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Sample records for acid doped pbi

  1. Acid and alkali doped PBI electrolyte in electrochemical system

    NASA Astrophysics Data System (ADS)

    Xing, Baozhong

    In this work the conductivity of blank PBI membrane, acid doped PBI and alkaline doped PBI was systematically studied. A new methodology for sorption kinetics study in electrolyte solution has been established by monitoring the conductivity change during the sorption process. The model of the doping process and mechanism of conductivity are proposed. The performance of PBI (doped under optimum conditions) in fuel cell as PEM was evaluated. The experimental results show that the blank PBI in acid solution is an ionic insulator. It clarified the long time confusion in this area. The acid doped PBI membrane is an ionic conductor. The conductivity increases with the concentration of the acid solution. In high concentration acid solution, the conductivity increases with the type of acid in the order: H2SO 4 > H3PO4 > HClO4 > HNO3 > HCl. The kinetics of the doping process was studied, by a continuous method. The ionic conductivity mechanism was established. The PBI membranes doped with H2SO4 and H3PO4 exhibit better performance than NafionRTM. The doped FBI has more resistance to CO poison. 3% CO in H2 has little effect on the H3PO 4 doped PBI membrane at 185°C. The conductivity of the alkali doped PBI membrane changes with the concentration of the alkaline solution and the type of the alkalis. The conductivity has a maximum in KOH and NaOH solution. The maximum conductivity in KOH is higher than in NaOH and LiOH. It is about 5 times of that of NafionRTM in alkaline solution. The two-step sorption process in alkaline solution was observed. The first step is the permeation process of the alkalis in the PBI membrane. The permeation is the results of diffusion and interaction. It is concluded that the permeation process is controlled by the rate of interaction between the alkali and PBI molecule. The second step is the relaxation process in the membrane. This step contributes more to the conductivity for the membrane than the first step. The ionic conductivity mechanism

  2. A Comparative Study of Phosphoric Acid-doped m-PBI Membranes

    SciTech Connect

    Perry, Kelly A; More, Karren Leslie; Payzant, E Andrew; Meisner, Roberta A; Sumpter, Bobby G; Benicewicz, Brian

    2014-01-01

    Phosphoric acid (PA)-doped m-polybenzimidazole (PBI) membranes used in high temperature fuel cells and hydrogen pumps were prepared by a conventional imbibing process and a sol-gel fabrication process. A comparative study was conducted to investigate the critical properties of PA doping levels, ionic conductivities, mechanical properties, and molecular ordering. This systematic study found that sol-gel PA-doped m-PBI membranes were able to absorb higher acid doping levels and to achieve higher ionic conductivities than conventionally imbibed membranes when treated in an equivalent manner. Even at similar acid loadings, the sol-gel membranes exhibited higher ionic conductivities. Heat treatment of conventionally imbibed membranes with 29wt% solids caused a significant reduction in mechanical properties; conversely, sol-gel membranes exhibited an enhancement in mechanical properties. From X-ray structural studies and atomistic simulations, both conventionally imbibed and sol-gel membranes exhibited d-spacings of 3.5 and 4.6 , which were tentatively attributed to parallel ring stacking and staggered side-to-side packing, respectively, of the imidazole rings in these aromatic hetercyclic polymers. An anisotropic staggered side-to-side chain packing present in the conventional membranes may be root to the reduction in mechanical properties.

  3. An investigation of Pt alloy oxygen reduction catalysts in phosphoric acid doped PBI fuel cells

    NASA Astrophysics Data System (ADS)

    Mamlouk, M.; Scott, K.

    A study of a phosphoric acid doped polybenzimidazole (PBI) membrane fuel cell using commercial carbon supported, Pt alloy oxygen reduction catalysts is reported. The cathodes were made from PTFE bonded carbon supported Pt alloys without PBI but with phopshoric acid added to the electrode for ionic conductivity. Polarisation data for fuel cells with cathodes made with alloys of Pt with Ni, Co, Ru and Fe are compared with those with Pt alone as cathode at temperatures between 120 and 175 °C. With the same loading of Pt enhancement in cell performance was achieved with all alloys except Pt-Ru, in the low current density activation kinetics region of operation. The extent of enhancement depended upon the operating temperature and also the catalyst loading. In particular a Pt-Co alloy produced performance significantly better than Pt alone, e.g. a peak power, with low pressure air, of 0.25 W cm -2 with 0.2 mg Pt cm -2 of a 20 wt% Pt-Co catalyst.

  4. Influence of doping in InP buffer on photoluminescence behavior of InPBi

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Pan, Wenwu; Cao, Chunfang; Wu, Xiaoyan; Wang, Shumin; Gong, Qian

    2016-11-01

    InP1- x Bi x epilayers with 1.0% bismuth concentration were grown on InP(001) substrates by gas-source molecular beam epitaxy. Silicon and beryllium were doped into the InP buffer layer, and their influences on the photoluminescence (PL) emission of InPBi were investigated. The PL emission of InPBi was found to be intensified by beryllium doping into the InP buffer layer. However, there was no influence of silicon doping. To investigate the reason for the PL intensity enhancement of InPBi, the carrier transport behavior at the interface was also discussed.

  5. ELECTROCHEMICAL PROPERTIES, MECHANICAL TESTING, AND GEL MORPHOLOGY STUDY OF PHOSPHORIC ACID-DOPED META-POLYBENZIMIDAZOLE MEMBRANES VIA CONVENTIONALLY IMBIBING AND THE SOL-GEL PROCESS

    SciTech Connect

    Perry, Kelly A; More, Karren Leslie; Benicewicz, Brian

    2009-01-01

    Proton exchange membrane (PEM) research has been directed at phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes since the 1990s. PEM fuel cells based on PA-doped PBI membranes produced via a sol-gel transition process have achieved lifetimes >10,000hrs with low degradation rates. It has been suggested that the gel morphology of the PA-doped PBI membranes is responsible for their excellent electrochemical performance. Thus, a study has been underway to characterize the microstructure of PA-doped PBI membranes, and to correlate structure with performance. However, PA-doped PBI membranes present special challenges for microscopy analysis, as these membranes are extremely sensitive to the electron beam and high vacuum conditions. This paper will discuss and compare the mechanical, electrochemical, and cryo-SEM analyses of PA-doped meta-PBI membranes produced via conventional imbibing and the sol-gel process.

  6. Transport Properties Of PbI2 Doped Silver Oxysalt Based Amorphous Solid Electrolytes

    NASA Astrophysics Data System (ADS)

    Shrisanjaykumar Jayswal, Manishkumar

    Solid electrolytes are a class of materials that conduct electricity by means of motion of ions like Ag+, Na+, Li +, Cu+, H+, F-, O -2 etc. in solid phase. The host materials include crystalline, polycrystalline, glasses, polymers and composites. Ion conducting glasses are one of the most sought after solid electrolytes that are useful in various electrochemical applications like solid state batteries, gas sensors, supercapacitors, electrochromic devices, to name a few. Since the discovery of fast silver ion transport in silver oxyhalide glasses at the end of the 1960s, many glasses showing large ionic conductivity up to 10-4 10-2 S/cm at room temperature have been developed, chiefly silver and copper ion conductors. The silver ion conducting glasses owe their high ionic conductivity mainly to stabilized alpha-AgI. AgI, as we know, undergoes a structural phase transition from wurtzite (beta phase) at room temperature to body centered cubic (alpha phase) structure at temperatures higher than 146 °C. The alpha-AgI possesses approximately six order of higher ionic conductivity than beta-AgI. The high ionic conductivity of alpha-AgI is attributed to its molten sublattice type of structure, which facilitates easy Ag+ ion migration, like a liquid. And hence, several attempts have been made to stabilize it at room temperature in crystalline as well as non-crystalline hosts like oxide and non-oxide glasses. Recently, in order to stabilize AgI in glasses, instead of directly doping it, indirect routes have also been explored. Where, a metal iodide salt along with silver oxide or silver phosphate is taken and an exchange reaction permitted by Hard and Soft, Acid and Base (HSAB) principle occurs between the two and AgI and metal oxide form in the glass forming melt. Work done in the present thesis has been organized in seven chapters as follows: Chapter 1: A review and background information of different solid electrolyte materials and their development is presented. Along

  7. Photovoltaic properties of Cu-doped CH3NH3PbI3 with perovskite structure

    NASA Astrophysics Data System (ADS)

    Shirahata, Yasuhiro; Oku, Takeo

    2017-01-01

    Photovoltaic properties of copper (Cu)-doped perovskite (CH3NH3PbCuxI3+x) photovoltaic devices with different Cu content were investigated. The CH3NH3PbCuxI3+x films were polycrystalline with a tetragonal system, and their lattice constants and crystallite size varied with Cu doping. Compared to conversion efficiencies of non-doped CH3NH3PbI3 photovoltaic device, those of CH3NH3PbCuxI3+x photovoltaic devises increased. The improvement of photovoltaic properties was attributed to partial substitution of Cu at the Pb sites.

  8. Tunable Br-doping CH3NH3PbI3-xBrx thin films for efficient planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Li, Nannan; Shi, Chengwu; Li, Long; Zhang, Zhengguo; Ma, Chengfeng

    2017-04-01

    In this paper, the relationship of the Br contents in precursor solutions of the CH3NH3Br/CH3NH3I mixture and in the resulting CH3NH3PbI3-xBrx thin films was systemically explored and the tunable Br-doping CH3NH3PbI3-xBrx thin films were successfully obtained by the sequential deposition methods. The influence of CH3NH3Br content in the methylammonium halide mixture solutions on the chemical composition, optical absorption, crystal phase and morphology of CH3NH3PbI3-xBrx thin films and the photovoltaic performance of the corresponding planar perovskite solar cells were investigated. The result revealed that the Br contents in CH3NH3PbI3-xBrx thin films linearly increased with the increase of Br contents in the methylammonium halide mixture solutions. The planar perovskite solar cell based on the high crystallinity and less grain boundary CH3NH3PbI3-xBrx thin films using the methylammonium halide mixture solutions with the molar ratio of CH3NH3Br/CH3NH3I = 10/90 achieved a best photoelectric conversion efficiency (PCE) of 14.88% with an open-circuit voltage (Voc) of 1.03 V, a short-circuit photocurrent density (Jsc) of 20.62 mA cm-2 and a fill factor (FF) of 0.70 and an average PCE of 14.21 ± 0.67% with Voc of 1.02 ± 0.02 V, Jsc of 20.67 ± 0.15 mA cm-2 and FF of 0.67 ± 0.05.

  9. Thermal stability of proton conducting acid doped polybenzimidazole in simulated fuel cell environments

    SciTech Connect

    Samms, S.R.; Wasmus, S.; Savinell, R.F.

    1996-04-01

    Recently, polybenzimidazole membrane doped with phosphoric acid (PBI) was found to have promising properties for use as a polymer electrolyte in a high temperature (ca. 150 to 200 C) proton exchange membrane direct methanol fuel cell. However, operation at 200 C in strongly reducing and oxidizing environments introduces concerns of the thermal stability of the polymer electrolyte. To simulate the conditions in a high temperature fuel cell, PBI samples were loaded with fuel cell grade platinum black, doped with ca. 480 mole percent phosphoric acid (i.e., 4.8 H{sub 3}PO{sub 4} molecules per PBI repeat unit) and heated under atmospheres of either nitrogen, 5% hydrogen, or air in a thermal gravimetric analyzer. The products of decomposition were taken directly into a mass spectrometer for identification. In all cases weight loss below 400 C was found to be due to loss of water. Judging from the results of these tests, the thermal stability of PBI is more than adequate for use as a polymer electrolyte in a high temperature fuel cell.

  10. Nonstoichiometric acid-base reaction as reliable synthetic route to highly stable CH3NH3PbI3 perovskite film

    NASA Astrophysics Data System (ADS)

    Long, Mingzhu; Zhang, Tiankai; Chai, Yang; Ng, Chun-Fai; Mak, Thomas C. W.; Xu, Jianbin; Yan, Keyou

    2016-11-01

    Perovskite solar cells have received worldwide interests due to swiftly improved efficiency but the poor stability of the perovskite component hampers the device fabrication under normal condition. Herein, we develop a reliable nonstoichiometric acid-base reaction route to stable perovskite films by intermediate chemistry and technology. Perovskite thin-film prepared by nonstoichiometric acid-base reaction route is stable for two months with negligible PbI2-impurity under ~65% humidity, whereas other perovskites prepared by traditional methods degrade distinctly after 2 weeks. Route optimization involves the reaction of PbI2 with excess HI to generate HPbI3, which subsequently undergoes reaction with excess CH3NH2 to deliver CH3NH3PbI3 thin films. High quality of intermediate HPbI3 and CH3NH2 abundance are two important factors to stable CH3NH3PbI3 perovskite. Excess volatile acid/base not only affords full conversion in nonstoichiometric acid-base reaction route but also permits its facile removal for stoichiometric purification, resulting in average efficiency of 16.1% in forward/reverse scans.

  11. Effects of halogen doping on the photovoltaic properties of HC(NH2)2PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Umemoto, Yuri; Suzuki, Atsushi; Oku, Takeo

    2017-01-01

    Fabrication and characterization of perovskite-based solar cell using TiO2 as an electron transporting layer and 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino) -9,9'-spirobifluorene as a hole transporting layer (HTL) have been performed for improving the photovoltaic performance. The purpose of the present study is to investigate a role of halogen doping using iodine, bromine and chlorine compounds on the photovoltaic performance such as short-circuit current density, open-circuit voltage, conversion efficiency and microstructures of HC(NH2)2PbI3-x-yBrxCly perovskite solar cells. The photovoltaic properties were investigated by current-voltage curves under light irradiation, incident photon to current conversion efficiency, X-ray diffraction and optical microscopy. The photovoltaic performance and optical properties were influenced by halogen addition into the perovskite crystal structure.

  12. Thermal properties of phosphoric acid-doped polybenzimidazole membranes in water and methanol-water mixtures

    NASA Astrophysics Data System (ADS)

    Nores-Pondal, Federico J.; Buera, M. Pilar; Corti, Horacio R.

    The thermal properties of phosphoric acid-doped poly[2-2‧-(m-phenylene)-5-5‧ bi-benzimidazole] (PBI) and poly[2,5-benzimidazole] (ABPBI) membranes, ionomeric materials with promising properties to be used as electrolytes in direct methanol and in high temperature polymer electrolyte membrane (PEM) fuel cells, were studied by means of differential scanning calorimetry (DSC) technique in the temperature range from -145 °C to 200 °C. The DSC scans of samples equilibrated in water at different relative humidities (RH) and in liquid water-methanol mixtures were analyzed in relation to glass transition, water crystallization/melting and solvent desorption in different temperature regions. The thermal relaxation observed in the very low temperature region could be ascribed to the glass transition of the H 3PO 4-H 2O mixture confined in the polymeric matrix. After cooling the samples up to -145 °C, frozen water was detected in PBI and ABPBI at different RH, although at 100% RH less amount of water had crystallized than that observed in Nafion membranes under the same conditions. Even more important is the fact that the freezing degree of water is much lower in ABPBI membranes equilibrated in liquid water-methanol mixtures than that observed for PBI and, in a previous study, for Nafion. Thus, apart from other well known properties, acid-doped ABPBI emerges as an excellent ionomer for applications in direct methanol fuel cells working in cold environments.

  13. Dimensionally-stable phosphoric acid-doped polybenzimidazoles for high-temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Xiaobai; Ma, Hongwei; Shen, Yanchao; Hu, Wei; Jiang, Zhenhua; Liu, Baijun; Guiver, Michael D.

    2016-12-01

    Phosphoric acid-doped polybenzimidazole (PA-m-PBI) membranes are widely investigated for high temperature proton exchange membrane fuel cells because of their low cost and high performance. For this system, a major challenge is in achieving a good compromise between the phosphoric acid doping level and the membrane dimensional-mechanical stability. Different from the established PA-m-PBI system, the present work investigates two types of PA-PBI membranes incorporating flexible ether linkages and asymmetric bulky pendants (phenyl and methylphenyl), which exhibit much better dimensional-mechanical stability after immersing in PA solution, even at high temperature for an extended period. This superior stability allowed higher acid doping levels (20.6 and 24.6) to be achieved, thus increasing proton conductivity (165 and 217 mS cm-1 at 200 °C under anhydrous conditions) as well as significantly improving fuel cell performance. The peak power densities in hydrogen/air fuel cell were 279 and 320 mW cm-2 at 160 °C, without humidification. Molecular simulation, density and fractional free volume, and wide-angle X-ray diffraction were used to investigate their structure-property relationships.

  14. Microwave-assisted synthesis of Gd3+ doped PbI2 hierarchical nanostructures for optoelectronic and radiation detection applications

    NASA Astrophysics Data System (ADS)

    Shkir, Mohd.; AlFaify, S.; Yahia, I. S.; Ganesh, V.; Shoukry, H.

    2017-03-01

    In this work, we report the simple, low temperature and rapid microwave-assisted synthesis of undoped and Gadolinium (III) doped lead iodide with different morphologies, i.e. nanorods of average diameter 200 nm and hierarchical (flower-shaped) nanosheets of thicknesses less than 100 nm. Prepared nanostructures were typify in details using a variety of analytical techniques that reveal the well crystallinity with hexagonal structure. We found that by changing the concentrations of Gadolinium (III) one can tailor the size and shape of nanostructures of lead iodide. The presence of Gadolinium (III) doping was assessed by energy dispersive X-ray analysis. Optical band gap and Photoluminescence intensity are found to be enhanced due to Gadolinium (III) doping. The value of Gamma linear absorption coefficient is found to be enriched with doping, which suggests its application in radiation detection.

  15. Elucidating the band structure and free charge carrier dynamics of pure and impurities doped CH3NH3PbI(3-x)Cl(x) perovskite thin films.

    PubMed

    Zhang, Zhen-Yu; Chen, Xin; Wang, Hai-Yu; Xu, Ming; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo

    2015-11-28

    CH3NH3PbI3-xClx perovskite material has been commonly used as the free charge generator and reservoir in highly efficient perovskite-based solid-state solar photovoltaic devices. However, many of the underlying fundamental photophysical mechanisms in this material such as the perovskite transition band structure as well as the dependent relationship between the carrier properties and lattice properties still lack sufficient understanding. Here, we elucidated the fundamental band structure of the pure CH3NH3PbI3-xClx pervoskite lattice, and then reported about the dependent relationship between the free charge carrier characteristic and the different CH3NH3PbI3-xClx pervoskite lattice thin films utilizing femtosecond time-resolved pump-probe technologies. The data demonstrated that the pure perovskite crystal band structure should only have one conduction and one valence band rather than dual valences, and the pure perovskite lattice could trigger more free charge carriers with a slower recombination rate under an identical pump intensity compared with the impurities doped perovskite crystal. We also investigated the perovskite film performance when exposed to moisture and water, the corresponding results gave us a dip in the optimization of the performance of perovskite based devices, and so as a priority this material should be isolated from moisture (water). This work may propose a deeper perspective on the comprehension for this material and it is useful for future optimization of applications in photovoltaic and light emission devices.

  16. New insights into organic-inorganic hybrid perovskite CH3NH3PbI3 nanoparticles. An experimental and theoretical study of doping in Pb2+ sites with Sn2+, Sr2+, Cd2+ and Ca2+

    NASA Astrophysics Data System (ADS)

    Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Cruz Hernández, Norge; Piñero, Jose Carlos; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; de Los Santos, Desireé M.; Aguilar, Teresa; Martín-Calleja, Joaquín

    2015-03-01

    This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb2+ position with Sn2+, Sr2+, Cd2+ and Ca2+. The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn2+, Sr2+ and Cd2+ did not modify the normal tetragonal phase. When doping with Ca2+, the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr2+ < Cd2+ < Ca2+ < CH3NH3PbI3 ~ Sn2+. The biggest decrease was generated by Sr2+, which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn2+ ~ Pb2+ > Cd2+ > Sr2+ for the tetragonal structure and Pb2+ > Ca2+ for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn2+-doped tetragonal structures, which were different from those doped with Sr2+ and Cd2+. Furthermore, when Cd2+ was incorporated, the Cd-I interaction was strengthened. For Ca2+ doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb2+ position with Sn2+, Sr2+, Cd2+ and Ca2+. The incorporation of the dopants into the crystalline structure was analysed

  17. Phosphoric acid distribution and its impact on the performance of polybenzimidazole membranes

    NASA Astrophysics Data System (ADS)

    Mack, Florian; Heissler, Stefan; Laukenmann, Ruben; Zeis, Roswitha

    2014-12-01

    Phosphoric acid doped polybenzimidazole (PBI) is the most common membrane material for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC). The PBI membrane is usually doped by immersion in hot phosphoric acid. Immersion time and acid temperature affect the doping level of the membrane. In this work we studied the influence of doping time and temperature on the ex-situ and in-situ proton conductivities of poly (2, 5-benzimidazole) (AB-PBI) membranes as well as the fuel cell performance. Confocal Raman microscopy was employed to spatially resolve the acid distribution within the AB-PBI membranes. Therefore the interactions between the basic nitrogen-sides of the AB-PBI polymer and the phosphoric acid protons were investigated. We found that membranes with a 6 h doping time had significantly higher proton conductivity than those doped for only 3 h. In terms of absolute acid up-take, however, the difference was rather small. This result shows that the doping level alone does not define the conductivity of the membrane. The conductivity is also influenced by the micro acid distribution within the membrane. Highest membrane conductivity and fuel cell performance with fumapem AM cross-linked membranes were achieved with a doping time of 6 h and a doping temperature of 120 °C.

  18. Ultrathin metallized PBI paper

    NASA Technical Reports Server (NTRS)

    Chenevey, E. C.

    1978-01-01

    A study to determine the feasibility of preparing ultrathin papers with a target weight of 3.5 g/m squared from polybenzimidazole (PBI) fibrids was undertaken. Small hand sheets of target weight were fabricated. They were light brown, low density materials with sufficient strength to be readily handleable. Characterization of these sheets included strength, fold endurance, thermal gravimetric analysis in air and nitrogen and photomicrographs. Two different batches of PBI fibrids were studied and differences in fabrication performance were noted. In neither case could target weight papers be prepared using conventional paper making techniques.

  19. Synthesis of High Molecular Weight Para-Phenylene PBI

    DTIC Science & Technology

    1974-11-01

    give high molecular weight m-phenylene PBI (Reference 7). The polymer was completely soluble in methanesulfonic acid and 98% formic acid . Polymer with...mono- mer is a white crystalline solid which can be quantitatively hydrolized in an acid medium to give the free TAB. Stoichiometric quantities of IX...WEIGHT "PARA"-PHENYLENE PBI TECHNICAL REPORT AFML-TR-74-199 NOVEMBER 1974 Distribution limited to U.S.Government agencies only, test and evaluation

  20. InPBi single crystals grown by molecular beam epitaxy.

    PubMed

    Wang, K; Gu, Y; Zhou, H F; Zhang, L Y; Kang, C Z; Wu, M J; Pan, W W; Lu, P F; Gong, Q; Wang, S M

    2014-06-26

    InPBi was predicted to be the most robust infrared optoelectronic material but also the most difficult to synthesize within In-VBi (V = P, As and Sb) 25 years ago. We report the first successful growth of InPBi single crystals with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InPBi thin films reveal excellent surface, structural and optical qualities making it a promising new III-V compound family member for heterostructures. The Bi concentration is found to be 2.4 ± 0.4% with 94 ± 5% Bi atoms at substitutional sites. Optical absorption indicates a band gap of 1.23 eV at room temperature while photoluminescence shows unexpectedly strong and broad light emission at 1.4-2.7 μm which can't be explained by the existing theory.

  1. Ultrafine PBI fibers and yarns

    NASA Technical Reports Server (NTRS)

    Leal, J. R.; Tan, M.

    1979-01-01

    Gentle precisely controlled process is used to draw polybenzimidazole (PBI) fibers to denier as low as 0.17 per fiber. Yarns of lightweight fibers could be useful in applications where lightweight textiles must withstand high temperatures, corrosion, or radiation.

  2. Acid doping of polyaniline: Spectroscopic and electrochemical studies

    SciTech Connect

    Hatchett, D.W.; Josowicz, M.; Janata, J.

    1999-12-16

    A detailed investigation of the acid doping behavior of polyaniline has led to a robust and reproducible procedure for controlled adjustment of the redox state of dry polyaniline films. The initial step in this procedure is the casting of PANI films from formic acid. The subsequent exchange of the trapped formic acid for other primary dopants obtained from mono- and polyprotic acids (e.g., CH{sub 3}COO{sup {minus}}, BF{sub 4}{sup {minus}}, HSO{sub 4}{sup {minus}}, SO{sub 4}{sup 2{minus}}, H{sub 2}PO{sub 4}{sup {minus}}, and HPO{sub 4}{sup 2{minus}}) is demonstrated. The voltammetric and the spectroscopic behavior of the PANI doped with different anions indicate that both the protons and the anions of dopant acids influence the structure and redox properties of the polymer. The redox state of PANI doped with homologous series of chloroacetic and carboxylic acids correlates with the pK{sub a} of the dopant acid. These results show that it is possible to prepare the polymer with a desired oxidation state according to the pK{sub a} of the dopant acid of a given homologous series. The exchange of the formic acid for both stronger and weaker doping acid can be repeatedly accomplished by electrochemical cycling.

  3. PbI2-Based Dipping-Controlled Material Conversion for Compact Layer Free Perovskite Solar Cells.

    PubMed

    Zheng, Enqiang; Wang, Xiao-Feng; Song, Jiaxing; Yan, Lulin; Tian, Wenjing; Miyasaka, Tsutomu

    2015-08-19

    A two-step sequential deposition method has been extensively employed to prepare the CH3NH3PbI3 active layer from the PbI2 precursor in perovskite solar cells (PSCs). The variation of the photovoltaic performance of PSCs made by this method was always attributed to different dipping times that induce complete/incomplete conversion of PbI2 into CH3NH3PbI3. To solve this issue, we employed a solvent vapor annealing (SVA) method to prepare PbI2 crystallites with large grain size for preparation of high quality perovskite. With this method, the increased PbI2 dipping time in CH3NH3I solution was found to reduce the photovoltaic performance of resulting PSCs without a significant change in PbI2/CH3NH3PbI3 contents in the perovskite films. We attribute this abnormal reduction of the photovoltaic performance to intercalation/deintercalation of the PbI2 core with a CH3NH3PbI3 shell, which causes the doping effect on both the PbI2 and CH3NH3PbI3 crystal lattices and the formation of a CH3NH3PbI3 capping layer on the surface, as revealed by UV-vis absorption, X-ray diffraction, FT-IR, and scanning electron microscope measurements. Based on our findings, a multistep dipping-drying process was employed as an alternative method to improve the crystalline quality. The method achieved power conversion efficiency up to 11.4% for the compact layer free PSC sharing a simple device structure of ITO/perovskite/spiro-OMeTAD/Ag.

  4. Vacuum thermal evaporation of polyaniline doped with camphor sulfonic acid

    SciTech Connect

    Boyne, Devon; Menegazzo, Nicola; Pupillo, Rachel C.; Rosenthal, Joel; Booksh, Karl S.

    2015-05-15

    Intrinsically conducting polymers belong to a class of organic polymers with intriguing electronic and physical properties specifically for electro-optical applications. Significant interest into doped polyaniline (PAni) can be attributed to its high conductivity and environmental stability. Poor dissolution in most solvents has thus far hindered the successful integration of PAni into commercial applications, which in turn, has led to the investigations of various deposition and acidic doping methods. Physical vapor deposition methods, including D.C. magnetron sputtering and vacuum thermal evaporation, have shown exceptional control over physical film properties (thickness and morphology). However, resulting films are less conductive than films deposited by conventional methods (i.e., spin and drop casting) due to interruption of the hyperconjugation of polymer chains. Specifically, vacuum thermal evaporation requires a postdoping process, which results in incorporation of impurities and oxidation of surface moieties. In this contribution, thermally evaporated films, sequentially doped by vacuum evaporation of an organic acid (camphorsulfonic acid, CSA) is explored. Spectroscopic evidence confirms the successful doping of PAni with CSA while physical characterization (atomic force microscopy) suggests films retain good morphology and are not damaged by the doping process. The procedure presented herein also combines other postpreparation methods in an attempt to improve conductivity and/or substrate adhesion.

  5. The effect of porosity on performance of phosphoric acid doped polybenzimidazole polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Celik, Muhammet; Genc, Gamze; Elden, Gulsah; Yapici, Huseyin

    2016-03-01

    A polybenzimidazole (PBI) based polymer electrolyte fuel cells, which called high temperature polymer electrolyte fuel cells (HT-PEMS), operate at higher temperatures (120-200°C) than conventional PEM fuel cells. Although it is known that HT-PEMS have some of the significant advantages as non-humidification requirements for membrane and the lack of liquid water at high temperature in the fuel cell, the generated water as a result of oxygen reduction reaction causes in the degradation of these systems. The generated water absorbed into membrane side interacts with the hydrophilic PBI matrix and it can cause swelling of membrane, so water transport mechanism in a membrane electrode assembly (MEA) needs to be well understood and water balance must be calculated in MEA. Therefore, the water diffusion transport across the electrolyte should be determined. In this study, various porosity values of gas diffusion layers are considered in order to investigate the effects of porosity on the water management for two phase flow in fuel cell. Two-dimensional fuel cell with interdigitated flow-field is modelled using COMSOL Multiphysics 4.2a software. The operating temperature and doping level is selected as 160°C and 6.75mol H3PO4/PBI, respectively.

  6. A simple fabrication of CH3NH3PbI3 perovskite for solar cells using low-purity PbI2

    NASA Astrophysics Data System (ADS)

    Guo, Nanjie; Zhang, Taiyang; Li, Ge; Xu, Feng; Qian, Xufang; Zhao, Yixin

    2017-01-01

    The CH3NH3PbI3 (MAPbI3) perovskite was usually prepared by high-purity PbI2 with high cost. The low cost and low-purity PbI2 was seldom reported for fabrication of MAPbI3 because it cannot even dissolve well in widely adopted solvent of DMF. We developed an easy method to adapt low-purity PbI2 for fabrication of high quality MAPbI3 just by the simple addition of some hydrochloric acid into the mixture of low-purity PbI2, MAI and DMF. This straightforward method can not only help dissolve the low quality PbI2 by reacting with some impurities in DMF, but also lead to a successful fabrication of high-quality perovskite solar cells with up to 14.80% efficiency comparable to the high quality PbI2 precursors. Project supported by the National Natural Science Foundation of China (Nos. 51372151, 21303103) and Houyingdong Grant (No. 151046).

  7. Effect of the filtration of PbI2 solution for zinc oxide nanowire based perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Mijanur Rahman, Md.; Uekawa, Naofumi; Shiba, Fumiyuki; Okawa, Yusuke; Sakai, Masatoshi; Yamamoto, Kazunuki; Kudo, Kazuhiro; Konishi, Takehisa

    2016-01-01

    Zinc oxide (ZnO) nanowires (NWs) are grown on fluorine-doped tin oxide (FTO) glass substrates via a simple reactive evaporation method without the presence of any catalysts or additives. The ZnO NWs show high crystallinity and preferential elongation along the c-axis of the hexagonal wurtzite crystal structure. The highly crystalline NWs as electron transporting layer have been used to fabricate the CH3NH3PbI3 perovskite solar cells and their photovoltaic performance were investigated. In this report, we studied the effect of filtration of PbI2-solution on surface morphology of CH3NH3PbI3 layer. Spin-coating of the filtered PbI2-solution leads to a better crystallization and relatively homogenous coverage of the CH3NH3PbI3 film, resulting in an enhancement of the solar cell efficiency compared to the cell fabricated using non-filtrated PbI2-solution. By synthesizing the CH3NH3PbI3 film using filtrated PbI2-solution, we achieved the best power conversion efficiency of 4.8% with a current density of 7.6 mA cm-2, the open circuit voltage of 0.79 V and fill factor of 0.63.

  8. Ultralow denier polybenzimidazole (PBI) yarns

    NASA Technical Reports Server (NTRS)

    Tan, M.; Leal, J. R.

    1977-01-01

    A study to determine the feasibility of preparing ultralow denier polybenzimidazole (PBI) yarns was undertaken. Conditions that presently yield multifilament yarns with bundle deniers ranging from 75 to 15,000 were used as a baseline. From this starting point, process parameters were identified that give five filament yarns with yarn densiers as low as 0.80. Physical properties from such ultralow denier yarns were at levels that would permit subsequent fabrication into fabrics.

  9. The Electropolymerization and Characterizations of Acid Red Dye Doped Polyaniline

    NASA Astrophysics Data System (ADS)

    Li, Xin; Liang, Fei-Yue; Liao, Jia-Xing; Wang, Rui; Zheng, Yi-Ping; Xian, Ze-Yu

    2016-05-01

    The electrochromic properties of an electrochemical polymerized composite consisted of polyaniline doped with acid red dye (PANI-ARD) are reported. The structures of PANIARD were characterized via cycle voltammograms, spectroelectrochemistry and colorimetric analysis. Film of the PANI-ARD composites of different concentrations appears violet, aubergine in the neutral state and darkblue in the oxidized state, which are different from the pure PANI of yellow (-0.8V) and blue (1.0V). The oxidation and reduction response speed of PANI-ARD was a bit lower than those obtained in pure PANI. It is shown that acid dye doping is an effective method to broaden the color change range of the electrochromicmateials.

  10. Systematic characterization of a PBI/H3PO4 sol-gel membrane-Modeling and simulation

    NASA Astrophysics Data System (ADS)

    Siegel, C.; Bandlamudi, G.; Heinzel, A.

    2011-03-01

    This work presents a three-dimensional, steady-state, non-isothermal model of a high-temperature polymer-electrolyte-membrane fuel cell (HTPEMFC) using a phosphoric acid-doped polybenzimidazole (PBI/H3PO4) sol-gel membrane. The model accounts for the gold-plated copper current collector plates, the bipolar plates, all gas flow channels (flow-field), the gas diffusion layers, the reaction layers, and the membrane. Electrochemical reactions are modeled using an agglomerate approach and include the gas diffusivity and the gas solubility. The conductivity of the membrane is modeled using the Arrhenius equation to describe the temperature dependence. Finite elements are used to discretize all computational subdomains, and a commercially available code is used to solve the problem. The predicted values are compared to typical operating conditions, and a good agreement is found. The current density, the solid- and fluid-(gas)-phase temperatures and other quantities are analyzed throughout the computational subdomains. It was observed that the Arrhenius approach is valid in a certain temperature range and may overpredict the PBI/H3PO4 sol-gel membrane conductivity at higher solid-phase temperatures. Moreover, it is shown how the fluid-(gas)-phase temperature influences the solid-phase temperature and the current density distribution. Concrete values are deduced from the simulations and discussed according to experimental test.

  11. Growth and characterization of KDP crystals doped with L-aspartic acid.

    PubMed

    Krishnamurthy, R; Rajasekaran, R; Samuel, Bincy Susan

    2013-03-01

    Potassium Dihydrogen Phosphate (KDP) doped with L-aspartic acid has been grown by solvent slow evaporation technique from a mixture of aqueous solution of KDP and 0.7% of L-aspartic acid at room temperature. The grown crystals were characterized by powder X-ray diffraction, UV-visible, FTIR analysis. The doping of aspartic acid was confirmed by FTIR spectrum. The Nonlinear optical property (SHG) of L-aspartic acid doped KDP has been confirmed. Microhardness studies were carried out on the grown crystal.

  12. Growth and characterization of KDP crystals doped with L-aspartic acid

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, R.; Rajasekaran, R.; Samuel, Bincy Susan

    2013-03-01

    Potassium Dihydrogen Phosphate (KDP) doped with L-aspartic acid has been grown by solvent slow evaporation technique from a mixture of aqueous solution of KDP and 0.7% of L-aspartic acid at room temperature. The grown crystals were characterized by powder X-ray diffraction, UV-visible, FTIR analysis. The doping of aspartic acid was confirmed by FTIR spectrum. The Nonlinear optical property (SHG) of L-aspartic acid doped KDP has been confirmed. Microhardness studies were carried out on the grown crystal.

  13. Unravelling the Effects of Grain Boundary and Chemical Doping on Electron-Hole Recombination in CH3NH3PbI3 Perovskite by Time-Domain Atomistic Simulation.

    PubMed

    Long, Run; Liu, Jin; Prezhdo, Oleg V

    2016-03-23

    Advancing organohalide perovskite solar cells requires understanding of carrier dynamics. Electron-hole recombination is a particularly important process because it constitutes a major pathway of energy and current losses. Grain boundaries (GBs) are common in methylammonium lead iodine CH3NH3PbI3 (MAPbI3) perovskite polycrystalline films. First-principles calculations have suggested that GBs have little effect on the recombination; however, experiments defy this prediction. Using nonadiabatic (NA) molecular dynamics combined with time-domain density functional theory, we show that GBs notably accelerate the electron-hole recombination in MAPbI3. First, GBs enhance the electron-phonon NA coupling by localizing and contributing to the electron and hole wave functions and by creating additional phonon modes that couple to the electronic degrees of freedom. Second, GBs decrease the MAPbI3 bandgap, reducing the number of vibrational quanta needed to accommodate the electronic energy loss. Third, the phonon-induced loss of electronic coherence remains largely unchanged and not accelerated, as one may expect from increased electron-phonon coupling. Further, replacing iodines by chlorines at GBs reduces the electron-hole recombination. By pushing the highest occupied molecular orbital (HOMO) density away from the boundary, chlorines restore the NA coupling close to the value observed in pristine MAPbI3. By introducing higher-frequency phonons and increasing fluctuation of the electronic gap, chlorines shorten electronic coherence. Both factors compete successfully with the reduced bandgap relative to pristine MAPbI3 and favor long excited-state lifetimes. The simulations show excellent agreement with experiment and characterize how GBs and chlorine dopants affect electron-hole recombination in perovskite solar cells. The simulations suggest a route to increased photon-to-electron conversion efficiencies through rational GB passivation.

  14. Doping optimization of polypyrrole with toluenesulfonic acid using Box-Behnken design

    SciTech Connect

    Syed Draman, Sarifah Fauziah; Daik, Rusli; El-Sheikh, Said M.; Latif, Famiza Abdul

    2013-11-27

    A three-level Box-Behnken design was employed in doping optimization of polypyrrole with toluenesulfonic acid (TSA-doped PPy). The material was synthesized via chemical oxidative polymerization using pyrrole, toluenesulfonic acid (TSA) and ammonium persulfate (APS) as monomer, dopant and oxidant, respectively. The critical factors selected for this study were concentration of dopant, molar ratio between dopant to monomer (pyrrole) and concentration of oxidant. Obtaining adequate doping level of TSA-doped PPy is crucial because it affects the charge carriers for doped PPy and usually be responsible for electronic mobility along polymeric chain. Furthermore, the doping level also affects other properties such as electrical and thermal conductivity. Doping level was calculated using elemental analysis. SEM images shows that the prepared TSA-doped PPy particles are spherical in shape with the diameters of about. The range of nanoparticles size is around 80-100 nm. The statistical analysis based on a Box–Behnken design showed that 0.01 mol of TSA, 1:1 mole ratio TSA to pyrrole and 0.25 M APS were the optimum conditions for sufficient doping level.

  15. Exceptionally crystalline and conducting acid doped polyaniline films by level surface assisted solution casting approach

    NASA Astrophysics Data System (ADS)

    Puthirath, Anand B.; Methattel Raman, Shijeesh; Varma, Sreekanth J.; Jayalekshmi, S.

    2016-04-01

    Emeraldine salt form of polyaniline (PANI) was synthesized by chemical oxidative polymerisation method using ammonium persulfate as oxidant. Resultant emeraldine salt form of PANI was dedoped using ammonia solution and then re-doped with camphor sulphonic acid (CSA), naphthaline sulphonic acid (NSA), hydrochloric acid (HCl), and m-cresol. Thin films of these doped PANI samples were deposited on glass substrates using solution casting method with m-cresol as solvent. A level surface was employed to get homogeneous thin films of uniform thickness. Detailed X-ray diffraction studies have shown that the films are exceptionally crystalline. The crystalline peaks observed in the XRD spectra can be indexed to simple monoclinic structure. FTIR and Raman spectroscopy studies provide convincing explanation for the exceptional crystallinity observed in these polymer films. FESEM and AFM images give better details of surface morphology of doped PANI films. The DC electrical conductivity of the samples was measured using four point probe technique. It is seen that the samples also exhibit quite high DC electrical conductivity, about 287 S/cm for CSA doped PANI, 67 S/cm for NSA doped PANI 65 S/cm for HCl doped PANI, and just below 1 S/cm for m-cresol doped PANI. Effect of using the level surface for solution casting is studied and correlated with the observed crystallinity.

  16. Palladium nanoparticles supported on titanium doped graphitic carbon nitride for formic acid dehydrogenation.

    PubMed

    Wu, Yongmei; Wen, Meicheng; Navlani-García, Miriam; Kuwahara, Yasutaka; Mori, Kohsuke; Yamashita, Hiromi

    2017-02-28

    Pd nanoparticles (NPs) supported on Ti-doped graphitic carbon nitride (g-C₃N₄) were synthetised by a deposition-precipitation route and a subsequent reduction with NaBH₄. The features of Pd supported Ti-doped g-C₃N₄ were studied by XRD, TEM, FT-IR, XPS, EXAFS and N₂ physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti-doped g-C₃N₄. Compared with Pd loaded on pristine g-C₃N₄, Pd NPs supported Ti-doped g-C₃N₄ catalyst exhibited a high activity in formic acid dehydrogenation in water at room temperature. The enhanced activity can be attributed to the small Pd NPs size as well as the strong interaction between Pd NPs and Ti-doped g-C₃N₄.

  17. Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals

    SciTech Connect

    Raghavan, C.M.; Sankar, R.; Mohan Kumar, R.; Jayavel, R.

    2008-02-05

    Effect of amino acids (L-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern.

  18. Photoelectrocatalytic degradation of benzoic acid using Au doped TiO2 thin films.

    PubMed

    Mohite, V S; Mahadik, M A; Kumbhar, S S; Hunge, Y M; Kim, J H; Moholkar, A V; Rajpure, K Y; Bhosale, C H

    2015-01-01

    Highly transparent pure and Au doped TiO2 thin films are successfully deposited by using simple chemical spray pyrolysis technique. The effect of Au doping onto the structural and physicochemical properties has been investigated. The PEC study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=1.81mA and Voc=890mV) relatively higher at 3at.% Au doping percentage. XRD study shows that the films are nanocrystalline in nature with tetragonal crystal structure. FESEM images show that the film surface covered with a smooth, uniform, compact and rice shaped nanoparticles. The Au doped thin films exhibit indirect band gap, decreases from 3.23 to 3.09eV with increase in Au doping. The chemical composition and valence states of pure and Au doped TiO2 films are studied by using X-ray photoelectron spectroscopy. The photocatalytic degradation effect is 49% higher in case 3at.% Au doped TiO2 than the pure TiO2 thin film photoelectrodes in the degradation of benzoic acid. It is revealed that Au doped TiO2 can be reused for five cycles of experiments without a requirement of post-treatment while the degradation efficiency was retained.

  19. Flame retardant treatments of PBI fabric.

    NASA Technical Reports Server (NTRS)

    Temin, S. C.

    1972-01-01

    Fabrics knitted or woven from polybenzimidazole (PBI) fibers were treated to reduce flammability in oxygen atmospheres, particularly that of 5 psia oxygen. Bromination to approximately 15% weight gain of such fabrics led to markedly lower burning rates; samples brominated to over 80% weight gain were self-extinguishing in 5 psia oxygen. The loss in tensile strength of fabrics due to bromination was negligible although shrinkage was observed. Free fibers showed negligible losses on bromination. Treatment of PBI fabric with organophosphorus compounds also achieved self-extinguishing character in 5 psia oxygen but the enhanced flameproofing was largely lost on leaching. Reaction with POCl3 in pyridine led to a permanent reduction in flammability.

  20. Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Jung, Kyung-Hye; Ferraris, John P.

    2016-10-01

    Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities.

  1. Refractive index modulation in polymer film doped with diazo Meldrum's acid

    NASA Astrophysics Data System (ADS)

    Zanutta, Alessio; Villa, Filippo; Bertarelli, Chiara; Bianco, Andrea

    2016-08-01

    Diazo Meldrum's acid undergoes a photoreaction induced by UV light and it is used as photosensitizer in photoresists. Upon photoreaction, a change in refractive index occurs, which makes this system interesting for volume holography. We report on the sublimation effect at room temperature and the effect of photoirradiation on the refractive index in thin films of CAB (Cellulose acetate butyrate) doped with different amount of diazo Meldrum's acid. A net modulation of the refractive index of 0.01 is achieved with 40% of doping ratio together with a reduction of the film thickness.

  2. Effect of NaCl and KCl doping on the growth of sulphamic acid crystals

    NASA Astrophysics Data System (ADS)

    Thaila, T.; Kumararaman, S.

    2011-11-01

    The nonlinear optical single crystals of doped sulphamic acid (SA) were grown from aqueous solution by doping with NaCl and KCl using slow evaporation method. Powder X-ray diffraction studies confirm that the grown crystals belong to orthorhombic system. The density and melting point measurements of the grown crystals were determined by floatation technique and capillary tube method, respectively. The range of optical transmittance was ascertained by recording the UV-Vis-NIR spectrum. Atomic absorption study reveals the presence of dopants in the doped crystals. The thermal analyses indicated that the doped SA crystals are more stable than pure crystals. The Vicker's microhardness studies revealed that the dopants increased the hardness of the crystals. SHG efficiency studies of the crystals are found to be increased in the presence of NaCl and KCl dopants.

  3. Nickel embedded in N-doped porous carbon for the hydrogenation of nitrobenzene to p-aminophenol in sulphuric acid.

    PubMed

    Wang, Tao; Dong, Zhen; Fu, Teng; Zhao, Yanchao; Wang, Tian; Wang, Yongzheng; Chen, Yi; Han, Baohang; Ding, Weiping

    2015-12-28

    An acid-resistant catalyst composed of nickel embedded in N-doped porous carbon is developed for the catalytic hydrogenation of nitrobenzene (NB) to p-aminophenol (PAP). The catalyst, due to a special electron donation from nickel to the N-doped porous carbon, shows an excellent catalytic performance and stability in sulphuric acid solution.

  4. Chlorine Incorporation in the CH3NH3PbI3 Perovskite: Small Concentration, Big Effect.

    PubMed

    Quarti, Claudio; Mosconi, Edoardo; Umari, Paolo; De Angelis, Filippo

    2017-01-03

    The role of chlorine doping in CH3NH3PbI3 represents an important open issue in the use of hybrid perovskites for photovoltaic applications. In particular, even if a positive role of chlorine doping on perovskite film formation and on material morphology has been demonstrated, an inherent positive effect on the electronic and photovoltaic properties cannot be excluded. Here we carried out periodic density functional theory and Car-Parrinello molecular dynamics simulations, going down to ∼1% doping, to investigate the effect of chlorine on CH3NH3PbI3. We found that such a small doping has important effects on the dynamics of the crystalline structure, both with respect to the inorganic framework and with respect to the cation libration motion. Together, we observe a dynamic spatial localization of the valence and conduction states in separated spatial material regions, which takes place in the 10(-1) ps time scale and which could be the key to ease of exciton dissociation and, likely, to small charge recombination in hybrid perovskites. Moreover, such localization is enhanced by chlorine doping, demonstrating an inherent positive role of chlorine doping on the electronic properties of this class of materials.

  5. Evaluation of the acid properties of porous zirconium-doped and undoped silica materials

    SciTech Connect

    Fuentes-Perujo, D.; Santamaria-Gonzalez, J.; Merida-Robles, J.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.; Maireles-Torres, P. . E-mail: maireles@uma.es; Moreno-Tost, R.

    2006-07-15

    A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N{sub 2} adsorption at 77 K. Their acid properties have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites. - Graphical abstract: The adsorption of basic probe molecules and the catalytic behaviour have revealed that MSU-type materials are more acidic than the analogous MCM-41 solids, mainly after the incorporation of zirconium into the silica framework.

  6. Light stability tests of CH3NH3PbI3 perovskite solar cells using porous carbon counter electrodes.

    PubMed

    Ito, Seigo; Mizuta, Gai; Kanaya, Shusaku; Kanda, Hiroyuki; Nishina, Tomoya; Nakashima, Seiji; Fujisawa, Hironori; Shimizu, Masaru; Haruyama, Yuichi; Nishino, Hitoshi

    2016-10-21

    The CH3NH3PbI3 perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO2/porous TiO2-perovskite/porous ZrO2-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CH3NH3PbI3 perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm(-2)). Considering the color variation of the CH3NH3PbI3 perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CH3NH3PbI3 perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.

  7. Mechanism of proton transport in ionic-liquid-doped perfluorosulfonic acid membranes.

    PubMed

    Kumar, Milan; Venkatnathan, Arun

    2013-11-21

    Ionic-liquid-doped perfluorosulfonic acid membranes (PFSA) are promising electrolytes for intermediate/high-temperature fuel cell applications. In the present study, we examine proton-transport pathways in a triethylammonium-triflate (TEATF) ionic liquid (IL)-doped Nafion membrane using quantum chemistry calculations. The IL-doped membrane matrix contains triflic acid (TFA), triflate anions (TFA(-)), triethylamine (TEA), and triethylammonium cations (TEAH(+)). Results show that proton abstraction from the sulfonic acid end groups in the membrane by TFA(-) facilitates TEAH(+) interaction with the side-chains. In the IL-doped PFSA membrane matrix, proton transfer from TFA to TEA and TFA to TFA(-) occurs. However, proton transfer from a tertiary amine cation (TEAH(+)) to a tertiary amine (TEA) does not occur without an interaction with an anion (TFA(-)). An anion interaction with the amine increases its basicity, and as a consequence, it takes a proton from a cation either instantly (if the cation is freely moving) or with a small activation energy barrier of 2.62 kcal/mol (if the cation is interacting with another anion). The quantum chemistry calculations predict that anions are responsible for proton-exchange between cations and neutral molecules of a tertiary amine. Results from this study can assist the experimental choice of IL to provide enhanced proton conduction in PFSA membrane environments.

  8. A comparison study of rhodamine B photodegradation over nitrogen-doped lamellar niobic acid and titanic acid under visible-light irradiation.

    PubMed

    Li, Xiukai; Kikugawa, Naoki; Ye, Jinhua

    2009-01-01

    A solid-state reaction method with urea as a nitrogen precursor was used to prepare nitrogen-doped lamellar niobic and titanic solid acids (i.e., HNb(3)O(8) and H(2)Ti(4)O(9)) with different acidities for visible-light photocatalysis. The photocatalytic activities of the nitrogen-doped solid acids were evaluated for rhodamine B (RhB) degradation and the results were compared with those obtained over the corresponding nitrogen-doped potassium salts. Techniques such as XRD, BET, SEM, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy were adopted to explore the nature of the materials as well as the characteristics of the doped nitrogen species. It was found that the intercalation of the urea precursor helped to stabilize the layered structures of both lamellar solid acids and enabled easier nitrogen doping. The effects of urea intercalation were more significant for the more acidic HNb(3)O(8) sample than for the less acidic H(2)Ti(4)O(9). Compared with the nitrogen-doped KNb(3)O(8) and K(2)Ti(4)O(9) samples, the nitrogen-doped HNb(3)O(8) and H(2)Ti(4)O(9) solid acids absorb more visible light and exhibit a superior activity for RhB photodegradation under visible-light irradiation. The nitrogen-doped HNb(3)O(8) sample performed the best among all the samples. The results of the current study suggest that the protonic acidity of the lamellar solid-acid sample is a key factor that influences nitrogen doping and the resultant visible-light photocatalysis.

  9. Chemical doping of MoS2 multilayer by p-toluene sulfonic acid

    PubMed Central

    Andleeb, Shaista; Kumar Singh, Arun; Eom, Jonghwa

    2015-01-01

    We report the tailoring of the electrical properties of mechanically exfoliated multilayer (ML) molybdenum disulfide (MoS2) by chemical doping. Electrical charge transport and Raman spectroscopy measurements revealed that the p-toluene sulfonic acid (PTSA) imposes n-doping in ML MoS2. The shift of threshold voltage for ML MoS2 transistor was analyzed as a function of reaction time. The threshold voltage shifted toward more negative gate voltages with increasing reaction time, which indicates an n-type doping effect. The shift of the Raman peak positions was also analyzed as a function of reaction time. PTSA treatment improved the field-effect mobility by a factor of ~4 without degrading the electrical characteristics of MoS2 devices. PMID:27877810

  10. Poly (acrylic acid)-capped lanthanide-doped BaFCl nanocrystals: synthesis and optical properties.

    PubMed

    Ju, Qiang; Luo, Wenqin; Liu, Yongsheng; Zhu, Haomiao; Li, Renfu; Chen, Xueyuan

    2010-07-01

    Water-soluble lanthanide-doped BaFCl nanophosphors with the surface functionalized by a layer of poly (acrylic acid) are synthesized via a facile one-step solvothermal method. Intense long-lived luminescence is realized from visible to near-infrared (NIR) by doping with different lanthanide ions. The emission and excitation spectra of Eu(3+) indicate that the doped lanthanide ions occupy a site close to the surface of the nanoparticles. Strong NIR emissions of Nd(3+) and green luminescence of Tb(3+) using Ce(3+) as sensitizers are also achieved in BaFCl nanoparticles. The synthesized nanoparticles featuring long-lived luminescence in either visible or NIR regions may have potential applications as luminescent labels for biological applications.

  11. Photocatalytic activity of S- and F-doped TiO(2) in formic acid mineralization.

    PubMed

    Dozzi, Maria Vittoria; Livraghi, Stefano; Giamello, Elio; Selli, Elena

    2011-03-02

    Two series of doped titanium dioxide samples (S-TiO(2) and F-TiO(2)) were prepared by the sol-gel method in the presence of different amounts of dopant source (thiourea and NH(4)F, respectively), followed by calcination at 500, 600 or 700 °C, and characterised by BET, UV-vis absorption, XPS, HRTEM, XRD and EPR analyses. Reference undoped materials were prepared by the same synthetic procedure. Their photocatalytic activity under visible light was investigated employing the photocatalytic degradation of formic acid in aqueous suspension as test reaction. S-doped TiO(2) showed a photocatalytic activity quite similar to that of undoped materials. In this regard, the insertion of S, characterised by a relatively large ionic radius, into the TiO(2) crystalline structure appears rather difficult, as confirmed by XPS analysis. On the contrary, moderate F doping was beneficial in increasing the rate of formic acid photocatalytic degradation, especially for photocatalysts calcined at high temperature, consisting of highly crystalline pure anatase, in which the rate of detrimental charge carrier recombination was reduced. For both series of doped materials, high doping levels appear to limit the semiconductor photoactivity, probably due to the formation of a progressively increasing number of charge recombination centres. The EPR characterisation of the investigated doped TiO(2) samples evidenced the presence of nitrogen containing species (nitric oxide radical encapsulated in micro-void, with no photoactivity, and N(b)˙ species, active in visible light sensitisation) and of titanium reduced centres Ti(3+), due to charge imbalance consequent to dopant introduction in the TiO(2) lattice either in anionic (F(-)) or in cationic form (S(6+)).

  12. Uptake of formic acid on thin ice films and on ice doped with nitric acid between 195 and 211 K.

    PubMed

    Romanias, Manolis N; Zogka, Antonia G; Stefanopoulos, Vassileios G; Papadimitriou, Vassileios C; Papagiannakopoulos, Panos

    2010-12-17

    The adsorption of formic acid on thin ice films and on ice doped with nitric acid (1.96, 7.69 and 53.8 wt%) is studied as a function of temperature T=195-211 K and gas concentration (0.33-10.6)×10(11) molecule cm(-3). Experiments are performed in a Knudsen flow reactor coupled with a quadrupole mass spectrometer. The initial uptake coefficients γ are strongly and inversely dependent on the ice temperature. Initial uptake is determined at low surface coverages and ranges from (0.65-3.78)×10(-3). The adsorption uptake of formic acid on pure ice films and on ice lightly doped with HNO(3) is a reversible process, and the adsorption isotherms exhibit Langmuir behaviour. N(max)(1) is (2.94±0.67)×10(14) molecule cm(-2), in good agreement with previous measurements. The temperature dependence of K(Lin) is very well represented by the expression: K(Lin)(1)=(1.43±0.32)×10(-8) exp[(4720±520)/T] cm(3) molecule(-1); the quoted uncertainty is at the 95% level of confidence and includes systematic uncertainties. Formic acid uptakes on ice films highly doped with HNO(3) (53.8 wt%) are two orders of magnitude higher than those measured on pure ice films and irreversible, thus indicating the formation of a supercooled liquid layer on the ice films upon which dissolution of formic acid occurs. Finally, the atmospheric lifetime of formic acid due to heterogeneous loss on cirrus cloud ice particles and the removal of formic acid by adsorption are estimated under conditions related to the upper troposphere.

  13. Growth of DL-malic acid-doped ammonium dihydrogen phosphate crystal and its characterization

    NASA Astrophysics Data System (ADS)

    Rajesh, P.; Ramasamy, P.

    2009-06-01

    Single crystals of DL-malic acid-doped ammonium dihydrogen phosphate have been grown using slow evaporation method and also by Sankaranarayanan-Ramasamy (SR) method with the vision to improve the properties of the ADP crystals. The characterization of grown crystals was made by single-crystal X-ray diffraction, powder X-ray diffraction, UV-vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), Vicker's microhardness, dielectric measurements, high-resolution X-ray diffraction (HRXRD) and second-harmonic studies. Structural difference between pure and doped crystal has been studied by XRD analysis. Functional groups were identified by FTIR spectroscopy. The grown crystals were found to be transparent in the entire visible region. Decomposition temperatures of the grown crystals were measured by DTA. Vicker's hardness study carried out on (0 0 1) face at room temperature shows increased hardness of the doped crystals and SR-method-grown crystals. Dielectric measurements reveal that SR-method-grown DLM-doped ADP crystals have low dielectric loss. Crystalline perfection of the grown crystals is analyzed using HRXRD. Preliminary measurements indicate that the second harmonic generation efficiency of the doped crystals at a fundamental wavelength of 1064 nm is roughly 1.5 times greater than that of pure ADP.

  14. Superconducting properties of adipic-acid-doped bulk MgB2 superconductor

    NASA Astrophysics Data System (ADS)

    Vajpayee, Arpita; Awana, V. P. S.; Bhalla, G. L.; Bhobe, P. A.; Nigam, A. K.; Kishan, H.

    2009-01-01

    We report the effect of adipic acid (C6H10O4) doping on lattice parameters, microstructure, critical temperature (Tc), current density (Jc) and irreversibility field (Hirr) for an MgB2 superconductor. Actual carbon (C) substitution level for boron (B) is estimated to be from 0.40 at.% to 2.95 at.% for different doping levels. A reduction in Tc from 38.43 to 34.93 K and in lattice parameter a from 3.084(3) Å to 3.075(6) Å is observed for the 10 wt% C6H10O4 doped sample in comparison to pristine MgB2. This is an indication of C substitution at boron sites, with the C coming from the decomposition of C6H10O4 at the time of reaction. Interestingly the doped samples have resulted in significant enhancement of Jc and Hirr. All the doped samples exhibit the Jc value of the order of 104 A cm-2 at 5 K and 8 T, which is higher by an order of magnitude as compared to the undoped sample. This result indicates that C6H10O4 is a promising material for MgB2 for obtaining the excellent Jc values under higher magnetic fields.

  15. Iminodiacetic acid doped ferroelectric triglycine sulphate crystal: Crystal growth and characterization

    NASA Astrophysics Data System (ADS)

    Rai, Chitharanjan; Narayana Moolya, B.; Dharmaprakash, S. M.

    2011-01-01

    Single crystals of iminodiacetic acid (HN(CH 2COOH) 2) doped triglycine sulphate (IDATGS) crystals have been grown from aqueous solution containing 1-10 mol% of iminodiacetic acid at constant temperature by slow evaporation technique. The effects of different amounts of doping entities on the growth habit have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. The grown crystals were subjected to Fourier transform infrared (FTIR) spectroscopy studies to find the presence of various functional groups qualitatively. The dielectric permittivity has been studied as a function of temperature. An increase in the transition temperature (49.2-49.7 °C) of IDATGS crystals is observed. The dielectric constant ( ε‧ max) of IDATGS crystals vary in the range 922-2410 compared to pure TGS ( Tc=49.12 °C and ε‧ max=3050). Curie Weiss constants Cp and Cf in the paraelectric and ferroelectric phases were determined. The transition temperature ( Tc) is found to decrease with increase in dopant concentration. P- E hysteresis studies show the presence of internal bias field in the crystal. Piezoelectric measurements were also carried out at room temperature. Domain patterns on b-cut plates were observed using scanning electron microscope. The micro hardness studies reveal that the doped crystals are harder than the pure TGS crystals. The low dielectric constant, higher transition temperature, internal bias field and hardness suggest that IDATGS crystals could be a potential material for IR detectors.

  16. 3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

    PubMed Central

    Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

    2016-01-01

    A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g−1 is realized for the optimised case of binary doping over the entire range of 1 A g−1 to 40 A g−1 with stability of 500 cycles at 40 A g−1. Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system. PMID:26867570

  17. 3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

    NASA Astrophysics Data System (ADS)

    Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

    2016-02-01

    A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g‑1 is realized for the optimised case of binary doping over the entire range of 1 A g‑1 to 40 A g‑1 with stability of 500 cycles at 40 A g‑1. Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system.

  18. Enhancing proton conduction via doping of supramolecular liquid crystals (4-alkoxybenzoic acids) with imidazole

    NASA Astrophysics Data System (ADS)

    Liang, Ting; Wu, Yong; Tan, Shuai; Yang, Xiaohui; Wei, Bingzhuo

    2015-09-01

    Enhancing proton conduction via doping was first achieved in hydrogen-bonded liquid crystals consisting of benzoic acids. Supramolecular liquid crystals formed by pure 4-alkoxybenzoic acids (nAOBA, n = 8, 10, 12) exhibited the maximum proton conductivity of 5.0 × 10-8 S cm-1. Doping of nAOBA with 25 mol% imidazole (Im0.25) had little impact on mesomorphism but increased proton conductivities by at least 3 orders of magnitude. The liquid crystals formed by nAOBA-Im0.25 exhibited the maximum proton conductivity of 1.9 × 10-4 S cm-1. It was proposed that structure diffusion of imidazole bridged interdimer proton transfer to form continuous conducting pathways in mesomorphic nAOBA-Im0.25.

  19. Investigations on the electrical and structural properties of polyaniline doped with camphor sulphonic acid

    NASA Astrophysics Data System (ADS)

    Saravanan, S.; Joseph Mathai, C.; Anantharaman, M. R.; Venkatachalam, S.; Prabhakaran, P. V.

    2006-07-01

    Polyaniline is chemically synthesised and doped with camphor sulphonic acid. FTIR studies carried out on these samples indicate that the aromatic rings are retained after polymerisation. The percentage of crystallinity for polyaniline doped with camphor sulphonic acid has been estimated from the X-ray diffraction studies and is around 56% with respect to polyaniline emeraldine base. The change in dielectric permittivity with respect to temperature and frequency is explained on the basis of interfacial polarisation. AC conductivity is evaluated from the observed dielectric permittivity. The values of AC and DC conductivity and activation energy are calculated. The activation energy values suggested that the hopping conduction is the prominent conduction mechanism in this system.

  20. Ferromagnetic Conducting Lignosulfonic Acid-doped Polyaniline Nanocomposites

    NASA Technical Reports Server (NTRS)

    Viswansthan, Tito (Inventor); Berry, Brian (Inventor)

    2004-01-01

    A conductive ferromagnetic composition of matter comprising sulfonated lignin or a sulfonated polyflavonoid, or derivatives thereof, and ferromagnetic iron oxide particles is disclosed. Among the uses of the composition is to shield electromagnetic radiation. The ferromagnetic iron oxide particles of the composition are surprisingly stable to acid, and are easily and inexpensively formed from iron cations in solution.

  1. Transport Properties of 60% camphor sulfonic acid (CSA) doped polyanilines.

    NASA Astrophysics Data System (ADS)

    Lee, W.-P.; Gudmundsdottir, A.; Platz, M. S.; Epstein, A. J.; Monkman, A. P.

    1998-03-01

    We report correlated σ_DC(T) and S(T) of unstretched and stretched polyaniline films prepared from m-cresol using 0.60 HCSA per ring. For unstretched film with σ_DC(300K) ~ 270 S/cm and σ(10K)/σ(300K) ~ 0.6 showing a metallic state near an insulator-metal transition(IMT), S(300K) is +8.5 ± 0.5 μV/K with nearly linear S(T) similar to that reported earlier for PAN-CSA fibers.(Y.Z. Wang, et al.), Synth. Met. 68, 207 (1995) For unstretched film on the insulator side of the IMT, σ_DC(300K) is ~ 85 S/cm with σ(10K)/σ(300K) ~ 0.28 and S(300K) is +5.5 ± 0.5 μV/K. For stretched film, σ_DC(300K) and S(300K) for parallel and perpendicular the stretched direction are ~ 630, ~ 90 S/cm, and +10 ± 0.5 and +7 ± 0.5 μV/K, respectively. They are on the metallic side of the IMT with σ(10K)/σ(300K) ~ 0.45, have nearly temperature independent σ_parallel(T)/σ_perpendicular(T), and have nearly linear S(T). Thermoelectric power results for these CSA doped polyaniline samples with different σ(T) are discussed in terms of an effective medium model in accord with inhomogeneous disorder present.(F. Zuo, et al.), Phys. Rev. B 36, 3475 (1987)

  2. Electroactive self-doped poly(amic acid) with oligoaniline and sulfonic acid groups: synthesis and electrochemical properties.

    PubMed

    Chi, Maoqiang; Wang, Shutao; Liang, Yuan; Chao, Danming; Wang, Ce

    2014-06-01

    A novel poly(amic acid) with pendant aniline tetramer and sulfonic acid groups (ESPAA) was synthesized by ternary polymerization and characterized by Fourier-transform infrared spectra, ((1))H NMR and gel permeation chromatography. The polymer showed good thermal stability and excellent solubility in the common organic solvents. The electrochemical properties were investigated carefully on a CHI 660A Electrochemical Workstation. The polymer displayed good electroactivity in acid, neutral and even in alkaline solutions (pH=1-10) due to the self-doping effect between aniline tetramer and sulfonic/carboxylic acid groups. It also exhibited satisfactory electrochromic performance with high contrast value, acceptable coloration efficiency and fast switching time in the range of pH=1-9.

