evidence of charge separation associated with the n=2 instability is observed. The transport due to charge separation is estimated. Charge neutralization can provide an alternative method to stabilize the n=2 mode. An experiment is proposed to test this method with two probes inserted into the plasma from two azimuthally separated ports and an external shorting circuit, to constantly neutralize the charge separation, thus suppress the growth of the n=2 mode. [4pt] [1] R.J. Goldston and P.H. Rutherford, Introduction to Plasma Physics (Institute of Physics Publishing, Bristol, 2000).[0pt] [2]. M.W. Binderbauer et al, Phys. Rev. Lett. 105, 045003 (2010).

Evaluation of differences between dual salt-pH gradient elution and mono gradient elution using a thermodynamic model: Simultaneous separation of six monoclonal antibody charge and size variants on preparative-scale ion exchange chromatographic resin.

PubMed

Lee, Yi Feng; Jöhnck, Matthias; Frech, Christian

2018-02-21

The efficiencies of mono gradient elution and dual salt-pH gradient elution for separation of six mAb charge and size variants on a preparative-scale ion exchange chromatographic resin are compared in this study. Results showed that opposite dual salt-pH gradient elution with increasing pH gradient and simultaneously decreasing salt gradient is best suited for the separation of these mAb charge and size variants on Eshmuno ® CPX. Besides giving high binding capacity, this type of opposite dual salt-pH gradient also provides better resolved mAb variant peaks and lower conductivity in the elution pools compared to single pH or salt gradients. To have a mechanistic understanding of the differences in mAb variants retention behaviors of mono pH gradient, parallel dual salt-pH gradient, and opposite dual salt-pH gradient, a linear gradient elution model was used. After determining the model parameters using the linear gradient elution model, 2D plots were used to show the pH and salt dependencies of the reciprocals of distribution coefficient, equilibrium constant, and effective ionic capacity of the mAb variants in these gradient elution systems. Comparison of the 2D plots indicated that the advantage of opposite dual salt-pH gradient system with increasing pH gradient and simultaneously decreasing salt gradient is the noncontinuous increased acceleration of protein migration. Furthermore, the fitted model parameters can be used for the prediction and optimization of mAb variants separation in dual salt-pH gradient and step elution. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018. © 2018 American Institute of Chemical Engineers.

Compression Ratio Ion Mobility Programming (CRIMP) Accumulation and Compression of Billions of Ions for Ion Mobility-Mass Spectrometry Using Traveling Waves in Structures for Lossless Ion Manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Garimella, Sandilya V. B.; Hamid, Ahmed M.

We report on the implementation of a traveling wave (TW) based compression ratio ion mobility programming (CRIMP) approach within Structures for Lossless Ion Manipulations (SLIM) that enables both greatly enlarged trapped ion charge capacities and also their subsequent efficient compression for use in ion mobility (IM) separations. Ion accumulation is conducted in a long serpentine path TW SLIM region after which CRIMP allows the large ion populations to be ‘squeezed’. The compression process occurs at an interface between two SLIM regions, one operating conventionally and the second having an intermittently pausing or ‘stuttering’ TW, allowing the contents of multiple binsmore » of ions from the first region to be merged into a single bin in the second region. In this initial work stationary voltages in the second region were used to block ions from exiting the first (trapping) region, and the resumption of TWs in the second region allows ions to exit, and the population to also be compressed if CRIMP is applied. In our initial evaluation we show that the number of charges trapped for a 40 s accumulation period was ~5×109, more than two orders of magnitude greater than the previously reported charge capacity using an ion funnel trap. We also show that over 1×109 ions can be accumulated with high efficiency in the present device, and that the extent of subsequent compression is only limited by the space charge capacity of the trapping region. Lower compression ratios allow increased IM peak heights without significant loss of signal, while excessively large compression ratios can lead to ion losses and other artifacts. Importantly, we show that extended ion accumulation in conjunction with CRIMP and multiple passes provides the basis for a highly desirable combination of ultra-high sensitivity and ultra-high resolution IM separations using SLIM.« less

The role of interfacial water layer in atmospherically relevant charge separation

NASA Astrophysics Data System (ADS)

Bhattacharyya, Indrani

Charge separation at interfaces is important in various atmospheric processes, such as thunderstorms, lightning, and sand storms. It also plays a key role in several industrial processes, including ink-jet printing and electrostatic separation. Surprisingly, little is known about the underlying physics of these charging phenomena. Since thin films of water are ubiquitous, they may play a role in these charge separation processes. This talk will focus on the experimental investigation of the role of a water adlayer in interfacial charging, with relevance to meteorologically important phenomena, such as atmospheric charging due to wave actions on oceans and sand storms. An ocean wave generates thousands of bubbles, which upon bursting produce numerous large jet droplets and small film droplets that are charged. In the 1960s, Blanchard showed that the jet droplets are positively charged. However, the charge on the film droplets was not known. We designed an experiment to exclusively measure the charge on film droplets generated by bubble bursting on pure water and aqueous salt solution surfaces. We measured their charge to be negative and proposed a model where a slight excess of hydroxide ions in the interfacial water layer is responsible for generating these negatively charged droplets. The findings from this research led to a better understanding of the ionic disposition at the air-water interface. Sand particles in a wind-blown sand layer, or 'saltation' layer, become charged due to collisions, so much so, that it can cause lightning. Silica, being hydrophilic, is coated with a water layer even under low-humidity conditions. To investigate the importance of this water adlayer in charging the silica surfaces, we performed experiments to measure the charge on silica surfaces due to contact and collision processes. In case of contact charging, the maximum charge separation occurred at an optimum relative humidity. On the contrary, in collisional charging process, no humidity effect was observed. We proposed an ion transfer mechanism in case of contact charging. However, an electron transfer mechanism explained the collisional charging process. The effects of temperature, surface roughness, and chemical nature of surface were also studied for both contact and collisional charging processes.

Room-temperature in situ fabrication of Bi2O3/g-C3N4 direct Z-scheme photocatalyst with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

He, Rongan; Zhou, Jiaqian; Fu, Huiqing; Zhang, Shiying; Jiang, Chuanjia

2018-02-01

Constructing direct Z-scheme heterojunction is an effective approach to separating photogenerated charge carriers and improving the activity of semiconductor photocatalysts. Herein, a composite of bismuth(III) oxide (Bi2O3) and graphitic carbon nitride (g-C3N4) was in situ fabricated at room temperature by photoreductive deposition of Bi3+ and subsequent air-oxidation of the resultant metallic Bi. Quantum-sized ω-Bi2O3 nanoparticles approximately 6 nm in diameter were uniformly distributed on the surface of mesoporous g-C3N4. The as-prepared Bi2O3/g-C3N4 composite exhibited higher photocatalytic activity than pure Bi2O3 and g-C3N4 for photocatalytic degradation of phenol under visible light. Reactive species trapping experiments revealed that superoxide radicals and photogenerated holes played important roles in the photocatalytic degradation of phenol. The enhanced photocatalytic activity, identification of reactive species and higher rate of charge carrier recombination (as indicated by stronger photoluminescence intensity) collectively suggest that the charge migration within the Bi2O3/g-C3N4 composite followed a Z-scheme mechanism. Photogenerated electrons on the conduction band of Bi2O3 migrate to the valence band of g-C3N4 and combine with photogenerated holes therein. At the cost of these less reactive charge carriers, the Z-scheme heterojunction enables efficient charge separation, while preserving the photogenerated electrons and holes with stronger redox abilities, which is beneficial for enhanced photocatalytic activity.

Distorted Carbon Nitride Structure with Substituted Benzene Moieties for Enhanced Visible Light Photocatalytic Activities.

PubMed

Kim, Hyejin; Gim, Suji; Jeon, Tae Hwa; Kim, Hyungjun; Choi, Wonyong

2017-11-22

Carbon nitride (CN) is being intensively investigated as a low-cost visible light active photocatalyst, but its practical applications are limited because of the fast charge pair recombination and low visible light absorption. Here, we introduce a new strategy for enhancing its visible light photocatalytic activity by designing the CN structure in which the nitrogen of tertiary amine is substituted with a benzene molecule connected by three heptazine rings. The intramolecular benzene doping induced the structural changes from planar symmetric structure to distorted geometry, which could be predicted by density functional theory calculation. This structural distortion facilitated the spatial separation of photogenerated charge pairs and retarded charge recombination via exciton dissociation. Such unique properties of the benzene-incorporated CN were confirmed by the photoluminescence (PL) and photoelectrochemical analyses. The optimal loading of benzene doping reduced the PL of the conjugated ring system (π → π* transition) but enhanced the PL of the forbidden n → π* transition at the nitrogen atoms with lone pair electrons due to the distortion from the planar geometry. The photoelectrode of benzene-doped CN exhibited higher photocurrent and lower charge transfer resistance than bare CN electrode, indicating that the photogenerated charge pairs are more efficiently separated. As a result, the benzene-doped CN markedly increased the photocatalytic activity for the degradation of various organic pollutants and that for H 2 O 2 production (via O 2 reduction). This study proposes a simple strategy for chemical structural modification of carbon nitride to boost the visible light photocatalytic activity.

Photovoltaic Performance of Inverted Polymer Solar Cells Using Hybrid Carbon Quantum Dots and Absorption Polymer Materials

NASA Astrophysics Data System (ADS)

Lim, Hwain; Lee, Kyu Seung; Liu, Yang; Kim, Hak Yong; Son, Dong Ick

2018-05-01

We report the synthesis and characterization of the carbon quantum dots (C-dots) easily obtained from citric acid and ethanediamine, and also investigated structural, optical and electrical properties. The C-dots have extraordinary optical and electrical features such as absorption of ultraviolet range and effective interface for charge separation and transport in active layer, which make them attractive materials for applications in photovoltaic devices (PV). The C-dots play important roles in charge extraction in the PV structures, they can be synthesized by a simple method and used to insert in active layer of polymer solar cells. In this study, we demonstrate that improve charge transport properties of inverted polymer solar cells (iPSCs) with C-dots and structural, optical and electrical properties of C-dots. As a result, iPSCs with C-dots showed enhancement of more than 30% compared with that of the contrast device in power conversion efficiency.

A Nonmetal Plasmonic Z-Scheme Photocatalyst with UV- to NIR-Driven Photocatalytic Protons Reduction.

PubMed

Zhang, Zhenyi; Huang, Jindou; Fang, Yurui; Zhang, Mingyi; Liu, Kuichao; Dong, Bin

2017-05-01

Ultrabroad-spectrum absorption and highly efficient generation of available charge carriers are two essential requirements for promising semiconductor-based photocatalysts, towards achieving the ultimate goal of solar-to-fuel conversion. Here, a fascinating nonmetal plasmonic Z-scheme photocatalyst with the W 18 O 49 /g-C 3 N 4 heterostructure is reported, which can effectively harvest photon energies spanning from the UV to the nearinfrared region and simultaneously possesses improved charge-carrier dynamics to boost the generation of long-lived active electrons for the photocatalytic reduction of protons into H 2 . By combining with theoretical simulations, a unique synergistic photocatalysis effect between the semiconductive Z-scheme charge-carrier separation and metal-like localized-surface-plasmon-resonance-induced "hot electrons" injection process is demonstrated within this binary heterostructure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Charge Separation and Recombination at Polymer-Fullerene Heterojunctions: Delocalization and Hybridization Effects.

PubMed

D'Avino, Gabriele; Muccioli, Luca; Olivier, Yoann; Beljonne, David

2016-02-04

We address charge separation and recombination in polymer/fullerene solar cells with a multiscale modeling built from accurate atomistic inputs and accounting for disorder, interface electrostatics and genuine quantum effects on equal footings. Our results show that bound localized charge transfer states at the interface coexist with a large majority of thermally accessible delocalized space-separated states that can be also reached by direct photoexcitation, thanks to their strong hybridization with singlet polymer excitons. These findings reconcile the recent experimental reports of ultrafast exciton separation ("hot" process) with the evidence that high quantum yields do not require excess electronic or vibrational energy ("cold" process), and show that delocalization, by shifting the density of charge transfer states toward larger effective electron-hole radii, may reduce energy losses through charge recombination.

Charge state breeding experiences and plans at TRIUMF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ames, F., E-mail: ames@triumf.ca; Marchetto, M.; Mjøs, A.

At the Isotope Separation and ACceleration (ISAC) facility at TRIUMF, an electron cyclotron resonance ion source (ECRIS) has been set up for the charge state breeding of radioactive ions. In order to reduce background from stable ions generated in the ECRIS, several measures, including changing materials for the plasma chamber and the surrounding components, have been implemented. Further reduction has been achieved by using the post-accelerator chain as a mass filter. Since the implementation of those measures in 2013, physics experiments with accelerated radioactive isotopes of Rb, Sr, K, and Mg have been performed. In most cases, a charge breedingmore » efficiency of several percent has been achieved. With the planned expansion of the isotope production capabilities at TRIUMF within the Advanced Rare IsotopE Laboratory project, two new target stations, one using photo-fission induced by a high-power electron beam at 50 MeV and the other one using 480 MeV protons as at ISAC, will be put into operation within the next 5 yr. Additionally, a new electron beam ion source (EBIS) based charge state breeding system will be installed. Background from such a source is expected to be much lower. The drawback is that for the efficient operation of such a system, pulsed beam operation is required, which makes the installation of an additional ion buncher in front of the EBIS necessary.« less

Boosted output performance of triboelectric nanogenerator via electric double layer effect

PubMed Central

Chun, Jinsung; Ye, Byeong Uk; Lee, Jae Won; Choi, Dukhyun; Kang, Chong-Yun; Kim, Sang-Woo; Wang, Zhong Lin; Baik, Jeong Min

2016-01-01

For existing triboelectric nanogenerators (TENGs), it is important to explore unique methods to further enhance the output power under realistic environments to speed up their commercialization. We report here a practical TENG composed of three layers, in which the key layer, an electric double layer, is inserted between a top layer, made of Al/polydimethylsiloxane, and a bottom layer, made of Al. The efficient charge separation in the middle layer, based on Volta's electrophorus, results from sequential contact configuration of the TENG and direct electrical connection of the middle layer to the earth. A sustainable and enhanced output performance of 1.22 mA and 46.8 mW cm−2 under low frequency of 3 Hz is produced, giving over 16-fold enhancement in output power and corresponding to energy conversion efficiency of 22.4%. Finally, a portable power-supplying system, which provides enough d.c. power for charging a smart watch or phone battery, is also successfully developed. PMID:27703165

Heterostructured TiO2/NiTiO3 Nanorod Arrays for Inorganic Sensitized Solar Cells with Significantly Enhanced Photovoltaic Performance and Stability.

PubMed

Li, Yue-Ying; Wang, Jian-Gan; Sun, Huan-Huan; Wei, Bingqing

2018-04-11

Organic dyes used in the conventional dye-sensitized solar cells (DSSCs) suffer from poor light stability and high cost. In this work, we demonstrate a new inorganic sensitized solar cell based on ordered one-dimensional semiconductor nanorod arrays of TiO 2 /NiTiO 3 (NTO) heterostructures prepared via a facile two-step hydrothermal approach. The semiconductor heterostructure arrays are highly desirable and promising for DSSCs because of their direct charge transport capability and slow charge recombination rate. The low-cost NTO inorganic semiconductor possesses an appropriate band gap that matches well with TiO 2 , which behaves like a "dye" to enable efficient light harvesting and fast electron-hole separation. The solar cells constructed by the ordered TiO 2 /NTO heterostructure photoanodes show a significantly improved power conversion efficiency, high fill factor, and more promising, outstanding life stability. The present work will open up an avenue to design heterostructured inorganics for high-performance solar cells.

Plasmonic Enhancement in BiVO4 Photonic Crystals for Efficient Water Splitting

PubMed Central

Zhang, Liwu; Lin, Chia-Yu; Valev, Ventsislav K; Reisner, Erwin; Steiner, Ullrich; Baumberg, Jeremy J

2014-01-01

Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H2 conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO4 photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm−2 at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode. PMID:24916174

Polar Fluctuations in Metal Halide Perovskites Uncovered by Acoustic Phonon Anomalies

DOE PAGES

Guo, Peijun; Xia, Yi; Gong, Jue; ...

2017-09-28

Solution-processable metal-halide perovskites (MHPs) offer great promise for efficient light harvesting and emitting devices due to their long carrier lifetime and superior carrier transport characteristics. Ferroelectric effects, a hallmark of traditional oxide perovskites, was proposed to be a mechanism to suppress carrier recombination and enhance charge transport in MHPs, but the existence and influence of such polar order is still of considerable debate. Here we performed transient reflection measurements on single crystals of both inorganic and organic-inorganic (hybrid) MHPs over a range of temperatures, and demonstrate significant phonon softening in the cubic phases close to the cubic-to-tetragonal phase transition temperatures.more » Such phonon softening indicates the formation of polar domains, which grow in size upon cooling and can persist in the low-temperature tetragonal and orthorhombic phases. Our results link the extraordinary electronic properties of MHPs to the spontaneous polarizations which can contribute to more efficient charge separation and characteristics of an indirect bandgap.« less

Plasmonic enhancement in BiVO4 photonic crystals for efficient water splitting.

PubMed

Zhang, Liwu; Lin, Chia-Yu; Valev, Ventsislav K; Reisner, Erwin; Steiner, Ullrich; Baumberg, Jeremy J

2014-10-15

Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H2 conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO4 photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm(-2) at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Field-induced exciton dissociation in PTB7-based organic solar cells

NASA Astrophysics Data System (ADS)

Gerhard, Marina; Arndt, Andreas P.; Bilal, Mühenad; Lemmer, Uli; Koch, Martin; Howard, Ian A.

2017-05-01

The physics of charge separation in organic semiconductors is a topic of ongoing research of relevance to material and device engineering. Herein, we present experimental observations of the field and temperature dependence of charge separation from singlet excitons in PTB7 and PC71BM , and from charge-transfer states created across interfaces in PTB 7 /PC71BM bulk heterojunction solar cells. We obtain this experimental data by time-resolving the near infrared emission of the states from 10 K to room temperature and electric fields from 0 to 2.5 MVcm -1 . Examining how the luminescence is quenched by field and temperature gives direct insight into the underlying physics. We observe that singlet excitons can be split by high fields, and that disorder broadens the high threshold fields needed to split the excitons. Charge-transfer (CT) states, on the other hand, can be separated by both field and temperature. Also, the data imply a strong reduction of the activation barrier for charge splitting from the CT state relative to the exciton state. The observations provided herein of the field-dependent separation of CT states as a function of temperature offer a rich data set against which theoretical models of charge separation can be rigorously tested; it should be useful for developing the more advanced theoretical models of charge separation.

Ultrathin self-assembled anionic polymer membranes for superfast size-selective separation

NASA Astrophysics Data System (ADS)

Deng, Chao; Zhang, Qiu Gen; Han, Guang Lu; Gong, Yi; Zhu, Ai Mei; Liu, Qing Lin

2013-10-01

Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m-2 h-1 bar-1) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles.Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m-2 h-1 bar-1) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles. Electronic supplementary information (ESI) available: Synthesis and characterization of SPEK-C; effect of the sulfonation degree on membrane formation; structure and properties of the self-assembled membranes; separation of cyt.c by the self-assembled membranes; size-selective separation of gold nanoparticles by the self-assembled membranes; comparison with commercial flat sheet ultrafiltration membranes. See DOI: 10.1039/c3nr03362g

77 FR 69522 - Self-Regulatory Organizations; National Stock Exchange, Inc.; Notice of Filing and Immediate...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-19

... participants to: (1) Charge a flat fee per quotation update; (2) charge a separate flat fee per quotation... to: (1) Charge a flat fee per quotation update; (2) charge a separate flat fee per quotation update... fund the NSX's regulatory oversight of Order Delivery participants. Quotation Update Fee for Existing...

Low roll-off and high efficiency orange OLEDs using green and red dopants in an exciplex forming co-host

NASA Astrophysics Data System (ADS)

Lee, Sunghun; Kim, Kwon-Hyeon; Yoo, Seung-Jun; Park, Young-Seo; Kim, Jang-Joo

2013-09-01

We present high efficiency orange emitting OLEDs with low driving voltage and low roll-off of efficiency using an exciplex forming co-host by (1) co-doping of green and red emitting phosphorescence dyes in the host and (2) red and green phosphorescent dyes doped in the host as separate red and green emitting layers. The orange OLEDs achieved a low turn-on voltage of 2.4 V and high external quantum efficiencies (EQE) of 25.0% and 22.8%, respectively. Moreover, the OLEDs showed low roll-off of efficiency with an EQE of over 21% and 19.6% at 10,000 cd/m2, respectively. The devices displayed good orange color with very little color shift with increasing luminance. The transient electroluminescence of the OLEDs indicated that both energy transfer and direct charge trapping took place in the devices.

CdSe quantum dot-fullerene hybrid nanocomposite for solar energy conversion: electron transfer and photoelectrochemistry.

PubMed

Bang, Jin Ho; Kamat, Prashant V

2011-12-27

The development of organic/inorganic hybrid nanocomposite systems that enable efficient solar energy conversion has been important for applications in solar cell research. Nanostructured carbon-based systems, in particular C(60), offer attractive strategies to collect and transport electrons generated in a light harvesting assembly. We have assembled CdSe-C(60) nanocomposites by chemically linking CdSe quantum dots (QDs) with thiol-functionalized C(60). The photoinduced charge separation and collection of electrons in CdSe QD-C(60) nanocomposites have been evaluated using transient absorption spectroscopy and photoelectrochemical measurements. The rate constant for electron transfer between excited CdSe QD and C(60) increased with the decreasing size of the CdSe QD (7.9 × 10(9) s(-1) (4.5 nm), 1.7 × 10(10) s(-1) (3.2 nm), and 9.0 × 10(10) s(-1) (2.6 nm)). Slower hole transfer and faster charge recombination and transport events were found to dominate over the forward electron injection process, thus limiting the deliverance of maximum power in CdSe QD-C(60)-based solar cells. The photoinduced charge separation between CdSe QDs and C(60) opens up new design strategies for developing light harvesting assemblies.

