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Sample records for acceptor dye molecules

  1. Intramolecular charge transfer in donor-acceptor molecules

    SciTech Connect

    Slama-Schwok, A.; Blanchard-Desce, M.; Lehn, J.M. )

    1990-05-17

    The photophysical properties of donor-acceptor molecules, push-pull polyenes and carotenoids, have been studied by absorption and fluorescence spectroscopy. The compounds bear various acceptor and donor groups, linked together by chains of different length and structure. The position of the absorption and fluorescence maxima and their variation in solvents of increasing polarity are in agreement with long-distance intramolecular charge-transfer processes, the linker acting as a molecular wire. The effects of the linker length and structure and of the nature of acceptor and donor are presented.

  2. A Systematic Study on the Influence of Electron-Acceptors in Phenanthrocarbazole Dye-Sensitized Solar Cells.

    PubMed

    Yang, Lin; Yao, Zhaoyang; Liu, Jiao; Wang, Junting; Wang, Peng

    2016-04-20

    In this work, by conjugating 2-cyanoacrylic acid (CA), 4-(benzo[c][1,2,5]thiadiazol-7-yl)benzoic acid (BTBA), 4-(7-ethynylbenzo[c][1,2,5]thiadiazol-4-yl)benzoic acid (EBTBA), and 4-((7-ethynylbenzo[c][1,2,5]thiadiazol-4-yl)ethynyl)benzoic acid (EBTEBA) to a binary electron-donor diphenylamine-phenanthrocarbazole (DPA-PC), we systematically investigate the impacts of electron-acceptors upon energy level, energy gap, light-harvesting ability, photovoltaic parameter, and cell stability of donor-acceptor dyes in photoelectrochemical cells. In conjunction with an ionic liquid composite electrolyte, the DPA-PC dye with EBTEBA as electron-acceptor yields a high power conversion efficiency of 8% and an outstanding stability after a 1000 h aging test under the soaking of full sunlight at 60 °C in a dye-sensitized solar cell. Femtosecond fluorescence up-conversion measurements have suggested that energy relaxation and electron injection both occur to dye molecules in the nonequilibrium excited states. Moreover, the time constants of injecting electrons from dye molecules in the excited states to titania are very dispersive for over 1 order of magnitude, mainly owing to the broad energy distribution of excited states. PMID:27045539

  3. Efficient Synthesis and Photosensitizer Performance of Nonplanar Organic Donor-Acceptor Molecules.

    PubMed

    Yuan, Yuping; Michinobu, Tsuyoshi; Satoh, Norifusa; Ashizawa, Minoru; Han, Liyuan

    2015-08-01

    Nonplanar organic donor-acceptor molecules bearing a carboxylic acid group were synthesized by the formal [2+2] cycloaddition-retroelectrocyclization reaction between aniline-substituted alkynes and tetracyanoethylene (TCNE) or 7,7,8,8-tetracyanoquinodimethane (TCNQ). This reaction offers an atom-economic one-step approach to donor-acceptor chromophores in satisfactory high yields. The resulting donor-acceptor molecules were characterized by conventional analytical techniques. In addition, the nonplanarity and intermolecular interactions were investigated by X-ray crystallography. The energy levels and intramolecular charge-transfer (CT), evaluated by UV-Vis-near IR spectroscopy and electrochemistry, suggested that there is a linear correlation between the optical and electrochemical band gaps. Based on these structural and electronic analyses, the photosensitizer performances of the donor-acceptor molecules in dye-sensitized solar cells (DSSCs) were initially investigated using TiO2 or SnO2 electrodes. Although the power conversion efficiencies were limited, the incident-photon-to-current-conversion efficiency (IPCE) spectra indicated a better photocurrent generation for the devices on SnO2 as compared to those on TiO2. PMID:26369162

  4. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    PubMed Central

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-01-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures. PMID:26891851

  5. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    NASA Astrophysics Data System (ADS)

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-02-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures.

  6. Synthesis and Characterization of Organic Dyes Containing Various Donors and Acceptors

    PubMed Central

    Wu, Tzi-Yi; Tsao, Ming-Hsiu; Chen, Fu-Lin; Su, Shyh-Gang; Chang, Cheng-Wen; Wang, Hong-Paul; Lin, Yuan-Chung; Ou-Yang, Wen-Chung; Sun, I-Wen

    2010-01-01

    New organic dyes comprising carbazole, iminodibenzyl, or phenothiazine moieties, respectively, as the electron donors, and cyanoacetic acid or acrylic acid moieties as the electron acceptors/anchoring groups were synthesized and characterized. The influence of heteroatoms on carbazole, iminodibenzyl and phenothiazine donors, and cyano-substitution on the acid acceptor is evidenced by spectral, electrochemical, photovoltaic experiments, and density functional theory calculations. The phenothiazine dyes show solar-energy-to-electricity conversion efficiency (η) of 3.46–5.53%, whereas carbazole and iminodibenzyl dyes show η of 2.43% and 3.49%, respectively. PMID:20162019

  7. Proficiency of acceptor-donor-acceptor organic dye with spiro-MeOTAD HTM on the photovoltaic performance of dye sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Ramavenkateswari, K.; Venkatachalam, P.

    2016-08-01

    This work investigates the proficiency of acceptor-donor-acceptor (A-D-A) organic dye Diisopropyl azodicarboxylate (DIAC) as photosensitizer on the photovoltaic parameters of silver (Ag) doped TiO2 photoanode dye-sensitized solar cells (DSSCs) with quasi-solid state electrolyte/hole transport material (HTM) spiro-MeOTAD. TNSs (TiO2 nanosticks) photoanodes are prepared through sol-gel method and hydrothermal technique. X-ray powder diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and BET measurement were used to characterize the structure and morphology of TiO2 nanostructures. The Diisopropyl azodicarboxylate organic dye with TNPs-Ag@TNSs composite photoanode structure and spiro-MeOTAD HTM exhibited better power conversion efficiency (PCE). [Figure not available: see fulltext.

  8. Spectral Fine Tuning of Cyanine Dyes: Electron Donor-Acceptor Substituted Analogues of Thiazole Orange†

    PubMed Central

    Rastede, Elizabeth E.; Tanha, Matteus; Yaron, David; Watkins, Simon C.; Waggoner, Alan S.; Armitage, Bruce A.

    2015-01-01

    The introduction of electron donor and acceptor groups at strategic locations on a fluorogenic cyanine dye allows fine-tuning of the absorption and emission spectra while preserving the ability of the dye to bind to biomolecular hosts such as double-stranded DNA and a single-chain antibody fragment originally selected for binding to the parent unsubstituted dye, thiazole orange (TO). The observed spectral shifts are consistent with calculated HOMO-LUMO energy gaps and reflect electron density localization on the quinoline half of TO in the LUMO. A dye bearing donating methoxy and withdrawing trifluoromethyl groups on the benzothiazole and quinoline rings, respectively, shifts the absorption spectrum to sufficiently longer wavelengths to allow excitation at green wavelengths as opposed to the parent dye, which is optimally excited in the blue. PMID:26171668

  9. Spectral fine tuning of cyanine dyes: electron donor-acceptor substituted analogues of thiazole orange.

    PubMed

    Rastede, Elizabeth E; Tanha, Matteus; Yaron, David; Watkins, Simon C; Waggoner, Alan S; Armitage, Bruce A

    2015-09-26

    The introduction of electron donor and acceptor groups at strategic locations on a fluorogenic cyanine dye allows fine-tuning of the absorption and emission spectra while preserving the ability of the dye to bind to biomolecular hosts such as double-stranded DNA and a single-chain antibody fragment originally selected for binding to the parent unsubstituted dye, thiazole orange (TO). The observed spectral shifts are consistent with calculated HOMO-LUMO energy gaps and reflect electron density localization on the quinoline half of TO in the LUMO. A dye bearing donating methoxy and withdrawing trifluoromethyl groups on the benzothiazole and quinoline rings, respectively, shifts the absorption spectrum to sufficiently longer wavelengths to allow excitation at green wavelengths as opposed to the parent dye, which is optimally excited in the blue. PMID:26171668

  10. Does the Donor-π-Acceptor Character of Dyes Improve the Efficiency of Dye-Sensitized Solar Cells?

    PubMed

    Ip, Chung Man; Troisi, Alessandro

    2016-08-01

    We quantified the donor-π-acceptor (D-π-A) character of a large number of dyes (116) used in dye-sensitized solar cells (DSSCs) and correlated them with the power conversion efficiency of the corresponding cell. The result indicates that there is no correlation between different measures of D-π-A strength and efficiency; that is, the effect of the D-π-A character is completely washed out by other effects. We propose that other design rules should be identified by statistically testing them against the now rich set of experimentally available data. PMID:27434300

  11. Theoretical insight on novel donor-acceptor exTTF-based dyes for dye-sensitized solar cells.

    PubMed

    Calbo, Joaquín; Viruela, Pedro M; Ortí, Enrique

    2014-04-01

    A thorough density functional theory study is performed for the three carboxyl-based derivatives of the exTTF-TCF chromophore, where the π-extended tetrathiafulvalene (exTTF) electron-donor is linked to the tricyanofuran (TCF) electron-acceptor through an ethylene bridge, as dyes for dye-sensitized solar cells. Calculations predict that the carboxyl group in the acceptor moiety adopts an adequate orientation for an efficient anchoring on the semiconductor TiO₂ surface. The carboxylic acid group holds a negative charge twice larger than the cyano moiety that favors the electron injection to the semiconductor. Time-dependent calculations allow for the assignment of the absorption bands in the UV-vis spectrum of exTTF-TCF and confirm the presence of two low-lying charge-transfer electronic transitions that account for the moderately-intense absorption in the 450-800 nm range. The striking optical absorption properties of exTTF-TCF are preserved for the carboxylic analogues. Finally, periodic calculations show relevant topological differences between the carboxylic derivatives anchored on the TiO₂ surface, which would notably influence in the power conversion efficiency of a dye-sensitized solar cell. PMID:24643466

  12. Highly efficient donor-acceptor hydrazone dyes-inorganic Si/TiO₂ hybrid solar cells.

    PubMed

    Al-Sehemi, Abdullah G; Irfan, Ahmad; Al-Melfi, Mohrah Abdullah M

    2015-06-15

    We have synthesized the two donor-bridge-acceptor organic dyes (hydrazone dye 1 (HD1) and hydrazone dye 2 (HD2)) with the aim to enhance intra-molecular charge transfer then characterized by FTIR and NMR. The ground state geometries have been optimized at three different levels of theories, i.e., B3LYP/6-31G, B3LYP/6-31G and Hartee-Fock HF/6-31G. The absorption spectra and oscillator strengths in different solvents have been computed and compared with the experimental data. The vibrational spectral assignments have been performed on the recorded FTIR spectra based on the theoretical predicted wavenumbers at three different levels of theories. The effect of different solvents (CHCl3, CH3CN and C2H5OH) has been studied on the absorption wavelengths. Furthermore, we have computed the ionization potentials, electron affinities and reorganization energies of studied compounds and shed light on the charge transport properties. The hetero-junction solar cell devices were fabricated by organic-inorganic hetero-junction (Si/TiO2/dye) then the efficiency has been measured by applying the incident power 30, 50 and 70 mW/cm(2). The maximum efficiency 3.12% has been observed for HD1. PMID:25766477

  13. Organic Materials in the Undergraduate Laboratory: Microscale Synthesis and Investigation of a Donor-Acceptor Molecule

    ERIC Educational Resources Information Center

    Pappenfus, Ted M.; Schliep, Karl B.; Dissanayake, Anudaththa; Ludden, Trevor; Nieto-Ortega, Belen; Lopez Navarrete, Juan T.; Ruiz Delgado, M. Carmen; Casado, Juan

    2012-01-01

    A series of experiments for undergraduate courses (e.g., organic, physical) have been developed in the area of small molecule organic materials. These experiments focus on understanding the electronic and redox properties of a donor-acceptor molecule that is prepared in a convenient one-step microscale reaction. The resulting intensely colored…

  14. Effects of the acceptor unit in dyes with acceptor-bridge-donor architecture on the electron photo-injection mechanism and aggregation in DSSCs.

    PubMed

    Zarate, Ximena; Claveria-Cadiz, Francisca; Arias-Olivares, David; Rodriguez-Serrano, Angela; Inostroza, Natalia; Schott, Eduardo

    2016-09-21

    Dye-sensitized solar cells (DSSCs) are devices that convert light to electrical energy. Nowadays, researchers have focused on the understanding of the performance of dyes in solar cells. In this way, new efficient dyes have been obtained which can act as efficient light-harvesting compounds where the combination and the balance of acceptor(A)-bridge-donor(D) architectures confer suitable attributes and properties to the dye. Herein, we have carried out a DFT study on the optical and electronic properties of eight different A motifs and their influence on the electron photo-injection (PI) mechanisms through type I (indirect) or type II (direct) pathways in A-bridge-D dyes in DSSCs. The models consisted of thiophene as a bridge and triphenylamine as a D anchored to a TiO2 anatase cluster. All geometry optimizations were calculated using the B3LYP, CAM-B3LYP and BHandHLYP functionals combined with the 6-31G(d,p) basis set for C, H, N, O and S and the LANL2DZ pseudopotential for Ti atoms. Most of the A dyes display optoelectronic properties consistent with a type-I (indirect) mechanism except for the A5 dye where the results suggest a type-II (direct) PI pathway. In addition, molecular dynamics (MD) simulations have been carried out in order to describe the formation of dye dimers and analyze the stability of the aggregates due to intermolecular interactions. The observed trends indicate that dyes with A2 and A5 anchoring groups have less tendency to dimerize due to weaker intermolecular interactions resulting in less stable dimer complexes. Specifically, we found that the A motif influences the PI by a dye and the dimerization profiles. PMID:27530076

  15. New organic donor-acceptor-π-acceptor sensitizers for efficient dye-sensitized solar cells and photocatalytic hydrogen evolution under visible-light irradiation.

    PubMed

    Li, Xing; Cui, Shicong; Wang, Dan; Zhou, Ying; Zhou, Hao; Hu, Yue; Liu, Jin-Gang; Long, Yitao; Wu, Wenjun; Hua, Jianli; Tian, He

    2014-10-01

    Two organic donor-acceptor-π-acceptor (D-A-π-A) sensitizers (AQ and AP), containing quinoxaline/pyrido[3,4-b]pyrazine as the auxiliary acceptor, have been. Through fine-tuning of the auxiliary acceptor, a higher designed and synthesized photoelectric conversion efficiency of 6.02% for the AQ-based dye-sensitized solar cells under standard global AM1.5 solar conditions was achieved. Also, it was found that AQ-Pt/TiO2 photocatalysts displayed a better rate of H2 evolution under visible-light irradiation (420 nm<λ<780 nm) because of the stability of the oxidized states and the lower rates of electron recombination. Importantly, sensitizers AQ and AP-Pt/TiO2 showed strong photocatalytic activity during continuous light soaking for 10 h with methanol as the sacrificial electron donor. Additionally, the processes of their intermolecular electron transfer were further investigated theoretically by using time-dependent DFT. The calculated results indicate that the auxiliary acceptor plays the role of an electron trap and results in broad spectral responses. PMID:25154958

  16. Enhanced anaerobic fermentation with azo dye as electron acceptor: simultaneous acceleration of organics decomposition and azo decolorization.

    PubMed

    Li, Yang; Zhang, Yaobin; Quan, Xie; Zhang, Jingxin; Chen, Shuo; Afzal, Shahzad

    2014-10-01

    Accumulation of hydrogen during anaerobic processes usually results in low decomposition of volatile organic acids (VFAs). On the other hand, hydrogen is a good electron donor for dye reduction, which would help the acetogenic conversion in keeping low hydrogen concentration. The main objective of the study was to accelerate VFA composition through using azo dye as electron acceptor. The results indicated that the azo dye serving as an electron acceptor could avoid H2 accumulation and accelerate anaerobic digestion of VFAs. After adding the azo dye, propionate decreased from 2400.0 to 689.5mg/L and acetate production increased from 180.0 to 519.5mg/L. It meant that the conversion of propionate into acetate was enhanced. Fluorescence in situ hybridization analysis showed that the abundance of propionate-utilizing acetogens with the presence of azo dye was greater than that in a reference without azo dye. The experiments via using glucose as the substrate further demonstrated that the VFA decomposition and the chemical oxygen demand (COD) removal increased by 319.7mg/L and 23.3% respectively after adding the azo dye. Therefore, adding moderate azo dye might be a way to recover anaerobic system from deterioration due to the accumulation of H2 or VFAs. PMID:25288539

  17. Tracking molecular resonance forms of donor–acceptor push–pull molecules by single-molecule conductance experiments

    PubMed Central

    Lissau, Henriette; Frisenda, Riccardo; Olsen, Stine T.; Jevric, Martyn; Parker, Christian R.; Kadziola, Anders; Hansen, Thorsten; van der Zant, Herre S. J.; Brøndsted Nielsen, Mogens; Mikkelsen, Kurt V.

    2015-01-01

    The ability of molecules to change colour on account of changes in solvent polarity is known as solvatochromism and used spectroscopically to characterize charge-transfer transitions in donor–acceptor molecules. Here we report that donor–acceptor-substituted molecular wires also exhibit distinct properties in single-molecule electronics under the influence of a bias voltage, but in absence of solvent. Two oligo(phenyleneethynylene) wires with donor–acceptor substitution on the central ring (cruciform-like) exhibit remarkably broad conductance peaks measured by the mechanically controlled break-junction technique with gold contacts, in contrast to the sharp peak of simpler molecules. From a theoretical analysis, we explain this by different degrees of charge delocalization and hence cross-conjugation at the central ring. Thus, small variations in the local environment promote the quinoid resonance form (off), the linearly conjugated (on) or any form in between. This shows how the conductance of donor–acceptor cruciforms is tuned by small changes in the environment. PMID:26667583

  18. Role of functionalized acceptors in heteroleptic bipyridyl Cu(I) complexes for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Lu, Xiaoqing; Shao, Yang; Li, Ke; Zhao, Zigang; Wei, Shuxian; Guo, Wenyue

    2016-07-01

    The intrinsic optoelectronic properties of heteroleptic bipyridyl Cu(I) complexes bearing functionalized acceptor subunits have been investigated by density functional theory and time-dependent DFT. The Cu(I) complexes exhibit distorted trigonal-pyramidal geometries and typical metal-to-ligand electron transfer characteristics at the long wavelength region. Replacing carboxylic acid with cyanoacrylic acid in acceptor subunits stabilizes the LUMO levels, thus lowering the HOMOLUMO energy gaps and facilitating favorable donor-to-acceptor intramolecular electron transfer and charge separation. Introduction of heteroaromatic groups and cyanoacrylic acid significantly improves the light-harvesting capability of the complexes. Our results highlight the effect of functionalized acceptors on the optoelectronic properties of bipyridyl Cu(I) complexes and provide a fresh perspective on screening of efficient sensitizers for dye-sensitized solar cells.

  19. The Nature of the Donor Motif in Acceptor-Bridge-Donor Dyes as an Influence in the Electron Photo-Injection Mechanism in DSSCs.

    PubMed

    Zarate, Ximena; Schott-Verdugo, Stephan; Rodriguez-Serrano, Angela; Schott, Eduardo

    2016-03-10

    The combination and balance of acceptor(A)-bridge-donor(D) architecture of molecules confer suitable attributes and/or properties to act as efficient light-harvesting and sensitizers in dye sensitized solar cells (DSSCs). An important process in a DSSC performance is the electron photoinjection (PI) mechanism which can take place either via type I (indirect), that consists in injecting from the excited state of the dye to the semiconductor, or type II (direct), where the PI is from the ground state of the dye to the semiconductor upon photoexcitation. Here, we present a computational study about the role of the donor motif in the PI mechanisms displayed from a family of 11 A-bridge-D structured dyes to a (TiO2)15 anatase cluster. To this end, different donor motifs (D1-D11) were evaluated while the A and bridge motifs remained the same. All the computations were carried out within the DFT framework, using the B3LYP, PW91, PBE, M06L and CAM-B3LYP functionals. The 6-31G(d) basis set was employed for nonmetallic atoms and the LANL2DZ pseudopotential for Ti atoms. The solvation effects were incorporated using the polarized continuum model (PCM) for acetonitrile. As benchmark systems, alizarin and naphthalenediol dyes were analyzed, as they are known to undergo Type I and Type II PI pathways in DSSCs, respectively. Donors in the studied family of dyes could influence to drive Type I or II PI since it was found that D2 could show some Type II PI route, showing a new absorption band, although with CAM-B3LYP this shows a very low oscillator strength, while the remaining dyes behave according to Type I photoinjectors. Finally, the photovoltaic parameters that govern the light absorption process were evaluated, as the use of these criteria could be applied to predict the efficiency of the studied dyes in DSSCs devices. PMID:26900717

  20. Thermally activated delayed fluorescence evidence in non-bonding transition electron donor-acceptor molecules

    NASA Astrophysics Data System (ADS)

    Marghad, Ikbal; Clochard, M. C.; Ollier, N.; Wade, Travis L.; Aymes-Chodur, C.; Renaud, C.; Zissis, G.

    2015-09-01

    The exhibition of thermally activated delayed fluorescence on triazine derivative by the introduction of a nonbonding part is demonstrated. Two molecules containing triazine core as acceptor and carbazole part as donor has been synthesized and characterized. One of these molecules bears an additional nonbonding part by the means of a phenoxy group. The results indicated that the molecule bearing the nonbonding molecular part (phenoxy) exhibit thermally activated delayed fluorescence while not on molecule free of non-bonding group. The results are supported by, photoluminescence, spectral analysis time-resolved fluorescence and time-dependent density functional estimation

  1. Acceptor-donor-acceptor-based small molecules with varied crystallinity: processing additive-induced nanofibril in blend film for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Li, Chao; Chen, Yujin; Zhao, Yue; Wang, Huifang; Zhang, Wei; Li, Yaowen; Yang, Xiaoming; Ma, Changqi; Chen, Liwei; Zhu, Xiulin; Tu, Yingfeng

    2013-09-01

    A series of acceptor-donor-acceptor-based small molecules (SMs) with varied crystallinity were successfully synthesized. The processing additive can induce the SMs to self-organize as nanofibrils with higher crystallinity and controlled scales of nanofibrils, which have significant influence on the photovoltaic performance.A series of acceptor-donor-acceptor-based small molecules (SMs) with varied crystallinity were successfully synthesized. The processing additive can induce the SMs to self-organize as nanofibrils with higher crystallinity and controlled scales of nanofibrils, which have significant influence on the photovoltaic performance. Electronic supplementary information (ESI) available: Synthetic process and characterizations of SMs; TGA, electrochemical properties, molecular orbital surfaces of SMs; AFM images of SM:PC71BM blend films; EQE curves; optical, electrochemical properties and photovoltaic parameters. See DOI: 10.1039/c3nr03048b

  2. Fluorescence characteristics and photostability of benzoxazole derived donor-acceptor dyes in constrained media.

    PubMed

    Fayed, Tarek A; Etaiw, Safaa El-Din H

    2006-10-01

    The spectroscopic properties and photoreactivity of 2-(4-dimethylaminostryl)benzoxazole and its butadienyl analogue (abbreviated as DMASBO and BODB, respectively) were investigated in thin films of PS, PMMA and PVA polymer matrices as well as immobilized on silica surface. The experimental results showed that the investigated benzoxazole derivatives are sensitive to the polarity of its microenvironment even in the glassy matrices and in the solid state. The micropolarity of PVA and silica surface is greater than that of PMMA and PS. The combined results of fluorescence quantum yield and photoisomerization indicated that the size of the free volume within the polymer matrix influence strongly the photochemical reactivity of the used dyes. In PVA, which offers the smaller free volume, the photoreaction is totally blocked while the fluorescence yield is extremely enhanced relative to those in solutions and other polymer matrices. This is associated with an emission of green laser from DMASBO-PVA doped film when pumped by nitrogen laser (337 nm). The results showed that the present dyes are excellent probes for non-fluorescent systems presenting constrained geometry. The spectra of amorphous solid thin films of both dyes were also measured and show large red shifts relative to those in solutions indicating symmetric aggregation of molecules in the solid crystals. PMID:16500138

  3. Photoinduced electron transfer across fixed distances in chlorophyll donor-acceptor molecules

    SciTech Connect

    Wasielewski, M.R.; Johnson, D.G.; Svec, W.A.

    1987-06-01

    The primary events of photosynthesis are a series of rapid, unidirectional electron transfer events between donors and acceptors that are positioned in the reaction center protein at precise spatial orientations and distances relative to one another. Recent work suggests that electron transfer rates depend on distance and free energy of reaction in porphyrin-quinone models in which the distance and orientation of the donor relative to the acceptor is highly restricted. Spacer molecules were developed which were used to link chlorophyll donors with either chlorophyll or quinone acceptors to produce models in which the donor-acceptor distance is well-defined. Recent theoretical studies and photochemical hole-burning experiments have suggested that the actual primary event of photosynthesis is the production of an intramolecular charge transfer state involving the two bacteriochlorophyll molecules of the special pair dimer. This possibility was explored with symmetric, fixed distance chlorophyll dimer. The chlorophyll macrocycles share a common vinyl group at the 2-position. This linkage serves to increase the degree of electronic coupling between the macrocycles. This dimer exhibits a remarkable decrease in fluorescence quantum yield as the dielectric constant of the medium in which it is dissolved increases. This decrease is accompanied by a proportional decrease in the lowest excited singlet state lifetime as measured by picosecond fluorescence and absorption. 11 refs., 2 figs.

  4. Rationally designed donor-acceptor scheme based molecules for applications in opto-electronic devices.

    PubMed

    Subash Sundar, T; Sen, R; Johari, P

    2016-04-01

    Several donor (D)-acceptor (A) based molecules are rationally designed by adopting three different schemes in which the conjugation length, strength of the donor and acceptor moieties, and planarity of the molecules are varied. These variations are made by introducing a π-conjugated linkage unit, terminating the ends of the moieties by different electron donating and accepting functional groups, and fusing the donor and acceptor moieties, respectively. Our DFT and TDDFT based calculations reveal that using the above-mentioned design schemes, the electronic and optical properties of the D-A based molecules can be largely tuned. While introduction of a linkage and fusing of moieties enhance the π-π interaction, addition of electron donating groups (-CH3, -OH, and -NH2) and electron accepting groups (-CF3, -CN, -NO2, and -NH3(+)) varies the strength of the donor and acceptor moieties. These factors lead to modulation of the HOMO and LUMO energy levels and facilitate the engineering of the HOMO-LUMO gap and the optical gap over a wide range of ∼0.7-3.7 eV. Moreover, on the basis of calculated ionization potential and reorganization energy, most of the investigated molecules are predicted to be air stable and to exhibit high electron mobility, with the possibility of the presence of ambipolar characteristics in a few of them. The results of our calculations not only demonstrate the examined molecules to be the potential materials for organic opto-electronic devices, but also establish an understanding of the composition-structure-property correlation, which will provide guidelines for designing and synthesizing new materials of choice. PMID:26972386

  5. A donor-acceptor triptycene-coumarin hybrid dye featuring a charge separated excited state and AIE properties.

    PubMed

    Qian, Rui; Tong, Hongjuan; Huang, Cui; Li, Junhao; Tang, Yun; Wang, Rui; Lou, Kaiyan; Wang, Wei

    2016-06-14

    A triptycene-coumarin hybrid dye DCT-1 with a 1,4-dimethoxybenzene group as the electron donor and a coumarin fluorophore as the acceptor on the separated fins of a triptycene was synthesized. DCT-1 features a charge separated excited state with emissions sensitive to solvent polarities. Moreover, DCT-1 also exhibits aggregation-induced emission properties in water with excellent photostability and pH-stability for potential cell imaging applications. PMID:27186970

  6. Efficiency improvement of new Tetrathienoacene-based dyes by enhancing donor, acceptor and bridge units, a theoretical study.

    PubMed

    Tavangar, Zahra; Zareie, Nazanin

    2016-10-01

    A series of metal free Tetrathienoacene-based (TTA-based) organic dyes are designed and investigated as sensitizers for application in dye sensitized solar cells (DSSCs). Density function theory and time dependent density function theory calculations were performed on these dyes at vacuum and orthodichlorobenzene as the solvent. Effects of changing π-conjugation bridges and different functional groups in acceptor and donor units were investigated. UV-Vis absorption spectra were simulated to show the wavelength shifting and absorption properties. Inserting nitro and acyl chloride functional groups in acceptor and NH2 in donor units leads to the reduction of HOMO-LUMO gap by lowering the lowest unoccupied molecular orbital (LUMO) energy level and raising the highest occupied molecular orbital (HOMO) energy level and the increase in effective parameters in DSSC' efficiency. The results show that changing spacer units from thiophene to furan has a great effect on electronic structure and absorption spectra. Investigation of the electron distributions of frontier orbitals shows the HOMO and LUMO localization in donor and acceptor, respectively. Some key parameters that were studied here include light harvesting efficiency, free energy of electron injection and open circuit photo-voltage. PMID:27258685

  7. Structural effects on the photoelectrochemical properties of new push-pull dyes based on vinazene acceptor triphenylamine donor

    NASA Astrophysics Data System (ADS)

    Arcos, Wilmmer A.; Guimarães, Robson R.; Insuasty, Braulio; Araki, Koiti; Ortiz, Alejandro

    2016-05-01

    The push-pull behavior of novel dyes, based on vinazene electron-acceptor groups linked to arrays of triphenylamine (TPA) electron-donor group, was studied by electronic absorption and emission spectroscopy, as well as by cyclic voltammetry. The most stable ground state structure and their electronic properties were modeled by density functional theory (DFT) calculations using the B3LYP functional and 6-31G++ basis set, whereas the electronic properties in the excited states were calculated by TD-DFT, under the same functional and basis set, using SCF and PCM methods. The theoretical calculations matched well with experimental data, showing that λmax of the lowest energy absorption band can be assigned to an intramolecular charge transfer transition. In fact, the HOMO and LUMO are respectively localized on the TPA donor and the dicyanomethylene acceptor moiety confirming a remarkable push-pull character. Photoelectrochemical cells parameters were correlated with dyes structural properties showing to be consistent with the anchoring through the nitrogen atoms of CN groups. The nature of the donor-acceptor groups, conformation and number of anchoring CN groups (2 seems to be the best) strongly influenced the overall efficiency of dye sensitized solar cells.

  8. Threshold-like complexation of conjugated polymers with small molecule acceptors in solution within the neighbor-effect model.

    PubMed

    Sosorev, Andrey Yu; Parashchuk, Olga D; Zapunidi, Sergey A; Kashtanov, Grigoriy S; Golovnin, Ilya V; Kommanaboyina, Srikanth; Perepichka, Igor F; Paraschuk, Dmitry Yu

    2016-02-14

    In some donor-acceptor blends based on conjugated polymers, a pronounced charge-transfer complex (CTC) forms in the electronic ground state. In contrast to small-molecule donor-acceptor blends, the CTC concentration in polymer:acceptor solution can increase with the acceptor content in a threshold-like way. This threshold-like behavior was earlier attributed to the neighbor effect (NE) in the polymer complexation, i.e., next CTCs are preferentially formed near the existing ones; however, the NE origin is unknown. To address the factors affecting the NE, we record the optical absorption data for blends of the most studied conjugated polymers, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene) (P3HT), with electron acceptors of fluorene series, 1,8-dinitro-9,10-antraquinone (), and 7,7,8,8-tetracyanoquinodimethane () in different solvents, and then analyze the data within the NE model. We have found that the NE depends on the polymer and acceptor molecular skeletons and solvent, while it does not depend on the acceptor electron affinity and polymer concentration. We conclude that the NE operates within a single macromolecule and stems from planarization of the polymer chain involved in the CTC with an acceptor molecule; as a result, the probability of further complexation with the next acceptor molecules at the adjacent repeat units increases. The steric and electronic microscopic mechanisms of NE are discussed. PMID:26799407

  9. Tailoring of Energy Levels in D-π-A Organic Dyes via Fluorination of Acceptor Units for Efficient Dye-Sensitized Solar Cells

    PubMed Central

    Lee, Min-Woo; Kim, Jae-Yup; Son, Hae Jung; Kim, Jin Young; Kim, BongSoo; Kim, Honggon; Lee, Doh-Kwon; Kim, Kyungkon; Lee, Duck-Hyung; Ko, Min Jae

    2015-01-01

    A molecular design is presented for tailoring the energy levels in D-π-A organic dyes through fluorination of their acceptor units, which is aimed at achieving efficient dye-sensitized solar cells (DSSCs). This is achieved by exploiting the chemical structure of common D-π-A organic dyes and incorporating one or two fluorine atoms at the ortho-positions of the cyanoacetic acid as additional acceptor units. As the number of incorporated fluorine atoms increases, the LUMO energy level of the organic dye is gradually lowered due to the electron-withdrawing effect of fluorine, which ultimately results in a gradual reduction of the HOMO-LUMO energy gap and an improvement in the spectral response. Systematic investigation of the effects of incorporating fluorine on the photovoltaic properties of DSSCs reveals an upshift in the conduction-band potential of the TiO2 electrode during impedance analysis; however, the incorporation of fluorine also results in an increased electron recombination rate, leading to a decrease in the open-circuit voltage (Voc). Despite this limitation, the conversion efficiency is gradually enhanced as the number of incorporated fluorine atoms is increased, which is attributed to the highly improved spectral response and photocurrent. PMID:25591722

  10. Theoretical Study of Donor - Spacer - Acceptor Structure Molecule for Molecular Rectifier

    NASA Astrophysics Data System (ADS)

    Mizuseki, Hiroshi; Kenji, Niimura; Belosludov, Rodion; Farajian, Amir; Kawazoe, Yoshiyuki

    2003-03-01

    Recently, the molecular electronics has attracted strong attention as a ``post-silicone technology'' to establish a future nanoscale electronic devices. To realize this molecular device, unimolecular rectifiering function is one of the most important constituents in nanotechnology [C. Majumder, H. Mizuseki, and Y. Kawazoe, Molecular Scale Rectifier: Theoretical Study, J. Phys. Chem. A, 105 (2001) 9454-9459.]. In the present study, the geometric and electronic structure of alkyl derivative C37H50N4O4 (PNX) molecule, (donor - spacer - acceptor), a leading candidate of molecular rectifying device, has been investigated theoretically using ab initio quantum mechanical calculation. The results suggest that in such donor-acceptor molecular complexes, while the lowest unoccupied orbital concentrates on the acceptor subunit, the highest occupied molecular orbital is localized on the donor subunit. The approximate potential differences for optimized PNX molecule have been estimated at the B3PW91/6-311g++(d,p) level of theory, which achieves quite good agreement with experimentally reported results. This study was performed through Special Coordination Funds for Promoting Science and Technology of the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government.

  11. Variable temperature EPR studies of Illinois No. 6 coal treated with donor and acceptor molecules

    SciTech Connect

    Thompson, R.L.; Rothenberger, K.S.; Retcofsky, H.L.

    1996-10-01

    Variable, temperature EPR studies of Illinois No. 6 coal, its pyridine extract, and samples of each after treatment with known donor and acceptor molecules are reported. The purpose of the study was to explore the origin of the EPR signals near g = 2 and to assess the contribution of certain non-bonded interactions in coal. Curie Law behavior is exhibited for each sample indicating that the EPR signals are dominated by doublet state radicals. No evidence for thermally accessible, low-lying triplet states, such as those found in some charge-transfer complexes, was found. Infrared spectroscopy reveals, however, that some electron density is transferred from the coal after treatment with acceptors such as TCNQ and TCNE. EPR studies of chromat graphic fractions of the pyridine extract (approximately five percent of the whole coal), both untreated and treated with TTF and TCNE, indicated some minor contributions of low-lying triplet states.

  12. Benzo[c][1,2,5]thiadiazole Donor-Acceptor Dyes: A Synthetic, Spectroscopic, and Computational Study.

    PubMed

    Barnsley, Jonathan E; Shillito, Georgina E; Larsen, Christopher B; van der Salm, Holly; Wang, Lei E; Lucas, Nigel T; Gordon, Keith C

    2016-03-24

    The synthesis, optical characterization and computational modeling of seven benzo[c][1,2,5]thiadiazole (BTD) donor-acceptor dyes are reported. These dyes have been studied using electrochemical analysis, electronic absorption, emission, and Raman and resonance Raman spectroscopies coupled with various density functional theoretical approaches. Crystal structure geometries on a number of these compounds are also reported. The optical spectra are dominated by low energy charge-transfer states; this may be modulated by the coupling between donor and acceptor through variation in donor energy, variation of the donor-acceptor torsion angle, and incorporation of an insulating bridge. These modifications result in a perturbation of the excitation energy for this charge-transfer transition of up to ∼2000 cm(-1). Emission spectra exhibit significant solvatochromisim, with Lippert-Mataga analysis yielding Δμ between 8 and 33 D. Predicted λmax, ε, and Raman cross sections calculated by M06L, B3LYP, PBE0, M06, CAM-B3LYP, and ωB97XD DFT functionals were compared to experimental results and analyzed using multivariate analysis, which shows that hybrid functionals with 20-27% HF best predict ground state absorption, while long-range corrected functionals best predict molecular polarizabilities. PMID:26918584

  13. X-ray absorption spectroscopy of biomimetic dye molecules for solar cells

    SciTech Connect

    Cook, Peter L.; Liu Xiaosong; Himpsel, F. J.; Yang Wanli

    2009-11-21

    Dye-sensitized solar cells are potentially inexpensive alternatives to traditional semiconductor solar cells. In order to optimize dyes for solar cells we systematically investigate the electronic structure of a variety of porphyrins and phthalocyanines. As a biological model system we use the heme group in cytochrome c which plays a role in biological charge transfer processes. X-ray absorption spectroscopy of the N 1s and C 1s edges reveals the unoccupied molecular orbitals and the orientation of the molecules in thin films. The transition metal 2p edges reflect the oxidation state of the central metal atom, its spin state, and the ligand field of the surrounding N atoms. The latter allows tuning of the energy position of the lowest unoccupied orbital by several tenths of an eV by tailoring the molecules and their deposition. Fe and Mn containing phthalocyanines oxidize easily from +2 to +3 in air and require vacuum deposition for obtaining a reproducible oxidation state. Chlorinated porphyrins, on the other hand, are reduced from +3 to +2 during vacuum deposition at elevated temperatures. These findings stress the importance of controlled thin film deposition for obtaining photovoltaic devices with an optimum match between the energy levels of the dye and those of the donor and acceptor electrodes, together with a molecular orientation for optimal overlap between the {pi} orbitals in the direction of the carrier transport.

  14. Proton Donor/acceptor Propensities of Ammonia: Rotational Studies of its Molecular Complexes with Organic Molecules

    NASA Astrophysics Data System (ADS)

    Giuliano, Barbara M.; Maris, Assimo; Melandri, Sonia; Favero, Laura B.; Evangelisti, Luca; Caminati, Walther

    2009-06-01

    We studied the rotational spectra of the adducts of ammonia with several organic molecules, namely tert-butanol, glycidol, ethyl alcohol, anisol and 1,4-difluorobenzene. The adducts with glycidol and ethanol have been observed for both conformers of the substrate molecule. Based on the rotational and ^{14}N quadrupole coupling constants of the various complexes, we found a considerably different behaviour of ammonia, with respect to water, in its proton donor/acceptor double role. In the interaction with the three alcohol molecules, NH_{3} acts as a proton acceptor and the OH groups as a proton donor. However, in the case of glycidol-NH_{3}, a secundary N-H\\cdotsO interaction occurrs between ammonia and the ether oxygen. This interaction generates a sizable V_{3} barrier to the internal rotation of the NH_{3} moiety, while NH_{3} undergoes a free rotation in tert-butanol-NH_{3} and in ethanol-NH_{3}. As to the anisole-NH_{3} and 1,4-difluorobenzene-NH_{3} complexes, the NH_{3} group explicits its double proton donor/acceptor role, although through two weak (C_{Me}-H\\cdotsN and N-H\\cdotsπ) H-bonds. There is, however, an important difference between the two complexes, because in the first one NH_{3} lies out of the aromatic plane, while in the second one it is in the plane of the aromatic ring. B. M. Giuliano, M. C. Castrovilli, A. Maris, S. Melandri, W. Caminati and E. A. Cohen, Chem.Phys.Lett., 2008, 463, 330 B. M. Giuliano, S. Melandri, A. Maris, L. B. Favero and W. Caminati, Angew.Chem.Int.Ed., 2009, 48, 1102

  15. Memory-switching phenomenon in acceptor-rich organic molecules: impedance spectroscopic studies.

    PubMed

    Bandyopadhyay, Anirban; Pal, Amlan J

    2005-04-01

    We have studied memory-switching phenomena in terms of impedance spectroscopy in a series of xanthene-class fluorescein molecules. Frequency response studies have revealed that the electronic conduction mechanism was largely tuned by increasing the number of acceptor groups attached to the molecular backbone. In molecules with weak intermolecular interactions, the transition between a low- and a high-conducting state has been associated with a change in bulk resistance and dielectric properties. The devices in the two states remained a parallel combination of a resistor and a capacitor (C(P)-R(P)) network. In devices based on Rose Bengal, which exhibits a strong dipole-dipole interaction due to its acceptor groups, the switching between the states has been modeled as a transition between a C(P)-R(P) network in the off-state and a distributed resistor-capacitor (R-C) line network in the on-state. Instead of isolated clusters, a highly coupled network of reduced Rose Bengal molecules with strong dipole-dipole interaction yielded the high-conducting state. Under a "write-read-erase-read" sequence, the device switched between the two networks reversibly for many cycles. PMID:16851669

  16. Single-molecule interfacial electron transfer in donor-bridge-nanoparticle acceptor complexes.

    PubMed

    Jin, Shengye; Snoeberger, Robert C; Issac, Abey; Stockwell, David; Batista, Victor S; Lian, Tianquan

    2010-11-18

    Photoinduced interfacial electron transfer (IET) in sulforhodamine B (SRhB)-aminosilane-Tin oxide (SnO(2)) nanoparticle donor-bridge-acceptor complexes has been studied on a single molecule and ensemble average level. On both SnO(2) and ZrO(2), the sum of single molecule fluorescence decays agree with the ensemble average results, suggesting complete sampling of molecules under single molecule conditions. Shorter fluorescence lifetime on SnO(2) than on ZrO(2) is observed and attributed to IET from SRhB to SnO(2). Single molecule lifetimes fluctuate with time and vary among different molecules, suggesting both static and dynamic IET heterogeneity in this system. Computational modeling of the complexes shows a distribution of molecular conformation, leading to a distribution of electronic coupling strengths and ET rates. It is likely that the conversion between these conformations led to the fluctuation of ET rate and fluorescence lifetime on the single molecule level. PMID:20225886

  17. Circle chain embracing donor-acceptor organic dye: simultaneous improvement of photocurrent and photovoltage for dye-sensitized solar cells.

    PubMed

    Liu, Jian; Numata, Youhei; Qin, Chuanjiang; Islam, Ashraful; Yang, Xudong; Han, Liyuan

    2013-09-01

    We demonstrate for the first time that employing a circle chain embracing π-conjugated backbone is a promising strategy to construct superior organic sensitizers for dye-sensitized solar cells (DSCs), with simultaneous improvement of photocurrent and photovoltage. A DSC based on one circle chain embracing dye produced a high conversion efficiency of 8.34%. PMID:23604204

  18. Solvent-tuned intramolecular charge-recombination rates in a conjugated donor-acceptor molecule

    NASA Technical Reports Server (NTRS)

    Khundkar, Lutfur R.; Stiegman, A. E.; Perry, Joseph W.

    1990-01-01

    The nonradiative charge-recombination rates from the charge-transfer state of a new conjugated donor-acceptor molecule (p-cyano-p-prime-methylthiodiphenylacetylene) can be tuned over almost an order of magnitude by varying the polarity of the solvent. These measurements of intramolecular recombination show a turnover of rates as a function of emission energy, consistent with the 'normal' and 'inverted' behavior of Marcus theory. Steady-state spectra and time-resolved measurements make it possible to quantitatively compare thermal and optical electron-transfer rates as a function of driving force and demonstrate their correspondence.

  19. Deterministically Polarized Fluorescence from Single Dye Molecules Aligned in Liquid Crystal Host

    SciTech Connect

    Lukishova, S.G.; Schmid, A.W.; Knox, R.; Freivald, P.; Boyd, R. W.; Stroud, Jr., C. R.; Marshall, K.L.

    2005-09-30

    We demonstrated for the first time to our konwledge deterministically polarized fluorescence from single dye molecules. Planar aligned nematic liquid crystal hosts provide deterministic alignment of single dye molecules in a preferred direction.

  20. Electroluminescence from completely horizontally oriented dye molecules

    NASA Astrophysics Data System (ADS)

    Komino, Takeshi; Sagara, Yuta; Tanaka, Hiroyuki; Oki, Yuji; Nakamura, Nozomi; Fujimoto, Hiroshi; Adachi, Chihaya

    2016-06-01

    A complete horizontal molecular orientation of a linear-shaped thermally activated delayed fluorescent guest emitter 2,6-bis(4-(10Hphenoxazin-10-yl)phenyl)benzo[1,2-d:5,4-d'] bis(oxazole) (cis-BOX2) was obtained in a glassy host matrix by vapor deposition. The orientational order of cis-BOX2 depended on the combination of deposition temperature and the type of host matrix. Complete horizontal orientation was obtained when a thin film with cis-BOX2 doped in a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) host matrix was fabricated at 200 K. The ultimate orientation of guest molecules originates from not only the kinetic relaxation but also the kinetic stability of the deposited guest molecules on the film surface during film growth. Utilizing the ultimate orientation, a highly efficient organic light-emitting diode with the external quantum efficiency of 33.4 ± 2.0% was realized. The thermal stability of the horizontal orientation of cis-BOX2 was governed by the glass transition temperature (Tg) of the CBP host matrix; the horizontal orientation was stable unless the film was annealed above Tg.

  1. Highly efficient donor-acceptor hydrazone dyes-inorganic Si/TiO2 hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Al-Sehemi, Abdullah G.; Irfan, Ahmad; Al-Melfi, Mohrah Abdullah M.

    2015-06-01

    We have synthesized the two donor-bridge-acceptor organic dyes (hydrazone dye 1 (HD1) and hydrazone dye 2 (HD2)) with the aim to enhance intra-molecular charge transfer then characterized by FTIR and NMR. The ground state geometries have been optimized at three different levels of theories, i.e., B3LYP/6-31G∗, B3LYP/6-31G∗∗ and Hartee-Fock HF/6-31G∗∗. The absorption spectra and oscillator strengths in different solvents have been computed and compared with the experimental data. The vibrational spectral assignments have been performed on the recorded FTIR spectra based on the theoretical predicted wavenumbers at three different levels of theories. The effect of different solvents (CHCl3, CH3CN and C2H5OH) has been studied on the absorption wavelengths. Furthermore, we have computed the ionization potentials, electron affinities and reorganization energies of studied compounds and shed light on the charge transport properties. The hetero-junction solar cell devices were fabricated by organic-inorganic hetero-junction (Si/TiO2/dye) then the efficiency has been measured by applying the incident power 30, 50 and 70 mW/cm2. The maximum efficiency 3.12% has been observed for HD1.

  2. Indolo[3,2-b]carbazole-based multi-donor-π-acceptor type organic dyes for highly efficient dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Qian, Xing; Shao, Li; Li, Hongmei; Yan, Rucai; Wang, Xiaoying; Hou, Linxi

    2016-07-01

    Four novel indolo[3,2-b]carbazole-based multi-donor-π-acceptor type organic dyes QX01-04 have been designed, synthesized, and applied for dye-sensitized solar cells. These dyes consist of an indolo[3,2-b]carbazole core acting as the main donor group, a couple of groups such as ethylbenzene, N,N-diethylaniline, ethyloxylbenzene, and octyloxylbenzene acting as the secondary donors. The photophysical, electrochemical, and theoretical studies indicate that the four dyes are all capable as the photosensitizers. When introducing N,N-diethylaniline as the secondary donor, QX02 exhibits a broader absorption region and significantly improved IPCE values, which ensured a good light-harvesting ability and a high Jsc of 15.2 mA cm-2. Finally, QX02-based cell achieved a high efficiency of 8.09% which is very close to that of the commercial N719-based cell (8.26%) under 100 mW cm-2 irradiation.

  3. The optical properties of molecules and chromogenic aggregates of xanthene dyes

    NASA Astrophysics Data System (ADS)

    Mikheev, Yu. A.; Guseva, L. N.; Ershov, Yu. A.

    2009-05-01

    The UV absorption spectra of rhodamine B and G molecules isolated from industrial dye samples were obtained. Two procedures were used. In one of them, rhodamine B molecules were displaced with water into a heptane layer from a solution of the dye in an alcohol-heptane mixture. The second procedure involved heating of the dye introduced into cellulose triacetate films. Individual rhodamine molecules (namely, dye cation-chlorine anion ion pairs) prepared by both methods did not absorb visible light. The spectra of individual rhodamine molecules coincided with the spectra of so-called pseudoleucobases of xanthene dyes reported in the literature. The conclusion was drawn that the chromaticity property in the series of xanthene dyes appeared because of the formation of supramolecular dimeric and larger aggregates, as was earlier established for triphenylmethane dyes (TPMDs) and copper phthalocyanine (CuPc). At the same time, individual xanthene dye molecules, like TPMD and CuPc molecules, are not chromogens.

  4. Easy Access to NO2 -Containing Donor-Acceptor-Acceptor Electron Donors for High Efficiency Small-Molecule Organic Solar Cells.

    PubMed

    Ting, Hao-Chun; Yang, Ya-Ting; Chen, Chia-Hsun; Lee, Jiun-Haw; Chang, Jung-Hung; Wu, Chih-I; Chiu, Tien-Lung; Lin, Chi-Feng; Chung, Chin-Lung; Wong, Ken-Tsung

    2016-06-22

    Two donor-acceptor-acceptor (D-A-A)-type molecules incorporating nitrobenzoxadiazole (NBO) as the A-A block and ditolylamine as the D block bridged through a phenylene (PNBO) and a thiophene (TNBO) spacer were synthesized in a one-step coupling reaction. Their electronic, photophysical, and thermal properties; crystallographic analysis; and theoretical calculations were studied to establish a clear structure-property relationship. The results indicate that the quinoidal character of the thiophene bridge strongly governs the structural features and crystal packings (herringbone vs. brickwork) and thus the physical properties of the compounds. PNBO and TNBO were utilized as electron donors combined with C70 as the electron acceptor in the active layer of vacuum-processed bulk heterojunction small-molecule organic solar cells (SMOSCs). The power conversion efficiency of both PNBO- and TNBO-based OSCs exceeded 5 %. The ease of accessibility of PNBO and TNBO demonstrates the potential for simple and economical synthesis of electron donors in vacuum-processed SMOSCs. PMID:27213296

  5. Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules IV: Electron-Propagator Methods.

    PubMed

    Dolgounitcheva, O; Díaz-Tinoco, Manuel; Zakrzewski, V G; Richard, Ryan M; Marom, Noa; Sherrill, C David; Ortiz, J V

    2016-02-01

    Comparison of ab initio electron-propagator predictions of vertical ionization potentials and electron affinities of organic, acceptor molecules with benchmark calculations based on the basis set-extrapolated, coupled cluster single, double, and perturbative triple substitution method has enabled identification of self-energy approximations with mean, unsigned errors between 0.1 and 0.2 eV. Among the self-energy approximations that neglect off-diagonal elements in the canonical, Hartree-Fock orbital basis, the P3 method for electron affinities, and the P3+ method for ionization potentials provide the best combination of accuracy and computational efficiency. For approximations that consider the full self-energy matrix, the NR2 methods offer the best performance. The P3+ and NR2 methods successfully identify the correct symmetry label of the lowest cationic state in two cases, naphthalenedione and benzoquinone, where some other methods fail. PMID:26730459

  6. A small-molecule dye for NIR-II imaging

    NASA Astrophysics Data System (ADS)

    Antaris, Alexander L.; Chen, Hao; Cheng, Kai; Sun, Yao; Hong, Guosong; Qu, Chunrong; Diao, Shuo; Deng, Zixin; Hu, Xianming; Zhang, Bo; Zhang, Xiaodong; Yaghi, Omar K.; Alamparambil, Zita R.; Hong, Xuechuan; Cheng, Zhen; Dai, Hongjie

    2016-02-01

    Fluorescent imaging of biological systems in the second near-infrared window (NIR-II) can probe tissue at centimetre depths and achieve micrometre-scale resolution at depths of millimetres. Unfortunately, all current NIR-II fluorophores are excreted slowly and are largely retained within the reticuloendothelial system, making clinical translation nearly impossible. Here, we report a rapidly excreted NIR-II fluorophore (~90% excreted through the kidneys within 24 h) based on a synthetic 970-Da organic molecule (CH1055). The fluorophore outperformed indocyanine green (ICG)--a clinically approved NIR-I dye--in resolving mouse lymphatic vasculature and sentinel lymphatic mapping near a tumour. High levels of uptake of PEGylated-CH1055 dye were observed in brain tumours in mice, suggesting that the dye was detected at a depth of ~4 mm. The CH1055 dye also allowed targeted molecular imaging of tumours in vivo when conjugated with anti-EGFR Affibody. Moreover, a superior tumour-to-background signal ratio allowed precise image-guided tumour-removal surgery.

  7. A small-molecule dye for NIR-II imaging.

    PubMed

    Antaris, Alexander L; Chen, Hao; Cheng, Kai; Sun, Yao; Hong, Guosong; Qu, Chunrong; Diao, Shuo; Deng, Zixin; Hu, Xianming; Zhang, Bo; Zhang, Xiaodong; Yaghi, Omar K; Alamparambil, Zita R; Hong, Xuechuan; Cheng, Zhen; Dai, Hongjie

    2016-02-01

    Fluorescent imaging of biological systems in the second near-infrared window (NIR-II) can probe tissue at centimetre depths and achieve micrometre-scale resolution at depths of millimetres. Unfortunately, all current NIR-II fluorophores are excreted slowly and are largely retained within the reticuloendothelial system, making clinical translation nearly impossible. Here, we report a rapidly excreted NIR-II fluorophore (∼90% excreted through the kidneys within 24 h) based on a synthetic 970-Da organic molecule (CH1055). The fluorophore outperformed indocyanine green (ICG)-a clinically approved NIR-I dye-in resolving mouse lymphatic vasculature and sentinel lymphatic mapping near a tumour. High levels of uptake of PEGylated-CH1055 dye were observed in brain tumours in mice, suggesting that the dye was detected at a depth of ∼4 mm. The CH1055 dye also allowed targeted molecular imaging of tumours in vivo when conjugated with anti-EGFR Affibody. Moreover, a superior tumour-to-background signal ratio allowed precise image-guided tumour-removal surgery. PMID:26595119

  8. Morphological study on small molecule acceptor-based organic solar cells with efficiencies beyond 7% (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ma, Wei; Yan, He

    2015-10-01

    Despite the essential role of fullerenes in achieving best-performance organic solar cells (OSCs), fullerene acceptors have several drawbacks including poor light absorption, high-cost production and purification. For this reason, small molecule acceptor (SMA)-based OSCs have attracted much attention due to the easy tunability of electronic and optical properties of SMA materials. In this study, polymers with temperature dependent aggregation behaviors are combined with various small molecule acceptor materials, which lead to impressive power conversion efficiencies of up to 7.3%. The morphological and aggregation properties of the polymer:small molecule blends are studied in details. It is found that the temperature-dependent aggregation behavior of polymers allows for the processing of the polymer solutions at moderately elevated temperature, and more importantly, controlled aggregation and strong crystallization of the polymer during the film cooling and drying process. This results in a well-controlled and near-ideal polymer:small molecule morphology that is controlled by polymer aggregation during warm casting and thus insensitive to the choice of small molecules. As a result, several cases of highly efficient (PCE between 6-7.3%) SMA OSCs are achieved. The second part of this presentation will describe the morphology of a new small molecule acceptor with a unique 3D structure. The relationship between molecular structure and morphology is revealed.

  9. Photophysical Properties and Efficient, Stable, Electrogenerated Chemiluminescence of Donor-Acceptor Molecules Exhibiting Thermal Spin Upconversion.

    PubMed

    Ishimatsu, Ryoichi; Edura, Tomohiko; Adachi, Chihaya; Nakano, Koji; Imato, Toshihiko

    2016-03-24

    The photophysical properties and electrogenerated chemiluminescence (ECL) of three donor-acceptor molecules composed of dicyanobenzene and methyl-, tert-butyl-, and phenyl-substituted carbazolyl groups, 1,2,3,5-tetrakis(3,6-disubstituted-carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN-Me, 4CzIPN-tBu, and 4CzIPN-Ph, respectively) are described. These molecules show delayed fluorescence as a result of thermal spin upconversion from the lowest triplet state to the lowest singlet state at room temperature. The three molecules showed yellow to yellowish-red ECL. Remarkably, the ECL efficiencies of 4CzIPN-tBu in dichloromethane reached almost 40 %. Moreover, stable ECL was emitted from 4CzIPN-tBu and 4CzIPN-Ph. In case of 4CzIPN-Me, the ECL intensity decreased during voltage cycles because of polymerization. Quantum chemical calculations revealed that polymerization was inhibited by the steric hindrance of the bulky tert-butyl and phenyl groups on the carbazolyl moieties and lowered the spin density on the carbazolyl groups through electron conjugation for 4CzIPN-Ph. PMID:26916843

  10. Theoretical study of the interaction of electron donor and acceptor molecules with monolayer WS2

    NASA Astrophysics Data System (ADS)

    Zhou, C. J.; Yang, W. H.; Wu, Y. P.; Lin, W.; Zhu, H. L.

    2015-07-01

    With the aim of understanding recent experimental data concerning molecular doping in WS2-based FET gas sensors, we have investigated the interaction of NH3 and H2O molecules with monolayer WS2, by means of first-principles calculations. The structural relaxations and total energy calculations are performed to determine the preferential binding configurations and it is found that both NH3 and H2O molecules are physisorbed on monolayer WS2. The Bader analysis combined with the plane-averaged differential charge density results indicate that NH3 acts as the electron donor, while H2O acts as the electron acceptor, leading to n- and p-type doping of WS2, respectively. The charge transfer mechanism is discussed in light of the mixing of the molecular highest occupied molecular orbital and lowest unoccupied molecular orbital with the underlying WS2 orbitals. In addition, the modification of the work function is found to be almost linearly dependent on the total charge transfer. The modification of the work function and the carrier concentration can be obtained by tuning the molecule coverages, without destroying the band structure of monolayer WS2. The electrical sensitivities to the gas adsorption make WS2 a gas sensor that promises wide-ranging applications.

  11. Microscopic observation of dye molecules for solar cells on a titania surface

    NASA Astrophysics Data System (ADS)

    Koshiya, Shogo; Yamashita, Shunsuke; Kimoto, Koji

    2016-04-01

    The lateral distribution and coverage of Ru-based dye molecules, which are used for dye-sensitized solar cells (DSCs), were directly examined on a titania surface using high-resolution scanning transmission electron microscopy (STEM). The clean surface of a free-standing titania nanosheet was first confirmed with atomic resolution, and then, the nanosheet was used as a substrate. A single dye molecule on the titania nanosheet was visualized for the first time. The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules. The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies.

  12. Microscopic observation of dye molecules for solar cells on a titania surface

    PubMed Central

    Koshiya, Shogo; Yamashita, Shunsuke; Kimoto, Koji

    2016-01-01

    The lateral distribution and coverage of Ru-based dye molecules, which are used for dye-sensitized solar cells (DSCs), were directly examined on a titania surface using high-resolution scanning transmission electron microscopy (STEM). The clean surface of a free-standing titania nanosheet was first confirmed with atomic resolution, and then, the nanosheet was used as a substrate. A single dye molecule on the titania nanosheet was visualized for the first time. The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules. The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies. PMID:27087005

  13. Microscopic observation of dye molecules for solar cells on a titania surface.

    PubMed

    Koshiya, Shogo; Yamashita, Shunsuke; Kimoto, Koji

    2016-01-01

    The lateral distribution and coverage of Ru-based dye molecules, which are used for dye-sensitized solar cells (DSCs), were directly examined on a titania surface using high-resolution scanning transmission electron microscopy (STEM). The clean surface of a free-standing titania nanosheet was first confirmed with atomic resolution, and then, the nanosheet was used as a substrate. A single dye molecule on the titania nanosheet was visualized for the first time. The quantitative STEM images revealed an inhomogeneous dye-molecule distribution at the early stage of its absorption, i.e., the aggregation of the dye molecules. The majority of the titania surface was not covered by dye molecules, suggesting that optimization of the dye molecule distribution could yield further improvement of the DSC conversion efficiencies. PMID:27087005

  14. Investigating the Energy Transfer from Dye Molecules to DNA Stabilized Au Nanoparticles.

    PubMed

    Patel, Arun Singh; Sahoo, Harekrushna; Mohanty, T

    2016-09-01

    Double-stranded DNA stabilized gold nanoparticles (Au NPs) are synthesized by chemical reduction method and characterized with different spectroscopic techniques such as UV-Visible absorption, Fourier transform infrared (FTIR), & circular-dichroism (CD) as well as transmission electron microscopy (TEM). These NPs show absorption maximum at 520 nm and size of most of the particles are of the order of 3.5 ± 1.0 nm. These Au NPs show crystalline nature as confirmed from electron diffraction pattern. The effect of formation of Au NPs on the macromolecule has been studied using infrared and circular dichroism spectroscopy. Formation of NPs causes conformational changes in the DNA molecules. These Au NPs are further used as resonant energy acceptor of fluorescence emission from dye molecules (Rhodamine 6G). The fluorescence intensity of Rhodamine 6G (R6G) is quenched in presence of Au NPs. The effect of DNA molecules on the fluorescence quenching and the rate of energy transfer from R6G molecules to Au NPs have been explored. PMID:27422695

  15. Electronic structure of Fe- vs. Ru-based dye molecules

    SciTech Connect

    Johnson, Phillip S.; Himpsel, F. J.; Cook, Peter L.; Zegkinoglou, Ioannis; Garcia-Lastra, J. M.; Rubio, Angel; Ruther, Rose E.; Hamers, Robert J.

    2013-01-28

    In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe- and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-{pi}* transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-{pi}* transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.

  16. Theoretical investigation of self-assembled donor-acceptor phthalocyanine complexes and their application in dye-sensitized solar cells.

    PubMed

    Yu, Lijuan; Lin, Li; Liu, Yuwen; Li, Renjie

    2015-06-01

    A theoretical investigation of self-assembled donor-acceptor dyads (ZnPca, ZnPcb and ZnPcc) formed by axial coordination of zinc phthalocyanines appended with 4-carboxyl pyridine has been conducted with the density functional theory (DFT) method and time-dependent DFT (TD-DFT) calculations. A comparison between the molecular structures, atomic charges, molecular orbitals, UV-vis spectra and infrared (IR) spectra has been studied. Further, as sensitizers for the TiO2-based dye-sensitized solar cells, the photovoltaic performances have been investigated. The ZnPcc-sensitized solar cell exhibits a higher conversion efficiency than the ZnPcb and ZnPca-sensitized ones under AM 1.5G solar irradiation, while the ZnPca-sensitized cell performs the poorest due to the lack of peripheral substituents (n-butyoxyl groups) which can be confirmed by the result of the theoretical research. It shows that the directionality of charge transfer in the self-assembled donor-acceptor dyads is important and benefit for the efficiency of the DSSC. PMID:25917246

  17. Charge transfer in the electron donor-acceptor complexes of a meso-phenol BODIPY dye with chloranils and fullerenes

    NASA Astrophysics Data System (ADS)

    Karmakar, Animesh; Chaudhuri, Tandrima; Mula, Soumyaditya; Chattopadhyay, Subrata

    2015-02-01

    UV-Vis spectral investigations of electron donor-acceptor complexes of laser dye 2,6-Diethyl-4,4-difluoro-1,3,5,7-tetramethyl-8-(4‧-hydroxyphenyl)-4-bora-3a,4a-diaza-s-indecene (1c) with chloranils and fullerenes are reported in toluene medium. Well defined charge transfer (CT) absorption bands have been located in the visible region. Oscillator strengths, transition dipole and resonance energies of the CT complexes have been estimated. Vertical ionization potential of 1c has been determined utilizing Mulliken's equation. A possible mechanism for the interaction between electronic subsystems of chloranils, [60]- and [70]fullerenes with three different BODIPY dyes (1a, 1b and 1c shown in Fig. 1) have been discussed in comparing the parameters like degree of charge transfer and binding constant in nonpolar toluene. Comparison of 1c complexes is done with DFT/B3LYP/6-31G optimized gas phase geometries.

  18. Method and apparatus for passive optical dosimeter comprising caged dye molecules

    DOEpatents

    Sandison, David R.

    2001-07-03

    A new class of ultraviolet dosimeters is made possible by exposing caged dye molecules, which generate a dye molecule on exposure to ultraviolet radiation, to an exterior environment. Applications include sunburn monitors, characterizing the UV exposure history of UV-sensitive materials, especially including structural plastics, and use in disposable `one-use` optical equipment, especially medical devices.

  19. Synthesis, Structure, and Optical Studies of Donor-Acceptor-Type Near-Infrared (NIR) Aza-Boron-Dipyrromethene (BODIPY) Dyes.

    PubMed

    Balsukuri, Naresh; Lone, Mohsin Y; Jha, Prakash C; Mori, Shigeki; Gupta, Iti

    2016-05-20

    Six donor-acceptor-type near-infrared (NIR) aza-boron-dipyrromethene (BODIPY) dyes and their corresponding aza-dipyrrins were designed and synthesized. The donor moieties at the 1,7-positions of the aza-BODIPY core were varied from naphthyl to N-phenylcarbazole to N-butylcarbazole. The 3,5-positions were also substituted with phenyl or thienyl groups in the aza-BODIPYs. Photophysical, electrochemical, and computational studies were carried out. The absorption and emission spectra of aza-BODIPYs were significantly redshifted (≈100 nm) relative to the parent tetraphenylaza-BODIPY. Fluorescence studies suggested effective energy transfer (up to 93 %) from donor groups to the aza-BODIPY core in all of the compounds under study. Time-dependent (TD)-DFT studies indicated effective electronic interactions between energy donor groups and aza-dipyrrin unit in all the aza-BODIPYs studied. The HOMO-LUMO gap (ΔE) calculated from cyclic voltammetry data was found to be lower for six aza-BODIPYs relative to their corresponding aza-dipyrrins. PMID:26918806

  20. Physical description of the impregnation mechanism of dye molecules in contact with porous electrodes

    NASA Astrophysics Data System (ADS)

    Shahzad, N.; Alexe-Ionescu, A. L.; Tresso, E.; Barbero, G.

    2013-05-01

    We propose and discuss two models that take into account the decreasing of the bulk density of dyes molecules in contact with a porous electrode. We show that the models based on the standard adsorption phenomenon have to be considered just as fitting models, of limited physical significance. A more physical model has to take into account the diffusion of dye molecules into the channels present in the porous electrode and also the adsorption of dye molecules on the lateral surfaces of these channels. The agreement between the theoretical prediction of such a model and the experimental data is reasonably good.

  1. Graphene-catalyzed photoreduction of dye molecules revealed by graphene enhanced Raman spectroscopy.

    PubMed

    Lee, Bora; Kang, Jin Hyoun; Jo, Insu; Shin, Dongha; Hong, Byung Hee

    2016-02-01

    The unique electrical and optical properties of graphene have enabled its application in various photocatalysis reactions. However, graphene needs to be combined with photosensitizing co-catalysts such as TiO2 due to its negligible visible light absorption. Here, we report that the single layer graphene by itself is capable of catalyzing the photoreduction of dye molecules, which has been revealed by graphene-enhanced Raman spectroscopy studies. The proposed mechanism involves the electron transfer from graphene to temporarily empty HOMO states of photoexcited dye molecules, which can be interpreted as ultrafast hole transfer from dyes to graphene. We also confirm that graphene-encapsulated nitrobenzene dyes show less photoreduction, implying that the ambient hydrogen molecules are the important source of photoreduction into aniline dyes. The photocatalytic reactivity of graphene would find numerous energy and environmental applications in the future. PMID:26784530

  2. Systematic Investigations on the Roles of the Electron Acceptor and Neighboring Ethynylene Moiety in Porphyrins for Dye-Sensitized Solar Cells.