  3. Impedance Profiling: A Convenient Technique for Determining the Redox or Protonic Acid Doping Characteristics of Conducting Polymers

    DTIC Science & Technology

    1991-03-18

    public release and sale; its distribution is unlimited. IMPEDANCE PROFILING: A CONVENIENT TECHNIqUE FOR DETERMINING THE REDOX OR PROTONIC ACID DOPING...methods. Results for the oxidative doping of trans-(CH)x in HBF 4 (48% aq.)/H 2 02 , and in CF3 COOH (80%, aq.)/H 20 2 , for cis- (CH)x in iodine / CCl4 ...TECHNIQUE FOR DETERMINING THE REDOX OR PROTONIC ACID DOPING CHARACTERISTICS OF CONDUCTING POLYMERS" 12. PERSONAL AUTHOR(S) D.B. Swanson, A.G. MacDiarmid and

  4. Doping Polypyrrole Films with 4-N-Pentylphenylboronic Acid to Enhance Affinity towards Bacteria and Dopamine

    PubMed Central

    Padiolleau, Laurence; Chen, Xi; Jafari, Mohammad Javad; Sheikhzadeh, Elham; Turner, Anthony P. F.; Jager, Edwin W. H.; Beni, Valerio

    2016-01-01

    Here we demonstrate the use of a functional dopant as a fast and simple way to tune the chemical affinity and selectivity of polypyrrole films. More specifically, a boronic-functionalised dopant, 4-N-Pentylphenylboronic Acid (PBA), was used to provide to polypyrrole films with enhanced affinity towards diols. In order to prove the proposed concept, two model systems were explored: (i) the capture and the electrochemical detection of dopamine and (ii) the adhesion of bacteria onto surfaces. The chemisensor, based on overoxidised polypyrrole boronic doped film, was shown to have the ability to capture and retain dopamine, thus improving its detection; furthermore the chemisensor showed better sensitivity in comparison with overoxidised perchlorate doped films. The adhesion of bacteria, Deinococcus proteolyticus, Escherichia coli, Streptococcus pneumoniae and Klebsiella pneumoniae, onto the boric doped polypyrrole film was also tested. The presence of the boronic group in the polypyrrole film was shown to favour the adhesion of sugar-rich bacterial cells when compared with a control film (Dodecyl benzenesulfonate (DBS) doped film) with similar morphological and physical properties. The presented single step synthesis approach is simple and fast, does not require the development and synthesis of functional monomers, and can be easily expanded to the electrochemical, and possibly chemical, fabrication of novel functional surfaces and interfaces with inherent pre-defined sensing and chemical properties. PMID:27875555

  5. Doping Polypyrrole Films with 4-N-Pentylphenylboronic Acid to Enhance Affinity towards Bacteria and Dopamine.

    PubMed

    Golabi, Mohsen; Padiolleau, Laurence; Chen, Xi; Jafari, Mohammad Javad; Sheikhzadeh, Elham; Turner, Anthony P F; Jager, Edwin W H; Beni, Valerio

    2016-01-01

    Here we demonstrate the use of a functional dopant as a fast and simple way to tune the chemical affinity and selectivity of polypyrrole films. More specifically, a boronic-functionalised dopant, 4-N-Pentylphenylboronic Acid (PBA), was used to provide to polypyrrole films with enhanced affinity towards diols. In order to prove the proposed concept, two model systems were explored: (i) the capture and the electrochemical detection of dopamine and (ii) the adhesion of bacteria onto surfaces. The chemisensor, based on overoxidised polypyrrole boronic doped film, was shown to have the ability to capture and retain dopamine, thus improving its detection; furthermore the chemisensor showed better sensitivity in comparison with overoxidised perchlorate doped films. The adhesion of bacteria, Deinococcus proteolyticus, Escherichia coli, Streptococcus pneumoniae and Klebsiella pneumoniae, onto the boric doped polypyrrole film was also tested. The presence of the boronic group in the polypyrrole film was shown to favour the adhesion of sugar-rich bacterial cells when compared with a control film (Dodecyl benzenesulfonate (DBS) doped film) with similar morphological and physical properties. The presented single step synthesis approach is simple and fast, does not require the development and synthesis of functional monomers, and can be easily expanded to the electrochemical, and possibly chemical, fabrication of novel functional surfaces and interfaces with inherent pre-defined sensing and chemical properties.

  6. Biocompatibility of electrospun halloysite nanotube-doped poly(lactic-co-glycolic acid) composite nanofibers.

    PubMed

    Qi, Ruiling; Cao, Xueyan; Shen, Mingwu; Guo, Rui; Yu, Jianyong; Shi, Xiangyang

    2012-01-01

    Organic/inorganic hybrid nanofiber systems have generated great interest in the area of tissue engineering and drug delivery. In this study, halloysite nanotube (HNT)-doped poly(lactic-co-glycolic acid) (PLGA) composite nanofibers were fabricated via electrospinning and the influence of the incorporation of HNTs within PLGA nanofibers on their in vitro biocompatibility was investigated. The morphology, mechanical and thermal properties of the composite nanofibers were characterized by scanning electron microscopy (SEM), tensile test, differential scanning calorimetry and thermogravimetric analysis. The adhesion and proliferation of mouse fibroblast cells cultured on both PLGA and HNT-doped PLGA fibrous scaffolds were compared through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay of cell viability and SEM observation of cell morphology. We show that the morphology of the PLGA nanofibers does not appreciably change with the incorporation of HNTs, except that the mean diameter of the fibers increased with the increase of HNT incorporation in the composite. More importantly, the mechanical properties of the nanofibers were greatly improved. Similar to electrospun PLGA nanofibers, HNT-doped PLGA nanofibers were able to promote cell attachment and proliferation, suggesting that the incorporation of HNTs within PLGA nanofibers does not compromise the biocompatibility of the PLGA nanofibers. In addition, we show that HNT-doped PLGA scaffolds allow more protein adsorption than those without HNTs, which may provide sufficient nutrition for cell growth and proliferation. The developed electrospun HNT-doped composite fibrous scaffold may find applications in tissue engineering and pharmaceutical sciences.

  7. Polypyrrole electrodes doped with sulfanilic acid azochromotrop for electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Chen, S.; Zhitomirsky, I.

    2013-12-01

    In this work we demonstrate the feasibility of deposition of polypyrrole (PPy) films by electropolymerization on stainless steel substrates and fabrication of PPy powders by chemical polymerization using sulfanilic acid azochromotrop (SPADNS) as a new anionic dopant. The problem of low adhesion of PPy films to stainless steel substrates is addressed by the use of SPADNS, which exhibits chelating properties, promoting film formation. The use of fine particles, prepared by the chemical polymerization method, allows impregnation of Ni foams and fabrication of porous electrodes with high materials loading for electrochemical supercapacitors (ES). PPy films and Ni foam based PPy electrodes show capacitive behaviour in Na2SO4 electrolyte. The electron microscopy studies, impedance spectroscopy data and analysis of the SPADNS structure provide an insight into the factors, controlling capacitive behaviour. The Ni foam based electrodes offer advantages of improved capacitive behaviour at high materials loadings and good cycling stability. The area normalized and volume normalized specific capacitances are as high as 5.43 F cm-2 and 93.6 F cm-3, respectively, for materials loading of 35.4 mg cm-2. The capacitance retention of Ni foam based electrodes is 91.5% after 1000 cycles. The Ni foam based PPy electrodes are promising for application in ES.

  8. Investigation to the deep center related properties of low temperature grown InPBi with Hall and photoluminescence

    SciTech Connect

    Wang, Peng; Pan, Wenwu; Wu, Xiaoyan; Wang, Kai; Yue, Li; Gong, Qian; Wang, Shumin

    2015-12-15

    InP{sub 1-x}Bi{sub x} epilayers with bismuth (Bi) concentration x= 1.0% were grown on InP by gas source molecular beam epitaxy (GS-MBE) at low temperature (LT). Bi incorporation decreased the intrinsic free electron concentration of low temperature grown InP indicated by hall analysis. It is concluded that deep level center was introduced by Bi. Influence of Si doping on the InP{sub 1-x}Bi{sub x} films Photoluminescence (PL) was investigated. N-type doping in the InP{sub 1-x}Bi{sub x} epilayers was found to be effective at PL enhancement. Blue shift of InPBi PL emission wavelength was observed as the Si doping concentration increasing. Two independent peaks were fitted and their temperature dependence behavior was observed to be distinct obviously. Two individual radiative recombination processes were expected to be involved.

  9. Carbon doping of MgB 2 by toluene and malic-acid-in-toluene

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, S. D.; Susner, M. A.; Yang, Y.; Collings, E. W.; Sumption, M. D.; Rindfleisch, M. A.; Boone, R.

    2011-02-01

    The decomposition of malic acid (C 4H 6O 5) in the presence of Mg and B was studied using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) which revealed that malic acid reacted with Mg but not B. Also, the addition of toluene (C 7H 8) to dissolve malic acid followed by subsequent drying resulted in no reaction with Mg, indicating that the malic acid had decomposed during the dissolution/drying stage. The total carbon contributed by toluene versus a toluene/5 wt.% malic acid mixture was measured using a LECO CS600 carbon analyzer. The toluene sample contained ∼0.4 wt.% C while the toluene/malic acid mixture had ∼1.5 wt.% C, demonstrating that the toluene contributed a significant amount of carbon to the final product. Resistivity measurements on powder-in-tube MgB 2 monofilamentary wires established that the toluene/malic acid doped sample had the highest B c2. However, the toluene-only sample had the highest transport J c over most of the magnetic field range (0-9 T), equaled only by that of toluene/malic-acid sample in fields above 9 T.

  10. Modulated CH3NH3PbI3-xBrx film for efficient perovskite solar cells exceeding 18.

    PubMed

    Tu, Yongguang; Wu, Jihuai; Lan, Zhang; He, Xin; Dong, Jia; Jia, Jinbiao; Guo, Panfeng; Lin, Jianming; Huang, Miaoliang; Huang, Yunfang

    2017-03-17

    The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3-xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3-xBrx film.

  11. Effect of Morphology Control of Light Absorbing Layer on CH3NH3PbI3 Perovskite Solar Cells.

    PubMed

    Lei, Binglong; Eze, Vincent Obiozo; Mori, Tatsuo

    2016-04-01

    As one of the most significant components of perovskite solar cells, the perovskite light absorbing layer demands high quality to guarantee extraordinary power conversion efficiency (PCE). We have fabricated series of CH3NH3PbI3 perovskite solar cells by virtue of gas-flowing assisting (GFA), spin coating twice for the Pbl2 layer and dipping the semi-samples in a thermal CH3NH3I solution, by which some undesirable perovskite morphologies can be effectively avoided. The modified conductions have also dramatically improved the perovskite layer and elevated the coverage ratio from 53.6% to 79.5%. All the fabrication processes, except the steps for deposition of the hole transport material (HTM) and back gold electrode, have been conducted in air and an average PCE of 6.6% has been achieved by initiatively applying N,N'-bis(1-naphtyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) doped by MoO3 as HTM. The CH3NH3PbI3 perovskite's morphology and its coverage ratio to the underneath TiO2 mesoporic layer are evaluated to account for the cells' performance. It has demonstrated that higher homogeneity and coverage ratio of the CH3NH3PbI3 layer have most significantly contributed to the solar cells' light conversion efficiency. Keywords: Perovskite, Solar Cell, Morphology, Coverage Ratio, Hole Transport Material.

  12. Effects of SbBr3 addition to CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Oku, Takeo; Ohishi, Yuya; Suzuki, Atsushi

    2017-01-01

    TiO2/CH3NH3Pb1-xSbxI3-2xBr3x-based photovoltaic devices were fabricated, and effects of SbBr3 addition to CH3NH3PbI3 precursor solutions on the photovoltaic properties were investigated. The short-circuit current densities and photoconversion efficiencies were improved by adding a small amount of SbBr3 to the perovskite phase, which would be due to a doping effect of Sb or Br atoms at the Pb or I sites.

  13. Magnetic resonance and electrical properties of p-toluene sulphonic acid doped polyaniline

    NASA Astrophysics Data System (ADS)

    Arora, Manju; Arya, S. K.; Barala, Sunil Kumar; Saini, Parveen

    2013-06-01

    p-Toluene Sulphonic Acid (PTSA) doped polyaniline (PANI) analogues were synthesized by oxidative chemical polymerization method and characterized by TGA FTIR and EPR spectroscopic techniques. FTIR spectra indicates the formation of PTSA doped PANI and also revealed the dopant ions mediated interactions between polymeric chain through weak hydrogen bonding. TGA plots revealed that there is systematic variation in the weight loss at ˜300 °C from ˜4% to ˜38% with increase in dopant concentration from 0.01 N to 1.0 N. Magnetic resonance spectra of polaron charge carriers exhibit the single Lorentzian line signal with the Dysonian contribution indicating formation of metal-like domains. The polarons are localized in these domains by strong interaction between the neighboring conducting chains, in which the charge is transferred by quasi-three-dimensional (Q3D) delocalized electron. In higher concentration analogue some of polarons merge into diamagnetic bipolarons and this reduces intensity of EPR signal. The electrical conductivity of the 1.0 N PTSA doped sample was ˜4.5 S/cm which satisfies the EMI shielding criteri.

  14. Dual activities of the anti-cancer drug candidate PBI-05204 provide neuroprotection in brain slice models for neurodegenerative diseases and stroke

    PubMed Central

    Van Kanegan, Michael J.; Dunn, Denise E.; Kaltenbach, Linda S.; Shah, Bijal; He, Dong Ning; McCoy, Daniel D.; Yang, Peiying; Peng, Jiangnan; Shen, Li; Du, Lin; Cichewicz, Robert H.; Newman, Robert A.; Lo, Donald C.

    2016-01-01

    We previously reported neuroprotective activity of the botanical anti-cancer drug candidate PBI-05204, a supercritical CO2 extract of Nerium oleander, in brain slice and in vivo models of ischemic stroke. We showed that one component of this neuroprotective activity is mediated through its principal cardiac glycoside constituent, oleandrin, via induction of the potent neurotrophic factor brain-derived neurotrophic factor (BDNF). However, we also noted that the concentration-relation for PBI-05204 in the brain slice oxygen-glucose deprivation (OGD) model is considerably broader than that for oleandrin as a single agent. We thus surmised that PBI-05204 contains an additional neuroprotective component(s), distinct from oleandrin. We report here that neuroprotective activity is also provided by the triterpenoid constituents of PBI-05204, notably oleanolic acid. We demonstrate that a sub-fraction of PBI-05204 (Fraction 0–4) containing oleanolic and other triterpenoids, but without cardiac glycosides, induces the expression of cellular antioxidant gene transcription programs regulated through antioxidant transcriptional response elements (AREs). Finally, we show that Fraction 0–4 provides broad neuroprotection in organotypic brain slice models for neurodegeneration driven by amyloid precursor protein (APP) and tau implicated in Alzheimer’s disease and frontotemporal dementias, respectively, in addition to ischemic injury modeled by OGD. PMID:27172999

  15. Dual activities of the anti-cancer drug candidate PBI-05204 provide neuroprotection in brain slice models for neurodegenerative diseases and stroke.

    PubMed

    Van Kanegan, Michael J; Dunn, Denise E; Kaltenbach, Linda S; Shah, Bijal; He, Dong Ning; McCoy, Daniel D; Yang, Peiying; Peng, Jiangnan; Shen, Li; Du, Lin; Cichewicz, Robert H; Newman, Robert A; Lo, Donald C

    2016-05-12

    We previously reported neuroprotective activity of the botanical anti-cancer drug candidate PBI-05204, a supercritical CO2 extract of Nerium oleander, in brain slice and in vivo models of ischemic stroke. We showed that one component of this neuroprotective activity is mediated through its principal cardiac glycoside constituent, oleandrin, via induction of the potent neurotrophic factor brain-derived neurotrophic factor (BDNF). However, we also noted that the concentration-relation for PBI-05204 in the brain slice oxygen-glucose deprivation (OGD) model is considerably broader than that for oleandrin as a single agent. We thus surmised that PBI-05204 contains an additional neuroprotective component(s), distinct from oleandrin. We report here that neuroprotective activity is also provided by the triterpenoid constituents of PBI-05204, notably oleanolic acid. We demonstrate that a sub-fraction of PBI-05204 (Fraction 0-4) containing oleanolic and other triterpenoids, but without cardiac glycosides, induces the expression of cellular antioxidant gene transcription programs regulated through antioxidant transcriptional response elements (AREs). Finally, we show that Fraction 0-4 provides broad neuroprotection in organotypic brain slice models for neurodegeneration driven by amyloid precursor protein (APP) and tau implicated in Alzheimer's disease and frontotemporal dementias, respectively, in addition to ischemic injury modeled by OGD.

  16. Fabrication of folic acid sensor based on the Cu doped SnO2 nanoparticles modified glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Lavanya, N.; Radhakrishnan, S.; Sudhan, N.; Sekar, C.; Leonardi, S. G.; Cannilla, C.; Neri, G.

    2014-07-01

    A novel folic acid biosensor has been fabricated using Cu doped SnO2 nanoparticles (NPs) synthesized by a simple microwave irradiation method. Powder XRD and TEM studies confirmed that both the pure and Cu doped SnO2 (Cu: 0, 10, 20wt%) crystallized in tetragonal rutile-type structure with spherical morphology. The average crystallite size of pure SnO2 was estimated to be around 16 nm. Upon doping, the crystallite sizes decreased to 9 nm and 5 nm for 10 and 20wt% Cu doped SnO2 respectively. XPS studies confirmed the electronic state of Sn and Cu to be 4+ and 2+ respectively. Cu (20wt%) doped SnO2 NPs are proved to be a good sensing element for the determination of folic acid (FA). Cu-SnO2 NPs (20wt%) modified glassy carbon electrode (GCE) exhibited the lowest detection limit of 0.024 nM over a wide folic acid concentration range of 1.0 × 10-10 to 6.7 × 10-5 M at physiological pH of 7.0. The fabricated sensor is highly selective towards the determination of FA even in the presence of a 100 fold excess of common interferent ascorbic acid. The sensor proved to be useful for the estimation of FA content in pharmaceutical sample with satisfactory recovery.

  17. Photocatalytic decomposition of perfluorooctanoic acid by iron and niobium co-doped titanium dioxide.

    PubMed

    Estrellan, Carl Renan; Salim, Chris; Hinode, Hirofumi

    2010-07-15

    The photocatalytic decomposition of perfluorooctanoic acid (PFOA) in aqueous solution using Fe and Nb co-doped TiO(2) (Fe:Nb-TiO(2)) prepared by sol-gel method was investigated. The photocatalytic activity of Fe:Nb-TiO(2) towards PFOA degradation was compared to that of pure TiO(2) synthesized using the same method, and that of the commercially available TiO(2) photocatalyst, Aeroxide TiO(2) P25 (AO-TiO(2) P25). The photocatalysts were characterized by XRD, DRS, BET-N(2) adsorption isotherm, and SEM-EDX techniques and the data were correlated to the photocatalytic activity. Fe:Nb-TiO(2) showed the highest activity compared to the undoped TiO(2) and the commercially available TiO(2). Such activity was attributable to the effects of co-doping both on the physico-chemical properties and surface interfacial charge transfer mechanisms. Perfluorocarboxylic acids (PFCAs) with shorter carbon chain length and fluoride ions were identified as photocatalytic reaction intermediates and products.

  18. Ammonia gas sensing behavior of tanninsulfonic acid doped polyaniline-TiO₂ composite.

    PubMed

    Bairi, Venu Gopal; Bourdo, Shawn E; Sacre, Nicolas; Nair, Dev; Berry, Brian C; Biris, Alexandru S; Viswanathan, Tito

    2015-10-16

    A highly active tannin doped polyaniline-TiO₂ composite ammonia gas sensor was developed and the mechanism behind the gas sensing activity was reported for the first time. A tanninsulfonic acid doped polyaniline (TANIPANI)-titanium dioxide nanocomposite was synthesized by an in situ polymerization of aniline in the presence of tanninsulfonic acid and titanium dioxide nanoparticles. X-ray diffraction and thermogravimetric analysis were utilized to determine the incorporation of TiO₂ in TANIPANI matrix. UV-Visible and infrared spectroscopy studies provided information about the electronic interactions among tannin, polyaniline, and TiO₂. Scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) surface analysis techniques were used to investigate the metal oxide dispersions inside polyaniline matrix. Gas sensors were prepared by spin coating solutions of TANIPANI-TiO₂ and TANIPANI composites onto glass slides. Sensors were tested at three different concentrations (20 ppm, 40 ppm, and 60 ppm) of ammonia gas at ambient temperature conditions by measuring the changes in surface resistivity of the films with respect to time. Ammonia gas sensing plots are presented showing the response values, response times and recovery times. The TANIPANI-TiO₂ composite exhibited better response and shorter recovery times when compared to TANIPANI control and other polyaniline composites that have been reported in the literature. For the first time a proposed mechanism of gas sensing basing on the polaron band localization and its effects on the gas sensing behavior of polyaniline are reported.

  19. Characterization of nano-lead-doped active carbon and its application in lead-acid battery

    NASA Astrophysics Data System (ADS)

    Hong, Bo; Jiang, Liangxing; Xue, Haitao; Liu, Fangyang; Jia, Ming; Li, Jie; Liu, Yexiang

    2014-12-01

    In this paper, nano-lead-doped active carbon (nano-Pb/AC) composite with low hydrogen evolution current for lead-acid battery was prepared by ultrasonic-absorption and chemical-precipitate method. The nano-Pb/AC composite was characterized by SEM, EDS and TEM. The electrochemical characterizations are performed by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) in a three-electrode system. Since intermediate adsorption is the rate-determining step, the hydrogen evolution reaction (HER) is markedly inhibited as the intermediate adsorption impedance of nano-Pb/AC increased. Meanwhile, the working potential of nano-Pb/AC is widened to the whole potential region of Pb negative plate (from -1.36 V to -0.86 V vs. Hg/HgSO4) in lead-acid battery. In addition, nano-Pb can improve the interfacial compatibility between AC and Pb paste, accordingly relieve the symptoms of carbon floatation. Finally, 2.0 V single-cell flooded lead-acid batteries with 1.0 wt.% nano-Pb/AC or 1.0 wt.% AC addition in negative active materials are assembled. The cell performances test results show that the 3 h rate capacity, quick charging performance, high current discharging performance and cycling performance of nano-Pb/AC modified battery are all improved compared with regular lead-acid battery and AC modified lead-acid battery.

  20. Collagen biomaterial doped with colominic acid for cell culture applications with regard to peripheral nerve repair.

    PubMed

    Bruns, Stephanie; Stark, Yvonne; Röker, Stefanie; Wieland, Martin; Dräger, Gerald; Kirschning, Andreas; Stahl, Frank; Kasper, Cornelia; Scheper, Thomas

    2007-09-15

    Colominic acid (CA) is a homopolymer of sialic acid residues and is solely composed of polymerised units of alpha-2,8-linked N-acetylneuraminic acid. CA is a specific derivative of polysialic acid (PSA), produced as the capsular polysaccharide of Escherichia coli K1 derived molecule of PSA. PSA in vivo plays a significant role in synaptic plasticity and neural development. The use of collagen materials doped with defined CA is presented for the cultivation of various cell lines relevant for possible applications in Tissue Engineering. First, the release behaviour under culture conditions of the collagen-based (C-CA) materials was investigated by thiobarbituric acid assay. Additionally, the established cell lines, PC-12 and immortalised Schwann cells (ISC), used for neurobiological and neurochemical studies and the model liver cell line Hep-G2 as indicator for biocompatibility testing, were cultured on the C-CA matrix. Cell proliferation (MTT-test) and cell adhesion (DAPI-staining) of the cell lines on the matrices were observed. Likewise, gene expression of the marker genes thyrosine hydroxylase for the PC-12 cells, and albumin, transferrin and CYP3A4 for the Hep-G2 cells was evaluated via RT-PCR. The results indicate that CA integration in established biomaterial constructs enhances cell proliferation and offers promising features as conduits additive in regarding peripheral nerve regeneration.

  1. Comparative NH 3-sensing characteristic studies of PANI/TiO II nanocomposite thin films doped with different acids

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Jiang, Yadong; Xie, Guangzhong; Yu, Junsheng; Ying, Zhihua; Chen, Xuan

    2008-02-01

    Polyaniline/titanium dioxide (PANI/TiO II) nanocomposite thin films were synthesized by in-situ self-assembly method, which were doped with p-toluene sulphonic acid (p-TSA) and hydrochloric acid (HCl), respectively. The thin films were characterized by using UV-Vis absorption spectroscopy and scanning electron microscope (SEM), and the NH 3 gas sensitive properties of the thin films were investigated at room temperature. The results showed that the PANI/TiO II thin film doped with HCl was superior to that doped with p-TSA in terms of response-recovery characteristics. The surface morphology characterization of the thin films were performed to explain the different gas-sensing properties.

  2. Cadmium ion-doped magnetic poly(styrene-acrylic acid) nanospheres for sensitive electrochemical immunoassay.

    PubMed

    Zhang, Bing; Cui, Yuling; Liu, Bingqian; Chen, Huafeng; Chen, Guonan; Tang, Dianping

    2012-05-15

    A novel class of molecular tags, cadmium ion-doped magnetic poly(styrene-acrylic acid) nanospheres (Cd-MPSA), was first synthesized and functionalized with polyclonal rabbit anti-human luteinizing hormone antibodies (PAb(2)) for highly efficient electrochemical immunoassay of luteinizing hormone (LH). Transmission electron microscope (TEM) and Fourier transform infrared spectroscope (FTIR) were employed to characterize the prepared Cd-MPSA. By using Cd-MPSA-labeled PAb(2) as molecular tags, a novel sandwich-type immunoassay protocol was built for determination of LH on monoclonal mouse anti-human luteinizing hormone antibody (MAb(1))-functionalized gold electrode. The assay was carried out in pH 5.3 HAc-NaAc buffer solution by square wave voltammetry (SWV). The signal was obtained by the reduction of the doped cadmium ions in the Cd-MPSA. Under optimal conditions, the currents increased with the increasing LH level in the sample, and exhibited a linear range from 0.25 to 240 mIU mL(-1) with a detection limit of 0.08 mIU mL(-1) LH at 3s(B). The precision, reproducibility, and specificity were acceptable. No obvious difference was encountered in the analysis of spiking LH samples into newborn calf serum with the referenced values.

  3. Charge storage in polymer acid-doped polyaniline-based layer-by-layer electrodes.

    PubMed

    Jeon, Ju-Won; O'Neal, Josh; Shao, Lin; Lutkenhaus, Jodie L

    2013-10-23

    Polymeric electrodes that can achieve high doping levels and store charge reversibly are desired for electrochemical energy storage because they can potentially achieve high specific capacities and energies. One such candidate is the polyaniline:poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA) complex, a water-processable complex obtained via template polymerization that is known to reversibly achieve high doping levels at potentials of up to 4.5 V versus Li/Li+. Here, for the first time, PANI:PAAMPSA is successfully incorporated into layer-by-layer (LbL) electrodes. This processing technique is chosen for its ability to blend species on a molecular level and its ability to conformally coat a substrate. Three different polyaniline-based LbL electrodes comprised of PANI/PAAMPSA, PANI/PANI:PAAMPSA, and linear poly(ethylenimine)/PANI:PAAMPSA are compared in terms of film growth, charge storage, and reversibility. We found that the reversibility of PANI:PAAMPSA is retained within the LbL electrodes and that the PANI/PANI:PAAMPSA electrode exhibits the best performance in terms of capacity and cycle life. These results provide general guidelines for the assembly of PANI:PAAMPSA in LbL films and also demonstrate their potential as electrochemically active components in electrodes.

  4. Study of spatial rings in TPPOH4 doped in boric acid glass

    NASA Astrophysics Data System (ADS)

    Rao Allam, Srinivasa; Dar, Mudasir H.; Venkatramaiah, N.; Venkatesan, R.; Sharan, Alok

    2015-02-01

    Single beam optical nonlinearity is studied in TPPOH4 doped in boric acid sandwiched films between two microscope glass slides at three different molar concentrations (4×10-4M, 1×10-4M, 5×10-5M). It shows absorption peak at 700nm with bandwidth of 70nm. We have used diode laser output at 671nm to probe resonant optical nonlinearities. We have observed interesting phenomena of formation of spatial concentric rings centered on the z-axis of the sample. To our knowledge this is first such observation of spatial rings in these systems. We have carried out studies to separate the contribution to the ring formation due to absorptive/refractive optical nonlinearity and the thermal nonlinearity.

  5. Ammonia Gas Sensing Behavior of Tanninsulfonic Acid Doped Polyaniline-TiO2 Composite

    PubMed Central

    Bairi, Venu Gopal; Bourdo, Shawn E.; Sacre, Nicolas; Nair, Dev; Berry, Brian C.; Biris, Alexandru S.; Viswanathan, Tito

    2015-01-01

    A highly active tannin doped polyaniline-TiO2 composite ammonia gas sensor was developed and the mechanism behind the gas sensing activity was reported for the first time. A tanninsulfonic acid doped polyaniline (TANIPANI)-titanium dioxide nanocomposite was synthesized by an in situ polymerization of aniline in the presence of tanninsulfonic acid and titanium dioxide nanoparticles. X-ray diffraction and thermogravimetric analysis were utilized to determine the incorporation of TiO2 in TANIPANI matrix. UV-Visible and infrared spectroscopy studies provided information about the electronic interactions among tannin, polyaniline, and TiO2. Scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) surface analysis techniques were used to investigate the metal oxide dispersions inside polyaniline matrix. Gas sensors were prepared by spin coating solutions of TANIPANI-TiO2 and TANIPANI composites onto glass slides. Sensors were tested at three different concentrations (20 ppm, 40 ppm, and 60 ppm) of ammonia gas at ambient temperature conditions by measuring the changes in surface resistivity of the films with respect to time. Ammonia gas sensing plots are presented showing the response values, response times and recovery times. The TANIPANI-TiO2 composite exhibited better response and shorter recovery times when compared to TANIPANI control and other polyaniline composites that have been reported in the literature. For the first time a proposed mechanism of gas sensing basing on the polaron band localization and its effects on the gas sensing behavior of polyaniline are reported. PMID:26501291

  6. Polyaniline nanotubes and their dendrites doped with different naphthalene sulfonic acids

    SciTech Connect

    Zhang Zhiming; Wei Zhixiang; Zhang Lijuan; Wan Meixiang . E-mail: wanmx@iccas.ac.cn

    2005-03-01

    Polyaniline (PANI) nanotubes (130-250 nm in average diameter) doped with {alpha}-naphthalene sulfonic acid ({alpha}-NSA), {beta}-naphthalene sulfonic acid ({beta}-NSA) and 1,5-naphthalene disulfonic acid were synthesized via a self-assembly process. It was found that the formation yield, morphology (hollow or solid), size, crystalline and electrical properties of the nanostructures are affected by the position and number of -SO{sub 3}H groups attached to the naphthalene ring of NSA as well as the synthesis conditions. Moreover, these nanotubes aggregate to form a dendritic morphology when the polymerization is performed at a static state. The micelles composed of dopant or dopant/anilinium cations might act in a template-like fashion in forming self-assembled PANI nanotubes, which was further confirmed by X-ray diffraction measurements, while the aggregated morphology of the nanotubes might result from polymer chain interactions including {pi}-{pi} interactions, hydrogen and ionic bonds.

  7. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

    PubMed Central

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-01-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

  8. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells.

    PubMed

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-02-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells.

  9. KDP crystal doped with L-arginine amino acid: growth, structure perfection, optical and strength characteristics

    NASA Astrophysics Data System (ADS)

    Pritula, I. M.; Kostenyukova, E. I.; Bezkrovnaya, O. N.; Kolybaeva, M. I.; Sofronov, D. S.; Dolzhenkova, E. F.; Kanaev, A.; Tsurikov, V.

    2016-07-01

    Potassium Dihydrogen Phosphate (KDP) crystal doped with L-arginine (L-arg) amino acid with 1.4 wt% concentration in the solution was grown onto a point seed by the method of temperature reduction. For the first time an attempt was made to grow large-size (7 × 6 × 8 cm3) optically transparent crystals, which allowed to analyze the effect of L-arg additive on the physical properties of the different growth sectors ({100} and {101}) of KDP. The incorporation of L-arg into both growth sectors of the crystal was confirmed by the methods of optical and IR spectroscopy and found to be caused by the ability of the amino acid to form hydrogen bonds with the face {100} and electrostatically interact with the positively charged face {101} of KDP crystal. A slight variation in the unit cell parameters was reported, the elementary cell volume of KDP:L-arg crystal increased in comparison with the one of pure KDP by 2·10-2 and 2.07·10-2 Å3 in the sectors {100} and {101}, respectively. It was found that the doping of L-arg enhanced the SHG efficiency of KDP and depended on the crystal growth sectors. The SHG efficiency of KDP:L-arg was by a factor 2.53 and 3.95 higher in comparison with those of pure KDP for {101} and {100} growth sector, respectively. The doping was found to lead to softening of both faces by ∼3-10% and ∼14-17% in the sectors {101} and {100}, respectively. Investigation of the influence of L-arg molecules on the bulk laser damage threshold of the crystals showed that the bulk laser damage threshold of the samples of KDP:L-arg crystal was higher than the one of the pure crystal in the sector {101} and lower in the sector {100}. The correlation between microhardness and laser damage threshold were discussed. The study is helpful for further searching, designing and simulation of hybrid NLO materials.

  10. Fabrication of multi-non-metal-doped TiO{sub 2} nanotubes by anodization in mixed acid electrolyte

    SciTech Connect

    Lei Lecheng Su Yaling; Zhou Minghua; Zhang Xingwang; Chen Xiuqin

    2007-12-04

    Multi-non-metal-doped TiO{sub 2} nanotubes were fabricated by electrochemical anodization of Ti in the mixed acid electrolyte of C{sub 2}H{sub 2}O{sub 4}.2H{sub 2}O and HIO{sub 3} containing NH{sub 4}F. The samples were annealed in air and characterized by FE-SEM, XRD, XPS and DRS. The results indicate non-metals of N, F and I are successfully doped into TiO{sub 2} nanotubes in aqueous solution by adjusting the electrolyte composition. The multi-non-metal-doped samples display a significant visible-light response. Additionally, the atomic concentration of non-metals is closely related with the electrolyte composition.

  11. Sulfur and iron co-doped titanoniobate nanosheets: a novel efficient solid acid catalyst for alcoholysis of styrene epoxide at room temperature.

    PubMed

    Zhang, Lihong; Hu, Chenhui; Zhang, Junfeng; Cheng, Liyuan; Zhai, Zheng; Chen, Jing; Ding, Weiping; Hou, Wenhua

    2013-09-04

    Sulfur and iron co-doped titanoniobate nanosheets were prepared and evaluated in alcoholysis of styrene epoxide. The resultant co-doped catalyst exhibited excellent catalytic performance (yield of 99% with methanol as the nucleophile in only 1 h at room temperature) and may act as a promising candidate in many acid-catalyzed reactions.

  12. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    PubMed Central

    2013-01-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail. PMID:24369051

  13. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors.

    PubMed

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-26

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

  14. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

  15. Exploring the Photovoltaic Performance of All-Inorganic Ag2PbI4/PbI2 Blends.

    PubMed

    Frolova, Lyubov A; Anokhin, Denis V; Piryazev, Alexey A; Luchkin, Sergey Yu; Dremova, Nadezhda N; Troshin, Pavel A

    2017-04-06

    We present an all-inorganic photoactive material composed of Ag2PbI4 and PbI2, which shows unexpectedly good photovoltaic performance in planar junction solar cells delivering external quantum efficiencies of ∼60% and light power conversion efficiencies of ∼3.9%. The revealed characteristics are among the best reported to date for metal halides with nonperovskite crystal structure. Most importantly, the obtained results suggest a possibility of reaching high photovoltaic efficiencies for binary and, probably, also ternary blends of different inorganic semiconductor materials. This approach, resembling the bulk heterojunction concept guiding the development of organic photovoltaics for two decades, opens wide opportunities for rational design of novel inorganic and hybrid materials for efficient and sustainable photovoltaic technologies.

  16. Facile synthesis of nitrogen-doped graphene supported AuPd-CeO2 nanocomposites with high-performance for hydrogen generation from formic acid at room temperature.

    PubMed

    Wang, Zhi-Li; Yan, Jun-Min; Zhang, Yue-Fei; Ping, Yun; Wang, Hong-Li; Jiang, Qing

    2014-03-21

    AuPd-CeO2 nanocomposites directly nucleated and grown on nitrogen-doped reduced graphene oxide, exhibit excellent catalytic activity and 100% hydrogen selectivity toward formic acid decomposition for hydrogen generation without any additives at room temperature.

  17. Improvement of holographic thermal stability in phenanthrenequinone-doped poly(methyl methacrylate-co-methacrylic acid) photopolymer

    NASA Astrophysics Data System (ADS)

    Yu, Dan; Liu, Hongpeng; Wang, Heng; Wang, Jian; Jiang, Yongyuan; Sun, Xiudong

    2011-08-01

    Experimental studies of holographic thermal stability in phenanthrenequinone (PQ)-doped poly(methyl methacrylate-co-methacrylic acid) [P(MMA-co-MAA)] photopolymers are presented. A possibility to improve the thermal stability of holograms is demonstrated by doping methacrylic acid (MAA) into the poly(methyl methacrylate) (PMMA) polymer matrix. MAA as a copolymerization monomer can form a more stable polymer matrix with methyl methacrylate (MMA) monomer and increase average molecular weight of photoproducts, which finally depress the diffusion of photoproduct. The optimized MAA concentration copolymerized into P(MMA-co-MAA) polymer matrix can bring nearly a month's lifetime of gratings, which is obviously an improvement over the usual PQ-PMMA material under thermal treatment.

  18. Sulfuric acid doped poly diaminopyridine/graphene composite to remove high concentration of toxic Cr(VI).

    PubMed

    Dinda, Diptiman; Kumar Saha, Shyamal

    2015-06-30

    Sulfuric acid doped diaminopyridine polymers are synthesized in situ on graphene oxide surface via mutual oxidation-reduction technique. Exploiting large and highly porous surface, we have used this polymer composite as an adsorbent to remove high concentration of toxic Cr(VI) from water. It shows very high adsorption capacity (609.76 mg g(-1)) during removal process. The composite takes only 100 min to remove high concentration of 500 mg L(-1) Cr(VI) from water. Interesting features for this material is the enhancement of removal efficiency at lower acidic condition due to the formation of acid doped emeraldine salt during polymerization. XPS and AAS measurements reveal that our prepared material mainly follows reduction mechanism at higher acidic condition while anions exchange mechanism at lower acidic condition during the removal experiments. Good recycling ability with ∼ 92% removal efficiency after fifth cycle is also noticed for this material. Easy preparation, superior stability in acidic condition, remarkable removal efficiency and excellent recycling ability make this polymer composite an efficient material for modern filtration units in waste water purification.

  19. Modulated CH3NH3PbI3‑xBrx film for efficient perovskite solar cells exceeding 18%

    NASA Astrophysics Data System (ADS)

    Tu, Yongguang; Wu, Jihuai; Lan, Zhang; He, Xin; Dong, Jia; Jia, Jinbiao; Guo, Panfeng; Lin, Jianming; Huang, Miaoliang; Huang, Yunfang

    2017-03-01

    The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3‑xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3‑xBrx film.

  20. Modulated CH3NH3PbI3−xBrx film for efficient perovskite solar cells exceeding 18%

    PubMed Central

    Tu, Yongguang; Wu, Jihuai; Lan, Zhang; He, Xin; Dong, Jia; Jia, Jinbiao; Guo, Panfeng; Lin, Jianming; Huang, Miaoliang; Huang, Yunfang

    2017-01-01

    The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3−xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3−xBrx film. PMID:28303938

  1. Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions.

    PubMed

    Chen, Chong; Li, Chunxi; Li, Fumin; Wu, Fan; Tan, Furui; Zhai, Yong; Zhang, Weifeng

    2014-01-01

    In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%.

  2. Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions

    PubMed Central

    2014-01-01

    In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

  3. Effect of iron doped lead oxide on the performance of lead acid batteries

    NASA Astrophysics Data System (ADS)

    Liu, Jianwen; Yang, Danni; Gao, Linxia; Zhu, Xinfeng; Li, Lei; Yang, Jiakuan

    2011-10-01

    In order to investigate effect of iron on the performance of lead acid batteries, we systematically study the chemical characteristics, electrochemical characteristics, battery capacity and cycle life using iron-doped lead oxide in this article. Cyclic voltammetry results show that positive discharge current decreases sharply with the increasing content of Fe2O3 from 0.05 wt.% to 2 wt.%. The release of H2 and O2 are promoted accompanying the increase of Fe2O3 contents. The chemical analysis confirms that the strength of Fe3+, Fe2+ concentration is simultaneously increased with the increase of iron contents after 50 voltammetry cycles. X-ray diffraction phase analysis shows that the amount of PbSO4 increases with the increasing iron content in the positive plates after 50 discharge cycles. Morphologies of positive plates show that many agglomerates from PbSO4 crystals appear. The SEM observations illustrate that there is a lower porosity and specific surface area in the positive active material with iron after 50 discharge cycles. The mechanism of iron decreasing capacity, cycle-life and promoting the release of H2 and O2 has been elucidated in details. We support it is the "redox-diffusion" process of multiple-valence iron and formation of PbSO4 on electrodes that result in above performances.

  4. Nitrogen doped graphene quantum dots based long-persistent chemiluminescence system for ascorbic acid imaging.

    PubMed

    Chen, Hongjun; Wang, Qin; Shen, Qinpeng; Liu, Xin; Li, Wang; Nie, Zhou; Yao, Shouzhuo

    2017-05-15

    High photo-intensity and sluggish flight attenuation are important to highly sensitive chemluminescence imaging. Herein, we present a copper ion catalyzed long-persistent chemiluminescent imaging system of nitrogen-doped graphene quantum dots (NGQDs) for ascorbic acid detection in fruit. NGQDs as luminescent probe are fabricated, emitting out chemluminescence with the direct oxidation by H2O2. In addition, Cu(2+) ion enlarges over two order magnitudes of NGQDs CL intensity (214 times) due to its catalyzed Fenton-like reaction for H2O2 decomposition, and displaying unique specificity against other metal ions. As a result, the twinkling luminescence of NGQDs is boosted and changes to hold persistent with small decay in the presence of copper ion exhibiting potential for CL imaging. As an imaging model, a visual sensor based on Cu(2+)/NGQDs/H2O2 is developed for AA quantitative monitoring with a limit of detection (LOD) of 0.5μM (S/N=3) and applied in real AA detection in fruit. The CL imaging method demonstrated with high stability and proper sensitivity would provide a convenient and visual tool for AA determination, displaying promising candidates for imaging sensing.

  5. Enhanced in vitro cell activity on silicon-doped vaterite/poly(lactic acid) composites.

    PubMed

    Obata, Akiko; Tokuda, Shingo; Kasuga, Toshihiro

    2009-01-01

    A biodegradable composite with silicon-species releasability was prepared using poly(l-lactic acid) (PLLA) and silicon-doped vaterite (SiV) particles. SiV with particle diameters of approximately 1 mum was prepared using aminopropyltriethoxysilane (APTES) as the silicon species by a carbonation process and then mixed with PLLA in methylene chloride according to a SiV to PLLA weight ratio of 1:2, resulting in the preparation of composite slurry. A composite film was prepared by dipping a cover glass in the slurry. The composite films were incubated in a culture medium for 7 days and the silicon concentration of the medium was measured to estimate the species releasability of the composites. A trace amount of silicon species was continuously released from the composites for 7 days, the amount depending on the content of APTES in SiV. On the composite releasing silicon species, mouse osteoblast-like cells (MC3T3-E1 cells) were significantly stimulated to proliferate and differentiate in comparison with those on a composite containing no silicon species. The proliferation of the cells on the composites releasing larger amounts of silicon species (0.51mgl(-1)day(-1)) was higher than that on the composites releasing smaller amount of the species (0.21mgl(-1)day(-1)). The silicon species in the composites were effective in enhancing the cellular functions. The composites were expected to be useful as a scaffold material for bone tissue engineering.

  6. Microwave activated electrochemical degradation of 2,4-dichlorophenoxyacetic acid at boron-doped diamond electrode.

    PubMed

    Gao, Junxia; Zhao, Guohua; Shi, Wei; Li, Dongming

    2009-04-01

    A method for improving the oxidation ability of the electrode is proposed by using microwave activation in electrochemical oxidation. The electrochemical degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) with microwave radiation (MW-EC) was carried out in a continuous flow system under atmospheric pressure. In 3 h the removal of COD, ACE (average current efficiency) and Cl(-) concentration was 1.63, 2.25 and 1.67 times as that without microwave radiation, respectively. The high degradation ability was resulted from the more active centers at the electrode surface due to the microwave radiation. The decay kinetics of 2,4-D followed a pseudo first-order reaction. The rate constant was increased to 2.16x10(-4) s(-1) with the microwave radiation, while it was 8.52x10(-5) s(-1) with electrochemical treatment only (EC). Under both conditions, the main intermediates were identified and quantified by High Performance Liquid Chromatography (HPLC). The formation rate of intermediate products and further degradation rate were increased by about 50-120% with the microwave radiation. The activation of electrochemical oxidation by microwave was discussed from the diffusion process, adsorption and the temperature at boron-doped diamond (BDD) electrode.

  7. Optical emissions of Ce3+ doped Sulphamic acid single crystals by low temperature unidirectional growth technique

    NASA Astrophysics Data System (ADS)

    Brahmaji, B.; Rajyalakshmi, S.; Satya Kamal, Ch; Atla, Veerendra; Veeraiah, V.; Venkateswara Rao, K.; Ramachandra Rao, K.

    2017-02-01

    Cerium doped Sulphamic acid (SA) single crystal was synthesized and grown in large size for its cerium ion optical emissions. The photoluminescence emission of unidirectional grown crystals was found to have a broad band from 300 nm to 400 nm, centered at 318 nm (5d → 4f (2F5/2, 2F7/2), due to ground state crystal field splitting. The respective excitation spectra show peak at 273 nm, which is attributed to transitions from the 4f(2F5/2) ground state to first and second excited level of 5d configuration of Ce3+. The nature of decay curve is bi exponential with an average decay life time (τavg) of 20.12 ns. The lattice parameters were determined by X-ray diffraction analysis and the crystalline perfection of grown single crystals have been checked by High Resolution X-ray Diffraction (HRXRD) studies. The vacancy defects are predominant and causes tensile stress in the lattice by incorporation of Ce3+ ions. Functional group analysis and SEM with EDAX reveals that Ce3+ ion is incorporated in the crystal system. The lower cutoff wavelength found at 340 nm and the respective band gap was calculated as 4.6eV. The dielectric measurements were done at different temperatures and the nonlinear optical efficiency was observed as 3.5 times that of standard potassium dihydrogen phosphate (KDP) single crystals. In the present study, sulphamic acid acts as a prominent host material for probing Ce3+ ion emissions for optical device applications.

  8. Low thermal budget n-type doping into Ge(001) surface using ultraviolet laser irradiation in phosphoric acid solution

    SciTech Connect

    Takahashi, Kouta E-mail: kurosawa@alice.xtal.nagoya-u.ac.jp; Sakashita, Mitsuo; Takeuchi, Wakana; Nakatsuka, Osamu; Kurosawa, Masashi E-mail: kurosawa@alice.xtal.nagoya-u.ac.jp; Ikenoue, Hiroshi; Zaima, Shigeaki

    2016-02-01

    We have investigated phosphorus (P) doping into Ge(001) surfaces by using ultraviolet laser irradiation in phosphoric acid solution at room temperature. We demonstrated that the diffusion depth of P in Ge and the concentration of electrically activated P can be controlled by the number of laser shots. Indeed, a high concentration of electrically activated P of 2.4 × 10{sup 19} cm{sup −3} was realized by 1000-times laser shots at a laser energy of 1.0 J/cm{sup 2}, which is comparable or better than the counterparts of conventional n-type doping using a high thermal budget over 600 °C. The generation current is dominant in the reverse bias condition for the laser-doped pn-junction diodes independent on the number of laser shots, thus indicating low-damage during the pn-junction formation. These results open up the possibility for applicable low thermal budget doping process for Ge-based devices fabricated on flexible substrates as well as Si electronics.

  9. Lowering the platinum loading of high temperature polymer electrolyte membrane fuel cells with acid doped polybenzimidazole membranes

    NASA Astrophysics Data System (ADS)

    Martin, S.; Li, Q.; Jensen, J. O.

    2015-10-01

    Membrane electrode assemblies (MEAs) with ultra-low Pt loading electrodes were prepared for high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) based on acid doped polybenzimidazole. With no electrode binders or ionomers, the triple phase boundary of the catalyst layer was established by the acid transfer from the acid doped membrane to the electrodes and can therefore be tailored by using catalysts with varied Pt to C ratios. With a loading of ca. 0.1 mgPtcm-2 on each electrode the best performance was obtained with electrodes prepared from 10 wt.% Pt/C due to the improved Pt dispersion, extended triple phase boundary upon the acid transfer and the alleviated acid flooding of the catalytic layer. The MEA delivered a peak power density of 482 mW cm-2 for H2/O2 and 321 mW cm-2 for H2/air, corresponding to an overall Pt utilization of 2.5 and 1.7 kW gPt-1, respectively. The durability test revealed no net voltage decay during more than 1700 h of uninterrupted operation at 200 mA cm-2 and 160 °C.

  10. The interaction of propionic and butyric acids with ice and HNO₃-doped ice surfaces at 195-212 K.

    PubMed

    Romanias, Manolis N; Papadimitriou, Vassileios C; Papagiannakopoulos, Panos

    2014-12-04

    The interaction of propionic and butyric acids on ice and HNO3-doped ice were studied between 195 and 212 K and low concentrations, using a Knudsen flow reactor coupled with a quadrupole mass spectrometer. The initial uptake coefficients (γ0) of propionic and butyric acids on ice as a function of temperature are given by the expressions: γ0(T) = (7.30 ± 1.0) × 10(-10) exp[(3216 ± 478)/T] and γ0(T) = (6.36 ± 0.76) × 10(-11) exp[(3810 ± 434)/T], respectively; the quoted error limits are at 95% level of confidence. Similarly, γ0 of propionic acid on 1.96 wt % (A) and 7.69 wt % (B) HNO3-doped ice with temperature are given as γ(0,A)(T) = (2.89 ± 0.26) × 10(-8) exp[(2517 ± 266)/T] and γ(0,B)(T) = (2.77 ± 0.29) × 10(-7) exp[(2126 ± 206)/T], respectively. The results show that γ0 of C1 to C4 n-carboxylic acids on ice increase with the alkyl-group length, due to lateral interactions between alkyl-groups that favor a more perpendicular orientation and well packing of H-bonded monomers on ice. The high uptakes (>10(15) molecules cm(-2)) and long recovery signals indicate efficient growth of random multilayers above the first monolayer driven by significant van der Waals interactions. The heterogeneous loss of both acids on ice and HNO3-doped ice particles in dense cirrus clouds is estimated to take a few minutes, signifying rapid local heterogeneous removal by dense cirrus clouds.

  11. Fabrication and characterization of Sb-doped Sn02 thin films derived from methacrylic acid modified tin(IV)alkoxides

    NASA Astrophysics Data System (ADS)

    Kololuoma, Terho K.; Tolonen, Ari; Johansson, Leena-Sisko; Campbell, Joseph M.; Karkkainen, Ari H. O.; Hiltunen, Marianne; Haatainen, Tomi; Rantala, Juha T.

    2002-10-01

    We report on the fabrication of transparent, conductive and directly photopatternable, pure and Sb-doped tin dioxide thin films. Precursors used were antimony(III)isopropoxide and a photo-reactive tin alkoxide synthesized from tin(IV)isopropoxide and methacrylic acid. The synthesis of methacrylic acid modified tin alkoxide was monitored in-situ using IR- and ESI-TOF mass spectroscopic techniques. Sb-doped organo-tin films were deposited via single layer spin coating. After deposition the films were patterned via photopolymerization, using a mercury I-line UV-lamp. All investigated materials could be patterned with 3 μm features. After development in isopropanol, the films were annealed in air, in order to obtain crystalline and conductive films. The electrical conductivities of the annealed thin films with, and without, UV-irradiation were determined using a linear four-point method. The direct photopatterning process was found to increase the film conductivity for all the Sb-doping levels tested. The mechanisms for the increased conductivity were characterized using AFM, XPS and XRD techniques.

  12. Kinetics of the electrochemical mineralization of perfluorooctanoic acid on ultrananocrystalline boron doped conductive diamond electrodes.

    PubMed

    Urtiaga, Ane; Fernández-González, Carolina; Gómez-Lavín, Sonia; Ortiz, Inmaculada

    2015-06-01

    This work deals with the electrochemical degradation and mineralization of perfluorooctanoic acid (PFOA). Model aqueous solutions of PFOA (100mg/L) were electro-oxidized under galvanostatic conditions in a flow-by undivided cell provided with a tungsten cathode and an anode formed by a commercial ultrananocrystalline boron doped diamond (BDD) coating on a niobium substrate. A systematic experimental study was conducted in order to analyze the influence of the following operation variables: (i) the supporting electrolyte, NaClO4 (1.4 and 8.4g/L) and Na2SO4 (5g/L); (ii) the applied current density, japp, in the range 50-200 A/m(2) and (iii) the hydrodynamic conditions, in terms of flowrate in the range 0.4×10(-4)-1.7×10(-4)m(3)/s and temperature in the range 293-313K. After 6h of treatment and at japp 200A/m(2), PFOA removal was higher than 93% and the mineralization ratio, obtained from the decrease of the total organic carbon (TOC) was 95%. The electrochemical generation of hydroxyl radicals in the supporting electrolyte was experimentally measured based on their reaction with dimethyl sulfoxide. The enhanced formation of hydroxyl radicals at higher japp was related to the faster kinetics of PFOA removal. The fitting of experimental data to the proposed kinetic model provided the first order rate constants of PFOA degradation, kc(1) that moved from 2.06×10(-4) to 15.58×10(-4)s(-1), when japp varied from 50 to 200A/m(2).

  13. Cancellous bone healing around strontium-doped hydroxyapatite in osteoporotic rats previously treated with zoledronic acid.

    PubMed

    Li, Yunfeng; Shui, Xueping; Zhang, Li; Hu, Jing

    2016-04-01

    Bisphosphonates (BPs) are potent anti-osteoporotic agents. Strontium-doped hydroxyapatite (HA) (SrHA) has been reported to increase bone density and improve trabecular microarchitecture in osteoporotic animals. But information about the effect of SrHA on the surrounding bone tissue in osteoporotic animals previously on BPs treatment is limited. We hypothesize that SrHA will induce increased bone density in the vicinity of the material when compared to HA, even in osteoporotic animals previously treated with BPs. HA and 10%SrHA (HA with 10 mol % calcium substituted by strontium) implants were prepared and characterized by scanning electronic microscopy (SEM), X-ray photoemission spectroscopy (XPS), and X-ray diffraction (XRD). Osteoporotic animal model was established by bilateral ovariectomy. Twelve weeks later, all OVX rats accepted subcutaneous injection of zoledronic acid (ZOL) at the dose of 1.5 μg/kg weekly for another twelve weeks. Subsequently, rod-shaped HA and SrHA implants were inserted in the distal femur of the OVX animals previously treated with ZOL. Eight weeks after implantation, specimens were harvested for histological and micro-computed tomography (micro-CT) analysis. Compared to HA, 10%SrHA raised the percent bone volume by 32.7%, the mean trabecular thickness by 36.5%, the mean trabecular number by 34.3%, the mean connectivity density by 38.4%, while the mean trabecular separation showed no significant difference. 10%SrHA also increased the bone area density by 36.3% in histological analysis. Results from this study indicated that 10%SrHA increased bone density and improved trabecular microarchitecture around implants in osteoporotic animals previously treated with ZOL when compared to HA.

  14. Nitrogen-doped carbon nanofoam derived from amino acid chelate complex for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Ramakrishnan, Prakash; Shanmugam, Sangaraju

    2016-06-01

    We report a novel strategy to fabricate the nitrogen-doped mesoporous carbon nanofoam structures (N-MCNF), derived from magnesium amino acid chelate complex (Mg-acc-complex) for its application towards high performance supercapacitor (SCs) system. A series of N-MCNF with well-connected carbon nanofoam structure have been developed by varying the synthesis temperature. The fabricated N-MCNF material possesses a high surface area (1564 m2 g-1) and pore volume (1.767 cm3 g-1) with nitrogen content of 3.42 wt%. A prototypical coin cell type symmetric N-MCNF SC device has been assembled with 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIMBF4] ionic liquid electrolyte, and evaluated for SCs studies. The N-MCNF with high textural properties delivers unprecedented SC performance, such as high specific capacitance (204 Fg-1 at 0.25 Ag-1, 25 °C), high energy density (63.4 Wh kg-1), high power density (35.9 kW kg-1) and long-term cycle life (32,500 cycles). Significantly, N-MCNF materials exhibited high power rate performance, at 500 mV-1 (115 Fg-1) and 25 Ag-1 (166 Fg-1) owing to the uniform mesopore size distribution (∼4 nm). The N-MCNF SC device delivered maximum energy densities of 83.4 and 93.3 Wh kg-1 at 60 °C and 90 °C, respectively. Such outstanding N-MCNF SC device is successfully demonstrated in solar energy harvester applications.

  15. Raman scattering investigations of the interaction of a COV with pure and acid doped ice particles

    NASA Astrophysics Data System (ADS)

    Facq, S.; Oancea, A.; Focsa, C.; Chazallon, B.

    2009-04-01

    Ice present in polar stratosphere is as well a common component of the troposphere, particularly in cirrus clouds widespread in tropopause and upper troposphere region. With water droplets, ice constitutes the condensed matter that can interact with atmospheric trace gases via many different trapping processes (co-deposition i.e; incorporation during growing ice conditions, adsorption, freezing etc). The incorporation of trace gases in ice surface/volume can both affect the atmospheric chemistry and the ice structure and reactivity. This can therefore modify the nature and composition of the incorporated species in ice, or in the gas phase. Recently, field measurements have demonstrated the presence of nitric acid in ice particles from cirrus clouds(1,2) (concentration between 0.63 wt% and 2.5 wt %). Moreover, laboratory experiments have shown that the uptake of atmospheric trace gases can be enhanced up to 1 or 2 orders of magnitude in these doped ice particles. Among trace gases capable to interact with atmospheric condensed matter figure volatile organic compounds such as aldehydes, ketones and alcohols (ex: ethanol and methanol). They play an important role in the upper troposphere (3,4) and snowpack chemistry (5) as they can be easily photolysed, producing free radicals and so influence the oxidizing capacity and the ozone-budget of the atmosphere (3,4). The temperature range at which these physico-chemical processes occur extents between ~ 190 K and 273K. Interaction between ice and trace gases are therefore largely dependent on the ice surface properties as well as on the phase formation dynamic (crystalline or not). This study aims to examine and characterize the incorporation of a COV (ex: ethanol), at the surface or in the volume of ice formed by different growth mechanisms (vapour deposition or droplets freezing). Vibrational spectra of water OH and ethanol CH-spectral regions are analysed using confocal micro-Raman spectroscopy at different temperatures

  16. Oxidative degradation of acid orange 7 using Ag-doped zinc oxide thin films.

    PubMed

    Shinde, S S; Bhosale, C H; Rajpure, K Y

    2012-12-05

    Ag-doped ZnO thin films with preferred c-axis orientation along (002) have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Ag-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal (wurtzite) crystal structure. The effect of Ag loading on the photocatalytic activity of Ag-doped ZnO in the degradation of azo dye is studied and results are compared with pure ZnO. The results show that the rate of degradation of azo dye over Ag-doped ZnO is much higher as compared to pure ZnO. Ag doping in ZnO is highly effective and can significantly enhance the photocatalytic degradation and mineralization of azo dye. The enhancement of photocatalytic activity of Ag-doped ZnO thin films is mainly due to their smaller crystallite size and capability for reducing the electron-hole pair recombination. Kinetic parameters have been investigated in terms of a first order rate equation. The rate constant (-k) for this heterogeneous photocatalysis is evaluated as a function of the initial concentration of original species. Substantial reduction in azo dye is achieved as analyzed from COD and TOC studies.

  17. Mineralization of the recalcitrant oxalic and oxamic acids by electrochemical advanced oxidation processes using a boron-doped diamond anode.

    PubMed

    Garcia-Segura, Sergi; Brillas, Enric

    2011-04-01

    Oxalic and oxamic acids are the ultimate and more persistent by-products of the degradation of N-aromatics by electrochemical advanced oxidation processes (EAOPs). In this paper, the kinetics and oxidative paths of these acids have been studied for several EAOPs using a boron-doped diamond (BDD) anode and a stainless steel or an air-diffusion cathode. Anodic oxidation (AO-BDD) in the presence of Fe(2+) (AO-BDD-Fe(2+)) and under UVA irradiation (AO-BDD-Fe(2+)-UVA), along with electro-Fenton (EF-BDD), was tested. The oxidation of both acids and their iron complexes on BDD was clarified by cyclic voltammetry. AO-BDD allowed the overall mineralization of oxalic acid, but oxamic acid was removed much more slowly. Each acid underwent a similar decay in AO-BDD-Fe(2+) and EF-BDD, as expected if its iron complexes were not attacked by hydroxyl radicals in the bulk. The faster and total mineralization of both acids was achieved in AO-BDD-Fe(2+)-UVA due to the high photoactivity of their Fe(III) complexes that were continuously regenerated by oxidation of their Fe(II) complexes. Oxamic acid always released a larger proportion of NH(4)(+) than NO(3)(-) ion, as well as volatile NO(x) species. Both acids were independently oxidized at the anode in AO-BDD, but in AO-BDD-Fe(2+)-UVA oxamic acid was more slowly degraded as its content decreased, without significant effect on oxalic acid decay. The increase in current density enhanced the oxidation power of the latter method, with loss of efficiency. High Fe(2+) contents inhibited the oxidation of Fe(II) complexes by the competitive oxidation of Fe(2+) to Fe(3+). Low current densities and Fe(2+) contents are preferable to remove more efficiently these acids by the most potent AO-BDD-Fe(2+)-UVA method.

  18. Phosphorus-doped carbon nanotubes supported low Pt loading catalyst for the oxygen reduction reaction in acidic fuel cells

    NASA Astrophysics Data System (ADS)

    Liu, Ziwu; Shi, Qianqian; Zhang, Rufan; Wang, Quande; Kang, Guojun; Peng, Feng

    2014-12-01

    To develop low-cost and efficient cathode electrocatalysts for fuel cells in acidic media, phosphorus-doped carbon nanotubes (P-CNTs) supported low Pt loading catalyst (0.85% Pt) is designed. The as-prepared Pt/P-CNTs exhibit significantly enhanced electrocatalytic oxygen reduction reaction (ORR) activity and long-term stability due to the stronger interaction between Pt and P-CNTs, which is proven by X-ray photoelectron spectroscopic analysis and density functional theory calculations. Moreover, the as-prepared Pt/P-CNTs also display much better tolerance to methanol crossover effects, showing a good potential application for future proton exchange membrane fuel cell devices.

  19. Influence of variously functionalized SBA-15 fillers on conductivity and electrochemical properties of PBI composite membranes for high temperature polymer fuel cells

    NASA Astrophysics Data System (ADS)

    Angioni, S.; Villa, D. C.; Cattaneo, A. S.; Mustarelli, P.; Quartarone, E.

    2015-10-01

    The use of inorganic fillers is an interesting strategy to improve the electrochemical performances of PBI membranes for application as electrolytes in HT-PEMFCs. Here, we prepared several mesoporous silica (SBA-15) based hybrids, functionalised with different moieties, namely acidic (SO3H-), basic (NH2-), and amphoteric (SO3H-NH2) units. The electrochemical properties of the resulting electrolytes were investigated in terms of proton transport and functional tests by varying the silica functionalization degree in the range 10-70 mol%, as well as the particles loading in the polymer (0-30 wt%). The actual effectiveness of the SBA-15 functionalization process in improving the electrolyte properties was compared with both the unfilled membrane and the one filled with pristine SBA-15. The best conductivity (∼90 mS cm-1 at 120 °C, 30%RH) was obtained with PBI composites loaded with 30 wt% of non-functionalized SBA-15. The use of fillers functionalized with acidic, basic of amphoteric groups did not lead to improvements with respect to pure SBA-15. This could be related to the set up of significant interactions between the functionalised fillers and H3PO4, which negatively influence the proton mobility. Encouraging MEA results (power peak >320 mW cm-2) were obtained in case of membranes based on pure SBA-15. These performances make the SBA-15/PBI composites particularly interesting for application in HT-PEMFCs.

  20. Perovskite CH3NH3PbI3 crystals and films. Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Semenova, O. I.; Yudanova, E. S.; Yeryukov, N. A.; Zhivodkov, Y. A.; Shamirzaev, T. S.; Maximovskiy, E. A.; Gromilov, S. A.; Troitskaia, I. B.

    2017-03-01

    Synthesis of organometal halide perovskite CH3NH3PbI3 has received much attention recently because of promising photosensitive properties usable for solid state solar cell (SSSC). Here the crystals of tetragonal phase (I4/mcm, a =8.8743 Å, c =12.6708 Å) of CH3NH3PbI3 were prepared. Formation of the CH3NH3PbI3 crystals was controlled by the SEM, EDS, XRD and Raman spectroscopy. Optical characteristics of the crystals were obtained using PL spectrometry and spectral ellipsometry methods. PL spectra of orthorhombic phase of CH3NH3PbI3 crystals were recorded the first time. Taking into account the practice use, the CH3NH3PbI3 films are obtained via the sol-gel method with ;spin-on; coating of CH3NH3PbI3 sol. The films are 500 nm in thickness and exhibit an openwork structure. Such a structure is optimal for SSSC construction because it increases the surface contact area between CH3NH3PbI3 and p-conductor.

  1. Optical and Atomic Force Microscopy Characterization of PbI2 Quantum Dots

    NASA Technical Reports Server (NTRS)

    Mu, R.; Tung, Y. S.; Ueda, A.; Henderson, D. O.

    1997-01-01

    Lead iodide (PbI2) clusters were synthesized from the chemical reaction of NaI (or KI) with Pb(NO3)2 in H2O, D2O, CH3OH, and C3H7OH media. The observation of the absorption features above 350 nm with the help of integrating sphere accessory strongly suggests the quantum dot formation of PbI2 in solution. Spectral comparison between the synthesized PbI2 clusters in solution and PbI2 nanophase by impregnation of PbI2 in four different pore-sized porous silica indicates that the PbI2 cluster size in solution is less than 2.5 nm in lateral dimension. Atomic force microscopy (AFM) measurements show that the PbL clusters deposited onto three different molecularly flat surfaces are single-layered. The measured height is 1.0 - 0.1 nm. The swollen layer thickness can be attributed to the intralayer contraction from the strong lateral interaction among PbI2 molecules, which is supported by ab initio calculation. Raman scattering measurement of LO and TO modes of PbI2 in bulk and in the confined state were also conducted in 50-150 cu cm region. The observed three bands at 74, %, 106 1/cm are assigned to TO2, LO2, and LO, mode, respectively. The relatively small red-shift in LO modes may be caused by the surface phonon polaritons of PbI2 nanophase in the porous silica.

  2. Spectroscopic Constants and Potential Energy Curves of PbI

    NASA Astrophysics Data System (ADS)

    Benavidesgarcia, M.; Balasubramanian, K.

    1993-10-01

    The spectroscopic constants and potential energy curves of the PbI diatomic were computed using complete active space SCF (CASSCF) followed by first-order CI (FOCI) and second-order CI (SOCI) calculations which included 607 000 configurations. Spin-orbit coupling was studied using the relativistic CI (RCI) method. The spectroscopic properties of the 2Π1/2 state are Re = 2.885 Å, ωe, = 153 cm-1, and De = 2.54(eV), while for the 2Π3/2 state the corresponding values are Re = 2.859 Å, ωe = 162 cm-1, and Te = 8255 cm-1. Our computed constants are in good agreement with experiment for the observed states. We also computed the properties and curves for several excited states which are yet to be observed.

  3. Uptake measurements of acetic acid on ice and nitric acid-doped thin ice films over upper troposphere/lower stratosphere temperatures.

    PubMed

    Romanias, Manolis N; Zogka, Antonia G; Papadimitriou, Vassileios C; Papagiannakopoulos, Panos

    2012-03-08

    The adsorption of gaseous acetic acid (CH(3)C(O)OH) on thin ice films and on ice doped with nitric acid (1.96 and 7.69 wt %) was investigated over upper troposphere and lower stratosphere (UT/LS) temperatures (198-208 K), and at low gas concentrations. Experiments were performed in a Knudsen flow reactor coupled to a quadrupole mass spectrometer. The initial uptake coefficients, γ(0), on thin ice films or HNO(3)-doped ice films were measured at low surface coverage. In all cases, γ(0) showed an inverse temperature dependence, and for pure thin ice films, it was given by the expression γ(0)(T) = (4.73 ± 1.13) × 10(-17) exp[(6496 ± 1798)/T]; the quoted errors are the 2σ precision of the linear fit, and the estimated systematic uncertainties are included in the pre-exponential factor. The inverse temperature dependence suggests that the adsorption process occurs via the formation of an intermediate precursor state. Uptakes were well represented by the Langmuir adsorption model, and the saturation surface coverage, N(max), on pure thin ice films was (2.11 ± 0.16) × 10(14) molecules cm(-2), independent of temperature in the range 198-206 K. Light nitration (1.96 and 7.69 wt %) of ice films resulted in more efficient CH(3)C(O)OH uptakes and larger N(max) values that may be attributed to in-bulk diffusion or change in nature of the gas-ice surface interaction. Finally, it was estimated that the rate of adsorption of acetic acid on high-density cirrus clouds in the UT/LS is fast, and this is reflected in the short atmospheric lifetimes (2-8 min) of acetic acid; however, the extent of this uptake is minor resulting in at most a 5% removal of acetic acid in UT/LS cirrus clouds.