Photophysical Properties of Novel Organic, Inorganic, and Hybrid Semiconductor Materials

NASA Astrophysics Data System (ADS)

Chang, Angela Yenchi

For the past 200 years, novel materials have driven technological progress, and going forward these advanced materials will continue to deeply impact virtually all major industrial sectors. Therefore, it is vital to perform basic and applied research on novel materials in order to develop new technologies for the future. This dissertation describes the results of photophysical studies on three novel materials with electronic and optoelectronic applications, namely organic small molecules DTDCTB with C60 and C70, colloidal indium antimonide (InSb) nanocrystals, and an organic-inorganic hybrid perovskite with the composition CH3NH3PbI 3-xClx, using transient absorption (TA) and photoluminescence (PL) spectroscopy. In chapter 2, we characterize the timescale and efficiency of charge separation and recombination in thin film blends comprising DTDCTB, a narrow-band gap electron donor, and either C60 or C70 as an electron acceptor. TA and time-resolved PL studies show correlated, sub-picosecond charge separation times and multiple timescales of charge recombination. Our results indicate that some donors fail to charge separate in donor-acceptor mixed films, which suggests material manipulations may improve device efficiency. Chapter 3 describes electron-hole pair dynamics in strongly quantum-confined, colloidal InSb nanocrystal quantum dots. For all samples, TA shows a bleach feature that, for several picoseconds, dramatically red-shifts prior to reaching a time-independent position. We suggest this unusual red-shift relates transient population flow through two energetically comparable conduction band states. From pump-power-dependent measurements, we also determine biexciton lifetimes. In chapter 4, we examine carrier dynamics in polycrystalline methylammonium lead mixed halide perovskite (CH3NH3PbI3-xCl x) thin films as functions of temperature and photoexcitation wavelength. At room temperature, the long-lived TA signals stand in contrast to PL dynamics, where the latter present a fast decay process prior to slower recombination. We show that this PL feature persists with similar decay amplitude and timescale for temperatures down to the phase transition temperature, and that it depends on pump photon energy at room temperature. Together with high-level electronic structure and dynamics calculations, we suggest the fast PL decay relates a characteristic organic-to-inorganic sub-lattice equilibration timescale at optoelectronic-relevant excitation energies.

Facile fabrication of BiVO4 nanofilms with controlled pore size and their photoelectrochemical performances.

PubMed

Feng, Chenchen; Jiao, Zhengbo; Li, Shaopeng; Zhang, Yan; Bi, Yingpu

2015-12-28

We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO(4) photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures.

Band engineering in core/shell ZnTe/CdSe for photovoltage and efficiency enhancement in exciplex quantum dot sensitized solar cells.

PubMed

Jiao, Shuang; Shen, Qing; Mora-Seró, Iván; Wang, Jin; Pan, Zhenxiao; Zhao, Ke; Kuga, Yuki; Zhong, Xinhua; Bisquert, Juan

2015-01-27

Even though previously reported CdTe/CdSe type-II core/shell QD sensitizers possess intrinsic superior optoelectronic properties (such as wide absorption range, fast charge separation, and slow charge recombination) in serving as light absorbers, the efficiency of the resultant solar cell is still limited by the relatively low photovoltage. To further enhance photovoltage and cell efficiency accordingly, ZnTe/CdSe type-II core/shell QDs with much larger conduction band (CB) offset in comparison with that of CdTe/CdSe (1.22 eV vs 0.27 eV) are adopted as sensitizers in the construction of quantum dot sensitized solar cells (QDSCs). The augment of band offset produces an increase of the charge accumulation across the QD/TiO2 interface under illumination and induces stronger dipole effects, therefore bringing forward an upward shift of the TiO2 CB edge after sensitization and resulting in enhancement of the photovoltage of the resultant cell devices. The variation of relative chemical capacitance, Cμ, between ZnTe/CdSe and reference CdTe/CdSe cells extracted from impedance spectroscopy (IS) characterization under dark and illumination conditions clearly demonstrates that, under light irradiation conditions, the sensitization of ZnTe/CdSe QDs upshifts the CB edge of TiO2 by the level of ∼ 50 mV related to that in the reference cell and results in the enhancement of V(oc) of the corresponding cell devices. In addition, charge extraction measurements have also confirmed the photovoltage enhancement in the ZnTe/CdSe cell related to reference CdTe/CdSe cell. Furthermore, transient grating (TG) measurements have revealed a faster electron injection rate for the ZnTe/CdSe-based QDSCs in comparison with the CdSe cells. The resultant ZnTe/CdSe QD-based QDSCs exhibit a champion power conversion efficiency of 7.17% and a certified efficiency of 6.82% under AM 1.5 G full one sun illumination, which is, as far as we know, one of the highest efficiencies for liquid-junction QDSCs.

Sensitization of TiO₂ nanosheets with Cu-biphenylamine frame work to enhance photocatalytic degradation performance of toxic organic contaminants: Synthesis, mechanism and kinetic studies.

PubMed

Khan, Muhammad Asim; Mutahir, Sadaf; Wang, Fengyun; Lei, Wu; Xia, Mingzhu

2018-06-25

TNS/Cu(X) composite materials were firstly synthesized via simple overnight stirring of TNS in the methanolic solution of Cu complexes. The developed TNS/Cu(X) composites having a well-designed nanostructure, in which TNS and Cu complexes were closely bounded with each other. Biphenylamine complexes fixed on TNS surface in form of Nano-capsules, which were confirmed by TEM and SEM, thus improving the surface area and subsequently charge separation. Innovatively merged photocatalysts of Cu complexes with TNS were successfully verified for photocatalytic mineralization of colored and colorless organic contaminants under the visible light degradation. As compared to original TNS, TNS/Cu(BA) showed prominent improvement in the catalytic actions. Kinetics i.e. t1/2 (half-life times period), Kapp, and R2 (linear regression co-efficient) were also studied. The amended materials created charge separation, by means of electrons gathering at the higher CB, and holes gathering at lower level VB of Cu complex, therefore improving mineralization efficiency of electrons and holes. TNS/Cu(BA) degrade 99% to 99.6% of MO & RhB dyes in 120 min, and 160 min, respectively, and 68 % of phenol and 53% of TCP were destroyed in 180 min. The resilient holes can directly destroy MO, RhB, phenol, and TCP. © 2018 IOP Publishing Ltd.

Oxidation driven ZnS Core-ZnO shell photocatalysts under controlled oxygen atmosphere for improved photocatalytic solar water splitting

NASA Astrophysics Data System (ADS)

Bak, Daegil; Kim, Jung Hyeun

2018-06-01

Zinc type photocatalysts attract great attentions in solar hydrogen production due to their easy availability and benign environmental characteristics. Spherical ZnS particles are synthesized with a facile hydrothermal method, and they are further used as core materials to introduce ZnO shell layer surrounding the core part by partial oxidation under controlled oxygen contents. The resulting ZnS core-ZnO shell photocatalysts represent the heterostructural type II band alignment. The existence of oxide layer also influences on proton adsorption power with an aid of strong base cites derived from highly electronegative oxygen atoms in ZnO shell layer. Photocatalytic water splitting reaction is performed to evaluate catalyst efficiency under standard one sun condition, and the highest hydrogen evolution rate (1665 μmolg-1h-1) is achieved from the sample oxidized at 16.2 kPa oxygen pressure. This highest hydrogen production rate is achieved in cooperation with increased light absorption and promoted charge separations. Photoluminescence analysis reveals that the improved visible light response is obtained after thermal oxidation process due to the oxygen vacancy states in the ZnO shell layer. Therefore, overall photocatalytic efficiency in solar hydrogen production is enhanced by improved charge separations, crystallinity, and visible light responses from the ZnS core-ZnO shell structures induced by thermal oxidation.

Controlled Synthesis of CuS/TiO2 Heterostructured Nanocomposites for Enhanced Photocatalytic Hydrogen Generation through Water Splitting.

PubMed

Chandra, Moumita; Bhunia, Kousik; Pradhan, Debabrata

2018-04-16

Photocatalytic hydrogen (H 2 ) generation through water splitting has attracted substantial attention as a clean and renewable energy generation process that has enormous potential in converting solar-to-chemical energy using suitable photocatalysts. The major bottleneck in the development of semiconductor-based photocatalysts lies in poor light absorption and fast recombination of photogenerated electron-hole pairs. Herein we report the synthesis of CuS/TiO 2 heterostructured nanocomposites with varied TiO 2 contents via simple hydrothermal and solution-based process. The morphology, crystal structure, composition, and optical properties of the as-synthesized CuS/TiO 2 hybrids are evaluated in detail. Controlling the CuS/TiO 2 ratio to an optimum value leads to the highest photocatalytic H 2 production rate of 1262 μmol h -1 g -1 , which is 9.7 and 9.3 times higher than that of pristine TiO 2 nanospindles and CuS nanoflakes under irradiation, respectively. The enhancement in the H 2 evolution rate is attributed to increased light absorption and efficient charge separation with an optimum CuS coverage on TiO 2 . The photoluminescence and photoelectrochemical measurements further confirm the efficient separation of charge carriers in the CuS/TiO 2 hybrid. The mechanism and synergistic role of CuS and TiO 2 semiconductors for enhanced photoactivity is further delineated.

Magnetic-Nanoflocculant-Assisted Water-Nonpolar Solvent Interface Sieve for Microalgae Harvesting.

PubMed

Lee, Kyubock; Na, Jeong-Geol; Seo, Jung Yoon; Shim, Tae Soup; Kim, Bohwa; Praveenkumar, Ramasamy; Park, Ji-Yeon; Oh, You-Kwan; Jeon, Sang Goo

2015-08-26

Exploitation of magnetic flocculants is regarded as a very promising energy-saving approach to microalgae harvesting. However, its practical applicability remains limited, mainly because of the problem of the postharvest separation of magnetic flocculants from microalgal flocs, which is crucial both for magnetic-flocculant recycling and high-purity microalgal biomasses, but which is also a very challenging and energy-consuming step. In the present study, we designed magnetic nanoflocculants dually functionalizable by two different organosilane compounds, (3-aminopropyl)triethoxysilane (APTES) and octyltriethoxysilane (OTES), which flocculate negatively charged microalgae and are readily detachable at the water-nonpolar organic solvent (NOS) interface only by application of an external magnetic field. APTES functionalization imparts a positive zeta potential charge (29.6 mV) to magnetic nanoflocculants, thereby enabling microalgae flocculation with 98.5% harvesting efficiency (with a dosage of 1.6 g of dMNF/g of cells). OTES functionalization imparts lipophilicity to magnetic nanoflocculants to make them compatible with NOS, thus effecting efficient separation of magnetic flocculants passing through the water-NOS interface sieve from hydrophilic microalgae. Our new energy-saving approach to microalgae harvesting concentrates microalgal cultures (∼1.5 g/L) up to 60 g/L, which can be directly connected to the following process of NOS-assisted wet lipid extraction or biodiesel production, and therefore provides, by simplifying multiple downstream processes, a great potential cost reduction in microalgae-based biorefinement.

Surface-modified microbubbles (colloidal gas aphrons) for nanoparticle removal in a continuous bubble generation-flotation separation system.

PubMed

Zhang, Ming; Guiraud, Pascal

2017-12-01

The treatment of nanoparticle (NP) polluted aqueous suspensions by flotation can be problematic due to the low probability of collision between particles and bubbles. To overcome this limitation, the present work focuses on developing an enhanced flotation technique using the surface-functionalized microbubbles - colloidal gas aphrons (CGAs). The CGA generator was adapted to be air flow rate controlled based on the classical Sebba system; thus it could be well adopted in a continuous flotation process. Cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were employed for CGA creation. Positively surface-charged CTAB-CGAs (∼44.1 μm in size) and negatively surface-charged SDS-CGAs (∼42.1 μm in size) were produced at the optimum stirring speed of 8000 rpm. The half-life of CGAs varied from 100 s to 340 s under the tested conditions, which was largely sufficient for transferring CGAs from bubble generator to flotation cell. The air flow led to less stable CTAB-CGAs but apparently enhanced the stability of SDS-CGAs at higher air flow rates. In the presence of air flow, the drainage behavior was not much related to the type of surfactants. The continuous CGA-flotation trials highlighted the effective separation of silica nanoparticles - the removal efficiencies of different types of SiO 2 NPs could reach approximately 90%-99%; however, at equivalent surfactant concentrations, no greater than 58% of NPs were removed when surfactants and bubbles were separately added into the flotation cell. The SiO 2 NPs with small size were removed more efficiently by the CGA-flotation process. For the flotation with CTAB-CGAs, the neutral and basic initial SNP suspension was recommended, whereas the SDS-CGAs remained high flotation efficiency over all investigated pH. The good performance of CGA-flotation might be interpreted: most of the surfactant molecules well covered/coated on the surfaces of stable CGAs and thus fully contacted with NPs, resulting in the efficient utilization of surfactants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Exceptionally Long-Lived Charge Separated State in Zeolitic Imidazolate Framework: Implication for Photocatalytic Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pattengale, Brian; Yang, Sizhuo; Ludwig, John

2016-06-22

Zeolitic Imidazolate Frameworks (ZIFs) have emerged as a novel class of porous metal-organic frameworks (MOFs) for catalysis application because of their exceptional thermal and chemical stability. Inspired by the broad absorption of ZIF-67 in UV-visible-near IR region, we explored its excited state and charge separation dynamics, properties essential for photocatalytic applications, using optical (OTA) and X-ray transient absorption (XTA) spectroscopy. OTA results show that an exceptionally long-lived excited state is formed after photoexcitation. This long-lived excited state was confirmed to be the charge separated state with ligandto-metal charge transfer character using XTA. The surprisingly long-lived charge separated state, together withmore » its intrinsic hybrid nature, all point to its potential application in heterogeneous photocatalysis and energy conversion.« less

D-π-A Compounds with Tunable Intramolecular Charge Transfer Achieved by Incorporation of Butenolide Nitriles as Acceptor Moieties.

PubMed

Moreno-Yruela, Carlos; Garín, Javier; Orduna, Jesús; Franco, Santiago; Quintero, Estefanía; López Navarrete, Juan T; Diosdado, Beatriz E; Villacampa, Belén; Casado, Juan; Andreu, Raquel

2015-12-18

Chromophores where a polyenic spacer separates a 4H-pyranylidene or benzothiazolylidene donor and three different butenolide nitriles have been synthesized and characterized. The role of 2(5H)-furanones as acceptor units on the polarization and the second-order nonlinear (NLO) properties has been studied. Thus, their incorporation gives rise to moderately polarized structures with NLO responses that compare favorably to those of related compounds featuring more efficient electron-withdrawing moieties. Derivatives of the proaromatic butenolide PhFu show the best nonlinearities. Benzothiazolylidene-containing chromophores present less alternated structures than their pyranylidene analogues, and, unlike most merocyanines, the degree of charge transfer does not decrease on lengthening the π-bridge.

Distinct enhancement of sub-bandgap photoresponse through intermediate band in high dose implanted ZnTe:O alloys

NASA Astrophysics Data System (ADS)

Li, Jing; Ye, Jiandong; Ren, Fangfang; Tang, Dongming; Yang, Yi; Tang, Kun; Gu, Shulin; Zhang, Rong; Zheng, Youdou

2017-03-01

The demand for high efficiency intermediate band (IB) solar cells is driving efforts in producing high quality IB photovoltaic materials. Here, we demonstrate ZnTe:O highly mismatched alloys synthesized by high dose ion implantation and pulsed laser melting exhibiting optically active IB states and efficient sub-gap photoresponse, as well as investigate the effect of pulsed laser melting on the structural and optical recovery in detail. The structural evolution and vibrational dynamics indicates a significant structural recovery of ZnTe:O alloys by liquid phase epitaxy during pulsed laser melting process, but laser irradiation also aggravates the segregation of Te in ZnTe:O alloys. A distinct intermediate band located at 1.8 eV above valence band is optically activated as evidenced by photoluminescence, absorption and photoresponse characteristics. The carrier dynamics indicates that carriers in the IB electronic states have a relatively long lifetime, which is beneficial for the fast separation of carriers excited by photons with sub-gap energy and thus the improved overall conversion efficiency. The reproducible capability of implantation and laser annealing at selective area enable the realization of high efficient lateral junction solar cells, which can ensure extreme light trapping and efficient charge separation.

Separating large microscale particles by exploiting charge differences with dielectrophoresis.

PubMed

Polniak, Danielle V; Goodrich, Eric; Hill, Nicole; Lapizco-Encinas, Blanca H

2018-04-13

Dielectrophoresis (DEP), the migration of particles due to polarization effects under the influence of a nonuniform electric field, was employed for characterizing the behavior and achieving the separation of larger (diameter >5 μm) microparticles by exploiting differences in electrical charge. Usually, electrophoresis (EP) is the method of choice for separating particles based on differences in electrical charge; however, larger particles, which have low electrophoretic mobilities, cannot be easily separated with EP-based techniques. This study presents an alternative for the characterization, assessment, and separation of larger microparticles, where charge differences are exploited with DEP instead of EP. Polystyrene microparticles with sizes varying from 5 to 10 μm were characterized employing microdevices for insulator-based dielectrophoresis (iDEP). Particles within an iDEP microchannel were exposed simultaneously to DEP, EP, and electroosmotic (EO) forces. The electrokinetic behavior of four distinct types of microparticles was carefully characterized by means of velocimetry and dielectrophoretic capture assessments. As a final step, a dielectropherogram separation of two distinct types of 10 μm particles was devised by first characterizing the particles and then performing the separation. The two types of 10 μm particles were eluted from the iDEP device as two separate peaks of enriched particles in less than 80 s. It was demonstrated that particles with the same size, shape, surface functionalization, and made from the same bulk material can be separated with iDEP by exploiting slight differences in the magnitude of particle charge. The results from this study open the possibility for iDEP to be used as a technique for the assessment and separation of biological cells that have very similar characteristics (shape, size, similar make-up), but slight variance in surface electrical charge. Copyright © 2018 Elsevier B.V. All rights reserved.

Strong Cation Exchange Chromatography in Analysis of Posttranslational Modifications: Innovations and Perspectives

PubMed Central

Edelmann, Mariola J.

2011-01-01

Strong cation exchange (SCX) chromatography has been utilized as an excellent separation technique that can be combined with reversed-phase (RP) chromatography, which is frequently used in peptide mass spectrometry. Although SCX is valuable as the second component of such two-dimensional separation methods, its application goes far beyond efficient fractionation of complex peptide mixtures. Here I describe how SCX facilitates mapping of the protein posttranslational modifications (PTMs), specifically phosphorylation and N-terminal acetylation. The SCX chromatography has been mainly used for enrichment of these two PTMs, but it might also be beneficial for high-throughput analysis of other modifications that alter the net charge of a peptide. PMID:22174558

Unravelling Photocarrier Dynamics beyond the Space Charge Region for Photoelectrochemical Water Splitting

DOE PAGES

Zhang, Wenrui; Yan, Danhua; Appavoo, Kannatassen; ...

2017-04-18

Semiconductor photoelectrodes for photoelectrochemical (PEC) water splitting require efficient carrier generation, separation, and transport at and beyond the space charge region (SCR) formed at the aqueous interface. The trade-off between photon collection and minority carrier delivery governs the photoelectrode design and implies maximum water splitting efficiency at an electrode thickness equivalent to the light absorption depth. Here, using planar ZnO thin films as a model system, we identify the photocarriers beyond the SCR as another significant source to substantially enhance the PEC performance. The high-quality ZnO films synthesized by pulsed laser deposition feature very few deep trap states and supportmore » a long photocarrier lifetime. Combined with photoelectrochemical characterization, ultrafast spectroscopy, and numerical calculations, it is revealed that engineering the exciton concentration gradient by film thickness facilitates the inward diffusion of photocarriers from the neighboring illuminated region to the SCR and, therefore, achieves a record high quantum efficiency over 80% at a thickness far beyond its light absorption depth and the SCR width. Furthermore, these results elucidate the important role of the photocarriers beyond SCR for the PEC process and provide new insight into exploring the full potential for efficient photoelectrode materials with large exciton diffusivity.« less

Real time charge efficiency monitoring for nickel electrodes in NICD and NIH2 cells

NASA Astrophysics Data System (ADS)

Zimmerman, A. H.

1987-09-01

The charge efficiency of nickel-cadmium and nickel-hydrogen battery cells is critical in spacecraft applications for determining the amount of time required for a battery to reach a full state of charge. As the nickel-cadmium or nickel-hydrogen batteries approach about 90 percent state of charge, the charge efficiency begins to drop towards zero, making estimation of the total amount of stored charge uncertain. Charge efficiency estimates are typically based on prior history of available capacity following standardized conditions for charge and discharge. These methods work well as long as performance does not change significantly. A relatively simple method for determining charge efficiencies during real time operation for these battery cells would be a tremendous advantage. Such a method was explored and appears to be quite well suited for application to nickel-cadmium and nickel-hydrogen battery cells. The charge efficiency is monitored in real time, using only voltage measurements as inputs. With further evaluation such a method may provide a means to better manage charge control of batteries, particularly in systems where a high degree of autonomy or system intelligence is required.

Combined effects of space charge and energetic disorder on photocurrent efficiency loss of field-dependent organic photovoltaic devices

NASA Astrophysics Data System (ADS)

Yoon, Sangcheol; Park, Byoungchoo; Hwang, Inchan

2015-11-01

The loss of photocurrent efficiency by space-charge effects in organic solar cells with energetic disorder was investigated to account for how energetic disorder incorporates space-charge effects, utilizing a drift-diffusion model with field-dependent charge-pair dissociation and suppressed bimolecular recombination. Energetic disorder, which induces the Poole-Frenkel behavior of charge carrier mobility, is known to decrease the mobility of charge carriers and thus reduces photovoltaic performance. We found that even if the mobilities are the same in the absence of space-charge effects, the degree of energetic disorder can be an additional parameter affecting photocurrent efficiency when space-charge effects occur. Introducing the field-dependence parameter that reflects the energetic disorder, the behavior of efficiency loss with energetic disorder can differ depending on which charge carrier is subject to energetic disorder. While the energetic disorder that is applied to higher-mobility charge carriers decreases photocurrent efficiency further, the efficiency loss can be suppressed when energetic disorder is applied to lower-mobility charge carriers.

Real time charge efficiency monitoring for nickel electrodes in NICD and NIH2 cells

NASA Technical Reports Server (NTRS)

Zimmerman, A. H.

1987-01-01

The charge efficiency of nickel-cadmium and nickel-hydrogen battery cells is critical in spacecraft applications for determining the amount of time required for a battery to reach a full state of charge. As the nickel-cadmium or nickel-hydrogen batteries approach about 90 percent state of charge, the charge efficiency begins to drop towards zero, making estimation of the total amount of stored charge uncertain. Charge efficiency estimates are typically based on prior history of available capacity following standardized conditions for charge and discharge. These methods work well as long as performance does not change significantly. A relatively simple method for determining charge efficiencies during real time operation for these battery cells would be a tremendous advantage. Such a method was explored and appears to be quite well suited for application to nickel-cadmium and nickel-hydrogen battery cells. The charge efficiency is monitored in real time, using only voltage measurements as inputs. With further evaluation such a method may provide a means to better manage charge control of batteries, particularly in systems where a high degree of autonomy or system intelligence is required.

Photoinduced electron transfer in a ferrocene-distyryl BODIPY dyad and a ferrocene-distyryl BODIPY-C60 triad.