    PubMed

    Wei, Tiantian; Sun, Xi; Li, Xin; Ågren, Hans; Xie, Yongshu

    2015-10-01

    Cyanoacrylic and carboxyl groups have been developed as the most extensively used electron acceptor and anchoring group for the design of sensitizers for dye-sensitized solar cells. In terms of the photoelectric conversion efficiency, each of them has been demonstrated to be superior to the other one in certain cases. Herein, to further understand the effect of these two groups on cell efficiencies, a series of porphyrin sensitizers were designed and synthesized, with the acceptors systematically varied, and the effect of the neighboring ethynylene unit was also investigated. Compared with the sensitizer XW5 which contains a carboxyphenyl anchoring moiety directly linked to the meso-position of the porphyrin framework, the separate introduction of a strongly electron-withdrawing cyanoacrylic acid as the anchoring group or the insertion of an ethynylene unit can achieve broadened light absorption and IPCE response, resulting in higher Jsc and higher efficiency. Thus, compared with the efficiency of 4.77% for XW5, dyes XW1 and XW6 exhibit higher efficiencies of 7.09% and 5.92%, respectively. Simultaneous introduction of the cyanoacrylic acid and the ethynylene units into XW7 can further broaden light absorption and thus further improve the Jsc. However, XW7 exhibits the lowest Voc value, which is not only related to the floppy structure of the cyanoacrylic group but also related to the aggravated dye aggregation effect due to the extended framework. As a result, XW7 exhibits a relatively low efficiency of 5.75%. These results indicate that the combination of the ethynylene and cyanoacrylic groups is an unsuccessful approach. To address this problem, a cyano substituent was introduced to XW8 at the ortho position of the carboxyl group in the carboxyphenyl acceptor. Thus, XW8 exhibits the highest efficiency of 7.59% among these dyes. Further cosensitization of XW8 with XS3 dramatically improved the efficiency to 9.31%. PMID:26355437

  3. Imposed Orientation of Dye Molecules by Liquid Crystals and an Electric Field.

    ERIC Educational Resources Information Center

    Sadlej-Sosnowska, Nina

    1980-01-01

    Describes experiments using dye solutions in liquid crystals in which polar molecules are oriented in an electrical field and devices are constructed to change their color in response to an electric signal. (CS)

  4. Exciton dissociation at organic small molecule donor-acceptor interfaces (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Robey, Steven W.

    2015-08-01

    Exciton dissociation at organic semiconductor donor-acceptor (D-A) heterojunctions is critical for the performance of organic photovoltaic (OPV) structures. Interfacial charge separation and recombination processes control device efficiency. We have investigated these fundamental interfacial issues using time-resolved two-photon photoemission (TR-2PPE), coupled with the formation of well-controlled D-A structures by organic molecular beam epitaxy. The interfacial electronic and molecular structure of these model interfaces was well-characterized using scanning tunneling microscopy and ultraviolet photoemission. Exciton dissociation dynamics were investigated by using a sub-picosecond pump pulse to create Pc π-->π* transitions, producing a population of singlet (S1) Pc excitons. The subsequent decay dynamics of this population was monitored via photoemission with a time-delayed UV pulse. For CuPcC60 interfaces, S1 exciton population decay in the interfacial CuPc layer was much faster than decay in the bulk due to interfacial charge separation. The rate constant for exciton dissociation was found to be ≍ 7 x 10 12 sec-1 (≍ 140 fs). Excitons that lose energy via intersystem crossing (ISC) to triplet levels dissociate approximately 500 to 1000 times slower. The dependence of exciton dissociation on separation was also studied. Exciton dissociation falls of rapidly with distance from the interface. Dissociation from the 2nd, and subsequent, layers of H2Pc is reduced by at least a factor of 10 from that in the interfacial layer. Finally, investigations of the relative efficiency for interfacial exciton dissociation by alternative acceptors based on perylene cores, (perylene tetracarboxylic dianhydride, or PTCDA) compared to fullerene-based acceptors such as C60 will also be discussed.

  5. Optical Properties of 1,3-Bisdicyanovinylindane, an Electro-Acceptor, Attached Bisthienylethene Molecule.

    PubMed

    Lil, Xiaochuan; Han, Yuzhen; Son, Young-A

    2016-02-01

    An electron acceptor, 1,3-bisdicyanovinylindane, was attached to the skeleton of bisthienylethene. Photochromic behavior was investigated in THF. Under exposure of UVNisible light cycles, the solution color can be toggled between colorless and yellow. Good fatigue resistance and photo-/thermal-stability were demonstrated with acceptable degradation. A full-photo mode switch was established. Optimized structure and molecular orbital of ring-open and ring-closed isomers were calculated on the platform of DmoP. The photochromic behavior was further supported by the required distance between photocyclizing atoms in antiparallel conformation. The absorption spectra change derived from calculation was in agreement with the experimental results. PMID:27433664

  6. Electronic structure of p-type perylene monoimide-based donor-acceptor dyes on the nickel oxide (100) surface: a DFT approach.

    PubMed

    Kontkanen, O V; Niskanen, M; Hukka, T I; Rantala, T T

    2016-05-25

    A p-type dye-sensitized solar cell, where the dye injects a hole into the semiconductor, could be combined with a typical Grätzel cell to create an efficient tandem device. However, the current p-type devices suffer from low efficiency. Here, geometries and electronic structures of four perylenemonoimide-based dyes () both as free and adsorbed on the NiO(100) semiconductor surface have been investigated to gain a better understanding of the p-type devices. In particular, the electronic transitions relevant to charge transfer between the dye and the surface have been identified. Excitations have been evaluated using the time-dependent DFT calculations, and the roles of frontier orbitals and band edges in transitions have been assessed. The adsorbed dyes can adopt either upright or slightly tilted geometries depending on the structure of the anchoring group and the binding mode of the dye. The adsorption slightly lowers the NiO band gap, from 4.06 eV to 3.90-3.96 eV, depending on the surface-adsorbate system and the band gaps of the dye molecules by 0.1-0.2 eV. Additionally, the adsorption mode of dye moves the LUMO+1 level down by 0.5 eV. The effective mass of charge carrier holes is significantly smaller at the NiO surface than in the bulk indicating the importance of surface conductivity. We also found that the potential drop, i.e. the driving force for charge transfer from NiO to the dye molecule, depends on the adsorption mode of . PMID:27224900

  7. Probes labelled with energy transfer coupled dyes

    DOEpatents

    Mathies, R.A.; Glazer, A.; Ju, J.

    1997-11-18

    Compositions are provided comprising sets of fluorescent labels carrying pairs of donor and acceptor dye molecules, designed for efficient excitation of the donors at a single wavelength and emission from the acceptor in each of the pairs at different wavelengths. The different molecules having different donor-acceptor pairs can be modified to have substantially the same mobility under separation conditions, by varying the distance between the donor and acceptor in a given pair. Particularly, the fluorescent compositions find use as labels in sequencing nucleic acids. 7 figs.

  8. Probes labelled with energy transfer coupled dyes

    DOEpatents

    Mathies, Richard A.; Glazer, Alexander; Ju, Jingyue

    1997-01-01

    Compositions are provided comprising sets of fluorescent labels carrying pairs of donor and acceptor dye molecules, designed for efficient excitation of the donors at a single wavelength and emission from the acceptor in each of the pairs at different wavelengths. The different molecules having different donor-acceptor pairs can be modified to have substantially the same mobility under separation conditions, by varying the distance between the donor and acceptor in a given pair. Particularly, the fluorescent compositions find use as labels in sequencing nucleic acids.

  9. Aggregation of dye molecules and its influence on the spectral luminescent properties of solutions

    NASA Astrophysics Data System (ADS)

    Yuzhakov, V. I.

    1992-06-01

    The principal results of studies carried out in recent years on the molecular aggregation of organic dyes and pigments in solutions are examined and surveyed in the present review. Attention is concentrated on the influence of association on the photoenergetics of the dye molecules. Theoretical studies on the spectral-luminescent spectroscopic characteristics of the molecular aggregates are briefly considered. Studies on the anisotropy of the absorption and on the emission from the associated species are described. Investigations of the concentration depolarisation and concentration quenching of the fluorescence of dye solutions are subjected to a critical analysis. The results of studies of the mixed association of dye molecules and of its influence on the lasing characteristics of the solutions are presented. The physicochemical conditions affecting the efficiency of the association process are examined. The bibliography includes 251 references.

  10. Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules III: A Benchmark of GW Methods.

    PubMed

    Knight, Joseph W; Wang, Xiaopeng; Gallandi, Lukas; Dolgounitcheva, Olga; Ren, Xinguo; Ortiz, J Vincent; Rinke, Patrick; Körzdörfer, Thomas; Marom, Noa

    2016-02-01

    The performance of different GW methods is assessed for a set of 24 organic acceptors. Errors are evaluated with respect to coupled cluster singles, doubles, and perturbative triples [CCSD(T)] reference data for the vertical ionization potentials (IPs) and electron affinities (EAs), extrapolated to the complete basis set limit. Additional comparisons are made to experimental data, where available. We consider fully self-consistent GW (scGW), partial self-consistency in the Green's function (scGW0), non-self-consistent G0W0 based on several mean-field starting points, and a "beyond GW" second-order screened exchange (SOSEX) correction to G0W0. We also describe the implementation of the self-consistent Coulomb hole with screened exchange method (COHSEX), which serves as one of the mean-field starting points. The best performers overall are G0W0+SOSEX and G0W0 based on an IP-tuned long-range corrected hybrid functional with the former being more accurate for EAs and the latter for IPs. Both provide a balanced treatment of localized vs delocalized states and valence spectra in good agreement with photoemission spectroscopy (PES) experiments. PMID:26731609

  11. Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules II: Non-Empirically Tuned Long-Range Corrected Hybrid Functionals.

    PubMed

    Gallandi, Lukas; Marom, Noa; Rinke, Patrick; Körzdörfer, Thomas

    2016-02-01

    The performance of non-empirically tuned long-range corrected hybrid functionals for the prediction of vertical ionization potentials (IPs) and electron affinities (EAs) is assessed for a set of 24 organic acceptor molecules. Basis set-extrapolated coupled cluster singles, doubles, and perturbative triples [CCSD(T)] calculations serve as a reference for this study. Compared to standard exchange-correlation functionals, tuned long-range corrected hybrid functionals produce highly reliable results for vertical IPs and EAs, yielding mean absolute errors on par with computationally more demanding GW calculations. In particular, it is demonstrated that long-range corrected hybrid functionals serve as ideal starting points for non-self-consistent GW calculations. PMID:26731340

  12. Donor-acceptor small molecules for organic photovoltaics: single-atom substitution (Se or S).

    PubMed

    He, Xiaoming; Cao, Bing; Hauger, Tate C; Kang, Minkyu; Gusarov, Sergey; Luber, Erik J; Buriak, Jillian M

    2015-04-22

    Two isostructural low-band-gap small molecules that contain a one-atom substitution, S for Se, were designed and synthesized. The molecule 7,7'-[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene]bis[6-fluoro-4-(5'-hexyl-2,2'-bithiophen-5-yl)benzo[c][1,2,5]thiadiazole] (1) and its selenium analogue 7,7'-[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene]bis[6-fluoro-4-(5'-hexyl-2,2'-bithiophen-5-yl)benzo[c][1,2,5]selenodiazole] (2) are both based on the electron-rich central unit benzo[1,2-b:4,5-b']dithiophene. The aim of this work was to investigate the effect of one-atom substitution on the optoelectronic properties and photovoltaic performance of devices. Theoretical calculations revealed that this one-atom variation has a small but measurable effect on the energy of frontier molecular orbital (HOMO and LUMO), which, in turn, can affect the absorption profile of the molecules, both neat and when mixed in a bulk heterojunction (BHJ) with PC71BM. The Se-containing variant 2 led to higher efficiencies [highest power conversion efficiency (PCE) of 2.6%] in a standard organic photovoltaic architecture, when combined with PC71BM after a brief thermal annealing, than the S-containing molecule 1 (highest PCE of 1.0%). Studies of the resulting morphologies of BHJs based on 1 and 2 showed that one-atom substitution could engender important differences in the solubilities, which then influenced the crystal orientations of the small molecules within this thin layer. Brief thermal annealing resulted in rotation of the crystalline grains of both molecules to more energetically favorable configurations. PMID:25808481

  13. Structural control of donor-acceptor mechanically interlocked molecules and supramolecular complexes

    NASA Astrophysics Data System (ADS)

    Friedman, Douglas Cary

    aided the structural analysis, are described. The final chapter describes how to control the secondary structure of donor-acceptor oligorotaxanes in which electron-poor tetracationic cyclophanes encircle electron-rich aromatic recognition sites linked by polyether chains. Design aspects, including built-in [pi···pi] stacking and [C--H···O] and [C--H···pi] interactions, are critical to ensure the discrete, extended secondary structures envisioned in the design and which are evidenced by comprehensive 1H NMR spectroscopic analyses.

  14. Synthesis of an A-D-A type of molecule used as electron acceptor for improving charge transfer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Chao-Zhi; Gu, Shu-Duo; Shen, Dan; Yuan, Yang; Zhang, Mingdao

    2016-08-01

    Electron-accepting molecules play an important role in developing organic solar cells. A new type of A-D-A molecule, 3,6-di([7-(5-bromothiophen-2-yl)-1,5,2,4,6,8-dithiotetrazocin-3-yl]thiophen-2-yl)-9-(2-ethylhexyl)carbazole, was synthesized. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels are -3.55 and -5.85 eV, respectively. Therefore, the A-D-A type of compound could be used as electron acceptor for fabricating organic solar cell with a high open circuit voltage. Gibbs free energy (-49.2 kJ/mol) reveals that the process of A-D-A acceptor accepting an electron from poly(3-hexylthiophene) at excited state is spontaneous. The value of entropy (118 J/mol) in the process of an electron transferring from P3HT to the A-D-A acceptor at organic interface suggests that electrons generated from separation of electron-hole pairs at donor/acceptor interface would be delocalized efficiently. Therefore, the A-D-A molecule would be a potential acceptor for efficient organic BHJ solar cells.

  15. Increased Efficiency in Small Molecule Organic Solar Cells Through the Use of a 56-π Electron Acceptor - Methano Indene Fullerene

    NASA Astrophysics Data System (ADS)

    Ryan, James W.; Matsuo, Yutaka

    2015-02-01

    Organic solar cells (OSCs) offer the possibility of harnessing the sun's ubiquitous energy in a low-cost, environmentally friendly and renewable manner. OSCs based on small molecule semiconductors (SMOSCs) - have made a substantial improvement in recent years and are now achieving power conversion efficiencies (PCEs) that match those achieved for polymer:fullerene OSCs. To date, all efficient SMOSCs have relied on the same fullerene acceptor, PCBM, in order to achieve high performance. The use of PCBM however, is unfavourable due to its low lying LUMO level, which limits the open-circuit voltage (VOC). Alternative fullerene derivatives with higher lying LUMOs are thus required to improve the VOC. The challenge, however, is to prevent the typical concomitant decrease in the short circuit current density (JSC) when using a higher LUMO fullerene. In this communication, we address the issue by applying methano indene fullerene, MIF, a bis-functionalised C60 fullerene that has a LUMO level 140 mV higher than PCBM, in solution processed SMOSCs with a well known small molecule donor, DPP(TBFu)2. MIF-based devices show an improved VOC of 140 mV over PC61BM and only a small decrease in the JSC, with the PCE increasing to 5.1% (vs. 4.5% for PC61BM).

  16. Structural systematic features of photoelectric effect in aromatic polymers with polymethine dyes

    SciTech Connect

    Aleksandrova, E. L.

    2007-12-15

    The structural systematic features of quantum-yield variation in charge-carrier photogeneration are investigated for polymer systems with molecules into which polymethine dyes of various structures had been introduced. The correlations between the quantum yields and the second-harmonic-generation efficiency in the media containing such dyes are revealed, and relations of the quantum yields to such dye-molecule structural parameters as the ionization potential of its donor fragment, the electron affinity of its acceptor fragment, and the electron-transfer distance between donor and acceptor fragments of the dye molecule are established.

  17. Indan-1,3-dione electron-acceptor small molecules for solution-processable solar cells: a structure-property correlation.

    PubMed

    Winzenberg, Kevin N; Kemppinen, Peter; Scholes, Fiona H; Collis, Gavin E; Shu, Ying; Singh, Th Birendra; Bilic, Ante; Forsyth, Craig M; Watkins, Scott E

    2013-07-18

    A structure-device performance correlation in bulk heterojunction solar cells for new indandione-derived small molecule electron acceptors, FEHIDT and F8IDT, is presented. Devices based on the former exhibit higher power conversion efficiency (2.4%) and higher open circuit voltage, a finding consistent with reduced intermolecular interactions. PMID:23739171

  18. The interplay of thermally activated delayed fluorescence (TADF) and room temperature organic phosphorescence in sterically-constrained donor-acceptor charge-transfer molecules.

    PubMed

    Ward, Jonathan S; Nobuyasu, Roberto S; Batsanov, Andrei S; Data, Przemyslaw; Monkman, Andrew P; Dias, Fernando B; Bryce, Martin R

    2016-02-11

    A series of phenothiazine-dibenzothiophene-S,S-dioxide charge-transfer molecules have been synthesized. Increasing steric restriction around the donor-acceptor bond significantly alters contributions from TADF and phosphorescence. Bulky substituents on the 1-(and 9) position(s) of the phenothiazine result in no TADF in the solid state; instead strong phosphorescence is observed at ambient temperature. PMID:26750426

  19. Cooperative Emission of Dye Molecules at High Dephasing Rates

    NASA Astrophysics Data System (ADS)

    Klochkov, V. P.; Verkhovskiĭ, E. B.

    2000-05-01

    The dependence of the emission of a concentrated (˜1019 cm-3 solution of Rhodamine C on the power density Φ of exciting laser radiation was studied. The emission intensity for the power density of exciting radiation above ˜1025 cm-2 s-1 was found to have a nearly quadratic dependence on the power density Φ, and this emission was interpreted as the cooperative spontaneous emission of a Dicke type. For Φ≲1025 cm-2 s-1, the emission intensity increased with increasing Φ according to the exponential law. This emission was interpreted as the amplified spontaneous emission. The spectra of cooperative emission depended on the pump radiation power only weakly. The absence of lasing in dye solutions at high concentrations, which is a well-known phenomenon, was shown to be caused by the development of the cooperative spontaneous emission and not by the concentration quenching, and the former process is more rapid than the latter.

  20. A proactive role of water molecules in acceptor recognition by protein O-fucosyltransferase 2.

    PubMed

    Valero-González, Jessika; Leonhard-Melief, Christina; Lira-Navarrete, Erandi; Jiménez-Osés, Gonzalo; Hernández-Ruiz, Cristina; Pallarés, María Carmen; Yruela, Inmaculada; Vasudevan, Deepika; Lostao, Anabel; Corzana, Francisco; Takeuchi, Hideyuki; Haltiwanger, Robert S; Hurtado-Guerrero, Ramon

    2016-04-01

    Protein O-fucosyltransferase 2 (POFUT2) is an essential enzyme that fucosylates serine and threonine residues of folded thrombospondin type 1 repeats (TSRs). To date, the mechanism by which this enzyme recognizes very dissimilar TSRs has been unclear. By engineering a fusion protein, we report the crystal structure of Caenorhabditis elegans POFUT2 (CePOFUT2) in complex with GDP and human TSR1 that suggests an inverting mechanism for fucose transfer assisted by a catalytic base and shows that nearly half of the TSR1 is embraced by CePOFUT2. A small number of direct interactions and a large network of water molecules maintain the complex. Site-directed mutagenesis demonstrates that POFUT2 fucosylates threonine preferentially over serine and relies on folded TSRs containing the minimal consensus sequence C-X-X-S/T-C. Crystallographic and mutagenesis data, together with atomic-level simulations, uncover a binding mechanism by which POFUT2 promiscuously recognizes the structural fingerprint of poorly homologous TSRs through a dynamic network of water-mediated interactions. PMID:26854667

  1. Acceptor End-Capped Oligomeric Conjugated Molecules with Broadened Absorption and Enhanced Extinction Coefficients for High-Efficiency Organic Solar Cells.

    PubMed

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

    2016-07-01

    Acceptor end-capping of oligomeric conjugated molecules is found to be an effective strategy for simultaneous spectral broadening, extinction coefficient enhancement, and energy level optimization, resulting in profoundly enhanced power conversion efficiencies (of 9.25% and 8.91%) compared to the original oligomers. This strategy is effective in overcoming the absorption disadvantage of oligomers and small molecules due to conjugation limitation. PMID:27172541

  2. Dye energy transfer in xerogel matrices and application to solid-state dye lasers

    NASA Astrophysics Data System (ADS)

    Nhung, Tran Hong; Canva, Michael; Chaput, Frédéric; Goudket, Hélène; Roger, Gisèle; Brun, Alain; Manh, Dang Duc; Hung, Nguyen Dai; Boilot, Jean-Pierre

    2004-03-01

    Laser dyes Rhodamine B and Perylene Red were incorporated at different relative concentrations into hybrid matrices synthesized using the sol-gel process. Energy transfer from Rhodamine B-donor to Perylene Red-acceptor molecules was observed. Using the different co-doped samples, solid-state dye laser systems were achieved with tuning band position control and increased efficiency with respect to the materials using solely one type of dye.

  3. Microscopic simulations of electronic excitations in donor-acceptor heterojunctions of small-molecule based solar cells

    NASA Astrophysics Data System (ADS)

    Baumeier, Bjoern

    2015-03-01

    Fundamental processes involving electronic excitations govern the functionality of molecular materials in which the dynamics of excitons and charges is determined by an interplay of molecular electronic structure and morphological order. To understand, e.g., charge separation and recombination at donor-acceptor heterojunctions in organic solar cells, knowledge about the microscopic details influencing these dynamics in the bulk and across the interface is required. For a set of prototypical heterojunctions of small-molecule donor materials with C60, we employ a hybrid QM/MM approach linking density-functional and many-body Green's functions theory and analyze the charged and neutral electronic excitations therein. We pay special attention the spatially-resolved electron/hole transport levels, as well as the relative energies of Frenkel and charge-transfer excitations at the interface. Finally, we link the molecular architecture of the donor material, its orientation on the fullerene substrate as well as mesoscale order to the solar cell performance.

  4. (Dibenzoylmethanato)boron difluoride derivatives containing triphenylamine moieties: a new type of electron-donor/π-acceptor system for dye-sensitized solar cells.

    PubMed

    Mizuno, Yosuke; Yisilamu, Yilihamu; Yamaguchi, Tomoya; Tomura, Masaaki; Funaki, Takashi; Sugihara, Hideki; Ono, Katsuhiko

    2014-10-01

    (Dibenzoylmethanato)boron difluoride derivatives containing triphenylamine moieties were synthesized as a new type of electron-donor/π-acceptor system. These new compounds exhibited long-wavelength absorptions in the UV/Vis spectra, and reversible oxidation and reduction waves in cyclic voltammetry experiments. Their amphoteric redox properties are based on their resonance hybrid forms, in which a positive charge is delocalized on the triphenylamine moieties and a negative charge is localized on the boron atoms. Molecular orbital (MO) calculations indicate that their HOMO and LUMO energies vary with the number of phenylene rings connected to the difluoroboron-chelating ring. This is useful for optimizing the HOMO and LUMO levels to an iodine redox (I(-)/I3(-)) potential and a titanium dioxide conduction band, respectively. Dye-sensitized solar cells fabricated by using these compounds as dye sensitizers exhibited solar-to-electric power conversion efficiencies of 2.7-4.4 % under AM 1.5 solar light. PMID:25170797

  5. Donors contribute more than acceptors to increase the two-photon activity--a case study with cyclopenta[b]naphthalene based molecules.

    PubMed

    Alam, Md Mehboob

    2014-12-21

    In the present work, we address the question -"which among the electron donors and the electron acceptors contribute more to the two-photon (TP) activity of a donor-π-acceptor type of molecule?" For this purpose we have performed ab initio calculations to calculate the TP transition probability (δTP) of a recently synthesized (Benedetti et al., J. Am. Chem. Soc., 2012, 134(30), 12418-12421) cyclopenta[b]naphthalene based chemo-sensor and its derivatives containing different electron donor and acceptor groups. Our study revealed that both under vacuum and in solvent phases, an increase in electron donor strength (-OMe, -NH2, -NMe2) increases the δTP value up to five times, whereas, an increase in the acceptor group strength (-COCH3, -NO2, -CN) increases it by a factor of two only. The highest δTP value is obtained for the molecule having the strongest donor-acceptor pair (-CN, -NMe2) considered in this work. We have also noted that, the removal of the cyclopentane ring from the original system increases the δTP value by ∼20% and the replacement of the naphthyl group by the benzene ring decreases it by ∼70%. All these results are explained by inspecting different TP tensor elements and different transition moment vectors involved in a two-state model approach. A close scrutiny of different parameters in 2SM clearly reveals that upon increasing the strength of either the donor or the acceptor group the parameters change in favour of increasing the overall δTP values but in the case of donors this effect is much larger. PMID:25367708

  6. Superresolution imaging of single DNA molecules using stochastic photoblinking of minor groove and intercalating dyes.

    PubMed

    Miller, Helen; Zhou, Zhaokun; Wollman, Adam J M; Leake, Mark C

    2015-10-15

    As proof-of-principle for generating superresolution structural information from DNA we applied a method of localization microscopy utilizing photoblinking comparing intercalating dye YOYO-1 against minor groove binding dye SYTO-13, using a bespoke multicolor single-molecule fluorescence microscope. We used a full-length ∼49 kbp λ DNA construct possessing oligo inserts at either terminus allowing conjugation of digoxigenin and biotin at opposite ends for tethering to a glass coverslip surface and paramagnetic microsphere respectively. We observed stochastic DNA-bound dye photoactivity consistent with dye photoblinking as opposed to binding/unbinding events, evidenced through both discrete simulations and continuum kinetics analysis. We analyzed dye photoblinking images of immobilized DNA molecules using superresolution reconstruction software from two existing packages, rainSTORM and QuickPALM, and compared the results against our own novel home-written software called ADEMS code. ADEMS code generated lateral localization precision values of 30-40 nm and 60-70 nm for YOYO-1 and SYTO-13 respectively at video-rate sampling, similar to rainSTORM, running more slowly than rainSTORM and QuickPALM algorithms but having a complementary capability over both in generating automated centroid distribution and cluster analyses. Our imaging system allows us to observe dynamic topological changes to single molecules of DNA in real-time, such as rapid molecular snapping events. This will facilitate visualization of fluorescently-labeled DNA molecules conjugated to a magnetic bead in future experiments involving newly developed magneto-optical tweezers combined with superresolution microscopy. PMID:25637032

  7. Optical orientation of azo dye molecules in a thin solid film upon nonlinear excitation by femtosecond laser pulses

    SciTech Connect

    Yongseok, Jung; Kozenkov, V M; Magnitskiy, Sergey A; Nagorskiy, Nikolay M

    2006-11-30

    The orientation of molecules in an amorphous pure azo dye film upon nonlinear excitation is detected for the first time. The simultaneous increase and decrease in the film transmission by a factor of 2.5 for orthogonal polarisations of probe radiation indicated the appearance of orientation order in the film caused by the reorientation of azo dye molecules. Due to a high photostability of the AD-1 azo dye demonstrated in single-photon experiments and a high efficiency of nonlinear orientation obtained in experiments with femtosecond pulses, this dye can be widely used in three-dimensional nanophotonic devices such as photonic crystals, optical computers, and optical memory. (letters)

  8. Two-photon absorption and spectroscopy of the lowest two-photon transition in small donor-acceptor-substituted organic molecules

    NASA Astrophysics Data System (ADS)

    Beels, Marten T.; Biaggio, Ivan; Reekie, Tristan; Chiu, Melanie; Diederich, François

    2015-04-01

    We determine the dispersion of the third-order polarizability of small donor-acceptor substituted organic molecules using wavelength-dependent degenerate four-wave mixing experiments in solutions with varying concentrations. We find that donor-acceptor-substituted molecules that are characterized by extremely efficient off-resonant nonlinearities also have a correspondingly high two-photon absorption cross section. The width and shape of the first two-photon resonance for these noncentrosymmetric molecules follows what is expected from their longest wavelength absorption peak, and the observed two-photon absorption cross sections are record high when compared to the available literature data, the size of the molecule, and the fundamental limit for two-photon absorption to the lowest excited state, which is essentially determined by the number of conjugated electrons and the excited-state energies. The two-photon absorption of the smallest molecule, which only has 16 electrons in its conjugated system, is one order of magnitude larger than for the molecule called AF-50, a reference molecule for two-photon absorption [O.-K. Kim et al., Chem. Mater. 12, 284 (2000), 10.1021/cm990662r].

  9. Functionalization of boron-doped nanocrystalline diamond with N3 dye molecules.

    PubMed

    Yeap, W S; Liu, X; Bevk, D; Pasquarelli, A; Lutsen, L; Fahlman, M; Maes, W; Haenen, K

    2014-07-01

    N3 dye molecules [cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II)] are covalently attached to boron-doped nanocrystalline diamond (B:NCD) thin films through a combination of coupling chemistries, i.e., diazonium, Suzuki, and EDC-NHS. X-ray and ultraviolet photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy are used to verify the covalent bonding of the dye on the B:NCD surface (compared to a hydrogen-terminated reference). The spectroscopic results confirm the presence of a dense N3 chromophore layer, and the positions of the frontier orbitals of the dye relative to the band edge of the B:NCD thin film are inferred as well. Proof-of-concept photoelectrochemical measurements show a strong increase in the photocurrent compared to non-dye-functionalized B:NCD films. This study opens up the possibility of applying N3-sensitized B:NCD thin films as hole conductors in dye-sensitized solar cells. PMID:24915549

  10. In Situ Mapping of the Molecular Arrangement of Amphiphilic Dye Molecules at the TiO₂ Surface of Dye-Sensitized Solar Cells.

    PubMed

    Voïtchovsky, Kislon; Ashari-Astani, Negar; Tavernelli, Ivano; Tétreault, Nicolas; Rothlisberger, Ursula; Stellacci, Francesco; Grätzel, Michael; Harms, Hauke A

    2015-05-27

    Amphiphilic sensitizers are central to the function of dye-sensitized solar cells. It is known that the cell's performance depends on the molecular arrangement and the density of the dye on the semiconductor surface, but a molecular-level picture of the cell-electrolyte interface is still lacking. Here, we present subnanometer in situ atomic force microscopy images of the Z907 dye at the surface of TiO2 in a relevant liquid. Our results reveal changes in the conformation and the lateral arrangement of the dye molecules, depending on their average packing density on the surface. Complementary quantitative measurements on the ensemble of the film are obtained by the quartz-crystal microbalance with dissipation technique. An atomistic picture of the dye coverage-dependent packing, the effectiveness of the hydrophobic alkyl chains as blocking layer, and the solvent accessibility is obtained from molecular dynamics simulations. PMID:25936429

  11. Optical devices based on dye-coated superconductor junctions: An example of a composite molecule-superconductor device

    SciTech Connect

    Zhao, J.; Jurbergs, D.; Yamazi, B.; McDevitt, J.T.

    1992-03-25

    High-temperature superconductors provide new opportunities as materials used in the construction of hybrid molecule-superconductor components. Here, the authors describe fabrication methods for and operation of optical sensors based on molecular dye-coated superconductor junctions. Devices prepared from yttrium barium cuprates and using octaethylporphyrin, phthalocyanine, and rhodamine 6G as dyes have been prepared. 9 refs., 1 fig.

  12. Impact of local compressive stress on the optical transitions of single organic dye molecules

    NASA Astrophysics Data System (ADS)

    Stöttinger, Sven; Hinze, Gerald; Diezemann, Gregor; Oesterling, Ingo; Müllen, Klaus; Basché, Thomas

    2014-03-01

    The ability to mechanically control the optical properties of individual molecules is a grand challenge in nanoscience and could enable the manipulation of chemical reactivity at the single-molecule level. In the past, light has been used to alter the emission wavelength of individual molecules or modulate the energy transfer quantum yield between them. Furthermore, tensile stress has been applied to study the force dependence of protein folding/unfolding and of the chemistry and photochemistry of single molecules, although in these mechanical experiments the strength of the weakest bond limits the amount of applicable force. Here, we show that compressive stress modifies the photophysical properties of individual dye molecules. We use an atomic force microscope tip to prod individual molecules adsorbed on a surface and follow the effect of the applied force on the electronic states of the molecule by fluorescence spectroscopy. Applying a localized compressive force on an isolated molecule induces a stress that is redistributed throughout the structure. Accordingly, we observe reversible spectral shifts and even shifts that persist after retracting the microscope tip, which we attribute to transitions to metastable states. Using quantum-mechanical calculations, we show that these photophysical changes can be associated with transitions among the different possible conformers of the adsorbed molecule.

  13. Controlled energy transfer between isolated donor-acceptor molecules intercalated in thermally self-ensemble two-dimensional hydrogen bonding cages

    NASA Astrophysics Data System (ADS)

    Al Attar, Hameed A.; Monkman, Andrew P.

    2012-12-01

    Thermally assembled hydrogen bonding cages which are neither size nor guest specific have been developed using a poly (vinyl alcohol) (PVA) host. A water-soluble conjugated polymer poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylene, disodium salt-alt-1,4-phenylene) (PPP-OPSO3) as a donor and tris(2,2-bipyridyl)- ruthenium(II) [Ru(bpy)32+] as an acceptor have been isolated and trapped in such a PVA matrix network. This is a unique system that shows negligible exciton diffusion and the donor and acceptor predominantly interact by a direct single step excitation transfer process (DSSET). Singlet and triplet exciton quenching have been studied. Time-resolved fluorescence lifetime measurement at different acceptor concentrations has enabled us to determine the dimensionality of the energy-transfer process within the PVA scaffold. Our results reveal that the PVA hydrogen bonding network effectively isolates the donor-acceptor molecules in a two-dimensional layer structure (lamella) leading to the condition where a precise control of the energy and charge transfer is possible.

  14. Enhancement of p-Type Dye-Sensitized Solar Cell Performance by Supramolecular Assembly of Electron Donor and Acceptor

    PubMed Central

    Tian, Haining; Oscarsson, Johan; Gabrielsson, Erik; Eriksson, Susanna K.; Lindblad, Rebecka; Xu, Bo; Hao, Yan; Boschloo, Gerrit; Johansson, Erik M. J.; Gardner, James M.; Hagfeldt, Anders; Rensmo, Håkan; Sun, Licheng

    2014-01-01

    Supramolecular interactions based on porphyrin and fullerene derivatives were successfully adopted to improve the photovoltaic performance of p-type dye-sensitized solar cells (DSCs). Photoelectron spectroscopy (PES) measurements suggest a change in binding configuration of ZnTCPP after co-sensitization with C60PPy, which could be ascribed to supramolecular interaction between ZnTCPP and C60PPy. The performance of the ZnTCPP/C60PPy-based p-type DSC has been increased by a factor of 4 in comparison with the DSC with the ZnTCPP alone. At 560 nm, the IPCE value of DSCs based on ZnTCPP/C60PPy was a factor of 10 greater than that generated by ZnTCPP-based DSCs. The influence of different electrolytes on charge extraction and electron lifetime was investigated and showed that the enhanced Voc from the Co2+/3+(dtbp)3-based device is due to the positive EF shift of NiO. PMID:24603319

  15. Encapsulation of dye molecules and nanoparticles in hollow organogel fibers of a nonchiral polyurethane model compound.

    PubMed

    Khan, Mostofa Kamal; Sundararajan, Pudupadi

    2011-01-24

    We present the case of a nonchiral organogelator that forms hollow fibers and encapsulates silver nanoparticles (SNP) and a dye molecule. The biscarbamate molecule (a model compound for polyurethanes), which has two hydrogen-bonding motifs symmetrically attached to n-dodecyl side chains (C(12)), gels benzonitrile with hollow fibrillar morphology. The C(12) molecules form sheets that eventually wrap into hollow fibers to form the gel network. Herein, two-component gels were prepared with C(12) as one component and SNP, phthalocyanine (Pc), or perylene (Pe) as the other. Microscopic analysis and partial melting experiments confirmed the inclusion of the silver nanoparticles and phthalocyanine into the hollow fibers. On the other hand, Pe molecules tend to form crystals at the outer surface of the C(12) fibers, which results in a significant increase in the width of the gel fibers. This difference in the behavior of Pc and Pe molecules were accounted for by their crystal geometry and significantly different crystal growth rate compared with that of C(12) fiber formation in the gels. Pc crystallizes in a needle shape that facilitates occlusion in the gel fibers, whereas Pe forms large platelets. X-ray diffraction and spectroscopic analysis of the two-component gels along with their neat components confirmed that there was no change in the packing behavior of the Pc and Pe molecules in the gels. Therefore, these are examples of two-component physical gels in which the Pc crystals are occluded within the hollow fibers of C(12) by physical mixing of the components without the aid of any inter-molecular interactions between the different components. We have thus shown that lumen-loaded gel fibers with nanoparticles and dye molecules can be prepared by the two-component gel route, provided that the above growth rate, shape, and size conditions are satisfied. PMID:21243684

  16. Lifetime of fluorescent dye molecules in dense aqueous suspensions of polystyrene nanoparticles.

    PubMed

    Scalia, Giuseppe; Scheffold, Frank

    2015-11-16

    We study the lifetime of two common fluorescent dye molecules from the Alexa Fluor NHS Ester family dissolved in water in an opaque aqueous dispersion of dielectric polystyrene nanoparticles. We investigate the role of the dispersion composition by varying the particle concentration and adding SDS (sodium dodecyl sulfate) surfactant molecules. The observed strong changes in lifetime of Alexa 430 can be attributed to the relative contribution of radiative and non-radiative decay channels while the lifetime of the Alexa 488 dye depends only weakly on the sample composition. For Alexa 430, a dye with a rather low quantum yield in aqueous solution, the addition of polystyrene nanoparticles leads to a significant enhancement in quantum yield and an associated increase of the fluorescent lifetime by up to 55 %. We speculate that the increased quantum yield can be attributed to the hydrophobic effect on the structure of water in the boundary layer around the polystyrene particles in suspension. Adding SDS acts as a quencher. Over a range of particle concentrations the particle induced increase of the lifetime can be completely compensated by adding SDS. PMID:26698418

  17. Shedding light on the photostability of two intermolecular charge-transfer complexes between highly fluorescent bis-1,8-naphthalimide dyes and some π-acceptors: A spectroscopic study in solution and solid states

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.; Ismail, Lamia A.; Adam, Abdel Majid A.

    2015-01-01

    Given the great importance of the various uses of 1,8-naphthalimides in the trends of biology, medicine and industry, the current study focused on extending the scope of these dyes by introducing some of their charge-transfer (CT) complexes. For this purpose, two highly fluorescent bis-1,8-naphthalimide dyes and their complexes with some π-acceptors have been synthesized and characterized spectroscopically. The π-acceptors include picric acid (PA), chloranilic acid (CLA), tetracyanoquinodimethane (TCNQ) and dichlorodicyanobenzoquinone (DDQ). The molecular structure, spectroscopic and fluorescence properties as well as the binding modes were deduced from IR, UV-vis and 1H NMR spectral studies. The binding ratio of complexation was determined to be 1:1 according to the elemental analyses and photometric titrations. It has been found that the order of acceptance ability for the different acceptors is TCNQ > DDQ > CLA > PA. The photostability of 1,8-naphthalimide dye as a donor and its charge-transfer complex doped in polymethyl methacrylate/PMMA were exposed to UV-Vis radiation and the change in the absorption spectra was achieved at different times during irradiation period.

  18. Shedding light on the photostability of two intermolecular charge-transfer complexes between highly fluorescent bis-1,8-naphthalimide dyes and some π-acceptors: a spectroscopic study in solution and solid states.

    PubMed

    Refat, Moamen S; Ismail, Lamia A; Adam, Abdel Majid A

    2015-01-01

    Given the great importance of the various uses of 1,8-naphthalimides in the trends of biology, medicine and industry, the current study focused on extending the scope of these dyes by introducing some of their charge-transfer (CT) complexes. For this purpose, two highly fluorescent bis-1,8-naphthalimide dyes and their complexes with some π-acceptors have been synthesized and characterized spectroscopically. The π-acceptors include picric acid (PA), chloranilic acid (CLA), tetracyanoquinodimethane (TCNQ) and dichlorodicyanobenzoquinone (DDQ). The molecular structure, spectroscopic and fluorescence properties as well as the binding modes were deduced from IR, UV-vis and (1)H NMR spectral studies. The binding ratio of complexation was determined to be 1:1 according to the elemental analyses and photometric titrations. It has been found that the order of acceptance ability for the different acceptors is TCNQ>DDQ>CLA>PA. The photostability of 1,8-naphthalimide dye as a donor and its charge-transfer complex doped in polymethyl methacrylate/PMMA were exposed to UV-Vis radiation and the change in the absorption spectra was achieved at different times during irradiation period. PMID:25022501

  19. Thermodynamic Driving Forces for Dye Molecule Position and Orientation in Nanoconfined Solvents.

    PubMed

    Harvey, Jacob A; Thompson, Ward H

    2015-07-23

    The results of replica exchange molecular dynamics simulations of a coumarin 153 (C153) dye molecule dissolved in ethanol confined within a 2.4 nm hydrophilic amorphous silica pore are presented. The C153 dye position and orientation distributions provide insight into time-dependent fluorescence measurements in nanoconfined solvents as well as general features of chemistry in mesoporous materials. In addition to the distributions themselves, the free energy, internal energy, and entropic contributions have been calculated to explore the factors determining the distributions. The most likely location of C153 is found to be near the pore surface, but two possible hydrogen-bonding structures lead to differing orientations. Internal energy and entropy are found to be competing forces within the pore, with entropy playing a significant role with unexpected consequences. These results represent a crucial step in determining how the nanoconfining framework can affect measurements of solvation dynamics. PMID:25295835

  20. Electron and hole transfer dynamics of a triarylamine-based dye with peripheral hole acceptors on TiO2 in the absence and presence of solvent.

    PubMed

    Oum, Kawon; Flender, Oliver; Lohse, Peter W; Scholz, Mirko; Hagfeldt, Anders; Boschloo, Gerrit; Lenzer, Thomas

    2014-05-01

    We investigated photoinduced primary charge transfer processes of the sensitizer E6 on TiO2 without solvent and in contact with the organic solvent acetonitrile and the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate [C2mim](+)[B(CN)4](-) using transient absorption spectroscopy, spectroelectrochemistry, and DFT/TDDFT calculations. E6, which belongs to a family of triarylamine dyes for solar cell applications, features two peripheral triarylamine units which are connected via diether spacer groups to the core chromophore and are designed to act as hole traps. This function was confirmed by spectroelectrochemistry, where the E6˙(+) radical cation shows a considerably blue-shifted absorption compared to dyes without these two substituents. This indicates that one of the terminal triarylamine units must carry the positive charge. After photoexcitation of E6 at 520 nm (S0 → S1 band), electrons are injected into TiO2 predominantly within the cross-correlation time (<80 fs), with some subsequent delayed electron injection (τ ca. 250 fs). Importantly, a transient Stark shift (electrochromism) is observed (time constants ca. 0.8 and 12 ps) which is related to a changing electric field generated by the E6˙(+) radical cations and injected electrons. This field induces absorption shifts of the dye species on the surface. Interestingly, these dynamics are largely unaffected by solvent molecules. However, pronounced differences are observed on longer timescales. In contact with solvent, one observes an increase in the E6˙(+) absorption band above 600 nm with a time constant of 75 ps. This is assigned to hole transfer from the core chromophore to one of the peripheral triarylamine substituents. Electron-cation recombination occurs on much longer timescales and is multiexponential, with time constants of ca. 100 μs, 1 ms and 15 ms. Because of hole trapping, it is slower than for similar dyes lacking the peripheral triarylamines. Additional experiments were

  1. Evaluation of thermodynamic and photophysical properties of tricarbocyanine near-IR dyes in organized media using single-molecule monitoring

    NASA Astrophysics Data System (ADS)

    Soper, Steven A.; Legendre, Benjamin L., Jr.; Huang, Jiping

    1995-05-01

    Detection of single NIR fluorescent dye molecules in the organized media sodium dodecyl sulfate (SDS) and triton X-100 surfactnts above their critical micelle concentrations was used to determine partition coefficients and photophysical properties of dye molecules resident within the micelle aggregate. Inspection of the filtered data showed evidence of large amplitude photon bursts arising from single molecular events in these organized media. In pure H 2O containing dye, no bursts were observed. The results indicate that only molecules resident within the hydrophobic core of the micelle were detected. From the number of events observed and the number of events expected, partition coefficients ( Kp) for IR-132 in SDS and triton X-100 solutions were calculated. In addition, the photon yield per molecule associated with only those molecules resident within the hydrophobic cavity of the micelle was determined.

  2. Playing with dye molecules at the inner and outer surface of zeolite L

    NASA Astrophysics Data System (ADS)

    Calzaferri, Gion; Brühwiler, Dominik; Megelski, Silke; Pfenniger, Michel; Pauchard, Marc; Hennessy, Brian; Maas, Huub; Devaux, André; Graf, Urs

    2000-06-01

    Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to

  3. Strength of interactions between immobilized dye molecules and sol-gel matrices.

    PubMed

    Ismail, Fanya; Schoenleber, Monika; Mansour, Rolan; Bastani, Behnam; Fielden, Peter; Goddard, Nicholas J

    2011-02-21

    In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel. PMID:21120245

  4. Factoring the contribution of through-space and through-bond interactions to rates of photoinduced electron transfer in donor- spacer-acceptor molecules using ultrafast transient absorption spectroscopy

    SciTech Connect

    Gosztola, D.; Wang, Bing; Wasielewski, M.R. |

    1996-06-01

    Contributions from through-space and through-bond interactions to the electronic coupling matrix elements for photoinduced charge separation and recombination in linked donor-spacer-acceptor molecules were studied. The molecules consisted of a 4-piperidinyl-naphthalene-1,8-dicarboximide electron donor and a N-(n-octyl)pyromellitimide electron acceptor attached to the 1,5- and 1,8-positions of either anthracene or dibenzobicyclo(2.2.2)octatriene spacers.

  5. Rapid Energy Transfer Enabling Control of Emission Polarization in Perylene Bisimide Donor-Acceptor Triads.

    PubMed

    Menelaou, Christopher; ter Schiphorst, Jeroen; Kendhale, Amol M; Parkinson, Patrick; Debije, Michael G; Schenning, Albertus P H J; Herz, Laura M

    2015-04-01

    Materials showing rapid intramolecular energy transfer and polarization switching are of interest for both their fundamental photophysics and potential for use in real-world applications. Here, we report two donor-acceptor-donor triad dyes based on perylene-bisimide subunits, with the long axis of the donors arranged either parallel or perpendicular to that of the central acceptor. We observe rapid energy transfer (<2 ps) and effective polarization control in both dye molecules in solution. A distributed-dipole Förster model predicts the excitation energy transfer rate for the linearly arranged triad but severely underestimates it for the orthogonal case. We show that the rapid energy transfer arises from a combination of through-bond coupling and through-space transfer between donor and acceptor units. As they allow energy cascading to an excited state with controllable polarization, these triad dyes show high potential for use in luminescent solar concentrator devices. PMID:26262968

  6. Large pi-aromatic molecules as potential sensitizers for highly efficient dye-sensitized solar cells.

    PubMed

    Imahori, Hiroshi; Umeyama, Tomokazu; Ito, Seigo

    2009-11-17

    Recently, dye-sensitized solar cells have attracted much attention relevant to global environmental issues. Thus far, ruthenium(II) bipyridyl complexes have proven to be the most efficient TiO(2) sensitizers in dye-sensitized solar cells. However, a gradual increment in the highest power conversion efficiency has been recognized in the past decade. More importantly, considering that ruthenium is a rare metal, novel dyes without metal or using inexpensive metal are desirable for highly efficient dye-sensitized solar cells. Large pi-aromatic molecules, such as porphyrins, phthalocyanines, and perylenes, are important classes of potential sensitizers for highly efficient dye-sensitized solar cells, owing to their photostability and high light-harvesting capabilities that can allow applications in thinner, low-cost dye-sensitized solar cells. Porphyrins possess an intense Soret band at 400 nm and moderate Q bands at 600 nm. Nevertheless, the poor light-harvesting properties relative to the ruthenium complexes have limited the cell performance of porphyrin-sensitized TiO(2) cells. Elongation of the pi conjugation and loss of symmetry in porphyrins cause broadening and a red shift of the absorption bands together with an increasing intensity of the Q bands relative to that of the Soret band. On the basis of the strategy, the cell performance of porphyrin-sensitized solar cells has been improved intensively by the enhanced light absorption. Actually, some push-pull-type porphyrins have disclosed a remarkably high power conversion efficiency (6-7%) that was close to that of the ruthenium complexes. Phthalocyanines exhibit strong absorption around 300 and 700 nm and redox features that are similar to porphyrins. Moreover, phthalocyanines are transparent over a large region of the visible spectrum, thereby enabling the possibility of using them as "photovoltaic windows". However, the cell performance was poor, owing to strong aggregation and lack of directionality in the

  7. Third order optical nonlinearities characteristics of Disperse Red1 organic dye molecules inside of polymeric nanocapsules

    NASA Astrophysics Data System (ADS)

    Sharifimehr, Mohammad Reza; Ayoubi, Kazem; Mohajerani, Ezeddin

    2015-11-01

    Measuring nonlinear optical response of a specific material in a mixture, not only leads to investigate the behavior of a particular component in various circumstances, but also can be a way to select suitable combination and optimum concentration of additives and therefore obtaining the maximum nonlinear optical signals. In this work, by using dual-arm Z-scan technique, the nonlinear refractive index of Disperse Red1 (DR1) organic dye molecules inside the core of prepared polymeric nanocapsules was measured among various materials which prepared nanocapsules were made of them. Then the measured value was compared with nonlinear refractive index of DR1 solved in dichloromethane.

  8. Synthesis, photophysical and electrochemical properties of two novel carbazole-based dye molecules

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Zhu, Weiju; Fang, Min; Yin, Fangfang; Li, Cun

    2015-01-01

    Two carbazole-based dye molecules: 3-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-2-cyano-acylic acid (D3) and 3-[5-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-thiophen-2-yl]-2-cyan-acylic acid (D4) were synthesized by an approach from carbazole derivate using Vilsmeier-Haack, Suzuki cross-coupling and Knoevenagel reactions. Their physical and electrochemical properties were investigated. D3 and D4 exhibit different optical properties, such as UV absorption, photoluminescence, fluorescence quantum yield and fluorescence lifetime in different solvents. Compared with D3 without a thiophene unit, the maximum absorption wavelength of D4 red-shift obviously and its fluorescence intensity is also enhanced. A shift of the EHOMO and ELUMO is observed for D3 (EHOMO = 2.06 V, ELUMO = -1.39 V vs. NHE) and D4 (EHOMO = 1.73 V, ELUMO = -1.33 V vs. NHE). D3 and D4 can be used as dyes for dye-sensitized solar cells (DSSCs) with TiO2 nanomaterial because their EHOMO are lower than the conduction band edge of TiO2 [-0.5 V (vs. NHE)] and their ELUMO are higher than the I3-/I- redox potential [0.42 V (vs. NHE)].

  9. Synthesis, photophysical and electrochemical properties of two novel carbazole-based dye molecules.

    PubMed

    Zhang, Qing; Zhu, Weiju; Fang, Min; Yin, Fangfang; Li, Cun

    2015-01-25

    Two carbazole-based dye molecules: 3-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-2-cyano-acylic acid (D3) and 3-[5-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-thiophen-2-yl]-2-cyan-acylic acid (D4) were synthesized by an approach from carbazole derivate using Vilsmeier-Haack, Suzuki cross-coupling and Knoevenagel reactions. Their physical and electrochemical properties were investigated. D3 and D4 exhibit different optical properties, such as UV absorption, photoluminescence, fluorescence quantum yield and fluorescence lifetime in different solvents. Compared with D3 without a thiophene unit, the maximum absorption wavelength of D4 red-shift obviously and its fluorescence intensity is also enhanced. A shift of the EHOMO and ELUMO is observed for D3 (EHOMO=2.06 V, ELUMO=-1.39 V vs. NHE) and D4 (EHOMO=1.73 V, ELUMO=-1.33 V vs. NHE). D3 and D4 can be used as dyes for dye-sensitized solar cells (DSSCs) with TiO2 nanomaterial because their EHOMO are lower than the conduction band edge of TiO2 [-0.5 V (vs. NHE)] and their ELUMO are higher than the I(3-)/I(-) redox potential [0.42 V (vs. NHE)]. PMID:25104283

  10. Determining the exact number of dye molecules attached to colloidal CdSe/ZnS quantum dots in Förster resonant energy transfer assemblies

    NASA Astrophysics Data System (ADS)

    Kaiser, Uwe; Jimenez de Aberasturi, Dorleta; Vázquez-González, Margarita; Carrillo-Carrion, Carolina; Niebling, Tobias; Parak, Wofgang J.; Heimbrodt, Wolfram

    2015-01-01

    Semiconductor quantum dots functionalized with organic dye molecules are important tools for biological sensor applications. Energy transfer between the quantum dot and the attached dyes can be utilized for sensing. Though important, the determination of the real number of dye molecules attached per quantum dot is rather difficult. In this work, a method will be presented to determine the number of ATTO-590 dye molecules attached to CdSe/ZnS quantum dots based on time resolved spectral analysis. The energy transfer from the excited quantum dot to the attached ATTO-590 dye leads to a reduced lifetime of the quantum dot's excitons. The higher the concentration of dye molecules, the shorter the excitonic lifetime becomes. However, the number of dye molecules attached per quantum dot will vary. Therefore, for correctly explaining the decay of the luminescence upon photoexcitation of the quantum dot, it is necessary to take into account the distribution of the number of dyes attached per quantum dot. A Poisson distribution of the ATTO-590 dye molecules not only leads to excellent agreement between experimental and theoretical decay curves but also additionally yields the average number of dye molecules attached per quantum dot. In this way, the number of dyes per quantum dot can be conveniently determined.

  11. Determining the exact number of dye molecules attached to colloidal CdSe/ZnS quantum dots in Förster resonant energy transfer assemblies

    SciTech Connect

    Kaiser, Uwe; Jimenez de Aberasturi, Dorleta; Vázquez-González, Margarita; Carrillo-Carrion, Carolina; Niebling, Tobias; Parak, Wofgang J.; Heimbrodt, Wolfram

    2015-01-14

    Semiconductor quantum dots functionalized with organic dye molecules are important tools for biological sensor applications. Energy transfer between the quantum dot and the attached dyes can be utilized for sensing. Though important, the determination of the real number of dye molecules attached per quantum dot is rather difficult. In this work, a method will be presented to determine the number of ATTO-590 dye molecules attached to CdSe/ZnS quantum dots based on time resolved spectral analysis. The energy transfer from the excited quantum dot to the attached ATTO-590 dye leads to a reduced lifetime of the quantum dot's excitons. The higher the concentration of dye molecules, the shorter the excitonic lifetime becomes. However, the number of dye molecules attached per quantum dot will vary. Therefore, for correctly explaining the decay of the luminescence upon photoexcitation of the quantum dot, it is necessary to take into account the distribution of the number of dyes attached per quantum dot. A Poisson distribution of the ATTO-590 dye molecules not only leads to excellent agreement between experimental and theoretical decay curves but also additionally yields the average number of dye molecules attached per quantum dot. In this way, the number of dyes per quantum dot can be conveniently determined.

  12. Understanding and controlling laser-matter interactions: From solvated dye molecules to polyatomic molecules in gas phase

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha

    The goal of my research is to obtain a better understanding of the various processes that occur during and following laser-matter interactions from both the physical and chemical point of view. In particular I focused my research on understanding two very important aspects of laser-matter interaction; 1) Intense laser-matter interactions for polyatomic molecules in the gas phase in order to determine to what extent processes like excitation, ionization and fragmentation can be controlled by modifying the phase and amplitude of the laser field according to the timescales for electronic, vibrational and rotational energy transfer. 2) Developing pulse shaping based single beam methods aimed at studying solvated molecules in order to elucidate processes like inhomogeneous broadening, solvatochromic shift and to determine the electronic coherence lifetimes of solvated molecules. The effect of the chirped femtosecond pulses on fluorescence and stimulated emission from solvated dye molecules was studied and it was observed that the overall effect depends quadratically on pulse energy, even where excitation probabilities range from 0.02 to 5%, in the so-called "linear excitation regime". The shape of the chirp dependence is found to be independent of the energy of the pulse. It was found that the chirp dependence reveals dynamics related to solvent rearrangement following excitation and also depends on electronic relaxation of the chromophore. Furthermore, the chirped pulses were found to be extremely sensitive to solvent environment and that the complementary phases having the opposite sign provide information about the electronic coherence lifetimes. Similar to chirped pulses, the effects of a phase step on the excitation spectrum and the corresponding changes to the stimulated emission spectrum were also studied and it was found that the coherent feature on the spectrum is sensitive to the dephasing time of the system. Therefore a single phase scanning method can

  13. Structure-properties relationships in triarylamine-based donor-acceptor molecules containing naphtyl groups as donor material for organic solar cells

    PubMed Central

    Mohamed, Salma; Demeter, Dora; Laffitte, Jean-Alex; Blanchard, Philippe; Roncali, Jean

    2015-01-01

    The effects of replacing the phenyl rings of triphenylamine (TPA) by naphtyl groups are analysed on a series of push-pull molecules containing a 2-thienyl-dicyanovinyl acceptor group. UV-Vis absorption spectroscopy and cyclic voltammetry show that the introduction of one or two naphtyl groups in the structure has limited effects on the optical properties and energy levels of the molecule. On the other hand, the evaluation of the compounds as donor material in bi-layer solar cells with C60 as acceptor shows that the number and mode of linkage of the naphtyl groups exert a marked influence on the power conversion efficiency (PCE) of the cell. Two naphtyl groups lead to a decrease of PCE with respect to TPA, while a single naphtyl group produces opposite effects depending on the linking mode. Compared to TPA, an alpha-naphtyl group leads to a small decrease of PCE while in contrast a beta-naphtyl leads to a ~35% increase of PCE due to improved short-circuit current density (Jsc) and fill-factor. The determination of the hole-mobility of these two donors by the space-charge-limited current method shows that these effects are correlated with the higher hole-mobility of the β-naphtyl compound. PMID:25761773

  14. Influence of the layer thickness and concentration of dye molecules on the emission amplification in cholesteric liquid crystals

    SciTech Connect

    Alaverdyan, R B; Gevorgyan, A A; Chilingaryan, A D; Chilingaryan, Yu S

    2008-05-31

    The propagation of light through a planar layer of a cholesteric liquid crystal doped with dye molecules is considered. The features of the emission spectra of the crystal are studied both in the absence and presence of dielectric boundaries. The increase in the emission intensity is investigated for different layer thicknesses and different concentrations of dye molecules. It is shown that an anomalously strong increase in the emission intensity with the diffraction intrinsic polarisation takes place in the case of a comparatively small crystal thickness and a relatively low concentration of dye molecules. The obtained results can be used for the development of miniature lasers with the circular polarisation of the fundamental radiation mode. (laser applications and other topics in quantum electronics)

  15. Single-Photon Source for Quantum Information Based on Single Dye Molecule Fluorescence in Liquid Crystal Host

    SciTech Connect

    Lukishova, S.G.; Knox, R.P.; Freivald, P.; McNamara, A.; Boyd, R.W.; Stroud, Jr., C.R.; Schmid, A.W.; Marshall, K.L.

    2006-08-18

    This paper describes a new application for liquid crystals: quantum information technology. A deterministically polarized single-photon source that efficiently produces photons exhibiting antibunching is a pivotal hardware element in absolutely secure quantum communication. Planar-aligned nematic liquid crystal hosts deterministically align the single dye molecules which produce deterministically polarized single (antibunched) photons. In addition, 1-D photonic bandgap cholesteric liquid crystals will increase single-photon source efficiency. The experiments and challenges in the observation of deterministically polarized fluorescence from single dye molecules in planar-aligned glassy nematic-liquid-crystal oligomer as well as photon antibunching in glassy cholesteric oligomer are described for the first time.

  16. A Research Module for the Organic Chemistry Laboratory: Multistep Synthesis of a Fluorous Dye Molecule.

    PubMed

    Slade, Michael C; Raker, Jeffrey R; Kobilka, Brandon; Pohl, Nicola L B

    2014-01-14

    A multi-session research-like module has been developed for use in the undergraduate organic teaching laboratory curriculum. Students are tasked with planning and executing the synthesis of a novel fluorous dye molecule and using it to explore a fluorous affinity chromatography separation technique, which is the first implementation of this technique in a teaching laboratory. Key elements of the project include gradually introducing students to the use of the chemical literature to facilitate their searching, as well as deliberate constraints designed to force them to think critically about reaction design and optimization in organic chemistry. The project also introduces students to some advanced laboratory practices such as Schlenk techniques, degassing of reaction mixtures, affinity chromatography, and microwave-assisted chemistry. This provides students a teaching laboratory experience that closely mirrors authentic synthetic organic chemistry practice in laboratories throughout the world. PMID:24501431

  17. Pulsed laser induced birefringence switching in a biopolymer matrix containing azo-dye molecules

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Jaroslaw; Ziemienczuk, Marta; Miniewicz, Andrzej

    2011-07-01

    All optical switching has been studied using the Optical Kerr Effect (OKE) configuration in a biopolymer matrix containing an azo-dye: the Disperse Orange 3 (DO3). The biopolymer system consisted of a deoxyribonucleic acid blended with cationic surfactant molecule cetyltrimethyl-ammonium chloride is suitable for optical quality thin film fabrication. The excitation beams inducing birefringence were delivered from a continuous wave laser at 532 nm and another nanosecond pulsed Nd: YAG laser. The birefringence was instantaneously monitored under crossed polarizer system by a weak non-absorbed light from a cw He-Ne laser working at 632.8 nm. Fast all optical switching process (in the range of microseconds) and excellent reversibility have been observed.

  18. Time resolved FRET measurement in various heterogeneous media using merocyanine dye as a donor

    NASA Astrophysics Data System (ADS)

    Kedia, Niraja; Bagchi, Sanjib

    2015-06-01

    Ultrafast fluorescence resonance energy transfer (FRET) from a merocyanine dye to a Rhodamine 6G (R6G) molecule in micelles formed by the surfactants SDS and DTAB and also in a catanionic vesicle formed by SDS and DTAB has been studied by picosecond time resolved emission spectroscopy. Here the dye acts as a donor molecule and R6G acts as the acceptor molecule. Multiple timescales of FRET have been detected, namely, an ultrafast component of 100-500 ps and relatively long component (1800-3300 ps). The different time scales are attributed to different donor-acceptor distances.

  19. Dye-Binding Assays for Evaluation of the Effects of Small Molecule Inhibitors on Amyloid (Aβ) Self-Assembly

    PubMed Central

    2012-01-01

    Dye-binding assays, such as those utilizing Congo red and thioflavin T, are among the most widely used tools to probe the aggregation of amyloidogenic biomolecules and for the evaluation of small molecule inhibitors of amyloid aggregation and fibrillization. A number of recent reports have indicated that these dye-binding assays could be prone to false positive effects when assessing inhibitors’ potential toward Aβ peptides, species involved in Alzheimer’s disease. Specifically, this review focuses on the application of thioflavin T for determining the efficiency of small molecule inhibitors of Aβ aggregation and addresses potential reasons that might be associated with the false positive effects in an effort to increase reliability of dye-binding assays. PMID:23173064

  20. A large βzzz of π-extended molecules tetra-substituted by meta-positioned donor-acceptor pairs

    NASA Astrophysics Data System (ADS)

    Tomonari, Mutsumi; Ookubo, Norio

    2003-07-01

    We computationally studied hyperpolarizability β of C 2v fused-ring molecules substituted by two pairs of meta- or para-positioned donor (D)-acceptor (A). In two types of meta-substituted isomers, the meta1-type showed small βzzz, being plausible since the meta-positioned D-A pairs indicated the resonance structures not preferable for the large charge transfer (CT). Nevertheless, the meta2-type showed a large βzzz resulting from a large forward CT associated with the HOMO-LUMO transition. This βzzz increased with the number of fused-rings (the x-extension) and decreased slightly with small structural changes by the geometry optimization, but these changes did not vary the dominant CT structure. The x-extension was ineffective to the large βzzz for the para-substituted isomer.

  1. The Human Iron–Sulfur Assembly Complex Catalyzes the Synthesis of [2Fe-2S] Clusters on ISCU2 That Can Be Transferred to Acceptor Molecules

    PubMed Central

    Fox, Nicholas G.; Chakrabarti, Mrinmoy; McCormick, Sean P.; Lindahl, Paul A.; Barondeau, David P.

    2015-01-01

    Iron–sulfur (Fe–S) clusters are essential protein cofactors for most life forms. In human mitochondria, the core Fe–S biosynthetic enzymatic complex (called SDUF) consists of NFS1, ISD11, ISCU2, and frataxin (FXN) protein components. Few mechanistic details about how this complex synthesizes Fe–S clusters and how these clusters are delivered to targets are known. Here circular dichroism and Mössbauer spectroscopies were used to reveal details of the Fe–S cluster assembly reaction on the SDUF complex. SDUF reactions generated [2Fe-2S] cluster intermediates that readily converted to stable [2Fe-2S] clusters bound to uncomplexed ISCU2. Similar reactions that included the apo Fe–S acceptor protein human ferredoxin (FDX1) resulted in formation of [2Fe-2S]-ISCU2 rather than [2Fe-2S]-FDX1. Subsequent addition of dithiothreitol (DTT) induced transfer of the cluster from ISCU2 to FDX1, suggesting that [2Fe-2S]-ISCU2 is an intermediate. Reactions that initially included DTT rapidly generated [2Fe-2S]-FDX1 and bypassed formation of [2Fe-2S]-ISCU2. In the absence of apo-FDX1, incubation of [2Fe-2S]-ISCU2 with DTT generated [4Fe-4S]-ISCU2 species. Together, these results conflict with a recent report of stable [4Fe-4S] cluster formation on the SDUF complex. Rather, they support a model in which SDUF builds transient [2Fe-2S] cluster intermediates that generate clusters on sulfur-containing molecules, including uncomplexed ISCU2. Additional small molecule or protein factors are required for the transfer of these clusters to Fe–S acceptor proteins or the synthesis of [4Fe-4S] clusters. PMID:26016389

  2. Charge transfer interactions of a Ru(II) dye complex and related ligand molecules adsorbed on Au(111)

    SciTech Connect

    Britton, Andrew J.; Weston, Matthew; O'Shea, James N.; Taylor, J. Ben; Rienzo, Anna; Mayor, Louise C.

    2011-10-28

    The interaction of the dye molecule, N3 (cis-bis(isothiocyanato)bis(2,2{sup '}-bipyridyl-4,4{sup '}-dicarboxylato) -ruthenium(II)), and related ligand molecules with a Au(111) surface has been studied using synchrotron radiation-based electron spectroscopy. Resonant photoemission spectroscopy (RPES) and autoionization of the adsorbed molecules have been used to probe the coupling between the molecules and the substrate. Evidence of charge transfer from the states near the Fermi level of the gold substrate into the lowest unoccupied molecular orbital (LUMO) of the molecules is found in the monolayer RPES spectra of both isonicotinic acid and bi-isonicotinic acid (a ligand of N3), but not for the N3 molecule itself. Calibrated x-ray absorption spectroscopy and valence band spectra of the monolayers reveals that the LUMO crosses the Fermi level of the surface in all cases, showing that charge transfer is energetically possible both from and to the molecule. A core-hole clock analysis of the resonant photoemission reveals a charge transfer time of around 4 fs from the LUMO of the N3 dye molecule to the surface. The lack of charge transfer in the opposite direction is understood in terms of the lack of spatial overlap between the {pi}*-orbitals in the aromatic rings of the bi-isonicotinic acid ligands of N3 and the gold surface.