  4. Highly efficient electrochemical degradation of perfluorooctanoic acid (PFOA) by F-doped Ti/SnO2 electrode.

    PubMed

    Yang, Bo; Jiang, Chaojin; Yu, Gang; Zhuo, Qiongfang; Deng, Shubo; Wu, Jinhua; Zhang, Hong

    2015-12-15

    The novel F-doped Ti/SnO2 electrode prepared by SnF4 as the single-source precursor was used for electrochemical degradation of aqueous perfluorooctanoic acid (PFOA). Higher oxidation reactivity and significantly longer service life were achieved for Ti/SnO2-F electrode than Ti/SnO2-X (X=Cl, Br, I, or Sb) electrode, which could decomposed over 99% of PFOA (50 mL of 100 mg L(-1)) within 30-min electrolysis. The property of Ti/SnO2-F electrode and its electrooxidation mechanism were investigated by XRD, SEM-EDX, EIS, LSV, and interfacial resistance measurements. We propose that the similar ionic radii of F and O as well as strong electronegativity of F caused its electrochemical stability with high oxygen evolution potential (OEP) and smooth surface to generate weakly adsorbed OH. The preparation conditions of electrode were also optimized including F doping amount, calcination temperature, and dip coating times, which revealed the formation process of electrode. Additionally, the major mineralization product, F(-), and low concentration of shorter chain perfluorocarboxylic acids (PFCAs) were detected in solution. So the reaction pathway of PFOA electrooxidation was proposed by intermediate analysis. These results demonstrate that Ti/SnO2-F electrode is promising for highly efficient treatment of PFOA in wastewater.

  5. Ni-Mo Nanocatalysts on N-Doped Graphite Nanotubes for Highly Efficient Electrochemical Hydrogen Evolution in Acid.

    PubMed

    Wang, Teng; Guo, Yanru; Zhou, Zhenxing; Chang, Xinghua; Zheng, Jie; Li, Xingguo

    2016-11-22

    Developing noble-metal-free catalysts for electrochemical hydrogen evolution reactions (HER) with superior stability in acid is of critical importance for large-scale, low-cost hydrogen production from water electrolysis. Herein, we report a highly efficient and stable noble-metal-free HER catalyst, which is composed of Ni and Mo2C nanocrystals supported on N-doped graphite nanotubes. This catalyst shows very low overpotential (65 mV in 0.5 M H2SO4 at a current density of 10 mA cm(-2) with a Tafel plot of 67 mV/dec) and good stability for HER in acidic electrolyte, which is a promising noble-metal-free HER catalyst.

  6. Protonic Acid Doping of Two Classes of the Emeraldine Form of Polyaniline

    DTIC Science & Technology

    1992-06-05

    less than 10%) by IICI solutions with pH as low as 2.5, but when still lower pl is applied , the doping level rapidly increases. Treating the EB-I with...jClicruical Phyisics Program, TIhc Ohio State Uiiivcrsity, Columibus, Ohlio 4132 10-1106 [JSee, fur example, Proceedinigs of Internimial

  7. Facile synthesis of nitrogen-doped graphene supported AuPd-CeO2 nanocomposites with high-performance for hydrogen generation from formic acid at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Li; Yan, Jun-Min; Zhang, Yue-Fei; Ping, Yun; Wang, Hong-Li; Jiang, Qing

    2014-02-01

    AuPd-CeO2 nanocomposites directly nucleated and grown on nitrogen-doped reduced graphene oxide, exhibit excellent catalytic activity and 100% hydrogen selectivity toward formic acid decomposition for hydrogen generation without any additives at room temperature.AuPd-CeO2 nanocomposites directly nucleated and grown on nitrogen-doped reduced graphene oxide, exhibit excellent catalytic activity and 100% hydrogen selectivity toward formic acid decomposition for hydrogen generation without any additives at room temperature. Electronic supplementary information (ESI) available: Experimental procedures; XPS, TEM, MS, GC, and EDX data; and the results of H2 generation from FA experiments. See DOI: 10.1039/c3nr05809c

  8. Au/ZnO hybrid nanocatalysts impregnated in N-doped graphene for simultaneous determination of ascorbic acid, acetaminophen and dopamine.

    PubMed

    Chen, Xianlan; Zhang, Guowei; Shi, Ling; Pan, Shanqing; Liu, Wei; Pan, Hiabo

    2016-08-01

    The formation of nitrogen-doped (N-doped) graphene uses hydrothermal method with urea as reducing agent and nitrogen source. The surface elemental composition of the catalyst was analyzed through XPS, which showed a high content of a total N species (7.12at.%), indicative of the effective N-doping, present in the form of pyridinic N, pyrrolic N and graphitic N groups. Moreover, Au nanoparticles deposited on ZnO nanocrystals surface, forming Au/ZnO hybrid nanocatalysts, undergo a super-hydrophobic to super-hydrophilic conversion. Herein, we present Au/ZnO hybrid nanocatalysts impregnated in N-doped graphene sheets through sonication technique of the Au/ZnO/N-doped graphene hybrid nanostructures. The as-prepared Au/ZnO/N-doped graphene hybrid nanostructure modified glassy carbon electrode (Au/ZnO/N-doped graphene/GCE) was first employed for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and acetaminophen (AC). The oxidation over-potentials of AA, DA and AC decreased dramatically, and their oxidation peak currents increased significantly at Au/ZnO/N-doped graphene/GCE compared to those obtained at the N-doped graphene/GCE and bare CCE. The peak separations between AA and DA, DA and AC, and AC and AA are large up to 195, 198 and 393mV, respectively. The calibration curves for AA, DA and AC were obtained in the range of 30.00-13.00×10(3), 2.00-0.18×10(3) and 5.00-3.10×10(3)μM, respectively. The detection limits (S/N=3) were 5.00, 0.40 and 0.80μM for AA, DA and AC, respectively.

  9. Enhanced photovoltaic performance of CH3NH3PbI3 perovskite solar cells through interfacial engineering using self-assembling monolayer.

    PubMed

    Zuo, Lijian; Gu, Zhuowei; Ye, Tao; Fu, Weifei; Wu, Gang; Li, Hanying; Chen, Hongzheng

    2015-02-25

    Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). The surface properties of the substrates on which crystalline perovskite thin films form are expected to affect greatly the crystallization and, thus, the resulting morphology. However, this topic is seldom examined in PSC. Here we developed a facile but efficient method of modifying the ZnO-coated substrates with 3-aminopropanioc acid (C3-SAM) to direct the crystalline evolution and achieve the optimal morphology of CH3NH3PbI3 perovskite film. With incorporation of the C3-SAM, highly crystalline CH3NH3PbI3 films were formed with reduced pin-holes and trap states density. In addition, the work function of the cathode was better aligned with the conduction band minimum of perovskite for efficient charge extraction and electronic coupling. As a result, the PSC performance remarkably increased from 9.81(±0.99)% (best 11.96%) to 14.25(±0.61)% (best 15.67%). We stress the importance of morphology control through substrate surface modification to obtain the optimal morphology and device performance of PSC, which should generate an impact on developing highly efficient PSC and future commercialization.

  10. Defining the Operational Conditions for High Temperature Polymer Fuel Cells in Naval Environments

    DTIC Science & Technology

    2008-12-31

    benefits of both Proton Exchange Membrane Fuel Cells (PEMFCs) and phosphoric acid fuel cell technologies: a solid polymer electrolyte, the PBI ...PEMFC and phosphoric acid fuel cell technologies: a solid polymer electrolyte, the PBI membrane, but with higher temperature (160°C) operation. PBI ...high-temperature polymer fuel cell is emerging, based on phosphoric- acid -doped polybenzimidazole ( PBI ) membranes. PBI technology combines some of the

  11. Preparation and characterization of mesoporous N-doped and sulfuric acid treated anatase TiO{sub 2} catalysts and their photocatalytic activity under UV and Vis illumination

    SciTech Connect

    Kun, Robert; Tarjan, Sandor; Oszko, Albert; Seemann, Torben; Zoellmer, Volker; Busse, Matthias; Dekany, Imre

    2009-11-15

    Nitrogen-doped TiO{sub 2} catalysts were prepared by a precipitation method. The samples were calcined at 400 deg. C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N{sub 2}-adsorption was used for structural characterization and UV-diffuse reflectance (UV-DR) was applied to investigate the optical properties of the as-prepared samples. It was found that microporous N-doped catalysts have solely anatase crystalline structure. Acidic treatment of the calcined samples was performed using sulfuric acid agitation. The crystalline structure remained unchanged due to surface treatment, while the porosity and the surface areas (a{sub BET}{sup S}) were decreased dramatically. Optical characterization of the doped catalysts showed that they could be excited by visible light photons in the 400-500 nm wavelength range (lambda{sub g,1}={approx}390 nm, lambda{sub g,2}={approx}510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO{sub 2} powders. Finally the catalysts were tested in the photocatalytic degradation of phenol in aqueous suspensions. Two different light sources were used; one of them was a UV-rich high pressure Hg-lamp, while the other was a tubular visible light source. We found that using visible light illumination N-doped, acid treated TiO{sub 2} samples were more catalytically active than non-doped TiO{sub 2} catalysts. - Graphical abstract: The effect of the acid treatment on the visible-light-driven photocatalytic activity of the N-doped, anatase TiO{sub 2} catalysts.

  12. A first-principles study on the effect of phosphorus-doped palladium catalyst for formic acid dissociation

    NASA Astrophysics Data System (ADS)

    He, Feng; Li, Kai; Yin, Cong; Wang, Ying; Jiao, Menggai; Tang, Hao; Wu, Zhijian

    2016-11-01

    The effect of phosphorus-doped Pd(111) catalyst for the formic acid (HCOOH) dissociation has been investigated by using the density functional theory. The adsorption configurations and active sites of the intermediates involved in the HCOOH dissociation on the Pd/P(111) surface are studied. Our results showed that the doping of P on Pd catalyst could strengthen the adsorption of the intermediates. The Pd/P(111) catalyst exhibits higher catalytic activity by the easy formation of CO2 and H2 compared with the Pd(111) catalyst. The dominant HCOOH dissociation product on Pd/P(111) surface is CO2 rather than CO. Based on the computational hydrogen electrode (CHE) model, we found that CO formation is unfavorable on Pd/P(111) under the anode potential condition compared with the Pd(111) catalyst. Furthermore, the microkinetic analysis based on the DFT calculations showed that at high temperatures, the HCOOH dissociation is disfavored on the Pd/P(111) surface.

  13. Synthesis, characterization and binding interactions of amino acids coupled perylene diimides with colloidal doped and undoped TiO2

    NASA Astrophysics Data System (ADS)

    Kavery, E.; Nagarajan, N.; Paramaguru, G.; Renganathan, R.

    2015-07-01

    Two sensitizers based on amino acids coupled with perylene moiety having absorption in the visible region have been designed and their interaction with doped and undoped TiO2 for the application of dye sensitized solar cells (DSSCs) has been studied. The synthesized compounds PDI-PA and PDI-AA were characterized using 1H and 13C NMR, Mass and FT-IR spectroscopic techniques. The optical properties and lifetime measurements of the sensitizers were analyzed using various solvents with different polarity. The solvatochromism effect was studied using Lippert-Mataga plot. The electrochemical studies of both dyes were investigated in DMF with various scan rate ranging from 200 to 1000 mV s-1. Colloidal doped and undoped TiO2 was prepared and characterized by using absorption measurements. Binding ability of the sensitizers with the nanoparticles was studied through absorption, fluorescence quenching, cyclic voltammetry and FT-IR measurements. Results obtained from all the above analysis suggest the mode of quenching may be static. The binding constant values were calculated using Kamat-Fox equation indicates the binding behavior of the sensitizers with the nanoparticles. The fluorescence quenching was mainly attributed to electron transfer from the excited state of PDI's to the conduction band of colloidal semiconductors. The electron transfer mechanism was explained based on the Rehm-Weller equation as well as the energy level diagram.

  14. Sonochemical synthesis of Pr-doped ZnO nanoparticles for sonocatalytic degradation of Acid Red 17.

    PubMed

    Khataee, Alireza; Karimi, Atefeh; Arefi-Oskoui, Samira; Darvishi Cheshmeh Soltani, Reza; Hanifehpour, Younes; Soltani, Behzad; Joo, Sang Woo

    2015-01-01

    Undoped and Pr-doped ZnO nanoparticles were prepared using a simple sonochemical method, and their sonocatalytic activity was investigated toward degradation of Acid Red 17 (AR17) under ultrasonic (US) irradiation. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The extent of sonocatalytic degradation was higher compared with sonolysis alone. The decolorization efficiency of sonolysis alone, sonocatalysis with undoped ZnO and 5% Pr-doped ZnO was 24%, 46% and 100% within reaction time of 70min, respectively. Sonocatalytic degradation of AR17 increased with increasing the amount of dopant and catalyst dosage and decreasing initial dye concentration. Natural pH was favored the sonocatalytic degradation of AR17. With the addition of chloride, carbonate and sulfate as radical scavengers, the decolorization efficiency was decreased from 100% to 65%, 71% and 89% at the reaction time of 70min, respectively, indicating that the controlling mechanism of sonochemical degradation of AR17 is the free radicals (not pyrolysis). The addition of peroxydisulfate and hydrogen peroxide as enhancer improved the degradation efficiency from 79% to 85% and 93% at the reaction time of 50min, respectively. The result showed good reusability of the synthesized sonocatalyst.

  15. Transparent indium oxide films doped with high Lewis acid strength Ge dopant for phosphorescent organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kang, Sin-Bi; Lim, Jong-Wook; Lee, Sunghun; Kim, Jang-Joo; Kim, Han-Ki

    2012-08-01

    We report on Ge-doped In2O3(IGO) films prepared by co-sputtering GeO2 and In2O3 targets for anode of phosphorescent organic light-emitting diodes (POLEDs). Under optimized annealing conditions, the IGO film exhibited a low sheet resistance of 14.0 Ω/square, a high optical transmittance of 86.9% and a work function of 5.2 eV, comparable to conventional Sn-doped In2O3 (ITO) films. Due to the higher Lewis acid strength of the Ge4+ ion (3.06) than that of Sn3+(1.62), the IGO film showed higher transparency in the near infrared and higher carrier mobility of 39.16 cm2 V-1 s-1 than the ITO films. In addition, the strongly preferred (2 2 2) orientation of the IGO grains, caused by Zone II grain growth during rapid thermal annealing, increased the carrier mobility and improved the surface morphology of the IGO film. POLEDs fabricated on IGO anodes showed identical current density-voltage-luminance curves and efficiencies to POLEDs with ITO electrodes due to the low sheet resistance and high transmittance of the IGO anode.

  16. Doping effect of dodecyl benzene sulphonic acid in poly(3-hexylthiophene)-P3HT-films

    NASA Astrophysics Data System (ADS)

    Alveroglu, Esra

    2015-04-01

    We demonstrated that how dodecyl benzene sulphonic acid (DBSA) as a small-molecular dopant, affects the spectroscopic, electronic and structural properties of poly(3-hexylthiophene) (P3HT). The DBSA volume ratio was varied from 0.001 μL to 30 μL per 1 mL P3HT solvent in p-xylene. DBSA doping reaction was confirmed by the emerging huge absorption peak at the wavelength of ∼800 nm while the ionization potential and nanostructure of P3HT films were highly affected. Additionally, conductivity of P3HT films increased nearly 1000 times at 30 μL DBSA. The crystallinity, as well as the conductivity and the UV-Vis absorption changed with the presence of P3HT. P3HT grain sized crystals seems to be disturbed by the addition of DBSA, but still remained even more DBSA was introduced. DBSA doping has interesting properties when incorporated in OFTs, OPVs and bioelectronics applications, so addition of DBSA can open new pathways for structural, spectroscopic and electronic control of organic semiconductor's blends.

  17. Effect of organic acids and nano-sized ceramic doping on PEO-based solid polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Park, Jae Won; Jeong, Euh Duck; Won, Mi-Sook; Shim, Yoon-Bo

    Composite solid polymer electrolytes (CSPEs) consisting of polyethyleneoxide (PEO), LiClO 4, organic acids (malonic, maleic, and carboxylic acids), and/or Al 2O 3 were prepared in acetonitrile. CSPEs were characterized by Brewster Angle Microscopy (BAM), thermal analysis, ac impedance, cyclic voltammetry, and tested for charge-discharge capacity with the Li or LiNi 0.5Co 0.5O 2 electrodes coated on stainless steel (SS). The morphologies of the CSPE films were homogeneous and porous. The differential scanning calorimetric (DSC) results suggested that performance of the CSPE film was highly enhanced by the acid and inorganic additives. The composite membrane doped with organic acids and ceramic showed good conductivity and thermal stability. The ac impedance data, processed by non-linear least square (NLLS) fitting, showed good conducting properties of the composite films. The ionic conductivity of the film consisting of (PEO) 8LiClO 4:citric acid (99.95:0.05, w/w%) was 3.25 × 10 -4 S cm -1 and 1.81 × 10 -4 S cm -1 at 30 °C. The conductivity has further improved to 3.81 × 10 -4 S cm -1 at 20 °C by adding 20 w/w% Al 2O 3 filler to the (PEO) 8LiClO 4 + 0.05% carboxylic acid composite. The experimental data for the full cell showed an upper limit voltage window of 4.7 V versus Li/Li + for CSPE at room temperature.

  18. Thin-Film Transformation of NH4 PbI3 to CH3 NH3 PbI3 Perovskite: A Methylamine-Induced Conversion-Healing Process.

    PubMed

    Zong, Yingxia; Zhou, Yuanyuan; Ju, Minggang; Garces, Hector F; Krause, Amanda R; Ji, Fuxiang; Cui, Guanglei; Zeng, Xiao Cheng; Padture, Nitin P; Pang, Shuping

    2016-11-14

    Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH4 PbI3 non-perovskite thin film converts stepwise into a dense, ultrasmooth, textured CH3 NH3 PbI3 perovskite thin film. Owing to the beneficial phase/structural development of the thin film, its photovoltaic properties undergo dramatic enhancement during this NH4 PbI3 -to-CH3 NH3 PbI3 transformation process. The chemical origins of this transformation are studied at various length scales.

  19. Novel Proton Conducting Solid Bio-polymer Electrolytes Based on Carboxymethyl Cellulose Doped with Oleic Acid and Plasticized with Glycerol

    PubMed Central

    Chai, M. N.; Isa, M. I. N.

    2016-01-01

    The plasticized solid bio-polymer electrolytes (SBEs) system has been formed by introducing glycerol (Gly) as the plasticizer into the carboxymethyl cellulose (CMC) doped with oleic acid (OA) via solution casting techniques. The ionic conductivity of the plasticized SBEs has been studied using Electrical Impedance Spectroscopy. The highest conductivity achieved is 1.64 × 10−4 S cm−1 for system containing 40 wt. % of glycerol. FTIR deconvolution technique had shown that the conductivity of CMC-OA-Gly SBEs is primarily influenced by the number density of mobile ions. Transference number measurement has shown that the cation diffusion coefficient and ionic mobility is higher than anion which proved the plasticized polymer system is a proton conductor. PMID:27265642

  20. Dual responsive dysprosium-doped hydroxyapatite particles and toxicity reduction after functionalization with folic and glucuronic acids.

    PubMed

    Sánchez Lafarga, Ana Karen; Pacheco Moisés, Fermín P; Gurinov, Andrey; Ortiz, Genaro Gabriel; Carbajal Arízaga, Gregorio Guadalupe

    2015-03-01

    The development of probes for biomedical applications demands materials with low toxicity levels besides fluorescence or magnetic properties to be detected by confocal microscopes or MRI resonators. Several drug delivery systems or other biomedical materials prepared with hydroxyapatite have been proposed, however, toxicity effects might arise when the size of particles is nanometric. In this study, hydroxyapatite functionalized with glucuronic or folic acids presented lower oxidative stress, measured from lipoperoxides and nitric oxide indicators in rats than pure hydroxyapatite. In separated experiments, hydroxyapatite was doped with dysprosium cations by coprecipitation producing a single crystal phase with fluorescent properties easily visualized by confocal microscopy when excited at 488nm. These particles also presented the ability to modify the proton relaxation time in T1 maps collected by magnetic resonance imaging. These modified hydroxyapatite nanoparticles could be candidates to design bimodal probes with low toxicity.

  1. Enhanced selectivity of boron doped diamond electrodes for the detection of dopamine and ascorbic acid by increasing the film thickness

    NASA Astrophysics Data System (ADS)

    Qi, Yao; Long, Hangyu; Ma, Li; Wei, Quiping; Li, Site; Yu, Zhiming; Hu, Jingyuan; Liu, Peizhi; Wang, Yijia; Meng, Lingcong

    2016-12-01

    In this paper, boron doped diamond (BDD) with different thickness were prepared by hot filament chemical vapor deposition. The performance of BDD electrodes for detecting dopamine (DA) and ascorbic acid (AA) were investigated. Scanning electron microscopy and Raman spectra reveal the grain size increases and the film quality improves with the increase of film thickness. Electrochemical test show that the transfer coefficient in [Fe3 (CN) 6]3-/4- redox system increases with the increase of the film thickness. The results of selectivity and sensitivity for DA mixed with AA detection show that 8h-BDD and 12h-BDD electrodes possess well selective separated oxidation peaks of DA and AA, and the 12h-BDD electrode exhibits optimal sensitivity until the DA concentration drops to 1 μ M.

  2. Chemometric study on the electrochemical incineration of nitrilotriacetic acid using platinum and boron-doped diamond anode.

    PubMed

    Zhang, Chunyong; He, Zhenzhu; Wu, Jingyu; Fu, Degang

    2015-07-01

    This study investigated the electrochemical incineration of nitrilotriacetic acid (NTA) at boron-doped diamond (BDD) and platinum (Pt) anodes. Trials were performed in the presence of sulfate electrolyte media under recirculation mode. The parameters that influence the degradation efficiency were investigated, including applied current density, flow rate, supporting electrolyte concentration and reaction time. To reduce the number of experiments, the system had been managed under chemometric technique named Doehlert matrix. As a consequence, the mineralization of NTA demonstrated similar behavior upon operating parameters on these two anodes. Further kinetic study indicated that the degradations followed pseudo-first-order reactions for both BDD and Pt anodes, and the reaction rate constant of the former was found to be higher than that of the latter. Such difference could be interpreted by results from fractal analysis. In addition, a reaction sequence for NTA mineralization considering all the detected intermediates was also proposed.

  3. Voltammetric determination of mixtures of caffeine and chlorogenic acid in beverage samples using a boron-doped diamond electrode.

    PubMed

    Yardım, Yavuz; Keskin, Ertugrul; Şentürk, Zühre

    2013-11-15

    Herein, a boron-doped diamond (BDD) electrode that is anodically pretreated was used for the simultaneous determination of caffeine (CAF) and chlorogenic acid (CGA) by cyclic and adsorptive stripping voltammetry. The dependence of peak current and potential on pH, scan rate, accumulation parameters and other experimental variables were studied. By using square-wave stripping mode after 60 s accumulation under open-circuit voltage, the BDD electrode was able to separate the oxidation peak potentials of CAF and CGA present in binary mixtures by about 0.4V in Britton-Robinson buffer at pH 1.0. The limits of detection were 0.107 µg mL(-1) (5.51×10(-7) M) for CAF, and 0.448 µg mL(-1) (1.26×10(-6) M) for CGA. The practical applicability of this methodology was tested in commercially available beverage samples.

  4. Novel Proton Conducting Solid Bio-polymer Electrolytes Based on Carboxymethyl Cellulose Doped with Oleic Acid and Plasticized with Glycerol

    NASA Astrophysics Data System (ADS)

    Chai, M. N.; Isa, M. I. N.

    2016-06-01

    The plasticized solid bio-polymer electrolytes (SBEs) system has been formed by introducing glycerol (Gly) as the plasticizer into the carboxymethyl cellulose (CMC) doped with oleic acid (OA) via solution casting techniques. The ionic conductivity of the plasticized SBEs has been studied using Electrical Impedance Spectroscopy. The highest conductivity achieved is 1.64 × 10‑4 S cm‑1 for system containing 40 wt. % of glycerol. FTIR deconvolution technique had shown that the conductivity of CMC-OA-Gly SBEs is primarily influenced by the number density of mobile ions. Transference number measurement has shown that the cation diffusion coefficient and ionic mobility is higher than anion which proved the plasticized polymer system is a proton conductor.

  5. Investigation into the Advantages of Pure Perovskite Film without PbI2 for High Performance Solar Cell

    PubMed Central

    Kwon, Uisik; Hasan, Md Mehedi; Yin, Wenping; Kim, Dasom; Ha, Na Young; Lee, Soonil; Ahn, Tae Kyu; Park, Hui Joon

    2016-01-01

    In CH3NH3PbI3-based high efficiency perovskite solar cells (PSCs), tiny amount of PbI2 impurity was often found with the perovskite crystal. However, for two-step solution process-based perovskite films, most of findings have been based on the films having different morphologies between with and without PbI2. This was mainly due to the inferior morphology of pure perovskite film without PbI2, inevitably produced when the remaining PbI2 forced to be converted to perovskite, so advantages of pure perovskite photoactive layer without PbI2 impurity have been overlooked. In this work, we designed a printing-based two-step process, which could not only generate pure perovskite crystal without PbI2, but also provide uniform and full surface coverage perovskite film, of which nanoscale morphology was comparable to that prepared by conventional two-step solution process having residual PbI2. Our results showed that, in two-step solution process-based PSC, pure perovskite had better photon absorption and longer carrier lifetime, leading to superior photocurrent generation with higher power conversion efficiency. Furthermore, this process was further applicable to prepare mixed phase pure perovskite crystal without PbI2 impurity, and we showed that the additional merits such as extended absorption to longer wavelength, increased carrier lifetime and reduced carrier recombination could be secured. PMID:27786257

  6. Investigation into the Advantages of Pure Perovskite Film without PbI2 for High Performance Solar Cell.

    PubMed

    Kwon, Uisik; Hasan, Md Mehedi; Yin, Wenping; Kim, Dasom; Ha, Na Young; Lee, Soonil; Ahn, Tae Kyu; Park, Hui Joon

    2016-10-27

    In CH3NH3PbI3-based high efficiency perovskite solar cells (PSCs), tiny amount of PbI2 impurity was often found with the perovskite crystal. However, for two-step solution process-based perovskite films, most of findings have been based on the films having different morphologies between with and without PbI2. This was mainly due to the inferior morphology of pure perovskite film without PbI2, inevitably produced when the remaining PbI2 forced to be converted to perovskite, so advantages of pure perovskite photoactive layer without PbI2 impurity have been overlooked. In this work, we designed a printing-based two-step process, which could not only generate pure perovskite crystal without PbI2, but also provide uniform and full surface coverage perovskite film, of which nanoscale morphology was comparable to that prepared by conventional two-step solution process having residual PbI2. Our results showed that, in two-step solution process-based PSC, pure perovskite had better photon absorption and longer carrier lifetime, leading to superior photocurrent generation with higher power conversion efficiency. Furthermore, this process was further applicable to prepare mixed phase pure perovskite crystal without PbI2 impurity, and we showed that the additional merits such as extended absorption to longer wavelength, increased carrier lifetime and reduced carrier recombination could be secured.

  7. Investigation into the Advantages of Pure Perovskite Film without PbI2 for High Performance Solar Cell

    NASA Astrophysics Data System (ADS)

    Kwon, Uisik; Hasan, Md Mehedi; Yin, Wenping; Kim, Dasom; Ha, Na Young; Lee, Soonil; Ahn, Tae Kyu; Park, Hui Joon

    2016-10-01

    In CH3NH3PbI3-based high efficiency perovskite solar cells (PSCs), tiny amount of PbI2 impurity was often found with the perovskite crystal. However, for two-step solution process-based perovskite films, most of findings have been based on the films having different morphologies between with and without PbI2. This was mainly due to the inferior morphology of pure perovskite film without PbI2, inevitably produced when the remaining PbI2 forced to be converted to perovskite, so advantages of pure perovskite photoactive layer without PbI2 impurity have been overlooked. In this work, we designed a printing-based two-step process, which could not only generate pure perovskite crystal without PbI2, but also provide uniform and full surface coverage perovskite film, of which nanoscale morphology was comparable to that prepared by conventional two-step solution process having residual PbI2. Our results showed that, in two-step solution process-based PSC, pure perovskite had better photon absorption and longer carrier lifetime, leading to superior photocurrent generation with higher power conversion efficiency. Furthermore, this process was further applicable to prepare mixed phase pure perovskite crystal without PbI2 impurity, and we showed that the additional merits such as extended absorption to longer wavelength, increased carrier lifetime and reduced carrier recombination could be secured.

  8. Hollow nitrogen-doped carbon microspheres pyrolyzed from self-polymerized dopamine and its application in simultaneous electrochemical determination of uric acid, ascorbic acid and dopamine.

    PubMed

    Xiao, Chunhui; Chu, Xiaochen; Yang, Yan; Li, Xing; Zhang, Xiaohua; Chen, Jinhua

    2011-02-15

    Hollow nitrogen-doped carbon microspheres (HNCMS) as a novel carbon material have been prepared and the catalytic activities of HNCMS-modified glassy carbon (GC) electrode towards the electro-oxidation of uric acid (UA), ascorbic acid (AA) and dopamine (DA) have also been investigated. Comparing with the bare GC and carbon nanotubes (CNTs) modified GC (CNTs/GC) electrodes, the HNCMS modified GC (HNCMS/GC) electrode has higher catalytic activities towards the oxidation of UA, AA and DA. Moreover, the peak separations between AA and DA, and DA and UA at the HNCMS/GC electrode are up to 212 and 136 mV, respectively, which are superior to those at the CNTs/GC electrode (168 and 114 mV). Thus the simultaneous determination of UA, AA and DA was carried out successfully. In the co-existence system of UA, AA and DA, the linear response range for UA, AA and DA are 5-30 μM, 100-1000 μM and 3-75 μM, respectively and the detection limits (S/N = 3) are 0.04 μM, 0.91 μM and 0.02 μM, respectively. Meanwhile, the HNCMS/GC electrode can be applied to measure uric acid in human urine, and may be useful for measuring abnormally high concentration of AA or DA. The attractive features of HNCMS provide potential applications in the simultaneous determination of UA, AA and DA.

  9. Nitrogen-doped, FeNi alloy nanoparticle-decorated graphene as an efficient and stable electrode for electrochemical supercapacitors in acid medium

    NASA Astrophysics Data System (ADS)

    El-Deen, Ahmed G.; El-Newehy, Mohamed; Kim, Cheol Sang; Barakat, Nasser AM

    2015-03-01

    Nitrogen-doped graphene decorated by iron-nickel alloy is introduced as a promising electrode material for supercapacitors. Compared to pristine and Ni-decorated graphene, in acid media, the introduced electrode revealed excellent specific capacitance as the corresponding specific capacitance was multiplied around ten times with capacity retention maintained at 94.9% for 1,000 cycles. Briefly, iron acetate, nickel acetate, urea, and graphene oxide were ultrasonicated and subjected to MW heating and then sintered with melanin in Ar. The introduced N-doped FeNi@Gr exhibits remarkable electrochemical behavior with long-term stability.

  10. Simultaneous voltammetric determination of paracetamol and ascorbic acid using a boron-doped diamond electrode modified with Nafion and lead films.

    PubMed

    Tyszczuk-Rotko, Katarzyna; Bęczkowska, Ilona; Wójciak-Kosior, Magdalena; Sowa, Ireneusz

    2014-11-01

    The paper describes the fabrication and application of a novel sensor (a boron-doped diamond electrode modified with Nafion and lead films) for the simultaneous determination of paracetamol and ascorbic acid by differential pulse voltammetry. The main advantage of the lead film and polymer covered boron-doped diamond electrode is that the sensitivity of the stripping responses is increased and the separation of paracetamol and ascorbic acid signals is improved due to the modification of the boron-doped diamond surface by the lead layer. Additionally, the repeatability of paracetamol and ascorbic acid signals is improved by the application of the Nafion film coating. In the presence of oxygen, linear calibration curves were obtained in a wide concentration range from 5×10(-7) to 2×10(-4) mol L(-1) for paracetamol and from 1×10(-6) to 5×10(-4) mol L(-1) for ascorbic acid. The analytical utility of the differential pulse voltammetric method elaborated was tested in the assay of paracetamol and ascorbic acid in commercially available pharmaceutical formulations and the method was validated by high performance liquid chromatography coupled with diode array detector.

  11. Growth of thin, c-axis oriented Sr-doped LaP3O9 electrolyte membranes in condensed phosphoric acid solutions

    NASA Astrophysics Data System (ADS)

    Hatada, Naoyuki; Takahashi, Kota; Adachi, Yoshinobu; Uda, Tetsuya

    2016-08-01

    Proton-conducting Sr-doped LaP3O9 has potential application as electrolytes in intermediate temperature fuel cells, but reduction of the electrical resistance of the electrolyte membranes is necessary for practical applications. In this study, we focused on reducing the resistance by reducing the electrolyte thickness, while maintaining a preferable microstructure for proton conduction (c-axis orientation and absence of the small-crystal layer). Thin, c-axis oriented Sr-doped LaP3O9 membranes were successfully obtained in condensed phosphoric acid solutions by a novel "two-step precipitation method". In this method, Sr-doped LaP3O9 powder was artificially deposited on the surface of the carbon paper supports as seeds, and then columnar crystals were grown "downward" in the solutions. We expect that this method will be utilized to produce LaP3O9 electrolyte membranes with lower electrical resistance.

  12. Photoelectric characteristics of CH3NH3PbI3/p-Si heterojunction

    NASA Astrophysics Data System (ADS)

    Yamei, Wu; Ruixia, Yang; Hanmin, Tian; Shuai, Chen

    2016-05-01

    Organic-inorganic hybrid perovskite CH3NH3PbI3 film is prepared on p-type silicon substrate using the one-step solution method to form a CH3NH3PbI3/p-Si heterojunction. The film morphology and structure are characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The photoelectric properties of the CH3NH3PbI3/p-Si heterojunction are studied by testing the current-voltage (I-V) with and without illumination and capacitance-voltage (C-V) characteristics. It turns out from the I-V curve without illumination that the CH3NH3PbI3/p-Si heterojunction has a rectifier feature with the rectification ratio over 70 at the bias of ±5 V. Also, there appears a photoelectric conversion phenomenon on this heterojunction with a short circuit current (Isc) of 0.16 μA and an open circuit voltage (Voc) of about 10 mV The high frequency C-V characteristic of the Ag/CH3NH3PbI3/p-Si heterojunction turns out to be similar to that of the metal-insulator-semiconductor (MIS) structure, and a parallel translation of the C-V curve along the forward voltage axis is found. This parallel translation means the existence of defects at the CH3NH3PbI3/p-Si interface and positive fixed charges in the CH3NH3PbI3 layer. The defects at the interface of the CH3NH3PbI3/p-Si heterojunction result in the dramatic decline of the Voc. Besides, the C-V test of CH3NH3PbI3 film shows a non-linear dielectric property and the dielectric value is about 4.64 as calculated. Project supported by the Hebei Province Natural Science Foundation of China (No. F2014202184) and the Tianjin Natural Science Foundation of China (No. 15JCZDJC37800).

  13. Polybenzimidazole (PBI) as a matrix resin precursor for carbon/carbon composites

    SciTech Connect

    Sandor, R.B. )

    1991-04-01

    Polybenzimidazole (PBI) is used to make continuous fiber prepregs with excellent room temperature drape and tack. Composite panels, tubes and complex shapes are fabricated using either autoclave processing, Thermoclave {reg sign} technique, compression molding or filament winding. The as-cured composites have excellent mechanical properties and the unique ability (among organic polymeric composites) to retain properties at temperatures approaching 1,800F. The PBI/carbon composites can then be used as precursors for carbon/carbon composites. PBI has a high carbonization yield ({approximately} 78%), and emits virtually no offgases to 550C which permits rapid processing. In addition, PBI laminates exhibit 40% less volumetric shrinkage than phenolic laminates. This paper presents a comprehensive study which compares the pyrolysis behavior of laminates made with phenolic and PBI resins on T-300 8HS. With this combination of high performance properties Celazole parts are currently being used for the chemical process and oil recovery industries where the key demands are thermal stability and chemical resistance. In general industrial applications, Celazole is well suited for bearings, sleeves, rollers and other parts where hardness, low friction high compressive strength and thermal and dimensional stability are required.

  14. Electric polarization of CH3NH3PbI3 and enhancement by Cl substitution

    NASA Astrophysics Data System (ADS)

    Yan, Wen-Li; Lu, Guang-Hong; Liu, Feng

    As a prototype of organic-inorganic hybrid perovskite, CH3NH3PbI3 has attracted extensive attention recently due to its applications in high power-conversion-efficiency solar cells. In comparison with its inorganic perovskite counterparts such as CsPbI3, the organic cation CH3NH3+ is expected to play multiple important roles in distorting crystal structures and thus band structures as well as creating local electrically polarized domains to help separate charge carriers. Using first-principles method and berry phase theory, the electric polarization vectors of CH3NH3PbI3 have been calculated. The off-center displacement of Pb within the PbI6 octahedral is shown to introduce major intrinsic polarization, with additional contributions from off-center displacement of CH3NH3+ within PbI3 cage and charge polarization within the organic cation. With chlorine substitution of iodine, the electronegativity difference between halogen and Pb becomes larger, and the lattice distortion and hence the electric polarization increases, which provides a possible mechanism to further assist charge carrier separation in solar cell devices. This is consistent with enhanced photovoltaics properties of CH3NH3PbI3-xClx found in recent experiments. This work is supported by China Scholarship Council (Grant No. 201306020117) and US DOE-BES (Grant No. DE-FG02-04ER46148).

  15. Polybenzimidazole (PBI) functionalized nanographene as highly stable catalyst support for polymer Electrolyte membrane fuel cells (PEMFCs)

    DOE PAGES

    Xin, Le; Yang, Fan; Qiu, Yang; ...

    2016-08-25

    Nanoscale graphenes were used as cathode catalyst supports in proton exchange membrane fuel cells (PEMFCs). Surface-initiated polymerization that covalently bonds polybenzimidazole (PBI) polymer on the surface of graphene supports enables the uniform distribution of the Pt nanoparticles, as well as allows the sealing of the unterminated carbon bonds usually present on the edge of graphene from the chemical reduction of graphene oxide. The nanographene effectively shortens the length of channels and pores for O2 diffusion/water dissipation and significantly increases the primary pore volume. Further addition of p-phenyl sulfonic functional graphitic carbon particles as spacers, increases the specific volume of themore » secondary pores and greatly improves O2 mass transport within the catalyst layers. The developed composite cathode catalyst of Pt/PBI-nanographene (50 wt%) + SO3H-graphitic carbon black demonstrates a higher beginning of life (BOL) PEMFC performance as compared to both Pt/PBI-nanographene (50 wt%) and Pt/PBI-graphene (50 wt%) + SO3H-graphitic carbon black (GCB). Accelerated stress tests show excellent support durability compared to that of traditional Pt/Vulcan XC72 catalysts, when subjected to 10,000 cycles from 1.0 V to 1.5 V. As a result, this study suggests the promise of using PBI-nanographene + SO3H-GCB hybrid supports in fuel cells to achieve the 2020 DOE targets for transportation applications.« less

  16. Polybenzimidazole (PBI) functionalized nanographene as highly stable catalyst support for polymer Electrolyte membrane fuel cells (PEMFCs)

    SciTech Connect

    Xin, Le; Yang, Fan; Qiu, Yang; Uzunoglu, Aytekin; Rockward, Tommy; Borup, Rodney L.; Stanciu, Lia A.; Li, Wenzhen; Xie, Jian

    2016-08-25

    Nanoscale graphenes were used as cathode catalyst supports in proton exchange membrane fuel cells (PEMFCs). Surface-initiated polymerization that covalently bonds polybenzimidazole (PBI) polymer on the surface of graphene supports enables the uniform distribution of the Pt nanoparticles, as well as allows the sealing of the unterminated carbon bonds usually present on the edge of graphene from the chemical reduction of graphene oxide. The nanographene effectively shortens the length of channels and pores for O2 diffusion/water dissipation and significantly increases the primary pore volume. Further addition of p-phenyl sulfonic functional graphitic carbon particles as spacers, increases the specific volume of the secondary pores and greatly improves O2 mass transport within the catalyst layers. The developed composite cathode catalyst of Pt/PBI-nanographene (50 wt%) + SO3H-graphitic carbon black demonstrates a higher beginning of life (BOL) PEMFC performance as compared to both Pt/PBI-nanographene (50 wt%) and Pt/PBI-graphene (50 wt%) + SO3H-graphitic carbon black (GCB). Accelerated stress tests show excellent support durability compared to that of traditional Pt/Vulcan XC72 catalysts, when subjected to 10,000 cycles from 1.0 V to 1.5 V. As a result, this study suggests the promise of using PBI-nanographene + SO3H-GCB hybrid supports in fuel cells to achieve the 2020 DOE targets for transportation applications.

  17. Acid-doped polymer nanofiber framework: Three-dimensional proton conductive network for high-performance fuel cells

    NASA Astrophysics Data System (ADS)

    Tanaka, Manabu; Takeda, Yasushi; Wakiya, Takeru; Wakamoto, Yuta; Harigaya, Kaori; Ito, Tatsunori; Tarao, Takashi; Kawakami, Hiroyoshi

    2017-02-01

    High-performance polymer electrolyte membranes (PEMs) with excellent proton conductivity, gas barrier property, and membrane stability are desired for future fuel cells. Here we report the development of PEMs based on our proposed new concept ;Nanofiber Framework (NfF).; The NfF composite membranes composed of phytic acid-doped polybenzimidazole nanofibers (PBINf) and Nafion matrix show higher proton conductivity than the recast-Nafion membrane without nanofibers. A series of analyses reveal the formation of three-dimensional network nanostructures to conduct protons and water effectively through acid-condensed layers at the interface of PBINf and Nafion matrix. In addition, the NfF composite membrane achieves high gas barrier property and distinguished membrane stability. The fuel cell performance by the NfF composite membrane, which enables ultra-thin membranes with their thickness less than 5 μm, is superior to that by the recast-Nafion membrane, especially at low relative humidity. Such NfF-based high-performance PEM will be accomplished not only by the Nafion matrix used in this study but also by other polymer electrolyte matrices for future PEFCs.

  18. Removal of aqueous Hg(II) and Cr(VI) using phytic acid doped polyaniline/cellulose acetate composite membrane.

    PubMed

    Li, Renjie; Liu, Lifen; Yang, Fenglin

    2014-09-15

    Conductive composite membrane-phytic acid (PA) doped polyaniline (PANI)/cellulose acetate (CA) (PANI-PA/CA) was prepared in a simple and environmental-friendly method, in which aniline was blended with CA/PA solution and polymerized before the phase conversion. The resultant composite membranes were characterized by SEM, EDX, FTIR-ATR, BET and electrical resistance measurements. When used as adsorbent for Hg(II) and Cr(VI) ions, the prepared composite membrane exhibits excellent adsorption capability. The adsorption of Hg(II) and Cr(VI) follows a pseudo-second-order kinetic model and best fits the Langmuir isotherm model, with the maximum adsorption capacity reaching 280.11 and 94.34 mg g(-1), respectively. The heavy metal loaded composite membrane can be regenerated and reused after treatment with acid or alkali solution, making it a promising and practical adsorbent for Hg(II) and Cr(VI) removal. Tests with river water were also carried out, indicating good performance and application.

  19. Enhanced photocatalytic degradation of humic acids using Al and Fe co-doped TiO2 nanotubes under UV/ozonation for drinking water purification.

    PubMed

    Yuan, Rongfang; Zhou, Beihai; Hua, Duo; Shi, Chunhong

    2013-11-15

    O3/UV/TiO2 was used to effectively decompose humic acids (HAs) in drinking water. To obtain a large specific surface area and low band gap energy, Al and Fe co-doped TiO2 nanotubes were successfully synthesized using the hydrothermal method. The effect of the optimal co-doped TiO2 nanotubes catalyst on the HAs removal efficiency through O3/UV/co-doped TiO2 process was investigated. The highest HAs removal efficiency (79.4%) that exhibited a pseudo-first-order rate constant of 0.172 min(-1) was achieved, in the presence of 550 °C calcined 1.0% co-doped TiO2 nanotubes with an Al:Fe ratio of 0.25:0.75. The effects of calcination temperature and doping concentration on anatase phase weight fractions, average crystallite sizes, Brunauer-Emmett-Teller surface area, catalyst band gap energy, and catalyst photocatalytic activity were also discussed. The inorganic anions also affected the catalyst photocatalytic ability. In a neutral solution, SO4(2-) slightly promoted HAs removal. However, HCO3(-) was found to significantly inhibit the catalyst activity, whereas Cl(-) had negligible effect on photocatalytic ability.

  20. Mineralization of salicylic acid in acidic aqueous medium by electrochemical advanced oxidation processes using platinum and boron-doped diamond as anode and cathodically generated hydrogen peroxide.

    PubMed

    Guinea, Elena; Arias, Conchita; Cabot, Pere Lluís; Garrido, José Antonio; Rodríguez, Rosa María; Centellas, Francesc; Brillas, Enric

    2008-01-01

    Solutions containing 164 mg L(-1) salicylic acid of pH 3.0 have been degraded by electrochemical advanced oxidation processes such as anodic oxidation, anodic oxidation with electrogenerated H(2)O(2), electro-Fenton, photoelectro-Fenton and solar photoelectro-Fenton at constant current density. Their oxidation power has been comparatively studied in a one-compartment cell with a Pt or boron-doped diamond (BDD) anode and a graphite or O(2)-diffusion cathode. In the three latter procedures, 0.5mM Fe(2+) is added to the solution to form hydroxyl radical (()OH) from Fenton's reaction between Fe(2+) and H(2)O(2) generated at the O(2)-diffusion cathode. Total mineralization is attained for all methods with BDD and for photoelectro-Fenton and solar photoelectro-Fenton with Pt. The poor decontamination achieved in anodic oxidation and electro-Fenton with Pt is explained by the slow removal of most pollutants by ()OH formed from water oxidation at the Pt anode in comparison to their quick destruction with ()OH produced at BDD. ()OH generated from Fenton's reaction oxidizes rapidly all aromatic pollutants, but it cannot destroy final Fe(III)-oxalate complexes. Solar photoelectro-Fenton treatments always yield quicker degradation rate due to the very fast photodecarboxylation of these complexes by UVA irradiation supplied by solar light. The effect of current density on the degradation rate, efficiency and energy cost of all methods is examined. The salicylic acid decay always follows a pseudo-first-order kinetics. 2,3-Dihydroxybenzoic, 2,5-dihydroxybenzoic, 2,6-dihydroxybenzoic, alpha-ketoglutaric, glycolic, glyoxylic, maleic, fumaric, malic, tartronic and oxalic acids are detected as oxidation products. A general reaction sequence for salicylic acid mineralization considering all these intermediates is proposed.

  1. Novel electrochemical sensor based on N-doped carbon nanotubes and Fe3O4 nanoparticles: simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid.

    PubMed

    Fernandes, Diana M; Costa, Marta; Pereira, Clara; Bachiller-Baeza, Belén; Rodríguez-Ramos, Inmaculada; Guerrero-Ruiz, Antonio; Freire, Cristina

    2014-10-15

    A new modified electrode based on N-doped carbon nanotubes functionalized with Fe3O4 nanoparticles (Fe3O4@CNT-N) has been prepared and applied on the simultaneous electrochemical determination of small biomolecules such as dopamine (DA), uric acid (UA) and ascorbic acid (AA) using voltammetric methods. The unique properties of CNT-N and Fe3O4 nanoparticles individually and the synergetic effect between them led to an improved electrocatalytic activity toward the oxidation of AA, DA and UA. The overlapping anodic peaks of these three biomolecules could be resolved from each other due to their lower oxidation potentials and enhanced oxidation currents when using the Fe3O4@CNT-N modified electrode. The linear response ranges for the square wave voltammetric determination of AA, DA and UA were 5-235, 2.5-65 and 2.5-85μmoldm(-3) with detection limit (S/N=3) of 0.24, 0.050 and 0.047μmoldm(-3), respectively. These results show that Fe3O4@CNT-N nanocomposite is a promising candidate of cutting-edge electrode materials for electrocatalytic applications.

  2. Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells

    PubMed Central

    Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djurišić, Aleksandra B.; Leung, Wallace Woon-fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

    2014-01-01

    We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12 hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04 V, short circuit current density (JSC) 23 mA/cm2, and fill factor 0.64 had been achieved for our champion device. PMID:25341527

  3. Credible evidence for the passivation effect of remnant PbI2 in CH3NH3PbI3 films in improving the performance of perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Shimao; Dong, Weiwei; Fang, Xiaodong; Zhang, Qingli; Zhou, Shu; Deng, Zanhong; Tao, Ruhua; Shao, Jingzhen; Xia, Rui; Song, Chao; Hu, Linhua; Zhu, Jun

    2016-03-01

    The role of remnant PbI2 in CH3NH3PbI3 films is still controversial, some investigations have revealed that the remnant PbI2 plays a passivation role, reduces the charge recombination in perovskite solar cells (PSCs), and improves the performance of PSCs, but the opposing views state that remnant PbI2 has no passivation effect and it would deteriorate the stability of the devices. In our investigation, the CH3NH3PbI3 films have been prepared by a two-step spin-coating method and the content of the remnant PbI2 in CH3NH3PbI3 films has been tuned by varying the preparation temperature. It has been found that increasing the heating temperature could increase the coverage of spin-coated PbI2 films, which has led to high coverage CH3NH3PbI3 films and more remnant PbI2 in CH3NH3PbI3 films, and as a result, the performance of PSCs was enhanced obviously and the maximum power conversion efficiency of 14.32 +/- 0.28% was achieved by the PSCs prepared at 130/120 °C (PbI2 films were heated at 130 °C and CH3NH3PbI3 films were heated at 120 °C). Furthermore, the dark current, electrochemical impedance spectroscopy and time-resolved fluorescence emission decay measurements revealed that the charge recombination in PSCs has been gradually suppressed and the fluorescence emission lifetime has gradually increased with the content of remnant PbI2 increasing. Thus, the passivation effects of the unreacted and decomposed PbI2 in improving the performance of PSCs have been confirmed unquestionably.The role of remnant PbI2 in CH3NH3PbI3 films is still controversial, some investigations have revealed that the remnant PbI2 plays a passivation role, reduces the charge recombination in perovskite solar cells (PSCs), and improves the performance of PSCs, but the opposing views state that remnant PbI2 has no passivation effect and it would deteriorate the stability of the devices. In our investigation, the CH3NH3PbI3 films have been prepared by a two-step spin-coating method and the

  4. Single-Wall Carbon Nanotube Doping in Lead-Acid Batteries: A New Horizon.

    PubMed

    Banerjee, Anjan; Ziv, Baruch; Shilina, Yuliya; Levi, Elena; Luski, Shalom; Aurbach, Doron

    2017-02-01

    The addition of single-wall carbon nanotubes (SWCNT) to lead-acid battery electrodes is the most efficient suppresser of uncontrolled sulfation processes. Due to the cost of SWCNT, we studied the optimization loading of SWCNT in lead-acid battery electrodes. We optimized the SWCNT loading concentrations in both the positive and negative plates, separately. Loadings of 0.01% and 0.001% in the positive and negative active masses were studied, respectively. Two volts of lead-acid laboratory cells with sulfuric acid, containing silica gel-type electrolytes, were cycled in a 25% and 50% depth-of-discharge (DOD) cycling with a charging rate of C and 2C, respectively, and discharge rates of C/2 and C, respectively. All tests successfully demonstrated an excellent service life up to about 1700 and 1400 cycles for 25% and 50% DOD operations, respectively, at a low loading level of SWCNT. This performance was compared with CNT-free cells and cells with a multiwall carbon nanotube (MWCNT) additive. The outstanding performance of the lead-acid cells with the SWCNT additive is due to the oxidative stability of the positive plates during charging and the efficient reduction in sulfation in both plates while forming conducting active-material matrices.

  5. A doped polyaniline modified electrode amperometric biosensor for gluconic acid determination in grapes.

    PubMed

    Albanese, Donatella; Malvano, Francesca; Sannini, Adriana; Pilloton, Roberto; Di Matteo, Marisa

    2014-06-23

    In winemaking gluconic acid is an important marker for quantitative evaluation of grape infection by Botrytis cinerea. A screen-printed amperometric bienzymatic sensor for the determination of gluconic acid based on gluconate kinase (GK) and 6-phospho-D-gluconate dehydrogenase (6PGDH) coimmobilized onto polyaniline/poly (2-acrylamido-2-methyl-1-propanesulfonic acid; PANI-PAAMPSA) is reported in this study. The conductive polymer electrodeposed on the working electrode surface allowed the detection of NADH at low potential (0.1 V) with a linear range from 4 × 10(-3) to 1 mM (R2 = 0.99) and a sensitivity of 419.44 nA∙mM(-1). The bienzymatic sensor has been optimized with regard to GK/6PGDH enzymatic unit ratio and ATP/NADP+ molar ratio which resulted equal to 0.33 and 1.2, respectively. Under these conditions a sensitivity of 255.2 nA∙mM(-1), a limit of detection of 5 μM and a Relative Standard Deviation (RSD) of 4.2% (n = 5) have been observed. Finally, the biosensor has been applied for gluconic acid measurements in must grape samples and the matrix effect has been taken into consideration. The results have been compared with those obtained on the same samples with a commercial kit based on a spectrophotometric enzyme assay and were in good agreement, showing the capability of the bienzymatic PANI-PAAMPSA biosensor for gluconic acid measurements and thus for the evaluation of Botrytis cinerea infection in grapes.

  6. Fabrication and characterization of perovskite-type solar cells with Nb-doped TiO2 layers

    NASA Astrophysics Data System (ADS)

    Saito, Jo; Oku, Takeo; Suzuki, Atsushi; Akiyama, Tsuyoshi

    2016-02-01

    Organic-inorganic hybrid heterojunction solar cells containing perovskite CH3NH3PbI3 using Nb-doped TiO2 as an electron-transporting layer were fabricated and characterized. Nb-doped TiO2 layer showed an improvement of the short-circuit current density and power conversion efficiency using Ti0.95Nb0.05O2.

  7. EPR and optical studies of VO2+ doped potassium succinate-succinic acid single crystal - Substitutional incorporation

    NASA Astrophysics Data System (ADS)

    Juliet sheela, K.; Radha Krishnan, S.; Shanmugam, V. M.; Subramanian, P.

    2017-03-01

    EPR and optical absorption studies of VO2+ doped potassium succinate-succinic acid (KSSA) single crystal has been examined at room temperature. EPR spectrum shows that well resolved hyperfine lines. The angular variation of the EPR spectra has shown that two different VO2+ complexes are located in different chemical environments. Among the number of sites, two sites have been followed and reported here. From the EPR analysis, spin Hamiltonian parameters g and A tensors and their directional cosines are evaluated. Both the sites experience rhombic crystal field symmetry around the impurity ion. The VO2+ ion entering the site location of potassium ion has coordination of eight oxygen atoms in a distorted dodecahedral arrangement. The Optical absorption spectrum studied at room temperature shows bands corresponding to C4v symmetry. The crystal field parameter and tetragonal field parameters are calculated. From the Optical and EPR data various molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

  8. A voltammetric determination of caffeic acid in red wines based on the nitrogen doped carbon modified glassy carbon electrode

    PubMed Central

    Karikalan, Natarajan; Karthik, Raj; Chen, Shen-Ming; Chen, Hsi-An

    2017-01-01

    We reported an electrochemical determination of caffeic acid (CA) based on the nitrogen doped carbon (NDC). The described sensor material was prepared by the flame synthesis method, which gave an excellent platform for the synthesis of carbon nanomaterials with the hetero atom dopant. The synthesized material was confirmed by various physical characterizations and it was further characterized by different electrochemical experiments. The NDC modified glassy carbon electrode (NDC/GCE) shows the superior electrocatalytic performance towards the determination of CA with the wide linear concentration range from 0.01 to 350 μM. It achieves the lowest detection limit of 0.0024 μM and the limit of quantification of 0.004 μM. The NDC/GCE-CA sensor reveals the good selectivity, stability, sensitivity and reproducibility which endorsed that the NDC is promising electrode for the determination of CA. In addition, NDC modified electrode is applied to the determination of CA in red wines and acquired good results. PMID:28378813

  9. Targeting and Photodynamic Killing of Cancer Cell by Nitrogen-Doped Titanium Dioxide Coupled with Folic Acid

    PubMed Central

    Xie, Jin; Pan, Xiaobo; Wang, Mengyan; Yao, Longfang; Liang, Xinyue; Ma, Jiong; Fei, Yiyan; Wang, Pei-Nan; Mi, Lan

    2016-01-01

    Titanium dioxide (TiO2) has attracted wide attention as a potential photosensitizer (PS) in photodynamic therapy (PDT). However, bare TiO2 can only be excited by ultraviolet illumination, and it lacks specific targeting ligands, which largely impede its application. In our study, we produced nitrogen-doped TiO2 and linked it with an effective cancer cell targeting agent, folic acid (FA), to obtain N-TiO2-FA nanoconjugates. Characterization of N-TiO2-FA included Zeta potential, absorption spectra and thermogravimetric analysis. The results showed that N-TiO2-FA was successfully produced and it possessed better dispersibility in aqueous solution than unmodified TiO2. The N-TiO2-FA was incubated with human nasopharyngeal carcinoma (KB) and human pulmonary adenocarcinoma (A549) cells. The KB cells that overexpress folate receptors (FR) on cell membranes were used as FR-positive cancer cells, while A549 cells were used as FR-negative cells. Laser scanning confocal microscopy results showed that KB cells had a higher uptake efficiency of N-TiO2-FA, which was about twice that of A549 cells. Finally, N-TiO2-FA is of no cytotoxicity, and has a better photokilling effect on KB cells under visible light irradiation. In conclusion, N-TiO2-FA can be as high-value as a PS in cancer targeting PDT.

  10. Improvement in fingerprint detection using Tb(III)-dipicolinic acid complex doped nanobeads and time resolved imaging.

    PubMed

    Hauser, Frank M; Knupp, Gerd; Officer, Simon

    2015-08-01

    This paper deals with the synthesis and application of lanthanide complex doped nanobeads used as a luminescent fingerprint powder. Due to their special optical properties, namely a long emission lifetime, sharp emission profiles and large Stokes shifts, luminescent lanthanide complexes are useful for discriminating against signals from background emissions. This is a big advantage because latent fingerprints placed on multicoloured fluorescent surfaces are difficult to develop with conventional powders. The complex of 2,6-dipicolinic acid (DPA) and terbium ([Tb(DPA)3](3-)) is used for this purpose. Using the Stöber process, this complex is incorporated into a silica matrix forming nanosized beads (230-630nm). It is shown that the [Tb(DPA)3](3-) is successfully incorporated into the beads and that these beads exhibit the wanted optical properties of the complex. A phenyl functionalisation is applied to increase the lipophilicity of the beads and finally the beads are used to develop latent fingerprints. A device for time resolved imaging was built to improve the contrast between developed fingerprint and different background signals, whilst still detecting the long lasting luminescence of the complex. The developed fingerprint powder is therefore promising to develop fingerprints on multicoloured fluorescent surfaces.

  11. Surface plasmon resonance based fiber optic trichloroacetic acid sensor utilizing layer of silver nanoparticles and chitosan doped hydrogel.

    PubMed

    Semwal, Vivek; Shrivastav, Anand M; Gupta, Banshi D

    2017-02-10

    In this study, we report a silver nanoparticles/chitosan doped hydrogel-based fiber optic sensor for the detection of trichloroacetic acid (TCA). The sensor is based on the combined phenomenon of localized and propagating surface plasmons. The sensing relies on the interaction of TCA with silver nanoparticles (AgNP) which results in the electron transfer between the negative group of TCA and positive amino group of AgNP stabilizer (chitosan). This alters the mechanical properties/refractive index of the AgNP embedded hydrogel matrix as well as the refractive index of the AgNP. The change in refractive index of both in turn changes the effective refractive index of the nanocomposite hydrogel layer which can be determined using the Maxwell-Garnet Theory. Four stage optimization of the probe fabrication parameters is performed to obtain the best performance of the sensing probe. The sensor operates in the TCA concentration range 0-120 μm which is harmful for the humans and environment. The shift in peak extinction wavelength observed for the same TCA concentration range is 42 nm. The sensor has the linearity range for the TCA concentration range of 40-100 μm. The sensor possesses high sensitivity, selectivity and numerous other advantages such as ease of handling, quick response, modest cost and capability of online monitoring and remote sensing.

  12. Surface plasmon resonance based fiber optic trichloroacetic acid sensor utilizing layer of silver nanoparticles and chitosan doped hydrogel

    NASA Astrophysics Data System (ADS)

    Semwal, Vivek; Shrivastav, Anand M.; Gupta, Banshi D.

    2017-02-01

    In this study, we report a silver nanoparticles/chitosan doped hydrogel-based fiber optic sensor for the detection of trichloroacetic acid (TCA). The sensor is based on the combined phenomenon of localized and propagating surface plasmons. The sensing relies on the interaction of TCA with silver nanoparticles (AgNP) which results in the electron transfer between the negative group of TCA and positive amino group of AgNP stabilizer (chitosan). This alters the mechanical properties/refractive index of the AgNP embedded hydrogel matrix as well as the refractive index of the AgNP. The change in refractive index of both in turn changes the effective refractive index of the nanocomposite hydrogel layer which can be determined using the Maxwell-Garnet Theory. Four stage optimization of the probe fabrication parameters is performed to obtain the best performance of the sensing probe. The sensor operates in the TCA concentration range 0-120 μm which is harmful for the humans and environment. The shift in peak extinction wavelength observed for the same TCA concentration range is 42 nm. The sensor has the linearity range for the TCA concentration range of 40-100 μm. The sensor possesses high sensitivity, selectivity and numerous other advantages such as ease of handling, quick response, modest cost and capability of online monitoring and remote sensing.

  13. Highly sensitive detection of influenza virus by boron-doped diamond electrode terminated with sialic acid-mimic peptide

    PubMed Central

    Matsubara, Teruhiko; Ujie, Michiko; Yamamoto, Takashi; Akahori, Miku; Einaga, Yasuaki; Sato, Toshinori

    2016-01-01

    The progression of influenza varies according to age and the presence of an underlying disease; appropriate treatment is therefore required to prevent severe disease. Anti-influenza therapy, such as with neuraminidase inhibitors, is effective, but diagnosis at an early phase of infection before viral propagation is critical. Here, we show that several dozen plaque-forming units (pfu) of influenza virus (IFV) can be detected using a boron-doped diamond (BDD) electrode terminated with a sialic acid-mimic peptide. The peptide was used instead of the sialyloligosaccharide receptor, which is the common receptor of influenza A and B viruses required during the early phase of infection, to capture IFV particles. The peptide, which was previously identified by phage-display technology, was immobilized by click chemistry on the BDD electrode, which has excellent electrochemical characteristics such as low background current and weak adsorption of biomolecules. Electrochemical impedance spectroscopy revealed that H1N1 and H3N2 IFVs were detectable in the range of 20–500 pfu by using the peptide-terminated BDD electrode. Our results demonstrate that the BDD device integrated with the receptor-mimic peptide has high sensitivity for detection of a low number of virus particles in the early phase of infection. PMID:27457924

  14. Amperometric ascorbic acid sensor based on doped ferrites nanoparticles modified glassy carbon paste electrode.

    PubMed

    Dimitrijević, Teodora; Vulić, Predrag; Manojlović, Dragan; Nikolić, Aleksandar S; Stanković, Dalibor M

    2016-07-01

    In this study, a novel electrochemical sensor for quantification of ascorbic acid with amperometric detection in physiological conditions was constructed. For this purpose, cobalt and nickel ferrites were synthesized using microwave and ultrasound assistance, characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffraction (XRPD), and used for modification of glassy carbon paste electrode (GCPE). It was shown that introducing these nanoparticles to the structure of GCPE led to increasing analytical performance. Co ferrite modified GCPE (CoFeGCPE) showed better characteristics toward ascorbic acid sensing. The limit of detection (LOD) obtained by sensor was calculated to be 0.0270 mg/L, with linear range from 0.1758 to 2.6010 mg/L. This sensor was successfully applied for practical analysis, and the obtained results demonstrated that the proposed procedure could be a promising replacement for the conventional electrode materials and time-consuming and expensive separation methods.

  15. Acid synthesis of luminescent amine-functionalized or erbium-doped silica spheres for biological applications.

    PubMed

    Enrichi, Francesco; Trave, Enrico; Bersani, Marco

    2008-03-01

    In this work we discuss and investigate the morphological and optical properties of luminescent silica spheres which can have interesting applications in bioimaging and biosensing. The spheres are synthesized following an acid route by the hydrolysis and condensation of tetraethylortosilicate (TEOS) and can be functionalized by incorporation of aminopropyl-triethoxysilane (APTES) during the synthesis, inducing a significant luminescence that can be attributed to a recombination mechanism from localized organic defects related to -NH(2) groups. It is shown that the acid synthesis route produces very regular spherical particles, but their diameter vary in the range of 200-4,000 nm. The luminescence properties have been investigated and optimized by variation of the annealing temperature for the functionalized spheres, obtaining the most efficient PL emission after a thermal treatment of 1 h at 600 degrees C in air. Moreover, the possibility to introduce rare earths like erbium in the spheres was also studied and the corresponding Er(3) luminescence emission at 1.53 microm is reported in terms of intensity and lifetime, pointing out that erbium can be easily and efficiently incorporated during the acid synthesis giving high PL intensity with a good lifetime of 3.9 ms.

  16. Preparation and characterization of 5-sulphosalicylic acid doped tetraethoxysilane composite ion-exchange material by sol-gel method.

    PubMed

    Rehman, Suhail-ul; Islam, Nasarul; Ahad, Sozia; Fatima, Syed Zeeshan; Pandith, Altaf Hussain

    2013-09-15

    In this manuscript, we report the preparation and characterization of sulphosalicylic doped tetraethoxysilane (SATEOS), composite material by sol-gel method as a new ion exchanger for the removal of Ni(II) from aqueous solution. The fine granular material was prepared by acid catalyzed condensation polymerization through sol-gel mechanism in the presence of cationic surfactant. The material has an ion exchange capacity of 0.64 mequiv./g(dry) for sodium ions, 0.60 mequiv./g(dry) for potassium ions, 1.84 mequiv./g(dry) for magnesium ions, 1.08 mequiv./g(dry) for calcium ions and 1.36 mequiv./g(dry) for strontium ions. Its X-ray diffraction studies suggest that it is crystalline in nature. The material has been characterized by SEM, IR, TGA and DTG so as to identify the various functional groups and ion exchange sites present in this material. Quantum chemical computations at DFT/B3LYP/6-311G (d,p) level on model systems were performed to substantiate the structural conclusions based ion instrumental techniques. Investigations into the elution behaviour, ion exchange reversibility and distribution capacities of this material towards certain environmentally hazardous metal ions are also performed. The material shows good chemical stability towards acidic conditions and exhibits fast elution of exchangeable H(+) ions under neutral conditions. This material shows remarkable selectivity for Ni(II) and on the basis of its Kd value (4×10(2) in 0.01M HClO4) some binary separations of Ni(II) from other metal ions are performed.

  17. Doped copolymer of polyanthranilic acid and o-aminophenol (AA-co-OAP): Synthesis, spectral characterization and the use of the doped copolymer as precursor of α-Fe2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Hosny, Nasser Mohammed; Nowesser, Nourhan; Al-Hussaini, A. S.; Zoromba, Mohamed Shafick

    2016-02-01

    The copolymer of anthranilic acid and o-aminophenol (AA-co-OAP) was synthesized and characterized by IR, UV-Vis. and thermal analyses (TGA). Linear chain mode was suggested for the pure (AA-co-OAP). The effect of inclusion of MnCl2, CoCl2, NiCl2, CuCl2 and FeCl3 on the spectral, thermal and optical properties of AA-co-OAP has been studied. Octahedral stereochemistry was suggested for Fe, Mn and Ni doped AA-co-OAP, while tetrahedral and square-planar geometries were suggested for Co and Cu doped AA-co-OAP, respectively. Fe doped AA-co-OAP has been used as a precursor for α-Fe2O3 nanoparticles by thermal decomposition route at 800 °C. The obtained hematite has been characterized by XRD and TEM. The average size of the prepared nanoparticles was estimated as 34 nm. The optical band gap of the synthesized hematite nanoparticles was measured and compared with the bulk.