PubMed

Liu, Jian-Yong; El-Khouly, Mohamed E; Fukuzumi, Shunichi; Ng, Dennis K P

2012-06-04

A ferrocene-distyryl BODIPY dyad and a ferrocene-distyryl BODIPY-C(60) triad are synthesized and characterized. Upon photoexcitation at the distyryl BODIPY unit, these arrays undergo photoinduced electron transfer to form the corresponding charge-separated species. Based on their redox potentials, determined by cyclic voltammetry, the direction of the charge separation and the energies of these states are revealed. Femtosecond transient spectroscopic studies reveal that a fast charge separation (k(CS) =1.0×10(10) s(-1)) occurs for both the ferrocene-distyryl BODIPY dyad and the ferrocene-distyryl BODIPY-C(60) triad, but that a relatively slow charge recombination is observed only for the triad. The lifetime of the charge-separated state is 500 ps. Charge recombination of the dyad and triad leads to population of the triplet excited sate of ferrocene and the ground state, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of an EBIS charge breeder for the Rare Isotope Science Project

NASA Astrophysics Data System (ADS)

Son, Hyock-Jun; Park, Young-Ho; Kondrashev, Sergey; Kim, Jongwon; Lee, Bong Ju; Chung, Moses

2017-10-01

In Korea, a heavy ion accelerator facility called RAON is being designed to produce various rare isotopes for the Rare Isotope Science Project (RISP) (Jeong, 2016) [1], (Moon, 2014) [2]. This facility is designed to use both In-flight Fragment (IF) and Isotope Separation On-Line (ISOL) techniques in order to produce a wide variety of RI beams for nuclear physics experiments. An Electron Beam Ion Source (EBIS) will be used for charge breeding of Rare Isotope (RI) beams in the ISOL system. The charge-to-mass ratio (q/A) of the RI beams after charge breeding is ≥1/4. The highly charged RI beams will be accelerated by a linac post-accelerator and delivered to a low energy (∼18 MeV/u) experimental hall or the IF system. The RAON EBIS will use a 3 A electron gun and a 6 T superconducting solenoid for high capacity, high efficiency, and short breeding time. In front of the charge breeder, an RFQ cooler-buncher will be used to deliver a bunched beam with small emittance to the EBIS charge breeder. The main design of the RAON EBIS has been carried out on the basis of several beam analyses and technical reviews. In this paper, current progress of the development of the RAON EBIS charge breeder will be presented.

A simple transferable adaptive potential to study phase separation in large-scale xMgO-(1-x)SiO2 binary glasses.

PubMed

Bidault, Xavier; Chaussedent, Stéphane; Blanc, Wilfried

2015-10-21

A simple transferable adaptive model is developed and it allows for the first time to simulate by molecular dynamics the separation of large phases in the MgO-SiO2 binary system, as experimentally observed and as predicted by the phase diagram, meaning that separated phases have various compositions. This is a real improvement over fixed-charge models, which are often limited to an interpretation involving the formation of pure clusters, or involving the modified random network model. Our adaptive model, efficient to reproduce known crystalline and glassy structures, allows us to track the formation of large amorphous Mg-rich Si-poor nanoparticles in an Mg-poor Si-rich matrix from a 0.1MgO-0.9SiO2 melt.

Phthalimide Copolymer Solar Cells

NASA Astrophysics Data System (ADS)

Xin, Hao; Guo, Xugang; Ren, Guoqiang; Kim, Felix; Watson, Mark; Jenekhe, Samson

2010-03-01

Photovoltaic properties of bulk heterojunction solar cells based on phthalimide donor-acceptor copolymers have been investigated. Due to the strong π-π stacking of the polymers, the state-of-the-art thermal annealing approach resulted in micro-scale phase separation and thus negligible photocurrent. To achieve ideal bicontinuous morphology, different strategies including quickly film drying and mixed solvent for film processing have been explored. In these films, nano-sale phase separation was achieved and a power conversion efficiency of 3.0% was obtained. Absorption and space-charge limited current mobility measurements reveal similar light harvesting and hole mobilities in all the films, indicating that the morphology is the dominant factor determining the photovoltaic performance. Our results demonstrate that for highly crystalline and/or low-solubility polymers, finding a way to prevent polymer aggregation and large scale phase separation is critical to realizing high performance solar cells.

Hole transfer from CdSe nanoparticles to TQ1 polymer in hybrid solar cell device

NASA Astrophysics Data System (ADS)

Sohail, Muhammad; Shah, Zawar Hussain; Saeed, Shomaila; Bibi, Nasreen; Shahbaz, Sadia; Ahmed, Safeer; Shabbir, Saima; Siddiq, Muhammad; Iqbal, Azhar

2018-05-01

In view of realizing the economic viability, we fabricate a solar cell device containing low band gap and easily processable polymer 5-yl-8-(thiophene-2,5-diyl)-2,3-bis(3-(octyloxy)phenyl) quinoxaline (TQ1) and CdSe nanoparticles (NPs) and investigate its charge transport properties. When the TQ1 is combined with the CdSe NPs a strong photoluminescence quenching and shortening of photoluminescence lifetime of the TQ1 is observed indicating exciton transfer from TQ1 to the CdSe NPs. The time-resolved photoluminescence further reveals that the exciton transfer from the polymer to CdSe NPs is very efficient (68%) and it occurs in <1 ns. The exciton transfer from TQ1 to the NPs and electron-hole pair separation followed by hole transfer from the NPs to the TQ1 at the interface indeed increases the lifetime of the charge carriers. This in turn increases the efficiency of the solar cell as compared to polymer only device. These observations suggest the importance of other II-VI semiconductor NPs to achieve higher efficiency for photovoltaic devices containing TQ1 polymer.

Unified Electromagnetic-Electronic Design of Light Trapping Silicon Solar Cells

PubMed Central

Boroumand, Javaneh; Das, Sonali; Vázquez-Guardado, Abraham; Franklin, Daniel; Chanda, Debashis

2016-01-01

A three-dimensional unified electromagnetic-electronic model is developed in conjunction with a light trapping scheme in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. The comparison between a bare and light trapping cell shows significant enhancement in photon absorption and electron collection. The model further demonstrates that in order to achieve high energy conversion efficiency, charge separation must be optimized through control of the doping profile and surface passivation. Despite having a larger number of surface defect states caused by the surface patterning in light trapping cells, we show that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. The fundamental physics behind this specific design approach is validated through its application to a 3 μm thick functional light trapping solar cell which shows 192% efficiency enhancement with respect to the bare cell of same thickness. Such a unified design approach will pave the path towards achieving the well-known Shockley-Queisser (SQ) limit for c-Si in thin-film (<30 μm) geometries. PMID:27499446

Semiconductor nanostructures for artificial photosynthesis

NASA Astrophysics Data System (ADS)

Yang, Peidong

2012-02-01

Nanowires, with their unique capability to bridge the nanoscopic and macroscopic worlds, have already been demonstrated as important materials for different energy conversion. One emerging and exciting direction is their application for solar to fuel conversion. The generation of fuels by the direct conversion of solar energy in a fully integrated system is an attractive goal, but no such system has been demonstrated that shows the required efficiency, is sufficiently durable, or can be manufactured at reasonable cost. One of the most critical issues in solar water splitting is the development of a suitable photoanode with high efficiency and long-term durability in an aqueous environment. Semiconductor nanowires represent an important class of nanostructure building block for direct solar-to-fuel application because of their high surface area, tunable bandgap and efficient charge transport and collection. Nanowires can be readily designed and synthesized to deterministically incorporate heterojunctions with improved light absorption, charge separation and vectorial transport. Meanwhile, it is also possible to selectively decorate different oxidation or reduction catalysts onto specific segments of the nanowires to mimic the compartmentalized reactions in natural photosynthesis. In this talk, I will highlight several recent examples in this lab using semiconductor nanowires and their heterostructures for the purpose of direct solar water splitting.

Solar photovoltaic charging of lithium-ion batteries

NASA Astrophysics Data System (ADS)

Gibson, Thomas L.; Kelly, Nelson A.

Solar photovoltaic (PV) charging of batteries was tested by using high efficiency crystalline and amorphous silicon PV modules to recharge lithium-ion battery modules. This testing was performed as a proof of concept for solar PV charging of batteries for electrically powered vehicles. The iron phosphate type lithium-ion batteries were safely charged to their maximum capacity and the thermal hazards associated with overcharging were avoided by the self-regulating design of the solar charging system. The solar energy to battery charge conversion efficiency reached 14.5%, including a PV system efficiency of nearly 15%, and a battery charging efficiency of approximately 100%. This high system efficiency was achieved by directly charging the battery from the PV system with no intervening electronics, and matching the PV maximum power point voltage to the battery charging voltage at the desired maximum state of charge for the battery. It is envisioned that individual homeowners could charge electric and extended-range electric vehicles from residential, roof-mounted solar arrays, and thus power their daily commuting with clean, renewable solar energy.

Formation of ion clusters in the phase separated structures of neutral-charged polymer blends

NASA Astrophysics Data System (ADS)

Kwon, Ha-Kyung; Olvera de La Cruz, Monica

2015-03-01

Polyelectrolyte blends, consisting of at least one charged species, are promising candidate materials for fuel cell membranes, for their mechanical stability and high selectivity for proton conduction. The phase behavior of the blends is important to understand, as this can significantly affect the performance of the device. The phase behavior is controlled by χN, the Flory-Huggins parameter multiplied by the number of mers, as well as the electrostatic interactions between the charged backbone and the counterions. It has recently been shown that local ionic correlations, incorporated via liquid state (LS) theory, enhance phase separation of the blend, even in the absence of polymer interactions. In this study, we show phase diagrams of neutral-charged polymer blends including ionic correlations via LS theory. In addition to enhanced phase separation at low χN, the blends show liquid-liquid phase separation at high electrostatic interaction strengths. Above the critical strength, the charged polymer phase separates into ion-rich and ion-poor regions, resulting in the formation of ion clusters within the charged polymer phase. This can be shown by the appearance of multiple spinodal and critical points, indicating the coexistence of several charge separated phases. This work was performed under the following financial assistance award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD).

Photoelectrodes based on 2D opals assembled from Cu-delafossite double-shelled microspheres for an enhanced photoelectrochemical response.

PubMed

Oh, Yunjung; Yang, Wooseok; Tan, Jeiwan; Lee, Hyungsoo; Park, Jaemin; Moon, Jooho

2018-02-22

Although a unique light-harvesting property was recently demonstrated in a photocathode based on 2-dimensional (2D) opals of CuFeO 2 -shelled SiO 2 microspheres, the performance of a monolayer of ultra-thin CuFeO 2 -shelled microspheres is limited by ineffective charge separation. Herein, we propose an innovative design rule, in which an inner CuFeO 2 /outer CuAlO 2 double-shelled heterojunction is formed on each partially etched microsphere to obtain a hexagonally assembled 2D opal photoelectrode. Our Cu-delafossite double-shelled photocathode shows a dramatically improved charge separation capability, with a 9-fold increase in the photocurrent compared to that of the single-shelled counterpart. Electrochemical impedance spectroscopy clearly confirms the reduced charge transport/transfer resistance associated with the Cu-delafossite double-shelled photocathode, while surface photovoltage spectra reveal enhanced polarization of the photogenerated carrier, indicating improved charge separation capability with the aid of the heterojunction. Our finding sheds light on the importance of heterojunction interfaces in achieving optimal charge separation in opal architectures as well as the inner-shell/electrolyte interface to expedite charge separation/transport.

Quantum modeling of ultrafast photoinduced charge separation

NASA Astrophysics Data System (ADS)

Rozzi, Carlo Andrea; Troiani, Filippo; Tavernelli, Ivano

2018-01-01

Phenomena involving electron transfer are ubiquitous in nature, photosynthesis and enzymes or protein activity being prominent examples. Their deep understanding thus represents a mandatory scientific goal. Moreover, controlling the separation of photogenerated charges is a crucial prerequisite in many applicative contexts, including quantum electronics, photo-electrochemical water splitting, photocatalytic dye degradation, and energy conversion. In particular, photoinduced charge separation is the pivotal step driving the storage of sun light into electrical or chemical energy. If properly mastered, these processes may also allow us to achieve a better command of information storage at the nanoscale, as required for the development of molecular electronics, optical switching, or quantum technologies, amongst others. In this Topical Review we survey recent progress in the understanding of ultrafast charge separation from photoexcited states. We report the state-of-the-art of the observation and theoretical description of charge separation phenomena in the ultrafast regime mainly focusing on molecular- and nano-sized solar energy conversion systems. In particular, we examine different proposed mechanisms driving ultrafast charge dynamics, with particular regard to the role of quantum coherence and electron-nuclear coupling, and link experimental observations to theoretical approaches based either on model Hamiltonians or on first principles simulations.

Acquisition of a High Performance Computer Cluster for Materials Research and Education

DTIC Science & Technology

2015-04-17

separation in all-organic and hybrid organic- inorganic solar cells. The outcome of the project 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13...diffusion and interfacial charge separation in all-organic and hybrid organic- inorganic solar cells. The outcome of the project is the development...simulations to predict charge carrier mobilities, exciton diffusion and interfacial charge separation in all- organic and hybrid organic- inorganic solar

Charge separation at nanoscale interfaces: energy-level alignment including two-quasiparticle interactions.

PubMed

Li, Huashan; Lin, Zhibin; Lusk, Mark T; Wu, Zhigang

2014-10-21

The universal and fundamental criteria for charge separation at interfaces involving nanoscale materials are investigated. In addition to the single-quasiparticle excitation, all the two-quasiparticle effects including exciton binding, Coulomb stabilization, and exciton transfer are considered, which play critical roles on nanoscale interfaces for optoelectronic applications. We propose a scheme allowing adding these two-quasiparticle interactions on top of the single-quasiparticle energy level alignment for determining and illuminating charge separation at nanoscale interfaces. Employing the many-body perturbation theory based on Green's functions, we quantitatively demonstrate that neglecting or simplifying these crucial two-quasiparticle interactions using less accurate methods is likely to predict qualitatively incorrect charge separation behaviors at nanoscale interfaces where quantum confinement dominates.

Directional charge separation in isolated organic semiconductor crystalline nanowires

DOE PAGES

Labastide, J. A.; Thompson, H. B.; Marques, S. R.; ...

2016-02-25

One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized alongmore » the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry.« less

Materials and systems for unassisted photoelectrochemical solar fuels production (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lee, Jae Sung

2016-10-01

About 400 semiconductor solids are known to have photocatalytic activity for water splitting. Yet there is no single material that could satisfy all the requirements for desired photocatalysts: i) suitable band gap energy (1.7 eV< Eg < 2.3 eV) for high efficiency, ii) proper band position for reduction and/or oxidation of water, iii) long-term stability in aqueous solutions, iv) low cost, v) high crystallinity, and vi) high conductivity. Hence, in the selection of photocatalytic materials, we better start from intrinsically stable materials made of earth-abundant elements. The band bap energy is also the primary consideration to absorb ample amount of solar energy of wide wavelength spectrum. It sets the limit of theoretically maximum efficiency and it could also be extended by band engineering techniques. Upon selection of the candidate materials, we can also modify the materials for full utilization their potentials. The main path of efficiency loss in PEC water splitting process is recombination of photoelectrons and holes. We discuss the material designs including i) p-n heterojunction photoanodes for effective electron-hole separation, ii) electron highway to facilitate interparticle electron transfer, iii) metal or anion doping to improve conductivity of the semiconductor and to extend the range of light absorption, iv) one-dimensional nanomaterials to secure a short hole diffusion distance and vectoral electron transfer, and v) loading co-catalysts for facile charge separation. High efficiency has been demonstrated for all these examples due to efficient electron-hole separation. Finally, total systems for unassisted solar fuel production are demonstrated.

Nanostructured organic/inorganic semicondutor photovoltaics: Investigation on morphology and optoelectronics performance

NASA Astrophysics Data System (ADS)

Wanninayake, Aruna Pushpa Kumara

Organic solar cell is a promising technology because of the versatility of organic materials in terms of tunability of their electrical and optical properties. In addition, their relative insensitivity to film imperfections potentially allows for very low-cost high-throughput roll-to-roll processing. However, the power conversion efficiency of organic solar cell is still limited and needs to be improved in order to be competitive with grid parity. This work is focused on the design and characterization of a new organic/inorganic hybrid device to enhance the efficiency factors of bilayer organic solar cells such as: light absorption, exciton diffusion, exciton dissociation, charge transportation and charge collection at the electrodes. In a hybrid solar cell operation, external quantum efficiency is determined by these five factors. The external quantum efficiency has linear relationship to the power conversation efficiency via short circuit current density. Bulk heterojunction (BHJ) PSCs benefit from a homogeneous donor-acceptor (D-A) contact interface compared to their inorganic counterpart. A homogenous D-A interface offers a longer free path for charge carriers, resulting in a longer diffusional pathway and a larger coulomb interaction between electrons and holes. This is triggered by the low dielectric constant of organic semiconductors. Among various conventional donor-acceptor structures, poly(3-hexylthiophene)/[6,6]-phenyl-C70-butyric acid methyl ester (P3HT/PCBM) mixture is the most promising and ideal donor-acceptor pair due to their unique properties. In order to take benefits from both organic and inorganic materials, inorganic nanoparticles are incorporated in this donor-acceptor polymer structure. Light trapping enhances light absorption and increases efficiencies with thinner device structure. In this study, copper oxide nanoparticles are used in the P3HT/PC70BM active layer to optimize the optical absorption properties in the blend. In addition, zinc oxide nanoparticles are used for tuning the conjugated polymer films due to their high electron accepting ability and optical absorption properties. In the zinc oxide structure, electrons exhibit higher mobility, which enhances the exciton dissociation efficiency. In addition, metal nanoparticles such as gold are added to the hole transport layer to enhance the overall hole transport ability. The optimum morphology of P3HT/PCBM films is described by two main features: 1) the molecular ordering within the donor or acceptor phase, which affects the photon absorption and carrier mobility; and 2) the scale of phase separation between the donor and the acceptor, which can directly influence the exciton dissociation and charge transport and/or collection processes. Hence, the molecular ordering and the phase separation between the donor and acceptor phases are crucial for solar cells with high efficiency. Optimization of the morphology of the organic/inorganic hybrid layers will be achieved via thermal annealing. The main goal of this work is to fabricate inorganic nanoparticles incorporated polymer PV devices with increased power conversion efficiency (PCE). This goal is achieved through four research objectives which are 1) enhancement of exciton generation and morphology by CuO NPs, 2) enhancement of exciton transportation and carrier diffusion by thermal annealing, 3) Improvement of exciton dissociation and electron mobility using ZnO NPs, and 4) improvement of hole collection ability using Au NPs. The key findings in this research can be applied to fabricate solar cells with higher power conversion efficiencies.

Ultrafast Photoinduced Electron Transfer in a π-Conjugated Oligomer/Porphyrin Complex.

PubMed

Aly, Shawkat M; Goswami, Subhadip; Alsulami, Qana A; Schanze, Kirk S; Mohammed, Omar F

2014-10-02

Controlling charge transfer (CT), charge separation (CS), and charge recombination (CR) at the donor-acceptor interface is extremely important to optimize the conversion efficiency in solar cell devices. In general, ultrafast CT and slow CR are desirable for optimal device performance. In this Letter, the ultrafast excited-state CT between platinum oligomer (DPP-Pt(acac)) as a new electron donor and porphyrin as an electron acceptor is monitored for the first time using femtosecond (fs) transient absorption (TA) spectroscopy with broad-band capability and 120 fs temporal resolution. Turning the CT on/off has been shown to be possible either by switching from an organometallic oligomer to a metal-free oligomer or by controlling the charge density on the nitrogen atom of the porphyrin meso unit. Our time-resolved data show that the CT and CS between DPP-Pt(acac) and cationic porphyrin are ultrafast (approximately 1.5 ps), and the CR is slow (ns time scale), as inferred from the formation and the decay of the cationic and anionic species. We also found that the metallic center in the DPP-Pt(acac) oligomer and the positive charge on the porphyrin are the keys to switching on/off the ultrafast CT process.

Coating polymeric carbon nitride photoanodes on conductive Y:ZnO nanorod arrays for overall water splitting.

PubMed

Fang, Yuanxing; Xu, Yuntao; Li, Xiaochun; Ma, Yiwen; Wang, Xinchen

2018-06-14

Solar-to-fuel conversion via photoelectrochemical (PEC) water splitting has the potential to ease current energy and environmental concerns. In pursuit of sustainability, polymeric carbon nitride (PCN) photosensitizers are receiving increasing attention as replacements for their inorganic counterparts. However, intense charge recombination, primarily because of the numerous surface defects, limits the use of PCN in PEC systems. Herein, photoanodes are designed by coating PCN films onto highly conductive yttrium (Y) doped zinc oxide (ZnO) nanorods (NRs) serving as charge collectors. The generation of charge carriers can therefore be promoted by this type II heterostructure. Accordingly, the charge collectors would be kept nearby for charge separation and transport to be used in the interfacial redox reactions. As such, the photocurrent density of the polymer electrode is improved to an exceptional value of 0.4 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) in a Na2SO4 electrolyte solution under AM 1.5 illumination. The result reveals a more than 50-fold enhancement over the PCN films achieved by powder, and the efficiency can be preserved at ca. 95% for 160 minutes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design rules for charge-transport efficient host materials for phosphorescent organic light-emitting diodes.

PubMed

May, Falk; Al-Helwi, Mustapha; Baumeier, Björn; Kowalsky, Wolfgang; Fuchs, Evelyn; Lennartz, Christian; Andrienko, Denis

2012-08-22

The use of blue phosphorescent emitters in organic light-emitting diodes (OLEDs) imposes demanding requirements on a host material. Among these are large triplet energies, the alignment of levels with respect to the emitter, the ability to form and sustain amorphous order, material processability, and an adequate charge carrier mobility. A possible design strategy is to choose a π-conjugated core with a high triplet level and to fulfill the other requirements by using suitable substituents. Bulky substituents, however, induce large spatial separations between conjugated cores, can substantially reduce intermolecular electronic couplings, and decrease the charge mobility of the host. In this work we analyze charge transport in amorphous 2,8-bis(triphenylsilyl)dibenzofuran, an electron-transporting material synthesized to serve as a host in deep-blue OLEDs. We show that mesomeric effects delocalize the frontier orbitals over the substituents recovering strong electronic couplings and lowering reorganization energies, especially for electrons, while keeping energetic disorder small. Admittance spectroscopy measurements reveal that the material has indeed a high electron mobility and a small Poole-Frenkel slope, supporting our conclusions. By linking electronic structure, molecular packing, and mobility, we provide a pathway to the rational design of hosts with high charge mobilities.

Means and method of detection in chemical separation procedures

DOEpatents

Yeung, Edward S.; Koutny, Lance B.; Hogan, Barry L.; Cheung, Chan K.; Ma, Yinfa

1993-03-09

A means and method for indirect detection of constituent components of a mixture separated in a chemical separation process. Fluorescing ions are distributed across the area in which separation of the mixture will occur to provide a generally uniform background fluorescence intensity. For example, the mixture is comprised of one or more charged analytes which displace fluorescing ions where its constituent components separate to. Fluorescing ions of the same charge as the charged analyte components cause a displacement. The displacement results in the location of the separated components having a reduced fluorescence intensity to the remainder of the background. Detection of the lower fluorescence intensity areas can be visually, by photographic means and methods, or by automated laser scanning.