  3. Quantitative Structure of an Acetate Dye Molecule Analogue at the TiO2–Acetic Acid Interface

    PubMed Central

    2016-01-01

    The positions of atoms in and around acetate molecules at the rutile TiO2(110) interface with 0.1 M acetic acid have been determined with a precision of ±0.05 Å. Acetate is used as a surrogate for the carboxylate groups typically employed to anchor monocarboxylate dye molecules to TiO2 in dye-sensitized solar cells (DSSC). Structural analysis reveals small domains of ordered (2 × 1) acetate molecules, with substrate atoms closer to their bulk terminated positions compared to the clean UHV surface. Acetate is found in a bidentate bridge position, binding through both oxygen atoms to two 5-fold titanium atoms such that the molecular plane is along the [001] azimuth. Density functional theory calculations provide adsorption geometries in excellent agreement with experiment. The availability of these structural data will improve the accuracy of charge transport models for DSSC. PMID:27110318

  4. Increased Efficiency in Small Molecule Organic Solar Cells Through the Use of a 56-π Electron Acceptor – Methano Indene Fullerene

    PubMed Central

    Ryan, James W.; Matsuo, Yutaka

    2015-01-01

    Organic solar cells (OSCs) offer the possibility of harnessing the sun's ubiquitous energy in a low-cost, environmentally friendly and renewable manner. OSCs based on small molecule semiconductors (SMOSCs) – have made a substantial improvement in recent years and are now achieving power conversion efficiencies (PCEs) that match those achieved for polymer:fullerene OSCs. To date, all efficient SMOSCs have relied on the same fullerene acceptor, PCBM, in order to achieve high performance. The use of PCBM however, is unfavourable due to its low lying LUMO level, which limits the open-circuit voltage (VOC). Alternative fullerene derivatives with higher lying LUMOs are thus required to improve the VOC. The challenge, however, is to prevent the typical concomitant decrease in the short circuit current density (JSC) when using a higher LUMO fullerene. In this communication, we address the issue by applying methano indene fullerene, MIF, a bis-functionalised C60 fullerene that has a LUMO level 140 mV higher than PCBM, in solution processed SMOSCs with a well known small molecule donor, DPP(TBFu)2. MIF-based devices show an improved VOC of 140 mV over PC61BM and only a small decrease in the JSC, with the PCE increasing to 5.1% (vs. 4.5% for PC61BM). PMID:25661976

  5. A linewidth-narrowed and frequency-stabilized dye laser for application in laser cooling of molecules.

    PubMed

    Dai, D P; Xia, Y; Yin, Y N; Yang, X X; Fang, Y F; Li, X J; Yin, J P

    2014-11-17

    We demonstrate a robust and versatile solution for locking the continuous-wave dye laser for applications in laser cooling of molecules which need linewidth-narrowed and frequency-stabilized lasers. The dye laser is first stabilized with respect to a reference cavity by Pound-Drever-Hall (PDH) technique which results in a single frequency with the linewidth 200 kHz and short-term stabilization, by stabilizing the length of the reference cavity to a stabilized helium-neon laser we simultaneously transfer the ± 2 MHz absolute frequency stability of the helium-neon laser to the dye laser with long-term stabilization. This allows the dye laser to be frequency chirped with the maximum 60 GHz scan range while its frequency remains locked. It also offers the advantages of locking at arbitrary dye laser frequencies, having a larger locking capture range and frequency scanning range to be implemented via software. This laser has been developed for the purpose of laser cooling a molecular magnesium fluoride beam. PMID:25402105

  6. Revealing the interactions between pentagon-octagon-pentagon defect graphene and organic donor/acceptor molecules: a theoretical study.

    PubMed

    Li, Jie-Wei; Liu, Yu-Yu; Xie, Ling-Hai; Shang, Jing-Zhi; Qian, Yan; Yi, Ming-Dong; Yu, Ting; Huang, Wei

    2015-02-21

    Defect engineering and the non-covalent interaction strategy allow for dramatically tuning the optoelectronic features of graphene. Herein, we theoretically investigated the intrinsic mechanism of non-covalent interactions between pentagon-octagon-pentagon (5-8-5) defect graphene (DG) and absorbed molecules, tetrathiafulvalene (TTF), perfluoronaphthalene (FNa), tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), through geometry, distance, interaction energy, Mulliken charge distribution, terahertz frequency vibration, visualization of the interactions, charge density difference, electronic transition behaviour, band structure and density of state. All the calculations were performed using density functional theory including a dispersion correction (DFT-D). The calculated results indicate that the cyano- (CN) group (electron withdraw group) in TCNQ and F4TCNQ, rather than the F group, gain the electron from DG effectively and exhibit much stronger interactions via wavefunction overlap with DG, leading to a short non-covalent interaction distance, a large interaction energy and a red-shift of out-of-plane terahertz frequency vibration, changing the bands near the Fermi level and enhancing the infrared (IR) light absorption significantly. The enhancement of such IR absorbance offering a broader absorption (from 300 to 1200 nm) will benefit light harvesting in potential applications of solar energy conversion. PMID:25559269

  7. Bi-anchoring organic sensitizers of type D-(π-A)2 comprising thiophene-2-acetonitrile as π-spacer and malonic acid as electron acceptor for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Reddy, Gachumale Saritha; Ramkumar, Sekar; Asiri, Abdullah M.; Anandan, Sambandam

    2015-06-01

    Two new bi-anchoring organic sensitizers of type D-(π-A)2 comprising the identical π-spacer (thiophene-2-acetonitrile) and electron acceptor (malonic acid) but different aryl amine as electron donors (diphenylamine and carbazole) were synthesized, characterized and fabricated metal free dye-sensitized solar cell devices. The intra molecular charge transfer property and electrochemical property of these dyes were investigated by molecular absorption, emission, cyclic voltammetric experiments and in addition, quantum chemical calculation studies were performed to provide sufficient driving force for the electron injection into the conduction band of TiO2 which leads to efficient charge collection. Among the fabricated devices, carbazole based device exhibits high current conversion efficiency (η = 4.7%) with a short circuit current density (JSC) 15.3 mA/cm2, an open circuit photo voltage (VOC) of 0.59 V and a fill factor of 0.44 under AM 1.5 illumination (85 mW/cm2) compared to diphenylamine based device.

  8. Bi-anchoring organic sensitizers of type D-(π-A)₂ comprising thiophene-2-acetonitrile as π-spacer and malonic acid as electron acceptor for dye sensitized solar cell applications.

    PubMed

    Reddy, Gachumale Saritha; Ramkumar, Sekar; Asiri, Abdullah M; Anandan, Sambandam

    2015-06-15

    Two new bi-anchoring organic sensitizers of type D-(π-A)2 comprising the identical π-spacer (thiophene-2-acetonitrile) and electron acceptor (malonic acid) but different aryl amine as electron donors (diphenylamine and carbazole) were synthesized, characterized and fabricated metal free dye-sensitized solar cell devices. The intra molecular charge transfer property and electrochemical property of these dyes were investigated by molecular absorption, emission, cyclic voltammetric experiments and in addition, quantum chemical calculation studies were performed to provide sufficient driving force for the electron injection into the conduction band of TiO2 which leads to efficient charge collection. Among the fabricated devices, carbazole based device exhibits high current conversion efficiency (η=4.7%) with a short circuit current density (JSC) 15.3 mA/cm(2), an open circuit photo voltage (VOC) of 0.59 V and a fill factor of 0.44 under AM 1.5 illumination (85 mW/cm(2)) compared to diphenylamine based device. PMID:25801442

  9. Orientation and electronic structure of ion exchanged dye molecules on mica: An X-ray absorption study

    SciTech Connect

    Fischer, D.; Caseri, W.R.; Haehner, G.

    1998-02-15

    Dye molecules are frequently used to determine the specific surface area and the ion exchange capacity of high-surface-area materials such as mica. The organic molecules are often considered to be planar and to adsorb in a flat orientation. In the present study the authors have investigated the orientation and electronic structure of crystal violet (CV) and malachite green (MG) on muscovite mica, prepared by immersing the substrates for extended periods into aqueous solutions of the dyes of various concentrations. The K{sup +} ions of the mica surface are replaced by the organic cations via ion exchange. X-ray photoelectron spectroscopy reveals that only one amino group is involved in the interaction of CV and MG with the muscovite surface, i.e., certain resonance structures are abolished upon adsorption. With near edge X-ray absorption fine structure spectroscopy a significant tilt angle with respect to the surface was found for all investigated species. A flat orientation, as has often been proposed before, can effectively be ruled out. Hence, results are in marked contrast to the often quoted orientation and suggest that the specific surface areas determined with dyes may, in general, be overestimated.

  10. UV-Vis spectral investigation of photophysical properties of a solvatochromic electron donor/acceptor dye within a reverse micelle domain

    NASA Astrophysics Data System (ADS)

    Sarkar, Amrita; Kedia, Niraja; Purkayastha, Pradipta; Bagchi, Sanjib

    2014-01-01

    The optical response of a solvatochromic dye, [(E)-3-(1-methyl-1H-indol-3-yl)-1-phenylprop-2-en-1-one], N1, has been studied in the AOT/n-heptane/water reverse micellar media using steady-state and time-resolved techniques. To this end variation in the photophysical properties of N1 have been systematically studied as a function of water pool size (w0). Micropolarity, microviscosity, and relative permittivity of the immediate microenvironment surrounding the probe has been estimated from the limiting values of the photophysical parameters of N1 at high w0. Information about the location of the dye in the reverse micellar media has been obtained using the observed results.

  11. Spectroscopic studies of interactions between dyes and model molecules of Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Elhaddaoui, A.; Delacourte, A.; Turrell, S.

    1993-06-01

    Raman, FTIR, fluorescence, and UV-visible spectra are used to study interactions between amuloid-labelling dyes and poly-L-lysine and bovine insulin, two proteins which play the role of models of (beta) amyloid of Alzheimers disease. It is found that though the (beta) conformation of the peptide is not essential, it helps to encourage binding which appears to be stable and specific in nature, involving SO3- groups of the dyes and NH2 groups of the proteins.

  12. Influence of silver nanoparticles on relaxation processes and efficiency of dipole - dipole energy transfer between dye molecules in polymethylmethacrylate films

    NASA Astrophysics Data System (ADS)

    Bryukhanov, V. V.; Konstantinova, E. I.; Borkunov, R. Yu; Tsarkov, M. V.; Slezhkin, V. A.

    2015-10-01

    The fluorescence and phosphorescence of dyes in thin polymethylmethacrylate (PMMA) films in the presence of ablated silver nanoparticles has been investigated in a wide temperature range by methods of femtosecond and picosecond laser photoexcitation. The fluorescence and phosphorescence times, as well as spectral and kinetic characteristics of rhodamine 6G (R6G) molecules in PMMA films are measured in a temperature range of 80 - 330 K. The temperature quenching activation energy of the fluorescence of R6G molecules in the presence of ablated silver nanoparticles is found. The vibrational relaxation rate of R6G in PMMA films is estimated, the efficiency of the dipole - dipole electron energy transfer between R6G and brilliant green molecules (enhanced by plasmonic interaction with ablated silver nanoparticles) is analysed, and the constants of this energy transfer are determined.

  13. pMINERVA: A donor-acceptor system for the in vivo recombineering of scFv into IgG molecules.

    PubMed

    Batonick, M; Kiss, M M; Fuller, E P; Magadan, C M; Holland, E G; Zhao, Q; Wang, D; Kay, B K; Weiner, M P

    2016-04-01

    Phage display is the most widely used method for selecting binding molecules from recombinant antibody libraries. However, validation of the phage antibodies often requires early production of the cognate full-length immunoglobulin G (IgG). The conversion of phage library outputs to a full immunoglobulin via standard subcloning is time-consuming and limits the number of clones that can be evaluated. We have developed a novel system to convert scFvs from a phage display vector directly into IgGs without any in vitro subcloning steps. This new vector system, named pMINERVA, makes clever use of site-specific bacteriophage integrases that are expressed in Escherichia coli and intron splicing that occurs within mammalian cells. Using this system, a phage display vector contains both bacterial and mammalian regulatory regions that support antibody expression in E. coli and mammalian cells. A single-chain variable fragment (scFv) antibody is expressed on the surface of bacteriophage M13 as a genetic fusion to the gpIII coat protein. The scFv is converted to an IgG that can be expressed in mammalian cells by transducing a second E. coli strain. In that strain, the phiC31 recombinase fuses the heavy chain constant domain from an acceptor plasmid to the heavy chain variable domain and introduces controlling elements upstream of the light chain variable domain. Splicing in mammalian cells removes a synthetic intron containing the M13 gpIII gene to produce the fusion of the light chain variable domain to the constant domain. We show that phage displaying a scFv and recombinant IgGs generated using this system are expressed at wild-type levels and retain normal function. Use of the pMINERVA completely eliminates the labor-intensive subcloning and DNA sequence confirmation steps currently needed to convert a scFv into a functional IgG Ab. PMID:26851519

  14. Thermally stable molecules with large dipole moments and polarizabilities and applications thereof

    NASA Technical Reports Server (NTRS)

    Marder, Seth R. (Inventor); Peyghambarian, Nasser (Inventor); Kippelen, Bernard (Inventor); Volodin, Boris (Inventor); Hendrickx, Eric (Inventor)

    2002-01-01

    Disclosed are fused ring bridge, ring-locked dyes that form thermally stable photorefractive compositions. The fused ring bridge structures are .pi.-conjugated bonds in benzene-, naphthalene- or anthracene-derived fused ring systems that connect donor and acceptor groups. The donor and acceptor groups contribute to a high molecular dipole moment and linear polarizability anisotropy. The polarization characteristics of the dye molecules are stabilized since the bonds in the fused ring bridge are not susceptible to rotation, reducing the opportunity for photoisomerization. The dyes are compatible with polymeric compositions, including thermoplastics. The dyes are electrically neutral but have charge transport, electronic and orientational properties such that upon illumination of a composition containing the dye, the dye facilitates refractive index modulation and a photorefractive effect that can be utilized advantageously in numerous applications such as in optical quality devices and biological imaging.

  15. Resonance energy transfer in DNA duplexes labeled with localized dyes.

    PubMed

    Cunningham, Paul D; Khachatrian, Ani; Buckhout-White, Susan; Deschamps, Jeffrey R; Goldman, Ellen R; Medintz, Igor L; Melinger, Joseph S

    2014-12-18

    The growing maturity of DNA-based architectures has raised considerable interest in applying them to create photoactive light harvesting and sensing devices. Toward optimizing efficiency in such structures, resonant energy transfer was systematically examined in a series of dye-labeled DNA duplexes where donor-acceptor separation was incrementally changed from 0 to 16 base pairs. Cyanine dyes were localized on the DNA using double phosphoramidite attachment chemistry. Steady state spectroscopy, single-pair fluorescence, time-resolved fluorescence, and ultrafast two-color pump-probe methods were utilized to examine the energy transfer processes. Energy transfer rates were found to be more sensitive to the distance between the Cy3 donor and Cy5 acceptor dye molecules than efficiency measurements. Picosecond energy transfer and near-unity efficiencies were observed for the closest separations. Comparison between our measurements and the predictions of Förster theory based on structural modeling of the dye-labeled DNA duplex suggest that the double phosphoramidite linkage leads to a distribution of intercalated and nonintercalated dye orientations. Deviations from the predictions of Förster theory point to a failure of the point dipole approximation for separations of less than 10 base pairs. Interactions between the dyes that alter their optical properties and violate the weak-coupling assumption of Förster theory were observed for separations of less than four base pairs, suggesting the removal of nucleobases causes DNA deformation and leads to enhanced dye-dye interaction. PMID:25397906

  16. Intracavity Dye-Laser Absorption Spectroscopy (IDLAS) for application to planetary molecules

    NASA Technical Reports Server (NTRS)

    Lang, Todd M.; Allen, John E., Jr.

    1990-01-01

    Time-resolved, quasi-continuous wave, intracavity dye-laser absorption spectroscopy is applied to the investigation of absolute absorption coefficients for vibrational-rotational overtone bands of water at visible wavelengths. Emphasis is placed on critical factors affecting detection sensitivity and data analysis. Typical generation-time dependent absorption spectra are given.

  17. Density functional study of the electronic structure of dye-functionalized fullerenes and their model donor-acceptor complexes containing P3HT.

    PubMed

    Baruah, Tunna; Garnica, Amanda; Paggen, Marina; Basurto, Luis; Zope, Rajendra R

    2016-04-14

    We study the electronic structure of C60 fullerenes functionalized with a thiophene-diketo-pyrrolopyrrole-thiophene based chromophore using density functional theory combined with large polarized basis sets. As the attached chromophore has electron donor character, the functionalization of the fullerene leads to a donor-acceptor (DA) system. We examine in detail the effect of the linker and the addition site on the electronic structure of the functionalized fullerenes. We further study the electronic structure of these DA complexes with a focus on the charge transfer excitations. Finally, we examine the interface of the functionalized fullerenes with the widely used poly(3-hexylthiophene-2,5-diyl) (P3HT) donor. Our results show that all functionalized fullerenes with an exception of the C60-pyrrolidine [6,6], where the pyrrolidine is attached at a [6,6] site, have larger electron affinities relative to the pristine C60 fullerene. We also estimate the quasi-particle gap, lowest charge transfer excitation energy, and the exciton binding energies of the functionalized fullerene-P3MT model systems. Results show that the exciton binding energies in these model complexes are slightly smaller compared to a similarly prepared phenyl-C61-butyric acid methyl ester (PCBM)-P3MT complex. PMID:27083718

  18. Density functional study of the electronic structure of dye-functionalized fullerenes and their model donor-acceptor complexes containing P3HT

    NASA Astrophysics Data System (ADS)

    Baruah, Tunna; Garnica, Amanda; Paggen, Marina; Basurto, Luis; Zope, Rajendra R.

    2016-04-01

    We study the electronic structure of C60 fullerenes functionalized with a thiophene-diketo-pyrrolopyrrole-thiophene based chromophore using density functional theory combined with large polarized basis sets. As the attached chromophore has electron donor character, the functionalization of the fullerene leads to a donor-acceptor (DA) system. We examine in detail the effect of the linker and the addition site on the electronic structure of the functionalized fullerenes. We further study the electronic structure of these DA complexes with a focus on the charge transfer excitations. Finally, we examine the interface of the functionalized fullerenes with the widely used poly(3-hexylthiophene-2,5-diyl) (P3HT) donor. Our results show that all functionalized fullerenes with an exception of the C60-pyrrolidine [6,6], where the pyrrolidine is attached at a [6,6] site, have larger electron affinities relative to the pristine C60 fullerene. We also estimate the quasi-particle gap, lowest charge transfer excitation energy, and the exciton binding energies of the functionalized fullerene-P3MT model systems. Results show that the exciton binding energies in these model complexes are slightly smaller compared to a similarly prepared phenyl-C61-butyric acid methyl ester (PCBM)-P3MT complex.

  19. Catalyzed degradation of azo dyes under ambient conditions.

    PubMed

    Wu, Jin-Ming; Wen, Wei

    2010-12-01

    Phase-pure layered perovskite La(4)Ni(3)O(10) powders were synthesized by a solution combustion approach. It is found that, in the presence of the La(4)Ni(3)O(10) powders, aqueous azo dyes can be degraded catalytically and efficiently under ambient conditions. Neither light nor additional reagents are needed in the catalytic reaction. The dye degradation procedure can be accelerated markedly by magnetic stirring. A systemic series of chemical and electrochemical experiments suggested that the dye degradation proceeds through electron transfers from the dye molecules to the catalyst and then to electron acceptors such as dissolved oxygen. The present catalytic degradation requires no additional reagents or external energy input, which hence provides a potentially low-cost alternative for the remediation of azo-dye effluents. PMID:21049925

  20. Detection of smectites in ppm and sub-ppm concentrations using dye molecule sensors

    NASA Astrophysics Data System (ADS)

    Lofaj, Marcel; Bujdák, Juraj

    2012-03-01

    Methylene blue and rhodamine 6G were used as molecular sensors for the spectrophotometric titrations of the aqueous colloids of clay minerals (montmorillonite, illite and kaolinite). The dyes adsorbed on colloid particles form molecular aggregates, which exhibit spectral properties significantly different from those of dye solutions. Spectrophotometric titrations provide the most sensitive detection of smectites in aqueous colloids (sub-ppm concentrations); and the sensitivity further increases using second derivative spectroscopy. The endpoint of spectrophotometric titrations can be used for the determination of exchange capacity of the mineral in colloids and in this way to estimate its amount. The method is selective only to expandable clays, which was proven by experiments with kaolinite and illite. Spectrophotometric titrations have promising future in the analysis of clays and can be applied in many fields of geology, mineralogy, chemistry, material sciences or in industry. Its application may expand to the analysis of other nanomaterials built from charged particles and exhibiting metachromasy in the systems with organic dyes.

  1. DONOR-ACCEPTOR INTERACTIONS OF NITROGEN*

    PubMed Central

    Kimura, J. E.; Szent-Györgyi, A.

    1969-01-01

    The nitrogen atoms of organic molecules readily enter into donor-acceptor interactions, giving off an electron from their lone pair. Under favorable conditions the acceptor can form free radicals. S and O atoms behave likewise but less intensely. PMID:4306047

  2. Quantifying charge transfer energies at donor-acceptor interfaces in small-molecule solar cells with constrained DFTB and spectroscopic methods.

    PubMed

    Scholz, Reinhard; Luschtinetz, Regina; Seifert, Gotthard; Jägeler-Hoheisel, Till; Körner, Christian; Leo, Karl; Rapacioli, Mathias

    2013-11-27

    Charge transfer states around the donor-acceptor interface in an organic solar cell determine the device performance in terms of the open circuit voltage. In the present work, we propose a computational scheme based on constrained density functional tight binding theory (c-DFTB) to assess the energy of the lowest charge transfer (CT) state in such systems. A comparison of the c-DFTB scheme with Hartree-Fock based configuration interaction of singles (CIS) and with time-dependent density functional theory (TD-DFT) using the hybrid functional B3LYP reveals that CIS and c-DFTB reproduce the correct Coulomb asymptotics between cationic donor and anionic acceptor configurations, whereas TD-DFT gives a qualitatively wrong excitation energy. Together with an embedding scheme accounting for the polarizable medium, this c-DFTB scheme is applied to several donor-acceptor combinations used in molecular solar cells. The external quantum efficiency of photovoltaic cells based on zinc phthalocyanine-C60 blends reveals a CT band remaining much narrower than the density of states of acceptor HOMO and donor LUMO, an observation which can be interpreted in a natural way in terms of Marcus transfer theory. A detailed comparison with c-DFTB calculations reveals an energy difference of 0.32 eV between calculated and observed absorption from the electronic ground state into the CT state. In a blend of a functionalized thiophene and C60, the photoluminescence spectra differ significantly from neat films, allowing again an assignment to CT states. The proposed computational scheme reproduces the observed trends of the observed open circuit voltages in photovoltaic devices relying on several donor-acceptor blends, finding an offset of 1.16 eV on average. This value is similar as in polymer-fullerene photovoltaic systems where it amounts to about 0.9 eV, indicating that the photophysics of CT states in molecular donor-acceptor blends and in polymer-fullerene blends are governed by the

  3. Quantifying charge transfer energies at donor-acceptor interfaces in small-molecule solar cells with constrained DFTB and spectroscopic methods

    NASA Astrophysics Data System (ADS)

    Scholz, Reinhard; Luschtinetz, Regina; Seifert, Gotthard; Jägeler-Hoheisel, Till; Körner, Christian; Leo, Karl; Rapacioli, Mathias

    2013-11-01

    Charge transfer states around the donor-acceptor interface in an organic solar cell determine the device performance in terms of the open circuit voltage. In the present work, we propose a computational scheme based on constrained density functional tight binding theory (c-DFTB) to assess the energy of the lowest charge transfer (CT) state in such systems. A comparison of the c-DFTB scheme with Hartree-Fock based configuration interaction of singles (CIS) and with time-dependent density functional theory (TD-DFT) using the hybrid functional B3LYP reveals that CIS and c-DFTB reproduce the correct Coulomb asymptotics between cationic donor and anionic acceptor configurations, whereas TD-DFT gives a qualitatively wrong excitation energy. Together with an embedding scheme accounting for the polarizable medium, this c-DFTB scheme is applied to several donor-acceptor combinations used in molecular solar cells. The external quantum efficiency of photovoltaic cells based on zinc phthalocyanine-C60 blends reveals a CT band remaining much narrower than the density of states of acceptor HOMO and donor LUMO, an observation which can be interpreted in a natural way in terms of Marcus transfer theory. A detailed comparison with c-DFTB calculations reveals an energy difference of 0.32 eV between calculated and observed absorption from the electronic ground state into the CT state. In a blend of a functionalized thiophene and C60, the photoluminescence spectra differ significantly from neat films, allowing again an assignment to CT states. The proposed computational scheme reproduces the observed trends of the observed open circuit voltages in photovoltaic devices relying on several donor-acceptor blends, finding an offset of 1.16 eV on average. This value is similar as in polymer-fullerene photovoltaic systems where it amounts to about 0.9 eV, indicating that the photophysics of CT states in molecular donor-acceptor blends and in polymer-fullerene blends are governed by the same

  4. High-efficiency organic light-emitting diodes utilizing thermally activated delayed fluorescence from triazine-based donor-acceptor hybrid molecules

    NASA Astrophysics Data System (ADS)

    Youn Lee, Sae; Yasuda, Takuma; Nomura, Hiroko; Adachi, Chihaya

    2012-08-01

    We have designed and synthesized a high-efficiency purely organic luminescent material, 2,4-bis{3-(9 H-carbazol-9-yl)-9 H-carbazol-9-yl}-6-phenyl-1,3,5-triazine (CC2TA) comprising the bicarbazole donor and phenyltriazine acceptor units, which is capable of emitting thermally activated delayed fluorescence. The molecular design of CC2TA allows spatial separation of HOMO and LUMO on the donor and acceptor fragments, respectively, leading to an exceptionally small singlet-triplet exchange energy (ΔEST = 0.06 eV) together with a high triplet energy. Furthermore, a high external electroluminescence quantum efficiency as high as 11% ± 1% has been achieved in the sky-blue organic light-emitting diodes employing CC2TA as an emitter.

  5. Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules I. Reference Data at the CCSD(T) Complete Basis Set Limit.

    PubMed

    Richard, Ryan M; Marshall, Michael S; Dolgounitcheva, O; Ortiz, J V; Brédas, Jean-Luc; Marom, Noa; Sherrill, C David

    2016-02-01

    In designing organic materials for electronics applications, particularly for organic photovoltaics (OPV), the ionization potential (IP) of the donor and the electron affinity (EA) of the acceptor play key roles. This makes OPV design an appealing application for computational chemistry since IPs and EAs are readily calculable from most electronic structure methods. Unfortunately reliable, high-accuracy wave function methods, such as coupled cluster theory with single, double, and perturbative triples [CCSD(T)] in the complete basis set (CBS) limit are too expensive for routine applications to this problem for any but the smallest of systems. One solution is to calibrate approximate, less computationally expensive methods against a database of high-accuracy IP/EA values; however, to our knowledge, no such database exists for systems related to OPV design. The present work is the first of a multipart study whose overarching goal is to determine which computational methods can be used to reliably compute IPs and EAs of electron acceptors. This part introduces a database of 24 known organic electron acceptors and provides high-accuracy vertical IP and EA values expected to be within ±0.03 eV of the true non-relativistic, vertical CCSD(T)/CBS limit. Convergence of IP and EA values toward the CBS limit is studied systematically for the Hartree-Fock, MP2 correlation, and beyond-MP2 coupled cluster contributions to the focal point estimates. PMID:26731487

  6. Excitation laser energy dependence of surface-enhanced fluorescence showing plasmon-induced ultrafast electronic dynamics in dye molecules

    NASA Astrophysics Data System (ADS)

    Itoh, Tamitake; Yamamoto, Yuko S.; Tamaru, Hiroharu; Biju, Vasudevanpillai; Murase, Norio; Ozaki, Yukihiro

    2013-06-01

    We find unique properties accompanying surface-enhanced fluorescence (SEF) from dye molecules adsorbed on Ag nanoparticle aggregates, which generate surface-enhanced Raman scattering. The properties are observed in excitation laser energy dependence of SEF after excluding plasmonic spectral modulation in SEF. The unique properties are large blue shifts of fluorescence spectra, deviation of ratios between anti-Stokes SEF intensity and Stokes from those of normal fluorescence, super-broadening of Stokes spectra, and returning to original fluorescence by lower energy excitation. We elucidate that these properties are induced by electromagnetic enhancement of radiative decay rates exceeding the vibrational relaxation rates within an electronic excited state, which suggests that molecular electronic dynamics in strong plasmonic fields can be largely deviated from that in free space.

  7. Dependence of Purcell effect on fluorescence wavelength in dye molecules on metal-dielectric multilayer hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Tsurumachi, Noriaki; Izawa, Hayato; Tomioka, Ryo; Sakata, Tomohiro; Suzuki, Makoto; Tanaka, Yasuhiro; Shimokawa, Fusao; Nakanishi, Shunsuke

    2016-02-01

    Recently, the enhancement of spontaneous emission, i.e., broadband Purcell effect, has been achieved using hyperbolic metamaterials. Hyperbolic metamaterials, which can be realized using a metal-dielectric multilayer structure, have an extremely large optical anisotropy of permittivity in both the parallel and perpendicular directions to the propagation of light, especially when the signs of permittivities in both directions differ. In this study, we investigated the conditions for realizing the broadband Purcell effect using dye molecules with different fluorescence wavelengths. Our fabricated metal-dielectric multilayer structure exhibited hyperbolic dispersion at wavelengths beyond 500 nm. In the case of coumarin 500 whose fluorescence peak is located at 500 nm, no broadband Purcell effect was observed. However, in the case of pyridine 1 whose fluorescence peak is located at 650 nm, we observed the successfull fluorescence lifetime shortening, i.e., the broadband Purcell effect.

  8. Acceptor Products of Alternansucrase with Gentiobiose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the presence of suitable acceptor molecules, dextransucrase makes a homologous series of oligosaccharides in which the isomers differ by a single glucosyl unit, whereas alternansucrase synthesizes one trisaccharide, two tetrasaccharides, etc. Previously, we showed that alternansucrase only forms...

  9. Towards the coupling of single photons from dye molecules to a photonic waveguide

    NASA Astrophysics Data System (ADS)

    Polisseni, Claudio; Kho, Kiang Wei; Major, Kyle; Grandi, Samuele; Boisser, Sebastien; Hwang, Jaesuk; Clark, Alex; Hinds, Edward

    Single photons are very attractive for quantum information processing given their long coherence time and their ability to carry information in many degrees of freedom. A current challenge is the efficient generation of single photons in a photonic chip in order to scale up the complexity of quantum operations. We have proposed that a dibenzoterrylene (DBT) molecule inside an anthracene (AC) crystal could couple lifetime-limited indistinguishable single photons into a photonic waveguide if deposited in its vicinity. In this talk I describe the recent progress towards the realization of this proposal. A new method has been developed for evaporating AC and DBT to produce crystals that are wide and thin. The crystals are typically several microns across and have remarkably uniform thickness, which we control between 20 and 150 nm. The crystal growth is carried out in a glove bag in order to exclude oxygen, which improves the photostability of the DBT molecules by orders of magnitude. We image the fluorescence of single DBT molecules using confocal microscopy and analyse the polarization of this light to determine the alignment of the molecules. I will report on our efforts to control the alignement of the molecules by aligning the host matrix with the substrate.

  10. Hyperpolarizabilities βzzz and βzxx of π-extended molecules tetra-substituted by ortho-positioned donor-acceptor pairs as analyzed by homologous substitution model

    NASA Astrophysics Data System (ADS)

    Tomonari, Mutsumi; Ookubo, Norio

    2002-01-01

    Hyperpolarizability β of fused-ring molecules tetra-substituted by two ortho-positioned donor (D)-acceptor (A) were studied for three types of C 2v isomers, using simplified sum-over-states (SOS) calculation, missing-orbital analysis (MOA), and homologous substitution model. The model is comprised of two molecules, one di-substituted by two D's, the other by two A's at the sites homologous as a whole to tetra-substitution. Ortho1-type with two D-A pairs at molecular x-edges showed larger βzxx than that of the model, exhibiting charge-transfer (CT), nevertheless all isomer types could show CT enhancement according to resonant structures. The substitution model successfully described qualitatively magnitudes and signs for β for all isomers.

  11. Fully resonant four-wave mixing spectroscopy of pentacene and dye molecules in condensed phases

    SciTech Connect

    Chang, T.C.

    1985-01-01

    Four-wave mixing spectroscopy (FWM) including coherent antistokes Raman spectroscopy (CARS) and coherent stokes Raman spectroscopy (CSRS) have been studied for pentacene doped in naphthalene crystals at low temperatures (4.5 to 35 K) in order to investigate nonlinear optical behavior of the third-order nonlinear susceptibility, X/sup (3)/. Further, its application to study of cresyl violet perchlorate embedded in polyacrylic acid and in polyvinyl carbazole has been examined. The theoretical basis for line narrowing has been established for fully resonant four wave mixing for a four-level system. A careful line-narrowing study for the pentacene 755 cm/sup -1/ resonance in naphthalene illustrates that line narrowing is operative. Temperature dependent studies indicate that the excited state population mechanism for negative detuning involves phonon hotband absorption. Power broadening data are discussed in terms of dynamic Stark shifts resulting from the site inhomogeneous line broadening of vibronic transitions. Cresyl violet perchlorate in polyacrylic acid shows that the CARS intensity of the excited state resonance at 585 cm/sup -1/ depends on the location of the omega/sub 1/-field within the severely inhomogeneously broadened absorption profile of the dye. It is argued that the linear electron-phonon interaction is an important mechanism for the intensity of the excited state resonance.

  12. Spectrally resolved analysis of fluorescence blinking of single dye molecules in polymers at low temperatures

    NASA Astrophysics Data System (ADS)

    Orlov, S. V.; Naumov, A. V.; Vainer, Yu. G.; Kador, Lothar

    2012-11-01

    We present a method for the spectrally resolved analysis of fluorescence blinking of single quantum emitters. It is based on the well-known technique of repeated recording of single-molecule (SM) fluorescence excitation spectra. The potential of our approach is presented for the example of single tetra-tert-butylterrylene molecules in an amorphous polymer matrix (polyisobutylene), which exhibit fluorescence blinking at cryogenic temperatures. Measuring the spectral dependence of the blinking statistics improves the possibility to clarify the microscopic nature of the dark state(s) of the emitters. We demonstrate how the blinking statistics can be definitely attributed to conformational changes in the local environment of a SM and how the parameters of the corresponding elementary excitations can be measured. The analysis of the blinking statistics as a function of the optical excitation frequency allows us to discriminate between photo-induced and spontaneous transitions into a dark state.

  13. Effects of end-capped acceptors subject to subtle structural changes on solution-processable small molecules for organic solar cells.

    PubMed

    Deng, Dan; Zhang, Yajie; Zhu, Lingyun; Zhang, Jianqi; Lu, Kun; Wei, Zhixiang

    2015-04-14

    Self-assembly is crucial for small molecular organic solar cells, which are extremely sensitive to the molecular structure. In this work, three subtle structural changed end-capped acceptors with increased electron withdrawing ability, named octyl 2-cyanoacetate (=CNCOOC8H17), 3-oxoundecanenitrile (=CNCOC8H17), and 2-(octylsulfonyl) acetonitrile (=CNSOOC8H17), were synthesized and introduced into a planar conjugated backbone using ethylhexyl-thiophene substituted benzodithiophene (TBDT) as a core and trithiophene as a π-bridge (labelled M1, M2 and M3, respectively). Their effects on absorption, thermal properties, and morphologies were studied and compared. In particular, the molecular packing of the three materials varied significantly, and the hole mobilities differed by orders of magnitude. As a result, the fill factors of devices varied from 52% to 72%. Combining the effects of electron-withdrawing capability and molecular packing, the power conversion efficiencies of the optimized devices increased from 3.0% for M3 to 6.4% for M1 and M2. The relationship between end-capped acceptors and photovoltaic properties would generate valuable insights into further producing more efficient solution-processable organic solar cells. PMID:25742902

  14. N-acetylation of three aromatic amine hair dye precursor molecules eliminates their genotoxic potential.

    PubMed

    Zeller, Andreas; Pfuhler, Stefan

    2014-01-01

    N-acetylation has been described as a detoxification reaction for aromatic amines; however, there is only limited data available showing that this metabolic conversion step changes their genotoxicity potential. To extend this database, three aromatic amines, all widely used as precursors in oxidative hair dye formulations, were chosen for this study: p-phenylenediamine (PPD), 2,5-diaminotoluene (DAT) and 4-amino-2-hydroxytoluene (AHT). Aiming at a deeper mechanistic understanding of the interplay between activation and detoxification for this chemical class, we compared the genotoxicity profiles of the parent compounds with those of their N-acetylated metabolites. While PPD, DAT and AHT all show genotoxic potential in vitro, their N-acetylated metabolites completely lack genotoxic potential as shown in the Salmonella typhimurium reversion assay, micronucleus test with cultured human lymphocytes (AHT), chromosome aberration assay with V79 cells (DAT) and Comet assay performed with V79 cells. For the bifunctional aromatic amines studied (PPD and DAT), monoacetylation was sufficient to completely abolish their genotoxic potential. Detoxification through N-acetylation was further confirmed by comparing PPD, DAT and AHT in the Comet assay using standard V79 cells (N-acetyltransferase (NAT) deficient) and two NAT-proficient cell lines,V79NAT1*4 and HaCaT (human keratinocytes). Here we observed a clear shift of dose-response curves towards decreased genotoxicity of the parent aromatic amines in the NAT-proficient cells. These findings suggest that genotoxic effects will only be found at concentrations where the N-acetylation (detoxifying) capacity of the cells is overwhelmed, indicating that a 'first-pass' effect in skin could be taken into account for risk assessment of these topically applied aromatic amines. The findings also indicate that the use of liver S-9 preparations, which generally underestimate Phase II reactions, contributes to the generation of irrelevant

  15. Single-molecule imaging at high fluorophore concentrations by local activation of dye.

    PubMed

    Geertsema, Hylkje J; Schulte, Aartje C; Spenkelink, Lisanne M; McGrath, William J; Morrone, Seamus R; Sohn, Jungsan; Mangel, Walter F; Robinson, Andrew; van Oijen, Antoine M

    2015-02-17

    Single-molecule fluorescence microscopy is a powerful tool for observing biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Making use of short-distance energy-transfer mechanisms, only the fluorescence from those proteins that bind to their substrate is activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease on DNA in the presence of a background of hundreds of nanomolar Cy5 fluorophore. PMID:25692599

  16. Single-molecule imaging at high fluorophore concentrations by local activation of dye

    SciTech Connect

    Geertsema, Hylkje J.; Mangel, Walter F.; Schulte, Aartje C.; Spenkelink, Lisanne M.; McGrath, William J.; Morrone, Seamus R.; Sohn, Jungsan; Robinson, Andrew; van Oijen, Antoine M.

    2015-02-17

    Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use of short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.

  17. Single-molecule imaging at high fluorophore concentrations by local activation of dye

    DOE PAGESBeta

    Geertsema, Hylkje J.; Mangel, Walter F.; Schulte, Aartje C.; Spenkelink, Lisanne M.; McGrath, William J.; Morrone, Seamus R.; Sohn, Jungsan; Robinson, Andrew; van Oijen, Antoine M.

    2015-02-17

    Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use ofmore » short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.« less

  18. Single-Molecule Imaging at High Fluorophore Concentrations by Local Activation of Dye

    PubMed Central

    Geertsema, Hylkje J.; Schulte, Aartje C.; Spenkelink, Lisanne M.; McGrath, William J.; Morrone, Seamus R.; Sohn, Jungsan; Mangel, Walter F.; Robinson, Andrew; van Oijen, Antoine M.

    2015-01-01

    Single-molecule fluorescence microscopy is a powerful tool for observing biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Making use of short-distance energy-transfer mechanisms, only the fluorescence from those proteins that bind to their substrate is activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease on DNA in the presence of a background of hundreds of nanomolar Cy5 fluorophore. PMID:25692599

  19. 2012 ELECTRON DONOR-ACCEPTOR INTERACTIONS GORDON RESEARCH CONFERENCE, AUGUST 5-10, 2012

    SciTech Connect

    McCusker, James

    2012-08-10

    The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

  20. [1]Benzothieno[3,2-b]benzothiophene-Based Organic Dyes for Dye-Sensitized Solar Cells.

    PubMed

    Capodilupo, Agostina L; Fabiano, Eduardo; De Marco, Luisa; Ciccarella, Giuseppe; Gigli, Giuseppe; Martinelli, Carmela; Cardone, Antonio

    2016-04-15

    Three new metal-free organic dyes with the [1]benzothieno[3,2-b]benzothiophene (BTBT) π-bridge, having the structure donor-π-acceptor (D-π-A) and labeled as 19, 20 and 21, have been designed and synthesized for application in dye-sensitized solar cells (DSSC). Once the design of the π-acceptor block was fixed, containing the BTBT as the π-bridge and the cyanoacrylic group as the electron acceptor and anchoring unit, we selected three donor units with different electron-donor capacity, in order to assemble new chromophores with high molar extinction coefficients (ε), whose absorption features well reflect the good performance of the final DSSC devices. Starting with the 19 dye, which shows a molar extinction coefficient ε of over 14,000 M(-1) cm(-1) and takes into account the absorption maximun at the longer wavelength, the substitution of the BFT donor unit with the BFA yields a great enhancement of absorptivity (molar extinction coefficient ε > 42,000 M(-1) cm(-1)), until reaching the higher value (ε > 69,000 M(-1) cm(-1)) with the BFPhz donor unit. The good general photovoltaic performances obtained with the three dyes highlight the suitable properties of electron-transport of the BTBT as the π-bridge in organic chromophore for DSSC, making this very cheap and easy to synthesize molecule particularly attractive for efficient and low-cost photovoltaic devices. PMID:26986652

  1. Self-assembly in the mixtures of surfactant and dye molecule controlled via temperature and β-cyclodextrin recognition.

    PubMed

    Wang, Dong; Long, Panfeng; Dong, Renhao; Hao, Jingcheng

    2012-10-01

    A new ternary system of tetradecyldimethylamine oxide (C(14)DMAO)/4-phenylazo benzoic acid (AzoH)/H(2)O was first investigated, and it was found that the self-assembly can be regulated via temperature and β-cyclodextrin (β-CD) recognition. In the temperature regulated self-assembly, the self-assembled phase structural transition between wormlike micelles and multilamellar vesicles (onions) were determined by cryogenic-transmission electron microscopy (cryo-TEM) images and (2)H nuclear magnetic resonance ((2)H NMR) spectra. The phase structural transition temperatures (PSTT) controlled by changing the amount of AzoH were measured by differential scanning calorimetry analysis. The self-assembled phase structural transition mechanism was discussed. It is argued that the self-assembled phase structural transition is the synergetic balance among the hydrophilic headgroup, steric structures of the hydrophobic chain, and membrane charge. β-CD molecules were used as controlling hands to modulate the phase structural transition of self-assembly of the C(14)DMAO/AzoH/H(2)O system in solution via snatching C(14)DMAO molecules. The phase structural transitions from the threadlike micellar phase to the lamellar phase and from the lamellar phase to the vesicular phase can each be controlled because of the β-CD molecular recognition. The phase structural transitions were confirmed by cryo-TEM observations and (2)H NMR measurements. The rheological properties were also investigated to display the importance in the phase structural transition. It was found that the dye molecule, AzoH, is harder to enclose by β-CD than by C(14)DMAO because of the lower complex stability constant (i.e., K(C(14)DMAO@β-CD) ≫ K(AzoH@β-CD). Therefore, the phase structural transition is mainly controlled by the inclusion of C(14)DMAO into the hydrophobic cavity of β-CD molecules. The phase structural transition controlled via temperature and β-CD may find potential applications such as in

  2. Resonance energy transfer and competing processes in donor-acceptor of sodium zinc (II)-2,9,16,23-phthalocyanine tetracarboxylate molecule.

    PubMed

    Al-Omari, Saleh

    2016-06-01

    An important issue that should be taken into consideration when applying the molecules in photodynamic therapy (PDT) of cancer is the occurrence of homo-resonance energy transfer process between them. We have determined the probability of energy transfer for sodium zinc (II)-2,9,16,23-phthalocyanine tetracarboxylate (ZnPc(COONa)4) molecules in aqueous NaOH solution. The homo-quenching effect of the molecule was also measured by calculating the diffusion controlled bimolecular rate constant of k q = 6.5 × 10(9) M(-1)s(-1), which did not show a significant competition with the rate constant of homo-resonance energy transfer process at the applied concentration of the molecules (6 μM). The Förster radius (R  0) for ZnPc(COONa)4 molecules was calculated to be 42 Å. The availability of these calculations should facilitate the potential application of ZnPc(COONa)4 molecule as an anticancer drug in PDT. PMID:27008342

  3. Impact of the different electron-releasing subunits on the dye-sensitized solar cell performance of new triphenylamine-benzimidazole based molecules

    NASA Astrophysics Data System (ADS)

    Dinçalp, Haluk; Saltan, Gözde Murat; Aykut, Deniz; Zafer, Ceylan

    2015-10-01

    New triphenylamine-benzimidazole type small molecules with different electron-releasing groups were designed and synthesized to investigate their photovoltaic performances in dye sensitized solar cells (DSSCs). Their good visible absorptions covering the 400-535 nm in addition to suitable lowest unoccupied molecular orbital (LUMO) energy levels between -3.03 and -3.11 eV make good candidates them for DSSC devices. Fluorescence quenching studies of the dyes with pristine titania support the good electron injection to conduction band of TiO2. Time resolved measurements of the dyes in solutions indicate the occurence of charge generation during the excited state. One of the used dyes in DSSC devices, TPA5a, carrying a methoxy group in triphenylamine part of the structure, gave much higher power conversion efficiency (PCE) value of 4.31% as compared to the other derivatives. Device fabricated from TPA5a dye gives good external quantum efficiency (EQE) value above 70% at 460 nm. Also, electron impedance spectroscopy (EIS) analysis of the devices gives a good explanation of the understanding of the cell performances.

  4. Electron transfer in the quenching of protonated triplet methylene blue by ground-state molecules of the dye

    SciTech Connect

    Kamat, P.V.; Lichtin, N.N.

    1981-04-02

    A Q-switched pulsed ruby laser emitting at 694.3 nm was used in an investigation by means of flash photolysis-kinetic spectrophotometry of the mechanism of quenching of the monoprotonated lowest triplet state of methylene blue, /sup 3/MBH/sup 2 +/, by the ground state of the dye, MB/sup +/. Quenching in 0.01 N acid is accompanied by electron transfer to give the half-oxidized and half-reduced ion radicals, MB/sup 2 +/. and MBH/sup +/.. The absorption spectrum of MB/sup 2 +/. has been characterized in several media from 360 to 600 nm. The rate constant for quenching, k/sub q/, varies with solvent, ionic strength, and nature of anions with values around 1 x 10/sup 8/ M/sup -1/ s/sup -1/ in water, aqueous CH/sub 3/CN, and aqueous EtOH. The efficiency of net electron transfer in quenching, F/sub 1/(= k/sub et//k/sub q/), varies with solvent but is independent of the ionic strength or the nature of the anions. F/sub 1/ varies inversely with polarity of the solvent from 0.055 in water to 0.48 in 90% (vol/vol) aqueous CH/sub 3/CN. On the basis of analogy to the behavior of a number of other quenchers and the observed linear variation of the function ln ((1/F/sub 1/)-1) with Kosower's polarity parameter Z, it is suggested that reversible electron transfer is the only significant mechanism of quenching of /sup 3/MBH/sup 2 +/ by MB/sup +/(S/sub 0/). Both MBH/sup +/. and MB/sup 2 +/. decay by second-order processes in solvents containing 75% (vol/vol) or less of organic component but the specific rates are different for the two species in most media. It is suggested that in the latter media both cross reaction of MBH/sup +/. with MB/sup 2 +/. and biomolecular reaction of two molecules of the same radical occur. This study shows that ground-state quenching can significantly reduce the sunlight engineering efficency of photogalvanic conversion in systems incorporating relatively concentrated dyes.

  5. High Efficiency Forster Resonance Energy Transfer in Solid-State Dye Sensitized Solar Cells

    SciTech Connect

    Mor, Gopal K.; Basham, James; Paulose, Maggie; Kim, Sanghoon; Varghese, Oomman K.; Vaish, Amit; Yoriya, Sorachon; Grimes, Craig A.

    2010-07-14

    Solid-state dye-sensitized solar cells (SS-DSCs) offer the potential to make low cost solar power a reality, however their photoconversion efficiency must first be increased. The dyes used are commonly narrow band with high absorption coefficients, while conventional photovoltaic operation requires proper band edge alignment significantly limiting the dyes and charge transporting materials that can be used in combination. We demonstrate a significant enhancement in the light harvesting and photocurrent generation of SS-DSCs due to Förster resonance energy transfer (FRET). TiO{sub 2} nanotube array films are sensitized with red/near IR absorbing SQ-1 acceptor dye, subsequently intercalated with Spiro-OMeTAD blended with a visible light absorbing DCM-pyran donor dye. The calculated Förster radius is 6.1 nm. The donor molecules contribute a FRET-based maximum IPCE of 25% with a corresponding excitation transfer efficiency of approximately 67.5%.

  6. Towards building artificial light harvesting complexes: enhanced singlet-singlet energy transfer between donor and acceptor pairs bound to albumins.

    PubMed

    Kumar, Challa V; Duff, Michael R

    2008-12-01

    Specific donor and acceptor pairs have been assembled in bovine serum albumin (BSA), at neutral pH and room temperature, and these dye-protein complexes indicated efficient donor to acceptor singlet-singlet energy transfer. For example, pyrene-1-butyric acid served as the donor and Coumarin 540A served as the acceptor. Both the donor and the acceptor bind to BSA with affinity constants in excess of 2x10(5) M(-1), as measured in absorption and circular dichroism (CD) spectral titrations. Simultaneous binding of both the donor and the acceptor chromophores was supported by CD spectra and one chromophore did not displace the other from the protein host, even when limited concentrations of the host were used. For example, a 1:1:1 complex between the donor, acceptor and the host can be readily formed, and spectral data clearly show that the binding sites are mutually exclusive. The ternary complexes (two different ligands bound to the same protein molecule) provided opportunities to examine singlet-singlet energy transfer between the protein-bound chromophores. Donor emission was quenched by the addition of the acceptor, in the presence of limited amounts of BSA, while no energy transfer was observed in the absence of the protein host, under the same conditions. The excitation spectra of the donor-acceptor-host complexes clearly show the sensitization of acceptor emission by the donor. Protein denaturation, as induced by the addition of urea or increasing the temperature to 360 K, inhibited energy transfer, which indicate that protein structure plays an important role. Sensitization also proceeded at low temperature (77 K) and diffusion of the donor or the acceptor is not required for energy transfer. Stern-Volmer quenching plots show that the quenching constant is (3.1+/-0.2)x10(4) M(-1), at low acceptor concentrations (<35 microM). Other albumins such as human and porcine proteins also served as good hosts for the above experiments. For the first time, non

  7. Associative Memory Acceptors.

    ERIC Educational Resources Information Center

    Card, Roger

    The properties of an associative memory are examined in this paper from the viewpoint of automata theory. A device called an associative memory acceptor is studied under real-time operation. The family "L" of languages accepted by real-time associative memory acceptors is shown to properly contain the family of languages accepted by one-tape,…

  8. Localization microscopy of DNA in situ using Vybrant(®) DyeCycle™ Violet fluorescent probe: A new approach to study nuclear nanostructure at single molecule resolution.

    PubMed

    Żurek-Biesiada, Dominika; Szczurek, Aleksander T; Prakash, Kirti; Mohana, Giriram K; Lee, Hyun-Keun; Roignant, Jean-Yves; Birk, Udo J; Dobrucki, Jurek W; Cremer, Christoph

    2016-05-01

    Higher order chromatin structure is not only required to compact and spatially arrange long chromatids within a nucleus, but have also important functional roles, including control of gene expression and DNA processing. However, studies of chromatin nanostructures cannot be performed using conventional widefield and confocal microscopy because of the limited optical resolution. Various methods of superresolution microscopy have been described to overcome this difficulty, like structured illumination and single molecule localization microscopy. We report here that the standard DNA dye Vybrant(®) DyeCycle™ Violet can be used to provide single molecule localization microscopy (SMLM) images of DNA in nuclei of fixed mammalian cells. This SMLM method enabled optical isolation and localization of large numbers of DNA-bound molecules, usually in excess of 10(6) signals in one cell nucleus. The technique yielded high-quality images of nuclear DNA density, revealing subdiffraction chromatin structures of the size in the order of 100nm; the interchromatin compartment was visualized at unprecedented optical resolution. The approach offers several advantages over previously described high resolution DNA imaging methods, including high specificity, an ability to record images using a single wavelength excitation, and a higher density of single molecule signals than reported in previous SMLM studies. The method is compatible with DNA/multicolor SMLM imaging which employs simple staining methods suited also for conventional optical microscopy. PMID:26341267

  9. Applications of Metal Oxide Materials in Dye Sensitized Photoelectrosynthesis Cells for Making Solar Fuels: Let the Molecules do the Work

    SciTech Connect

    Alibabaei, Leila; Luo, Hanlin; House, Ralph L.; Hoertz, Paul G.; Lopez, Rene; Meyer, Thomas J.

    2013-01-01

    Solar fuels hold great promise as a permanent, environmentally friendly, long-term renewable energy source, that would be readily available across the globe. In this account, an approach to solar fuels is described based on Dye Sensitized Photoelectrosynthesis Cells (DSPEC) that mimic the configuration used in Dye Sensitized Solar Cells (DSSC), but with the goal of producing oxygen and a high energy solar fuel in the separate compartments of a photoelectrochemical cell rather than a photopotential and photocurrent.

  10. A study of donor-acceptor in the charge transfer molecular complexes of some thiacrown ethers with dihalogen molecules by DFT method.

    PubMed

    Oftadeh, Mohsen; Moghadary, Mitra; Solimannejad, Mohammad; Semnani, Abolfazl

    2013-01-01

    The molecular complexes of 1,3,5-trithiane, (TT), tetrathia-8-crown-4, (TT8C4), and trithia-9-crown-3 , (TT9C3) with dihalogens in the ground state were investigated in the gas and dicholoromethane phases using B3LYP method and 6-31G** and 6-31+G** bases sets. In both TT and TT8C4 complexes, it is predicted that charge transfer takes place from the dihalogen to the thiacrown ether molecule; the magnitude trend of the total CT was ICl > IBr > I2, and Cl2 > Br2 > I2, respectively. There was not such a trend with TT9C3. The frequency analysis showed that all complexes in the excited state were unstable. The analysis of natural bond orbitals and comparison of the calculated thermodynamic quantities of the complexes between the gas phase and tetrachloromethane solution confirmed the results. PMID:23841337

  11. X-ray photoelectron and optical absorption spectroscopic studies on the dye chlorodiane blue, used as a carrier generation molecule in organic photoconductors

    SciTech Connect

    Pacansky, J.; Waltman, R.J.

    1992-07-01

    The dye chlorodiane blue, used as a carrier generation molecule in organic photoconductors, is characterized via optical absorption and X-ray photoelectron spectroscopy, and the results are interpreted on the basis of ab initio quantum mechanical molecular models. These data indicate that chlorodiane blue exists as azo-enol and hydrazone-quinone chemical structures and it is the hydrazone-quinone form that provides the higher xerographic gain in electrophotographic applications. Optimized geometries, atomic charges, and molecular orbital plots and energies are reported for both the azo-enol and hydrazone-quinone forms of chlorodiane blue. The two structural forms of the dye are experimentally distinguishable via both optical absorption and X-ray photoelectron spectroscopy, and the wavelength and chemical shifts, respectively, are interpreted via the theoretical results. 29 refs., 9 figs., 4 tabs.

  12. Electron acceptor-dependent respiratory and physiological stratifications in biofilms.

    PubMed

    Yang, Yonggang; Xiang, Yinbo; Sun, Guoping; Wu, Wei-Min; Xu, Meiying

    2015-01-01

    Bacterial respiration is an essential driving force in biogeochemical cycling and bioremediation processes. Electron acceptors respired by bacteria often have solid and soluble forms that typically coexist in the environment. It is important to understand how sessile bacteria attached to solid electron acceptors respond to ambient soluble alternative electron acceptors. Microbial fuel cells (MFCs) provide a useful tool to investigate this interaction. In MFCs with Shewanella decolorationis, azo dye was used as an alternative electron acceptor in the anode chamber. Different respiration patterns were observed for biofilm and planktonic cells, with planktonic cells preferred to respire with azo dye while biofilm cells respired with both the anode and azo dye. The additional azo respiration dissipated the proton accumulation within the anode biofilm. There was a large redox potential gap between the biofilms and anode surface. Changing cathodic conditions caused immediate effects on the anode potential but not on the biofilm potential. Biofilm viability showed an inverse and respiration-dependent profile when respiring with only the anode or azo dye and was enhanced when respiring with both simultaneously. These results provide new insights into the bacterial respiration strategies in environments containing multiple electron acceptors and support an electron-hopping mechanism within Shewanella electrode-respiring biofilms. PMID:25495895

  13. Light-triggered assembly-disassembly of an ordered donor-acceptor π-stack using a photoresponsive dimethyldihydropyrene π-switch.

    PubMed

    Krishna, V Siva Rama; Samanta, Mousumi; Pal, Suman; Anurag, N P; Bandyopadhyay, Subhajit

    2016-06-28

    Self-organization of donor and acceptor π-systems forms alternate D-A stacks of the donor and acceptor molecules. Using a photochromic π-switch as a donor and an electron deficient acceptor dye such stacks were formed. Photomodulation of the donor unit with visible light led to a photoisomerized state having a non-planar structure with reduced donor ability, thereby causing destruction of the alternate D-A π-stacks. The formation and destruction of the stacks were studied by various spectroscopy methods. Both the stacks and the depleted stacks were studied by DLS and SEM experiments. The regeneration of the stacks occurred in solution with the reversal of the photoisomerization process with ultraviolet light. Computational and differential scanning calorimetric studies validated the thermodynamics of the formation of the stacks. This work presents a reversible assembly-disassembly of a donor-acceptor π system devoid of additional auxiliary non-covalent bonding motifs in the donor and acceptor molecules. PMID:26899505

  14. A simple approach for the synthesis of Ag-coated Ni@TiO{sub 2} nanocomposites as recyclable photocatalysts and SERS substrate to monitor catalytic degradation of dye molecules

    SciTech Connect

    Ding, Qianqian; Zhang, Li; Yang, Liangbao

    2014-05-01

    Graphical abstract: - Highlights: • A simple approach was used to synthesize Ag-coated Ni@TiO{sub 2} nanocomposites. • The nanocomposites can be the convenient and effective SERS substrate. • The nanocomposites can be a self-cleaning SERS substrate. • The nanocomposites can monitor the catalytic degradation of dye molecules. - Abstract: In this work, we demonstrate an extremely simple and speedy approach to synthesis Ag-coated Ni@TiO{sub 2} nanocomposites, which can be a convenient and effective substrate for surface enhanced Raman spectroscopy (SERS) observation. Due to possessing the excellent magnetic properties and stable catalytic properties at room temperature, the nanocomposites can clean themselves by photocatalytic degradation of dye molecules under irradiation with UV light into inorganic small molecules for the self-cleaning SERS detection. Furthermore, the nanocomposites can be used as the SERS substrate for monitoring the catalytic degradation of dye molecules.

  15. Enhanced stability of Zn2SnO4 with N719, N3 and eosin Y dye molecules for DSSC application.

    PubMed

    Pratim Das, Partha; Roy, Anurag; Das, Sumita; Devi, Parukuttyamma Sujatha

    2016-01-21

    In view of the increased prospects of Zn2SnO4 as an alternative photoanode for dye sensitized solar cells (DSSCs), we synthesized phase pure Zn2SnO4 nanostructures by a cost effective sonochemical technique. In order to establish the stability of this alternative photoanode in DSSCs, we further explored the interaction of the synthesized Zn2SnO4 with commonly used photosensitizers in DSSCs, such as N3, N719 and eosin Y. Based on the time dependent optical studies we could establish the prominence of anchoring groups in controlling the dye loading. Optical studies confirmed an enhanced stable interaction of Zn2SnO4 with all the studied sensitizers which could be beneficial in designing DSSC devices in future. In addition, we also established contact angle measurement as an indirect tool to understand the surface characteristics and thereby optimize the dye loading and stability of the photoanode surface. With the help of contact angle data, we could unequivocally establish the stability of the Zn2SnO4 photoanode surface modified with N3 and N719 dye molecules. Our studies further suggest the enhanced and superior stability of the prepared Zn2SnO4 compared to ZnO in different chemical environments. The quenching of the fluorescence and the abrupt decrease in the contact angle owing to an increase in the surface roughness further strengthen the above conclusion. To our best knowledge, this probably is the first report on the synthesis of Zn2SnO4 by a sonochemical process and its interaction with various photosensitizers. An exceptionally high open circuit voltage of >0.8 V was observed for all the devices fabricated with the synthesized ZTO as a photoanode. Our studies could pave way to future developments in the area of DSSCs using Zn2SnO4 as a photoanode. PMID:26498509

  16. Enhanced photostability of an anthracene-based dye due to supramolecular encapsulation: a new type of photostable fluorophore for single-molecule study.

    PubMed

    Mitsui, Masaaki; Higashi, Koji; Takahashi, Ryoya; Hirumi, Yohei; Kobayashi, Kenji

    2014-08-01

    For single-molecule fluorescence studies, highly photostable fluorophores are absolutely imperative, because photo-induced degradation (i.e., photobleaching) limits the observation time of individual molecules. Herein, the photophysics and photostability of a highly fluorescent 9,10-bis(phenylethynyl)anthracene derivative (G) and its self-assembled boronic ester encapsulation complex (G@Cap) embedded in a glassy polymer matrix are investigated by single-molecule fluorescence spectroscopy (SMFS). The heterogeneity of the fluorescence emission wavelength and triplet blinking kinetics of the guest G are significantly decreased by supramolecular encapsulation due to conformational restriction and reduced heterogeneity in the local environment. A nearly 10-fold increase in the photostability of G due to encapsulation is quantitatively confirmed by evaluating the photobleaching yields of G and G@Cap. In addition, it is found that the G@Cap is >30-fold more photostable than rhodamine 6G, a widely used fluorescent dye in single-molecule studies. These results demonstrate that the G@Cap can serve as a very bright, long-lasting fluorescent probe for single-molecule studies. PMID:24887756

  17. Energy relay from an unconventional yellow dye to CdS/CdSe quantum dots for enhanced solar cell performance.

    PubMed

    Narayanan, Remya; Das, Amrita; Deepa, Melepurath; Srivastava, Avanish Kumar

    2013-12-01

    A new design for a quasi-solid-state Forster resonance energy transfer (FRET) enabled solar cell with unattached Lucifer yellow (LY) dye molecules as donors and CdS/CdSe quantum dots (QDs) tethered to titania (TiO2 ) as acceptors is presented. The Forster radius is experimentally determined to be 5.29 nm. Sequential energy transfer from the LY dye to the QDs and electron transfer from the QDs to TiO2 is followed by fluorescence quenching and electron lifetime studies. Cells with a donor-acceptor architecture (TiO2 /CdS/CdSe/ZnS-LY/S(2-)-multi-walled carbon nanotubes) show a maximum incident photon-to-current conversion efficiency of 53 % at 530 nm. This is the highest efficiency among Ru-dye free FRET-enabled quantum dot solar cells (QDSCs), and is much higher than the donor or acceptor-only cells. The FRET-enhanced solar cell performance over the majority of the visible spectrum paves the way to harnessing the untapped potential of the LY dye as an energy relay fluorophore for the entire gamut of dye sensitized, organic, or hybrid solar cells. PMID:24259302

  18. Probing Single-Molecule T4 Lysozyme Conformational Dynamics by Intramolecular Fluorescence Energy Transfer

    SciTech Connect

    Chen, Yu; Hu, Dehong; Vorpagel, Erich R.; Lu, H PETER.

    2003-07-16

    We demonstrate the use of single-molecule spectroscopy to study enzyme conformational motions of T4 lysozyme under hydrolysis reaction of the polysaccharide walls of E. Coli B cells.By attaching a donoracceptor pair of dye molecules site-specifically to noninterfering sites on the enzyme, the hinge-bending motions of the enzyme are measured by monitoring the donor-acceptor emission intensity as a function of time. The overall enzymatic reaction rate constants are found to vary widely from molecule to molecule. The dominant contribution to this static inhomogeneity is attributed to enzyme searching for reactive sites on the substrate.

  19. Inter- and intra-molecular energy transfers of encapsulate dyes in dendrimers

    NASA Astrophysics Data System (ADS)

    Otomo, Akira; Zhou, Minniu; Furumi, Seiichi; Yokoyama, Shiyoshi; Mashiko, Shinro

    2002-12-01

    Dendrimers are capable to encapsulate small molecules inside them. Because three-dimensional structures of dendrimers are highly controllable, energy transfers among dye molecules encapsulated inside them can be controlled precisely. Electronic energy transfers from optical excited molecules are categorized into two classes, Forster and Dexter types. Inter-molecular interactions between encapsulated dyes can be expressed as the Forster (singlet-singlet) energy transfer, because the size of dendrimers extends to a few nanometers. We have evaluated time resolved optical responses in rhodamine-cored dendrimer films. Fast decay in fluorescent lifetime is observed and it depends on the dendrimer size. A low generation dendrimer shows lifetime as short as 10 psec without severe quenching of fluorescence. A quadratic dependence of the emission intensity on density of molecules indicates that the origin of the short lifetime is not only energy transfer, but also super-radiance. Since the Dexter (triplet-triplet) energy transfer occurs in short range of 1.0 nm, we attached both donor and acceptor molecules to a dendrimer for investigation. We demonstrated photocrosslinking via triplet-triplet energy transfer from donor molecules encapsulated to acceptors attached at the surface. This procedure of triplet-triplet energy transfer in dendritic molecules opens up way to design novel optical and electrical molecular devices.

  20. Donor-Acceptor-Donor Thienopyrazines via Pd-Catalyzed C-H Activation as NIR Fluorescent Materials.

    PubMed

    McNamara, Louis E; Liyanage, Nalaka; Peddapuram, Adithya; Murphy, J Scott; Delcamp, Jared H; Hammer, Nathan I

    2016-01-01

    A series of thienopyrazine-based donor-acceptor-donor (D-A-D) near-infrared (NIR) fluorescent compounds were synthesized through a rapid, palladium-catalyzed C-H activation route. The dyes were studied through computational analysis, electrochemical properties analysis, and characterization of their photophysical properties. Large Stokes shifts of approximately 175 nm were observed, which led to near-infrared emission. Computational evaluation shows that the origin of this large Stokes shift is a significant molecular reorganization particularly about the D-A bond. The series exhibits quantum yields of up to φ = >4%, with emission maxima ranging from 725 to 820 nm. The emission is strong in solution, in thin films, and also in isolation at the single-molecule level. Their stable emission at the single-molecule level makes these compounds good candidates for single-molecule photon sources in the near-infrared. PMID:26599501

  1. Alternansucrase acceptor products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The regioselectivity of alternansucrase (EC 2.4.1.140) differs from dextransucrase (EC 2.4.1.5) in ways that can be useful for the synthesis of novel oligosaccharide structures. For example, it has been recently shown that the major oligosaccharides produced when maltose is the acceptor include one...

  2. Concentration-dependent energy transfer studies in ternary dye mixture of Stilbene-420, Coumarin-540 and Nile Blue.

    PubMed

    Sharma, A K; Ahlawat, D S; Mohan, D; Singh, R D

    2009-01-01

    The energy transfer studies in the case of ternary dye mixture [Stilbene-420 (donor)+Coumarin-540 (intermediator)+Nile Blue (acceptor)] have been done and discussed through optical gain characteristics at various acceptor concentrations under nitrogen laser excitation. The concentration of the other two dyes were kept constant. It is observed that the concentration of the acceptor dye plays a very critical role in energy transfer dye laser (ETDL) as small change in its concentration varies the intensity of the laser output in the red region by large amount. Also, the highest laser output in the red region is obtained when the concentration of the acceptor dye is slightly higher than that of the intermediator dye. The present studies are helpful in deciding the optimum concentration of the acceptor dye to be used in ternary dye mixture for maximum gain and tuning range. The ternary dye mixture under study provides an ETDL tuning range up to 700 nm. PMID:18930436

  3. Concentration-dependent energy transfer studies in ternary dye mixture of Stilbene-420, Coumarin-540 and Nile Blue

    NASA Astrophysics Data System (ADS)

    Sharma, A. K.; Ahlawat, D. S.; Mohan, D.; Singh, R. D.

    2009-01-01

    The energy transfer studies in the case of ternary dye mixture [Stilbene-420 (donor) + Coumarin-540 (intermediator) + Nile Blue (acceptor)] have been done and discussed through optical gain characteristics at various acceptor concentrations under nitrogen laser excitation. The concentration of the other two dyes were kept constant. It is observed that the concentration of the acceptor dye plays a very critical role in energy transfer dye laser (ETDL) as small change in its concentration varies the intensity of the laser output in the red region by large amount. Also, the highest laser output in the red region is obtained when the concentration of the acceptor dye is slightly higher than that of the intermediator dye. The present studies are helpful in deciding the optimum concentration of the acceptor dye to be used in ternary dye mixture for maximum gain and tuning range. The ternary dye mixture under study provides an ETDL tuning range up to 700 nm.