  18. Ion-Exchange-Induced 2D-3D Conversion of HMA1-x FAx PbI3 Cl Perovskite into a High-Quality MA1-x FAx PbI3 Perovskite.

    PubMed

    Li, Ge; Zhang, Taiyang; Guo, Nanjie; Xu, Feng; Qian, Xufang; Zhao, Yixin

    2016-10-17

    High-quality phase-pure MA1-x FAx PbI3 planar films (MA=methylammonium, FA=formamidinium) with extended absorption and enhanced thermal stability are difficult to deposit by regular simple solution chemistry approaches owing to crystallization competition between the easy-to-crystallize but unwanted δ-FAPbI3 /MAPbI3 and FAx MA1-x PbI3 requiring rigid crystallization conditions. Here A 2D-3D conversion to transform compact 2D mixed composition HMA1-x FAx PbI3 Cl perovskite precursor films into 3D MA1-x FAx PbI3 (x=0.1-0.9) perovskites is presented. The designed Cl/I and H/FA(MA) ion exchange reaction induced fast transformation of compact 2D perovskite film, helping to form the phase-pure and high quality MA1-x FAx PbI3 without δ-FAPbI3 and MAPbI3 impurity. In all, we successfully developed a facile one-step method to fabricate high quality phase-pure MA1-x FAx PbI3 (x=0.1-0.9) perovskite films by 2D-3D conversion of HMA1-x FAx PbI3 Cl perovskite. This 2D-3D conversion is a promising strategy for lead halide perovskite fabrication.

  19. Periodic DFT study of acidic trace atmospheric gas molecule adsorption on Ca- and Fe-doped MgO(001) surface basic sites.

    PubMed

    Baltrusaitis, Jonas; Hatch, Courtney; Orlando, Roberto

    2012-08-02

    The electronic properties of undoped and Ca- or Fe-doped MgO(001) surfaces, as well as their propensity toward atmospheric acidic gas (CO2, SO2, and NO2) uptake was investigated with an emphasis on gas adsorption on the basic MgO oxygen surface sites, O(surf), using periodic density functional theory (DFT) calculations. Adsorption energy calculations show that MgO doping will provide stronger interactions of the adsorbate with the O(surf) sites than the undoped MgO for a given adsorbate molecule. Charge transfer from the iron atom in Fe-doped MgO(001) to NO2 was shown to increase the binding interaction between adsorbate by an order of magnitude, when compared to that of undoped and Ca-doped MgO(001) surfaces. Secondary binding interactions of adsorbate oxygen atoms were observed with surface magnesium sites at distances close to those of the Mg-O bond within the crystal. These interactions may serve as a preliminary step for adsorption and facilitate further adsorbate transformations into other binding configurations. Impacts on global atmospheric chemistry are discussed as these adsorption phenomena can affect atmospheric gas budgets via altered partitioning and retention on mineral aerosol surfaces.

  20. Influence of surfactant on dynamics of photoinduced motions in a dye-doped deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Jaroslaw; Parafiniuk, Kacper; Miniewicz, Andrzej; Rau, Ileana; Kajzar, Francois; Niziol, Jacek; Hebda, Edyta; Pielichowski, Jan; Sahraoui, Bouchta

    2012-10-01

    Pure deoxyribonucleic acid (DNA) is known to be soluble in water only and exhibits poor temperature stability. In contrary, it is well known that the complex of DNA - with cetyltrimethyl ammonium (CTMA) is soluble in alcohols and can be processed into very good optical quality thin films by solution casting and spin deposition. Despite the success of DNA-CTMA, there is still need for new cationic surfactants which would extend the range of available solvents for DNA complex. We test and present experimental results of influence of new surfactants based on benzalkonium chloride (BA), and didecyldimethylammonium chloride (DDCA) for applications in all optical switching.

  1. Optical and structural properties of PbI2 thin film produced via chemical dipping method

    NASA Astrophysics Data System (ADS)

    Kariper, İ. A.

    2016-06-01

    PbI2 thin films were deposited on glass substrates via chemical bath deposition. The characteristics of PbI2 thin films were examined through their structural and optical properties. X-ray diffraction spectra showed the presence of rhombohedral structure and atom planes were subject to change with the pH of the bath. Scanning electron microscope indicated uniform distribution of grains. Optical properties were examined via UV-VIS; optical spectrum of the thin films was measured at the range of 200-1100 nm wavelength. Optimum pH levels for producing thin films were found to be pH 4-5. It has been observed that transmission and optical band gap ( E g) increased with the pH of the bath, which varied between 66-95 and 2.24-2.50 %, respectively; on the other hand film thickness of PbI2 thin films was decreased with the pH of the bath. Energy-dispersive X-ray spectroscopy analysis were in accordance with theoretical value of PbI2 at pH = 4 and 5. Refractive index was negatively correlated with pH of the chemical bath; it has been calculated as 1.97, 1.40, 1.29 and 1.24 for the films produced at pH 2, 3, 4 and 5. The results of the study were compared with similar studies in the literature.

  2. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Rothmann, Mathias Uller; Li, Wei; Zhu, Ye; Bach, Udo; Spiccia, Leone; Etheridge, Joanne; Cheng, Yi-Bing

    2017-02-01

    Organic-inorganic hybrid perovskites are exciting candidates for next-generation solar cells, with CH3NH3PbI3 being one of the most widely studied. While there have been intense efforts to fabricate and optimize photovoltaic devices using CH3NH3PbI3, critical questions remain regarding the crystal structure that governs its unique properties of the hybrid perovskite material. Here we report unambiguous evidence for crystallographic twin domains in tetragonal CH3NH3PbI3, observed using low-dose transmission electron microscopy and selected area electron diffraction. The domains are around 100-300 nm wide, which disappear/reappear above/below the tetragonal-to-cubic phase transition temperature (approximate 57 °C) in a reversible process that often `memorizes' the scale and orientation of the domains. Since these domains exist within the operational temperature range of solar cells, and have dimensions comparable to the thickness of typical CH3NH3PbI3 films in the solar cells, understanding the twin geometry and orientation is essential for further improving perovskite solar cells.

  3. Automated Transportation Management System (ATMS) V2.0 logistics module PBI acceptance criteria

    SciTech Connect

    Weidert, R.S.

    1995-02-28

    This document defines the acceptance criteria for the Automated Transportation Management System V2.0 Logistics Module Performance Based Incentive (PBI). This acceptance criteria will be the primary basis for the generation of acceptance test procedures. The purpose of this document is to define the minimum criteria that must be fulfilled to guarantee acceptance of the Logistics Module.

  4. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3

    PubMed Central

    Rothmann, Mathias Uller; Li, Wei; Zhu, Ye; Bach, Udo; Spiccia, Leone; Etheridge, Joanne; Cheng, Yi-Bing

    2017-01-01

    Organic–inorganic hybrid perovskites are exciting candidates for next-generation solar cells, with CH3NH3PbI3 being one of the most widely studied. While there have been intense efforts to fabricate and optimize photovoltaic devices using CH3NH3PbI3, critical questions remain regarding the crystal structure that governs its unique properties of the hybrid perovskite material. Here we report unambiguous evidence for crystallographic twin domains in tetragonal CH3NH3PbI3, observed using low-dose transmission electron microscopy and selected area electron diffraction. The domains are around 100–300 nm wide, which disappear/reappear above/below the tetragonal-to-cubic phase transition temperature (approximate 57 °C) in a reversible process that often ‘memorizes' the scale and orientation of the domains. Since these domains exist within the operational temperature range of solar cells, and have dimensions comparable to the thickness of typical CH3NH3PbI3 films in the solar cells, understanding the twin geometry and orientation is essential for further improving perovskite solar cells. PMID:28230064

  5. Intercalation Crystallization of Phase-Pure ..alpha..-HC(NH2)2PbI3 upon Microstructurally Engineered PbI2 Thin Films for Planar Perovskite Solar Cells

    SciTech Connect

    Zhou, Yuanyuan; Yang, Mengjin; Kwun, Joonsuh; Game, Onkar S.; Zhao, Yixin; Pang, Shuping; Padture, Nitin P.; Zhu, Kai

    2016-03-28

    The microstructure of the solid-PbI2 precursor thin film plays an important role in the intercalation crystallization of the formamidinium lead triiodide perovskite (..alpa..-HC(NH2)2PbI3). It is shown that microstructurally engineered PbI2 thin films with porosity and low crystallinity are the most favorable for conversion into uniform-coverage, phase-pure ..alpha..-HC(NH2)2PbI3 perovskite thin films. Planar perovskite solar cells fabricated using these thin films deliver power conversion efficiency (PCE) up to 13.8%.

  6. Adverse Effects of Excess Residual PbI2 on Photovoltaic Performance, Charge Separation, and Trap-State Properties in Mesoporous Structured Perovskite Solar Cells.

    PubMed

    Wang, Hao-Yi; Hao, Ming-Yang; Han, Jun; Yu, Man; Qin, Yujun; Zhang, Pu; Guo, Zhi-Xin; Ai, Xi-Cheng; Zhang, Jian-Ping

    2017-03-17

    Organic-inorganic halide perovskite solar cells have rapidly come to prominence in the photovoltaic field. In this context, CH3 NH3 PbI3 , as the most widely adopted active layer, has been attracting great attention. Generally, in a CH3 NH3 PbI3 layer, unreacted PbI2 inevitably coexists with the perovskite crystals, especially following a two-step fabrication process. There appears to be a consensus that an appropriate amount of unreacted PbI2 is beneficial to the overall photovoltaic performance of a device, the only disadvantageous aspect of excess residual PbI2 being viewed as its insulating nature. However, the further development of such perovskite-based devices requires a deeper understanding of the role of residual PbI2 . In this work, PbI2 -enriched and PbI2 -controlled perovskite films, as two extreme cases, have been prepared by modulating the crystallinity of a pre-deposited PbI2 film. The effects of excess residual PbI2 have been elucidated on the basis of spectroscopic and optoelectronic studies. The initial charge separation, the trap-state density, and the trap-state distribution have all been found to be adversely affected in PbI2 -enriched devices, to the detriment of photovoltaic performance. This leads to a biphasic recombination process and accelerates the charge carrier recombination dynamics.

  7. Fiber opticpH sensor for the acidic range using fluorescent dye-doped sol-gel materials

    NASA Astrophysics Data System (ADS)

    Manyam, Upendra H.

    A plethora of new sensor technologies have emerged for chemical, biological, environmental and security applications. However, their adoption has been constrained by lack of integration of vastly different technical areas. Fiber optic chemical sensing is one such technology; a combination of spectroscopy, materials science and optical engineering. In this work, the example of an acidic pH sensor is used to individually develop these three areas and integrate them into a working device. Acidic pH is an important parameter in chemical processes, with no suitable optical alternatives. The fluorescent pH indicator 5-(and 6)-carboxydichlorofluorescein (CDCF) was doped in a sol-gel matrix. CDCF has a pKa of 4.53, making it well suited for the acidic range. MTMS and TEOS gels were developed as films with good mechanical and chemical stability. The pH state of the immobilized dye affects the ratio of the absorption peaks. The fluorescence spectrum was red shifted in the organically modified gel. The fluorescence of hybrid spin-coated thin films resembled that of TEOS gels rather than that of hybrid bulk gels. The pH response was reversible and repeatable with a dynamic range of 5 pH units. Changes in ionic strength cause hysteresis in the sensor's response, which disappears when the film surface is saturated with electrolytes. The mechanical strength of the films in air and when immersed in solution was improved by using specific aging routines. Photo-bleaching was reduced by limiting excitation time to the duration of the measurement. Sonication, organic modification and aging in pH 2 buffer reduced leaching of the dye. Solid surface energy of the gels increased with organic modification. Hybrid gels were hydrophobic, resulting in slow response times. The diffusion constant of hydronium ions was found to depend on protonation state of the indicator and ionic strength of the solution. The diffusion constant in 0%MTMS and 10%MTMS films was of the order of 10-9 cm2/s, while

  8. Tailoring nickel coatings via electrodeposition from a eutectic-based ionic liquid doped with nicotinic acid

    NASA Astrophysics Data System (ADS)

    Yang, Haiyan; Guo, Xingwu; Birbilis, Nick; Wu, Guohua; Ding, Wenjiang

    2011-08-01

    Pure nickel (Ni) was electrodeposited onto a copper (Cu) substrate from choline chloride-urea (1:2 molar ratio) eutectic-based ionic liquid (1:2 ChCl-urea IL) with 0-1200 mg/L additions of nicotinic acid (NA). The effect of NA on the voltammetric behavior of Ni (II) was investigated by cyclic voltammetry, whilst the nucleation/growth of Ni deposits was studied by chronoamperometry. The resultant surface morphologies and microstructures of the Ni coatings were revealed by SEM/EDXS, XRD and TEM, demonstrating that NA can inhibit, hence tailor, the Ni deposition and serve as a very effective brightener producing highly uniform and smooth Ni deposits. The nucleation/growth process of Ni was not affected by the presence of NA, proceeding via three-dimensional instantaneous nucleation. NA has a profound grain refining effect with a grain size of ˜4.2 nm achievable.

  9. UV-A light-induced photodegradation of Acid Blue 113 in the presence of Sm-doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Pandiyarajan, Thangaraj; Mangalaraja, Ramalinga Viswanathan; Karthikeyan, Balasubramanian; Sathishkumar, Panneerselvam; Mansilla, Héctor D.; Contreras, David; Ruiz, José

    2015-05-01

    In this report, optical and photocatalytic degradation of Acid Blue 113 (AB 113) has been investigated in an aqueous heterogeneous media containing pure and Sm-doped ZnO nanostructures which were prepared by a simple wet chemical route. X-ray diffraction measurement confirmed that the prepared nanostructures were in hexagonal wurtzite structure and the dopant Sm ion was incorporated into the Zn lattice. Interesting morphological changes involving a nanosheet-star-spherical transition were observed upon Sm doping and annealing, which were identified through transmission electron microscope. Optical absorption measurements showed an exciton absorption band and a band gap narrowing with respect to the Sm concentrations. The photodegradation of Acid Blue 113 under UV-A radiation by using pure and Sm-doped ZnO nanostructures showed that samarium played an important role in the significant improvement of the photodegradation efficiency and the optimum amount of Sm ion was found to be 1 mmol %. Further, the possible degradation mechanism was proposed herein.

  10. Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization

    SciTech Connect

    Lazau, C.; Ratiu, C.; Orha, C.; Pode, R.; Manea, F.

    2011-11-15

    Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized by sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.

  11. Effective role of trifluoroacetic acid (TFA) to enhance the photocatalytic activity of F-doped TiO2 prepared by modified sol-gel method

    NASA Astrophysics Data System (ADS)

    Samsudin, Emy Marlina; Hamid, Sharifah Bee Abd; Juan, Joon Ching; Basirun, Wan Jefrey; Kandjani, Ahmad Esmaielzadeh; Bhargava, Suresh K.

    2016-03-01

    Highly photoactive mesoporous F-doped TiO2 with improved physico-chemical characteristics is achieved using modified sol-gel method. The usage of trifluoroacetic as fluorine precursor significantly modifies the morphology, size, pore shape, crystal phase, crystal structure, surface chemical state and to a lesser extent, {1 0 1} and {0 0 1} facets. The accessibility of fluoride ions on Tisbnd Osbnd Ti polymer chains during crystal growth during the sol-gel process remarkably influences the properties of catalyst. To the best of our knowledge, preparation of F-doped TiO2 using modified sol-gel and trifluoroacetic acid are limited, and still not enough. Thus this work provides additional insight by using an approach which is less hazardous, less costly and practical for large scale agile development in the photocatalysis industry.

  12. Combination of cathodic reduction with adsorption for accelerated removal of Cr(VI) through reticulated vitreous carbon electrodes modified with sulfuric acid-glycine co-doped polyaniline.

    PubMed

    Mo, Xi; Yang, Zhao-hui; Xu, Hai-yin; Zeng, Guang-ming; Huang, Jing; Yang, Xia; Song, Pei-pei; Wang, Li-ke

    2015-04-09

    Improving the reduction kinetics is crucial in the electroreduction process of Cr(VI). In this study, we developed a novel adsorption-electroreduction system for accelerated removal of Cr(VI) by employing reticulated vitreous carbon electrode modified with sulfuric acid-glycine co-doped polyaniline (RVC/PANI-SA-GLY). Firstly, response surface methodology confirmed the optimum polymerization condition of co-doped polyaniline for modifying electrodes (Aniline, sulfuric acid and glycine, respectively, of 0.2 mol/L, 0.85 mol/L, 0.93 mol/L) when untraditional dopant glycine was added. Subsequently, RVC/PANI-SA-GLY showed higher Cr(VI) removal percentages in electroreduction experiments over RVC electrode modified with sulfuric acid doped polyaniline (RVC/PANI-SA) and bare RVC electrode. In contrast to RVC/PANI-SA, the improvement by RVC/PANI-SA-GLY was more significant and especially obvious at more negative potential, lower initial Cr(VI) concentration, relatively less acidic solution and higher current densities, best achieving 7.84% higher removal efficiency with entire Cr(VI) eliminated after 900 s. Current efficiencies were likewise enhanced by RVC/PANI-SA-GLY under quite negative potentials. Fourier transform infrared (FTIR) and energy dispersive spectrometer (EDS) analysis revealed a possible adsorption-reduction mechanism of RVC/PANI-SA-GLY, which greatly contributed to the faster reduction kinetics and was probably relative to the absorption between protonated amine groups of glycine and HCrO4(-). Eventually, the stability of RVC/PANI-SA-GLY was proven relatively satisfactory.

  13. Complete doping in solid-state by silica-supported perchloric acid as dopant solid acid: Synthesis and characterization of the novel chiral composite of poly [(±)-2-(sec-butyl) aniline

    SciTech Connect

    Farrokhzadeh, Abdolkarim; Modarresi-Alam, Ali Reza

    2016-05-15

    Poly [(±)-2-(sec-butyl) aniline]/silica-supported perchloric acid composites were synthesized by combination of poly[(±)-2-sec-butylaniline] base (PSBA) and the silica-supported perchloric acid (SSPA) as dopant solid acid in solid-state. The X-ray photoelectron spectroscopy (XPS) and CHNS results confirm nigraniline oxidation state and complete doping for composites (about 75%) and non-complete for the PSBA·HCl salt (about 49%). The conductivity of samples was (≈0.07 S/cm) in agreement with the percent of doping obtained of the XPS analysis. Also, contact resistance was determined by circular-TLM measurement. The morphology of samples by the scanning electron microscopy (SEM) and their coating were investigated by XPS, SEM-map and energy-dispersive X-ray spectroscopy (EDX). The key benefits of this work are the preparation of conductive chiral composite with the delocalized polaron structure under green chemistry and solid-state condition, the improvement of the processability by inclusion of the 2-sec-butyl group and the use of dopant solid acid (SSPA) as dopant. - Highlights: • The solid-state synthesis of the novel chiral composites of poly[(±)-2-(sec-butyl)aniline] (PSBA) and silica-supported perchloric acid (SSPA). • It takes 120 h for complete deprotonation of PSBA.HCl salt. • Use of SSPA as dopant solid acid for the first time to attain the complete doping of PSBA. • The coating of silica surface with PSBA.

  14. Molecular dynamics investigation of separation of hydrogen sulfide from acidic gas mixtures inside metal-doped graphite micropores.

    PubMed

    Huang, Pei-Hsing

    2015-09-21

    The separation of poisonous compounds from various process fluids has long been highly intractable, motivating the present study on the dynamic separation of H2S in acidic-gas-mixture-filled micropores. The molecular dynamics approach, coupled with the isothermal-isochoric ensemble, was used to model the molecular interactions and adsorption of H2S/CO2/CO/H2O mixtures inside metal-doped graphite slits. Due to the difference in the adsorption characteristics between the two distinct adsorbent materials, the metal dopant in the graphitic micropores leads to competitive adsorption, i.e. the Au and graphite walls compete to capture free adsorbates. The effects of competitive adsorption, coupled with changes in the gas temperature, concentration, constituent ratio and slit width on the constituent separation of mixtures were systematically studied. The molecule-wall binding energies calculated in this work (those of H2S, H2O and CO on Au walls and those of H2O, CO and CO2 on graphite walls) show good agreement with those obtained using density functional theory (DFT) and experimental results. The z-directional self-diffusivities (Dz) for adsorbates inside the slit ranged from 10(-9) to 10(-7) m(2) s(-1) as the temperature was increased from 10 to 500 K. The values are comparable with those for a typical microporous fluid (10(-8)-10(-9) m(2) s(-1) in a condensed phase and 10(-6)-10(-7) m(2) s(-1) in the gaseous state). The formation of H-bonding networks and hydrates of H2S is disadvantageous for the separation of mixtures. The results indicate that H2S can be efficiently separated from acidic gas mixtures onto the Au(111) surface by (i) reducing the mole fraction of H2S and H2O in the mixtures, (ii) raising the gas temperature to the high temperature limit (≥400 K), and (iii) lowering the slit width to below the threshold dimension (≤23.26 Å).

  15. Direct Observation of Long Electron-Hole Diffusion Distance in CH3NH3PbI3 Perovskite Thin Film

    NASA Astrophysics Data System (ADS)

    Li, Yu; Yan, Weibo; Li, Yunlong; Wang, Shufeng; Wang, Wei; Bian, Zuqiang; Xiao, Lixin; Gong, Qihuang

    2015-09-01

    In high performance perovskite based solar cells, CH3NH3PbI3 is the key material. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. By coating the film with an electron or hole transfer layer, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or 2,2‧,7,7‧-tetrakis(N,N-di-p-methoxyphenylamine)-9,9‧-spirobifluorene (Spiro-OMeTAD) respectively, we observed the charge transfer directly through the fluorescence quenching. One-dimensional diffusion model was applied to obtain long charge diffusion distances in thick films, which is ~1.7 μm for electrons and up to ~6.3 μm for holes. Short diffusion distance of few hundreds of nanosecond was also observed in thin films. This thickness dependent charge diffusion explained the formerly reported short charge diffusion distance (~100 nm) in films and resolved its confliction to thick working layer (300-500 nm) in real devices. This study presents direct support to the high performance perovskite solar cells and will benefit the devices’ design.

  16. Unreacted PbI2 as a Double-Edged Sword for Enhancing the Performance of Perovskite Solar Cells.

    PubMed

    Jacobsson, T Jesper; Correa-Baena, Juan-Pablo; Halvani Anaraki, Elham; Philippe, Bertrand; Stranks, Samuel D; Bouduban, Marine E F; Tress, Wolfgang; Schenk, Kurt; Teuscher, Joël; Moser, Jacques-E; Rensmo, Håkan; Hagfeldt, Anders

    2016-08-17

    Lead halide perovskites have over the past few years attracted considerable interest as photo absorbers in PV applications with record efficiencies now reaching 22%. It has recently been found that not only the composition but also the precise stoichiometry is important for the device performance. Recent reports have, for example, demonstrated small amount of PbI2 in the perovskite films to be beneficial for the overall performance of both the standard perovskite, CH3NH3PbI3, as well as for the mixed perovskites (CH3NH3)x(CH(NH2)2)(1-x)PbBryI(3-y). In this work a broad range of characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photo electron spectroscopy (PES), transient absorption spectroscopy (TAS), UV-vis, electroluminescence (EL), photoluminescence (PL), and confocal PL mapping have been used to further understand the importance of remnant PbI2 in perovskite solar cells. Our best devices were over 18% efficient, and had in line with previous results a small amount of excess PbI2. For the PbI2-deficient samples, the photocurrent dropped, which could be attributed to accumulation of organic species at the grain boundaries, low charge carrier mobility, and decreased electron injection into the TiO2. The PbI2-deficient compositions did, however, also have advantages. The record Voc was as high as 1.20 V and was found in PbI2-deficient samples. This was correlated with high crystal quality, longer charge carrier lifetimes, and high PL yields and was rationalized as a consequence of the dynamics of the perovskite formation. We further found the ion migration to be obstructed in the PbI2-deficient samples, which decreased the JV hysteresis and increased the photostability. PbI2-deficient synthesis conditions can thus be used to deposit perovskites with excellent crystal quality but with the downside of grain boundaries enriched in organic species, which act as a barrier toward

  17. Effect of doping of calcium fluoride nanoparticles on the photoluminescence properties of europium complexes with benzoic acid derivatives as secondary ligands and 2-aminopyridine as primary ligand

    NASA Astrophysics Data System (ADS)

    Sharma, Garima; Narula, Anudeep Kumar

    2015-08-01

    The present article reports the synthesis of three Eu(III) complexes [Eu(BA)3(2-ap)] (1), [Eu(HBA)3(2-ap)] (2) and [Eu(ABA)3(2-ap)] (3) (BA = benzoic acid, HBA = 2-hydroxy benzoic acid, ABA = 2-amino benzoic acid and 2-ap = 2-aminopyridine) carried out in ethanol solution. The complexes were further doped with CaF2 nanoparticles and a change in the photoluminescence properties was observed. The compositions and structural investigation of the complexes were determined by elemental analysis and Fourier transform infrared spectroscopy (FTIR) which suggest the coordination of ligands with the central Eu(III) ion. The optical properties of the complexes were studied by Ultraviolet Visible absorption spectroscopy (UV-Vis) and photoluminescence studies (PL). The relative PL intensity was enhanced in the Eu(III) complexes doped with CaF2 nanoparticles as compared to the pure Eu(III) complexes, however the increase in intensity varied in the order of ligands ABA > HBA > BA. The photoluminescence lifetime decay curves also revealed the longer lifetime (τ) and higher quantum efficiency (η) for europium complexes with ABA ligands suggesting the efficient energy transfer and better sensitizing ability of the ligand to europium ion. The morphology of the synthesized compounds were studied by Scanning Electron Microscopy (SEM) revealing spherical morphology with agglomeration of the nanoparticles.

  18. Structural and optical study of spin-coated camphorsulfonic acid-doped polyaniline/titanium-di-oxide nanoparticles hybrid thin films

    NASA Astrophysics Data System (ADS)

    Geethalakshmi, D.; Muthukumarasamy, N.; Balasundaraprabhu, R.

    2015-06-01

    Polyaniline (PANI) doped with Camphorsulfonic acid (CSA) has been prepared by chemical oxidative polymerization and blend with titanium-di-oxide (TiO2) nanoparticles prepared by sol-gel method to form CSA-doped PANI/TiO2 hybrid thin films. The properties of as-deposited and heat-treated (100 °C) hybrid thin films having different PANI:TiO2 weight ratios (1:0.5, 1:1, and 1:2) have been compared. FTIR study indicated that chemical bonding between CSA-doped PANI and TiO2 has been formed. XRD studies reveal that the as-deposited hybrid thin films are of amorphous nature and heat-treatment of such films initiates crystallization. SEM study shows that as-deposited hybrid films are rough; increase in TiO2 ratio and heat-treatment increased the roughness due to coalescing and agglomeration. UV-visible absorbance of hybrid films shows its characteristic peak in the visible region along with a peak in UV range and its intensity increased with TiO2 ratio and heat-treatment due to agglomeration of TiO2 particles. Photoluminescence spectra revealed that emission occurs in visible region (495 nm) for as-deposited hybrid thin film and this emission increased with TiO2 ratio and heat-treatment of hybrid films.

  19. Metal-free N-doped carbon nanofibers as an efficient catalyst for oxygen reduction reactions in alkaline and acid media.

    PubMed

    Li, Ruchun; Shao, Xiaofeng; Li, Shuoshuo; Cheng, Pengpeng; Hu, Zhaoxia; Yuan, Dingsheng

    2016-12-16

    The development of metal-free catalysts to replace the use of Pt has played an important role in relation to its application to fuel cells. We report N-doped carbon nanofibers as the catalyst of an oxygen reduction reaction, which were synthesized via carbonizing bacterial cellulose-polypyrrole composites. The as-prepared material exhibited remarkable catalytic activity toward the oxygen reduction reaction with comparable onset potential and the ability to limit the current density of commercial Pt/C catalysts in both alkaline and acid media due to the unique porous three-dimensional network structure and the doped nitrogen atoms. The effect of N functionalities on catalytic behavior was systematically investigated. The results demonstrated that pyridinic-N was the dominating factor for catalytic performance toward the oxygen reduction reaction. Additionally, N-doped carbon nanofibers also demonstrated excellent cycling stability (93.2% and 89.4% retention of current density after chronoamperometry 20 000 s in alkaline and media, respectively), obviously superior to Pt/C.

  20. Metal-free N-doped carbon nanofibers as an efficient catalyst for oxygen reduction reactions in alkaline and acid media

    NASA Astrophysics Data System (ADS)

    Li, Ruchun; Shao, Xiaofeng; Li, Shuoshuo; Cheng, Pengpeng; Hu, Zhaoxia; Yuan, Dingsheng

    2016-12-01

    The development of metal-free catalysts to replace the use of Pt has played an important role in relation to its application to fuel cells. We report N-doped carbon nanofibers as the catalyst of an oxygen reduction reaction, which were synthesized via carbonizing bacterial cellulose-polypyrrole composites. The as-prepared material exhibited remarkable catalytic activity toward the oxygen reduction reaction with comparable onset potential and the ability to limit the current density of commercial Pt/C catalysts in both alkaline and acid media due to the unique porous three-dimensional network structure and the doped nitrogen atoms. The effect of N functionalities on catalytic behavior was systematically investigated. The results demonstrated that pyridinic-N was the dominating factor for catalytic performance toward the oxygen reduction reaction. Additionally, N-doped carbon nanofibers also demonstrated excellent cycling stability (93.2% and 89.4% retention of current density after chronoamperometry 20 000 s in alkaline and media, respectively), obviously superior to Pt/C.

  1. Layered Lithium-Rich Oxide Nanoparticles Doped with Spinel Phase: Acidic Sucrose-Assistant Synthesis and Excellent Performance as Cathode of Lithium Ion Battery.

    PubMed

    Chen, Min; Chen, Dongrui; Liao, Youhao; Zhong, Xiaoxin; Li, Weishan; Zhang, Yuegang

    2016-02-01

    Nanolayered lithium-rich oxide doped with spinel phase is synthesized by acidic sucrose-assistant sol-gel combustion and evaluated as the cathode of a high-energy-density lithium ion battery. Physical characterizations indicate that the as-synthesized oxide (LR-SN) is composed of uniform and separated nanoparticles of about 200 nm, which are doped with about 7% spinel phase, compared to the large aggregated ones of the product (LR) synthesized under the same condition but without any assistance. Charge/discharge demonstrates that LR-SN exhibits excellent rate capability and cyclic stability: delivering an average discharge capacity of 246 mAh g(-1) at 0.2 C (1C = 250 mA g(-1)) and earning a capacity retention of 92% after 100 cycles at 4 C in the lithium anode-based half cell, compared to the 227 mA g(-1) and the 63% of LR, respectively. Even in the graphite anode-based full cell, LR-SN still delivers a capacity of as high as 253 mAh g(-1) at 0.1 C, corresponding to a specific energy density of 801 Wh kg(-1), which are the best among those that have been reported in the literature. The separated nanoparticles of the LR-SN provide large sites for charge transfer, while the spinel phase doped in the nanoparticles facilitates lithium ion diffusion and maintains the stability of the layered structure during cycling.

  2. Explosive decomposition of a melamine-cyanuric acid supramolecular assembly for fabricating defect-rich nitrogen-doped carbon nanotubes with significantly promoted catalysis.

    PubMed

    Zhao, Zhongkui; Dai, Yitao; Ge, Guifang; Wang, Guiru

    2015-05-26

    A facile and scalable approach for fabricating structural defect-rich nitrogen-doped carbon nanotubes (MCSA-CNTs) through explosive decomposition of melamine-cyanuric acid supramolecular assembly is presented. In comparison to pristine carbon nanotubes, MCSA-CNT exhibits significantly enhanced catalytic performance in oxidant- and steam-free direct dehydrogenation of ethylbenzene, demonstrating the potential for metal-free clean and energy-saving styrene production. This finding also opens a new horizon for preparing highly-efficient carbocatalysts rich in structural defect sites for diverse transformations.

  3. A two-layer structured PbI2 thin film for efficient planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Ying, Chao; Shi, Chengwu; Wu, Ni; Zhang, Jincheng; Wang, Mao

    2015-07-01

    In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm-2 and a fill factor of 0.67.

  4. A two-layer structured PbI2 thin film for efficient planar perovskite solar cells.

    PubMed

    Ying, Chao; Shi, Chengwu; Wu, Ni; Zhang, Jincheng; Wang, Mao

    2015-07-28

    In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm(-2) and a fill factor of 0.67.

  5. Investigation of the Hydrolysis of Perovskite Organometallic Halide CH3NH3PbI3 in Humidity Environment

    NASA Astrophysics Data System (ADS)

    Zhao, Jiangtao; Cai, Bing; Luo, Zhenlin; Dong, Yongqi; Zhang, Yi; Xu, Han; Hong, Bin; Yang, Yuanjun; Li, Liangbin; Zhang, Wenhua; Gao, Chen

    2016-02-01

    Instability of emerging perovskite organometallic halide in humidity environment is the biggest obstacle for its potential applications in solar energy harvest and electroluminescent display. Understanding the detailed decay mechanism of these materials in moisture is a critical step towards the final appropriate solutions. As a model study presented in this work, in situ synchrotron radiation x-ray diffraction was combined with microscopy and gravimetric analysis to study the degradation process of CH3NH3PbI3 in moisture, and the results reveal that: 1) intermediate monohydrated CH3NH3PbI3·H2O is detected in the degradation process of CH3NH3PbI3 and the final decomposition products are PbI2 and aqueous CH3NH3I; 2) the aqueous CH3NH3I could hardly further decompose into volatile CH3NH2, HI or I2; 3) the moisture disintegrate CH3NH3PbI3 and then alter the distribution of the decomposition products, which leads to an incompletely-reversible reaction of CH3NH3PbI3 hydrolysis and degrades the photoelectric properties. These findings further elucidate the picture of hydrolysis process of perovskite organometallic halide in humidity environment.

  6. Ultrafine polybenzimidazole (PBI) fibers. [separators for alkaline batteries and dfuel cells

    NASA Technical Reports Server (NTRS)

    Chenevey, E. C.

    1979-01-01

    Mats were made from ultrafine polybenzimidazole (PBI) fibers to provide an alternate to the use of asbestos as separators in fuel cells and alkaline batteries. To minimize distortion during mat drying, a process to provide a dry fibrid was developed. Two fibrid types were developed: one coarse, making mats for battery separators; the other fine, making low permeability matrices for fuel cells. Eventually, it was demonstrated that suitable mat fabrication techniques yielded fuel cell separators from the coarser alkaline battery fibrids. The stability of PBI mats to 45% KOH at 123 C can be increased by heat treatment at high temperatures. Weight loss data to 1000 hours exposure show the alkali resistance of the mats to be superior to that of asbestos.

  7. Structural and optical characterizations of InPBi thin films grown by molecular beam epitaxy.

    PubMed

    Gu, Yi; Wang, Kai; Zhou, Haifei; Li, Yaoyao; Cao, Chunfang; Zhang, Liyao; Zhang, Yonggang; Gong, Qian; Wang, Shumin

    2014-01-13

    InPBi thin films have been grown on InP by gas source molecular beam epitaxy. A maximum Bi composition of 2.4% is determined by Rutherford backscattering spectrometry. X-ray diffraction measurements show good structural quality for Bi composition up to 1.4% and a partially relaxed structure for higher Bi contents. The bandgap was measured by optical absorption, and the bandgap reduction caused by the Bi incorporation was estimated to be about 56 meV/Bi%. Strong and broad photoluminescence signals were observed at room temperature for samples with xBi < 2.4%. The PL peak position varies from 1.4 to 1.9 μm, far below the measured InPBi bandgap.

  8. Using the iCARE for monitoring cognitive conflicts and anxiety in PBI classes

    NASA Astrophysics Data System (ADS)

    Kim, Yeounsoo

    2005-04-01

    Cognitive conflicts can cause some students to have high levels of anxiety during their learning, which, when not properly addressed, can have negative effects to students' motivations and performance. Based on the large amount of literatures on studies of cognitive conflicts and student anxiety, we developed an easy-to-use instrument, the In-class Conflict and Anxiety Recognition Evaluation (iCARE), for monitoring the status of students' cognitive conflicts and anxiety in the context of Physics by Inquiry (PbI) classes. In this poster, we present examples to show the types of information that can be obtained with iCARE in a PBI class and discuss how instructors can use such an instrument in instruction.

  9. Photovoltaic performance and the energy landscape of CH3NH3PbI3.

    PubMed

    Zhou, Yecheng; Huang, Fuzhi; Cheng, Yi-Bing; Gray-Weale, Angus

    2015-09-21

    Photovoltaic cells with absorbing layers of certain perovskites have power conversion efficiencies up to 20%. Among these materials, CH3NH3PbI3 is widely used. Here we use density-functional theory to calculate the energies and rotational energy barriers of a methylammonium ion in the α or β phase of CH3NH3PbI3 with differently oriented neighbouring methylammonium ions. Our results suggest the methylammonium ions in CH3NH3PbI3 prefer to rotate collectively, and to be parallel to their neighbours. Changes in polarization on rotation of methylammonium ions are two to three times larger than those on relaxation of the lead ion from the centre of its coordination shell. The preferences for parallel configuration and concerted rotation, with the polarisation changes, are consistent with ferroelectricity in the material, and indicate that this polarisation is governed by methylammonium orientational correlations. We show that the field due to this polarisation is strong enough to screen the field hindering charge transport, and find this screening field in agreement with experiment. We examine two possible mechanisms for the effect of methylammonium ion rotation on photovoltaic performance. One is that rearrangement of methylammoniums promotes the creation and transport of charge carriers. Some effective masses change greatly, but changes in band structure with methylammonium rotation are not large enough to explain current-voltage hysteresis behaviour. The second possible mechanism is that polarization screens the hindering electric field, which arises from charge accumulation in the transport layers. Polarization changes on methylammonium rotation favour this second mechanism, suggesting that collective reorientation of methylammonium ions in the bulk crystal are in significant part responsible for the hysteresis and power conversion characteristics of CH3NH3PbI3 photovoltaic cells.

  10. Complete doping in solid-state by silica-supported perchloric acid as dopant solid acid: Synthesis and characterization of the novel chiral composite of poly [(±)-2-(sec-butyl) aniline

    NASA Astrophysics Data System (ADS)

    Farrokhzadeh, Abdolkarim; Modarresi-Alam, Ali Reza

    2016-05-01

    Poly [(±)-2-(sec-butyl) aniline]/silica-supported perchloric acid composites were synthesized by combination of poly[(±)-2-sec-butylaniline] base (PSBA) and the silica-supported perchloric acid (SSPA) as dopant solid acid in solid-state. The X-ray photoelectron spectroscopy (XPS) and CHNS results confirm nigraniline oxidation state and complete doping for composites (about 75%) and non-complete for the PSBA·HCl salt (about 49%). The conductivity of samples was (≈0.07 S/cm) in agreement with the percent of doping obtained of the XPS analysis. Also, contact resistance was determined by circular-TLM measurement. The morphology of samples by the scanning electron microscopy (SEM) and their coating were investigated by XPS, SEM-map and energy-dispersive X-ray spectroscopy (EDX). The key benefits of this work are the preparation of conductive chiral composite with the delocalized polaron structure under green chemistry and solid-state condition, the improvement of the processability by inclusion of the 2-sec-butyl group and the use of dopant solid acid (SSPA) as dopant.

  11. Dual Mode Fluorophore-Doped Nickel Nitrilotriacetic Acid-Modified Silica Nanoparticles Combine Histidine-Tagged Protein Purification with Site-Specific Fluorophore Labeling

    PubMed Central

    Kim, Sung Hoon; Jeyakumar, M.; Katzenellenbogen, John A.

    2008-01-01

    We present the first example of a fluorophore-doped nickel chelate surface- modified silica nanoparticle that functions in a dual mode, combining histidine-tagged protein purification with site-specific fluorophore labeling. Tetramethylrhodamine (TMR)-doped silica nanoparticles, estimated to contain 700–900 TMRs per ca. 23-nm particle, were surface modified with nitrilotriacetic acid (NTA), producing TMR-SiO2-NTA-Ni+2. Silica-embedded TMR retains very high quantum yield, is resistant to quenching by buffer components and is modestly quenched and only to a certain depth (ca. 2 nm) by surface-attached Ni+2. When exposed to a bacterial lysate containing estrogen receptor α ligand binding domain (ERα) as a minor component, these beads showed very high specificity binding, enabling protein purification in one step. The capacity and specificity of these beads for binding a his-tagged protein were characterized by electrophoresis, radiometric counting, and MALDI-TOF MS. ERα, bound to TMR-SiO2-NTA-Ni++ beads in a site-specific manner, exhibited good activity for ligand binding and for ligand-induced binding to coactivators in solution FRET experiments and protein microarray fluorometric and FRET assays. This dual-mode type TMR-SiO2-NTA-Ni++ system represents a powerful combination of one-step histidine-tagged protein purification and site-specific labeling with multiple fluorophore species. BRIEFS Tetramethylrhodamine-doped silica nanoparticles surface modified with nitrilotriacetic acid are dual-mode agents that can be used to purify and site-specifically fluorophore label his-tagged proteins in one step for fluorometric and FRET experiments. PMID:17910454

  12. One-pot synthesis of antiviral acyclovir and other nucleosides derivatives using doped natural phosphate as lewis acid catalyst.

    PubMed

    Lazrek, Hassan B; Baddi, Laila; Smietana, Michael; Vasseur, Jean-Jacques; Sebti, Said; Zahouily, Mohamed

    2008-10-01

    Natural phosphate doped with iodine or potassium iodide is an active catalyst for the one-pot synthesis of acyclonucleosides. To demonstrate the utility of the new catalyst system, the highly important antiviral drug acyclovir was directly and regioselectively obtained from NAcG with no byproducts.

  13. The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

    2014-03-01

    A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu2+ and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1 × 10-9-1 × 10-6 M of folic acid with a correlation coefficient (R2) of 0.9991. The limit of detection of this system was found to be 1 × 10-10 M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

  14. The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals.

    PubMed

    Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

    2014-03-25

    A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu(2+) and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1×10(-9)-1×10(-)(6) M of folic acid with a correlation coefficient (R(2)) of 0.9991. The limit of detection of this system was found to be 1×10(-)(10) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

  15. High-efficiency perovskite solar cells based on the black polymorph of HC(NH2)2 PbI3.

    PubMed

    Lee, Jin-Wook; Seol, Dong-Jin; Cho, An-Na; Park, Nam-Gyu

    2014-08-06

    Perovskite solar cells with power conversion efficiencies exceeding 16% at AM 1.5 G one sun illumination are developed using the black polymorph of formamidnium lead iodide, HC(NH2)2 PbI3 . Compared with CH3 NH3 PbI3 , HC(NH2 )2 PbI3 extends its absoprtion to 840 nm and shows no phase transition between 296 and 423 K. Moreover, a solar cell based on HC(NH2 )2 PbI3 exhibits photostability and little I-V hysteresis.

  16. Electro-fenton and photoelectro-fenton degradation of sulfanilic acid using a boron-doped diamond anode and an air diffusion cathode.

    PubMed

    El-Ghenymy, Abdellatif; Garrido, José Antonio; Centellas, Francesc; Arias, Conchita; Cabot, Pere Lluís; Rodríguez, Rosa María; Brillas, Enric

    2012-04-05

    The mineralization of sulfanilic acid has been studied by electro-Fenton (EF) and photoelectro-Fenton (PEF) reaction with UVA light using an undivided electrochemical cell with a boron-doped diamond (BDD) anode and an air diffusion cathode able to generate H(2)O(2). Organics were then oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between generated H(2)O(2) and added Fe(2+). The UVA irradiation in PEF enhanced the production of hydroxyl radicals in the bulk, accelerating the removal of organics and photodecomposed intermediates like Fe(III)-carboxylate complexes. Partial decontamination of 1.39 mM sulfanilic acid solutions was achieved by EF until 100 mA cm(-2) at optimum conditions of 0.4 mM Fe(2+) and pH 3.0. The increase in current density and substrate content led to an almost total mineralization. In contrast, the PEF process was more powerful, yielding almost complete mineralization in less electrolysis time under comparable conditions. The kinetics for sulfanilic acid decay always followed a pseudo-first-order reaction. Hydroquinone and p-benzoquinone were detected as aromatic intermediates, whereas acetic, maleic, formic, oxalic, and oxamic acids were identified as generated carboxylic acids. NH(4)(+) ion was preferentially released in both treatments, along with NO(3)(-) ion in smaller proportion.

  17. Doping effects of transition metal elements to titanium dioxide for perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Saito, Jo; Suzuki, Atsushi; Akiyama, Tsuyoshi; Oku, Takeo

    2017-01-01

    Organic-inorganic hybrid heterojunction solar cells containing perovskite CH3NH3PbI3 using Nb, Ta, or V-doped TiO2 as electron-transporting layers were fabricated and characterized. By Nb doping, the conductivity and carrier density of the TiO2 increased, and its flat-band potential showed a positive shift. The short-circuit current density and power conversion efficiency of perovskite solar cells were improved by using Ti0.95Nb0.05O2 compared to undoped TiO2.

  18. Fabrication and Scale-up of Polybenzimidazole (PBI) Membrane Based System for Precombustion-Based Capture of Carbon Dioxide

    SciTech Connect

    Krishnan, Gopala; Jayaweera, Indira; Sanjrujo, Angel; O'Brien, Kevin; Callahan, Richard; Berchtold, Kathryn; Roberts, Daryl-Lynn; Johnson, Will

    2012-03-31

    The primary objectives of this project are to (1) demonstrate the performance and fabrication of a technically and economically viable pre-combustion-based CO{sub 2} capture system based on the high temperature stability and permeance of PBI membranes, (2) optimize a plan for integration of PBI capture system into an IGCC plant and (3) develop a commercialization plan that addresses technical issues and business issues to outline a clear path for technology transfer of the PBI membrane technology. This report describes research conducted from April 1, 2007 to March 30, 2012 and focused on achieving the above objectives. PBI-based hollow fibers have been fabricated at kilometer lengths and bundled as modules at a bench-scale level for the separation of CO{sub 2} from H{sub 2} at high temperatures and pressures. Long term stability of these fibers has been demonstrated with a relatively high H{sub 2}/CO{sub 2} selectivity (35 to 50) and H{sub 2} permeance (80 GPU) at temperatures exceeding 225°C. Membrane performance simulations and systems analysis of an IGCC system incorporating a PBI hollow fiber membrane modules have demonstrated that the cost of electricity for CO{sub 2} capture (<10%) using such a high temperature separator. When the cost of transporting, storing, and monitoring the CO{sub 2} is accounted for, the increase in the COE is only 14.4%.

  19. Surface Properties of CH3NH3PbI3 for Perovskite Solar Cells.

    PubMed

    Haruyama, Jun; Sodeyama, Keitaro; Han, Liyuan; Tateyama, Yoshitaka

    2016-03-15

    Perovskite solar cells (PSCs) have attracted considerable interest because of their high potential for solar energy conversion. Power conversion efficiencies of the PSCs have rapidly increased from 3.8 to over 20% only in the past few years. PSCs have several similarities to dye-sensitized solar cells in their device compositions; mesoporous TiO2 (mp-TiO2) is sensitized by light-absorbing components and placed into a medium containing hole transporting materials (HTMs). On the other hand, the perovskite materials for the light-harvesting, for example, CH3NH3PbI3 (MAPbI3), have a greater advantage for the photovoltaic applications; extremely long photocarrier diffusion lengths (over 1 μm) enable carrier transports without singnificant loss. In this respect, the surface states, that can be possible recombination centers, are also of great importance. Availability of solution processes is another important aspect in terms of low cost fabrication of PSCs. Two-step methods, where PbI2 is first introduced from solution onto a mp-TiO2 film and subsequently transformed into the MAPbI3 by the exposition of a solution containing MAI, suggest that use of such a high PbI2 concentration is crucial to obtain higher performance. The experiments also indicate that the PbI2-rich growth condition modifies TiO2/ or HTM/MAPbI3 interfaces in such a way that the photocarrier transport is improved. Thus, the characteristics of surfaces and interfaces play key roles in the high efficiencies of the PSCs. In this Account, we focus on the structural stability and electronic states of the representative (110), (001), (100), and (101) surfaces of tetragonal MAPbI3, which can be regarded as reasonable model HTM/MAPbI3 interfaces, by use of first-principles calculations. By examining various types of PbIx polyhedron terminations, we found that there are two major phases on all of the four surface facets. They can be classified as vacant- and flat-type terminations, and the former is more stable

  20. Demonstration of Next-Generation PEM CHP Systems for Global Markets Using PBI Membrane Technology

    SciTech Connect

    Vogel, John; Fritz Intwala, Katrina

    2009-08-01

    Plug Power and BASF have conducted eight years of development work prior to this project, demonstrating the potential of PBI membranes to exceed many DOE technical targets. This project consisted of; 1.The development of a worldwide system architecture; 2.Stack and balance of plant module development; 3.Development of an improved, lower cost MEA electrode; 4.Receipt of an improved MEA from the EU consortium; 5.Integration of modules into a system; and 6.Delivery of system to EU consortium for additional integration of technologies and testing.

  1. Domain Walls Conductivity in Hybrid Organometallic Perovskites and Their Essential Role in CH3NH3PbI3 Solar Cell High Performance

    PubMed Central

    Rashkeev, Sergey N.; El-Mellouhi, Fedwa; Kais, Sabre; Alharbi, Fahhad H.

    2015-01-01

    The past several years has witnessed a surge of interest in organometallic trihalide perovskites, which are at the heart of the new generation of solid-state solar cells. Here, we calculated the static conductivity of charged domain walls in n- and p- doped organometallic uniaxial ferroelectric semiconductor perovskite CH3NH3PbI3 using the Landau-Ginzburg-Devonshire (LGD) theory. We find that due to the charge carrier accumulation, the static conductivity may drastically increase at the domain wall by 3 – 4 orders of magnitude in comparison with conductivity through the bulk of the material. Also, a two-dimensional degenerated gas of highly mobile charge carriers could be formed at the wall. The high values of conductivity at domain walls and interfaces explain high efficiency in organometallic solution-processed perovskite films which contains lots of different point and extended defects. These results could suggest new routes to enhance the performance of this promising class of novel photovoltaic materials. PMID:26088321

  2. Shape-Evolution Control of hybrid perovskite CH3NH3PbI3 crystals via solvothermal synthesis

    NASA Astrophysics Data System (ADS)

    Zhang, Baohua; Guo, Fuqiang; Yang, Lianhong; Jia, Xiuling; Liu, Bin; Xie, Zili; Chen, Dunjun; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2017-02-01

    We systematically synthesized CH3NH3PbI3 crystals using solvothermal process, and the reaction conditions such as concentration of the precursor, temperature, time, and lead source have been comprehensively investigated to obtain shape-controlled CH3NH3PbI3 crystals. The results showed that the CH3NH3PbI3 crystals exhibit tetragonal phase and the crystals change from nanoparticles to hopper-faced cuboids. Photoluminescence spectra of the crystals obtained with different lead sources show a blue shift due to the presence of defects in the crystals, and the peak intensity is very sensitive to the lead sources. Moreover, impurities (undesirable byproducts and excess components like HI or CH3NH2) presented during crystal growth can result in hopper growth.

  3. Growth and spectral characterization of ethylene diamine tetra acetic acid (EDTA) doped zinc sulphate hepta hydrate - a semi organic NLO material.

    PubMed

    Ramachandra Raja, C; Ramamurthi, K; Manimekalai, R

    2012-12-01

    Semi-organic non-linear optical single crystals of ethylene diamine tetra acetic acid (EDTA) doped zinc sulphate hepta hydrate crystals were grown by slow evaporation solution growth technique, at room temperature, using de-ionized water as solvent. The modes of vibrations of different molecular groups present in the grown crystal were identified by FT-IR technique. The optical absorbance/transmittance was recorded in the wavelength range of 190-1100 nm. Thermal properties of the grown crystal were studied by thermo gravimetric analysis and differential thermal analysis. The melting point of the grown crystal was estimated by differential scanning calorimetric analysis. The inclusion of the dopant (EDTA) was confirmed by colorimetric estimation method. The second harmonic generation efficiency is about 30% of potassium dihydrogen orthophosphate.

  4. Identification of 11-Nor-delta9-tetrahydrocannabinol-9-carboxylic acid in urine by ion trap GC-MS-MS in the context of doping analysis.

    PubMed

    Caballero, Gerardo M; D'Angelo, Carlos; Fraguío, Mariá Sol; Centurión, Osvaldo Teme

    2004-01-01

    The purpose of this study is to develop a sensitive and specific alternative to current gas chromatography (GC)-mass spectrometry (MS) selected ion monitoring confirmation methods of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (cTHC) in human urine samples, in the context of doping analysis. An identification procedure based on the comparison, among suspicious and control samples, of the relative abundances of cTHC selected product ions obtained by GC-tandem MS in an ion trap is presented. The method complies with the identification criteria for qualitative assays established by sports authorities; the comparison procedure is precise, reproducible, specific, and sensitive, thus indicating that it is fit for the purpose of identification accordingly to World Antidoping Agency requirements.

  5. Nanocrystalline semiconductor doped rare earth oxide for the photocatalytic degradation studies on Acid Blue 113: A di-azo compound under UV slurry photoreactor.

    PubMed

    Suganya Josephine, G A; Mary Nisha, U; Meenakshi, G; Sivasamy, A

    2015-11-01

    Preventive measures for the control of environmental pollution and its remediation has received much interest in recent years due to the world-wide increase in the contamination of water bodies. Contributions of these harmful effluents are caused by the leather processing, pharmaceutical, cosmetic, textile, agricultural and other chemical industries. Nowadays, advanced oxidation processes considered to be better option for the complete destruction of organic contaminants in water and wastewater. Acid Blue 113 is a most widely used di-azo compound in leather, textile, dying and food industry as a color rending compound. In the present study, we have reported the photo catalytic degradation of Acid Blue 113 using a nanocrystalline semiconductor doped rare earth oxide as a photo catalyst under UV light irradiation. The photocatalyst was prepared by a simple precipitation technique and were characterized by XRD, FT-IR, UV-DRS and FE-SEM analysis. The experimental results proved that the prepared photo catalyst was nanocrystalline and highly active in the UV region. The UV-DRS results showed the band gap energy was 3.15eV for the prepared photo catalyst. The photodegradation efficiency was analyzed by various experimental parameters such as pH, catalyst dosage, variation of substrate concentration and effect of electrolyte addition. The photo degradation process followed a pseudo first order kinetics and was continuously monitored by UV-visible spectrophotometer. The experimental results proved the efficacy of the nanocrystalline zinc oxide doped dysprosium oxide which are highly active under UV light irradiations. It is also suggested that the prepared material would find wider applications in environmental remediation technologies to remove the carcinogenic and toxic moieties present in the industrial effluents.

  6. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., strontium salt(1:1:2), dysprosium and europium-doped. 721.9511 Section 721.9511 Protection of Environment...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new..., strontium salt(1:1:2), dysprosium and europium-doped. (PMN P-98-848; CAS No.181828-07-9) is subject...

  7. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., strontium salt(1:1:2), dysprosium and europium-doped. 721.9511 Section 721.9511 Protection of Environment...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new..., strontium salt(1:1:2), dysprosium and europium-doped. (PMN P-98-848; CAS No.181828-07-9) is subject...

  8. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., strontium salt(1:1:2), dysprosium and europium-doped. 721.9511 Section 721.9511 Protection of Environment...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new..., strontium salt(1:1:2), dysprosium and europium-doped. (PMN P-98-848; CAS No.181828-07-9) is subject...

  9. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., strontium salt(1:1:2), dysprosium and europium-doped. 721.9511 Section 721.9511 Protection of Environment...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new..., strontium salt(1:1:2), dysprosium and europium-doped. (PMN P-98-848; CAS No.181828-07-9) is subject...

  10. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., strontium salt(1:1:2), dysprosium and europium-doped. 721.9511 Section 721.9511 Protection of Environment...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new..., strontium salt(1:1:2), dysprosium and europium-doped. (PMN P-98-848; CAS No.181828-07-9) is subject...

  11. Boronic acid functionalized N-doped carbon quantum dots as fluorescent probe for selective and sensitive glucose determination

    NASA Astrophysics Data System (ADS)

    Jiang, Guohua; Jiang, Tengteng; Li, Xia; Wei, Zheng; Du, Xiangxiang; Wang, Xiaohong

    2014-04-01

    Nitrogen doped carbon quantum dots (NCQDs) of about 10 nm in diameter have been obtained by hydrothermal reaction from collagen. Because of the superiority of water dispersion, low toxicity and ease of functionlization, the NCQDs were designed as a glucose sensor after covalent grafting by 3-aminophenylboronic (APBA) (APBA-NCQDs). The as-prepared APBA-NCQDs were imparted with glucose sensitivity and selectivity from other saccharides via fluorescence (FL) quenching effect at physiological pH and at room temperature, which show high sensitivity and specificity for glucose determination with a wide range from 1 mM to 14 mM. FL quenching mechanism of APBA-NCQDs was also investigated by adding an external quencher. The APBA-NCQDs-based platform is an environmentally friendly way to substitute inorganic quantum dots containing heavy metals which offer a facile and low cost detection method.

  12. Airplane dopes and doping

    NASA Technical Reports Server (NTRS)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  13. Growing large columnar grains of CH3NH3PbI3 using the solid-state reaction method enhanced by less-crystallized nanoporous PbI2 films

    NASA Astrophysics Data System (ADS)

    Zheng, Huifeng; Wang, Weiqi; Liu, Yangqiao; Sun, Jing

    2017-03-01

    Compact, pinhole-free and PbI2-free perovskite films, are desirable for high-performance perovskite solar cells (PSCs), especially if large columnar grains are obtained in which the adverse effects of grain boundaries will be minimized. However, the conventional solid-state reaction methods, originated from the two-step method, failed to grow columnar grains of CH3NH3PbI3 in a facile way. Here, we demonstrate a strategy for growing large columnar grains of CH3NH3PbI3, by less-crystallized nanoporous PbI2 (ln-PbI2) film enhanced solid-state reaction method. We demonstrated columnar grains were obtainable only when ln-PbI2 films were applied. Therefore, the replacement of compact PbI2 by ln-PbI2 in the solid-sate reaction, leads to higher power conversion efficiency, better reproducibility, better stability and less hysteresis. Furthermore, by systematically investigating the effects of annealing temperature and duration, we found that an annealing temperature ≥120 °C was also critical for growing columnar grains. With the optimal process, a champion efficiency of 16.4% was obtained and the average efficiency reached 14.2%. Finally, the mechanism of growing columnar grains was investigated, in which a VPb″ -assisted hooping model was proposed. This work reveals the origins of grain growth in the solid-state reaction method, which will contribute to preparing high quality perovskite films with much larger columnar grains.

  14. Enhancement of periodate-hydrogen peroxide chemiluminescence by nitrogen doped carbon dots and its application for the determination of pyrogallol and gallic acid.

    PubMed

    Shah, Syed Niaz Ali; Li, Haifang; Lin, Jin-Ming

    2016-06-01

    A new sensitized chemiluminescence (CL) was developed to broaden the analytical application of KIO4-H2O2 system. The nitrogen doped carbon dots (N-CDs) dramatically boosted the CL intensity of KIO4-H2O2 system which was further enriched by basic medium. In light of EPR analysis, free radical scavenging studies and CL spectra the detail mechanism for the enhancement was conferred in the presence of N-CDs and NaOH. The results suggested that CL of KIO4-H2O2 system in the presence and absence of N-CDs and NaOH proceeds via radical pathway. The enhanced CL was used for the determination of pyrogallol and gallic acid in range of 1.0×10(-4)-1.0×10(-7)M with 4.6×10(-8) and 6.1×10(-8)M limit of detection respectively. The relative standard deviation (RSD) at a concentration of 10(-5) for gallic acid and pyrogallol was 1.4% and 2.3% respectively (n=11). The attained results unveil that the present method is sensitive, faster, simpler and less costly compared to other methods and could be applied to determine polyphenols in real samples.

  15. Phosphorescence detection of L-ascorbic acid with surface-attached N-acetyl-L-cysteine and L-cysteine Mn doped ZnS quantum dots.

    PubMed

    Bian, Wei; Ma, Jing; Guo, Wenrong; Lu, Dongtao; Fan, Meng; Wei, Yanli; Li, Yingfu; Shuang, Shaomin; Choi, Martin M F

    2013-11-15

    N-Acetyl-L-cysteine (NAC) and L-cysteine (Cys) capped Mn doped ZnS quantum dots (NAC-Mn/ZnS QDs and Cys-Mn/ZnS QDs) are firstly prepared by hydrothermal methods. These QDs display strong phosphorescence emission peaks at 583 and 580 nm upon excitation at 315 and 306 nm, respectively. Since their room-temperature phosphorescence is efficiently quenched by L-ascorbic acid (AA), they have been employed as phosphorescence probes for detecting AA. The linear working ranges are 2.5-37.5 and 2.5-47.5 µM and the limits of detection are 0.72 and 1.38 µM for NAC-Mn/ZnS QDs and Cys-Mn/ZnS QDs, respectively. The possible quenching mechanisms have been discussed in detail. The QDs probes are highly selective to AA over other common ions, amino acids, glucose and bovine serum album. Finally, they have been applied successfully for detection of AA in human urine samples with satisfactory results. The recoveries are 98-104%. Our work provides a simple and convenient phosphorescence method to determine AA in real samples.

  16. Direct quantification of 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid in urine by liquid chromatography/tandem mass spectrometry in relation to doping control analysis.

    PubMed

    Chebbah, C; Pozo, O J; Deventer, K; Van Eenoo, P; Delbeke, F T

    2010-04-30

    An accurate and precise method for the quantification of 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (THCA) in urine by liquid chromatography/tandem mass spectrometry (LC/MS/MS) for doping analysis purposes has been developed. The method involves the use of only 200 microL of urine and the use of D(9)-THCA as internal standard. No extraction procedure is used. The urine samples are hydrolysed using sodium hydroxide and diluted with a mixture of methanol/glacial acetic acid (1:1). Chromatographic separation is achieved using a C8 column with gradient elution. All MS and MS/MS parameters were optimised in both positive and negative electrospray ionisation modes. For the identification and the quantification of THCA three product ions are monitored in both ionisation modes. The method is linear over the studied range (5-40 ng/mL), with satisfactory intra-and inter-assay precision, and the relative standard deviations (RSDs) are lower than 15%. Good accuracy is achieved with bias less than 10% at all levels tested. No significant matrix effects are observed. The selectivity and specificity are satisfactory, and no interferences are detected. The LC/MS/MS method was applied for the analysis of 48 real urine samples previously analysed with a routine gas chromatography/mass spectrometry (GC/MS) method. A good correlation between the two methods was obtained (r(2) > 0.98) with a slope close to 1.

  17. Effect of PbI2 deposition rate on two-step PVD/CVD all-vacuum prepared perovskite

    NASA Astrophysics Data System (ADS)

    Ioakeimidis, Apostolos; Christodoulou, Christos; Lux-Steiner, Martha; Fostiropoulos, Konstantinos

    2016-12-01

    In this work we fabricate all-vacuum processed methyl ammonium lead halide perovskite by a sequence of physical vapour deposition of PbI2 and chemical vapour deposition (CVD) of CH3NH3I under a static atmosphere. We demonstrate that for higher deposition rate the (001) planes of PbI2 film show a higher degree of alignment parallel to the sample's surface. From X-ray diffraction data of the resulted perovskite film we derive that the intercalation rate of CH3NH3I is fostered for PbI2 films with higher degree of (001) planes alignment. The stoichiometry of the produced perovskite film is also studied by Hard X-ray photoelectron spectroscopy measurements. Complete all-vacuum perovskite solar cells were fabricated on glass/ITO substrates coated by an ultra-thin (5 nm) Zn-phthalocyanine film as hole selective layer. A dependence of residual PbI2 on the solar cells performance is displayed, while photovoltaic devices with efficiency up to η=11.6% were achieved.

  18. High efficiency CH3NH3PbI3:CdS perovskite solar cells with CuInS2 as the hole transporting layer

    NASA Astrophysics Data System (ADS)

    Chen, Chong; Zhai, Yong; Li, Fumin; Tan, Furui; Yue, Gentian; Zhang, Weifeng; Wang, Mingtai

    2017-02-01

    The CH3NH3PbI3:CdS composite films are prepared by a newly developed precursor blending solution method, which are further used to fabricate CH3NH3PbI3:CdS perovskite solar cells. Our experimental results demonstrate that the introduced CdS effectively improves the light absorption property of the ITO/CuInS2/Al2O3/CH3NH3PbI3:CdS film stack and decreases the charge recombination in the prepared solar cells due to the formation of CH3NH3PbI3/CdS bulk heterojunction. Furthermore, the formed CdS/CuInS2 heterojunction also contributes to the enhanced efficiency. As a consequence, the CH3NH3PbI3/CdS bulk heterojunction perovskite solar cells exhibit a maximum power conversion efficiency of (16.5 ± 0.2)%, which is 1.35 times the best efficiency of 12.2% of previously reported CdS/CH3NH3PbI3 bilayer solar cell. In addition, this efficiency is a 59% improvement compared with the efficiency of (10.4 ± 0.2)% for the ITO/CuInS2/Al2O3/CH3NH3PbI3/PC60BM/Ag cell without CdS.

  19. 4-Hydroxyphenylacetic acid oxidation in sulfate and real olive oil mill wastewater by electrochemical advanced processes with a boron-doped diamond anode.

    PubMed

    Flores, Nelly; Cabot, Pere Lluís; Centellas, Francesc; Garrido, José Antonio; Rodríguez, Rosa María; Brillas, Enric; Sirés, Ignasi

    2017-01-05

    The degradation of 4-hydroxyphenylacetic acid, a ubiquitous component of olive oil mill wastewater (OOMW), has been studied by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed in either a 0.050M Na2SO4 solution or a real OOMW at pH 3.0, using a cell with a boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 generation. Hydroxyl radicals formed at the BDD surface from water oxidation in all processes and/or in the bulk from Fenton's reaction between added Fe(2+) and generated H2O2 in EF and PEF were the main oxidants. In both matrices, the oxidation ability of the processes increased in the order AO-H2O2acid decay obeyed a pseudo-first-order kinetics. The PEF treatment of 1.03mM 4-hydroxyphenylacetic acid in 0.050M Na2SO4 allowed 98% mineralization at 360min even at low current density, whereas 80% mineralization and a significant enhancement of biodegradability were achieved with the real OOMW.

  20. Intense Pulsed Light Sintering of CH3NH3PbI3 Solar Cells.

    PubMed

    Lavery, Brandon W; Kumari, Sudesh; Konermann, Hannah; Draper, Gabriel L; Spurgeon, Joshua; Druffel, Thad

    2016-04-06

    Perovskite solar cells utilizing a two-step deposited CH3NH3PbI3 thin film were rapidly sintered using an intense pulsed light source. For the first time, a heat treatment has shown the capability of sintering methylammonium lead iodide perovskite and creating large crystal sizes approaching 1 μm without sacrificing surface coverage. Solar cells with an average efficiency of 11.5% and a champion device of 12.3% are reported. The methylammonium lead iodide perovskite was subjected to 2000 J of energy in a 2 ms pulse of light generated by a xenon lamp, resulting in temperatures significantly exceeding the degradation temperature of 150 °C. The process opens up new opportunities in the manufacturability of perovskite solar cells by eliminating the rate-limiting annealing step, and makes it possible to envision a continuous roll-to-roll process similar to the printing press used in the newspaper industry.

  1. Electronic structure evolution of fullerene on CH3NH3PbI3

    DOE PAGES

    Wang, Chenggong; Wang, Congcong; Liu, Xiaoliang; ...

    2015-03-19

    The thickness dependence of fullerene on CH3NH3PbI3 perovskitefilm surface has been investigated by using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy(XPS), and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital and highest occupied molecular orbital (HOMO) can be observed directly with IPES and UPS. It is observed that the HOMO level in fullerene shifts to lower binding energy. The XPS results show a strong initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskitefilm to fullerene molecules. Further deposition of fullerene forms C60 solid, accompanied by the reduction ofmore » the electron transfer. As a result, the strongest electron transfer happened at 1/4 monolayer of fullerene.« less

  2. Fabrication and characterization of methylene-blue-doped polyvinyl alcohol-polyacrylic acid blend for holographic recording.