Means and method of detection in chemical separation procedures

DOEpatents

Yeung, E.S.; Koutny, L.B.; Hogan, B.L.; Cheung, C.K.; Yinfa Ma.

1993-03-09

A means and method are described for indirect detection of constituent components of a mixture separated in a chemical separation process. Fluorescing ions are distributed across the area in which separation of the mixture will occur to provide a generally uniform background fluorescence intensity. For example, the mixture is comprised of one or more charged analytes which displace fluorescing ions where its constituent components separate to. Fluorescing ions of the same charge as the charged analyte components cause a displacement. The displacement results in the location of the separated components having a reduced fluorescence intensity to the remainder of the background. Detection of the lower fluorescence intensity areas can be visually, by photographic means and methods, or by automated laser scanning.

Electrophoretic sample insertion. [device for uniformly distributing samples in flow path

NASA Technical Reports Server (NTRS)

Mccreight, L. R. (Inventor)

1974-01-01

Two conductive screens located in the flow path of an electrophoresis sample separation apparatus are charged electrically. The sample is introduced between the screens, and the charge is sufficient to disperse and hold the samples across the screens. When the charge is terminated, the samples are uniformly distributed in the flow path. Additionally, a first separation by charged properties has been accomplished.

TiO2 nanocrystals decorated Z-schemed core-shell CdS-CdO nanorod arrays as high efficiency anodes for photoelectrochemical hydrogen generation.

PubMed

Li, Chia-Hsun; Hsu, Chan-Wei; Lu, Shih-Yuan

2018-07-01

TiO 2 nanocrystals decorated core-shell CdS-CdO nanorod arrays, TiO 2 @CdO/CdS NR, were fabricated as high efficiency anodes for photoelctrochemical hydrogen generation. The novel sandwich heterostructure was constructed from first growth of CdS nanorod arrays on a fluorine doped tin oxide (FTO) substrate with a hydrothermal process, followed by in situ generation of CdO thin films of single digit nanometers from the CdS nanorod surfaces through thermal oxidation, and final decoration of TiO 2 nanocrystals of 10-20 nm via a successive ionic layer absorption and reaction process. The core-shell CdS-CdO heterostructure possesses a Z-scheme band structure to enhance interfacial charge transfer, facilitating effective charge separation to suppress electron-hole recombination within CdS for much improved current density generation. The final decoration of TiO 2 nanocrystals passivates surface defects and trap states of CdO, further suppressing surface charge recombination for even higher photovoltaic conversion efficiencies. The photoelectrochemical performances of the plain CdS nanorod array were significantly improved with the formation of the sandwich heterostructure, achieving a photo current density of 3.2 mA/cm 2 at 1.23 V (vs. RHE), a 141% improvement over the plain CdS nanorod array and a 32% improvement over the CdO/CdS nanorod array. Copyright © 2018 Elsevier Inc. All rights reserved.

Freezing, fragmentation, and charge separation in sonic sprayed water droplets

NASA Astrophysics Data System (ADS)

Zilch, Lloyd W.; Maze, Joshua T.; Smith, John W.; Jarrold, Martin F.

2009-06-01

Water droplets are generated by sonic spray, transferred into vacuum through a capillary interface, and then passed through two image charge detectors separated by a drift region. The image charge detectors measure the charge and velocity of each droplet. For around 1% of the droplets, the charge changes significantly between the detectors. In some cases it increases, in others it decreases, and for some droplets the charge changes polarity. We attribute the charge changing behavior to fragmentation caused by freezing. Simulations indicate that the time required for a droplet to cool and freeze in vacuum depends on its size, and that droplets with radii of 1-2 [mu]m have the right size to freeze between the two detectors. These sizes correspond to the smaller end of the distribution present in the experiment. When the charge on a droplet increases or changes polarity, fragmentation must be accompanied by charge separation where fragments carry away opposite charges. In some cases, two fission fragments were observed in the second charge detector. We show examples where the droplet breaks apart to give fragments of the same charge and opposite charges. The fragmentation and charge changing behavior found here is consistent with what has been found in the freezing of larger suspended and supported droplets.

Glycosaminoglycan blotting on nitrocellulose membranes treated with cetylpyridinium chloride after agarose-gel electrophoretic separation.

PubMed

Maccari, Francesca; Volpi, Nicola

2002-09-01

We describe a method for blotting and immobilizing several nonsulfated and sulfated complex polysaccharides on membranes made hydrophilic and positively charged by a cationic detergent after their separation by conventional agarose gel electrophoresis. Nitrocellulose membranes were derivatized with the cationic detergent cetylpyridinium chloride (CPC) and mixtures of glycosaminoglycans (GAGs) were capillary-blotted after their separation in agarose gel electrophoresis in barium acetate/1,2-diaminopropane. Single purified species of variously sulfated polysaccharides were transferred onto the derivatized membranes after electrophoresis with an efficiency of 100% and stained with alcian blue (irreversible staining) and toluidine blue (reversible staining) permitting about 0.1 nug threshold of detection. Nonsulfated polyanions, hyaluronic acid, a fructose-containing polysaccharide with a chondroitin backbone purified from Escherichia coli U1-41, and its defructosylated product, were also electrophoretically separated and transferred onto membranes. The limit of detection for desulfated GAGs was about 0.1-0.5 nug after irreversible or reversible staining. GAG extracts from bovine, lung and aorta, and human aorta and urine were separated by agarose gel electrophoresis and blotted on CPC-treated nitrocellulose membranes. The polysaccharide composition of these extracts was determined. The membrane stained with toluidine blue (reversible staining) was destained and the same lanes used for immunological detection or other applications. Reversible staining was also applied to recover single species of polysaccharides after electrophoretic separation of mixtures of GAGs and their transfer onto membranes. Single bands were released from the membrane with an efficiency of 70-100% for further biochemical characterization.

Device and method for separating minerals, carbon and cement additives from fly ash

DOEpatents

Link, Thomas A.; Schoffstall, Micael R.; Soong, Yee

2004-01-27

A process for separating organic and inorganic particles from a dry mixture by sizing the particles into isolated fractions, contacting the sized particles to a charged substrate and subjecting the charged particles to an electric field to separate the particles.

Electronic Interactions of Michler's Ketone with DNA Bases in Synthetic Hairpins.

PubMed

Jalilov, Almaz S; Young, Ryan M; Eaton, Samuel W; Wasielewski, Michael R; Lewis, Frederick D

2015-01-01

The mechanism and dynamics of photoinduced electron transfer in two families of DNA hairpins possessing Michler's ketone linkers have been investigated by means of steady state and time-resolved transient absorption and emission spectroscopies. The excited state behavior of the diol linker employed in hairpin synthesis is similar to that of Michler's ketone in methanol solution. Hairpins possessing only a Michler's ketone linker undergo fast singlet state charge separation and charge recombination with an adjacent purine base, attributed to well-stacked ground state conformations, and intersystem crossing to the triplet state, attributed to poorly stacked ground state conformations. The failure of the triplet to undergo electron transfer reactions on the 7 ns time scale of our measurements is attributed to the low triplet energy and reduction potential of the twisted triplet state. Hairpins possessing both a Michler's ketone linker and a perylenediimide base surrogate separated by four base pairs undergo photoinduced hole transport from the diimide to Michler's ketone upon excitation of the diimide. The efficiency of hole transport is dependent upon the sequence of the intervening purine bases. © 2014 The American Society of Photobiology.

Conjugated polymer/nanocrystal nanocomposites for renewable energy applications in photovoltaics and photocatalysis.

PubMed

Su, Yu-Wei; Lin, Wei-Hao; Hsu, Yung-Jung; Wei, Kung-Hwa

2014-11-01

Conjugated polymer/nanocrystal composites have attracted much attention for use in renewable energy applications because of their versatile and synergistic optical and electronic properties. Upon absorbing photons, charge separation occurs in the nanocrystals, generating electrons and holes for photocurrent flow or reduction/oxidation (redox) reactions under proper conditions. Incorporating these nanocrystals into conjugated polymers can complement the visible light absorption range of the polymers for photovoltaics applications or allow the polymers to sensitize or immobilize the nanocrystals for photocatalysis. Here, the current developments of conjugated polymer/nanocrystal nanocomposites for bulk heterojunction-type photovoltaics incorporating Cd- and Pb-based nanocrystals or quantum dots are reviewed. The effects of manipulating the organic ligands and the concentration of the nanocrystal precursor, critical factors that affect the shape and aggregation of the nanocrystals, are also discussed. In the conclusion, the mechanisms through which conjugated polymers can sensitize semiconductor nanocrystals (TiO2 , ZnO) to ensure efficient charge separation, as well as how they can support immobilized nanocrystals for use in photocatalysis, are addressed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced Drug Photosafety by Interchromophoric Interaction Owing to Intramolecular Charge Separation.

PubMed

Li, Ming-De; Yan, Zhiping; Zhu, Ruixue; Phillips, David Lee; Aparici-Espert, Isabel; Lhiaubet-Vallet, Virginie; Miranda, Miguel A

2018-05-02

Imatinib is a synthetic tyrosinase inhibitor that is employed for the treatment of some kinds of human cancer. This drug has a low phototoxicity towards DNA, but its pyridylpyrimidine (1) fragment by itself exhibits significant phototoxicitiy. The intrinsic mechanism that leads to the enhanced photosafety of Imatinib is not yet known. Here, the properties of the excited state and interchromophoric interactions of Imatinib have been explored by using ultrafast laser flash photolysis and agarose electrophoresis studies. An intramolecular charge separation was directly observed for the irradiated Imatinib, which accounts for the relaxation of its excited state. An anionic form of pyridylpyrimidine (1) was deduced from the results of time-resolved resonance Raman spectra and by quenching experimental studies on compound 1 and diaminotoluene. In contrast, compound 1 efficiently transformed into triplet excited states with a long lifetime, which explained the phototoxicity associated with this fragment. This work provides insight into how to design drugs with lower phototoxicitiy or improved photostability by using interchromophoric interactions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Probing interfacial energetics and charge transfer kinetics in semiconductor nanocomposites: New insights into heterostructured TiO 2/BiVO 4 photoanodes

DOE PAGES

Hess, Lucas H.; Cooper, Jason K.; Loiudice, Anna; ...

2017-02-28

Heterostructured nanocomposites offer promise for creating systems exhibiting functional properties that exceed those of the isolated components. For solar energy conversion, such combinations of semiconducting nanomaterials can be used to direct charge transfer along pathways that reduce recombination and promote efficient charge extraction. However, interfacial energetics and associated kinetic pathways often differ significantly from predictions derived from the characteristics of pure component materials, particularly at the nanoscale. Here, the emergent properties of TiO 2/BiVO 4 nanocomposite photoanodes are explored using a combination of X-ray and optical spectroscopies, together with photoelectrochemical (PEC) characterization. Application of these methods to both the puremore » components and the fully assembled nanocomposites reveals unpredicted interfacial energetic alignment, which promotes ultrafast injection of electrons from BiVO 4 into TiO 2. Physical charge separation yields extremely long-lived photoexcited states and correspondingly enhanced photoelectrochemical functionality. This work highlights the importance of probing emergent interfacial energetic alignment and kinetic processes for understanding mechanisms of solar energy conversion in complex nanocomposites.« less

Delayed Triplet-State Formation through Hybrid Charge Transfer Exciton at Copper Phthalocyanine/GaAs Heterojunction.

PubMed

Lim, Heeseon; Kwon, Hyuksang; Kim, Sang Kyu; Kim, Jeong Won

2017-10-05

Light absorption in organic molecules on an inorganic substrate and subsequent electron transfer to the substrate create so-called hybrid charge transfer exciton (HCTE). The relaxation process of the HCTE states largely determines charge separation efficiency or optoelectronic device performance. Here, the study on energy and time-dispersive behavior of photoelectrons at the hybrid interface of copper phthalocyanine (CuPc)/p-GaAs(001) upon light excitation of GaAs reveals a clear pathway for HCTE relaxation and delayed triplet-state formation. According to the ground-state energy level alignment at the interface, CuPc/p-GaAs(001) shows initially fast hole injection from GaAs to CuPc. Thus, the electrons in GaAs and holes in CuPc form an unusual HCTE state manifold. Subsequent electron transfer from GaAs to CuPc generates the formation of the triplet state in CuPc with a few picoseconds delay. Such two-step charge transfer causes delayed triplet-state formation without singlet excitation and subsequent intersystem crossing within the CuPc molecules.

Triphenylamine-Based Push–Pull Molecule for Photovoltaic Applications: From Synthesis to Ultrafast Device Photophysics

PubMed Central

2017-01-01

Small push–pull molecules attract much attention as prospective donor materials for organic solar cells (OSCs). By chemical engineering, it is possible to combine a number of attractive properties such as broad absorption, efficient charge separation, and vacuum and solution processabilities in a single molecule. Here we report the synthesis and early time photophysics of such a molecule, TPA-2T-DCV-Me, based on the triphenylamine (TPA) donor core and dicyanovinyl (DCV) acceptor end group connected by a thiophene bridge. Using time-resolved photoinduced absorption and photoluminescence, we demonstrate that in blends with [70]PCBM the molecule works both as an electron donor and hole acceptor, thereby allowing for two independent channels of charge generation. The charge-generation process is followed by the recombination of interfacial charge transfer states that takes place on the subnanosecond time scale as revealed by time-resolved photoluminescence and nongeminate recombination as follows from the OSC performance. Our findings demonstrate the potential of TPA-DCV-based molecules as donor materials for both solution-processed and vacuum-deposited OSCs. PMID:28413568

Tribo-charging properties of waste plastic granules in process of tribo-electrostatic separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jia, E-mail: weee@sjtu.edu.cn; Wu, Guiqing; Xu, Zhenming

Highlights: • The cyclone charging was more effective and stable than vibrating charging. • The small particle size was better changed than large ones and was more suitable recycled by TES. • The drying pretreatment is good for improving the short-term charging effect. - Abstract: Plastic products can be found everywhere in people’s daily life. With the consistent growth of plastic consumption, more and more plastic waste is generated. Considering the stable chemical and physics characteristics of plastic, regular waste management methods are not suitable for recycling economic strategy of each government, which has become a serious environmental problem. Recyclingmore » plastic waste is considered to be the best way to treat it, because it cannot only deduce the waste but also save the energy to produce new virgin plastic. Tribo-electrostatic separation is strongly recommended for plastic separation as it can preserve the original properties of plastic and has little additional pollution. In this study, plastic granules are generated by crushing plastic waste in waste electric and electronic equipment. The tribo-charging properties of plastic waste were studied by vibrating tribo-charging and cyclone tribo-charging. The triboelectric series obtained by vibrating was: (−)-PE–PS–PC–PVC–ABS–PP-(+), while the triboelectric series obtained by cyclone was (−)-PE–PS–PC–PVC–ABS–PP-(+). Further, the cyclone charging was more effective and stable than vibrating charging. The impact factors experiments showed that small particle size was better changed than large ones and were more suitable recycled by tribo-electrostatic separation. High relative humidity was identified as impede charging effect. The results of this study will help defining the operating parameters of subsequent separator.« less

"Light sail" acceleration reexamined.

PubMed

Macchi, Andrea; Veghini, Silvia; Pegoraro, Francesco

2009-08-21

The dynamics of the acceleration of ultrathin foil targets by the radiation pressure of superintense, circularly polarized laser pulses is investigated by analytical modeling and particle-in-cell simulations. By addressing self-induced transparency and charge separation effects, it is shown that for "optimal" values of the foil thickness only a thin layer at the rear side is accelerated by radiation pressure. The simple "light sail" model gives a good estimate of the energy per nucleon, but overestimates the conversion efficiency of laser energy into monoenergetic ions.

Synthesis of zwitterionic salts of pyridinium-Meldrum acid and barbiturate through unique four-component reactions.

PubMed

Wang, Qi-Fang; Hui, Li; Hou, Hong; Yan, Chao-Guo

2010-03-08

An efficient synthetic procedure for the preparation of the unusual charge-separated pyridinium-Meldrum acid and N,N-dimethylbarbiturate acid zwitterionic salts was developed though a unique one-pot four-component reaction involving pyridine, aromatic aldehyde, Meldrum acid or N,N-dimethylbarbituric acid, and p-nitrobenzyl bromide in acetonitrile. By varying combinations of four components involving nitrogen-containing heterocycles, we conveniently established reactive alpha-halomethylene compounds, aldehydes and beta-dicarbonyl compounds a library of zwitterionic salts.

Low temperature ion source for calutrons

DOEpatents

Veach, Allen M.; Bell, Jr., William A.; Howell, Jr., George D.

1981-01-01

A new ion source assembly for calutrons has been provided for the efficient separation of elements having high vapor pressures. The strategic location of cooling pads and improved insulation permits operation of the source at lower temperatures. A vapor valve constructed of graphite and located in a constantly increasing temperature gradient provides reliable control of the vapor flow from the charge bottle to the arc chamber. A pronounced saving in calutron operating time and equipment maintenance has been achieved with the use of the present ion source.

Photocatalytic overall water splitting promoted by an α-β phase junction on Ga2O3.

PubMed

Wang, Xiang; Xu, Qian; Li, Mingrun; Shen, Shuai; Wang, Xiuli; Wang, Yaochuan; Feng, Zhaochi; Shi, Jingying; Han, Hongxian; Li, Can

2012-12-21

When Alpha met Beta: a tuneable α-β surface phase junction on Ga(2)O(3) can significantly improve photocatalytic overall water splitting into H(2) and O(2) over individual α-Ga(2)O(3) or β-Ga(2)O(3) surface phases. This enhanced photocatalytic performance is mainly attributed to the efficient charge separation and transfer across the α-β phase junction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low temperature ion source for calutrons

DOEpatents

Veach, A.M.; Bell, W.A. Jr.; Howell, G.D. Jr.

1979-10-10

A new ion source assembly for calutrons has been provided for the efficient separation of elements having high vapor pressures. The strategic location of cooling pads and improved insulation permits operation of the source at lower temperatures. A vapor valve constructed of graphite and located in a constantly increasing temperature gradient provides reliable control of the vapor flow from the charge bottle to the arc chamber. A pronounced saving in calutron operating time and equipment maintenance has been achieved with the use of the present ion source.

Conjugated block copolymers as model materials to examine charge transfer in donor-acceptor systems

NASA Astrophysics Data System (ADS)

Gomez, Enrique; Aplan, Melissa; Lee, Youngmin

Weak intermolecular interactions and disorder at junctions of different organic materials limit the performance and stability of organic interfaces and hence the applicability of organic semiconductors to electronic devices. The lack of control of interfacial structure has also prevented studies of how driving forces promote charge photogeneration, leading to conflicting hypotheses in the organic photovoltaic literature. Our approach has focused on utilizing block copolymer architectures -where critical interfaces are controlled and stabilized by covalent bonds- to provide the hierarchical structure needed for high-performance organic electronics from self-assembled soft materials. For example, we have demonstrated control of donor-acceptor heterojunctions through microphase-separated conjugated block copolymers to achieve 3% power conversion efficiencies in non-fullerene photovoltaics. Furthermore, incorporating the donor-acceptor interface within the molecular structure facilitates studies of charge transfer processes. Conjugated block copolymers enable studies of the driving force needed for exciton dissociation to charge transfer states, which must be large to maximize charge photogeneration but must be minimized to prevent losses in photovoltage in solar cell devices. Our work has systematically varied the chemical structure, energetics, and dielectric constant to perturb charge transfer. As a consequence, we predict a minimum dielectric constant needed to minimize the driving force and therefore simultaneously maximize photocurrent and photovoltage in organic photovoltaic devices.

Electrophoretic Separation of Single Particles Using Nanoscale Thermoplastic Columns.

PubMed

Weerakoon-Ratnayake, Kumuditha M; Uba, Franklin I; Oliver-Calixte, Nyoté J; Soper, Steven A

2016-04-05

Phenomena associated with microscale electrophoresis separations cannot, in many cases, be applied to the nanoscale. Thus, understanding the electrophoretic characteristics associated with the nanoscale will help formulate relevant strategies that can optimize the performance of separations carried out on columns with at least one dimension below 150 nm. Electric double layer (EDL) overlap, diffusion, and adsorption/desorption properties and/or dielectrophoretic effects giving rise to stick/slip motion are some of the processes that can play a role in determining the efficiency of nanoscale electrophoretic separations. We investigated the performance characteristics of electrophoretic separations carried out in nanoslits fabricated in poly(methyl methacrylate), PMMA, devices. Silver nanoparticles (AgNPs) were used as the model system with tracking of their transport via dark field microscopy and localized surface plasmon resonance. AgNPs capped with citrate groups and the negatively charged PMMA walls (induced by O2 plasma modification of the nanoslit walls) enabled separations that were not apparent when these particles were electrophoresed in microscale columns. The separation of AgNPs based on their size without the need for buffer additives using PMMA nanoslit devices is demonstrated herein. Operational parameters such as the electric field strength, nanoslit dimensions, and buffer composition were evaluated as to their effects on the electrophoretic performance, both in terms of efficiency (plate numbers) and resolution. Electrophoretic separations performed at high electric field strengths (>200 V/cm) resulted in higher plate numbers compared to lower fields due to the absence of stick/slip motion at the higher electric field strengths. Indeed, 60 nm AgNPs could be separated from 100 nm particles in free solution using nanoscale electrophoresis with 100 μm long columns.

Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

DOE PAGES

Yu M. Zhong; Nam, Chang -Yong; Trinh, M. Tuan; ...

2015-09-18

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealedmore » both electron and hole transfer processes at the donor–acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. As a result, this study describes a new motif for designing highly efficient acceptors for organic solar cells.« less

Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells.

PubMed

Zhong, Yu; Trinh, M Tuan; Chen, Rongsheng; Purdum, Geoffrey E; Khlyabich, Petr P; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; Zhang, Boyuan; Wang, Wei; Nam, Chang-Yong; Sfeir, Matthew Y; Black, Charles T; Steigerwald, Michael L; Loo, Yueh-Lin; Ng, Fay; Zhu, X-Y; Nuckolls, Colin

2015-09-18

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

Method and apparatus using an active ionic liquid for algae biofuel harvest and extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salvo, Roberto Di; Reich, Alton; Dykes, Jr., H. Waite H.