  4. Fluorene-based sensitizers with a phenothiazine donor: effect of mode of donor tethering on the performance of dye-sensitized solar cells.

    PubMed

    Baheti, Abhishek; Justin Thomas, K R; Li, Chun-Ting; Lee, Chuan-Pei; Ho, Kuo-Chuan

    2015-02-01

    Two types of fluorene-based organic dyes featuring T-shape/rod-shape molecular configuration with phenothiazine donor and cyanoacrylic acid acceptor have been synthesized and characterized as sensitizers for dye-sensitized solar cells. Phenothiazine is functionalized at either nitrogen (N10) or carbon (C3) to obtain T-shape and rod-like organic dyes, respectively. The effect of structural alternation on the optical, electrochemical, and the photovoltaic properties is investigated. The crystal structure determination of the dye containing phenyl linker revealed cofacial slip-stack columnar packing of the molecules. The trends in the optical properties of the dyes are interpreted using time-dependent density functional theory (TDDFT) computations. The rod-shaped dyes exhibited longer wavelength absorption and low oxidation potentials when compared to the corresponding T-shaped dyes attributable to the favorable electronic overlap between the phenothiazine unit and the rest of the molecule in the former dyes. However, the T-shaped dyes showed better photovoltaic properties due to the lowest unoccupied molecular orbital (LUMO) energy level favorable for electron injection into the conduction band of TiO2 and appropriate orientation of the phenothiazine unit rendering effective surface blocking to suppress the recombination of electrons between the electrolyte I3(-) and TiO2. The electrochemical impedance spectroscopy investigations provide further support for the variations in the electron injection and transfer kinetics due to the structural modifications. PMID:25557120

  5. Dye-modified nanochannel materials for photoelectronic and optical devices.

    PubMed

    Calzaferri, Gion; Li, Huanrong; Brühwiler, Dominik

    2008-01-01

    Artificial photonic antenna systems have been realised by incorporating organic dyes into zeolite L. The size and aspect ratio of the cylindrically shaped zeolite crystals can be tuned over a wide range, adding to the versatility of this host material. A 600 nm sized crystal, for example, consists of about 96 000 one-dimensional channels oriented parallel to the cylinder axis. Geometrical constraints imposed by the host structure lead to supramolecular organisation of the guests, allowing high concentrations of non- or only very weakly interacting dye molecules. A special twist is added to these systems by plugging the channel openings with a second type of fluorescent dye, a so-called stopcock molecule. The two types of molecules are precisely tuned to each other; the stopcocks are able to accept excitation energy from the dyes in the channels, but cannot pass it back. The supramolecular organisation of dyes in the zeolite channels corresponds to a first stage of organisation, allowing light-harvesting within the volume of a cylindrical crystal and radiationless energy transport to either the cylinder ends or centre. The second stage of organisation represents the coupling to an external acceptor or donor stopcock fluorophore at the channel entrances, which can then trap or inject electronic excitation energy. The third stage of organisation is realised by interfacing the material to an external device through a stopcock intermediate. We observed that electronic-excitation-energy transfer in dye-zeolite L materials occurs mainly along the channel axis and we have shown that macroscopically organised materials can be prepared. The new materials offer unique possibilities as building blocks for optical, electro-optical and sensing devices. PMID:18626875

  6. J-aggregates of organic dye molecules complexed with iron oxide nanoparticles for imaging-guided photothermal therapy under 915-nm light.

    PubMed

    Song, Xuejiao; Gong, Hua; Liu, Teng; Cheng, Liang; Wang, Chao; Sun, Xiaoqi; Liang, Chao; Liu, Zhuang

    2014-11-12

    Recently, the development of nano-theranostic agents aiming at imaging guided therapy has received great attention. In this work, a near-infrared (NIR) heptamethine indocyanine dye, IR825, in the presence of cationic polymer, polyallylamine hydrochloride (PAH), forms J-aggregates with red-shifted and significantly enhanced absorbance. After further complexing with ultra-small iron oxide nanoparticles (IONPs) and the followed functionalization with polyethylene glycol (PEG), the obtained IR825@PAH-IONP-PEG composite nanoparticles are highly stable in different physiological media. With a sharp absorbance peak, IR825@PAH-IONP-PEG can serve as an effective photothermal agent under laser irradiation at 915 nm, which appears to be optimal in photothermal therapy application considering its improved tissue penetration compared with 808-nm light and much lower water heating in comparison to 980-nm light. As revealed by magnetic resonance (MR) imaging, those nanoparticles after intravenous injection exhibit high tumor accumulation, which is then harnessed for in vivo photothermal ablation of tumors, achieving excellent therapeutic efficacy in a mouse tumor model. This study demonstrates for the first time that J-aggregates of organic dye molecules are an interesting class of photothermal material, which when combined with other imageable nanoprobes could serve as a theranostic agent for imaging-guided photothermal therapy of cancer. PMID:24976309

  7. The dual transcriptional regulator CysR in Corynebacterium glutamicum ATCC 13032 controls a subset of genes of the McbR regulon in response to the availability of sulphide acceptor molecules

    PubMed Central

    Rückert, Christian; Milse, Johanna; Albersmeier, Andreas; Koch, Daniel J; Pühler, Alfred; Kalinowski, Jörn

    2008-01-01

    Background Regulation of sulphur metabolism in Corynebacterium glutamicum ATCC 13032 has been studied intensively in the last few years, due to its industrial as well as scientific importance. Previously, the gene cg0156 was shown to belong to the regulon of McbR, a global transcriptional repressor of sulphur metabolism in C. glutamicum. This gene encodes a putative ROK-type regulator, a paralogue of the activator of sulphonate utilisation, SsuR. Therefore, it is an interesting candidate for study to further the understanding of the regulation of sulphur metabolism in C. glutamicum. Results Deletion of cg0156, now designated cysR, results in the inability of the mutant to utilise sulphate and aliphatic sulphonates. DNA microarray hybridisations revealed 49 genes with significantly increased and 48 with decreased transcript levels in presence of the native CysR compared to a cysR deletion mutant. Among the genes positively controlled by CysR were the gene cluster involved in sulphate reduction, fpr2 cysIXHDNYZ, and ssuR. Gel retardation experiments demonstrated that binding of CysR to DNA depends in vitro on the presence of either O-acetyl-L-serine or O-acetyl-L-homoserine. Mapping of the transcription start points of five transcription units helped to identify a 10 bp inverted repeat as the possible CysR binding site. Subsequent in vivo tests proved this motif to be necessary for CysR-dependent transcriptional regulation. Conclusion CysR acts as the functional analogue of the unrelated LysR-type regulator CysB from Escherichia coli, controlling sulphide production in response to acceptor availability. In both bacteria, gene duplication events seem to have taken place which resulted in the evolution of dedicated regulators for the control of sulphonate utilisation. The striking convergent evolution of network topology indicates the strong selective pressure to control the metabolism of the essential but often toxic sulphur-containing (bio-)molecules. PMID:18854009

  8. Characteristics of nanostructure dye-sensitized solar cells using food dyes

    NASA Astrophysics Data System (ADS)

    Hosseinnezhad, M.; Rouhani, S.

    2016-01-01

    Dye-sensitized solar cells (DSSCs) were prepared using various food dyes. Food dyes are economically superior to organometallic dyes since they are nontoxic and inexpensive. The spectrophotometric evaluation of chosen food dyes in solution and on a TO2 substrate show that the dyes form J-aggregation on the photoelectrode substrate. Oxidation of potential measurements for used food dyes ensured an energetically permissible and thermodynamically favorable charge transfer throughout the continuous cycle of a photo-electric conversion. The performance of dye-sensitized solar cells based on food dyes was studied. The results illustrate that the dye containing carboxylic acid and sulfonic acid as the acceptor group gave the maximum conversion efficiency 4.20%.

  9. Characteristics of nanostructure dye-sensitized solar cells using food dyes

    NASA Astrophysics Data System (ADS)

    Hosseinnezhad, M.; Rouhani, S.

    2016-01-01

    Dye-sensitized solar cells (DSSCs) were prepared using various food dyes. Food dyes are economically superior to organometallic dyes since they are nontoxic and inexpensive. The spectrophotometric evaluation of chosen food dyes in solution and on a TiO2 substrate show that the dyes form J-aggregation on the photoelectrode substrate. Oxidation of potential measurements for used food dyes ensured an energetically permissible and thermodynamically favorable charge transfer throughout the continuous cycle of a photo-electric conversion. The performance of dye-sensitized solar cells based on food dyes was studied. The results illustrate that the dye containing carboxylic acid and sulfonic acid as the acceptor group gave the maximum conversion efficiency 4.20%.

  10. Fluorescence Detection of Single DNA Molecules.

    PubMed

    Huang, Weidong; Wang, Yue; Wang, Zhimin

    2015-09-01

    Single-molecule detection (SMD) and single-molecule fluorescence resonance energy transfer (smFRET) were conducted using Cy3- and Cy5-labeled single-strand DNAs (ssDNAs) either immobilized on substrates or encapsulated in microdroplets. High-quality fluorescent images were obtained using a total internal reflection fluorescence microscope (TIRFM). In the substrate system, deposition of a low concentration of fluorescence molecules on substrates through electrostatic adsorption showed that most of the fluorescence spots were single molecules, and the mean value of signal to noise ratio (S/N) reached 6.9 ± 0.34. smFRET analysis was conducted through immobilization of donor- and acceptor-labeled oligonucleotides on substrates. In the droplet system, fluorophor-labeled oligonucleotides were injected into T-type microfluidics. Single and double fluorophor-labeled DNA molecules encapsulated in droplets were detected, the FRET efficiency and inter-dye distance of a single donor-acceptor pair were measured accurately. smFRET was conducted detailedly in the tortuous channel for the first time. PMID:26215080

  11. Oxygen as Acceptor.

    PubMed

    Borisov, Vitaliy B; Verkhovsky, Michael I

    2015-01-01

    Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate-specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophosphate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and dimethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O₂ is served by two major oxidoreductases (oxidases), cytochrome bo₃ encoded by cyoABCDE and cytochrome bd encoded by cydABX. Terminal oxidases of aerobic respiratory chains of bacteria, which use O₂ as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo₃ and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo₃ and cytochrome bd. The E. coli membrane contains three types of quinones that all have an octaprenyl side chain (C₄₀). It has been proposed that the bo₃ oxidase can have two ubiquinone-binding sites with different affinities. "WHAT'S NEW" IN THE REVISED ARTICLE: The revised article comprises additional information about subunit composition of cytochrome bd and its role in bacterial resistance to nitrosative and oxidative stresses. Also, we present the novel data on the electrogenic function of appBCX-encoded cytochrome bd-II, a second bd-type oxidase that had been thought not to contribute to generation of a proton motive force in E

  12. Bright, Red Single-Molecule Emitters: Synthesis and Properties of Environmentally Sensitive Dicyanomethylenedihydrofuran (DCDHF) Fluorophores with Bisaromatic Conjugation

    PubMed Central

    Lu, Zhikuan; Liu, Na; Lord, Samuel J.; Bunge, Scott D.; Moerner, W. E.; Twieg, Robert. J.

    2009-01-01

    A group of new fluorescent dye materials for single-molecule imaging applications comprised of an amine donor, a π-system comprised of phenyl and thiophene rings and a 2-dicyanomethylene-3-cyano-2,5-dihydrofuran acceptor group have been synthesized. Relative to comparable single-ring compounds these doubly aromatic conjugated fluorophores have red-shifted absorption and emission usually accompanied by significantly increased quantum yields. Solvatochromism studies indicate that the photophysical properties of these dyes are sensitive to the solvent polarity and environmental rigidity. Photophysical studies demonstrate that these DCDHF dye materials are strong single-molecule emitters and the total number of detected photons per molecule is among the highest thus far for this family of fluorophores. PMID:20140061

  13. Coordination programming of photofunctional molecules.

    PubMed

    Sakamoto, Ryota; Kusaka, Shinpei; Hayashi, Mikihiro; Nishikawa, Michihiro; Nishihara, Hiroshi

    2013-01-01

    Our recent achievements relating to photofunctional molecules are addressed. Section 1 discloses a new concept of photoisomerization. Pyridylpyrimidine-copper complexes undergo a ring inversion that can be modulated by the redox state of the copper center. In combination with an intermolecular photoelectron transfer (PET) initiated by the metal-to-ligand charge transfer (MLCT) transition of the Cu(I) state, we realize photonic regulation of the ring inversion. Section 2 reports on the first examples of heteroleptic bis(dipyrrinato)zinc(II) complexes. Conventional homoleptic bis(dipyrrinato)zinc(II) complexes suffered from low fluorescence quantum yields, whereas the heteroleptic ones feature bright fluorescence even in polar solvents. Section 3 describes our new findings on Pechmann dye, which was first synthesized in 1882. New synthetic procedures for Pechmann dye using dimethyl bis(arylethynyl)fumarate as a starting material gives rise to its new structural isomer. We also demonstrate potentiality of a donor-acceptor-donor type of Pechmann dye in organic electronics. PMID:23563859

  14. Influence of the glass transition on rotational dynamics of dyes in thin polymer films: single-molecule and ensemble experiments.

    PubMed

    Araoz, Beatriz; Carattino, Aquiles; Täuber, Daniela; von Borczyskowski, Christian; Aramendia, Pedro F

    2014-11-13

    We performed polarized fluorescence emission studies of Nile Red (NR) in poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA) at the single molecule (SM) and at the ensemble level to study the in cage movements of the ground-state molecule in polymer films of nanometric thickness at room temperature. Experiments were performed with wide field irradiation. At the ensemble level, the linearly polarized irradiation was used to induce a photoselection by bleaching, which is compensated by rotational diffusion. Both results show an appreciable difference in mobility of NR in the films that is correlated with the different glass-transition temperatures of the films, particularly in PEMA, which displays a clearly distinct behavior between the 200 nm films, representing a rigid environment, and the 25 nm ones, showing much higher mobility. We developed a model of broad application for polarized photobleaching that allows obtaining rotational diffusion coefficients and photobleaching quantum yields in an easy way from ensemble experiments. The parameters obtained from ensemble measurements correlate well with the results from SM experiments. PMID:24870555

  15. Theoretical and experimental investigations of the 2-(4-chlorophenyl)-3-{[5-(2-cyano-2-phenylethenyl)]furan-2-yl}acrylonitrile molecule as a potential acceptor in organic solar cells

    NASA Astrophysics Data System (ADS)

    Kazici, Mehmet; Bozar, Sinem; Aydin Yuksel, Sureyya; Ongul, Fatih; Gokce, Halil; Gunes, Serap; Yorur Goreci, Cigdem

    2016-06-01

    A novel soluble asymmetric acrylonitrile derivative, 2-(4-Chlorophenyl)-3-{[5-(2-cyano-2-phenylethenyl)]furan-2-yl}acrylonitrile (CPCPFA, 3) was synthesized in three steps by Knoevenagel condensation. The structure of the CPCPFA was characterized using UV–vis, FTIR, 1H NMR, 13C NMR, and LC-MS. CPCPFA was evaluated as an electron acceptor in bulk heterojunction organic solar cells. Its optical and electronic properties as well as photovoltaic performance were investigated.

  16. Theoretical and experimental investigations of the 2-(4-chlorophenyl)-3-{[5-(2-cyano-2-phenylethenyl)]furan-2-yl}acrylonitrile molecule as a potential acceptor in organic solar cells.

    PubMed

    Kazici, Mehmet; Bozar, Sinem; Yuksel, Sureyya Aydin; Ongul, Fatih; Gokce, Halil; Gunes, Serap; Goreci, Cigdem Yorur

    2016-06-10

    A novel soluble asymmetric acrylonitrile derivative, 2-(4-Chlorophenyl)-3-{[5-(2-cyano-2-phenylethenyl)]furan-2-yl}acrylonitrile (CPCPFA, 3) was synthesized in three steps by Knoevenagel condensation. The structure of the CPCPFA was characterized using UV-vis, FTIR, (1)H NMR, (13)C NMR, and LC-MS. CPCPFA was evaluated as an electron acceptor in bulk heterojunction organic solar cells. Its optical and electronic properties as well as photovoltaic performance were investigated. PMID:27145976

  17. Enhanced Charge Mobility in Polymer Nanocomposites Incorporating Donor-Acceptor Interfaces

    NASA Astrophysics Data System (ADS)

    Tameev, Alexey R.; Nikitenko, Vladimir R.; Vannikov, Anatoly V.

    2011-01-01

    Charge carrier transport in donor-acceptor (D-A) composites based on either poly(N-vinyl carbazole) or polyimide derivative incorporating either carbon single-walled nanotubes or nanocrystals of J-aggregated cyanine dyes is shown to exhibit a similar behavior. In the composite films, polymer/nanomaterial interface provides pathways of the high conductivity. Charge-transfer states (CTS) formed at the D-A interface are involved in the transport. The charge transport along the interface is suggested to arise due to the D-A integer charge transfer and strong interaction between adjacent opposite charges located on the donor and acceptor molecules. The approach based on the concept of sequence of charge carrier transfers through charge transfer states describes the increased electron and hole mobility in the composites. The approach predicts enhanced conductivity with reduced activation energy. Moreover, once the density of electron-hole pairs at the interface is rather high, significant part of the charge carriers can avoid hopping transport resulting in conductivity of metal type. The value of two-dimensional conductivity is estimated by numerical modeling.

  18. Influence of ZnO nanoparticles on Coumarin-503 and Coumarin-540 dye mixture for energy transfer distributed feedback dye lasers

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, G. V.; Basheer Ahamed, M.

    2016-07-01

    Using organic dyes Coumarin-503 (C503) and Coumarin-540 (C540) as donor and acceptor dyes, respectively, and Nd-YAG as pumping source (355 nm), an energy transfer-distributed feedback dye laser (ETDFDL) was constructed and its characteristics studied. Theoretical studies such as critical transfer radius (Ro), critical concentration (Co), and half quenching concentration (C1/2) were carried out using the absorption and fluorescence spectra of donor and acceptor dyes. On varying the input pump energy to the nanoparticle-incorporated ETDFDL and keeping the acceptor and donor dye concentrations constant, the lasing output obtained was found to be higher than that without the use of nanoparticles. This enhancement was due to the size, shape, and coupling between nanoparticles with the dye mixture. Tunability in the range of 435-553 nm was obtained for both donor (C503) and acceptor (C540) DFDL as a function of the angle of interfering beams of the pump laser.

  19. Donor-acceptor electron transport mediated by solitons.

    PubMed

    Brizhik, L S; Piette, B M A G; Zakrzewski, W J

    2014-11-01

    We study the long-range electron and energy transfer mediated by solitons in a quasi-one-dimensional molecular chain (conjugated polymer, alpha-helical macromolecule, etc.) weakly bound to a donor and an acceptor. We show that for certain sets of parameter values in such systems an electron, initially located at the donor molecule, can tunnel to the molecular chain, where it becomes self-trapped in a soliton state, and propagates to the opposite end of the chain practically without energy dissipation. Upon reaching the end, the electron can either bounce back and move in the opposite direction or, for suitable parameter values of the system, tunnel to the acceptor. We estimate the energy efficiency of the donor-acceptor electron transport depending on the parameter values. Our calculations show that the soliton mechanism works for the parameter values of polypeptide macromolecules and conjugated polymers. We also investigate the donor-acceptor electron transport in thermalized molecular chains. PMID:25493866

  20. Donor-acceptor electron transport mediated by solitons

    NASA Astrophysics Data System (ADS)

    Brizhik, L. S.; Piette, B. M. A. G.; Zakrzewski, W. J.

    2014-11-01

    We study the long-range electron and energy transfer mediated by solitons in a quasi-one-dimensional molecular chain (conjugated polymer, alpha-helical macromolecule, etc.) weakly bound to a donor and an acceptor. We show that for certain sets of parameter values in such systems an electron, initially located at the donor molecule, can tunnel to the molecular chain, where it becomes self-trapped in a soliton state, and propagates to the opposite end of the chain practically without energy dissipation. Upon reaching the end, the electron can either bounce back and move in the opposite direction or, for suitable parameter values of the system, tunnel to the acceptor. We estimate the energy efficiency of the donor-acceptor electron transport depending on the parameter values. Our calculations show that the soliton mechanism works for the parameter values of polypeptide macromolecules and conjugated polymers. We also investigate the donor-acceptor electron transport in thermalized molecular chains.

  1. Does the position of the electron-donating nitrogen atom in the ring system influence the efficiency of a dye-sensitized solar cell? A computational study.

    PubMed

    Biswas, Abul Kalam; Barik, Sunirmal; Das, Amitava; Ganguly, Bishwajit

    2016-06-01

    We have reported a number of new metal-free organic dyes (2-6) that have cyclic asymmetric benzotripyrrole derivatives as donor groups with peripheral nitrogen atoms in the ring, fluorine and thiophene groups as π-spacers, and a cyanoacrylic acid acceptor group. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to examine the influence of the position of the donor nitrogen atom and π-conjugation on solar cell performance. The calculated electron-injection driving force (ΔG inject), electron-regeneration driving force (ΔG regen), light-harvesting efficiency (LHE), dipole moment (μ normal), and number of electrons transferred (∆q) indicate that dyes 3, 4, and 6 have significantly higher efficiencies than reference dye 1, which exhibits high efficiency. We also extended our comparison to some other reported dyes, 7-9, which have a donor nitrogen atom in the middle of the ring system. The computed results suggest that dye 6 possesses a higher incident photon to current conversion efficiency (IPCE) than reported dyes 7-9. Thus, the use of donor groups with peripheral nitrogen atoms appears to lead to more efficient dyes than those in which the nitrogen atom is present in the middle of the donor ring system. Graphical Abstract The locations of the nitrogen atoms in the donor groups in the designed dye molecules have an important influence on DSSC efficiency. PMID:27155868

  2. Fluorescence quenching and photocatalytic degradation of textile dyeing waste water by silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Kavitha, S. R.; Umadevi, M.; Janani, S. R.; Balakrishnan, T.; Ramanibai, R.

    2014-06-01

    Silver nanoparticles (Ag NPs) of different sizes have been prepared by chemical reduction method and characterized using UV-vis spectroscopy and transmission electron microscopy (HRTEM). Fluorescence spectral analysis showed that the quenching of fluorescence of textile dyeing waste water (TDW) has been found to decrease with decrease in the size of the Ag NPs. Experimental results show that the silver nanoparticles can quench the fluorescence emission of adsorbed TDW effectively. The fluorescence interaction between Ag NPs (acceptor) and TDW (donor) confirms the Förster Resonance Energy Transfer (FRET) mechanism. Long range dipole-dipole interaction between the excited donor and ground state acceptor molecules is the dominant mechanism responsible for the energy transfer. Furthermore, photocatalytic degradation of TDW was measured spectrophotometrically by using silver as nanocatalyst under UV light illumination. The kinetic study revealed that synthesized Ag NPs was found to be effective in degrading TDW.

  3. Physiological and electrochemical effects of different electron acceptors on bacterial anode respiration in bioelectrochemical systems.

    PubMed

    Yang, Yonggang; Xiang, Yinbo; Xia, Chunyu; Wu, Wei-Min; Sun, Guoping; Xu, Meiying

    2014-07-01

    To understand the interactions between bacterial electrode respiration and the other ambient bacterial electron acceptor reductions, alternative electron acceptors (nitrate, Fe2O3, fumarate, azo dye MB17) were added singly or multiply into Shewanella decolorationis microbial fuel cells (MFCs). All the added electron acceptors were reduced simultaneously with current generation. Adding nitrate or MB17 resulted in more rapid cell growth, higher flavin concentration and higher biofilm metabolic viability, but lower columbic efficiency (CE) and normalized energy recovery (NER) while the CE and NER were enhanced by Fe2O3 or fumarate. The added electron acceptors also significantly influenced the cyclic voltammetry profile of anode biofilm probably via altering the cytochrome c expression. The highest power density was observed in MFCs added with MB17 due to the electron shuttle role of the naphthols from MB17 reduction. The results provided important information for MFCs applied in practical environments where contains various electron acceptors. PMID:24862003

  4. Effect of electron withdrawing unit for dye-sensitized solar cell based on D-A-π-A organic dyes

    SciTech Connect

    Kwon, Dong Yuel; Chang, Dong Min; Kim, Young Sik

    2014-10-15

    Highlights: • To gain the red-shifted absorption spectra, withdrawing unit was substituted in dye. • By the introduction of additional withdrawing unit, LUMOs level of dye are decreased. • Decreasing LUMOs level of dye caused the red-shifted absorption spectra of dye. • Novel acceptor, DCRD, showed better photovoltaic properties than cyanoacetic acid. - Abstract: In this work, two novel D-A-π-A dye sensitizers with triarylamine as an electron donor, isoindigo and cyano group as electron withdrawing units and cyanoacetic acid and 2-(1,1-dicyanomethylene) rhodanine as an electron acceptor for an anchoring group (TICC, TICR) were designed and investigated with the ID6 dye as the reference. The difference in HOMO and LUMO levels were compared according to the presence or absence of isoindigo in ID6 (TC and ID6). To gain insight into the factors responsible for photovoltaic performance, we used density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. Owing to different LUMO levels for each acceptor, the absorption band and molar extinction coefficient of each dye was different. Among the dyes, TICR showed more red-shifted and broader absorption spectra than other dyes and had a higher molar extinction coefficient than the reference. It is expected that TICR would show better photovoltaic properties than the other dyes, including the reference dye.

  5. A study of the role played by the Hartree-Fock orbital exchange in the formation of the energy of the first singlet charge-transfer excited state by the example of JK-62 and JK-201 sensitizing dye molecules

    NASA Astrophysics Data System (ADS)

    Baryshnikov, G. V.; Minaev, B. F.; Slepets, A. A.; Minaeva, V. A.

    2014-03-01

    Based on the time-dependent density functional theory with the use of the functionals B3LYP, B97-2, BHandHLYP, BMK, MPWB1K, PBE1W, PBE1PBE, τ-HCTHh, and TPSS in the 6-31G(d) basis set of atomic orbitals, we have performed a quantum-chemical investigation of electronic and spectral properties of JK-62 and JK-201 bis-dimethylfluorenyl dye sensitizers for Grätzel photoelectric converters. In terms of the Bader theory, we have done a complete analysis of the electron-density distribution function in the dye molecules under study, which proves the occurrence of intramolecular nonvalent interactions, which, in turn, stabilize a planar mutual arrangement of structural fragments of dye molecules. The role that the Hartree-Fock orbital exchange plays in the energy formation of the first and most intense electronic transition, which is responsible for the primary current generation in a solar cell, has been elucidated.

  6. Membrane-Inspired Acidically Stable Dye-Sensitized Photocathode for Solar Fuel Production.

    PubMed

    Click, Kevin A; Beauchamp, Damian R; Huang, Zhongjie; Chen, Weilin; Wu, Yiying

    2016-02-01

    Tandem dye-sensitized photoelectrochemical cells (DSPECs) for water splitting are a promising method for sustainable energy conversion but so far have been limited by their lack of aqueous stability and photocurrent mismatch between the cathode and anode. In nature, membrane-enabled subcellular compartmentation is a general approach to control local chemical environments in the cell. The hydrophobic tails of the lipid make the bilayer impermeable to ions and hydrophilic molecules. Herein we report the use of an organic donor-acceptor dye that prevents both dye desorption and semiconductor degradation by mimicking the hydrophobic/hydrophilic properties of lipid bilayer membranes. The dual-functional photosensitizer (denoted as BH4) allows for efficient light harvesting while also protecting the semiconductor surface from protons and water via its hydrophobic π linker. The protection afforded by this membrane-mimicking dye gives this system excellent stability in extremely acidic (pH 0) conditions. The acidic stability also allows for the use of cubane molybdenum-sulfide cluster as the hydrogen evolution reaction (HER) catalyst. This system produces a proton-reducing current of 183 ± 36 μA/cm(2) (0 V vs NHE with 300 W Xe lamp) for an unprecedented 16 h with no degradation. These results introduce a method for developing high-current, low-pH DSPECs and are a significant move toward practical dye-sensitized solar fuel production. PMID:26744766

  7. Shape, size and composition dependence of efficiency and dynamics of Förster resonance energy transfer in dye-silica nanoconjugates

    NASA Astrophysics Data System (ADS)

    Dhir, Anjali; Datta, Anindya

    2016-06-01

    The role of relative concentrations of energy donors (fluorescein, D), acceptors (rhodamine, A) and silica on Förster resonance energy transfer (FRET) efficiency and dynamics in dye silica conjugates has been studied, as a part of our initial attempts to ascertain the potential of dye-silica nanoconjugates as light harvesting nanoantennae. Two types of dye-silica nanoconjugates, prepared by the co-condensation method, have been examined. The first is based on silica nanoshells (SNS-dye) while the second is based on silica nanoparticles (SNP-dye). Both these nanostructures have a diameter of approximately 25 nm. Efficient energy transfer (91% and 97%, respectively) has been observed in both, for total fluorophore concentration upto 5–6 mmol, irrespective of the D : A ratio. The lower efficiency at dye concentrations greater than these has been rationalized by the competitive self-quenching of D. A risetime of approximately 500 fs is observed in the A emission in SNS-dye, but there is no such feature in SNP-dye. The shape and size dependence of the FRET efficiency and dynamics has been rationalized as follows: the initial step of dye rich core formation in nanoparticles results in high proximity of dye molecules to each other, leading to highly efficient FRET than in nanoshells. In larger SNP-dye nanoconjugates of 65 nm in diameter, the FRET efficiency decreases to 85%, while a risetime in D emission emerges. This provides support to the proposed correlation between efficiency and packing. Hence, it is inferred that total fluorophore concentration, rather than D : A ratios, governs the FRET dynamics and efficiency in these systems.

  8. Highly Fluorescent dye-nanoclay Hybrid Materials Made from Different Dye Classes.

    PubMed

    Grabolle, Markus; Starke, Marian; Resch-Genger, Ute

    2016-04-12

    Nanoclays like laponites, which are commercially avaible in large quantities for a very moderate price, provide a facile solubilization strategy for hydrophobic dyes without the need for chemical functionalization and can act as a carrier for a high number of dye molecules. This does not require reactive dyes, amplifies fluorescence signals from individual emitters due to the high number of dyes molecules per laponite disk, and renders hydrophobic emitters applicable in aqueous environments. Aiming at the rational design of bright dye-loaded nanoclays as a new class of fluorescent reporters for bioanalysis and material sciences and the identification of dye structure-property relationships, we screened a series of commercial fluorescent dyes, differing in dye class, charge, and character of the optical transitions involved, and studied the changes of their optical properties caused by clay adsorption at different dye loading concentrations. Upon the basis of our dye loading density-dependent absorption and fluorescence measurements with S2105 and Lumogen F Yellow 083, we could identify two promising dye-nanoclay hybrid materials that reveal high fluorescence quantum yields of the nanoclay-adsorbed dyes of at least 0.20 and low dye self-quenching even at high dye-loading densities of up to 50 dye molecules per laponite platelet. PMID:27007448

  9. Optical properties of thin merocyanine dye layers for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Dikova, J.; Kitova, S.; Stoyanova, D.; Vasilev, A.; Deligeorgiev, T.; Angelova, S.

    2014-05-01

    The potentiality was studied of our newly synthesized push-pull type merocyanine dye, labeled A1, for use as an electron donating component in solution-processed bulk heterojunction (BHJ) organic solar cells. For the purpose, a soluble n-type fullerene, (6,6)-phenyl C61 butyric acid methyl ester (PCBM), which is currently and in the ear future without an alternative, was chosen as an acceptor. The optical constants (n and k) of thin films obtained by spin coating from solutions in chlorobenzene of A1 and of an A1/PCBM blend were determined by spectrophotometric measurements. Further, an optical simulation of a standard BHJ cell with an active layer of an A1dye/PCMB blend was performed using a transfer-matrix formalism. Thus, the optimum thickness of the active layer was calculated to be about 80 nm, which provides overlapping of the total absorption with the solar spectrum in the broad range 400 nm - 800 nm. Finally, the maximum current density, Jsc, was determined to be 13 mA cm2 assuming that the internal quantum efficiency, IQE, is unity. Comparing the calculated Jsc with data on some advanced small-molecule BHJ devices, the prospects for practical applications of the new merocyanine dye are discussed.

  10. Reactive Fluorescent Dyes For Urethane Coatings

    NASA Technical Reports Server (NTRS)

    Willis, Paul B.; Cuddihy, Edward F.

    1991-01-01

    Molecules of fluorescent dyes chemically bound in urethane conformal-coating materials to enable nondestructive detection of flaws in coats through inspection under ultraviolet light, according to proposal. Dye-bonding technique prevents outgassing of dyes, making coating materials suitable for use where flaw-free coats must be assured in instrumentation or other applications in which contamination by outgassing must be minimized.

  11. Optical Excitation in Donor-Pt-Acceptor Complexes: Role of the Structure.

    PubMed

    Gong, Zu-Yong; Duan, Sai; Tian, Guangjun; Zhang, Guozhen; Jiang, Jun; Luo, Yi

    2016-05-26

    The optical properties of the Pt complexes in the form of donor-metal-acceptor (D-M-A) were studied at the first-principles level. Calculated results show that for the frontier molecular orbitals (MOs) of a D-M-A structure the energies of unoccupied frontier MO can be mainly determined by the interaction between M and A, whereas the M-A and M-D interactions both determine the energies of occupied frontier MO. By developing a straightforward transition dipole decomposition method, we found that not only the local excitations in D but also those in A can significantly contribute to the charge-transfer (CT) excitation. Furthermore, the calculations also demonstrate that by tuning the dihedral angle between D and A the transition probability can be precisely controlled so as to broaden the spectrum region of photoabsorption. For the D-M-A molecule with a delocalized π system in A, the CT excitation barely affects the electronic structures of metal, suggesting that the oxidation state of the metal can be kept during the excitation. These understandings for the optical properties of the D-M-A molecule would be useful for the design of dye-sensitized solar cells, photocatalysis, and luminescence systems. PMID:27135840

  12. Metal oxide-encapsulated dye-sensitized photoanodes for dye-sensitized solar cells

    DOEpatents

    Hupp, Joseph T.; Son, Ho-Jin

    2016-01-12

    Dye-sensitized semiconducting metal oxide films for photoanodes, photoanodes incorporating the films and DSCs incorporating the photoanodes are provided. Also provided are methods for making the dye sensitized semiconducting metal oxide films. The methods of making the films are based on the deposition of an encapsulating layer of a semiconducting metal oxide around the molecular anchoring groups of photosensitizing dye molecules adsorbed to a porous film of the semiconducting metal oxide. The encapsulating layer of semiconducting metal oxide is formed in such a way that it is not coated over the chromophores of the adsorbed dye molecules and, therefore, allows the dye molecules to remain electrochemically addressable.

  13. Spectral, thermal and kinetic studies of charge-transfer complexes formed between the highly effective antibiotic drug metronidazole and two types of acceptors: σ- and π-acceptors.

    PubMed

    Refat, Moamen S; Saad, Hosam A; Adam, Abdel Majid A

    2015-04-15

    Understanding the interaction between drugs and small inorganic or organic molecules is critical in being able to interpret the drug-receptor interactions and acting mechanism of these drugs. A combined solution and solid state study was performed to describe the complexation chemistry of drug metronidazole (MZ) which has a broad-spectrum antibacterial activity with two types of acceptors. The acceptors include, σ-acceptor (i.e., iodine) and π-acceptors (i.e., dichlorodicyanobenzoquinone (DDQ), chloranil (CHL) and picric acid (PA)). The molecular structure, spectroscopic characteristics, the binding modes as well as the thermal stability were deduced from IR, UV-vis, (1)H NMR and thermal studies. The binding ratio of complexation (MZ: acceptor) was determined to be 1:2 for the iodine acceptor and 1:1 for the DDQ, CHL or PA acceptor, according to the CHN elemental analyses and spectrophotometric titrations. It has been found that the complexation with CHL and PA acceptors increases the values of enthalpy and entropy, while the complexation with DDQ and iodine acceptors decreases the values of these parameters compared with the free MZ donor. PMID:25677533

  14. Spectral, thermal and kinetic studies of charge-transfer complexes formed between the highly effective antibiotic drug metronidazole and two types of acceptors: σ- and π-acceptors

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.; Saad, Hosam A.; Adam, Abdel Majid A.

    2015-04-01

    Understanding the interaction between drugs and small inorganic or organic molecules is critical in being able to interpret the drug-receptor interactions and acting mechanism of these drugs. A combined solution and solid state study was performed to describe the complexation chemistry of drug metronidazole (MZ) which has a broad-spectrum antibacterial activity with two types of acceptors. The acceptors include, σ-acceptor (i.e., iodine) and π-acceptors (i.e., dichlorodicyanobenzoquinone (DDQ), chloranil (CHL) and picric acid (PA)). The molecular structure, spectroscopic characteristics, the binding modes as well as the thermal stability were deduced from IR, UV-vis, 1H NMR and thermal studies. The binding ratio of complexation (MZ: acceptor) was determined to be 1:2 for the iodine acceptor and 1:1 for the DDQ, CHL or PA acceptor, according to the CHN elemental analyses and spectrophotometric titrations. It has been found that the complexation with CHL and PA acceptors increases the values of enthalpy and entropy, while the complexation with DDQ and iodine acceptors decreases the values of these parameters compared with the free MZ donor.

  15. Donor-acceptor type co-crystals of arylthio-substituted tetrathiafulvalenes and fullerenes.

    PubMed

    Lu, Xiaofeng; Sun, Jibin; Zhang, Shangxi; Ma, Longfei; Liu, Lei; Qi, Hui; Shao, Yongliang; Shao, Xiangfeng

    2015-01-01

    A series of donor-acceptor type co-crystals of fullerene (as the acceptor) and arylthio-substituted tetrathiafulvalene derivatives (Ar-S-TTF, as the donor) were prepared and their structural features were thoroughly investigated. The formation of co-crystals relies on the flexibility of Ar-S-TTF and the size matches between Ar-S-TTF and fullerene. Regarding their compositions, the studied co-crystals can be divided into two types, where types I and II have donor:acceptor ratios of 1:1 and 1:2, respectively. Multiple intermolecular interactions are observed between the donor and acceptor, which act to stabilize the structures of the resulting co-crystals. In the type I co-crystals, the fullerene molecule is surrounded by four Ar-S-TTF molecules, that is, two Ar-S-TTF molecules form a sandwich structure with one fullerene molecule and the other two Ar-S-TTF molecules interact with the fullerene molecule along their lateral axes. In the type II co-crystals, one fullerene molecule has the donor-acceptor mode similar to that in type I, whereas the other fullerene molecule is substantially surrounded by the aryl groups on Ar-S-TTF molecules and the solvent molecules. PMID:26199659

  16. Dye Painting!

    ERIC Educational Resources Information Center

    Johnston, Ann

    This resource provides practical instructions for applying color and design directly to fabric. Basic information about the dye painting process is given. The guide addresses the technical aspects of fabric dye and color use and offers suggestions for fabric manipulation and dye application in order to achieve various design effects. This…

  17. An overview of molecular acceptors for organic solar cells

    NASA Astrophysics Data System (ADS)

    Hudhomme, Piétrick

    2013-07-01

    Organic solar cells (OSCs) have gained serious attention during the last decade and are now considered as one of the future photovoltaic technologies for low-cost power production. The first dream of attaining 10% of power coefficient efficiency has now become a reality thanks to the development of new materials and an impressive work achieved to understand, control and optimize structure and morphology of the device. But most of the effort devoted to the development of new materials concerned the optimization of the donor material, with less attention for acceptors which to date remain dominated by fullerenes and their derivatives. This short review presents the progress in the use of non-fullerene small molecules and fullerene-based acceptors with the aim of evaluating the challenge for the next generation of acceptors in organic photovoltaics.

  18. Acceptors in ZnO

    SciTech Connect

    McCluskey, Matthew D. Corolewski, Caleb D.; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T.; Walter, Eric D.; Norton, M. Grant; Harrison, Kale W.; Ha, Su

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence indicates these point defects have acceptor levels 3.2, 1.4, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO{sub 2} contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals is attributed to an acceptor, which may involve a Zn vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g{sub ⊥} = 2.0015 and g{sub //} = 2.0056, along with an isotropic center at g = 2.0035.

  19. Acceptors in ZnO

    SciTech Connect

    Mccluskey, Matthew D.; Corolewski, Caleb; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T.; Walter, Eric D.; Norton, M. G.; Harrison, Kale W.; Ha, Su Y.

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence shows that these point defects have acceptor levels 3.2, 1.5, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO2 contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals has been attributed to an acceptor, which may involve a zinc vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g = 2.0033 and g = 2.0075, along with an isotropic center at g = 2.0053.

  20. Adsorption geometry, molecular interaction, and charge transfer of triphenylamine-based dye on rutile TiO{sub 2}(110)

    SciTech Connect

    Yu Shun; Ahmadi, Sareh; Weissenrieder, Jonas; Goethelid, Mats; Zuleta, Marcelo; Tian Haining; Yang Xichuan; Schulte, Karina; Pietzsch, Annette; Hennies, Franz

    2010-12-14

    The fast development of new organic sensitizers leads to the need for a better understanding of the complexity and significance of their adsorption processes on TiO{sub 2} surfaces. We have investigated a prototype of the triphenylamine-cyanoacrylic acid (donor-acceptor) on rutile TiO{sub 2} (110) surface with special attention on the monolayer region. This molecule belongs to the type of dye, some of which so far has delivered the record efficiency of 10%-10.3% for pure organic sensitizers [W. Zeng, Y. Cao, Y. Bai, Y. Wang, Y. Shi, M. Zhang, F. Wang, C. Pan, and P. Wang, Chem. Mater. 22, 1915 (2010)]. The molecular configuration of this dye on the TiO{sub 2} surface was found to vary with coverage and adopt gradually an upright geometry, as determined from near edge x-ray absorption fine structure spectroscopy. Due to the molecular interaction within the increasingly dense packed layer, the molecular electronic structure changes systematically: all energy levels shift to higher binding energies, as shown by photoelectron spectroscopy. Furthermore, the investigation of charge delocalization within the molecule was carried out by means of resonant photoelectron spectroscopy. A fast delocalization ({approx}1.8 fs) occurs at the donor part while a competing process between delocalization and localization takes place at the acceptor part. This depicts the ''push-pull'' concept in donor-acceptor molecular system in time scale.

  1. Computational design of donor-bridge-acceptor systems exhibiting pronounced quantum interference effects.

    PubMed

    Gorczak, Natalie; Renaud, Nicolas; Galan, Elena; Eelkema, Rienk; Siebbeles, Laurens D A; Grozema, Ferdinand C

    2016-03-01

    Quantum interference is a well-known phenomenon that dictates charge transport properties of single molecule junctions. However, reports on quantum interference in donor-bridge-acceptor molecules are scarce. This might be due to the difficulties in meeting the conditions for the presence of quantum interference in a donor-bridge-acceptor system. The electronic coupling between the donor, bridge, and acceptor moieties must be weak in order to ensure localised initial and final states for charge transfer. Yet, it must be strong enough to allow all bridge orbitals to mediate charge transfer. We present the computational route to the design of a donor-bridge-acceptor molecule that features the right balance between these contradicting requirements and exhibits pronounced interference effects. PMID:26878200

  2. Molecule-Based Water-Oxidation Catalysts (WOCs): Cluster-Size-Dependent Dye-Sensitized Polyoxometalates for Visible-Light-Driven O2 Evolution

    PubMed Central

    Gao, Junkuo; Cao, Shaowen; Tay, Qiuling; Liu, Yi; Yu, Lingmin; Ye, Kaiqi; Mun, Peter Choon Sze; Li, Yongxin; Rakesh, Ganguly; Loo, Say Chye Joachim; Chen, Zhong; Zhao, Yang; Xue, Can; Zhang, Qichun

    2013-01-01

    From atomic level to understand the cluster-size-dependant behavior of dye-sensitized photocatalysts is very important and helpful to design new photocatalytic materials. Although the relationship between the photocatalytic behaviors and particles' size/shape has been widely investigated by theoretical scientists, the experimental evidences are much less. In this manuscript, we successfully synthesized three new ruthenium dye-sensitized polyoxometalates (POM-n, n relate to different size clusters) with different-sized POM clusters. Under visible-light illumination, all three complexes show the stable O2 evolution with the efficient order POM-3 > POM-2 > POM-1. This cluster-size-dependent catalytic behavior could be explained by the different numbers of M = Ot (terminal oxygen) bonds in each individual cluster because it is well-known that Mo = Ot groups are the catalytically active sites for photooxidation reaction. The proposed mechanism of water oxidation for the dye-sensitized POMs is radical reaction process. This research could open up new perspectives for developing new POM-based WOCs. PMID:23676701

  3. Molecular Engineering of Pyrido[3,4-b]pyrazine-Based Donor-Acceptor-π-Acceptor Organic Sensitizers: Effect of Auxiliary Acceptor in Cobalt- and Iodine-Based Electrolytes.

    PubMed

    Liu, Bo; Giordano, Fabrizio; Pei, Kai; Decoppet, Jean-David; Zhu, Wei-Hong; Zakeeruddin, Shaik M; Grätzel, Michael

    2015-12-14

    Due to the ease of tuning its redox potential, the cobalt-based redox couple has been extensively applied for highly efficient dye-sensitized solar cells (DSSCs) with extraordinarily high photovoltages. However, a cobalt electrolyte needs particular structural changes in the organic dye components to obtain such high photovoltages. To achieve high device performance, specific requirements in the molecular tailoring of organic sensitizers still need to be met. Besides the need for large electron donors, studies of the auxiliary acceptor segment of donor-acceptor-π-acceptor (D-A-π-A) organic sensitizers are still rare in molecular optimization in the context of cobalt electrolytes. In this work, two novel organic D-A-π-A-type sensitizers (IQ13 and IQ17) have been developed and exploited in cobalt- and iodine-based redox electrolyte DSSCs, specifically to provide insight into the effect of π-bridge modification in different electrolytes. The investigation has been focused on the additional electron-withdrawing acceptor capability with grafted long alkoxy chains. Optoelectronic transient measurements have indicated that IQ17 containing a pyrido[3,4-b]pyrazine moiety bearing long alkoxyphenyl chains is more suitable for application in cobalt-based DSSCs. PMID:26548926

  4. Efficiency and stability of spectral sensitization of boron-doped-diamond electrodes through covalent anchoring of a donor-acceptor organic chromophore (P1).

    PubMed

    Krysova, Hana; Barton, Jan; Petrak, Vaclav; Jurok, Radek; Kuchar, Martin; Cigler, Petr; Kavan, Ladislav

    2016-06-28

    A novel procedure is developed for chemical modification of H-terminated B-doped diamond surfaces with a donor-π-bridge-acceptor molecule (P1). A cathodic photocurrent near 1 μA cm(-2) flows under 1 Sun (AM 1.5) illumination at the interface between the diamond electrode and aqueous electrolyte solution containing dimethylviologen (electron mediator). The efficiency of this new electrode outperforms that of the non-covalently modified diamond with the same dye. The found external quantum efficiency of the P1-sensitized diamond is not far from that of the flat titania electrode sensitized by a standard organometallic dye used in solar cells. However, the P1 dye, both pure and diamond-anchored, shows significant instability during illumination by solar light. The degradation is a two-stage process in which the initially photo-generated products further decompose in complicated dark reactions. These findings need to be taken into account for optimization of organic chromophores for solar cells in general. PMID:27264474

  5. Computational study of diketopyrrolopyrrole-based organic dyes for dye sensitized solar cell applications.

    PubMed

    Fan, Wenjie; Tan, Dazhi; Zhang, Qijian; Wang, Huaxing

    2015-04-01

    Four diketopyrrolopyrrole (DPP)-based organic dyes utilizing the donor-π-acceptor motif were investigated by density functional theory (DFT) and time-dependent DFT (TDDFT) approaches. The four dyes were composed of different donor groups, i.e. indoline, carbazole, triphenylamine, and coumarin. We investigated the effects of the DPP unit and different donors on the spectra and electrochemical properties of the dyes, respectively. In comparison with the model dye which adopts a phenylene unit as the π-spacer, the DPP dyes all display remarkably enhanced spectral responses in the visible region of the solar spectrum. The key to this increase was the incorporation of electron-deficient DPP moieties to the molecular core, which significantly lowers LUMO levels and therefore reduces the band gap. The dye/(TiO2)46 anatase nanoparticle systems were also simulated to show the electronic structures at the interface. We studied some key properties including absorption spectra, light-harvesting efficiency, molecular orbital distributions, and injection time of electrons from the excited state of dye to the conduction band of TiO2. The dye DPP-I with indoline moiety as the electron donor demonstrates desirable energetic, electronic, and spectroscopic parameters for dye sensitized solar cells (DSSCs) applications. Our theoretical study is expected to provide valuable insights into the molecular design of novel DPP-based organic dyes for the optimizations of DSSCs. PMID:25662565

  6. Mapping of the active site of Escherichia coli methionyl-tRNA synthetase: Identification of amino acid residues labeled by periodate-oxidized tRNA sup fMet molecules having modified lengths at the 3 prime -acceptor end

    SciTech Connect

    Hountondji, C.; Schmitter, J.M.; Beauvallet, C.; Blanquet, S. )

    1990-09-04

    Initiator tRNA molecules modified at the 3{prime}-end and lacking either A{sub 76} (tRNA-C{sub 75}), the C{sub 75}-A{sub 76} (tRNA-C{sub 74}), the C{sub 74}-C{sub 75}-A{sub 76} (tRNA-A{sub 73}), or the A{sub 73}-C{sub 74}-C{sub 75}-A{sub 76} (tRNA-A{sub 72}) nucleotides were prepared stepwise by repeated periodate, lysine, and alkaline phosphatase treatments. When incubated with trypsin-modified methionyl-tRNA synthetase (MTS{sub T}), excess amounts of the dialdehyde derivative of each of these shortened tRNAs (tRNA-C{sub 75}ox, tRNA-A{sub 73}ox, and tRNA-A{sub 72}ox) abolished both the isotopic ({sup 32}P)PP{sub i}ATP exchange and the tRNA aminoacylation activities of the enzyme. In the presence of limiting concentrations of the various tRNAox species, the relative extents of inactivation of the enzyme were consistent with the formation of 1:1 complexes of the reacting tRNAs with the monomeric modified synthetase. Specificity of the labeling was further established by demonstrating that tRNA-C{sub 75}ox binds the enzyme with an equilibrium constant and stoichiometry values in good agreement with those for the binding of nonoxidized tRNA-C{sub 75}. The peptides of MTS{sub T} labeled with either tRNA-C{sub 75}ox or tRNA-C{sub 74}ox were identified. In a previous work all these peptides but one (peptide D) had been already found labeled upon MTS{sub T} incubation with ({sup 14}C)tRNA-A{sub 76}ox. According to the crystallographic structure of MTS{sub T}, the labeled residues K335, K61, K142, K147, and K149 are within a sphere of about 5.5-{angstrom} radius. The present results therefore argue for a marked flexibility of the 3{prime}-end of the enzyme-bound tRNA, enabling it to contact any of the identified reacting residues. Such a cluster of basic amino acids may reflect ionic requirements in the guiding of the negatively charged CCA arm of tRNA toward enzyme-bound methionyl-adenylate.

  7. FRET Sensor for Erythrosine Dye Based on Organic Nanoparticles: Application to Analysis of Food Stuff.

    PubMed

    Mahajan, Prasad G; Bhopate, Dhanaji P; Kolekar, Govind B; Patil, Shivajirao R

    2016-07-01

    An aqueous suspension of fluorescent nanoparticles (PHNNPs) of naphthol based fluorescent organic compound 1-[(Z)-(2-phenylhydrazinylidene) methyl] naphthalene -2-ol (PHN) were prepared using reprecipitation method shows bathochromically shifted aggregation induced enhanced emission (AIEE) in the spectral region where erythrosine (ETS) food dye absorbs strongly. The average size of 72.6 nm of aqueous suspension of PHNNPs obtained by Dynamic light scattering results shows a narrow particle size distribution. The negative zeta potential of nano probe (-22.6 mV) responsible to adsorb oppositely charged analyte on its surface and further permit to bind nano probe and analyte within the close distance proximity required for efficient fluorescence resonance energy transfer (FRET) to take place from donor (PHNNPs) to acceptor (ETS). Systematic FRET experiments performed by measuring fluorescence quenching of PHNNPs with successive addition of ETS solution exploited the use of the PHNNPs as a novel nano probe for the detection of ETS in aqueous solution with extremely lower limit of detection equal to 3.6 nM (3.1 ng/mL). The estimation of photo kinetic and thermodynamic parameters such as quenching rate constant, enthalpy change (∆H), Gibbs free energy change (∆G) and entropy change (∆S) was obtained by the quenching results obtained at different constant temperatures which were found to fit the well-known Stern-Volmer relation. The mechanism of binding and fluorescence quenching of PHNNPs by ETS food dye is proposed on the basis of results obtained in photophysical studies, thermodynamic parameter, energy transfer efficiency, critical energy transfer distance (R0) and distance of approach between donor-acceptor molecules (r). The proposed FRET method based on fluorescence quenching of PHNNPs was successfully applied to develop an analytical method for estimation of ETS from food stuffs without interference of other complex ingredients. Graphical Abstract A

  8. Free Carrier Generation in Organic Photovoltaic Bulk Heterojunctions of Conjugated Polymers with Molecular Acceptors: Planar versus Spherical Acceptors

    SciTech Connect

    Nardes, Alexandre M.; Ferguson, Andrew J.; Wolfer, Pascal; Gui, Kurt; Burn, Paul L.; Meredith, Paul; Kopidakis, Nikos

    2014-03-05

    We present a comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85 % of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. Here, we propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  9. The Structure-property Relationships of D-π-A BODIPY Dyes for Dye-sensitized Solar Cells.

    PubMed

    Mao, Mao; Song, Qin-Hua

    2016-04-01

    BODIPY dyes have attracted considerable attention as potential photosensitizers in dye-sensitized solar cells (DSSCs) owing to their excellent optical properties and facile structural modification. This account focuses on recent advances in the molecular design of D-π-A BODIPY dyes for applications in DSSCs. Special attention has been paid to the structure-property relationships of D-π-A BODIPY dyes for DSSCs. The developmental process in the modified position at the BODIPY core with a donor/acceptor is described. The devices based on 2,6-modified BODIPY dyes exhibit better photovoltaic performance over other modified BODIPY dyes. Meanwhile, the research reveals the correlation of molecular structures (various donor chromophores, extended units, molecular frameworks, and long alkyl groups) with their photophysical and electrochemical properties and relates it to their performance in DSSCs. The structure-property relationships give valuable information and guidelines for designing new D-π-A BODIPY dyes for DSSCs. PMID:26846846

  10. Fluorescence spectroscopy of single molecules at room temperature and its applications

    SciTech Connect

    Ha, Taekjip

    1996-12-01

    We performed fluorescence spectroscopy of single and pairs of dye molecules on a surface at room temperature. Near field scanning optical microscope (NSOM) and far field scanning optical microscope with multi-color excitation/detection capability were built. The instrument is capable of optical imaging with 100nm resolution and has the sensitivity necessary for single molecule detection. A variety of dynamic events which cannot be observed from an ensemble of molecules is revealed when the molecules are probed one at a time. They include (1) spectral jumps correlated with dark states, (2) individually resolved quantum jumps to and from the meta-stable triplet state, (3) rotational jumps due to desorption/readsorption events of single molecules on the surface. For these studies, a computer controlled optical system which automatically and rapidly locates and performs spectroscopic measurements on single molecules was developed. We also studied the interaction between closely spaced pairs of molecules. In particular, fluorescence resonance energy transfer between a single resonant pair of donor and acceptor molecules was measured. Photodestruction dynamics of the donor or acceptor were used to determine the presence and efficiency of energy transfer Dual molecule spectroscopy was extended to a non-resonant pair of molecules to obtain high resolution differential distance information. By combining NSOM and dual color scheme, we studied the co-localization of parasite proteins and host proteins on a human red blood cell membrane infected with malaria. These dual-molecule techniques can be used to measure distances, relative orientations, and changes in distances/orientations of biological macromolecules with very good spatial, angular and temporal resolutions, hence opening new capabilities in the study of such systems.

  11. Can aliphatic anchoring groups be utilised with dyes for p-type dye sensitized solar cells?

    PubMed

    Hao, Yan; Wood, Christopher J; Clark, Charlotte A; Calladine, James A; Horvath, Raphael; Hanson-Heine, Magnus W D; Sun, Xue-Zhong; Clark, Ian P; Towrie, Michael; George, Michael W; Yang, Xichuan; Sun, Licheng; Gibson, Elizabeth A

    2016-05-01

    A series of novel laterally anchoring tetrahydroquinoline derivatives have been synthesized and investigated for their use in NiO-based p-type dye-sensitized solar cells. The kinetics of charge injection and recombination at the NiO-dye interface for these dyes have been thoroughly investigated using picosecond transient absorption and time-resolved infrared measurements. It was revealed that despite the anchoring unit being electronically decoupled from the dye structure, charge injection occurred on a sub picosecond timescale. However, rapid recombination was also observed due to the close proximity of the electron acceptor on the dyes to the NiO surface, ultimately limiting the performance of the p-DSCs. PMID:27055102

  12. Failure of the IDA in FRET Systems at Close Inter-Dye Distances Is Moderated by Frequent Low κ(2) Values.

    PubMed

    Spiegel, J Dominik; Fulle, Simone; Kleinschmidt, Martin; Gohlke, Holger; Marian, Christel M

    2016-09-01

    Förster resonance energy transfer (FRET) is analyzed in terms of distance- and orientation-dependent interactions between the transition dipole moments of the involved donor and acceptor molecules. However, the ideal dipole approximation (IDA) is known to fail at short donor-acceptor distances. In this work, we model FRET in a Cy5- and Alexa Fluor 488-labeled double-stranded RNA by means of combined molecular dynamics (MD) simulations and quantum-chemical calculations involving the IDA as well as the more sophisticated monomer transition density (MTD) approach. To this end, the relaxed ground-state geometries of the dyes were fitted to the MD-based structures. Although substantial deviations between IDA and MTD results can be observed for individual snapshots, the statistical impact of the failure on the FRET rates is negligible in the chosen examples. Our results clearly demonstrate that the IDA-based Förster model can still be applied to systems with small donor-acceptor distances, provided that the dyes are not trapped in arrangements with a high IDA failure and that the distribution of the relative transition dipole orientations is fairly isotropic. PMID:27490865

  13. J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes.

    PubMed

    Kuroda, Shin-ichi

    2004-12-13

    size of the J-aggregates of 10(3). The second topic is the control of the J-band peak wavelengths by mixing two different kinds of dye molecules. The first case is the mixture of a J-forming 6-Me-DS and non-J-forming merocyanine analog, DO with benzo-oxazole instead of benzothiazole of DS. The second case is the mixture of both J-forming dyes but with different J-band peak positions, 6-Me-DS and another analog of 5-Cl-DS. The optical peak shifts depending on the molar mixing ratio will be presented. The last topic is related to the elucidation of electronic states of dye molecules in the J-aggregates. Light-induced ESR (LESR) of DS films with stable isotope ((15)N or (13)C)-substituted dyes provide clear evidence for the photoinduced charge transfer by the detection of hyperfine structures. Moreover, infrared (IR) spectroscopy of (13)C-enriched dye identifies the IR absorption peak of the relevant carbon in the chromophore. The results give evidence for the enhanced intramolecular charge transfer of dyes in the J-aggregates compared with an isolated merocyanine composed of donor and acceptor moiety. Lastly, the Cl attachment in 5-Cl-DS leads to a significant enhancement of the nitrogen hyperfine coupling in the LESR spectra. These examples and others demonstrate the potential of LB films of merocyanines in the studies of the nanosized molecular aggregates in monolayer assemblies. PMID:15589808

  14. Thiophene-based dyes for probing membranes.

    PubMed

    López-Duarte, Ismael; Chairatana, Phoom; Wu, Yilei; Pérez-Moreno, Javier; Bennett, Philip M; Reeve, James E; Boczarow, Igor; Kaluza, Wojciech; Hosny, Neveen A; Stranks, Samuel D; Nicholas, Robin J; Clays, Koen; Kuimova, Marina K; Anderson, Harry L

    2015-03-28

    We report the synthesis of four new cationic dipolar push–pull dyes, together with an evaluation of their photophysical and photobiological characteristics pertinent to imaging membranes by fluorescence and second harmonic generation (SHG). All four dyes consist of an N,N-diethylaniline electron-donor conjugated to a pyridinium electron-acceptor via a thiophene bridge, with either vinylene (–CH=CH–) or ethynylene (–C≡C–) linking groups, and with either singly-charged or doubly-charged pyridinium terminals. The absorption and fluorescence behavior of these dyes were compared to a commercially available fluorescent membrane stain, the styryl dye FM4-64. The hyperpolarizabilities of all dyes were compared using hyper-Rayleigh scattering at 800 nm. Cellular uptake, localization, toxicity and phototoxicity were evaluated using tissue cell cultures (HeLa, SK-OV-3 and MDA-231). Replacing the central alkene bridge of FM4-64 with a thiophene does not substantially change the absorption, fluorescence or hyperpolarizability, whereas changing the vinylene-links to ethynylenes shifts the absorption and fluorescence to shorter wavelengths, and reduces the hyperpolarizability by about a factor of two. SHG and fluorescence imaging experiments in live cells showed that the doubly-charged thiophene dyes localize in plasma membranes, and exhibit lower internalization rates compared to FM4-64, resulting in less signal from the cell cytosol. At a typical imaging concentration of 1 μM, the doubly-charged dyes showed no significant light or dark toxicity, whereas the singly-charged dyes are phototoxic even at 0.5 μM. The doubly-charged dyes showed phototoxicity at concentrations greater than 10 μM, although they do not generate singlet oxygen, indicating that the phototoxicity is type I rather than type II. The doubly-charged thiophene dyes are more effective than FM4-64 as SHG dyes for live cells. PMID:25703541

  15. Improved Charge-Transfer Fluorescent Dyes

    NASA Technical Reports Server (NTRS)

    Meador, Michael

    2005-01-01

    Improved charge-transfer fluorescent dyes have been developed for use as molecular probes. These dyes are based on benzofuran nuclei with attached phenyl groups substituted with, variously, electron donors, electron acceptors, or combinations of donors and acceptors. Optionally, these dyes could be incorporated as parts of polymer backbones or as pendant groups or attached to certain surfaces via self-assembly-based methods. These dyes exhibit high fluorescence quantum yields -- ranging from 0.2 to 0.98, depending upon solvents and chemical structures. The wavelengths, quantum yields, intensities, and lifetimes of the fluorescence emitted by these dyes vary with (and, hence, can be used as indicators of) the polarities of solvents in which they are dissolved: In solvents of increasing polarity, fluorescence spectra shift to longer wavelengths, fluorescence quantum yields decrease, and fluorescence lifetimes increase. The wavelengths, quantum yields, intensities, and lifetimes are also expected to be sensitive to viscosities and/or glass-transition temperatures. Some chemical species -- especially amines, amino acids, and metal ions -- quench the fluorescence of these dyes, with consequent reductions in intensities, quantum yields, and lifetimes. As a result, the dyes can be used to detect these species. Another useful characteristic of these dyes is a capability for both two-photon and one-photon absorption. Typically, these dyes absorb single photons in the ultraviolet region of the spectrum (wavelengths < 400 nm) and emit photons in the long-wavelength ultraviolet, visible, and, when dissolved in some solvents, near-infrared regions. In addition, these dyes can be excited by two-photon absorption at near-infrared wavelengths (600 to 800 nm) to produce fluorescence spectra identical to those obtained in response to excitation by single photons at half the corresponding wavelengths (300 to 400 nm). While many prior fluorescent dyes exhibit high quantum yields

  16. Eugenic metal-free sensitizers with double anchors for high performance dye-sensitized solar cells.

    PubMed

    Hung, Wei-I; Liao, You-Ya; Lee, Ting-Hui; Ting, Yu-Chien; Ni, Jen-Shyang; Kao, Wei-Siang; Lin, Jiann T; Wei, Tzu-Chien; Yen, Yung-Sheng

    2015-02-01

    A series of new phenothiazine-based dyes (HL5-HL7) with double acceptors/anchors have been synthesized and used as the sensitizers for highly efficient dye-sensitized solar cells (DSSCs). Among them, the HL7-based cell exhibits the best efficiency of 8.32% exceeding the N719-based cell (7.35%) by ∼13%. PMID:25555237

  17. Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens

    NASA Technical Reports Server (NTRS)

    Nealson, K. H.; Moser, D. P.; Saffarini, D. A.

    1995-01-01

    Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically at the expense of many different electron acceptors and is often found in abundance at redox interfaces in nature. Such redox interfaces are often characterized by very strong gradients of electron acceptors resulting from rapid microbial metabolism. The coincidence of S. putrefaciens abundance with environmental gradients prompted an examination of the ability of MR-1 to sense and respond to electron acceptor gradients in the laboratory. In these experiments, taxis to the majority of the electron acceptors that S. putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite, elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter was very weak and nitrate and nitrite respiration was normal in the presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1 revealed that several electron acceptors that could not be used for anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56, which was unable to respire nitrite, showed normal taxis to nitrite, as well as the inhibition of taxis to other electron acceptors by nitrite. These results indicate that electron acceptor taxis in S. putrefaciens does not conform to the paradigm established for Escherichia coli and several other bacteria. Carbon chemo-taxis was also unusual in this organism: of all carbon compounds tested, the only positive response observed was to formate under anaerobic conditions.

  18. Glucansucrase acceptor reactions with D-mannose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The main acceptor product of glucansucrases with D-mannose has not previously been identified. We used glucansucrases that form water-insoluble a-D-glucans to produce increased yields of acceptor products from D-mannose, and identified the major product as 6-O-a-D-glucopyranosyl-D-mannose. Glucansuc...

  19. Phenylazoindole dyes 3: Determination of azo-hydrazone tautomers of new phenylazoindole dyes in solution and solid state

    NASA Astrophysics Data System (ADS)

    Babür, Banu; Seferoğlu, Nurgül; Aktan, Ebru; Hökelek, Tuncer; Şahin, Ertan; Seferoğlu, Zeynel

    2015-02-01

    A new two series of phenylazo indole dyes was synthesized and the structures of the dyes were confirmed by UV-vis, FT-IR, HRMS and 1H/13C NMR spectroscopic techniques. Five of these dyes (I, I‧, II‧, III and III‧) were also characterized in solid state by using single crystal X-ray diffraction studies besides other spectroscopic techniques. The geometries of the azo and hydrazone tautomeric forms of the dyes were optimized by using Density Functional Theory (DFT). In addition, the effects of the donor and acceptor groups on the azo and hydrazone forms of the dyes were evaluated experimentally and theoretically. The results indicate that the phenylazoindole dyes derived from 2-phenyl indole as coupling component exist as azo form in solution, gas phase and solid state.

  20. Diversity of sugar acceptor of glycosyltransferase 1 from Bacillus cereus and its application for glucoside synthesis.

    PubMed

    Chiu, Hsi-Ho; Shen, Mo-Yuan; Liu, Yuan-Ting; Fu, Yu-Lieh; Chiu, Yu-An; Chen, Ya-Huei; Huang, Chin-Ping; Li, Yaw-Kuen

    2016-05-01

    Glycosyltransferase 1 from Bacillus cereus (BcGT1) catalyzes the transfer of a glucosyl moiety from uridine diphosphate glucose (UDP-glucose) to various acceptors; it was expressed and characterized. The specificity of acceptors was found to be broad: more than 20 compounds classified into O-, S-, and N-linkage glucosides can be prepared with BcGT1 catalysis. Based on this work, we conclude that the corresponding acceptors of these compounds must possess the following features: (1) the acceptors must contain at least one aromatic or fused-aromatic or heteroaromatic ring; (2) the reactive hydroxyl or sulfhydryl or amino group can attach either on the aromatic ring or on its aliphatic side chain; and (3) the acceptors can be a primary, secondary, or even a tertiary amine. Four representative acceptors-fluorescein methyl ester, 17-β-estradiol, 7-mercapto-4-methylcoumarin, and 6-benzylaminopurine-were chosen as a candidate acceptor for O-, S-, and N-glucosidation, respectively. These enzymatic products were purified and the structures were confirmed with mass and NMR spectra. As all isolated glucosides are β-anomers, BcGT1 is confirmed to be an inverting enzyme. This study not only demonstrates the substrate promiscuity of BcGT1 but also showed the great application prospect of this enzyme in bioconversion of valuable bioactive molecules. PMID:26795959

  1. Fluorescence upconversion properties of a class of improved pyridinium dyes induced by two-photon absorption

    NASA Astrophysics Data System (ADS)

    Xu, Guibao; Hu, Dawei; Zhao, Xian; Shao, Zongshu; Liu, Huijun; Tian, Yupeng

    2007-06-01

    We report the fluorescence upconversion properties of a class of improved pyridinium toluene- p-sulfonates having donor- π-acceptor (D- π-A) structure under two-photon excitation at 1064 nm. The experimental results show that both the two-photon excited (TPE) fluorescence lifetime and the two-photon pumped (TPP) energy upconversion efficiency were increased with the enhancement of electron-donating capability of the donor in the molecule. It is also indicated that an overlong alkyl group tends to result in a weakened molecular conjugation, leading to a decreased two-photon absorption (TPA) cross section. By choosing the donor, we can obtain a longest fluorescence lifetime of 837 ps, a highest energy upconversion efficiency of ˜6.1%, and a maximum TPA cross-section of 8.74×10 -48 cm 4 s/photon in these dyes.

  2. Theoretical design and screening of alkyne bridged triphenyl zinc porphyrins as sensitizer candidates for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Xianxi; Chen, Qianqian; Sun, Huafei; Pan, Tingting; Hu, Guiqi; Ma, Ruimin; Dou, Jianmin; Li, Dacheng; Pan, Xu

    2014-01-01

    Alkyne bridged porphyrins have been proved very promising sensitizers for dye-sensitized solar cells (DSSCs) with the highest photo-to-electric conversion efficiencies of 11.9% solely and 12.3% co-sensitized with other sensitizers achieved. Developing better porphyrin sensitizers with wider electronic absorption spectra to further improve the efficiencies of corresponding solar cells is still of great significance for the application of DSSCs. A series of triphenyl zinc porphyrins (ZnTriPP) differing in the nature of a pendant acceptor group and the conjugated bridge between the porphyrin nucleus and the acceptor unit were modeled and their electronic and spectral properties calculated using density functional theory. As compared with each other and the experimental results of the compounds used in DSSCs previously, the molecules with a relatively longer conjugative linker and a strong electron-withdrawing group such as cyanide adjacent to the carboxyl acid group seem to provide wider electronic absorption spectra and higher photo-to-electric conversion efficiencies. The dye candidates ZnTriPPE, ZnTriPPM, ZnTriPPQ, ZnTriPPR and ZnTriPPS designed in the current work were found promising to provide comparable photo-to-electric conversion efficiencies to the record 11.9% of the alkyne bridged porphyrin sensitizer YD2-o-C8 reported previously.

  3. Screening π-conjugated bridges of organic dyes for dye-sensitized solar cells with panchromatic visible light harvesting

    NASA Astrophysics Data System (ADS)

    Yang, Zhenqing; Liu, Chunmeng; Shao, Changjin; Zeng, Xiaofei; Cao, Dapeng

    2016-07-01

    Developing highly efficient organic dyes with panchromatic visible light harvesting for dye-sensitized solar cells (DSSCs) is still one of the most important scientific challenges. Here, we design a series of phenothiazine derivative organic dyes with donor–π–acceptor (D–π–A) structure using density functional theory (DFT) and time-dependent DFT (TDDFT) based on experimentally synthesized typical SH-6 organic dyes. Results indicate that the newly designed BUCT13 – BUCT30 dyes show smaller HOMO–LUMO energy gaps, higher molar extinction coefficients and obvious redshifts compared to the SH-6 dye, and the maximum absorption peaks of eight dyes are greater than 650 nm among the newly designed dyes. In particular, BUCT27 exhibits a 234 nm redshift and the maximum molar extinction coefficient with an increment of about 80% compared to the SH-6 dye. BUCT19 exhibits not only a 269 nm redshift and higher molar extinction coefficient with an increment of about 50% compared to the SH-6 dye, but the extremely broad absorption spectrum covering the entire visible range up to the near-IR region of 1200 nm. It is expected that this work can provide a new strategy and guidance for the investigation of these dye-sensitized devices.

  4. Screening π-conjugated bridges of organic dyes for dye-sensitized solar cells with panchromatic visible light harvesting.

    PubMed

    Yang, Zhenqing; Liu, Chunmeng; Shao, Changjin; Zeng, Xiaofei; Cao, Dapeng

    2016-07-01

    Developing highly efficient organic dyes with panchromatic visible light harvesting for dye-sensitized solar cells (DSSCs) is still one of the most important scientific challenges. Here, we design a series of phenothiazine derivative organic dyes with donor-π-acceptor (D-π-A) structure using density functional theory (DFT) and time-dependent DFT (TDDFT) based on experimentally synthesized typical SH-6 organic dyes. Results indicate that the newly designed BUCT13 - BUCT30 dyes show smaller HOMO-LUMO energy gaps, higher molar extinction coefficients and obvious redshifts compared to the SH-6 dye, and the maximum absorption peaks of eight dyes are greater than 650 nm among the newly designed dyes. In particular, BUCT27 exhibits a 234 nm redshift and the maximum molar extinction coefficient with an increment of about 80% compared to the SH-6 dye. BUCT19 exhibits not only a 269 nm redshift and higher molar extinction coefficient with an increment of about 50% compared to the SH-6 dye, but the extremely broad absorption spectrum covering the entire visible range up to the near-IR region of 1200 nm. It is expected that this work can provide a new strategy and guidance for the investigation of these dye-sensitized devices. PMID:27188528

  5. Exciton annihilation in dye-sensitized nanocrystalline semiconductor films

    NASA Astrophysics Data System (ADS)

    Namekawa, Akihiro; Katoh, Ryuzi

    2016-08-01

    Exciton annihilation in dye-sensitized nanocrystalline semiconductor (Al2O3) films has been studied through laser-induced fluorescence spectroscopy. The relative quantum yield of the fluorescence decreases with increasing excitation light intensity, the indication being that exciton annihilation occurred. The rate constants of the annihilation were estimated for three dyes, N719, D149, and MK2, that are known to be sensitizing dyes for efficient dye-sensitized solar cells. The hopping time between dye molecules and the diffusion length of excitons within their lifetime were also estimated to facilitate discussion of the relevance of exciton annihilation to primary processes in dye-sensitized solar cells.

  6. Bright Solid-State Emission of Disilane-Bridged Donor-Acceptor-Donor and Acceptor-Donor-Acceptor Chromophores.

    PubMed

    Shimada, Masaki; Tsuchiya, Mizuho; Sakamoto, Ryota; Yamanoi, Yoshinori; Nishibori, Eiji; Sugimoto, Kunihisa; Nishihara, Hiroshi

    2016-02-01

    The development of disilane-bridged donor-acceptor-donor (D-Si-Si-A-Si-Si-D) and acceptor-donor-acceptor (A-Si-Si-D-Si-Si-A) compounds is described. Both types of compound showed strong emission (λem =ca. 500 and ca. 400 nm, respectively) in the solid state with high quantum yields (Φ: up to 0.85). Compound 4 exhibited aggregation-induced emission enhancement in solution. X-ray diffraction revealed that the crystal structures of 2, 4, and 12 had no intermolecular π-π interactions to suppress the nonradiative transition in the solid state. PMID:26822564

  7. Photoinduced electron tunneling between randomly dispersed donors and acceptors in frozen glasses and other rigid matrices.

    PubMed

    Wenger, Oliver S

    2013-07-14

    In fluid solution un-tethered donors and acceptors can diffuse freely, and consequently the donor-acceptor distance is usually not fixed on the timescale of an electron transfer event. When attempting to investigate the influence of driving-force changes or donor-acceptor distance variations on electron transfer rates this can be a problem. In rigid matrices diffusion is suppressed, and it becomes possible to investigate fixed-distance electron transfer. This method represents an attractive alternative to investigate rigid rod-like donor-bridge-acceptor molecules which have to be made in elaborate syntheses. This perspective focuses specifically on the distance dependence of photoinduced electron transfer which occurs via tunneling of charge carriers through rigid matrices over distances between 1 and 33 Å. Some key aspects of the theoretical models commonly used for analyzing kinetic data of electron tunneling through rigid matrices are recapitulated. New findings from this rather mature field of research are emphasized. PMID:23722299

  8. Blinking fluorescence of single donor-acceptor pairs: Important role of ``dark'' states in resonance energy transfer via singlet levels

    NASA Astrophysics Data System (ADS)

    Osad'ko, I. S.; Shchukina, A. L.

    2012-06-01

    The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=IA/(IA+ID), where ID and IA are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FTD/(1+FTD). Here F is the rate of energy transfer, and TD is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FTD≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F¯(F)TD/[1+F¯(F)TD]. Here F¯(F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F¯(F) are derived. In this case the energy transfer efficiency will be far from 100% even at FTD≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities wND(t) and wNA(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy transfer rate F and for all four types of D-A pair. Comparison of the calculated D

  9. Virtual screening of electron acceptor materials for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Halls, Mathew D.; Djurovich, Peter J.; Giesen, David J.; Goldberg, Alexander; Sommer, Jonathan; McAnally, Eric; Thompson, Mark E.

    2013-10-01

    Virtual screening involves the generation of structure libraries, automated analysis to predict properties related to application performance and subsequent screening to identify lead systems and estimate critical structure-property limits across a targeted chemical design space. This approach holds great promise for informing experimental discovery and development efforts for next-generation materials, such as organic semiconductors. In this work, the virtual screening approach is illustrated for nitrogen-substituted pentacene molecules to identify systems for development as electron acceptor materials for use in organic photovoltaic (OPV) devices. A structure library of tetra-azapentacenes (TAPs) was generated by substituting four nitrogens for CH at 12 sites on the pentacene molecular framework. Molecular properties (e.g. ELUMO, Eg and μ) were computed for each candidate structure using hybrid DFT at the B3LYP/6-311G** level of theory. The resulting TAPs library was then analyzed with respect to intrinsic properties associated with OPV acceptor performance. Marcus reorganization energies for charge transport for the most favorable TAP candidates were then calculated to further determine suitability as OPV electron acceptors. The synthesis, characterization and OPV device testing of TAP materials is underway, guided by these results.

  10. Oligomer Molecules for Efficient Organic Photovoltaics.

    PubMed

    Lin, Yuze; Zhan, Xiaowei

    2016-02-16

    Solar cells, a renewable, clean energy technology that efficiently converts sunlight into electricity, are a promising long-term solution for energy and environmental problems caused by a mass of production and the use of fossil fuels. Solution-processed organic solar cells (OSCs) have attracted much attention in the past few years because of several advantages, including easy fabrication, low cost, lightweight, and flexibility. Now, OSCs exhibit power conversion efficiencies (PCEs) of over 10%. In the early stage of OSCs, vapor-deposited organic dye materials were first used in bilayer heterojunction devices in the 1980s, and then, solution-processed polymers were introduced in bulk heterojunction (BHJ) devices. Relative to polymers, vapor-deposited small molecules offer potential advantages, such as a defined molecular structure, definite molecular weight, easy purification, mass-scale production, and good batch-to-batch reproducibility. However, the limited solubility and high crystallinity of vapor-deposited small molecules are unfavorable for use in solution-processed BHJ OSCs. Conversely, polymers have good solution-processing and film-forming properties and are easily processed into flexible devices, whereas their polydispersity of molecular weights and difficulty in purification results in batch to batch variation, which may hamper performance reproducibility and commercialization. Oligomer molecules (OMs) are monodisperse big molecules with intermediate molecular weights (generally in the thousands), and their sizes are between those of small molecules (generally with molecular weights <1000) and polymers (generally with molecular weights >10000). OMs not only overcome shortcomings of both vapor-deposited small molecules and solution-processed polymers, but also combine their advantages, such as defined molecular structure, definite molecular weight, easy purification, mass-scale production, good batch-to-batch reproducibility, good solution processability

  11. Stability and efficiency of dye-sensitized solar cells based on papaya-leaf dye

    NASA Astrophysics Data System (ADS)

    Suyitno, Suyitno; Saputra, Trisma Jaya; Supriyanto, Agus; Arifin, Zainal

    2015-09-01

    The present article reports on the enhancement of the performance and stability of natural dye-based dye-sensitized solar cells (DSSCs). Natural dyes extracted from papaya leaves (PL) were investigated as sensitizers in TiO2-based DSSCs and evaluated in comparison with N719 dye. The acidity of the papaya-leaf extract dyes was tuned by adding benzoic acid. The TiO2 film-coated fluorine-doped tin oxide glass substrates were prepared using the doctor-blade method, followed by sintering at 450 °C. The counter electrode was coated by chemically deposited catalytic platinum. The working electrodes were immersed in N719 dye and papaya dye solutions with concentrations of 8 g/100 mL. The absorbance spectra of the dyes were obtained by ultra-violet-visible spectroscopy. The energy levels of the dyes were measured by the method of cyclic voltammetry. In addition, Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. The DSSC based on the N719 dye displayed a highest efficiency of 0.87% whereas those based on papaya-leaf dye achieved 0.28% at pH 3.5. The observed improved efficiency of the latter was attributed to the increased current density value. Furthermore, the DSSCs based on papaya-leaf dye with pH 3.5-4 exhibited better stability than those based on N719 dye. However, further studies are required to improve the current density and stability of natural dye-based DSSCs, including the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing it.

  12. Stability and efficiency of dye-sensitized solar cells based on papaya-leaf dye.

    PubMed

    Suyitno, Suyitno; Saputra, Trisma Jaya; Supriyanto, Agus; Arifin, Zainal

    2015-09-01

    The present article reports on the enhancement of the performance and stability of natural dye-based dye-sensitized solar cells (DSSCs). Natural dyes extracted from papaya leaves (PL) were investigated as sensitizers in TiO2-based DSSCs and evaluated in comparison with N719 dye. The acidity of the papaya-leaf extract dyes was tuned by adding benzoic acid. The TiO2 film-coated fluorine-doped tin oxide glass substrates were prepared using the doctor-blade method, followed by sintering at 450 °C. The counter electrode was coated by chemically deposited catalytic platinum. The working electrodes were immersed in N719 dye and papaya dye solutions with concentrations of 8 g/100 mL. The absorbance spectra of the dyes were obtained by ultra-violet-visible spectroscopy. The energy levels of the dyes were measured by the method of cyclic voltammetry. In addition, Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. The DSSC based on the N719 dye displayed a highest efficiency of 0.87% whereas those based on papaya-leaf dye achieved 0.28% at pH 3.5. The observed improved efficiency of the latter was attributed to the increased current density value. Furthermore, the DSSCs based on papaya-leaf dye with pH 3.5-4 exhibited better stability than those based on N719 dye. However, further studies are required to improve the current density and stability of natural dye-based DSSCs, including the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing it. PMID:25875031

  13. Monitoring Integrated Activity of Individual Neurons Using FRET-Based Voltage-Sensitive Dyes.

    PubMed

    Briggman, Kevin L; Kristan, William B; González, Jesús E; Kleinfeld, David; Tsien, Roger Y

    2015-01-01

    Pairs of membrane-associated molecules exhibiting fluorescence resonance energy transfer (FRET) provide a sensitive technique to measure changes in a cell's membrane potential. One of the FRET pair binds to one surface of the membrane and the other is a mobile ion that dissolves in the lipid bilayer. The voltage-related signal can be measured as a change in the fluorescence of either the donor or acceptor molecules, but measuring their ratio provides the largest and most noise-free signal. This technology has been used in a variety of ways; three are documented in this chapter: (1) high throughput drug screening, (2) monitoring the activity of many neurons simultaneously during a behavior, and (3) finding synaptic targets of a stimulated neuron. In addition, we provide protocols for using the dyes on both cultured neurons and leech ganglia. We also give an updated description of the mathematical basis for measuring the coherence between electrical and optical signals. Future improvements of this technique include faster and more sensitive dyes that bleach more slowly, and the expression of one of the FRET pair genetically. PMID:26238052

  14. Ultrasound energy to accelerate dye uptake and dye-fiber interaction of reactive dye on knitted cotton fabric at low temperatures.

    PubMed

    Tissera, Nadeeka D; Wijesena, Ruchira N; de Silva, K M Nalin

    2016-03-01

    Acoustic cavitation formed due to propagation of ultrasound wave inside a dye bath was successfully used to dye cotton fabric with a reactive dye at lower temperatures. The energy input to the system during sonication was 0.7 W/cm(2). This was within the energy range that contributes towards forming cavitation during ultra-sonication. The influence of ultrasound treatment on dye particle size and fiber morphology is discussed. Particle size analysis of the dye bath revealed ultra-sonication energy was capable of de-agglomeration of hydrolyzed dye molecules during dyeing. SEM micrograph and AFM topographical image of the fiber surface revealed fiber morphology remains unchanged after the sonication. The study was extended in understanding the contribution of ultrasound method of dyeing towards achieving good color strength on the fabric, compared to the normal heating method of dyeing. Study showed color strength obtained using ultra sound method of dyeing is higher compared to normal heating dyeing. Ultrasound energy was able to achieve the good color strength on cotton fabric at very low temperature such as 30 °C, which was approximately 230% more than the color strength achieved in normal heating method of dyeing. This indicates that energy input to the system using ultrasound was capable of acting as an effective alternative method of dyeing knitted cotton fabrics with reactive dye. PMID:26585007

  15. A comparative study of semi-squaraine and squaraine dyes using computational techniques: tuning the charge transfer/biradicaloid character by substitution.

    PubMed

    Puyad, Avinash L; Chaitanya, Gunturu Krishna; Prabhakar, Chetti; Bhanuprakash, Kotamarthi

    2013-01-01

    Semi-squaraines (SMSQ) are known as donor-acceptor (D-A) type molecules whereas squaraines (SQ), which differs from SMSQ by an extra donor group, are more or less biradicaloids in nature. The effect of the additional donor group in SQ, which changes the nature of the molecule, on geometrical and electronic structure are studied here and compared with the corresponding SMSQ. It is noticed from the geometrical parameters that, a strong resonance exists in SQ whereas disparity in carbon-carbon bond lengths of central C4 ring is seen in SMSQ dyes. The increasing and decreasing of antibonding interactions between central C4 ring and side donor groups cause destabilization of HOMO and stabilization of LUMO respectively in case of SQ compared to SMSQ molecules. This leads to decreasing the HOMO-LUMO gap and promotes biradicaloid character of SQ. The absorption maxima obtained by using TD-DFT method with BLYP, B3LYP, BHandHLYP, CAM-B3LYP and M06-2X functionals are not in good agreement with experimental results. On the other hand SAC-CI method gives better results for all the molecules. From this work we can evolve a design principle of these molecules which play a role as sensitizers in dye sensitized solar cells. PMID:22878861

  16. Dye-sensitized photocatalytic hydrogen production: distinct activity in a glucose derivative of a phenothiazine dye.

    PubMed

    Manfredi, N; Cecconi, B; Calabrese, V; Minotti, A; Peri, F; Ruffo, R; Monai, M; Romero-Ocaña, I; Montini, T; Fornasiero, P; Abbotto, A

    2016-05-19

    A thiophene-based donor-acceptor phenothiazine dye has been functionalized with a peripheral glucose unit (PTZ-GLU) to bust its affinity to water and enhance dye-sensitized photogeneration of hydrogen. Compared to the corresponding alkyl derivative (PTZ-ALK), as well as the common hydrophilic triethylene glycol substitution (PTZ-TEG), the sugar derivative shows a lower contact angle; PTZ-GLU performed twice more efficient than PTZ-TEG in the photogeneration of hydrogen in terms of evolved gas and turnover number. PMID:27063187

  17. Salicylic Acid-Based Organic Dyes Acting as the Photosensitizer for Solar Cells.

    PubMed

    Hong, Sungjun; Park, Jae-Hyeong; Han, Ah-Reum; Ko, Kwan-Woo; Eom, Jin Hee; Namgoong, Sung Keon; Lo, Alvie S V; Gordon, Keith C; Yoon, Sungho; Han, Chi-Hwan

    2016-05-01

    A D-π-A metal-free organic dye, featuring salicylic acid as a novel acceptor/anchoring unit, has been designed, synthesized and applied to dye-sensitized solar cell. The detailed photophysical, electrochemical, photovoltaic and sensitizing properties of the organic dye were investigated, in addition to the computational studies of the dye and dye-(TiO2)6 system. A solar cell device using this new organic dye as a sensitizer produced a solar to electric power conversion efficiency (PCE) of 3.49% (J(sc) = 6.69 mAcm-2, V(oc) = 0.74 V and ff = 0.70) under 100 mWcm(-2) simulated AM 1.5 G solar irradiation, demonstrating that the salicylic acid-based organic dye is a suitable alternative to currently used organometallic dyes. PMID:27483839

  18. Nonlinear solid-state filter based on photochromism induced by 2-photon absorption in a dye-doped sol-gel

    NASA Astrophysics Data System (ADS)

    Gvishi, Raz; Zhao, Peng; Hu, Honghua; Strum, Galit; Tal, Amir; Grinvald, Shmuel; Bar, Galit; Bekere, Laura; Lokshin, Vladimir; Khodorkovsky, Vladimir; Sigalov, Mark; Hagan, David; Van Stryland, Eric

    2014-10-01

    There is much interest in enhancement of the absorbance performance of nonlinear absorber solid-state filters. In this work we present an advanced reversible nonlinear filter based on a dye-doped sol-gel matrix. The absorbance enhancement was achieved by using a combination of two absorption mechanisms in the same molecule; a photochromic absorption which is induced by 2-photon absorption (2PA). The 2PA serves as the trigger for initiating the photochromism through Förster-resonance-energy-transfer (FRET) between the fluorescent donor and the photochromic acceptor. We synthesized a new bifunctional-chromophore that incorporated a carbazole-derived 2PA fluorescent donor and a chromene-derived photochromic acceptor, covalently linked together in a single molecule by a ~6 Å carboxyl group or oxygen bridge. The bifunctional-chromophore was doped in an inorganic-organic hybrid matrix prepared by the fast-sol-gel process. These materials solidify without shrinkage or formation of cracks and present promising properties as optical matrices for smart filters. The dye-doped sol-gel disc presents high transparency in the visible region ("colorless"), which under UV-irradiation (one-photon absorption in the photochromic part of the molecule), transforms into a strongly absorbing filter ("dark colored"), due to the conversion of the photochromic moiety to its "open" absorbing form. We have demonstrated that this ring-opening can also be induced by visible-light (620 nm) using the 2PA carbazole-derived moiety of the molecule. We have studied the fabrication routes and optical performance of these filters. We present studies of the 2PA mechanism of the carbazole derivative, FRET efficiency of the combined-molecule as well as in solutions of the individual moieties, and reversible dynamics of the photochromic moiety.

  19. Synthetic CO.sub.2 acceptor

    DOEpatents

    Lancet, Michael S.; Curran, George P.

    1981-08-18

    A synthetic CO.sub.2 acceptor consisting essentially of at least one compound selected from the group consisting of calcium oxide and calcium carbonate supported in a refractory carrier matrix, the carrier having the general formula Ca.sub.5 (SiO.sub.4).sub.2 CO.sub.3. A method for producing the synthetic CO.sub.2 acceptor is also disclosed.

  20. π-Spacer effect in dithiafulvenyl-π-phenothiazine dyes for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofeng; Gou, Faliang; Zhao, Dongning; Shi, Jian; Gao, Hong; Zhu, Zhenping; Jing, Huanwang

    2016-08-01

    New dithiafulvenyl-π-phenothiazine dyes have been devised and prepared for dye-sensitized solar cells. Various π-spacers have been successfully introduced into the skeleton of dithiafulvenyl and phenothiazine unit to generate novel D-π-D-A dyes (DPP-1 ∼ 4). All dyes have been characterized with NMR, HRMS, UV-vis and fluorescence spectra, and taken into cyclic voltammetry measurements. The devices of new dyes have been determined by photoelectrochemical experiments (IV, IPCE and EIS), in which, solar cell of DPP-4 with biphenyl ring π-spacer enhances obviously its photoelectric conversion efficiency to 7.66% reaching 94% of N719-based standard cell and displays good long-term stability with quasi-solid-state electrolyte. Density functional theory (DFT) calculations of new dyes provide further insight into the molecular geometries and the impacts of the torsion angles on their photovoltaic performance. Large dihedral angles in DPP dyes induce good charge separation for efficient unidirectional flow of electron from donor to acceptor.

  1. π-Spacer effect in dithiafulvenyl-π-phenothiazine dyes for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofeng; Gou, Faliang; Zhao, Dongning; Shi, Jian; Gao, Hong; Zhu, Zhenping; Jing, Huanwang

    2016-08-01

    New dithiafulvenyl-π-phenothiazine dyes have been devised and prepared for dye-sensitized solar cells. Various π-spacers have been successfully introduced into the skeleton of dithiafulvenyl and phenothiazine unit to generate novel D-π-D-A dyes (DPP-1 ∼ 4). All dyes have been characterized with NMR, HRMS, UV-vis and fluorescence spectra, and taken into cyclic voltammetry measurements. The devices of new dyes have been determined by photoelectrochemical experiments (IV, IPCE and EIS), in which, solar cell of DPP-4 with biphenyl ring π-spacer enhances obviously its photoelectric conversion efficiency to 7.66% reaching 94% of N719-based standard cell and displays good long-term stability with quasi-solid-state electrolyte. Density functional theory (DFT) calculations of new dyes provide further insight into the molecular geometries and the impacts of the torsion angles on their photovoltaic performance. Large dihedral angles in DPP dyes induce good charge separation for efficient unidirectional flow of electron from donor to acceptor.

  2. Nanostructured donor-acceptor self assembly with improved photoconductivity.

    PubMed

    Saibal, B; Ashar, A Z; Devi, R Nandini; Narayan, K S; Asha, S K

    2014-11-12

    Nanostructured supramolecular donor-acceptor assemblies were formed when an unsymmetrical N-substituted pyridine functionalized perylenebisimide (UPBI-Py) was complexed with oligo(p-phenylenevinylene) (OPVM-OH) complementarily functionalized with hydroxyl unit and polymerizable methacrylamide unit at the two termini. The resulting supramolecular complex [UPBI-Py (OPVM-OH)]1.0 upon polymerization by irradiation in the presence of photoinitiator formed well-defined supramolecular polymeric nanostructures. Self-assembly studies using fluorescence emission from thin film samples showed that subtle structural changes occurred on the OPV donor moiety following polymerization. The 1:1 supramolecular complex showed red-shifted aggregate emission from both OPV (∼500 nm) and PBI (∼640 nm) units, whereas the OPV aggregate emission was replaced by intense monomeric emission (∼430 nm) upon polymerizing the methacrylamide units on the OPVM-OH. The bulk structure was studied using wide-angle X-ray diffraction (WXRD). Complex formation resulted in distinct changes in the cell parameters of OPVM-OH. In contrast, a physical mixture of 1 mol each of OPVM-OH and UPBI-Py prepared by mixing the powdered solid samples together showed only a combination of reflections from both parent molecules. Thin film morphology of the 1:1 molecular complex as well as the supramolecular polymer complex showed uniform lamellar structures in the domain range <10 nm. The donor-acceptor supramolecular complex [UPBI-Py (OPVM-OH)]1.0 exhibited space charge limited current (SCLC) with a bulk mobility estimate of an order of magnitude higher accompanied by a higher photoconductivity yield compared to the pristine UPBI-Py. This is a very versatile method to obtain spatially defined organization of n and p-type semiconductor materials based on suitably functionalized donor and acceptor molecules resulting in improved photocurrent response using self-assembly. PMID:25283356

  3. Dye laser amplifier

    DOEpatents

    Moses, Edward I.

    1992-01-01

    An improved dye laser amplifier is disclosed. The efficiency of the dye lr amplifier is increased significantly by increasing the power of a dye beam as it passes from an input window to an output window within the dye chamber, while maintaining the intensity of the dye beam constant.

  4. Dye laser amplifier

    DOEpatents

    Moses, E.I.

    1992-12-01

    An improved dye laser amplifier is disclosed. The efficiency of the dye laser amplifier is increased significantly by increasing the power of a dye beam as it passes from an input window to an output window within the dye chamber, while maintaining the intensity of the dye beam constant. 3 figs.

  5. Differences in gene expression of human xylosyltransferases and determination of acceptor specificities for various proteoglycans

    SciTech Connect

    Roch, Christina; Kuhn, Joachim; Kleesiek, Knut; Goetting, Christian

    2010-01-01

    The xylosyltransferase (XT) isoforms XT-I and XT-II initiate the posttranslational glycosaminoglycan (GAG) synthesis. Here, we determined the relative expression of both isoforms in 33 human cell lines. The majority of tested cell lines showed dominant XYLT2 gene expression, while only in 23132/87, JAR, NCI-H510A and THP-1 was the XT-I mRNA expression higher. Nearly equal expression levels were detected in six cell lines. Additionally, to shed light on putative differences in acceptor specificities the acceptor properties of potential acceptor sequences were determined. Peptides were expressed as glutathione-S-transferase fusion proteins containing putative or known GAG attachment sites of in vivo proteoglycans. Kinetic analysis showed that K{sub m} and V{sub max} values for XT-I mediated xylosylation were slightly higher than those for XT-II, and that XT-I showed a lesser stringency concerning the acceptor sequence. Mutagenesis of the bikunin peptide sequence in the G-S-G attachment site and flanking regions generated potential acceptor molecules. Here, mutations on the N-terminal side and the attachment site were found to be more susceptible to a loss of acceptor function than mutations in the C-terminus. Altogether the known consensus sequence a-a-a-a-G-S-G-a-a/G-a ('a' representing Asp or Glu) for XT-I mediated xylosylation could be approved and additionally extended to apply to XT-II as well.

  6. Non-fullerene acceptors: exciton dissociation with PTCDA versus C60.

    PubMed

    Dutton, Gregory J; Robey, Steven W

    2015-06-28

    Extensive development of new polymer and small molecule donors has helped produce a steady increase in the efficiency of organic photovoltaic (OPV) devices. However, OPV technology would also benefit from the introduction of non-fullerene acceptors. Unfortunately, efforts to replace fullerenes have typically led to significantly reduced efficiencies. A number of possible explanations for reduced efficiencies with non-fullerene acceptors compared to fullerene acceptors have been suggested, including the formation of unfavorable morphologies in non-fullerene systems and/or favorable excitation/carrier delocalization in fullerenes. In addition, enhanced exciton dissociation associated with fundamental characteristics of the fullerene molecular electronic states has also been suggested. We used time-resolved two-photon photoemission (TR-2PPE) to directly compare exciton dissociation at interfaces between zinc phthalocyanine (ZnPc) interfaces and the non-fullerene acceptor, perylene tetracarboxylic dianhydride (PTCDA) versus dissociation measured at the analogous interface with C60, and thus help discriminate between these potential explanations. Exciton dissociation rates are comparable for phthalocyanine interfaces with both acceptors, allowing us to suggest a hierarchy for the importance of various effects producing higher efficiencies with fullerene acceptors. PMID:26027544

  7. Characterization of thermally stable dye-doped polyimide based electrooptic materials

    SciTech Connect

    Meinhardt, M.B.; Cahill, P.A.; Seager, C.H.; Beuhler, A.J.; Wargowski, D.A.

    1993-12-31

    Polymeric electrooptic materials have the potential to replace electronic switches in applications which require minimization of heat dissipation while maintaining high switching speeds. Polyimide matrices incorporating electrooptic dyes are promising materials for such applications due to their low cost and compatibility with existing processing environments. Preparation and characterization of novel dye-doped polyimide films for electrooptics is described. Thermal stabilities of donor-acceptor 2,5-diaryl oxazoles were evaluated by differential scanning calorimetry. Absorptive losses in thin films of Ultradel 9000D{reg_sign} doped with donor-acceptor oxazoles were measured by photothermal deflection spectroscopy. Absorptive losses at high doping levels may be explainable by dye-dye aggregation or dye degradation during the curing process. Lower doping levels, however, show losses of {le} 3.0 dB/cm at 830 nm and {le} 2.4 dB/cm at 1,320 nm.

  8. The electronic structure engineering of organic dye sensitizers for solar cells: The case of JK derivatives.

    PubMed

    Zhang, Cai-Rong; Ma, Jin-Gang; Zhe, Jian-Wu; Jin, Neng-Zhi; Shen, Yu-Lin; Wu, You-Zhi; Chen, Yu-Hong; Liu, Zi-Jiang; Chen, Hong-Shan

    2015-11-01

    The design and development of novel dye sensitizers are effective method to improve the performance of dye-sensitized solar cells (DSSCs) because dye sensitizers have significant influence on photo-to-current conversion efficiency. In the procedure of dye sensitizer design, it is very important to understand how to tune their electronic structures and related properties through the substitution of electronic donors, acceptors, and conjugated bridges in dye sensitizers. Here, the electronic structures and excited-state properties of organic JK dye sensitizers are calculated by using density functional theory (DFT) and time dependent DFT methods. Based upon the calculated results, we investigated the role of different electronic donors, acceptors, and π-conjugated bridges in the modification of electronic structures, absorption properties, as well as the free energy variations for electron injection and dye regeneration. In terms of the analysis of transition configurations and molecular orbitals, the effective chromophores which are favorable for electron injection in DSSCs are addressed. Meanwhile, considering the absorption spectra and free energy variation, the promising electronic donors, π-conjugated bridges, and acceptors are presented to design dye sensitizers. PMID:26116996

  9. Accurate simulation of optical properties in dyes.

    PubMed

    Jacquemin, Denis; Perpète, Eric A; Ciofini, Ilaria; Adamo, Carlo

    2009-02-17

    Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them. PMID:19113946

  10. Light-induced noncentrosymmetry in acceptor-donor-substituted azobenzene solutions

    NASA Astrophysics Data System (ADS)

    Zhao, Jiang; Si, Jinhai; Wang, Yougui; Ye, Peixian; Fu, Xingfa; Qiu, Ling; Shen, Yuquan

    1995-10-01

    Light-induced noncentrosymmetry was achieved experimentally in acceptor-donor-substituted azobenzene solutions and observed by phase-matched nondegenerate six-wave mixing. The microscopic origin of the induced noncentrosymmetry was found to be orientational hole burning, which was distinguished directly with net orientation of molecules by experimental observations. The decay time of the induced noncentrosymmetry depended on the rotational orientation time of the sample's molecule, which varied linearly with the viscosity of the solvent.

  11. Monitoring the dye impregnation time of nanostructured photoanodes for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Shahzad, N.; Pugliese, D.; Lamberti, A.; Sacco, A.; Virga, A.; Gazia, R.; Bianco, S.; Shahzad, M. I.; Tresso, E.; Pirri, C. F.

    2013-06-01

    Dye-sensitized solar cells (DSSCs) are getting increasing attention as low-cost, easy-to-prepare and colored photovoltaic devices. In the current work, in view of optimizing the fabrication procedures and understanding the mechanisms of dye attachment to the semiconductor photoanode, absorbance measurements have been performed at different dye impregnation times ranging from few minutes to 24 hours using UV-Vis spectroscopy. In addition to the traditional absorbance experiments, based on diffuse and specular reflectance on dye impregnated thin films and on the desorption of dye molecules from the photoanodes by means of a basic solution, an alternative in-situ solution depletion measurement, which enables fast and continuous evaluation of dye uptake, is presented. Photoanodes have been prepared with two different nanostructured semiconducting films: mesoporous TiO2, using a commercially available paste from Solaronix, and sponge-like ZnO obtained in our laboratory from sputtering and thermal annealing. Two different dyes have been analyzed: Ruthenizer 535-bisTBA (N719), which is widely used because it gives optimal photovoltaic performances, and a new metal-free organic dye based on a hemisquaraine molecule (CT1). Dye sensitized cells were fabricated using a customized microfluidic architecture. The results of absorbance measurements are presented and discussed in relation to the obtained solar energy conversion efficiencies and the incident photon-to-electron conversion efficiencies (IPCE).

  12. Synthesis, characterization and optoelectronic properties of a new perylene diimide-benzimidazole type solar light harvesting dye

    NASA Astrophysics Data System (ADS)

    Dinçalp, Haluk; Çimen, Oguzhan; Ameri, Tayebeh; Brabec, Christoph J.; İçli, Sıddık

    2014-07-01

    A perylene diimide type small molecule (BI-PDI) has been synthesized through Suzuki coupling reaction between N,N‧-bis(2,6-diisopropylphenyl)-1,7-dibromoperylene-3,4,9,10-tetracarboxylic diimide and 2-(2-hydroxyphenyl)-7-phenyl-1H-benzimidazole-4-boronic acid. BI-PDI small molecule has showed an absorption band between 350 and 750 nm on thin films. HOMO and LUMO energy levels of BI-PDI dye have been calculated to be about -5.92 eV and -3.82 eV, respectively. Solution-processed bulk heterojunction (BHJ) solar cells have been constructed using BI-PDI as donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as acceptor or poly(3-hexylthiophene) (P3HT) as donor and BI-PDI as acceptor. The external quantum efficiencies (EQE) of the devices cover the most of the visible region between 400 and 700 nm for both configurations. Photovoltaic performances of BI-PDI-based organic solar cells are limited by the aggregation tendency of PDI structure and poor hole/electron mobilities of the active layer.

  13. Reverse micelles for the removal of dyes from aqueous solutions.

    PubMed

    Majhi, S; Sharma, Y C; Upadhyay, S N

    2009-08-01

    The ability of reverse micelles to solvate organic dyes in the aqueous core was investigated with methyl orange (MO) and methylene blue (MB) using hexadecyl trimethyl ammonium bromide (HTAB) and sodium dodecyl benzene sulphonate (SDBS) surfactants in a polar amyl alcohol medium. The removal trend of the dyes from water was studied with different concentrations of the dyes. The effects of NaCl and CaCl2 salts on removal efficiency of the surfactants were investigated and results were compared. It was observed that the separation of dyes from the aqueous phase to the organic phase depends on the electrostatic interaction between the dye molecule and surfactant head groups. In the case of NaCl, with increasing salt concentration, the removal (%) of dye decreases. For CaCl2, removal of methyl orange shows a gradual increase with increasing dye concentration, whereas, for methylene blue, its removal decreases with increasing dye concentration. PMID:19803326

  14. Non-fullerene electron acceptors for use in organic solar cells.

    PubMed

    Nielsen, Christian B; Holliday, Sarah; Chen, Hung-Yang; Cryer, Samuel J; McCulloch, Iain

    2015-11-17

    The active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted to optimize the absorbing, energetic, and transport properties of the donor material, fullerenes remain as the exclusive electron acceptor in all high performance devices. Very recently, some new non-fullerene acceptors have been demonstrated to outperform fullerenes in comparative devices. This Account describes this progress, discussing molecular design considerations and the structure-property relationships that are emerging. The motivation to replace fullerene acceptors stems from their synthetic inflexibility, leading to constraints in manipulating frontier energy levels, as well as poor absorption in the solar spectrum range, and an inherent tendency to undergo postfabrication crystallization, resulting in device instability. New acceptors have to address these limitations, providing tunable absorption with high extinction coefficients, thus contributing to device photocurrent. The ability to vary and optimize the lowest unoccupied molecular orbital (LUMO) energy level for a specific donor polymer is also an important requirement, ensuring minimal energy loss on electron transfer and as high an internal voltage as possible. Initially perylene diimide acceptors were evaluated as promising acceptor materials. These electron deficient aromatic molecules can exhibit good electron transport, facilitated by close packed herringbone crystal motifs, and their energy levels can be synthetically tuned. The principal drawback of this class of materials, their tendency to crystallize on too large a length scale for an optimal heterojunction nanostructure, has been shown to be overcome through introduction of conformation twisting through steric effects. This has been primarily achieved by coupling two units together, forming dimers with

  15. Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

    PubMed Central

    2015-01-01

    Conspectus The active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted to optimize the absorbing, energetic, and transport properties of the donor material, fullerenes remain as the exclusive electron acceptor in all high performance devices. Very recently, some new non-fullerene acceptors have been demonstrated to outperform fullerenes in comparative devices. This Account describes this progress, discussing molecular design considerations and the structure–property relationships that are emerging. The motivation to replace fullerene acceptors stems from their synthetic inflexibility, leading to constraints in manipulating frontier energy levels, as well as poor absorption in the solar spectrum range, and an inherent tendency to undergo postfabrication crystallization, resulting in device instability. New acceptors have to address these limitations, providing tunable absorption with high extinction coefficients, thus contributing to device photocurrent. The ability to vary and optimize the lowest unoccupied molecular orbital (LUMO) energy level for a specific donor polymer is also an important requirement, ensuring minimal energy loss on electron transfer and as high an internal voltage as possible. Initially perylene diimide acceptors were evaluated as promising acceptor materials. These electron deficient aromatic molecules can exhibit good electron transport, facilitated by close packed herringbone crystal motifs, and their energy levels can be synthetically tuned. The principal drawback of this class of materials, their tendency to crystallize on too large a length scale for an optimal heterojunction nanostructure, has been shown to be overcome through introduction of conformation twisting through steric effects. This has been primarily achieved by coupling two units together

  16. Functionalized dye encapsulated polymer nanoparticles attached with a BSA scaffold as efficient antenna materials for artificial light harvesting.

    PubMed

    Jana, Bikash; Bhattacharyya, Santanu; Patra, Amitava

    2016-09-21

    A potential strategy for a new generation light harvesting system is multi-chromophoric donor-acceptor pairs where light energy is absorbed by an antenna complex and subsequently transfers its energy to the acceptor via energy transfer. Here, we design a system of a functionalized polymer nanoparticle-protein scaffold for efficient light harvesting and white light generation where a dye doped polymer nanoparticle acts as a donor and a dye encapsulated BSA protein acts as an acceptor. Analysis reveals that 91.3% energy transfer occurs from the dye doped polymer nanoparticle to the dye encapsulated BSA protein. The antenna effect of this light harvesting system is found to be 31 at a donor to acceptor ratio of 0.82 : 1 which is unprecedented. The enhanced effective molar extinction coefficient of the acceptor dye is potential for the light harvesting system. Bright white light emission with a quantum yield of 14% under single wavelength excitation is obtained by changing the ratio of donor to acceptor. Analysis reveals that the efficient energy transfer in this polymer-protein assembly may open up new possibilities in designing artificial light harvesting systems for future applications. PMID:27546792

  17. Hair dye poisoning

    MedlinePlus

    Hair tint poisoning ... Different types of hair dye contain different harmful ingredients. The harmful ingredients in permanent dyes are: Naphthylamine Other aromatic amino compounds Phenylenediamines Toluene ...

  18. Just Dyeing to Find Out.

    ERIC Educational Resources Information Center

    Monhardt, Becky Meyer

    1996-01-01

    Presents a multidisciplinary unit on natural dyes designed to take advantage of the natural curiosity of middle school students. Discusses history of dyes, natural dyes, preparation of dyes, and the dyeing process. (JRH)

  19. Improving the dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Willig, Frank

    2007-09-01

    Two dye sensitized solar cells (DSC) can be joined to form a tandem cell with two separate absorption ranges for the two different absorber materials. This can enhance the solar conversion efficiency and in particular the photovoltage of the DSC. Water splitting appears as a realistic long term target. The DSC tandem can be realized as n-n junction employing known dye molecules with optimal absorption spectra. Dye molecules with elongated shapes can be realized by covalently attaching a conducting bridge group terminated by an anchor group to a desired chromophore. Due to the long conducting bridge group separating the hole state of the dye from the surface of the semiconductor recombination is slowed down. The ordered molecular structure can be self-assembled on the recently introduced rod or cylinder shaped oxide electrodes but will not slow down recombination in the nm-cavities of the conventional TiO II Graetzel electrode.

  20. Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye

    NASA Astrophysics Data System (ADS)

    El-Mossalamy, E. H.; Obaid, A. Y.; El-Daly, S. A.

    2011-10-01

    The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2×10 -3 mol dm -3 of DEAC gives laser emission in the blue region on pumping with nitrogen laser ( λex=337.1 nm). The laser parameters such as tuning range, gain coefficient ( α), emission cross section ( σe), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl 4 at a wavelength of 366 nm. The values of photochemical yield ( ϕc) and rate constant ( k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH 3CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex.

  1. Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

    PubMed Central

    Schmid, Thibault E; Drissi-Amraoui, Sammy; Crévisy, Christophe; Baslé, Olivier

    2015-01-01

    Summary The copper-catalyzed asymmetric conjugate addition (ACA) of nucleophiles onto polyenic Michael acceptors represents an attractive and powerful methodology for the synthesis of relevant chiral molecules, as it enables in a straightforward manner the sequential generation of two or more stereogenic centers. In the last decade, various chiral copper-based catalysts were evaluated in combination with different nucleophiles and Michael acceptors, and have unambiguously demonstrated their usefulness in the control of the regio- and enantioselectivity of the addition. The aim of this review is to report recent breakthroughs achieved in this challenging field. PMID:26734090

  2. Molecular orientation of rhodamine dyes on surfaces of layered silicates.

    PubMed

    Bujdák, Juraj; Iyi, Nobuo

    2005-03-17

    Films of the layered silicates fluorohectorite (FH) and saponite (Sap) with various rhodamine dyes were prepared. The dyes with acidic as well as large hydrophobic groups in their molecule were not adsorbed on the surface of FH, which was interpreted in terms of high charge density on the surface of this silicate. All adsorbed dyes formed similar forms, such as isolated cations and H-type molecular aggregates, which were characterized by different spectral properties. Polarized ultraviolet-visible (UV-vis) spectroscopy was used for the characterization of the molecular orientation of dye chromophores on the silicate surface. The isolated dye cations and species, which absorbed light at the low energy part of the spectra, were only slightly tilted with respect to the plane of the silicate surface. The cations forming H-aggregates and absorbing light at low wavelengths were oriented in a nearly perpendicular fashion. The nearly perpendicular orientation was observed as a strong increase of dichroic ratio with film tilting. The orientation of the cations in H-aggregates depends partially on the structure of the dye molecule, namely, on the type of amino group (primary, secondary, or tertiary) in the dye molecule. The type of amino groups probably plays a role in the suitable orientation of dye cations for effective electrostatic interaction between the cations and the negatively charged siloxane surface. X-ray powder diffraction could not distinguish dye phases of dye monomers and molecular aggregates. PMID:16851539

  3. Uniform silica nanoparticles encapsulating two-photon absorbing fluorescent dye

    SciTech Connect

    Wu Weibing; Liu Chang; Wang Mingliang; Huang Wei; Zhou Shengrui; Jiang Wei; Sun Yueming; Cui Yiping; Xu Chunxinag

    2009-04-15

    We have prepared uniform silica nanoparticles (NPs) doped with a two-photon absorbing zwitterionic hemicyanine dye by reverse microemulsion method. Obvious solvatochromism on the absorption spectra of dye-doped NPs indicates that solvents can partly penetrate into the silica matrix and then affect the ground and excited state of dye molecules. For dye-doped NP suspensions, both one-photon and two-photon excited fluorescence are much stronger and recorded at shorter wavelength compared to those of free dye solutions with comparative overall dye concentration. This behavior is possibly attributed to the restricted twisted intramolecular charge transfer (TICT), which reduces fluorescence quenching when dye molecules are trapped in the silica matrix. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells with low cytotoxicity. - Graphical abstract: Water-soluble silica NPs doped with a two-photon absorbing zwitterionic hemicyanine dye were prepared. They were found of enhanced one-photon and two-photon excited fluorescence compared to free dye solutions. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells.

  4. Detailed analysis of ultrathin fluorescent red dye interlayer for organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Zang, Yue; Yu, Jun-Sheng; Wang, Na-Na; Jiang, Ya-Dong

    2011-01-01

    The influence of an ultrathin 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) fluorescent dye layer at donor/acceptor heterojunction on the performance of small-molecule organic photovoltaic (OPV) cell is studied. The structure of OPV cell is of indium-tin oxide (ITO)/copper phthalocyanine (CuPc)/DCJTB/fullerene (C60)/bathophenanthroline (Bphen)/Ag. The results show that open circuit voltage (VOC) increases to 0.57 V as the film thickness of DCJTB layer increases from 0.2 to 2.0 nm. By using an equivalent circuit model, the enhancement of VOC is found to be attributed to the reduced reverse saturation current density (JS) which is due to the lower highest occupied molecular orbital (HOMO) level in DCJTB than that in CuPc. Also, the short circuit current density (JSC) is affected when the DCJTB layer becomes thicker, resulting from the high series resistance RSA due to the low charge carrier mobility of fluorescent red dye.

  5. Pyridine as proton acceptor in the concerted proton electron transfer oxidation of phenol.

    PubMed

    Bonin, Julien; Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel

    2011-06-01

    Taking pyridine as a prototypal example of biologically important nitrogen bases involved in proton-coupled electron transfers, it is shown with the example of the photochemically triggered oxidation of phenol by Ru(III)(bpy)(3) that this proton acceptor partakes in a concerted pathway whose kinetic characteristics can be extracted from the overall kinetic response. The treatment of these data, implemented by the results of a parallel study carried out in heavy water, allowed the determination of the intrinsic kinetic characteristics of this proton acceptor. Comparison of the reorganization energies and of the pre-exponential factors previously derived for hydrogen phosphate and water (in water) as proton acceptors suggests that, in the case of pyridine, the proton charge is delocalized over a primary shell of water molecules firmly bound to the pyridinium cation. PMID:21499600

  6. Incorporation of a Michael acceptor enhances the antitumor activity of triterpenoic acids.

    PubMed

    Heller, Lucie; Schwarz, Stefan; Perl, Vincent; Köwitsch, Alexander; Siewert, Bianka; Csuk, René

    2015-08-28

    Finding and developing drugs for the treatment of cancer has been challenging scientists for many decades, and using compounds of natural origin represents one of several strategies. Triterpenoic acids are a very promising class of secondary metabolites being able to induce apoptosis while their cytotoxicity is low. Therefore, derivatizations have to be conducted to improve cytotoxicity while retaining their ability to induce programmed cell death. The incorporation of a Michael acceptor into molecules resulted very often in drugs of improved cytotoxicity. Thus, in this study we synthesized and evaluated several Michael acceptor substituted compounds derived from glycyrrhetinic, ursolic, oleanolic and platanic acid. The influence of the presence of such a functional group onto the cytotoxicity was investigated in colorimetric sulforhodamine B assays employing several human cancer cell lines. EC50 values in the single-digit micromolar range were measured. Thus, the incorporation of a Michael acceptor unit into triterpenoic acids enhances the cytotoxicity of these compounds significantly. PMID:26177446

  7. Changing the acceptor identity of a transfer RNA by altering nucleotides in a "variable pocket".

    PubMed

    McClain, W H; Foss, K

    1988-09-30

    The specificity of tRNA(Arg) (arginine transfer RNA) for aminoacylation (its acceptor identity) were first identified by computer analysis and then examined with amber suppressor tRNAs in Escherichia coli. On replacing two nucleotides in tRNA(Phe) (phenylalanine transfer RNA) with the corresponding nucleotides from tRNA(Arg), the acceptor identity of the resulting tRNA was changed to that of tRNA(Arg). The nucleotides used in the identity transformation occupy a "variable pocket" structure on the surface of the tRNA molecule where two single-stranded loop segments interact. The middle nucleotide in the anticodon also probably contributes to the interaction, since an amber suppressor of tRNA(Arg) had an acceptor identity for lysine as well as arginine. PMID:2459773

  8. Electron Donor Acceptor Interactions. Final Progress Report

    SciTech Connect

    2002-08-16

    The Gordon Research Conference (GRC) on Electron Donor Acceptor Interactions was held at Salve Regina University, Newport, Rhode Island, 8/11-16/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  9. Benzimidazole-Branched Isomeric Dyes: Effect of Molecular Constitution on Photophysical, Electrochemical, and Photovoltaic Properties.

    PubMed

    Bodedla, Govardhana Babu; Justin Thomas, K R; Fan, Miao-Syuan; Ho, Kuo-Chuan

    2016-01-15

    Three benzimidazole-based isomeric organic dyes possessing two triphenylamine donors and a cyanoacrylic acid acceptor are prepared by stoichiometrically controlled Stille or Suzuki-Miyaura coupling reaction which predominantly occurs on the N-butyl side of benzimidazole due to electronic preferences. Combined with the steric effect of the N-butyl substituent, placement of the acceptor segment at various nuclear positions of benzimidazole such as C2, C4, and C7 led to remarkable variations in intramolecular charge transfer absorption, electron injection efficiency, and charge recombination kinetics. The substitution of acceptor on the C4 led to red-shifted absorption, while that on C7 retarded the charge transfer due to twisting in the structure caused by the butyl group. Because of the cross-conjugation nature and poor electronic interaction between the donor and acceptor, the dye containing triphenylamine units on C4 and C7 and the acceptor unit on C2 showed the low oxidation potential. Thus, this dye possesses favorable HOMO and LUMO energy levels to render efficient sensitizing action in solar cells. Consequently, it results in high power conversion efficiency (5.01%) in the series with high photocurrent density and open circuit voltage. The high photocurrent generation by this dye is reasoned to it exceptional charge collection efficiency as determined from the electron impedance spectroscopy. PMID:26679036

  10. Dye-sensitized solar cells using natural dyes as sensitizers from Malaysia local fruit `Buah Mertajam'

    NASA Astrophysics Data System (ADS)

    Hambali, N. A. M. Ahmad; Roshidah, N.; Hashim, M. Norhafiz; Mohamad, I. S.; Saad, N. Hidayah; Norizan, M. N.

    2015-05-01

    We experimentally demonstrate the high conversion efficiency, low cost, green technology and easy to fabricate dye-sensitized solar cells (DSSCs) using natural anthocyanin dyes as sensitizers. The DSSCs was fabricated by using natural anthocyanin dyes which were extracted from different parts of the plants inclusive `Buah Mertajam', `Buah Keriang Dot', `Bunga Geti', Hibiscus, Red Spinach and Henna. The natural anthocyanin dyes that found in flower, leaves and fruits were extracted by the simple procedures. This anthocyanin dye is used to replace the expensive chemical synthetic dyes due to its ability to effectively attach into the surface of Titanium dioxide (TiO2). A natural anthocyanin dyes molecule adsorbs to each particle of the TiO2 and acts as the absorber of the visible light. A natural anthocyanin dye from Buah Mertajam shows the best performance with the conversion efficiency of 5.948% and fill factor of 0.708 followed by natural anthocyanin dyes from `Buah Keriang Dot', `Bunga Geti', Hibiscus, Red Spinach and Henna. Buah Mertajam or scientifically known as eriglossum rubiginosum is a local Malaysia fruit.

  11. Modeling of the dye loading time influence on the electrical impedance of a dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Pugliese, D.; Shahzad, N.; Sacco, A.; Tresso, E.; Alexe-Ionescu, A. L.

    2013-09-01

    A hemisquaraine dye molecule (CT1) was used as TiO2 sensitizer. The influence of the dye-adsorption time on the electrical impedance of a CT1-based dye-sensitized solar cell (DSC) was analyzed. Differently from what we observed with commercial Ru dye-based DSC, a non-monotonic effect of the impregnation time on the impedance has been found and the dye loading time is much reduced, a desirable outcome in economic grounds. This feature is analyzed in terms of the dye molecules tendency to aggregate close to the TiO2/electrolyte interface. A physical model that fits well the experimental data is proposed, which also takes into account a correction related to the difference between the illuminated area of the cell and the total area available in the electrical measurements.

  12. Molecular aggregation of rhodamine dyes in dispersions of layered silicates: influence of dye molecular structure and silicate properties.

    PubMed

    Bujdák, Juraj; Iyi, Nobuo

    2006-02-01

    The molecular aggregation of six rhodamine dyes (rhodamine 560, B, 3B, 19, 6G, 123) in layered silicate (saponite and fluorohectorite) dispersions was investigated by using visible (vis) spectroscopy. The dye molecular aggregation was influenced by the properties of both the silicates and the dyes themselves. The layer charge of the silicates enhanced the molecular aggregation of the hydrophilic, cationic dyes. The presence of a carboxyl acid group in the dye molecules inhibited adsorption of the dyes on the surface of fluorohectorite, a silicate with a high charge density. A lower or no adsorption could be observed by vis spectroscopy. Strong association of the dyes to the silicate surface led to remarkable changes in the dye spectra, mainly due to the molecular aggregation. Dye assemblies initially formed after mixing the dye solutions with silicate dispersions were unstable. Decomposition of the dye molecular assemblies, and the formation of new species or molecular aggregate rearrangements, were studied on the bases of time-difference spectra. The reaction pathways were specific, not only for the dyes, depending upon their molecular structure and properties, but also on the silicate substrates. PMID:16471802

  13. Novel planar and star-shaped molecules: Synthesis, electrochemical and photophysical properties

    NASA Astrophysics Data System (ADS)

    Niu, Qingfen; Lu, Yunqiang; Sun, Hongjian; Li, Xiaoyan

    2013-04-01

    Three novel planar and star-shaped molecules containing thiophene-functionalized group and acetylenic spacers, 4-((5″-iodo-[2,2':5',2″-terthiophen]-5-yl)ethynyl)aniline (I3TEA), 4,4'-([2,2':5',2″-terthiophene]-5,5″-diylbis(ethyne-2,1-diyl))dianiline (3TDDA), 1,3,5-tris((5-((trimethylsilyl)ethynyl)thiophen-2-yl)ethynyl)benzene (TETEB) were synthesized through Sonogashira coupling reaction. Their photophysical and electrochemical properties were explored by UV-vis, photoluminescence (PL) emission and DFT calculation. Three compounds possess unusual phenomena of PL, with the concentration of gradually decreased, the intensity of PL firstly increased and then decreased, this may be due to the aggregate-enhanced emission (AEE) effect and aggregation-caused quenching (ACQ) effect. Their spectroscopic data demonstrate that D-π-A-π-D structured organic dye 3TDDA based on NH2 as donor units and 3T as acceptor units with acetylenic spacers π-conjugated chain between them exhibits good luminescent properties. Dye I3TEA with donor(D)-acceptor(A) structure shows good charge transfer because of amino functional group and iodine atom. Octupolar organic π-conjugated star-shaped molecule TETEB possesses excellent luminescent properties because of its unique structure applied in the optoelectronic field. The redox curves and results of DFT calculations suggest that three compounds have low ionization potential and low Eoxd. All the good properties demonstrate three compounds could be promising candidates for photovoltaic materials.

  14. Computational design of small phenothiazine dyes for dye-sensitized solar cells by functionalizations affecting the thiophene unit.

    PubMed

    Tu, Wei Han; Tan, Yi Yin; Rege, Omkar; Manzhos, Sergei

    2015-04-01

    We present a computational density functional theory study of the potential to improve the solar absorbance of small organic dyes featuring a phenothiazine donor and an acceptor moiety that combines a thiophene unit and a cyanoacrylic group. We consider different conjugation orders and functional groups on and around the thiophene unit, including electron-donating and electron-withdrawing moieties (H, F, CH3, CF3, and CN). We predict that by combining change of conjugation order and functionalization with electron withdrawing CN groups, it must be possible to decrease the excitation energy by up to 60 % vs. the parent dye (which would correspond to a redshift of the absorption peak maximum from 450 nm to 726 nm), effectively enabling red light absorption with small dyes. The contraction of the band gap is mostly due to the stabilization of the LUMO (by up to 1.8 eV), so that-in spite of the kinetic redundancy of the parent dye with respect to the conduction-band minimum of TiO2-care must be taken to ensure efficient injection when using the dyes in dye-sensitized solar cells. By studying 50 dyes, of which 44 are new dyes that are studied for the first time in this work, we identify parameters (such as charges, dihedral angles between donor and acceptor groups, bond length alternation) which can serve as predictors of the band gap. We find that bond length alternation or dihedral angles are not good predictors, while the charge on the thiophene unit is. PMID:25750021

  15. Cyanine dyes with high-absorbance cross section as donor chromophores in energy transfer labels

    DOEpatents

    Glazer, Alexander N.; Mathies, Richard A.; Hung, Su-Chun; Ju, Jingyue

    1998-01-01

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures.

  16. Methods of sequencing and detection using energy transfer labels with cyanine dyes as donor chromophores

    DOEpatents

    Glazer, Alexander N.; Mathies, Richard A.; Hung, Su-Chun; Ju, Jingyue

    2000-01-01

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures.

  17. Cyanine dyes with high-absorbance cross section as donor chromophores in energy transfer labels

    DOEpatents

    Glazer, A.N.; Mathies, R.A.; Hung, S.C.; Ju, J.

    1998-12-29

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures. 22 figs.

  18. The Tetrathiafulvalene-based Donor-acceptor Diads for Molecular Electronics

    NASA Astrophysics Data System (ADS)

    Perepichka, Dmitrii F.; Bryce, Martin R.; Ho, Gregory; Heath, James R.; Pearson, Christopher; Petty, Michael C.

    2004-03-01

    The challenge of covalent linking a strong electron donor (as tetrathiafulvalene, TTF) to a strong acceptor (as tetracyanoquinodimethane, TCNQ) was laid down by Aviram and Ratner, who proposed that a single donor-sigma-acceptor molecule could rectify an electric current. Although numerous organic compounds have been tested in metal-molecule-metal junctions, they had substantially higher HOMO-LUMO gap (Eg >0.5 eV) and, in most cases, high dipole moment due to conjugated character of the linker. Those molecules re-orient in the electric field limiting the device stability. Recently, we have pioneered the synthesis of DsigmaA molecules with the HOMO-LUMO gap 0.17-0.3 eV, including the original TTF-TCNQ.* We will present the intriguing electronic properties of these compounds, including the conformational control of the Eg and the thermoexcited electron transfer. The compounds form high-quality LB films, suitable for molecular electronics applications. In Si-molecule-Ti junctions, the rectification ratio increases as molecules align perpendicularly to the surface, and the device stability override significantly the related system based on D-pi-A molecules. * Perepichka, et al., Angew. Chem. Int. Ed. 2003, 42, 4635.

  19. Fluorescence Quenching of (Dimethylamino)naphthalene Dyes Badan and Prodan by Tryptophan in Cytochromes P450 and Micelles

    PubMed Central

    2015-01-01

    Fluorescence of 2-(N,N-dimethylamino)-6-propionylnaphthalene dyes Badan and Prodan is quenched by tryptophan in Brij 58 micelles as well as in two cytochrome P450 proteins (CYP102, CYP119) with Badan covalently attached to a cysteine residue. Formation of nonemissive complexes between a dye molecule and tryptophan accounts for about 76% of the fluorescence intensity quenching in micelles, the rest is due to diffusive encounters. In the absence of tryptophan, fluorescence of Badan-labeled cytochromes decays with triexponential kinetics characterized by lifetimes of about 100 ps, 700–800 ps, and 3 ns. Site mutation of a histidine residue in the vicinity of the Badan label by tryptophan results in shortening of all three decay lifetimes. The relative amplitude of the fastest component increases at the expense of the two slower ones. The average quenching rate constants are 4.5 × 108 s–1 (CYP102) and 3.7 × 108 s–1 (CYP119), at 288 K. Cyclic voltammetry of Prodan in MeCN shows a reversible reduction peak at −1.85 V vs NHE that becomes chemically irreversible and shifts positively upon addition of water. A quasireversible reduction at −0.88 V was observed in an aqueous buffer (pH 7.3). The excited-state reduction potential of Prodan (and Badan) is estimated to vary from about +0.6 V (vs NHE) in polar aprotic media (MeCN) to approximately +1.6 V in water. Tryptophan quenching of Badan/Prodan fluorescence in CYPs and Brij 58 micelles is exergonic by ≤0.5 V and involves tryptophan oxidation by excited Badan/Prodan, coupled with a fast reaction between the reduced dye and water. Photoreduction is a new quenching mechanism for 2-(N,N-dimethylamino)-6-propionylnaphthalene dyes that are often used as solvatochromic polarity probes, FRET donors and acceptors, as well as reporters of solvation dynamics. PMID:25079965

  20. Theoretica Study of Asymmetric Double D-π-A Organic Sensitizers for Efficient Dye-Sensitized Solar Cells.

    PubMed

    Kwon, Dong Yuel; Lee, Gun Hyung; Kim, Young Sik

    2015-03-01

    Three novel dye sensitizers that were based on asymmetric double D-π-A chains with phenoxazine (POZ) and diphenylamine (DPA) as electron donors and cyanoacetic acid (CA) and 2-(1,1- dicyanomethylene) rhodanine (RD) as electron acceptors (DCPR, DRPC, DRPR) were designed, theoretically investigated, and compared with the reference dye based on asymmetric double D-π-A chains (DCPC). Using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations, we gained insight into the factors responsible for the photovoltaic properties of the dye sensitizers. Due to the different HOMO levels of each donor and the different LUMO levels of each acceptor, the absorption spectrum of each dye showed different shapes. Among the dyes, DRPR showed a broader and more bathochromically shifted absorption band than the other dies. It also showed a higher molar extinction coefficient than that of the reference dye (DCPC). This work suggests optimizing the chain of electron donors and acceptors in dye sensitizers based on asymmetric double D-π-A chains would produce good photovoltaic properties for dye-sensitized solar cells (DSSCs). PMID:26413690

  1. Understanding the charge-transfer phenomena between prototypical electron-donors and acceptors: TTF-TCNQ as an example

    NASA Astrophysics Data System (ADS)

    Park, Changwon; Atalla, Viktor; Smith, Sean; Yoon, Mina

    2014-03-01

    It is widely accepted that the charge transfer between the conventional electron donor and acceptor molecules is independent of their relative configurations and electrons are always transferred from the molecule with the lower ionization potential, the electron-donor, to the high electron affinity molecule, the electron-acceptor. Conventional first-principles density functional theory (DFT) supports this conclusion. However, the computational results are dominated by a term in the DFT exchange-correlation functional, which often results in qualitatively and quantitatively wrong conclusion due to an artifact. In our study of prototypical electron donor-acceptor molecules, TTF-TCNQ, we show that the conventional electronic picture is not valid and the relative orientation between TTF and TCNQ is equally important as the electronic structure of the individual molecules. Our results show that the current understanding of the donor-acceptor interaction and charge transfer mechanism has to be modified. This research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Office of Basic Energy Sciences, U.S. Department of Energy.

  2. Charge Transfer Dynamics at Dye-Sensitized ZnO and TiO2 Interfaces Studied by Ultrafast XUV Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Borgwardt, Mario; Wilke, Martin; Kampen, Thorsten; Mähl, Sven; Xiao, Manda; Spiccia, Leone; Lange, Kathrin M.; Kiyan, Igor Yu.; Aziz, Emad F.

    2016-04-01

    Interfacial charge transfer from photoexcited ruthenium-based N3 dye molecules into ZnO thin films received controversial interpretations. To identify the physical origin for the delayed electron transfer in ZnO compared to TiO2, we probe directly the electronic structure at both dye-semiconductor interfaces by applying ultrafast XUV photoemission spectroscopy. In the range of pump-probe time delays between 0.5 to 1.0 ps, the transient signal of the intermediate states was compared, revealing a distinct difference in their electron binding energies of 0.4 eV. This finding strongly indicates the nature of the charge injection at the ZnO interface associated with the formation of an interfacial electron-cation complex. It further highlights that the energetic alignment between the dye donor and semiconductor acceptor states appears to be of minor importance for the injection kinetics and that the injection efficiency is dominated by the electronic coupling.

  3. Charge Transfer Dynamics at Dye-Sensitized ZnO and TiO2 Interfaces Studied by Ultrafast XUV Photoelectron Spectroscopy

    PubMed Central

    Borgwardt, Mario; Wilke, Martin; Kampen, Thorsten; Mähl, Sven; Xiao, Manda; Spiccia, Leone; Lange, Kathrin M.; Kiyan, Igor Yu.; Aziz, Emad F.

    2016-01-01

    Interfacial charge transfer from photoexcited ruthenium-based N3 dye molecules into ZnO thin films received controversial interpretations. To identify the physical origin for the delayed electron transfer in ZnO compared to TiO2, we probe directly the electronic structure at both dye-semiconductor interfaces by applying ultrafast XUV photoemission spectroscopy. In the range of pump-probe time delays between 0.5 to 1.0 ps, the transient signal of the intermediate states was compared, revealing a distinct difference in their electron binding energies of 0.4 eV. This finding strongly indicates the nature of the charge injection at the ZnO interface associated with the formation of an interfacial electron-cation complex. It further highlights that the energetic alignment between the dye donor and semiconductor acceptor states appears to be of minor importance for the injection kinetics and that the injection efficiency is dominated by the electronic coupling. PMID:27073060

  4. Charge Transfer Dynamics at Dye-Sensitized ZnO and TiO2 Interfaces Studied by Ultrafast XUV Photoelectron Spectroscopy.