    PubMed

    Ushamani, Mythili; Sreekumar, Krishnapillai; Kartha, Cheranellore S; Joseph, Rani

    2004-06-20

    A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and tested for holographic recording. It was found to have good characteristics such as high sensitivity, storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl alcohol/polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements, etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix. The results of experimental investigations into the properties of this new material are reported.

  3. Photocatalytic degradation of humic acids using substrate-supported Fe³⁺-doped TiO₂ nanotubes under UV/O₃ for water purification.

    PubMed

    Yuan, Rongfang; Zhou, Beihai; Zhang, Xuemin; Guan, Huanhuan

    2015-11-01

    In this paper, Fe(3+)-doped TiO2 nanotubes (Fe-TNTs) were successfully synthesized using hydrothermal method. Four different types of substrates, more specifically, ceramsite, zeolite, activated alumina, and activated carbon (AC), have been investigated in the study. The substrate-supported Fe-TNTs were used to effectively decompose humic acids (HAs) in water under O3/UV conditions. The experiment results show that the highest photocatalytic activity was obtained in the presence of AC-supported 1.0 atomic percent (at.%) Fe-TNTs calcined at 500 °C, as HAs was removed by 97.4%, with a pseudo-first-order rate constant of 0.126/min. The removal efficiencies of HAs reduced when the catalysts was repeatedly used, since the amount of adsorption sites of the supporting substrates decreased. However, even after the catalyst was repeatedly used for five times, the removal efficiency of HAs in the presence of AC-supported catalyst, which was 78.5%, was still sufficient in water treatment. The enhanced photocatalytic activity of AC-supported Fe-TNTs was related to a synergistic effect of AC adsorption and Fe-TNT photocatalytic ozonation.

  4. Minimizing Unintentional Strain and Doping of Single-Layer Graphene on SiO2 in Aqueous Environments by Acid Treatments.

    PubMed

    Masuda, Katsuya; Sano, Masahito

    2015-05-05

    The effects of treating SiO2/Si with either acidic or alkaline solutions on single-layer graphene were investigated using Raman microscopy. It is well-known that in air graphene on SiO2 is unintentionally strained and hole-doped to different degrees, varying widely by sample. It is also known that various amine compounds act as electron donors to graphitic materials. In this study, a SiO2/Si substrate was simply dipped in either a concentrated HCl solution or pH 9.0 NaOH solution and then rinsed, prior to transferring graphene on it. The G and 2D peaks were followed at a fixed position on a single-layer graphene flake in water and various concentrations of pH 7.4 tris(hydroxymethyl)aminomethane (Tris) buffer. The results demonstrate that these treatments reduce the sample variation, improve the stability against Tris, and even bring some graphene samples close to a freestanding state. The Raman analysis reveals that the main effect of dipping is to relieve strain. The undoping effect on some samples is explained by the HCl solution becoming trapped between the graphene and SiO2 surface.

  5. Electrochemical behavior of chlorogenic acid at a boron-doped diamond electrode and estimation of the antioxidant capacity in the coffee samples based on its oxidation peak.

    PubMed

    Yardım, Yavuz

    2012-04-01

    In this study, an electroanalytical methodology for the determination of chlorogenic acid (CGA) was achieved at a boron-doped diamond electrode under adsorptive transfer stripping voltammetric conditions. The values obtained for CGA were used to estimate the antioxidant properties of the coffee sample based on CGA oxidation. By using square-wave stripping mode, the compound yielded a well-defined voltammetric response at +0.49 V with respect to Ag/AgCl in Britton-Robinson buffer at pH 3.0 (after 120 s accumulations at a fixed potential of 0.40 V). At the optimum experimental conditions, linear calibration curve is obtained within the concentration range of 0.25 to 4.0 μg mL⁻¹ with the limit of detection 0.049 μg mL⁻¹ . The developed protocol was successfully applied for the analysis of antioxidant capacity in the coffee products such as Turkish coffee and instant coffee.

  6. Non-redox modulated fluorescence strategy for sensitive and selective ascorbic acid detection with highly photoluminescent nitrogen-doped carbon nanoparticles via solid-state synthesis.

    PubMed

    Zhu, Xiaohua; Zhao, Tingbi; Nie, Zhou; Liu, Yang; Yao, Shouzhuo

    2015-08-18

    Highly photoluminescent nitrogen-doped carbon nanoparticles (N-CNPs) were prepared by a simple and green route employing sodium alginate as a carbon source and tryptophan as both a nitrogen source and a functional monomer. The as-synthesized N-CNPs exhibited excellent water solubility and biocompatibility with a fluorescence quantum yield of 47.9%. The fluorescence of the N-CNPs was intensively suppressed by the addition of ascorbic acid (AA). The mechanism of the fluorescence suppression of the N-CNPs was investigated, and the synergistic action of the inner filter effect (IFE) and the static quenching effect (SQE) contributed to the intensive fluorescence suppression, which was different from those reported for the traditional redox-based fluorescent probes. Owing to the spatial effect and hydrogen bond between the AA and the groups on the N-CNP surface, excellent sensitivity and selectivity for AA detecting was obtained in a wide linear relationship from 0.2 μM to 150 μM. The detection limit was as low as 50 nM (signal-to-noise ratio of 3). The proposed sensing systems also represented excellent sensitivity and selectivity for AA analysis in human biological fluids, providing a valuable platform for AA sensing in clinic diagnostic and drug screening.

  7. Metal ions doped chitosan-poly(acrylic acid) nanospheres: Synthesis and their application in simultaneously electrochemical detection of four markers of pancreatic cancer.

    PubMed

    Rong, Qinfeng; Feng, Feng; Ma, Zhanfang

    2016-01-15

    In this work, a one-pot method was designed to synthesize copper ions, cadmium ions, lead ions and zinc ions doped chitosan-poly(acrylic acid) nanospheres. Those nanospheres can not only produce independent electrochemical signals, but also react with glutaraldehyde (GA) to immobilize different labeled antibodies. Using the modified nanospheres as immunoprobes, a sandwich-type immunosensor was fabricated to simultaneous detection of four tumor markers (CEA, CA199, CA125 and CA242) of pancreatic cancer. This designed immunosensor exhibited good linear relationships in range from 0.1 to 100ng mL(-1) for CEA, 1 to 150UmL(-1) for CA199, CA125 and CA242, corresponding detection limits 0.02ng mL(-1), 0.4UmL(-1), 0.3UmL(-1) and 0.4UmL(-1), respectively. Meanwhile, the immunosensor was applied in analysis of clinical serum samples, whose results were well agreed with the enzyme-linked immunosorbent assay (ELISA), indicating that the proposed immunosensor gave a hope for the identification and validation of specific early cancer.

  8. A simple synthesis of nitrogen doped porous graphitic carbon: Electrochemical determination of paracetamol in presence of ascorbic acid and p-aminophenol.

    PubMed

    Biswas, Sudip; Chakraborty, Dipanjan; Das, Rashmita; Bandyopadhyay, Rajib; Pramanik, Panchanan

    2015-08-26

    Graphite paste electrode modified with nitrogen doped porous carbon (NDPC) is used for the detections of paracetamol (PCM), ascorbic acid (AA) and p-aminophenol (PAP) at relatively low concentration. NDPC is synthesized by direct carbonization of Zn(OAc)2 incorporated melamine-formaldehyde resin microsphere. The NDPC shows small pore diameters centered at 3.14 nm and 8.12 nm and has a pseudo graphitic structure with reasonable porous matrix. The lower limit of detections (S/N = 3) for PCM, AA, and PAP are found to be 30 nM, 720 nM and 10 nM respectively. Under optimized experimental condition, the linear ranges of determination for PCM and AA are 1-400 μM, 10-2700 μM respectively in mixture. Similarly for PCM and PAP mixture, the linear ranges of determination are found to be 1-90 μM. It is also used for the analysis of urine and pharmaceutical products with better sensitivity.

  9. Kinetic study of formic acid degradation by Fe3+ doped TiO2 self-cleaning nanostructure surfaces prepared by cold spray

    NASA Astrophysics Data System (ADS)

    Sayyar, Zahra; Akbar Babaluo, Ali; Shahrouzi, Javad Rahbar

    2015-04-01

    A self-cleaning solution was introduced in this paper based on sol-gel and was applied for preparing self-cleaning TiO2. Fe3+ ions have been doped into the TiO2 crystal lattice. XRD analysis indicated that the obtained TiO2 powder contains mainly the anatase phase and TiO2 powder has a crystallite size distribution of 10-12 nm. SEM micrographs have also confirmed nanometric distribution of the obtained powder. A series of uniform and transparent TiO2 and Fe/TiO2 films were prepared by cold spray technique which may result in high uniformity in the final coated surfaces. Photocatalytic activity of the thin films was investigated through degradation of aqueous formic acid under UV-visible light. The Langmuir-Hinshelwood kinetic model was used to interpret quantitatively the observed kinetic experimental result. Comparative study of the obtained coated surfaces with those of uncoated surfaces, demonstrated a remarkable performance. The Fe/TiO2 films and their calcination at 650 °C demonstrated the highest photocatalytic activity.

  10. Poly(acrylic acid) modified lanthanide-doped GdVO4 hollow spheres for up-conversion cell imaging, MRI and pH-dependent drug release

    NASA Astrophysics Data System (ADS)

    Kang, Xiaojiao; Yang, Dongmei; Dai, Yunlu; Shang, Mengmeng; Cheng, Ziyong; Zhang, Xiao; Lian, Hongzhou; Ma, Ping'an; Lin, Jun

    2012-12-01

    In this study, multifunctional poly(acrylic acid) modified lanthanide-doped GdVO4 nanocomposites [PAA@GdVO4: Ln3+ (Ln = Yb/Er, Yb/Ho, Yb/Tm)] were constructed by filling PAA hydrogel into GdVO4 hollow spheres via photoinduced polymerization. The up-conversion (UC) emission colors (green, red and blue) can be tuned by changing the codopant compositions in the matrices. The composites have potential applications as bio-probes for cell imaging. Meanwhile, the hybrid spheres can act as T1 contrast agents for magnetic resonance imaging (MRI) owing to the existence of Gd3+ ions on the surface of composites. Due to the nature of PAA, DOX-loaded PAA@GdVO4:Yb3+/Er3+ system exhibits pH-dependent drug releasing kinetics. A lower pH offers a faster drug release rate. Such character makes the loaded DOX easily released at cancer cells. The cell uptake process of drug-loaded composites was observed by using confocal laser scanning microscopy (CLSM). The results indicate the potential application of the multifunctional composites as theragnostics (effective bimodal imaging probes and pH-responsive drug carriers).

  11. Cobalt carbonate dumbbells for high-capacity lithium storage: A slight doping of ascorbic acid and an enhancement in electrochemical performances

    NASA Astrophysics Data System (ADS)

    Zhao, Shiqiang; Wei, Shanshan; Liu, Rui; Wang, Yuxi; Yu, Yue; Shen, Qiang

    2015-06-01

    Synthesis of materials with desirable nanostructures is a hot research topic owing to their enhanced performances in contrast to the bulk counterparts. Herein, dumbbell-shaped cobalt carbonate (CoCO3) nano architectures and the bulk counterpart of CoCO3 rhombohedra are prepared via a facile hydrothermal route in the presence and absence of ascorbic acid (AA), respectively. By comparison, it has been found that: the addition of AA in the hydrothermal crystallization system changes the shape of the building blocks from Co2CO3(OH)2 nanosheets to CoCO3 nanoparticles, and then further influences the final configuration of the products. When applied as anodes of lithium ion batteries, CoCO3 dumbbells deliver a 100th capacity of 1042 mAh g-1 at 200 mA g-1 and even exhibit a long-term value of 824 mAh g-1 over 500 cycles at 1000 mA g-1, which are much higher than the rhombohedral counterparts with corresponding 540 and 481 mAh g-1 respectively. The much higher capacity, better cycling stability and enhanced rate performance of CoCO3 dumbbells can be attributed to the higher specific surface area, smaller charge transport resistance and better structure stability resulting from the slight doping (∼4.6 wt%) of AA, and also relate with a novel lithium storage mechanism in CoCO3.

  12. N-doped carbon dots derived from bovine serum albumin and formic acid with one- and two-photon fluorescence for live cell nuclear imaging.

    PubMed

    Tan, Mingqian; Li, Xintong; Wu, Hao; Wang, Beibei; Wu, Jing

    2015-12-01

    Carbon dots with both one- and two-photon fluorescence have drawn great attention for biomedical imaging. Herein, nitrogen-doped carbon dots were facilely developed by one-pot hydrothermal method using bovine serum albumin and formic acid as carbon sources. They are highly water-soluble with strong fluorescence when excited with ultraviolet or near infrared light. The carbon dots have a diameter of ~8.32 nm and can emit strong two-photon induced fluorescence upon excitation at 750 nm with a femtosecond laser. X-ray photoelectron spectrometer analysis revealed that the carbon dots contained three components, C, N and O, corresponding to the peak at 285, 398 and 532 eV, respectively. The Fourier-transform infrared spectroscopy analysis revealed that there are carboxyl and carboxylic groups on the surface, which allowed further linking of functional molecules. pH stability study demonstrated that the carbon dots are able to be used in a wide range of pH values. The fluorescence mechanism is also discussed in this study. Importantly, these carbon dots are biocompatible and highly photostable, which can be directly applied for both one- and two-photon living cell imaging. After proper surface functionalization with TAT peptide, they can be used as fluorescent probes for live cell nuclear-targeted imaging.

  13. High-Performance Flexible Solid-State Carbon Cloth Supercapacitors Based on Highly Processible N-Graphene Doped Polyacrylic Acid/Polyaniline Composites

    PubMed Central

    Wang, Yongguang; Tang, Shaochun; Vongehr, Sascha; Ali Syed, Junaid; Wang, Xiangyu; Meng, Xiangkang

    2016-01-01

    Improving the solubility of conductive polymers to facilitate processing usually decreases their conductivity, and they suffer from poor cycling stability due to swelling-shrinking during charging cycles. We circumvent these problems with a novel preparation method for nitrogen-doped graphene (NG) enhanced polyacrylic acid/polyaniline (NG-PAA/PANI) composites, ensuring excellent processibility for scalable production. The content of PANI is maximized under the constraint of still allowing defect-free coatings on filaments of carbon cloth (CC). The NG content is then adjusted to optimize specific capacitance. The optimal CC electrodes have 32 wt.% PANI and 1.3 wt.% NG, thus achieving a high capacitance of 521 F/g at 0.5 F/g. A symmetric supercapacitor made from 20 wt.% PANI CC electrodes has more than four times the capacitance (68 F/g at 1 A/g) of previously reported flexible capacitors based on PANI-carbon nanotube composites, and it retains the full capacitance under large bending angles. The capacitor exhibits high energy and power densities (5.8 Wh/kg at 1.1 kW/kg), a superior rate capability (still 81% of the 1 A/g capacitance at 10 A/g), and long-term electrochemical stability (83.2% retention after 2000 cycles). PMID:26883179

  14. Simple quantitation of formoterol and 11-nor-Δ(9)-tetrahydrocannabinol-9-carboxylic acid in human urine by liquid chromatography-tandem mass spectrometry in doping control.

    PubMed

    Lee, Kang Mi; Kim, Ho Jun; Son, Junghyun; Park, Ju-Hyung; Kwon, Oh-Seung; Lee, Jaeick

    2014-09-15

    11-nor-Δ(9)-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) and formoterol are newly revised prohibited threshold substances (150 ng/mL for THC-COOH and 40 ng/mL for formoterol) by the World Anti-Doping Agency (WADA). In continuation of our direct quantitation work of the prohibited threshold substances, direct LC-MS/MS methods combined with a simple sample preparation procedure have been developed and validated for the measurement of these two threshold substances in urine samples. After the enzymatic hydrolysis of urine samples, the resulting samples were diluted with acetonitrile and centrifuged. The supernatant was directly analyzed by LC-MS/MS using the selected reaction monitoring mode. The calibration curve range of the assay was ranged over 50-200% of the threshold value according to WADA guidelines. The limit of detection and limit of quantification were 6.1 and 18.4 ng/mL for THC-COOH and 2.0 and 6.2 ng/mL for formoterol, respectively. Intra- and inter-day precisions were between 2.08% and 7.28% and the accuracies ranged from 95.16% to 104.49%. The present methods were successfully applied to the analysis of the proficiency test samples.

  15. Aptameric Recognition-Modulated Electroactivity of Poly(4-Styrenesolfonic Acid)-Doped Polyaniline Films for Single-Shot Detection of Tetrodotoxin

    PubMed Central

    Fomo, Gertrude; Waryo, Tesfaye T.; Sunday, Christopher E.; Baleg, Abd A.; Baker, Priscilla G.; Iwuoha, Emmanuel I.

    2015-01-01

    The work being reported is the first electrochemical sensor for tetrodotoxin (TTX). It was developed on a glassy carbon electrodes (C) that was modified with poly(4-styrenesolfonic acid)-doped polyaniline film (PANI/PSSA). An amine-end functionalized TTX-binding aptamer, 5′-NH2-AAAAATTTCACACGGGTGCCTCGGCTGTCC-3′ (NH2-Apt), was grafted via covalent glutaraldehyde (glu) cross-linking. The resulting aptasensor (C//PANI+/PSSA-glu-NH2-Apt) was interrogated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in sodium acetate buffer (NaOAc, pH 4.8) before and after 30 min incubation in standard TTX solutions. Both CV and EIS results confirmed that the binding of the analyte to the immobilized aptamer modulated the electrochemical properties of the sensor: particularly the charge transfer resistance (Rct) of the PANI+/PSSA film, which served as a signal reporter. Based on the Rct calibration curve of the TTX aptasensor, the values of the dynamic linear range (DLR), sensitivity and limit of detection (LOD) of the sensor were determined to be 0.23–1.07 ng·mL−1 TTX, 134.88 ± 11.42 Ω·ng·mL−1 and 0.199 ng·mL−1, respectively. Further studies are being planned to improve the DLR as well as to evaluate selectivity and matrix effects in real samples. PMID:26370994

  16. Miniaturized graphite sensors doped with metal-bathophenanthroline complexes for the selective potentiometric determination of uric acid in biological fluids.

    PubMed

    Hassan, S S; Rizk, N M

    1997-08-01

    Miniaturized poly(vinyl chloride) matrix membrane sensors in an all-solid-state graphite support, responsive to urate anion, were developed. The membranes incorporate lipophilic ion-pair complexes of urate anion with ruthenium(III), iron(II), nickel(II) and copper(I) bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) counter cations. The sensors demonstrate a near-Nernstian response to urate over the concentration range 1 x 10(-2)-1 x 10(-5) mol l-1 and have micromolar detection limits and good selectivity properties. The response is virtually unaffected by pH changes in the range 7-10 and the response times are 5-10 s in aqueous solutions and in human serum and urine samples. A flow injection detector incorporating an iron(II) bathophenanthroline-urate graphite sensor was used for continuous monitoring of uric acid. The minimum detectable concentration was approximately 8 micrograms ml-1 and the sample throughput was approximately 120 h-1. Direct potentiometric determination of uric acid in the static and hydrodynamic modes of operation over the range 15 micrograms ml-1-1.5 mg ml-1 showed average recoveries of 98.7 and 97.8% with RSDs of 0.6 and 0.7%, respectively. Application of the method to the determination of uric acid in human serum and urine gave results that compared favourably with those obtained by the standard spectrophotometric method.

  17. Multifunctional electroactive electrospun nanofiber structures from water solution blends of PVA/ODA-MMT and poly(maleic acid-alt-acrylic acid): effects of Ag, organoclay, structural rearrangement and NaOH doping factors

    NASA Astrophysics Data System (ADS)

    Şimşek, Murat; Rzayev, Zakir M. O.; Bunyatova, Ulviya

    2016-06-01

    Novel multifunctional colloidal polymer nanofiber electrolytes were fabricated by green reactive electrospinning nanotechnology from various water solution/dispersed blends of poly (vinyl alcohol-co-vinyl acetate) (PVA)/octadecyl amine-montmorillonite (ODA-MMT) as matrix polymer nanocomposite and poly(maleic acid-alt-acrylic acid) (poly(MAc-alt-AA) and/or its Ag-carrying complex as partner copolymers. Polymer nanofiber electrolytes were characterized using FTIR, XRD, thermal (DSC, TGA-DTG), SEM, and electrical analysis methods. Effects of partner copolymers, organoclay, in situ generated silver nanoparticles (AgNPs), and annealing procedure on physical and chemical properties of polymer composite nanofibers were investigated. The electrical properties (resistance, conductivity, activation energy) of nanofibers with/without NaOH doping agent were also evaluated. This work presented a structural rearrangement of nanofiber mats by annealing via decarboxylation of anhydride units with the formation of new conjugated double bond sites onto partner copolymer main chains. It was also found that the semiconductor behaviors of nanofiber structures were essentially improved with increasing temperature and fraction of partner copolymers as well as presence of organoclay and AgNPs in nanofiber composite.

  18. Solution-processed flexible planar perovskite solar cells: A strategy to enhance efficiency by controlling the ZnO electron transfer layer, PbI2 phase, and CH3NH3PbI3 morphologies

    NASA Astrophysics Data System (ADS)

    Jung, Kyungeun; Lee, Jeongwon; Kim, Joosun; Chae, Weon-Sik; Lee, Man-Jong

    2016-08-01

    This paper reports a synergistic strategy to enhance the power conversion efficiency (PCE) of flexible planar perovskite solar cells (PSCs) by controlling the thickness of the ZnO electron transport layer (ETL), PbI2 phase, and size/morphology of the perovskite (MAPbI3) absorber layer. To optimize the size/morphology of MAPbI3 via a two-step spin coating process, various volumes of CH3NH3I precursor solutions with a constant concentration were continuously coated, which greatly affected the grain growth condition of the MAPbI3. In addition, the remnant PbI2 phase in the MAPbI3, which acted as a recombination barrier, was simultaneously controlled. This strategic method to synergistically combine the major factors affecting the final PCE resulted in the best efficiency of 12.3%, which is the highest efficiency among ZnO-ETL-based flexible planar PSCs to date.

  19. Qualitative detection of diuretics and acidic metabolites of other doping agents in human urine by high-performance liquid chromatography-tandem mass spectrometry: comparison between liquid-liquid extraction and direct injection.

    PubMed

    Deventer, K; Pozo, O J; Van Eenoo, P; Delbeke, F T

    2009-07-31

    Direct injection of urine has gained interest in the field of analytical toxicology, including doping control analysis. However, implementation of a direct urinalysis method for the LC-MS/MS detection of 34 diuretics and 9 other doping agents yielded several analytical problems, which were not observed using a traditional liquid-liquid extraction. Therefore a comparative study was made between liquid-liquid extraction and direct injection. Comparison of validation results showed that the liquid-liquid extraction at pH 7 allows to analyze samples without major drawbacks regarding matrix effects. Hence, good sensitivity was observed and detection limits ranged between 1 and 250 ng/mL for all compounds. In the direct injection approach shifted retention times were observed for several acidic and basic compounds due to unwanted matrix effects. This shift was reduced by a 25-fold dilution of the urine samples. Besides the improved retention time stability the diluted samples also exhibited lower ion suppression than the undiluted ones. After 25-fold dilution, detection limits ranged between 10 and 250 ng/mL for all compounds. Since these detection limits are at or below the minimum required performance level, imposed by the World Anti-Doping Agency, the method could be applied to routine anti-doping analysis. Samples, previously declared positive, were reanalysed using both the liquid-liquid extraction and direct injection. With both techniques all 26 samples were found to be positive, showing the applicability of direct injection for the analysis of diuretics.

  20. Intrinsic Raman Signatures of Pristine Hybrid Perovskite CH3NH3PbI3 and its Multiple Stages of Structure Transformation

    SciTech Connect

    Chen, Qiong; Liu, Henan; Kim, Hui-Seon; Liu, Yucheng; Yang, Mengjin; Yue, Naili; Ren, Gang; Zhu, Kai; Liu, Shengzhong; Park, Nam-Gyu; Zhang, Yong

    2016-11-21

    By performing spatially resolved Raman and photoluminescence spectroscopy with different illumination conditions, we have achieved a unified understanding towards the spectroscopy signatures of the organic-inorganic hybrid perovskite, transforming from the pristine state (CH3NH3PbI3 or MAPbI3) to fully degraded state (i.e., PbI2), for samples with varying crystalline domain size from mesoscopic scale to macroscopic size, synthesized by three different techniques.

  1. A novel transformation route from PbS to CH3NH3PbI3 for fabricating curved and large-area perovskite films.

    PubMed

    Luo, Paifeng; Zhou, Shengwen; Liu, Zhaofan; Xia, Wei; Sun, Lin; Cheng, Jigui; Xu, Chenxi; Lu, Yingwei

    2016-09-28

    We present a new transformation route from PbS to CH3NH3PbI3 for the facile preparation of perovskites with all kinds of shapes via vapor-assisted chemical bath deposition (VACBD). As such, curved and large-area CH3NH3PbI3 films with high quality are successfully achieved, which are suitable for the manufacturing scale-up of perovskite solar cells.

  2. Structural, electronic and photoluminescence properties of Eu3+-doped CaYAlO4 obtained by using citric acid complexes as precursors

    NASA Astrophysics Data System (ADS)

    Perrella, R. V.; Júnior, C. S. Nascimento; Góes, M. S.; Pecoraro, E.; Schiavon, M. A.; Paiva-Santos, C. O.; Lima, H.; Couto dos Santos, M. A.; Ribeiro, S. J. L.; Ferrari, J. L.

    2016-07-01

    The search for new materials that meet the current technological demands for photonic applications, make the Rare Earth ions embedded in inorganic oxides as excellent candidates for several technological devices. This work presents the synthesis of Eu3+-doped CaYAlO4 using citric acid as ligand to form a complex precursor. The methodology used has big draw due to its easy handling and low cost of the materials. The thermal analysis of viscous solutions was evaluated and the obtained compounds show the formation of a polycrystalline tetragonal phase. Rietveld refinement was used to understand the structural and the cell parameters of the crystalline phase as a function of temperature of heat-treatment. Crystallite size and microstrain were determined and were shown to have a direct relationship with the temperature of the heat-treatment. The band-gap of the CaYAlO4 doped with 1 and 10 mol% of Eu3+ showed values close to 4.30 eV, resulting in their transparency in the visible region between 330 and 750 nm. Besides the intense photoluminescence from Eu3+, a study was conducted to evaluate the possible position of the Eu3+ in the CaYAlO4 as host lattice. Lifetime of the emission decay from Eu3+ excited state 5D0 show that CaYAlO4 is a good host to rare earth ions, once it can avoid clustering of these ions in concentration as high as 10 mol%. The predictions of the sublevels of the 7F1 crystal field level are discussed through the method of equivalent nearest neighbours (MENN). The intensity parameters (Ωλ, λ = 2 and 4) are reproduced with physically reasonable values of average polarizabilities. The set of charge factors used in both calculations are in good agreement with the charge of the europium ion described by the Batista-Longo improved model (BLIM). The quantum efficiencies of the materials were calculated based on Judd-Ofelt theory. Based on the results obtained in this work, the materials have potential use in photonic devices such as lasers and solid

  3. Self-doping effect in poly(o-methoxyaniline)/poly(3-thiopheneacetic acid) layer-by-layer films.

    PubMed

    Trivinho-Strixino, Francisco; Pereira, Ernesto C; Mello, Sarita V; Oliveira, Osvaldo N

    2004-04-27

    Nanostructured films from two conducting polymers, poly(o-methoxyaniline) (POMA) and poly(3-thiopheneacetic acid) (PTAA), were fabricated with the layer-by-layer (LBL) technique. The electrochemical response of the LBL films differs from that of a POMA cast film, even in a potential range where PTAA is inactive. This is attributed to differences in the diffusion-controlled charge and mass transport, where distinct ionic species participate in the LBL films, as demonstrated by quartz crystal microbalance measurements. The results show that the transport properties of conducting polymers can be changed by alternation with layers of appropriate materials in LBL films.

  4. O2 and H2O2 transformation steps for the oxygen reduction reaction catalyzed by graphitic nitrogen-doped carbon nanotubes in acidic electrolyte from first principles calculations.

    PubMed

    Li, Yuhang; Zhong, Guoyu; Yu, Hao; Wang, Hongjuan; Peng, Feng

    2015-09-14

    It is highly challenging but extremely desirable to develop carbon catalysts with high oxygen reduction reaction (ORR) activity and stability in acidic medium for commercial application. In this paper, based on density functional theory (DFT) calculations with long range interaction correction and solvation effects, the elementary transformations of all the probable intermediates in the ORR and the hydrogen peroxide reduction reaction (HPRR) over graphitic nitrogen-doped carbon nanotubes (NCNTs) in acidic medium were evaluated, and it was found that all the rate determining steps are related to the bonding hydroxyl group because of the strong interaction between the hydroxyl group and carbon. Thus, it is hard for the direct four-electron ORR and the two-electron HPRR to proceed. Together with hydrogen peroxide disproportionation (HPD), a mixed mechanism for the ORR in acidic electrolyte was proposed, where the two-electron and three-electron ORRs and HPD dominate the electrode reaction. The experimental result for the ORR catalyzed by NCNTs in acidic electrolyte also well illustrated the rationality of the theoretical calculations. This study not only gives new insights into the effect of graphitic nitrogen doping on the ORR catalyzed by carbon, but also provides a guide to design carbon catalysts with high ORR activity in acidic electrolyte.

  5. A facile, solvent vapor-fumigation-induced, self-repair recrystallization of CH3NH3PbI3 films for high-performance perovskite solar cells.

    PubMed

    Zhu, Weidong; Yu, Tao; Li, Faming; Bao, Chunxiong; Gao, Hao; Yi, Yong; Yang, Jie; Fu, Gao; Zhou, Xiaoxin; Zou, Zhigang

    2015-03-12

    A high-quality CH3NH3PbI3 film is crucial in the manufacture of a high-performance perovskite solar cell. Here, a recrystallization process via facile fumigation with DMF vapor has been successfully introduced to self-repair of CH3NH3PbI3 films with poor coverage and low crystallinity prepared by the commonly used one-step spin-coating method. We found that the CH3NH3PbI3 films with dendritic structures can spontaneously transform to the uniform ones with full coverage and high crystallinity by adjusting the cycles of the recrystallization process. The mesostructured perovskite solar cells based on these repaired CH3NH3PbI3 films showed reproducible optimal power conversion efficiency (PCE) of 11.15% and average PCE of 10.25±0.90%, which are much better than that of devices based on the non-repaired CH3NH3PbI3 films. In addition, the hysteresis phenomenon in the current-voltage test can also be effectively alleviated due to the quality of the films being improved in the optimized devices. Our work proved that the fumigation of solvent vapor can modify metal organic perovskite films such as CH3NH3PbI3. It offers a novel and attractive way to fabricate high-performance perovskite solar cells.

  6. Poly-glutamic acid modified carbon nanotube-doped carbon paste electrode for sensitive detection of L-tryptophan.

    PubMed

    Liu, Xiao; Luo, Liqiang; Ding, Yaping; Ye, Daixin

    2011-08-01

    A novel poly-glutamic acid (PGA) film modified carbon paste electrode (CPE) incorporating carbon nanotubes (CNTs) was first prepared for the determination of l-tryptophan (l-Trp). Scanning electron microscopy and Fourier transform infrared spectroscopy were applied for characterization of the surface morphology of the modified electrodes and cyclic voltammetry was used to investigate the electrochemical properties of the proposed electrode towards the oxidation of l-Trp. Optimization of the experimental parameters was performed with regard to pH, ratio of CNTs, concentration of glutamic acid, electro-polymerization cycles, accumulation time and concentration of sodium dodecylbenzene sulfonate. The linearity between the oxidation peak current and the l-Trp concentration was obtained in the range of 5.0×10(-8) to 1.0×10(-4)M with a detection limit of 1.0×10(-8)M (S/N=3) and the sensitivity was calculated to be 1143.79μA∙mM(-1)∙cm(-2). In addition, the PGA modified CPE incorporating CNTs displayed high selectivity, good stability and reproducibility, making it suitable for the routine analysis of l-Trp in clinical use.

  7. Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications.

    PubMed

    Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2014-08-20

    Using time-resolved photoluminescence and transient absorption measurements at room temperature, we report excitation-intensity-dependent photocarrier recombination processes in thin films made from the organo-metal halide perovskite semiconductor CH3NH3PbI3 for solar-cell applications. The photocarrier dynamics are well described by a simple rate equation including single-carrier trapping and electron-hole radiative recombination. This result provides clear evidence that the free-carrier model is better than the exciton model for interpreting the optical properties of CH3NH3PbI3. The observed large two-carrier recombination rate suggests the promising potential of perovskite semiconductors for optoelectronic device applications. Our findings provide the information about the dynamical behaviors of photoexcited carriers that is needed for developing high-efficiency perovskite solar cells.

  8. CH3NH3PbI3, A Potential Solar Cell Candidate: Structural and Spectroscopic Investigations.

    PubMed

    Nandi, Pronoy; Giri, Chandan; Joseph, Boby; Rath, S; Manju, U; Topwal, D

    2016-12-15

    Hybrid organic-inorganic metal halides of the type CH3NH3PbX3 have emerged as potential materials for photovoltaic applications. In this paper we discuss structural, electronic, and optical spectroscopy investigations performed on high quality single crystals of CH3NH3PbI3. Our results conclusively suggest that CH3NH3PbI3 crystallizes in centrosymmetric space group and the methylammonium moiety exhibits disordered packing at room temperature. Extracted values of the exciton binding energy, the electron-phonon coupling constant, and the schematic energy level diagram constructed from the emission broadening, Raman, and photoemission spectroscopy measurements clearly show the potential of this system in photovoltaic applications.

  9. Boron doping a semiconductor particle

    DOEpatents

    Stevens, Gary Don; Reynolds, Jeffrey Scott; Brown, Louanne Kay

    1998-06-09

    A method (10,30) of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried (16), with the boron film then being driven (18) into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out (38) into piles and melted/fused (40) with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements.

  10. Boron doping a semiconductor particle

    DOEpatents

    Stevens, G.D.; Reynolds, J.S.; Brown, L.K.

    1998-06-09

    A method of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried, with the boron film then being driven into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out into piles and melted/fused with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements. 2 figs.

  11. The influence of γ-rays irradiation on the structure and crystallinity of heteropoly acid doped PVA

    NASA Astrophysics Data System (ADS)

    Mahmoud, Waleed E.; Al-Ghamdi, A. A.; Kadi, Mohammad W.

    2012-06-01

    This contribution represents the manufacturing of a hybrid organic-inorganic proton conducting compound, which involves the introduction of heteropoly acid (HPA) of different concentrations into poly-vinyl alcohol (PVA). These compounds were irradiated by γ-rays at different doses of 10, 20, 30, and 40 kGy. The unirradiated and irradiated compounds were characterized by XRD and DSC. The XRD results showed that the crystallinity and d-spacing were strongly influenced by the amount of HPA and irradiation doses. The DSC results showed that the melting point was decreased as a result of HPA concentration and irradiation doses. The degree of crystallinity calculated from XRD is in good agreement with that calculated from DSC. The activation energy of the Unirradiated and irradiated compounds was calculated using the Flynn-Wall-Ozawa model.

  12. Influence of surfactant on dynamics of photoinduced motions and light emission of a dye-doped deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Sznitko, Lech; Parafiniuk, Kacper; Miniewicz, Andrzej; Rau, Ileana; Kajzar, Francois; Niziol, Jacek; Hebda, Edyta; Pielichowski, Jan; Sahraoui, Bouchta; Mysliwiec, Jaroslaw

    2013-10-01

    Pure deoxyribonucleic acid (DNA) is known to be soluble in water only and exhibits poor temperature stability. In contrary, it is well known that the complex of DNA - with cetyltrimethyl ammonium (CTMA) is insoluble in water but soluble in alcohols and can be processed into very good optical quality thin films by solution casting or spin deposition. Despite the success of DNA-CTMA, there is still need for new cationic surfactants which would extend the range of available solvents for DNA complex. We test and present experimental results of influence of new surfactants replacing CTMA in the DNA complex and based on benzalkonium chloride (BA) and didecyldimethylammonium chloride (DDCA) on their optical properties. Particularly, we were interested in all optical switching and light generation in amplified spontaneous emission process in these materials.

  13. The effect of doping acid on the third-order nonlinearity of carboxymethyl cellulose by the Z-scan technique

    NASA Astrophysics Data System (ADS)

    Jafari, A.; Naderali, R.; Motiei, H.

    2017-02-01

    The studies on the third-order nonlinear optical properties of carboxymethyl cellulose nanocomposite in the absence and presence of inorganic acid as a dopant was reported. The Z-scan technique was used to measure the nonlinear refraction n2, and absorption β, indexes and the third-order nonlinear susceptibility χ3. Characterization of this nanocomposite was performed by using scanning electron microscopy and Ultraviolet-Visible absorption spectroscopy in two different solvents; Dimethylformamide and N-Methylpyrrolidone. Additionally X-ray diffraction was used to study their crystal structure. The measured values of the nonlinear refraction of each sample in both of the solutions were in the order of 10-9m2/w and the corresponding third-order nonlinear susceptibilities were in the order 10-4 esu.

  14. Revealing the role of organic cations in hybrid halide perovskite CH3NH3PbI3

    PubMed Central

    Motta, Carlo; El-Mellouhi, Fedwa; Kais, Sabre; Tabet, Nouar; Alharbi, Fahhad; Sanvito, Stefano

    2015-01-01

    The hybrid halide perovskite CH3NH3PbI3 has enabled solar cells to reach an efficiency of about 20%, demonstrating a pace for improvements with no precedents in the solar energy arena. Despite such explosive progress, the microscopic origin behind the success of such material is still debated, with the role played by the organic cations in the light-harvesting process remaining unclear. Here van der Waals-corrected density functional theory calculations reveal that the orientation of the organic molecules plays a fundamental role in determining the material electronic properties. For instance, if CH3NH3 orients along a (011)-like direction, the PbI6 octahedral cage will distort and the bandgap will become indirect. Our results suggest that molecular rotations, with the consequent dynamical change of the band structure, might be at the origin of the slow carrier recombination and the superior conversion efficiency of CH3NH3PbI3. PMID:25912782

  15. Origin of High Electronic Quality in Solar Cell Absorber CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Yin, Wanjian; Shi, Tingting; Wei, Suhua; Yan, Yanfa

    Thin-film solar cells based on CH3NH3PbI3 halide perovskites have recently shown remarkable performance. First-principle calculations and molecular dynamic simulations show that the structure of pristine CH3NH3PbI3 is much more disordered than the inorganic archetypal thin-film semiconductor CdTe. However, the structural disorders from thermal fluctuation, point defects and grain boundaries introduce rare deep defect states within the bandgaps; therefore, the material has high electronic quality. We have further shown that this unusually high electronic quality is attributed to the unique electronic structures of halide perovskite: the strong coupling between cation lone-pair Pb s orbitals and anion p orbitals and the large atomic size of constitute cation atoms. We further found that although CH3NH3PbI3 GBs do not introduce a deep gap state, the defect level close to the VBM can still act as a shallow hole trap state. Cl and O can spontaneously segregate into GBs and passivate those defect levels and deactivate the trap state.

  16. Inkjet-Printed Photodetector Arrays Based on Hybrid Perovskite CH3NH3PbI3 Microwires.

    PubMed

    Liu, Yang; Li, Fushan; Perumal Veeramalai, Chandrasekar; Chen, Wei; Guo, Tailiang; Wu, Chaoxing; Kim, Tae Whan

    2017-04-05

    Hybrid perovskite CH3NH3PbI3 has attracted extensive research interests in optoelectronic devices in recent years. Herein an inkjet printing method has been employed to deposit a perovskite CH3NH3PbI3 layer. By choosing the proper solvent and controlling the crystal growth rate, hybrid perovskite CH3NH3PbI3 nanowires, microwires, a network, and islands were synthesized by means of inkjet printing. Electrode-gap-electrode lateral-structured photodetectors were fabricated with these different crystals, of which a hybrid perovskite microwire-based photodetector would balance the uniformity and low defects to obtain a switching ratio of 16000%, responsivity of 1.2 A/W, and normalized detectivity of 2.39 × 10(12) Jones at a light power density of 0.1 mW/cm(2). Furthermore, the hybrid perovskite microwire-based photodetector arrays were fabricated and applied in an imaging sensor, from which the clear mapping of the light source signal was successfully obtained. This work paves the way for the realization of low-cost, solution-processed, and high-performance hybrid perovskite-based photodetector arrays.

  17. Termination Dependence of Tetragonal CH3NH3PbI3 Surfaces for Perovskite Solar Cells.

    PubMed

    Haruyama, Jun; Sodeyama, Keitaro; Han, Liyuan; Tateyama, Yoshitaka

    2014-08-21

    We investigated the termination dependence of structural stability and electronic states of the representative (110), (001), (100), and (101) surfaces of tetragonal CH3NH3PbI3 (MAPbI3), the main component of a perovskite solar cell (PSC), by density functional theory calculations. By examining various types of PbIx polyhedron terminations, we found that a vacant termination is more stable than flat termination on all of the surfaces, under thermodynamic equilibrium conditions of bulk MAPbI3. More interestingly, both terminations can coexist especially on the more probable (110) and (001) surfaces. The electronic structures of the stable vacant and PbI2-rich flat terminations on these two surfaces largely maintain the characteristics of bulk MAPbI3 without midgap states. Thus, these surfaces can contribute to the long carrier lifetime actually observed for the PSCs. Furthermore, the shallow surface states on the (110) and (001) flat terminations can be efficient intermediates of hole transfer. Consequently, the formation of the flat terminations under the PbI2-rich condition will be beneficial for the improvement of PSC performance.

  18. Study of Relaxation Dynamics in Mixed Iodide Doped Silver-Vanado-Borate Superionic Glass System

    NASA Astrophysics Data System (ADS)

    Sharma, Poonam; Kanchan, D. K.; Pant, Meenakshi; Gondaliya, Nirali; Jayswal, Manish S.

    2011-07-01

    Electrical conductivity and impedance measurements were carried out for a new mixed metal iodide salt doped silver vanado-borate i.e., [(PbI2-CuI)-Ag2O-V2O5-B2O3] super-ionic glass system. The impedance plots (Z″ vs. Z') for all the prepared glass samples were recorded and found to exhibit depressed semi circles over the studied temperature range. Frequency dependence of the imaginary part of impedance Z″ and the imaginary part of modulus M″ at different temperatures were also investigated. Also, relaxation dynamics in framework of modulus formalism has been discussed.

  19. Enhanced performance of Zn(II)-doped lead-acid batteries with electrochemical active carbon in negative mass

    NASA Astrophysics Data System (ADS)

    Xiang, Jiayuan; Hu, Chen; Chen, Liying; Zhang, Dong; Ding, Ping; Chen, Dong; Liu, Hao; Chen, Jian; Wu, Xianzhang; Lai, Xiaokang

    2016-10-01

    The effect and mechanism of Zn(II) on improving the performances of lead-acid cell with electrochemical active carbon (EAC) in negative mass is investigated. The hydrogen evolution of the cell is significantly reduced due to the deposition of Zn on carbon surface and the increased porosity of negative mass. Zn(II) additives can also improve the low-temperature and high-rate capacities of the cell with EAC in negative mass, which ascribes to the formation of Zn on lead and carbon surface that constructs a conductive bridge among the active mass. Under the co-contribution of EAC and Zn(II), the partial-state-of-charge cycle life is greatly prolonged. EAC optimizes the NAM structure and porosity to enhance the charge acceptance and retard the lead sulfate accumulation. Zn(II) additive reduces the hydrogen evolution during charge process and improves the electric conductivity of the negative electrode. The cell with 0.6 wt% EAC and 0.006 wt% ZnO in negative mass exhibits 90% reversible capacity of the initial capacity after 2100 cycles. In contrast, the cell with 0.6 wt% EAC exhibits 84% reversible capacity after 2100 cycles and the control cell with no EAC and Zn(II) exhibits less than 80% reversible capacity after 1350 cycles.

  20. Mn-doped ZnS quantum dot imbedded two-fragment imprinting silica for enhanced room temperature phosphorescence probing of domoic acid.

    PubMed

    Dan, Li; Wang, He-Fang

    2013-05-21

    A novel strategy was presented to construct the enhanced molecularly imprinted polymer (MIP)-based room temperature phosphorescence (RTP) probe by combining the RTP of Mn-doped ZnS quantum dots (Mn-ZnS QDs) and two-fragment imprinting. Two fragments or structurally similar parts of the target analytes were used as the dummy templates. Polyethyleneimine capped Mn-ZnS (PEI-Mn-ZnS) QDs, offering the binding sites to interact with the carboxyl groups of templates, were imbedded into MIPs by the hydrolysis of tetraethoxysilane. The rebinding of the target analytes to their fragments' cavities (recognition sites) modulated the selective aggregation of Mn-ZnS QDs in QDs-MIPs and resulted in the RTP enhancement. This new method was suitable for the selective enhanced RTP detection of nonphosphorescent analytes without any derivatization and inducers. The proposed methodology was applied to construct the high selective enhanced MIP-based RTP probe for domoic acid (DA) detection. The RTP enhancement of two-fragment imprinting silica was about 2 times of one-fragment imprinting silica and 4 times of the nonimprinting silica. The two-fragment imprinting silica exhibited the linear RTP enhancement to DA in the range of 0.25-3.5 μM in buffer and 0.25-1.5 μM in shellfish sample. The precision for 11 replicate detections of 1.25 μM DA was 0.65% (RSD), and the limit of detection was 67 nM in buffer and 2.0 μg g(-1) wet weight (w/w) in shellfish sample.

  1. The efficiency limit of CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Sha, Wei E. I.; Ren, Xingang; Chen, Luzhou; Choy, Wallace C. H.

    2015-06-01

    With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also clarified. The efficiency limit of perovskite cells (without the angular restriction) is about 31%, which approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide (GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200 nm-thick perovskite solar cell, through integrating a wavelength-dependent angular-restriction design with a textured light-trapping structure. Additionally, the influence of the trap-assisted nonradiative recombination on the device efficiency is investigated. The work is fundamentally important to high-performance perovskite photovoltaics.

  2. Modeling the PbI2 formation in perovskite solar cells using XRD/XPS patterns

    NASA Astrophysics Data System (ADS)

    Sohrabpoor, Hamed; Elyasi, Majid; Aldosari, Marouf; Gorji, Nima E.

    2016-09-01

    The impact of prolonged irradiation and air humidity on the stability of perovskite solar cells is modeled using X-ray diffraction and X-ray photoelectron spectroscopy patterns reported in the literature. Light or air-moisture causes the formation of a thin PbI2 or oxide defective layers (in nanoscale) at the interface of perovskite/hole-transport-layer or at the junction with metallic back contact. This thin layer blocks the carrier transport/passivation at the interfaces and cause degradation of device parameters. Variation in thickness of defective layers, changes the XRD and XPS peaks. This allows detection and estimation of the type, crystallinity and thickness of the defective layer. A simple model is developed here to extract the thickness of such thin defective layers formed in nanometer scale at the back region of several perovskite devices. Based on this information, corrected energy band diagram of every device before and after degradation/aging is drawn and discussed in order to obtain insight into the carrier transport and charge collection at the barrier region. In addition, graphene contacted perovskite devices are investigated showing that honey-comb network of graphene contact reduces the effect of aging leading to formation of a thinner defective layer at the perovskite surface compared to perovskite devices with conventional inorganic contacts i.e. Au, Al.

  3. Computed and Experimental Absorption Spectra of the Perovskite CH3NH3PbI3.

    PubMed

    Zhu, Xi; Su, Haibin; Marcus, Rudolph A; Michel-Beyerle, Maria E

    2014-09-04

    Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe-Salpeter equation augmented with the analysis of a conceptual hydrogen-like model. The computed absorption spectrum unravels a remarkable absorption "gap" between the first two absorption peaks. This discontinuity is maintained in the calculated tetragonal structure that, however, is not stable at low temperature. Most importantly, the discontinuity is also observed in the experimental absorption spectrum of the orthorhombic single crystal at low temperature (4 K). However, in contrast to the single crystal, in a polycrystalline perovskite film at 5 K the "gap" is filled by a monotonously increasing absorption throughout the visible range. This feature of thin films points to the potential significance of defect absorption for the excellent light harvesting properties of perovskite-based solar cells.

  4. Ferroelectricity of CH3NH3PbI3 Perovskite.

    PubMed

    Fan, Zhen; Xiao, Juanxiu; Sun, Kuan; Chen, Lei; Hu, Yating; Ouyang, Jianyong; Ong, Khuong P; Zeng, Kaiyang; Wang, John

    2015-04-02

    Ferroelectricity has been believed to be an important but controversial origin of the excellent photovoltaic performance of organometal trihalide perovskites (OTPs). Here we investigate the ferroelectricity of a prototype OTP, CH3NH3PbI3 (MAPbI3), both theoretically and experimentally. Our first-principles calculations based on 3-D periodic boundary conditions reveal that a ferroelectric structure with polarization of ∼8 μC/cm(2) is the globally stable one among all possible tetragonal structures; however, experimentally no room-temperature ferroelectricity is observed by using polarization-electric field hysteresis measurements and piezoresponse force microscopy. The discrepancy between our theoretical and experimental results is attributed to the dynamic orientational disorder of MA(+) groups and the semiconducting nature of MAPbI3 at room temperature. Therefore, we conclude that MAPbI3 is not ferroelectric at room temperature; however, it is possible to induce and experimentally observe apparent ferroelectric behavior through our proposed ways. Our results clarify the controversy of the ferroelectricity in MAPbI3 and also provide valuable guidance for future studies on this active topic.

  5. Negative thermal quenching of below-bandgap photoluminescence in InPBi

    NASA Astrophysics Data System (ADS)

    Chen, Xiren; Wu, Xiaoyan; Yue, Li; Zhu, Liangqing; Pan, Wenwu; Qi, Zhen; Wang, Shumin; Shao, Jun

    2017-01-01

    This paper reports a temperature-dependent (10-280 K) photoluminescence (PL) study of below-bandgap electron-hole recombinations and anomalous negative thermal quenching of PL intensity in InP1-xBix (x = 0.019 and 0.023). Four PL features are well resolved by curve-fitting of the PL spectra, of which the energies exhibit different temperature dependence. The integral intensities of the two high-energy features diminish monotonically as temperature rises up, while those of the two low-energy features decrease below but increase anomalously above 180 K. A phenomenological model is established that the residual electrons in the final state of the PL transition transfer into nonradiative state via thermal hopping, and the thermal hopping produces in parallel holes in the final state and hence enhances the radiative recombination significantly. A reasonable interpretation of the PL processes in InPBi is achieved, and the activation energies of the PL quenching and thermal hopping are deduced.

  6. Insight into the CH3NH3PbI3/C interface in hole-conductor-free mesoscopic perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Li, Jiangwei; Niu, Guangda; Li, Wenzhe; Cao, Kun; Wang, Mingkui; Wang, Liduo

    2016-07-01

    Perovskite solar cells (PSCs) with hole-conductor-free mesoscopic architecture have shown superb stability and great potential in practical application. The printable carbon counter electrodes take full responsibility of extracting holes from the active CH3NH3PbI3 absorbers. However, an in depth study of the CH3NH3PbI3/C interface properties, such as the structural formation process and the effect of interfacial conditions on hole extraction, is still lacking. Herein, we present, for the first time, an insight into the spatial confinement induced CH3NH3PbI3/C interface formation by in situ photoluminescence observations during the crystallization process of CH3NH3PbI3. The derived reaction kinetics allows a quantitative description of the perovskite formation process. In addition, we found that the interfacial contact between carbon and perovskite was dominant for hole extraction efficiency and associated with the photovoltaic parameter of short circuit current density (JSC). Consequently, we conducted a solvent vapor assisted process of PbI2 diffusion to carefully control the CH3NH3PbI3/C interface with less unreacted PbI2 barrier. The improvement of interface conditions thereby contributes to a high hole extraction proved by the charge extraction resistance and PL lifetime change, resulting in the increased JSC valve.Perovskite solar cells (PSCs) with hole-conductor-free mesoscopic architecture have shown superb stability and great potential in practical application. The printable carbon counter electrodes take full responsibility of extracting holes from the active CH3NH3PbI3 absorbers. However, an in depth study of the CH3NH3PbI3/C interface properties, such as the structural formation process and the effect of interfacial conditions on hole extraction, is still lacking. Herein, we present, for the first time, an insight into the spatial confinement induced CH3NH3PbI3/C interface formation by in situ photoluminescence observations during the crystallization

  7. MOVPE growth of Ga(PBi) on GaP and GaP on Si with Bi fractions up to 8%

    NASA Astrophysics Data System (ADS)

    Nattermann, L.; Beyer, A.; Ludewig, P.; Hepp, T.; Sterzer, E.; Volz, K.

    2017-04-01

    Dilute bismide containing materials can play an important role in addressing the issue of finding new highly efficient lasers for telecommunications as well as sensing applications. In the last several years a growing body of literature has emerged, particularly on the growth of Ga(AsBi). However, the metal organic vapor phase epitaxy growth of Ga(AsBi) with high amounts of Bi, which are necessary to overcome Auger recombination and reach telecommunications wavelengths, still remains a challenge. Ga(PBi) could be a promising alternative, but has not been deposited with significant amounts of Bi so far. A second argument for Ga(PBi) is that it could be grown on GaP, which was already deposited on Si. A number of researchers have reported theoretical calculations on the band structure of Ga(PBi), but experimental results are still lacking. In this work we present the first Ga(PBi) structures, grown by metal organic vapor phase epitaxy on GaP and on GaP on Si. By careful characterization with high resolution X-ray diffraction, atomic force microscopy, secondary ion mass spectrometry and scanning transmission electron microscopy, we will show that we have realized high quality Ga(PBi) with Bi fractions over 8%.

  8. All solid-state solar cells based on CH3NH3PbI3-sensitized TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Yang, Xiuchun; Liu, Wei; Ren, Peng

    2016-09-01

    TiO2 nanotube arrays (TiO2 NTAs) were firstly used as photoanode in methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 NTAs heterojunction solar cell, where CH3NH3PbI3 functions as both light absorber and hole conductor. The composition, structure and photoelectrochemical properties of the as-prepared samples were characterized by x-ray diffractometer (XRD), field-emission scanning electron microscope (FE-SEM), ultraviolet-visible (UV-vis) spectrophotometer and electrochemical workstation. The results indicate that the as-prepared CH3NH3PbI3 belongs to the cubic crystal system, and TiO2 NTAs sensitized by 0.3 M CH3NH3I and PbI2 exhibit the best photoelectrochemical properties with an open-circuit voltage of 0.422 V and a short-circuit current density of 173.4 μA cm-2. The EIS result shows that the extremely large resistance at CH3NH3PbI3/FTO interface contributes to the low current density of the perovskite solar cell.

  9. Charge transport in bulk CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

    Slonopas, Andre; Foley, Benjamin J.; Choi, Joshua J.; Gupta, Mool C.

    2016-02-01

    The variation of leakage current and polarization hysteresis properties for bulk CH3NH3PbI3 perovskite was studied as a function of temperature to understand the reported hysteresis in photocurrent and the role of ferroelectricity. The leakage current decreased by two orders of magnitude when the temperature was lowered from 350 K to 100 K. The transitions in leakage current were observed at structural phase transition temperatures. The temperature dependence study allowed the identification of current conduction mechanism based on various models for ferroelectrics and insulating materials. Our results show that the leakage current is governed by the space charge limited conduction mechanism which should be considered in addition to ion conduction and ferroelectricity when analyzing current-voltage hysteresis for thin film and bulk materials. The Mott's variable range hopping model fits well to the experimental data indicating the charge conduction is through hopping mechanism from 300 K to 160 K and possibly tunneling below 160 K. The conclusions from polarization hysteresis study are: (1) the hysteresis loop shape is highly dependent upon frequency and show non-saturating behavior, an indicative of strong non-ferroelectric contributions such as resistive component. (2) No domain switching current was observed between the temperature range of 100 K-350 K. (3) An electric field off-set was observed in polarization-electric field curves and it was dependent upon the frequency and temperature. This offset could be caused by the accumulation of vacancies at one interface, which could give rise to hysteresis in forward and reverse bias photocurrent. (4) The time dependence study of instantaneous current as the voltage was increased linearly show strong resistive contribution to hysteresis loop at temperatures above 200 K and capacitive contribution at 100 K.

  10. Ultrabroad Photoluminescence and Electroluminescence at New Wavelengths from Doped Organometal Halide Perovskites.

    PubMed

    Zhou, Yang; Yong, Zi-Jun; Zhang, Kai-Cheng; Liu, Bo-Mei; Wang, Zhao-Wei; Hou, Jing-Shan; Fang, Yong-Zheng; Zhou, Yi; Sun, Hong-Tao; Song, Bo

    2016-07-21

    Doping of semiconductors by introducing foreign atoms enables their widespread applications in microelectronics and optoelectronics. We show that this strategy can be applied to direct bandgap lead-halide perovskites, leading to the realization of ultrawide photoluminescence (PL) at new wavelengths enabled by doping bismuth (Bi) into lead-halide perovskites. Structural and photophysical characterization reveals that the PL stems from one class of Bi doping-induced optically active center, which is attributed to distorted [PbI6] units coupled with spatially localized bipolarons. Additionally, we find that compositional engineering of these semiconductors can be employed as an additional way to rationally tune the PL properties of doped perovskites. Finally, we accomplished the electroluminescence at cryogenic temperatures by using this system as an emissive layer, marking the first electrically driven devices using Bi-doped photonic materials. Our results suggest that low-cost, earth-abundant, solution-processable Bi-doped perovskite semiconductors could be promising candidate materials for developing optical sources operating at new wavelengths.

  11. Enhanced electronic properties in mesoporous TiO2 via lithium doping for high-efficiency perovskite solar cells

    PubMed Central

    Giordano, Fabrizio; Abate, Antonio; Correa Baena, Juan Pablo; Saliba, Michael; Matsui, Taisuke; Im, Sang Hyuk; Zakeeruddin, Shaik M.; Nazeeruddin, Mohammad Khaja; Hagfeldt, Anders; Graetzel, Michael

    2016-01-01

    Perovskite solar cells are one of the most promising photovoltaic technologies with their extraordinary progress in efficiency and the simple processes required to produce them. However, the frequent presence of a pronounced hysteresis in the current voltage characteristic of these devices arises concerns on the intrinsic stability of organo-metal halides, challenging the reliability of technology itself. Here, we show that n-doping of mesoporous TiO2 is accomplished by facile post treatment of the films with lithium salts. We demonstrate that the Li-doped TiO2 electrodes exhibit superior electronic properties, by reducing electronic trap states enabling faster electron transport. Perovskite solar cells prepared using the Li-doped films as scaffold to host the CH3NH3PbI3 light harvester produce substantially higher performances compared with undoped electrodes, improving the power conversion efficiency from 17 to over 19% with negligible hysteretic behaviour (lower than 0.3%). PMID:26758549

  12. Enhanced electrical property of Ni-doped CoOx hole transport layer for inverted perovskite solar cells.

    PubMed

    Huang, Aibin; Yu, Yu; Liu, Yan; Yang, Songwang; Lei, Lei; Bao, Shanhu; Cao, Xun; Jin, Ping

    2017-03-15

    Ultrathin Ni doped CoOx (Ni:CoOx) films were demonstrated by direct current (DC) co-sputtering at room temperature and employed as inorganic hole transport materials for inverted perovskite solar cells. P-type Ni2+ doping introduced in this work was designed to adjust the valence band position of CoOx to match the highest occupied molecular orbital of perovskite absorber material (CH3NH3PbI3), which would effectively inhibit recombination of photo-induced electrons and holes. Moreover, the hole extraction capacity would be further enhanced as a result of the appropriate Ni2+ doping, and hence the power conversion efficiency (PCE) of the devices increased from 3.68% to 9.60%. The optimized performance was also accompanied by decent stability as a result of its intrinsic stability and conductivity.

  13. Mechanical signatures of degradation of the photovoltaic perovskite CH3NH3PbI3 upon water vapor exposure

    NASA Astrophysics Data System (ADS)

    Spina, Massimo; Karimi, Ayat; Andreoni, Wanda; Pignedoli, Carlo A.; Náfrádi, Bálint; Forró, László; Horváth, Endre

    2017-03-01

    We report on the mechanical properties of CH3NH3PbI3 photovoltaic perovskite measured by nanoindentation. The Young's modulus (E) of the pristine sample is 20.0 ± 1.5 GPa, while the hardness (H) is 1.0 ± 0.1 GPa. Upon extended exposure to water vapor, both quantities decrease dramatically and the sample changes color from silver-black to yellow. Calculations based on density functional theory support this trend in the mechanical response. Chemical treatment of the degraded crystal in methylammonium iodide solution recovers the color of the pristine sample and the values of E and H within 50%.

  14. Nano metal-enhanced power conversion efficiency in CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Yu, Jing; Zhang, Chao; Yang, Siyu; Chen, Meina; Lei, Fengcai; Man, Baoyuan

    2017-04-01

    Nano metal-enhanced power conversion efficiency (PCE) in CH3NH3PbI3 solar cells utilizing the forward scattering effect of metal nanoparticles has been researched in this paper by finite difference time domain method. Two structures are designed in the research to explore this feasibility, by adjusting the materials, sizes and surface coverages of metal nanoparticles, both of them exhibit the exciting results bringing the max PCE enhancements by 12.18% and 8.03% respectively. Especially, considering the huge handleability of the second structure, this method has large applications in further improving the performance for other perovskite solar cells.

  15. Diffusion length of photo-generated charge carriers in layers and powders of CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

    Dittrich, Th.; Lang, F.; Shargaieva, O.; Rappich, J.; Nickel, N. H.; Unger, E.; Rech, B.

    2016-08-01

    The diffusion or transport lengths of photo-generated charge carriers in CH3NH3PbI3 layers (thickness up to 1 μm) and powders have been directly measured with high accuracy by modulated surface photovoltage after Goodman. The values of the diffusion lengths of photo-generated charge carriers ranged from 200 nm to tenths of μm. In thin CH3NH3PbI3 layers, the transport lengths corresponded to the layer thickness whereas in thicker layers and in crystallites of CH3NH3PbI3 powders the grain size limited the diffusion length. For grains, the diffusion length of photo-generated charge carriers depended on the measurement conditions.

  16. Inkjet printing and instant chemical transformation of a CH3NH3PbI3/nanocarbon electrode and interface for planar perovskite solar cells.

    PubMed

    Wei, Zhanhua; Chen, Haining; Yan, Keyou; Yang, Shihe

    2014-11-24

    A planar perovskite solar cell that incorporates a nanocarbon hole-extraction layer is demonstrated for the first time by an inkjet printing technique with a precisely controlled pattern and interface. By designing the carbon plus CH3NH3I ink to transform PbI2 in situ to CH3NH3PbI3, an interpenetrating seamless interface between the CH3NH3PbI3 active layer and the carbon hole-extraction electrode was instantly constructed, with a markedly reduced charge recombination compared to that with the carbon ink alone. As a result, a considerably higher power conversion efficiency up to 11.60% was delivered by the corresponding solar cell. This method provides a major step towards the fabrication of low-cost, large-scale, metal-electrode-free but still highly efficient perovskite solar cells.

  17. Electroluminescence from perovskite LEDs with the structure of Ag/Spiro-OMeTAD/CH3NH3PbI3/TiO2/FTO

    NASA Astrophysics Data System (ADS)

    Wang, Minhuan; Shi, Yantao; Bian, Jiming; Dong, Qingshun; Sun, Hongjun; Liu, Hongzhu; Luo, Yingmin; Zhang, Yuzhi

    2016-10-01

    The perovskite light-emitting diodes (Pe-LEDs) with the structure of Ag/Spiro-OMeTAD/CH3NH3PbI3/TiO2/FTO were synthesized, where the CH3NH3PbI3 perovskite layer was deposited by a two-step spin-coating process. A dominant near-infrared electroluminescence (EL) at 773 nm was detected from the Pe-LEDs under forward bias at room temperature. The origin and mechanism of the EL were discussed in comparison with the photoluminescence (PL) spectra, and it was attributed to the radiative recombination of electrons and holes confined in the CH3NH3PbI3 emissive layer. Moreover, the corresponding energy band diagrams was proposed to illustrate the carrier transport mechanism in the Pe-LED device.

  18. Highly doped silicon nanowires by monolayer doping.

    PubMed

    Veerbeek, Janneke; Ye, Liang; Vijselaar, Wouter; Kudernac, Tibor; van der Wiel, Wilfred G; Huskens, Jurriaan

    2017-02-23

    Controlling the doping concentration of silicon nanostructures is challenging. Here, we investigated three different monolayer doping techniques to obtain silicon nanowires with a high doping dose. These routes were based on conventional monolayer doping, starting from covalently bound dopant-containing molecules, or on monolayer contact doping, in which a source substrate coated with a monolayer of a carborane silane was the dopant source. As a third route, both techniques were combined to retain the benefits of conformal monolayer formation and the use of an external capping layer. These routes were used for doping fragile porous nanowires fabricated by metal-assisted chemical etching. Differences in porosity were used to tune the total doping dose inside the nanowires, as measured by X-ray photoelectron spectroscopy and secondary ion mass spectrometry measurements. The higher the porosity, the higher was the surface available for dopant-containing molecules, which in turn led to a higher doping dose. Slightly porous nanowires could be doped via all three routes, which resulted in highly doped nanowires with (projected areal) doping doses of 10(14)-10(15) boron atoms per cm(2) compared to 10(12) atoms per cm(2) for a non-porous planar sample. Highly porous nanowires were not compatible with the conventional monolayer doping technique, but monolayer contact doping and the combined route resulted for these highly porous nanowires in tremendously high doping doses up to 10(17) boron atoms per cm(2).

  19. Dielectric and Thermodynamic Signatures of Low-Temperature Glassy Dynamics in the Hybrid Perovskites CH3NH3PbI3 and HC(NH2)2PbI3.

    PubMed

    Fabini, Douglas H; Hogan, Tom; Evans, Hayden A; Stoumpos, Constantinos C; Kanatzidis, Mercouri G; Seshadri, Ram

    2016-02-04

    Hybrid main group halide perovskites hold great technological promise in optoelectronic applications and present rich and complex evolution of structure and dynamics. Here we present low-temperature dielectric measurements and calorimetry of APbI3 [A = CH3NH3(+), HC(NH2)2(+)] that suggest glassy behavior on cooling. In both compounds, the dielectric loss displays frequency-dependent peaks below 100 K characteristic of a glassy slowing of relaxation dynamics, with HC(NH2)2PbI3 exhibiting greater glass fragility. Consistent with quenched disorder, the low-temperature heat capacity of both perovskites deviates substantially from the ∼T(3) acoustic phonon contribution predicted by the Debye model. We suggest that static disorder of the A-site molecular cation, potentially coupled to local distortions of the Pb-I sublattice, is responsible for these phenomena. The distinct low-temperature dynamics observed in these two perovskites suggest qualitative differences in the interaction between the molecular cation and the surrounding inorganic framework, with potential implications for defect screening and device performance at ambient temperatures.