The invention relates to use of an active ionic liquid to dissolve algae cell walls. The ionic liquid is used to, in an energy efficient manner, dissolve and/or lyse an algae cell walls, which releases algae constituents used in the creation of energy, fuel, and/or cosmetic components. The ionic liquids include ionic salts having multiple charge centers, low, very low, and ultra low melting point ionic liquids, and combinations of ionic liquids. An algae treatment system is described, which processes wet algae in a lysing reactor, separates out algae constituent products, and optionally recovers the ionic liquid in an energymore » efficient manner.« less

Ultrafine Ti4+ doped α-Fe2O3 nanorod array photoanodes with high charge separation efficiency for solar water splitting

NASA Astrophysics Data System (ADS)

Liu, Yilin; Liu, Jie; Luo, Wenjun; Wen, Xin; Liu, Xiaokang; Zou, Zhigang; Huang, Wei

2017-06-01

Hematite (α-Fe2O3) is a promising photoanode material for solar water splitting due to its suitable band gap, earth-abundance, excellent stability and non-toxicity. However, a short hole diffusion length limits its performance. A nanorod array structure can shorten hole transfer distance to photoelectrode/electrolyte interface and decrease recombination of photo-generated carriers. However, average diameters of all previously reported nanorods are over 50 nm, thus being too thick for holes to transfer to the interface. It is still a big challenge to prepare a Fe2O3 nanorod array photoelectrode with finer diameter. In this study, we prepare an ultrafine α-Fe2O3 nanorod array film with average diameter about 25 nm by calcining γ-FeOOH for the first time. The ultrafine nanorod array photoanode indicates much higher carrier separation efficiency and performance than a conventional nanorod array film.

Abnormal strong burn-in degradation of highly efficient polymer solar cells caused by spinodal donor-acceptor demixing

PubMed Central

Li, Ning; Perea, José Darío; Kassar, Thaer; Richter, Moses; Heumueller, Thomas; Matt, Gebhard J.; Hou, Yi; Güldal, Nusret S.; Chen, Haiwei; Chen, Shi; Langner, Stefan; Berlinghof, Marvin; Unruh, Tobias; Brabec, Christoph J.

2017-01-01

The performance of organic solar cells is determined by the delicate, meticulously optimized bulk-heterojunction microstructure, which consists of finely mixed and relatively separated donor/acceptor regions. Here we demonstrate an abnormal strong burn-in degradation in highly efficient polymer solar cells caused by spinodal demixing of the donor and acceptor phases, which dramatically reduces charge generation and can be attributed to the inherently low miscibility of both materials. Even though the microstructure can be kinetically tuned for achieving high-performance, the inherently low miscibility of donor and acceptor leads to spontaneous phase separation in the solid state, even at room temperature and in the dark. A theoretical calculation of the molecular parameters and construction of the spinodal phase diagrams highlight molecular incompatibilities between the donor and acceptor as a dominant mechanism for burn-in degradation, which is to date the major short-time loss reducing the performance and stability of organic solar cells. PMID:28224984

Utilization of photoinduced charge-separated state of donor-acceptor-linked molecules for regulation of cell membrane potential and ion transport.

PubMed

Numata, Tomohiro; Murakami, Tatsuya; Kawashima, Fumiaki; Morone, Nobuhiro; Heuser, John E; Takano, Yuta; Ohkubo, Kei; Fukuzumi, Shunichi; Mori, Yasuo; Imahori, Hiroshi

2012-04-11

The control of ion transport across cell membranes by light is an attractive strategy that allows targeted, fast control of precisely defined events in the biological membrane. Here we report a novel general strategy for the control of membrane potential and ion transport by using charge-separation molecules and light. Delivery of charge-separation molecules to the plasma membrane of PC12 cells by a membranous nanocarrier and subsequent light irradiation led to depolarization of the membrane potential as well as inhibition of the potassium ion flow across the membrane. Photoregulation of the cell membrane potential and ion transport by using charge-separation molecules is highly promising for control of cell functions. © 2012 American Chemical Society

Metal oxide composite enabled nanotextured Si photoanode for efficient solar driven water oxidation.

PubMed

Sun, Ke; Pang, Xiaolu; Shen, Shaohua; Qian, Xueqiang; Cheung, Justin S; Wang, Deli

2013-05-08

We present a study of a transition metal oxide composite modified n-Si photoanode for efficient and stable water oxidation. This sputter-coated composite functions as a protective coating to prevent Si from photodecomposition, a Schottky heterojunction, a hole conducting layer for efficient charge separation and transportation, and an electrocatalyst to reduce the reaction overpotential. The formation of mixed-valence oxides composed of Ni and Ru effectively modifies the optical, electrical, and catalytic properties of the coating material, as well as the interfaces with Si. The successful application of this oxide composite on nanotextured Si demonstrates improved conversion efficiency due to enhanced catalytic activity, minimized reflection, and increased surface reaction sites. Although the coated nanotextured Si shows a noticeable degradation from 500 cycles of operation, the oxide composite provides a simple method to enable unstable photoanode materials for solar fuel conversion.

Invited review article: physics and Monte Carlo techniques as relevant to cryogenic, phonon, and ionization readout of Cryogenic Dark Matter Search radiation detectors.

PubMed

Leman, Steven W

2012-09-01

This review discusses detector physics and Monte Carlo techniques for cryogenic, radiation detectors that utilize combined phonon and ionization readout. A general review of cryogenic phonon and charge transport is provided along with specific details of the Cryogenic Dark Matter Search detector instrumentation. In particular, this review covers quasidiffusive phonon transport, which includes phonon focusing, anharmonic decay, and isotope scattering. The interaction of phonons in the detector surface is discussed along with the downconversion of phonons in superconducting films. The charge transport physics include a mass tensor which results from the crystal band structure and is modeled with a Herring-Vogt transformation. Charge scattering processes involve the creation of Neganov-Luke phonons. Transition-edge-sensor (TES) simulations include a full electric circuit description and all thermal processes including Joule heating, cooling to the substrate, and thermal diffusion within the TES, the latter of which is necessary to model normal-superconducting phase separation. Relevant numerical constants are provided for these physical processes in germanium, silicon, aluminum, and tungsten. Random number sampling methods including inverse cumulative distribution function (CDF) and rejection techniques are reviewed. To improve the efficiency of charge transport modeling, an additional second order inverse CDF method is developed here along with an efficient barycentric coordinate sampling method of electric fields. Results are provided in a manner that is convenient for use in Monte Carlo and references are provided for validation of these models.

Broadband Light Absorption and Efficient Charge Separation Using a Light Scattering Layer with Mixed Cavities for High-Performance Perovskite Photovoltaic Cells with Stability.

PubMed

Moon, Byeong Cheul; Park, Jung Hyo; Lee, Dong Ki; Tsvetkov, Nikolai; Ock, Ilwoo; Choi, Kyung Min; Kang, Jeung Ku

2017-08-01

CH 3 NH 3 PbI 3 is one of the promising light sensitizers for perovskite photovoltaic cells, but a thick layer is required to enhance light absorption in the long-wavelength regime ranging from PbI 2 absorption edge (500 nm) to its optical band-gap edge (780 nm) in visible light. Meanwhile, the thick perovskite layer suppresses visible-light absorption in the short wavelengths below 500 nm and charge extraction capability of electron-hole pairs produced upon light absorption. Herein, we find that a new light scattering layer with the mixed cavities of sizes in 100 and 200 nm between transparent fluorine-doped tin oxide and mesoporous titanium dioxide electron transport layer enables full absorption of short-wavelength photons (λ < 500 nm) to the perovskite along with enhanced absorption of long-wavelength photons (500 nm < λ < 780 nm). Moreover, the light-driven electric field is proven to allow efficient charge extraction upon light absorption, thereby leading to the increased photocurrent density as well as the fill factor prompted by the slow recombination rate. Additionally, the photocurrent density of the cell with a light scattering layer of mixed cavities is stabilized due to suppressed charge accumulation. Consequently, this work provides a new route to realize broadband light harvesting of visible light for high-performance perovskite photovoltaic cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Motion-based, high-yielding, and fast separation of different charged organics in water.

PubMed

Xuan, Mingjun; Lin, Xiankun; Shao, Jingxin; Dai, Luru; He, Qiang

2015-01-12

We report a self-propelled Janus silica micromotor as a motion-based analytical method for achieving fast target separation of polyelectrolyte microcapsules, enriching different charged organics with low molecular weights in water. The self-propelled Janus silica micromotor catalytically decomposes a hydrogen peroxide fuel and moves along the direction of the catalyst face at a speed of 126.3 μm s(-1) . Biotin-functionalized Janus micromotors can specifically capture and rapidly transport streptavidin-modified polyelectrolyte multilayer capsules, which could effectively enrich and separate different charged organics in water. The interior of the polyelectrolyte multilayer microcapsules were filled with a strong charged polyelectrolyte, and thus a Donnan equilibrium is favorable between the inner solution within the capsules and the bulk solution to entrap oppositely charged organics in water. The integration of these self-propelled Janus silica micromotors and polyelectrolyte multilayer capsules into a lab-on-chip device that enables the separation and analysis of charged organics could be attractive for a diverse range of applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photosystem II Peripheral Accessory Chlorophyll Mutants in Chlamydomonas reinhardtii. Biochemical Characterization and Sensitivity to Photo-Inhibition12

PubMed Central

Ruffle, Stuart V.; Wang, Jun; Johnston, Heather G.; Gustafson, Terry L.; Hutchison, Ronald S.; Minagawa, Jun; Crofts, Anthony; Sayre, Richard T.

2001-01-01

In addition to the four chlorophylls (Chls) involved in primary charge separation, the photosystem II (PSII) reaction center polypeptides, D1 and D2, coordinate a pair of symmetry-related, peripheral accessory Chls. These Chls are axially coordinated by the D1-H118 and D2-H117 residues and are in close association with the proximal Chl antennae proteins, CP43 and CP47. To gain insight into the function(s) of each of the peripheral Chls, we generated site-specific mutations of the amino acid residues that coordinate these Chls and characterized their energy and electron transfer properties. Our results demonstrate that D1-H118 and D2-H117 mutants differ with respect to: (a) their relative numbers of functional PSII complexes, (b) their relative ability to stabilize charge-separated states, (c) light-harvesting efficiency, and (d) their sensitivity to photo-inhibition. The D2-H117N and D2-H117Q mutants had reduced levels of functional PSII complexes and oxygen evolution capacity as well as reduced light-harvesting efficiencies relative to wild-type cells. In contrast, the D1-H118Q mutant was capable of near wild-type rates of oxygen evolution at saturating light intensities. The D1-H118Q mutant also was substantially more resistant to photo-inhibition than wild type. This reduced sensitivity to photo-inhibition is presumably associated with a reduced light-harvesting efficiency in this mutant. Finally, it is noted that the PSII peripheral accessory Chls have similarities to a to a pair of Chls also present in the PSI reaction center complex. PMID:11598237

Electron in higher-dimensional weakly charged rotating black hole spacetimes

NASA Astrophysics Data System (ADS)

Cariglia, Marco; Frolov, Valeri P.; Krtouš, Pavel; Kubizňák, David

2013-03-01

We demonstrate separability of the Dirac equation in weakly charged rotating black hole spacetimes in all dimensions. The electromagnetic field of the black hole is described by a test field approximation, with the vector potential proportional to the primary Killing vector field. It is shown that the demonstrated separability can be intrinsically characterized by the existence of a complete set of mutually commuting first-order symmetry operators generated from the principal Killing-Yano tensor. The presented results generalize the results on integrability of charged particle motion and separability of charged scalar field studied in V. P. Frolov and P. Krtous [Phys. Rev. D 83, 024016 (2011)].

Magnetically separable maghemite/montmorillonite composite as an efficient heterogeneous Fenton-like catalyst for phenol degradation.

PubMed

Jin, Mingjie; Long, Mingce; Su, Hanrui; Pan, Yue; Zhang, Qiuzhuo; Wang, Juan; Zhou, Baoxue; Zhang, Yanwu

2017-01-01

To develop highly efficient and conveniently separable iron containing catalysts is crucial to remove recalcitrant organic pollutants in wastewater through a heterogeneous Fenton-like reaction. A maghemite/montmorillonite composite was synthesized by a coprecipitation and calcination method. The physiochemical properties of catalysts were characterized by XRD, TEM, nitrogen physisorption, thermogravimetric analysis/differential scanning calorimetry (TG/DSC), zeta potential, and magnetite susceptibility measurements. The influence of calcination temperatures and reaction parameters was investigated. The calcined composites retain magnetism because the presence of montmorillonite inhibited the growth of γ-Fe 2 O 3 nanoparticles, as well as their phase transition. The catalytic activities for phenol degradation were significantly enhanced by calcinations, which strengthen the interaction between iron oxides and aluminosilicate framework and result in more negatively charged surface. The composite (73 m 2 /g) calcined at 350 °C had the highest catalytic activities, with more than 99 % phenol reduction after only 35 min reaction at pH 3.6. Simultaneously, this catalyst exhibited high stability, low iron leaching, and magnetically separable ability for consecutive usage, making it promising for the removal of recalcitrant organic pollutants in wastewater.

Through-Space Charge Interaction Substituent Effects in Molecular Catalysis Leading to the Design of the Most Efficient Catalyst of CO2-to-CO Electrochemical Conversion.

PubMed

Azcarate, Iban; Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel

2016-12-28

The starting point of this study of through-space substituent effects on the catalysis of the electrochemical CO 2 -to-CO conversion by iron(0) tetraphenylporphyrins is the linear free energy correlation between through-structure electronic effects and the iron(I/0) standard potential that we established separately. The introduction of four positively charged trimethylanilinium groups at the para positions of the tetraphenylporphyrin (TPP) phenyls results in an important positive deviation from the correlation and a parallel improvement of the catalytic Tafel plot. The assignment of this catalysis boosting effect to the Coulombic interaction of these positive charges with the negative charge borne by the initial Fe 0 -CO 2 adduct is confirmed by the negative deviation observed when the four positive charges are replaced by four negative charges borne by sulfonate groups also installed in the para positions of the TPP phenyls. The climax of this strategy of catalysis boosting by means of Coulombic stabilization of the initial Fe 0 -CO 2 adduct is reached when four positively charged trimethylanilinium groups are introduced at the ortho positions of the TPP phenyls. The addition of a large concentration of a weak acid-phenol-helps by cleaving one of the C-O bonds of CO 2 . The efficiency of the resulting catalyst is unprecedented, as can be judged by the catalytic Tafel plot benchmarking with all presently available catalysts of the electrochemical CO 2 -to-CO conversion. The maximal turnover frequency (TOF) is as high as 10 6 s -1 and is reached at an overpotential of only 220 mV; the extrapolated TOF at zero overpotential is larger than 300 s -1 . This catalyst leads to a highly selective formation of CO (practically 100%) in spite of the presence of a high concentration of phenol, which could have favored H 2 evolution. It is also very stable, showing no significant alteration after more than 80 h of electrolysis.

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link

PubMed Central

Lee, Hyung-Min; Ghovanloo, Maysam

2014-01-01

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35-μm 4-metal 2-poly standard CMOS process in 2.1 mm2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μF capacitors up to ±2 V in 420 μs, achieving a high measured charging efficiency of 82%. PMID:24678284

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link.

PubMed

Lee, Hyung-Min; Ghovanloo, Maysam

2013-10-01

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35- μ m 4-metal 2-poly standard CMOS process in 2.1 mm 2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μ F capacitors up to ±2 V in 420 μ s, achieving a high measured charging efficiency of 82%.

Thin film separators with ion transport properties for energy applications

NASA Astrophysics Data System (ADS)

Li, Zhongyuan

2017-09-01

Recent years, along with the increasing need of energy, energy storage also becomes a challenging problem which we need to deal with. The batterieshave a good developing prospect among energy storage system in storing energy such as wind, solar and geothermal energy. One hurdle between the lab-scale experiment and industry-scale application of the advanced batteries is the urgent need for limiting charging capacity degradation and improving cycling stability, known as the shuttle effect in lithium-sulfur batteries or electroosmotic drag coefficient in fuel-cell batteries. The microporous separator between the cathode and anode could be molecular engineered to possessesion selective permeation properties, which can greatly improves the energy efficiency and extends application range of the battery. The present review offers the fundamental fabrication methods of separator film with different material. The review also contains the chemical or physical structure of different materials which are used in making separator film. A table offers the reader a summary of properties such as ionic conductivity, ionic exchange capacity and current density etc.

Potential of ethylenediaminedi(o-hydroxyphenylacetic acid) and N,N'-bis(hydroxybenzyl)ethylenediamine-N,N'-diacetic acid for the determination of metal ions by capillary electrophoresis.

PubMed

Krokhin, O V; Kuzina, O V; Hoshino, H; Shpigun, O A; Yotsuyanagi, T

2000-08-25

Two aromatic polyaminocarboxylate ligands, ethylenediaminedi(o-hydroxyphenylacetic acid) (EDDHA) and N,N'-bis(hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED), were applied for the separation of transition and heavy metal ions by the ion-exchange variant of electrokinetic chromatography. EDDHA structure contains two chiral carbon centers. It makes it impossible to use the commercially available ligand. All the studied metal ions showed two peaks, which correspond to meso and rac forms of the ligand. The separation of metal-HBED chelates was performed using poly(diallyldimethylammonium) polycations in mixed acetate-hydroxide form. Simultaneous separation of nine single- and nine double-charged HBED chelates, including In(III), Ga(III), Co(II)-(III) and Mn(II)-(III) pairs demonstrated the efficiency of 40,000-400,000 theoretical plates. The separation of Co(III), Fe(III) complexes with different arrangements of donor groups and oxidation of Co(II), Mn(H), Fe(II) ions in reaction with HBED have been discussed.

Organic-inorganic hybrid nanostructures for solar cell applications

NASA Astrophysics Data System (ADS)

AbdulAlmohsin, Samir M.

The enticing electro-optical properties of nanostructured materials such as carbon nanotubes, graphene, CdS nanocrystals and ZnO nanowrie bring new vigor into the innovation of photovoltaics. The main purpose of this dissertation is to develop novel nano-structured materials for low cost solar cell applications. Fabrication, characterization, and solar cell application of organic-inorganic hybrid structures are the main focus of this research. Polyaniline (PANI)/multi-walled carbon nanotube (MWNT) composite films were synthesized by an electrochemical polymerization of aniline with airbrushed MWNTs on ITO substrates. It was found that the incorporation of MWNTs in PANI effectively increase the film conductivity with a percolation threshold of 5% of nanotubes in the composite. The solar cell performance strongly depends on the conductivity of the composite films, which can be tuned by adjusting nanotube concentration. A higher conductivity resulted in a better cell performance, resulting from an efficient charge collection. This study indicates that PANI/MWNT composite films with optimized conductivity are potentially useful for low-cost hybrid solar cell applications. CdS nanocrystal-sensitized solar cells (NCSSCs) were investigated by using polyaniline (PANI) as a replacement for conventional platinum counter electrode. The growth time of the nanocrystals significantly affects the solar cell performance. At an optimum growth, the NCSSCs exhibit 0.83% of the conversion efficiency in comparison to 0.13% for the identical cells without CdS nanocrystals. Electrochemical impedance spectroscopy showed that the charge transfer in the solar cells with CdS nanocrystals was improved. The enhanced overall energy conversion efficiency by nanocrystals is attributed to improved light absorption and suppressed recombination rate of interfacial charges at the injection, resulting in significantly improved charge transfer and electron lifetime. In addition, the PANI electrodes with large surface area and ideal corrosion-inertness toward polysulfide redox exhibit promising application potential as a counter electrode for NCSSCs. This study demonstrates that the solution grown CdS nanocrystals and polyaniline are potentially useful for fabricating high performance NCSSCs, which is technically attractive for large scale and economic production. A hybrid structure containing graphene-enriched poly (3-hexylthiophene) (G-P3HT) or poly (3-hexylthiophene):(6, 6)-phenyl C60 butyric acid methyl esterand tetra (4-carboxyphenyle) porphyrin-grafted ZnO nanowire arrays was investigated for nanowire/polymer hybrid solar cells. The vertically aligned nanowires embedded in the organic films act as an active n-type semiconductor and a high-efficiency charge collection electrode. The grafting surface of ZnO nanowires by porphyrin was found to significantly improve the cell efficiency as compared with those using pristine ZnO nanowires. The improvement is attributed to the enhanced light harvesting and charge injection with the presence of porphyrin at the junction interface. A comparison study showed that the use of G-P3HT further increase the efficiency of the nanowire solar cells from 0.09 to 0.4%, benefiting from the improved hole collection with graphene in the polymer. This study indicates that hybrid structure comprising surface modified, vertically aligned ZnO nanowire arrays embedded in G-P3HT is promising for solar cell applications. A combination of bulk heterojunction of P3HT: PCBM with ZnO nanorod arrays was also studied for solar cell applications. In the P3HT: PCBM devices, electron donors such as poly (3-hexythiophene) (P3HT) and acceptors as (6, 6)-phenyl C61 butyric acid methyl ester (PCBM) are blended to form one mixed layer (a bulk heterojunction). The charge separation of photo-induced excitons is greatly enhanced by ultra-fast electron transfer and large interface between the two components. However, the charge collection is one of the main limitations for improving cell efficiency. In this study, ZnO nanowire arrys have been used to facilitate efficient charge collection electrodes for improving the energy conversion efficiency.

Molecular design and nanoscale engineering of organic nanofibril donor-acceptor heterojunctions

NASA Astrophysics Data System (ADS)

Huang, Helin

Organic nanofibril heterojunction materials have gained increasing research interest due to their broad applications in organic semiconductor devices. In order to enhance the device performance, we have investigated the structure-property relationship of these nanostructures by designing and synthesizing functional building block molecules, selfassembling the molecules into well-defined nanofibers, fabricating the nanofibers into optical and electrical devices, and testing their photoconductivity and sensor properties. In Chapter 2, we present a simple approach to fabricate efficient nanofibril heterojunctions by interfacial engineering of electron donor (D) coating onto acceptor (A) nanofibers. The nanofibers both create a large D/A interface for increased charge separation and act as long-range transport pathways for photogenerated charge carriers towards the electrodes, and the alkyl groups modified at the A molecules not only enable effective surface adsorption of D molecules on the nanofibers for effective electron-transfer communication, but also spatially separate the photogenerated charge carriers to prevent their recombination. In Chapter 3, we further investigated the effect of D molecular structure and coating morphology on photoconductivity of organic nanofiber materials. A series of D molecules with varying side-chain modifications were synthesized and investigated for the different intermolecular arrangements caused by pi-pi stacking in balance with steric hindrance of side-chains. Different molecular assemblies of D resulted in distinctive phase segregation between D and A nanofiber, which significantly affects the interfacial charge separation. In Chapter 4, we developed an alternative nanofibril heterojunction structure that is composed of D as the nanofiber, onto which a monolayer of A molecule was coated. Due to the strong redox (charge transfer) interaction between D and A, the nanofibril junction demonstrated high conductivity even without light illumination, which makes this material suitable for applications in chemiresistor sensors for detection of amines. In Chapter 5, a series of perylene tetracarboxylic monoimides were synthesized through a one-step reaction between cycloalkyl amines and the parent perylene dianhydride. The selection of appropriate reaction medium is the most critical for achieving the high purity of product. This approach opens up a new way for large scale production of the monoimides, which are the precursor for making a variety of perylene based building block molecules.