    PubMed

    Borgwardt, Mario; Wilke, Martin; Kampen, Thorsten; Mähl, Sven; Xiao, Manda; Spiccia, Leone; Lange, Kathrin M; Kiyan, Igor Yu; Aziz, Emad F

    2016-01-01

    Interfacial charge transfer from photoexcited ruthenium-based N3 dye molecules into ZnO thin films received controversial interpretations. To identify the physical origin for the delayed electron transfer in ZnO compared to TiO2, we probe directly the electronic structure at both dye-semiconductor interfaces by applying ultrafast XUV photoemission spectroscopy. In the range of pump-probe time delays between 0.5 to 1.0 ps, the transient signal of the intermediate states was compared, revealing a distinct difference in their electron binding energies of 0.4 eV. This finding strongly indicates the nature of the charge injection at the ZnO interface associated with the formation of an interfacial electron-cation complex. It further highlights that the energetic alignment between the dye donor and semiconductor acceptor states appears to be of minor importance for the injection kinetics and that the injection efficiency is dominated by the electronic coupling. PMID:27073060

  5. Highly efficient photocathodes for dye-sensitized tandem solar cells.

    PubMed

    Nattestad, A; Mozer, A J; Fischer, M K R; Cheng, Y-B; Mishra, A; Bäuerle, P; Bach, U

    2010-01-01

    Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5-15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes. The donor-acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components. PMID:19946281

  6. Highly efficient photocathodes for dye-sensitized tandem solar cells

    NASA Astrophysics Data System (ADS)

    Nattestad, A.; Mozer, A. J.; Fischer, M. K. R.; Cheng, Y.-B.; Mishra, A.; Bäuerle, P.; Bach, U.

    2010-01-01

    Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5-15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes. The donor-acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.

  7. ANALYSIS OF ANIONIC METALLIZED AZO AND FORMAZAN DYES BY CAPILLARY ELECTROPHORESIS/MASS SPECTROMETRY

    EPA Science Inventory

    Capillary electrophoresis-mass spectrometry was applied to the separation of several anionic dyes containing copper(II), chromium(III), or cobalt(III) as part of the dye molecule. The dyes were separated using a 110 cmX50 mu m uncoated fused-silica capillary and a 5 mM ammonium a...

  8. Photobleaching effect in azo-dye containing epoxy resin films: the potentiality of carbon nanotubes as azo-dye dispensers

    NASA Astrophysics Data System (ADS)

    Díaz Costanzo, Guadalupe; Goyanes, Silvia; Ledesma, Silvia

    2015-04-01

    Azo-dye molecules may suffer from bleaching under certain illumination conditions. When this photoinduced process occurs, it generates an irreversible effect that is characterized by the loss of absorption of the dye molecule. Moreover, the well-known isomerization of azodye molecules does not occur anymore. In this work it is shown how the addition of a small amount of multi-walled carbon nanotubes (MWCNTs) helps to decrease the bleaching effect in a photosensitive guest-host azo-polymer film. Two different systems were fabricated using an epoxy resin as polymer matrix. An azo-dye, Disperse Orange 3, was used as photosensitive material in both systems and MWCNTs were added into one of them. The optical response of the polymeric systems was studied considering the degree of photoinduced birefringence. Photobleaching of the azo-dye was observed in all cases however, the effect is lower for the composite material containing 0.2 wt % MWCNTs. The weak interaction between MWCNTs and dye molecules is less favorable when the material is heated. The optical behavior of the heated composite material suggests that carbon nanotubes can be potentially used as azo dye dispensers. The results are interpreted in terms of the non-covalent interaction between azo-dye molecules and MWCNTs.

  9. Inhibition of the water oxidizing complex of photosystem II and the reoxidation of the quinone acceptor QA- by Pb2+.

    PubMed

    Belatik, Ahmed; Hotchandani, Surat; Carpentier, Robert

    2013-01-01

    The action of the environmental toxic Pb(2+) on photosynthetic electron transport was studied in thylakoid membranes isolated from spinach leaves. Fluorescence and thermoluminescence techniques were performed in order to determine the mode of Pb(2+) action in photosystem II (PSII). The invariance of fluorescence characteristics of chlorophyll a (Chl a) and magnesium tetraphenylporphyrin (MgTPP), a molecule structurally analogous to Chl a, in the presence of Pb(2+) confirms that Pb cation does not interact directly with chlorophyll molecules in PSII. The results show that Pb interacts with the water oxidation complex thus perturbing charge recombination between the quinone acceptors of PSII and the S2 state of the Mn4Ca cluster. Electron transfer between the quinone acceptors QA and QB is also greatly retarded in the presence of Pb(2+). This is proposed to be owing to a transmembrane modification of the acceptor side of the photosystem. PMID:23861859

  10. Inhibition of the Water Oxidizing Complex of Photosystem II and the Reoxidation of the Quinone Acceptor QA− by Pb2+

    PubMed Central

    Belatik, Ahmed; Hotchandani, Surat; Carpentier, Robert

    2013-01-01

    The action of the environmental toxic Pb2+ on photosynthetic electron transport was studied in thylakoid membranes isolated from spinach leaves. Fluorescence and thermoluminescence techniques were performed in order to determine the mode of Pb2+ action in photosystem II (PSII). The invariance of fluorescence characteristics of chlorophyll a (Chl a) and magnesium tetraphenylporphyrin (MgTPP), a molecule structurally analogous to Chl a, in the presence of Pb2+ confirms that Pb cation does not interact directly with chlorophyll molecules in PSII. The results show that Pb interacts with the water oxidation complex thus perturbing charge recombination between the quinone acceptors of PSII and the S2 state of the Mn4Ca cluster. Electron transfer between the quinone acceptors QA and QB is also greatly retarded in the presence of Pb2+. This is proposed to be owing to a transmembrane modification of the acceptor side of the photosystem. PMID:23861859

  11. Extension lifetime for dye-sensitized solar cells through multiple dye adsorption/desorption process

    NASA Astrophysics Data System (ADS)

    Chiang, Yi-Fang; Chen, Ruei-Tang; Shen, Po-Shen; Chen, Peter; Guo, Tzung-Fang

    2013-03-01

    In this study, we propose a novel concept of extending the lifetime of dye-sensitized solar cells (DSCs) and reducing the costs of re-conditioning DSCs by recycling the FTO/TiO2 substrates. The photovoltaic performances of DSCs using substrates with various cycles of dye uptake and rinse off history are tested. The results show that dye adsorption and Voc are significantly increased under multiple dye adsorption/desorption process and resulted in the improvement of power conversion efficiency. Moreover, the dyeing kinetics is faster after multiple recycling processes, which is favorable for the industrial application. With surface analysis and charge transport characteristics, we also demonstrate the optimal functionality of TiO2/dye interface for the improved Voc and efficiency. The results confirm that the improved performances are due to increased dye loading and dense packing of dye molecules. Our results are beneficial for the understanding on the extension of DSCs lifetime after long-term operation in the application of DSC modules. This approach may also be applied in the replacement of newly synthesized photosensitizes to the active cells.

  12. Dipole-Dipole Interaction Driven Self-Assembly of Merocyanine Dyes: From Dimers to Nanoscale Objects and Supramolecular Materials.

    PubMed

    Würthner, Frank

    2016-05-17

    π-Conjugation between heterocyclic donor (D) and acceptor (A) groups via a polymethine chain leads to dyes with dipole moments greater than 10 D. These dipole moments direct the self-assembly of the dyes into antiparallel dimer aggregates, even in dilute solution, with binding strengths that are far beyond those observed for other π-scaffolds whose self-assembly is driven primarily by dispersion forces. The combination of directionality and exceptional binding strength of dipolar interactions between D-π-A dyes indeed resembles the situation of the hydrogen bond. Thus, similar to the latter, dipolar interactions between merocyanine dyes, a unique class of D-π-A chromophores, can be utilized to construct sophisticated supramolecular architectures of predictable geometry, particularly in low polarity environments. For bis(merocyanine) dyes it has been demonstrated that the self-assembly pathway is encoded in the tether between the two constituent merocyanine chromophores. If the tether enables the antiparallel stacking of the two appended dyes, folding takes place, which may be followed by further self-assembly into extended H-aggregate π-stacks at higher concentrations in solvents of low polarity. For tethers that do not support folding, the formation of bimolecular complexes of four merocyanine units, cyclic oligomers, and supramolecular polymers has been observed. For the former case, that is, formation of a bimolecular stack of four merocyanine units from tweezer-type molecules, association constants >10(9) M(-1) were measured in chloroform. On the other hand, because only one π-face is utilized in the formation of supramolecular polymers from bis(merocyanine) dyes, higher hierarchical structures typically originate in which the other π-face is surrounded by an antiparallel π-stacked neighbor molecule. Among the observed self-assembled structures, nanorods in particular have attracted considerable attention because their self-assembly into well-defined H

  13. Process for separating and recovering an anionic dye from an aqueous solution

    DOEpatents

    Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

    1998-01-01

    A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution.

  14. Process for separating and recovering an anionic dye from an aqueous solution

    DOEpatents

    Rogers, R.; Horwitz, E.P.; Bond, A.H.

    1998-01-13

    A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution. 7 figs.

  15. Stimulated Raman scattering of laser dye mixtures dissolved in multiple scattering media

    SciTech Connect

    Yashchuk, V P; Komyshan, A O; Tikhonov, E A; Olkhovyk, L A

    2014-10-31

    Stimulated Raman scattering (SRS) of a mixture of rhodamine 6G and pyrromethene 605 laser dyes in vesicular films is studied. It is shown that a peculiar interaction of dyes occurs under conditions of multiple scattering of light from vesicles. This interaction manifests itself as SRS excitation of one of the dyes by random lasing of the other dye, provided that the random lasing spectrum overlaps the Stokes lines of the first dye. In addition, there is energy transfer between molecules of these dyes if their luminescence and absorption spectra overlap. The results obtained confirm that the mechanism of SRS from laser dyes in multiple scattering media is similar to that in coherent-active Raman spectroscopy. These results extend the possibility of determining the vibrational spectrum of dye molecules from their secondary radiation in these media. (nonlinear optical phenomena)

  16. Analysis of nonlinear optical properties in donor–acceptor materials

    SciTech Connect

    Day, Paul N.; Pachter, Ruth; Nguyen, Kiet A.

    2014-05-14

    Time-dependent density functional theory has been used to calculate nonlinear optical (NLO) properties, including the first and second hyperpolarizabilities as well as the two-photon absorption cross-section, for the donor-acceptor molecules p-nitroaniline and dimethylamino nitrostilbene, and for respective materials attached to a gold dimer. The CAMB3LYP, B3LYP, PBE0, and PBE exchange-correlation functionals all had fair but variable performance when compared to higher-level theory and to experiment. The CAMB3LYP functional had the best performance on these compounds of the functionals tested. However, our comprehensive analysis has shown that quantitative prediction of hyperpolarizabilities is still a challenge, hampered by inadequate functionals, basis sets, and solvation models, requiring further experimental characterization. Attachment of the Au{sub 2}S group to molecules already known for their relatively large NLO properties was found to further enhance the response. While our calculations show a modest enhancement for the first hyperpolarizability, the enhancement of the second hyperpolarizability is predicted to be more than an order of magnitude.

  17. Diffusion of dye solution in the intermolecular nanostructure of polydimethylsiloxane

    NASA Astrophysics Data System (ADS)

    Saito, Mitsunori; Nishimura, Tatsuya; Sakiyama, Kohei; Nakagawa, Michinori

    2012-09-01

    Polydimethylsiloxane (PDMS) contains a large, flexible free space between weakly-bonded molecules, which allows notable molecular diffusion. A toluene solution of diarylethene (photochromic dye) was mixed with a PDMS oil, and then the mixture was cured in a glass vessel by adding a curing agent. Violet laser (405 nm wavelength) irradiation induced an absorption band at around 530 nm, and consequently, the irradiated portion exhibited a red color. The colored portion gradually expanded to the entire sample because of diffusion of the dye molecules. This diffusion characteristic was used for improving an organic dye durability against a photo-induced degradation.

  18. Extended emission wavelength of random dye lasers by exploiting radiative and non-radiative energy transfer

    NASA Astrophysics Data System (ADS)

    Wan Ismail, Wan Zakiah; Goldys, Ewa M.; Dawes, Judith M.

    2016-02-01

    We demonstrate long-wavelength operation (>700 nm) of random dye lasers (using a methylene blue dye) with the addition of rhodamine 6G and titania, enabled by radiative and non-radiative energy transfer. The pump energy is efficiently absorbed and transferred to the acceptors, to support lasing in random dye lasers in the near infrared. The optimum random laser performance with the highest emission intensity and the lowest lasing threshold was achieved for a concentration of methylene blue as the acceptor equal to 6× the concentration of rhodamine 6G (donor). Excessive levels of methylene blue increased the lasing threshold and broadened the methylene blue emission linewidth due to dye quenching from re-absorption. This is due to competition between the donor emission and energy transfer and between absorption loss and fluorescence quenching. The radiative and non-radiative energy transfer is analyzed as a function of the acceptor concentration and pump energy density, with consideration of the spectral overlap. The dependence of the radiative and non-radiative transfer efficiency on the acceptor concentration is obtained, and the energy transfer parameters, including the radiative and non-radiative energy transfer rate constants ( K R and K NR), are investigated using Stern-Volmer analysis. The analysis indicates that radiative energy transfer is the dominant energy transfer mechanism in this system.

  19. Alkyl Chlorides as Hydrogen Bond Acceptors

    SciTech Connect

    Nadas, Janos I; Vukovic, Sinisa; Hay, Benjamin

    2012-01-01

    To gain an understanding of the role of an alkyl chloride as a hydrogen bond acceptor, geometries and interaction energies were calculated at the MP2/aug-cc-pVDZ level of theory for complexes between ethyl chloride and representative hydrogen donor groups. The results establish that these donors, which include hydrogen cyanide, methanol, nitrobenzene, pyrrole, acetamide, and N-methylurea, form X-H {hor_ellipsis} Cl hydrogen bonds (X = C, N, O) of weak to moderate strength, with {Delta}E values ranging from -2.8 to -5.3 kcal/mol.

  20. Enhancement of the efficiency of dye lasers using electron energy transfer processes

    NASA Astrophysics Data System (ADS)

    Levin, M. B.; Uzhinov, B. M.

    1990-04-01

    Various types of electron energy transfer processes are considered, which are associated with the introduction of energy donors (Dn) and triplet quenchers (TQ) into the acceptor dye solutions with the use of luminescent light filters (LLF) in the pumping system. Mixed solutions are proposed which make it possible to increase the efficiency of the coumarine 314 dye laser by a factor of 1.8. In lasers using unsubstituted and B rhodamines, the simultaneous action of Dn, TQ, and LLF leads, in the optimal cases, to a three-to-ten-fold increase in the efficiency, making the efficiency of these dyes close to that of rhodamine 6G.

  1. Synthesis and characterization of a highly strained donor-acceptor nanohoop.

    PubMed

    Van Raden, J M; Darzi, E R; Zakharov, L N; Jasti, R

    2016-06-15

    A highly-strained, nitrogen-doped cycloparaphenylene (CPP), aza[6]CPP, was synthesized and then converted to a donor-acceptor nanohoop, N-methylaza[6]CPP, via alkylation of the nitrogen center. The energy levels of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) for both molecules were then probed by cyclic voltammetry (CV), which revealed that the donor-acceptor nanohoop had a significantly lower LUMO energy relative to [6]CPP and aza[6]CPP. Density functional theory (DFT) revealed that the donor-acceptor nanohoop underwent a redistribution of the frontier molecular orbital (FMO) density such that a significant portion of the LUMO density resided upon the electron-deficient nitrogen-containing ring. This localization of LUMO density caused a large lowering in the LUMO energy of nearly a full electron volt, while the HOMO energy was less affected due to a large centralization of the FMO on the electron-rich phenylene backbone. This ultimately resulted in a net lowering of the HOMO-LUMO energy gap which was observed both experimentally and computationally. In addition, N-methylaza[6]CPP has a significantly lower energy LUMO than N-methylaza[8]CPP, illustrating that the FMO levels of donor-acceptor nanohoops can be tuned by adjusting the hoop size. PMID:26881906

  2. How intermolecular geometrical disorder affects the molecular doping of donor-acceptor copolymers

    NASA Astrophysics Data System (ADS)

    di Nuzzo, Daniele; Fontanesi, Claudio; Jones, Rebecca; Allard, Sybille; Dumsch, Ines; Scherf, Ullrich; von Hauff, Elizabeth; Schumacher, Stefan; da Como, Enrico

    2015-03-01

    Molecular doping of conjugated polymers represents an important strategy for improving organic electronic devices. However, the widely reported low efficiency of doping remains a crucial limitation to obtain high performance. Here we investigate how charge transfer between dopant and donor-acceptor copolymers is affected by the spatial arrangement of the dopant molecule with respect to the copolymer repeat unit. We p-dope a donor-acceptor copolymer and probe its charge-sensitive molecular vibrations in films by infrared spectroscopy. We find that, compared with a related homopolymer, a four times higher dopant/polymer molar ratio is needed to observe signatures of charges. By DFT methods, we simulate the vibrational spectra, moving the dopant along the copolymer backbone and finding that efficient charge transfer occurs only when the dopant is close to the donor moiety. Our results show that the donor-acceptor structure poses an obstacle to efficient doping, with the acceptor moiety being inactive for p-type doping.

  3. Laser dye stability

    NASA Astrophysics Data System (ADS)

    Fletcher, N.

    1980-06-01

    Lasing characteristics and bleaching of four Eastman Kodak ir dyes have been examined in dimethyl sulfoxide. These ir dyes are shown to improve in performance in the absence of oxygen. Their photochemical stability was found to be comparable to the quinolone laser dyes when exposed to flashlamp excitation. Photodecomposition of the ir dyes under lasing conditions was found to vary between 1.6 and 6×10-10 moles of dye for each joule (electrical) of input energy; in comparison, the photodecomposition values for the better coumarin dyes was 0.2 to 1.0×10-10 moles/J at a concentration of 1.0×10-4 M in ethanol. It was also found that increasing the concentration of these tricarbocyanine dyes gives a marked improvement in the useful lifetime of these solutions as lasing media in the absence of oxygen.

  4. Ultrasonic dyeing of cellulose nanofibers.

    PubMed

    Khatri, Muzamil; Ahmed, Farooq; Jatoi, Abdul Wahab; Mahar, Rasool Bux; Khatri, Zeeshan; Kim, Ick Soo

    2016-07-01

    Textile dyeing assisted by ultrasonic energy has attained a greater interest in recent years. We report ultrasonic dyeing of nanofibers for the very first time. We chose cellulose nanofibers and dyed with two reactive dyes, CI reactive black 5 and CI reactive red 195. The cellulose nanofibers were prepared by electrospinning of cellulose acetate (CA) followed by deacetylation. The FTIR results confirmed complete conversion of CA into cellulose nanofibers. Dyeing parameters optimized were dyeing temperature, dyeing time and dye concentrations for each class of the dye used. Results revealed that the ultrasonic dyeing produced higher color yield (K/S values) than the conventional dyeing. The color fastness test results depicted good dye fixation. SEM analysis evidenced that ultrasonic energy during dyeing do not affect surface morphology of nanofibers. The results conclude successful dyeing of cellulose nanofibers using ultrasonic energy with better color yield and color fastness results than conventional dyeing. PMID:26964959

  5. Ruthenium phthalocyanine-bipyridyl dyads as sensitizers for dye-sensitized solar cells: dye coverage versus molecular efficiency.

    PubMed

    Rawling, Tristan; Austin, Christine; Buchholz, Florian; Colbran, Stephen B; McDonagh, Andrew M

    2009-04-01

    The application of ruthenium phthalocyanine complexes as sensitizing dyes in dye-sensitized solar cells (DSCs) is explored. Four monomeric complexes are reported which vary in peripheral substitution and axial ligand anchoring groups. Sensitizing dyes containing two ruthenium centers are also presented. These dyads, which contain ruthenium phthalocyanine and bipyridyl chromophores, were prepared using a protection/deprotection strategy that allows for convenient purification. DSCs fabricated using the phthalocyanine complexes and dyads were less efficient than those incorporating a standard DSC dye. However, on the basis of the number of molecules bound to the TiO(2) electrode surfaces, several of the new complexes were more efficient at photocurrent generation. The results highlight the importance of molecular size, and thus the dye coverage of the electrode surface in the design of new sensitizing dyes. PMID:19278209

  6. Isolation of colour components from native dye-bearing plants in northeastern India.

    PubMed

    Bhuyan, Ranjana; Saikia, C N

    2005-02-01

    Recently dyes derived from natural sources have emerged as important alternatives to synthetic dyes. A study was initiated in the year 2000 at the RRL (CSIR), Jorhat to extract dyes from parts of five different plant species indigenous to northeastern India. The colour components responsible for dyeing were isolated and their chemical constituents were established based on chemical and spectroscopic investigations. The principal colour components from the species Morinda angustifolia Roxb., Rubia cordifolia Linn. and Tectona grandis Linn. were found to contain mainly anthraquinone moieties in their molecules. Those from the species Mimusops elengi Linn. and Terminalia arjuna (Roxb.) Wight & Arn. contained flavonoid moieties in their molecules. The absorption of dye (%) on fibres increased with increasing concentrations of dye in the dye-bath. Maximum absorption of dyes on fibres was obtained at 3% concentration of dyes obtained from R. cordfolia (35.350%), M. angustifolia (31.580%) and T. grandis (25.888%) and at 4% concentration of the dyes from M. elengi (31.917%) and T. arjuna (12.246%). The K/S values were found to increase with the increase in concentration of mordants. The colour co-ordinates of dyed samples were found to lie in the yellow-red quadrant of the colour space diagram. The dyes obtained from the native plants may be alternative sources to synthetic dyes for the dyeing of natural silk and cotton. PMID:15474939

  7. Functional behavior of bio-electrochemical treatment system with increasing azo dye concentrations: Synergistic interactions of biocatalyst and electrode assembly.

    PubMed

    Sreelatha, S; Velvizhi, G; Naresh Kumar, A; Venkata Mohan, S

    2016-08-01

    Treatment of dye bearing wastewater through biological machinery is particularly challenging due to its recalcitrant and inhibitory nature. In this study, functional behavior and treatment efficiency of bio-electrochemical treatment (BET) system was evaluated with increasing azo dye concentrations (100, 200, 300 and 500mg dye/l). Maximum dye removal was observed at 300mg dye/l (75%) followed by 200mg dye/l (65%), 100mg dye/l (62%) and 500mg dye/l (58%). Concurrent increment in dye load resulted in enhanced azo reductase and dehydrogenase activities respectively (300mg dye/l: 39.6U; 4.96μg/ml). Derivatives of cyclic voltammograms also supported the involvement of various membrane bound redox shuttlers, viz., cytochrome-c, cytochrome-bc1 and flavoproteins during the electron transfer. Bacterial respiration during BET operation utilized various electron acceptors such as electrodes and dye intermediates with simultaneous bioelectricity generation. This study illustrates the synergistic interaction of biocatalyst with electrode assembly for efficient treatment of azo dye wastewater. PMID:27067459

  8. Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

    PubMed Central

    Christmann, Julien; Ibrahim, Ahmad; Stefano, Luciano H Di; Allonas, Xavier

    2014-01-01

    Summary The combination of a dye which absorbs the photon, an electron acceptor and an electron donor leading to energy conversion through electron transfer, was the basis of the so called three-component systems. In this paper, an experimental work combining Rose bengal dye with a triazine derivative as electron acceptor and ethyl 4-(dimethylamino)benzoate as electron donor, will underline the benefit of the photocyclic behavior of three-component systems leading to the dye regeneration. A thermodynamic approach of the photocycle is presented, followed by a mechanistic and computational study of ideal photocycles, in order to outline the specific kinetics occuring in so called photocatalytic systems. The simple kinetic model used is enough to outline the benefit of the cyclic system and to give the basic requirements in term of chemical combination needed to be fulfilled in order to obtain a photocatalytic behavior. PMID:24991243

  9. Polymer composites containing photochromic dye solution

    NASA Astrophysics Data System (ADS)

    Saito, Mitsunori; Sakiyama, Kohei; Mochizuki, Ryosuke; Ohashi, Kenji

    2010-05-01

    Photochromic polymer composites were fabricated by encapsulating dye solution in a polycarbonate membrane. The membrane contained through holes of 50 nm diameter. These nanoholes provided a sufficient free volume for the dye molecules to change their structure in the photochromic isomerization process. A polymer composite containing a toluene solution of diarylethene exhibited red color when it was irradiated with violet laser, and returned to the transparent state by green laser irradiation. Another polymer composite containing spiropyran turned to blue by ultraviolet lamp irradiation and returned to the transparent state by green laser irradiation. A nonlinear input-output characteristic and a rewritable-grating function were demonstrated by using these photochromic polymers.

  10. Remarkable Dependence of the Final Charge Separation Efficiency on the Donor-Acceptor Interaction in Photoinduced Electron Transfer.

    PubMed

    Higashino, Tomohiro; Yamada, Tomoki; Yamamoto, Masanori; Furube, Akihiro; Tkachenko, Nikolai V; Miura, Taku; Kobori, Yasuhiro; Jono, Ryota; Yamashita, Koichi; Imahori, Hiroshi

    2016-01-11

    The unprecedented dependence of final charge separation efficiency as a function of donor-acceptor interaction in covalently-linked molecules with a rectilinear rigid oligo-p-xylene bridge has been observed. Optimization of the donor-acceptor electronic coupling remarkably inhibits the undesirable rapid decay of the singlet charge-separated state to the ground state, yielding the final long-lived, triplet charge-separated state with circa 100% efficiency. This finding is extremely useful for the rational design of artificial photosynthesis and organic photovoltaic cells toward efficient solar energy conversion. PMID:26610285

  11. Dye-linked D-amino acid dehydrogenases: biochemical characteristics and applications in biotechnology.

    PubMed

    Satomura, Takenori; Sakuraba, Haruhiko; Suye, Shin-Ichiro; Ohshima, Toshihisa

    2015-11-01

    Dye-linked D-amino acid dehydrogenases (Dye-DADHs) catalyze the dehydrogenation of free D-amino acids in the presence of an artificial electron acceptor. Although Dye-DADHs functioning in catabolism of L-alanine and as primary enzymes in electron transport chains are widely distributed in mesophilic Gram-negative bacteria, biochemical and biotechnological information on these enzymes remains scanty. This is in large part due to their instability after isolation. On the other hand, in the last decade, several novel types of Dye-DADH have been found in thermophilic bacteria and hyperthermophilic archaea, where they contribute not only to L-alanine catabolism but also to the catabolism of other amino acids, including D-arginine and L-hydroxyproline. In this minireview, we summarize recent developments in our understanding of the biochemical characteristics of Dye-DADHs and their specific application to electrochemical biosensors. PMID:26362681

  12. Quantum computing with acceptor spins in silicon

    NASA Astrophysics Data System (ADS)

    Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

    2016-06-01

    The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin–orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin–orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin–orbit induced dipole–dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin–orbit terms are responsible for sweet spots in the dephasing time {T}2* as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin–orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.

  13. Electronic structures and optical properties of organic dye sensitizer NKX derivatives for solar cells: a theoretical approach.

    PubMed

    Zhang, Cai-Rong; Liu, Li; Liu, Zi-Jiang; Shen, Yu-Lin; Sun, Yi-Tong; Wu, You-Zhi; Chen, Yu-Hong; Yuan, Li-Hua; Wang, Wei; Chen, Hong-Shan

    2012-09-01

    The photon to current conversion efficiency of dye-sensitized solar cells (DSCs) can be significantly affected by dye sensitizers. The design of novel dye sensitizers with good performance in DSCs depend on the dye's information about electronic structures and optical properties. Here, the geometries, electronic structures, as well as the dipole moments and polarizabilities of organic dye sensitizers C343 and 20 kinds of NKX derivatives were calculated using density functional theory (DFT), and the computations of the time dependent DFT with different functionals were performed to explore the electronic absorption properties. Based upon the calculated results and the reported experimental work, we analyzed the role of different conjugate bridges, chromophores, and electron acceptor groups in tuning the geometries, electronic structures, optical properties of dye sensitizers, and the effects on the parameters of DSCs were also investigated. PMID:23117291

  14. Novel D-A-π-A organic dyes based on 3-dimensional triarylamine and benzothiadiazole derivatives for high-performance dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Huang, Hongli; Chen, Huajie; Long, Jun; Wang, Guo; Tan, Songting

    2016-09-01

    Organic dyes with a 3-dimensional (3D) structure is helpful for retarding dyes aggregation and charge recombination as well as improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this contribution, a novel 3D triarylamine derivative (IDTTPA) featuring an indenothiophenene unit has been designed, synthesized, and applied to develop a 3D organic dyes. Two novel D-A-π-A organic dyes (CD1 and CD2) based on IDTTPA as the electron donors, 2,1,3-benzothiadiazole derivatives as the auxiliary acceptors, and formic acid as the anchoring groups have been successfully synthesized and applied in DSSCs. The effects of the fluoro substitute groups on the photophysical, electrochemical, and photovoltaic properties are investigated. The results indicate that the fluoro-containing dye CD2 exhibits higher molar extinction coefficient, stronger light-capturing ability, and better photovoltaic performance than those of CD1 dye without fluoro substitute. Investigation of the DSSCs performance shows that CD2-based DSSCs exhibit a high PCE value of 7.91%, higher than that of CD1-based DSSCs (6.29%), even higher than that of the reference DSSCs based on N719 (7.49%). This works has demonstrated that this kind of 3D unit (IDTTPA) is a strong and promising electron donor unit to develop high efficiency metal-free organic dyes.

  15. Significant Influences of Elaborately Modulating Electron Donors on Light Absorption and Multichannel Charge-Transfer Dynamics for 4-(Benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic Acid Dyes.

    PubMed

    Wang, Erfeng; Yao, Zhaoyang; Zhang, Yiqiang; Shao, Guosheng; Zhang, Min; Wang, Peng

    2016-07-20

    4-(Benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTEBA) as a promising electron acceptor has been used in the highly efficient organic dye-sensitized solar cells (DSCs) recently. Because of its strong electron-deficient character, BTEBA could bring forth a remarkable decline in the energy level of the lowest unoccupied molecular orbital (LUMO) and further reduce the energy gap of dye molecules significantly. In this contribution, two metal-free organic dyes WEF1 and WEF2 were synthesized by simply combining BTEBA with two slightly tailored electron-releasing moieties: 4-hexylphenyl substituted indaceno[1,2-b:5,6-b']dithiophene (IDT) and cyclopenta[1,2-b:5,4-b']dithiophene[2',1':4,5]thieno[2,3-d]thiophene (CPDTDT), which were screened rationally from an electron-donor pool via computational simulation. With respect to those of WEF1, WEF2-sensitized solar cells demonstrate a far better short-circuit photocurrent density (JSC) and open-circuit photovoltage (VOC), resulting in a ∼50% improved power conversion efficiency of 10.0% under irradiance of 100 mW cm(-2) AM1.5G sunlight. We resorted to theoretical calculations, electrical measurements, steady-state, and time-resolved spectroscopic methods to shed light on the fatal influences of elaborately modulating electron donors on light absorption, interfacial energetics, and multichannel charge-transfer dynamics. PMID:27331621

  16. Studies in treatment of disperse dye waste: Membrane-wet oxidation process

    SciTech Connect

    Dhale, A.D.; Mahajani, V.V.

    2000-07-01

    An integrated process, membrane-wet oxidation (MEMWO) has been demonstrated to treat the disperse dye bath waste. The dye bath waste stream containing azo class disperse dye CL 79, was studied to demonstrate the process. A nanofiltration membrane (MPT 30) showed > 99% color and 97% chemical oxygen demand (COD) rejection of dye compound. The concentrate was then treated by wet oxidation (WO) process. WO of dye was studied in the range of 160--225 C and oxygen partial pressure 0.69--1.38 MPa. A homogeneous copper sulfate was found to be a suitable catalyst to effectively destroy the dye as well as the real waste. While non catalytic WO of dye achieved 75% reduction in COD during 120 min with 99% color destruction, the catalytic WO showed about 90% reduction in COD. The performance of WO of actual waste stream was comparable with that of pure dye molecule.

  17. Aromatic donor-acceptor interactions in non-polar environments.

    PubMed

    Prentice, Giles M; Pascu, Sofia I; Filip, Sorin V; West, Kevin R; Pantoş, G Dan

    2015-05-14

    We have evaluated the strength of aromatic donor-acceptor interactions between dialkyl naphthalenediimide and dialkoxynaphthalene in non-polar environments. (1)H NMR, UV-vis spectroscopy and isothermal titration calorimetry were used to characterise this interaction. We concluded that the strength of donor-acceptor interactions in heptane is sufficient to drive supramolecular assemblies in this and other aliphatic solvents. PMID:25875729

  18. Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells.

    PubMed

    Yang, Wenxing; Vlachopoulos, Nick; Hao, Yan; Hagfeldt, Anders; Boschloo, Gerrit

    2015-06-28

    Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E(0) = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline dye D149. The origin of this improvement was found to be the increased dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the oxidized dye with a driving force of only ∼0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to oxidized dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO(+) redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be ∼0.5 μm, which is smaller than the ∼2.8 μm found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and dyes with a minimal need of driving force for high regeneration yields. PMID:26016854

  19. Dyes and Redox Couples with Matched Energy Levels: Elimination of the Dye-Regeneration Energy Loss in Dye-Sensitized Solar Cells.

    PubMed

    Jiang, Dianlu; Darabedian, Narek; Ghazarian, Sevak; Hao, Yuanqiang; Zhgamadze, Maxim; Majaryan, Natalie; Shen, Rujuan; Zhou, Feimeng

    2015-11-16

    In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔG(reg)(0)≥0.5 eV) is usually required for effective dye regeneration, which results in a major energy loss and limits the energy-conversion efficiency of state-of-art DSSCs. We demonstrate that when dye molecules and redox couples that possess similar conjugated ligands are used, efficient dye regeneration occurs with zero or close-to-zero driving force. By using Ru(dcbpy)(bpy)2(2+) as the dye and Ru(bpy)2(MeIm)2(3+//2+) as the redox couple, a short-circuit current (J(sc)) of 4 mA cm(-2) and an open-circuit voltage (V(oc)) of 0.9 V were obtained with a ΔG(reg)(0) of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)2(SCN)2(1+/0) (ΔG(reg)(0)=0.0 eV), which produced an J(sc) of 2.5 mA cm(-2) and V(oc) of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. This proof-of-concept study demonstrates that high V(oc) values can be attained by significantly curtailing the dye-regeneration force. PMID:26314383

  20. Acceptor impurity activation in III-nitride light emitting diodes

    SciTech Connect

    Römer, Friedhard Witzigmann, Bernd

    2015-01-12

    In this work, the role of the acceptor doping and the acceptor activation and its impact on the internal quantum efficiency (IQE) of a Gallium Nitride (GaN) based multi-quantum well light emitting diode is studied by microscopic simulation. Acceptor impurities in GaN are subject to a high activation energy which depends on the presence of proximate dopant atoms and the electric field. A combined model for the dopant ionization and activation barrier reduction has been developed and implemented in a semiconductor carrier transport simulator. By model calculations, we demonstrate the impact of the acceptor activation mechanisms on the decay of the IQE at high current densities, which is known as the efficiency droop. A major contributor to the droop is the electron leakage which is largely affected by the acceptor doping.

  1. Cyclopenta[b]naphthalene cyanoacrylate dyes: Synthesis and evaluation as fluorescent molecular rotors

    PubMed Central

    Kocsis, Laura S.; Elbel, Kristyna M.; Hardigree, Billie A.

    2015-01-01

    We describe the design, synthesis and fluorescent profile of a family of environment-sensitive dyes in which a dimethylamino (donor) group is conjugated to a cyanoacrylate (acceptor) unit via a cyclopenta[b]naphthalene ring system. This assembly satisfies the typical D-π-A motif of a fluorescent molecular rotor and exhibits solvatochromic and viscosity-sensitive fluorescence emission. The central naphthalene ring system of these dyes was synthesized via a novel intramolecular dehydrogenative dehydro-Diels-Alder (IDDDA) reaction that permits incorporation of the donor and acceptor groups in variable positions around the aromatic core. A bathochromic shift of excitation and emission peaks was observed with increasing solvent polarity but the dyes exhibited a complex emission pattern with a second red emission band when dissolved in nonpolar solvents. Consistent with other known molecular rotors, the emission intensity increased with increasing viscosity. Interestingly, closer spatial proximity between the donor and the acceptor groups led to decreased viscosity sensitivity combined with an increased quantum yield. This observation indicates that structural hindrance of intramolecular rotation dominates when the donor and acceptor groups are in close proximity. The examined compounds give insight into how excited state intramolecular rotation can be influenced by both the solvent and the chemical structure. PMID:25614187

  2. Gain measurements in binary and ternary dye mixture solutions under nitrogen laser excitation

    NASA Astrophysics Data System (ADS)

    Sanghi, Sujata; Mohan, D.; Singh, R. D.

    1997-05-01

    Energy transfer studies in the case of binary [Coumarin 485 (C485) + Rhodamine 610 perchlorate (Rh 610)] and ternary [C440 + C485 + Rh610 perchlorate] dye mixture solutions in ethanol have been made and discussed through optical gain characteristics at various acceptor concentrations and pump powers of the N 2-laser. In case of binary mixtures, we observe that the optical gain of the acceptor dye (Rh610) improves and the threshold power required for lasing action decreases when donor dye (C485) is added. The concentration dependence of peak gain and peak lasing wavelength of the energy transfer dye laser (ETDL) has been studied. The results have also been compared with the optical gain characteristics of these dyes in single component solutions. The energy transfer rate constants ( KF, the Förster type non-radiative and KR, the radiative rate constants) and critical transfer radius ( Ro) have been calculated using a Stern-Volmer analysis of the pump power dependence of the gain. From the experimental results, we find that the dominant mechanism responsible for efficient excitation transfer in this bimixture is of a radiative nature. Further, the gain equation for a ternary dye mixture has been derived using the transfer rate constants for two different possible bimixtures; C440 + C485 and C485 + Rh610, which is helpful in obtaining the optimum concentration to be used in the ternary mixture for higher gains.

  3. Hair dye poisoning

    MedlinePlus

    ... temporary dyes are: Arsenic Bismuth Denatured alcohol Lead ( lead poisoning ) Mercury Pyrogallol Silver Hair dyes may contain other ... infection. Continued exposure to lead or mercury can lead to permanent brain and nervous system damage. Alternative ... References Lee DC. Hydrocarbons. In: Marx JA, Hockberger ...

  4. Oxazine laser dyes

    DOEpatents

    Hammond, Peter R.; Field, George F.

    1992-01-01

    New oxazine compounds useful as dye laser media in solution, are superiior to prior art materials. The oxazine dyes useful when pumped by the 578.2 nm copper line to operate in the 700-800 nm range are described by formula I ##STR1##

  5. Polyphosphazenes with Immobilized Dyes as Potential Color Filter Materials.

    PubMed

    Li, Zhongjing; Allcock, Harry R

    2015-06-24

    Red, green, and blue dye molecules were linked covalently to polyphosphazenes to generate soluble, film-forming materials appropriate for the formation of patterned tricolor filters for possible use in liquid crystalline and other display devices or in camera sensors. The monofunctional dyes (a red 1-[(E)-(4-nitrophenyl)diazenyl]-2-naphthol, a green tetraphenylporphyrin [5-(4-hydroxyphenyl)-10,15,20-tetraphenylporphyrin], and a toluidine blue dye) were employed as representative chromophores. The cosubstituents employed included 2,2,2-trifluoroethoxy with and without aryloxy groups or cyclopentanoxy groups. The optical densities were varied by adopting several dye-to-cosubstituent side group ratios. These dyes are models for a wide range of different chromophores that can be linked to polyphosphazene chains. PMID:26018938

  6. Monolithic dye laser amplifier

    DOEpatents

    Kuklo, Thomas C.

    1993-01-01

    A fluid dye laser amplifier for amplifying a dye beam by pump beams has a channel structure defining a channel through which a laseable fluid flows and the dye and pump beams pass transversely to one another through a lasing region. The channel structure is formed with two pairs of mutually spaced-apart and mutually confronting glass windows, which are interlocked and make surface-contacts with one another and surround the lasing region. One of the glass window pairs passes the dye beam and the other passes the pump beams therethrough and through the lasing region. Where these glass window pieces make surface-contacts, glue is used to join the pieces together to form a monolithic structure so as to prevent the dye in the fluid passing through the channel from entering the space between the mutually contacting glass window pieces.

  7. Monolithic dye laser amplifier

    DOEpatents

    Kuklo, T.C.

    1993-03-30

    A fluid dye laser amplifier for amplifying a dye beam by pump beams has a channel structure defining a channel through which a laseable fluid flows and the dye and pump beams pass transversely to one another through a lasing region. The channel structure is formed with two pairs of mutually spaced-apart and mutually confronting glass windows, which are interlocked and make surface-contacts with one another and surround the lasing region. One of the glass window pairs passes the dye beam and the other passes the pump beams therethrough and through the lasing region. Where these glass window pieces make surface-contacts, glue is used to join the pieces together to form a monolithic structure so as to prevent the dye in the fluid passing through the channel from entering the space between the mutually contacting glass window pieces.

  8. Preparation and spectral characterization of polymeric nanocapsules containing DR1 organic dye

    NASA Astrophysics Data System (ADS)

    Sharifimehr, Mohammad Reza; Ghanbari, Khadijeh; Ayoubi, Kazem; Mohajerani, Ezedin

    2015-07-01

    In order to provide necessary degree of freedom for organic dye molecules in optical applications and also for safety improvement, water insoluble Disperse Red 1 (DR1) dye molecules were placed inside the polymeric nanocapsules along with suitable surfactants and using controlled phase-separation method. TEM images were used to investigate the morphology of prepared nanocapsules. Total dye concentration for a solution consist of obtained polymeric nanocapsules was determined using decomposition of nanocapsules and a reference absorption spectrum. Absorption spectrum of a solution containing DR1 and dichloromethane was also compared with prepared nanocapsules at the same dye concentration, thereby a red-shift in absorption spectrum was detected.

  9. Hydrogen evolution by photocatalytic reactions of some organic dyes and semiconductors

    NASA Astrophysics Data System (ADS)

    Sakata, T.; Kawai, T.; Koiso, T.; Okuyama, M.

    Various organic dyes and powdered semiconductors are illuminated by visible light to bring about methylviologen - MV(2+) - reduction and hydrogen evolution from water, in an effort to study an 'artificial photosynthesis' process. MV(2+) is used as an electron acceptor, EDTA as an electron donor, and photochemical reactions are carried out both in nonaqueous solutions, such as dimethylsulfoxide, methanol, and in their mixtures with water. A 500W Xe lamp and a monochromator are used for monochromatic illumination at the peak wavelength of the visible absorption band of each molecule. The reduced MV(+) is monitored by a spectrophotometer, and a thermopile is used to determine the quantum efficiency of the reaction. Zn-chlorophyl-a and Zn-tetraphenylporphine show quite a high quantum efficiency. The preparation of the TiO2-RuO2 photocatalyst is described. The band gap illumination of TiO2 mixed with RuO2 leads to a continuous, catalytic production of hydrogen and oxygen from gaseous water at room temperature. The rate of hydrogen evolution per 100 mg of TiO2-RuO2, for 20 hours, is 11 micromoles at the stationary state.

  10. Efficient photoinduced orthogonal energy and electron transfer reactions via phospholipid membrane-bound donors and acceptors

    SciTech Connect

    Clapp, P.J.; Armitage, B.; Roosa, P.; O'Brien, D.F. )

    1994-10-05

    A three component, liposome-bound photochemical molecular device (PMD) consisting of energy and electron transfer reactions is described. Bilayer membrane surface-associated dyes, 5,10,15,20-tetrakis[4-(trimethylammonio)-phenyl]-21H,2 3H-porphine tetra-p-tosylate salt and N,N[prime]-bis[(3-trimethylammonio)propyl]thiadicarbocya nine tribromide, are the energy donor and acceptor, respectively, in a blue light stimulated energy transfer reaction along the vesicle surface. The electronically excited cyanine is quenched by electron transfer from the phospholipid membrane bound triphenylbenzyl borate anion, which is located in the lipid bilayer interior. The PMD exhibits sequential reactions following electronic excitation with the novel feature that the steps proceed with orthogonal orientation: energy transfer occurs parallel to the membrane surface, and electron transfer occurs perpendicular to the surface. Photobleaching and fluorescence quenching experiments verify the transfer reactions, and Stern-Volmer analysis was used to estimate the reaction rate constants. At the highest concentrations examined of energy and electron acceptor ca. 60% of the photoexcited porphyrins were quenched by energy transfer to the cyanine. 56 refs., 6 figs., 3 tabs.

  11. A strategy to minimize the energy offset in carrier injection from excited dyes to inorganic semiconductors for efficient dye-sensitized solar energy conversion.

    PubMed

    Fujisawa, Jun-Ichi; Osawa, Ayumi; Hanaya, Minoru

    2016-08-10

    Photoinduced carrier injection from dyes to inorganic semiconductors is a crucial process in various dye-sensitized solar energy conversions such as photovoltaics and photocatalysis. It has been reported that an energy offset larger than 0.2-0.3 eV (threshold value) is required for efficient electron injection from excited dyes to metal-oxide semiconductors such as titanium dioxide (TiO2). Because the energy offset directly causes loss in the potential of injected electrons, it is a crucial issue to minimize the energy offset for efficient solar energy conversions. However, a fundamental understanding of the energy offset, especially the threshold value, has not been obtained yet. In this paper, we report the origin of the threshold value of the energy offset, solving the long-standing questions of why such a large energy offset is necessary for the electron injection and which factors govern the threshold value, and suggest a strategy to minimize the threshold value. The threshold value is determined by the sum of two reorganization energies in one-electron reduction of semiconductors and typically-used donor-acceptor (D-A) dyes. In fact, the estimated values (0.21-0.31 eV) for several D-A dyes are in good agreement with the threshold value, supporting our conclusion. In addition, our results reveal that the threshold value is possible to be reduced by enlarging the π-conjugated system of the acceptor moiety in dyes and enhancing its structural rigidity. Furthermore, we extend the analysis to hole injection from excited dyes to semiconductors. In this case, the threshold value is given by the sum of two reorganization energies in one-electron oxidation of semiconductors and D-A dyes. PMID:27452717

  12. Electrochromism of a fused acceptor-donor-acceptor triad covering entire UV-vis and near-infrared regions.

    PubMed

    Yao, Bin; Ye, Xichong; Zhang, Jie; Wan, Xinhua

    2014-10-17

    A novel fused acceptor-donor-acceptor (A-D-A) type panchromatically electrochromic compound was synthesized. It exhibited intensive absorption bands covering entire UV-vis and near-infrared regions upon reduction to the radical anionic state, owing to the simultaneous presence of π*-π* transitions and intervalence charge transfer. PMID:25268224

  13. Acceptor and Excitation Density Dependence of the Ultrafast Polaron Absorption Signal in Donor-Acceptor Organic Solar Cell Blends.

    PubMed

    Zarrabi, Nasim; Burn, Paul L; Meredith, Paul; Shaw, Paul E

    2016-07-21

    Transient absorption spectroscopy on organic semiconductor blends for solar cells typically shows efficient charge generation within ∼100 fs, accounting for the majority of the charge carriers. In this Letter, we show using transient absorption spectroscopy on blends containing a broad range of acceptor content (0.01-50% by weight) that the rise of the polaron signal is dependent on the acceptor concentration. For low acceptor content (<10% by weight), the polaron signal rises gradually over ∼1 ps with most polarons generated after 200 fs, while for higher acceptor concentrations (>10%) most polarons are generated within 200 fs. The rise time in blends with low acceptor content was also found to be sensitive to the pump fluence, decreasing with increasing excitation density. These results indicate that the sub-100 fs rise of the polaron signal is a natural consequence of both the high acceptor concentrations in many donor-acceptor blends and the high excitation densities needed for transient absorption spectroscopy, which results in a short average distance between the exciton and the donor-acceptor interface. PMID:27355877

  14. Transition metal-free generation of the acceptor/acceptor-carbene viaα-elimination: synthesis of fluoroacetyl cyclopropanes.

    PubMed

    Wang, Yongdong; Han, Jing; Chen, Jie; Cao, Weiguo

    2016-05-21

    An efficient transition metal-free approach for the generation of acceptor/acceptor-carbene followed by trapping with alkenes to provide fluoroacetyl cyclopropanes has been described. The resulting cyclopropanes could be further converted into the fluoromethyl dihydrofurans or fluorodihydropyrroles through ring-expansion processes. PMID:27125517

  15. Thiadiazole molecules and poly(ethylene glycol)-block-polylactide self-assembled nanoparticles as effective photothermal agents.

    PubMed

    Sun, Tingting; Qi, Ji; Zheng, Min; Xie, Zhigang; Wang, Zhiyuan; Jing, Xiabin

    2015-12-01

    A new photothermal nano-agent was obtained by the coprecipitation of 2,5-Bis(2,5-bis(2-thienyl)-N-dodecyl pyrrole) thieno[3,4-b][1,2,5] thiadiazole (TPT-TT) and a biodegradable amphiphilic block copolymer, methoxypoly(ethylene glycol)2K-block-poly(D,L-lactide)2K (mPEG2K-PDLLA2K). TPT-TT, a donor-acceptor-donor (D-A-D) type small molecule, with bis(2-thienyl)-N-alkylpyrrole (TPT) as the donor and thieno[3,4-b]thiadiazole (TT) as the acceptor was a strong near infrared (NIR) absorber, which could convert the absorbed light energy into heat. The formation of TPT-TT nanoparticles (TPT-NPs), which possessed high stability in water, was confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). TPT-NPs showed high photothermal conversion efficiency (32%) and excellent photostability and heating reproducibility. The photostability of TPT-TT NPs was much better than that of indocyanine green (ICG), a federal drug administration (FDA) approved NIR dye. Besides, TPT-TT NPs exhibited significant photothermal therapeutic effect toward human cervical carcinoma (HeLa) and human liver hepatocellular carcinoma (HepG2) cells, while no appreciable dark cytotoxicity was observed. These results highlight the potential of TPT-TT NPs as an effective photothermal agent for cancer therapy. PMID:26398145

  16. Triphenylamine based organic dyes for dye sensitized solar cells: A theoretical approach

    NASA Astrophysics Data System (ADS)

    Mohankumar, V.; Pandian, Muthu Senthil; Ramasamy, P.

    2016-05-01

    The geometry, electronic structure and absorption spectra for newly designed triphenylamine based organic dyes were investigated by density functional theory (DFT) and time dependent density functional theory (TD-DFT) with the Becke 3-Parameter-Lee-Yang-parr(B3LYP) functional, where the 6-31G(d,p) basis set was employed. All calculations were performed using the Gaussian 09 software package. The calculated HOMO and LUMO energies show that charge transfer occurs in the molecule. Ultraviolet-visible (UV-vis) spectrum was simulated by TD-DFT in gas phase. The calculation shows that all of the dyes can potentially be good sensitizers for DSSC. The LUMOs are just above the conduction band of TiO2 and their HOMOs are under the reduction potential energy of the electrolytes (I-/I3-) which can facilitate electron transfer from the excited dye to TiO2 and charge regeneration process after photo oxidation respectively. The simulated absorption spectrum of dyes match with solar spectrum. Frontier molecular orbital results show that among all the three dyes, the "dye 3" can be used as potential sensitizer for DSSC.

  17. Irradiation treatment of azo dye containing wastewater: An overview

    NASA Astrophysics Data System (ADS)

    Wojnárovits, László; Takács, Erzsébet

    2008-03-01

    The radiation-induced decolouration and degradation of aqueous solutions of azo dyes and their model compounds (anilines, phenols, triazines) are reviewed together with practical applications and the experimental methods (pulse radiolysis, steady-state gamma radiolysis, as well as end-product analysis) used for studying the reactions. The proposed mechanisms and the rate coefficients for the reactions of rad OH, e aq- and rad H water radiolysis intermediates with the dye molecules and with model compounds are summarized.

  18. TEXTILE DYES AND DYEING EQUIPMENT: CLASSIFICATION, PROPERTIES, AND ENVIRONMENTAL ASPECTS

    EPA Science Inventory

    The report gives results of a study of available information on textile dyeing equipment, dyeing procedures, and dye chemistry, to serve as background data for estimating the properties and evaluating the associated risks of new commercial dyestuffs. It reports properties of dyes...

  19. Structure and spectral properties of truxene dye S5

    NASA Astrophysics Data System (ADS)

    Baryshnikov, G. V.; Minaev, B. F.; Minaeva, V. A.; Ning, Z.; Zhang, Q.

    2012-02-01

    On the ground of functional theory with the B3LYP and BMK functionals, we have studied the structure and optical properties of a truxene dye sensitizer S5 for photoelectric transducers. Based on the calculations of the vertical excitations energy of the dye molecule and accounting the influence of the solvent, we have revealed a positive solvatochromic effect that is weak compared to results obtained in the vacuum approximation. We have studied new features describing stabilization of the planar structure of the cyanothiophene-acrylic fragment of the S5 dye.

  20. In-Situ Spectroscopic Analyses of the Dye Uptake on ZnO and TiO2 Photoanodes for Dye-Sensitized Solar Cells.

    PubMed

    Shahzad, Nadia; Pugliese, Diego; Shahzad, Muhammad Imran; Tresso, Elena

    2015-08-01

    UV-Vis spectroscopic measurements have been performed on Dye-Sensitized Solar Cell (DSSC) photoanodes at different dye impregnation times ranging from few minutes to 24 hours. In addition to the traditional absorbance experiments, based on diffuse and specular reflectance of dye impregnated thin films and on the desorption of dye molecules from the photoanodes by means of a basic solution, an alternative in-situ solution depletion measurement, which enables fast and continuous evaluation of dye uptake, has been employed. Two different nanostructured semiconducting oxide films (mesoporous TiO2 and sponge-like ZnO) and two different dyes, the traditional Ruthenizer 535-bisTBA (N719) and a newly introduced metal-free organic dye based on a hemi-squaraine molecule (CT1), have been analyzed. DSSCs have been fabricated with the dye-impregnated photoanodes using a customized microfluidic architecture. The dye adsorption results are discussed and correlated to the obtained DSSC electrical performances such as photovoltaic conversion efficiencies and Incident Photon-to-electron Conversion Efficiency (IPCE) spectra. It is shown that simple UV-Vis measurements can give useful insights on the dye adsorption mechanisms and on the evaluation of the optimal impregnation times. PMID:26369186

  1. Dynamic Characteristics of Aggregation Effects of Organic Dyes in Dye-Sensitized Solar Cells.

    PubMed

    Feng, Shuai; Li, Quan-Song; Sun, Ping-Ping; Niehaus, Thomas A; Li, Ze-Sheng

    2015-10-14

    Two organic dyes (LS-1 and IQ4) containing identical electron donor and acceptor units but distinct π units result in significantly different power conversion efficiency of the corresponding dye-sensitized solar cells (DSSCs): LS-1, 4.4%, and IQ4, 9.2%. Herein, we combine first-principle calculations and molecular dynamics to explore the aggregation effects of LS-1 and IQ4 by comparing their optical properties and intermolecular electronic couplings. The calculated absorption spectra are in good agreement with the experimental observations and reveal them to be evidently affected by the dimerization. Furthermore, molecular dynamics simulations show that steric hindrance induced by the diphenylquinoxaline unit in IQ4 can elongate the distances between intermolecular π units or electron donors, which are responsible for the fact that the intermolecular electronic coupling of LS-1 is about 10 times larger than that of IQ4. More importantly, the aggregated IQ4 remains almost perpendicular to the TiO2 surface, whereas LS-1 gradually tilts during the dynamic simulation, impacting electron injection and recombination in several ways, which clarifies why IQ4 leads to larger photocurrent and higher conversion efficiency. The deep understanding of the dye aggregation effects sheds new light on the complex factors determining DSSC function and paves the way for rational design of high-efficiency self-anti-aggregation sensitizers. PMID:26391331

  2. Dye system for dye laser applications

    DOEpatents

    Hammond, Peter R.

    1991-01-01

    A dye of the DCM family, [2-methyl-6-[2-(1,2,3,4-tetrahydro-1-methyl-6-quinolinyl)ethenyl]-4H-pyran -4-ylidene]-propanedinitrile, dissolved in 2-phenoxyethanol, is non-mutagenic, stable and efficient, particularly in a pumped continuous wave laser system.

  3. TDDFT screening auxiliary withdrawing group and design the novel D-A-π-A organic dyes based on indoline dye for highly efficient dye-sensitized solar cells.

    PubMed

    Yang, Zhenqing; Liu, Yun; Liu, Chunmeng; Lin, Chundan; Shao, Changjin

    2016-10-01

    Based on the experimentally synthesized dye JZ145, we designed a series of novel D-A-π-A dyes SPL201-SPL211 with different π-conjugated bridges and a new auxiliary withdrawing group for highly efficient dye-sensitized solar cells (DSSCs) using density functional theory (DFT) and time-dependent DFT(TDDFT). The molecular structures, energy levels, absorption spectra, light-harvesting efficiency (LHE), driving force of injection(ΔGinj) and regeneration(ΔGreg), electron dipole moment (μnormal) and lifetime of the first excited state(τ) were all scrutinized in details. Results reveal that the additional withdrawing group A2 and the π-conjugated group di-η-hexyl-substituted cyclopentadithiophene (CPDT) are more promising functional groups for the organic dyes with D-A-π-A structure. We further designed SPL212 and SPL213 by employing indoline group as donor, the above screened functional groups as π-conjugated bridge and additional withdrawing group, biscarbodithiolic acid and dicyanovinyl sulfonic acid groups as acceptor group. We found that SPL212 exhibits not only a higher molar extinction coefficient with an increment of 30.8%, larger excited state lifetime and an obvious redshift of 201nm but also a broader absorption spectrum covering the entire visible range even up to near-IR of 1200nm compared to JZ145. So, SPL212 can be used as a promising candidate for DSSCs. In addition, the results also prove that biscarbodithiolic acid may be more favorable than dicyanovinylsulfonic acid as acceptor group in DSSCs. PMID:27269476

  4. Large Spatially Resolved Rectification in a Donor-Acceptor Molecular Heterojunction.

    PubMed

    Smerdon, Joseph A; Giebink, Noel C; Guisinger, Nathan P; Darancet, Pierre; Guest, Jeffrey R

    2016-04-13

    We demonstrate that rectification ratios (RR) of ≳250 (≳1000) at biases of 0.5 V (1.2 V) are achievable at the two-molecule limit for donor-acceptor bilayers of pentacene on C60 on Cu using scanning tunneling spectroscopy and microscopy. Using first-principles calculations, we show that the system behaves as a molecular Schottky diode with a tunneling transport mechanism from semiconducting pentacene to Cu-hybridized metallic C60. Low-bias RRs vary by two orders-of-magnitude at the edge of these molecular heterojunctions due to increased Stark shifts and confinement effects. PMID:26964012

  5. Photon upconversion in supramolecular gel matrixes: spontaneous accumulation of light-harvesting donor-acceptor arrays in nanofibers and acquired air stability.

    PubMed

    Duan, Pengfei; Yanai, Nobuhiro; Nagatomi, Hisanori; Kimizuka, Nobuo

    2015-02-11

    Efficient triplet-triplet annihilation (TTA)-based photon upconversion (UC) is achieved in supramolecular organogel matrixes. Intense UC emission was observed from donor (sensitizer)-acceptor (emitter) pairs in organogels even under air-saturated condition, which solved a major problem: deactivation of excited triplet states and TTA-UC by molecular oxygen. These unique TTA-UC molecular systems were formed by spontaneous accumulation of donor and acceptor molecules in the gel nanofibers which are stabilized by developed hydrogen bond networks. These molecules preorganized in nanofibers showed efficient transfer and migration of triplet energy, as revealed by a series of spectroscopic, microscopic, and rheological characterizations. Surprisingly, the donor and acceptor molecules incorporated in nanofibers are significantly protected from the quenching action of dissolved molecular oxygen, indicating very low solubility of oxygen to nanofibers. In addition, efficient TTA-UC is achieved even under excitation power lower than the solar irradiance. These observations clearly unveil the adaptive feature of host gel nanofiber networks that allows efficient and cooperative inclusion of donor-acceptor molecules while maintaining their structural integrity. As evidence, thermally induced reversible assembly/disassembly of supramolecular gel networks lead to reversible modulation of the UC emission intensity. Moreover, the air-stable TTA-UC in supramolecular gel nanofibers was generally observed for a wide combination of donor-acceptor pairs which enabled near IR-to-yellow, red-to-cyan, green-to-blue, and blue-to-UV wavelength conversions. These findings provide a new perspective of air-stable TTA-UC molecular systems; spontaneous and adaptive accumulation of donor and acceptor molecules in oxygen-blocking, self-assembled nanomatrixes. The oxygen-barrier property of l-glutamate-derived organogel nanofibers has been unveiled for the first time, which could find many

  6. Performance of Kerria japonica and Rosa chinensis flower dyes as sensitizers for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Hemalatha, K. V.; Karthick, S. N.; Justin Raj, C.; Hong, N.-Y.; Kim, S.-K.; Kim, H.-J.

    2012-10-01

    The natural dyes carotenoid and anthocyanin were extracted from Kerria japonica and Rosa chinensis, respectively, using a simple extraction technique without any further purification. They were then used as sensitizers in dye-sensitized solar cells (DSSCs), and their characteristics were studied. The ranges of short-circuit current (JSC) from 0.559 to 0.801 (mA/cm2), open-circuit voltage (VOC) from 0.537 to 0.584 V, and fill factor from 0.676 to 0.705 were obtained for the DSSCs made using the extracted dyes. Sugar molecules were added externally to the dye for stabilization and to increase the conversion efficiency. The efficiencies of the K. japonica and R. chinensis dyes were 0.22% and 0.29%, respectively; after the addition of sugar, the efficiency increased to 0.29% for K. japonica and decreased to 0.27% for R. chinensis. Thus, the addition of sugar molecules increased the conversion efficiency slightly with the carotenoid dye of K. japonica, while there was no considerable change with the anthocyanin of R. chinensis. This paper briefly discusses the simple extraction technique of these natural dyes and their performance in DSSCs.

  7. Performance of Kerria japonica and Rosa chinensis flower dyes as sensitizers for dye-sensitized solar cells.

    PubMed

    Hemalatha, K V; Karthick, S N; Justin Raj, C; Hong, N-Y; Kim, S-K; Kim, H-J

    2012-10-01

    The natural dyes carotenoid and anthocyanin were extracted from Kerria japonica and Rosa chinensis, respectively, using a simple extraction technique without any further purification. They were then used as sensitizers in dye-sensitized solar cells (DSSCs), and their characteristics were studied. The ranges of short-circuit current (J(SC)) from 0.559 to 0.801(mA/cm(2)), open-circuit voltage (V(OC)) from 0.537 to 0.584 V, and fill factor from 0.676 to 0.705 were obtained for the DSSCs made using the extracted dyes. Sugar molecules were added externally to the dye for stabilization and to increase the conversion efficiency. The efficiencies of the K. japonica and R. chinensis dyes were 0.22% and 0.29%, respectively; after the addition of sugar, the efficiency increased to 0.29% for K. japonica and decreased to 0.27% for R. chinensis. Thus, the addition of sugar molecules increased the conversion efficiency slightly with the carotenoid dye of K. japonica, while there was no considerable change with the anthocyanin of R. chinensis. This paper briefly discusses the simple extraction technique of these natural dyes and their performance in DSSCs. PMID:22698848

  8. Promotion of Förster resonance energy transfer in a saponite clay containing luminescent polyhedral oligomeric silsesquioxane and rhodamine dye.

    PubMed

    Olivero, Francesco; Carniato, Fabio; Bisio, Chiara; Marchese, Leonardo

    2014-01-01

    A new hybrid photostable saponite clay with embedded donor-acceptor dyes was prepared and characterized in this work. The saponite is intercalated with a luminescent polyhedral oligomeric silsesquioxane, which transfers the photoexcitation energy directly to an acceptor dye (rhodamine B). The obtained composite material was characterized by means of XRD, TEM microscopy, and UV/Vis and photoluminescence spectroscopy. A physicochemical study showed that the system behaved as an efficient Förster resonance energy transfer pair, owing to the very good spectral overlap of donor emission (λem =510-540 nm) and acceptor absorption in the λ=530-570 nm range. The hybrid material represents the first example of a photonic antenna based on a synthetic saponite clay and can be considered a step forward in the search for new, efficient, and stable materials suitable for light-harvesting applications. PMID:24124165

  9. Dyeing of Polyester with Disperse Dyes: Part 2. Synthesis and Dyeing Characteristics of Some Azo Disperse Dyes for Polyester Fabrics.

    PubMed

    Al-Etaibi, Alya M; Alnassar, Huda S; El-Apasery, Morsy Ahmed

    2016-01-01

    The goal of this study was to utilize carrier for accelerating the rate of dyeing not only to enhance dyeing of polyester fabrics dyed with disperse dyes 3a,b, but also to save energy. Both the color strength expressed as dye uptake and the fastness properties of the dyed fabrics were evaluated. PMID:27367659

  10. Three holes bound to a double acceptor - Be(+) in germanium

    NASA Technical Reports Server (NTRS)

    Haller, E. E.; Mcmurray, R. E., Jr.; Falicov, L. M.; Haegel, N. M.; Hansen, W. L.

    1983-01-01

    A double acceptor binding three holes has been observed for the first time with photoconductive far-infrared spectroscopy in beryllium-doped germanium single crystals. This new center, Be(+), has a hole binding energy of about 5 meV and is only present when free holes are generated by ionization of either neutral shallow acceptors or neutral Be double acceptors. The Be(+) center thermally ionizes above 4 K. It disappears at a uniaxial stress higher than about a billion dyn/sq cm parallel to (111) as a result of the lifting of the valence-band degeneracy.

  11. Fluorescent styryl dyes of the RH series affect a potential drop on the membrane/solution boundary.

    PubMed

    Malkov, D Y; Sokolov, V S

    1996-01-31

    The effects of the adsorption of the fluorescent potential-sensitive dyes RH-421, RH-237 and RH-160 on the bilayer lipid membrane were studied. It was shown that a dipole potential drop, positive in the hydrophobic part of the membrane, arose due to the dye adsorption. The dye adsorption led to a considerable increase of the rate constant of hydrophobic anion translocation through the membrane, but did not affect their partition coefficient between membrane and water. It implies that the region of the membrane where the potential drops is located deeper than the adsorption plane of hydrophobic ions. The values of boundary potential differences were estimated by two independent methods with unilateral and bilateral application of the dyes to lipid bilayer membranes. The results suggest that RH dye molecules penetrate through the lipid bilayers. The values of zeta-potential in liposomes did not change on dye adsorption. Hence, dye molecules are adsorbed in a form that does not change the surface charge. We estimated the effects of electric field of dye dipole layer on an individual dipole located in the same layer and on ion transport through a membrane protein Na+/K+-ATPase. It turned out that the local electric field of each dye dipole decayed so rapidly that a neighbouring dye molecule did not feel it. It also appeared that RH dyes could have but a minor effect on the electrogenic transport performed by the sodium pump in the examined range of dye concentrations. PMID:8593277

  12. Chemical stabilization of laser dyes

    NASA Astrophysics Data System (ADS)

    Koch, Tad H.

    1987-05-01

    Coumarin laser dyes upon excitation degrade to produce products which absorb at the lasing wavelength. This results in attenuation of dye laser output through interference of stimulated emission. The roles of singlet oxygen and excitation intensity on dye degradation were explored. Singlet oxygen is formed but its reactions with the dye do not appear to be a major cause of dye laser output deterioration. High light intensity results in dye sensitized, solvent oligomerization to yield materials which interfere with dye stimulated emission. 1, 4-Diazabicyclo2,2,2octane (DABCO)inhibits this oligomerization.