  20. Bulk intermixing-type perovskite CH3NH3PbI3/TiO2 nanorod hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Li, Shao-Sian; Wang, Ying-Chiao; Tsai, Chin-Ming; Wen, Cheng-Yen; Yu, Chia-Hao; Yang, Yu-Pei; Lin, Jou-Chun; Wang, Di-Yan; Chen, Chia-Chun; Yeh, Yun-Chieh; Chen, Chun-Wei

    2015-08-01

    To replace high-temperature sintered scaffold materials in conventional CH3NH3PbI3-based solar cells, this study demonstrates a new device structure of a bulk intermixing (BI)-type CH3NH3PbI3/TiO2 nanorod (NR) hybrid solar cell, where dispersed TiO2 NRs from chemical synthesis are intermixed with the perovskite absorbing layer to form a BI-type perovskite/TiO2 NR hybrid for device fabrication. Through interface engineering between the TiO2 NR surface and the photoactive perovskite material of CH3NH3PbI3 by ligand exchange treatment, a remarkable power conversion efficiency (PCE) of over 12% was achieved based on the simple BI-type CH3NH3PbI3/TiO2 NR hybrid device structure. The proposed hybrids not only provide great flexibility for deposition on various substrates through spin coating at low temperatures but also enable layer-by-layer deposition for the future development of perovskite-based multi-junction solar cells.To replace high-temperature sintered scaffold materials in conventional CH3NH3PbI3-based solar cells, this study demonstrates a new device structure of a bulk intermixing (BI)-type CH3NH3PbI3/TiO2 nanorod (NR) hybrid solar cell, where dispersed TiO2 NRs from chemical synthesis are intermixed with the perovskite absorbing layer to form a BI-type perovskite/TiO2 NR hybrid for device fabrication. Through interface engineering between the TiO2 NR surface and the photoactive perovskite material of CH3NH3PbI3 by ligand exchange treatment, a remarkable power conversion efficiency (PCE) of over 12% was achieved based on the simple BI-type CH3NH3PbI3/TiO2 NR hybrid device structure. The proposed hybrids not only provide great flexibility for deposition on various substrates through spin coating at low temperatures but also enable layer-by-layer deposition for the future development of perovskite-based multi-junction solar cells. Electronic supplementary information (ESI) available: TiO2 synthesis and ligand exchange process, device fabrication and

  1. Electrical field profile and doping in planar lead halide perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Guerrero, Antonio; Juarez-Perez, Emilio J.; Bisquert, Juan; Mora-Sero, Ivan; Garcia-Belmonte, Germà

    2014-09-01

    Hybrid lead halide perovskites (PVKs) have emerged as novel materials for photovoltaics and have rapidly reached very large solar to electricity power conversion efficiencies. As occurring with other kind of solar technologies establishing the working energy-band diagram constitutes a primary goal for device physics analysis. Here, the macroscopic electrical field distribution is experimentally determined using capacitance-voltage and Kelvin probe techniques. Planar structures comprising CH3NH3PbI3-xClx PVK exhibit p-doping character and form a p-n heterojunction with n-doped TiO2 compact layers. Depletion width at equilibrium within the PVK bulk has an extent about 300 nm (approximately half of the layer thickness), leaving as a consequence a significant neutral zone towards the anode contact. Charge collection properties are then accessible relying on the relative weight that diffusion and drift have as carrier transport driven forces.

  2. Gene doping.

    PubMed

    Azzazy, Hassan M E

    2010-01-01

    Gene doping abuses the legitimate approach of gene therapy. While gene therapy aims to correct genetic disorders by introducing a foreign gene to replace an existing faulty one or by manipulating existing gene(s) to achieve a therapeutic benefit, gene doping employs the same concepts to bestow performance advantages on athletes over their competitors. Recent developments in genetic engineering have contributed significantly to the progress of gene therapy research and currently numerous clinical trials are underway. Some athletes and their staff are probably watching this progress closely. Any gene that plays a role in muscle development, oxygen delivery to tissues, neuromuscular coordination, or even pain control is considered a candidate for gene dopers. Unfortunately, detecting gene doping is technically very difficult because the transgenic proteins expressed by the introduced genes are similar to their endogenous counterparts. Researchers today are racing the clock because assuring the continued integrity of sports competition depends on their ability to develop effective detection strategies in preparation for the 2012 Olympics, which may mark the appearance of genetically modified athletes.

  3. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    DOE PAGES

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G.; ...

    2014-12-19

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms,more » which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.« less

  4. Formation Dynamics of CH3NH3PbI3 Perovskite Following Two-Step Layer Deposition.

    PubMed

    Patel, Jay B; Milot, Rebecca L; Wright, Adam D; Herz, Laura M; Johnston, Michael B

    2016-01-07

    Hybrid metal-halide perovskites have emerged as a leading class of semiconductors for optoelectronic devices because of their desirable material properties and versatile fabrication methods. However, little is known about the chemical transformations that occur in the initial stages of perovskite crystal formation. Here we follow the real-time formation dynamics of MAPbI3 from a bilayer of lead iodide (PbI2) and methylammonium iodide (MAI) deposited through a two-step thermal evaporation process. By lowering the substrate temperature during deposition, we are able to initially inhibit intermixing of the two layers. We subsequently use infrared and visible light transmission, X-ray diffraction, and photoluminescence lifetime measurements to reveal the room-temperature transformations that occur in vacuum and ambient air, as MAI diffuses into the PbI2 lattice to form MAPbI3. In vacuum, the transformation to MAPbI3 is incomplete as unreacted MAI is retained in the film. However, exposure to moist air allows for conversion of the unreacted MAI to MAPbI3, demonstrating that moisture is essential in making MAI more mobile and thus aiding perovskite crystallization. These dynamic processes are reflected in the observed charge-carrier lifetimes, which strongly fluctuate during periods of large ion migration but steadily increase with improving crystallinity.

  5. Preclinical Justification of pbi-shRNA EWS/FLI1 Lipoplex (LPX) Treatment for Ewing's Sarcoma

    PubMed Central

    Rao, Donald D.; Jay, Christopher; Wang, Zhaohui; Luo, Xiuquan; Kumar, Padmasini; Eysenbach, Hilary; Ghisoli, Maurizio; Senzer, Neil; Nemunaitis, John

    2016-01-01

    The EWS/FLI1 fusion gene is well characterized as a driver of Ewing's sarcoma. Bi-shRNA EWS/FLI1 is a functional plasmid DNA construct that transcribes both siRNA and miRNA-like effectors each of which targets the identical type 1 translocation junction region of the EWS/FLI1 transcribed mRNA sequence. Previous preclinical and clinical studies confirm the safety of this RNA interference platform technology and consistently demonstrate designated mRNA and protein target knockdown at greater than 90% efficiency. We initiated development of pbi-shRNA EWS/FLI1 lipoplex (LPX) for the treatment of type 1 Ewing's sarcoma. Clinical-grade plasmid was manufactured and both sequence and activity verified. Target protein and RNA knockdown of 85–92% was demonstrated in vitro in type 1 human Ewing's sarcoma tumor cell lines with the optimal bi-shRNA EWS/FLI1 plasmid. This functional plasmid was placed in a clinically tested, liposomal (LP) delivery vehicle followed by in vivo verification of activity. Type 1 Ewing's sarcoma xenograft modeling confirmed dose related safety and tumor response to pbi-shRNA EWS/FLI1 LPX. Toxicology studies in mini-pigs with doses comparable to the demonstrated in vivo efficacy dose resulted in transient fever, occasional limited hypertension at low- and high-dose assessment and transient liver enzyme elevation at high dose. These results provide the justification to initiate clinical testing. PMID:27166877

  6. Dynamic Growth of Pinhole-Free Conformal CH3NH3PbI3 Film for Perovskite Solar Cells.

    PubMed

    Li, Bo; Tian, Jianjun; Guo, Lixue; Fei, Chengbin; Shen, Ting; Qu, Xuanhui; Cao, Guozhong

    2016-02-01

    Two-step dipping is one of the popular low temperature solution methods to prepare organic-inorganic halide perovskite (CH3NH3PbI3) films for solar cells. However, pinholes in perovskite films fabricated by the static growth method (SGM) result in low power conversion efficiency (PCE) in the resulting solar cells. In this work, the static dipping process is changed into a dynamic dipping process by controlled stirring PbI2 substrates in CH3NH3I isopropanol solution. The dynamic growth method (DGM) produces more nuclei and decreases the pinholes during the nucleation and growth of perovskite crystals. The compact perovskite films with free pinholes are obtained by DGM, which present that the big perovskite particles with a size of 350 nm are surrounded by small perovskite particles with a size of 50 nm. The surface coverage of the perovskite film is up to nearly 100%. Such high quality perovskite film not only eliminated pinholes, resulting in reduced charge recombination of the solar cells, but also improves the light harvesting efficiency. As a result, the PCE of the perovskite solar cells is increased from 11% for SGM to 13% for DGM.

  7. Multiple-stage structure transformation of organic-inorganic hybrid perovskite CH3NH3PbI3

    DOE PAGES

    Chen, Qiong; Liu, Henan; Kim, Hui -Seon; ...

    2016-09-15

    In this study, by performing spatially resolved Raman and photoluminescence spectroscopy with varying excitation wavelength, density, and data acquisition parameters, we achieve a unified understanding towards the spectroscopy signatures of the organic-inorganic hybrid perovskite, transforming from the pristine state (CH3NH3PbI3) to the fully degraded state (i.e., PbI2) for samples with varying crystalline domain size from mesoscopic scale (approximately 100 nm) to macroscopic size (centimeters), synthesized by three different techniques. We show that the hybrid perovskite exhibits multiple stages of structure transformation occurring either spontaneously or under light illumination, with exceptionally high sensitivity to the illumination conditions (e.g., power, illumination time,more » and interruption pattern). We highlight four transformation stages (stages I-IV, with stage I being the pristine state) along either the spontaneous or photoinduced degradation path exhibiting distinctly different Raman spectroscopy features at each stage, and point out that previously reported Raman spectra in the literature reflect highly degraded structures of either stage III or stage IV. Additional characteristic optical features of partially degraded materials under the joint action of spontaneous and photodegradation are also given. This study offers reliable benchmark results for understanding the intrinsic material properties and structure transformation of this unique category of hybrid materials, and the findings are pertinently important to a wide range of potential applications where the hybrid material is expected to function in greatly different environment and light-matter interaction conditions.« less

  8. Vibrational energies and full analytic potential energy functions of PbI and InI from pure microwave data

    NASA Astrophysics Data System (ADS)

    Yoo, Ji Ho; Köckert, Hansjochen; Mullaney, John C.; Stephens, Susanna L.; Evans, Corey J.; Walker, Nicholas R.; Le Roy, Robert. J.

    2016-12-01

    Pure rotational spectra of PbI and InI are interpreted to yield a full analytic potential energy function for each molecule. Rotational spectra for PbI have been retrieved from literature sources to perform the analysis. Rotational transition frequencies for excited vibrational states of InI (0 < v < 11) are measured during this work. Ignoring hyperfine splittings, Bv and Dv values are used to generate a set of "synthetic" pure R (0) transitions for each vibrational level. These are then fitted to an "Expanded Morse Oscillator" (EMO) potential using the direct-potential-fit program, dPOTFIT. The well-depth parameter, De , is fixed at a literature value, while values of the equilibrium distance re and EMO exponent-coefficient expansion (potential-shape) parameters are determined from the fits. Comparison with potential functions determined after including older mid-IR and visible electronic transition data shows that our analysis of the pure microwave data alone yields potential energy functions that accurately predict (to better than 1%) the overtone vibrational energies far beyond the range spanned by the levels for which the microwave data is available.

  9. The pure rotational spectra of the open-shell diatomic molecules PbI and SnI

    SciTech Connect

    Evans, Corey J. E-mail: nick.walker@newcastle.ac.uk; Needham, Lisa-Maria E.; Walker, Nicholas R. E-mail: nick.walker@newcastle.ac.uk; Köckert, Hansjochen; Zaleski, Daniel P.; Stephens, Susanna L.

    2015-12-28

    Pure rotational spectra of the ground electronic states of lead monoiodide and tin monoiodide have been measured using a chirped pulsed Fourier transform microwave spectrometer over the 7-18.5 GHz region for the first time. Each of PbI and SnI has a X {sup 2}Π{sub 1/2} ground electronic state and may have a hyperfine structure that aids the determination of the electron electric dipole moment. For each species, pure rotational transitions of a number of different isotopologues and their excited vibrational states have been assigned and fitted. A multi-isotopologue Dunham-type analysis was carried out on both species producing values for Y{sub 01}, Y{sub 02}, Y{sub 11}, and Y{sub 21}, along with Λ-doubling constants, magnetic hyperfine constants and nuclear quadrupole coupling constants. The Born-Oppenheimer breakdown parameters for Pb have been evaluated and the parameter rationalized in terms of finite nuclear field effects. Analysis of the bond lengths and hyperfine interaction indicates that the bonding in both PbI and SnI is ionic in nature. Equilibrium bond lengths have been evaluated for both species.

  10. Depletion region effect of highly efficient hole conductor free CH3NH3PbI3 perovskite solar cells.

    PubMed

    Aharon, Sigalit; Gamliel, Shany; El Cohen, Bat; Etgar, Lioz

    2014-06-14

    The inorganic-organic perovskite is currently attracting a lot of attention due to its use as a light harvester in solar cells. The large absorption coefficients, high carrier mobility and good stability of organo-lead halide perovskites present good potential for their use as light harvesters in mesoscopic heterojunction solar cells. This work concentrated on a unique property of the lead halide perovskite, its function simultaneously as a light harvester and a hole conductor in the solar cell. A two-step deposition technique was used to optimize the perovskite deposition and to enhance the solar cell efficiency. It was revealed that the photovoltaic performance of the hole conductor free perovskite solar cell is strongly dependent on the depletion layer width which was created at the TiO2-CH3NH3PbI3 junction. X-ray diffraction measurements indicate that there were no changes in the crystallographic structure of the CH3NH3PbI3 perovskite over time, which supports the high stability of these hole conductor free perovskite solar cells. Furthermore, the power conversion efficiency of the best cells reached 10.85% with a fill factor of 68%, a Voc of 0.84 V, and a Jsc of 19 mA cm(-2), the highest efficiency to date of a hole conductor free perovskite solar cell.

  11. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    SciTech Connect

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G.; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2014-12-19

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms, which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.

  12. Understanding ground- and excited-state properties of perylene tetracarboxylic acid bisimide crystals by means of quantum chemical computations.

    PubMed

    Zhao, Hong-Mei; Pfister, Johannes; Settels, Volker; Renz, Manuel; Kaupp, Martin; Dehm, Volker C; Würthner, Frank; Fink, Reinhold F; Engels, Bernd

    2009-11-04

    Quantum chemical protocols explaining the crystal structures and the visible light absorption properties of 3,4:9,10-perylene tetracarboxylic acid bisimide (PBI) derivates are proposed. Dispersion-corrected density functional theory has provided an intermolecular potential energy of PBI dimers showing several energetically low-lying minima, which corresponds well with the packing of different PBI dyes in the solid state. While the dispersion interaction is found to be crucial for the binding strength, the minimum structures of the PESs are best explained by electrostatic interactions. Furthermore, a method is introduced, which reproduces the photon energies at the absorption maxima of PBI pigments within 0.1 eV. It is based on time-dependent Hartree-Fock (TD-HF) excitation energies calculated for PBI dimers with the next-neighbor arrangement in the pigment and incorporates crystal packing effects. This success provides clear evidence that the electronically excited states, which determine the color of these pigments, have no significant charge-transfer character. The developed protocols can be applied in a routine manner to understand and to predict the properties of such pigments, which are important materials for organic solar cells and (opto-)electronic devices.

  13. High-performance perovskite CH3NH3PbI3 thin films for solar cells prepared by single-source physical vapour deposition

    NASA Astrophysics Data System (ADS)

    Fan, Ping; Gu, Di; Liang, Guang-Xing; Luo, Jing-Ting; Chen, Ju-Long; Zheng, Zhuang-Hao; Zhang, Dong-Ping

    2016-07-01

    In this work, an alternative route to fabricating high-quality CH3NH3PbI3 thin films is proposed. Single-source physical vapour deposition (SSPVD) without a post-heat-treating process was used to prepare CH3NH3PbI3 thin films at room temperature. This new process enabled complete surface coverage and moisture stability in a non-vacuum solution. Moreover, the challenges of simultaneously controlling evaporation processes of the organic and inorganic sources via dual-source vapour evaporation and the heating process required to obtain high crystallization were avoided. Excellent composition with stoichiometry transferred from the powder material, a high level of tetragonal phase-purity, full surface coverage, well-defined grain structure, high crystallization and reproducibility were obtained. A PCE of approximately 10.90% was obtained with a device based on SSPVD CH3NH3PbI3. These initial results suggest that SSPVD is a promising method to significantly optimize perovskite CH3NH3PbI3 solar cell efficiency.

  14. Antiferroelectric-to-Ferroelectric Switching in CH3NH3PbI3 Perovskite and Its Potential Role in Effective Charge Separation in Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Sewvandi, Galhenage A.; Hu, Dengwei; Chen, Changdong; Ma, Hao; Kusunose, Takafumi; Tanaka, Yasuhiro; Nakanishi, Shunsuke; Feng, Qi

    2016-08-01

    Perovskite solar cells (PSCs) often suffer from large performance variations which impede to define a clear charge-transfer mechanism. Ferroelectric polarization is measured numerically using CH3NH3PbI3 (M A PbI3 ) pellets to overcome the measurement issues such as pinholes and low uniformity of thickness, etc., with M A PbI3 thin films. M A PbI3 perovskite is an antiferroelectric semiconductor which is different from typical semiconducting materials and ferroelectric materials. The effect of polarization carrier separation on the charge-transfer mechanism in the PSCs is elucidated by using the results of ferroelectric and structural studies on the perovskite. The ferroelectric polarization contributes to an inherent carrier-separation effect and the I - V hysteresis. The ferroelectric and semiconducting synergistic charge-separation effect gives an alternative category of solar cells, ferroelectric semiconductor solar cells. Our findings identify the ferroelectric semiconducting behavior of the perovskite absorber as being significant to the improvement of the ferroelectric PSCs performances in future developments.

  15. Mesoscopic TiO2/CH3NH3PbI3 perovskite solar cells with new hole-transporting materials containing butadiene derivatives.

    PubMed

    Lv, Songtao; Han, Liying; Xiao, Junyan; Zhu, Lifeng; Shi, Jiangjian; Wei, Huiyun; Xu, Yuzhuan; Dong, Juan; Xu, Xin; Li, Dongmei; Wang, Shirong; Luo, Yanhong; Meng, Qingbo; Li, Xianggao

    2014-07-04

    Two new triphenylamine-based hole-transporting materials (HTMs) containing butadiene derivatives are employed in CH3NH3PbI3 perovskite solar cells. Up to 11.63% of power conversion efficiency (PCE) has been achieved. Advantages such as easy synthesis, low cost and relatively good cell performance exhibit a possibility for commercial applications in the future.

  16. P3HT:DiPBI bulk heterojunction solar cells: morphology and electronic structure probed by multiscale simulation and UV/vis spectroscopy.

    PubMed

    Winands, Thorsten; Böckmann, Marcus; Schemme, Thomas; Ly, Phong-Minh Timmy; de Jong, Djurre H; Wang, Zhaohui; Denz, Cornelia; Heuer, Andreas; Doltsinis, Nikos L

    2016-02-17

    Coarse grained molecular dynamics simulations are performed for a mixture of poly(3-hexylthiophene) (P3HT) and diperylene bisimide (DiPBI). The effect of different annealing and cooling protocols on the morphology is investigated and the resulting domain structures are analyzed. In particular, π-stacked clusters of DiPBI molecules are observed whose size decreases with increasing temperature. Domain structure and diffusivity data suggest that the DiPBI subsystem undergoes an order → disorder phase transition between 700 and 900 K. Electronic structure calculations based on density functional theory are carried out after backmapping the coarse grained model onto an atomistic force field representation built upon first principles. UV/vis absorption spectra of the P3HT:DiPBI mixture are computed using time-dependent density functional linear response theory and recorded experimentally for a spin-coated thin film. It is demonstrated that the absorption spectrum depends sensitively on the details of the amorphous structure, thus providing valuable insight into the morphology. In particular, the results show that the tempering procedure has a significant influence on the material's electronic properties. This knowledge may help to develop effective processing routines to enhance the performance of bulk heterojunction solar cells.

  17. Growth and evolution of solution-processed CH3NH3PbI3-xClx layer for highly efficient planar-heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Jiang; Lin, Jiahui; Xue, Qifan; Ye, Qinyan; He, Xulin; Ouyang, Liangqi; Zhuang, Daming; Liao, Cheng; Yip, Hin-Lap; Mei, Jun; Lau, Woon-Ming

    2016-01-01

    Methylammoniumn lead iodide perovskites have attracted great attention in photovoltaic research community. In this work, we demonstrate the results of studies focusing on the chemical reaction of CH3NH3PbI3-xClx layer formation during the annealing of perovskite precursor films. We identified two kinds of grain morphologies during the formation of perovskite films grown from non-stoichiometric precursor solution. To form single-phase and high absorbance perovskite films, higher concentration of chloride in precursor solution needs longer annealing time and only a very low Cl content could be incorporated in the final CH3NH3PbI3-xClx films. Adding PbCl2-3CH3NH3I to PbI2-CH3NH3I precursor solution can allow a good control of the growth rate and morphology for the final perovskite film, and is beneficial to the photovoltaic performance of perovskite devices. By employing the precursor solutions of PbCl2, PbI2 and CH3NH3I with a mole ratio of 1:1:4 and inserting an ultrathin amino-functionalized polymer interlayer, we achieved planar perovskite solar cell with maximum power conversion efficiency of over 15%.

  18. Perovskite CH3NH3PbI3(Cl) Single Crystals: Rapid Solution Growth, Unparalleled Crystalline Quality, and Low Trap Density toward 10(8) cm(-3).

    PubMed

    Lian, Zhipeng; Yan, Qingfeng; Gao, Taotao; Ding, Jie; Lv, Qianrui; Ning, Chuangang; Li, Qiang; Sun, Jia-Lin

    2016-08-03

    Single crystal reflects the intrinsic physical properties of a material, and single crystals with high-crystalline quality are highly desired for the acquisition of high-performance devices. We found that large single crystals of perovskite CH3NH3PbI3(Cl) could be grown rapidly from chlorine-containing solutions. Within 5 days, CH3NH3PbI3(Cl) single crystal as large as 20 mm × 18 mm × 6 mm was harvested. As a most important index to evaluate the crystalline quality, the full width at half-maximum (fwhm) in the high-resolution X-ray rocking curve (HR-XRC) of as-grown CH3NH3PbI3(Cl) single crystal was measured as 20 arcsec, which is far superior to so far reported CH3NH3PbI3 single crystals (∼1338 arcsec). The unparalleled crystalline quality delivered a low trap-state density of down to 7.6 × 10(8) cm(-3), high carrier mobility of 167 ± 35 cm(2) V(-1) s(-1), and long transient photovoltaic carrier lifetime of 449 ± 76 μs. The improvement in the crystalline quality, together with the rapid growth rate and excellent carrier transport property, provides state-of-the-art single crystalline hybrid perovskite materials for high-performance optoelectronic devices.

  19. Structures and Electronic Properties of Different CH3NH3PbI3/TiO2 Interface: A First-Principles Study

    PubMed Central

    Geng, Wei; Tong, Chuan-Jia; Liu, Jiang; Zhu, Wenjun; Lau, Woon-Ming; Liu, Li-Min

    2016-01-01

    Methylammonium lead iodide perovskite, CH3NH3PbI3, has attracted particular attention due to its fast increase in efficiency in dye sensitization TiO2 solid-state solar cells. We performed first-principles calculations to investigate several different types of CH3NH3PbI3/TiO2 interfaces. The interfacial structures between the different terminated CH3NH3PbI3 and phase TiO2 are thoroughly explored, and the calculated results suggest that the interfacial Pb atoms play important roles in the structure stability and electronic properties. A charge transfer from Pb atoms to the O atoms of TiO2 lead to the band edge alignment of Pb-p above Ti-d about 0.4 eV, suggesting a better carries separation. On the other hand, for TiO2, rutile (001) is the better candidate due to the better lattice and atoms arrangement match with CH3NH3PbI3. PMID:26846401

  20. Species Boundaries and Interrelationships of Solanum Sect. Petota (Wild and Cultivated Potatoes) are Drastically Altered as a Result of PBI-Funded Research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In 1990, the latest comprehensive taxonomic monograph of Solanum section Petota Dumort, recognized 232 species partitioned into 21 series. PBI-sponsored research has drastically altered knowledge of their species boundaries and interrelationships. The series contains diploids (2n = 2x = 24), tetrapl...

  1. Species Boundaries and Interrelationships of Solanum Sect. Petota (Wild and Cultivated Potatoes) are Drastically Altered as a Result of PBI-Funded Research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In 1990, the latest comprehensive taxonomic monograph of Solanum section Petota Dumort recognized 232 species partitioned into 21 series. PBI-sponsored research has drastically altered knowledge of their species boundaries and interrelationships. The series contains diploids (2n = 2x = 24), tetraplo...

  2. Structures and Electronic Properties of Different CH3NH3PbI3/TiO2 Interface: A First-Principles Study.

    PubMed

    Geng, Wei; Tong, Chuan-Jia; Liu, Jiang; Zhu, Wenjun; Lau, Woon-Ming; Liu, Li-Min

    2016-02-05

    Methylammonium lead iodide perovskite, CH3NH3PbI3, has attracted particular attention due to its fast increase in efficiency in dye sensitization TiO2 solid-state solar cells. We performed first-principles calculations to investigate several different types of CH3NH3PbI3/TiO2 interfaces. The interfacial structures between the different terminated CH3NH3PbI3 and phase TiO2 are thoroughly explored, and the calculated results suggest that the interfacial Pb atoms play important roles in the structure stability and electronic properties. A charge transfer from Pb atoms to the O atoms of TiO2 lead to the band edge alignment of Pb-p above Ti-d about 0.4 eV, suggesting a better carries separation. On the other hand, for TiO2, rutile (001) is the better candidate due to the better lattice and atoms arrangement match with CH3NH3PbI3.

  3. High-performance perovskite CH3NH3PbI3 thin films for solar cells prepared by single-source physical vapour deposition

    PubMed Central

    Fan, Ping; Gu, Di; Liang, Guang-Xing; Luo, Jing-Ting; Chen, Ju-Long; Zheng, Zhuang-Hao; Zhang, Dong-Ping

    2016-01-01

    In this work, an alternative route to fabricating high-quality CH3NH3PbI3 thin films is proposed. Single-source physical vapour deposition (SSPVD) without a post-heat-treating process was used to prepare CH3NH3PbI3 thin films at room temperature. This new process enabled complete surface coverage and moisture stability in a non-vacuum solution. Moreover, the challenges of simultaneously controlling evaporation processes of the organic and inorganic sources via dual-source vapour evaporation and the heating process required to obtain high crystallization were avoided. Excellent composition with stoichiometry transferred from the powder material, a high level of tetragonal phase-purity, full surface coverage, well-defined grain structure, high crystallization and reproducibility were obtained. A PCE of approximately 10.90% was obtained with a device based on SSPVD CH3NH3PbI3. These initial results suggest that SSPVD is a promising method to significantly optimize perovskite CH3NH3PbI3 solar cell efficiency. PMID:27426686

  4. MOF-Templated Assembly Approach for Fe3C Nanoparticles Encapsulated in Bamboo-Like N-Doped CNTs: Highly Efficient Oxygen Reduction under both Acidic and Basic Conditions.

    PubMed

    Aijaz, Arshad; Masa, Justus; Rösler, Christoph; Antoni, Hendrik; Fischer, Roland A; Schuhmann, Wolfgang; Muhler, Martin

    2017-03-29

    Developing high-performance non-precious metal cata¬lysts (NPMCs) for the oxygen reduction reaction (ORR) is of critical importance for sustainable energy conversion. We report a novel NPMC consisting of iron carbide (Fe3C) nanoparticles encapsulated in N-doped bamboo-like carbon nanotubes (b-NCNTs), synthesized by a new metal-organic framework (MOF)-templated assembly approach. The electrocatalyst exhibits excellent ORR activity in 0.1 M KOH (0.89 V at -1 mA cm-2) and in 0.5 M H2SO4 (0.73 V at -1 mA cm-2) with a hydrogen peroxide yield of below 1% in both electrolytes. Due to encapsulation of the Fe3C nanoparticles inside porous b-NCNTs, the reported NPMC retains its high ORR activity after ~70 h in both alkaline and acidic media.

  5. Hysteresis dependence on CH3NH3PbI3 deposition method in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Fernandes, Silvia Leticia; Bregadiolli, Bruna Andressa; Véron, Anna Christina; Nüesch, Frank A.; Zaghete, Maria Aparecida; Graeff, Carlos Frederico de Oliveira

    2016-09-01

    CH3NH3PbI3 perovskite solar cells are one of the most exciting technologies in the renewable energy field, resulting in over 20% power conversion efficiency. Deep understanding of the working principle is now required to turn the high efficiency solar cells into a reliable technology. In this work we have explored the role of deposition method on the crystallinity of perovskite films and its influence on the hysteresis behavior of the current-voltage characteristics. In addition Nb2O5 was used as hole blocking layer and its influence is also discussed. We have found that hysteresis is strongly dependent on both; perovskite deposition method and Nb2O5 thickness. The ideal condition where the hysteresis is suppressed or minimized was achieved by using the sequential deposition method for the perovskite semiconductor and a hole blocking layer of 50 nm.

  6. High performance photodetector based on 2D CH3NH3PbI3 perovskite nanosheets

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Shivananju, B. N.; Zhang, Yupeng; Li, Shaojuan; Bao, Qiaoliang

    2017-03-01

    In this work, a high performance vertical-type photodetector based on two-dimensional (2D) CH3NH3PbI3 perovskite nanosheets was fabricated. The low trap density of the perovskite nanosheets and their short carrier diffusion distance result in a significant performance enhancement of the perovskite-based photodetector. The photoresponsivity of this vertical-type photodetector is as high as 36 mA W‑1 at visible wavelength, which is much better than traditional perovskite photodetectors (0.34 mA W‑1). Compared with traditional planar-type perovskite-based photodetectors, this vertical-type photodetector also shows the advantages of low-voltage operation and large responsivity. These results may pave the way for exploiting high performance perovskite-based photodetectors with an ingenious device design.

  7. Controlled growth of CH3NH3PbI3 nanowires in arrays of open nanofluidic channels

    PubMed Central

    Spina, Massimo; Bonvin, Eric; Sienkiewicz, Andrzej; Forró, László; Horváth, Endre

    2016-01-01

    Spatial positioning of nanocrystal building blocks on a solid surface is a prerequisite for assembling individual nanoparticles into functional devices. Here, we report on the graphoepitaxial liquid-solid growth of nanowires of the photovoltaic compound CH3NH3PbI3 in open nanofluidic channels. The guided growth, visualized in real-time with a simple optical microscope, undergoes through a metastable solvatomorph formation in polar aprotic solvents. The presently discovered crystallization leads to the fabrication of mm2-sized surfaces composed of perovskite nanowires having controlled sizes, cross-sectional shapes, aspect ratios and orientation which have not been achieved thus far by other deposition methods. The automation of this general strategy paves the way towards fabrication of wafer-scale perovskite nanowire thin films well-suited for various optoelectronic devices, e.g. solar cells, lasers, light-emitting diodes and photodetectors. PMID:26806213

  8. Controlled growth of CH3NH3PbI3 nanowires in arrays of open nanofluidic channels

    NASA Astrophysics Data System (ADS)

    Spina, Massimo; Bonvin, Eric; Sienkiewicz, Andrzej; Forró, László; Horváth, Endre

    2016-01-01

    Spatial positioning of nanocrystal building blocks on a solid surface is a prerequisite for assembling individual nanoparticles into functional devices. Here, we report on the graphoepitaxial liquid-solid growth of nanowires of the photovoltaic compound CH3NH3PbI3 in open nanofluidic channels. The guided growth, visualized in real-time with a simple optical microscope, undergoes through a metastable solvatomorph formation in polar aprotic solvents. The presently discovered crystallization leads to the fabrication of mm2-sized surfaces composed of perovskite nanowires having controlled sizes, cross-sectional shapes, aspect ratios and orientation which have not been achieved thus far by other deposition methods. The automation of this general strategy paves the way towards fabrication of wafer-scale perovskite nanowire thin films well-suited for various optoelectronic devices, e.g. solar cells, lasers, light-emitting diodes and photodetectors.

  9. Highly efficient and stable Zr-doped nanocrystalline PbO2 electrode for mineralization of perfluorooctanoic acid in a sequential treatment system.

    PubMed

    Xu, Zesheng; Yu, Yanxin; Liu, Han; Niu, Junfeng

    2017-02-01

    Zr-doped nanocrystalline PbO2 (Zr-PbO2) film electrodes were prepared at different bath temperatures. The Zr-PbO2 electrode doped at 75°C (75-Zr-PbO2) featured high oxygen evolution overpotential, large effective area and good electrocatalytic performance. The oxygen evolution potential and the effective area of 75-Zr-PbO2 achieved 1.91V (vs. SCE) and 9.1cm(2), respectively. The removal efficiency and the defluorination ratio of PFOA reached 97.0% and 88.1% after 90min electrolysis. The primary mineralization products (i.e., F(-) and intermediates) and their change trends were determined. The 75-Zr-PbO2 electrode was introduced to sequentially treat the PFOA wastewater. In an 116h of 75-Zr-PbO2 electrocatalysis sequential process, the PFOA, PFHpA, PFHxA, PFPeA, PFBA, PFPrA, TFA, and TOC concentrations were reduced to below 30, 2.5, 1.3, 1.0, 0.5, 0.2, 0.1, and 9mgL(-1), respectively, demonstrating the promising application of the sequential treatment system for the treatment of PFOA wastewater.

  10. Enhanced Charge Carrier Transport and Device Performance Through Dual-Cesium Doping in Mixed-Cation Perovskite Solar Cells with Near Unity Free Carrier Ratios.

    PubMed

    Ye, Tao; Petrović, Miloš; Peng, Shengjie; Yoong, Jeremy Lee Kong; Vijila, Chellappan; Ramakrishna, Seeram

    2017-01-25

    PbI2-enriched mixed perovskite film [FA0.81MA0.15Pb(I0.836Br0.15)3] has been widely studied due to its great potential in perovskite solar cell (PSC) applications. Herein, a FA0.81MA0.15Pb(I0.836Br0.15)3 film has been fabricated with the temperature-dependent optical absorption spectra utilized to determine its exciton binding energy. A ∼13 meV exciton binding energy is estimated, and a near-unity fraction of free carriers out of the total photoexcitons has been obtained in the solar cell operating regime at equilibrium state. PSCs are fabricated with this mixed perovskite film, but a significant electron transport barrier at the TiO2-perovskite interface limited their performance. Cs2CO3 and CsI are then utilized as functional enhancers with which to substantially balance the electron and hole transport and increase the carriers (both electrons and holes) mobilities in PSCs, resulting in much-improved solar-cell performance. The modified PSCs exhibit reproducible power conversion efficiency (PCE) values with little hysteresis effect in the J-V curves, achieving PCEs up to 19.5% for the Cs2CO3-modified PSC and 20.6% when subsequently further doped with CsI.

  11. New insights into organic-inorganic hybrid perovskite CH₃NH₃PbI₃ nanoparticles. An experimental and theoretical study of doping in Pb²⁺ sites with Sn²⁺, Sr²⁺, Cd²⁺ and Ca²⁺.

    PubMed

    Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Hernández, Norge Cruz; Piñero, Jose Carlos; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; De los Santos, Desireé M; Aguilar, Teresa; Martín-Calleja, Joaquín

    2015-04-14

    This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb(2+) position with Sn(2+), Sr(2+), Cd(2+) and Ca(2+). The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn(2+), Sr(2+) and Cd(2+) did not modify the normal tetragonal phase. When doping with Ca(2+), the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr(2+) < Cd(2+) < Ca(2+) < CH3NH3PbI3 ≈ Sn(2+). The biggest decrease was generated by Sr(2+), which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn(2+) ≈ Pb(2+) > Cd(2+) > Sr(2+) for the tetragonal structure and Pb(2+) > Ca(2+) for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn(2+)-doped tetragonal structures, which were different from those doped with Sr(2+) and Cd(2+). Furthermore, when Cd(2+) was incorporated, the Cd-I interaction was strengthened. For Ca(2+) doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.

  12. One-pot environmentally friendly amino acid mediated synthesis of N-doped graphene-silver nanocomposites with an enhanced multifunctional behavior.

    PubMed

    Khandelwal, Mahima; Kumar, Anil

    2016-03-28

    The present paper reports the one-pot synthesis of N-doped graphene-Ag nanocomposites (N-GrAg) involving the in situ generation of Ag nanoparticles (NPs). The simultaneous reduction of GO and Ag(+) to produce N-GrAg has been achieved under mild reaction conditions using an environmentally benign reducing agent, glycine, in aqueous medium without adding any external stabilizer. XRD and SAED analyses revealed the presence of Ag in the fcc structure. HRTEM analysis shows a 'd' spacing of 0.236 nm corresponding to the highest intensity (111) reflection of Ag which matches the fcc structure. The N-doping of graphene and its uniform decoration by Ag NPs (with an av. dia. of 17.5 nm) having a relatively low surface atomic % of Ag (0.309) are evidenced by TEM and XPS analyses. Raman spectroscopy has also revealed that the decoration of N-Gr with Ag NPs resulted in the enhancement of the D and G bands by about 365%. The presence of Ag in N-GrAg prevents the folding of the graphene sheet as was revealed by TEM analysis. The supramolecular interactions of Ag with different moieties of N in N-GrAg were evidenced by IR, (13)C NMR and XPS analyses, which resulted in the enhancement of its surface area and electrical conductivity as compared to that of N-Gr. The presence of Ag NPs on N-Gr increased the current response in cyclic voltammetry by more than seven fold as compared to that of N-Gr. These nanocomposites exhibited a fairly high SERS activity for 4-aminothiophenol, employed as the probe molecule, and allowed its detection at a 50 nM concentration even for the fairly small sized Ag NPs used in the present work.

  13. The Influence of Morphology and PbI2 on the Intrinsic Trap State Distribution in Perovskite Films Determined by Using Temperature-Dependent Fluorescence Spectroscopy.

    PubMed

    Wang, Yi; Wang, Hao-Yi; Yu, Man; Fu, Li-Min; Qin, Yujun; Zhang, Jian-Ping; Ai, Xi-Cheng

    2017-02-02

    Perovskite films with different particle sizes and PbI2 contents were prepared by using a controlled single or sequential method. By means of temperature-dependent fluorescence spectroscopy, the energetic distribution of intrinsic intragap trap states in perovskite was quantitatively determined, and the radiative charge recombinations through the band edge and via trap states were studied. Furthermore, a series of thermodynamic parameters, such as the demarcation energy between radiative and nonradiative recombination regions, detrapping activation energy, and characteristic temperature, were extracted based on which of the possible radiative and nonradiative recombination mechanisms were proposed. In addition, the correlation between the morphology of the perovskite films, the PbI2 content, and the energetic distribution of the trap states was investigated. Finally, we discuss the structure-function relationship of perovskite films prepared by different methods.

  14. Cubic Perovskite Structure of Black Formamidinium Lead Iodide, α-[HC(NH2)2]PbI3, at 298 K

    PubMed Central

    2015-01-01

    The structure of black formamidinium lead halide, α-[HC(NH2)2]PbI3, at 298 K has been refined from high resolution neutron powder diffraction data and found to adopt a cubic perovskite unit cell, a = 6.3620(8) Å. The trigonal planar [HC(NH2)2]+ cations lie in the central mirror plane of the unit cell with the formamidinium cations disordered over 12 possible sites arranged so that the C–H bond is directed into a cube face, whereas the −NH2 groups hydrogen bond (NH···I = 2.75–3.00 Å) with the iodide atoms of the [PbI3]− framework. High atomic displacement parameters for the formamidinium cation are consistent with rapid molecular rotations at room temperature as evidenced in ab initio molecular dynamic simulations.

  15. Methylamine-Gas-Induced Defect-Healing Behavior of CH3NH3PbI3 Thin Films for Perovskite Solar Cells.

    PubMed

    Zhou, Zhongmin; Wang, Zaiwei; Zhou, Yuanyuan; Pang, Shuping; Wang, Dong; Xu, Hongxia; Liu, Zhihong; Padture, Nitin P; Cui, Guanglei

    2015-08-10

    We report herein the discovery of methylamine (CH3NH2) induced defect-healing (MIDH) of CH3NH3PbI3 perovskite thin films based on their ultrafast (seconds), reversible chemical reaction with CH3NH2 gas at room temperature. The key to this healing behavior is the formation and spreading of an intermediate CH3NH3PbI3⋅xCH3NH2 liquid phase during this unusual perovskite-gas interaction. We demonstrate the versatility and scalability of the MIDH process, and show dramatic enhancement in the performance of perovskite solar cells (PSCs) with MIDH. This study represents a new direction in the formation of defect-free films of hybrid perovskites.

  16. Inverted planar NH2CH=NH2PbI3 perovskite solar cells with 13.56% efficiency via low temperature processing.

    PubMed

    Yuan, Da-Xing; Gorka, Adam; Xu, Mei-Feng; Wang, Zhao-Kui; Liao, Liang-Sheng

    2015-08-14

    In this work, NH2CH=NH2PbI3 (FAPbI3) was employed for light harvesting in inverted planer perovskite solar cells for the first time. Except for the silver cathode, all layers were solution-processed under or below 140 °C. The effect of the annealing process on device performance was investigated. The FAPbI3 solar cells based on a slowed-down annealing shows superior performance compared to the CH3NH3PbI3 (MAPbI3)-based devices, especially for the short circuit current density. A power conversion efficiency of 13.56% was obtained with high short circuit current density of 21.48 mA cm(-2). This work paves the way for low-temperature fabrication of efficient inverted planer structure FAPbI3 perovskite solar cells.

  17. Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 Perovskites for Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Umari, Paolo; Mosconi, Edoardo; de Angelis, Filippo

    2014-03-01

    Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I1-xClx)3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7 eV) being only partly compensated by the conduction band downshift (~0.2 eV).

  18. Liquid phase deposition of TiO2 nanolayer affords CH3NH3PbI3/nanocarbon solar cells with high open-circuit voltage.

    PubMed

    Chen, Haining; Wei, Zhanhua; Yan, Keyou; Yi, Ya; Wang, Jiannong; Yang, Shihe

    2014-01-01

    Hybrid organic/inorganic perovskite solar cells are attracting intense attention and further developments largely hinge on understanding the fundamental issues involved in the cell operation. In this paper, a liquid phase deposition (LPD) method is developed to design and grow a TiO(2) nanolayer at room temperature for carbon-based perovskite solar cells. The TiO(2) nanolayer grown on FTO glass is compact but polycrystalline consisting of tiny anatase TiO(2) nanocrystals intimately stacked together. By directly exploiting this TiO(2) nanolayer in a solar cell of TiO(2) nanolayer/CH(3)NH(3)PbI(3)/nanocarbon, we have achieved a Voc as high as 1.07 V, the highest value reported so far for hole transporter-free CH(3)NH(3)PbI(3) solar cells. This is rationalized by the slower electron injection and longer electron lifetime due to the TiO(2) nanolayer, which enhances the electron accumulation in CH(3)NH(3)PbI(3) and consequently the Voc. By employing a rutile TiO(2) nanorod (NR) array as a base structure for the LPD-TiO(2) nanolayer to support the CH(3)NH(3)PbI(3) layer, the photocurrent density is considerably increased without obviously compromising the Voc (1.01 V). As a result, the power conversion efficiency is boosted from 3.67% to 8.61%. More elaborate engineering of the TiO(2) nanolayer by LPD in conjunction with judicious interfacing with other components has the potential to achieve higher performances for this type of solar cell.

  19. Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode

    PubMed Central

    Ku, Zhiliang; Rong, Yaoguang; Xu, Mi; Liu, Tongfa; Han, Hongwei

    2013-01-01

    A mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell is developed with low-cost carbon counter electrode (CE) and full printable process. With carbon black/spheroidal graphite CE, this mesoscopic heterojunction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the conventional Au version. PMID:24185501

  20. Electron–acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

    PubMed Central

    Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; Yartsev, Arkady

    2017-01-01

    Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V−1 s−1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3. PMID:28176755

  1. CH3NH3PbI3-xClx under Different Fabrication Strategies: Electronic Structures and Energy-Level Alignment with an Organic Hole Transport Material.

    PubMed

    Wang, Rongbin; Wu, Chen; Hu, Yun; Li, Jitao; Shen, Pengfei; Wang, Qi; Liao, Liangsheng; Liu, Lijia; Duhm, Steffen

    2017-03-01

    We report a photoelectron spectroscopy study on the electronic structure of CH3NH3PbI3-xClx thin films fabricated by physical evaporation from CH3NH3I and PbCl2 precursors, including (1) simultaneously evaporation and (2) sequential evaporation. The results are compared with CH3NH3PbI3-xClx made using conventional solution chemistry (i.e., spin-coating). Depending on the fabrication method, CH3NH3PbI3-xClx films show different chemical constituents in the near-surface region, leading to disparities in their energetic levels. The chemical identities of the surface species are revealed by an in situ study on the sequentially evaporated film. Moreover, air-exposure treatment also greatly alters the energetic levels of the film. Using hole transport layer of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (NPB) as a model system, we find that the energy-level alignment with the spin-coated film after air exposure is most suitable for efficient hole transport.

  2. Crack-free CH3NH3PbI3 layer via continuous dripping method for high-performance mesoporous perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Guo; Zheng, Jianghui; Zheng, LingLing; Yan, Xin; Lin, Huangding; Zhang, Fengyan

    2017-01-01

    The past five years have witnessed the uniquely rapid emergence of the mixed organic-inorganic halide perovskite solar cells. Here, a modified deposition process, continuous dripping method, is reported for fabricating high-performance and reproducible perovskite solar cells. We have systematically investigated the impact of different molar ratio of lead iodide (PbI2) to dimethylsulfoxide (DMSO) on the growth, morphology and crystallinity of CH3NH3PbI3 (MAPbI3) films obtained via this process. The high power conversion efficiency (PCE) perovskite solar cell originates in crack-free and highly crystallographic perovskite films prepared with optimized ratio of PbI2 to DMSO in first precursor solution. The best PCE of 17.76% and an average PCE of 16.37 ± 0.51% were obtained via this process. Moreover, the conventional solution two steps method was also carried out as a comparison to this process. This work provides a new simple solution approach to obtain high quality of perovskite thin films for high-performance and reproducible PSCs.

  3. Efficient hybrid mesoscopic solar cells with morphology-controlled CH3NH3PbI3-xClx derived from two-step spin coating method.

    PubMed

    Xu, Yuzhuan; Zhu, Lifeng; Shi, Jiangjian; Lv, Songtao; Xu, Xin; Xiao, Junyan; Dong, Juan; Wu, Huijue; Luo, Yanhong; Li, Dongmei; Meng, Qingbo

    2015-02-04

    A morphology-controlled CH3NH3PbI3-xClx film is synthesized via two-step solution deposition by spin-coating a mixture solution of CH3NH3Cl and CH3NH3I onto the TiO2/PbI2 film for the first time. It is revealed that the existence of CH3NH3Cl is supposed to result in a preferential growth along the [110] direction of perovskite, which can improve both the crystallinity and surface coverage of perovskite and reduce the pinholes. Furthermore, the formation process of CH3NH3PbI3-xClx perovskite is explored, in which intermediates containing chlorine are suggested to exist. 13.12% of power conversion efficiency has been achieved for the mesoscopic cell, higher than 12.08% of power conversion efficiency of the devices fabricated without CH3NH3Cl via the same process. The improvement mainly lies in the increasing open-circuit photovoltage which is ascribed to the reduction of reverse saturation current density.

  4. Electron-acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons.

    PubMed

    Mante, Pierre-Adrien; Stoumpos, Constantinos C; Kanatzidis, Mercouri G; Yartsev, Arkady

    2017-02-08

    Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm(2) V(-1) s(-1), respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

  5. Electron–acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

    DOE PAGES

    Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; ...

    2017-02-08

    The intrinsic properties of CH3NH3PbI3 are still largely unknown in spite of the great amount of attention it has received for its solar cell application. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. Furthermore, we apply this method to characterize a CH3NH3PbI3 single crystal.We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using themore » deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. These results reveal high electron and hole mobilities of 2,800 and 9,400 cm2V-1 s -1 , respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.« less

  6. Monitoring a Silent Phase Transition in CH3NH3PbI3 Solar Cells via Operando X-ray Diffraction

    DOE PAGES

    Schelhas, Laura T.; Christians, Jeffrey A.; Berry, Joseph J.; ...

    2016-10-13

    The relatively modest temperature of the tetragonal-to-cubic phase transition in CH3NH3PbI3 perovskite is likely to occur during real world operation of CH3NH3PbI3 solar cells. In this work, we simultaneously monitor the structural phase transition of the active layer along with solar cell performance as a function of the device operating temperature. The tetragonal to cubic phase transition is observed in the working device to occur reversibly at temperatures between 60.5 and 65.4 degrees C. In these operando measurements, no discontinuity in the device performance is observed, indicating electronic behavior that is insensitive to the structural phase transition. Here, this decouplingmore » of device performance from the change in long-range order across the phase transition suggests that the optoelectronic properties are primarily determined by the local structure in CH3NH3PbI3. That is, while the average crystal structure as probed by X-ray diffraction shows a transition from tetragonal to cubic, the local structure generally remains well characterized by uncorrelated, dynamic octahedral rotations that order at elevated temperatures but are unchanged locally.« less

  7. Electron-hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals

    DOE PAGES

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; ...

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm–2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals thanmore » in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.« less

  8. Complex Refractive Index Spectra of CH3NH3PbI3 Perovskite Thin Films Determined by Spectroscopic Ellipsometry and Spectrophotometry.

    PubMed

    Löper, Philipp; Stuckelberger, Michael; Niesen, Bjoern; Werner, Jérémie; Filipič, Miha; Moon, Soo-Jin; Yum, Jun-Ho; Topič, Marko; De Wolf, Stefaan; Ballif, Christophe

    2015-01-02

    The complex refractive index (dielectric function) of planar CH3NH3PbI3 thin films at room temperature is investigated by variable angle spectroscopic ellipsometry and spectrophotometry. Knowledge of the complex refractive index is essential for designing photonic devices based on CH3NH3PbI3 thin films such as solar cells, light-emitting diodes, or lasers. Because the directly measured quantities (reflectance, transmittance, and ellipsometric spectra) are inherently affected by multiple reflections, the complex refractive index has to be determined indirectly by fitting a model dielectric function to the experimental spectra. We model the dielectric function according to the Forouhi-Bloomer formulation with oscillators positioned at 1.597, 2.418, and 3.392 eV and achieve excellent agreement with the experimental spectra. Our results agree well with previously reported data of the absorption coefficient and are consistent with Kramers-Kronig transformations. The real part of the refractive index assumes a value of 2.611 at 633 nm, implying that CH3NH3PbI3-based solar cells are ideally suited for the top cell in monolithic silicon-based tandem solar cells.

  9. Electron-acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

    NASA Astrophysics Data System (ADS)

    Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; Yartsev, Arkady

    2017-02-01

    Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V-1 s-1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

  10. Antibody-based donor-acceptor spatial reconfiguration in decorated lanthanide-doped nanoparticle colloids for the quantification of okadaic acid biotoxin.

    PubMed

    Stipić, Filip; Burić, Petra; Jakšić, Željko; Pletikapić, Galja; Dutour Sikirić, Maja; Zgrablić, Goran; Frkanec, Leo; Lyons, Daniel M

    2015-11-01

    With the increasing movement away from the mouse bioassay for the detection of toxins in commercially harvested shellfish, there is a growing demand for the development of new and potentially field-deployable tests in its place. In this direction we report the development of a simple and sensitive nanoparticle-based luminescence technique for the detection of the marine biotoxin okadaic acid. Photoluminescent lanthanide nanoparticles were conjugated with fluorophore-labelled anti-okadaic acid antibodies which, upon binding to okadaic acid, gave rise to luminescence resonance energy transfer from the nanoparticle to the organic fluorophore dye deriving from a reduction in distance between the two. The intensity ratio of the fluorophore: nanoparticle emission peaks was found to correlate with okadaic acid concentration, and the sensor showed a linear response in the 0.37-3.97 μM okadaic acid range with a limit of detection of 0.25 μM. This work may have important implications for the development of new, cheap, and versatile biosensors for a range of biomolecules and that are sufficiently simple to be applied in the field or at point-of-care.

  11. Enhancement of CO2 Adsorption and Catalytic Properties by Fe-Doping of [Ga2(OH)2(L)] (H4L = Biphenyl-3,3',5,5'-tetracarboxylic Acid), MFM-300(Ga2).

    PubMed

    Krap, Cristina P; Newby, Ruth; Dhakshinamoorthy, Amarajothi; García, Hermenegildo; Cebula, Izabela; Easun, Timothy L; Savage, Mathew; Eyley, Jennifer E; Gao, Shan; Blake, Alexander J; Lewis, William; Beton, Peter H; Warren, Mark R; Allan, David R; Frogley, Mark D; Tang, Chiu C; Cinque, Gianfelice; Yang, Sihai; Schröder, Martin

    2016-02-01

    Metal-organic frameworks (MOFs) are usually synthesized using a single type of metal ion, and MOFs containing mixtures of different metal ions are of great interest and represent a methodology to enhance and tune materials properties. We report the synthesis of [Ga2(OH)2(L)] (H4L = biphenyl-3,3',5,5'-tetracarboxylic acid), designated as MFM-300(Ga2), (MFM = Manchester Framework Material replacing NOTT designation), by solvothermal reaction of Ga(NO3)3 and H4L in a mixture of DMF, THF, and water containing HCl for 3 days. MFM-300(Ga2) crystallizes in the tetragonal space group I4122, a = b = 15.0174(7) Å and c = 11.9111(11) Å and is isostructural with the Al(III) analogue MFM-300(Al2) with pores decorated with -OH groups bridging Ga(III) centers. The isostructural Fe-doped material [Ga(1.87)Fe(0.13)(OH)2(L)], MFM-300(Ga(1.87)Fe(0.13)), can be prepared under similar conditions to MFM-300(Ga2) via reaction of a homogeneous mixture of Fe(NO3)3 and Ga(NO3)3 with biphenyl-3,3',5,5'-tetracarboxylic acid. An Fe(III)-based material [Fe3O(1.5)(OH)(HL)(L)(0.5)(H2O)(3.5)], MFM-310(Fe), was synthesized with Fe(NO3)3 and the same ligand via hydrothermal methods. [MFM-310(Fe)] crystallizes in the orthorhombic space group Pmn21 with a = 10.560(4) Å, b = 19.451(8) Å, and c = 11.773(5) Å and incorporates μ3-oxo-centered trinuclear iron cluster nodes connected by ligands to give a 3D nonporous framework that has a different structure to the MFM-300 series. Thus, Fe-doping can be used to monitor the effects of the heteroatom center within a parent Ga(III) framework without the requirement of synthesizing the isostructural Fe(III) analogue [Fe2(OH)2(L)], MFM-300(Fe2), which we have thus far been unable to prepare. Fe-doping of MFM-300(Ga2) affords positive effects on gas adsorption capacities, particularly for CO2 adsorption, whereby MFM-300(Ga(1.87)Fe(0.13)) shows a 49% enhancement of CO2 adsorption capacity in comparison to the homometallic parent material. We thus report

  12. Enhancement of CO2 Adsorption and Catalytic Properties by Fe-Doping of [Ga2(OH)2(L)] (H4L = Biphenyl-3,3′,5,5′-tetracarboxylic Acid), MFM-300(Ga2)

    PubMed Central

    2016-01-01

    Metal–organic frameworks (MOFs) are usually synthesized using a single type of metal ion, and MOFs containing mixtures of different metal ions are of great interest and represent a methodology to enhance and tune materials properties. We report the synthesis of [Ga2(OH)2(L)] (H4L = biphenyl-3,3′,5,5′-tetracarboxylic acid), designated as MFM-300(Ga2), (MFM = Manchester Framework Material replacing NOTT designation), by solvothermal reaction of Ga(NO3)3 and H4L in a mixture of DMF, THF, and water containing HCl for 3 days. MFM-300(Ga2) crystallizes in the tetragonal space group I4122, a = b = 15.0174(7) Å and c = 11.9111(11) Å and is isostructural with the Al(III) analogue MFM-300(Al2) with pores decorated with −OH groups bridging Ga(III) centers. The isostructural Fe-doped material [Ga1.87Fe0.13(OH)2(L)], MFM-300(Ga1.87Fe0.13), can be prepared under similar conditions to MFM-300(Ga2) via reaction of a homogeneous mixture of Fe(NO3)3 and Ga(NO3)3 with biphenyl-3,3′,5,5′-tetracarboxylic acid. An Fe(III)-based material [Fe3O1.5(OH)(HL)(L)0.5(H2O)3.5], MFM-310(Fe), was synthesized with Fe(NO3)3 and the same ligand via hydrothermal methods. [MFM-310(Fe)] crystallizes in the orthorhombic space group Pmn21 with a = 10.560(4) Å, b = 19.451(8) Å, and c = 11.773(5) Å and incorporates μ3-oxo-centered trinuclear iron cluster nodes connected by ligands to give a 3D nonporous framework that has a different structure to the MFM-300 series. Thus, Fe-doping can be used to monitor the effects of the heteroatom center within a parent Ga(III) framework without the requirement of synthesizing the isostructural Fe(III) analogue [Fe2(OH)2(L)], MFM-300(Fe2), which we have thus far been unable to prepare. Fe-doping of MFM-300(Ga2) affords positive effects on gas adsorption capacities, particularly for CO2 adsorption, whereby MFM-300(Ga1.87Fe0.13) shows a 49% enhancement of CO2 adsorption capacity in comparison to the homometallic parent material. We thus report herein the

  13. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C6H11NH3)2[PbI4].

    PubMed

    Yangui, A; Pillet, S; Mlayah, A; Lusson, A; Bouchez, G; Triki, S; Abid, Y; Boukheddaden, K

    2015-12-14

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C6H11NH3)2[PbI4] (abbreviated as C6PbI4) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C6PbI4, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ∼138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI6 octahedron. The resulting incommensurate spatial modulation of the Pb-I distances (and Pb-I-Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ∼130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with targeted properties.

  14. Do grain boundaries dominate non-radiative recombination in CH 3 NH 3 PbI 3 perovskite thin films?

    DOE PAGES

    Yang, Mengjin; Zeng, Yining; Li, Zhen; ...

    2017-01-13

    Here, we examine GBs with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier atmore » GBs. Even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.« less

  15. Piezoelectric scattering limited mobility of hybrid organic-inorganic perovskites CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Lu, Ying-Bo; Kong, Xianghua; Chen, Xiaobin; Cooke, David G.; Guo, Hong

    2017-02-01

    Carrier mobility is one of the most important parameters for semiconducting materials and their use in optoelectronic devices. Here we report a systematic first principles analysis of the acoustic phonon scattering mechanism that limits the mobility of CH3NH3PbI3 (MAPbI3) perovskites. Due to the unique hybrid organic-inorganic structure, the mechanical, electronic and transport properties are dominated by the same factor, i.e. the weak interatomic bond and the easy rotation of methylammonium (MA) molecules under strain. Both factors make MAPbI3 soft. Rotation of MA molecule induces a transverse shift between Pb and I atoms, resulting in a very low deformation potential and a strong piezoelectricity in MAPbI3. Hence the carrier mobility of pristine MAPbI3 is limited by the piezoelectric scattering, which is consistent to the form of its temperature dependence. Our calculations suggest that in the pristine limit, a high mobility of about several thousand cm2 V‑1 S‑1 is expected for MAPbI3.

  16. Mapping the Photoresponse of CH3NH3PbI3 Hybrid Perovskite Thin Films at the Nanoscale.

    PubMed

    Kutes, Yasemin; Zhou, Yuanyuan; Bosse, James L; Steffes, James; Padture, Nitin P; Huey, Bryan D

    2016-06-08

    Perovskite solar cells (PSCs) based on thin films of organolead trihalide perovskites (OTPs) hold unprecedented promise for low-cost, high-efficiency photovoltaics (PVs) of the future. While PV performance parameters of PSCs, such as short circuit current, open circuit voltage, and maximum power, are always measured at the macroscopic scale, it is necessary to probe such photoresponses at the nanoscale to gain key insights into the fundamental PV mechanisms and their localized dependence on the OTP thin-film microstructure. Here we use photoconductive atomic force microscopy spectroscopy to map for the first time variations of PV performance at the nanoscale for planar PSCs based on hole-transport-layer free methylammonium lead triiodide (CH3NH3PbI3 or MAPbI3) thin films. These results reveal substantial variations in the photoresponse that correlate with thin-film microstructural features such as intragrain planar defects, grains, grain boundaries, and notably also grain-aggregates. The insights gained into such microstructure-localized PV mechanisms are essential for guiding microstructural tailoring of OTP films for improved PV performance in future PSCs.

  17. Strong covalency-induced recombination centers in perovskite solar cell material CH3NH3PbI3.

    PubMed

    Agiorgousis, Michael L; Sun, Yi-Yang; Zeng, Hao; Zhang, Shengbai

    2014-10-15

    Inorganic-organic hybrid perovskites are a new family of solar cell materials, which have recently been used to make solar cells with efficiency approaching 20%. Here, we report the unique defect chemistry of the prototype material, CH3NH3PbI3, based on first-principles calculation. We found that both the Pb cations and I anions in this material exhibit strong covalency as characterized by the formation of Pb dimers and I trimers with strong covalent bonds at some of the intrinsic defects. The Pb dimers and I trimers are only stabilized in a particular charge state with significantly lowered energy, which leads to deep charge-state transition levels within the band gap, in contradiction to a recent proposal that this system has only shallow intrinsic defects. Our results show that, in order to prevent the deep-level defects from being effective recombination centers, the equilibrium carrier concentrations should be controlled so that the Fermi energy is about 0.3 eV away from the band edges. Beyond this range, according to a Shockley-Read-Hall analysis, the non-equilibrium carrier lifetime will be strongly affected by the concentration of I vacancies and the anti-site defects with I occupying a CH3NH3 site.

  18. Piezoelectric scattering limited mobility of hybrid organic-inorganic perovskites CH3NH3PbI3

    PubMed Central

    Lu, Ying-Bo; Kong, Xianghua; Chen, Xiaobin; Cooke, David G.; Guo, Hong

    2017-01-01

    Carrier mobility is one of the most important parameters for semiconducting materials and their use in optoelectronic devices. Here we report a systematic first principles analysis of the acoustic phonon scattering mechanism that limits the mobility of CH3NH3PbI3 (MAPbI3) perovskites. Due to the unique hybrid organic-inorganic structure, the mechanical, electronic and transport properties are dominated by the same factor, i.e. the weak interatomic bond and the easy rotation of methylammonium (MA) molecules under strain. Both factors make MAPbI3 soft. Rotation of MA molecule induces a transverse shift between Pb and I atoms, resulting in a very low deformation potential and a strong piezoelectricity in MAPbI3. Hence the carrier mobility of pristine MAPbI3 is limited by the piezoelectric scattering, which is consistent to the form of its temperature dependence. Our calculations suggest that in the pristine limit, a high mobility of about several thousand cm2 V−1 S−1 is expected for MAPbI3. PMID:28150743

  19. High intrinsic carrier mobility and photon absorption in the perovskite CH3NH3PbI3.

    PubMed

    Wang, Youwei; Zhang, Yubo; Zhang, Peihong; Zhang, Wenqing

    2015-05-07

    The carrier transport and optical properties of the hybrid organic-inorganic perovskite CH3NH3PbI3 are investigated using first-principles approaches. We found that the electron and hole mobilities could reach surprisingly high values of 7-30 × 10(3) and 1.5-5.5 × 10(3) cm(2) V(-1) s(-1), respectively, and both are estimated to be much higher than the current experimental measurements. The high carrier mobility is ascribed to the intrinsically small effective masses of anti-bonding band-edge states. The above results imply that there is still space to improve the performance of related solar cells. This material also has a sharp photon absorption edge and an absorption coefficient as high as 10(5) cm(-1), both of which contribute to effective utilization of solar radiation. Although band-edge states are mainly derived from the inorganic ions of Pb and I, thermal movement of the organic base has indirect influences on the bandgap and carrier effective masses, resulting in the temperature-dependent solar cell efficiencies.

  20. Atomic partial charges on CH3NH3PbI3 from first-principles electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Madjet, Mohamed E.; El-Mellouhi, Fedwa; Carignano, Marcelo A.; Berdiyorov, Golibjon R.

    2016-04-01

    We calculated the partial charges in methylammonium (MA) lead-iodide perovskite CH3NH3PbI3 in its different crystalline phases using different first-principles electronic charge partitioning approaches, including the Bader, ChelpG, and density-derived electrostatic and chemical (DDEC) schemes. Among the three charge partitioning methods, the DDEC approach provides chemically intuitive and reliable atomic charges for this material, which consists of a mixture of transition metals, halide ions, and organic molecules. The DDEC charges are also found to be robust against the use of hybrid functionals and/or upon inclusion of spin-orbit coupling or dispersive interactions. We calculated explicitly the atomic charges with a special focus on the dipole moment of the MA molecules within the perovskite structure. The value of the dipole moment of the MA is reduced with respect to the isolated molecule due to charge redistribution involving the inorganic cage. DDEC charges and dipole moment of the organic part remain nearly unchanged upon its rotation within the octahedral cavities. Our findings will be of both fundamental and practical importance, as the accurate and consistent determination of the atomic charges is important in order to understand the average equilibrium distribution of the electrons and to help in the development of force fields for larger scale atomistic simulations to describe static, dynamic, and thermodynamic properties of the material.

  1. Do grain boundaries dominate non-radiative recombination in CH3NH3PbI 3 perovskite thin films?

    DOE PAGES

    Yang, Mengjin; Zeng, Yining; Li, Zhen; ...

    2017-01-13

    Here, we examine GBs with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier atmore » GBs. Lastly, even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.« less

  2. Do grain boundaries dominate non-radiative recombination in CH3NH3PbI3 perovskite thin films?

    PubMed

    Yang, Mengjin; Zeng, Yining; Li, Zhen; Kim, Dong Hoe; Jiang, Chun-Sheng; van de Lagemaat, Jao; Zhu, Kai

    2017-02-15

    Here, we examine grain boundaries (GBs) with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier at GBs. Even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.

  3. Temperature-Dependent Electric Field Poling Effects in CH3NH3PbI3 Optoelectronic Devices.

    PubMed

    Zhang, Chuang; Sun, Dali; Liu, Xiaojie; Sheng, Chuan-Xiang; Vardeny, Zeev Valy

    2017-04-06

    Organo-lead halide perovskites show excellent optoelectronic properties; however, the unexpected inconsistency in forward-backward I-V characteristics remains a problem for fabricating solar panels. Here we have investigated the reasons behind this "hysteresis" by following the changes in photocurrent and photoluminescence under electric field poling in transverse CH3NH3PbI3-based devices from 300 to 10 K. We found that the hysteresis disappears at cryogenic temperatures, indicating the "freeze-out" of the ionic diffusion contribution. When the same device is cooled under continuous poling, the built-in electric field from ion accumulation brings significant photovoltaic effect even at 10 K. From the change of photoluminescence upon polling, we found a second dipole-related mechanism which enhances radiative recombination upon the alignment of the organic cations. The ionic origin of hysteresis was also verified by applying a magnetic field to affect the ion diffusion. These findings reveal the coexistence of ionic and dipole-related mechanisms for the hysteresis in hybrid perovskites.

  4. Stable and durable CH3NH3PbI3 perovskite solar cells at ambient conditions

    NASA Astrophysics Data System (ADS)

    Rajamanickam, Nagalingam; Kumari, Sudesh; Kalyan Vendra, Venkat; Lavery, Brandon W.; Spurgeon, Joshua; Druffel, Thad; Sunkara, Mahendra K.

    2016-06-01

    Degradation of metal-organic halide perovskites when exposed to ambient conditions is a crucial issue that needs to be addressed for commercial viability of perovskite solar cells (PSCs). Here, a concept of encapsulating CH3NH3PbI3 perovskite crystals with a multi-functional graphene-polyaniline (PANI) composite coating to protect the perovskite against degradation from moisture, oxygen and UV light is presented. Hole-conducting polymers containing 2D layered sheet materials are presented here as multi-functional materials with oxygen and moisture impermeability. Specific studies involving PANI and graphene composites as coatings for perovskite crystals exhibited resistance to moisture and oxygen under continued exposure to UV and visible light. Most importantly, no perovskite degradation was observed even after 96 h of exposure of the PSCs to extremely high humidity (99% relative humidity). Our observations and results on perovskite protection with graphene/conducting polymer composites open up opportunities for glove-box-free and atmospheric processing of PSCs.