Electric and hybrid vehicles charge efficiency tests of ESB EV-106 lead acid batteries

NASA Technical Reports Server (NTRS)

Rowlette, J. J.

1981-01-01

Charge efficiencies were determined by measurements made under widely differing conditions of temperature, charge procedure, and battery age. The measurements were used to optimize charge procedures and to evaluate the concept of a modified, coulometric state of charge indicator. Charge efficiency determinations were made by measuring gassing rates and oxygen fractions. A novel, positive displacement gas flow meter which proved to be both simple and highly accurate is described and illustrated.

Double Super-Exchange in Silicon Quantum Dots Connected by Short-Bridged Networks

NASA Astrophysics Data System (ADS)

Li, Huashan; Wu, Zhigang; Lusk, Mark

2013-03-01

Silicon quantum dots (QDs) with diameters in the range of 1-2 nm are attractive for photovoltaic applications. They absorb photons more readily, transport excitons with greater efficiency, and show greater promise in multiple-exciton generation and hot carrier collection paradigms. However, their high excitonic binding energy makes it difficult to dissociate excitons into separate charge carriers. One possible remedy is to create dot assemblies in which a second material creates a Type-II heterojunction with the dot so that exciton dissociation occurs locally. This talk will focus on such a Type-II heterojunction paradigm in which QDs are connected via covalently bonded, short-bridge molecules. For such interpenetrating networks of dots and molecules, our first principles computational investigation shows that it is possible to rapidly and efficiently separate electrons to QDs and holes to bridge units. The bridge network serves as an efficient mediator of electron superexchange between QDs while the dots themselves play the complimentary role of efficient hole superexchange mediators. Dissociation, photoluminescence and carrier transport rates will be presented for bridge networks of silicon QDs that exhibit such double superexchange. This material is based upon work supported by the Renewable Energy Materials Research Science and Engineering Center (REMRSEC) under Grant No. DMR-0820518 and Golden Energy Computing Organization (GECO).

Isobar Separation in a Multiple-Reflection Time-of-Flight Mass Spectrometer by Mass-Selective Re-Trapping.

PubMed

Dickel, Timo; Plaß, Wolfgang R; Lippert, Wayne; Lang, Johannes; Yavor, Mikhail I; Geissel, Hans; Scheidenberger, Christoph

2017-06-01

A novel method for (ultra-)high-resolution spatial mass separation in time-of-flight mass spectrometers is presented. Ions are injected into a time-of-flight analyzer from a radio frequency (rf) trap, dispersed in time-of-flight according to their mass-to-charge ratios and then re-trapped dynamically in the same rf trap. This re-trapping technique is highly mass-selective and after sufficiently long flight times can provide even isobaric separation. A theoretical treatment of the method is presented and the conditions for optimum performance of the method are derived. The method has been implemented in a multiple-reflection time-of-flight mass spectrometer and mass separation powers (FWHM) in excess of 70,000, and re-trapping efficiencies of up to 35% have been obtained for the protonated molecular ion of caffeine. The isobars glutamine and lysine (relative mass difference of 1/4000) have been separated after a flight time of 0.2 ms only. Higher mass separation powers can be achieved using longer flight times. The method will have important applications, including isobar separation in nuclear physics and (ultra-)high-resolution precursor ion selection in multiple-stage tandem mass spectrometry. Graphical Abstract ᅟ.

Isobar Separation in a Multiple-Reflection Time-of-Flight Mass Spectrometer by Mass-Selective Re-Trapping

NASA Astrophysics Data System (ADS)

Dickel, Timo; Plaß, Wolfgang R.; Lippert, Wayne; Lang, Johannes; Yavor, Mikhail I.; Geissel, Hans; Scheidenberger, Christoph

2017-06-01

A novel method for (ultra-)high-resolution spatial mass separation in time-of-flight mass spectrometers is presented. Ions are injected into a time-of-flight analyzer from a radio frequency (rf) trap, dispersed in time-of-flight according to their mass-to-charge ratios and then re-trapped dynamically in the same rf trap. This re-trapping technique is highly mass-selective and after sufficiently long flight times can provide even isobaric separation. A theoretical treatment of the method is presented and the conditions for optimum performance of the method are derived. The method has been implemented in a multiple-reflection time-of-flight mass spectrometer and mass separation powers (FWHM) in excess of 70,000, and re-trapping efficiencies of up to 35% have been obtained for the protonated molecular ion of caffeine. The isobars glutamine and lysine (relative mass difference of 1/4000) have been separated after a flight time of 0.2 ms only. Higher mass separation powers can be achieved using longer flight times. The method will have important applications, including isobar separation in nuclear physics and (ultra-)high-resolution precursor ion selection in multiple-stage tandem mass spectrometry. [Figure not available: see fulltext.

Triboelectrostatic separation for granular plastic waste recycling: a review.

PubMed

Wu, Guiqing; Li, Jia; Xu, Zhenming

2013-03-01

The world's plastic consumption has increased incredibly in recent decades, generating more and more plastic waste, which makes it a great public concern. Recycling is the best treatment for plastic waste since it cannot only reduce the waste but also reduce the consumption of oil for producing new virgin plastic. Mechanical recycling is recommended for plastic waste to avoid the loss of its virgin value. As a mechanical separation technology, triboelectrostatic separation utilizes the difference between surface properties of different materials to get them oppositely charged, deflected in the electric field and separately collected. It has advantages such as high efficiency, low cost, no concern of water disposal or secondary pollution and a relatively wide processing range of particle size especially suitable for the granular plastic waste. The process of triboelectrostatic separation for plastic waste is reviewed in this paper. Different devices have been developed and proven to be effective for separation of plastic waste. The influence factors are also discussed. It can be concluded that the triboelectrostatic separation of plastic waste is a promising technology. However, more research is required before it can be widely applied in industry. Copyright © 2012 Elsevier Ltd. All rights reserved.

Tribocharging Lunar Soil for Electrostatic Beneficiation

NASA Technical Reports Server (NTRS)

2008-01-01

Future human lunar habitation requires using in situ materials for both structural components and oxygen production. Lunar bases must be constructed from thermal-and radiation-shielding materials that will provide significant protection from the harmful cosmic energy which normally bombards the lunar surface. In addition, shipping oxygen from Earth is weight-prohibitive, and therefore investigating the production of breathable oxygen from oxidized mineral components is a major ongoing NASA research initiative. Lunar regolith may meet the needs for both structural protection and oxygen production. Already a number of oxygen production technologies are being tested, and full-scale bricks made of lunar simulant have been sintered. The beneficiation, or separation, of lunar minerals into a refined industrial feedstock could make production processes more efficient, requiring less energy to operate and maintain and producing higher-performance end products. The method of electrostatic beneficiation used in this research charges mineral powders (lunar simulant) by contact with materials of a different composition. The simulant acquires either a positive or negative charge depending upon its composition relative to the charging material.

The physics of charge separation preceding lightning strokes in thunderclouds

NASA Technical Reports Server (NTRS)

Kyrala, Ali

1987-01-01

The physics of charge separation preceding lightning strokes in thunderclouds is presented by three types of arguments: An explanation is given for the aggregation of electrical charges of like sign overcoming Coulomb repulsion by attraction due to exchange interaction. The latter is well known in quantum mechanics from the theories of the nuclear bond and the covalent bond. A classical electrostatic model of charge balls of segregated positive and negative charges in the thundercloud is presented. These charge balls can only be maintained in temporarily stable locations by a containing vortex. Because they will be of different sizes and masses, they will stabilize at different altitudes when drag forces are included with the given electrostatic force. The question of how the charges become concentrated again after lightning discharges is approached by means of the collisional Boltzmann transport equation to explain quasi-periodic recharging. It is shown that solutions cannot be separable in both position and time if they are to represent aggregation.

Imaging the Anomalous Charge Distribution Inside CsPbBr3 Perovskite Quantum Dots Sensitized Solar Cells.

PubMed

Panigrahi, Shrabani; Jana, Santanu; Calmeiro, Tomás; Nunes, Daniela; Martins, Rodrigo; Fortunato, Elvira

2017-10-24

Highly luminescent CsPbBr 3 perovskite quantum dots (QDs) have gained huge attention in research due to their various applications in optoelectronics, including as a light absorber in photovoltaic solar cells. To improve the performances of such devices, it requires a deeper knowledge on the charge transport dynamics inside the solar cell, which are related to its power-conversion efficiency. Here, we report the successful fabrication of an all-inorganic CsPbBr 3 perovskite QD sensitized solar cell and the imaging of anomalous electrical potential distribution across the layers of the cell under different illuminations using Kelvin probe force microscopy. Carrier generation, separation, and transport capacity inside the cells are dependent on the light illumination. Large differences in surface potential between electron and hole transport layers with unbalanced carrier separation at the junction have been observed under white light (full solar spectrum) illumination. However, under monochromatic light (single wavelength of solar spectrum) illumination, poor charge transport occurred across the junction as a consequence of less difference in surface potential between the active layers. The outcome of this study provides a clear idea on the carrier dynamic processes inside the cells and corresponding surface potential across the layers under the illumination of different wavelengths of light to understand the functioning of the solar cells and ultimately for the improvement of their photovoltaic performances.

Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy

PubMed Central

Ghadiri, Elham; Zakeeruddin, Shaik M.; Hagfeldt, Anders; Grätzel, Michael; Moser, Jacques-E.

2016-01-01

Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and –690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded. PMID:27095505

Charge-specific size-dependent separation of water-soluble organic molecules by fluorinated nanoporous networks

NASA Astrophysics Data System (ADS)

Byun, Jeehye; Patel, Hasmukh A.; Thirion, Damien; Yavuz, Cafer T.

2016-11-01

Molecular architecture in nanoscale spaces can lead to selective chemical interactions and separation of species with similar sizes and functionality. Substrate specific sorbent chemistry is well known through highly crystalline ordered structures such as zeolites, metal organic frameworks and widely available nanoporous carbons. Size and charge-dependent separation of aqueous molecular contaminants, on the contrary, have not been adequately developed. Here we report a charge-specific size-dependent separation of water-soluble molecules through an ultra-microporous polymeric network that features fluorines as the predominant surface functional groups. Treatment of similarly sized organic molecules with and without charges shows that fluorine interacts with charges favourably. Control experiments using similarly constructed frameworks with or without fluorines verify the fluorine-cation interactions. Lack of a σ-hole for fluorine atoms is suggested to be responsible for this distinct property, and future applications of this discovery, such as desalination and mixed matrix membranes, may be expected to follow.

Charge-specific size-dependent separation of water-soluble organic molecules by fluorinated nanoporous networks

PubMed Central

Byun, Jeehye; Patel, Hasmukh A.; Thirion, Damien; Yavuz, Cafer T.

2016-01-01

Molecular architecture in nanoscale spaces can lead to selective chemical interactions and separation of species with similar sizes and functionality. Substrate specific sorbent chemistry is well known through highly crystalline ordered structures such as zeolites, metal organic frameworks and widely available nanoporous carbons. Size and charge-dependent separation of aqueous molecular contaminants, on the contrary, have not been adequately developed. Here we report a charge-specific size-dependent separation of water-soluble molecules through an ultra-microporous polymeric network that features fluorines as the predominant surface functional groups. Treatment of similarly sized organic molecules with and without charges shows that fluorine interacts with charges favourably. Control experiments using similarly constructed frameworks with or without fluorines verify the fluorine-cation interactions. Lack of a σ-hole for fluorine atoms is suggested to be responsible for this distinct property, and future applications of this discovery, such as desalination and mixed matrix membranes, may be expected to follow. PMID:27830697

The impact of long-range electron-hole interaction on the charge separation yield of molecular photocells

NASA Astrophysics Data System (ADS)

Nemati Aram, Tahereh; Ernzerhof, Matthias; Asgari, Asghar; Mayou, Didier

2017-01-01

We discuss the effects of charge carrier interaction and recombination on the operation of molecular photocells. Molecular photocells are devices where the energy conversion process takes place in a single molecular donor-acceptor complex attached to electrodes. Our investigation is based on the quantum scattering theory, in particular on the Lippmann-Schwinger equation; this minimizes the complexity of the problem while providing useful and non-trivial insight into the mechanism governing photocell operation. In this study, both exciton pair creation and dissociation are treated in the energy domain, and therefore there is access to detailed spectral information, which can be used as a framework to interpret the charge separation yield. We demonstrate that the charge carrier separation is a complex process that is affected by different parameters, such as the strength of the electron-hole interaction and the non-radiative recombination rate. Our analysis helps to optimize the charge separation process and the energy transfer in organic solar cells and in molecular photocells.

Rapid, efficient charging of lead-acid and nickel-zinc traction cells

NASA Technical Reports Server (NTRS)

Smithrick, J. J.

1978-01-01

Lead-acid and nickel-zinc traction cells were rapidly and efficiently charged using a high rate tapered direct current (HRTDC) charge method which could possibly be used for on-the-road service recharge of electric vehicles. The HRTDC method takes advantage of initial high cell charge acceptance and uses cell gassing rate and temperature as an indicator of charging efficiency. On the average, in these preliminary tests, 300 amp-hour nickel-zinc traction cells were given a HRTDC (initial current 500 amps, final current 100 amps) to 78 percent of rated amp-hour capacity within 53 minutes at an amp-hour efficiency of 92 percent and an energy efficiency of 52 percent. Three hundred amp-hour lead-acid traction cells were charged to 69 percent of rated amp-hour capacity within 46 minutes at an amp-hour efficiency of 91 percent with an energy efficiency of 64 percent. In order to find ways to further decrease the recharge times, the effect of periodically (0 to 400 Hz) pulse discharging cells during a constant current charging process (94% duty cycle) was investigated. Preliminary data indicate no significant effect of this type of pulse discharging during charge on charge acceptance of lead-acid or nickel-zinc cells.

Zeolitic imidazolate framework-8 for efficient adsorption and removal of Cr(VI) ions from aqueous solution.

PubMed

Niknam Shahrak, Mahdi; Ghahramaninezhad, Mahboube; Eydifarash, Mohsen

2017-04-01

Heavy metals are emerging toxic pollutants in which the development of advanced materials for their efficient adsorption and separation is thus of great significance in environmental sciences point of view. In this study, one of the zinc-based zeolitic imidazolate framework materials, known as ZIF-8, has been synthesized and used for chromium(VI) contaminant removal from water for the first time. The as-synthesized ZIF-8 adsorbent was characterized with different methodologies such as powder X-ray diffraction (XRD), thermo-gravimetric analysis, FT-IR, nuclear magnetic resonance spectroscopy, and UV-Vis spectra of solid state. Various factors affecting removal percentage (efficiency) are experimentally investigated including pH of solution, adsorbent dosage, contact time and initial concentration of Cr(VI) to achieve the optimal condition. The obtained results indicate that the ZIF-8 shows good performance for the Cr(VI) removal from aqueous solution so that 60 min mixing of 2 g of ZIF-8 adsorbent with the 2.5 ppm of Cr(VI) solution in a neutral environment will result in the highest separation efficiency around 70%. The time needed to reach the equilibrium (maximum separation efficiency) is only 60 min for a concentration of 5 mg L -1 . Structure stability in the presence of water is also carefully examined by XRD determination of ZIF-8 under different contact times in aqueous solution, which suggests that the structure is going to be destructed after 60 min immersed in solution. Electrostatic interaction of Cr(VI) anions by positively charged ZIF-8 is responsible for Cr(VI) adsorption and separation. Moreover, equilibrium adsorption study reveals that the Cr(VI) removal process using ZIF-8 nicely fits the Langmuir and Toth isotherm models which mean the adsorbent has low heterogeneous surface with different distributions of adsorption energies during Cr(VI) adsorption. Equilibrium adsorption capacity is observed around 0.25 for 20 mg L -1 of initial Cr(VI) solutions.

Quantum Efficiency and Bandgap Analysis for Combinatorial Photovoltaics: Sorting Activity of Cu–O Compounds in All-Oxide Device Libraries

PubMed Central

2014-01-01

All-oxide-based photovoltaics (PVs) encompass the potential for extremely low cost solar cells, provided they can obtain an order of magnitude improvement in their power conversion efficiencies. To achieve this goal, we perform a combinatorial materials study of metal oxide based light absorbers, charge transporters, junctions between them, and PV devices. Here we report the development of a combinatorial internal quantum efficiency (IQE) method. IQE measures the efficiency associated with the charge separation and collection processes, and thus is a proxy for PV activity of materials once placed into devices, discarding optical properties that cause uncontrolled light harvesting. The IQE is supported by high-throughput techniques for bandgap fitting, composition analysis, and thickness mapping, which are also crucial parameters for the combinatorial investigation cycle of photovoltaics. As a model system we use a library of 169 solar cells with a varying thickness of sprayed titanium dioxide (TiO2) as the window layer, and covarying thickness and composition of binary compounds of copper oxides (Cu–O) as the light absorber, fabricated by Pulsed Laser Deposition (PLD). The analysis on the combinatorial devices shows the correlation between compositions and bandgap, and their effect on PV activity within several device configurations. The analysis suggests that the presence of Cu4O3 plays a significant role in the PV activity of binary Cu–O compounds. PMID:24410367

Recent Advances in Photoelectrochemical Applications of Silicon Materials for Solar-to-Chemicals Conversion.

PubMed

Zhang, Doudou; Shi, Jingying; Zi, Wei; Wang, Pengpeng; Liu, Shengzhong Frank

2017-11-23

Photoelectrochemical (PEC) technology for the conversion of solar energy into chemicals requires cost-effective photoelectrodes to efficiently and stably drive anodic and/or cathodic half-reactions to complete the overall reactions for storing solar energy in chemical bonds. The shared properties among semiconducting photoelectrodes and photovoltaic (PV) materials are light absorption, charge separation, and charge transfer. Earth-abundant silicon materials have been widely applied in the PV industry, and have demonstrated their efficiency as alternative photoabsorbers for photoelectrodes. Many efforts have been made to fabricate silicon photoelectrodes with enhanced performance, and significant progress has been achieved in recent years. Herein, recent developments in crystalline and thin-film silicon-based photoelectrodes (including amorphous, microcrystalline, and nanocrystalline silicon) immersed in aqueous solution for PEC hydrogen production from water splitting are summarized, as well as applications in PEC CO 2 reduction and PEC regeneration of discharged species in redox flow batteries. Silicon is an ideal material for the cost-effective production of solar chemicals through PEC methods. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Stable Interfaces on SnO2 Surfaces for Charge-Transfer Applications

NASA Astrophysics Data System (ADS)

Benson, Michelle C.

The commercial market for solar harvesting devices as an alternative energy source requires them to be both low-cost and efficient to replace or reduce the dependence on fossil fuel burning. Over the last few decades there has been promising efforts towards improving solar devices by using abundant and non-toxic metal oxide nanomaterials. One particular metal oxide of interest has been SnO2 due to its high electron mobility, wide-band gap, and aqueous stability. However SnO2 based solar cells have yet to reach efficiency values of other metal oxides, like TiO2. The advancement of SnO2 based devices is dependent on many factors, including improved methods of surface functionalization that can yield stable interfaces. This work explores the use of a versatile functionalization method through the use of the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The CuAAC reaction is capable of producing electrochemically, photochemically, and electrocatalytically active surfaces on a variety of SnO2 materials. The resulting charge-transfer characteristics were investigated as well as an emphasis on understanding the stability of the resulting molecular linkage. We determined the CuAAC reaction is able to proceed through both azide-modified and alkyne-modified surfaces. The resulting charge-transfer properties showed that the molecular tether was capable of supporting charge separation at the interface. We also investigated the enhancement of electron injection upon the introduction of an ultra-thin ZrO2 coating on SnO2. Several complexes were used to fully understand the charge-transfer capabilities, including model systems of ferrocene and a ruthenium coordination complex, a ruthenium mononuclear water oxidation catalyst, and a commercial ruthenium based dye.

High open-circuit voltage small-molecule p-DTS(FBTTh 2 ) 2.ICBA bulk heterojunction solar cells – morphology, excited-state dynamics, and photovoltaic performance

DOE PAGES

Ko Kyaw, Aung Ko; Gehrig, Dominik; Zhang, Jie; ...

2014-11-27

The photovoltaic performance of bulk heterojunction solar cells using the solution-processable small molecule donor 7,7'-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl)bis(6-fluoro-4-(5'-hexyl-[2,2'-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole) (p-DTS(FBTTh 2) 2 in combination with indene-C60 bis-adduct (ICBA) as an acceptor is systematically optimized by altering the processing conditions. A high open-circuit voltage of 1 V, more than 0.2 V higher than that of a p-DTS(FBTTh 2) 2:PC 70BM blend, is achieved. However, the power conversion efficiency remains around 5% and thus is lower than ~8% previously reported for p-DTS(FBTTh 2) 2:PC 70BM. Transient absorption (TA) pump–probe spectroscopy over a wide spectral (Vis-NIR) and dynamic (fs to μs) range in combination with multivariate curvemore » resolution analysis of the TA data reveals that generation of free charges is more efficient in the blend with PC 70BM as an acceptor. In contrast, blends with ICBA create more coulombically bound interfacial charge transfer (CT) states, which recombine on the sub-nanosecond timescale by geminate recombination. Furthermore, the ns to μs charge carrier dynamics in p-DTS(FBTTh 2) 2:ICBA blends are only weakly intensity dependent implying a significant contribution of recombination from long-lived CT states and trapped charges, while those in p-DTS(FBTTh 2) 2:PC 70BM decay via an intensity-dependent recombination mechanism indicating that spatially separated (free) charge carriers are observed, which can be extracted as photocurrent from the device.« less

Tribo-charging properties of waste plastic granules in process of tribo-electrostatic separation.

PubMed

Li, Jia; Wu, Guiqing; Xu, Zhenming

2015-01-01

Plastic products can be found everywhere in people's daily life. With the consistent growth of plastic consumption, more and more plastic waste is generated. Considering the stable chemical and physics characteristics of plastic, regular waste management methods are not suitable for recycling economic strategy of each government, which has become a serious environmental problem. Recycling plastic waste is considered to be the best way to treat it, because it cannot only deduce the waste but also save the energy to produce new virgin plastic. Tribo-electrostatic separation is strongly recommended for plastic separation as it can preserve the original properties of plastic and has little additional pollution. In this study, plastic granules are generated by crushing plastic waste in waste electric and electronic equipment. The tribo-charging properties of plastic waste were studied by vibrating tribo-charging and cyclone tribo-charging. The triboelectric series obtained by vibrating was: (-)-PE-PS-PC-PVC-ABS-PP-(+), while the triboelectric series obtained by cyclone was (-)-PE-PS-PC-PVC-ABS-PP-(+). Further, the cyclone charging was more effective and stable than vibrating charging. The impact factors experiments showed that small particle size was better changed than large ones and were more suitable recycled by tribo-electrostatic separation. High relative humidity was identified as impede charging effect. The results of this study will help defining the operating parameters of subsequent separator. Copyright © 2014 Elsevier Ltd. All rights reserved.

Local electric field direct writing – Electron-beam lithography and mechanism

DOE PAGES

Jiang, Nan; Su, Dong; Spence, John C. H.

2017-08-24

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Local electric field direct writing – Electron-beam lithography and mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Nan; Su, Dong; Spence, John C. H.

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Physical effects of DCNQI derivatives doping as an N type organic semiconductor in organic photovoltaic cell performance.

PubMed

Lee, Joo Hyung; Oh, Se Young

2014-08-01

In the previous work, we have reported that organic photovoltaic (OPV) cells using DMDCNQI as an n-type second dopant material showed a high power conversion efficiency (PCE). In the present work, we have synthesized a novel DHDCNQI with long alkyl chains to improve the compatibility between the DHDCNQI dopant molecule and host P3HT polymer. We have fabricated OPV cells consisting of ITO/PEDOT:PSS/P3HT:PCBM:DHDCNQI/Al. We have investigated the characteristics of theses OPV cells using DCNQI derivative dopants from the measurements of the incident photon-to-current collection efficiency and photocurrent. The OPV cell using 3 wt% DHDCNQI exhibited a high PCE of 3.29% due to the high charge separation efficiency, good compatibility and low trap site effect.

Gold-silver@TiO2 nanocomposite-modified plasmonic photoanodes for higher efficiency dye-sensitized solar cells.

PubMed

Lim, Su Pei; Lim, Yee Seng; Pandikumar, Alagarsamy; Lim, Hong Ngee; Ng, Yun Hau; Ramaraj, Ramasamy; Bien, Daniel Chia Sheng; Abou-Zied, Osama K; Huang, Nay Ming

2017-01-04

In the present investigation, gold-silver@titania (Au-Ag@TiO 2 ) plasmonic nanocomposite materials with different Au and Ag compositions were prepared using a simple one-step chemical reduction method and used as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). The Au-Ag incorporated TiO 2 photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 7.33%, which is ∼230% higher than the unmodified TiO 2 photoanode (2.22%) under full sunlight illumination (100 mW cm -2 , AM 1.5G). This superior solar energy conversion efficiency was mainly due to the synergistic effect between the Au and Ag, and their surface plasmon resonance effect, which improved the optical absorption and interfacial charge transfer by minimizing the charge recombination process. The influence of the Au-Ag composition on the overall energy conversion efficiency was also explored, and the optimized composition with TiO 2 was found to be Au 75 -Ag 25 . This was reflected in the femtosecond transient absorption dynamics in which the electron-phonon interaction in the Au nanoparticles was measured to be 6.14 ps in TiO 2 /Au 75 :Ag 25 , compared to 2.38 ps for free Au and 4.02 ps for TiO 2 /Au 100 :Ag 0 . The slower dynamics indicates a more efficient electron-hole separation in TiO 2 /Au 75 :Ag 25 that is attributed to the formation of a Schottky barrier at the interface between TiO 2 and the noble metal(s) that acts as an electron sink. The significant boost in the solar energy conversion efficiency with the Au-Ag@TiO 2 plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSCs.

Collection of biological and non-biological particles by new and used filters made from glass and electrostatically charged synthetic fibers.

PubMed

Raynor, P C; Kim, B G; Ramachandran, G; Strommen, M R; Horns, J H; Streifel, A J

2008-02-01

Synthetic filters made from fibers carrying electrostatic charges and fiberglass filters that do not carry electrostatic charges are both utilized commonly in heating, ventilating, and air-conditioning (HVAC) systems. The pressure drop and efficiency of a bank of fiberglass filters and a bank of electrostatically charged synthetic filters were measured repeatedly for 13 weeks in operating HVAC systems at a hospital. Additionally, the efficiency with which new and used fiberglass and synthetic filters collected culturable biological particles was measured in a test apparatus. Pressure drop measurements adjusted to equivalent flows indicated that the synthetic filters operated with a pressure drop less than half that of the fiberglass filters throughout the test. When measured using total ambient particles, synthetic filter efficiency decreased during the test period for all particle diameters. For particles 0.7-1.0 mum in diameter, efficiency decreased from 92% to 44%. It is hypothesized that this reduction in collection efficiency may be due to charge shielding. Efficiency did not change significantly for the fiberglass filters during the test period. However, when measured using culturable biological particles in the ambient air, efficiency was essentially the same for new filters and filters used for 13 weeks in the hospital for both the synthetic and fiberglass filters. It is hypothesized that the lack of efficiency reduction for culturable particles may be due to their having higher charge than non-biological particles, allowing them to overcome the effects of charge shielding. The type of particles requiring capture may be an important consideration when comparing the relative performance of electrostatically charged synthetic and fiberglass filters. Electrostatically charged synthetic filters with high initial efficiency can frequently replace traditional fiberglass filters with lower efficiency in HVAC systems because properly designed synthetic filters offer less resistance to air flow. Although the efficiency of charged synthetic filters at collecting non-biological particles declined substantially with use, the efficiency of these filters at collecting biological particles remained steady. These findings suggest that the merits of electrostatically charged synthetic HVAC filters relative to fiberglass filters may be more pronounced if collection of biological particles is of primary concern.

Charge and spin in low-dimensional cuprates

NASA Astrophysics Data System (ADS)

Maekawa, Sadamichi; Tohyama, Takami

2001-03-01

One of the central issues in the study of high-temperature superconducting cuprates which are composed of two-dimensional (2D) CuO2 planes is whether the 2D systems with strong electron correlation behave as a Fermi liquid or a non-Fermi-liquid-like one-dimensional (1D) system with electron correlation. In this article, we start with the detailed examination of the electronic structure in cuprates and study theoretically the spin and charge dynamics in 1D and 2D cuprates. The theoretical background of spin-charge separation in the 1D model systems including the Hubbard and t-J models is presented. The first direct observation of collective modes of spin and charge excitations in a 1D cuprate, which are called spinons and holons respectively, in angle-resolved photoemission spectroscopy (ARPES) experiments is reviewed in the light of the theoretical results based on the numerically exact-diagonalization method. The charge and spin dynamics in 1D insulating cuprates is also discussed in connection with the spin-charge separation. The arguments are extended to the 2D cuprates, and the unique aspects of the electronic properties of high-temperature superconductors are discussed. Special emphasis is placed on the d-wave-like excitations in insulating 2D cuprates observed in ARPES experiments. We explain how the excitations are caused by the spin-charge separation. The charge stripes observed in the underdoped cuprates are examined in connection with spin-charge separation in real space.

Computational modeling of electrostatic charge and fields produced by hypervelocity impact

DOE PAGES

Crawford, David A.

2015-05-19

Following prior experimental evidence of electrostatic charge separation, electric and magnetic fields produced by hypervelocity impact, we have developed a model of electrostatic charge separation based on plasma sheath theory and implemented it into the CTH shock physics code. Preliminary assessment of the model shows good qualitative and quantitative agreement between the model and prior experiments at least in the hypervelocity regime for the porous carbonate material tested. The model agrees with the scaling analysis of experimental data performed in the prior work, suggesting that electric charge separation and the resulting electric and magnetic fields can be a substantial effectmore » at larger scales, higher impact velocities, or both.« less

Synthesis and Photophysical Characterization of an Artificial Photosynthetic Reaction Center Exhibiting Acid-Responsive Regulation of Charge Separation

NASA Astrophysics Data System (ADS)

Pahk, Ian

Non-photochemical quenching (NPQ) is a photoprotective regulatory mechanism essential to the robustness of the photosynthetic apparatus of green plants. Energy flow within the low-light adapted reaction centers is dynamically optimized to match the continuously fluctuating light conditions found in nature. Activated by compartmentalized decreases in pH resulting from photosynthetic activity during periods of elevated photon flux, NPQ induces rapid thermal dissipation of excess excitation energy that would otherwise overwhelm the apparatus's ability to consume it. Consequently, the frequency of charge separation decreases and the formation of potentially deleterious, high-energy intermediates slows, thereby reducing the threat of photodamage by disallowing their accumulation. Herein is described the synthesis and photophysical analysis of a molecular triad that mimics the effects of NPQ on charge separation within the photosynthetic reaction centers. Steady-state absorption and emission, time-resolved fluorescence, and transient absorption spectroscopies were used to demonstrate reversible quenching of the first singlet excited state affecting the quantum yield of charge separation by approximately one order of magnitude. As in the natural system, the populations of unquenched and quenched states and, therefore, the overall yields of charge separation were found to be dependent upon acid concentration.

A charge-stabilizing, multimodular, ferrocene-bis(triphenylamine)-zinc-porphyrin-fullerene polyad.

PubMed

Wijesinghe, Channa A; El-Khouly, Mohamed E; Zandler, Melvin E; Fukuzumi, Shunichi; D'Souza, Francis

2013-07-15

A novel multimodular donor-acceptor polyad featuring zinc porphyrin, fullerene, ferrocene, and triphenylamine entities was designed, synthesized, and studied as a charge-stabilizing, photosynthetic-antenna/reaction-center mimic. The ferrocene and fullerene entities, covalently linked to the porphyrin ring, were distantly separated to accomplish the charge-separation/hole-migration events leading to the creation of a long-lived charge-separated state. The geometry and electronic structures of the newly synthesized compound was deduced by B3LYP/3-21G(*) optimization, while the energy levels for different photochemical events was established using data from the optical absorption and emission, and electrochemical studies. Excitation of the triphenylamine entities revealed singlet-singlet energy transfer to the appended zinc porphyrin. As predicted from the energy levels, photoinduced electron transfer from both the singlet and triplet excited states of the zinc porphyrin to fullerene followed by subsequent hole migration involving ferrocene was witnessed from the transient absorption studies. The charge-separated state persisted for about 8.5 μs and was governed by the distance between the final charge-transfer product, that is, a species involving a ferrocenium cation and a fullerene radical anion, with additional influence from the charge-stabilizing triphenylamine entities located on the zinc-porphyrin macrocycle. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimizing multi-step B-side charge separation in photosynthetic reaction centers from Rhodobacter capsulatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faries, Kaitlyn M.; Kressel, Lucas L.; Dylla, Nicholas P.

Using high-throughput methods for mutagenesis, protein isolation and charge-separation functionality, we have assayed 40 Rhodobacter capsulatus reaction center (RC) mutants for their P+ QB- yield (P is a dimer of bacteriochlorophylls and Q is a ubiquinone) as produced using the normally inactive B-side cofactors BB and HB (where B is a bacteriochlorophyll and H is a bacteriopheophytin). Two sets of mutants explore all possible residues at M131 (M polypeptide, native residue Val near HB) in tandem with either a fixed His or a fixed Asn at L181 (L polypeptide, native residue Phe near BB). A third set of mutants exploresmore » all possible residues at L181 with a fixed Glu at M131 that can form a hydrogen bond to HB. For each set of mutants, the results of a rapid millisecond screening assay that probes the yield of P+ QB- are compared among that set and to the other mutants reported here or previously. For a subset of eight mutants, the rate constants and yields of the individual B-side electron transfer processes are determined via transient absorption measurements spanning 100 fs to 50 μs. The resulting ranking of mutants for their yield of P+ QB- from ultrafast experiments is in good agreement with that obtained from the millisecond screening assay, further validating the efficient, high-throughput screen for B-side transmembrane charge separation. Results from mutants that individually show progress toward optimization of P+ HB- → P+ QB- electron transfer or initial P* → P+ HB- conversion highlight unmet challenges of optimizing both processes simultaneously.« less

Thin-film Organic-based Solar Cells for Space Power

NASA Technical Reports Server (NTRS)

Bailey, Sheila G.; Harris, Jerry D.; Hepp, Aloysius F.; Anglin, Emily J.; Raffaelle, Ryne P.; Clark, Harry R., Jr.; Gardner, Susan T. P.; Sun, Sam S.

2002-01-01

Recent advances in dye-sensitized and organic polymer solar cells have lead NASA to investigate the potential of these devices for space power generation. Dye-sensitized solar cells were exposed to simulated low-earth orbit conditions and their performance evaluated. All cells were characterized under simulated air mass zero (AM0) illumination. Complete cells were exposed to pressures less than 1 x 10(exp -7) torr for over a month, with no sign of sealant failure or electrolyte leakage. Cells from Solaronix SA were rapid thermal cycled under simulated low-earth orbit conditions. The cells were cycled 100 times from -80 C to 80 C, which is equivalent to 6 days in orbit. The best cell had a 4.6 percent loss in efficiency as a result of the thermal cycling. In a separate project, novel -Bridge-Donor-Bridge- Acceptor- (-BDBA-) type conjugated block copolymer systems have been synthesized and characterized by photoluminescence (PL). In comparison to pristine donor or acceptor, the PL emissions of final -B-D-B-A- block copolymer films were quenched over 99 percent. Effective and efficient photo induced electron transfer and charge separation occurs due to the interfaces of micro phase separated donor and acceptor blocks. The system is very promising for a variety high efficiency light harvesting applications. Under an SBIR contract, fullerene-doped polymer-based photovoltaic devices were fabricated and characterized. The best devices showed overall power efficiencies of approx. 0.14 percent under white light. Devices fabricated from 2 percent solids content solutions in chlorobenzene gave the best results. Presently, device lifetimes are too short to be practical for space applications.

Thin-Film Organic-Based Solar Cells for Space Power

NASA Technical Reports Server (NTRS)

Bailey, Sheila G.; Harris, Jerry D.; Hepp, Aloysius F.; Anglin, Emily J.; Raffaelle, Ryne P.; Clark, Harry R., Jr.; Gardner, Susan T. P.; Sun, Sam S.

2001-01-01

Recent advances in dye-sensitized and organic polymer solar cells have lead NASA to investigate the potential of these devices for space power generation. Dye-sensitaized solar cells were exposed to simulated low-earth orbit conditions and their performance evaluated. All cells were characterized under simulated air mass zero (AM0) illumination. Complete cells were exposed to pressures less than 1 x 10 (exp -7)torr for over a month, with no sign of sealant failure or electrolyte leakage. Cells from Solaronix SA were rapid thermal cycled under simulated low-earth orbit conditions. The cells were cycled 100 times from -80 C to 80 C, which is equivalent to 6 days in orbit. The best cell had a 4.6% loss in efficiency as a result of the thermal cycling. In a separate project, novel -Bridge-Donor-Bridge-Acceptor- (-BDBA-) type conjugated block copolymer systems have been synthesized and characterized by photoluminescence (PL). In comparison to pristine donor or acceptor, the PL emissions of final -B-D-B-A- block copolymer films were quenched over 99%. Effective and efficient photo induced electron transfer and charge separation occurs due to the interfaces of micro phase separated donor and acceptor blocks. The system is very promising for a variety high efficiency light harvesting applications. Under an SBIR contract, fullerene-doped polymer-based photovoltaic devices were fabricated and characterized. The best devices showed overall power efficiencies of approximately 0.14% under white light. Devices fabricated from 2% solids content solutions in chlorobenzene gave the best results. Presently, device lifetimes are too short to be practical for space applications.

Impact of charge-transfer excitons in regioregular polythiophene on the charge separation at polythiophene-fullerene heterojunctions

NASA Astrophysics Data System (ADS)

Polkehn, M.; Tamura, H.; Burghardt, I.

2018-01-01

This study addresses the mechanism of ultrafast charge separation in regioregular oligothiophene-fullerene assemblies representative of poly-3-hexylthiophene (P3HT)-[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) heterojunctions, with special emphasis on the inclusion of charge transfer excitons in the oligothiophene phase. The formation of polaronic inter-chain charge separated species in highly ordered oligothiophene has been demonstrated in recent experiments and could have a significant impact on the net charge transfer to the fullerene acceptor. The present approach combines a first-principles parametrized multi-site Hamiltonian, based on time-dependent density functional theory calculations, with accurate quantum dynamics simulations using the multi-layer multi-configuration time-dependent Hartree method. Quantum dynamical studies are carried out for up to 182 electronic states and 112 phonon modes. The present analysis follows up on our previous study of (Huix-Rotllant et al 2015 J. Phys. Chem. Lett. 6 1702) and significantly expands the scope of this analysis by including the dynamical role of charge transfer excitons. Our investigation highlights the pronounced mixing of photogenerated Frenkel excitons with charge transfer excitons in the oligothiophene domain, and the opening of new transfer channels due the creation of such charge-separated species. As a result, it turns out that the interfacial donor/acceptor charge transfer state can be largely circumvented due to the presence of charge transfer excitons. However, the latter states in turn act as a trap, such that the free carrier yield observed on ultrafast time scales is tangibly reduced. The present analysis underscores the complexity of the transfer pathways at P3HT-PCBM type junctions.

Ultrafast photoinduced charge separation in metal-semiconductor nanohybrids.

PubMed

Mongin, Denis; Shaviv, Ehud; Maioli, Paolo; Crut, Aurélien; Banin, Uri; Del Fatti, Natalia; Vallée, Fabrice

2012-08-28

Hybrid nano-objects formed by two or more disparate materials are among the most promising and versatile nanosystems. A key parameter in their properties is interaction between their components. In this context we have investigated ultrafast charge separation in semiconductor-metal nanohybrids using a model system of gold-tipped CdS nanorods in a matchstick architecture. Experiments are performed using an optical time-resolved pump-probe technique, exciting either the semiconductor or the metal component of the particles, and probing the light-induced change of their optical response. Electron-hole pairs photoexcited in the semiconductor part of the nanohybrids are shown to undergo rapid charge separation with the electron transferred to the metal part on a sub-20 fs time scale. This ultrafast gold charging leads to a transient red-shift and broadening of the metal surface plasmon resonance, in agreement with results for free clusters but in contrast to observation for static charging of gold nanoparticles in liquid environments. Quantitative comparison with a theoretical model is in excellent agreement with the experimental results, confirming photoexcitation of one electron-hole pair per nanohybrid followed by ultrafast charge separation. The results also point to the utilization of such metal-semiconductor nanohybrids in light-harvesting applications and in photocatalysis.

Hybrid zinc oxide/graphene electrodes for depleted heterojunction colloidal quantum-dot solar cells.

PubMed

Tavakoli, Mohammad Mahdi; Aashuri, Hossein; Simchi, Abdolreza; Fan, Zhiyong

2015-10-07

Recently, hybrid nanocomposites consisting of graphene/nanomaterial heterostructures have emerged as promising candidates for the fabrication of optoelectronic devices. In this work, we have employed a facile and in situ solution-based process to prepare zinc oxide/graphene quantum dots (ZnO/G QDs) in a hybrid structure. The prepared hybrid dots are composed of a ZnO core, with an average size of 5 nm, warped with graphene nanosheets. Spectroscopic studies show that the graphene shell quenches the photoluminescence intensity of the ZnO nanocrystals by about 72%, primarily due to charge transfer reactions and static quenching. A red shift in the absorption peak is also observed. Raman spectroscopy determines G-band splitting of the graphene shell into two separated sub-bands (G(+), G(-)) caused by the strain induced symmetry breaking. It is shown that the hybrid ZnO/G QDs can be used as a counter-electrode for heterojunction colloidal quantum-dot solar cells for efficient charge-carrier collection, as evidenced by the external quantum efficiency measurement. Under the solar simulated spectrum (AM 1.5G), we report enhanced power conversion efficiency (35%) with higher short current circuit (80%) for lead sulfide-based solar cells as compared to devices prepared by pristine ZnO nanocrystals.

MoS2 quantum dots@TiO2 nanotube composites with enhanced photoexcited charge separation and high-efficiency visible-light driven photocatalysis

NASA Astrophysics Data System (ADS)

Zhao, Fenfen; Rong, Yuefei; Wan, Junmin; Hu, Zhiwen; Peng, Zhiqin; Wang, Bing

2018-03-01

MoS2 quantum dots (QDs) that are 5 nm in size were deposited on the surface of ultrathin TiO2 nanotubes (TNTs) with 5 nm wall thickness by using an improved hydrothermal method to form a MoS2 QDs@TNT visible-light photocatalyst. The ultrathin TNTs with high percentage of photocatalytic reactive facets were fabricated by the commercially available TiO2 nanoparticles (P25) through an improved hydrothermal method, and the MoS2 QDs were acquired by using a surfactant-assisted technique. The novel MoS2 QDs@TNT photocatalysts showed excellent photocatalytic activity with a decolorization rate of 92% or approximately 3.5 times more than that of pure TNTs for the high initial concentration of methylene blue solution (20 mg l-1) within 40 min under visible-light irradiation. MoS2 as the co-catalysts favored the broadening of TNTs into the visible-light absorption scope. The quantum confinement and edge effects of the MoS2 QDs and the heterojunction formed between the MoS2 QDs and TNTs efficiently extended the lifetime of photoinduced charges, impeded the recombination of photoexcited electron-hole pairs, and improved the visible-light-driven high-efficiency photocatalysis.

Simulations of stretching a flexible polyelectrolyte with varying charge separation

DOE PAGES

Stevens, Mark J.; Saleh, Omar A.

2016-07-22

We calculated the force-extension curves for a flexible polyelectrolyte chain with varying charge separations by performing Monte Carlo simulations of a 5000 bead chain using a screened Coulomb interaction. At all charge separations, the force-extension curves exhibit a Pincus-like scaling regime at intermediate forces and a logarithmic regime at large forces. As the charge separation increases, the Pincus regime shifts to a larger range of forces and the logarithmic regime starts are larger forces. We also found that force-extension curve for the corresponding neutral chain has a logarithmic regime. Decreasing the diameter of bead in the neutral chain simulations removedmore » the logarithmic regime, and the force-extension curve tends to the freely jointed chain limit. In conclusion, this result shows that only excluded volume is required for the high force logarithmic regime to occur.« less

Protein separation using an electrically tunable membrane

NASA Astrophysics Data System (ADS)

Jou, Ining; Melnikov, Dmitriy; Gracheva, Maria

Separation of small proteins by charge with a solid-state porous membrane requires control over the protein's movement. Semiconductor membrane has this ability due to the electrically tunable electric potential profile inside the nanopore. In this work we investigate the possibility to separate the solution of two similar sized proteins by charge. As an example, we consider two small globular proteins abundant in humans: insulin (negatively charged) and ubiquitin (neutral). We find that the localized electric field inside the pore either attracts or repels the charged protein to or from the pore wall which affects the delay time before a successful translocation of the protein through the nanopore. However, the motion of the uncharged ubiquitin is unaffected. The difference in the delay time (and hence the separation) can be further increased by the application of the electrolyte bias which induces an electroosmotic flow in the pore. NSF DMR and CBET Grant No. 1352218.

Charge Splitting In Situ Recorder (CSIR) for Real-Time Examination of Plasma Charging Effect in FinFET BEOL Processes

NASA Astrophysics Data System (ADS)

Tsai, Yi-Pei; Hsieh, Ting-Huan; Lin, Chrong Jung; King, Ya-Chin

2017-09-01

A novel device for monitoring plasma-induced damage in the back-end-of-line (BEOL) process with charge splitting capability is first-time proposed and demonstrated. This novel charge splitting in situ recorder (CSIR) can independently trace the amount and polarity of plasma charging effects during the manufacturing process of advanced fin field-effect transistor (FinFET) circuits. Not only does it reveal the real-time and in situ plasma charging levels on the antennas, but it also separates positive and negative charging effect and provides two independent readings. As CMOS technologies push for finer metal lines in the future, the new charge separation scheme provides a powerful tool for BEOL process optimization and further device reliability improvements.

Charge exchange molecular ion source

DOEpatents

Vella, Michael C.

2003-06-03

Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

Significance of surface charge and shell material of superparamagnetic iron oxide nanoparticle (SPION) based core/shell nanoparticles on the composition of the protein corona.

PubMed

Sakulkhu, Usawadee; Mahmoudi, Morteza; Maurizi, Lionel; Coullerez, Geraldine; Hofmann-Amtenbrink, Margarethe; Vries, Marcel; Motazacker, Mahdi; Rezaee, Farhad; Hofmann, Heinrich

2015-02-01

As nanoparticles (NPs) are increasingly used in many applications their safety and efficient applications in nanomedicine have become concerns. Protein coronas on nanomaterials' surfaces can influence how the cell "recognizes" nanoparticles, as well as the in vitro and in vivo NPs' behaviors. The SuperParamagnetic Iron Oxide Nanoparticle (SPION) is one of the most prominent agents because of its superparamagnetic properties, which is useful for separation applications. To mimic surface properties of different types of NPs, a core-shell SPION library was prepared by coating with different surfaces: polyvinyl alcohol polymer (PVA) (positive, neutral and negative), SiO2 (positive and negative), titanium dioxide and metal gold. The SPIONs with different surfaces were incubated at a fixed serum : nanoparticle surface ratio, magnetically trapped and washed. The tightly bound proteins were quantified and identified. The surface charge has a great impact on protein adsorption, especially on PVA and silica where proteins preferred binding to the neutral and positively charged surfaces. The importance of surface material on protein adsorption was also revealed by preferential binding on TiO2 and gold coated SPION, even negatively charged. There is no correlation between the protein net charge and the nanoparticle surface charge on protein binding, nor direct correlation between the serum proteins' concentration and the proteins detected in the coronas.

Mechanistic insights into the photoinduced charge carrier dynamics of BiOBr/CdS nanosheet heterojunctions for photovoltaic application.

PubMed

Jia, Huimin; Zhang, Beibei; He, Weiwei; Xiang, Yong; Zheng, Zhi

2017-03-02

The rational design of high performance hetero-structure photovoltaic devices requires a full understanding of the photoinduced charge transfer mechanism and kinetics at the interface of heterojunctions. In this paper, we intelligently fabricated p-BiOBr/n-CdS heterojunctions with perfect nanosheet arrays by using a facile successive ionic layer adsorption and reaction and chemical bath deposition methods at low temperature. A BiOBr/CdS heterojunction based solar cell has been fabricated which exhibited enhanced photovoltaic responses. Assisted by the surface photovoltage (SPV), transient photovoltage (TPV) and Kelvin probe technique, the photoinduced charge transfer dynamics on the BiOBr nanosheet and p-BiOBr/n-CdS interface were systematically investigated. It was found that the BiOBr/CdS nanosheet array heterojunctions were more efficient in facilitating charge carrier separation than both bare BiOBr and CdS films. The mechanism underlying the photoinduced charge carrier transfer behaviour was unravelled by allying the energy band of BiOBr/CdS p-n junctions from both the interfacial electric field and surface electric field. In addition, the CdS loading thickness in the p-BiOBr/n-CdS heterojunction and the incident wavelength affected greatly the transfer behavior of photoinduced charges, which was of great value for design of photovoltaic devices.

Enhancing Sensitivity of Liquid Chromatography-Mass Spectrometry of Peptides and Proteins Using Supercharging Agents.

PubMed

Nshanian, Michael; Lakshmanan, Rajeswari; Chen, Hao; Ogorzalek Loo, Rachel R; Loo, Joseph A

2018-04-01

Trifluoroacetic acid (TFA) is often used as a mobile phase modifier to enhance reversed phase chromatographic performance. TFA adjusts solution pH and is an ion-pairing agent, but it is not typically suitable for electrospray ionization-mass spectrometry (ESI-MS) and liquid chromatography/MS (LC/MS) because of its significant signal suppression. Supercharging agents elevate peptide and protein charge states in ESI, increasing tandem MS (MS/MS) efficiency. Here, LC/MS protein supercharging was effected by adding agents to LC mobile phase solvents. Significantly, the ionization suppression generally observed with TFA was, for the most part, rescued by supercharging agents, with improved separation efficiency (higher number of theoretical plates) and lowered detection limits.

Recent advancements in plasmon-enhanced promising third-generation solar cells

NASA Astrophysics Data System (ADS)

Thrithamarassery Gangadharan, Deepak; Xu, Zhenhe; Liu, Yanlong; Izquierdo, Ricardo; Ma, Dongling

2017-01-01

The unique optical properties possessed by plasmonic noble metal nanostructures in consequence of localized surface plasmon resonance (LSPR) are useful in diverse applications like photovoltaics, sensing, non-linear optics, hydrogen generation, and photocatalytic pollutant degradation. The incorporation of plasmonic metal nanostructures into solar cells provides enhancement in light absorption and scattering cross-section (via LSPR), tunability of light absorption profile especially in the visible region of the solar spectrum, and more efficient charge carrier separation, hence maximizing the photovoltaic efficiency. This review discusses about the recent development of different plasmonic metal nanostructures, mainly based on Au or Ag, and their applications in promising third-generation solar cells such as dye-sensitized solar cells, quantum dot-based solar cells, and perovskite solar cells.

A novel biasing dependent circuit model of resonant cavity enhanced avalanche photodetectors (RCE-APDs)

NASA Astrophysics Data System (ADS)

Abdelhamid, Mostafa R.; El-Batawy, Yasser M.; Deen, M. Jamal

2018-02-01

In Resonant Cavity Enhanced Photodetectors (RCE-PDs), the trade-off between the bandwidth and the quantum efficiency in the conventional photodetectors is overcome. In RCE-PDs, large bandwidth can be achieved using a thin absorption layer while the use of a resonant cavity allows for multiple passes of light in the absorption which boosts the quantum efficiency. In this paper, a complete bias-dependent model for the Resonant Cavity Enhanced-Separated Absorption Graded Charge Multiplication-Avalanche Photodetector (RCE-SAGCM-APD) is presented. The proposed model takes into account the case of drift velocities other than the saturation velocity, thus modeling this effect on the photodetector different design parameters such as Gain, Bandwidth and Gain-Bandwidth product.

A facile method for emulsified oil-water separation by using polyethylenimine-coated magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Lü, Ting; Qi, Dongming; Zhang, Dong; Lü, Yulan; Zhao, Hongting

2018-04-01

Oil spills and oily wastewater discharges from ships and industrial activities have serious impacts on the environment and human health. In this study, a class of easy-to-synthesize polyethylenimine (PEI)-coated Fe3O4 magnetic nanoparticles (MNPs) was successfully synthesized via a one-step coprecipitation method. The synthesized PEI-coated Fe3O4 MNPs were characterized by using multiple technologies and applied in emulsified oil-water separation for the first time. It was found that the PEI effectively tuned the surface charge and wettability of MNPs. As a result, the PEI-coated MNPs could successfully assemble at the oil-water interface and promote the coalescence of oil droplets, thereby facilitating the subsequent magnetic separation. Results showed that the oil-water separation performance was superior and enhanced with the increase of ionic strength. Recycling experiment indicated that the PEI-coated MNPs could be reused up to six times without showing a significant decrease in separation efficiency. All of these results suggested that the PEI-coated MNP could potentially be used as a class of promising nanomaterials for emulsified oil-water separation. [Figure not available: see fulltext.

Effect of positive pulse charge waveforms on the energy efficiency of lead-acid traction cells

NASA Technical Reports Server (NTRS)

Smithrick, J. J.

1981-01-01

The effects of four different charge methods on the energy conversion efficiency of 300 ampere hour lead acid traction cells were investigated. Three of the methods were positive pulse charge waveforms; the fourth, a constant current method, was used as a baseline of comparison. The positive pulse charge waveforms were: 120 Hz full wave rectified sinusoidal; 120 Hz silicon controlled rectified; and 1 kHz square wave. The constant current charger was set at the time average pulse current of each pulse waveform, which was 150 amps. The energy efficiency does not include charger losses. The lead acid traction cells were charged to 70 percent of rated ampere hour capacity in each case. The results of charging the cells using the three different pulse charge waveforms indicate there was no significant difference in energy conversion efficiency when compared to constant current charging at the time average pulse current value.

Efficient Simulation and Abuse Modeling of Mechanical-Electrochemical-Thermal Phenomena in Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santhanagopalan, Shriram; Smith, Kandler A; Graf, Peter A

NREL's Energy Storage team is exploring the effect of mechanical crush of lithium ion cells on their thermal and electrical safety. PHEV cells, fresh as well as ones aged over 8 months under different temperatures, voltage windows, and charging rates, were subjected to destructive physical analysis. Constitutive relationship and failure criteria were developed for the electrodes, separator as well as packaging material. The mechanical models capture well, the various modes of failure across different cell components. Cell level validation is being conducted by Sandia National Laboratories.

Theoretical study on the cooperative exciton dissociation process based on dimensional and hot charge-transfer state effects in an organic photocell

NASA Astrophysics Data System (ADS)

Shimazaki, Tomomi; Nakajima, Takahito

2016-06-01

This paper discusses the exciton dissociation process at the donor-acceptor interface in organic photocells. In our previous study, we introduced a local temperature to handle the hot charge-transfer (CT) state and calculated the exciton dissociation probability based on the 1D organic semiconductor model [T. Shimazaki and T. Nakajima, Phys. Chem. Chem. Phys. 17, 12538 (2015)]. Although the hot CT state plays an essential role in exciton dissociations, the probabilities calculated are not high enough to efficiently separate bound electron-hole pairs. This paper focuses on the dimensional (entropy) effect together with the hot CT state effect and shows that cooperative behavior between both effects can improve the exciton dissociation process. In addition, we discuss cooperative effects with site-disorders and external-electric-fields.

Tuning Light Emission of a Pressure-Sensitive Silicon/ZnO Nanowires Heterostructure Matrix through Piezo-phototronic Effects.

PubMed

Chen, Mengxiao; Pan, Caofeng; Zhang, Taiping; Li, Xiaoyi; Liang, Renrong; Wang, Zhong Lin

2016-06-28

Based on white light emission at silicon (Si)/ZnO hetrerojunction, a pressure-sensitive Si/ZnO nanowires heterostructure matrix light emitting diode (LED) array is developed. The light emission intensity of a single heterostructure LED is tuned by external strain: when the applied stress keeps increasing, the emission intensity first increases and then decreases with a maximum value at a compressive strain of 0.15-0.2%. This result is attributed to the piezo-phototronic effect, which can efficiently modulate the LED emission intensity by utilizing the strain-induced piezo-polarization charges. It could tune the energy band diagrams at the junction area and regulate the optoelectronic processes such as charge carriers generation, separation, recombination, and transport. This study achieves tuning silicon based devices through piezo-phototronic effect.

Separation of heat and charge currents for boosted thermoelectric conversion

NASA Astrophysics Data System (ADS)

Mazza, Francesco; Valentini, Stefano; Bosisio, Riccardo; Benenti, Giuliano; Giovannetti, Vittorio; Fazio, Rosario; Taddei, Fabio

2015-06-01

In a multiterminal device the (electronic) heat and charge currents can follow different paths. In this paper we introduce and analyze a class of multiterminal devices where this property is pushed to its extreme limits, with charge and heat currents flowing in different reservoirs. After introducing the main characteristics of this heat-charge current separation regime, we show how to realize it in a multiterminal device with normal and superconducting leads. We demonstrate that this regime allows us to control independently heat and charge flows and to greatly enhance thermoelectric performances at low temperatures. We analyze in detail a three-terminal setup involving a superconducting lead, a normal lead, and a voltage probe. For a generic scattering region we show that in the regime of heat-charge current separation both the power factor and the figure of merit Z T are highly increased with respect to a standard two-terminal system. These results are confirmed for the specific case of a system consisting of three coupled quantum dots.

The effect of charged groups on hydrophilic monolithic stationary phases on their chromatographic properties.

PubMed

Li, Haibin; Liu, Chusheng; Wang, Qiqin; Zhou, Haibo; Jiang, Zhengjin

2016-10-21

In order to investigate the effect of charged groups present in hydrophilic monolithic stationary phases on their chromatographic properties, three charged hydrophilic monomers, i.e. N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA), [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETA), and 3-sulfopropyl acrylate potassium salt (SPA) were co-polymerized with the crosslinker N,N'-methylenebisacrylamide (MBA), respectively. The physicochemical properties of the three resulting charged hydrophilic monolithic columns were evaluated using scanning electron microscopy, ζ-potential analysis and micro-HPLC. High column efficiency was obtained on the three monolithic columns at a linear velocity of 1mm/s using thiourea as test compound. Comparative characterization of the three charged HILIC phases was then carried out using a set of model compounds, including nucleobases, nucleosides, benzoic acid derivatives, phenols, β-blockers and small peptides. Depending on the combination of stationary phase/mobile phase/solute, both hydrophilic interaction and other potential secondary interactions, including electrostatic interaction, hydrogen-bonding interaction, molecular shape selectivity, could contribute to the over-all retention of the analytes. Because of the strong electrostatic interaction provided by the quaternary ammonium groups in the poly (AETA-co-MBA) monolith, this cationic HILIC monolith exhibited the strongest retention for benzoic acid derivatives and small peptides with distorted peak shapes and the weakest retention for basic β-blockers. The sulfonyl groups on the poly (SPA-co-MBA) hydrophilic monolith could provide strong electrostatic attraction and hydrogen bonding for positively charged analytes and hydrogen-donor/acceptor containing analytes, respectively. Therefore, basic drugs, nucleobases and nucleotides exhibited the strongest retention on this anionic monolith. Because of the weak but distinct cation exchange properties of the zwitterionic poly (SPDA-co-MBA) hydrophilic monolith, it exhibited the best separation for most test analytes (including phenols, β-blockers and small peptides) in terms of selectivity, peak shape and analysis time. The poly (AETA-co-MBA) hydrophilic monolithic column provides the best separation of nucleobases and nucleosides. These results could guide the selection and application of these charged HILIC monoliths in the future. Copyright © 2016 Elsevier B.V. All rights reserved.

Excited state electron transfer in systems with a well-defined geometry. [cyclophane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaufmann, K.J.

1980-12-01

The effect of temperature, dielectric strength and ligand on the structure of the mesopyropheophorbide cyclophanes will be studied. ESR, NMR, emission and absorption spectroscopy, as well as circular dichroism will be used. The changes in structure will be correlated with changes in the photochemical activity. Electron acceptors such as benzoquinone will be utilized to stabilize the charge separation. Charge separation in porphyrin quinone dimers will also be studied. It was found that electron transfer in the cyclophane system is relatively slow. This is presumably due to an orientation requirement for fast electron transfer. Solvent dielectric also is important in producingmore » a charge separation. Decreasing the temperature effects the yield of charge transfer, but not the kinetics.« less

Superconductivity, phase separation, and charge-transfer instability in the U = infinity limit of the three-band model of the CuO sub 2 planes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grilli, M.; Raimondi, R.; Castellani, C.

1991-07-08

The {ital U}={infinity} limit of the three-band Hubbard model with nearest-neighbor repulsion {ital V} is studied using the slave-boson approach and the large-{ital N} expansion technique to order 1/{ital N}. A charge-transfer instability is found as in weak-coupling theory. The charge-transfer instability is always associated with a diverging compressibility leading to a phase separation. Near the phase-separation, charge-transfer-instability region we find superconducting instabilities in the {ital s}- and {ital d}-wave channel. The requirement for superconductivity is that {ital V} be on the scale of the Cu-O hopping as suggested by Varma, Schmitt-Rink, and Abrahams.

Rapid preparative separation of monoclonal antibody charge variants using laterally-fed membrane chromatography.

PubMed

Sadavarte, Rahul; Madadkar, Pedram; Filipe, Carlos Dm; Ghosh, Raja

2018-01-15

Monoclonal antibodies undergo various forms of chemical transformation which have been shown to cause loss in efficacy and alteration in pharmacokinetic properties of these molecules. Such modified antibody molecules are known as variants. They also display physical properties such as charge that are different from intact antibody molecules. However, the difference in charge is very subtle and separation based on it is quite challenging. Charge variants are usually separated using ion-exchange column chromatography or isoelectric focusing. In this paper, we report a rapid and scalable method for fractionating monoclonal antibody charge variants, based on the use of cation exchange laterally-fed membrane chromatography (LFMC). Starting with a sample of monoclonal antibody hIgG1-CD4, three well-resolved fractions were obtained using either pH or salt gradient. These fractions were identified as acidic, neutral and basic variants. Each of these fractions contained intact heavy and light chains and so antibody fragmentation had no role in variant generation. The separation was comparable to that using column chromatography but was an order of magnitude faster. Copyright © 2017 Elsevier B.V. All rights reserved.

Polyaniline decorated Bi2MoO6 nanosheets with effective interfacial charge transfer as photocatalysts and optical limiters.

PubMed

Zhao, Wei; Li, Cheng; Wang, Aijian; Lv, Cuncai; Zhu, Weihua; Dou, Shengping; Wang, Qian; Zhong, Qin

2017-11-01

Polyaniline (PANI)-decorated Bi 2 MoO 6 nanosheets (BMO/PANI) were prepared by a facile solvothermal method. Different characterization techniques, including X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance ultraviolet-visible spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy, photocurrent spectroscopy, and nanosecond time-resolved emission studies, have been employed to investigate the structure, optical and electrical properties of the BMO/PANI composites. The wide absorption of the samples in the visible light region makes them suitable for nonlinear transmission and photocatalytic activity studies. The associated photocatalytic activity and optical nonlinearities for the BMO/PANI composites are shown to be dependent on the PANI loadings. The rational mechanisms responsible for deteriorating pollutants and improving optical nonlinearities were also proposed, which could be mainly attributed to the efficient interfacial charge transfer and the interfacial electronic interactions between PANI and Bi 2 MoO 6 . The photoluminescence spectroscopy, electrochemical impedance spectroscopy, and photocurrent spectroscopy studies confirmed that the interface charge separation efficiency was greatly improved by coupling Bi 2 MoO 6 with PANI. The tuning of photocatalysis and nonlinear optical behaviors with variation in the content of PANI provides an easy way to attain tunable properties, which are exceedingly required in optoelectronics applications.

Charge Carrier Dynamics and pH Effect on Optical Properties of Anionic and Cationic Porphyrin-Graphene Oxide Composites

NASA Astrophysics Data System (ADS)

Bajjou, O.; Bakour, A.; Khenfouch, M.; Baitoul, M.; Mothudi, B.; Maaza, M.; Faulques, E.

2018-02-01

Composites of graphene oxide (GO) functionalized with Sn(V) tetrakis (4-pyridyl)porphyrin (SnTPyP2+) and meso-tetrakis(4-phenylsulfonic acid)porphyrin (H4TPPS4 2- ) were prepared at different pH values.Successful synthesis of water-soluble stable suspension of GO-SnTPyP2+ and GO-H4TPPS4 2-was confirmed using various spectroscopic techniques, including scanning electronic microscopy (SEM), Raman spectroscopy, and ultraviolet-visible (UV-Vis) absorption. Variation of the pH was found to strongly influence the optical properties of the GO-SnTPyP2+ and GO-H4TPPS4 2-composites, as demonstrated by the UV-Vis absorption results. Steady-state photoluminescence (PL) and time-resolved PL (TRPL) results for both composites showed PL quenching and decrease in the exciton mean lifetime, suggesting strong excited-state interactions between the different components. Moreover, charge carrier dynamics study revealed that insertion of GO into both porphyrin derivatives led to faster mean lifetime for excitons with a slight advantage in the case of the cationic porphyrin-GO composite, making it a better choice for charge separation applications thanks to the higher efficiency of charge/energy transfer interactions.

Electronic structure and charge transfer excited states of endohedral fullerene containing electron donoracceptor complexes utilized in organic photovoltaics

NASA Astrophysics Data System (ADS)

Amerikheirabadi, Fatemeh

Organic Donor-Acceptor complexes form the main component of the organic photovoltaic devices (OPVs). The open circuit voltage of OPVs is directly related to the charge transfer excited state energies of these complexes. Currently a large number of different molecular complexes are being tested for their efficiency in photovoltaic devices. In this work, density functional theory as implemented in the NRLMOL code is used to investigate the electronic structure and related properties of these donor-acceptor complexes. The charge transfer excitation energies are calculated using the perturbative delta self-consistent field method recently developed in our group as the standard time dependent density functional approaches fail to accurately provide them. The model photovoltaics systems analyzed are as follows: Sc3N C 80--ZnTPP, Y3 N C80-- ZnTPP and Sc3 N C80-- ZnPc. In addition, a thorough analysis of the isolated donor and acceptor molecules is also provided. The studied acceptors are chosen from a class of fullerenes named trimetallic nitride endohedral fullerenes. These molecules have shown to possess advantages as acceptors such as long lifetimes of the charge-separated states.

Protein Corona Composition of Superparamagnetic Iron Oxide Nanoparticles with Various Physico-Chemical Properties and Coatings

NASA Astrophysics Data System (ADS)

Sakulkhu, Usawadee; Mahmoudi, Morteza; Maurizi, Lionel; Salaklang, Jatuporn; Hofmann, Heinrich

2014-05-01

Because of their biocompatibility and unique magnetic properties, superparamagnetic iron oxide nanoparticles NPs (SPIONs) are recognized as some of the most prominent agents for theranostic applications. Thus, understanding the interaction of SPIONs with biological systems is important for their safe design and efficient applications. In this study, SPIONs were coated with 2 different polymers: polyvinyl alcohol polymer (PVA) and dextran. The obtained NPs with different surface charges (positive, neutral, and negative) were used as a model study of the effect of surface charges and surface polymer materials on protein adsorption using a magnetic separator. We found that the PVA-coated SPIONs with negative and neutral surface charge adsorbed more serum proteins than the dextran-coated SPIONs, which resulted in higher blood circulation time for PVA-coated NPs than the dextran-coated ones. Highly abundant proteins such as serum albumin, serotransferrin, prothrombin, alpha-fetoprotein, and kininogen-1 were commonly found on both PVA- and dextran-coated SPIONs. By increasing the ionic strength, soft- and hard-corona proteins were observed on 3 types of PVA-SPIONs. However, the tightly bound proteins were observed only on negatively charged PVA-coated SPIONs after the strong protein elution.