  13. Design and characterisation of bodipy sensitizers for dye-sensitized NiO solar cells.

    PubMed

    Summers, Gareth H; Lefebvre, Jean-François; Black, Fiona A; Davies, E Stephen; Gibson, Elizabeth A; Pullerits, Tönu; Wood, Christopher J; Zidek, Karel

    2016-01-14

    A series of photosensitizers for NiO-based dye-sensitized solar cells is presented. Three model compounds containing a triphenylamine donor appended to a boron dipyrromethene (bodipy) chromophore have been successfully prepared and characterised using emission spectroscopy, electrochemistry and spectroelectrochemistry, to ultimately direct the design of dyes with more complex structures. Carboxylic acid anchoring groups and thiophene spacers were appended to the model compounds to provide five dyes which were adsorbed onto NiO and integrated into dye-sensitized solar cells. Solar cells incorporating the simple Bodipy-CO₂H dye were surprisingly promising relative to the more complex dye 4. Cell performances were improved with dyes which had increased electronic communication between the donor and acceptor, achieved by incorporating a less hindered bodipy moiety. Further increases in performances were obtained from dyes which contained a thiophene spacer. Thus, the best performance was obtained for 7 which generated a very promising photocurrent density of 5.87 mA cm(-2) and an IPCE of 53%. Spectroelectrochemistry combined with time-resolved transient absorption spectroscopy were used to determine the identity and lifetime of excited state species. Short-lived (ps) transients were recorded for 4, 5 and 7 which are consistent with previous studies. Despite a longer lived (25 ns) charge-separated state for 6/NiO, there was no increase in the photocurrent generated by the corresponding solar cell. PMID:26660278

  14. Time-Resolved Study on Xanthene Dye-Sensitized Carbon Nitride Photocatalytic Systems.

    PubMed

    Zhang, Huiyu; Li, Shuang; Lu, Rong; Yu, Anchi

    2015-10-01

    Dye sensitization is a promising strategy to extend the visible light absorption of carbon nitride (C3N4) and increase the photocatalytic hydrogen evolution efficiency of C3N4 under visible light irradiation. However, the interaction dynamics between C3N4 and a sensitized dye has not been reported in the literature. Herein, we selected four commonly used xanthene dyes such as fluorescein, dibromofluorescein, eosin Y, and erythrosine B and prepared their corresponding dye-sensitized-C3N4 composites. For the first time, we derived the electron transfer rate from the LUMO of each photoexcited xanthene dye to the conduction band of C3N4 using picoesecond time-resolved fluorescence measurements. We also obtained the reduction potentials of all selected xanthene dyes and C3N4 with cyclic voltammetry measurements. The cyclic voltammetry measurements gave a consistent result with the picosecond time-resolved fluorescence measurements. Besides, the possibility of the selected xanthene dye as an acceptor for the hole of the photoexcited C3N4 was also discussed. We believe this study is significant for the researcher to understanding the fundamental aspects in the xanthene dye-sensitized-C3N4 photocatalytic systems. PMID:26389679

  15. Synthesis, spectroscopic, thermal and electrochemical studies on thiazolyl azo based disperse dyes bearing coumarin

    NASA Astrophysics Data System (ADS)

    Özkütük, Müjgan; İpek, Ezgi; Aydıner, Burcu; Mamaş, Serhat; Seferoğlu, Zeynel

    2016-03-01

    In this study, seven novel thiazolyl azo disperse dyes (6a-g) were synthesized and fully characterized by FT-IR, 1H NMR, 13C NMR, and mass spectral techniques. The electronic absorption spectra of the dyes in solvents of different polarities cover a λmax range of 404-512 nm. The absorption properties of the dyes changed drastically upon acidification. This was due to the protonation of the nitrogen in the thiazole ring, which in turn increased the donor-acceptor interplay of the π system in the dyes, and therefore increased the absorption properties of the prepared dyes. Thermal analysis showed that these dyes are thermal stable up to 269 °C. Additionally, the electrochemical behavior of the dyes (6a-g) were investigated using cyclic voltammetric and chronoamperometric techniques, in the presence of 0.10 M tetrabutylammonium tetrafluoroborate, in dimethylsulfoxide, at a glassy carbon electrode. The number of transferred electrons, and the diffusion coefficient were determined by electrochemical methods. The results showed that, for all the dyes, one oxidation peak and two reduction peaks were observed.

  16. Fluorescent aggregates Cyan 40 and Thiazole Orange dyes in solution

    NASA Astrophysics Data System (ADS)

    Nizomov, Negmat; Kurtaliev, Eldar N.; Rahimov, Sherzod I.

    2012-12-01

    Absorption and fluorescence electronic spectra of cyanine dyes Cyan 40 and Thiazole Orange (TO) in water and in binary mixtures: water + ethanol, water + DMF, water + dioxane and chloroform + hexane were studied. It was revealed, that increase of concentration of Cyan 40 and TO dyes in water and chloroform + hexane binary mixture promotes the formation of fluorescent H-aggregates. Meanwhile, in contrary to the well-known fluorescent aggregates, electronic absorption band of aggregated molecules is shifted to the shorter wavelengths and fluorescence band is shifted to the longer wavelengths relative to the bands of the monomer molecules. Observed spectral changes are explained on the basis of Davidov's theory of molecular excitons as splitting of the electron-excited states due to the aggregation of dye molecules.

  17. Molecular engineering of D-D-π-A type organic dyes incorporating indoloquinoxaline and phenothiazine for highly efficient dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Qian, Xing; Wang, Xiaoying; Shao, Li; Li, Hongmei; Yan, Rucai; Hou, Linxi

    2016-09-01

    Four metal-free organic dyes QX05-08 based on indoloquinoxaline and phenothiazine have been successfully designed and synthesized for dye-sensitized solar cells. The D-D-π-A type dyes QX07 and QX08 consist of an indoloquinoxaline donor, a phenothiazine donor, a cyanoacrylic acid acceptor/anchoring group and a thiophene or furan π-bridge. Other simple D-π-A type dyes QX05 and QX06 based on indoloquinoxaline and phenothiazine respectively have also been synthesized for comparison. The D-D-π-A type dyes QX07 and QX08 present good balanced structures and show excellent photoelectric properties. Especially, the dye QX07 with a thiophene unit as the π-bridge exhibits the best photovoltaic performances in solar cells. A high power conversion efficiency up to 8.28% with a Jsc of 15.3 mA cm-2 and a Voc of 757 mV have been achieved by the dye QX07 using an iodine electrolyte under standard conditions.

  18. Fluorescent DNA Nanotags Featuring Covalently Attached Intercalating Dyes: Synthesis, Antibody Conjugation and Intracellular Imaging

    PubMed Central

    Stadler, Andrea L.; Santos, Junriz Delos; Stensrud, Elizabeth S.; Dembska, Anna; Silva, Gloria L.; Liu, Shengpeng; Shank, Nathaniel I.; Kunttas-Tatli, Ezgi; Sobers, Courtney J.; Gramlich, Philipp M. E.; Carell, Thomas; Peteanu, Linda A.; McCartney, Brooke M.; Armitage, Bruce A.

    2011-01-01

    We have synthesized fluorescent DNA duplexes featuring multiple thiazole orange (TO) intercalating dyes covalently attached to the DNA via a triazole linkage. The intercalating dyes stabilize the duplex against thermal denaturation and show bright fluorescence in the green. The emission color can be changed to orange or red by addition of energy-accepting Cy3 or Cy5 dyes attached covalently to the DNA duplex. The dye-modified DNA duplexes were then attached to a secondary antibody for intracellular fluorescence imaging of centrosomes in Drosophila embryos. Bright fluorescent foci were observed at the centrosomes in both the donor (TO) and acceptor (Cy5) channels, due to the fact that the energy transfer efficiency is moderate. Monitoring the Cy5 emission channel significantly minimized the background signal due to the large shift in emission wavelength allowed by energy transfer. PMID:21755981

  19. Plasma surface functionalization and dyeing kinetics of Pan-Pmma copolymers

    NASA Astrophysics Data System (ADS)

    Labay, C.; Canal, C.; Rodríguez, C.; Caballero, G.; Canal, J. M.

    2013-10-01

    Fiber surface modification with air corona plasma has been studied through dyeing kinetics under isothermal conditions at 30 °C on an acrylic-fiber fabric with a cationic dye (CI Basic Blue 3) analyzing the absorption, desorption and fixing on the surface of molecules having defined cationic character. The initial dyeing rate in the first 60 s indicates an increase of 58.3% in the dyeing rate due to the effect of corona plasma on the acrylic fiber surface. At the end of the dyeing process, the plasma-treated fabrics absorb 24.7% more dye, and the K/S value of the acrylic fabric increases by 8.8%. With selected dyestuff molecules, new techniques can be designed to amplify the knowledge about plasma-treated surface modifications of macromolecules.

  20. Bimolecular electron transfer reactions in coumarin amine systems: Donor acceptor orientational effect on diffusion-controlled reaction rates

    NASA Astrophysics Data System (ADS)

    Satpati, A. K.; Nath, S.; Kumbhakar, M.; Maity, D. K.; Senthilkumar, S.; Pal, H.

    2008-04-01

    representative acceptor and donor molecules.

  1. Fluorinated arene, imide and unsaturated pyrrolidinone based donor acceptor conjugated polymers: Synthesis, structure-property and device studies

    NASA Astrophysics Data System (ADS)

    Liyanage, Arawwawala Don Thilanga

    the structure-property study of imide functionalized D-A polymers. Here we used thiophene-imide (TPD) as the acceptor moiety and prepare several D-A polymers by varying the donor units. When selecting the donor units, more priority goes to the fused ring systems. One main reason to use imide functionality is due to the, open position of the imide nitrogen, which provides an attaching position to alkyl substituent. Through this we can easily manipulate solubility and solid state packing arrangement. Also these imide acceptors have low-lying LUMOs due to their electron deficient nature and this will allow tuning the optical energy gap by careful choice of donor materials with different electron donating ability. The fourth chapter mainly contribute to the synthesis and structure property study of a completely novel electron acceptor moiety consist of a unsaturated pyrrolidinone unit known as Pechmann dye (PD) core. Pechmann dyes are closely related to the Indigo family. This can refer as 3-butenolide dimer connected via an alkene bridge, containing a benzene ring at the 5 and 5' positions of the lactone rings. We have prepared several D-A polymers using this PD system with benzodithiophene (BDT) as the donor unit. Different to common D-A polymers the HOMO and LUMO of the PD acceptor moiety are energetically located within the gap of the BDT, so that the electronic and optical properties (HOMO-LUMO transition) are dictated by the PD properties. The promising electronic properties, band gaps, high absorption coefficients and broad absorption suggest this new D-A polymers as an interesting donor material for organic solar cell (OSC) applications. KEY WORDS: Organic semiconductor materials, Self assembly, (opto)-electronic properties, Donor-Acceptor conjugated polymers, Fluorinated arene, 3,3'-bithiophene donors, Thiophene-imide (TPD), Pechmann dye, benzodithiophene, organic solar cell.

  2. Relationship Between the Structure Parameters of a Solid Body and the Kinetics of Donor-Acceptor Interaction in Heterogeneous Systems

    NASA Astrophysics Data System (ADS)

    Khentov, V. Ya.; Khussein, Kh. Kh.

    2016-05-01

    Interaction of an organic ligand molecule with the surface of a d-metal or of disperse particles of chemical compounds containing covalent bonds in a nonaqueous solvent (direct synthesis of complex compounds) is determined by the structure parameters of the solid body. The relationships of the rate and energy of activation of the donor-acceptor interaction of the metal with the Grüneisen coefficient and the Debye temperature of the metal have been established.

  3. Relationship Between the Structure Parameters of a Solid Body and the Kinetics of Donor-Acceptor Interaction in Heterogeneous Systems

    NASA Astrophysics Data System (ADS)

    Khentov, V. Ya.; Khussein, Kh. Kh.

    2016-06-01

    Interaction of an organic ligand molecule with the surface of a d-metal or of disperse particles of chemical compounds containing covalent bonds in a nonaqueous solvent (direct synthesis of complex compounds) is determined by the structure parameters of the solid body. The relationships of the rate and energy of activation of the donor-acceptor interaction of the metal with the Grüneisen coefficient and the Debye temperature of the metal have been established.

  4. Nitrogen is a deep acceptor in ZnO

    DOE PAGESBeta

    Tarun, M. C.; Iqbal, M. Zafar; McCluskey, M. D.

    2011-04-14

    Zinc oxide is a promising material for blue and UV solid-state lighting devices, among other applications. Nitrogen has been regarded as a potential p-type dopant for ZnO. However, recent calculations indicate that nitrogen is a deep acceptor. This paper presents experimental evidence that nitrogen is, in fact, a deep acceptor and therefore cannot produce p-type ZnO. A broad photoluminescence (PL) emission band near 1.7 eV, with an excitation onset of ~2.2 eV, was observed, in agreement with the deep-acceptor model of the nitrogen defect. Thus the deep-acceptor behavior can be explained by the low energy of the ZnO valence bandmore » relative to the vacuum level.« less

  5. Nitrogen is a deep acceptor in ZnO

    SciTech Connect

    Tarun, M. C.; Iqbal, M. Zafar; McCluskey, M. D.

    2011-04-14

    Zinc oxide is a promising material for blue and UV solid-state lighting devices, among other applications. Nitrogen has been regarded as a potential p-type dopant for ZnO. However, recent calculations indicate that nitrogen is a deep acceptor. This paper presents experimental evidence that nitrogen is, in fact, a deep acceptor and therefore cannot produce p-type ZnO. A broad photoluminescence (PL) emission band near 1.7 eV, with an excitation onset of ~2.2 eV, was observed, in agreement with the deep-acceptor model of the nitrogen defect. Thus the deep-acceptor behavior can be explained by the low energy of the ZnO valence band relative to the vacuum level.

  6. Internally labeled Cy3/Cy5 DNA constructs show greatly enhanced photo-stability in single-molecule FRET experiments

    PubMed Central

    Lee, Wonbae; von Hippel, Peter H.; Marcus, Andrew H.

    2014-01-01

    DNA constructs labeled with cyanine fluorescent dyes are important substrates for single-molecule (sm) studies of the functional activity of protein–DNA complexes. We previously studied the local DNA backbone fluctuations of replication fork and primer–template DNA constructs labeled with Cy3/Cy5 donor–acceptor Förster resonance energy transfer (FRET) chromophore pairs and showed that, contrary to dyes linked ‘externally’ to the bases with flexible tethers, direct ‘internal’ (and rigid) insertion of the chromophores into the sugar-phosphate backbones resulted in DNA constructs that could be used to study intrinsic and protein-induced DNA backbone fluctuations by both smFRET and sm Fluorescent Linear Dichroism (smFLD). Here we show that these rigidly inserted Cy3/Cy5 chromophores also exhibit two additional useful properties, showing both high photo-stability and minimal effects on the local thermodynamic stability of the DNA constructs. The increased photo-stability of the internal labels significantly reduces the proportion of false positive smFRET conversion ‘background’ signals, thereby simplifying interpretations of both smFRET and smFLD experiments, while the decreased effects of the internal probes on local thermodynamic stability also make fluctuations sensed by these probes more representative of the unperturbed DNA structure. We suggest that internal probe labeling may be useful in studies of many DNA–protein interaction systems. PMID:24627223

  7. The electronic structure and second-order nonlinear optical properties of donor-acceptor acetylenes - A detailed investigation of structure-property relationships

    NASA Technical Reports Server (NTRS)

    Stiegman, A. E.; Graham, Eva; Khundkar, Lutfur R.; Perry, Joseph W.; Cheng, L.-T.; Perry, Kelly J.

    1991-01-01

    A series of donor-acceptor acetylene compounds was synthesized in which systematic changes in both the conjugation length and the donor-acceptor strength were made. The effect of these structural changes on the spectroscopic and electronic properties of the molecules and, ultimately, on the measured second-order molecular hyperpolarizabilities (beta) was investigated. It was found that increases in the donor-acceptor strength resulted in increases in the magnitude of beta. For this class of molecules, the increase is dominated by the energy of the intramolecular charge-transfer transition, while factors such as the ground to excited-state dipole moment change and the transition-moment integral are much less important. Increasing the conjugation length from one to two acetylene linkers did not result in an increase in the value of beta; however, beta increased sharply in going from two acetylenes to three. This increase is attributed to the superposition of several nearly isoenergetic excited states.

  8. Synthesis, Properties, and Design Principles of Donor–Acceptor Nanohoops

    PubMed Central

    2015-01-01

    We have synthesized a series of aza[8]cycloparaphenylenes containing one, two, and three nitrogens to probe the impact of nitrogen doping on optoelectronic properties and solid state packing. Alkylation of these azananohoops afforded the first donor–acceptor nanohoops where the phenylene backbone acts as the donor and the pyridinium units act as the acceptor. The impact on the optoelectronic properties was then studied experimentally and computationally to provide new insight into the effect of functionalization on nanohoops properties. PMID:27162989

  9. Photoconductivity of organic polymer films doped with porous silicon nanoparticles and ionic polymethine dyes

    SciTech Connect

    Davidenko, N. A. Skrichevsky, V. A.; Ishchenko, A. A.; Karlash, A. Yu.; Mokrinskaya, E. V.

    2009-05-15

    Features of electrical conductivity and photoconductivity of polyvinylbutyral films containing porous silicon nanoparticles and similar films doped with cationic and anionic polymethine dyes are studied. Sensitization of the photoelectric effect by dyes with different ionicities in films is explained by the possible photogeneration of holes and electrons from dye molecules and the intrinsic bipolar conductivity of porous silicon nanoparticles. It is assumed that the electronic conductivity in porous silicon nanoparticles is higher in comparison with p-type conductivity.

  10. Nanometer Resolution Imaging by SIngle Molecule Switching

    SciTech Connect

    Hu, Dehong; Orr, Galya

    2010-04-02

    The fluorescence intensity of single molecules can change dramatically even under constant laser excitation. The phenomenon is frequently called "blinking" and involves molecules switching between high and low intensity states.[1-3] In additional to spontaneous blinking, the fluorescence of some special fluorophores, such as cyanine dyes and photoactivatable fluorescent proteins, can be switched on and off by choice using a second laser. Recent single-molecule spectroscopy investigations have shed light on mechanisms of single molecule blinking and photoswitching. This ability to controllably switch single molecules led to the invention of a novel fluorescence microscopy with nanometer spatial resolution well beyond the diffraction limit.

  11. High-performance organic thin-film transistors of J-stacked squaraine dyes.

    PubMed

    Gsänger, Marcel; Kirchner, Eva; Stolte, Matthias; Burschka, Christian; Stepanenko, Vladimir; Pflaum, Jens; Würthner, Frank

    2014-02-12

    We have synthesized a series of dipolar squaraine dyes that contain dicyanovinyl groups as acceptor and benzannulated five-membered ring heterocycles with alkyl chains of varied length as donor moieties. Based on these squaraines, thin-film transistors (TFT) were fabricated by spin coating and solution shearing. Moreover, with one of these squaraine derivatives vacuum-deposited TFTs were prepared as well. Our detailed studies revealed that the transistor performance of the present series of squaraines is strongly dependent on their structural features as well as on the processing method of thin films. Thus, solution-sheared OTFTs of selenium squaraine bearing dodecyl substituents (denoted as Se-SQ-C12) performed best with a maximum hole mobility of 0.45 cm(2) V(-1) s(-1), which is by far the highest value yet reported for OTFTs based on squaraines. This value was even surpassed by vacuum-deposited thin films of n-butyl-substituted selenium squaraine Se-SQ-C4, the only sublimable compound in this series, exhibiting a record hole mobility of 1.3 cm(2) V(-1) s(-1). Furthermore, we have investigated the morphology of the thin films and the molecular packing of these squaraine dyes by optical spectroscopy, atomic force microscopy, and X-ray diffraction. These studies revealed a relationship between the molecular structure, packing motif, thin-film morphology, and transistor performance of the squaraine dyes. From the supramolecular point of view two packing features discovered in the single crystal structure of Se-SQ-C8 are of particular interest with regard to the structure-functionality relationship: The first is the slipped and antiparallel π-stacking motif which ensures cancellation of the molecules' dipole moments and J-type absorption band formation in thin films. The second is the presence of CN···Se noncovalent bonds which show similarities to the more common halogen-bonding interactions and which interconnect the individual one-dimensional slipped

  12. Efficiency Enhancement of Cocktail Dye of Ixora coccinea and Tradescantia spathacea in DSSC

    PubMed Central

    Zolkepli, Zularif; Lim, Andery; Ekanayake, Piyasiri; Tennakoon, Kushan

    2015-01-01

    The use of anthocyanin dyes extracted from epidermal leaves of Tradescantia spathacea (Trant) and petals of Ixora coccinea (IX) was evaluated in the application of dye-sensitized solar cells (DSSCs). Subsequently, cocktail anthocyanin dyes from these dyes were prepared and how they enhanced the cell's overall performance was assessed using five different volume-to-volume ratios. Cocktail dyes absorbed a wider range of light in the visible region, thus increasing the cell efficiencies of the cocktail dyes when compared to the DSSC sensitized by individual dyes. The surface charge (zeta-potential), average size of aggregated anthocyanin molecules (zetasizer), and anthocyanin stability in different storage temperatures were analyzed and recorded. Lower size of aggregated dye molecules as revealed from the cocktail dyes ensured better adsorption onto the TiO2 film. Tradescantia/Ixora pigments mixed in 1 : 4 ratio showed the highest cell efficiency of η = 0.80%, under the irradiance of 100 mW cm−2, with a short-circuit current density 4.185 mA/cm2, open-circuit voltage of 0.346 V, and fill factor of 0.499. It was found that the desired storage temperature for these cocktail dyes to be stable over time was −20°C, in which the anthocyanin half-life was about approximately 1727 days. PMID:26793239

  13. Supramolecular guest-host systems: combining high dye doping level with low aggregation tendency

    NASA Astrophysics Data System (ADS)

    Priimagi, Arri; Cattaneo, Stefano; Ras, Robin H. A.; Valkama, Sami; Ikkala, Olli; Kauranen, Martti

    2006-08-01

    We demonstrate that the aggregation tendency of dye molecules in a host polymer can be significantly reduced by exploiting non-covalent interactions between the host polymer and guest dye molecules. Such interactions occur spontaneously with no need for chemical synthesis, and could thus be utilized to combine the ease of processing of traditional guest-host systems with the high dye concentrations achievable in covalently linked systems. We studied the aggregation properties of the common azo-dye Disperse Red 1 in polymers with different functional groups. Compared to a nonpolar polymer (polystyrene), dye aggregation tendency is substantially reduced in polar polymer matrices containing hydrogen-bond donating [poly(vinylphenol)] or hydrogen-bond accepting [poly(4-vinylpyridine)] functional sites. Furthermore, by forming a polyelectrolyte-dye complex [Disperse Red 1/poly(styrenesulfonic acid)], a dye monomer can be attached to approximately each polymer unit, resulting in dye concentration of 63 wt. %. Complexation through proton transfer was further studied by using a fluorescent dye 5-phenyl-2-(4-pyridyl)oxazole. Our results indicate that polymer-dye complexes could provide a facile route for new type of optical materials, with potential applications in various fields of optics and photonics.

  14. Efficiency Enhancement of Cocktail Dye of Ixora coccinea and Tradescantia spathacea in DSSC.

    PubMed

    Zolkepli, Zularif; Lim, Andery; Ekanayake, Piyasiri; Tennakoon, Kushan

    2015-01-01

    The use of anthocyanin dyes extracted from epidermal leaves of Tradescantia spathacea (Trant) and petals of Ixora coccinea (IX) was evaluated in the application of dye-sensitized solar cells (DSSCs). Subsequently, cocktail anthocyanin dyes from these dyes were prepared and how they enhanced the cell's overall performance was assessed using five different volume-to-volume ratios. Cocktail dyes absorbed a wider range of light in the visible region, thus increasing the cell efficiencies of the cocktail dyes when compared to the DSSC sensitized by individual dyes. The surface charge (zeta-potential), average size of aggregated anthocyanin molecules (zetasizer), and anthocyanin stability in different storage temperatures were analyzed and recorded. Lower size of aggregated dye molecules as revealed from the cocktail dyes ensured better adsorption onto the TiO2 film. Tradescantia/Ixora pigments mixed in 1 : 4 ratio showed the highest cell efficiency of η = 0.80%, under the irradiance of 100 mW cm(-2), with a short-circuit current density 4.185 mA/cm(2), open-circuit voltage of 0.346 V, and fill factor of 0.499. It was found that the desired storage temperature for these cocktail dyes to be stable over time was -20°C, in which the anthocyanin half-life was about approximately 1727 days. PMID:26793239

  15. Energy level realignment in weakly interacting donor-acceptor binary molecular networks.

    PubMed

    Zhong, Jian-Qiang; Qin, Xinming; Zhang, Jia-Lin; Kera, Satoshi; Ueno, Nobuo; Wee, Andrew Thye Shen; Yang, Jinlong; Chen, Wei

    2014-02-25

    Understanding the effect of intermolecular and molecule-substrate interactions on molecular electronic states is key to revealing the energy level alignment mechanism at organic-organic heterojunctions or organic-inorganic interfaces. In this paper, we investigate the energy level alignment mechanism in weakly interacting donor-acceptor binary molecular superstructures, comprising copper hexadecafluorophthalocyanine (F16CuPc) intermixed with copper phthalocyanine (CuPc), or manganese phthalocynine (MnPc) on graphite. The molecular electronic structures have been systematically studied by in situ ultraviolet photoelectron spectroscopy (UPS) and low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) experiments and corroborated by density functional theory (DFT) calculations. As demonstrated by the UPS and LT-STM/STS measurements, the observed unusual energy level realignment (i.e., a large downward shift in donor HOMO level and a corresponding small upward shift in acceptor HOMO level) in the CuPc-F16CuPc binary superstructures originates from the balance between intermolecular and molecule-substrate interactions. The enhanced intermolecular interactions through the hydrogen bonding between neighboring CuPc and F16CuPc can stabilize the binary superstructures and modify the local molecular electronic states. The obvious molecular energy level shift was explained by gap-state-mediated interfacial charge transfer. PMID:24433044

  16. Organic donor-acceptor assemblies form coaxial p-n heterojunctions with high photoconductivity.

    PubMed

    Prasanthkumar, Seelam; Ghosh, Samrat; Nair, Vijayakumar C; Saeki, Akinori; Seki, Shu; Ajayaghosh, Ayyappanpillai

    2015-01-12

    The formation of coaxial p-n heterojunctions by mesoscale alignment of self-sorted donor and acceptor molecules, important to achieve high photocurrent generation in organic semiconductor-based assemblies, remains a challenging topic. Herein, we show that mixing a p-type π gelator (TTV) with an n-type semiconductor (PBI) results in the formation of self-sorted fibers which are coaxially aligned to form interfacial p-n heterojunctions. UV/Vis absorption spectroscopy, powder X-ray diffraction studies, atomic force microscopy, and Kelvin-probe force microscopy revealed an initial self-sorting at the molecular level and a subsequent mesoscale self-assembly of the resulted supramolecular fibers leading to coaxially aligned p-n heterojunctions. A flash photolysis time-resolved microwave conductivity (FP-TRMC) study revealed a 12-fold enhancement in the anisotropic photoconductivity of TTV/PBI coaxial fibers when compared to the individual assemblies of the donor/acceptor molecules. PMID:25430809

  17. Degradation of various dyes using Laccase enzyme.

    PubMed

    Dhaarani, S; Priya, A K; Rajan, T Vel; Kartic, D Navamani

    2012-10-01

    Disposal of untreated dyeing effluent in water bodies, from textile industries, cause serious environmental and health hazards. The chemical structures of dye molecules are designed to resist fading on exposure to light or chemical attack, and they prove to be quite resistant towards microbial degradation. Therefore, current conventional biological processes may not be able to meet wastewater discharge criteria and reuse. An enzymatic treatment undergoes oxidative cleavage avoiding formation of toxic amines. Laccase is a multi-copper containing protein that catalyzes the oxidation of a wide range of aromatic substrates concomitantly with the reduction of molecular oxygen to water. UV visible spectral analysis of various synthetic dyes was performed in the study and wavelengths of maximum absorbance determined. Laccase enzyme was obtained from the fungi Pleorotus ostreatus. The enzyme showed high efficiency against Malachite Green, Basic Red and Acid Majanta with decolorization capacities of 97%, 94% and 94% respectively. Further, these dyes can be used for optimization of degradation parameters and analysis of degradation products. PMID:25151712

  18. Tunable optofluidic distributed feedback dye lasers

    NASA Astrophysics Data System (ADS)

    Li, Zhenyu; Zhang, Zhaoyu; Emery, Teresa; Scherer, Axel; Psaltis, Demetri

    2006-08-01

    We demonstrated a continuously tunable optofluidic distributed feedback (DFB) dye laser on a monolithic poly(dimethylsiloxane) (PDMS) elastomer chip. The optical feedback was provided by a phase-shifted higher order Bragg grating embedded in the liquid core of a single mode buried channel waveguide. We achieved nearly 60nm continuously tunable output by mechanically varying the grating period with two dye molecules Rhodamine 6G (Rh6G) and Rhodamine 101 (Rh101). Single-mode operation was obtained with <0.1nm linewidth. Because of the higher order grating, a single laser, when operated with different dye solutions, can provide tunable output covering from near UV to near IR spectral region. The low pump threshold (< 1uJ) makes it possible to use a single high energy pulsed laser to pump hundreds of such lasers on a chip. An integrated array of five DFB dye lasers with different lasing wavelengths was also demonstrated. Such laser arrays make it possible to build highly parallel optical sensors on a chip. The laser chip is fully compatible with PDMS based soft microfluidics.

  19. Tuning the Electron Acceptor in Phthalocyanine-Based Electron Donor-Acceptor Conjugates.

    PubMed

    Sekita, Michael; Jiménez, Ángel J; Marcos, M Luisa; Caballero, Esmeralda; Rodríguez-Morgade, M Salomé; Guldi, Dirk M; Torres, Tomás

    2015-12-21

    Zinc phthalocyanines (ZnPc) have been attached to the peri-position of a perylenemonoimide (PMI) and a perylenemonoanhydride (PMA), affording electron donor-acceptor conjugates 1 and 2, respectively. In addition, a perylene-monoimide-monoanhydride (PMIMA) has been connected to a ZnPc through its imido position to yield the ZnPc-PMIMA conjugate 10. The three conjugates have been studied for photoinduced electron transfer. For ZnPc-PMIMA 10, electron transfer occurs upon both ZnPc and PMIMA excitation, giving rise to a long-lived (340 ps) charge-separated state. For ZnPc-PMI 1 and ZnPc-PMA 2, stabilization of the radical ion pair states by using polar media is necessary. In THF, photoexcitation of either ZnPc or PMI/PMA produces charge-separated states with lifetimes of 375 and 163 ps, respectively. PMID:26593778

  20. Effect of hydrophobicity of cationic carbocyanine dyes DiOC n on their binding to anionic surfactant micelles

    NASA Astrophysics Data System (ADS)

    Lebed, A. S.; Yefimova, S. L.; Guralchuk, G. Ya.; Sorokin, A. V.; Borovoy, I. A.; Malyukin, Yu. V.

    2010-05-01

    The interaction of a series of cationic dialkyloxacarbocyanine perchlorate (DiOC n ) dyes of different degrees of hydrophobicity with micelles of an anionic surfactant, sodium dodecylsulfate (SDS), has been studied spectrophotometrically in aqueous solutions. The Benesi-Hildebrand equation was used to calculate binding constants ( K b ) of the dyes to surfactant micelles, the fraction of dye bound to the micelles ( f mic ), and the standard free-energy change (Δ G 0) for the transfer of dye from the aqueous to micellar phase. It has been shown that the interaction of oppositely charged dye molecules and surfactant micelles is controlled by both electrostatic and hydrophobic interactions. A small increase in dye hydrophobicity due to lengthening of the hydrocarbon radical has been shown to cause an abrupt nonlinear increase of the fmic value. This points to a key role of hydrophobic interactions in the binding of dye molecules with the micelles.

  1. The Impact of Heterogeneity and Dark Acceptor States on FRET: Implications for Using Fluorescent Protein Donors and Acceptors

    PubMed Central

    Vogel, Steven S.; Nguyen, Tuan A.; van der Meer, B. Wieb; Blank, Paul S.

    2012-01-01

    Förster resonance energy transfer (FRET) microscopy is widely used to study protein interactions in living cells. Typically, spectral variants of the Green Fluorescent Protein (FPs) are incorporated into proteins expressed in cells, and FRET between donor and acceptor FPs is assayed. As appreciable FRET occurs only when donors and acceptors are within 10 nm of each other, the presence of FRET can be indicative of aggregation that may denote association of interacting species. By monitoring the excited-state (fluorescence) decay of the donor in the presence and absence of acceptors, dual-component decay analysis has been used to reveal the fraction of donors that are FRET positive (i.e., in aggregates)._However, control experiments using constructs containing both a donor and an acceptor FP on the same protein repeatedly indicate that a large fraction of these donors are FRET negative, thus rendering the interpretation of dual-component analysis for aggregates between separately donor-containing and acceptor-containing proteins problematic. Using Monte-Carlo simulations and analytical expressions, two possible sources for such anomalous behavior are explored: 1) conformational heterogeneity of the proteins, such that variations in the distance separating donor and acceptor FPs and/or their relative orientations persist on time-scales long in comparison with the excited-state lifetime, and 2) FP dark states. PMID:23152925

  2. Enhanced photodegradation of organic dyes adsorbed on a clay.

    PubMed

    Tani, Seiji; Yamaki, Hiroshi; Sumiyoshi, Azumi; Suzuki, Yasutaka; Hasegawa, Shinya; Yamazaki, Suzuko; Kawamata, Jun

    2009-01-01

    The interaction of three photoactive organic dyes, Rhodamine B, Rhodamine 6G and a stilbazolium derivative 4'-dimethylamino-N-methyl-4-stilbazolium with synthetic sodium-saponite has been examined by UV-visible absorption spectroscopy. In all cases, bathochromic shifts and the reduction of peak absorbance for the dyes were observed in the absorption spectra at a low dye concentration (25% adsorption of the cation exchange capacity (CEC) of the clay), although the shape and the width of their absorption bands were similar to those in aqueous solution. This absorption behavior indicates that the organic dye molecules adsorbed onto the surface of the negatively charged clay particles and the adsorbed molecules were well dispersed. The photodegradation of the organic dyes in aqueous solution and in the clay suspension has been also examined by the irradiation of a laser beam at a wavelength of 532 nm. We have found that the hybridization of the organic dyes with the exfoliated clay particles largely enhanced a photodegradation. The clay particles acted as a catalyst even at a high concentration such as approximately 300% of CEC. PMID:19441365

  3. Fluorescence quenching of (dimethylamino)naphthalene dyes Badan and Prodan by tryptophan in cytochromes P450 and micelles.

    PubMed

    Pospíšil, Petr; Luxem, Katja E; Ener, Maraia; Sýkora, Jan; Kocábová, Jana; Gray, Harry B; Vlček, Antonín; Hof, Martin

    2014-08-28

    Fluorescence of 2-(N,N-dimethylamino)-6-propionylnaphthalene dyes Badan and Prodan is quenched by tryptophan in Brij 58 micelles as well as in two cytochrome P450 proteins (CYP102, CYP119) with Badan covalently attached to a cysteine residue. Formation of nonemissive complexes between a dye molecule and tryptophan accounts for about 76% of the fluorescence intensity quenching in micelles, the rest is due to diffusive encounters. In the absence of tryptophan, fluorescence of Badan-labeled cytochromes decays with triexponential kinetics characterized by lifetimes of about 100 ps, 700-800 ps, and 3 ns. Site mutation of a histidine residue in the vicinity of the Badan label by tryptophan results in shortening of all three decay lifetimes. The relative amplitude of the fastest component increases at the expense of the two slower ones. The average quenching rate constants are 4.5 × 10(8) s(-1) (CYP102) and 3.7 × 10(8) s(-1) (CYP119), at 288 K. Cyclic voltammetry of Prodan in MeCN shows a reversible reduction peak at -1.85 V vs NHE that becomes chemically irreversible and shifts positively upon addition of water. A quasireversible reduction at -0.88 V was observed in an aqueous buffer (pH 7.3). The excited-state reduction potential of Prodan (and Badan) is estimated to vary from about +0.6 V (vs NHE) in polar aprotic media (MeCN) to approximately +1.6 V in water. Tryptophan quenching of Badan/Prodan fluorescence in CYPs and Brij 58 micelles is exergonic by ≤0.5 V and involves tryptophan oxidation by excited Badan/Prodan, coupled with a fast reaction between the reduced dye and water. Photoreduction is a new quenching mechanism for 2-(N,N-dimethylamino)-6-propionylnaphthalene dyes that are often used as solvatochromic polarity probes, FRET donors and acceptors, as well as reporters of solvation dynamics. PMID:25079965

  4. Study of excitation transfer in laser dye mixtures by direct measurement of fluorescence lifetime

    NASA Technical Reports Server (NTRS)

    Lin, C.; Dienes, A.

    1973-01-01

    By directly measuring the donor fluorescence lifetime as a function of acceptor concentration in the laser dye mixture Rhodamine 6G-Cresyl violet, we found that the Stern-Volmer relation is obeyed, from which the rate of excitation transfer is determined. The experimental results indicate that the dominant mechanism responsible for the efficient excitation transfer is that of resonance transfer due to long range dipole-dipole interaction.

  5. A DNA Crystal Designed to Contain Two Molecules per Asymmetric Unit

    SciTech Connect

    T Wang; R Sha; J Birktoft; J Zheng; C Mao; N Seeman

    2011-12-31

    We describe the self-assembly of a DNA crystal that contains two tensegrity triangle molecules per asymmetric unit. We have used X-ray crystallography to determine its crystal structure. In addition, we have demonstrated control over the colors of the crystals by attaching either Cy3 dye (pink) or Cy5 dye (blue-green) to the components of the crystal, yielding crystals of corresponding colors. Attaching the pair of dyes to the pair of molecules yields a purple crystal.

  6. Enhanced Photovoltaic Performances of Dye-Sensitized Solar Cells by Co-Sensitization of Benzothiadiazole and Squaraine-Based Dyes.

    PubMed

    Islam, Ashraful; Akhtaruzzaman, Md; Chowdhury, Towhid H; Qin, Chuanjiang; Han, Liyuan; Bedja, Idriss M; Stalder, Romain; Schanze, Kirk S; Reynolds, John R

    2016-02-24

    Dye-sensitized solar cells (DSSCs) based on a donor-acceptor-donor oligothienylene dye containing benzothiadiazole (T4BTD-A) were cosensitized with dyes containing cis-configured squaraine rings (HSQ3 and HSQ4). The cosensitized dyes showed incident monochromatic photon-to-current conversion efficiency (IPCE) greater than 70% in the 300-850 nm wavelength region. The individual overall conversion efficiencies of the sensitizers T4BTD-A, HSQ3, and HSQ4 were 6.4%, 4.8%, and 5.8%, respectively. Improved power conversion efficiencies of 7.0% and 7.7% were observed when T4BTD-A was cosensitized with HSQ3 and HSQ4, respectively, thanks to a significant increase in current density (JSC) for the cosensitized DSSCs. Intensity-modulated photovoltage spectroscopy results showed a longer lifetime for cosensitized T4BTD-A+HSQ3 and T4BTD-A+HSQ4 compared to that of HSQ3 and HSQ4, respectively. PMID:26812212

  7. Molecule nanoweaver

    DOEpatents

    Gerald, II; Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2009-03-10

    A method, apparatus, and system for constructing uniform macroscopic films with tailored geometric assemblies of molecules on the nanometer scale. The method, apparatus, and system include providing starting molecules of selected character, applying one or more force fields to the molecules to cause them to order and condense with NMR spectra and images being used to monitor progress in creating the desired geometrical assembly and functionality of molecules that comprise the films.

  8. Influence of dye content on the conduction band edge of titania in the steam-treated dye-dispersing titania electrodes.

    PubMed

    Setiawan, Rudi Agus; Nishikiori, Hiromasa; Tanaka, Nobuaki; Fujii, Tsuneo

    2014-01-01

    The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the conduction band edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of conduction band edge of the titania of the dye-dispersing titania. The conduction band edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania conduction band edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania conduction band edge corresponded to the change in the Voc value. PMID:24893823

  9. ESTIMATION OF IONIZATION CONSTANTS OF AZO DYES AND RELATED AROMATIC AMINES: ENVIRONMENTAL IMPLICATIONS

    EPA Science Inventory

    Ionization constants for 214 dye molecules were calculated from molecular structures using the chemical reactivity models developed in SPARC (SPARC Performs Automated Reasoning in Chemistry). hese models used fundamental chemical structure theory to predict chemical reactivities ...

  10. Synthesis of Charge Transfer Dyes for Use as Molecular Sensors in Biological Systems

    NASA Technical Reports Server (NTRS)

    Christie, Joseph J.

    2003-01-01

    This is a continuation of last year's project to synthesize tetraaryl substituted benzodifurans for use as molecular probes in biological systems. The project will involve the synthesis and chemical characterization of dyes and precursor molecules.

  11. Dye adsorption of cotton fabric grafted with PPI dendrimers: Isotherm and kinetic studies.

    PubMed

    Salimpour Abkenar, Samera; Malek, Reza Mohammad Ali; Mazaheri, Firouzmehr

    2015-11-01

    In this research, the cotton fabrics grafted with two generations of the poly(propylene imine) dendrimers were applied to adsorb textile dyes from aqueous solutions. Direct Red 80 (anionic dye), Disperse Yellow 42 (nonionic dye) and Basic Blue 9 (cationic dye) were selected as model dyes. The effect of various experimental parameters such as initial concentration of dyes, charge of dyes molecule, salt and pH was investigated on the adsorption process. Furthermore, kinetics and equilibrium of the adsorption process on the grafted samples were studied. It was found that maximum adsorption of anionic and disperse dyes took place at around pH 3, while cationic dye could be adsorbed at around pH 11. The Langmuir equation was able to describe the mechanism of dyes adsorption. In addition, the second-order equation was found to be fit with the kinetics data. Interestingly, it seems that the dye adsorption of the grafted fabrics is strongly pH dependent. PMID:26292774

  12. Electrochemical removal of synthetic textile dyes from aqueous solutions using Ti/Pt anode: role of dye structure.

    PubMed

    Araújo, Cynthia K C; Oliveira, Gustavo R; Fernandes, Nedja S; Zanta, Carmem L P S; Castro, Suely Souza Leal; da Silva, Djalma R; Martínez-Huitle, Carlos A

    2014-01-01

    In this work, the efficiency of electrochemical oxidation (EO) was investigated for removing a dye mixture containing Novacron Yellow (NY) and Remazol Red (RR) in aqueous solutions using platinum supported on titanium (Ti/Pt) as anode. Different current densities (20, 40 and 60 mA cm(-2)) and temperatures (25, 40 and 60 °C) were studied during electrochemical treatment. After that, the EO of each of these dyes was separately investigated. The EO of each of these dyes was performed, varying only the current density and keeping the same temperature (25 °C). The elimination of colour was monitored by UV-visible spectroscopy, and the degradation of organic compounds was analysed by means of chemical oxygen demand (COD). Data obtained from the analysis of the dye mixture showed that the EO process was effective in colour removal, in which more than 90% was removed. In the case of COD removal, the application of a current density greater than 40 mA cm(-2) favoured the oxygen evolution reaction, and no complete oxidation was achieved. Regarding the analysis of individual anodic oxidation dyes, it was appreciated that the data for the NY were very close to the results obtained for the oxidation of the dye mixture while the RR dye achieved higher colour removal but lower COD elimination. These results suggest that the oxidation efficiency is dependent on the nature of the organic molecule, and it was confirmed by the intermediates identified. PMID:24801286

  13. Water soluble laser dyes

    DOEpatents

    Hammond, Peter R.; Feeman, James F.; Field, George F.

    1998-01-01

    Novel water soluble dyes of the formula I are provided ##STR1## wherein R.sup.1 and R.sup.4 are alkyl of 1 to 4 carbon atoms or hydrogen; or R.sup.1 -R.sup.2 or R.sup.2 -R.sup.4 form part of aliphatic heterocyclic rings; R.sup.2 is hydrogen or joined with R.sup.1 or R.sup.4 as described above; R.sup.3 is --(CH.sub.2).sub.m --SO.sub.3.sup.-, where m is 1 to 6; X is N, CH or ##STR2## where Y is 2 --SO.sub.3.sup.- ; Z is 3, 4, 5 or 6 --SO.sub.3.sup.-. The novel dyes are particularly useful as the active media in water solution dye lasers.

  14. Water soluble laser dyes

    DOEpatents

    Hammond, P.R.; Feeman, J.F.; Field, G.F.

    1998-08-11

    Novel water soluble dyes of the formula 1 are provided by the formula described in the paper wherein R{sup 1} and R{sup 4} are alkyl of 1 to 4 carbon atoms or hydrogen; or R{sup 1}--R{sup 2} or R{sup 2}--R{sup 4} form part of aliphatic heterocyclic rings; R{sup 2} is hydrogen or joined with R{sup 1} or R{sup 4} as described above; R{sup 3} is --(CH{sub 2}){sub m}--SO{sub 3}{sup {minus}}, where m is 1 to 6; X is N, CH or formula 2 given in paper where Y is 2 --SO{sub 3}{sup {minus}} ; Z is 3, 4, 5 or 6 --SO{sub 3}{sup {minus}}. The novel dyes are particularly useful as the active media in water solution dye lasers.

  15. Laser dye technology

    SciTech Connect

    Hammond, P R

    1999-09-01

    The author has worked with laser dyes for a number of years. A first interest was in the Navy blue-green program where a flashlamp pumped dye laser was used as an underwater communication and detection device. It made use of the optical window of sea-water--blue for deep ocean, green for coastal water. A major activity however has been with the Atomic Vapor Laser Isotope Separation Program (AVLIS) at the Lawrence Livermore National Laboratory. The aim here has been enriching isotopes for the nuclear fuel cycle. The tunability of the dye laser is utilized to selectively excite one isotope in uranium vapor, and this isotope is collected electrostatically as shown in Figure 1. The interests in the AVLIS program have been in the near ultra-violet, violet, red and deep-red.

  16. Hair Dye and Hair Relaxers

    MedlinePlus

    ... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...

  17. Chemisorption of a thiol-functionalized ruthenium dye on zinc oxide nanoparticles: Implications for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Singh, Jagdeep; Im, Jisun; Whitten, James E.; Soares, Jason W.; Steeves, Diane M.

    2010-09-01

    ZnO is an alternative to TiO 2-based dye-sensitized solar cells (DSSCs). Adsorption of cis-ruthenium-bis[2,2'-bipyridine]-bis[4-thiopyridine] onto ZnO nanorods has been studied using X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS). XPS indicates chemisorption with a surface density of ca. 1 × 10 15 molecules/cm 2, confirming the possibility of using thiol-terminated dyes for ZnO-based DSSC devices. The energy level diagram, based on UPS and absorbance spectroscopy, indicates that the LUMO of this dye is lower in energy than the ZnO conduction band edge, providing minimal enthalpic driving force for photovoltaic electron injection. However, optimization of thiol-functionalized Ru dyes could result in competitive ZnO-based DSSCs.

  18. Metal-Free Sensitizers for Dye-Sensitized Solar Cells.

    PubMed

    Chaurasia, Sumit; Lin, Jiann T

    2016-06-01

    This review focuses on our work on metal-free sensitizers for dye-sensitized solar cells (DSSCs). Sensitizers based on D-A'-π-A architecture (D is a donor, A is an acceptor, A' is an electron-deficient entity) exhibit better light harvesting than D-π-A-type sensitizers. However, appropriate molecular design is needed to avoid excessive aggregation of negative charge at the electron-deficient entity upon photoexcitation. Rigidified aromatics, including aromatic segments comprising fused electron-excessive and -deficient units in the spacer, allow effective electronic communication, and good photoinduced charge transfer leads to excellent cell performance. Sensitizers with two anchors/acceptors, D(-π-A)2 , can more efficiently harvest light, inject electrons, and suppress dark current compared with congeners with a single anchor. Appropriate incorporation of heteroaromatic units in the spacer is beneficial to DSSC performance. High-performance, aqueous-based DSSCs can be achieved with a dual redox couple comprising imidazolium iodide and 2,2,6,6-tetramethylpiperidin-N-oxyl, and/or using dyes of improved wettability through the incorporation of a triethylene oxide methyl ether chain. PMID:27114164

  19. Hair care and dyeing.

    PubMed

    Draelos, Zoe Diana

    2015-01-01

    Alopecia can be effectively camouflaged or worsened through the use of hair care techniques and dyeing. Proper hair care, involving hair styling and the use of mild shampoos and body-building conditioners, can amplify thinning scalp hair; however, chemical processing, including hair dyeing, permanent waving, and hair straightening, can encourage further hair loss through breakage. Many patients suffering from alopecia attempt to improve their hair through extensive manipulation, which only increases problems. Frequent haircuts to minimize split ends, accompanied by gentle handling of the fragile fibers, is best. This chapter offers the dermatologist insight into hair care recommendations for the alopecia patient. PMID:26370650

  20. Dye filled security seal

    DOEpatents

    Wilson, Dennis C. W.

    1982-04-27

    A security seal for providing an indication of unauthorized access to a sealed object includes an elongate member to be entwined in the object such that access is denied unless the member is removed. The elongate member has a hollow, pressurizable chamber extending throughout its length that is filled with a permanent dye under greater than atmospheric pressure. Attempts to cut the member and weld it together are revealed when dye flows through a rupture in the chamber wall and stains the outside surface of the member.

  1. Cu(II)-selective bispidine-dye conjugates.

    PubMed

    Brox, Dominik; Comba, Peter; Herten, Dirk-Peter; Kimmle, Esther; Morgen, Michael; Rühl, Carmen L; Rybina, Arina; Stephan, Holger; Storch, Golo; Wadepohl, Hubert

    2015-07-01

    The substitution of tetradentate bispidine ligands with rhodamine and cyanine dye molecules, coupled to an amine donor, forming an amide as potential fifth donor, is described. Bispidines are known to lead to very stable Cu(II) complexes, and the coordination to Cu(II) was expected to efficiently quench the fluorescence of dye molecules. However, at physiological pH the amide is not coordinated, as shown by titration experiments and crystallographic structural data of three possible isomers of these complexes. This may be due to the specific cavity shape of bispidines and the Jahn-Teller lability of the Cu(II) center. While Cu(II) coordination in aqueous solution leads to efficient fluorescence quenching, experiments show that the complex stabilities are not large enough for Cu(II) sensing in biological media, and possibilities are discussed, how this may be achieved by optimized bispidine-dye conjugates. PMID:26048430

  2. Plasmonic nanoparticles enhanced dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Xu, Qi; Liu, Fang; Meng, Weisi; Huang, Yidong

    2013-12-01

    Here we present investigations on utilizing two kinds of plasmonic nanoparticles (NPs) to enhance the efficiency of dye sensitized solar cells (DSCs). The Au@PVP NPs is proposed and present the specialty of adhesiveness to dye molecules, which could help to localize additional dye molecules near the plasmonic NPs, hence increasing the optical absorption consequently the power conversion efficiency (PCE) of the DSCs by 30% from 3.3% to 4.3%. Meanwhile, an irregular Au-Ag alloy popcorn-shaped NPs (popcorn NPs) with plenty of fine structures is also proposed and realized to enhance the light absorption of DSC. A pronounced absorption enhancement in a broadband wavelength range is observed due to the excitation of localized surface plasmon at different wavelengths. The PCE is enhanced by 32% from 5.94% to 7.85%.

  3. The aqueous-polyelectrolyte dye solution as an active laser medium

    SciTech Connect

    Akimov, A I; Saletskii, A M

    2000-11-30

    The spectral, luminescent, and lasing properties of aqueous solutions of a cationic dye rhodamine 6G with additions of anion polyelectrolytes - polyacrylic and polymethacrylic acids - are studied. It is found that the energy and spectral properties of lasing of these solutions depend on the ratio of concentrations of polyelectrolyte and molecules. It is also found that the lasing parameters of aqueous-polyelectrolyte dye solutions can be controlled by changing the structure of the molecular system. The variation in the structure of aqueous-polyelectrolyte dye solutions of rhodamine 6G resulted in an almost five-fold increase in the lasing efficiency compared to that in aqueous dye solutions. (lasers, active media)

  4. Hair Dyes and Cancer Risk

    MedlinePlus

    ... including aromatic amines that were found to cause cancer in animals. In the mid- to late 1970s, however, manufacturers changed the components in dye products to eliminate some of these chemicals ... in hair dyes can cause cancer. Given the widespread use of hair dye products, ...

  5. Theory of Primary Photoexcitations in Donor-Acceptor Copolymers

    NASA Astrophysics Data System (ADS)

    Aryanpour, Karan; Dutta, Tirthankar; Huynh, Uyen N. V.; Vardeny, Zeev Valy; Mazumdar, Sumit

    2015-12-01

    We present a generic theory of primary photoexcitations in low band gap donor-acceptor conjugated copolymers. Because of the combined effects of strong electron correlations and broken symmetry, there is considerable mixing between a charge-transfer exciton and an energetically proximate triplet-triplet state with an overall spin singlet. The triplet-triplet state, optically forbidden in homopolymers, is allowed in donor-acceptor copolymers. For an intermediate difference in electron affinities of the donor and the acceptor, the triplet-triplet state can have a stronger oscillator strength than the charge-transfer exciton. We discuss the possibility of intramolecular singlet fission from the triplet-triplet state, and how such fission can be detected experimentally.

  6. Theory of Primary Photoexcitations in Donor-Acceptor Copolymers.

    PubMed

    Aryanpour, Karan; Dutta, Tirthankar; Huynh, Uyen N V; Vardeny, Zeev Valy; Mazumdar, Sumit

    2015-12-31

    We present a generic theory of primary photoexcitations in low band gap donor-acceptor conjugated copolymers. Because of the combined effects of strong electron correlations and broken symmetry, there is considerable mixing between a charge-transfer exciton and an energetically proximate triplet-triplet state with an overall spin singlet. The triplet-triplet state, optically forbidden in homopolymers, is allowed in donor-acceptor copolymers. For an intermediate difference in electron affinities of the donor and the acceptor, the triplet-triplet state can have a stronger oscillator strength than the charge-transfer exciton. We discuss the possibility of intramolecular singlet fission from the triplet-triplet state, and how such fission can be detected experimentally. PMID:26765027

  7. Enhancement of Spectral Response of Dye-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Chang, Shuai

    Dye-Sensitized solar cell (DSSC) is a class of third-generation solar devices. A notable feature of DSSC is that it can be manufactured by solution-based approach; this non-vacuum processing renders significant reduction in manufacturing costs. Different from conventional solar cells, in a DSSC, mesoporous semiconductor film with large surface areas is utilized for anchoring dye molecules, serving as light absorbing layer. Dye sensitizers play an important role in determining the final performance in DSSCs. Since the first highly-efficient DSSC was reported in 1991 sensitized by a ruthenium-based dye, numerous researchers have been focused on the development and characterization of various kinds of dyes for the applications in DSSCs. These include mainly metal complexes dyes, organic dyes, porphyrins and phthalocyanines dyes. The first part of my thesis work is to develop and test new dyes for DSSCs and a series of phenothiazine-based organic dyes and new porphyrin dyes are reported during the process. It has been realized that extending the response of dye sensitizers to a wider range of the solar spectrum is a key step in further improving the device efficiency. Typically, there are two ways for expanding the strong spectral response of DSSCs from visible to far red/NIR region. One approach is called co-sensitization. Herein, we demonstrate a new co-sensitization concept where small molecules is used to insert the interstitial site of between the pre-adsorbed large molecules. In this case, the co-adsorbed small ones is found to improve the light response and impede the back recombination, finally leading to the power conversion efficiency over 10% in conventional DSSC devices and a record-equaling efficiency of 9.2% in quasi-solid-state devices. I also implemented graphene sheets in the anode films for better charge transfer efficiency and break the energy conversion limit of co-sensitization in DSSCs. The optimal configuration between porphyrin dyes and

  8. Patterning microparticles on a template of aggregated cationic dye.

    PubMed

    Wexler, Allan; Switalski, Steven; Bennett, Grace; Lindner, Kimberly; Baptiste, Kenny; Slater, Gary

    2015-02-01

    Patternwise aggregation of charged molecules on a surface is potentially a facile approach to generate a template on which to pattern oppositely charged microparticles. We report on the patterning of silica microparticles by a system comprising a photopatternable copolymer and an aggregate forming penta-cationic cyanine dye. A thin film of the copolymer, composed of a molar excess of styrenesulfonic acid oxime ester to cross-linkable glycidyl methacrylate monomomers, was exposed through a mask and neutralized, resulting in a pattern of hydrophobic areas, and where exposed, a hydrophilic cross-linked film with sodium poly(styrenesulfonate) domains. The occurrence and locus of aggregation of an aqueous solution of the dye, applied to the patterned surface was established by absorbance and fluorescence spectroscopy and atomic force microscopy. In exposed areas, dye is imbibed and aggregation induced in sodium styrenesulfonate domains internal to the layer, whereas in the unexposed areas the dye aggregates on the hydrophobic surface. Aqueous anionic silica microparticles applied to the dye treated patterned surface and then rinsed, are retained in the unexposed areas having cationic surface aggregates, but rejected from the exposed areas with internal dye aggregates as these areas retain net negative charge. Mask exposure, absent dye treatment, did not result in patterning as negatively charged microparticles were nowhere retained, and positively charged particles were everywhere retained. The extent of surface coverage by the dye in unexposed areas was deposition time dependent, and ranged from isolated patches covering about 20 percent of the polymer surface to a surface saturated layer, with silica particle patterning robust over the range of dye surface coverages studied. The force requirements to pattern the denser than water silica microparticles are identified, and particle and polymer film surface potentials that meet the critical repulsion force requirement

  9. Self-assembly properties of semiconducting donor-acceptor-donor bithienyl derivatives of tetrazine and thiadiazole-effect of the electron accepting central ring.

    PubMed

    Zapala, Joanna; Knor, Marek; Jaroch, Tomasz; Maranda-Niedbala, Agnieszka; Kurach, Ewa; Kotwica, Kamil; Nowakowski, Robert; Djurado, David; Pecaut, Jacques; Zagorska, Malgorzata; Pron, Adam

    2013-11-26

    Scanning tunneling microscopy was used to study the effect of the electron-accepting unit and the alkyl substituent's position on the type and extent of 2D supramolecular organization of penta-ring donor-acceptor-donor (DAD) semiconductors, consisting of either tetrazine or thiadiazole central acceptor ring symmetrically attached to two bithienyl groups. Microscopic observations of monomolecular layers on HOPG of four alkyl derivatives of the studied adsorbates indicate significant differences in their 2D organizations. Ordered monolayers of thiadiazole derivatives are relatively loose and, independent of the position of alkyl substituents, characterized by large intermolecular separation of acceptor units in the adjacent molecules located in the face-to-face configuration. The 2D supramolecular architecture in both derivatives of thiadiazole is very sensitive to the alkyl substituent's position. Significantly different behavior is observed for derivatives of tetrazine (which is a stronger electron acceptor). Stronger intermolecular DA interactions in these adsorbates generate an intermolecular shift in the monolayer, which is a dominant factor determining the 2D structural organization. As a consequence of this molecular arrangement, tetrazine groups (A segments) face thiophene rings (D segments) of the neighboring molecules. Monolayers of tetrazine derivatives are therefore much more densely packed and characterized by similar π-stacking of molecules independently of the position of alkyl substituents. Moreover, a comparative study of 3D supramolecular organization, deduced from the X-ray diffraction patterns, is also presented clearly confirming the polymorphism of the studied adsorbates. PMID:24228736

  10. First principles DFT study of dye-sensitized CdS quantum dots

    SciTech Connect

    Jain, Kalpna; Singh, Kh. S.; Kishor, Shyam; Josefesson, Ida; Odelius, Michael; Ramaniah, Lavanya M.

    2014-04-24

    Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6−311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.

  11. Donor-acceptor chemistry in the main group.

    PubMed

    Rivard, Eric

    2014-06-21

    This Perspective article summarizes recent progress from our laboratory in the isolation of reactive main group species using a general donor-acceptor protocol. A highlight of this program is the use of carbon-based donors in combination with suitable Lewis acidic acceptors to yield stable complexes of parent Group 14 element hydrides (e.g. GeH2 and H2SiGeH2). It is anticipated that this strategy could be extended to include new synthetic targets from throughout the Periodic Table with possible applications in bottom-up materials synthesis and main group element catalysis envisioned. PMID:24788390

  12. Acceptors in bulk and nanoscale ZnO

    NASA Astrophysics Data System (ADS)

    McCluskey, M. D.

    2012-02-01

    Zinc oxide (ZnO) is a semiconductor that emits bright UV light, with little wasted heat. This intrinsic feature makes it a promising material for energy-efficient white lighting, nano-lasers, and other optical applications. For devices to be competitive, however, it is necessary to develop reliable p-type doping. Although substitutional nitrogen has been considered as a potential p-type dopant for ZnO, theoretical and experimental work indicates that nitrogen is a deep acceptor and will not lead to p-type conductivity. This talk will highlight recent experiments on ZnO:N at low temperatures. A red/near-IR photoluminescence (PL) band is correlated with the presence of deep nitrogen acceptors. PL excitation (PLE) measurements show an absorption threshold of 2.26 eV, in good agreement with theory. Magnetic resonance experiments provide further evidence for this assignment. The results of these studies seem to rule out group-V elements as shallow acceptors in ZnO, contradicting numerous reports in the literature. If these acceptors do not work as advertised, is there a viable alternative? Optical studies on ZnO nanocrystals show some intriguing leads. At liquid-helium temperatures, a series of sharp IR absorption peaks arise from an unknown acceptor impurity. The data are consistent with a hydrogenic acceptor 0.46 eV above the valence band edge. While this binding energy is still too deep for many practical applications, it represents a significant improvement over the ˜ 1.3 eV binding energy for nitrogen acceptors. Nanocrystals present another twist. Due to their high surface-to-volume ratio, surface states are especially important. Specifically, electron-hole recombination at the surface give rises to a red luminescence band. From our PL and IR experiments, we have developed a ``unified'' model that attempts to explain acceptor and surface states in ZnO nanocrystals. This model could provide a useful framework for designing future nanoscale ZnO devices.

  13. Sodium acceptor doping of ZnO crystals

    NASA Astrophysics Data System (ADS)

    Parmar, Narendra S.; Joni, I. Made; Lynn, Kelvin G.

    2016-02-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion using sodium dispensers. Secondary-ion mass spectrometry measurement shows the diffusion of sodium with concentration ˜1×1018 cm-3 in near surface region. Photoluminescence (PL) measurements show donor acceptor pair (DAP) emission at 408 nm at room temperature which exhibits a blue-shift to 404 nm at 9 K. DC Hall measurements show the mixed conduction due to low Hall voltage in these samples. PL measurements and variable temperature resistivity measurements suggest that the sodium acceptor activation energy is ˜0.300 eV.

  14. Degradation characteristic of monoazo, diazo and anthraquinone dye by UV / H2O2 process

    NASA Astrophysics Data System (ADS)

    Abidin, Che Zulzikrami Azner; Fahmi, Muhammad Ridwan; Fazara, Md Ali Umi; Nadhirah, Siti Nurfatin

    2014-10-01

    In this study, the degradation characteristic of monoazo, diazo and anthraquinone dye by UV / H2O2 process was evaluated based on the trend of color, chemical oxygen demand (COD) and total organic carbon (TOC) removal. Three types of dyes consist of monoazo, diazo and anthraquinone dyes were used to compare the degradation mechanism of the dyes. The UV / H2O2 experiments were conducted in a laboratory scale cylindrical glass reactor operated in semi-batch mode. The UV/Vis characterization of monoazo, diazo and anthraquinone dye indicated that the rapid degradation of the dyes by UV / H2O2 process is meaningful with respect to decolourization, as a result of the azo bonds and substitute antraquinone chromophore degradation. However, this process is not efficient for aromatic amines removal. The monoazo MO was difficult to be decolorized than diazo RR120 dye, which imply that number of sulphonic groups in the dye molecules determines the reactivity with hydroxyl radical. The increased in COD removal is the evidence for oxidation and decreased in carbon content of dye molecules. TOC removal analysis shows that low TOC removal of monoazo MO and diazo RR120, as compared to anthraquinone RB19 may indicate an accumulation of by-products that are resistant to the H2O2 photolysis.

  15. Alzheimer's Dye Test?

    ERIC Educational Resources Information Center

    Science Teacher, 2005

    2005-01-01

    Massachusetts Institute of Technology (MIT) scientists have developed a new dye that could offer noninvasive early diagnosis of Alzheimer's disease, a discovery that could aid in monitoring the progression of the disease and in studying the efficacy of new treatments to stop it. The work is published in Angewandte Chemie. Today, doctors can only…

  16. Vegetable Dyeing of Wool

    ERIC Educational Resources Information Center

    Greenberg, Pearl

    1976-01-01

    In keeping with the Bicentennial celebration, many art teachers will find themselves "looking back" to crafts of the American past. Dyeing is certainly one that was used extensively and here a professor in a Fine Arts Department details how the process takes place. (Author/RK)

  17. Simultaneous SERS and surface-enhanced fluorescence from dye-embedded metal core-shell nanoparticles.

    PubMed

    Zhou, Yan; Zhang, Peng

    2014-05-21

    We demonstrate a methodology to prepare Au-core-Ag-shell nanoparticles displaying both SERS and surface-enhanced fluorescence (SEF) activities simultaneously by embedding dye molecules between the core and the shell. Polyelectrolytes are used to adjust the spacing and the dye position between the core and the shell. Layer-by-layer polyelectrolyte deposition can serve as an effective and flexible way to introduce various types of dye molecules into the nanostructures. Results from the spectral measurements shed light on the intricacy between SERS and SEF. PMID:24695881

  18. NIR fluorescent dyes: versatile vehicles for marker and probe applications

    NASA Astrophysics Data System (ADS)

    Patonay, Gabor; Chapman, Gala; Beckford, Garfield; Henary, Maged

    2013-02-01

    The use of the NIR spectral region (650-900 nm) is advantageous due to the inherently lower background interference and the high molar absorptivities of NIR chromophores. Near-Infrared (NIR) dyes are increasingly used in the biological and medical field. The binding characteristics of NIR dyes to biomolecules are possibly controlled by several factors, including hydrophobicity, size and charge just to mention a few parameters. Binding characteristics of symmetric carbocyanines and found that the hydrophobic nature of the NIR dye is only partially responsible for the binding strength. Upon binding to biomolecules significant fluorescence enhancement can be observed for symmetrical carbocyanines. This fluorescence amplification facilitates the detection of the NIR dye and enhances its utility as NIR reporter. This manuscript discusses some probe and marker applications of such NIR fluorescent dyes. One application discussed here is the use of NIR dyes as markers. For labeling applications the fluorescence intensity of the NIR fluorescent label can significantly be increased by enclosing several dye molecules in nanoparticles. To decrease self quenching dyes that have relatively large Stokes' shift needs to be used. This is achieved by substituting meso position halogens with amino moiety. This substitution can also serve as a linker to covalently attach the dye molecule to the nanoparticle backbone. We report here on the preparation of NIR fluorescent silica nanoparticles. Silica nanoparticles that are modified with aminoreactive moieties can be used as bright fluorescent labels in bioanalytical applications. A new bioanalytical technique to detect and monitor the catalytic activity of the sulfur assimilating enzyme using NIR dyes is reported as well. In this spectroscopic bioanalytical assay a family of Fischer based n-butyl sulfonate substituted dyes that exhibit distinct variation in absorbance and fluorescence properties and strong binding to serum albumin as its

  19. Boron(III)-Containing Donor-Acceptor Compound with Goldlike Reflective Behavior for Organic Resistive Memory Devices.

    PubMed

    Poon, Chun-Ting; Wu, Di; Yam, Vivian Wing-Wah

    2016-03-01

    A small-molecule-based boron(III)-containing donor-acceptor compound has been designed and synthesized. Interesting goldlike reflective behavior was observed in the neat thin-film sample from simple spin-coating preparation, which can serve as a potential organic thin-film optical reflector. The small thickness in nanometer range and the relatively smooth surface morphology, together with simple preparation and easy solution processability, are attractive features for opening up new avenues for the fabrication of reflective coatings. Moreover, this donor-acceptor compound has been employed in the fabrication of organic resistive memory device, which exhibited good performance with low turn-on voltage, small operating bias, large ON/OFF ratio, and long retention time. PMID:26879606

  20. Solvent-modified ultrafast decay dynamics in conjugated polymer/dye labeled single stranded DNA

    NASA Astrophysics Data System (ADS)

    Kim, Inhong; Kang, Mijeong; Woo, Han Young; Oh, Jin-Woo; Kyhm, Kwangseuk

    2015-07-01

    We have investigated that organic solvent (DMSO, dimethyl sulfoxide) modifies energy transfer efficiency between conjugated polymers (donors) and fluorescein-labeled single stranded DNAs (acceptors). In a mixture of buffer and organic solvent, fluorescence of the acceptors is significantly enhanced compared to that of pure water solution. This result can be attributed to change of the donor-acceptor environment such as decreased hydrophobicity of polymers, screening effect of organic solvent molecules, resulting in an enhanced energy transfer efficiency. Time-resolved fluorescence decay of the donors and the acceptors was modelled by considering the competition between the energy harvesting Foerster resonance energy transfer and the energy-wasting quenching. This enables to quantity that the Foerster distance (R0 = 43.3 Å) and resonance energy transfer efficiency (EFRET = 58.7 %) of pure buffer solution become R0 = 38.6 Å and EFRET = 48.0 % when 80% DMSO/buffer mixture is added.

  1. Dye-Sensitized Approaches to Photovoltaics

    NASA Astrophysics Data System (ADS)

    Grätzel, Michael

    2008-03-01

    Sensitization of wide band-gap semiconductors to photons of energy less than the band-gap is a key step in two technically important processes - panchromatic photography and photoelectrochemical solar cells. In both cases the photosensitive species is not the semiconductor - silver halide or metal oxide - but rather an electrochemically active dye. The gap between the highest occupied molecular level (HOMO) and the lowest unoccupied molecular level (LUMO) is less than the band-gap of the semiconductor with which it is associated. It can therefore absorb light of a wavelength longer than that to which the semiconductor itself is sensitive. The electrochemical process is initiated when the dye molecule relaxes from its photoexcited level by electron injection into the semiconductor, which therefore acts as a photoanode. If the dye is in contact with a redox electrolyte, the negative charge represented by the lost electron can be recovered from the reduced state of the redox system, which in return is regenerated by charge transfer from a cathode. An external load completes the electrical circuit. The system therefore represents a conversion of the energy of absorbed photons into an electrical current by a regenerative device in every functional respect analogous to a solid-state photovoltaic cell. As in any engineering system, choice of materials, their optimization and their synergy are essential to efficient operation. While a semiconductor-electrolyte contact is analogous to a Schottky contact, in that a barrier is established between two materials of different conduction mechanism, with the possibility of optical absorption, charge carrier pair generation and separation, it should be remembered that the photogenerated valence band hole in the semiconductor represents a powerful oxidizing agent. Given that the band-gap is related to the strength and therefore the stability of chemical bonding within the semiconductor, for narrow-gap materials the most likely

  2. Novel dye sensitizers of polymeric metal complexes with benzodithiophene derivatives as donor and their photovoltaic performance.

    PubMed

    Liao, Yanlong; Hu, Jiaomei; Xie, Qiufang; Peng, Dahai; Liu, Ye; Zhu, Chunxiao; Zhong, Chaofan

    2016-01-15

    Four novel donor-acceptor (D-A) type conjugated polymeric metal complexes (P1-P4) bearing benzodithiophene or carbazole derivative as donors were synthesized, characterized and applied as dye sensitizers in dye-sensitized solar cells (DSSCs). Salicylaldehyde derivative complexes acted as electron acceptors, Zn(II) or Cd(II) was chosen as the coordinated metal ion, and diaminomaleonitrile was ancillary ligand in these structures. The thermal, photophysical, electrochemical and photovoltaic properties of these polymeric metal complexes were investigated by FT-IR, GPC, TGA, DSC, UV-Vis absorption spectroscopy, elemental analysis, cyclic voltammetry (CV), J-V curves and IPCE plots. These polymer dyes exhibit good thermal stability for their application in DSSCs. The DSSC device based on P2 which contains benzodithiophene derivative as donor and Cd(II) as coordination ion, exhibited the highest power conversion efficiency of 2.43% (J(sc)=4.95 mA/cm(2), V(oc) =0.71 V, FF=69.3%) under AM 1.5 G solar irradiation. It indicates a new way to design dye sensitizers for DSSCs. PMID:26474240

  3. Novel dye sensitizers of polymeric metal complexes with benzodithiophene derivatives as donor and their photovoltaic performance

    NASA Astrophysics Data System (ADS)

    Liao, Yanlong; Hu, Jiaomei; Xie, Qiufang; Peng, Dahai; Liu, Ye; Zhu, Chunxiao; Zhong, Chaofan

    2016-01-01

    Four novel donor-acceptor (D-A) type conjugated polymeric metal complexes (P1-P4) bearing benzodithiophene or carbazole derivative as donors were synthesized, characterized and applied as dye sensitizers in dye-sensitized solar cells (DSSCs). Salicylaldehyde derivative complexes acted as electron acceptors, Zn(II) or Cd(II) was chosen as the coordinated metal ion, and diaminomaleonitrile was ancillary ligand in these structures. The thermal, photophysical, electrochemical and photovoltaic properties of these polymeric metal complexes were investigated by FT-IR, GPC, TGA, DSC, UV-Vis absorption spectroscopy, elemental analysis, cyclic voltammetry (CV), J-V curves and IPCE plots. These polymer dyes exhibit good thermal stability for their application in DSSCs. The DSSC device based on P2 which contains benzodithiophene derivative as donor and Cd(II) as coordination ion, exhibited the highest power conversion efficiency of 2.43% (Jsc = 4.95 mA/cm2, Voc = 0.71 V, FF = 69.3%) under AM 1.5 G solar irradiation. It indicates a new way to design dye sensitizers for DSSCs.

  4. Three Redox States of a Diradical Acceptor-Donor-Acceptor Triad: Gating the Magnetic Coupling and the Electron Delocalization.

    PubMed

    Souto, Manuel; Lloveras, Vega; Vela, Sergi; Fumanal, Maria; Ratera, Imma; Veciana, Jaume

    2016-06-16

    The diradical acceptor-donor-acceptor triad 1(••), based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)-vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1(•-), and triradical cation species, 1(•••+), obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations. PMID:27231856

  5. Organic dyes incorporating the dithieno[3',2':3,4;2″,3″:5,6]benzo[1,2-c]furazan moiety for dye-sensitized solar cells.

    PubMed

    Ni, Jen-Shyang; You, Jian-Hao; Hung, Wei-I; Kao, Wei-Siang; Chou, Hsien-Hsin; Lin, Jiann T

    2014-12-24

    New D-π-A'-π-A type sensitizers (JH dyes), comprised arylamine as the electron donor, dithieno[3',2':3,4;2″,3″:5,6]benzo[1,2-c]furazan (DTBF) in the conjugated spacer, and 2-cyanoacrylic acid as both the acceptor and anchor, have been synthesized. The JH dyes have broad absorption spectra covering the range of 350 to 600 nm with the highest molar extinction coefficient up to >40 000 M(-1) cm(-1). The dye-sensitized solar cells (DSSCs) fabricated from the dyes exhibited light-to-electricity conversions ranging from 1.42 to 6.18% under simulated AM 1.5 G illumination. Upon adding 10 mM CDCA as the coadsorbent, the best performance cell has the power conversion efficiency of 7.33%, which is close to that of N719-based standard DSSC (7.56%). PMID:25470385

  6. Photoswitchable semiconductor nanocrystals with self-regulating photochromic Förster resonance energy transfer acceptors

    NASA Astrophysics Data System (ADS)

    Díaz, Sebastián A.; Gillanders, Florencia; Jares-Erijman, Elizabeth A.; Jovin, Thomas M.

    2015-01-01

    Photoswitchable molecules and nanoparticles constitute superior biosensors for a wide range of industrial, research and biomedical applications. Rendered reversible by spontaneous or deterministic means, such probes facilitate many of the techniques in fluorescence microscopy that surpass the optical resolution dictated by diffraction. Here we have devised a family of photoswitchable quantum dots (psQDs) in which the semiconductor core functions as a fluorescence donor in Förster resonance energy transfer (FRET), and multiple photochromic diheteroarylethene groups function as acceptors upon activation by ultraviolet light. The QDs were coated with a polymer bearing photochromic groups attached via linkers of different length. Despite the resulting nominal differences in donor-acceptor separation and anticipated FRET efficiencies, the maximum quenching of all psQD preparations was 38±2%. This result was attributable to the large ultraviolet absorption cross-section of the QDs, leading to preferential cycloreversion of photochromic groups situated closer to the nanoparticle surface and/or with a more favourable orientation.

  7. A charge carrier transport model for donor-acceptor blend layers

    NASA Astrophysics Data System (ADS)

    Fischer, Janine; Widmer, Johannes; Kleemann, Hans; Tress, Wolfgang; Koerner, Christian; Riede, Moritz; Vandewal, Koen; Leo, Karl

    2015-01-01

    Highly efficient organic solar cells typically comprise donor-acceptor blend layers facilitating effective splitting of excitons. However, the charge carrier mobility in the blends can be substantially smaller than in neat materials, hampering the device performance. Currently, available mobility models do not describe the transport in blend layers entirely. Here, we investigate hole transport in a model blend system consisting of the small molecule donor zinc phthalocyanine (ZnPc) and the acceptor fullerene C60 in different mixing ratios. The blend layer is sandwiched between p-doped organic injection layers, which prevent minority charge carrier injection and enable exploiting diffusion currents for the characterization of exponential tail states from a thickness variation of the blend layer using numerical drift-diffusion simulations. Trap-assisted recombination must be considered to correctly model the conductivity behavior of the devices, which are influenced by local electron currents in the active layer, even though the active layer is sandwiched in between p-doped contacts. We find that the density of deep tail states is largest in the devices with 1:1 mixing ratio (Et = 0.14 eV, Nt = 1.2 × 1018 cm-3) directing towards lattice disorder as the transport limiting process. A combined field and charge carrier density dependent mobility model are developed for this blend layer.

  8. A charge carrier transport model for donor-acceptor blend layers

    SciTech Connect

    Fischer, Janine Widmer, Johannes; Koerner, Christian; Vandewal, Koen; Leo, Karl; Kleemann, Hans; Tress, Wolfgang; Riede, Moritz

    2015-01-28

    Highly efficient organic solar cells typically comprise donor-acceptor blend layers facilitating effective splitting of excitons. However, the charge carrier mobility in the blends can be substantially smaller than in neat materials, hampering the device performance. Currently, available mobility models do not describe the transport in blend layers entirely. Here, we investigate hole transport in a model blend system consisting of the small molecule donor zinc phthalocyanine (ZnPc) and the acceptor fullerene C{sub 60} in different mixing ratios. The blend layer is sandwiched between p-doped organic injection layers, which prevent minority charge carrier injection and enable exploiting diffusion currents for the characterization of exponential tail states from a thickness variation of the blend layer using numerical drift-diffusion simulations. Trap-assisted recombination must be considered to correctly model the conductivity behavior of the devices, which are influenced by local electron currents in the active layer, even though the active layer is sandwiched in between p-doped contacts. We find that the density of deep tail states is largest in the devices with 1:1 mixing ratio (E{sub t} = 0.14 eV, N{sub t} = 1.2 × 10{sup 18 }cm{sup −3}) directing towards lattice disorder as the transport limiting process. A combined field and charge carrier density dependent mobility model are developed for this blend layer.

  9. 18F-Labeled Silicon-Based Fluoride Acceptors: Potential Opportunities for Novel Positron Emitting Radiopharmaceuticals

    PubMed Central

    Bernard-Gauthier, Vadim; Wängler, Carmen; Wängler, Bjoern; Schirrmacher, Ralf

    2014-01-01

    Background. Over the recent years, radiopharmaceutical chemistry has experienced a wide variety of innovative pushes towards finding both novel and unconventional radiochemical methods to introduce fluorine-18 into radiotracers for positron emission tomography (PET). These “nonclassical” labeling methodologies based on silicon-, boron-, and aluminium-18F chemistry deviate from commonplace bonding of an [18F]fluorine atom (18F) to either an aliphatic or aromatic carbon atom. One method in particular, the silicon-fluoride-acceptor isotopic exchange (SiFA-IE) approach, invalidates a dogma in radiochemistry that has been widely accepted for many years: the inability to obtain radiopharmaceuticals of high specific activity (SA) via simple IE. Methodology. The most advantageous feature of IE labeling in general is that labeling precursor and labeled radiotracer are chemically identical, eliminating the need to separate the radiotracer from its precursor. SiFA-IE chemistry proceeds in dipolar aprotic solvents at room temperature and below, entirely avoiding the formation of radioactive side products during the IE. Scope of Review. A great plethora of different SiFA species have been reported in the literature ranging from small prosthetic groups and other compounds of low molecular weight to labeled peptides and most recently affibody molecules. Conclusions. The literature over the last years (from 2006 to 2014) shows unambiguously that SiFA-IE and other silicon-based fluoride acceptor strategies relying on 18F− leaving group substitutions have the potential to become a valuable addition to radiochemistry. PMID:25157357

  10. 1,8-Naphthalimide-Based Planar Small Molecular Acceptor for Organic Solar Cells.

    PubMed

    Zhang, Jicheng; Zhang, Xuejuan; Xiao, Hongmei; Li, Guangwu; Liu, Yahui; Li, Cuihong; Huang, Hui; Chen, Xuebo; Bo, Zhishan

    2016-03-01

    Four small molecular acceptors (SM1-4) comprising a central benzene core, two thiophene bridges and two 1,8-naphthalimide (NI) terminal groups were designed and synthesized by direct C-H activation. SM1 has a planar chemical structure and forms H-aggregation as films. By attachment of different substituents on the central benzene ring, the dihedral angles between the two NI end groups of SM1-4 gradually increased, leading to a gradual decrease of planarity. SM1-4 all possess a high-lying LUMO level, matching with wide band gap (WBG) polymer donors which usually have a high-lying LUMO level. When used in OSCs, devices based on SM1 and WBG donor PCDTBT-C12 gave higher electron mobility, superior film morphology and better photovoltaic performance. After optimization, a PCE of 2.78% with a V(oc) of 1.04 V was achieved for SM1 based devices, which is among the highest PCEs with a V(oc) higher than 1 V. Our results have demonstrated that NI based planar small molecules are potential acceptors for WBG polymer based OSCs. PMID:26845638

  11. Construction of an upconversion nanoprobe with few-atom silver nanoclusters as the energy acceptor.

    PubMed

    Xiao, Yan; Zeng, Lingyu; Xia, Tian; Wu, Zhengjun; Liu, Zhihong

    2015-04-27

    Herein we report that few-atom silver nanoclusters (Ag NCs) can be effective energy acceptors for upconversion phosphors (UCPs). A luminescence resonance energy transfer (LRET) probe for biothiols was constructed by decorating UCPs with dithiol-stabilized Ag NCs. Owing to the unique properties of ultrasmall NCs, properties which bridge the gap between those of small molecules and those of nanoparticles, the use of approximately 1.9 nm Ag NCs as energy acceptors endows the probe with high energy-transfer efficiency, good biocompatibility, and flexibility. The UCP-Ag NC nanoprobe enables rapid and robust target assay in solutions. It was also uploaded into living cells and used to detect intracellular biothiol levels with high discrimination. Moreover, the probe shows transportability in vivo and can be used for tissue imaging. The facile growth of few-atom metal NCs on diverse templates may enable the development of various nanoprobes combining UCPs and metal NCs. PMID:25753304

  12. Optical spacing effect in organic photovoltaic cells incorporating a dilute acceptor layer

    SciTech Connect

    Menke, S. Matthew; Lindsay, Christopher D.; Holmes, Russell J.

    2014-06-16

    The addition of spacing layers in organic photovoltaic cells (OPVs) can enhance light absorption by optimizing the spatial distribution of the incident optical field in the multilayer structure. We explore the optical spacing effect in OPVs achieved using a diluted electron acceptor layer of C{sub 60}. While optical spacing is often realized by optimizing buffer layer thickness, we find that optical spacing via dilution leads to cells with similar or enhanced photocurrent. This is observed despite a smaller quantity of absorbing molecules, suggesting a more efficient use of absorbed photons. In fact, dilution is found to concentrate optical absorption near the electron donor-acceptor interface, resulting in a marked increase in the exciton diffusion efficiency. Contrasting the use of changes in thickness to engineer optical absorption, the use of dilution does not significantly alter the overall thickness of the OPV. Optical spacing via dilution is shown to be a viable alternative to more traditional optical spacing techniques and may be especially useful in the continued optimization of next-generation, tandem OPVs where it is important to minimize competition for optical absorption between individual sub-cells.

  13. Optofluidic microcavities: Dye-lasers and biosensors

    PubMed Central

    Chen, Y.; Lei, L.; Zhang, K.; Shi, J.; Wang, L.; Li, H.; Zhang, X. M.; Wang, Y.; Chan, H. L. W.

    2010-01-01

    Optofluidic microcavities are integrated elements of microfluidics that can be explored for a large variety of applications. In this review, we first introduce the physics basis of optical microcavities and microflow control. Then, we describe four types of optofluidic dye lasers developed so far based on both simple and advanced device fabrication technologies. To illustrate the application potential of such devices, we present two types of laser intracavity measurements for chemical solution and single cell analyses. In addition, the possibility of single molecule detection is discussed. All these recent achievements demonstrated the great importance of the topics in biology and several other disciplines. PMID:24753719

  14. Covalent non-fused tetrathiafulvalene-acceptor systems.

    PubMed

    Pop, Flavia; Avarvari, Narcis

    2016-06-28

    Covalent donor-acceptor (D-A) systems have significantly contributed to the development of many organic materials and to molecular electronics. Tetrathiafulvalene (TTF) represents one of the most widely studied donor precursors and has been incorporated into the structure of many D-A derivatives with the objective of obtaining redox control and modulation of the intramolecular charge transfer (ICT), in order to address switchable emissive systems and to take advantage of its propensity to form regular stacks in the solid state. In this review, we focus on the main families of non-fused TTF-acceptors, which are classified according to the nature of the acceptor: nitrogen-containing heterocycles, BODIPY, perylenes and electron poor unsaturated hydrocarbons, as well as radical acceptors. We describe herein the most representative members of each family with a brief mention of their synthesis and a special focus on their D-A characteristics. Special attention is given to ICT and its modulation, fluorescence quenching and switching, photoconductivity, bistability and spin distribution by discussing and comparing spectroscopic and electrochemical features, photophysical properties, solid-state properties and theoretical calculations. PMID:27193500

  15. Fine structure of the Mn acceptor in GaAs

    NASA Astrophysics Data System (ADS)

    Krainov, I. V.; Debus, J.; Averkiev, N. S.; Dimitriev, G. S.; Sapega, V. F.; Lähderanta, E.

    2016-06-01

    We reveal the electronic level structure of the Mn acceptor, which consists of a valence-band hole bound to an Mn2 + ion, in presence of applied uniaxial stress and an external magnetic field in bulk GaAs. Resonant spin-flip Raman scattering is used to measure the g factor of the AMn0 center in the ground and excited states with the total angular momenta F =1 and F =2 and characterize the optical selection rules of the spin-flip transitions between these Mn-acceptor states. We determine the random stress fields near the Mn acceptor, the constant of the antiferromagnetic exchange interaction between the valence-band holes and the electrons of the inner Mn2 + shell as well as the deformation potential for the exchange energy. The p -d exchange energy, in particular, decreases significantly with increasing compressive stress. By combining the experimental Raman study with the developed theoretical model on the scattering efficiency, in which also the random local and external uniaxial stresses and magnetic field are considered, the fine structure of the Mn acceptor is determined in full detail.

  16. Coumarin-bearing triarylamine sensitizers with high molar extinction coefficient for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Changjian; Gao, Jianrong; Cui, Yanhong; Li, Ting; Han, Liang

    2015-01-01

    Coumarin unit is introduced into triarylamine and three organic sensitizers are designed and synthesized with triarylamine bearing coumarin moiety as the electron donor, conjugated system containing thiophene unit as the π-bridge, and cyanoacetic acid moiety as the electron acceptor. The light-harvesting capabilities and photovoltaic performance of these dyes are investigated systematically with the comparison of different π-bridges. High molar extinction coefficients are observed in these triarylamine dyes and the photocurrent and photovoltage are increased with the introduction of another thiophene or benzene. Optimal photovoltaic performance (η = 6.24%, Voc = 690 mV, Jsc = 14.33 mA cm-2, and ff = 0.63) is observed in the DSSC based on dye with thiophene-phenyl unit as the π-conjugated bridge under 100 mW cm-2 simulated AM 1.5 G solar irradiation.

  17. High-repetition-rate, narrow-band dye lasers with water as a solvent for dyes

    NASA Astrophysics Data System (ADS)

    Ray, Alok K.; Sinha, Sucharita; Kundu, Soumitra; Kumar, Sasi; Nair, Sivagiriyal Karunakaran Sreenivasan; Pal, Tamal; Dasgupta, Kamalesh

    2002-03-01

    The performance of a copper vapor laser-pumped narrow-band dye laser in oscillator-amplifier configuration with water-based binary mixture solvents is described. Although oscillator efficiency in water-surfactant (sodium lauryl sulfate) solvent was comparable with that that employed pure ethanolic solvent, amplifier efficiency was found to be lower. Experiments that were carried out with vertically polarized pump beams and either horizontally or vertically polarized signal beams show that, in case of both the pump and signal having orthogonal polarization (horizontal) and same polarization (vertical), the extraction efficiency for both ethanolic and water-micelle media increased substantially from 15.7% to 18.5% and from 10% to 12.5%, respectively. However, the relative difference remained nearly the same, indicating that a slower orientational diffusion of excited dye molecules in a micellar medium is not responsible for a decrease in amplifier efficiency. Amplifier efficiency comparable with that containing ethanolic dye solutions could be obtained with a binary solvent that comprises a mixture of water and about 30% n-propanol. The performances of two efficient dyes, Rhodamine-6G and Kiton Red S, using water-based solvents were studied.

  18. Development of imide- and imidazole-containing electron acceptors for use in donor-acceptor conjugated compounds and polymers

    NASA Astrophysics Data System (ADS)

    Li, Duo

    Conjugated organic compounds and polymers have attracted significant attention due to their potential application in electronic devices as semiconducting materials, such as organic solar cells (OSCs). In order to tune band gaps, donor-acceptor (D-A) structure is widely used, which has been proved to be one of the most effective strategies. This thesis consists of three parts: 1) design, syntheses and characterization of new weak acceptors based on imides and the systematic study of the structure-property relationship; (2) introduction of weak and strong acceptors in one polymer to achieve a broad coverage of light absorption and improve the power conversion efficiency (PCE); (3) modification of benzothiadiazole (BT) acceptor in order to increase the electron withdrawing ability. Imide-based electron acceptors, 4-(5-bromothiophen-2-y1)-2-(2-ethylhexyl)-9- phenyl- 1H-benzo[f]isoindole-1,3(2H)-dione (BIDO-1) and 4,9-bis(5-bromothiophen-2-yl)-2-(2-ethylhexyl)-benzo[f]isoindole-1,3-dione (BIDO-2), were designed and synthesized. In this design, naphthalene is selected as its main core to maintain a planar structure, and thienyl groups are able to facilitate the bromination reaction and lower the band gap. BIDO-1 and BIDO-2 were successfully coupled with different donors by both Suzuki cross-coupling and Stille cross-coupling reactions. Based on the energy levels and band gaps of the BIDO-containing compounds and polymers, BIDO-1 and BIDO-2 are proved to be weak electron acceptors. Pyromellitic diimide (PMDI) was also studied and found to be a stronger electron acceptor than BIDO . In order to obtain broad absorption coverage, both weak acceptor ( BIDO-2) and strong acceptor diketopyrrolopyrrole (DPP) were introduced in the same polymer. The resulting polymers show two absorption bands at 400 and 600 nm and two emission peaks at 500 and 680 nm. The band gaps of the polymers are around 1.6 eV, which is ideal for OSC application. The PCE of 1.17% was achieved. Finally

  19. Anaerobic methanotrophy in tidal wetland: Effects of electron acceptors

    NASA Astrophysics Data System (ADS)

    Lin, Li-Hung; Yu, Zih-Huei; Wang, Pei-Ling

    2016-04-01

    Wetlands have been considered to represent the largest natural source of methane emission, contributing substantially to intensify greenhouse effect. Despite in situ methanogenesis fueled by organic degradation, methanotrophy also plays a vital role in controlling the exact quantity of methane release across the air-sediment interface. As wetlands constantly experience various disturbances of anthropogenic activities, biological burrowing, tidal inundation, and plant development, rapid elemental turnover would enable various electron acceptors available for anaerobic methanotrophy. The effects of electron acceptors on stimulating anaerobic methanotrophy and the population compositions involved in carbon transformation in wetland sediments are poorly explored. In this study, sediments recovered from tidally influenced, mangrove covered wetland in northern Taiwan were incubated under the static conditions to investigate whether anaerobic methanotrophy could be stimulated by the presence of individual electron acceptors. Our results demonstrated that anaerobic methanotrophy was clearly stimulated in incubations amended with no electron acceptor, sulfate, or Fe-oxyhydroxide. No apparent methane consumption was observed in incubations with nitrate, citrate, fumarate or Mn-oxides. Anaerobic methanotrophy in incubations with no exogenous electron acceptor appears to proceed at the greatest rates, being sequentially followed by incubations with sulfate and Fe-oxyhydroxide. The presence of basal salt solution stimulated methane oxidation by a factor of 2 to 3. In addition to the direct impact of electron acceptor and basal salts, incubations with sediments retrieved from low tide period yielded a lower rate of methane oxidation than from high tide period. Overall, this study demonstrates that anaerobic methanotrophy in wetland sediments could proceed under various treatments of electron acceptors. Low sulfate content is not a critical factor in inhibiting methane

  20. Cell tracing dyes significantly change single cell mechanics

    PubMed Central

    Lulevich, Valentin; Shih, Yi-Ping; Lo, Su Hao; Liu, Gang-yu

    2009-01-01

    Cell tracing dyes are very frequently utilized in cellular biology research because they provide highly sensitive fluorescent tags that do not compromise cellular functions such as growth and proliferation. In many investigations concerning cellular adhesion and mechanics, fluorescent dyes have been employed with the assumption of little impact on the results. Using the single-cell compression technique developed by our team, the single-cell mechanics of MDA-MB-468 and MLC-SV40 cells were investigated as a function of dye uptake. Cell tracing dyes increase living cell stiffness 3-6 times and cell-to-probe adhesion up to 7 times. These results suggest a more significant effect than toxins, such as Thrombin. A simple analytical model was derived to enable the extraction of the Young’s moduli of the cell membrane and cytoskeleton from the force-deformation profiles measured for individual cells. The increase in Young’s modulus of the membrane is 3-7 times, which is more significant than that of the cytoskeleton (1.1-3.4 times). We propose that changes in cell mechanics upon the addition of fluorescent tracing dye are primarily due to incorporation of amphiphilic dye molecules into the cellular plasma membrane, which increases the lateral interaction among phospholipid chains and thus enhances their rigidity and adhesion. PMID:19366241

  1. Influence of the donor size in D-π-A organic dyes for dye-sensitized solar cells.

    PubMed

    Yang, Jiabao; Ganesan, Paramaguru; Teuscher, Joël; Moehl, Thomas; Kim, Yong Joo; Yi, Chenyi; Comte, Pascal; Pei, Kai; Holcombe, Thomas W; Nazeeruddin, Mohammad Khaja; Hua, Jianli; Zakeeruddin, Shaik M; Tian, He; Grätzel, Michael

    2014-04-16

    We report two new molecularly engineered push-pull dyes, i.e., YA421 and YA422, based on substituted quinoxaline as a π-conjugating linker and bulky-indoline moiety as donor and compared with reported IQ4 dye. Benefitting from increased steric hindrance with the introduction of bis(2,4-dihexyloxy)benzene substitution on the quinoxaline, the electron recombination between redox electrolyte and the TiO2 surface is reduced, especially in redox electrolyte employing Co(II/III) complexes as redox shuttles. It was found that the open circuit photovoltages of IQ4, YA421, and YA422 devices with cobalt-based electrolyte are higher than those with iodide/triiodide electrolyte by 34, 62, and 135 mV, respectively. Moreover, the cells employing graphene nanoplatelets on top of gold spattered film as a counter electrode (CE) show lower charge-transfer resistance compared to platinum as a CE. Consequently, YA422 devices deliver the best power conversion efficiency due to higher fill factor, reaching 10.65% at AM 1.5 simulated sunlight. Electrochemical impedance spectroscopy and transient absorption spectroscopy analysis were performed to understand the electrolyte influence on the device performances with different counter electrode materials and donor structures of donor-π-acceptor dyes. Laser flash photolysis experiments indicate that even though the dye regeneration of YA422 is slower than that of the other two dyes, the slower back electron transfer of YA422 contributes to the higher device performance. PMID:24655036

  2. Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C60 donor-acceptor conjugate.

    PubMed

    Martínez, Juan Pablo; Solà, Miquel; Voityuk, Alexander A

    2016-06-01

    Fullerene-based molecular heterojunctions such as the [6,6]-pyrrolidine-C60 donor-acceptor conjugate containing triphenylamine (TPA) are potential materials for high-efficient dye-sensitized solar cells. In this work, we estimate the rate constants for the photoinduced charge separation and charge recombination processes in TPA-C60 using the unrestricted and time-dependent DFT methods. Different schemes are applied to evaluate excited state properties and electron transfer parameters (reorganization energies, electronic couplings, and Gibbs energies). The use of open-shell singlet or triplet states, several density functionals, and continuum solvation models is discussed. Strengths and limitations of the computational approaches are highlighted. The present benchmark study provides an overview of the expected performance of DFT-based methodologies in the description of photoinduced charge transfer reactions in fullerene heterojunctions. © 2016 Wiley Periodicals, Inc. PMID:26992355

  3. Single-molecule Förster resonance energy transfer study of protein dynamics under denaturing conditions

    PubMed Central

    Kuzmenkina, Elza V.; Heyes, Colin D.; Nienhaus, G. Ulrich

    2005-01-01

    Proteins are highly complex systems, exhibiting a substantial degree of structural variability in their folded state. In the presence of denaturants, the heterogeneity is greatly enhanced, and fluctuations among vast numbers of folded and unfolded conformations occur via many different pathways. Here, we have studied the structure and dynamics of the small enzyme ribonuclease HI (RNase H) in the presence of the chemical denaturant guanidinium chloride (GdmCl) using single-molecule fluorescence microscopy, with a particular focus on the characterization of the unfolded-state ensemble. A dye pair was specifically attached to the enzyme to measure structural changes through Förster resonance energy transfer (FRET). Enzyme immobilization on star-polymer surfaces that were specially developed for negligible interaction with folded and unfolded proteins enabled us to monitor conformational changes of individual proteins for several hundred seconds. FRET efficiency histograms were calculated from confocal scan images. They showed an expansion of the unfolded proteins with increasing GdmCl concentration. Cross-correlation analysis of donor and acceptor fluorescence intensity time traces from single molecules revealed reconfiguration of the polypeptide chain on a timescale of ≈20 μs at 1.7 M GdmCl. Slow conformational dynamics gave rise to characteristic, stepwise FRET efficiency changes. Transitions between folded and unfolded enzyme molecules occurred on the 100-s timescale, in excellent agreement with bulk denaturation experiments. Transitions between unfolded conformations were more frequent, with characteristic times of ≈2 s. These data were analyzed to obtain information on the free energy landscape of RNase H in the presence of chemical denaturants. PMID:16221762

  4. Cyanine dyes with high absorption cross section as donor chromophores in energy transfer primers

    SciTech Connect

    Hung, Su-Chung; Ju, Jingyue; Mathies, R.A.; Glazer, A.N.

    1996-12-01

    Energy transfer (ET) fluorescent primers are significantly superior to single dye-labeled primers for DNA sequencing and multiplex genetic analyses. We describe here ET primers in which a donor chromophore with a large absorption cross section but a low fluorescence quantum yield is exploited to increase the Stokes-shifted fluorescence emission of acceptor dyes. The new ET primers have 3-({var_epsilon}-carboxy-pentyl)-3{prime}-ethyl-5,5{prime}-dimethyloxacarbocyanine (CYA; {var_epsilon}{sub M}{sup 488 nm} 142,000 M{sup -1} cm{sup -1}) at the 5{prime}-end as a common energy donor, and fluorescein or rhodamine derivatives (FAM, R6G, TAMRA, and ROX), attached to a modified thymidine 10 bases away within the primer sequence, as acceptors. With 488-nm excitation, the fluorescence emission intensity of these four ET primers is 1.4- to 24-fold stronger than that of the corresponding primers labeled only with the single acceptor dye. When compared with the corresponding ET primers with a fluorescein derivative (FAM; {var_epsilon}{sub M}{sup 488 nm} 60,000 M{sup -1} cm{sup -1}) as donor, the fluorescence emissions of primers with CYA as donor and FAM, R6G, TAMRA, and ROX as acceptors are respectively 0.8-, 1.0-, 1.7-, and 1.7-fold as intense. The low fluorescence quantum yield of the CYA donor resulted in distinct fluorescence signals for the DNA-sequencing fragments with much lower crosstalk between the four detection channels than that seen with ET primers based on a FAM donor. With single-stranded M13mp18 DNA as the template, the CYA ET primers provided DNA sequences on a four-color capillary sequencer with 100% accuracy in the first 500 bases. 15 refs., 7 figs., 1 tab.

  5. Dye removal from textile dye wastewater using recycled alum sludge.

    PubMed

    Chu, W

    2001-09-01

    The removal of dyes from textile dying wastewater by recycled alum sludge (RAS) generated by the coagulation process itself was studied and optimized. One hydrophobic and one hydrophilic dye were used as probes to examine the performance of this process. It was found that RAS is a good way of removing hydrophobic dye in wastewater, while simultaneously reducing the fresh alum dosage, of which one third of the fresh alum can be saved. The back-diffusion of residued dye from the recycling sludge is detected but is easily controlled as long as a small amount of fresh alum is added to the system. The use of RAS is not recommended for the removal of hydrophilic dyes, since the high solubility characteristics of such dyes can cause deterioration in the water quality during recycling. PMID:11487111

  6. Fiberized fluorescent dye microtubes

    NASA Astrophysics Data System (ADS)

    Vladev, Veselin; Eftimov, Tinko

    2013-03-01

    In the present work we study the effect of the length of fluorescent dye-filled micro-capillaries on the fluorescence spectra. Two types of micro-capillaries have been studied: a 100 μm inner diameter fused silica capillary with a transparent coating and one of the holes of a fiber optic glass ferrule with 125 μm inner diameter. The tubes were filled with solutions of Rhodamine 6G dissolved in ethanol and then in glycerin. Experimental data show that the maximum fluorescence and the largest spectral widths are observed for a sample length of about 0.25 mm for the used concentration. This results show that miniature tunable fiberized dye lasers can be developed using available standard micro-and fibre-optic components.

  7. Azaquinolone dye lasers

    DOEpatents

    Hammond, Peter R.; Atkins, Ronald L.; Henry, Ronald A.; Fletcher, Aaron N.

    1978-01-01

    A dye laser comprising a laser dye solution of a compound having the general structure: ##STR1## wherein at least one of the 5, 6 and 8 ring positions is occupied by a nitrogen atom in lieu of the corresponding CR group and X is OH, alkoxy, or amino including amino substituted by at least one of the following: alkyl, aryl, acyl, aracyl, a group which taken together with the nitrogen atom of the amino group forms a heterocyclic ring, or part of one or two 5 or 6 membered aliphatic heterocyclic rings attached to ring A at positions 6 or 8 or both depending on where the N in ring A is located. R.sub.1, R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.8 are hydrogen or other groups as defined below. The compounds lase in the blue to near ultraviolet region.

  8. Azacoumarin dye lasers

    DOEpatents

    Hammond, Peter R.; Atkins, Ronald L.; Henry, Ronald A.; Fletcher, Aaron N.

    1978-01-01

    A dye laser comprising a laser dye solution of a compound having the general structure: ##STR1## wherein at least one of the 5, 6 and 8 ring positions is occupied by a nitrogen atom in lieu of the corresponding CR group and X is OH, alkoxy, or amino including amino substituted by at least one of the following: alkyl, aryl, acyl, aracyl, a group which taken together with the nitrogen atom of the amino group forms a heterocyclic ring, or part of one or two 5 or 6 membered aliphatic heterocyclic rings attached to ring A at positions 6 or 8 or both depending on where the N in ring A is located. R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.8 are hydrogen or other groups as defined below. The compounds lase in the blue-green to near ultraviolet region.

  9. Photovoltaic and Spectral Properties of Conjugated Polymer Poly(3-octylthiophene) Doped with Various Acceptor Materials

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Hsien; Chen, Wei-Hsin; Su, Mu-Ting; Lai, Tzay-Shing; Lee, Wei

    2010-08-01

    We propose a novel approach for enhancement of efficiency of polymer-based photovoltaic devices by means of a low-molar-mass liquid crystal as a dopent. The active layers of the photovoltaic cells are primarily fabricated from the conjugated polymer poly(3-octylthiophene) as well as various acceptor substances including single-wall carbon nanotubes, buckminsterfullerene and the nematic liquid crystal E7 for comparison. The current-voltage characteristics are measured in dark and under green light illumination at wavelength of 514.5 nm. The power conversion efficiency for the active layer doped with E7 is the best among all cells in the simplest monolayer cell structure. Owing to the superior miscibility and orientational order of the nematic liquid crystal, E7 molecules may have promoted a composite film with fewer defects and locally helped the macromolecules align more orderly and consequently improved the charge-carrier transport, leading to the higher photocurrent and power conversion efficiency.

  10. Study of the generation characteristics of laser converters with dye-based wide-aperture solid--liquid active elements

    SciTech Connect

    Eremenko, A.S.; Zemskii, V.I.; Kolesnikov, Y.L.; Malinin, B.G.; Meshkovsky, I.K.; Savkin, N.P.; Stepanov, V.E.; Shildyaev, V.S.

    1986-11-01

    The lasing characteristics of an active element, consisting of a fine porous silicate matrix, has been studied. Molecules of a dye (rhodamine 6G) and an ethanol solution of the same dye were introduced into the cells. It has been shown that under conditions of large heat release (when thermooptical distortions begin to appear in the dye solutions), the solid--liquid element preserves the stability of its own lasing characteristics.

  11. Organic Semiconductors based on Dyes and Color Pigments.

    PubMed

    Gsänger, Marcel; Bialas, David; Huang, Lizhen; Stolte, Matthias; Würthner, Frank

    2016-05-01

    Organic dyes and pigments constitute a large class of industrial products. The utilization of these compounds in the field of organic electronics is reviewed with particular emphasis on organic field-effect transistors. It is shown that for most major classes of industrial dyes and pigments, i.e., phthalocyanines, perylene and naphthalene diimides, diketopyrrolopyrroles, indigos and isoindigos, squaraines, and merocyanines, charge-carrier mobilities exceeding 1 cm(2) V(-1) s(-1) have been achieved. The most widely investigated molecules due to their n-channel operation are perylene and naphthalene diimides, for which even values close to 10 cm(2) V(-1) s(-1) have been demonstrated. The fact that all of these π-conjugated colorants contain polar substituents leading to strongly quadrupolar or even dipolar molecules suggests that indeed a much larger structural space shows promise for the design of organic semiconductor molecules than was considered in this field traditionally. In particular, because many of these dye and pigment chromophores demonstrate excellent thermal and (photo-)chemical stability in their original applications in dyeing and printing, and are accessible by straightforward synthetic protocols, they bear a particularly high potential for commercial applications in the area of organic electronics. PMID:27028553

  12. Simultaneous micro-electromembrane extractions of anions and cations using multiple free liquid membranes and acceptor solutions.

    PubMed

    Kubáň, Pavel; Boček, Petr

    2016-02-18

    Micro-electromembrane extractions (μ-EMEs) across free liquid membranes (FLMs) were applied to simultaneous extractions of anions and cations. A transparent narrow-bore polymeric tubing was filled with adjacent plugs of μL volumes of aqueous and organic solutions, which formed a stable five-phase μ-EME system. For the simultaneous μ-EMEs of anions and cations, aqueous donor solution was the central phase, which was sandwiched between two organic FLMs and two aqueous acceptor solutions. On application of electric potential, anions and cations in the donor solution migrated across the two FLMs and into the two peripheral acceptor solutions in the direction of anode and cathode, respectively. Visual monitoring of anionic (tartrazine) and cationic (phenosafranine) dye confirmed their simultaneous μ-EMEs and their rapid (in less than 5 min) transfers into anolyte and catholyte, respectively. The concept of simultaneous μ-EMEs was further examined with selected model analytes; KClO4 was used for μ-EMEs of inorganic anions and cations and ibuprofen and procaine for μ-EMEs of acidic and basic drugs. Quantitative analyses of the resulting acceptor solutions were carried out by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D). Good extraction recoveries (91-94%) and repeatability of peak areas (≤6.3%) were achieved for 5 min μ-EMEs of K(+) and ClO4(-). Extraction recoveries and repeatability of peak areas for 5 min μ-EMEs of ibuprofen and procaine were also satisfactory and ranged from 35 to 63% and 7.6 to 11.3%, respectively. Suitability of the presented micro-extraction procedure was further demonstrated on simultaneous μ-EMEs with subsequent CE-C(4)D of ibuprofen and procaine from undiluted human urine samples. PMID:26826693

  13. DFT and TD-DFT study on geometries, electronic structures and electronic absorption of some metal free dye sensitizers for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Mohr, T.; Aroulmoji, V.; Ravindran, R. Samson; Müller, M.; Ranjitha, S.; Rajarajan, G.; Anbarasan, P. M.

    2015-01-01

    The geometries, electronic structures, polarizabilities and hyperpolarizabilities of 2-hydroxynaphthalene-1,4-dione (henna1), 3-(5-((1E)-2-(1,4-dihydro-1,4-dioxonaphthalen-3-yloxy) vinyl) thiophen-2-yl)-2-isocyanoacrylic acid (henna2) and anthocyanin dye sensitizers were studied based on density functional theory (DFT) using the hybrid functional B3LYP. The Ultraviolet-Visible (UV-Vis) spectrum was investigated by using a hybrid method which combines the properties and dynamics of many-body in the presence of time-dependent (TD) potentials, i.e. TDSCF-DFT (B3LYP). Features of the electronic absorption spectrum in the visible and near-UV regions were plotted and assigned based on TD-DFT calculations. Due to the absorption, bands of the metal-organic compound are n → π* present. The calculated results suggest that the three lowest energy excited states of the investigated dye sensitizers are due to photoinduced electron transfer processes. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer is owing to an electron injection process from excited dye to the semiconductor's conduction band. The role of linking the henna1 dye with a carboxylic acid via a thiophene bridge was analyzed. The results are that using a stronger π-conjugate bridge as well as a strong donator and acceptor group enhances the efficiency.

  14. Photoinduced hole-transfer in semiconducting polymer/low-bandgap cyanine dye blends: evidence for unit charge separation quantum yield.

    PubMed

    Castro, Fernando A; Benmansour, Hadjar; Moser, Jacques-E; Graeff, Carlos F O; Nüesch, Frank; Hany, Roland

    2009-10-21

    Power-conversion efficiencies of organic heterojunction solar cells can be increased by using semiconducting donor-acceptor materials with complementary absorption spectra extending to the near-infrared region. Here, we used continuous wave fluorescence and absorption, as well as nanosecond transient absorption spectroscopy to study the initial charge transfer step for blends of a donor poly(p-phenylenevinylene) derivative and low-band gap cyanine dyes serving as electron acceptors. Electron transfer is the dominant relaxation process after photoexcitation of the donor. Hole transfer after cyanine photoexcitation occurs with an efficiency close to unity up to dye concentrations of approximately 30 wt%. Cyanines present an efficient self-quenching mechanism of their fluorescence, and for higher dye loadings in the blend, or pure cyanine films, this process effectively reduces the hole transfer. Comparison between dye emission in an inert polystyrene matrix and the donor matrix allowed us to separate the influence of self-quenching and charge transfer mechanisms. Favorable photovoltaic bilayer performance, including high open-circuit voltages of approximately 1 V confirmed the results from optical experiments. The characteristics of solar cells using different dyes also highlighted the need for balanced adjustment of the energy levels and their offsets at the heterojunction when using low-bandgap materials, and accentuated important effects of interface interactions and solid-state packing on charge generation and transport. PMID:20449035

  15. Pyrimidine-2-carboxylic Acid as an Electron-Accepting and Anchoring Group for Dye-Sensitized Solar Cells.

    PubMed

    Wu, Zhifang; Li, Xin; Ågren, Hans; Hua, Jianli; Tian, He

    2015-12-01

    We report a new dye (INPA) adopting pyrimidine-2-carboxylic acid as an electron-accepting and anchoring group to be used in dye-sensitized solar cells. IR spectral analysis indicates that the anchoring group may form two coordination bonds with TiO2 and so facilitate the interaction between the anchoring group and TiO2. The INPA-based cell exhibits an overall conversion efficiency of 5.45%, which is considerably higher than that obtained with cyanoacrylic acid commonly used as the electron acceptor. PMID:26581583

  16. FRET efficiency in surface complexes of CdSe/ZnS quantum dots with azo-dyes

    NASA Astrophysics Data System (ADS)

    Annas, Kirill I.; Gromova, Yuliya A.; Orlova, Anna O.; Maslov, Vladimir G.; Fedorov, Anatoly V.; Baranov, Alexander V.

    2016-04-01

    Photoinduced dissociation of surface complexes of CdSe/ZnS quantum dots with azo-dye 1-(2- pyridylazo)-2-naphthol (PAN) was investigated. It was shown that the Förster resonance energy transfer contributes in the complexes photodissociation rate, which depends on resonance condition between electronic levels of donor (quantum dots) and acceptor (azo-dye) and donor photoluminescent quantum yield. It has allowed to estimate energy transfer efficiency in the complexes and disclosed a new nonradiative channel that has minor contribution in the deactivation of excited states of quantum dots in the complexes.

  17. Cold Pad-Batch dyeing method for cotton fabric dyeing with reactive dyes using ultrasonic energy.

    PubMed

    Khatri, Zeeshan; Memon, Muhammad Hanif; Khatri, Awais; Tanwari, Anwaruddin

    2011-11-01

    Reactive dyes are vastly used in dyeing and printing of cotton fibre. These dyes have a distinctive reactive nature due to active groups which form covalent bonds with -OH groups of cotton through substitution and/or addition mechanism. Among many methods used for dyeing cotton with reactive dyes, the Cold Pad Batch (CPB) method is relatively more environment friendly due to high dye fixation and non requirement of thermal energy. The dyed fabric production rate is low due to requirement of at least twelve hours batching time for dye fixation. The proposed CPB method for dyeing cotton involves ultrasonic energy resulting into a one third decrease in batching time. The dyeing of cotton fibre was carried out with CI reactive red 195 and CI reactive black 5 by conventional and ultrasonic (US) method. The study showed that the use of ultrasonic energy not only shortens the batching time but the alkalis concentrations can considerably be reduced. In this case, the colour strength (K/S) and dye fixation (%F) also enhances without any adverse effect on colour fastness of the dyed fabric. The appearance of dyed fibre surface using scanning electron microscope (SEM) showed relative straightening of fibre convolutions and significant swelling of the fibre upon ultrasonic application. The total colour difference values ΔE (CMC) for the proposed method, were found within close proximity to the conventionally dyed sample. PMID:21550289

  18. Interstellar molecules

    NASA Astrophysics Data System (ADS)

    Smith, D.

    1987-09-01

    Some 70 different molecular species have so far been detected variously in diffuse interstellar clouds, dense interstellar clouds, and circumstellar shells. Only simple (diatomic and triatomic) species exist in diffuse clouds because of the penetration of destructive UV radiations, whereas more complex (polyatomic) molecules survive in dense clouds as a result of the shielding against this UV radiation provided by dust grains. A current list of interstellar molecules is given together with a few other molecular species that have so far been detected only in circumstellar shells. Also listed are those interstellar species that contain rare isotopes of several elements. The gas phase ion chemistry is outlined via which the observed molecules are synthesized, and the process by which enrichment of the rare isotopes occurs in some interstellar molecules is described.

  19. Interstellar Molecules

    ERIC Educational Resources Information Center

    Solomon, Philip M.

    1973-01-01

    Radioastronomy reveals that clouds between the stars, once believed to consist of simple atoms, contain molecules as complex as seven atoms and may be the most massive objects in our Galaxy. (Author/DF)

  20. Modeling Molecules

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The molecule modeling method known as Multibody Order (N) Dynamics, or MBO(N)D, was developed by Moldyn, Inc. at Goddard Space Flight Center through funding provided by the SBIR program. The software can model the dynamics of molecules through technology which stimulates low-frequency molecular motions and properties, such as movements among a molecule's constituent parts. With MBO(N)D, a molecule is substructured into a set of interconnected rigid and flexible bodies. These bodies replace the computation burden of mapping individual atoms. Moldyn's technology cuts computation time while increasing accuracy. The MBO(N)D technology is available as Insight II 97.0 from Molecular Simulations, Inc. Currently the technology is used to account for forces on spacecraft parts and to perform molecular analyses for pharmaceutical purposes. It permits the solution of molecular dynamics problems on a moderate workstation, as opposed to on a supercomputer.

  1. Dye-coated europium monosulfide

    SciTech Connect

    Kar, Srotoswini; Dollahon, Norman R.; Stoll, Sarah L.

    2011-05-15

    Nanoparticles of EuS were synthesized using europium dithiocarbamate complexes. The resulting nanoparticles were coated with the dye, 1-pyrene carboxylic acid and the resulting material was characterized using X-ray powder diffraction, TEM, and UV-visible spectroscopy. Fluorescence spectroscopy was used to determine the relative energy of the conduction band edge to the excited state energy of the dye. -- Graphical abstract: Dye sensitized magnetic semiconductor materials were prepared by synthesizing EuS nanoparticles using single source precursors and coating with the dye, 1-pyrene carboxylic acid. Display Omitted highlights: > Synthesized EuS nanoparticles, 11{+-}2.4 nm characterized using XRD, TEM, and UV-vis. spect. > Grafted a dye to the surface and characterized the product using XRD, FTIR, UV-vis., and TEM. > Studied the photophysical properties using fluorescence spectroscopy. > Determined the relative dye excited state to the conduction band of the semiconductor.

  2. Spectroscopic studies of the interaction of bichromophoric cyanine dyes with DNA. Effect of ionic strength.

    PubMed

    Schaberle, Fábio A; Kuz'min, Vladimir A; Borissevitch, Iouri E

    2003-05-01

    Spectroscopic characteristics of a cyanine dye with two chromophores (biscyanine dye, BCD) in aqueous solutions and effects of NaCl and DNA upon these characteristics have been studied by optical absorption, circular dichroism (CD) and fluorescence spectroscopies. In homogeneous solutions, BCD is characterized by intense optical absorption (epsilon =1.33 x 10(5) M(-1) x cm(-1)) and weak fluorescence (phi(fl)=0.018) in the wavelength region greater than 600 nm. The dye forms H-aggregates at low concentrations (10(-6) M). NaCl stimulates the formation of both H- and J-aggregates of the dye at much lower dye concentrations, while DNA in low concentrations (<10(-6) M) stimulated the formation of just J-aggregates on the surface of the DNA molecule. Higher DNA concentrations induce the dye to disaggregate, and there exists an equilibrium between three dye forms: free monomers, J-aggregates and bound monomers, the maximum content of J-aggregates was observed at [DNA]/[BCD]=0.6+/-0.2 and total disaggregation at [DNA]/[BCD]=190+/-20. J-aggregates are characterized by phi(fl)=0.05 and bound monomers by phi(fl)=0.44. In the presence of NaCl, total disaggregation was observed at [DNA]/[BCD]=570+/-10 due to competition between Na(+) and the dye molecules for DNA electronegative binding sites. PMID:12726994

  3. Mechanisms of electron acceptor utilization: Implications for simulating anaerobic biodegradation

    USGS Publications Warehouse

    Schreiber, M.E.; Carey, G.R.; Feinstein, D.T.; Bahr, J.M.

    2004-01-01

    Simulation of biodegradation reactions within a reactive transport framework requires information on mechanisms of terminal electron acceptor processes (TEAPs). In initial modeling efforts, TEAPs were approximated as occurring sequentially, with the highest energy-yielding electron acceptors (e.g. oxygen) consumed before those that yield less energy (e.g., sulfate). Within this framework in a steady state plume, sequential electron acceptor utilization would theoretically produce methane at an organic-rich source and Fe(II) further downgradient, resulting in a limited zone of Fe(II) and methane overlap. However, contaminant plumes often display much more extensive zones of overlapping Fe(II) and methane. The extensive overlap could be caused by several abiotic and biotic processes including vertical mixing of byproducts in long-screened monitoring wells, adsorption of Fe(II) onto aquifer solids, or microscale heterogeneity in Fe(III) concentrations. Alternatively, the overlap could be due to simultaneous utilization of terminal electron acceptors. Because biodegradation rates are controlled by TEAPs, evaluating the mechanisms of electron acceptor utilization is critical for improving prediction of contaminant mass losses due to biodegradation. Using BioRedox-MT3DMS, a three-dimensional, multi-species reactive transport code, we simulated the current configurations of a BTEX plume and TEAP zones at a petroleum- contaminated field site in Wisconsin. Simulation results suggest that BTEX mass loss due to biodegradation is greatest under oxygen-reducing conditions, with smaller but similar contributions to mass loss from biodegradation under Fe(III)-reducing, sulfate-reducing, and methanogenic conditions. Results of sensitivity calculations document that BTEX losses due to biodegradation are most sensitive to the age of the plume, while the shape of the BTEX plume is most sensitive to effective porosity and rate constants for biodegradation under Fe(III)-reducing and

  4. Mechanisms of electron acceptor utilization: implications for simulating anaerobic biodegradation.

    PubMed

    Schreiber, M E; Carey, G R; Feinstein, D T; Bahr, J M

    2004-09-01

    Simulation of biodegradation reactions within a reactive transport framework requires information on mechanisms of terminal electron acceptor processes (TEAPs). In initial modeling efforts, TEAPs were approximated as occurring sequentially, with the highest energy-yielding electron acceptors (e.g. oxygen) consumed before those that yield less energy (e.g., sulfate). Within this framework in a steady state plume, sequential electron acceptor utilization would theoretically produce methane at an organic-rich source and Fe(II) further downgradient, resulting in a limited zone of Fe(II) and methane overlap. However, contaminant plumes often display much more extensive zones of overlapping Fe(II) and methane. The extensive overlap could be caused by several abiotic and biotic processes including vertical mixing of byproducts in long-screened monitoring wells, adsorption of Fe(II) onto aquifer solids, or microscale heterogeneity in Fe(III) concentrations. Alternatively, the overlap could be due to simultaneous utilization of terminal electron acceptors. Because biodegradation rates are controlled by TEAPs, evaluating the mechanisms of electron acceptor utilization is critical for improving prediction of contaminant mass losses due to biodegradation. Using BioRedox-MT3DMS, a three-dimensional, multi-species reactive transport code, we simulated the current configurations of a BTEX plume and TEAP zones at a petroleum-contaminated field site in Wisconsin. Simulation results suggest that BTEX mass loss due to biodegradation is greatest under oxygen-reducing conditions, with smaller but similar contributions to mass loss from biodegradation under Fe(III)-reducing, sulfate-reducing, and methanogenic conditions. Results of sensitivity calculations document that BTEX losses due to biodegradation are most sensitive to the age of the plume, while the shape of the BTEX plume is most sensitive to effective porosity and rate constants for biodegradation under Fe(III)-reducing and

  5. Enumerating molecules.

    SciTech Connect

    Visco, Donald Patrick, Jr.; Faulon, Jean-Loup Michel; Roe, Diana C.

    2004-04-01

    This report is a comprehensive review of the field of molecular enumeration from early isomer counting theories to evolutionary algorithms that design molecules in silico. The core of the review is a detail account on how molecules are counted, enumerated, and sampled. The practical applications of molecular enumeration are also reviewed for chemical information, structure elucidation, molecular design, and combinatorial library design purposes. This review is to appear as a chapter in Reviews in Computational Chemistry volume 21 edited by Kenny B. Lipkowitz.

  6. Effect of Donor-Acceptor Coupling on TICT Dynamics in the Excited States of Two Dimethylamine Substituted Chalcones.

    PubMed

    Ghosh, Rajib; Palit, Dipak K

    2015-11-12

    Significant effect of coupling between the electron donor and acceptor groups in intramolecular charge transfer (ICT) dynamics has been demonstrated by comparing the photophysical properties of two isomeric N,N-dimethylaminochalcone derivatives (namely, DMAC-A and DMAC-B). In the case of the DMAC-B molecule, the distance between the donor (N,N-dimethylaniline or DMA) and the acceptor (carbonyl) groups is larger by one ethylene unit as compared to that in the case of DMAC-A. The excited singlet (S1) states of both the isomers have strong ICT character but their photophysical properties are remarkably different. In polar solvents, fluorescence quantum yields (and the lifetimes of the S1 state) of DMAC-A are more than 2 orders of magnitude lower (and shorter) than those of DMAC-B. Remarkable differences in the photophysical properties of these two isomers arise due to occurrence of the ultrafast twisting of the DMA group (or the TICT process) during the course of deactivation of the S1 state of the DMAC-A molecule, but not in the case of DMAC-B. In the later case, because of the presence of a large energy barrier along the twisting coordinate(s), TICT is not a feasible process, and hence, the S1 state of DMAC-B has the planar ICT structure. In the DMAC-A molecule, the strength of coupling between the donor and acceptor groups is relatively stronger because of a shorter distance between these groups. Femtosecond transient absorption spectroscopic measurements and DFT/TDDFT calculations have been adopted to establish the above aspects of the relaxation dynamics of the S1 states of these two isomeric chalcones. PMID:26480238

  7. Single Molecule Studies on Dynamics in Liquid Crystals

    PubMed Central

    Täuber, Daniela; von Borczyskowski, Christian

    2013-01-01

    Single molecule (SM) methods are able to resolve structure related dynamics of guest molecules in liquid crystals (LC). Highly diluted small dye molecules on the one hand explore structure formation and LC dynamics, on the other hand they report about a distortion caused by the guest molecules. The anisotropic structure of LC materials is used to retrieve specific conformation related properties of larger guest molecules like conjugated polymers. This in particular sheds light on organization mechanisms within biological cells, where large molecules are found in nematic LC surroundings. This review gives a short overview related to the application of highly sensitive SM detection schemes in LC. PMID:24077123

  8. Merocyanine dyes with improved photostability.

    PubMed

    Toutchkine, Alexei; Nguyen, Dan-Vinh; Hahn, Klaus M

    2007-07-19

    Merocyanine dyes have proven valuable for live cell fluorescence imaging applications, but many structures have been limited by rapid photobleaching. We show that photostability is substantially enhanced for merocyanines having a cyano group at a specific position in the central polymethine chain. Evidence is presented that this is due to reduction in reactivity of the dyes with singlet oxygen. These results point toward cyano-substitution as a general strategy for improving dye performance in imaging applications. PMID:17583344

  9. Rigid Conjugated Twisted Truxene Dimers and Trimers as Electron Acceptors.

    PubMed

    Zhang, Gang; Lami, Vincent; Rominger, Frank; Vaynzof, Yana; Mastalerz, Michael

    2016-03-14

    A new class of rigid twisted truxenone oligomers with an enlarged π backbone has been established by oxidative dimerization reactions. The resulting extended conjugated systems have large extinction coefficients and low-lying LUMO levels and show good solubility in common organic solvents, thus making them attractive compounds as new electron acceptors in organic electronics. Their suitability as electron acceptors has been demonstrated in bulk-heterojunction organic solar cells with 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}) (PTB7) as the donor material. PMID:26891096

  10. Probing the spin states of a single acceptor atom.

    PubMed

    van der Heijden, Joost; Salfi, Joe; Mol, Jan A; Verduijn, Jan; Tettamanzi, Giuseppe C; Hamilton, Alex R; Collaert, Nadine; Rogge, Sven

    2014-03-12

    We demonstrate a single-hole transistor using an individual acceptor dopant embedded in a silicon channel. Magneto-transport spectroscopy reveals that the ground state splits as a function of magnetic field into four states, which is unique for a single hole bound to an acceptor in a bulk semiconductor. The two lowest spin states are heavy (|m(j)| = 3/2) and light (|m(j)| = 1/2) hole-like, a two-level system that can be electrically driven and is characterized by a magnetic field dependent and long relaxation time, which are properties of interest for qubits. Although the bulklike spin splitting of a boron atom is preserved in our nanotransistor, the measured Landé g-factors, |g(hh)| = 0.81 ± 0.06 and |g(lh)| = 0.85 ± 0.21 for heavy and light holes respectively, are lower than the bulk value. PMID:24571637

  11. Interface effects on acceptor qubits in silicon and germanium.

    PubMed

    Abadillo-Uriel, J C; Calderón, M J

    2016-01-15

    Dopant-based quantum computing implementations often require the dopants to be situated close to an interface to facilitate qubit manipulation with local gates. Interfaces not only modify the energies of the bound states but also affect their symmetry. Making use of the successful effective mass theory we study the energy spectra of acceptors in Si or Ge taking into account the quantum confinement, the dielectric mismatch and the central cell effects. The presence of an interface puts constraints to the allowed symmetries and leads to the splitting of the ground state in two Kramers doublets (Mol et al 2015 Appl. Phys. Lett. 106 203110). Inversion symmetry breaking also implies parity mixing which affects the allowed optical transitions. Consequences for acceptor qubits are discussed. PMID:26618443

  12. Defect Donor and Acceptor in GaN

    SciTech Connect

    Look, D.C.; Reynolds, D.C.; Hemsky, J.W.; Sizelove, J.R.; Jones, R.L.

    1997-09-01

    High-energy (0.7{endash}1MeV) electron irradiation in GaN grown on sapphire produces shallow donors and deep or shallow acceptors at equal rates, 1{plus_minus}0.2 cm{sup {minus}1}. The data, in conjunction with theory, are consistent only with the shallow donor being the N vacancy, and the acceptor the N interstitial. The N-vacancy donor energy is 64{plus_minus}10 meV, much larger than the value of 18meV found for the residual donor (probably Si) in this material. The Hall-effect measurements also reveal a degenerate n -type layer at the GaN/sapphire interface which must be accounted for to get the proper donor activation energy. {copyright} {ital 1997} {ital The American Physical Society}

  13. An extended Foerster-Dexter model for correlated donor-acceptor placement in solid state materials

    NASA Astrophysics Data System (ADS)

    Rotman, S. R.; Hartmann, F. X.

    1987-09-01

    The current theory of donor-acceptor interactions in solid-state materials is based on a random distribution of donors and acceptors through the crystal. In this paper, we present a model to calculate the observable transfer rates for the correlated positioning of donors and acceptors in laser materials. Chemical effects leading to such correlations are discussed.

  14. Naphtho[2,3-c][1,2,5]thiadiazole and 2H-Naphtho[2,3-d][1,2,3]triazole-Containing D-A-π-A Conjugated Organic Dyes for Dye-Sensitized Solar Cells.

    PubMed

    Yen, Yung-Sheng; Ni, Jen-Shyang; Hung, Wei-I; Hsu, Chih-Yu; Chou, Hsien-Hsin; Lin, Jiann-T Suen

    2016-03-01

    Dipolar dyes comprising an arylamine as the electron donor, a cyanoacrylic acid as electron acceptor, and an electron deficient naphtho[2,3-c][1,2,5]thiadiazole (NTD) or naphtho[2,3-d][1,2,3]triazole (NTz) entity in the conjugated spacer, were developed and used as the sensitizers in dye-sensitized solar cells (DSSCs). The introduction of the NTD unit into the molecular frame distinctly narrows the HOMO/LUMO gap with electronic absorption extending to >650 nm. However, significant charge trapping and dye aggregation were found in these dyes. Under standard global AM 1.5 G illumination, the best cell photovoltaic performance achieved 6.37 and 7.53% (∼94% relative to N719-based standard cell) without and with chenodeoxycholic acid (CDCA) coadsorbent, respectively. Without CDCA, the NTz dyes have higher power conversion efficiency (7.23%) than NTD dyes due to less charge trapping, dye aggregation, and better dark current suppression. PMID:26891701

  15. The Chemistry of Plant and Animal Dyes.

    ERIC Educational Resources Information Center

    Sequin-Frey, Margareta

    1981-01-01

    Provides a brief history of natural dyes. Chemical formulas are provided for flavonoids, luteolin, genistein, brazilin, tannins, terpenes, naphthoquinone, anthraquinone, and dyes with an alkaloid structure. Also discusses chemical background of different dye processes. (CS)

  16. Quantum confined acceptors and donors in InSe nanosheets

    SciTech Connect

    Mudd, G. W.; Patanè, A. Makarovsky, O.; Eaves, L.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.; Fay, M. W.; Zólyomi, V.; Falko, V.

    2014-12-01

    We report on the radiative recombination of photo-excited carriers bound at native donors and acceptors in exfoliated nanoflakes of nominally undoped rhombohedral γ-polytype InSe. The binding energies of these states are found to increase with the decrease in flake thickness, L. We model their dependence on L using a two-dimensional hydrogenic model for impurities and show that they are strongly sensitive to the position of the impurities within the nanolayer.

  17. Can nitro groups really anchor onto TiO2? Case study of dye-to-TiO2 adsorption using azo dyes with NO2 substituents.

    PubMed

    Zhang, Lei; Cole, Jacqueline M

    2016-07-28

    The nitro group has recently been suggested as a new type of anchor for dye-sensitized solar cells (DSSCs) and has shown promising optoelectronic properties. Considering the excellent electron withdrawing ability of the nitro group and wider materials selection brought about by this substituent, it is helpful to evaluate the interfacial structures and photophysics of more organic dyes where NO2 poses as the dye-to-TiO2 anchor. A computational study on a family of azo dyes bearing a nitro group is presented, where the effect of certain side groups on their optical properties is examined. Both isolated dye molecules and dye/TiO2 nanocomposites are studied via density functional theory and time-dependent density functional theory, with complementary experimental UV/vis absorption spectroscopy and photovoltaic device testing. Results demonstrate that these nitro-containing dyes prefer a monodentate anchoring mode on a TiO2 cluster. These nitro dyes reveal weak, but non-negligible, adsorption onto TiO2; yet, very low photovoltaic performance once incorporated into a DSSC device. This poor delivery of nitro groups as DSSC anchors is ostensibly inconsistent with previous findings; but is rationalized via the "auxiliary anchor" concept. PMID:27356762

  18. Enzyme-mediated bacterial biodegradation of an azo dye (C.I. Acid blue 113): reuse of treated dye wastewater in post-tanning operations.

    PubMed

    Senthilvelan, T; Kanagaraj, J; Panda, R C

    2014-11-01

    "Dyeing" is a common practice used to color the hides during the post-tanning operations in leather processing generating plenty of wastewater. The waste stream containing dye as pollutant is severely harmful to living beings. An azo dye (C.I. Acid Blue 113) has been biodegraded effectively by bacterial culture mediated with azoreductase enzyme to reduce the pollution load in the present investigation. The maximum rate of dye degradation was found to be 96 ± 4 and 92 ± 4 % for the initial concentrations of 100 and 200 mg/l, respectively. The enzyme activity was measured using NADH as a substrate. Fourier transform infrared spectroscopy (FT-IR) analysis was confirmed that the transformation of azo linkage could be transformed into N2 or NH3 or incorporated into complete biomass. Breaking down of dye molecules to various metabolites (such as aniline, naphthalene-1,4-diamine, 3-aminobenzenesulfonic acid, naphthalene-1-sulfonic acid, 8-aminonaphthalene-1-sulfonic acid, 5,8-diaminonaphthalene-1-sulfonic acid) was confirmed by gas chromatography and mass spectra (GC-MS) and mass (electrospray ionization (ESI)) spectra analysis. The treated wastewater could be reused for dyeing operation in the leather processing, and the properties of produced leather were evaluated by conventional methods that revealed to have improved dye penetration into the grain layer of experimental leather sample and resulted in high levelness of dyeing, which helps to obtain the desired smoothness and soft leather properties. PMID:25163883

  19. Parameters of a dye laser with transverse pumping

    SciTech Connect

    Burakov, V.S.; Samson, A.M.; Zhukovskii, V.V.; Isaevich, A.V.

    1987-12-01

    The authors describe a new method for determining the excitation and output parameters of dye laser media under conditions of transverse optical pumping by laser radiation. The dye is modeled as a medium with two electron-vibrational levels. The method is based on the variation of the value of the distance on the mirror reflection coefficients of the resonator and on estimates of inactive or parasitic losses, the probability of exciting active dye molecules with the radiation incident on the front face of the cell, and the unsaturated gain coefficient of that output frequency. Experimental data are then derived for these conditions for a rhodamine 4C solution in ethanol. Pumping was done using a neodymium laser.

  20. Photoinduced translational molecular mobility in solid nanostructured azo dye films

    SciTech Connect

    Ezhov, A A; Kozenkov, V M; Magnitskii, Sergey A; Nagorskii, Nikolay M; Panov, Vladimir I

    2011-11-30

    A new mechanism controlling the molecular motion in thin azo-containing films during a photoinduced change in the surface nanorelief is found. It is shown experimentally that exposure of a solid AD-1 azo dye, deposited on a glass substrate, to incoherent linearly polarised light leads to formation of nanostructures with a characteristic size of 200 nm, which are similar to droplets of melt of this dye on the same substrate. It is shown that photoinduced mass transport in a solid AD-1 azo dye film can be explained by the mobility of molecules related to their trans-cis-photoisomerisation, which leads to film softening with subsequent formation of spherical protrusions under surface tension forces.