  5. Organic-inorganic halide perovskite solar cell with CH3NH3PbI2Br as hole conductor

    NASA Astrophysics Data System (ADS)

    Zhang, Shufang; Zhang, Chenming; Bi, Enbing; Miao, Xiaoliang; Zeng, Haibo; Han, Liyuan

    2017-01-01

    Perovskite solar cells (PSCs) have attracted enormous interest as the most remarkably growing photovoltaic devices. With the power conversion efficiencies of PSCs excessing 20%, great challenges have been focused on the issues of cost and long-term stability which are majorly related to the hole transport materials. In contrast, the PSCs without special hole conductors show great potential for commercial applications due to their cost-effective and fairly stable features. However, the inferior charge separation at the CH3NH3PbI3 (MAPbI3) and back electrode interface limits the cells for high efficiency. Our strategy is to arrange suitable energy band alignment at the interface to enhance the charge separation. We herein report a MAPbI3/MAPbI2Br cascade structured PSC with MAPbI2Br majorly acting as a hole conductor. The conversion efficiency of the PSCs is greatly improved and a high efficiency of 15.83% is achieved. This new design of using organic-inorganic halide perovskites as hole conductors provides an efficient approach for improving the performance of low-cost PSCs.

  6. Graphene doping methods and device applications.

    PubMed

    Oh, Jong Sik; Kim, Kyong Nam; Yeom, Geun Young

    2014-02-01

    Graphene has recently been studied as a promising material to replace and enhance conventional electronic materials in various fields such as electronics, photovoltaics, sensors, etc. However, for the electronic applications of graphene prepared by various techniques such as chemical vapor deposition, chemical exfoliation, mechanical exfoliation, etc., critical limitations are found due to the defects in the graphene in addition to the absence of a semiconducting band gap. For that, many researchers have investigated the doped graphene which is effective to tailor its electronic property and chemical reactivity. This work presents a review of the various graphene doping methods and their device applications. As doping methods, direct synthesis method and post treatment method could be categorized. Because the latter case has been widely investigated and used in various electronic applications, we will focus on the post treatment method. Post treatment method could be further classified into wet and dry doping methods. In the case of wet doping, acid treatment, metal chloride, and organic material coating are the methods used to functionalize graphene by using dip-coating, spin coating, etc. Electron charge transfer achieved from graphene to dopants or from dopants to graphene makes p-type or n-type graphenes, respectively, with sheet resistance reduction effect. In the case of dry doping, it can be further categorized into electrostatic field method, evaporation method, thermal treatment method, plasma treatment method, etc. These doping techniques modify Fermi energy level of graphene and functionalize the property of graphene. Finally, some perspectives and device applications of doped graphene are also briefly discussed.

  7. Electrochemiluminescence sensor for melamine based on a Ru(bpy)₃²⁺-doped silica nanoparticles/carboxylic acid functionalized multi-walled carbon nanotubes/Nafion composite film modified electrode.

    PubMed

    Chen, Xiaomei; Lian, Sai; Ma, Ying; Peng, Aihong; Tian, Xiaotian; Huang, Zhiyong; Chen, Xi

    2016-01-01

    In this work, a sensitive electrochemiluminescence (ECL) sensor for the determination of melamine (MEL) was developed based on a Ru(bpy)3(2+)-doped silica nanoparticles (RUDS)/carboxylic acid functionalized multi-walled carbon nanotubes (CMWCNTs)/Nafion composite film modified electrode. The homogeneous spherical RUDS were synthesized by a reverse microemulsion method. As Ru(bpy)3(2+) were encapsulated in the RUDS, Ru(bpy)3(2+) dropping from the modified electrode can be greatly prevented, which is helpful for obtaining a stable ECL signal. Moreover, to improve the conductivity of the film and promote the electron transfer rate on electrode surface, CMWCNTs with excellent electrical conductivity and large surface area were applied in the construction of the sensing film. As CMWCNTs acted as electron bridges making more Ru(bpy)3(2+) participate in the reaction, the ECL intensity was greatly enhanced. Under the optimum conditions, the relative ECL signal (△IECL) was proportional to the logarithmic MEL concentration ranging from 5×10(-13) to 1×10(-7) mol L(-1) with a detection limit of 1×10(-13) mol L(-1). To verify the reliability, the thus-fabricated ECL sensor was applied to determine the concentration of MEL in milk. Based on these investigations, the proposed ECL sensor exhibited good feasibility and high sensitivity for the determination of MEL, promising the applicability of this sensor in practical analysis.

  8. Doped liquid nitrobenzene is ferroelectric.

    PubMed

    Shelton, David P; Quine, Zachary

    2007-11-28

    The high resolution hyper-Rayleigh light scattering spectrum for liquid nitrobenzene doped with triflic acid (CF(3)SO(3)H) shows a narrow spike at zero frequency shift which has the polarization signature of a polar longitudinal collective mode. This spectral spike disappears for pure nitrobenzene. The spectral spike is interpreted as due to ferroelectric domains in the liquid. The dopant molecules appear to induce ferroelectric organization of the nitrobenzene molecules which is otherwise absent in the pure liquid. Estimated domain size is 34 nm and relaxation time is 50 ns.

  9. The Anti-Doping Movement.

    PubMed

    Willick, Stuart E; Miller, Geoffrey D; Eichner, Daniel

    2016-03-01

    Historical reports of doping in sports date as far back as the ancient Greek Olympic Games. The anti-doping community considers doping in sports to be cheating and a violation of the spirit of sport. During the past century, there has been an increasing awareness of the extent of doping in sports and the health risks of doping. In response, the anti-doping movement has endeavored to educate athletes and others about the health risks of doping and promote a level playing field. Doping control is now undertaken in most countries around the world and at most elite sports competitions. As athletes have found new ways to dope, however, the anti-doping community has endeavored to strengthen its educational and deterrence efforts. It is incumbent upon sports medicine professionals to understand the health risks of doping and all doping control processes.

  10. Acid diffusion through polyaniline membranes

    SciTech Connect

    Su, T.M.; Huang, S.C.; Conklin, J.A.

    1995-12-01

    Polyaniline membranes in the undoped (base) and doped (acid) forms are studied for their utility as pervaporation membranes. The separation of water from mixtures of propionic acid, acetic acid and formic acid have been demonstrated from various feed compositions. Doped polyaniline displays an enhanced selectivity of water over these organic acids as compared with undoped polyaniline. For as-cast polyaniline membranes a diffusion coefficient (D) on the order of 10{sup -9} cm{sup 2}/sec has been determined for the flux of protons through the membranes using hydrochloric acid.

  11. Polarization induced doped transistor

    SciTech Connect

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  12. Folic acid-targeted magnetic Tb-doped CeF3 fluorescent nanoparticles as bimodal probes for cellular fluorescence and magnetic resonance imaging.

    PubMed

    Ma, Zhi-Ya; Liu, Yu-Ping; Bai, Ling-Yu; An, Jie; Zhang, Lin; Xuan, Yang; Zhang, Xiao-Shuai; Zhao, Yuan-Di

    2015-10-07

    Magnetic fluorescent nanoparticles (NPs) have great potential applications for diagnostics, imaging and therapy. We developed a facile polyol method to synthesize multifunctional Fe3O4@CeF3:Tb@CeF3 NPs with small size (<20 nm), high water solubility and good biocompatibility. The NPs were modified by ligand exchange reactions with citric acid (CA) to obtain carboxyl-functionalized NPs (Fe3O4@CeF3:Tb@CeF3-COOH). Folic acid (FA) as an affinity ligand was then covalently conjugated onto NPs to yield Fe3O4@CeF3:Tb@CeF3-FA NPs. They were then applied as multimodal imaging agents for simultaneous in vitro targeted fluorescence imaging and magnetic resonance imaging (MRI) of HeLa cells with overexpressed folate receptors (FR). The results indicated that these NPs had strong luminescence and enhanced T2-weighted MR contrast and would be promising candidates as multimodal probes for both fluorescence and MRI imaging.

  13. Synthesis, characterization and fuel cell performance tests of boric acid and boron phosphate doped, sulphonated and phosphonated poly(vinyl alcohol) based composite membranes

    NASA Astrophysics Data System (ADS)

    Şahin, Alpay; Ar, İrfan

    2015-08-01

    The aim of this study is to synthesize a composite membrane having high proton conductivity, ion exchange capacity and chemical stability. In order to achieve this aim, poly(vinyl alcohol) (PVA) based composite membranes are synthesized by using classic sol-gel method. Boric acid (H3BO3) and boron phosphate (BPO4) are added to the membrane matrix in different ratios in order to enhance the membrane properties. Characterization tests, i.e; FT-IR analysis, mechanical strength tests, water hold-up capacities, swelling properties, ion exchange capacities, proton conductivities and fuel cell performance tests of synthesized membranes are carried out. As a result of performance experiments highest performance values are obtained for the membrane containing 15% boron phosphate at 0.6 V and 750 mA/cm2. Water hold-up capacity, swelling ratio, ion exchange capacity and proton conductivity of this membrane are found as 56%, 8%, 1.36 meq/g and 0.37 S/cm, respectively. These values are close to the values obtained ones for perfluorosulphonic acid membranes. Therefore this membrane can be regarded as a promising candidate for usage in fuel cells.

  14. Interfacial electronic structure at the CH3NH3PbI3/MoOx interface

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Liu, Xiaoliang; Lyu, Lu; Xie, Haipeng; Zhang, Hong; Niu, Dongmei; Huang, Han; Bi, Cheng; Xiao, Zhengguo; Huang, Jinsong; Gao, Yongli

    2015-05-01

    Interfacial electronic properties of the CH3NH3PbI3 (MAPbI3)/MoOx interface are investigated using ultraviolet photoemission spectroscopy and X-ray photoemission spectroscopy. It is found that the pristine MAPbI3 film coated onto the substrate of poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate)/indium tin oxide by two-step method behaves as an n-type semiconductor, with a band gap of ˜1.7 eV and a valence band edge of 1.40 eV below the Fermi energy (EF). With the MoOx deposition of 64 Å upon MAPbI3, the energy levels of MAPbI3 shift toward higher binding energy by 0.25 eV due to electron transfer from MAPbI3 to MoOx. Its conduction band edge is observed to almost pin to the EF, indicating a significant enhancement of conductivity. Meanwhile, the energy levels of MoOx shift toward lower binding energy by ˜0.30 eV, and an interface dipole of 2.13 eV is observed at the interface of MAPbI3/MoOx. Most importantly, the chemical reaction taking place at this interface results in unfavorable interface energy level alignment for hole extraction. A potential barrier of ˜1.36 eV observed for hole transport will impede the hole extraction from MAPbI3 to MoOx. On the other hand, a potential barrier of ˜0.14 eV for electron extraction is too small to efficiently suppress electrons extracted from MAPbI3 to MoOx. Therefore, such an interface is not an ideal choice for hole extraction in organic photovoltaic devices.

  15. Iron (III) chloride doping of CVD graphene.

    PubMed

    Song, Yi; Fang, Wenjing; Hsu, Allen L; Kong, Jing

    2014-10-03

    Chemical doping has been shown as an effective method of reducing the sheet resistance of graphene. We present the results of our investigations into doping large area chemical vapor deposition graphene using Iron (III) Chloride (FeCl(3)). It is shown that evaporating FeCl(3) can increase the carrier concentration of monolayer graphene to greater than 10(14) cm(-2) and achieve resistances as low as 72 Ω sq(-1). We also evaluate other important properties of the doped graphene such as surface cleanliness, air stability, and solvent stability. Furthermore, we compare FeCl(3) to three other common dopants: Gold (III) Chloride (AuCl(3)), Nitric Acid (HNO(3)), and TFSA ((CF(3)SO(2))(2)NH). We show that compared to these dopants, FeCl(3) can not only achieve better sheet resistance but also has other key advantages including better solvent stability.

  16. Absorption enhancement in CH3NH3PbI3 solar cell using a TiO2/MoS2 nanocomposite electron selective contact

    NASA Astrophysics Data System (ADS)

    Imran Ahmed, Muhammad; Hussain, Zakir; Khalid, Amir; Noman Amin, Hafiz Muhammad; Habib, Amir

    2016-04-01

    In the present contribution, perovskite absorbers have been combined with few layer thick MoS2 semiconductor to put together a solar cell allowing broad spectrum harvesting of solar radiations. Such modification allows to achieve solar light harvesting at the band edges, addressing a drawback of CH3NH3PbI3 absorbers. We recorded an improved efficiency from 3.7% to 4.3% on the back of this methodology. We have also worked out a novel methodology to synthesize TiO2/MoS2 nanocomposite by in situ dispersion of liquid exfoliated MoS2 sheets in the sol gel reaction.

  17. Perspective: Understanding of ripening growth model for minimum residual PbI2 and its limitation in the planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Se-Yun; Jo, Hyo Jeong; Sung, Shi-Joon; Kim, Dae-Hwan

    2016-10-01

    The power conversion efficiency of lead halide perovskite solar cells recently surpassed 22.1%. In this study, we suggest the perovskite absorber growth mechanism of the two-step process could be explained by an Ostwald ripening growth model for planar-structure perovskite solar cells. We attempt to find out the source of two main problems such as unreacted PbI2 and non-uniformed morphology by the proposed ripening growth mechanism and experimental results. This growth mechanism opens the way toward understanding a key aspect of the photovoltaic operation of high-efficiency, two-step perovskite solar cells.

  18. CH3NH3PbI3 films prepared by combining 1- and 2-step deposition: how crystal growth conditions affect properties.

    PubMed

    Mokhtar, Muhamad Z; Chen, Mu; Whittaker, Eric; Hamilton, Bruce; Aristidou, Nicholas; Ramadan, Simko; Gholinia, Ali; Haque, Saif A; O'Brien, Paul; Saunders, Brian R

    2017-02-24

    Perovskite solar cells continue to attract strong attention because of their unprecedented rate of power conversion efficiency increase. CH3NH3PbI3 (MAPbI3) is the most widely studied perovskite. Typically one-step (1-s) or two-step (2-s) deposition methods are used to prepare MAPbI3 films. Here, we investigate a new MAPbI3 film formation method that combines 1-s and 2-s deposition (termed 1 & 2-s) and uses systematic variation of the stoichiometric mole ratio (x) for the PbI2 + xMAI solutions employed. The PbI2 + xMAI solutions were used to deposit precursor films that were subsequently dipped in MAI solution as a second step to produce the final MAPbI3 films. The morphologies of the 1 & 2-s MAPbI3 films consisted of three crystal types: tree-like microcrystals (≫1 μm), cuboid meso-crystals (∼0.1-1 μm) and nanocrystals (∼50-80 nm). Each crystal type and their proportions were controlled by the value for x. The new 1 & 2-s deposition method produced MAPbI3 films with tuneable optoelectronic properties that were related to those for the conventional 1-s and 2-s films. However, the 1 & 2-s film properties were not simply a combination of those for the 1-s and 2-s films. The 1 & 2-s films showed enhanced light scattering and the photoluminescence spectra displayed a morphologically-dependent red-shift. The unique morphologies for the 1 & 2-s films also strongly influenced PbI2 conversion, power conversion efficiency, hysteresis and recombination. The trends for the performance parameters and hysteresis were compared for devices constructed using spiro-MeOTAD and P3HT and were similar. The 1 & 2-s method should apply to other perovskite formulations and the new insights concerning MAPbI3 crystal growth conditions, morphology and material properties established in this study should also be transferable.

  19. Phonon anharmonicity, lifetimes, and thermal transport in CH3NH3PbI3 from many-body perturbation theory

    NASA Astrophysics Data System (ADS)

    Whalley, Lucy D.; Skelton, Jonathan M.; Frost, Jarvist M.; Walsh, Aron

    2016-12-01

    Lattice vibrations in CH3NH3PbI3 are strongly interacting, with double-well instabilities present at the Brillouin zone boundary. Analysis within a first-principles lattice-dynamics framework reveals anharmonic potentials with short phonon quasiparticle lifetimes and mean free paths. The phonon behavior is distinct from the inorganic semiconductors GaAs and CdTe where three-phonon interaction strengths are three orders of magnitude smaller. The implications for the applications of hybrid halide perovskites arising from thermal conductivity, band-gap deformation, and charge-carrier scattering through electron-phonon coupling, are presented.

  20. Mesoporous PbI2 assisted growth of large perovskite grains for efficient perovskite solar cells based on ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Li, Shibin; Zhang, Peng; Chen, Hao; Wang, Yafei; Liu, Detao; Wu, Jiang; Sarvari, Hojjatollah; Chen, Zhi David

    2017-02-01

    Perovskite solar cells (PSCs) have attracted great attention due to their low cost and high power conversion efficiency (PCE). However, the defects and grain boundaries in perovskite films dramatically degrade their performance. Here, we show a two-step annealing method to produce mesoporous PbI2 films for growth of continuous, pinhole-free perovskite films with large grains, followed by additional ethanol vapor annealing of perovskite films to reduce the defects and grain boundaries. The large perovskite grains dramatically suppress the carrier recombination, and consequently we obtain ZnO-nanorod-based PSCs that exhibit the best efficiency of 17.3%, with high reproducibility.

  1. Aero dopes and varnishes

    NASA Technical Reports Server (NTRS)

    Britton, H T S

    1927-01-01

    Before proceeding to discuss the preparation of dope solutions, it will be necessary to consider some of the essential properties which should be possessed of a dope film, deposited in and on the surface of an aero fabric. The first is that it should tighten the material and second it should withstand weathering.

  2. Degradation of CH3NH3PbI3 perovskite due to soft x-ray irradiation as analyzed by an x-ray photoelectron spectroscopy time-dependent measurement method

    NASA Astrophysics Data System (ADS)

    Motoki, Keisuke; Miyazawa, Yu; Kobayashi, Daisuke; Ikegami, Masashi; Miyasaka, Tsutomu; Yamamoto, Tomoyuki; Hirose, Kazuyuki

    2017-02-01

    The effects of soft X-ray exposure on structures of CH3NH3PbI3 perovskite were investigated using an X-ray photoelectron spectroscopy (XPS) time-dependent measurement method. A crystalline sample was fabricated with the inverse-temperature crystallization method. The time evolutions of the core-level and valence-band spectra were recorded to determine the compositional ratios and valence band electronic structure of the sample, respectively. In addition, first-principles calculations were conducted to evaluate the valence band XPS spectra. The in situ XPS analysis combined with theoretical calculations demonstrated a degradation of the surface of CH3NH3PbI3 perovskite into PbI2 owing to the evaporation of methylammonium iodide.

  3. Stable and low-cost mesoscopic CH3NH3PbI2 Br perovskite solar cells by using a thin poly(3-hexylthiophene) layer as a hole transporter.

    PubMed

    Zhang, Meng; Lyu, Miaoqiang; Yu, Hua; Yun, Jung-Ho; Wang, Qiong; Wang, Lianzhou

    2015-01-02

    Mesoscopic perovskite solar cells using stable CH3 NH3 PbI2 Br as a light absorber and low-cost poly(3-hexylthiophene) (P3HT) as hole-transporting layer were fabricated, and a power conversion efficiency of 6.64 % was achieved. The partial substitution of iodine with bromine in the perovskite led to remarkably prolonged charge carrier lifetime. Meanwhile, the replacement of conventional thick spiro-MeOTAD layer with a thin P3HT layer has significantly reduced the fabrication cost. The solar cells retained their photovoltaic performance well when they were exposed to air without any encapsulation, presenting a favorable stability. The combination of CH3 NH3 PbI2 Br and P3HT may render a practical and cost-effective solid-state photovoltaic system. The superior stability of CH3 NH3 PbI2 Br is also promising for other photoconversion applications.

  4. Doping Level of Boron-Doped Diamond Electrodes Controls the Grafting Density of Functional Groups for DNA Assays.

    PubMed

    Švorc, Ĺubomír; Jambrec, Daliborka; Vojs, Marian; Barwe, Stefan; Clausmeyer, Jan; Michniak, Pavol; Marton, Marián; Schuhmann, Wolfgang

    2015-09-02

    The impact of different doping levels of boron-doped diamond on the surface functionalization was investigated by means of electrochemical reduction of aryldiazonium salts. The grafting efficiency of 4-nitrophenyl groups increased with the boron levels (B/C ratio from 0 to 20,000 ppm). Controlled grafting of nitrophenyldiazonium was used to adjust the amount of immobilized single-stranded DNA strands at the surface and further on the hybridization yield in dependence on the boron doping level. The grafted nitro functions were electrochemically reduced to the amine moieties. Subsequent functionalization with a succinic acid introduced carboxyl groups for subsequent binding of an amino-terminated DNA probe. DNA hybridization significantly depends on the probe density which is in turn dependent on the boron doping level. The proposed approach opens new insights for the design and control of doped diamond surface functionalization for the construction of DNA hybridization assays.

  5. Molecularly doped metals.

    PubMed

    Avnir, David

    2014-02-18

    The many millions of organic, inorganic, and bioorganic molecules represent a very rich library of chemical, biological, and physical properties that do not show up among the approximately 100 metals. The ability to imbue metals with any of these molecular properties would open up tremendous potential for the development of new materials. In addition to their traditional features and their traditional applications, metals would have new traits, which would merge their classical virtues such as conductivity and catalytic activity with the diverse properties of these molecules. In this Account, we describe a new materials methodology, which enables, for the first time, the incorporation and entrapment of small organic molecules, polymers, and biomolecules within metals. These new materials are denoted dopant@metal. The creation of dopant@metal yields new properties that are more than or different from the sum of the individual properties of the two components. So far we have developed methods for the doping of silver, copper, gold, iron, palladium, platinum, and some of their alloys, as well as Hg-Ag amalgams. We have successfully altered classical metal properties (such as conductivity), induced unorthodox properties (such as rendering a metal acidic or basic), used metals as heterogeneous matrices for homogeneous catalysts, and formed new metallic catalysts such as metals doped with organometallic complexes. In addition, we have created materials that straddle the border between polymers and metals, we have entrapped enzymes to form bioactive metals, we have induced chirality within metals, we have made corrosion-resistant iron, we formed efficient biocidal materials, and we demonstrated a new concept for batteries. We have developed a variety of methods for synthesizing dopant@metals including aqueous homogeneous and heterogeneous reductions of the metal cations, reductions in DMF, electrochemical entrapments, thermal decompositions of zerovalent metal carbonyls

  6. Doped graphene supercapacitors

    NASA Astrophysics Data System (ADS)

    Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-12-01

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

  7. Novel nanorose-like Ce(III)-doped and undoped Cu(II)-biphenyl-4,4-dicarboxylic acid (Cu(II)-BPDCA) MOSs as visible light photocatalysts: synthesis, characterization, photodegradation of toxic dyes and optimization.

    PubMed

    Mousavinia, S E; Hajati, S; Ghaedi, M; Dashtian, K

    2016-04-28

    A novel nanorose-like metal organic system (MOS) based on Cu(II) and biphenyl-4,4-dicarboxylic acid (Cu-BPDCA) was hydrothermally synthesized and characterized via EDS, FE-SEM, XRD, DRS and FT-IR analysis. This novel nanomaterial was found to be of narrow energy band gap (1.24 eV) and thus it was applied as a photocatalyst driven by visible light for the degradation of the rose bengal (RB) and eosin Y (EY) dyes. For further improvement in the photocatalytic performance of Cu-BPDCA, it was doped with a trace amount of Ce(III) in a simple way followed by characterization. The achieved improvement is due to the formation of a large number of O2⁻˙ and ˙OH radicals compared to the case of undoped Cu-BPDCA. The influence of important variables such as initial dye concentration, photocatalyst dosage and time of irradiation on the photocatalytic degradation efficiency was studied and optimized using central composite design. The optimum condition for the photodegradation of RB was found to be 40 min, 4.0 mg L(-1) and 0.015 g, corresponding to the irradiation time, RB concentration and photocatalyst mass, respectively. The photodegradation of EY was optimized at 4.0, 76 min, 5.9 mg L(-1) and 0.015 g corresponding to the pH, irradiation time, EY concentration and photocatalyst mass, respectively. At these optimum conditions, the photocatalytic degradation percentages of RB and EY with a desirability of 0.95 and 1.0 were found to be 78.90% and 67.63%, respectively. Kinetics study showed that the Langmuir-Hinshelwood kinetics model suitably fits the experimental data. From the Langmuir-Hinshelwood kinetics model, a significantly high photodegradation to surface adsorption ratio was obtained which is the great advantage of this work in addition to applying visible light.

  8. Antiferroelectric Nature of CH3NH3PbI3‑xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-07-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3‑xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3‑xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

  9. Facile Face-Down Annealing Triggered Remarkable Texture Development in CH3NH3PbI3 Films for High-Performance Perovskite Solar Cells.

    PubMed

    Zhu, Weidong; Kang, Lei; Yu, Tao; Lv, Bihu; Wang, Yangrunqian; Chen, Xingyu; Wang, Xiaoyong; Zhou, Yong; Zou, Zhigang

    2017-02-22

    Herein, we demonstrate that the facile face-down annealing route which effectively confines the evaporation of residual solvent molecules in one-step deposited precursor films can controllably enable the formation of (110) textured CH3NH3PbI3 films consisting of high-crystallinity well-ordered micrometer-sized grains that span vertically the entire film thickness. Such microstructural features dramatically decrease nonradiative recombination sites as well as greatly improve the transport property of charge carries in the films compared with that of the nontextured ones obtained by the conventional annealing route. As a consequence, the planar-heterojunction perovskite solar cells with these textured CH3NH3PbI3 films exhibit significantly enhanced power conversion efficiency (PCE) along with small hysteresis and excellent stability. The champion cell yields impressive PCE boosting to 18.64% and a stabilized value of around 17.22%. Particularly, it can maintain 86% of its initial value after storage for 20 days in ambient conditions with relative humidity of 10-20%. Our work suggests a facile and effective route for further boosting the efficiency and stability of low-cost perovskite solar cells.

  10. Effects of incorporating PbS quantum dots in perovskite solar cells based on CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Wang, Wenyong

    2015-10-01

    PbS quantum dots (QDs), prepared by the successive ionic layer adsorption and reaction (SILAR) method, are incorporated in perovskite solar cells based on CH3NH3PbI3. Enhanced light absorption in the wavelength range of 330-1400 nm is observed, and the cell prepared with 2 SILAR coating cycles exhibits the best photovoltaic performance. It is observed that the PbS QDs can reduce the TiO2 decomposition damage to the CH3NH3PbI3 films and promote the stability of the modified perovskite solar cells. Charge transfer dynamics in the perovskite solar cells is studied with intensity modulated photocurrent/photovoltage spectroscopy, and improved charge diffusion lengths are obtained for the modified cells, with the best value of 0.86 μm obtained for the device prepared with 2 SILAR coating cycles. This improvement could be attributed to the enhanced electron transport and reduced electron recombination processes in the device structures after incorporating PbS QDs.

  11. The nature of hydrogen-bonding interaction in the prototypic hybrid halide perovskite, tetragonal CH3NH3PbI3

    PubMed Central

    Lee, June Ho; Lee, Jung-Hoon; Kong, Eui-Hyun; Jang, Hyun Myung

    2016-01-01

    In spite of the key role of hydrogen bonding in the structural stabilization of the prototypic hybrid halide perovskite, CH3NH3PbI3 (MAPbI3), little progress has been made in our in-depth understanding of the hydrogen-bonding interaction between the MA+-ion and the iodide ions in the PbI6-octahedron network. Herein, we show that there exist two distinct types of the hydrogen-bonding interaction, naming α- and β-modes, in the tetragonal MAPbI3 on the basis of symmetry argument and density-functional theory calculations. The computed Kohn-Sham (K-S) energy difference between these two interaction modes is 45.14 meV per MA-site with the α-interaction mode being responsible for the stable hydrogen-bonding network. The computed bandgap (Eg) is also affected by the hydrogen-bonding mode, with Eg of the α-interaction mode (1.73 eV) being significantly narrower than that of the β-interaction mode (2.03 eV). We have further estimated the individual bonding strength for the ten relevant hydrogen bonds having a bond critical point. PMID:26892429

  12. Nanoscale charge localization induced by random orientations of organic molecules in hybrid perovskite CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Wang, Lin-Wang

    2015-03-01

    Perovskite-based solar cells have achieved high solar-energy conversion efficiencies and attracted wide attentions nowadays. Despite the rapid progress in solar-cell devices, many fundamental issues of the hybrid perovskites have not been fully understood. Experimentally, it is well known that in CH3NH3PbI3, the organic molecules CH3NH3 are randomly orientated at the room temperature, but the impact of the random molecular orientation has not been investigated. Using linear-scaling ab-initiomethods, we have calculated the electronic structures of the tetragonal phase of CH3NH3PbI3 with randomly orientated organic molecules in large supercells up to ~20,000 atoms. Due to the dipole moment of the organic molecule, the random orientation creates a novel system with long-range potential fluctuations unlike alloys or other conventional disordered systems. We find that the charge densities of the conduction-band minimum and the valence-band maximum are localized separately in nanoscales due to the potential fluctuations. The charge localization causes electron-hole separation and reduces carrier recombination rates, which may contribute to the long carrier lifetime observed in experiments. We have also proposed a model to explain the charge localization.

  13. Antiferroelectric Nature of CH3NH3PbI3−xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    PubMed Central

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-01-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3−xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3−xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation. PMID:27468802

  14. Using elemental Pb surface as a precursor to fabricate large area CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    He, Yingying; Lei, Yan; Yang, Xiaogang; Lu, Kai; Liu, Songzi; Gu, Longyan; Zheng, Zhi

    2016-12-01

    The development of new chemical methods to prepare large area perovskite thin film solar cells is desirable for potential future industrial applications. In this paper, a novel fabrication of perovskite CH3NH3PbI3 thin films based on direct metal surface elemental reaction (DMSER) method in an ambient atmosphere is discussed. The as-prepared CH3NH3PbI3 thin films are highly pure and crystalline. Consequent Transient photovoltaic (TPV) tests were conducted and show that these thin films have a long minority carrier lifetime as good as the perovskite thin films obtained via common two-step method from the literature. Although there have been many studies that have developed perovskite solar cells (PSCs) during the past five years, the current study is the first report using elemental Pb as a precursor to fabricate perovskite solar cells, which were found to be relatively stable upon storage without encapsulation in glove box for more than 200 days. This Pb-initiated in-situ reaction allows for the fabrication of large area and uniform perovskite thin films. For example, in our preliminary studies, we have fabricated large area solar cell device samples (1.10 ± 0.05 cm2) and have evaluated their photovoltaic performance under standard conditions (AM 1.5, 100 mW cm-2).

  15. Coexistence of Two Electronic Nano-Phases on a CH3NH3PbI3-xClx Surface Observed in STM Measurements.

    PubMed

    Yost, Andrew J; Pimachev, Artem; Ho, Chun-Chih; Darling, Seth B; Wang, Leeyih; Su, Wei-Fang; Dahnovsky, Yuri; Chien, TeYu

    2016-10-10

    Scanning tunneling microscopy is utilized to investigate the local density of states of a CH3NH3PbI3-xClx perovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH3NH3PbI3-xClx perovskite layer are observed by the dI/dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface. Density functional theory calculations indicate that the observed electronic phases are associated with local deviation of I/Cl ratio, rather than different orientations of the electric dipole moments in the ferroelectric phases. By comparing the calculated results with experimental data we conclude that phase A (lower contrast in dI/dV mapping at -2.0 V bias) contains a lower I/Cl ratio than that in phase B (higher contrast in dI/dV).

  16. Coexistence of two electronic nano-phases on a CH3NH3PbI3–xClx surface observed in STM measurements

    DOE PAGES

    Yost, Andrew J.; Pimachev, Artem; Ho, Chun -Chih; ...

    2016-10-10

    Scanning tunneling microscopy is utilized to investigate the local density of states of a CH3NH3PbI3-xClx perovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH3NH3PbI3-xClx perovskite layer are observed by the dI/ dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface. Density functional theory calculations indicate that the observed electronic phases are associated with local deviation of I/Cl ratio, rather than different orientations ofmore » the electric dipole moments in the ferroelectric phases. Furthermore, by comparing the calculated results with experimental data we conclude that phase A (lower contrast in dI/dV mapping at -2.0 V bias) contains a lower I/Cl ratio than that in phase B (higher contrast in dI/dV).« less

  17. Isoelectronic co-doping

    DOEpatents

    Mascarenhas, Angelo

    2004-11-09

    Isoelectronic co-doping of semiconductor compounds and alloys with deep acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, N and Bi, to customize solar cells, thermal voltaic cells, light emitting diodes, photodetectors, and lasers on GaP, InP, GaAs, Ge, and Si substrates. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  18. Marijuana as doping in sports.

    PubMed

    Campos, Daniel R; Yonamine, Mauricio; de Moraes Moreau, Regina L

    2003-01-01

    A high incidence of positive cases for cannabinoids, in analyses for doping control in sports, has been observed since the International Olympic Committee (IOC) included them in the 1989 list of prohibited drugs under the title of classes of prohibited substances in certain circumstances. Where the rules of sports federations so provide, tests are conducted for marijuana, hashish or any other cannabis product exposure by means of urinalysis of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (carboxy-THC) the main metabolite of delta-9-tetrahydrocannabinol (THC). Concentrations >15 ng/mL (cut-off value) in confirmatory analytical procedures are considered doping. Cannabis is an illicit drug in several countries and has received much attention in the media for its potential therapeutic uses and the efforts to legalise its use. Studies have demonstrated that the use of cannabinoids can reduce anxiety, but it does not have ergogenic potential in sports activities. An increase in heart rate and blood pressure, decline of cardiac output and reduced psychomotor activity are some of the pharmacological effects of THC that will determine a decrease in athletic performance. An ergolytic activity of cannabis products has been observed in athletes of several different sport categories. In Brazil, analyses for doping control in sports, performed in our laboratories, have detected positive cases for carboxy-THC in urine samples of soccer, volleyball, cycling and other athletes. It is our intention to discuss in this article some points that may discourage individuals from using cannabis products during sports activities, even in the so-called permitted circumstances defined by the IOC and some sports federations.

  19. Improving the performance of perovskite solar cells with glycerol-doped PEDOT:PSS buffer layer

    NASA Astrophysics Data System (ADS)

    Jian-Feng, Li; Chuang, Zhao; Heng, Zhang; Jun-Feng, Tong; Peng, Zhang; Chun-Yan, Yang; Yang-Jun, Xia; Duo-Wang, Fan

    2016-02-01

    In this paper, we investigate the effects of glycerol doping on transmittance, conductivity and surface morphology of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)) (PEDOT:PSS) and its influence on the performance of perovskite solar cells. . The conductivity of PEDOT:PSS is improved obviously by doping glycerol. The maximum of the conductivity is 0.89 S/cm when the doping concentration reaches 6 wt%, which increases about 127 times compared with undoped. The perovskite solar cells are fabricated with a configuration of indium tin oxide (ITO)/PEDOT:PSS/CH3NH3PbI3/PC61BM/Al, where PEDOT:PSS and PC61BM are used as hole and electron transport layers, respectively. The results show an improvement of hole charge transport as well as an increase of short-circuit current density and a reduction of series resistance, owing to the higher conductivity of the doped PEDOT:PSS. Consequently, it improves the whole performance of perovskite solar cell. The power conversion efficiency (PCE) of the device is improved from 8.57% to 11.03% under AM 1.5 G (100 mW/cm2 illumination) after the buffer layer has been modified. Project supported by the National Natural Science Foundation of China (Grant Nos. 61264002, 61166002, 91333206, and 51463011), the Natural Science Foundation of Gansu Province, China (Grant No. 1308RJZA159), the New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-13-0840), the Research Project of Graduate Teacher of Gansu Province, China (Grant No. 2014A-0042), and the Postdoctoral Science Foundation from Lanzhou Jiaotong University, China.

  20. Detonation nanodiamonds for doping Kevlar.

    PubMed

    Comet, Marc; Pichot, Vincent; Siegert, Benny; Britz, Fabienne; Spitzer, Denis

    2010-07-01

    This paper reports on the first attempt to enclose diamond nanoparticles--produced by detonation--into a Kevlar matrix. A nanocomposite material (40 wt% diamond) was prepared by precipitation from an acidic solution of Kevlar containing dispersed nanodiamonds. In this material, the diamond nanoparticles (Ø = 4 nm) are entirely wrapped in a Kevlar layer about 1 nm thick. In order to understand the interactions between the nanodiamond surface and the polymer, the oxygenated surface functional groups of nanodiamond were identified and titrated by Boehm's method which revealed the exclusive presence of carboxyl groups (0.85 sites per nm2). The hydrogen interactions between these groups and the amide groups of Kevlar destroy the "rod-like" structure and the classical three-dimensional organization of this polymer. The distortion of Kevlar macromolecules allows the wrapping of nanodiamonds and leads to submicrometric assemblies, giving a cauliflower structure reminding a fractal object. Due to this structure, the macroscopic hardness of Kevlar doped by nanodiamonds (1.03 GPa) is smaller than the one of pure Kevlar (2.31 GPa). To our knowledge, this result is the first illustration of the change of the mechanical properties induced by doping the Kevlar with nanoparticles.

  1. [Doping: effectiveness, consequences, prevention].

    PubMed

    Guezennec, C Y

    2001-02-01

    The use of doping is linked with the history of sports. Doping abuse escalated until the mid sixties when government and sports authorities responded with antidoping laws and drug testing. Today, the details of substances detected in controls give a good indication on the importance of doping use. Three classes of pharmaceuticals account for most of the positive controls. They are anabolic steroids, stimulants and narcotics. Their use can be related with the goal of the athletes. Anabolic steroids are mainly used in sports such as bodybuilding or weight lifting in order to develop strength. Stimulants are used in sports were speed favors performance. All the products that enhance blood oxygen transportation are used in endurance sports, their efficacy is not scientifically demonstrated, but their use does result in real risks. Several studies have evidenced the medical problems resulting from prolonged doping. Doping control is impaired by the fact that many products now used, e.g. EPO or rhGH, are not detectable. Regular medical examination of athletes could help prevent use of doping.

  2. Hole-Conductor-Free, Metal-Electrode-Free TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on a Low-Temperature Carbon Electrode.

    PubMed

    Zhou, Huawei; Shi, Yantao; Dong, Qingshun; Zhang, Hong; Xing, Yujin; Wang, Kai; Du, Yi; Ma, Tingli

    2014-09-18

    Low cost, high efficiency, and stability are straightforward research challenges in the development of organic-inorganic perovskite solar cells. Organolead halide is unstable at high temperatures or in some solvents. The direct preparation of a carbon layer on top becomes difficult. In this study, we successfully prepared full solution-processed low-cost TiO2/CH3NH3PbI3 heterojunction (HJ) solar cells based on a low-temperature carbon electrode. Power conversion efficiency of mesoporous (M-)TiO2/CH3NH3PbI3/C HJ solar cells based on a low-temperature-processed carbon electrode achieved 9%. The devices of M-TiO2/CH3NH3PbI3/C HJ solar cells without encapsulation exhibited advantageous stability (over 2000 h) in air in the dark. The ability to process low-cost carbon electrodes at low temperature on top of the CH3NH3PbI3 layer without destroying its structure reduces the cost and simplifies the fabrication process of perovskite HJ solar cells. This ability also provides higher flexibility to choose and optimize the device, as well as investigate the underlying active layers.

  3. Influence of PbCl2 content in PbI2 solution of DMF on the absorption, crystal phase, morphology of lead halide thin films and photovoltaic performance in planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Mao; Shi, Chengwu; Zhang, Jincheng; Wu, Ni; Ying, Chao

    2015-11-01

    In this paper, the influence of PbCl2 content in PbI2 solution of DMF on the absorption, crystal phase and morphology of lead halide thin films was systematically investigated and the photovoltaic performance of the corresponding planar perovskite solar cells was evaluated. The result revealed that the various thickness lead halide thin film with the small sheet-like, porous morphology and low crystallinity can be produced by adding PbCl2 powder into PbI2 solution of DMF as a precursor solution. The planar perovskite solar cell based on the 300-nm-thick CH3NH3PbI3-xClx thin film by the precursor solution with the mixture of 0.80 M PbI2 and 0.20 M PbCl2 exhibited the optimum photoelectric conversion efficiency of 10.12% along with an open-circuit voltage of 0.93 V, a short-circuit photocurrent density of 15.70 mA cm-2 and a fill factor of 0.69.

  4. Electrical characteristics and doping mechanism of DNA molecules doped with iodine solutions.

    PubMed

    Kim, Nam-Hoon; Lee, Woo Cheol; Roh, Yonghan

    2010-05-01

    This study examined the electrical characteristics of deoxyribonucleic acid (DNA) molecules doped with iodine solution and their chemical state changes before and after doping. The experiments were progressed in each lambda (A), poly(dA)-poly(dT) and poly(dG)-poly(dC) DNA under the same conditions. The authors prepared 20 nm gap Au/Ti electrodes fabricated by e-beam lithography. DNA solutions were dropped on the nano gap of the electrodes and DNA films were formed by drying in a vacuum. DNA films were doped with an iodine solution dissolved in methanol. The authors measured the electrical conductivity of DNA molecules as the number of iodine doping times in 10(-2) torr vacuum. As increase of the iodine solution doping number, the electrical conductivity of three sorts of DNA molecules was remarkably improved respectively. X-ray photoelectron spectroscopy (XPS) was performed to inspect the electrical conduction mechanism that holes on DNA nitrogen region were generated by transferring electrons to iodine molecules.

  5. Photocatalysis with chromium-doped TiO2: bulk and surface doping.

    PubMed

    Ould-Chikh, Samy; Proux, Olivier; Afanasiev, Pavel; Khrouz, Lhoussain; Hedhili, Mohamed N; Anjum, Dalaver H; Harb, Moussab; Geantet, Christophe; Basset, Jean-Marie; Puzenat, Eric

    2014-05-01

    The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts.

  6. Effect of doping on photovoltaic characteristics of graphene

    NASA Astrophysics Data System (ADS)

    Deepshikha

    2016-12-01

    Chemical doping of CVD grown graphene by introducing PTSA ( n-type) and NBD ( p-type) dopants is explored. This type of doping is key building block for photovoltaic and optoelectronic devices. Doped graphene samples display (1) high transmittance in the visible and near-infrared spectrum and (2) tunable graphene sheet resistance and work function. Large area and uniform graphene films were produced by chemical vapor deposition on copper foils and transferred onto quartz as transparent substrates. For n doping, a solution of p-toluenesulfonic acid (PTSA) was first dropped and spin-coated on the graphene/quartz and then annealed at 100°C for 10 min to make graphene uniformly n-type. Subsequently, a bare graphene was transferred on another quartz substrate, a solution of 4-nitrobenzenediazonium tetrafluoroborate (NBD) was dropped and spin-coated on the surface of graphene and similarly annealed. As a result, the graphene was p and n doped on the different quartz substrates. Doped graphene samples were characterized by different techniques. Experimental results suggested that doped graphene sheets with tunable electrical resistance and high optical transparency can be incorporated into photovoltaics and optoelectronics devices.

  7. Physically Cross-linked Polymer Binder Induced by Reversible Acid-Base Interaction for High-Performance Silicon Composite Anodes.

    PubMed

    Lim, Sanghyun; Chu, Hodong; Lee, Kukjoo; Yim, Taeeun; Kim, Young-Jun; Mun, Junyoung; Kim, Tae-Hyun

    2015-10-28

    Silicon is greatly promising for high-capacity anode materials in lithium-ion batteries (LIBs) due to their exceptionally high theoretical capacity. However, it has a big challenge of severe volume changes during charge and discharge, resulting in substantial deterioration of the electrode and restricting its practical application. This conflict requires a novel binder system enabling reliable cyclability to hold silicon particles without severe disintegration of the electrode. Here, a physically cross-linked polymer binder induced by reversible acid-base interaction is reported for high performance silicon-anodes. Chemical cross-linking of polymer binders, mainly based on acidic polymers including poly(acrylic acid) (PAA), have been suggested as effective ways to accommodate the volume expansion of Si-based electrodes. Unlike the common chemical cross-linking, which causes a gradual and nonreversible fracturing of the cross-linked network, a physically cross-linked binder based on PAA-PBI (poly(benzimidazole)) efficiently holds the Si particles even after the large volume changes due to its ability to reversibly reconstruct ionic bonds. The PBI-containing binder, PAA-PBI-2, exhibited large capacity (1376.7 mAh g(-1)), high Coulombic efficiency (99.1%) and excellent cyclability (751.0 mAh g(-1) after 100 cycles). This simple yet efficient method is promising to solve the failures relating with pulverization and isolation from the severe volume changes of the Si electrode, and advance the realization of high-capacity LIBs.

  8. Delta-doping of Semiconductors

    NASA Astrophysics Data System (ADS)

    Schubert, E. F.

    2005-08-01

    Part I: 1. Introduction E. F. Schubert; Part II: 2. Electronic structure of delta-doped semiconductors C. R. Proetto; Part III: 3. Recent progress in delta-like confinement of impurities in GaAs K. H. Ploog; 4. Flow-rate modulation epitaxy (FME) of III-V semiconductors T. Makimoto and Y. Horikoshi; 5. Gas source molecular beam epitaxy (MBE) of delta-doped III-V semiconductors D. Ritter; 6. Solid phase epitaxy for delta-doping in silicon I. Eisele; 7. Low temperature MBE of silicon H.-J. Gossmann; Part IV: 8. Secondary ion mass spectrometry of delta-doped semiconductors H. S. Luftmann; 9. Capacitance-voltage profiling E. F. Schubert; 10. Redistribution of impurities in III-V semiconductors E. F. Schubert; 11. Dopant diffusion and segregation in delta-doped silicon films H.-J. Gossmann; 12. Characterisation of silicon and delta-doped structures in GaAs R. C. Newman; 13. The DX-center in silicon delta-doped GaAs and AlxGa1-xAs P. M. Koenraad; Part V: 14. Luminescence and ellipsometry spectroscopy H. Yao and E. F. Schubert; 15. Photoluminescence and Raman spectroscopy of single delta-doped III-V semiconductor heterostructures J. Wagner and D. Richards; 16. Electron transport in delta-doped quantum wells W. T. Masselink; 17. Electron mobility in delta-doped layers P. M. Koenraad; 18. Hot electrons in delta-doped GaAs M. Asche; 19. Ordered delta-doping R. L. Headrick, L. C. Feldman and B. E. Weir; Part IV: 20. Delta-doped channel III-V field effect transistors (FETs) W.-P. Hong; 21. Selectively doped heterostructure devices E. F. Schubert; 22. Silicon atomic layer doping FET K. Nakagawa and K. Yamaguchi; 23. Planar doped barrier devices R. J. Malik; 24. Silicon interband and intersubband photodetectors I. Eisele; 25. Doping superlattice devices E. F. Schubert.

  9. Origin and structure of polar domains in doped molecular crystals

    PubMed Central

    Meirzadeh, E.; Azuri, I.; Qi, Y.; Ehre, D.; Rappe, A. M.; Lahav, M.; Kronik, L.; Lubomirsky, I.

    2016-01-01

    Doping is a primary tool for the modification of the properties of materials. Occlusion of guest molecules in crystals generally reduces their symmetry by the creation of polar domains, which engender polarization and pyroelectricity in the doped crystals. Here we describe a molecular-level determination of the structure of such polar domains, as created by low dopant concentrations (<0.5%). The approach comprises crystal engineering and pyroelectric measurements, together with dispersion-corrected density functional theory and classical molecular dynamics calculations of the doped crystals, using neutron diffraction data of the host at different temperatures. This approach is illustrated using centrosymmetric α-glycine crystals doped with minute amounts of different L-amino acids. The experimentally determined pyroelectric coefficients are explained by the structure and polarization calculations, thus providing strong support for the local and global understanding of how different dopants influence the properties of molecular crystals. PMID:27824050

  10. Porous and shape-anisotropic single crystals of the semiconductor perovskite CH3NH3PbI3 from a single-source precursor.

    PubMed

    Kollek, Tom; Gruber, Dominik; Gehring, Julia; Zimmermann, Eugen; Schmidt-Mende, Lukas; Polarz, Sebastian

    2015-01-19

    Significant progress in solar-cell research is currently made by the development of metal-organic perovskites (MOPs) owing to their superior properties, such as high absorption coefficients and effective transport of photogenerated charges. As for other semiconductors, it is expected that the properties of MOPs may be significantly improved by a defined nanostructure. However, their chemical sensitivity (e.g., towards hydrolysis) prohibits the application of methods already known for the synthesis of other nanomaterials. A new and general method for the synthesis of various (CH3NH3)PbI3 nanostructures from a novel single-source precursor is presented. Nanoporous MOP single crystals are obtained by a crystal-to-crystal transformation that is accompanied by spinodal demixing of the triethylene glycol containing precursor structure. Selective binding of a capping agent can be used to tune the particle shape of the MOP nanocrystals.

  11. Thermodynamic Origin of Photoinstability in the CH3NH3Pb(I1–xBrx)3 Hybrid Halide Perovskite Alloy

    PubMed Central

    2016-01-01

    The formation of solid-solutions of iodide, bromide, and chloride provides the means to control the structure, band gap, and stability of hybrid halide perovskite semiconductors for photovoltaic applications. We report a computational investigation of the CH3NH3PbI3/CH3NH3PbBr3 alloy from density functional theory with a thermodynamic analysis performed within the generalized quasi-chemical approximation. We construct the phase diagram and identify a large miscibility gap, with a critical temperature of 343 K. The observed photoinstability in some mixed-halide solar cells is explained by the thermodynamics of alloy formation, where an initially homogeneous solution is subject to spinodal decomposition with I and Br-rich phases, which is further complicated by a wide metastable region defined by the binodal line. PMID:26952337

  12. Origin and elimination of photocurrent hysteresis by fullerene passivation in CH3NH3PbI3 planar heterojunction solar cells

    DOE PAGES

    Shao, Yuchuan; Xiao, Zhengguo; Bi, Cheng; ...

    2014-12-15

    The large photocurrent hysteresis observed in many organometal trihalide perovskite solar cells has become a major hindrance impairing the ultimate performance and stability of these devices, while its origin was unknown. Here we demonstrate the trap states on the surface and grain boundaries of the perovskite materials to be the origin of photocurrent hysteresis and that the fullerene layers deposited on perovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent hysteresis. Fullerenes deposited on the top of the perovskites reduce the trap density by two orders of magnitude and double the power conversion efficiency of CH3NH3PbI3more » solar cells. As a result, the elucidation of the origin of photocurrent hysteresis and its elimination by trap passivation in perovskite solar cells provides important directions for future enhancements to device efficiency.« less

  13. Antisolvent-assisted powder engineering for controlled growth of hybrid CH3NH3PbI3 perovskite thin films

    NASA Astrophysics Data System (ADS)

    Choi, Yong Chan; Lee, Se Won; Kim, Dae-Hwan

    2017-02-01

    We develop antisolvent-assisted powder engineering for the controlled growth of hybrid inorganic-organic CH3NH3PbI3 (MAPbI3) perovskite thin films. The powders, which are used as the precursors for solution processing, are synthesized by pouring a MAPbI3 precursor solution into various antisolvents, such as dichloromethane, chloroform, diethyl ether, and toluene. Two types of powders having different colors are obtained, depending on the antisolvent used. The choice of the antisolvent used for synthesizing the powders strongly influences not only the phases of the powders but also the morphology and structure of the thin films subsequently fabricated by solution processing. This, in turn, affects the photovoltaic performance.

  14. Direct Conversion of CH3NH3PbI3 from Electrodeposited PbO for Highly Efficient Planar Perovskite Solar Cells

    PubMed Central

    Huang, Jin-hua; Jiang, Ke-jian; Cui, Xue-ping; Zhang, Qian-qian; Gao, Meng; Su, Mei-ju; Yang, Lian-ming; Song, Yanlin

    2015-01-01

    Organic-inorganic hybrid perovskite materials have recently been identified as a promising light absorber for solar cells. In the efficient solar cells, the perovskite active layer has generally been fabricated by either vapor deposition or two-step sequential deposition process. Herein, electrochemically deposited PbO film is in situ converted into CH3NH3PbI3 through solid-state reaction with adjacent CH3NH3I layer, exhibiting a large-scale flat and uniform thin film with fully substrate coverage. The resultant planar heterojunction photovoltaic device yields a best power conversion efficiency of 14.59% and an average power conversion efficiency of 13.12 ± 1.08% under standard AM 1.5 conditions. This technique affords a facile and environment-friendly method for the fabrication of the perovskite based solar cells with high reproducibility, paving the way for the practical application. PMID:26510520

  15. Effective hole extraction using MoOx-Al contact in perovskite CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Zhao, Yixin; Nardes, Alexandre M.; Zhu, Kai

    2014-05-01

    We report an 11.4%-efficient perovskite CH3NH3PbI3 solar cell using low-cost molybdenum oxide/aluminum (i.e., MoOx/Al) as an alternative top contact to replace noble/precious metals (e.g., Au or Ag) for extracting photogenerated holes. The device performance of perovskite solar cells using a MoOx/Al top contact is comparable to that of cells using the standard Ag top contact. Analysis of impedance spectroscopy measurements suggests that using 10-nm-thick MoOx and Al does not affect charge-recombination properties of perovskite solar cells. Using a thicker (20-nm) MoOx layer leads to a lower cell performance caused mainly by a reduced fill factor. Our results suggest that MoOx/Al is promising as a low-cost and effective hole-extraction contact for perovskite solar cells.

  16. Fabrication and characteristics of CH3NH3PbI3 perovskite solar cells with molybdenum-selenide hole-transport layer

    NASA Astrophysics Data System (ADS)

    Chen, Lung-Chien; Tseng, Zong-Lieng; Chen, Cheng-Chiang; Hsiung Chang, Sheng; Ho, Cheng-Han

    2016-12-01

    We present a solar cell with an FTO/MoSe2/perovskite/C60/bathocuproine (BCP)/silver structure. The hole-transport material (HTM), active photovoltaic layer, electron-transport layer, and electron-buffer layer were made of MoSe2, perovskite, C60, and BCP, respectively. The domain sizes of the CH3NH3PbI3 (MAPbI3) perovskite films that were deposited on the MoSe2 HTM films following annealing at 500, 600, and 700 °C were determined to be 23, 25, and 27 nm, respectively, revealing that the domain size of the MAPbI3 perovskite film increased with the annealing temperature of the MoSe2 HTM film under it. Therefore, the crystallinities of the perovskite layers were improved by increasing the annealing temperatures of the HTM layers. Following optimization, the maximum power-conversion efficiency was 8.23%.

  17. Simplification of femtosecond transient absorption microscopy data from CH3NH3PbI3 perovskite thin films into decay associated amplitude maps

    DOE PAGES

    Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin; ...

    2016-02-16

    Our work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH3NH3PbI3) perovskite thin film allows us to simplify the dataset consisting of a 68 time-resolved images into 4 decay associated amplitude maps. Furthermore, these maps provide a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. This approach provides newmore » insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.« less

  18. Nanocrystal diffusion doping.

    PubMed

    Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R

    2013-09-25

    A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd(1-x)Mn(x)Se (0 ≤ x ≤ ∼0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange.

  19. Doping in Zinc Selenide

    NASA Astrophysics Data System (ADS)

    Wheeler, Edward Dean

    An experimental technique ensuring the incorporation of substitutional arsenic and copper doping in ZnSe is presented. Two techniques are investigated. In each, neutron transmutation doping is employed to introduce arsenic and copper dopants in ZnSe. In the first technique, as-grown crystals of ZnSe are exposed to thermal neutrons. The crystals are thermally annealed after irradiation in order to repair the neutron induced lattice damage. The thermal annealing schedules employed in this work, however, do not fully repair the ZnSe lattice. In the second technique, homoepitaxial layers of ZnSe are deposited with irradiated zinc and selenium as source materials. High quality layers of ZnSe, characterized by x-ray diffraction and low temperature photoluminescence, are produced. The long half lives of As^ {75} and Zn^{65} allow the epitaxial layers to be formed prior to nuclear decay. Since the nuclear recoil associated with the decays are not sufficient to displace the dopant nuclei from their substitutional lattice sites, the technique results in isolated As_{Se } or isolated Cu_{Zn } being introduced in layers of ZnSe after crystal growth. Since the dopants are introduced in the bulk crystal after crystal growth, the doping process is decoupled from any interactions present during crystal growth. A technique in which crystal doping is decoupled from crystal growth provides several unique probes for arsenic and copper doping in ZnSe.

  20. Lewis Acid-Base Adduct Approach for High Efficiency Perovskite Solar Cells.

    PubMed

    Lee, Jin-Wook; Kim, Hui-Seon; Park, Nam-Gyu

    2016-02-16

    Since the first report on the long-term durable 9.7% solid-state perovskite solar cell employing methylammonium lead iodide (CH3NH3PbI3), mesoporous TiO2, and 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-MeOTAD) in 2012, following the seed technologies on perovskite-sensitized liquid junction solar cells in 2009 and 2011, a surge of interest has been focused on perovskite solar cells due to superb photovoltaic performance and extremely facile fabrication processes. The power conversion efficiency (PCE) of perovskite solar cells reached 21% in a very short period of time. Such an unprecedentedly high photovoltaic performance is due to the intrinsic optoelectronic property of organolead iodide perovskite material. Moreover, a high dielectric constant, sub-millimeter scale carrier diffusion length, an underlying ferroelectric property, and ion migration behavior can make organolead halide perovskites suitable for multifunctionality. Thus, besides solar cell applications, perovskite material has recently been applied to a variety fields of materials science such as photodetectors, light emitting diodes, lasing, X-ray imaging, resistive memory, and water splitting. Regardless of application areas, the growth of a well-defined perovskite layer with high crystallinity is essential for effective utilization of its excellent physicochemical properties. Therefore, an effective methodology for preparation of high quality perovskite layers is required. In this Account, an effective methodology for production of high quality perovskite layers is described, which is the Lewis acid-base adduct approach. In the solution process to form the perovskite layer, the key chemicals of CH3NH3I (or HC(NH2)2I) and PbI2 are used by dissolving them in polar aprotic solvents. Since polar aprotic solvents bear oxygen, sulfur, or nitrogen, they can act as a Lewis base. In addition, the main group compound PbI2 is known to be a Lewis acid. Thus, PbI2 has a chance

  1. Electrochemical sensing behaviour of Ni doped Fe{sub 3}O{sub 4} nanoparticles

    SciTech Connect

    Suresh, R.; Giribabu, K.; Manigandan, R.; Narayanan, V.; Vijayalakshmi, L.; Stephen, A.

    2014-01-28

    Ni doped Fe{sub 3}O{sub 4} nanoparticles were synthesized by simple hydrothermal method. The prepared nanomaterials were characterized by X-ray diffraction analysis, DRS-UV-Visible spectroscopy and field emission scanning electron microscopy. The XRD confirms the phase purity of the synthesized Ni doped Fe{sub 3}O{sub 4} nanoparticles. The optical property of Ni doped Fe{sub 3}O{sub 4} nanoparticles were studied by DRS UV-Visible analysis. The electrochemical sensing property of pure and Ni doped Fe{sub 3}O{sub 4} nanoparticles were examined using uric acid as an analyte. The obtained results indicated that the Ni doped Fe{sub 3}O{sub 4} nanoparticles exhibited higher electrocatalytic activity towards uric acid.

  2. Doped zinc oxide microspheres

    DOEpatents

    Arnold, Jr., Wesley D.; Bond, Walter D.; Lauf, Robert J.

    1993-01-01

    A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel.

  3. Doped zinc oxide microspheres

    DOEpatents

    Arnold, W.D. Jr.; Bond, W.D.; Lauf, R.J.

    1993-12-14

    A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel. 4 figures.

  4. Dope, Fiends, and Myths.

    ERIC Educational Resources Information Center

    Reasons, Charles E.

    Since the social reality of the drug problem has largely emanated from the diffuse conceptions of the drug user, an analysis of the history of the "dope fiend" mythology is presented in this paper in an attempt to assess the manner in which certain publics are informed about the problem. A content analysis of drug-related imagery was made from…

  5. CSA doped polypyrrole-zinc oxide thin film sensor

    NASA Astrophysics Data System (ADS)

    Chougule, M. A.; Jundale, D. M.; Raut, B. T.; Sen, Shashwati; Patil, V. B.

    2013-02-01

    The polypyrrole-zinc oxide (PPy-ZnO) hybrid sensor doped with different weight ratios of camphor sulphonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy-ZnO hybrids were characterized by field emission scanning electron microscope (FESEM) and fourier transform infrared (FTIR) which proved the formation of polypyrrole, PPy-ZnO and the interaction between polypyrrole - ZnO (PPy-ZnO) hybrid with CSA doping. The gas sensing properties of the PPy-ZnO hybrid films doped with CSA have been studied for oxidizing (NO2) as well as reducing (H2S, NH3, CH4OH and CH3OH) gases at room temperature. We demonstrate that CSA doped PPy-ZnO hybrid films are highly selective to NO2 along with high-sensitivity at low concentration (80% to 100 ppm) and better stability, which suggested that the CSA doped PPy-ZnO hybrid films are potential candidate for NO2 detection at room temperature.

  6. Gene doping: an overview and current implications for athletes.

    PubMed

    van der Gronde, Toon; de Hon, Olivier; Haisma, Hidde J; Pieters, Toine

    2013-07-01

    The possibility of gene doping, defined as the transfer of nucleic acid sequences and/or the use of normal or genetically modified cells to enhance sport performance, is a real concern in sports medicine. The abuse of knowledge and techniques gained in the area of gene therapy is a form of doping, and is prohibited for competitive athletes. As yet there is no conclusive evidence that that gene doping has been practiced in sport. However, given that gene therapy techniques improve continuously, the likelihood of abuse will increase. A literature search was conducted to identify the most relevant proteins based on their current gene doping potential using articles from Pubmed, Scopus and Embase published between 2006 and 2011. The final list of selected proteins were erythropoietin, insulin-like growth factor, growth hormone, myostatin, vascular endothelial growth factor, fibroblast growth factor, endorphin and enkephalin, α actinin 3, peroxisome proliferator-activated receptor-delta (PPARδ) and cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C). We discuss these proteins with respect to their potential benefits, existing gene therapy experience in humans, potential risks, and chances of detection in current and future anti-doping controls. We have identified PPARδ and PEPCK-C as having high potential for abuse. But we expect that for efficiency reasons, there will be a preference for inserting gene target combinations rather than single gene doping products. This will also further complicate detection.

  7. Phonon Mode Transformation Across the Orthohombic-Tetragonal Phase Transition in a Lead Iodide Perovskite CH3NH3PbI3: A Terahertz Time-Domain Spectroscopy Approach.

    PubMed

    La-o-Vorakiat, Chan; Xia, Huanxin; Kadro, Jeannette; Salim, Teddy; Zhao, Daming; Ahmed, Towfiq; Lam, Yeng Ming; Zhu, Jian-Xin; Marcus, Rudolph A; Michel-Beyerle, Maria-Elisabeth; Chia, Elbert E M

    2016-01-07

    We study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3 thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. The carrier mobility values calculated from the low-temperature phonon mode frequencies, via two theoretical approaches, are found to agree reasonably with the experimental value (∼2000 cm(2) V(-1) s(-1)) from a previous time-resolved THz spectroscopy work. Thus, we have established a possible link between terahertz phonon modes and the transport properties of perovskite-based solar cells.

  8. Phonon Mode Transformation across the Orthohombic-Tetragonal Phase Transition in a Lead-Iodide Perovskite CH3NH3PbI3: a Terahertz Time-Domain Spectroscopy Approach

    NASA Astrophysics Data System (ADS)

    Chia, Elbert E. M.; La-O-Vorakiat, Chan; Kadro, Jeannette; Salim, Teddy; Zhao, Daming; Ahmed, Towfiq; Lam, Yeng Ming; Zhu, Jian-Xin; Marcus, Rudolph; Michel-Beyerle, Maria-Elisabeth

    Using terahertz time-domain spectroscopy (THz-TDS), we study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3 thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. King Mongkut's University of Technology Thonburi (Grant No. SCI58-003), Singapore MOE Tier 1 (RG13/12, RG123/14), ONR, ARO, NTU Biophysics Center, LANL LDRD, LANL CINT.

  9. Chemical instability leads to unusual chemical-potential-independent defect formation and diffusion in perovskite solar cell material CH 3 NH 3 PbI 3

    DOE PAGES

    Ming, Wenmei; Chen, Shiyou; East China Normal Univ.; ...

    2016-10-13

    Methylammonium (MA) lead triiodide (MAPbI3) has recently emerged as a promising solar cell material. But, MAPbI3 is known to have chemical instability, i.e., MAPbI3 is prone to decomposition into MAI and PbI2 even at moderate temperatures (e.g. 330 K). Here, we show that the chemical instability, as reflected by the calculated negligible enthalpy of formation of MAPbI3 (with respect to MAI and PbI2), has an unusual and important consequence for defect properties, i.e., defect formation energies in low-carrier-density MAPbI3 are nearly independent of the chemical potentials of constituent elements and thus can be uniquely determined. This allows straightforward calculations of defect concentrations and the activation energy of ionic conductivity (the sum of the formation energy and the diffusion barrier of the charged mobile defect) in MAPbI3. Furthermore, the calculated activation energy for ionic conductivity due to Vmore » $$+\\atop{1}$$ diffusion is in excellent agreement with the experimental values, which demonstrates unambiguously that V$$+\\atop{1}$$ is the dominant diffusing defect and is responsible for the observed ion migration and device polarization in MAPbI3 solar cells. The calculated low formation energy of a Frenkel pair (V$$+\\atop{1}$$ -I$$-\\atop{i}$$ and low diffusion barriers of V$$+\\atop{1}$$ and Image I$$-\\atop{i}$$ suggest that the iodine ion migration and the resulting device polarization may occur even in single-crystal devices and grain-boundary-passivated polycrystalline thin film devices (which were previously suggested to be free from ion-migration-induced device polarization), leading to device degradation. Moreover, the device polarization due to the Frenkel pair (which has a relatively low concentration) may take a long time to develop and thus may avoid the appearance of the current–voltage hysteresis at typical scan rates.« less

  10. Parameters Affecting I-V Hysteresis of CH3NH3PbI3 Perovskite Solar Cells: Effects of Perovskite Crystal Size and Mesoporous TiO2 Layer.

    PubMed

    Kim, Hui-Seon; Park, Nam-Gyu

    2014-09-04

    Current-voltage (I-V) characteristics of CH3NH3PbI3 perovskite solar cells are studied using a time-dependent current response with stepwise sweeping of the bias voltage. Compared with the crystalline Si solar cell showing time-independent current at a given bias voltage, the perovskite solar cells exhibit time-dependent current response. The current increases with time and becomes steady at forward scan from short-circuit to open-circuit, whereas it is decayed and saturated with time at reverse scan from open-circuit to short-circuit. Time-dependent current response eventually leads to I-V hysteresis depending on the scan direction and the scan rate. Crystal size of CH3NH3PbI3 and the mesoporous TiO2 (mp-TiO2) film are found to influence I-V hysteresis, where the I-V hysteresis is alleviated as crystal size increases and in the presence of mp-TiO2. The capacitance observed at low frequency (0.1 to 1 Hz), associated with dipole polarization, tends to diminish as size of perovskite and mp-TiO2 layer thickness increases, which suggests that the origin of hysteresis correlates to the capacitive characteristic of CH3NH3PbI3 and the degree of hysteresis depends strongly on perovskite crystal size and mesoporous TiO2 layer.

  11. Comparison of Recombination Dynamics in CH3NH3PbBr3 and CH3NH3PbI3 Perovskite Films: Influence of Exciton Binding Energy.

    PubMed

    Yang, Ye; Yang, Mengjin; Li, Zhen; Crisp, Ryan; Zhu, Kai; Beard, Matthew C

    2015-12-03

    Understanding carrier recombination in semiconductors is a critical component when developing practical applications. Here we measure and compare the monomolecular, bimolecular, and trimolecular (Auger) recombination rate constants of CH3NH3PbBr3 and CH3NH3PbI3. The monomolecular and bimolecular recombination rate constants for both samples are limited by trap-assisted recombination. The bimolecular recombination rate constant for CH3NH3PbBr3 is ∼3.3 times larger than that for CH3NH3PbI3 and both are in line with that found for radiative recombination in other direct-gap semiconductors. The Auger recombination rate constant is 4 times larger in lead-bromide-based perovskite compared with lead-iodide-based perovskite and does not follow the reduced Auger rate when the bandgap increases. The increased Auger recombination rate, which is enhanced by Coulomb interactions, can be ascribed to the larger exciton binding energy, ∼40 meV, in CH3NH3PbBr3 compared with ∼13 meV in CH3NH3PbI3.

  12. Ion track doping

    NASA Astrophysics Data System (ADS)

    Fink, D.; Chadderton, L. T.; Cruz, S. A.; Fahrner, W. R.; Hnatowicz, V.; Te Kaat, E. H.; Melnikov, A. A.; Varichenko, V. S.; Zaitsev, A. M.

    1994-10-01

    Longitudinal dopant distribution along ion tracks in soft (polymers [1?5]) and hard (diamond [6,7]) condensed carbonaceous matter have been studied by neutron depth profiling and cathodoluminesence. Both in-diffusion from the aqueous phase and energetic ion implantation were used in primary track doping. In-situ self-decoration of tracks and post-implantation with a secondary ion species were used in the specific case of ion implantation. Radial dopant distributions were also studied by means of a modified tomographic procedure. Decorative doping of ion bombarded solids is useful in probing track structure, and especially in pointing the way to potential development of nanometric-sized electronic devices.

  13. Erythropoietin and blood doping

    PubMed Central

    Robinson, N; Giraud, S; Saudan, C; Baume, N; Avois, L; Mangin, P; Saugy, M

    2006-01-01

    Objective and method To outline the direct and indirect approaches in the fight against blood doping in sports, the different strategies that have been used and are currently being used to fight efficiently against blood doping are presented and discussed. Results and conclusions The paper outlines the different approaches and diagnostic tools that some federations have to identify and target sportspeople demonstrating abnormal blood profiles. Originally blood tests were introduced for medical reasons and for limiting misuse of recombinant human erythropoietin (rHuEPO). In this way it became possible to prevent athletes with haematocrit levels well above normal, and potentially dangerous for their health, competing in sport. Today, with nearly a decade of blood testing experience, sports authorities should be familiar with some of the limitations and specially the ability of blood tests performed prior to competitions to fight efficiently against the misuse of rHuEPO, blood transfusion, and artificial haemoglobin. PMID:16799100

  14. Doping of carbon foams for use in energy storage devices

    DOEpatents

    Mayer, Steven T.; Pekala, Richard W.; Morrison, Robert L.; Kaschmitter, James L.

    1994-01-01

    A polymeric foam precursor, wetted with phosphoric acid, is pyrolyzed in an inert atmosphere to produce an open-cell doped carbon foam, which is utilized as a lithium intercalation anode in a secondary, organic electrolyte battery. Tests were conducted in a cell containing an organic electrolyte and using lithium metal counter and reference electrodes, with the anode located therebetween. Results after charge and discharge cycling, for a total of 6 cycles, indicated a substantial increase in the energy storage capability of the phosphorus doped carbon foam relative to the undoped carbon foam, when used as a rechargeable lithium ion battery.

  15. Doping of carbon foams for use in energy storage devices

    DOEpatents

    Mayer, S.T.; Pekala, R.W.; Morrison, R.L.; Kaschmitter, J.L.

    1994-10-25

    A polymeric foam precursor, wetted with phosphoric acid, is pyrolyzed in an inert atmosphere to produce an open-cell doped carbon foam, which is utilized as a lithium intercalation anode in a secondary, organic electrolyte battery. Tests were conducted in a cell containing an organic electrolyte and using lithium metal counter and reference electrodes, with the anode located there between. Results after charge and discharge cycling, for a total of 6 cycles, indicated a substantial increase in the energy storage capability of the phosphorus doped carbon foam relative to the undoped carbon foam, when used as a rechargeable lithium ion battery. 3 figs.

  16. Doped colorimetric assay liposomes

    DOEpatents

    Charych, Deborah; Stevens, Raymond C.

    2001-01-01

    The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

  17. [Doping in sports].

    PubMed

    Seĭfulla, R D; Rozhkova, E A; Rodchenkov, G M; Appolonova, S A; Kulikova, E V

    2006-01-01

    Drugs used by athletes for the improvement of results are described and classified with respect to chemical structure and pharmacological action. The main groups of drugs treated as doping are considered and the WADA requirements to prohibited preparations are formulated. The main effects produced by drugs on the athletes and animals (race horses, fight dogs, etc ) are described and the measures of therapy against side effects are outlined.

  18. [Doping and urologic tumors].

    PubMed

    Pinto, F; Sacco, E; Volpe, A; Gardi, M; Totaro, A; Calarco, A; Racioppi, M; Gulino, G; D'Addessi, A; Bassi, P F

    2010-01-01

    Several substances such as growth hormone (GH), erythropoietin (Epo), and anabolic steroids (AS) are improperly utilized to increase the performance of athletes. Evaluating the potential cancer risk associated with doping agents is difficult since these drugs are often used at very high doses and in combination with other licit or illicit drugs. The GH, via its mediator, the insulin-like growth factor 1 (IGF-1), is involved in the development and progression of cancer. Animal studies suggested that high levels of GH/IGF-1 increase progression of androgen-independent prostate cancer. Clinical data regarding prostate cancer are mostly based on epidemiological studies or indirect data such as IGF-1 high levels in patients with prostate cancer. Even if experimental studies showed a correlation between Epo and cancer, no clinical data are currently available on cancer development related to Epo as a doping agent. Androgens are involved in prostate carcinogenesis modulating genes that regulate cell proliferation, apoptosis and angiogenesis. Most information on AS is anecdotal (case reports on prostate, kidney and testicular cancers). Prospective epidemiologic studies failed to support the hypothesis that circulating androgens are positively associated with prostate cancer risk. Currently, clinical and epidemiological studies supporting association between doping and urological neoplasias are not available. Nowadays, exposure to doping agents starts more prematurely with a consequent longer exposition period; drugs are often used at very high doses and in combination with other licit or illicit drugs. Due to all these elements it is impossible to predict all the side effects, including cancer; more detailed studies are therefore necessary.

  19. Highly flexible InSnO electrodes on thin colourless polyimide substrate for high-performance flexible CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Il; Heo, Jin Hyuck; Park, Sung-Hyun; Hong, Ki Il; Jeong, Hak Gee; Im, Sang Hyuk; Kim, Han-Ki

    2017-02-01

    We fabricated high-performance flexible CH3NH3PbI3 (MAPbI3) perovskite solar cells with a power conversion efficiency of 15.5% on roll-to-roll sputtered ITO films on 60 μm-thick colourless polyimide (CPI) substrate. Due to the thermal stability of the CPI substrate, an ITO/CPI sample subjected to rapid thermal annealing at 300 °C showed a low sheet resistance of 57.8 Ω/square and high transmittance of 83.6%, which are better values than those of an ITO/PET sample. Outer and inner bending tests demonstrated that the mechanical flexibility of the ITO/CPI was superior to that of the conventional ITO/PET sample owing to the thinness of the CPI substrate. In addition, due to its good mechanical flexibility, the ITO/CPI showed no change in resistance after 10,000 cycle outer and inner dynamic fatigue tests. Flexible perovskite solar cells with the structure of Au/PTAA/MAPbI3/ZnO/ITO/CPI showed a high power conversion efficiency of 15.5%. The successful operation of these flexible perovskite solar cells on ITO/CPI substrate indicated that the ITO film on thermally stable CPI substrate is a promising of flexible substrate for high-temperature processing, a finding likely to advance the commercialization of cost-efficient flexible perovskite solar cells.

  20. Light Harvesting and Charge Recombination in CH3NH3PbI3 Perovskite Solar Cells Studied by Hole Transport Layer Thickness Variation.

    PubMed

    Marinova, Nevena; Tress, Wolfgang; Humphry-Baker, Robin; Dar, M Ibrahim; Bojinov, Vladimir; Zakeeruddin, Shaik Mohammed; Nazeeruddin, Mohammad Khaja; Grätzel, Michael

    2015-04-28

    A tailored optimization of perovskite solar cells requires a detailed understanding of the processes limiting the device efficiency. Here, we study the role of the hole transport layer (HTL) spiro-MeOTAD and its thickness in a mesoscopic TiO2-based solar cell architecture. We find that a sufficiently thick (200 nm) HTL not only increases the charge carrier collection efficiency but also the light harvesting efficiency. This is due to an enhanced reflection of a smooth HTL/Au-electrode interface. The rough CH3NH3PbI3 perovskite surface requires an HTL thickness of >400 nm to avoid surface recombination and guarantee a high open-circuit voltage. Analyses of the electroluminescence efficiency and the diode ideality factor show that the open-circuit voltage becomes completely limited by trap-assisted recombination in the perovskite for a thick HTL. Thus, spiro-MeOTAD is a very good HTL choice from the device physics' point of view. The fill factor analyzed by the Suns-Voc method is not transport limited, but trap-recombination limited as well. Consequently, a further optimization of the device has to focus on defects in the polycrystalline perovskite film.

  1. Effect of Thermal and Structural Disorder on the Electronic Structure of Hybrid Perovskite Semiconductor CH3NH3PbI3.

    PubMed

    Singh, Shivam; Li, Cheng; Panzer, Fabian; Narasimhan, K L; Graeser, Anna; Gujar, Tanaji P; Köhler, Anna; Thelakkat, Mukundan; Huettner, Sven; Kabra, Dinesh

    2016-08-04

    In this Letter, we investigate the temperature dependence of the optical properties of methylammonium lead iodide (MAPbI3 = CH3NH3PbI3) from room temperature to 6 K. In both the tetragonal (T > 163 K) and the orthorhombic (T < 163 K) phases of MAPbI3, the band gap (from both absorption and photoluminescence (PL) measurements) decreases with decrease in temperature, in contrast to what is normally seen for many inorganic semiconductors, such as Si, GaAs, GaN, etc. We show that in the perovskites reported here, the temperature coefficient of thermal expansion is large and accounts for the positive temperature coefficient of the band gap. A detailed analysis of the exciton line width allows us to distinguish between static and dynamic disorder. The low-energy tail of the exciton absorption is reminiscent of Urbach absorption. The Urbach energy is a measure of the disorder, which is modeled using thermal and static disorder for both the phases separately. The static disorder component, manifested in the exciton line width at low temperature, is small. Above 60 K, thermal disorder increases the line width. Both these features are a measure of the high crystal quality and low disorder of the perovskite films even though they are produced from solution.

  2. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

    PubMed Central

    March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

    2016-01-01

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years. PMID:27974815

  3. Density Functional Calculations of Native Defects in CH 3 NH 3 PbI 3 : Effects of Spin–Orbit Coupling and Self-Interaction Error

    DOE PAGES

    Du, Mao-Hua

    2015-04-02

    We know that native point defects play an important role in carrier transport properties of CH3NH3PbI3. However, the nature of many important defects remains controversial due partly to the conflicting results reported by recent density functional theory (DFT) calculations. In this Letter, we show that self-interaction error and the neglect of spin–orbit coupling (SOC) in many previous DFT calculations resulted in incorrect positions of valence and conduction band edges, although their difference, which is the band gap, is in good agreement with the experimental value. Moreover, this problem has led to incorrect predictions of defect-level positions. Hybrid density functional calculations,more » which partially correct the self-interaction error and include the SOC, show that, among native point defects (including vacancies, interstitials, and antisites), only the iodine vacancy and its complexes induce deep electron and hole trapping levels inside of the band gap, acting as nonradiative recombination centers.« less

  4. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy.

    PubMed

    March, Samuel A; Clegg, Charlotte; Riley, Drew B; Webber, Daniel; Hill, Ian G; Hall, Kimberley C

    2016-12-15

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2-55 meV) reported in recent years.

  5. Effect of Lattice Screening on Excitonic and Optical Properties in CH3NH3PbI3 Solar Cell Materials

    NASA Astrophysics Data System (ADS)

    Leveillee, Joshua; Schleife, Andre; Andre Schleife Research Group Team

    Hybrid Organo-Metallic Perovskites have made great strides towards becoming a next generation solar cell material. Though high performing experimental devices have been constructed from these perovskites, the fundamental optical and electronic physics of these systems remains an active area of research. A large lattice dielectric constant in the Methylammonium(CH3NH3)-Lead(Pb)-Iodide(I3) system potentially contributes to the screening of the electron-hole interaction. The strongly increased dielectric screening due to lattice contributions has been suggested to reduce the exciton binding energy and strongly effects the optical band gap. In this study, we seek to understand, from first principles, the interplay between lattice screening and exciton binding energy. We use density functional theory for ground state calculations and the Bethe-Salpeter equation for the optical polarization function, from which we calculate optical spectra and excitonic properties. We will discuss differences between lattice and electronic screening and the effect on the optical properties of multiple CH3NH3PbI3 phases. Supported by NSF Grand Number: CBET-1437230.

  6. Nano-structured CuO-Cu2O Complex Thin Film for Application in CH3NH3PbI3 Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Chen, Lung-Chieh; Chen, Cheng-Chiang; Liang, Kai-Chieh; Chang, Sheng Hsiung; Tseng, Zhong-Liang; Yeh, Shih-Chieh; Chen, Chin-Ti; Wu, Wen-Ti; Wu, Chun-Guey

    2016-09-01

    Nano-structured CuO-Cu2O complex thin film-based perovskite solar cells were fabricated on an indium tin oxide (ITO)-coated glass and studied. Copper (Cu) thin films with a purity of 99.995 % were deposited on an ITO-coated glass by magnetron reactive sputtering. To optimize the properties of the nano-structured CuO-Cu2O complex thin films, the deposited Cu thin films were thermally oxidized at various temperatures from 300 to 400 °C. A CH3NH3PbI3 perovskite absorber was fabricated on top of CuO-Cu2O complex thin film by a one-step spin-coating process with a toluene washing treatment. Following optimization, the maximum power conversion efficiency (PCE) exceeded 8.1 %. Therefore, the low-cost, solution-processed, stable nano-structured CuO-Cu2O complex thin film can be used as an alternative hole transport layer (HTL) in industrially produced perovskite solar cells.

  7. Nano-structured CuO-Cu2O Complex Thin Film for Application in CH3NH3PbI3 Perovskite Solar Cells.

    PubMed

    Chen, Lung-Chieh; Chen, Cheng-Chiang; Liang, Kai-Chieh; Chang, Sheng Hsiung; Tseng, Zhong-Liang; Yeh, Shih-Chieh; Chen, Chin-Ti; Wu, Wen-Ti; Wu, Chun-Guey

    2016-12-01

    Nano-structured CuO-Cu2O complex thin film-based perovskite solar cells were fabricated on an indium tin oxide (ITO)-coated glass and studied. Copper (Cu) thin films with a purity of 99.995 % were deposited on an ITO-coated glass by magnetron reactive sputtering. To optimize the properties of the nano-structured CuO-Cu2O complex thin films, the deposited Cu thin films were thermally oxidized at various temperatures from 300 to 400 °C. A CH3NH3PbI3 perovskite absorber was fabricated on top of CuO-Cu2O complex thin film by a one-step spin-coating process with a toluene washing treatment. Following optimization, the maximum power conversion efficiency (PCE) exceeded 8.1 %. Therefore, the low-cost, solution-processed, stable nano-structured CuO-Cu2O complex thin film can be used as an alternative hole transport layer (HTL) in industrially produced perovskite solar cells.

  8. Electron Transfer from Triplet State of TIPS-Pentacene Generated by Singlet Fission Processes to CH3NH3PbI3 Perovskite.

    PubMed

    Lee, Sangsu; Hwang, Daesub; Jung, Seok Il; Kim, Dongho

    2017-02-16

    To reveal the applicability of singlet fission processes in perovskite solar cell, we investigated electron transfer from TIPS-pentacene to CH3NH3PbI3 (MAPbI3) perovskite in film phase. Through the observation of the shorter fluorescence lifetime in TIPS-pentacene/MAPbI3 perovskite bilayer film (5 ns) compared with pristine MAPbI3 perovskite film (20 ns), we verified electron-transfer processes between TIPS-pentacene and MAPbI3 perovskite. Furthermore, the observation of singlet fission processes, a faster decay rate, TIPS-pentacene cations, and the analysis of kinetic profiles of the intensity ratio between 500 and 525 nm in the TA spectra of the TIPS-pentacene/MAPbI3 perovskite bilayer film indicate that electron transfer occurs from triplet state of TIPS-pentacene generated by singlet fission processes to MAPbI3 perovskite conduction band. We believe that our results can provide useful information on the design of solar cells sensitized by singlet fission processes and pave the way for new types of perovskite solar cells.

  9. On the Role of Interfaces in Planar-Structured HC(NH2 )2 PbI3 Perovskite Solar Cells.

    PubMed

    Seol, Dong-Jin; Lee, Jin-Wook; Park, Nam-Gyu

    2015-07-20

    Planar-structured HC(NH2 )2 PbI3 (FAPbI3 ) perovskite solar cells were prepared via a two-step deposition process. To investigate the role of interface, the perovskite morphology was intentionally modified by varying HC(NH2 )2 I concentration. Surface and grain sizes of the deposited FAPbI3 became rougher and larger as the HC(NH2 )2 I concentration decreased from 58.2 to 40.7 mM. Average photocurrent was improved but photovoltage deteriorated slightly with decreasing concentration. Consequently, the average efficiency was improved from 7.82 % to 10.70 % and the best efficiency of 12.17 % was obtained at 40.7 mM. Photoluminescence (PL) at TiO2 /FAPbI3 interface was reduced with decreasing concentration, which was, however, reversed at FAPbI3 /spiro-MeOTAD one. By correlating PL data and the photovoltaic performance, we concluded that the TiO2 /perovskite interface plays a crucial role in determining photocurrent while the perovskite/spiro-MeOTAD interface is important in governing photovoltage.

  10. Photoluminescence study of time- and spatial-dependent light induced trap de-activation in CH3NH3PbI3 perovskite films.

    PubMed

    Fu, Xiao; Jacobs, Daniel A; Beck, Fiona J; Duong, The; Shen, Heping; Catchpole, Kylie R; White, Thomas P

    2016-08-10

    Organometal halide perovskite-based solar cells have rapidly achieved high efficiency in recent years. However, many fundamental recombination mechanisms underlying the excellent performance are still not well understood. Here we apply confocal photoluminescence microscopy to investigate the time and spatial characteristics of light-induced trap de-activation in CH3NH3PbI3 perovskite films. Trap de-activation is characterized by a dramatic increase in PL emission during continuous laser illumination accompanied by a lateral expansion of the PL enhancement far beyond the laser spot. These observations are attributed to an oxygen-assisted trap de-activation process associated with carrier diffusion. To model this effect, we add a trap de-activation term to the standard semiconductor carrier recombination and diffusion models. With this approach we are able to reproduce the observed temporal and spatial dependence of laser induced PL enhancement using realistic physical parameters. Furthermore, we experimentally investigate the role of trap diffusion in this process, and demonstrate that the trap de-activation is not permanent, with the traps appearing again once the illumination is turned off. This study provides new insights into recombination and trap dynamics in perovskite films that could offer a better understanding of perovskite solar cell performance.

  11. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

    NASA Astrophysics Data System (ADS)

    March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

    2016-12-01

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years.

  12. Solid-State Mesostructured Perovskite CH3NH3PbI3 Solar Cells: Charge Transport, Recombination, and Diffusion Length.

    PubMed

    Zhao, Yixin; Nardes, Alexandre M; Zhu, Kai

    2014-02-06

    We report on the effect of TiO2 film thickness on charge transport and recombination in solid-state mesostructured perovskite CH3NH3PbI3 (via one-step coating) solar cells using spiro-MeOTAD as the hole conductor. Intensity-modulated photocurrent/photovoltage spectroscopies show that the transport and recombination properties of solid-state mesostructured perovskite solar cells are similar to those of solid-state dye-sensitized solar cells. Charge transport in perovskite cells is dominated by electron conduction within the mesoporous TiO2 network rather than from the perovskite layer. Although no significant film-thickness dependence is found for transport and recombination, the efficiency of perovskite cells increases with TiO2 film thickness from 240 nm to about 650-850 nm owing primarily to the enhanced light harvesting. Further increasing film thickness reduces cell efficiency associated with decreased fill factor or photocurrent density. The electron diffusion length in mesostructured perovskite cells is longer than 1 μm for over four orders of magnitude of light intensity.

  13. Synthesis and conductivity of indium-doped tin pyrophosphates

    SciTech Connect

    Garzon, Fernando H; Mukundan, Rangachary; Brosha, Eric L

    2008-01-01

    We have synthesized indium-doped tin pyrophosphates as high-temperature anhydrous proton conductors. The ratio of tin to indium was varied using two different synthetic methods. The first is a high-temperature reaction in which a paste containing the reactants in excess phosphoric acid was heated for various amounts of time at various temperatures. The second method is a solution precipitation procedure followed by calcination, which offers several advantages over traditional synthetic techniques. These advantages inc 1 ude better stoichiometric control, lower temperature requirements, and chemically uniform products. Several phosphate sources were investigated, including phosphoric acid, pyrophosphoric acid, and potassium pyrophosphate. The resulting indium-doped tin pyrophosphates had good proton conductivity over a wide temperature range with no humidification.

  14. Doping level dependent space charge limited conduction in polyaniline nanoparticles

    NASA Astrophysics Data System (ADS)

    Nath, Chandrani; Kumar, A.

    2012-11-01

    Spherical shaped polyaniline nanoparticles of average diameter ˜4 nm were doped with different concentration of hydrochloric acid. The x-ray diffraction studies reveal an increase in crystallinity with doping. Temperature dependent current-voltage measurements on the different nanoparticle samples indicate the prevalence of bulk-controlled space charge limited conduction (SCLC) mechanism in the high voltage (>1 V) region while the ohmic conduction dominates at the lower voltage (<1 V) region. With increasing doping the nature of SCLC changes from trap-free SCLC to Child-Langmuir type SCLC via exponential trap-limited SCLC. Moreover, the field and temperature dependence of mobility exhibits the universal Poole-Frenkel behavior. The energetic disorder parameter, spatial disorder parameter, inter-site distance, and localization length have been extracted employing the uncorrelated and the correlated Gaussian disorder model.

  15. Electrochemical mineralization pathway of quinoline by boron-doped diamond anodes.

    PubMed

    Wang, Chunrong; Ma, Keke; Wu, Tingting; Ye, Min; Tan, Peng; Yan, Kecheng

    2016-04-01

    Boron-doped diamond anodes were selected for quinoline mineralization, and the resulting intermediates, phenylpropyl aldehyde, phenylpropionic acid, and nonanal were identified and followed during quinoline oxidation by gas chromatography-mass spectrometry and high-performance liquid chromatography. The evolutions of formic acid, acetic acid, oxalic acid, NO2(-), NO3(-), and NH4(+) were quantified. A new reaction pathway for quinoline mineralization by boron-doped diamond anodes has been proposed, where the pyridine ring in quinoline is cleaved by a hydroxyl radical giving phenylpropyl aldehyde and NH4(+). Phenylpropyl aldehyde is quickly oxidized into phenylpropionic acid, and the benzene ring is cleaved giving nonanal. This is further oxidized to formic acid, acetic acid, and oxalic acid. Finally, these organic intermediates are mineralized to CO2 and H2O. NH4(+) is also oxidized to NO2(-) and on to NO3(-). The results will help to gain basic reference for clearing intermediates and their toxicity.

  16. Novel polybenzimidazole derivatives for high temperature polymer electrolyte membrane fuel cell applications

    NASA Astrophysics Data System (ADS)

    Xiao, Lixiang

    Recent advances have made polymer electrolyte membrane fuel cells (PEMFCs) a leading alternative to internal combustion engines for both stationary and transportation applications. In particular, high temperature polymer electrolyte membranes operational above 120°C without humidification offer many advantages including fast electrode kinetics, high tolerance to fuel impurities and simple thermal and water management systems. A series of polybenzimidazole (PBI) derivatives including pyridine-based PBI (PPBI) and sulfonated PBI (SPBI) homopolymers and copolymers have been synthesized using polyphosphoric acid (PPA) as both solvent and polycondensation agent. High molecular weight PBI derivative polymers were obtained with well controlled backbone structures in terms of pyridine ring content, polymer backbone rigidity and degree of sulfonation. A novel process, termed the PPA process, has been developed to prepare phosphoric acid (PA) doped PBI membranes by direct-casting of the PPA polymerization solution without isolation or re-dissolution of the polymers. The subsequent hydrolysis of PPA to PA by moisture absorbed from the atmosphere usually induced a transition from the solution-like state to a gel-like state and produced PA doped PBI membranes with a desirable suite of physiochemical properties characterized by the PA doping levels, mechanical properties and proton conductivities. The effects of the polymer backbone structure on the polymer characteristics and membrane properties, i.e., the structure-property relationships of the PBI derivative polymers have been studied. The incorporation of additional basic nitrogen containing pyridine rings and sulfonic acid groups enhanced the polymer solubility in acid and dipolar solvents while retaining the inherently high thermal stability of the PBI heteroaromatic backbone. In particular, the degradation of the SPBI polymers with reasonable high molecular weights commenced above 450°C, notably higher than other

  17. Antimony-doped graphene nanoplatelets

    PubMed Central

    Jeon, In-Yup; Choi, Min; Choi, Hyun-Jung; Jung, Sun-Min; Kim, Min-Jung; Seo, Jeong-Min; Bae, Seo-Yoon; Yoo, Seonyoung; Kim, Guntae; Jeong, Hu Young; Park, Noejung; Baek, Jong-Beom

    2015-01-01

    Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb3+ and Sb5+) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalysts. PMID:25997811

  18. [Medication, athletes and doping regulations].

    PubMed

    Hartgens, F

    2008-08-16

    Doping is defined as an offence of the antidopingcode of the World Anti-Doping Agency (WADA). To uphold the code WADA has composed a list of prohibited substances and methods. The composition of the list is based on three mainstays: fair play, health risks and spirit of the sport. Among the prohibited substances are anabolic agents, erythropoietin, beta2-sympathicomimetics, growth hormone and masking agents. For some medications athletes may receive a therapeutic use exemption. Enforcement of the antidoping-code is performed by doping controls. For this purpose, blood and urine samples of athletes are collected and analysed. In 2006 approximately 200,000 samples were analysed worldwide, with 1.96% being tested positive. All physicians should be aware of the possibility that athletes use medication subjected to the doping regulations. There are guidelines for physicians on doping-related issues in medical practice.

  19. Antimony-doped graphene nanoplatelets

    NASA Astrophysics Data System (ADS)

    Jeon, In-Yup; Choi, Min; Choi, Hyun-Jung; Jung, Sun-Min; Kim, Min-Jung; Seo, Jeong-Min; Bae, Seo-Yoon; Yoo, Seonyoung; Kim, Guntae; Jeong, Hu Young; Park, Noejung; Baek, Jong-Beom

    2015-05-01

    Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb3+ and Sb5+) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalysts.

  20. Study of the growth and pyroelectric properties of TGS crystals doped with aniline-family dipolar molecules

    NASA Astrophysics Data System (ADS)

    Zhang, Kecong; Song, Jiancheng; Wang, Min; Fang, Changshui; Lu, Mengkai

    1987-04-01

    TGS crystals doped with aniline-family dipolar molecules (aniline, 2-aminobenzoic acid, 3-aminobenzoic acid, 3-aminobenzene-sulphonic acid, 4-aminobenzenesulphonic acid and 4-nitroraniline) have been grown by the slow-cooling solution method. The influence of these dopants on the growth habits, crystal morphology pyroelectric properties, and structure parameters of TGS crystals has been systematically investigated. The effects of the domain structure of the seed crystal on the pyroelectric properties of the doped crystals have been studied. It is found that the spontaneous polarization (P), pyroelectric coefficient (lambda), and internal bias field of the doped crystals are slightly higher than those of the pure TGS, and the larger the dipole moment of the dopant molecule, the higher the P and lambda of the doped TGS crystal.

  1. Arsenic doped zinc oxide

    SciTech Connect

    Volbers, N.; Lautenschlaeger, S.; Leichtweiss, T.; Laufer, A.; Graubner, S.; Meyer, B. K.; Potzger, K.; Zhou Shengqiang

    2008-06-15

    As-doping of zinc oxide has been approached by ion implantation and chemical vapor deposition. The effect of thermal annealing on the implanted samples has been investigated by using secondary ion mass spectrometry and Rutherford backscattering/channeling geometry. The crystal damage, the distribution of the arsenic, the diffusion of impurities, and the formation of secondary phases is discussed. For the thin films grown by vapor deposition, the composition has been determined with regard to the growth parameters. The bonding state of arsenic was investigated for both series of samples using x-ray photoelectron spectroscopy.

  2. Effect of doping on single-walled carbon nanotubes network of different metallicity.

    PubMed

    Tey, Ju Nie; Ho, Xinning; Wei, Jun

    2012-10-03

    Effects of doping on single-walled carbon nanotubes (SWNT) networks with different metallicity are reported through the study of sheet resistance changes upon annealing and acid treatment. SWNT film with high metallic tube content is found to have relatively good chemical stability against post treatments, as demonstrated from its stable film performance in ambient after annealing, and merely 15% reduction in sheet resistance upon sulfuric acid treatment. Conversely, film stability of SWNT film with low metallic content which comprises largely of semiconducting SWNT varies with days in ambient, and its sheet resistance changes drastically after treated with acid, indicating the extreme sensitivity of semiconducting SWNT to surrounding environment. The results suggest that annealing removes unintentional oxygen doping from the ambient and shifts the Fermi level towards the intrinsic Fermi level. Acid treatment, on the other hand, introduces physisorbed and chemisorbed oxygen and shifts the Fermi level away from the intrinsic level and increases the hole doping.

  3. Interaction between Nitrogen and Sulfur in Co-Doped Graphene and Synergetic Effect in Supercapacitor

    PubMed Central

    Wang, Tao; Wang, Lu-Xiang; Wu, Dong-Ling; Xia, Wei; Jia, Dian-Zeng

    2015-01-01

    The co-doping of graphene with nitrogen and sulfur was investigated aiming at understanding their interactions with the presence of oxygen in graphene. The co-doped graphene (NS-G) was synthesized via a one-pot hydrothermal route using graphene oxide as starting material and L-cysteine, an amino acid containing both N and S, as the doping agent. The obtained NS-G with a three-dimensional hierarchical structure containing both macropores and mesopores exhibited excellent mechanical stabilities under both wet and dry conditions. As compared to N or S singly doped graphene, the co-doped sample contains significantly higher concentrations of N and S species especially pyrollic N groups. The co-doped sample considerably outperformed the singly doped samples when used as free-standing electrode in supercapacitors due to enhanced pseudocapacitance. The simultaneous incorporation of S and N species with the presence of oxygen significantly modified the surface chemistry of carbon leading to considerably higher doping levels, although directly bonding between N and S is neither likely nor detected. Hence, the synergetic effect between N and S occurred through carbon atoms in neighboring hexagonal rings in a graphene sheet. PMID:25880811

  4. Influence of iron doping on tetravalent nickel content in catalytic oxygen evolving films.

    PubMed

    Li, Nancy; Bediako, D Kwabena; Hadt, Ryan G; Hayes, Dugan; Kempa, Thomas J; von Cube, Felix; Bell, David C; Chen, Lin X; Nocera, Daniel G

    2017-02-14

    Iron doping of nickel oxide films results in enhanced activity for promoting the oxygen evolution reaction (OER). Whereas this enhanced activity has been ascribed to a unique iron site within the nickel oxide matrix, we show here that Fe doping influences the Ni valency. The percent of Fe(3+) doping promotes the formation of formal Ni(4+), which in turn directly correlates with an enhanced activity of the catalyst in promoting OER. The role of Fe(3+) is consistent with its behavior as a superior Lewis acid.

  5. Chemical Vapor Deposition of Phosphorous- and Boron-Doped Graphene Using Phenyl-Containing Molecules.

    PubMed

    Mekan Ovezmyradov; Magedov, Igor V; Frolova, Liliya V; Chandler, Gary; Garcia, Jill; Bethke, Donald; Shaner, Eric A; Kalugin, Nikolai G

    2015-07-01

    Simultaneous chemical vapor deposition (CVD) of graphene and "in-situ" phosphorous or boron doping of graphene was accomplished using Triphenylphosphine (TPP) and 4-Methoxyphenylboronic acid (4-MPBA). The TPP and 4-MPBA molecules were sublimated and supplied along with CH4 molecules during graphene growth at atmospheric pressure. The grown graphene samples were characterized using Raman spectroscopy. Phosphorous and boron presence in phosphorous and boron doped graphene was confirmed with Auger electron spectroscopy. The possibility of obtaining phosphorous and boron doped graphene using solid-source molecule precursors via CVD can lead to an easy and rapid production of modified large area graphene.

  6. High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Yen, Chih-Feng; Fan, Cho-Han

    2014-09-01

    The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.

  7. Temperature dependence of the hole density in high-TC superconductors Bi2-yPbySr2CaCu2O8+δ

    NASA Astrophysics Data System (ADS)

    Ghafari, A.; Janowitz, C.; Ariffin, A. K.; Dwelk, H.; Krapf, A.; Manzke, R.

    2013-02-01

    One of the most puzzling anomalies of high-TC cuprates is the strong temperature dependence of the Hall coefficient (RH) and the hole density (nH). Gor’kov and Teitel’baum (GT) proposed by using experimental data of La2-xSrxCuO4 (LSCO) a two fluid model. The number of holes per Cu atom nH, changes with temperature according to nH(T,x) = n0(x) + n1(x)exp(-Δ(x)/T) [1]. To clarify the temperature dependence of nH we have determined nH from X-ray absorption spectra (XAS) at the CuL3 edge for nearly optimum and slightly underdoped Bi2-yPbySr2CaCu2O8+δ single crystals yielding directly the absolute value of nH in the CuO2 planes and also its change with temperature nH(T). It shows pronounced structures between 10 K and 300 K. The temperature dependence puts constraints to the applicability of previously developed models: (i) the two-band model without any explicit temperature dependence and (ii) the formula of GT, because the latter is not able to fit our data over the whole temperature range from 10 K to 300 K. Instead the thermal behavior of nH proposes a function with at least three terms, i.e. a third term added to the formula of GT is of exponential form ∼T3/2.

  8. Enhanced performance of CH3NH3PbI3-x Cl x perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface.

    PubMed

    Wang, Wen; Zhang, Zongbao; Cai, Yangyang; Chen, Jinshan; Wang, Jianming; Huang, Riyan; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2016-12-01

    In this work, perovskite solar cells (PSCs) with CH3NH3PbI3-x Cl x as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3-x Cl x perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI3-x Cl x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO2 film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH3NH3I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH3NH3I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices.

  9. Enhanced performance of CH3NH3PbI3- x Cl x perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface

    NASA Astrophysics Data System (ADS)

    Wang, Wen; Zhang, Zongbao; Cai, Yangyang; Chen, Jinshan; Wang, Jianming; Huang, Riyan; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2016-06-01

    In this work, perovskite solar cells (PSCs) with CH3NH3PbI3- x Cl x as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3- x Cl x perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI3- x Cl x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO2 film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH3NH3I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH3NH3I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices.

  10. Optimizing doped libraries by using genetic algorithms

    NASA Astrophysics Data System (ADS)

    Tomandl, Dirk; Schober, Andreas; Schwienhorst, Andreas

    1997-01-01

    The insertion of random sequences into protein-encoding genes in combination with biologicalselection techniques has become a valuable tool in the design of molecules that have usefuland possibly novel properties. By employing highly effective screening protocols, a functionaland unique structure that had not been anticipated can be distinguished among a hugecollection of inactive molecules that together represent all possible amino acid combinations.This technique is severely limited by its restriction to a library of manageable size. Oneapproach for limiting the size of a mutant library relies on `doping schemes', where subsetsof amino acids are generated that reveal only certain combinations of amino acids in a proteinsequence. Three mononucleotide mixtures for each codon concerned must be designed, suchthat the resulting codons that are assembled during chemical gene synthesis represent thedesired amino acid mixture on the level of the translated protein. In this paper we present adoping algorithm that `reverse translates' a desired mixture of certain amino acids into threemixtures of mononucleotides. The algorithm is designed to optimally bias these mixturestowards the codons of choice. This approach combines a genetic algorithm with localoptimization strategies based on the downhill simplex method. Disparate relativerepresentations of all amino acids (and stop codons) within a target set can be generated.Optional weighing factors are employed to emphasize the frequencies of certain amino acidsand their codon usage, and to compensate for reaction rates of different mononucleotidebuilding blocks (synthons) during chemical DNA synthesis. The effect of statistical errors thataccompany an experimental realization of calculated nucleotide mixtures on the generatedmixtures of amino acids is simulated. These simulations show that the robustness of differentoptima with respect to small deviations from calculated values depends on their concomitantfitness. Furthermore

  11. Nanocrystal doped matrixes

    DOEpatents

    Parce, J. Wallace; Bernatis, Paul; Dubrow, Robert; Freeman, William P.; Gamoras, Joel; Kan, Shihai; Meisel, Andreas; Qian, Baixin; Whiteford, Jeffery A.; Ziebarth, Jonathan

    2010-01-12

    Matrixes doped with semiconductor nanocrystals are provided. In certain embodiments, the semiconductor nanocrystals have a size and composition such that they absorb or emit light at particular wavelengths. The nanocrystals can comprise ligands that allow for mixing with various matrix materials, including polymers, such that a minimal portion of light is scattered by the matrixes. The matrixes of the present invention can also be utilized in refractive index matching applications. In other embodiments, semiconductor nanocrystals are embedded within matrixes to form a nanocrystal density gradient, thereby creating an effective refractive index gradient. The matrixes of the present invention can also be used as filters and antireflective coatings on optical devices and as down-converting layers. Processes for producing matrixes comprising semiconductor nanocrystals are also provided. Nanostructures having high quantum efficiency, small size, and/or a narrow size distribution are also described, as are methods of producing indium phosphide nanostructures and core-shell nanostructures with Group II-VI shells.

  12. Glycolic acid modulates the mechanical property and degradation of poly(glycerol, sebacate, glycolic acid).

    PubMed

    Sun, Zhi-Jie; Wu, Lan; Huang, Wei; Chen, Chang; Chen, Yan; Lu, Xi-Li; Zhang, Xiao-Lan; Yang, Bao-Feng; Dong, De-Li

    2010-01-01

    The development of biodegradable materials with controllable degradation properties is beneficial for a variety of applications. Poly(glycerol-sebacate) (PGS) is a promising candidate of biomaterials; so we synthesize a series of poly(glycerol, sebacate, glycolic acid) (PGSG) with 1:2:0, 1:2:0.2, 1:2:0.4, 1:2:0.6, 1:2:1 mole ratio of glycerol, sebacate, and glycolic acid to elucidate the relation of doped glycolic acid to the degradation rate and mechanical properties. The microstructures of the polymers with different doping of glycolic acid were dissimilar. PGSG with glycolic acid in the ratio of 0.2 displayed an integral degree of ordering, different to those with glycolic acid in the ratio of 0, 0.4, 0.6, and 1, which showed mild phase separation structure. The number, DeltaH(m), and temperature of the PGSG melting peaks tended to decrease with the increasing ratio of doped glycolic acid. In vitro and in vivo degradation tests showed that the degradation rate of PGSG with glycolic acid in the ratio of 0.2 was slowest, but in the ratio range of 0, 0.4, and 0.6, the degradation rate increased with the increase of glycolic acid. All PGSG samples displayed good tissue response and anticoagulant effects. Our data suggest that doping glycolic acid can modulate the microstructure and degree of crosslinking of PGS, thereby control the degradation rate of PGS.

  13. Direct observation of dramatically enhanced hole formation in a perovskite-solar-cell material spiro-OMeTAD by Li-TFSI doping

    NASA Astrophysics Data System (ADS)

    Namatame, Miki; Yabusaki, Masaki; Watanabe, Takahiro; Ogomi, Yuhei; Hayase, Shuzi; Marumoto, Kazuhiro

    2017-03-01

    Electron spin resonance (ESR) spectroscopy of 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene (spiro-OMeTAD) thin films and perovskite (CH3NH3PbI3)/spiro-OMeTAD layered films are reported. Clear ESR signals (g = 2.0030) were observed by adding a dopant lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) to the spiro-OMeTAD thin films, which directly showed the spin (hole) formation in spiro-OMeTAD by the Li-TFSI doping. The number of spins in the spiro-OMeTAD thin film has increased by more than two orders of magnitude by the Li-TFSI doping under dark conditions, which demonstrates from a microscopic viewpoint that Li-TFSI has high doping effects for the spiro-OMeTAD thin films. Under simulated solar irradiation, the spin density in the spiro-OMeTAD thin films and the perovskite/spiro-OMeTAD layered films largely increased by the Li-TFST doping due to the formation of long-lived holes in spiro-OMeTAD. The transient responses of the number of photogenerated spins, Nspin, of the layered films upon the light irradiation showed the increase and the decrease in the Nspin due to the hole transfer and recombination at the perovskite/spiro-OMeTAD interface. The states of long-lived holes in the spiro-OMeTAD layers were analyzed using the simulation of the ESR spectra, which reveals the mobile photogenerated holes with a lifetime >10 μs.

  14. Epitaxial Silicon Doped With Antimony

    NASA Technical Reports Server (NTRS)

    Huffman, James E.; Halleck, Bradley L.

    1996-01-01

    High-purity epitaxial silicon doped with antimony made by chemical vapor deposition, using antimony pentachloride (SbCI5) as source of dopant and SiH4, SiCI2H2, or another conventional source of silicon. High purity achieved in layers of arbitrary thickness. Epitaxial silicon doped with antimony needed to fabricate impurity-band-conduction photodetectors operating at wavelengths from 2.5 to 40 micrometers.

  15. Color stable manganese-doped phosphors

    DOEpatents

    Lyons, Robert Joseph [Burnt Hills, NY; Setlur, Anant Achyut [Niskayuna, NY; Deshpande, Anirudha Rajendra [Twinsburg, OH; Grigorov, Ljudmil Slavchev [Sofia, BG

    2012-08-28

    A process for preparing color stable Mn.sup.+4 doped phosphors includes providing a phosphor of formula I; A.sub.x[MF.sub.y]:Mn.sup.+4 I and contacting the phosphor in particulate form with a saturated solution of a composition of formula II in aqueous hydrofluoric acid; A.sub.x[MF.sub.y]; II wherein A is Li, Na, K, Rb, Cs, NR.sub.4 or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, lower alkyl, or a combination thereof; x is the absolute value of the charge of the [MF.sub.y] ion; and y is 5, 6 or 7. In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof. A lighting apparatus capable of emitting white light includes a semiconductor light source; and a phosphor composition radiationally coupled to the light source, and which includes a color stable Mn.sup.+4 doped phosphor.

  16. Study of the structure and mechanical properties of pure and doped polyaniline

    NASA Astrophysics Data System (ADS)

    Shaktawat, Vinodini; Saxena, N. S.; Sharma, Kananbala

    2011-03-01

    Polyaniline (PANI) doped with different protonic acids was chemically synthesized using ammonium persulfate as an oxidant. These samples were characterized through scanning electron microscopy-energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy, which confirms the acid doping. Variation of complex elastic modulus and mechanical loss factor (tan δ) has been studied with temperature of pellet of conducting PANI. It has been observed that complex modulus decreases with temperature due to thermal expansion of films. On the other hand, tan δ increases up to characteristic temperature, beyond which it shows a decreasing trend towards melting. The phase transition temperature of pure PANI is 106.1°C and is shifted to higher temperatures i.e. 137.1°C, 134°C, 138.8°C, 118.3°C, and 109.7°C with doping of PANI by protonic acids.

  17. Modification of neodymium-doped ZnO hybrid nanoparticles under mild hydrothermal conditions.

    PubMed

    Shahmoradi, Behzad; Soga, K; Ananda, S; Somashekar, R; Byrappa, K

    2010-07-01

    The morphology and particle size of neodymium-doped ZnO hybrid nanoparticles were tailored through fabrication under mild hydrothermal conditions (T = 150-250 degrees C, P = autogeneous, t = 18 h) for the first time using two surface modifiers: caprylic acid and n-butylamine. Characterization of these nanoparticles was carried out using powder XRD, FTIR, SEM, zeta-potential analysis and UV-vis spectroscopy. The results revealed that modification of ZnO nanoparticles using neodymium as a dopant and caprylic acid or n-butylamine as a surfactant could change the optical and physical properties of the surface-modified neodymium-doped ZnO hybrid nanoparticles. The work proved the efficiency of caprylic acid and n-butylamine as suitable surfactants for surface modification of neodymium-doped ZnO hybrid nanoparticles.

  18. Properties and electrochemical characteristics of boron-doped multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tsierkezos, Nikos G.; Ritter, Uwe; Nugraha Thaha, Yudi; Krischok, Stefan; Himmerlich, Marcel; Downing, Clive

    2015-10-01

    Boron-doped multi-walled carbon nanotubes were synthesized upon decomposition of ethyl alcohol and boric acid via chemical vapor deposition. The boron-doped nanotubes were treated with hydrochloric acid and were characterized by means of scanning electron and transmission electron microscopy in conjunction with energy-dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. The electrochemistry of ferrocyanide/ferricyanide on boron-doped nanotubes was studied in temperature range of 283.15-303.15 K. The findings exhibit an improvement of films' current response and kinetics of electron transfer with the rise in temperature. The kinetics for electron transfer enhances and the redox process occurs slightly more spontaneously upon acid treatment.

  19. Substitutional doping in nanocrystal superlattices

    NASA Astrophysics Data System (ADS)

    Cargnello, Matteo; Johnston-Peck, Aaron C.; Diroll, Benjamin T.; Wong, Eric; Datta, Bianca; Damodhar, Divij; Doan-Nguyen, Vicky V. T.; Herzing, Andrew A.; Kagan, Cherie R.; Murray, Christopher B.

    2015-08-01

    Doping is a process in which atomic impurities are intentionally added to a host material to modify its properties. It has had a revolutionary impact in altering or introducing electronic, magnetic, luminescent, and catalytic properties for several applications, for example in semiconductors. Here we explore and demonstrate the extension of the concept of substitutional atomic doping to nanometre-scale crystal doping, in which one nanocrystal is used to replace another to form doped self-assembled superlattices. Towards this goal, we show that gold nanocrystals act as substitutional dopants in superlattices of cadmium selenide or lead selenide nanocrystals when the size of the gold nanocrystal is very close to that of the host. The gold nanocrystals occupy random positions in the superlattice and their density is readily and widely controllable, analogous to the case of atomic doping, but here through nanocrystal self-assembly. We also show that the electronic properties of the superlattices are highly tunable and strongly affected by the presence and density of the gold nanocrystal dopants. The conductivity of lead selenide films, for example, can be manipulated over at least six orders of magnitude by the addition of gold nanocrystals and is explained by a percolation model. As this process relies on the self-assembly of uniform nanocrystals, it can be generally applied to assemble a wide variety of nanocrystal-doped structures for electronic, optical, magnetic, and catalytic materials.

  20. Genetic Doping and Health Damages

    PubMed Central

    Fallahi, AA; Ravasi, AA; Farhud, DD

    2011-01-01

    Background: Use of genetic doping or gene transfer technology will be the newest and the lethal method of doping in future and have some unpleasant consequences for sports, athletes, and outcomes of competitions. The World Anti-Doping Agency (WADA) defines genetic doping as “the non-therapeutic use of genes, genetic elements, and/or cells that have the capacity to enhance athletic performance ”. The purpose of this review is to consider genetic doping, health damages and risks of new genes if delivered in athletes. Methods: This review, which is carried out by reviewing relevant publications, is primarily based on the journals available in GOOGLE, ELSEVIER, PUBMED in fields of genetic technology, and health using a combination of keywords (e.g., genetic doping, genes, exercise, performance, athletes) until July 2010. Conclusion: There are several genes related to sport performance and if they are used, they will have health risks and sever damages such as cancer, autoimmunization, and heart attack. PMID:23113049

  1. Synthesis, linear optical, non-linear optical, thermal and mechanical characterizations of dye-doped semi-organic NLO crystals

    NASA Astrophysics Data System (ADS)

    Sesha Bamini, N.; Vidyalakshmy, Y.; Choedak, Tenzin; Kejalakshmy, N.; Muthukrishnan, P.; Ancy, C. J.

    2015-06-01

    Organic laser dyes Coumarin 485, Coumarin 540 and Rhodamine 590 Chloride were used to dope potassium acid phthalate crystals (KAP). Dye-doped KAP crystals with different dye concentrations such as 0.01 mM, 0.03 mM, 0.05 mM, 0.07 mM and 0.09 mM (in the KAP growth solution) were grown. The linear optical, non-linear optical, mechanical and thermal characterizations of dye-doped KAP crystals were studied and compared to understand the effect of dye and dye concentration on the KAP crystal. Absorption and emission studies of KAP and dye-doped KAP single crystals indicated the inclusion of the dye into the KAP crystal lattice. The effect of dye and its concentration on the SHG efficiency of the KAP crystal was studied using the Kurtz and Perry powder technique. It was observed that the absorption maximum wavelength and concentration of the dye used for doping the KAP single crystal decided the SHG efficiency of the dye-doped KAP single crystals. The mechanical hardness of the dye-doped and undoped (pure) KAP single crystals were studied using the Vickner’s microhardness test. It was observed that doping the KAP crystals with the laser dyes changed them from softer material to harder material. Etching studies showed an improvement in the optical quality of the KAP crystal after doping with laser dyes.

  2. Influence of void-free perovskite capping layer on the charge recombination process in high performance CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Fu, Kunwu; Nelson, Christopher T.; Scott, Mary Cooper; Minor, Andrew; Mathews, Nripan; Wong, Lydia Helena

    2016-02-01

    void free perovskite capping layer surface on the charge recombination processes within the mesoscopic perovskite solar cells is further scrutinized via charge extraction measurement. Modulation of precursor solution concentrations in order to further improve the perovskite layer surface morphology leads to higher efficiency and lower charge recombination rates. Inhibited charge recombination in these solar cells also matches with the higher charge density and slower photovoltage decay profiles measured. Electronic supplementary information (ESI) available: UV-Vis, PL and XRD of MAPbI3, internal quantum efficiency of perovskite devices, top-view SEM images of PbI2 films, cross section view of FIB cut samples, electron diffraction peak intensity vs. diffraction angle of TiO2/MAPbI3 perovskite samples from single and sequential deposition methods. See DOI: 10.1039/c5nr06362k

  3. Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4

    PubMed Central

    Yangui, Aymen; Sy, Mouhamadou; Li, Liang; Abid, Younes; Naumov, Panče; Boukheddaden, Kamel

    2015-01-01

    The dynamics of the thermally induced first-order structural phase transition in a high-quality single crystal of the organic-inorganic perovskite (C12H25NH3)2PbI4 was investigated by optical microscopy. The propagation of the straight phase front (habit plane) during the phase transition along the cooling and heating pathways of the thermal hysteresis was observed. The thermochromic character of the transition allowed monitoring of the thermal dependence of average optical density and aided the visualization of the interface propagation. The thermal hysteresis loop is 10 K wide, and the interface velocity is constant at V ≈ 1.6 mm s–1. The transition is accompanied with sizeable change in crystal size, with elongation of ~6% along the b axis and compression of ~ –2% along the a axis, in excellent agreement with previously reported X-ray diffraction data. The progression of the habit plane is at least 160 times faster than in spin-crossover materials, and opens new prospects for organic-inorganic perovskites as solid switching materials. Moreover, the crystals of (C12H25NH3)2PbI4 are unusually mechanically robust and present excellent resilience to thermal cycling. These hitherto unrecognized properties turn this and possibly similar hybrid perovskites into perspective candidates as active medium for microscopic actuation. PMID:26568147

  4. Effects of precursor solution composition on the performance and I-V hysteresis of perovskite solar cells based on CH3NH3PbI3-xClx.

    PubMed

    Zhang, Z L; Men, B Q; Liu, Y F; Gao, H P; Mao, Y L

    2017-12-01

    Precursor solution of CH3NH3PbI3-xClx for perovskite solar cells was conventionally prepared by mixing PbCl2 and CH3NH3I with a mole ratio of 1:3 (PbCl2:CH3NH3I). While in the present study, CH3NH3PbI3-xClx-based solar cells were fabricated using the precursor solutions containing PbCl2 and CH3NH3I with the mole ratios of 1:3, 1.05:3, 1.1:3, and 1.15:3, respectively. The results display that the solar cells with the mole ratio of 1.1:3 present higher power conversion efficiency and less I-V hysteresis than those with the mole ratio of 1:3. Based on some investigations, it is concluded that the higher efficiency could be due to the smooth and pinhole free film formation, high optical absorption, suitable energy band gap, and the large electron transfer efficiency, and the less I-V hysteresis may be attributed to the small low frequency capacitance of the device.

  5. Effects of precursor solution composition on the performance and I-V hysteresis of perovskite solar cells based on CH3NH3PbI3-xClx

    NASA Astrophysics Data System (ADS)

    Zhang, Z. L.; Men, B. Q.; Liu, Y. F.; Gao, H. P.; Mao, Y. L.

    2017-02-01

    Precursor solution of CH3NH3PbI3-xClx for perovskite solar cells was conventionally prepared by mixing PbCl2 and CH3NH3I with a mole ratio of 1:3 (PbCl2:CH3NH3I). While in the present study, CH3NH3PbI3-xClx-based solar cells were fabricated using the precursor solutions containing PbCl2 and CH3NH3I with the mole ratios of 1:3, 1.05:3, 1.1:3, and 1.15:3, respectively. The results display that the solar cells with the mole ratio of 1.1:3 present higher power conversion efficiency and less I-V hysteresis than those with the mole ratio of 1:3. Based on some investigations, it is concluded that the higher efficiency could be due to the smooth and pinhole free film formation, high optical absorption, suitable energy band gap, and the large electron transfer efficiency, and the less I-V hysteresis may be attributed to the small low frequency capacitance of the device.

  6. Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4

    NASA Astrophysics Data System (ADS)

    Yangui, Aymen; Sy, Mouhamadou; Li, Liang; Abid, Younes; Naumov, Panče; Boukheddaden, Kamel

    2015-11-01

    The dynamics of the thermally induced first-order structural phase transition in a high-quality single crystal of the organic-inorganic perovskite (C12H25NH3)2PbI4 was investigated by optical microscopy. The propagation of the straight phase front (habit plane) during the phase transition along the cooling and heating pathways of the thermal hysteresis was observed. The thermochromic character of the transition allowed monitoring of the thermal dependence of average optical density and aided the visualization of the interface propagation. The thermal hysteresis loop is 10 K wide, and the interface velocity is constant at V ≈ 1.6 mm s-1. The transition is accompanied with sizeable change in crystal size, with elongation of ~6% along the b axis and compression of ~ -2% along the a axis, in excellent agreement with previously reported X-ray diffraction data. The progression of the habit plane is at least 160 times faster than in spin-crossover materials, and opens new prospects for organic-inorganic perovskites as solid switching materials. Moreover, the crystals of (C12H25NH3)2PbI4 are unusually mechanically robust and present excellent resilience to thermal cycling. These hitherto unrecognized properties turn this and possibly similar hybrid perovskites into perspective candidates as active medium for microscopic actuation.

  7. Influence of cysteine doping on photoluminescence intensity from semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kurnosov, N. V.; Leontiev, V. S.; Linnik, A. S.; Karachevtsev, V. A.

    2015-03-01

    Photoluminescence (PL) from semiconducting single-walled carbon nanotubes can be applied for detection of cysteine. It is shown that cysteine doping (from 10-8 to 10-3 M) into aqueous suspension of nanotubes with adsorbed DNA leads to increase of PL intensity. The PL intensity was enhanced by 27% at 10-3 M cysteine concentration in suspension. Most likely, the PL intensity increases due to the passivation of p-defects on the nanotube by the cysteine containing reactive thiol group. The effect of doping with other amino acids without this group (methionine, serine, aspartic acid, lysine, proline) on the PL intensity is essentially weaker.

  8. Highly reproducible, efficient hysteresis-less CH3NH3PbI3-xClx planar hybrid solar cells without requiring heat-treatment

    NASA Astrophysics Data System (ADS)

    Heo, Jin Hyuck; Im, Sang Hyuk

    2016-01-01

    CH3NH3PbI3-xClx(MAPbI3-xClx) mixed halide perovskite powder with uniform composition was synthesized via simple solution chemistry, which demonstrates highly reproducible, efficient planar type MAPbI3-xClx mixed halide perovskite solar cells. Pure MAPbI3-xClx mixed halide perovskite powder was synthesized by reacting a 3 : 1 molar ratio of MAI : PbCl2 powder mixture in isopropanol (IPA) solution for 30 min at 60 °C with subsequent repeated centrifugation and washing in IPA. IPA functions as both the reaction medium for the formation of MAPbI3-xClx mixed halide and a selective remover of unreacted MAI and MACl byproducts. Accordingly, we could deposit a pinhole-free dense MAPbI3-xClx mixed halide perovskite film on a TiO2/FTO substrate through a simple one step spin-coating of pure MAPbI3-xClx mixed halide perovskite powder in DMF solution with HI additive, without further long heat-treatment processes. The deposited MAPbI3-xClx mixed halide perovskite film revealed uniform composition throughout the entire area, and the ratio of Cl to I + Cl and I + Cl to Pb was constant at ~0.03 and ~1/3, respectively. On the other hand, the conventional MAPbI3-xClx mixed halide perovskite film prepared by the long heat-treatment process had non-uniform composition because the ratio of Cl to I + Cl fluctuated greatly from 0 to 7.2. The average efficiency of planar type MAPbI3-xClx mixed halide perovskite solar cells was 18.65% +/- 0.30% and the champion cell had 1.11 V Voc, 22.1 mA cm-2Jsc, 77% F.F., and 18.9% η for forward scan conditions and 1.11 V Voc, 22.1 mA cm-2Jsc, 78% F.F., and 19.1% η for reverse scan conditions. Although the thickness of the MAPbI3-xClx mixed halide perovskite layer varied from ~500 nm to ~900 nm, the efficiency was within the range of 18.3%-19.0%.CH3NH3PbI3-xClx(MAPbI3-xClx) mixed halide perovskite powder with uniform composition was synthesized via simple solution chemistry, which demonstrates highly reproducible, efficient planar type MAPbI3-x

  9. Doping and thrombosis in sports.

    PubMed

    Lippi, Giuseppe; Banfi, Giuseppe

    2011-11-01

    Historically, humans have long sought to enhance their "athletic" performance to increase body weight, aggressiveness, mental concentration and physical strength, contextually reducing fatigue, pain, and improving recovery. Although regular training is the mainstay for achieving these targets, the ancillary use of ergogenic aids has become commonplace in all sports. The demarcation between ergogenic aids and doping substances or practices is continuously challenging and mostly based on perceptions regarding the corruption of the fairness of competition and the potential side effects or adverse events arising from the use of otherwise unnecessary ergogenic substances. A kaleidoscope of side effects has been associated with the use of doping agents, including behavioral, skeletal, endocrinologic, metabolic, hemodynamic, and cardiovascular imbalances. Among the various doping substances, the most striking association with thrombotic complications has been reported for androgenic anabolic steroids (i.e., cardiomyopathy, fatal and nonfatal arrhythmias, myocardial infarction [MI], intracardiac thrombosis, stroke, venous thromboembolism [VTE], limb arterial thrombosis, branch retinal vein occlusion, cerebral venous sinus thrombosis) and blood boosting (i.e., VTE and MI, especially for epoetin and analogs). The potential thrombotic complication arising from misuse of other doping agents such as the administration of cortisol, growth hormone, prolactin, cocaine, and platelet-derived preparations is instead speculative or anecdotal at best. The present article provides an overview on the epidemiological association as well as the underlying biochemical and biological mechanisms linking the practice of doping in sports with the development of thrombosis.

  10. Enhancing charge storage of conjugated polymer electrodes with phenolic acids

    NASA Astrophysics Data System (ADS)

    Wagner, Michal; Rębiś, Tomasz; Inganäs, Olle

    2016-01-01

    We here present studies of electrochemical doping of poly(1-aminoanthraquinone) (PAAQ) films with three structurally different phenolic acids. The examined phenolic acids (sinapic, ferulic and syringic acid) were selected due to their resemblance to redox active groups, which can be found in lignin. The outstanding electrochemical stability of PAAQ films synthesized for this work enabled extensive cycling of phenolic acid-doped PAAQ films. Potentiodynamic and charge-discharge studies revealed that phenolic acid-doped PAAQ films exhibited enhanced capacitance in comparison to undoped PAAQ films, together with appearance of redox activity characteristics specific for each dopant. Electrochemical kinetic studies performed on microelectrodes affirmed the fast electron transfer for hydroquinone-to-quinone reactions with these phenolic compounds. These results imply the potential application of phenolic acids in cheap and degradable energy storage devices.

  11. [Xenon: From rare gaz to doping product].

    PubMed

    Tassel, Camille; Le Daré, Brendan; Morel, Isabelle; Gicquel, Thomas

    2016-04-01

    Doping is defined as the use of processes or substances to artificially increase physical or mental performance. Xenon is a noble gas used as an anesthetic and recently as a doping agent. Xenon is neuroprotective as an antagonist of NMDA glutamate receptors. Xenon stimulates the synthesis of erythropoietin (EPO) by increase of hypoxia inducible factor (HIF). Xenon would be a new doping product, maintaining doping methods ahead of detection.

  12. Developing strategies for detection of gene doping.

    PubMed

    Baoutina, Anna; Alexander, Ian E; Rasko, John E J; Emslie, Kerry R

    2008-01-01

    It is feared that the use of gene transfer technology to enhance athletic performance, the practice that has received the term 'gene doping', may soon become a real threat to the world of sport. As recognised by the anti-doping community, gene doping, like doping in any form, undermines principles of fair play in sport and most importantly, involves major health risks to athletes who partake in gene doping. One attraction of gene doping for such athletes and their entourage lies in the apparent difficulty of detecting its use. Since the realisation of the threat of gene doping to sport in 2001, the anti-doping community and scientists from different disciplines concerned with potential misuse of gene therapy technologies for performance enhancement have focused extensive efforts on developing robust methods for gene doping detection which could be used by the World Anti-Doping Agency to monitor athletes and would meet the requirements of a legally defensible test. Here we review the approaches and technologies which are being evaluated for the detection of gene doping, as well as for monitoring the efficacy of legitimate gene therapy, in relation to the detection target, the type of sample required for analysis and detection methods. We examine the accumulated knowledge on responses of the body, at both cellular and systemic levels, to gene transfer and evaluate strategies for gene doping detection based on current knowledge of gene technology, immunology, transcriptomics, proteomics, biochemistry and physiology.

  13. Incubational domain characterization in lightly doped ceria

    SciTech Connect

    Li Zhipeng; Mori, Toshiyuki; John Auchterlonie, Graeme; Zou Jin; Drennan, John

    2012-08-15

    Microstructures of both Gd- and Y-doped ceria with different doping level (i.e., 10 at% and 25 at%) have been comprehensively characterized by means of high resolution transmission electron microscopy and selected area electron diffraction. Coherent nano-sized domains can be widely observed in heavily doped ceria. Nevertheless, it was found that a large amount of dislocations actually exist in lightly doped ceria instead of heavily doped ones. Furthermore, incubational domains can be detected in lightly doped ceria, with dislocations located at the interfaces. The interactions between such linear dislocations and dopant defects have been simulated accordingly. As a consequence, the formation mechanism of incubational domains is rationalized in terms of the interaction between intrinsic dislocations of doped ceria and dopant defects. This study offers the insights into the initial state and related mechanism of the formation of nano-sized domains, which have been widely observed in heavily rare-earth-doped ceria in recent years. - Graphical abstract: Interactions between dislocations and dopants lead to incubational domain formation in lightly doped ceria. Highlights: Black-Right-Pointing-Pointer Microstructures were characterized in both heavily and light Gd-/Y-doped ceria. Black-Right-Pointing-Pointer Dislocations are existed in lightly doped ceria rather than heavily doped one. Black-Right-Pointing-Pointer Interactions between dislocations and dopant defects were simulated. Black-Right-Pointing-Pointer Formation of dislocation associated incubational domain is rationalized.

  14. Synthesis and organic surface modification of luminescent, lanthanide-doped core/shell nanomaterials (LnF3@SiO2@NH2@organic acid) for potential bioapplications: spectroscopic, structural, and in vitro cytotoxicity evaluation.

    PubMed

    Runowski, Marcin; Ekner-Grzyb, Anna; Mrówczyńska, Lucyna; Balabhadra, Sangeetha; Grzyb, Tomasz; Paczesny, Jan; Zep, Anna; Lis, Stefan

    2014-08-12

    A facile coprecipitation reaction between Ce(3+), Gd(3+), Tb(3+), and F(-) ions, in the presence of glycerine as a capping agent, led to the formation of ultrafine, nanocrystalline CeF3:Tb(3+) 5%, Gd(3+) 5% (LnF3). The as-prepared fluoride nanoparticles were successfully coated with an amine modified silica shell. Subsequently, the obtained LnF3@SiO2@NH2 nanostructures were conjugated with 4-ethoxybenzoic acid in order to prove the possibility of organic modification and obtain a new functional nanomaterial. All of the nanophosphors synthesized exhibited intense green luminescence under UV light irradiation. Based on TEM (transmission electron microscopy) measurements, the diameters of the cores (≈12 nm) and core/shell particles (≈50 nm) were determined. To evaluate the cytotoxic activity of the nanomaterials obtained, their effect on human erythrocytes was investigated. LnF3 nanoparticles were bound to the erythrocyte membrane, without inducing any cytotoxic effects. After coating with silica, the nanoparticles revealed significant cytotoxicity. However, further functionalization of the nanomaterial with -NH2 groups as well as conjugation with 4-ethoxybenzoic acid entailed a decrease in cytotoxicity of the core/shell nanoparticles.

  15. Properties of doped semiconducting materials

    NASA Astrophysics Data System (ADS)

    Zemskov, V. S.

    The papers contained in this volume focus on the physicochemical principles of the doping of semiconductor materials. Topics discussed include impurity atoms and atomic levels, phase diagrams of the semiconductor-dopant system, distribution coefficients, dopant diffusion, and macro- and microsegregation of doping components. Attention is also given to the interaction between dopant atoms and lattice defects and the structure and decomposition of semiconductor-dopant solid solutions. Experimental data are presented for single crystals and epitaxial films of III-V, IV-VI, and II-VI semiconductors.

  16. Method of doping a semiconductor

    DOEpatents

    Yang, Chiang Y.; Rapp, Robert A.

    1983-01-01

    A method for doping semiconductor material. An interface is established between a solid electrolyte and a semiconductor to be doped. The electrolyte is chosen to be an ionic conductor of the selected impurity and the semiconductor material and electrolyte are jointly chosen so that any compound formed from the impurity and the semiconductor will have a free energy no lower than the electrolyte. A potential is then established across the interface so as to allow the impurity ions to diffuse into the semiconductor. In one embodiment the semiconductor and electrolyte may be heated so as to increase the diffusion coefficient.

  17. Controlled doping by self-assembled dendrimer-like macromolecules

    PubMed Central

    Wu, Haigang; Guan, Bin; Sun, Yingri; Zhu, Yiping; Dan, Yaping

    2017-01-01

    Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 1017 cm−3. Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon. PMID:28145485

  18. Controlled doping by self-assembled dendrimer-like macromolecules

    NASA Astrophysics Data System (ADS)

    Wu, Haigang; Guan, Bin; Sun, Yingri; Zhu, Yiping; Dan, Yaping

    2017-02-01

    Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 1017 cm‑3. Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon.

  19. High deuteron polarization in trityl radical doped deuterated polystyrene

    NASA Astrophysics Data System (ADS)

    Wang, Li; Berlin, A.; Doshita, N.; Herick, J.; Hess, C.; Iwata, T.; Kondo, K.; Meyer, W.; Reicherz, G.

    2013-11-01

    Deuterated polystyrene for polarized solid targets has been prepared by chemical doping with the trityl radical ‘Finland D36’ (AH 110 355 deutero acid form). Thin foils doped with various radical densities have been produced using tetrahydrofuran as solvent. Dynamic nuclear polarization technique has been applied to polarize deuterons in the samples (98%-D) at the temperature range of about 1 K and magnetic fields of 2.5 T and 5.0 T. A maximum deuteron polarization of -61.5% with a build-up time of 100 min has been achieved at 5.0 T and about 500 mK at a radical density of 1.16×1019 spins/g.

  20. Controlled doping by self-assembled dendrimer-like macromolecules.

    PubMed

    Wu, Haigang; Guan, Bin; Sun, Yingri; Zhu, Yiping; Dan, Yaping

    2017-02-01

    Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 10(17) cm(-3). Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon.