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Sample records for acid doped polybenzimidazole

  1. Acid doped polybenzimidazoles, a new polymer electrolyte

    Wainright, J.S.; Wang, J.T.; Savinell, R.F.; Litt, M.; Moaddel, H.; Rogers, C. [Case Western Reserve Univ., Cleveland, OH (United States)

    1994-12-31

    Polybenzimidazole films doped with phosphoric acid are being investigated as potential polymer electrolytes for use in hydrogen/air and direct methanol fuel cells. The advantages of this electrolyte include good mechanical properties, and low vapor permeability. Combined, these factors allow for the use of thin (< 0.005 cm) membranes in fuel cells without excessive adverse effects from fuel gas crossover to the cathode compartment and subsequent cathode depolarization. In this paper the authors discuss experimental data on the proton conductivity, thermal stability and gas permeability of this material.

  2. Acid-doped polybenzimidazoles: A new polymer electrolyte

    Wainright, J.S.; Wang, J.T.; Weng, D.; Savinell, R.F.; Litt, M. [Case Western Reserve Univ., Cleveland, OH (United States)

    1995-07-01

    Polybenzimidazole films doped with phosphoric acid are being investigated as potential polymer electrolytes for use in hydrogen/air and direct methanol fuel cells. In this paper, the authors present experimental findings on the proton conductivity, water content, and methanol vapor permeability of this material, as well as preliminary fuel cell results. The low methanol vapor permeability of these electrolytes significantly reduces the adverse effects of methanol crossover typically observed in direct methanol polymer electrolyte membrane fuel cells.

  3. Durability Issues of High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, phosphoric acid doped polybenzimidazole (PBI) membrane represents an effective approach, which in recent years has motivated extensive research activities with great progress. As...

  4. Physicochemical properties of phosphoric acid doped polybenzimidazole membranes for fuel cells

    He, Ronghuan; Li, Qingfeng; Bach, Anders;

    2006-01-01

    Polybenzimidazole (PBI) membranes have been prepared with different molecular weights. The water and acid swelling, mechanical strength,gas permeability and proton conductivity were studied for the pristine and acid doped PBI membranes. When doped with 5 mol of phosphoric acid per mole repeat unit...

  5. Water Uptake and Acid Doping of Polybenzimidazoles as Electrolyte Membranes for Fuel Cells

    Qingfeng, Li; He, R.; Berg, Rolf W.; Hjuler, Hans Aage; Bjerrum, Niels J.

    Acid-doped polybenzimidazole (PBI) membranes have been demonstrated for fuel cell applications with advanced features such as high operating temperatures, little humidification, excellent CO tolerance, and promising durability. The water uptake and acid doping of PBI membranes have been studied...

  6. Proton conductivity of phosphoric acid doped polybenzimidazole and its composites with inorganic proton conductors

    He, Ronghuan; Qingfeng, Li; Gang, Xiao;

    2003-01-01

    Phosphoric acid doped polybenzimidazole (PBI) and PBI composite membranes have been prepared in the present work. The PBI composites contain inorganic proton conductors including zirconium phosphate (ZrP), (Zr(HPO4)2·nH2O), phosphotungstic acid (PWA), (H3PW12O40·nH2O) and silicotungstic acid (Si...

  7. Catalyst Degradation in High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    Cleemann, Lars Nilausen; Buazar, F.; Li, Qingfeng; Jensen, Jens Oluf; Pan, Chao; Steenberg, T.; Dai, S.; Bjerrum, Niels J.

    2013-01-01

    Degradation of carbon supported platinum catalysts is a major failure mode for the long term durability of high temperature proton exchange membrane fuel cells based on phosphoric acid doped polybenzimidazole membranes. With Vulcan carbon black as a reference, thermally treated carbon black and...

  8. Doping phosphoric acid in polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

    He, Ronghuan; Li, Qingfeng; Jensen, Jens Oluf;

    2007-01-01

    Polybenzimidazole (PBI) membranes were doped in phosphoric acid solutions of different concentrations at room temperature. The doping chemistry was studied using the Scatchard method. The energy distribution of the acid complexation in polymer membranes is heterogeneous, that is, there are two...... different types of sites in PBI for the acid doping. The protonation constants of PBI by phosphoric acid are found to be 12.7 L mol(-1) (K-1) for acid complexing sites with higher affinity, and 0.19 L mol(-1) (K-2) for the sites with lower affinity. The dissociation constants for the complexing acid onto...... these two types of PBI sites are found to be 5.4 X 10(-4) and 3.6 X 10(-2), respectively, that is, about 10 times smaller than that of aqueous phosphoric acid in the first case but 5 times higher in the second. The proton conducting mechanism is also discussed....

  9. Water uptake and acid doping of polybenzimidazoles as electrolyte membranes for fuel cells

    Li, Qingfeng; He, Ronghuan; Berg, Rolf W.; Hjuler, Hans A.; Bjerrum, Niels J. [Department of Chemistry, Technical University of Denmark, DK-2800 Lyngby (Denmark)

    2004-03-15

    Acid-doped polybenzimidazole (PBI) membranes have been demonstrated for fuel cell applications with advanced features such as high operating temperatures, little humidification, excellent CO tolerance, and promising durability. The water uptake and acid doping of PBI membranes have been studied. The water uptake of PBI from the vapour phase is only slightly increased as the atmospheric humidity increases up to unity (100%). Little difference is observed for the water uptake from vapour and liquid phases, behaving very differently from Nafion membranes. When doped with phosphoric acid at low levels (<2), the active sites of the imidazole ring are preferably occupied by the doping acid and the water uptake is consequently lower. At higher acid doping levels, the water uptake is influenced by the excess of hygroscopic acid and higher water uptake than for Nafion membranes is observed. Upon doping, the acid is found to be concentrated inside the polymer. Only two molecules of phosphoric acid are bonded to each repeat unit of PBI, corresponding to the two nitrogen sites available. Infrared and Raman spectra show the presence of strong hydrogen bonds between phosphoric acid and nitrogen atoms of the imidazole rings. The excessive doping acid is 'free acid' that contributes to high conductivity but suffers from a fast washing out when adequate liquid is present.

  10. Phosphoric acid doped polybenzimidazole membranes: Physiochemical characterization and fuel cell applications [PEM fuel cells

    Qingfeng, Li; Hjuler, Hans Aage; Bjerrum, Niels

    2001-01-01

    A polymer electrolyte membrane fuel cell operational at temperatures around 150-200 degrees C is desirable for fast electrode kinetics and high tolerance to fuel impurities. For this purpose polybenzimidazole (PBI) membranes have been prepared and H/sub 3/PO/sub 4/-doped in a doping range from 30...

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

    Fernandez, Santiago Martin; Li, Qingfeng; Jensen, Jens Oluf

    2015-01-01

    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...

  12. Porous polybenzimidazole membranes doped with phosphoric acid: Preparation and application in high-temperature proton-exchange-membrane fuel cells

    Highlights: • Porous polybenzimidazole membrane was prepared with glucose as porogen. • Phosphoric acid content was as high as 15.7 mol H3PO4 per PBI repeat unit. • 200 h Constant current density test was carried out at 150 °C. • Degradation was due to the gap between membrane and catalyst layer. - Abstract: In this paper, the preparation and characterization of porous polybenzimidazole membranes doped with phosphoric acid were reported. For the preparation of porous polybenzimidazole membranes, glucose and saccharose were selected as porogen and added into PBI resin solution before solvent casting. The prepared porous PBI membranes had high proton conductivity and high content of acid doping at room temperature with 15.7 mol H3PO4 per PBI repeat unit, much higher than pure PBI membrane at the same condition. Further, the performance and stability of the porous PBI membrane in high-temperature proton-exchange-membrane fuel cells was tested. It was found that the cell performance remained stable during 200 h stability test under a constant current discharge of 0.5 A cm−2 except for the last fifty hours. The decay in the last fifty hours was ascribed to the delamination between the catalyst layer and membrane increasing the charge-transfer resistance

  13. Development and characterization of acid-doped polybenzimidazole/sulfonated polysulfone blend polymer electrolytes for fuel cells

    Hasiotis, C.; Li, Qingfeng; Deimede, V.;

    2001-01-01

    Polymeric membranes from blends of sulfonated polysulfones (SPSF) and polybenzimidazole (PBI) doped with phosphoric acid were developed as potential high-temperature polymer electrolytes for fuel cells and other electrochemical applications. The water uptake and acid doping of these polymeric...... was found to be higher than 10/sup -2/ S cm/sup -1/. Much improvement in the mechanical strength is observed for the blend polymer membranes, especially at higher temperatures. Preliminary work has demonstrated the feasibility of these polymeric membranes for fuel-cell applications...... membranes were investigated. Ionic conductivity of the membranes was measured in relation to temperature, acid doping level, sulfonation degree of SPSF, relative humidity, and blend composition. The conductivity of SPSF was of the order of 10/sup -3/ S cm/sup -1/. In the case of blends of PBI and SPSF it...

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

    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.

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

    Celik Muhammet

    2016-01-01

    Full Text Available 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.

  16. Acid-doped Polybenzimidazole Membranes as Electrolyte for Fuel Cells Operating Above 100°C

    Qingfeng, Li; Jensen, Jens Oluf; He, Ronhuan; Gang, Xiao; Gao, Ji-An; Berg, Rolf W.; Hjuler, Hans Aage; Hennesø, Erik; Bjerrum, Niels

    high operational temperatures, the development and evaluation of acid doped PBI membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physiochemical characterization and fuel cell tests. A high temperature PEMFC system operational at up to 200°C is demonstrated with no gas...

  17. Proton conductivity of phosphoric acid doped polybenzimidazole and its composites with inorganic protontic conductors

    Li, Qingfeng

    2003-01-01

    contain inorganic protonic conductors including zirconium phosphate (ZrP), (Zr(HPO4)2. nH2O); phosphotungstic acid (PWA), (H3PW12O40. nH2O); and silicotungstic acid (SiWA), (H4SiW12O40 . nH2O). The conductivity of phosphoric acid doped PBI and PBI composite membranes was found to be dependent on the acid...

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

    Nores-Pondal, Federico J.; Corti, Horacio R. [Grupo de Pilas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Av. General Paz 1499, B1650KNA San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Buera, M. Pilar [Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Cantilo s/n, Ciudad Universitaria (1428) Buenos Aires (Argentina)

    2010-10-01

    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{sub 3}PO{sub 4}-H{sub 2}O 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. (author)

  19. Performance Degradation Tests of Phosphoric Acid Doped Polybenzimidazole Membrane Based High Temperature Polymer Electrolyte Membrane Fuel Cells

    Zhou, Fan; Araya, Samuel Simon; Grigoras, Ionela;

    2015-01-01

    Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation of the HT-PEM fuel cell. Continuous tests with pure dry H2 and meth......Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation of the HT-PEM fuel cell. Continuous tests with pure dry H2...

  20. Performance Degradation Tests of Phosphoric Acid Doped Polybenzimidazole Membrane Based High Temperature Polymer Electrolyte Membrane Fuel Cells

    Zhou, Fan; Araya, Samuel Simon; Grigoras, Ionela; Andreasen, Søren Juhl; Kær, Søren Knudsen

    2015-01-01

    Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation of the HT-PEM fuel cell. Continuous tests with pure dry H2 and...... performance during the H2 continuous tests, because of a decrease in the reaction kinetic resistance mainly in the cathode due to the redistribution of PA between the membrane and electrodes. The performance of both single cells decreased in the following tests, with highest performance decay rate in the...... corrosion of carbon support in the catalyst layer and degradation of the PBI membrane. During the continuous test with methanol containing H2 as the fuel the reaction kinetic resistance and mass transfer resistance of both single cells increased, which may be caused by the adsorption of methanol...

  1. Oxidative degradation of acid doped polybenzimidazole membranes and fuel cell durability in the presence of ferrous ions

    Liao, Jianhui; Yang, Jingshuai; Li, Qingfeng; Cleemann, Lars Nilausen; Jensen, Jens Oluf; Bjerrum, Niels J.; He, Ronghuan; Xing, Wei

    2013-01-01

    . In this study effects of phosphoric acid and ferrous ions were investigated by measurements of the weight loss, intrinsic viscosity and size exclusion chromatography (SEC) of the polymer membranes. Ferrous ions resulted in, as expected, catalytic formation of peroxide radicals and hence the...

  2. Cross-linked polybenzimidazole membranes for high temperature proton exchange membrane fuel cells with dichloromethyl phosphinic acid as a cross-linker

    Noye, Pernille; Li, Qingfeng; Pan, Chao; Bjerrum, Niels

    2008-01-01

    Phosphoric acid doped polybenzimidazole (PBI) membranes have been covalently cross-linked with dichloromethyl phosphinic acid (DCMP). FT-IR measurements showed new bands originating from bonds between the hydrogen bearing nitrogen in the imidazole group of PBI and the CH2 group in DCMP. The...

  3. Heterogeneous anion conducting membranes based on linear and crosslinked KOH doped polybenzimidazole for alkaline water electrolysis

    Aili, David; Hansen, Martin Kalmar; Renzaho, Richard Fulgence;

    2013-01-01

    Polybenzimidazole is a highly hygroscopic polymer that can be doped with aqueous KOH to give a material with high ion conductivity in the 10−2Scm−1 range, which in combination with its low gas permeability makes it an interesting electrolyte material for alkaline water electrolysis. In this study...... membranes based on linear and crosslinked polybenzimidazole were evaluated for this purpose. Extensive characterization with respect to spectroscopic and physicochemical properties during aging in 6molL−1 KOH at 85°C for up to 176 days indicated structural stability of the high molecular weight specialty...... polymer, however, with limitations with respect to hydrolytic stability. The gradual decay of the average molecular weight resulted in a severe deterioration of the mechanical properties over time. Membranes based on crosslinked polybenzimidazole showed better stability than the membranes based on their...

  4. Amino-Functional Polybenzimidazole Blends with Enhanced Phosphoric Acid Mediated Proton Conductivity as Fuel Cell Electrolytes

    Aili, David; Javakhishvili, Irakli; Han, Junyoung;

    2016-01-01

    the phosphoric acid uptake and to obtain mechanically robust membranes, the amino-functional polybenzimidazole derivative is blended with high molecular weight poly [2,2′-(m-phenylene)-5,5′-bisbenzimidazole] at different ratios. Due to the high acid uptake, the homogenous blend membranes show enhanced proton...

  5. Synthesis of proton conducting sulfonated and phosphonated polybenzimidazoles

    Ng, F.; Peron, J.; Salunke, A.; Jones, D.J.; Roziere, J. [Montpellier Univ., Montpellier (France). Lab. des Agregats Moleculaires et Materiaux Inorganiques

    2006-07-01

    A study was conducted in which a new flexible polybenzimidazoles (PBI) was synthesized with a proton conductivity higher than 10-3 S/cm at room temperature, in the absence of any unbound acid. Polybenzimidazoles are particularly robust polymers that are stable under various chemical and thermal environments. It is difficult to achieve direct sulfonation in solution of commercially available PBI, although alternative types of PBI with different solubility properties may be modified in this way. Reaction at high temperature of sulfuric acid-doped PBI membranes results in cross-linked and poorly conducting systems. Although acid-doped PBI membranes have high conductivity, acid loss occurs at temperature and load cycling in an operating fuel cell. Alternative approaches have been suggested, such as direct sulfonation and polycondensation reaction involving building blocks functionalized with protogenic groups that lead to new functionalized polybenzimidazoles with suitable properties for fuel cell application. The membrane microstructure can be modified by controlling the position, number and distribution of the sulfonic (phosphonic) acid groups along the backbone. This also affects membrane swelling and conductivity. This study also investigated the influence of the degree of protogenic group functionalization of polymer and membrane properties such as Tg, film forming properties, membrane water uptake and conductivity, and surface hydrophobic/philic properties. It was concluded that the polymer's conductivity depends on the ion exchange capacity and on the nature of the component diacids that give flexibility to the functionalized polybenzimidazole chains.

  6. A novel amperometric sensor for peracetic acid based on a polybenzimidazole-modified gold electrode

    Hua, Mu-Yi, E-mail: huamy@mail.cgu.edu.t [Green Research Center, Department of Chemical and Materials Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kuei-Shan, Tao-Yuan 33302, Taiwan (China); Biosensor Group, Biomedical Engineering Research Center, Chang Gung University, 259 Wen-Hwa 1st Rd., Kuei-Shan, Tao-Yuan 33302, Taiwan (China); Chen, Hsiao-Chien [Green Research Center, Department of Chemical and Materials Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kuei-Shan, Tao-Yuan 33302, Taiwan (China); Biosensor Group, Biomedical Engineering Research Center, Chang Gung University, 259 Wen-Hwa 1st Rd., Kuei-Shan, Tao-Yuan 33302, Taiwan (China); Tsai, Rung-Ywan [Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Rd., Hsinchu 31040, Taiwan (China); Lin, Yu-Chen [Green Research Center, Department of Chemical and Materials Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kuei-Shan, Tao-Yuan 33302, Taiwan (China); Biosensor Group, Biomedical Engineering Research Center, Chang Gung University, 259 Wen-Hwa 1st Rd., Kuei-Shan, Tao-Yuan 33302, Taiwan (China)

    2011-04-30

    We have developed a peracetic acid (PAA) sensor based on a polybenzimidazole-modified gold (PBI/Au) electrode. Fourier transform infrared and X-ray photoelectron spectroscopy indicated that PAA oxidized 69.4% of the imine in PBI to form PBI N-oxide, increasing the electrochemical reduction current during cyclic voltammetry. The chemical oxidation of the PBI/Au electrode by PAA, followed by its electrochemical reduction, allowed PAA to be detected directly and consecutively by assessing its reduction current. The PAA sensor had a broad linear detection range (3.1 {mu}M-1.5 mM) and a rapid response time (3.9 s) at an applied potential of -0.3 V. Potentially interfering substances, such as hydrogen peroxide, acetic acid, and oxygen, had no effect on the ability of the probe to detect PAA, indicating high selectivity of the probe. Furthermore, the detection range, response time, and sensitivity of the sensor could all be improved by modification of the smooth planar electrode surface to a porous three-dimensional configuration. When compared to the analytical characteristics of other PAA sensors operating under optimal conditions, the three-dimensional PBI/Au electrode offers a rapid detection time, a usable linear range, and a relatively low detection limit.

  7. Benzimidazole grafted polybenzimidazoles for proton exchange membrane fuel cells

    Yang, Jingshuai; Aili, David; Li, Qingfeng;

    2013-01-01

    High molecular weight polybenzimidazole (PBI) was synthesized and grafted with benzimidazole pendant groups. The high molecular weight of PBI resulted in good film-forming properties and superior tensile strength. With a phosphoric acid doping level (ADL) of 13.1, a tensile strength of 16 MPa was...... achieved at room temperature. Grafting of benzimidazole moieties onto the PBI macromolecular chain introduced additional basic sites which allowed the membrane to achieve higher phosphoric acid uptakes. A molar acid conductivity, defined as the specific conductivity of each mole of doping acid, was...

  8. Performance of a direct glycerol fuel cell using KOH doped polybenzimidazole as electrolyte

    Nascimento, Ana P.; Linares, Jose J., E-mail: joselinares@unb.br [Universidade de Brasilia (UnB), Brasilia, DF (Brazil). Instituto de Quimica

    2014-03-15

    This paper studies the influence of the operating variables (glycerol concentration, temperature and feed rate) for a direct glycerol fuel cell fed with glycerol using polybenzimidazole (PBI) impregnated with KOH as electrolyte and Pt/C as catalyst. Temperature displays a beneficial effect up to 75 °C due to the enhanced conductivity and kinetics of the electrochemical reactions. The optimum cell feed corresponds to 1 mol L{sup -1} glycerol and 4 mol L{sup -1} KOH, supplying sufficient quantities of fuel and electrolyte without massive crossover nor mass transfer limitations. The feed rate increases the performance up to a limit of 2 mL min{sup -1}, high enough to guarantee the access of the glycerol and the exit of the products. Finally, the use of binary catalysts (PtRu/C and Pt{sub 3}Sn/C) is beneficial for increasing the cell performance. (author)

  9. Crosslinked Hexafluoropropylidene Polybenzimidazole Membranes with Chloromethyl Polysulfone for Fuel Cell Applications

    Yang, Jingshuai; Li, Qingfeng; Cleemann, Lars Nilausen;

    2013-01-01

    Hexafluoropropylidene polybenzimidazole (F6PBI) was synthesized with excellent chemical stability and improved solubility. When doped with phosphoric acid, however, the F6PBI membranes showed plastic deformation at elevated temperatures. Further efforts were made to covalently crosslink F6PBI...... solutions, and improved mechanical strength, especially at elevated temperatures. The superior characteristics of crosslinked membranes allowed for higher acid doping levels and therefore increased proton conductivity as well as significantly improved fuel cell performance and durability, as compared...

  10. High Molecular Weight Polybenzimidazole Membranes for High Temperature PEMFC

    Yang, Jingshuai; Cleemann, Lars Nilausen; Steenberg, T.;

    2014-01-01

    Da with good solubility in organic solvents. Membranes fabricated from the polymers were systematically characterized in terms of oxidative stability, acid doping and swelling, conductivity, mechanical strength and fuel cell performance and durability. With increased molecular weights the polymer...... membranes showed enhanced chemical stability towards radical attacks under the Fenton test, reduced volume swelling upon the acid doping and improved mechanical strength at acid doping levels of as high as about 11 mol H3PO4 per molar repeat polymer unit. The PBI‐78kDa/10.8PA membrane, for example......High temperature operation of proton exchange membrane fuel cells under ambient pressure has been achieved by using phosphoric acid doped polybenzimidazole (PBI) membranes. To optimize the membrane and fuel cells, high performance polymers were synthesized of molecular weights from 30 to 94 k...

  11. High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

    Li, Qingfeng; Jensen, Jens Oluf; Savinell, Robert F; Bjerrum, Niels J.

    2009-01-01

    To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, acid–base polymer membranes represent an effective approach. The phosphoric acid-doped polybenzimidazole membrane seems so far the most successful system in the field. It has in recent years motivated extensive research activities with great progress. This treatise is devoted to updating the development, covering polymer synthesis, membrane casting, physicochemical characte...

  12. meta-PBI/methylated PBI-OO blend membranes for acid doped HT PEMFC

    Cho, Hyeongrae; Hur, Eun; Henkensmeier, Dirk; Jeong, Gisu; Cho, Eunae; Kim, Hyoung Juhn; Jang, Jong Hyun; Lee, Kwan Young; Hjuler, Hans Aage; Li, Qingfeng; Jensen, Jens Oluf; Cleemann, Lars Nilausen

    2014-01-01

    Methylation of polybenzimidazole leads to positively charged polymer backbones, and moveable anions. Ion exchange of methylated PBI-OO in phosphoric acid (PA) shows that the resulting polymers dissolve. meta-PBI, however, absorbs about 400wt% PA while remaining a self supported membrane. We inves...... the fuel cell, blend membranes show similar or better performance than meta-PBI. In the TGA, blends doped in 20% PA showed a stable plateau between 115 and 180°C, while meta-PBI lost weight continuously....

  13. High temperature proton exchange membranes based on polybenzimidazole and clay composites for fuel cells

    Plackett, David; Siu, Ana; Li, Qingfeng;

    2011-01-01

    , acid doping and swelling, tensile strength, conductivity and hydrogen permeability as well as by fuel cell tests. For the composite membranes, high acid doping levels were achieved with sufficient mechanical strength and improved dimensional stability or reduced membrane swelling. At an acid doping......dispersion of modified laponite clay was achieved in polybenzimidazole (PBI) solutions which, when cast and allowed to dry, resulted in homogeneous and transparent composite membranes containing up to 20 wt% clay in the polymer. The clay was organically modified using a series of ammonium and...... pyridinium salts with varying polarity and hydrogen-bonding capacity. Clay modification by ion-exchange reactions involving replacement of interlayer inorganic cations was confirmed using X-ray photoelectron and infrared spectroscopy techniques. The cast PBI membranes were characterized by their water uptake...

  14. Developments of new proton conducting membranes based on different polybenzimidazole structures for fuel cells applications

    Carollo, A.; Quartarone, E.; Tomasi, C.; Mustarelli, P.; Belotti, F.; Magistris, A. [Department of Physical Chemistry, IENI-CNR and INSTM, University of Pavia Via Taramelli 16, 27100 Pavia (Italy); Maestroni, F.; Parachini, M.; Garlaschelli, L.; Righetti, P.P. [Department of Organic Chemistry, University of Pavia Via Taramelli 12, 27100 Pavia (Italy)

    2006-09-29

    The current goal on PEMFCs research points towards the optimization of devices working at temperatures above 100{sup o}C and at low humidity levels. Acid-doped polybenzimidazoles are particularly appealing because of high proton conductivity without humidification and promising fuel cells performances. In this paper we present the development of new proton conducting membranes based on different polybenzimidazole (PBI) structures. Phosphoric acid-doped membranes, synthesized from benzimidazole-based monomers with increased basicity and molecular weight, are presented and discussed. Test of methanol crossover and diffusion were performed in order to check the membrane suitability for DMFCs. Both the acid doping level and proton conductivity remarkably increase with the membrane molecular weight and basicity, which strictly depend on the amount of NH-groups as well as on their position in the polymer backbone. In particular, a conductivity value exceeding 0.1Scm{sup -1} at RH=40% and 80{sup o}C was reached in the case of the pyridine-based PBI. (author)

  15. Phosphoric acid doped membranes based on Nafion®, PBI and their blends – Membrane preparation, characterization and steam electrolysis testing

    Aili, David; Hansen, Martin Kalmar; Pan, Chao;

    2011-01-01

    ® and polybenzimidazole blend membranes was developed. Homogeneous binary membranes covering the whole composition range were prepared and characterized with respect to chemical and physiochemical properties such as water uptake, phosphoric acid doping, oxidative stability, mechanical strength and proton conductivity....... An MEA based on phosphoric acid doped Nafion® was operated at 130 °C at ambient pressure with a current density of 300 mA cm−2 at 1.75 V, with no membrane degradation observed during a test of 90 h. The PBI based MEAs showed better polarization curves (500 mA cm−2 at 1.75 V) but poor durability....

  16. Ionic conducting poly-benzimidazoles; Polybenzimidazoles conducteurs ioniques

    Jouanneau, J

    2006-11-15

    Over the last years, many research works have been focused on new clean energy systems. Hydrogen fuel cell seems to be the most promising one. However, the large scale development of this technology is still limited by some key elements. One of them is the polymer electrolyte membrane 'Nafion' currently used, for which the ratio performance/cost is too low. The investigations we carried out during this thesis work are related to a new class of ionic conducting polymer, the sulfonated poly-benzimidazoles (sPBI). Poly-benzimidazoles (PBI) are aromatic heterocyclic polymers well-known for their excellent thermal and chemical stability. Ionic conduction properties are obtained by having strong acid groups (sulfonic acid SO{sub 3}H) on the macromolecular structure. For that purpose, we first synthesized sulfonated monomers. Their poly-condensation with an appropriate non-sulfonated co-monomer yields to sPBI with sulfonation range from 0 to 100 per cent. Three different sPBI structures were obtained, and verified by appropriate analytical techniques. We also showed that the protocol used for the synthesis resulted in high molecular weights polymers. We prepared ionic conducting membrane by casting sPBI solutions on glass plates. Their properties of stability, water swelling and ionic conductivity were investigated. Surprisingly, the behaviour of sPBI was quite different from the other sulfonated aromatic polymers with same amount of SO{sub 3}H, their stability was much higher, but their water swelling and ionic conductivity were quite low. We attributed these differences to strong ionic interactions between the sulfonic acid groups and the basic benzimidazole groups of our polymers. However, we managed to solve this problem synthesizing very highly sulfonated PBI, obtaining membranes with a good balance between all the properties necessary. (author)

  17. Ionic conducting poly-benzimidazoles

    Over the last years, many research works have been focused on new clean energy systems. Hydrogen fuel cell seems to be the most promising one. However, the large scale development of this technology is still limited by some key elements. One of them is the polymer electrolyte membrane 'Nafion' currently used, for which the ratio performance/cost is too low. The investigations we carried out during this thesis work are related to a new class of ionic conducting polymer, the sulfonated poly-benzimidazoles (sPBI). Poly-benzimidazoles (PBI) are aromatic heterocyclic polymers well-known for their excellent thermal and chemical stability. Ionic conduction properties are obtained by having strong acid groups (sulfonic acid SO3H) on the macromolecular structure. For that purpose, we first synthesized sulfonated monomers. Their poly-condensation with an appropriate non-sulfonated co-monomer yields to sPBI with sulfonation range from 0 to 100 per cent. Three different sPBI structures were obtained, and verified by appropriate analytical techniques. We also showed that the protocol used for the synthesis resulted in high molecular weights polymers. We prepared ionic conducting membrane by casting sPBI solutions on glass plates. Their properties of stability, water swelling and ionic conductivity were investigated. Surprisingly, the behaviour of sPBI was quite different from the other sulfonated aromatic polymers with same amount of SO3H, their stability was much higher, but their water swelling and ionic conductivity were quite low. We attributed these differences to strong ionic interactions between the sulfonic acid groups and the basic benzimidazole groups of our polymers. However, we managed to solve this problem synthesizing very highly sulfonated PBI, obtaining membranes with a good balance between all the properties necessary. (author)

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

    Perry, Kelly A [ORNL; More, Karren Leslie [ORNL; Payzant, E Andrew [ORNL; Meisner, Roberta A [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Sumpter, Bobby G [ORNL; Benicewicz, Brian [ORNL

    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.

  19. An H3PO4-doped polybenzimidazole/Sn0.95Al0.05P2O7 composite membrane for high-temperature proton exchange membrane fuel cells

    Jin, Y. C.; Nishida, M.; Kanematsu, W.; Hibino, T.

    2011-08-01

    A polybenzimidazole (PBI)/Sn0.95Al0.05P2O7 (SAPO) composite membrane was synthesized by an in situ reaction of SnO2 and Al(OH)3-mixed powders with an H3PO4 solution in a PBI membrane. The formation of a single phase of SAPO in the PBI membrane was completed at a temperature of 250 °C. Thermogravimetric analysis showed that the PBI membrane was not subject to a serious damage by the presence of SAPO until 500 °C. Scanning electron microscopy revealed that SAPO particles with a diameter of approximately 300 nm were homogeneously dispersed and separated from each other in the PBI matrix. Proton magic angle spinning nuclear magnetic resonance spectra confirmed the presence of new protons originating from the SAPO particles in the composite membrane. As a consequence of the interaction of protons in the SAPO with those in the free H3PO4, the H3PO4-doped PBI/SAPO composite membrane exhibited conductivities several times higher than those of an H3PO4-doped PBI membrane at room temperature to 300 °C, which could contribute to the improved performance of H2/O2 fuel cells.

  20. Synthesis and characterization of pyridine-based polybenzimidazoles for high temperature polymer electrolyte membrane fuel cell applications

    Xiao, L.; Zhang, H.; Jana, T.; Scanlon, E.; Chen, R.; Choe, E.W.; Ramanathan, L.S.; Yu, S.; Benicewicz, B.C. [NYS Center for Polymer Synthesis, Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

    2005-04-01

    A series of polybenzimidazoles (PBIs) incorporating main chain pyridine groups were synthesized from the pyridine dicarboxylic acids (2,4-, 2,5-, 2,6- and 3,5-) and 3,3',4,4'-tetraaminobiphenyl, using polyphosphoric acid (PPA) as both solvent and polycondensation reagent. 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 state to a gel-like state and produced PA-doped PBI membranes with a desirable suite of physiochemical properties. The polymer structure characterization included inherent viscosity (I.V.) determination as a measurement of polymer molecular weight and thermal stability assessment via thermogravimetric analysis. Physiochemical properties of the doped membrane were studied by measurements of the PA doping level, ionic conductivity and mechanical properties. The resulting pyridine-based polybenzimidazole membranes displayed high PA doping levels, ranging from 15 to 25 mol of PA per PBI repeat unit, which contributed to their unprecedented high proton conductivities of 0.1 to 0.2 S cm{sup -1} at 160 C. The mechanical property measurements showed that the pyridine-based PBI membranes were thermally stable and maintained mechanical integrity even at high PA doping levels. Preliminary fuel cell tests demonstrated the feasibility of the novel pyridine-based PBI (PPBI) membranes from the PPA process for operating fuel cells at temperatures in excess of 120 C without any external humidification. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  1. Durability of symmetrically and asymmetrically porous polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

    Jheng, Li-Cheng; Chang, Wesley Jen-Yang; Hsu, Steve Lien-Chung; Cheng, Po-Yang

    2016-08-01

    Two types of porous polybenzimidazole (PBI) membranes with symmetric and asymmetric morphologies were fabricated by the template-leaching method and characterized by scanning electron microscope (SEM). Their physicochemical properties were compared in terms of acid-doping level, proton conductivity, mechanical strength, and oxidative stability. The durability of fuel cell operation is one of the most challenging for the PBI based membrane electrode assembly (MEA) used in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). In the present work, we carried out a long-term steady-state fuel cell test to compare the effect of membrane structure on the cell voltage degradation. It has also been demonstrated that the asymmetrically porous PBI could bring some notable improvements on the durability of fuel cell operation, the fuel crossover problem, and the phosphoric acid leakage.

  2. Precursor polymer compositions comprising polybenzimidazole

    Klaehn, John R.; Peterson, Eric S.; Orme, Christopher J.

    2015-07-14

    Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

  3. Sythesis and investigation of m-carborane-containing polybenzimidazoles

    New m-carborane-containing polybenzimidazoles (PBI) have been obtained by chemical cyclization of m-carborane-containing polyaminoamides (PAA) with the N-methyl-2-pyrrolidone-sulphuric anhydride complex or polyphosphoric acid esters being used as the cyclodehydrating reagents. The obtained m-carborane-containing PAA and PBI have been tested for solubility, heat resistance and chemical stability. The structure of m-carborane-containing PBI has been determined by abalysis of their infrared spectra

  4. Synthesis and properties of random copolymers of functionalised polybenzimidazoles for high temperature fuel cells

    Mader, J.A.; Benicewicz, B.C. [Department of Chemistry and Biochemistry and USC Nanocenter, University of South Carolina, 631 Sumter St., Columbia, SC 29208 (United States)

    2011-04-15

    A series of polybenzimidazoles (PBIs) incorporating main chain sulphonic acid groups were synthesised as random copolymers with p-PBI in varying ratios using polyphosphoric acid (PPA) as both the polymerisation solvent and polycondensation reagent. The PPA process was used to produce high molecular weight phosphoric acid (PA) doped PBI gel membranes in a one-step procedure. These membranes exhibit excellent mechanical properties (0.528-2.51 MPa tensile stress and 130-300% tensile strain) even at high acid doping levels [20-40 mol PA/PRU (polymer repeat unit)] and high conductivities (0.148-0.291 S cm{sup -1}) at elevated temperatures (>100 C) with no external humidification, depending on copolymer composition. Fuel cell testing was conducted with hydrogen fuel and air or oxygen oxidants for all membrane compositions at temperatures greater than 100 C without external feed gas humidification. Initial studies showed a maximum fuel performance of 0.675 V for the 25 mol% s-PBI/75 mol% p-PBI random copolymer at 180 C and 0.2 A cm{sup -2} with hydrogen and air, and 0.747 V for the same copolymer at 180 C and 0.2 A cm{sup -2} with hydrogen and oxygen. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Soluble N-Substituted Organosilane Polybenzimidazoles

    Klaehn, J. R.; Luther, T. A.; Orme, C. J.; Jones, M. G.; Wertsching, A. K.; Peterson, E. S.

    2007-10-01

    Six organosilane derivatives were synthesized, and are more soluble in common organic solvents (tetrahydrofuran and chloroform) than the parent polybenzimidazole. Our polymer modification pathway provides a straightforward synthesis that can be carried out at room temperature and give reasonable yields. Solution 1H NMR spectra of both the parent and deprotonated polybenzimidazoles are reported. Based upon the NMR analysis in CDCl3, nearly all of the benzimidazole N-H positions are substituted by the organosilane moieties. Some of the modified polymers have similar thermal properties compared to the parent polymer, and the average molecular weights are higher for the substituted polybenzimidazoles than the parent PBI.

  6. Oxidative degradation of polybenzimidazole membranes as electrolytes for high temperature proton exchange membrane fuel cells

    Liao, J.H.; Li, Qingfeng; Rudbeck, H.C.;

    2011-01-01

    Polybenzimidazole membranes imbibed with acid are emerging as a suitable electrolyte material for high-temperature polymer electrolyte fuel cells. The oxidative stability of polybenzimidazole has been identified as an important issue for the long-term durability of such cells. In this paper the...... oxidative degradation of the polymer membrane was studied under the Fenton test conditions by the weight loss, intrinsic viscosity, size exclusion chromatography, scanning electron microscopy and Fourier transform infrared spectroscopy. During the Fenton test, significant weight losses depending on the...

  7. Polybenzimidazoles Via Aromatic Nucleophilic Displacement

    Connell, John W. (Inventor); Hergerrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1997-01-01

    Novel molecular weight controlled and endcapped polybenzimidazoles (PBI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenylbenzimidazole) monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The PBI are endcapped with mono(hydroxyphenyl)benzimidazoles. The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. Mono(hydroxyphenyl)benzimidazoles are synthesized by reacting phenyl-4-hydroxybenzoate with aromatic (o-diamine)s in diphenylsulfone. Molecular weight controlled and endcapped PBI of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.

  8. Evaluation of polybenzimidazole glass-fabric laminates

    Mackay, H.A.

    1966-01-01

    Laminates prepared from polybenzimidazole and 1581-994S glass fabric have excellent short-time heat resistance to 800 deg F., and 100-hr. thermal stability at 600 deg F. These characteristics are based on mechanical-property strength retention and low resin weight loss. In spite of high cost and processing difficulties, polybenzimidazoles are being applied as laminates and adhesives for nose fairing, thermal insulation, aircraft leading edge, reentry nose cones, radomes, de-icer ducts, and in other areas where high temperature resistance is needed.

  9. Preparation of aromatic polyamidines and their transformation in polybenzimidazoles

    B. Ch. Kholkhoev

    2014-09-01

    Full Text Available Polymers with amidine groups –NH–C(=NH– in main chain were synthesized by two different approaches. The first strategy consists in polyaddition of dinitriles and diamines in acidic ionic liquids (ILs which act as catalyst and solvent, while the second approach is based on polycondensation of 4,4'-oxybis(benzoic acid diamide and diamines in Eaton’s reagent (ER. The resulting polyamidines (PADs with Mw up to 25 000 g/mol possess thermal stability on air up to 288°C, and good solubility in polar organic solvents. Moreover dehydrocyclization of obtained PADs into polybenzimidazoles (PBIs under the action of various oxidants was also studied in this work. The crosslinked films based on PBI and poly(amino imide resin (PAIR possess high mechanical characteristics. It has been proved that the crosslinked films based on PBI matrix are perspective materials for design the phosphoric acid electrolyte membranes for the medium temperature fuel cells.

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

    Boyne, Devon; Menegazzo, Nicola; Pupillo, Rachel C.; Rosenthal, Joel; Booksh, Karl S., E-mail: kbooksh@udel.edu [Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States)

    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.

  11. Fuel cell characteristics of the membrane electrode assemblies using phosphoric acid-doped poly membranes

    Fang, Liang; Sheng, Li; Guo, Xiaoxia; Fang, Jianhua; Ma, Zi-Feng

    2011-01-15

    Recently, there has been extensive research in the development of polymer electrolyte membrane fuel cells (PEMFCs) for transportation and portable power applications. Nafion has been widely used as electrolyte membranes, but it has several limitations. Thus intensive efforts have been devoted to the development of low-cost proton-conducting electrolytes used at elevated temperatures to reduce the impurities poisoning. Promising candidates are the PA-doped polybenzimidazoles, which can function at higher temperature under non-humidification conditions to eliminate the water management, promote the fuel impurities tolerance, increase the electrode kinetics and facilitate the heat recovery. In this study, the novel PA-doped OPBI membrane was chosen as the electrolyte, and one molecular weight mPBI was synthesized as the binder in catalyst layers. This optimized membrane electrode assemblies (MEAs) exhibited desirable performances in the electrochemical tests up to 160 degree C. This investigation opened up a new way to develop the practical proton-conducting fuel cell systems working at elevated temperatures.

  12. The Electrochemical Behavior of Phosphoric-Acid-Doped Poly(perfluorosulfonic Acid) Membranes

    Aili, David; Savinell, Robert F; Jensen, Jens Oluf;

    2014-01-01

    Highly conductive phosphoric-acid-doped poly(perfluorosulfonic acid) membranes have long been known to malfunction in fuel cells. This is investigated and found to be due to failure of the anode, in which a limiting current is observed in the very low current-density range. It is proposed...... that the strongly acidic sulfonic acid groups protonate the phosphoric acid under anhydrous conditions, forming excess proton defects that are involved in proton conduction by means of the vehicle mechanism. The slow back-diffusion of phosphoric acid molecules as proton carriers thus limits the long...

  13. Performance Evaluation of Polybenzimidazole for Potential Aerospace Applications

    Iqbal, H.M.S.

    2014-01-01

    With the increasing use of polymer based composite materials, there is an increasing demand of polymeric resins with high glass transition temperature, high thermal stability and excellent mechanical properties at high temperature. Polybenzimidazole (PBI) is a recently emerged high performance polymer. It has the highest glass transition temperature of any commercially available organic polymer, high decomposition temperature, good oxidation resistance and it maintains excellent strength at c...

  14. Hydroxyl pyridine containing polybenzimidazole membranes for proton exchange membrane fuel cells

    Yang, Jingshuai; Xu, Yixin; Zhou, Lu;

    2013-01-01

    , but also benefited the proton conduction, which was proved by the results of acid conductivities of the membranes with comparable acid doping levels. At an acid doping level of 8.6, i.e. 8.6mol acids per molar repeat unit of the polymer, the OHPyPBI membrane exhibited a proton conductivity of 0.102Scm...

  15. Quartz crystal microbalance and spectroscopy measurements for acid doping in polyaniline films

    Mohamad M Ayad and Eman A Zaki

    2008-01-01

    Full Text Available We investigated the doping of thin polyaniline (PANI films, prepared by the chemical oxidation of aniline, with different acids. The initial step in the investigation is the preparation of PANI films from aqueous hydrochloric acid solution. This is followed by dedoping with ammonia to obtain a PANI base, which is subsequently doped with strong acids (e.g. hydrochloric, sulfuric, phosphoric and trichloroacetic acids and with a weak acid (acetic acid. The dopant weight fraction (w, which is connected with the gain of mass during the doping of PANI, was determined in situ using a quartz crystal microbalance (QCM. The behavior of PANI upon doping with different anions derived from strong acids indicates that both proton and the anion uptake into the polymer chains occur sharply, rapidly, completely, and reversibly. However the uptake in the case in acetic acid is characterized by slow diffusion. The doping was studied at different concentrations of acetic acid. A second cycle of dedoping–redoping was also performed. The kinetics of the doping reaction is dominated by Fickian diffusion kinetics. The diffusion coefficients (D of the dopant ions into the PANI chains were determined using the QCM and by UV–Vis absorption spectroscopy in the range of (0.076–1.64× 10−15 cm2 s−1. It was found that D in the second cycle of doping is larger than that evaluated from the first cycle of doping for high concentrations of acetic acid. D for the diffusion and for the dopant ion expulsion from the PANI chains was also determined during the redoping process. It was found that D for acetic acid ions in the doping process is larger than that calculated for the dedoping process.

  16. Phosphoric acid doped AB-PBI membranes and its applications in high temperature PEMFC

    He, Ronghuan; Qingfeng, Li; Bjerrum, Niels

    2005-01-01

    Poly(2,5-benzimidazole) (ab-PBI) was prepared from 3,4-diaminobenzoic acid via a polymerisation reaction. The obtained polymer exhibits excellent thermal stability in a temperature range ….. The membrane of ab-PBI when doped with phosphoric acid at room temperaturepresents high proton conductivity......C with phosphoric acid doped ab-PBI as the electrolyte under atmospheric pressure at 200°C without humidification....

  17. Highly efficient sulfonated polybenzimidazole as a proton exchange membrane for microbial fuel cells

    Singha, Shuvra; Jana, Tushar; Modestra, J. Annie; Naresh Kumar, A.; Mohan, S. Venkata

    2016-06-01

    Although microbial fuel cells (MFCs) represent a promising bio-energy technology with a dual advantage (i.e., electricity production and waste-water treatment), their low power densities and high installation costs are major impediments. To address these bottlenecks and replace highly expensive Nafion, which is a proton exchange membrane (PEM), the current study focuses for the first time on membranes made from an easily synthesizable and more economical oxy-polybenzimidazole (OPBI) and its sulfonated analogue (S-OPBI) as alternate PEMs in single-chambered MFCs. The S-OPBI membrane exhibits better properties, with high water uptake, ion exchange capacity (IEC) and proton conductivity and a comparatively smaller degree of swelling compared to Nafion. The membrane morphology is characterized by atomic force microscopy, and the bright and dark regions of the S-OPBI membrane reveals the formation of ionic domains in the matrix, forming continuous water nanochannels when doped with water. These water-filled nanochannels are responsible for faster proton conduction in S-OPBI than in Nafion; therefore, the power output in the MFC with S-OPBI as the PEM is higher than in other MFCs. The open circuit voltage (460 mV), current generation (2.27 mA) and power density profile (110 mW/m2) as a function of time, as well as the polarization curves, exhibits higher current and power density (87.8 mW/m2) with S-OPBI compared to Nafion as the PEM.

  18. Porous poly(benzimidazole) membrane for all vanadium redox flow battery

    Luo, Tao; David, Oana; Gendel, Youri; Wessling, Matthias

    2016-04-01

    Porous poly(benzimidazole) (PBI) membranes of low vanadium ions permeability are described for an all vanadium redox flow battery (VRFB). The PBI membrane was prepared by a water vapour induced phase inversion process of a PBI polymer solution. The membrane has a symmetrical cross-sectional morphology. A low water permeability of 16.5 L (m2 h bar)-1 indicates the high hydraulic resistance stemming from a closed cell morphology with nanoporous characteristics. The PBI membrane doped with 2.5 M H2SO4 shows a proton conductivity of 16.6 mS cm-1 and VO2+ permeability as low as 4.5 × 10-8 cm2 min-1. The stability test of dense PBI membrane in VO2+ solution indicates good chemical stability. An all vanadium redox flow battery (VRFB) operated with the porous PBI membrane shows 98% coulombic efficiency and more than 10% higher energy efficiency compared to VRFB operated with Nafion 112 at applied current densities of 20-40 mA cm-2. High in situ stability of the porous PBI membrane was confirmed by about 50 cycles of continuous charge and discharge operation of the battery.

  19. Phosphoric acid doped imidazolium polysulfone membranes for high temperature proton exchange membrane fuel cells

    Yang, Jingshuai; Li, Qingfeng; Jensen, Jens Oluf;

    2012-01-01

    A novel acid–base polymer membrane is prepared by doping of imidazolium polysulfone with phosphoric acid for high temperature proton exchange membrane fuel cells. Polysulfone is first chloromethylated, followed by functionalization of the chloromethylated polysulfone with alkyl imidazoles i.......e. methyl (MePSU), ethyl (EtPSU) and butyl (BuPSU) imidazoliums, as revealed by 1H NMR spectra. The imidazolium polysulfone membranes are then doped with phosphoric acid and used as a proton exchange membrane electrolyte in fuel cells. An acid doping level of about 10–11mol H3PO4 per mole of the imidazolium...

  20. On the existence of ethylenediaminetetraacetic acid (EDTA) doped zinc sulphate heptahydrate crystal

    Srinivasan, Bikshandarkoil R.

    2015-01-01

    It is argued that the ethylenediaminetetraacetic acid (EDTA) doped zinc sulphate heptahydrate crystal reported by Raja et al Spectrochim Acta 99A (2012) 23 is the well known zinc sulphate heptahydrate.

  1. Growth and characterization studies of pure and tartaric acid doped benzilic acid crystals

    Gilda, M. J. Jarald Brigit; Devarajan, Prem Anand

    2016-04-01

    The organic nonlinear optical crystals of pure benzilic acid (PBA) and tartaric acid doped benzilic acid (TADBA) single crystals were grown by using slow evaporation method utilizing dimethyl formamide (DMF) as a solvent. Transparent single crystals of PBA and TADBA of dimensions 9×4×1 mm3 and 7×5×2 mm3 were grown after thirty days. Lattice parameters and space groups of PBA and TADBA were evaluated using single crystal X-ray diffraction analysis. Employing Fourier transform infrared spectral analysis, various functional groups in pure and doped crystals were ascertained. 1H and C13 nuclear magnetic resonance spectral analysis suggests the presence of hydrogen- and carbon-bonded network. Optical transparency of PBA and TADBA was investigated using ultraviolet-visible (UV-vis) spectral analysis whereas thermal properties of the grown crystals were studied by thermogravimetric and differential scanning calorimetry analyses. Second harmonic generation efficiency of PBA and TADBA was found to be 2.2 and 2.7 times higher than that of potassium dihydrogen phosphate.

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

    Syed Draman, Sarifah Fauziah; Daik, Rusli [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); El-Sheikh, Said M. [Nanostructured Materials and Nanotechnology Division, Central Metallurgical Research and Development Institute,11421 Cairo (Egypt); Latif, Famiza Abdul [Faculty of Applied Sciences, Universiti Teknologi MARA Malaysia 40450 Shah Alam, Selangor (Malaysia)

    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.

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

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

    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 TANIPAN...

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

    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.

  5. Studies on biphenyl disulphonic acid doped polyanilines: Synthesis, characterization and electrochemistry

    Chepuri R K Rao; R Muthukannan; M Vijayan

    2012-06-01

    In this article, we report on the results obtained for the efforts we made to bring processability to the conducting polyaniline and substituted polyanilines by designing and synthesizing a new disulphonic acid with a biphenyl moiety as spacer group, viz. 4,4'-biphenyldisulphonic acid (BPSA). When doped, the disulphonic acid acts as a spacer group between the polyaniline chains and facilitates increase in solubility and conductivity. The spacing effect is maximized when BPSA is used as doping agent in in situ polymerization reactions. The conductivity of polyaniline doped by BPSA is 4 S/cm and for the substituted polyanilines it ranged from 2 × 10-5 to 8 × 10-4 S/cm.

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

    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.

  7. Sterically Stabilized Poly(3,4-ethylenedioxythiophene) Colloidal Dispersions Doped with Different Sulfonic Acids

    Tie Jun WANG; Ping CHEN; Xiu Jie HU; Shu Yun ZHOU

    2006-01-01

    The preparation of sterically stabilized poly(3, 4-ethylenedioxythiophene)(PEDOT)colloidal dispersions doped with different sulfonic acids is described. Three different sulfonic acids, i.e., p-toluenesulfonic acid, β-naphthalenesuffonic acid and D-camphor-10-sulfonic acid are used, facilitating the preparation of sterically stable PEDOT colloidal particles. The influences of the dopants and concentration of polymeric stabilizer on the yields, morphologies and electrical properties of the resultant colloidal particles were investigated. The colloidal particles with the size ranging from 172 to 334 nm have been obtained in good yields. The compressed pellet conductivity was as high as 4.5 Scm-1.

  8. Performance Degradation Tests of Phosphoric Acid Doped PBI Membrane Based High Temperature PEM Fuel Cells

    Zhou, Fan; Araya, Samuel Simon; Grigoras, Ionela;

    2014-01-01

    Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation. Continuous tests with H2 and simulated reformate which was composed...

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

    Fuentes-Perujo, D.; Santamaría-González, J.; Mérida-Robles, J.; Rodríguez-Castellón, E.; Jiménez-López, A.; Maireles-Torres, P.; Moreno-Tost, R.; Mariscal, R.

    2006-07-01

    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 2 adsorption at 77 K. Their acid properties have been evaluated by NH 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.

  10. New Polymer Electrolyte Membranes Based on Acid Doped PBI For Fuel Cells Operating above 100°C

    Li, Qingfeng

    The technical achievement and challenges for the PEMFC technology based on perfluorosulfonic acid (PFSA) polymer membranes (e.g. Nafion®) are briefly discussed. The newest development for alternative polymer electrolytes for operation above 100°C. As one of the successful approaches to high...... operational temperatures, the development and evaluation of acid doped PBI membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physiochemical characterization and fuel cell tests....

  11. UV assisted photoelectrocatalytic oxidation of phthalic acid using spray deposited Al doped zinc oxide thin films

    Mahadik, M.A.; Shinde, S.S.; Hunge, Y.M.; Mohite, V.S.; Kumbhar, S.S.; Moholkar, A.V.; Rajpure, K.Y.; Bhosale, C.H., E-mail: chbhosale@gmail.com

    2014-10-25

    Highlights: • Nanostructured undoped and AZO thin films prepared by chemical spray pyrolysis. • Effect of Al doping on the structural, morphological and photoluminance properties. • Photocatalytic degradation of phthalic acid under UV light illumination. • Reaction kinetics and mineralization of phthalic acid. - Abstract: Undoped and Al doped ZnO (AZO) thin films are successfully prepared by spray pyrolysis technique at optimised substrate temperature of 400 °C onto amorphous and F:SnO{sub 2} coated glass substrates. Effect of Al doping on structural, morphological and optical properties of ZnO thin films is studied. Deposited films are polycrystalline with a hexagonal (wurtzite) crystal structure having (0 0 2) preferred orientation. The PEC characterization shows that, short circuit current (I{sub sc}) and open circuit voltage (V{sub oc}) are (I{sub sc} = 0.38 mA and V{sub oc} = 421 mV) relatively higher at the 3 at.% Al doping. SEM images show deposited thin films are compact and uniform with seed like grains. All films exhibit average transmittance of about 82% in the visible region and a sharp absorption onset at 375 nm corresponding to 3.3 eV. The photocatalytic activities of the large surface area (64 cm{sup 2}) Al-doped ZnO photocatalyst samples were evaluated by photoelectrocatalytic degradation of phthalic acid under UV light irradiation. The results show that the 3 at.% AZO thin film photocatalyst exhibited degradation of phthalic acid up to about 45% within 3 h with significant reduction in COD and TOC values.

  12. The Research on the Stability of TiO2,MoO3,PEO Doped Four-member Tungstic Acid Sols

    Kai RAO; Xiang Kai FU; Xiao Ping RAO

    2004-01-01

    The TiO2, MoO3, PEO doped four-member tungstic acid sols were prepared for the first time.The stability of different doped content sols were investigated and optimized with rotational viscometer.The four-member doped tungstic acid sol was very stable which could be stored more than two months at room temperature.The WO3 electrochromic film prepared from this doped four- member tungstic acid sol had excellent performance and longevity of service.

  13. Sonocatalytic degradation of Acid Blue 92 using sonochemically prepared samarium doped zinc oxide nanostructures.

    Khataee, Alireza; Saadi, Shabnam; Vahid, Behrouz; Joo, Sang Woo; Min, Bong-Ki

    2016-03-01

    Pure and Sm-doped ZnO nanoparticles were synthesized applying a simple sonochemical method. The nanocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques which confirmed the successful synthesis of the doped sonocatalyst. The sonocatalytic degradation of Acid Blue 92 (AB92), a model azo dye, was more than that with sonolysis alone. The 6% Sm-doped ZnO nanoparticles had a band gap of 2.8 eV and demonstrated the highest activity. The degradation efficiency (DE%) of sonolysis and sonocatalysis with undoped ZnO and 6% Sm-doped ZnO was 45.73%, 63.9%, and 90.10%, after 150 min of treatment, respectively. Sonocatalytic degradation of AB92 is enhanced with increasing the dopant amount and catalyst dosage and with decreasing the initial AB29 concentration. DE% declines with the addition of radical scavengers such as chloride, carbonate, sulfate, and tert-butanol. However, the addition of enhancers including potassium periodates, peroxydisulfate, and hydrogen peroxide improves DE% by producing more free radicals. The results show adequate reusability of the doped sonocatalyst. Degradation intermediates were recognized by gas chromatography-mass spectrometry (GC-MS). Using nonlinear regression analysis, an empirical kinetic model was developed to estimate the pseudo-first-order constants (kapp) as a function of the main operational parameters, including the initial dye concentration, sonocatalyst dosage, and ultrasonic power. PMID:26584981

  14. 3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

    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.

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

    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.

  16. PHOTO-INDUCED DOPED POLYANILINE BY THE VINYLIDENE CHLORIDE AND METHYL ACRYLATE COPOLYMER AS PHOTO ACID GENERATOR

    LI Suzhen; WAN Meixiang

    1997-01-01

    The emeraldine base form of polyaniline (PANI) can be doped by a photo-induced doping method. In this method a copolymer of vinylidene chloride and methyl acrylate (VCMAC) was used as photo acid generator which can release proton when it is exposed to ultraviolet light (λ = 254 nm). The structure of PANI-VCMAC system before and after irradiation was characterized by elemental analysis, IR, XPS, and SEM images. Results obtained indicate that the photo-induced doping characteristics, such as doping position and type of charge carriers, are similar to that of PANI doped with HCl. The poor roomtemperature conductivity (~ 10-5S/cm) of PANI-VCMAC system after irradiation may be due to low doping degree (~pH= 3) and the difference in morphology as compared with PANI-HCl film.

  17. Carbon doping of MgB{sub 2} by toluene and malic-acid-in-toluene

    Bohnenstiehl, S.D., E-mail: bohnenstiehl.1@osu.ed [Center for Superconducting and Magnetic Materials, Department of Materials Science and Engineering, Ohio State University, Columbus, OH (United States); Susner, M.A.; Yang, Y.; Collings, E.W.; Sumption, M.D. [Center for Superconducting and Magnetic Materials, Department of Materials Science and Engineering, Ohio State University, Columbus, OH (United States); Rindfleisch, M.A.; Boone, R. [Hyper Tech Research, Inc., 539 Industrial Mile Road, Columbus, OH 43228 (United States)

    2011-02-15

    Research highlights: {yields} Both toluene and malic acid contribute carbon to MgB{sub 2}. {yields} Toluene is more effective than malic acid for transport properties. {yields} Total carbon can be measured by LECO carbon analysis. - Abstract: The decomposition of malic acid (C{sub 4}H{sub 6}O{sub 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{sub 7}H{sub 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 {approx}0.4 wt.% C while the toluene/malic acid mixture had {approx}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{sub 2} monofilamentary wires established that the toluene/malic acid doped sample had the highest B{sub c2}. However, the toluene-only sample had the highest transport J{sub 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.

  18. Structure and properties of polybenzimidazole/silica nanocomposite electrolyte membrane: influence of organic/inorganic interface.

    Singha, Shuvra; Jana, Tushar

    2014-12-10

    Although increased number of reports in recent years on proton exchange membrane (PEM) developed from nanocomposites of polybenzimidazole (PBI) with inorganic fillers brought hope to end the saga of contradiction between proton conductivity and variety of stabilities, such as mechanical, thermal,chemical, etc.; it still remains a prime challenge to develop a highly conducting PEM with superior aforementioned stabilities. In fact the very limited understanding of the interactions especially interfacial interaction between PBI and inorganic filler leads to confusion over the choice of inorganic filler type and their surface functionalities. Taking clue from our earlier study based on poly(4,4'-diphenylether-5,5'-bibenzimidazole) (OPBI)/silica nanocomposites, where silica nanoparticles modified with short chain amine showed interfacial interaction-dependent properties, in this work we explored the possibility of enhanced interfacial interaction and control over the interface by optimizing the chemistry of the silica surface. We functionalized the surface of silica nanoparticles with a longer aliphatic chain having multiple amine groups (named as long chain amine modified silica and abbreviated as LAMS). FTIR and (13)C solid-state NMR provided proof of hydrogen bonding interactions between the amine groups of modifier and those of OPBI. LAMS nanoparticles yielded a more distinguished self-assembly extending all over the OPBI matrix with increasing concentrations. The crystalline nature of these self-assembled clusters was probed by wide-angle X-ray diffraction (WAXD) studies and the morphological features were captured by transmission electron microscope (TEM). We demonstrated the changes in storage modulus and glass transition temperature (Tg) of the membranes, the fundamental parameters that are more sensitive to interfacial structure using temperature dependent dynamic mechanical analysis (DMA). All the nanocomposite membranes displayed enhanced mechanical, thermal

  19. Synthesis and luminescence properties of dye-doped deoxyribonucleic acid films

    Dye-doped deoxyribonucleic acids (DNA)–tetradecyltrimethylammonium (TTA) films have been prepared. Rhodamine 6G, known as laser dyes, can be spontaneously doped by immersing the DNA–TTA film in rhodamine 6G-acetonitrile solutions. It is surmised that rhodamine 6G monomers and dimers diffuse within the hydrophobic TTA sites, and then monomers presumably intercalate between adjacent base pairs of DNA. Optical absorption spectra reveal that rhodamine 6G molecules in the sample undergo an unusual transformation from the dimer state to the monomer state with the elapse of time. Rhidamine 6G molecules doped in DNA–TTA show enhanced photostability and concentration quenching than those in PMMA. The environment, conformation and chemical stability of rhodamine 6G are different between DNA–TTA and PMMA, and are presumably modified by the intercalation. - Highlights: ► Rhodamine 6G can be spontaneously doped into DNA films by the immersion method. ► Rhodamine 6G molecules undergo an unusual transformation from the dimer to monomer state. ► Rhodamine 6G molecules in DNA films show enhanced photostability and concentration quenching than those in PMMA.

  20. Synthesis and luminescence properties of dye-doped deoxyribonucleic acid films

    Kitazawa, N., E-mail: nkita@nda.ac.jp [Department of Materials Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686 (Japan); Aroonjaeng, W.; Aono, M.; Watanabe, Y. [Department of Materials Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686 (Japan)

    2012-06-15

    Dye-doped deoxyribonucleic acids (DNA)-tetradecyltrimethylammonium (TTA) films have been prepared. Rhodamine 6G, known as laser dyes, can be spontaneously doped by immersing the DNA-TTA film in rhodamine 6G-acetonitrile solutions. It is surmised that rhodamine 6G monomers and dimers diffuse within the hydrophobic TTA sites, and then monomers presumably intercalate between adjacent base pairs of DNA. Optical absorption spectra reveal that rhodamine 6G molecules in the sample undergo an unusual transformation from the dimer state to the monomer state with the elapse of time. Rhidamine 6G molecules doped in DNA-TTA show enhanced photostability and concentration quenching than those in PMMA. The environment, conformation and chemical stability of rhodamine 6G are different between DNA-TTA and PMMA, and are presumably modified by the intercalation. - Highlights: Black-Right-Pointing-Pointer Rhodamine 6G can be spontaneously doped into DNA films by the immersion method. Black-Right-Pointing-Pointer Rhodamine 6G molecules undergo an unusual transformation from the dimer to monomer state. Black-Right-Pointing-Pointer Rhodamine 6G molecules in DNA films show enhanced photostability and concentration quenching than those in PMMA.

  1. Polybenzimidazole-decorated carbon nanotube: A high-performance proton conductor

    Majedi, Fatemeh Sadat [Laboratoire de Microsystemes (LMIS4), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland); Department of Biomedical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Hasani-Sadrabadi, Mohammad Mahdi [Laboratoire de Microsystemes (LMIS4), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland); Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Dashtimoghadam, Erfan [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Haghighi, Amir Hossein [Faculty of Engineering, Islamic Azad University, Shiraz Branch, Shiraz, Fars (Iran, Islamic Republic of); Bertsch, Arnaud; Renaud, Philippe [Laboratoire de Microsystemes (LMIS4), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland); Moaddel, Homayoun [Hydrogen and Fuel Cell Inc., Arcadia, CA (United States)

    2012-07-15

    Interaction between negatively charged Nafion {sup registered} and a positively charged polybenzimidazole-decorated carbon nanotube leads to the formation of an ionic complex with high charge density for proton conduction, which can lead to an improvement in transport properties. Here we investigate the high-temperature and low-humidity proton conductivity of this nanocomposite membrane as a potential membrane for fuel cell applications. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Electrochemical promotion of oxidative coupling of methane on platinum/polybenzimidazole catalyst

    Petrushina, Irina; Bandur, Viktor; Bjerrum, Niels;

    2002-01-01

    The electrochemical promotion of catalytic methane oxidation was studied using a (CH4,O-2,Ar), Pt\\polybenzimidazole (PBI)-H3PO4\\Pt,(H-2,Ar) fuel cell at 135degreesC. It has been found that C2H2, CO2, and water are the main oxidation products. Without polarization the yield of C2H2 was 0.9% and the...

  3. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus;

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell...

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

    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.

  5. EPR investigations of silicon carbide nanoparticles functionalized by acid doped polyaniline

    Karray, Fekri [Laboratoire des materiaux Ceramiques Composites et Polymeres, Faculte des Sciences de Sfax, BP 802, 3018 Sfax (Tunisia); Kassiba, Abdelhadi, E-mail: kassiba@univ-lemans.fr [Institute of Molecules and Materials of Le Mans (I3M), UMR-CNRS 6283, Universite du Maine, 72085 Le Mans (France)

    2012-06-15

    Nanocomposites (SiC-PANI) based on silicon carbide nanoparticles (SiC) encapsulated in conducting polyaniline (PANI) are synthesized by direct polymerization of PANI on the nanoparticle surfaces. The conductivity of PANI and the nanocomposites was modulated by several doping levels of camphor sulfonic acid (CSA). Electron paramagnetic resonance (EPR) investigations were carried out on representative SiC-PANI samples over the temperature range [100-300 K]. The features of the EPR spectra were analyzed taking into account the paramagnetic species such as polarons with spin S=1/2 involved in two main environments realized in the composites as well as their thermal activation. A critical temperature range 200-225 K was revealed through crossover changes in the thermal behavior of the EPR spectral parameters. Insights on the electronic transport properties and their thermal evolutions were inferred from polarons species probed by EPR and the electrical conductivity in doped nanocomposites.

  6. Dielectric properties of solution-grown-undoped and acrylic-acid-doped ethyl cellulose

    P K Khare; Sandeep K Jain

    2000-02-01

    Dielectric capacities and losses were measured, in the temperature (50–170°C) and frequency (01–100 kHz range), for undoped and acrylic acid (AA) doped ethyl cellulose (EC) films (thickness about 20 m) with progressive increase in the concentration of dopant in the polymer matrix. The variation of capacity with temperature is attributed to thermal expansion in the lower temperature region to the orientation of dipolar molecules in the neighbourhood of glass transition temperature () and random thermal motion of molecules above . The dielectric losses exhibit a broad peak. Doping with AA is found to affect the magnitude and position of the peak. AA is found to have a two-fold action. Firstly, it enhances the chain mobility and secondly, it increases the dielectric loss by forming charge transfer complexes.

  7. Synthesis and properties of segmented block copolymers of functionalised polybenzimidazoles for high-temperature PEM fuel cells

    Mader, J.A.; Benicewicz, B.C. [Department of Chemistry and Biochemistry and USC Nanocenter, University of South Carolina, 631 Sumter St., Columbia, SC 29208 (United States)

    2011-04-15

    A series of novel segmented block copolymers of sulphonated polybenzimidazole (PBI) (s-PBI) and p-PBI were prepared with various polymer ratios (10-90 mol% s-PBI; 90-10 mol% p-PBI). A two-step synthesis of oligomeric species, followed by combination and further polymerisation was used via the polyphosphoric acid (PPA) process. The membranes showed improved high-temperature proton conductivities and fuel cell performance over previous literature reports, with moderate incorporation of s-PBI into the copolymer showing the best results. The non-humidified fuel cell performance was extensively studied with various fuels and oxidants and showed excellent properties. Block copolymers that incorporated 40, 50 or 60 mol% s-PBI and the corresponding 60, 50 or 40 mol% p-PBI, at 0.2 A cm{sup -2} and 160 C, had hydrogen-air performances of 0.661-0.666 V, depending on composition. The performance was improved using hydrogen-oxygen, with voltages between 0.734 and 0.742 V at 0.2 A cm{sup -2} and 160 C. Fuel cells operating on a reformed hydrocarbon gas showed decreased performance (0.622-0.627 V, same conditions), especially at lower temperatures, but was significantly improved over previous literature reports of sulphonated PBI membranes operating at high temperatures. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. High performance B doped BiVO4 photocatalyst with visible light response by citric acid complex method.

    Wang, Min; Zheng, Haoyan; Liu, Qiong; Niu, Chao; Che, Yinsheng; Dang, Mingyan

    2013-10-01

    A B-doped BiVO4 photocatalyst was synthesized by citric acid complex method and using H3BO3 as the dopant source, and the photocatalyst was characterized with XPS, XRD, SEM, BET and UV-Vis DRS. The photocatalytic activity was evaluated by the photocatalytic degradation of a methyl orange (MO) solution under visible light. This assay revealed that both the pure BiVO4 and all of the B doped samples were the monoclinic phase. Doping the BiVO4 with B increased the number of V(4+) and oxygen vacancies, which led to the red shift of the absorbing boundary of the B-doped BiVO4 but had little influence on the morphology and crystal size. The B doping improved the photocatalytic activity, and the highest photocatalytic degradation rate of 98% occurred with a B dopant concentration of 0.04. PMID:23751222

  9. PEM steam electrolysis at 130 °C using a phosphoric acid doped short side chain PFSA membrane

    Hansen, Martin Kalmar; Aili, David; Christensen, Erik;

    2012-01-01

    Steam electrolysis test with a phosphoric acid doped Aquivion™ membrane was successfully conducted and current densities up to 775 mA cm-2 at 1.8 V was reached at 130 ºC and ambient pressure. A new composite membrane system using a perfluorosulfonic acid membrane (Aquivion™) as matrix and phospho......Steam electrolysis test with a phosphoric acid doped Aquivion™ membrane was successfully conducted and current densities up to 775 mA cm-2 at 1.8 V was reached at 130 ºC and ambient pressure. A new composite membrane system using a perfluorosulfonic acid membrane (Aquivion™) as matrix...... and phosphoric acid as proton conducting electrolyte was developed. Traditional perfluorosulfonic acid membranes do not possess sufficient dimensional stability and proton conductivity to be used at elevated temperatures and ambient pressures. The elevated temperature, high potentials and acidic conditions...

  10. Copper- or manganese-doped ZnS quantum dots as fluorescent probes for detecting folic acid in aqueous media

    3-Mercaptopropionic acid-capped core/shell ZnS:Cu/ZnS and ZnS:Mn/ZnS doped quantum dots (QDs) prepared through hydrothermal methods exhibit high photoluminescence intensity as well as good photostability. These water-dispersible nanoparticles exhibit high fluorescence sensitivity to folic acid due to the high affinity of the carboxylate groups and nitrogen atoms of folic acid towards the Zn surface atoms of the doped dots. Quenching of the fluorescence intensity of the QDs allows the detection of folic acid concentrations as low as 11 μM, thus affording a very sensitive system for the sensing of this biologically active molecule in aqueous solution. The possible quenching mechanism is discussed. - Graphical abstract: A sensitive method for the detection of folic acid based on the fluorescence quenching of Mn- or Cu-doped ZnS quantum dots was developed. Highlights: ► Quenching of the fluorescence intensity of doped ZnS QDs in the presence of folic acid. ► New fluorescent sensors for folic acid. ► Detection of folic acid concentrations as low as 11 μM in aqueous solution. ► The Perrin model and fluorescence lifetimes of ZnS:Mn QDs demonstrate a static quenching mechanism. ► Quenching efficiency of ZnS:Cu QDs correlates with the Stern-Volmer model.

  11. Simultaneous Chronoamperometric Sensing of Ascorbic Acid and Acetaminophen at a Boron-Doped Diamond Electrode

    Ciprian Radovan; Codruţa Cofan

    2008-01-01

    Cyclic voltammetry (CV) and chronoamperometry (CA) have been used to sense and determine simultaneously L-ascorbic acid (AA) and acetaminophen (AC) at a boron-doped diamond electrode (BDDE) in a Britton-Robinson buffer solution. The calibration plots of anodic current peak versus concentration obtained from CV and CA data for both investigated compounds in single and di-component solutions over the concentration range 0.01 mM – 0.1 mM proved to be linear, with very good correlation param...

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

    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.

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

    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. (paper)

  14. Structure and gelation properties of casein micelles doped with curcumin under acidic conditions.

    Khanji, Aya N; Michaux, Florentin; Jasniewski, Jordane; Petit, Jeremy; Lahimer, Emna; Cherif, Mohamed; Salameh, Dominique; Rizk, Toufic; Banon, Sylvie

    2015-12-01

    In this study, the ability of micellar casein (MC) to interact with curcumin during acidification and to produce acid gel was investigated. Steady-state fluorescence spectroscopy of curcumin variation and fluorescence quenching of caseins upon binding with curcumin molecules were evidenced. Increasing the temperature from 20 to 35 °C enhanced MC-curcumin interactions as reflected by the increase in the binding constant from 0.6 ± 0.3 × 10(4) to 6.6 ± 0.6 × 10(4) M(-1). From changes in entropy, enthalpy and Gibbs free energy, hydrophobic interactions were proposed as major binding forces. Static fluorescence MC quenching was demonstrated for the MC-curcumin complex during acidification. From pH 7.4 to pH 5.0, the binding site numbers varied in the range from 1.25 ± 0.05 to 1.49 ± 0.05 and the binding constant kb varied from 3.9 ± 0.4 × 10(4) to 7.5 ± 0.7 × 10(4) M(-1). Small angle X-ray scattering profiles demonstrated that the MC internal structure was unchanged upon curcumin binding. The ζ-potential value of curcumin-doped MC indicated that curcumin did not modify the global charge of MC particles. Acid gelation studied by oscillation rheology and static multiple light scattering at 20 and 35 °C led to a similar behavior for native and curcumin-doped MC suspensions. For the first time, it was demonstrated that the colloidal and functional properties of MC were unchanged when doped with curcumin during acidification. PMID:26419313

  15. Preparation and reactivity of carboxylic acid-terminated boron-doped diamond electrodes

    Niedziolka-Joensson, Joanna [Institut de Recherche Interdisciplinaire (IRI, USR 3078), Parc de la Haute Borne, 50 Avenue de Halley, BP 70478, 59658 Villeneuve d' Ascq (France); Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, UMR 8520), Cite Scientifique, Avenue Poincare, BP 60069, 59652 Villeneuve d' Ascq (France); Boland, Susan; Leech, Donal [School of Chemistry, National University of Irland, Galway (Ireland); Boukherroub, Rabah [Institut de Recherche Interdisciplinaire (IRI, USR 3078), Parc de la Haute Borne, 50 Avenue de Halley, BP 70478, 59658 Villeneuve d' Ascq (France); Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, UMR 8520), Cite Scientifique, Avenue Poincare, BP 60069, 59652 Villeneuve d' Ascq (France); Szunerits, Sabine, E-mail: sabine.szunerits@iri.univ-lille1.f [Institut de Recherche Interdisciplinaire (IRI, USR 3078), Parc de la Haute Borne, 50 Avenue de Halley, BP 70478, 59658 Villeneuve d' Ascq (France); Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, UMR 8520), Cite Scientifique, Avenue Poincare, BP 60069, 59652 Villeneuve d' Ascq (France)

    2010-01-01

    The paper reports on the formation of carboxy-terminated boron-doped diamond (BDD) electrodes. The carboxylic acid termination was prepared in a controlled way by reacting photochemically oxidized BDD with succinic anhydride. The resulting interface was readily employed for the linking of an amine-terminated ligand such as an osmium complex bearing an amine terminal group. The interfaces were characterized using X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Contact angle measurements were used to follow the changes in surface wetting properties due to surface functionalization. The chemical reactivity of the carboxyl-terminated BDD was investigated by covalent coupling of the acid groups to an amine-terminated osmium complex.

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

    The photocatalytic decomposition of perfluorooctanoic acid (PFOA) in aqueous solution using Fe and Nb co-doped TiO2 (Fe:Nb-TiO2) prepared by sol-gel method was investigated. The photocatalytic activity of Fe:Nb-TiO2 towards PFOA degradation was compared to that of pure TiO2 synthesized using the same method, and that of the commercially available TiO2 photocatalyst, Aeroxide TiO2 P25 (AO-TiO2 P25). The photocatalysts were characterized by XRD, DRS, BET-N2 adsorption isotherm, and SEM-EDX techniques and the data were correlated to the photocatalytic activity. Fe:Nb-TiO2 showed the highest activity compared to the undoped TiO2 and the commercially available TiO2. 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.

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

    Renan Estrellan, Carl, E-mail: estrellan.c.ac@m.titech.ac.jp [Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Salim, Chris; Hinode, Hirofumi [Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

    2010-07-15

    The photocatalytic decomposition of perfluorooctanoic acid (PFOA) in aqueous solution using Fe and Nb co-doped TiO{sub 2} (Fe:Nb-TiO{sub 2}) prepared by sol-gel method was investigated. The photocatalytic activity of Fe:Nb-TiO{sub 2} towards PFOA degradation was compared to that of pure TiO{sub 2} synthesized using the same method, and that of the commercially available TiO{sub 2} photocatalyst, Aeroxide TiO{sub 2} P25 (AO-TiO{sub 2} P25). The photocatalysts were characterized by XRD, DRS, BET-N{sub 2} adsorption isotherm, and SEM-EDX techniques and the data were correlated to the photocatalytic activity. Fe:Nb-TiO{sub 2} showed the highest activity compared to the undoped TiO{sub 2} and the commercially available TiO{sub 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. Continuous electrooxdiation of sulfuric acid on boron-doped diamond electrodes

    Highlights: • highly concentrated sulfuric acid was electrochemically oxidized to peroxosulfuric compounds • Diachem® boron-doped diamond electrodes were used both as anode and cathode to oxidize the sulfuric acid • a manufactured cation selective membrane was used in an unconventional electrolyte circuit • concentrations equivalent to a common SPM bath were reached • an alternative setup was applied using only one electrolyte circuit - ABSTRACT: This study reports on the electrochemical oxidation of highly concentrated sulfuric acid by Diachem® boron-doped diamond electrodes. The scope of this work was to evaluate a proposed continuous electrooxidation process in order to prepare a resist removal bath that contains equivalent amounts of peroxosulfuric compounds as a common SPM (sulfuric acid and hydrogen peroxide mixture) bath. The electrochemical processes at the electrode surface were investigated by cyclic voltammetry and by titration of the reaction products under real working conditions (> 80 wt% H2SO4). Furthermore, an alternative electrolysis test cell setup, exhibiting a thin and mechanically stable ion exchange membrane will be used. For this process only one electrolyte circuit is performed. The initial electrolysis product H2S2O8 immediately undergoes hydrolysis and forms H2SO5. The obtained concentration of H2SO5 was similar to a reference SPM bath (> 0.14 mol l−1 H2SO5 in 90 wt% H2SO4), even though the current efficiency was lower than for more diluted solutions. This can be attributed to a complex interplay of side and consumption reactions of peroxosulfuric compounds. This electrolysis bath has the potential to be a very promising alternative to standard SPM baths, as it operates as a continuous and sustainable process

  19. Synthesis and Characteristic Study on Complexes of Europium(Ⅲ) and Maleic Acid Doped with Non-Fluorescent Ions

    2007-01-01

    Complex of europium (Ⅲ) with maleic acid, and binuclear complexes of europium(Ⅲ)with maleic acid doped with non-fluorescent ions gadolinium, lanthanum and yttrium, were synthesized. The compositions and structures of complexes were characterized with elemental analysis, single crystal X-ray diffraction, IR and DSC-TG. Fluorescent properties were studied with fluorescence spectrum. The results indicated that the strongest fluorescent complexes were obtained when the ratio of europium and non-fluorescent ion was 8: 2. The order of Eu3+ fluorescence strengthened by three doped rare earths was Gd3+>La3+>Y3+.

  20. Inhibitive Effect of Hydrofluoric Acid Doped Poly Aniline (HFPANI on Corrosion of Iron in 1N Phosphoric Acid Solution

    G.Maheswari

    2015-03-01

    Full Text Available The inhibition effect of Hydrofluoric acid doped poly aniline HF-PANI on mild steel corrosion in 1N phosphoric acid has been studied by mass loss and polarization techniques and AC impedance measurements methods between 303 K and 333K.The inhibition efficiency increased with increase in concentration of HF PANI. The corrosion rate increased with increase in temperature and decreased with increase in concentration of inhibitor compared to blank. Potentiostatic polarization results revealed that HF-PANI act as mixed type inhibitor. The inhibitor of HF-PANI was chemically adsorbed and spontaneous adsorption on the mild steel surface .The values of activation energy (Ea, free energy of adsorption (ΔGads, heat of adsorption (Qads, enthalpy of adsorption (ΔH and entropy of adsorption (ΔS were calculated. The adsorption of inhibitor on mild steel surface has been found to obey Temkin’s adsorption isotherm. SEM analysis was agreed to establish the mechanism of corrosion inhibitor on mild steel corrosion in phosphoric acid medium.

  1. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus; Bjerrum, Niels; Bandur, Viktor

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell with participation of H+ or electrochemically produced hydrogen. When added, methane partially suppresses the electrochemical reduction of NO. Methane outlet concentration monitoring has shown the CH4 ...

  2. Experimental characterization and modeling of commercial polybenzimidazole-based MEA performance

    Korsgaard, Anders; Refshauge, R. H.; Nielsen, Mads Pagh; Bang, Mads; Kær, Søren Knudsen

    2006-01-01

    High temperature polymer fuel cells based on polybenzimidazole membranes (PBI) operated at 100-200 °C are currently receiving much attention in relation to fuel cell reforming systems due to two main reasons. At first they have proven to have excellent resistance to high CO concentrations, which...... decreases the number of system components in the fuel processing system. The preferential oxidation reactors can be left out and in addition a water condenser is not required. These system simplifications additionally decrease the parasitic losses associated with the components.  However, insufficient data...

  3. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice

  4. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    Zeng, Ya-Wen [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, De-Kun, E-mail: dkma@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Wang, Wei; Chen, Jing-Jing; Zhou, Lin; Zheng, Yi-Zhou [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Yu, Kang, E-mail: yukang62@126.com [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Huang, Shao-Ming, E-mail: smhuang@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2015-07-01

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice.

  5. Radiation and storage-induced ageing of polypyrrole doped with dodecylbenzene sulfonic acid

    Kappen, P.; Brack, N.; Hale, P. S.; Prissanaroon, W.; Welter, E.; Pigram, P. J.

    2005-04-01

    The effects of storage and exposure to X-rays on the surface chemistry of electrochemically prepared polypyrrole (PPy) doped with dodecylbenzene sulfonic acid (DBSA) were investigated using X-ray photoelectron spectroscopy (XPS). For irradiation, different photon sources (lab source and synchrotron radiation) and energies (1.4-9 keV) were chosen. This covers an energy range of relevance for many X-ray based investigations (e.g. XPS or X-ray absorption spectroscopy) of PPy[DBSA], PPy-metal interfaces, and transition metals embedded into PPy. The DBSA doping level and the concentration ratio of sulfonate species are discussed as a function of storage and irradiation times, and links between both ageing parameters are given. New sulfur species are found to emerge upon repeated soft X-ray irradiation. Severe changes in the polaron/bipolaron structure of PPy[DBSA] during exposure to high energy (several keV) synchrotron radiation are observed, and the results are discussed in the light of photon absorption and photoelectron generation in the polymer surface.

  6. Radiation and storage-induced ageing of polypyrrole doped with dodecylbenzene sulfonic acid

    The effects of storage and exposure to X-rays on the surface chemistry of electrochemically prepared polypyrrole (PPy) doped with dodecylbenzene sulfonic acid (DBSA) were investigated using X-ray photoelectron spectroscopy (XPS). For irradiation, different photon sources (lab source and synchrotron radiation) and energies (1.4-9 keV) were chosen. This covers an energy range of relevance for many X-ray based investigations (e.g. XPS or X-ray absorption spectroscopy) of PPy[DBSA], PPy-metal interfaces, and transition metals embedded into PPy. The DBSA doping level and the concentration ratio of sulfonate species are discussed as a function of storage and irradiation times, and links between both ageing parameters are given. New sulfur species are found to emerge upon repeated soft X-ray irradiation. Severe changes in the polaron/bipolaron structure of PPy[DBSA] during exposure to high energy (several keV) synchrotron radiation are observed, and the results are discussed in the light of photon absorption and photoelectron generation in the polymer surface

  7. Radiation and storage-induced ageing of polypyrrole doped with dodecylbenzene sulfonic acid

    Kappen, P. [Centre for Materials and Surface Science, La Trobe University, Vic. 3086 (Australia)]. E-mail: p.kappen@latrobe.edu.au; Brack, N. [Centre for Materials and Surface Science, La Trobe University, Vic. 3086 (Australia); Hale, P.S. [Centre for Materials and Surface Science, La Trobe University, Vic. 3086 (Australia); Prissanaroon, W.; Welter, E. [Hamburg Synchrotron Radiation Laboratory (HASYLAB), Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Pigram, P.J. [Centre for Materials and Surface Science, La Trobe University, Vic. 3086 (Australia)

    2005-04-30

    The effects of storage and exposure to X-rays on the surface chemistry of electrochemically prepared polypyrrole (PPy) doped with dodecylbenzene sulfonic acid (DBSA) were investigated using X-ray photoelectron spectroscopy (XPS). For irradiation, different photon sources (lab source and synchrotron radiation) and energies (1.4-9 keV) were chosen. This covers an energy range of relevance for many X-ray based investigations (e.g. XPS or X-ray absorption spectroscopy) of PPy[DBSA], PPy-metal interfaces, and transition metals embedded into PPy. The DBSA doping level and the concentration ratio of sulfonate species are discussed as a function of storage and irradiation times, and links between both ageing parameters are given. New sulfur species are found to emerge upon repeated soft X-ray irradiation. Severe changes in the polaron/bipolaron structure of PPy[DBSA] during exposure to high energy (several keV) synchrotron radiation are observed, and the results are discussed in the light of photon absorption and photoelectron generation in the polymer surface.

  8. Polybenzimidazole Membranes Containing Benzimidazole Side Groups for High Temprature Polymer Electrolyte Membrane Fuel Cells

    Yang, Jingshuai; Li, Xueyuan; Xu, Yizin;

    2013-01-01

    temperatures without humidification. At an acid doping level of 13.1 mol H3PO4 per average molar repeat unit, the PBI membranes with a benzimidazole grafting degree of 10.6% demonstrated a conductivity of 0.15 S cm-1 and a H2-air fuel cell peak power density of 378 mW cm-2 at 180 oC at ambient pressure without...

  9. Flexible, all-organic ammonia sensor based on dodecylbenzene sulfonic acid-doped polyaniline films

    A stable chlorobenzene dispersion of conducting polyaniline (PANI) has been obtained by doping emeraldine base with dodecylbenzene sulfonic acid (DBSA) and studied by spectrophotometric measurements in the UV-vis-IR range. The electrical properties of PANI: DBSA films obtained from the above dispersion have been investigated under different temperature and relative humidity conditions. All-organic chemoresistive devices have been developed by spin-coating the PANI: DBSA dispersion on flexible substrates, and then by depositing electrodes on the top, from a carbon nanotube conducting ink. Sensing tests performed under exposition to calibrated amounts of ammonia reveal that these simple and inexpensive sensors are able to detect ammonia at room temperature in a reliable way, with a sensitivity linearly related to concentration in the range between 5 ppm and 70 ppm.

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

    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

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

    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.

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

    Sánchez Lafarga, Ana Karen; Pacheco Moisés, Fermín P. [Departamento de Química, Universidad de Guadalajara, Marcelino García Barragán 1421, C.P. 44430, Guadalajara, Jalisco (Mexico); Gurinov, Andrey [Research Resources Center for Magnetic Resonance, Saint Petersburg State University, Universitetskij pr. 26, 198504 St. Petersburg (Russian Federation); Ortiz, Genaro Gabriel [Laboratorio Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente (CIBO), Instituto Mexicano de Seguro Social (IMSS), Guadalajara, Jalisco (Mexico); Carbajal Arízaga, Gregorio Guadalupe, E-mail: gregoriocarbajal@yahoo.com.mx [Departamento de Química, Universidad de Guadalajara, Marcelino García Barragán 1421, C.P. 44430, Guadalajara, Jalisco (Mexico)

    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 488 nm. 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. - Highlights: • Hydroxyapatite functionalized with glucuronic acid reduced oxidative stress in rats. • Functionalization with folic acid reduced oxidative stress in rats. • Dysprosium doping does not affect the crystalline structure of hydroxyapatite. • Dysprosium doped particles are visible in fluorescent microscope. • Dysprosium doped particles act as MRI contrast agents.

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

    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 488 nm. 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. - Highlights: • Hydroxyapatite functionalized with glucuronic acid reduced oxidative stress in rats. • Functionalization with folic acid reduced oxidative stress in rats. • Dysprosium doping does not affect the crystalline structure of hydroxyapatite. • Dysprosium doped particles are visible in fluorescent microscope. • Dysprosium doped particles act as MRI contrast agents

  14. Effect of sorbic acid doping on flux pinning in bulk MgB2 with the percolation model

    In this paper, we study the doping effect of sorbic acid (C6H8O2), from 0 to 20 wt.% of the total MgB2, on critical temperature (Tc), critical current density (Jc), irreversibility field (Hirr) and crystalline structure. The XRD patterns of samples show a slightly decrease in a-axis lattice parameter for doped samples, due to the partial substitution of carbon at boron site. On the other hand, we investigate the influence of doping on the behavior of flux pinning and Jc(B) in the framework of percolation theory and it is found that the Jc(B) behavior could be well fitted in high field region. The two key parameters, anisotropy and percolation threshold, play very important roles. It is believed that the enhancement of Jc is due to the reduction of anisotropy in high field region.

  15. Electrochemical promotion of NO reduction by hydrogen on a platinum/polybenzimidazole catalyst

    Petrushina, Irina; Bandur, Viktor; Cappeln, Frederik Vilhelm; Bjerrum, Niels; Sørensen, Rasmus Zink; Refshauge, R.H.; Li, Qingfeng

    2003-01-01

    The electrochemical promotion of catalytic NO reduction by hydrogen was studied using a (NO, H-2, Ar), Pt polybenzimidazole (PBI)-H3PO4\\Pt, (H-2, Ar) fuel cell at 135degreesC. A mixture of NO/H-2/Ar was used as the working mixture at one electrode and a mixture of H-2/Ar was used as reference and counter gas at the other electrode. Products of NO reduction (N-2 and H2O) were analyzed by an on-line mass spectrometer. At high NO+H-2+Ar flow rate (17 mL/min; 17 and 354 mL/min, respectively, at a...

  16. Polybenzimidazoles based on high temperature polymer electrolyte fuel cells

    Linares Leon, Jose Joaquin; Camargo, Ana Paula M.; Ashino, Natalia M.; Morgado, Daniella L.; Frollini, Elisabeth; Paganin, Valdecir A.; Gonzalez, Ernesto Rafael [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil); Bajo, Justo Lobato [University of Castilla-La Mancha, Ciudad Real (Spain). Dept. of Chemical Engineering

    2010-07-01

    This work presents an interesting approach in order to enhance the performance of Polymer Electrolyte Membrane Fuel Cells (PEMFC) by means of an increase in the operational temperature. For this, two polymeric materials, Poly(2,5-bibenzimidazole) (ABPBI) and Poly[2,2'-(m-phenyl en)-5,5' bib enzimidazol] (PBI), impregnated with phosphoric acid have been utilized. These have shown excellent properties, such as thermal stability above 500 deg C, reasonably high conductivity when impregnated with H{sub 3}PO{sub 4} and a low permeability to alcohols compared to Nafion. Preliminary fuel cells measurements on hydrogen based Polymer Electrolyte Membrane Fuel Cell (PEMFC) displayed an interestingly reasonable good fuel cell performance, a quite reduced loss when the hydrogen stream was polluted with carbon monoxide, and finally, when the system was tested with an ethanol/water (E/W) fuel, it displayed quite promising results that allows placing this system as an attractive option in order to increase the cell performance and deal with the typical limitations of low temperature Nafion-based PEMFC. (author)

  17. Development of Polybenzimidazole-Based High-Temperature Membrane and Electrode Assemblies for Stationary and Automotive Applications

    Vogel, John A.

    2008-09-03

    The program began on August 1, 2003 and ended on July 31, 2007. The goal of the project was to optimize a high-temperature polybenzimidazole (PBI) membrane to meet the performance, durability, and cost targets required for stationary fuel cell applications. These targets were identified in the Fuel Cell section (3.4) of DOE’s Hydrogen, Fuel Cells and Infrastructure Technologies Program Multi-Year Research, Development and Demonstration Plan. A membrane that operates at high temperatures is important to the fuel cell industry because it is insensitive to carbon monoxide (a poison to low-temperature fuel cells), and does not require complex water management strategies. Together, these two benefits greatly simplify the fuel cell system. As a result, the high-temperature fuel cell system realizes a cost benefit as the number of components is reduced by nearly 30%. There is also an inherent reliability benefit as components such as humidifiers and pumps for water management are unnecessary. Furthermore, combined heat and power (CHP) systems may be the best solution for a commercial, grid-connected, stationary product that must offer a cost benefit to the end user. For a low-temperature system, the quality of the heat supplied is insufficient to meet consumer needs and comfort requirements, so peak heaters or supplemental boilers are required. The higher operating temperature of PBI technology allows the fuel cell to meet the heat and comfort demand without the additional equipment. Plug Power, working with the Rensselaer Polytechnic Institute (RPI) Polymer Science Laboratory, made significant advances in optimizing the PBI membrane material for operation at temperatures greater than 160oC with a lifetime of 40,000 hours. Supporting hardware such as flow field plates and a novel sealing concept were explored to yield the lower-cost stack assembly and corresponding manufacturing process. Additional work was conducted on acid loss, flow field design and cathode electrode

  18. Electrochemical oxidation of oxalic acid in the presence of halides at boron doped diamond electrode

    Martinez-Huitle, C.A. [University of Milan, Milan (Italy). Dept. of Analytical Chemistry]. E-mail: Carlos.Martinez@unimi.it; Ferro, S.; Battisti, A. de [University of Ferrara (Italy). Dept. of Chemistry. Lab. of Electrochemistry; Reyna, S.; Cerro-Lopez, M.; Quiroz, M.A. [Universidad de las Americas-Puebla, Puebla (Mexico). Dept. de Quimica y Biologia. Lab. de Electroquimica]. E-mail: marcoa.quiroz@udlap.mx

    2008-07-01

    Aim of this work is to discuss the electrochemical oxidation of oxalic acid (OA), analyzing the influence of NaCl and NaBr. Experiments were carried out at boron-doped diamond (BDD) electrodes, in alkaline media. BDD electrodes have a poor superficial adsorptivity so their great stability toward oxidation allows the reaction to take place with reactants and intermediates in a non-adsorbed state. The process is significantly accelerated by the presence of a halogen salt in solution; interestingly, the mediated process does not depend on applied current density. Based on the results, bromide was selected as a suitable mediator during OA oxidation at BDD. Br{sup -} primarily acts in the volume of the solution, with the formation of strong oxidants; while Cl{sup -} action has shown lower improvements in the OA oxidation rate at BDD respect to the results reported using Pt electrode. Finally, the parameters of removal efficiency and energy consumption for the electrochemical incineration of OA were calculated. (author)

  19. Simultaneous Chronoamperometric Sensing of Ascorbic Acid and Acetaminophen at a Boron-Doped Diamond Electrode

    Ciprian Radovan

    2008-06-01

    Full Text Available Cyclic voltammetry (CV and chronoamperometry (CA have been used to sense and determine simultaneously L-ascorbic acid (AA and acetaminophen (AC at a boron-doped diamond electrode (BDDE in a Britton-Robinson buffer solution. The calibration plots of anodic current peak versus concentration obtained from CV and CA data for both investigated compounds in single and di-component solutions over the concentration range 0.01 mM – 0.1 mM proved to be linear, with very good correlation parameters. Sensitivity values and RSD of 2-3% were obtained for various situations, involving both individual and simultaneous presence of AA and AC. The chronoamperometric technique associated with standard addition in sequential one step and/or two successive and continuous chronoamperograms at two characteristic potential levels represented a feasible option for the simultaneous determination of AA and AC in real sample systems such as pharmaceutical formulations. The average values indicated by the supplier were confirmed to a very close approximation from chronoamperomgrams by using several additions with the application of suitable current correction factors.

  20. Comparison of chondroitin sulfate and hyaluronic Acid doped conductive polypyrrole films for adipose stem cells.

    Björninen, Miina; Siljander, Aliisa; Pelto, Jani; Hyttinen, Jari; Kellomäki, Minna; Miettinen, Susanna; Seppänen, Riitta; Haimi, Suvi

    2014-09-01

    Polypyrrole (PPy) is a conductive polymer that has aroused interest due to its biocompatibility with several cell types and high tailorability as an electroconductive scaffold coating. This study compares the effect of hyaluronic acid (HA) and chondroitin sulfate (CS) doped PPy films on human adipose stem cells (hASCs) under electrical stimulation. The PPy films were synthetized electrochemically. The surface morphology of PPy-HA and PPy-CS was characterized by an atomic force microscope. A pulsed biphasic electric current (BEC) was applied via PPy films non-stimulated samples acting as controls. Viability, attachment, proliferation and osteogenic differentiation of hASCs were evaluated by live/dead staining, DNA content, Alkaline phosphatase activity and mineralization assays. Human ASCs grew as a homogenous cell sheet on PPy-CS surfaces, whereas on PPy-HA cells clustered into small spherical structures. PPy-CS supported hASC proliferation significantly better than PPy-HA at the 7 day time point. Both substrates equally triggered early osteogenic differentiation of hASCs, although mineralization was significantly induced on PPy-CS compared to PPy-HA under BEC. These differences may be due to different surface morphologies originating from the CS and HA dopants. Our results suggest that PPy-CS in particular is a potential osteogenic scaffold coating for bone tissue engineering. PMID:24823653

  1. Z-scan measurements of single walled carbon nanotube doped acetylenedicarboxylic acid polymer under CW laser

    Zidan, M. D.; Allaf, A. W.; Allahham, A.; AL-Zier, A.

    2016-06-01

    Z-scan measurements of single walled carbon nanotube (SWCNT) doped with acetylenedicarboxylic acid (ADC) polymer are performed using a CW diode laser at 635 nm wavelength with 17 mW power. The nonlinear absorption coefficient (β), nonlinear refractive index (n2), the real and imaginary parts of the third-order nonlinear optical susceptibility (Re χ3), (Im χ3) of the investigated samples are calculated. It was found that the β values decrease with increase in on-axis input intensity I0. Also, these values are found to be proportional with sample concentrations. The excited-state absorption cross sections were calculated to be at σex=5.08×10-14 cm2 for the (SWCNT) and at 15.1×10-14 cm2 for the ADC polymer. It was found that the σex is larger than ground-state absorption cross sections, indicating that the reverse saturable absorption mechanism (RSA) is the dominating mechanism for the observed absorption nonlinearities.

  2. Assay of phospholipase A2 with E. coli membrane doped by 3H-arachidonic acid

    Objective: To develop a new radiochemistry method to assay the secretory phospholipase A2 (sPLA2) and cytosolic phospholipase A2 (cPLA2) with a same substrate. Methods: E.coli membrane doped by 3H-arachidonic acid was prepared and hydrolyzed by PLA2 in certain condition, and the enzyme activity was expressed with the hydrolyzing rate. Results: Intra-day coefficient of variation (CV) of cPLA2 was 5.2% and inter-day CV was 10.9%, and 4.9% and 7.8% for sPLA2 respectively. Results of a series proportional dilution assay showed a good linear relationship. Serum sPLA2 activities of patients with acute cholecystitis were significantly higher than that of normal control subjects. There was a significant difference of activities of sPLA2 and cPLA2 between the endotoxin induced leukemia cell K562 and control. Conclusions: This method is specific, stable and sensitive, it may be used in clinical and scientific research

  3. Photophysical characterization of cumarin-doped poly (lactic acid) microparticles and visualization of the biodistribution

    We prepared fluorescent coumarin dye-doped poly (acrylic acid) microparticles, which are well known as a biodegradable polyester, and the photophysical properties were characterized by scanning electron microscope, atomic force microscope and spectroscopic investigation. Spherical particles with diameters ranging from 0.5 to a few μm were obtained. Based on spectroscopic investigation, the internal environment was close to that of a polar solvent such as methanol, and the dyes were dispersed without aggregation inside the particles. The obtained particles were administered to a mouse through the tail vein, and the biodistribution was then observed after some organs were excited at 1-day and 1-week post-injection. The particles were accumulated in the organs, especially in the lung and spleen. After injection, the particles were trapped temporally in the lung, and then seemed to be transported to other organs by blood circulation. This tendency is similar to the biodistribution of TiO2 microparticles that we have reported previously.

  4. Photophysical characterization of cumarin-doped poly (lactic acid) microparticles and visualization of the biodistribution

    Abe, Shigeaki, E-mail: sabe@den.hokudai.ac.j [Department of Biomedical Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Sapporo 060-8586 (Japan); Kiba, Takayuki; Hosokawa, Kiyotada; Nitobe, Satoru; Hirota, Takashi; Kobayashi, Hirohisa [Division of Biotechnology and Macromolecular Chemistry, Graduate School of Hokkaido University, Sapporo 060-8628 (Japan); Akasaka, Tsukasa; Uo, Motohiro; Kuboki, Yoshinori [Department of Biomedical Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Sapporo 060-8586 (Japan); Sato, Shin-Ichiro [Division of Biotechnology and Macromolecular Chemistry, Graduate School of Hokkaido University, Sapporo 060-8628 (Japan); Watari, Fumio [Department of Biomedical Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Sapporo 060-8586 (Japan); Rosca, Iosif D. [Faculty of Engineering and Computer Science, Concordia University, 1455 de Maisonneuve Blvd. W, Montreal, QC H3G 1M8 (Canada)

    2010-08-15

    We prepared fluorescent coumarin dye-doped poly (acrylic acid) microparticles, which are well known as a biodegradable polyester, and the photophysical properties were characterized by scanning electron microscope, atomic force microscope and spectroscopic investigation. Spherical particles with diameters ranging from 0.5 to a few {mu}m were obtained. Based on spectroscopic investigation, the internal environment was close to that of a polar solvent such as methanol, and the dyes were dispersed without aggregation inside the particles. The obtained particles were administered to a mouse through the tail vein, and the biodistribution was then observed after some organs were excited at 1-day and 1-week post-injection. The particles were accumulated in the organs, especially in the lung and spleen. After injection, the particles were trapped temporally in the lung, and then seemed to be transported to other organs by blood circulation. This tendency is similar to the biodistribution of TiO{sub 2} microparticles that we have reported previously.

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

    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 × 1019 cm−3 was realized by 1000-times laser shots at a laser energy of 1.0 J/cm2, 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

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

    Takahashi, Kouta, E-mail: ktakahas@alice.xtal.nagoya-u.ac.jp, E-mail: kurosawa@alice.xtal.nagoya-u.ac.jp; Sakashita, Mitsuo; Takeuchi, Wakana; Nakatsuka, Osamu [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kurosawa, Masashi, E-mail: ktakahas@alice.xtal.nagoya-u.ac.jp, E-mail: kurosawa@alice.xtal.nagoya-u.ac.jp [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Ikenoue, Hiroshi [Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Zaima, Shigeaki [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    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.

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

    Takahashi, Kouta; Kurosawa, Masashi; Ikenoue, Hiroshi; Sakashita, Mitsuo; Takeuchi, Wakana; Nakatsuka, Osamu; 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 × 1019 cm-3 was realized by 1000-times laser shots at a laser energy of 1.0 J/cm2, 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.

  8. High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

    Li, Qingfeng; Jensen, Jens Oluf; Savinell, Robert F;

    2009-01-01

    havebeenmadeincluding spectroscopy,wateruptake and acid doping, thermal and oxidative stability, conductivity, electro-osmoticwater drag, methanol crossover, solubility and permeability of gases, and oxygen reduction kinetics. Related fuel cell technologies such as electrode and MEA fabrication have been developed...... with synthetically modified or N-substituted structures have been synthesized. Techniques for membrane casting from organic solutions and directly from acid solutions have been developed. Ionic and covalent cross-linking as well as inorganic–organic composites has been explored. Membrane characterizations......-term durability with a degradation rate of 5Vh−1 has been achieved under continuous operation with hydrogen and air at 150–160 ◦C. With load or thermal cycling, a performance loss of 300V per cycle or 40Vh−1 per operating hour was observed. Further improvement should be done by, e.g. optimizing the thermal...

  9. Oxygen reduction reaction over nitrogen-doped graphene oxide cathodes in acid and alkaline fuel cells at intermediate temperatures

    Highlights: • ORR for nitrogen-doped graphene in acid and alkaline fuel cells at intermediate temperatures. • Nitrogen-doped graphene had higher activity for the ORR than graphene. • The ORR activity was enhanced by an increase in the operating temperature. • The ORR activity was kept for long time in both acid and alkaline fuel cells. - Abstract: Graphene oxides with various nitrogen contents were prepared by annealing them in an NH3 flow between 350 and 850 °C, and their electrocatalytic properties toward the oxygen reduction reaction (ORR) in acid and alkaline fuel cells at intermediate temperatures were investigated. In both acid and alkaline fuel cells, graphene oxide treated with NH3 at 700 °C for 1 h was the most active cathode at operating temperatures between 75 and 200 °C, where the ORR activity was enhanced by an increase in the operating temperature. This cathode also exhibited high chemical and thermal stability toward the ORR. X-ray photoelectron and Raman spectroscopic measurements of the nitrogen-doped graphene oxides indicated that the pyridinic nitrogen introduced disordered edge planes into the graphene structure. BET analysis also revealed that the surface area of graphene oxide was increased by the exposure of such edge planes. These observations lead to the assumption that the defects introduced by pyridinic nitrogen act as active sites for the ORR. Considering the similarity in ORR activity between the acid and alkaline fuel cells, dissociative adsorption of O2 at the active site is a rate-determining step

  10. N-Co-O Triply Doped Highly Crystalline Porous Carbon: An Acid-Proof Nonprecious Metal Oxygen Evolution Catalyst.

    Yang, Shiliu; Zhan, Yi; Li, Jingfa; Lee, Jim Yang

    2016-02-10

    In comparison with nonaqueous Li-air batteries, aqueous Li-air batteries are kinetically more facile and there is more variety of non-noble metal catalysts available for oxygen electrocatalysis, especially in alkaline solution. The alkaline battery environment is however vulnerable to electrolyte carbonation by atmospheric CO2 resulting in capacity loss over time. The acid aqueous solution is immune to carbonation but is limited by the lack of effective non-noble metal catalysts for the oxygen evolution reaction (OER). This is contrary to the oxygen reduction reaction (ORR) in acid solution where a few good candidates exist. We report here the development of a N-Co-O triply doped carbon catalyst with substantial OER activity in acid solution by the thermal codecomposition of polyaniline, cobalt salt and cyanamide in nitrogen. Cyanamide and the type of cobalt precursor salt were found to determine the structure, crystallinity, surface area, extent of Co doping and consequently the OER activity of the final carbon catalyst in acid solution. We have also put forward some hypotheses about the active sites that may be useful for guiding further work. PMID:26795393

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

    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.

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

    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

  13. Development of Sensitive Analytical Approach for the Quantification of α-Lipoic Acid Using Boron Doped Diamond Electrode.

    Stankovic, Dalibor M; Mehmeti, Eda; Kalcher, Kurt

    2016-01-01

    A boron doped diamond (BDD) electrode was investigated for use as an electrochemical sensor for α-lipoic acid (LA) using amperometric and differential pulse voltammetric detection. LA displays a well expressed oxidation peak at +0.9 V vs. Ag/AgCl in solutions with a pH value of 3. It was found that signals obtained are linearly related to the concentration range from 0.3 to 105 μM with detection limit of 0.088 μM. Interferences by common compounds such as ascorbic acid, uric acid and dopamine were tested and the method was successfully applied to the determination of LA in human body fluids where it gave recoveries in the range from 95 to 97%. PMID:27506710

  14. Polybenzimidazole and sulfonated polyhedral oligosilsesquioxane composite membranes for high temperature polymer electrolyte membrane fuel cells

    Aili, David; Allward, Todd; Alfaro, Silvia Martinez;

    2014-01-01

    Composite membranes based on poly(2,2′(m-phenylene)-5,5́bibenzimidazole) (PBI) and sulfonated polyhedral oligosilsesquioxane (S-POSS) with S-POSS contents of 5 and 10wt.% were prepared by solution casting as base materials for high temperature polymer electrolyte membrane fuel cells. With membranes...... based on pure PBI as a reference point, the composite membranes were characterized with respect to spectroscopic and physicochemical properties. After doping with phosphoric acid, the composite membranes showed considerably improved ex situ proton conductivity under anhydrous as well as under fully...... humidified conditions in the 120-180°C temperature range. The conductivity improvements were also confirmed by in situ fuel cell tests at 160°C and further supported by the electrochemical impedance spectroscopy data based on the operating membrane electrode assemblies, demonstrating the technical...

  15. Polybenzimidazole and sulfonated polyhedral oligosilsesquioxane composite membranes for high temperature polymer electrolyte membrane fuel cells

    Composite membranes based on poly(2,2′(m-phenylene)-5,5′bibenzimidazole) (PBI) and sulfonated polyhedral oligosilsesquioxane (S-POSS) with S-POSS contents of 5 and 10 wt.% were prepared by solution casting as base materials for high temperature polymer electrolyte membrane fuel cells. With membranes based on pure PBI as a reference point, the composite membranes were characterized with respect to spectroscopic and physicochemical properties. After doping with phosphoric acid, the composite membranes showed considerably improved ex situ proton conductivity under anhydrous as well as under fully humidified conditions in the 120-180 °C temperature range. The conductivity improvements were also confirmed by in situ fuel cell tests at 160 °C and further supported by the electrochemical impedance spectroscopy data based on the operating membrane electrode assemblies, demonstrating the technical feasibility of the novel electrolyte materials

  16. Study of pure and L-tartaric acid doped ammonium dihydrogen phosphate single crystals: A novel nonlinear optical non-centrosymmetric crystal

    Hasmuddin, Mohd, E-mail: mhasmu@gmail.com [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Singh, Preeti [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Shkir, Mohd [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Department of Physics, School of Science, King Khalid University, P.O. Box. 9004, Abha 61413 (Saudi Arabia); Abdullah, M.M. [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Promising Centre for Sensors and Electronic Devices (PCSED), Department of Physics, College of Science and Arts, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Vijayan, N. [CSIR – National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110 012 (India); Ganesh, V. [Department of Physics, Kakatiya University, Warangal, Andhra Pradesh 506009 (India); Wahab, M.A., E-mail: mwahab@jmi.ac.in [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India)

    2014-04-01

    Single crystals of pure and L-tartaric acid (LTA) C{sub 4}H{sub 6}O{sub 6} doped ammonium dihydrogen phosphate (ADP) (NH{sub 4}) H{sub 2}PO{sub 4} were grown by slow evaporation solution technique (SEST) at ambient conditions. Powder X-ray diffraction (PXRD) analysis was carried out to confirm the crystal structure and no additional phase was observed due to doping except a systematic variation in peak intensities. Fourier transform infrared spectral analysis was done to examine the presence of various functional groups in the grown crystals. UV–VIS–NIR spectroscopic analysis was carried out to see the change in optical transparency of pure ADP and crystals due to LTA with different doping concentrations. Second harmonic generation (SHG) efficiency measurement was done to examine the enhancement in the nonlinear optical characteristics of the grown crystals. The effect of LTA dopant on crystal morphology, thermal and mechanical properties of ADP have also been presented in this paper. The above studies reveal the effect of incorporation of LTA into the lattice of ADP crystals. - Highlights: • LTA doped ADP crystals were grown for the first time. • Optical transmission was found to be higher at 1 mol% LTA doping. • SHG was found to be enhanced nonlinearly due to doping. • Thermal stability was found to higher at 1 mol% LTA doping. • Hardness was found to be increases with doping.

  17. Tartaric acid-assisted co-precipitation synthesis of Er3+-doped Lu2O3 nanopowders

    Neng Li Wang; Xi Yan Zhang; Peng He Wang

    2012-01-01

    Erbium-doped lutetia nanopowders were synthesized by a novel co-precipitation method using tartaric acid as precipitant.The properties of the samples were investigated by Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD),TG-DSC,field emission scanning electron microscopy (FE-SEM),and upeonversion luminescence analysis.Pure cubic Lu2O3 nanopowders were directly obtained when the precursor was calcined at 800 ℃ for 2 h,the samples showed strong upconversion luminescence under excitation of 980 nm laser diode.

  18. Parametric investigations on proton conducting membrane by radiation induced grafting of 4-vinylpyridine onto poly(vinylidene fluoride) and phosphoric acid doping

    Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films followed by doping with PA. The effect of grafting conditions on the degree of grafting (G%) was investigated. The acid doping conditions (G%, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were characterized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The membranes showed a thermal stability up to a temperature of ∝ 160 C, above which they undergo a multi-step degradation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in G% (doping level) and the temperature with a maximum proton conductivity of 62 mS cm-1 achieved at 100 C without any humidification. The results of the present study show that the prepared membrane has a potential to be proposed for operating polymer electrolyte membrane fuel cell above 80 C. (orig.)

  19. Parametric investigations on proton conducting membrane by radiation induced grafting of 4-vinylpyridine onto poly(vinylidene fluoride) and phosphoric acid doping

    Shamsaei, E.; Saidi, H. [Universiti Teknologi Malaysia, Kuala Lumpur (Malaysia). Inst. of Hydrogen Economy (IHE); Nasef, M.M. [Universiti Teknologi Malaysia, Kuala Lumpur (Malaysia). Inst. of Hydrogen Economy (IHE); Malaysia Japan International Institute of Technology (MJIIT), Kuala Lumpur (Malaysia); Yahaya, A.H. [Malaya Univ., Kuala Lumpur (Malaysia). Chemistry Dept.

    2014-07-01

    Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films followed by doping with PA. The effect of grafting conditions on the degree of grafting (G%) was investigated. The acid doping conditions (G%, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were characterized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The membranes showed a thermal stability up to a temperature of ∝ 160 C, above which they undergo a multi-step degradation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in G% (doping level) and the temperature with a maximum proton conductivity of 62 mS cm{sup -1} achieved at 100 C without any humidification. The results of the present study show that the prepared membrane has a potential to be proposed for operating polymer electrolyte membrane fuel cell above 80 C. (orig.)

  20. Transient Fluorescence Spectroscopy and laser induced fluorescence lifetimes of terbium doped dipicolinic acid

    Makoui, Anali

    We have investigated the use of deep UV laser induced fluorescence for the sensitive detection and spectroscopic lifetime studies of terbium doped dipicolinic acid (DPA-Tb) and used this to study the optical characteristics of DPA which is a chemical surrounding most bacterial spores. Background absorption spectra, fluorescence spectra, and Excitation Emission Matrix (EEM) spectra were made of the DPA-Tb complex, using both fixed 266 nm wavelength and tunable (220 nm--280 nm) UV laser excitations. Of importance, the fluorescence lifetimes of the four main fluorescence peaks (488 nm, 543 nm, 581 nm, and 618 nm) of the DPA-Tb complex have been measured for the first time to our knowledge. The lifetimes of all the fluorescing lines have been measured as a function of DPA-Tb concentration, solvent pH, and solvent composition, including that for the weakest fluorescing line of DPA-Tb at 618 nm. In addition, a new spectroscopic lifetime measurement technique, which we call "Transient Fluorescence Spectroscopy", was developed. In this technique, a weak, quasi-CW, amplitude modulated UV laser (8.5 kHz) was used to measure the lifetimes of the fluorescence lines, and yields insight into energy transfer and excitation lifetimes within the system. This technique is especially useful when a high power laser is not either available or not suitable. In the latter case, this would be when a high power pulsed deep-UV laser could produce bleaching or destruction of the biological specimen. In addition, this technique simulated the excitation and fluorescence emission of the DPA-Tb using a 4-level energy model, and solved the dynamic transient rate equations to predict the temporal behavior of the DPA-Tb emitted fluorescence. Excellent agreement between the experiments and the simulation were found. This technique has the potential to provide a more accurate value for the fluorescence lifetime values. In addition, with the use of asymmetric excitation waveforms, the dynamic

  1. Exceptional durability enhancement of PA/PBI based polymer electrolyte membrane fuel cells for high temperature operation at 200°C

    Aili, David; Zhang, Jin; Jakobsen, Mark Tonny Dalsgaard; Zhu, Haijin; Yang, Tianyu; Liu, Jian; Forsyth, Maria; Pan, Chao; Jensen, Jens Oluf; Cleemann, Lars Nilausen; Jiang, San Ping; Li, Qingfeng

    2016-01-01

    The incorporation of phosphotungstic acid functionalized mesoporous silica in phosphoric acid doped polybenzimidazole (PA/PBI) substantially enhances the durability of PA/PBI based polymer electrolyte membrane fuel cells for high temperature operation at 200°C.......The incorporation of phosphotungstic acid functionalized mesoporous silica in phosphoric acid doped polybenzimidazole (PA/PBI) substantially enhances the durability of PA/PBI based polymer electrolyte membrane fuel cells for high temperature operation at 200°C....

  2. Enhanced forward osmosis from chemically modified polybenzimidazole (PBI) nanofiltration hollow fiber membranes with a thin wall

    Wang, Kai Yu

    2009-04-01

    To develop high-flux and high-rejection forward osmosis (FO) membranes for water reuses and seawater desalination, we have fabricated polybenzimidazole (PBI) nanofiltration (NF) hollow fiber membranes with a thin wall and a desired pore size via non-solvent induced phase inversion and chemically cross-linking modification. The cross-linking by p-xylylene dichloride can finely tune the mean pore size and enhance the salt selectivity. High water permeation flux and improved salt selectivity for water reuses were achieved by using the 2-h modified PBI NF membrane which has a narrow pore size distribution. Cross-linking at a longer time produces even a lower salt permeation flux potentially suitable for desalination but at the expense of permeation flux due to tightened pore sizes. It is found that draw solution concentration and membrane orientations are main factors determining the water permeation flux. In addition, effects of membrane morphology and operation conditions on water and salt transport through membrane have been investigated. © 2008 Elsevier Ltd. All rights reserved.

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

    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. PMID:26183235

  4. A Study on Tannic Acid-doped Polypyrrole Films on Gold Electrodes for Selective Electrochemical Detection of Dopamine

    Shouzhuo Yao

    2005-04-01

    Full Text Available Tannic acid-doped polypyrrole (PPY/TA films have been grown on goldelectrodes for selective electrochemical detection of dopamine (DA. Electrochemicalquartz crystal microbalance (EQCM studies revealed that, in vivid contrast toperchlorate-doped polypyrrole films (PPY/ClO4-, the redox switching of PPY/TA filmsin aqueous solutions involved only cation transport if the solution pH was greater than3~4. The PPY/TA Au electrodes also exhibited attractive permselectivity forelectroactive cations, namely, effectively blocking the electrochemical reactions ofanionic ferricyanide and ascorbic acid (AA while well retaining the electrochemicalactivities of hexaammineruthenium (III and dopamine as cationic species. A 500 HzPPY/TA film could effectively block the redox current of up to 5.0 mM AA. Thecoexistence of ascorbic acid in the measurement solution notably enhanced the currentsignal for dopamine oxidation, due probably to the chemical regeneration of dopaminethrough an ascorbic acid-catalyzed reduction of the electro-oxidation product ofdopamine (EC’ mechanism, and the greatest amplification was found at an ascorbic acidconcentration of 1.0 mM. The differential pulse voltammetry peak current for DAoxidation was linear with DA concentration in the range of 0 to 10 μM, with sensitivityof 0.125 and 0.268 μA/μM, as well as lower detection limit of 2.0 and 0.3 μM in a PBSsolution without AA and with 1.0 mM coexisting AA, respectively.

  5. Mechanochemically assisted solid-state and citric acid complex syntheses of Cu-doped sodium cobaltite ceramics

    Pršić, S., E-mail: sanjaprsic@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia); Savić, S.M., E-mail: slavicas@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia); Branković, Z., E-mail: zorica.brankovic@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia); Vrtnik, S., E-mail: stane.vrtnik@ijs.si [Institute Jožef Stefan, Condensed Matter Physics, Jamova cesta 39, 1000 Ljubljana (Slovenia); Dapčević, A., E-mail: hadzi-tonic@tmf.bg.ac.rs [Department of General and Inorganic Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade (Serbia); Branković, G., E-mail: goran.brankovic@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia)

    2015-08-15

    Highlights: • Sodium cobaltite was synthesized by mechanochemically assisted solid-state reaction and citric acid complex (CAC) method. • We investigated effect of Cu-doping in NaCo{sub 2−x}Cu{sub x}O{sub 4} (x = 0, 0.01, 0.03, 0.05). • ICP analysis showed that the controlling of the samples composition is easier by the CAC method. • The Seebeck coefficient in Cu-doped samples was higher compared to the undoped one. • The highest figure of merit was observed in the sample with the lowest Cu concentration. - Abstract: In the last decade, the sodium cobaltite ceramic became a promising candidate for potential thermoelectric applications, because of its large thermopower and low resistivity. In this work, polycrystalline samples of NaCo{sub 2−x}Cu{sub x}O{sub 4} (x = 0, 0.01, 0.03, 0.05) were prepared using mechanochemically assisted solid-state reaction method (MASSR) and the citric acid complex method (CAC). Bulk samples were prepared by pressing into disc-shaped pellets and subsequently subjected to a thermal treatment at 880 °C in inert argon atmosphere. Changes in structural and microstructural characteristics of the samples, caused by the substitution of Cu for Co, were characterized using X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM), respectively. The results of inductively coupled plasma (ICP) analysis showed that the compositions of the final products correspond to γ-NaCo{sub 2}O{sub 4} and confirmed that desired compound was obtained in both syntheses procedures. The advantages and disadvantages of these two syntheses procedures have been observed and discussed: the CAC method enabled obtaining samples with higher density and fine microstructure compared to the MASSR method, thus better thermoelectric properties. The Cu{sup 2+} substitution led to the increase in Seebeck coefficient in both synthesis routes. The highest figure of merit of 0.022 at 300 K was observed for the sample doped with 1 mol% Cu, obtained by

  6. Photo-catalytic decolourisation of toxic dye with N-doped titania: A case study with Acid Blue 25

    Dhruba Chakrabortty; Susmita Sen Gupta

    2013-01-01

    Dyes are one of the hazardous water pollutants.Toxic Acid Blue 25,an anthraquinonic dye,has been decolourised by photo-catalysing it with nitrogen doped titania in aqueous medium.The photo catalyst was prepared from 15% TiCl3 and 25% aqueous NH3 solution as precursor.XRD and TEM revealed the formation of well crystalline anatase phase having particle size in the nano-range.BET surface area of the sample was higher than that of pure anatase TiO2.DRS showed higher absorption of radiation in visible range compared to pure anatase TiO2.XPS revealed the presence of nitrogen in N-Ti-O environment.The experimental parameters,namely,photocatalyst dose,initial dye concentration as well as solution pH influence the decolourisation process.At pH 3.0,the N-TiO2 could decolourise almost 100% Acid Blue 25 within one hour.The influence of N-TiO2 dose,initial concentration of Acid Blue 25 and solution pH on adsorption-desorption equilibrium is also studied.The adsorption process follows Lagergren first order kinetics while the modified Langmuir-Hinselwood model is suitably fitted for photocatalytic decolourisation of Acid Blue 25.

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

    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. PMID:27157730

  8. Thin film thermocouples for in situ membrane electrode assembly temperature measurements in a polybenzimidazole-based high temperature proton exchange membrane unit cell

    Ali, Syed Talat; Lebæk, Jesper; Nielsen, Lars Pleth;

    2010-01-01

    This paper presents Type-T thin film thermocouples (TFTCs) fabricated on Kapton (polyimide) substrate for measuring the internal temperature of PBI(polybenzimidazole)-based high temperature proton exchange membrane fuel cell (HT-PEMFC). Magnetron sputtering technique was employed to deposit a 2 mu...

  9. Shear bond strength of orthodontic brackets after acid-etched and erbium-doped yttrium aluminum garnet laser-etched

    Alavi, Shiva; Birang, Reza; Hajizadeh, Fatemeh

    2014-01-01

    Background: Laser ablation has been suggested as an alternative method to acid etching; however, previous studies have obtained contrasting results. The purpose of this study was to compare the shear bond strength (SBS) and fracture mode of orthodontic brackets that are bonded to enamel etched with acid and erbium-doped yttrium aluminum garnet (Er:YAG) laser. Materials and Methods: In this experimental in vitro study, buccal surfaces of 15 non-carious human premolars were divided into mesial and distal regions. Randomly, one of the regions was etched with 37% phosphoric acid for 15 s and another region irradiated with Er:YAG laser at 100 mJ energy and 20 Hz frequency for 20 s. Stainless steel brackets were then bonded using Transbond XT, following which all the samples were stored in distilled water for 24 h and then subjected to 500 thermal cycles. SBS was tested by a chisel edge, mounted on the crosshead of universal testing machine. After debonding, the teeth were examined under ×10 magnification and adhesive remnant index (ARI) score determined. SBS and ARI scores of the two groups were then compared using t-test and Mann-Whitney U test. Significant level was set at P < 0.05. Results: The mean SBS of the laser group (16.61 ± 7.7 MPa) was not significantly different from that of the acid-etched group (18.86 ± 6.09 MPa) (P = 0.41). There was no significant difference in the ARI scores between two groups (P = 0.08). However, in the laser group, more adhesive remained on the brackets, which is not suitable for orthodontic purposes. Conclusion: Laser etching at 100 mJ energy produced bond strength similar to acid etching. Therefore, Er:YAG laser may be an alternative method for conventional acid-etching. PMID:25097641

  10. Shear bond strength of orthodontic brackets after acid-etched and erbium-doped yttrium aluminum garnet laser-etched

    Shiva Alavi

    2014-01-01

    Full Text Available Background: Laser ablation has been suggested as an alternative method to acid etching; however, previous studies have obtained contrasting results. The purpose of this study was to compare the shear bond strength (SBS and fracture mode of orthodontic brackets that are bonded to enamel etched with acid and erbium-doped yttrium aluminum garnet (Er:YAG laser. Materials and Methods: In this experimental in vitro study, buccal surfaces of 15 non-carious human premolars were divided into mesial and distal regions. Randomly, one of the regions was etched with 37% phosphoric acid for 15 s and another region irradiated with Er:YAG laser at 100 mJ energy and 20 Hz frequency for 20 s. Stainless steel brackets were then bonded using Transbond XT, following which all the samples were stored in distilled water for 24 h and then subjected to 500 thermal cycles. SBS was tested by a chisel edge, mounted on the crosshead of universal testing machine. After debonding, the teeth were examined under Χ10 magnification and adhesive remnant index (ARI score determined. SBS and ARI scores of the two groups were then compared using t-test and Mann-Whitney U test. Significant level was set at P < 0.05. Results: The mean SBS of the laser group (16.61 ± 7.7 MPa was not significantly different from that of the acid-etched group (18.86 ± 6.09 MPa (P = 0.41. There was no significant difference in the ARI scores between two groups (P = 0.08. However, in the laser group, more adhesive remained on the brackets, which is not suitable for orthodontic purposes. Conclusion: Laser etching at 100 mJ energy produced bond strength similar to acid etching. Therefore, Er:YAG laser may be an alternative method for conventional acid-etching.

  11. Preparation and characterization of mesoporous N-doped and sulfuric acid treated anatase TiO2 catalysts and their photocatalytic activity under UV and Vis illumination

    Nitrogen-doped TiO2 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 N2-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 (aBETS) 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 (λg,1=∼390 nm, λg,2=∼510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO2 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 TiO2 samples were more catalytically active than non-doped TiO2 catalysts. - Graphical abstract: The effect of the acid treatment on the visible-light-driven photocatalytic activity of the N-doped, anatase TiO2 catalysts.

  12. Conversion of pristine and p-doped sulfuric-acid-treated single-walled carbon nanotubes to n-type materials by a facile hydrazine vapor exposure process

    Wang, Pen-Cheng, E-mail: wangpc@ess.nthu.edu.tw [Department of Engineering and System Science, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); Liao, Yu-Chun [Department of Engineering and System Science, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Lai, Yu-Ling; Lin, Ying-Chang [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Su, Ching-Yuan; Tsai, Chuen-Horng [Department of Engineering and System Science, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); Hsu, Yao-Jane, E-mail: yjhsu@nsrrc.org.tw [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Discovery of a facile method to n-dope carbon nanotubes by vapor-phase hydrazine. Black-Right-Pointing-Pointer Confirming covalently bound sulfonic groups on CNTs treated with sulfuric acid. Black-Right-Pointing-Pointer Spectroscopic investigation of CNTs' bonding structures after hydrazine treatment. Black-Right-Pointing-Pointer Proposing a cycloaddition reaction between graphenic domains of CNTs and reactive nitrogen-containing radicals thermally decomposed from hydrazine. Black-Right-Pointing-Pointer Establishing aziridine as a probable n-doping chemical entity on hydrazine-treated CNTs. - Abstract: It was found in this study that a facile vapor-phase hydrazine (N{sub 2}H{sub 4}) treatment could effectively convert pristine and even p-doped sulfuric-acid-treated single-walled cabon nanotubes (SWCNTs) to n-type materials. The Raman spectroscopy results show that the facile vapor-phase hydrazine treatment could suppress the intensity of SWCNTs' radial breathing modes and alter SWCNTs' D-band vs. G-band intensity ratio. The sheet resistance measurement results show that the n-doping effect exerted by the vapor-phase hydrazine treatment could overwhelmingly counteract sulfuric acid's p-doping effect and subdue the SWCNTs' acquired p-type characteristics rendered by the sulfuric acid treatment. The ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy results suggest that certain reactive nitrogen-containing radicals thermally decomposed from hydrazine, such as nitrene and amidogen, could covalently functionalize CNTs and then n-dope the functionalzed CNTs.

  13. Chlorine-doped reduced graphene oxide nanosheets as an efficient and stable electrode for supercapacitor in acidic medium.

    Kakaei, Karim; Hamidi, Milad; Husseindoost, Somayeh

    2016-10-01

    We demonstrate the efficient doping of reduced graphene oxide (RGO) by Chlorine and its capacitive performance was calculated by cyclic voltammetry and charge-discharge cycling in 1M H2SO4 solution. In this regard, we are prepared RGO nanosheets through a simple, eco-friendly and efficient electrochemical method, with selectively functionalized edges by chlorine which involves added the RGO to the halogen-containing acid solution and dispersed by ultrasonic. After synthesis, Cl-RGO is characterized using X-ray diffraction, Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, Energy-dispersive X-ray (EDX) spectroscopy and tunneling electron microscopy. FTIR spectra show the chlorine-containing functional groups. Energy-dispersive X-ray spectroscopy analysis confirmed the presence of doped chlorine in RGO. Raman spectroscopy shows a high density of defects in the RGO layer. Electrochemical characteristics of Cl-RGO are characterized by cyclic voltammetery, galvanostatic charge/discharge and electrochemical impedance spectroscopy. According to the galvanostatic charge/discharge analysis, Cl-RGO represents specific capacitance (Cs) of 178.4Fg(-1) at current density of 1Ag(-1), which is higher than that of RGO (100.5Fg(-1)) in H2SO4 solution. PMID:27388125

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

    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.

  15. Cyclic voltammetry and impedance studies of electrodeposited polypyrrole nanoparticles doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt

    Ebrahim, Sh. M., E-mail: shebrahim@igsr.alex.edu.e [Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Postal Code 21526, Alexandria (Egypt); Latif, M.M. Abd-El [Mubarak City for Scientific Research and Technology Applications, Institute of Advanced Technology and New Materials, Borg El-Arab City, Alexandria (Egypt); Gad, A.M.; Soliman, M.M. [Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Postal Code 21526, Alexandria (Egypt)

    2010-05-31

    Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPSNa), was carried out using chronoamperometric technique. Cyclic voltammetry measurements showed that the electroactivity of PPY films, doped with AMPSNa, increases with the film thickness. Scanning electron microscopy photographs revealed that the PPY particles are in the nano-scale range and that their size depends on the potential at which the PPY has formed. Electrochemical impedance spectroscopy (EIS), in the potential range of + 1.0 and - 1.0 V, revealed in the PPY film charge transfer domination with a semicircle at high frequencies, and anion diffusion dominance at low frequencies. EIS also showed that the charge transfer resistance of PPY film at - 1.0 V is lower than what is expected and that on increasing the thickness of the PPY films, the overall impedance decreases. The proposed equivalent circuit model, based on the double layer capacity and the Warburg impedance, was replaced by two constant-phase elements to fit the experimental work of this study. The values of the fractional exponent of the first constant phase element at approximately 0.5 indicate that the processes have a diffusion-limited nature.

  16. Nitrogen-doped carbon-TiO2 composite as support of Pd electrocatalyst for formic acid oxidation

    Qin, Yuan-Hang; Li, Yunfeng; Lam, Thomas; Xing, Yangchuan

    2015-06-01

    We report Pd nanoparticles supported on a composite consisting of oxide TiO2 and nitrogen-doped carbon for formic acid oxidation (FAO). The nitrogen-doped carbon-TiO2 (NCx-TiO2) composite support was prepared by a simple polymerization-pyrolysis process using commercial TiO2 nanoparticles (P25). Surface analysis showed that elements of Ti, C, O, and N were present on the composite surface, on which nitrogen existed in both pyridinic and quaternary forms. Pd nanoparticles with a mean size of ca. 4 nm were uniformly deposited on the composite via a polyol process. Electrochemical characterizations showed that the NCx-TiO2-supported Pd particles (Pd/NCx-TiO2) exhibited an electrocatalytic activity towards FAO that almost doubled that of the carbon black-supported Pd particles (Pd/C) with much enhanced electrocatalytic stability. The better performance of the composite supported Pd was attributed to a possible electronic structure modification in the metallic Pd particles and bifunctional effect produced by the NCx-TiO2 composite.

  17. Cyclic voltammetry and impedance studies of electrodeposited polypyrrole nanoparticles doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt

    Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPSNa), was carried out using chronoamperometric technique. Cyclic voltammetry measurements showed that the electroactivity of PPY films, doped with AMPSNa, increases with the film thickness. Scanning electron microscopy photographs revealed that the PPY particles are in the nano-scale range and that their size depends on the potential at which the PPY has formed. Electrochemical impedance spectroscopy (EIS), in the potential range of + 1.0 and - 1.0 V, revealed in the PPY film charge transfer domination with a semicircle at high frequencies, and anion diffusion dominance at low frequencies. EIS also showed that the charge transfer resistance of PPY film at - 1.0 V is lower than what is expected and that on increasing the thickness of the PPY films, the overall impedance decreases. The proposed equivalent circuit model, based on the double layer capacity and the Warburg impedance, was replaced by two constant-phase elements to fit the experimental work of this study. The values of the fractional exponent of the first constant phase element at approximately 0.5 indicate that the processes have a diffusion-limited nature.

  18. Electrochemical Oxidation of Methanol and Formic Acid in Fuel Cell Processes

    Seland, Frode

    2005-01-01

    The main objectives of the thesis work were: (1), to study the oxidation of methanol and formic acid on platinum electrodes by employing conventional and advanced electrochemical methods, and (2), to develop membrane electrode assemblies based on polybenzimidazole membranes that can be used in fuel cells up to 200 °C.D.c. voltammetry and a.c. voltammetry studies of methanol and formic acid on polycrystalline platinum in sulphuric acid electrolyte were performed to determine the mechanism and ...

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

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

    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.

  1. Photoluminescence and thermoluminescence study of KCaSO4Cl doped with Dy and Ce synthesized by acid distillation method

    Photoluminescence and thermoluminescence properties of KCaSO4Cl doped with dysprosium and cerium have been studied. Dy/Ce doped KCaSO4Cl phosphors were synthesized by the acid distillation method. The samples were characterized by XRD, SEM, PL and TL for structural, morphological and luminescence studies. The SEM image analysis of KCaSO4Cl phosphor shows nearly spherical particles with diameter varying between 3–10 μm. In the present host Dy3+ emission at 482 and 573 nm is observed due to 4F9/2→6H15/2 and 4F9/2→6H13/2 transition, respectively, whereas the PL emission spectra of KCaSO4Cl:Ce phosphor shows two luminescence bands at 307 nm and 326 nm and are attributed to the allowed inter configurational transitions from the 5d-level to the 2F5/2 and 2F7/2 levels of Ce3+ ion. Effect of annealing on the structure of the glow curve is investigated for KCaSO4Cl:Dy phosphors. Thermoluminescence linearity has been studied for 0.1–9000 Gy dose of gamma rays. Linear behavior over a large dose range between 0.1 Gy and 170 Gy was found. In addition to this trap parameters of KCaSO4Cl:Dy were studied using computerized glow curve deconvolution. -- Highlights: • The novel phosphor is first time prepared by acid distillation method. • This study reports the thermoluminescence properties of KCaSO4Cl irradiated with gamma rays. • The trapping analysis was done by GCD function and Chen's peak shape method. • Its good photoluminescence property can be utilized in display devices as well. • The phosphor can be used as a good dosimeter for measuring the high doses of γ-rays

  2. Synthesis, characterization and visible light photocatalytic activity of Cr 3+ , Ce 3+ and N co-doped TiO 2 for the degradation of humic acid

    Rashid, S. G.

    2015-01-01

    The synthesis, characterization and photocatalytic activity of Cr3+ and Ce3+ co-doped TiON (N-doped TiO2) for the degradation of humic acid with exposure to visible light is reported. The synthesized bimetal (Cr3+ + Ce3+) modified TiON (Cr-Ce/TiON), with an evaluated bandgap of 2.1 eV, exhibited an enhanced spectral response in the visible region as compared to pure and Ce3+ doped TiON (Ce/TiON). The XRD analysis revealed the insertion of Cr3+ and Ce3+ in the crystal lattice along with Ti4+ and N that resulted in the formation of a strained TiON anatase structure with an average crystallite size of ∼10 nm. Raman analysis also supported the formation of stressed rigid structures after bimetal doping. HRTEM confirmed the homogeneous distribution of both the doped metallic components in the crystal lattice of TiON without the formation of surface oxides of either Cr3+ or Ce3+. Electron energy loss spectroscopy (EELS) analysis revealed no change in the oxidation of either Cr or Ce during the synthesis. The synthesized Cr-Ce/TiON catalyst exhibited appreciable photocatalytic activity for the degradation of humic acid on exposure to visible light. Additionally, a noticeable mineralization of carbon rich humic acid was also witnessed. The photocatalytic activity of the synthesized catalyst was compared with pristine and Ce3+ doped TiON. © The Royal Society of Chemistry 2015.

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

    Baltrusaitis, Jonas; Hatch, Courtney; Orlando, Roberto

    2012-01-01

    The electronic properties of undoped and Ca or Fe doped MgO (001) surfaces, as well as their propensity towards atmospheric acidic gas (CO2, SO2 and NO2) uptake was investigated with an emphasis on gas adsorption on the basic MgO oxygen surface sites, Osurf, using periodic Density Functional Theory (DFT) calculations. Adsorption energy calculations show that MgO doping will provide stronger interactions of the adsorbate with the Osurf sites than the undoped MgO for a given adsorbate molecule....

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

    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.

  5. 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.

    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. PMID:17692891

  6. Thermal stability and surface acidity of mesoporous silica doubly doped by incorporation of sulfate and zirconium ions

    A sulfated Si-Zr-MCM-41 solid with highly ordered mesostructure was synthesized through a templated synthesis route where the CTAB surfactant was used as template. During the synthesis procedure, various amounts of (NH4)2SO4 were added into the mixed solution of Zr and Si precursors to in situ sulfate the MCM-41 solids, aiming to enhance the acidity and thermal stability. The resultant materials showed a long-range ordered hexagonal arrangement with high surface area larger than 797 m2/g and an average pore size distributed at approximate 2.5-2.8 nm. The high-resolution TEM observations confirmed that the order of the mesostructure gained when the molar ratio of SO42-/(ZrO2 + SiO2) increased from 0.1 to 0.3 but decreased as it reached 0.5, which is consistent with the results of 29Si MAS-NMR and XRD analysis. Compared to Si-MCM-41, the (Q2 + Q3)/Q4 ratio derived from the NMR spectra of the Zr-doped sample was higher, indicating that zirconium atoms were incorporated into the silica framework. Unexpectedly, in situ sulfation does not enhance the surface Broensted acidity, most likely due to the sulfur retained within the bulk of the materials; however, it indeed improved the thermal stability of the solid and long-range order of the structure

  7. Adsorption of Acid Yellow-73 and Direct Violet-51 Dyes from Textile Wastewater by Using Iron Doped Corncob Charcoal

    The presence of synthetic dyes in textile industry wastewater lead to deterioration of precious fresh water resources, making the need to remove dyes crucial for environmental protection. Recently, different techniques have been employed to remove these dyes from water resources. Among them, biosorption has gained tremendous popularity due to its eco-friendly nature and inexpensive method. In this study, the removal potential of two acid dyes, i.e. yellow-73 and direct violet-51, was assessed from textile effluent samples using iron modified corncob charcoal. The adsorption efficiency ranged between 93.93 97.96 % and 92.2 - 95.4 % for acid yellow-73 and direct violet-51, respectively. Furthermore, study highlights optimum parameters for successful adsorption of these dyes, such as stirring time (numbers), pH (numbers), temperature (numbers), and adsorbent dosage (numbers). Keeping in consideration these findings, we recommend the use of Iron Doped Corncob Charcoal (IDCC) as a low-cost, efficient alternative for wastewater treatment, primarily minimizing the detrimental effects of hazardous dyes. (author)

  8. Water-free Alkaline Polymer-inorganic Acid Complexes with High Conductivity at Ambient Temperature

    O.V.Chervakov; M.V.Andriianova; V.V.Riabenko; A.V.Markevich; E.M.Shembel; D.Meshri

    2007-01-01

    1 Results Recently increased interest is shown to proton conducting materials based on the alkaline polymer-inorganic acid complexes that is caused by a possibility of their application as the high-temperature electrolyte systems for various electrochemical devices (fuel cells,sensors,lithium power sources etc.).Complexes of inorganic acids with the alkaline polymers (polybenzimidazoles[1],polyvinylpyridines[2]) are characterized by high ionic conductivity at ambient temperatures (up to 10-2 Ω-1·cm-1) a...

  9. Voltammetric behaviour of levodopa and its quantification in pharmaceuticals using a -cyclodextrine doped poly (2,5-diaminobenzenesulfonic acid) modified electrode

    Mehmet Aslanoglu; Aysegul Kutluay; Sultan Goktas; Serpil Karabulut

    2009-03-01

    A cyclic voltammetric method based on a -cyclodextrine doped poly(2,5-diaminobenzenesulfonic acid) modified glassy carbon electrode (GCE) was developed for the determination of levodopa. Compared with bare GCE and poly(2,5-diaminobenzenesulfonic acid)/GCE, the poly(2,5-diaminobenzenesulfonic acid)--cyclodextrine/GCE exhibits a remarkable shift of the oxidation potentials of levodopa in the cathodic direction and a drastic enhancement of the anodic current response. The incorporation of -cyclodextrine into the polymer film exhibited that the electrode provides more stable and sensitive current responses for levodopa. Levodopa exhibited a single broad peak at about 0.6 V at bare GCE. However, at the -cyclodextrine doped poly(2,5-diaminobenzenesulfonic acid)/GCE, a well-defined redox wave of levodopa was obtained, with the oxidation and the reduction peak potential at 0.193 and 0.164 V, respectively. The separation of peak potentials was 29 mV. The linear current response was obtained in the range of 1.0 × 10-6 ∼ 2.0 ∼ 10-4 M with a detection limit of 4.18 ∼ 10-7 M for levodopa, The poly(2,5-diaminobenzenesulfonic acid)--cyclodextrine/GCE was also effective to simultaneously detect levodopa and ascorbic acid. The modified electrode has been successfully applied for the determination of levodopa in pharmaceuticals. The poly(2,5-diaminobenzenesulfonic acid)--cyclodextrine/GCE showed excellent stability and reproducibility.

  10. Graphitic carbon nitride nanosheets doped graphene oxide for electrochemical simultaneous determination of ascorbic acid, dopamine and uric acid

    Graphical abstract: Schematic drawing of electrochemical oxidize AA, DA and UA on graphitic carbon nitride nanosheets-graphene oxide composite modified electrode. - Highlights: • Synthesize g-C3N4, GO and CNNS-GO composite. • CNNS-GO composite was the first time for simultaneous determination of AA, DA and UA. • CNNS-GO/GCE displays fantastic selectivity and sensitivity for AA, DA and UA. • CNNS-GO/GCE was applied to detect real sample with satisfactory results. - Abstract: Graphitic carbon nitride nanosheets with a graphite-like structure have strong covalent bonds between carbon and nitride atoms, and nitrogen atoms in the carbon architecture can accelerate the electron transfer and enhance electrical properties effectually. The graphitic carbon nitride nanosheets-graphene oxide composite was synthesized. And the electrochemical performance of the composite was investigated by cyclic voltammetry and differential pulse voltammetry ulteriorly. Due to the synergistic effects of layer-by-layer structures by π-π stacking or charge-transfer interactions, graphitic carbon nitride nanosheets-graphene oxide composite can improved conductivity, electro-catalytic and selective oxidation performance. The proposed graphitic carbon nitride nanosheets-graphene oxide composite modified electrode was employed for simultaneous determination of ascorbic acid, dopamine and uric acid in their mixture solution, it exhibited distinguished sensitivity, wide linear range and low detection limit. Moreover, the modified electrode was applied to detect urine and dopamine injection sample, and then the samples were spiked with certain concentration of three substances with satisfactory recovery results

  11. The use of polybenzimidazole membranes in vanadium redox flow batteries leading to increased coulombic efficiency and cycling performance

    An issue with conventional vanadium redox flow batteries (VRFB) with Nafion membranes is the crossover of vanadium ions, resulting in low coulombic efficiency and rapid decay in capacity. In this work, a VRFB with a polybenzimidazole (PBI) membrane is tested and compared with the Nafion system. Results show that the PBI-based VRFB exhibits a substantially higher coulombic efficiency of up to 99% at current densities ranging from 20 mA cm−2 to 80 mA cm−2. More importantly, it is demonstrated that the PBI-based VRFB has a capacity decay rate of as low as 0.3% per cycle, which is four times lower than that of the Nafion system (1.3% per cycle). The improved coulombic efficiency and cycling performance are attributed to the low crossover of vanadium ions through the PBI membrane

  12. High fluorescence S, N co-doped carbon dots as an ultra-sensitive fluorescent probe for the determination of uric acid.

    Wang, Haiyan; Lu, Qiujun; Hou, Yuxin; Liu, Yalan; Zhang, Youyu

    2016-08-01

    Sulfur, nitrogen co-doped carbon dots (S, N co-doped C-dots) as highly selective fluorescent probe for uric acid (UA) detection were designed. The S, N co-doped C-dots with high quantum yield of 73.1% were prepared by hydrothermal method. It was found that the fluorescence of S, N co-doped C-dots was quenched apparently by hydroxyl radicals from Fenton reaction between H2O2 and Fe(2+). The production of H2O2 originated from the oxidization of UA by uricase. Therefore, an optical biosensor was developed for the detection of UA based on Fenton reaction and enzymatic reaction. Under the optimized conditions, two linear relationships between the ratio of fluorescence quenching of the C-dots and UA concentration were found in the range of 0.08-10µM and 10-50µM, respectively. The detection limit was down to 0.07µM. Moreover, the proposed biosensor was successfully applied to the detection of uric acid in human serum samples. PMID:27216657

  13. Phosphoric acid doped polysulfone membranes with aminopyridine pendant groups and imidazole cross-links

    Hink, Steffen; Elsøe, Katrine; Cleemann, Lars Nilausen;

    2015-01-01

    Udel polysulfone based membranes with 4-aminopyridine pendant groups and cross-linking imidazole units are synthesized in a simple two step reaction. The ratio of 4-aminopyridine and imidazole is varied and the materials are extensively characterized. The average phosphoric acid uptake (in 85 wt...... tests at 130 °C. The relationships between PA uptake, chemical composition and mechanical stability are reported. Proton conductivity and mechanical properties only depend on the phosphoric acid content, which, however is a function of the chemical composition....

  14. Selective interfacial synthesis of metal-organic frameworks on a polybenzimidazole hollow fiber membrane for gas separation

    Biswal, Bishnu P.; Bhaskar, Anand; Banerjee, Rahul; Kharul, Ulhas K.

    2015-04-01

    Metal-organic frameworks (MOFs) have gained immense attention as new age materials due to their tuneable properties and diverse applicability. However, efforts on developing promising materials for membrane based gas separation, and control over the crystal growth positions on polymeric hollow fiber membranes still remain key challenges. In this investigation, a new, convenient and scalable room temperature interfacial method for growing MOFs (ZIF-8 and CuBTC) on either the outer or inner side of a polybenzimidazole based hollow fiber (PBI-BuI-HF) membrane surface has been achieved in a controlled manner. This was made possible by the appropriate selection of an immiscible solvent pair and the synthetic conditions. The growth of MOFs on the PBI-BuI-HF membrane by the interfacial method was continuous and showed an appreciable gas separation performance, conveying promise for their applicability.Metal-organic frameworks (MOFs) have gained immense attention as new age materials due to their tuneable properties and diverse applicability. However, efforts on developing promising materials for membrane based gas separation, and control over the crystal growth positions on polymeric hollow fiber membranes still remain key challenges. In this investigation, a new, convenient and scalable room temperature interfacial method for growing MOFs (ZIF-8 and CuBTC) on either the outer or inner side of a polybenzimidazole based hollow fiber (PBI-BuI-HF) membrane surface has been achieved in a controlled manner. This was made possible by the appropriate selection of an immiscible solvent pair and the synthetic conditions. The growth of MOFs on the PBI-BuI-HF membrane by the interfacial method was continuous and showed an appreciable gas separation performance, conveying promise for their applicability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00299k

  15. Metal-polybenzimidazole complexes as a nonviral gene carrier: effects of the DNA affinity on gene delivery.

    Huang, Xueying; Dong, Xiongwei; Li, Xue; Meng, Xianggao; Zhang, Dan; Liu, Changlin

    2013-12-01

    The metal complex-based carriers are emerging likely as a new type of gene-delivery systems prone to systematic structural alteration and chemical tailoring. In our work, the DNA affinity of metal complexes with polybenzimidazoles was found to be one of the determinants that can regulate expression of the transgenes. Here, the correlations between the DNA affinity and transfection efficacy were explored by characterizing gene-delivering properties of a series of Co(2+)- and Ca(2+)-polybenzimidazole complexes. The binding equilibrium constants (Kobs) of the divalent metal complexes to DNA, which is considered as a measure of the DNA affinity of metal complexes, were evaluated by isothermal titration calorimetry (ITC) and UV-visible absorption titration. The properties of DNA condensates formed with the metal complexes including sizes, ζ potential and morphology were observed to be altered with Kobs values. The monodispersed spherical condensates were found only for the Ca(2+) complexes whose DNA affinity is weaker than that of the Co(2+) complexes. However, the cell internalization examination indicated that cell uptake of the DNA condensates is independent of homogeneity in their sizes and morphology. The comparison of transgene expression showed that that the Ca(2+) complex-mediated transfection has higher efficiency than the Co(2+) complexes under the conditions tested, and the transfection efficacy cannot be correlated with the cell uptake of DNA condensates. Moreover, the Ca(2+) complexes and their DNA condensates had lower cytotoxicity than the Co(2+) complexes. Thus, the DNA affinity should be one of the factors to be capable of regulating the gene-delivering property of metal complexes. PMID:24099694

  16. Studies of doped negative valve-regulated lead-acid battery electrodes

    Micka, Karel; Calábek, M.; Bača, P.; Křivák, P.; Lábus, R.; Bilko, R.

    2009-01-01

    Roč. 191, č. 1 (2009), s. 154-158. ISSN 0378-7753 Institutional research plan: CEZ:AV0Z40400503 Keywords : lead-acid * negative electrode * sulfation suppression Subject RIV: CG - Electrochemistry Impact factor: 3.792, year: 2009

  17. A Doped Polyaniline Modified Electrode Amperometric Biosensor for Gluconic Acid Determination in Grapes

    Donatella Albanese

    2014-06-01

    Full Text Available 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.

  18. Synthesis and luminescence properties of polymeric complexes of Cu(II), Zn(II) and Al(III) with functionalized polybenzimidazole containing 8-hydroxyquinoline side group

    Zhong, Chaofan; Wu, Qian; Guo, Rongfang; Zhang, Hailiang

    2008-02-01

    The polymeric ligand PBI-8Q ( 2) (functionalized polybenzimidazole containing 8-hydroxyquinoline side group) was successfully synthesized by the reaction of polybenzimidazole (PBI) ( 1) with 5-chloro-8-hydroxyquinoline (5-Cl-8Q) in DMSO solvent by using NaH as deprotonation reagent. Its corresponding metal complexes of Cu(II), Zn(II) and Al(III) were prepared and characterized through FT-IR, 1H NMR, molar conductance measurements and thermal analysis. The luminescence properties of all compounds were also studied by UV-vis and fluorescence spectra at ambient temperature. When excited from 338 to 415 nm, these compounds emit blue light of about 415 nm in solution and blue/green light from 483 to 552 nm in solid state, respectively. Thermal properties measurement and analysis show that they have good thermal stabilities.

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

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

    2015-01-01

    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 heati...

  20. Graphenated tantalum(IV) oxide and poly(4-styrene sulphonic acid)-doped polyaniline nanocomposite as cathode material in an electrochemical capacitor

    Nanostructured poly(4-styrene sulphonic acid) and tantalum (IV) oxide-doped polyaniline nanocomposite were synthesised and their electro-conductive properties were determined. The oxide was synthesized using a modified sol-gel method and then dispersed in acidic media through sonication and entrapped in-situ into the polymeric matrix during the oxidative chemical polymerization of aniline doped with poly(4-styrene sulphonic acid). The oxides and novel polymeric nanocomposite were characterised with TEM, SEM, EDX, XRD, FTIR, UV-visible to ascertain elemental and phase composition, successful polymerization, doping, morphology and entrapment of the metal oxide nanoparticles. The electro-conductivity of the nanomaterial was interrogated using scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). The material was then anchored on activated graphitic carbon and used in the design of an asymmetric supercapacitor cell using 6 M KOH aqueous electrolyte. Characteristically high specific capacitance values of 318.4 F/g with a corresponding energy and power densities of 1.57 kWh/kg and 0.435 kW/kg, respectively, were demonstrated. The cell also showed high coulombic efficiency of 94.9% with a long cycle life and good cycle stability making the nanomaterial suitable for constructing supercapacitor cell electrodes

  1. Photoinduced proton transfer coupled with energy transfer: Mechanism of sensitized luminescence of terbium ion by salicylic acid doped in polymer.

    Misra, Vinita; Mishra, Hirdyesh

    2008-06-28

    In the present work, excited state intramolecular proton transfer (ESIPT) in salicylic acid (SA) monoanion and subsequent sensitization of Tb(3+) ion in polyvinyl alcohol (PVA) have been studied. The study has been carried out both by steady state and time domain fluorescence measurement techniques at room temperature. It is found that the SA completely ionizes and exists as monoanion in PVA. It exhibits a large Stokes shifted blue emission (10 000 cm(-1)) due to ESIPT and shows a decay time of 6.85 ns. On the other hand, Tb(3+) ion shows a very weak green emission and a decay time of approximately 641 mus in PVA film. Upon incorporating Tb(3+) ion in SA doped PVA film, both intensity and decay time of SA decrease and sensitized emission from Tb(+3) ion along with 3.8 mus rise time is observed. Energy transfer is found to take place both from excited singlet as well as triplet states. A brief description of the properties of the present system from the viewpoint of luminescent solar collector material is addressed. PMID:18601359

  2. Fabrication of Nitrogen-Doped Mesoporous-Carbon-Coated Palladium Nanoparticles: An Intriguing Electrocatalyst for Methanol and Formic Acid Oxidation.

    Ray, Chaiti; Dutta, Soumen; Sahoo, Ramkrishna; Roy, Anindita; Negishi, Yuichi; Pal, Tarasankar

    2016-05-20

    Inspired by the attractive catalytic properties of palladium and the inert nature of carbon supports in catalysis, a concise and simple methodology for in situ nitrogen-doped mesoporous-carbon-supported palladium nanoparticles (Pd/N-C) has been developed by carbonizing a palladium dimethylglyoximate complex. The as-synthesized Pd/N-C has been exfoliated as a fuel cell catalyst by studying the electro-oxidation of methanol and formic acid. The material synthesized at 400 °C,namely, Pd/N-C-400,exhibitssuperior mass activity and stability among catalysts synthesized under different carbonization temperaturesbetween300 and 500 °C. The unique 1D porous structure in Pd/N-C-400 helps better electron transport at the electrode surface, which eventually leads to about five times better catalytic activity and about two times higher stability than that of commercial Pd/C. Thus, our designed sacrificial metal-organic templatedirected pathway becomes a promising technique for Pd/N-C synthesis with superior catalytic performances. PMID:27016895

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

    Jin Xie

    2016-06-01

    Full Text Available 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.

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

    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. PMID:27059753

  5. Growth of boric acid crystallites on the surface of boron-doped silicon carbide samples

    White crystallites were visually observed on fractured or polished surfaces of SiC samples (grain sizes below ∼500 nm) during exposure to air at room temperature for several days. Characterization of the crystallites by scanning electron microscopy, secondary ion mass spectroscopy, and X-ray diffraction identified B(OH)3 crystals with a strong (002) texture. The rate of boric acid formation was determined by a gravimetric experiment. The rate of weight gain increased significantly after an incubation period of 1 week. Nucleation is initially the rate-limiting process. Subsequently small B(OH)3 crystals form on the surface, whose growth rate is determined by grain boundary diffusion of boron to the SiC surface. An estimated grain boundary boron to the SiC surface. An estimated grain boundary diffusion coefficient of boron in SiC was many orders of magnitude higher than extrapolated literature values

  6. Investigations on the growth, optical, thermal, dielectric, and laser damage threshold properties of crystal violet dye-doped potassium acid phthalate single crystal

    Rao, G. Babu; Rajesh, P.; Ramasamy, P.

    2016-03-01

    Influence of crystal violet dye with different concentration on potassium acid phthalate single crystal grown by conventional method has been studied. No change has been observed in the structure, whereas changes have been observed in the external morphology of the crystal when the dyes are incorporated in the crystal lattice. Thermogravimetric and differential thermal analyses show the onset decomposition temperatures to be at 302, 285, 284, and 285 °C for pure, 0.1, 0.3, and 0.5 mol% crystal violet-doped potassium acid phthalate crystals, respectively. The dielectric measurement was carried out on the grown crystals as a function of frequency at various temperatures. In addition, strong luminescent emission bands at 638, 648, and 640 nm were observed in which the relative intensity was found to be reversed as a result of doping concentration. The laser damage threshold value significantly increased for dye-doped crystal in comparison with pure crystal which may make it suitable for the solid-state dye laser applications.

  7. Mechanical Stability of H3PO4-Doped PBI/Hydrophilic-Pretreated PTFE Membranes for High Temperature PEMFCs

    Graphical abstract: - Highlights: • PBI/PTFE membrane was prepared by porous PTFE with hydrophilic surface pretreatment. • The durability of the prepared PBI/PTFE membrane was compared with pure PBI, PBI with untreated PTFE, and PBI-Nafion with untreated PTFE membranes. • Accelerated durability tests and SEM showed improved durability based the PBI/PTFE membrane with pretreated PTFE. - Abstract: A novel polybenzimidazole (PBI)/poly(tetrafluoroethylene) (PTFE) composite membrane doped with phosphoric acid was fabricated for high temperature operation in a polymer electrolyte membrane (PEM) fuel cell. A hydrophilic surface pretreatment was applied to the porous PTFE matrix film to improve its interfacial adhesion to the PBI polymer, thereby avoiding the introduction of Nafion ionomer which is traditionally used as a coupling agent. The pretreated PTFE film was embedded within the composite membrane during solution-casting using 5wt% PBI/DMAc solution. The mechanical stability and durability of three types of MEAs assembled with PBI only, PBI with pretreated PTFE, and PBI-Nafion with untreated PTFE membranes were evaluated under an accelerated degradation testing protocol employing extreme temperature cycling. Degradation was characterized by recording polarization curves, hydrogen crossover, and proton resistance. Cross-sections of the membranes were examined before and after thermal cycling by scanning electron microscope. Energy-dispersive X-ray spectroscopy verified that the PBI is dispersed homogeneously in the porous PTFE matrix. Results show that the PBI composite membrane with pretreated PTFE has a lower degradation rate than the Nafion/PBI membrane with untreated PTFE. Thus, the hydrophilic pretreatment employed here greatly improved the mechanical stability of the composite membrane, which resulted in improved durability under an extreme thermal cycling regime

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

    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.

  9. Improved Durability of Electrocatalyst Based on Coating of Carbon Black with Polybenzimidazole and their Application in Polymer Electrolyte Fuel Cells.

    Fujigaya, Tsuyohiko; Hirata, Shinsuke; Berber, Mohamed R; Nakashima, Naotoshi

    2016-06-15

    Improvement of durability of the electrocatalyst has been the key issue to be solved for the practical application of polymer electrolyte membrane fuel cells. One of the promising strategies to improve the durability is to enhance the oxidation stability of the carbon-supporting materials. In this report, we describe in detail the mechanism of the stability improvement of carbon blacks (CBs; Vulcan and Ketjen) by coating with polybenzimidazole (PBI). Nitrogen adsorption experiments reveal that the PBI coating of CBs results in the capping of the gates of the CB-micropores by the PBI. Since the surface of the micropores inside the CBs are inherently highly oxidized, the capping of such pores effectively prevents the penetration of the electrolyte into the pore and works to avoid the further oxidation of interior of the micropore, which is proved by cyclic voltammogram measurements. Above mechanism agrees very well with the dramatic enhancement of the durability of the membrane electrode assembly fabricated using Pt on the PBI-coated CBs as an electrocatalyst compared to the conventional Pt/CB (PBI-non coated) catalyst. PMID:27227977

  10. Gypsum (CaSO42H2O) scaling on polybenzimidazole and cellulose acetate hollow fiber membranes under forward osmosis

    Chen, Si Cong

    2013-11-08

    We have examined the gypsum (CaSO42H2O) scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO) processes. Three hollow fiber membranes made of (1) cellulose acetate (CA), (2) polybenzimidazole (PBI)/polyethersulfone (PES) and (3) PBI-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) were studied. For the first time in FO processes, we have found that surface ionic interactions dominate gypsum scaling on the membrane surface. A 70% flux reduction was observed on negatively charged CA and PBI membrane surfaces, due to strong attractive forces. The PBI membrane surface also showed a slightly positive charge at a low pH value of 3 and exhibited a 30% flux reduction. The atomic force microscopy (AFM) force measurements confirmed a strong repulsive force between gypsum and PBI at a pH value of 3. The newly developed PBI-POSS/PAN membrane had ridge morphology and a contact angle of 51.42 14.85 after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 C. Minimal scaling and an only 1.3% flux reduction were observed at a pH value of 3. Such a ridge structure may reduce scaling by not providing a locally flat surface to the crystallite at a pH value of 3; thus, gypsum would be easily washed away from the surface. 2013 by the authors; licensee MDPI, Basel, Switzerland.

  11. Fouling behaviors of polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes for engineering osmosis processes

    Chen, Sicong

    2014-02-01

    This paper investigated the individual effects of reverse salt flux and permeate flux on fouling behaviors of as-spun and annealed polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes under forward osmosis (FO) and pressure retarded osmosis (PRO) processes. Two types of membrane fouling had been studied; namely, inorganic fouling (CaSO4·2H2O gypsum scaling) during FO operations and organic fouling (sodium alginate fouling) during PRO operations. It is found that gypsum scaling on the membrane surface may be inhibited and even eliminated with an increase in reverse MgCl2 flux due to competitive formations of MgSO4° and CaSO4·2H2O. In contrast, the increase of reverse NaCl flux exhibits a slight enhancement on alginate fouling in both FO and PRO processes. Comparing to the reverse salt flux, the permeate flux always plays a dominant role in fouling. Therefore, lesser fouling has been observed on the membrane surface under the pressurized PRO process than FO process because the reduced initial flux mitigates the fouling phenomena more significantly than the enhancement caused by an increase in reverse NaCl flux. © 2013 Elsevier B.V.

  12. Effects of the sintering temperature on the flux-pinning mechanism and the activation energy of malic-acid doped MgB2

    J Peleckis

    2012-12-01

    Full Text Available   The flux-pinning mechanism and activation energy of 10 wt % malic acid-doped MgB2 were investigated by measuring of the critical current density and resistivity as a function of magnetic field and temperature. A crossover field, Bsb, was observed from the single vortex to the small vortex bundle pinning regime. For the sintered sample, the temperature dependence of Bsb(T at low temperature is in good agreement with the δℓ pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation. The activation energy was decreased by increasing the magnetic field and increased by increasing sintering temperature.

  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

    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.

  14. POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

    2001-01-01

    A method for preparing polybenzimidazole or polybenzimidazole blend membranes and fabricating gas diffusion electrodes and membrane-electrode assemblies is provided for a high temperature polymer electrolyte membrane fuel cell. Blend polymer electrolyte membranes based on PBI and various...... thermoplastic polymers for high temperature polymer electrolyte fuel cells have also been developed. Miscible blends are used for solution casting of polymer membranes (solid electrolytes). High conductivity and enhanced mechanical strength were obtained for the blend polymer solid electrolytes. With the...... thermally resistant polymer, e.g., polybenzimidazole or a mixture of polybenzimidazole and other thermoplastics as binder, the carbon-supported noble metal catalyst is tape-cast onto a hydrophobic supporting substrate. When doped with an acid mixture, electrodes are assembled with an acid doped solid...

  15. A rapid microwave synthesis of nitrogen-sulfur co-doped carbon nanodots as highly sensitive and selective fluorescence probes for ascorbic acid.

    Duan, Junxia; Yu, Jie; Feng, Suling; Su, Li

    2016-06-01

    A ultrafast one-step microwave-assisted method was developed for the synthesis of nitrogen-sulfur co-doped carbon nanodots (N,S-CDs) by using ethylenediamine as the carbon source and sulfamic acid as the surface passivation reagent. The morphology and the properties of N,S-CDs were explored by a series of techniques, such as high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis absorption and fluorescence spectroscopy. The prepared N,S-CDs exhibit bright blue photoluminescence with a high fluorescence quantum yield (FLQY) up to 28%, and high stability and excellent water solubility. A N,S-CDs-based fluorescent probe was developed for sensitive detection ascorbic acid (AA) in the presence of Cu(2+), based on the mechanism that AA reduces Cu(2+) to Cu(+), then Cu(+) quenches the fluorescence of N,S-CDs through electron or energy transfer due to the interaction between Cu(+) and thiol ligand on the N,S-CDs surface. The observed linear response concentration range was from 0.057 to 4.0μM to AA with a detection limit as low as 18nM. The probe exhibited a highly selective response toward AA even in the presence of possible interfering substances, such as uric acid and citric acid. Moreover, these promising features made the sensing system used for the analysis of human serum and urine samples. PMID:27130124

  16. Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

    Pullamsetty, Ashok; Sundara, Ramaprabhu

    2016-10-01

    Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. PMID:27393888

  17. A Quaternary Polybenzimidazole Membrane for Intermediate Temperature Polymer Electrolyte Membrane Fuel Cells

    Xu, C.; Scott, K.; Li, Qingfeng;

    2013-01-01

    at 150 °C with the PA acid loading level of 3.5 PRU (amount of H3PO4 per repeat unit of polymer QPBI). The QPBI membrane was characterized in terms of composition, structure and morphology by NMR, FTIR, SEM, and EDX. The fuel cell performance with the membrane gave peak power densities of 440 and 240...

  18. White light emission from Mn2+ doped ZnS nanocrystals through the surface chelating of 8-hydroxyquinoline-5-sulfonic acid

    White light emitting semiconductor nanocrystals (NCs) have been successfully synthesized from 8-hydroxyquinoline-5-sulfonic acid (HQS) decorated manganese doped ZnS NCs through fine tuning the surface-coordination emission and dopant emission of the NC host. The HQS functionalized manganese doped ZnS NCs (QS-ZnS:Mn), with a cubic crystal structure, have the same diameter of about 4.0 nm as ZnS:Mn NCs without HQS. The intensity of the surface-coordination emission peak increased with increasing HQS content or augmenting excited wavelength. The emission of white light was achieved by carefully controlling the dosage of HQS in NCs and appropriately tuning the excited wavelength. The color coordinates (0.35, 0.34) for the efficient white light emitting NCs were very close to the ideal Commission Internationale de l'Eclairage (CIE) chromaticity coordinates for pure white light (0.33, 0.33). The photoluminescence (PL) decay study revealed that the white light emitting NCs exhibited maximum lifetime values at different emission peaks for different NC samples. The study results also indicated that the HQS molecules were attached to the surface of ZnS:Mn NCs in a single coordination fashion due to the steric hindrance effect of the special spherical surface of NCs, which made the QS-ZnS:Mn NCs possess stable and high fluorescent properties in different organic solvents as compared with the conventional small molecule complexes.

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

    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. PMID:26025644

  20. Synthesis and development of low cost, high temperature N-arylene polybenzimidazole foam material

    Harrison, E. S.

    1975-01-01

    Polymer (and foam) studies followed two basic routes: (1) formation of high molecular weight uncyclized polyamide followed by subsequent fusion and cyclodehydration to yield NABI (foam) and (2) polymer and foam formation by reaction of diphenyl esters (or anhydrides) with the tetramine. The latter route was found much more attractive since considerable versatility in both basic polymer structure and crosslinkability is achievable. Preliminary studies on BAB, phthalic anhydride (PA), and 3, 3 (prime), 4, 4(prime) benzo pheno netetracarboxylic acid dianhydride (BTDA) as crosslinked polymer precursors were conducted. Nonmelting rigid char forming foams with densities as low as 2.7 lb/cubic ft. were achieved. The program was successful in the preparation of a potentially low cost, low density, high char yield, high temperature foam material.

  1. Effects of the Doping ZnO on the property of Magnetic Solid Acid SO/sub 4/sup 2-/ZrO/sub 2-/Fe/sub 3/O/sub 4/

    Two kinds of magnetic solid acid catalysts are prepared via a simple chemical co-precipitation approach. The obtained materials are characterized by X-ray Diffraction, FT-IR Spectrometer, Different Scanning Calorimetry, Vibrating Sample Magnetometer, Transmission Electron Microscopy, High-resolution Transmission Electron Microscopy and Hammett indicator. The results indicate that the doping of ZnO restrains the phase transformation from tetragonal zirconia to monoclinic zirconia. Furthermore, the samples show a magnetic behavior. Saturation magnetization of the sample SO/sub 4//sup 2-/ /ZrO/sub 2/-Fe/sub 3/O/sub 4/ is smaller than SO/sub 4/sup 2/-/ZrO/sub 2/-Fe/sub 3/O/sub 4/-ZnO; Transmission Electron Microscopy results indicate that the increasing ZnO makes the grains size considerably smaller, and the High-resolution Transmission Electron Microscopy shows that the doping of ZnO maintains the desired tetragonal zirconia phase, and the interplanar spacing is d(101)=0.29 nm. Hammett indicator results show that the acid strength becomes stronger because of the doping of ZnO. The synthesis of methyl laurate as the probe reactions of magnetic solid acids is studied, and the result indicates that the doping of ZnO delays the deactivation rate of catalysts. (author)

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

    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.

  3. Palladium Nanoparticles Supported on Nitrogen and Sulfur Dual-Doped Graphene as Highly Active Electrocatalysts for Formic Acid and Methanol Oxidation.

    Zhang, Xin; Zhu, Jixin; Tiwary, Chandra Sekhar; Ma, Zhongyuan; Huang, Huajie; Zhang, Jianfeng; Lu, Zhiyong; Huang, Wei; Wu, Yuping

    2016-05-01

    Optimized designing of highly active electrocatalysts has been regarded as a critical point to the development of portable fuel cell systems with high power density. Here we report a facile and cost-effective strategy to synthesis of ultrafine Pd nanoparticles (NPs) supported on N and S dual-doped graphene (NS-G) nanosheets as multifunctional electrocatalysts for both direct formic acid fuel cell and direct methanol fuel cell. The incorporation of N and S atoms into graphene frameworks is achieved by a thermal treatment process, followed by the controlled growth of Pd NPs via a solvothermal approach. Owning to the unique structural features as well as the strong synergistic effects, the resulting Pd/NS-G hybrid exhibits outstanding electrocatalytic performance toward both formic acid and methanol electro-oxidation, such as higher anodic peak current densities and more exceptional catalytic stability than those of Pd/Vulcan XC-72R and Pd/undoped graphene catalysts. These findings open up new possibility in the construction of advanced Pd-based catalysts, which is conducive to solving the current bottlenecks of fuel cell technologies. PMID:27082661

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

    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. PMID:27130085

  5. Humidity sensing with doped polyaniline

    Jain, Shilpa; Chakane, Sanjay D. S.; Bhoraskar, S. V.; Samui, A. B.; Krishnamurthy, V. N.

    2001-03-01

    Polyaniline (PANI) was doped with different dopants like camphosulphoric acid (CSA), diphenyl phosphate (DPPH), Sulphonic acid (S) and Maleic acid (MAC) by chemical method. The samples were prepared in the form of pellets as well as films. Polyaniline doped with Maleic acid was found to be mechanically and chemically stable as compared to other dopants and therefore the effect of humidity on conductivity was further investigated. Films prepared out of styrene buryl acrylate copolymer with different concentrations of PANI Maleic acid were used for sensing humidity ranging between 20% to 90% relative humidity. A maximum change in the conductivity of three to four orders of magnitude was obtained for the Maleic acid doped polyaniline pellet while two orders of magnitude change was obtained for the film samples over the range of humidity measured.

  6. A glassy carbon electrode modified with a polyaniline doped with silicotungstic acid and carbon nanotubes for the sensitive amperometric determination of ascorbic acid

    We report on an electrochemical sensor for the sensitive amperometric determination of ascorbic acid (AA). Aniline containing suspended silicotungstic acid and carbon nanotubes was electropolymerized on the surface of a glassy carbon electrode in a single step which provides a simple and controllable method and greatly improves the electrocatalytic oxidation of AA. The effects of scan rate, solution pH and working potential were studied. A linear relationship exists between the current measured and the concentration of AA in the range from 1 μM to 10 μM and 0.01 mM to 9 mM, with a limit of detection as low as 0.51 μM (S/N = 3). The sensor is selective, stable and satisfyingly reliable in real sample experiments. In our eyes, it has a large potential for practical applications. (author)

  7. An investigation of proton conductivity of binary matrices sulfonated polysulfone/polyvinyltriazole after doping with inorganic acids

    Serkan Sevinç; Sevim Ünügür Çelik; Ayhan Bozkurt

    2015-04-01

    As anhydrous proton conductive membranes, sulfonated polysulfone (SPSU) and polyvinyl triazole were studied as binary matrices. The sulfonation of polysulfone was performed with trimethylsilylchlorosulfonate and high degree of sulfonation (140%) was obtained. Ion exchange capacity of SPSU was determined as 3.05 mmol−1/g. The polymer electrolyte membranes were prepared by blending of sulfonated polysulfone with polyvinyl triazole and phosphoric acid. Fourier transform infrared spectroscopy confirmed the sulfonation of the polysulfone and the ionic interaction between sulfonic acid and triazole units. Thermogravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to at least 150° C. Scanning electron microscopy analysis indicated the homogeneity of the ternary composites. The maximum proton conductivity has been measured as 3.63 × 10−4S cm−1 at 150° C.

  8. 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

    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.

  9. An ultrasensitive electrochemical sensor for simultaneous determination of xanthine, hypoxanthine and uric acid based on Co doped CeO2 nanoparticles.

    Lavanya, N; Sekar, C; Murugan, R; Ravi, G

    2016-08-01

    A novel electrochemical sensor has been fabricated using Co doped CeO2 nanoparticles for selective and simultaneous determination of xanthine (XA), hypoxanthine (HXA) and uric acid (UA) in a phosphate buffer solution (PBS, pH5.0) for the first time. The Co-CeO2 NPs have been prepared by microwave irradiation method and characterized by Powder XRD, Raman spectroscopy, HRTEM and VSM measurements. The electrochemical behaviours of XA, HXA and UA at the Co-CeO2 NPs modified glassy carbon electrode (GCE) were studied by cyclic voltammetry and square wave voltammetry methods. The modified electrode exhibited remarkably well-separated anodic peaks corresponding to the oxidation of XA, HXA and UA over the concentration range of 0.1-1000, 1-600 and 1-2200μM with detection limits of 0.096, 0.36, and 0.12μM (S/N=3), respectively. For simultaneous detection by synchronous change of the concentrations of XA, HXA and UA, the linear responses were in the range of 1-400μM each with the detection limits of 0.47, 0.26, and 0.43μM (S/N=3), respectively. The fabricated sensor was further applied to the detection of XA, HXA and UA in human urine samples with good selectivity and high reproducibility. PMID:27157753

  10. Synthesis of nitrogen-doped and amino acid-functionalized graphene quantum dots from glycine, and their application to the fluorometric determination of ferric ion

    We report on a single-step thermolysis strategy to prepare highly luminescent nitrogen-doped and amino acid-functionalized graphene quantum dots (NA-GQDs) by using glycine as both carbon and nitrogen source. The NA-GQDs display an excitation wavelength-dependent fluorescence with maximum excitation and emission wavelengths of 380 and 450 nm, respectively, and a quantum yield of ∼16 %. Fluorescence is quenched by Fe(III) and Hg(II), and the effect was used to develop a method for the determination of Fe(III). Quenching by Fe(III) is attributed to its higher thermodynamic affinity (compared to other transition-metal ions) for the ligands on the GQDs in which nitrogen atoms mainly act as the chelating atoms. A linear relationship was observed between fluorescence intensity and the concentration of Fe(III) over the 0.5 μM to 0.5 mM range. The detection limit is 0.1 μM. (author)

  11. Fluorine doped zinc oxide thin films deposited by chemical spray, starting from zinc pentanedionate and hydrofluoric acid: Effect of the aging time of the solution

    Fluorine doped zinc oxide thin films, ZnO:F, were deposited on sodocalcic glass substrates, starting from zinc pentanedionate and hydrofluoric acid, by the chemical spray technique. The effect of the aging time of the starting solution on the electrical, structural, morphological and optical characteristics of the ZnO thin films was studied. Uniform, adherent, and mirror-like films were deposited at different days. A high electrical resistivity, was found in the films deposited the first day. However, a decrease in the resistivity, until a minimum, in the order of 3 x 10-2 Ω cm was reached for films deposited after the starting solution was aged for twelve days. The films fit well with the hexagonal, wurtzite-type ZnO structure, with a (0 0 2) preferential growth. Variation in the grain size was observed as a consequence of the aging of the solution. An average crystallite size varied between 17.3 and 22.8 nm due to aging effect, and some variations in surface morphology were encountered. All the films are highly transparent in the near UV-vis range, with an average transmittance oscillating between 83% and 90%.

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

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

    2016-02-01

    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).

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

    Gertrude Fomo

    2015-09-01

    Full Text Available 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.

  14. Optical sensing of 3-phenoxybenzoic acid as a pyrethroid pesticides exposure marker by surface imprinting polymer capped on manganese-doped zinc sulfide quantum dots

    Vivek Pandey

    2015-09-01

    Full Text Available The present communication deals with the synthesis of luminescent Mn-doped ZnS quantum dots (QDs anchored to surface imprinted polymer for the optical sensing of 3-phenoxy benzoic acid (3-PBA in urine samples. The combination of sensing and surface functionalization not only improves the selectivity of the method, but also increases the optosensing ability of the material for non-phosphorescent substances. The developed material was utilized for the selective and sensitive detection of 3-PBA in urine samples. The proposed method shows good linearity with a regression coefficient (R2 of 0.98. The limit of detection was found to be 0.117 μM. The method has an acceptable precision and accuracy which are found to be less than 8% and 80–90% respectively at three different concentrations. The quenching constant of quantum dot-molecular imprinted polymer was found to be 3.4 times higher to that of the quantum dot-non imprinted polymer (QD-NIP as calculated by Stern–Volmer equation. The sensing method developed has shown immense utility to detect 3-PBA in complex biological samples like urine.

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

    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.

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

    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

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

    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

  18. EPR and optical absorption studies of Cu2+ doped L-histidinium dihydrogen phosphate–phosphoric acid single crystal

    The EPR spectra of Cu2+ in L-histidinium dihydrogen phosphate phosphoric acid at room temperature reveal the presence of two magnetically inequivalent Cu2+ sites in the lattice. The principal values of the g- and A-tensors indicate existence of rhombic symmetry around the Cu2+ ion. From the direction cosines of the principal values of the g- and A-tensors, the locations of Cu2+ in the lattice have been identified as substitutional sites. Optical absorption study shows four bands confirm the rhombic symmetry. Photoluminescence study also confirms the rhombic symmetry around the ions

  19. Effect of High Temperature on the Electrochemical and Optical Properties of Emeraldine Salt Doped with DBSA and Sulfuric Acid

    Salma Gul

    2015-01-01

    Full Text Available A comprehensive study of thermally treated polyaniline in its emeraldine salt form is presented here. It offers an understanding of the thermal stability of the polymer. Emeraldine salt was prepared by a novel emulsion polymerization pathway using dodecylbenzene sulfonic acid and sulfuric acid together as dopants. The effect of temperature and heating rate on the degradation of this emeraldine salt was studied via thermogravimetric analysis. The thermally analyzed sample was collected at various temperatures, that is, 250, 490, 500, and 1000°C. The gradual changes in the structure of the emeraldine salt were followed through cyclic voltammetry, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. Results demonstrate that emeraldine salt shows high thermal stability up to 500°C. This is much higher working temperature for the use of emeraldine salt in higher temperature applications. Further heat treatment seems to induce deprotonation in emeraldine salt. Cyclic voltammetry and ultraviolet-visible spectroscopy revealed that complete deprotonation takes place at 1000°C where it loses its electrical conductivity. It is interesting to note that after the elimination of the dopants, the basic backbone of emeraldine salt was not destroyed. The results reveal that the dopants employed have a stability effect on the skeleton of emeraldine salt.

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

    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. PMID:21640670

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

    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

  2. Study of polyaniline doped with trifluoromethane sulfonic acid in gas-diffusion electrodes for proton-exchange membrane fuel cells

    Gharibi, Hussein; Zhiani, Mohammad; Kheirmand, Mehdi; Kakaei, Karim [Department of Physical Chemistry, Faculty of Science, Tarbiat Modarres University, P.O. Box 14115-175, Tehran (Iran); Entezami, Ali Akbar [Faculty of Chemistry, Tabriz University, Tabriz (Iran); Mirzaie, Rasol Abdullah [Department of Chemistry, Faculty of Science, Shahid Rajaee University, Tehran (Iran)

    2006-04-21

    Polytetrafluoroethylene (PTFE)-bonded gas-diffusion electrodes (GDEs), modified with polyaniline as an electron and proton conductor in the catalyst layer, are prepared and evaluated for use in proton-exchange membrane fuel cells (PEMFCs). Polyaniline is coated on the GDE by electropolymerization of aniline and trifluoromethane sulfonic acid as the proton-conductive monomer. The electrodes are characterized by cyclic voltammetry, current-potential measurements, electrochemical impedance spectroscopy, and chronoamperometry. The polyaniline is found to be homogenously dispersed in the catalyst layer, making it a good candidate proton and electron conductor. Use of polyaniline instead of Nafion in the catalyst layer, increases the utility of the electrocatalyst by 18%. The results are consistent with the presence of polyaniline as a conductive polymer in the reaction layer reducing the polarization resistance of the electrode in comparison with that of a corresponding electrode containing Nafion. Thus, the present results indicate that PEMFCs using polyaniline-containing electrocatalysts should give superior performance to those using catalysts containing traditional ionomers. (author)

  3. Electrochemical Performance of a Carbon Nanotube/La-Doped TiO2 Nanocomposite and its Use for Preparation of an Electrochemical Nicotinic Acid Sensor

    Hanxing Liu

    2008-11-01

    Full Text Available A carbon nanotube/La-doped TiO2 (La-TiO2 nanocomposite (CLTN was prepared by a procedure similar to a complex/adsorption process. Scanning electron microscopy (SEM images show that the La-TiO2 distributes on the carbon nanotube walls. The CLTN was mixed with paraffin to form a CLTN paste for the CLTN paste electrode (CLTNPE. The electrochemical characteristics of CLTNPE were compared with that of conventional carbon electrodes such as the carbon paste electrode (CPE and glass carbon electrode (GC. The CLTNPE exhibits electrochemical activity and was used to investigate the electrochemistry of nicotinic acid (NA. The modified electrode has a strong electrocatalytic effect on the redox of NA. The cyclic voltammetry (CV redox potential of NA at the CLTNPE is 320 mV. The oxidation process of NA on the CLTNPE is pH dependent. A sensitive chronoamperometric response for NA was obtained covering a linear range from 1.0×10-6 mol·L-1 to 1.2×10-4 mol·L-1, with a detection limit of 2.7×10-7 mol·L-1. The NA sensor displays a remarkable sensitivity and stability. The mean recovery of NA in the human urine is 101.8%, with a mean variation coefficient (RSD of 2.6%.

  4. Gypsum (CaSO4·2H2O Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis

    Tai-Shung Chung

    2013-11-01

    Full Text Available We have examined the gypsum (CaSO4·2H2O scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO processes. Three hollow fiber membranes made of (1 cellulose acetate (CA, (2 polybenzimidazole (PBI/polyethersulfone (PES and (3 PBI-polyhedral oligomeric silsesquioxane (POSS/polyacrylonitrile (PAN were studied. For the first time in FO processes, we have found that surface ionic interactions dominate gypsum scaling on the membrane surface. A 70% flux reduction was observed on negatively charged CA and PBI membrane surfaces, due to strong attractive forces. The PBI membrane surface also showed a slightly positive charge at a low pH value of 3 and exhibited a 30% flux reduction. The atomic force microscopy (AFM force measurements confirmed a strong repulsive force between gypsum and PBI at a pH value of 3. The newly developed PBI-POSS/PAN membrane had ridge morphology and a contact angle of 51.42° ± 14.85° after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 °C. Minimal scaling and an only 1.3% flux reduction were observed at a pH value of 3. Such a ridge structure may reduce scaling by not providing a locally flat surface to the crystallite at a pH value of 3; thus, gypsum would be easily washed away from the surface.

  5. Boron doping a semiconductor particle

    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.

  6. Synthesis and characterization of Sn doped TiO2 photocatalysts: Effect of Sn concentration on the textural properties and on the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid

    Abstract: TiO2 and Sn-doped TiO2 materials were prepared by sol–gel method using titanium and tin alkoxides at different Sn concentration (0.1 mol%, 0.5 mol%, 1 mol%, 3 mol% and 5 mol%). Samples were characterized by thermo gravimetric analyzer with differential scanning calorimeter (TGA–DSC), X-ray Rietveld refinement, N2 adsorption (BET), transmission electron microscopy (TEM), UV–vis spectroscopies technology and Raman spectroscopy. Only anatase phase was observed in pure TiO2, whereas anatase and brookite were obtained in Sn-doped TiO2 samples. Sn dopant acts as a promoter in phase transformation of TiO2. The Rietveld refinements method was used to determine the relative weight of anatase and brookite, and crystallite size as a function of Sn concentration after calcination of samples at 673 K. It was also demonstrated the incorporation of Sn4+ into the anatase TiO2 structure. Sn4+ inhibits the growth of TiO2 crystallite size, which leads to an increase of the specific surface area of TiO2. From XRD analysis, the solid solution limit of Sn4+ into TiO2 is 5 mol% Sn. The photocatalytic activity on Sn4+ doped TiO2 was determined for the 2,4-dichlorophenoxyacetic acid reaction. The maximum in activity was attributed to the coexistence of anatase and brookite phases in the appropriate ratio and crystallite size

  7. CO tolerance by the PEMFC operational at temperatures up to 200°C

    Li, Qingfeng; He, Ronghuan; Gao, Ji-An; Jensen, Jens Oluf; Bjerrum, Niels

    The CO poisoning effect on carbon-supported platinum catalysts in polymer electrolyte membrane fuel cells has been investigated in a temperature range from 125 to 200°C with the phosphoric acid-doped polybenzimidazole membranes as electrolyte. The effect is very temperature-dependent and can be...

  8. The CO poisoning effect in PEMFCs operational at temperatures up to 200 degrees C

    Li, Qingfeng; He, Ronghuan; Gao, Ji-An; Jensen, Jens Oluf; Bjerrum, Niels

    2003-01-01

    The CO poisoning effect on carbon-supported platinum catalysts (at a loading of 0.5 mg Pt/cm(2) per electrode! in polymer electrolyte membrane fuel cells (PEMFCs) has been investigated in a temperature range from 125 to 200 degreesC with the phosphoric acid-doped polybenzimidazole membranes as...

  9. Fe3C-based oxygen reduction catalysts: synthesis, hollow spherical structures and applications in fuel cells

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei; Fernandez, Santiago Martin; Chenitz, Regis; Pan, Chao; Xing, Wei; Bjerrum, Niels J.; Li, Qingfeng

    2015-01-01

    and stability. A new ORR active phase of Fe3C nanoparticles encapsulated by thin graphitic layers is proposed. The activity and durability of the catalysts are demonstrated in both Nafion-based low temperature and acid doped polybenzimidazole-based high temperature proton exchange membrane fuel cells....

  10. Method of operating a direct dme fuel cell system

    2011-01-01

    The present invention relates to a method of operating a fuel cell system comprising one or more fuel cells with a proton exchange membrane, wherein the membrane is composed of a polymeric material comprising acid-doped polybenzimidazole (PBI). The method comprises adjusting the operating...

  11. Comparison between FTIR and XPS characterization of amino acid glycine adsorption onto diamond-like carbon (DLC) and silicon doped DLC

    Diamond-like carbon (DLC) coatings are extremely useful for creating biocompatible surfaces on medical implants. DLC and silicon doped DLC synthesized on silicon wafer substrate by using plasma enhanced chemical vapour deposition (PECVD). The adsorption of glycine onto prepared samples has been investigated with a range of surface analysis techniques. The effects of surface morphology on the interaction of glycine with doped and undoped DLC films have been investigated. The chemical composition of the surface before and after adsorption was analyzed using X-ray photoelectron spectroscopy (XPS). For undoped DLC the spectra show peaks at 285 eV (C 1s), 532 eV (O 1s) and in the case of Si-doped DLC films a band at ∼100 eV (Si 2p) is observed. Following exposure to solutions containing (0.001 M) glycine, for undoped DLC the peaks at ∼285.0, ∼399 and ∼532 eV reduced in intensity and for Si-DLC samples, the peak at 100 eV was reduced. This gives an indication of the quantitative change in the amounts of C, N and O on the surfaces. From Fourier transform infrared (FTIR) spectrum, the peaks occur the following functional groups were assigned as COO-R, COO-bar , -NH3+, NH2, C-H and C-C-N. Both XPS and FTIR spectroscopy confirm that glycine was bound onto the surfaces of the DLC and Si-DLC films via interaction of ionized carboxyl groups and the amino group did not play a significant role in the adsorption of glycine. These results from SE show that an adsorbed layer of glycine is higher at low silicon doping whilst increased doping levels led to a reduced adsorption compared to undoped DLC. Therefore doping of DLC may provide an approach to controlling the protein adsorption.

  12. Sporda Doping

    İmamoğlu, Osman

    2014-01-01

    Doping yeni bir şey değildir. Dopingli sporculara teşhis konulduğunda gündeme gelip çok konuşulmakta ve zamanla unutulup gitmektedir.Doping, organizmaya yabancı bir ajanın, hangi yoldan olursa olsun veya fizyolojik maddelerin anormal miktarlarda, alınması ya da anormal bir yolla bir şahsa yarışma esnasındaki performansı artırmak amacıyla uygulanan bazı psikolojik prosedürlerdir.Bazı anabolizmaların antrenman devrelerinde kullanılmaları bile doping sayılmaktadır.

  13. CO-DOPED POLYPYRROLE COATINGS FOR STAINLESS STEEL PROTECTION

    W. PRISSANAROON; Brack, N.; Pigram, P. J.; J. LIESEGANG

    2006-01-01

    Polypyrrole (PPy) films have been successfully electrodeposited on stainless steel substrates in aqueous solution. In this work, three systems of electrolytes were studied: oxalic acid, dodecylbenzenesulfonic acid (DBSA) and a mixture of oxalic acid and DBSA. A combination of XPS and TOF–SIMS revealed the formation of an iron oxalate layer at the interface between the oxalic acid-doped PPy (PPy(Ox)) and stainless steel and a thin layer of DBSA was observed at the interface between DBSA-doped ...

  14. Effect of chloride impurities on the performance and durability of polybenzimidazole-based high temperature proton exchange membrane fuel cells

    Ali, Syed Talat; Li, Qingfeng; Pan, Chao;

    2011-01-01

    performance loss was recovered when switching from the HCl solution back to pure water in the air humidifier. Under an accelerated aging performance test conducted through potential cycling between 0.9 V and 1.2 V, the PBI-based fuel cell initially containing 0.5 NaCl mg cm−2 on the cathode catalyst layer...... the Pt/C catalysts. Linear sweep voltammetry was employed to study the redox behavior of platinum in 85% phosphoric acid containing chloride ions, showing increase in oxidation and decrease in reduction current densities during the potential scans at room temperature. The potential scans at high...... temperatures in 85% phosphoric acid containing chloride ions showed both increase in oxidation and reduction current densities. The fuel cell performance, i.e. the current density at a constant voltage of 0.4 V and 0.5 V was found to be degraded as soon as HCl was introduced in the air humidifier. The...

  15. Polybenzimidazole/strontium cerate nanocomposites with enhanced proton conductivity for proton exchange membrane fuel cells operating at high temperature

    In this work, perovskite-type SrCeO3 nanoparticles were used for improving the properties of high temperature polybenzimodazole (PBI) based proton exchange membranes. Novel proton conducting membrane nanocomposites were prepared using different amounts of SrCeO3 nanopowders dispersed into by solution casting method.The nanocomposite membranes were studied by using AC impedance spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray and thermo gravimetric analysis. The prepared nanocomposite membranes showed a higher acid uptake, proton conductivity and thermal stability compared with the pure PBI membranes. The highest acid uptake (190%) and proton conductivity (0.105 S/cm at 180 °C and 0% RH) were observed for phosphoric acide-dopped PBI nanocomposite membranes containing 8 wt% of SrCeO3 nanoparticles (PSC8). The PSC8 nanocomposite membranes were tested in a fuel cell and the polarization and power curves were obtained at different temperatures. The PSC8 showed 0.44 W/cm2 power density and 0.88 A/ cm2 current density in 0.5 V at 180 °C. The result obtained from our studies shows the enhanced potential of the PSC8 as proton exchange membranes for high temperature proton exchange membrane fuel cells

  16. Synthesis and characterization of Sn doped TiO{sub 2} photocatalysts: Effect of Sn concentration on the textural properties and on the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid

    Rangel-Vázquez, I.; Del Angel, G.; Bertin, V. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); González, F. [Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); Vázquez-Zavala, A.; Arrieta, A. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); Padilla, J.M. [Universidad Tecnológica del Centro de Veracruz, Área de Tecnología, Av. Universidad Carretera Federal Cuitláhuac-La Tinaja No. 350, Cuitláhuac, Veracruz 94910 (Mexico); Barrera, A. [Universidad de Guadalajara, Centro Universitario de la Ciénega, Av. Universidad, Número 1115, Col. Linda Vista, Apdo. Postal 106, Ocotlán Jal. (Mexico); Ramos-Ramirez, E. [Departamento de Química, División de Ciencias Naturales y Exactas, Campus Guanajuato de la Universidad de Guanajuato Noria Alta S/N, Col. Noria Alta, Guanajuato, Gto. C.P. 36050 (Mexico)

    2015-09-15

    Abstract: TiO{sub 2} and Sn-doped TiO{sub 2} materials were prepared by sol–gel method using titanium and tin alkoxides at different Sn concentration (0.1 mol%, 0.5 mol%, 1 mol%, 3 mol% and 5 mol%). Samples were characterized by thermo gravimetric analyzer with differential scanning calorimeter (TGA–DSC), X-ray Rietveld refinement, N{sub 2} adsorption (BET), transmission electron microscopy (TEM), UV–vis spectroscopies technology and Raman spectroscopy. Only anatase phase was observed in pure TiO{sub 2}, whereas anatase and brookite were obtained in Sn-doped TiO{sub 2} samples. Sn dopant acts as a promoter in phase transformation of TiO{sub 2}. The Rietveld refinements method was used to determine the relative weight of anatase and brookite, and crystallite size as a function of Sn concentration after calcination of samples at 673 K. It was also demonstrated the incorporation of Sn{sup 4+} into the anatase TiO{sub 2} structure. Sn{sup 4+} inhibits the growth of TiO{sub 2} crystallite size, which leads to an increase of the specific surface area of TiO{sub 2}. From XRD analysis, the solid solution limit of Sn{sup 4+} into TiO{sub 2} is 5 mol% Sn. The photocatalytic activity on Sn{sup 4+} doped TiO{sub 2} was determined for the 2,4-dichlorophenoxyacetic acid reaction. The maximum in activity was attributed to the coexistence of anatase and brookite phases in the appropriate ratio and crystallite size.

  17. Effects of Zn/citric acid mole fraction on the structure and luminescence properties of the un-doped and 1.5% Pb{sup 2+} doped ZnAl{sub 2}O{sub 4} powders synthesized by citrate sol–gel method

    Motloung, S.V., E-mail: motloungsv@qwa.ufs.ac.za [Department of Physics, University of the Free State (Qwaqwa Campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa); Dejene, F.B. [Department of Physics, University of the Free State (Qwaqwa Campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa); Swart, H.C.; Ntwaeaborwa, O.M. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein 9300 (South Africa)

    2015-07-15

    Un-doped and 1.5% Pb{sup 2+}doped zinc aluminate (ZnAl{sub 2}O{sub 4}) was successfully prepared at a relatively low temperature (~80 °C) using the sol–gel process. The Zn/citric acid (CA) mole fraction was varied from 0.083 to 1.3. The X-ray diffraction (XRD) data revealed that most of the annealed samples consist of the cubic ZnAl{sub 2}O{sub 4} structure with ZnO impurities. The surface morphology of the phosphors was influenced by the Zn/CA mole fractions. The increase in the CA content lead to the morphological evolution and transformation from small particles to rods-like-needles. The nanopowder samples exhibited violet luminescence that varied from 400 to 410 nm, which suggested that the CA content affected the bandgap energy of the host. The results suggest that the emission originated either from the host, Pb{sup 2+} or ZnO impurities. Emission at 400 nm is attributed to the oxygen vacancies (V{sub 0}{sup *}) in the host and emission peak at 410 nm is attributed to the intrinsic defects emission of ZnO, while the emission at 552 nm is attributed to the second order emission of the excitation wavelength. The emission intensity was influenced by the Zn/CA mole fractions. The CIE colour coordinates of all samples are close to each other in the blue region. Two distinct peaks were observed at around 160 and 385 °C in thermo luminescence (TL) glow curve, which indicates that there are two set of traps. - Highlights: • Un-doped and 1.5% Pb{sup 2+}doped zinc aluminate (ZnAl{sub 2}O{sub 4}) was successfully prepared at a relatively low temperature (~80 °C) using the sol–gel process. • The increase in the catalyst content lead to the morphological evolution from small particles to rods-like-needles. • The catalyst content affected the band gap energy of the host. • Results showed that the emission can only arise from the host and ZnO impurities. • CIE colour coordinates of all samples is situated in the blue region of the chart.

  18. Electrochemical Performance of a Carbon Nanotube/La-Doped TiO2 Nanocomposite and its Use for Preparation of an Electrochemical Nicotinic Acid Sensor

    Hanxing Liu; Zhidong Lin; Jing Wu

    2008-01-01

    A carbon nanotube/La-doped TiO2 (La-TiO2) nanocomposite (CLTN) was prepared by a procedure similar to a complex/adsorption process. Scanning electron microscopy (SEM) images show that the La-TiO2 distributes on the carbon nanotube walls. The CLTN was mixed with paraffin to form a CLTN paste for the CLTN paste electrode (CLTNPE). The electrochemical characteristics of CLTNPE were compared with that of conventional carbon electrodes such as the carbon paste electrode (CPE) and glass carbon elec...

  19. Mineralization of phthalic acid by solar photoelectro-Fenton with a stirred boron-doped diamond/air-diffusion tank reactor: Influence of Fe3+ and Cu2+ catalysts and identification of oxidation products

    Highlights: • Almost total mineralization of phthalic acid by solar photoelectro-Fenton with Fe3+, Cu2+ and Fe3+–Cu2+ mixtures. • Hydroxyl radical generation from photo-Fenton reaction under solar radiation. • Enhancement of the mineralization rate using Fe3+ and small amounts of Cu2+. • Detection of eleven aromatic intermediates and six short-linear carboxylic acids. • Oxidation of Cu(II)-carboxylate complexes with ·OH and photolysis of Fe(III)-carboxylate species. -- Abstract: Here, the substrate decay and mineralization rate for 100 cm3 of a 2.0 mM phthalic acid solution in 0.10 M Na2SO4 of pH 3.0 have been studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). The electrochemical cell was a stirred tank reactor containing a 3 cm2 boron-doped diamond (BDD) anode and a 3 cm2 air-diffusion cathode that generates H2O2. Cu2+ and/or Fe3+ were added as catalysts with total concentration of 0.50 mM and a constant current density of 33.3 mA cm−2 was applied. In EF with Cu2+ or Fe3+ alone and SPEF with only Cu2+, phthalic acid decayed slowly and poor mineralization was reached because the main oxidant was ·OH produced at the BDD surface from water oxidation. In contrast, the substrate destruction was largely enhanced using SPEF with 0.50 mM Fe3+ since a high quantity of oxidant ·OH was produced in the bulk induced by photo-Fenton reaction. This treatment led to an almost total mineralization by the photolysis of generated Fe(III)-carboxylate complexes. In all cases, the decay of phthalic acid obeyed a pseudo-first-order reaction. The combination of Cu2+ and Fe3+ as catalysts accelerated the mineralization process in SPEF because Cu(II)-carboxylate complexes were also removed with ·OH formed from photo-Fenton reaction. The best SPEF process was found for 0.125 mM Cu2+ + 0.375 mM Fe3+, giving rise to 99% mineralization with 40% current efficiency and 0.294 kWh g−1 TOC energy consumption. Eleven aromatics and six short-linear carboxylic

  20. Mechanisms of doping graphene

    Pinto, H; Jones, R; Goss, J. P.; Briddon, P. R.

    2010-01-01

    We distinguish three mechanisms of doping graphene. Density functional theory is used to show that electronegative molecule like F4-TCNQ and electropositive metals like K dope graphene p- and n-type respectively. These dopants are expected to lead to a decrease in carrier mobility arising from Coulomb scattering but without any hysteresis effects. Secondly, a novel doping mechanism is exhibited by Au which dopes bilayer graphene but not single layer. Thirdly, electrochemical doping is effecte...

  1. Folic acid-conjugated chromium(III) doped nanoparticles consisting of mixed oxides of zinc, gallium and tin, and possessing near-infrared and long persistent phosphorescence for targeted imaging of cancer cells

    Folic acid-conjugated luminescent nanomaterials have long been widely used in targeted bioimaging, often simultaneously acting as vehicles for drug delivery. They often require, however, intense light sources for photoexcitation, and this often results in photo bleaching, strong luminescence background, and strong light scattering. This article describes the preparation of nanoparticles (NPs) of the type Zn1.1Ga1.8Sn0.1O4 doped with Cr(III) ions and surface-modified with folic acid. The functionalization of the NPs was monitored via measurement of zeta potentials, FTIR spectra and thermogravimetry. Cell viability and biocompatibility were tested using the MTT kit. The NPs have a size of 220 nm and were characterized by dynamic X-ray diffraction, light scattering, field emission scanning electron microscopy and high-resolution transmission electron microscopy. After annealing the NPs for 10 min at 300 °C and irradiating them with 254 nm light for 10 min, they display deep red emission that persists for up to 10 h. The NPs are easily dispersed, small-sized, and crystalline. In our perception, the new material with its long decay time offers quite novel features in terms of targeted optical imaging in providing high resolution, weak disturbance by background luminescence, and the absence of light scattering. They were successfully applied to image MCF-7 and A549 cells. (author)

  2. Electrochemical oxidation of acid black 210 dye on the boron-doped diamond electrode in the presence of phosphate ions: Effect of current density, pH, and chloride ions

    The electrochemical oxidation of acid black 210 dye (AB-210) on the boron-doped diamond (BDD) was investigated under different pH conditions. The best performance for the AB-210 oxidation occurred in alkaline phosphate solution. This is probably due to oxidizing agents such as phosphate radicals and peroxodiphosphate ions, which can be electrochemically produced with good yields on the BDD anode, mainly in alkaline solution. Under this condition, the COD (chemical oxygen demand) removal was higher than that obtained from the model proposed by Comninellis. Electrolyses performed in phosphate buffer and in the presence of chloride ions resulted in faster COD and color removals in acid and neutral solutions, but in alkaline phosphate solution, a better performance in terms of TOC removal was obtained in the absence of chloride. Moreover, organochloride compounds were detected in all electrolyses performed in the presence of chloride. The AB-210 electrooxidation on BDD using phosphate as supporting electrolyte proved to be interesting since oxidizing species generated from phosphate ions were able to completely degrade the dye without producing organochloride compounds.

  3. Study of hole mobility in poly(N-vinylcarbazole) films doped with CdSe/ZnS quantum dots encapsulated by 11-(N-carbazolyl) undecanoic acid (C11)

    Khetubol, Adis; Hassinen, Antti; Firdaus, Yuliar; Vanderlinden, Willem; Van Snick, Sven; Flamée, Stijn; Li, Bing; De Feyter, Steven; Hens, Zeger; Dehaen, Wim; Van der Auweraer, Mark

    2013-11-01

    We report the experimental study of hole transport in poly(vinylcarbazole) (PVK) films doped with colloidal CdSe/ZnS core-shell quantum dots (QDs) determined using the Time-of-Flight (TOF) method. The miscibility between PVK and the QDs is improved by capping the QDs with a novel 11-(N-carbazolyl) undecanoic acid (C11) ligand instead of commonly used organic ligands, such as oleic acid. The study of the hole mobility of the pristine and doped PVK films with a doping concentration of the C11 capped QDs ranging from 1.61 × 1017 to 7.10 × 1018 dots/cm3 was performed as a function of electric field and temperature in the range of 105-106 V/cm and 298-338 K, respectively. Upon increasing the QD concentration, a decrease of hole mobility was observed by up to nearly 2 orders in magnitude at a doping concentration of 3.87 × 1018 dots/cm3 at T = 298 K. This suggests that the QDs induce shallow hole traps. The field and temperature dependence of the hole mobility was characterized using the Bässler disorder model and showed an increase of the energetic disorder (σ) from 124 to 204 meV as well as of the spatial disorder (Σ) from 0.95 to 5 when the concentration of the QDs was increased to 3.87 × 1018 dots/cm3. At higher concentration of the QDs (7.10 × 1018 dots/cm3), an increase of the hole mobility was observed suggesting hopping of the holes through the QD clusters. In addition, we also found that for this high doping concentration, the field dependence of the hole mobility was no longer in agreement with the Bässler disorder model. One should consider that at this doping concentration, the volume occupied by the inorganic (CdSe + ZnS) and organic (C11) components of the QDs in the doped film was estimated to be 14.6 and 15.8 volume %, respectively. This implies that the volume fraction of the inorganic material is very close to the percolation threshold, which amounts to 17 volume % for small spherical particles embedded in a three dimensional matrix

  4. Remote gaseous acid sensing within a porphyrin-doped TiO2 sol-gel layer inside a structured optical fibre

    Huyang, George; Canning, John; Åslund, Mattias L.; Naqshbandi, Masood; Stocks, Danial; Crossley, Maxwell J.

    2010-09-01

    A porphyrin containing sol-gel layer has been deposited within the interior of the channels of a silica structured optical fibre. Gaseous HCl detection based on protonation of the porphyrin and observed as a change in the spectrum is demonstrated. This system is compared to previous work based on an acid sensor within a liquid-core fibre. The signal-to- noise of this type of fibre system shows a higher level of sensitivity than the liquid-core and has a forty-fold acid diffusion rate increase due to the different medium for acidification.

  5. Anomalous doping effects by nitric acid on the epitaxial graphene grown on Si-terminated 6H-SiC%Si面6H-SiC衬底外延石墨烯的异常硝酸掺杂效应

    郝昕; 王泽高; 刘竞博; 田洪军

    2013-01-01

    The nitric acid doping effects on the electrical properties of epitaxial graphene grown on Si-and Cterminated SiC,CVD graphene transferred onto SiO2/Si were investigated,respectively.The results show that the p-type doping and decrease in sheet resistance are originated from nitric acid doping with regard to the epitaxial graphene grown on C-terminated SiC and CVD graphene,which attribute to the charge transfer in the redox reaction between nitric acid and graphene.While as for the epitaxial graphene grown on Si-terminated SiC,the n-type doping and increase in sheet resistance are originated from nitric acid doping.The anomalous doping effects are due to the thermal energy generated by the redox reaction between nitric acid and graphene,which lead to oxygen desorption from the dangling bonds between the interface of buffer layer and SiC.Hence the coupling effect between the interface and substrate is effectively enhanced,which results in the increase in electron concentration and decrease in electron mobility.%比较研究了Si面、C面SiC外延石墨烯以及CVD石墨烯的硝酸掺杂效应.结果表明对C面SiC外延石墨烯和CVD石墨烯,硝酸掺杂显现出p型掺杂特性使其方阻降低,这是由于硝酸与石墨烯氧化还原反应过程中电荷转移所导致;而对于Si面SiC外延石墨烯,硝酸掺杂则显现出n型掺杂特性使其方阻增大,这种异常掺杂效应是由于硝酸与石墨烯发生氧化还原反应释放出的热量使悬挂键吸附的氧脱附,增强了石墨烯与衬底之间的耦合效应,从而使得电子浓度增大,电子的迁移率显著减小.

  6. 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)

    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

  7. Proton conductive membranes based on doped sulfonated polytriazole

    Boaventura, M.; Brandao, L.; Mendes, A. [Laboratorio de Engenharia de Processos, Ambiente e Energia (LEPAE), Faculdade de Engenharia da Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal); Ponce, M.L.; Nunes, S.P. [GKSS Research Centre Geesthacht GmbH, Max Planck Str. 1, D-21502, Geesthacht (Germany)

    2010-11-15

    This work reports the preparation and characterization of proton conducting sulfonated polytriazole membranes doped with three different agents: 1H-benzimidazole-2-sulfonic acid, benzimidazole and phosphoric acid. The modified membranes were characterized by scanning electron microscopy (SEM), infrared spectra, thermogravimetric analysis (TGA), dynamical mechanical thermal analysis (DMTA) and electrochemical impedance spectroscopy (EIS). The addition of doping agents resulted in a decrease of the glass transition temperature. For membranes doped with 85 wt.% phosphoric acid solution proton conductivity increased up to 2.10{sup -3} S cm{sup -1} at 120 C and at 5% relative humidity. The performance of the phosphoric acid doped membranes was evaluated in a fuel cell set-up at 120 C and 2.5% relative humidity. (author)

  8. 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.

    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. PMID:26695338

  9. Electro-Fenton, UVA photoelectro-Fenton and solar photoelectro-Fenton degradation of the drug ibuprofen in acid aqueous medium using platinum and boron-doped diamond anodes

    Skoumal, Marcel; Rodriguez, Rosa Maria; Cabot, Pere Lluis; Centellas, Francesc; Garrido, Jose Antonio; Arias, Conchita [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Brillas, Enric [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)], E-mail: brillas@ub.edu

    2009-02-28

    The degradation of a 41 mg dm{sup -3} ibuprofen (2-(4-isobutylphenyl)propionic acid) solution of pH 3.0 has been comparatively studied by electrochemical advanced oxidation processes (EAOPs) like electro-Fenton, UVA photoelectro-Fenton and solar photoelectro-Fenton at constant current density. Experiments were performed in a one-compartment cell with a Pt or boron-doped diamond (BDD) anode and an O{sub 2}-diffusion cathode. Heterogeneous hydroxyl radical ({center_dot}OH) is generated at the anode surface from water oxidation, while homogeneous {center_dot}OH is formed from Fenton's reaction between Fe{sup 2+} and H{sub 2}O{sub 2} generated at the cathode, being its production strongly enhanced from photo-Fenton reaction induced by sunlight. Higher mineralization is attained in all methods using BDD instead Pt, because the former produces greater quantity of {center_dot}OH enhancing the oxidation of pollutants. The mineralization rate increases under UVA and solar irradiation by the rapid photodecomposition of complexes of Fe(III) with acidic intermediates. The most potent method is solar photoelectro-Fenton with BDD giving 92% mineralization due to the formation of a small proportion of highly persistent final by-products. The effect of Fe{sup 2+} content, pH and current density on photoelectro-Fenton degradation has been studied. The ibuprofen decay always follows a pseudo-first-order kinetics and its destruction rate is limited by current density and UV intensity. Aromatics such as 1-(1-hydroxyethyl)-4-isobutylbenzene, 4-isobutylacetophenone, 4-isobutylphenol and 4-ethylbenzaldehyde, and carboxylic acids such as pyruvic, acetic, formic and oxalic have been identified as oxidation by-products. Oxalic acid is the ultimate by-product and the fast photodecarboxylation of its complexes with Fe(III) under UVA or solar irradiation explains the higher oxidation power of photoelectro-Fenton methods in comparison to electro-Fenton procedures.

  10. EPR and optical absorption studies of Cu{sup 2+} doped L-histidinium dihydrogen phosphate–phosphoric acid single crystal

    Prabakaran, R.; Sheela, K. Juliet; Rosy, S. Margret [Department of Physics, Gandhigram Rural Institute—Deemed University, Gandhigram, Dindigul-624302, Tamilnadu (India); Radha Krishnan, S.; Shanmugam, V.M. [CSIR-Central Electrochemical Research Institute, Karaikudi-630006, Tamilnadu (India); Subramanian, P., E-mail: psmanian_gri@yahoo.com [Department of Physics, Gandhigram Rural Institute—Deemed University, Gandhigram, Dindigul-624302, Tamilnadu (India)

    2014-02-01

    The EPR spectra of Cu{sup 2+} in L-histidinium dihydrogen phosphate phosphoric acid at room temperature reveal the presence of two magnetically inequivalent Cu{sup 2+} sites in the lattice. The principal values of the g- and A-tensors indicate existence of rhombic symmetry around the Cu{sup 2+} ion. From the direction cosines of the principal values of the g- and A-tensors, the locations of Cu{sup 2+} in the lattice have been identified as substitutional sites. Optical absorption study shows four bands confirm the rhombic symmetry. Photoluminescence study also confirms the rhombic symmetry around the ions.

  11. Emission spectra of the sol-gel glass doped with europium(III) complexes of picolinic acid N-oxide-A new UV-light sensor

    New europium complexes of picolinic acid N-oxides have been synthesised and introduced into sol-gel matrices. Their application as UV-light sensors has been considered. The sequence of the electronic levels for Eu3+ ions has been determined from the absorption and emission studies and assigned to the respective electron transitions. The lifetimes of the excited states have been detected and analysed. The role of the CT transition inside the picolinic ligand and its influence on the ligand to metal charge transfer (LMCT) have been discussed

  12. Investigation of carbon monoxide tolerance of platinum nanoparticles in the presence of optimum ratio of doped polyaniline with para toluene sulfonic acid and their utilization in a real passive direct methanol fuel cell

    Highlights: ► Onset potential of methanol oxidation on Pt/C-PANI-PTSA electrocatalysts is close to Pt–Ru catalyst. ► The methanol crossover in the presence of Pt/C-20%PANI-PTSA reduced by 59% compared with Pt/C (Electrochem). ► The energy efficiency of Pt/C-20%PANI-PTSA as anode is 2.18 times more than Pt/C. -- Abstract: Polyaniline fiber (PANI) was synthesized by chemical interfacial method and doped with para toluene sulfonic acid (PTSA) through a sequential doping–dedoping–redoping process resulting in PANI-PTSA. The doped material was utilized to fabricate Vulcan-polyaniline composite of C-PANI-PTSA. Next, through reduction, Pt particles were deposited on to this composite to produce a Pt/C-PANI-PTSA electrocatalyst. To investigate the PANI-PTSA interaction with the carbon support as well as, to consider its effect upon the catalytic activity of Pt/C-PANI-PTSA, electrocatalysts with different ratios of 10, 15, 20, 25 and 30 wt% were synthesized and their activity was compared with the Pt/C (Electrochem). Results revealed that, the peak current density in methanol electro-oxidation, electrochemical surface area, methanol diffusion coefficient, charge transfer resistance as well as; the stability of the Pt/C-20%PANI-PTSA electrocatalyst were all markedly improved for the synthesized material. Moreover, the Pt/C-20%PANI-PTSA was demonstrated to be more CO tolerant according to the CO stripping voltammetry test. Also powder XRD and TEM techniques were utilized to investigate the crystallite size and the surface morphologies of the catalysts. Finally, the performance of Pt/C-20%PANI-PTSA was compared with Pt/C (Electrochem) in a passive direct methanol fuel cell and the effect of PANI-PTSA on methanol crossover and fuel utilization was analyzed. Ultimately, the Pt/C-20%PANI-PTSA modified catalyst was shown to be more suitable for applying in the direct methanol fuel cells (DMFC) compared with the commercial Pt/C material

  13. New aspects of poly aniline doping: A study based on using electrochemical quartz crystal nano balance

    Oxidative and non-oxidative dopings of poly aniline different concentrations have been studied by electrochemical quartz crystal nano balance technique. Poly aniline was synthesized electrochemically on the gold electrode of quartz crystal using a galvanostatic electro polymerization method (1 ma/c m2). Electrochemically synthesized poly aniline film was exposed to different concentrations of various acidic solutions and the changes in the mass (frequency) of the polymer were recorded. Results showed that the extent and the rate of non-oxidative doping depend on the concentration and nature of dopant acid. The rate of doping in the case of a number of tested inorganic acids was as the order of: H3PO442SO4. Exposure of doped poly aniline to ammonia solution (0.5 M) resulted a mass reduction in the polymer film due to the non-oxidative un doping process. Further experiments showed that this doping/un doping behaviour is a completely reversible process. Mass changes of the polymer in oxidative doping/un doping process were also recorded. It was also found that at ph values lower than 1, the total mass change during oxidation of the polymer was dependent on acid (or proton) concentration. However, at ph values over 1, the mass change during oxidation was independent of acid (or proton) concentration. These two observations support two different mechanisms of doping suggested by other workers

  14. YAlO3/Fe掺杂ZnO复合物的制备、表征及对酸性红B的降解%Synthesis and Characterization of YAlO3/Fe-doped ZnO and Its Photocatalytic Oxidation of Acid Red B

    程春萍

    2012-01-01

    In this work,YAlO3/Fe -doped ZnO composite,a novel photocatalyst, was synthesized by ultrasonic disper-sion and liquid boiling method and characterized by X - ray diffraction ( XRD ) and scanning electron microscope ( SEM) , and its photocatalytic activities were evaluated through the degradation of acid red B under visible light irradiation. The effects of preparation conditions such as YAlO3 content, heat - treated temperature and heat - treated time on the photocatalytic activity of YAlO3/Fe - doped ZnO composite were examined. In addition,the influences of visible light irradiation time and YAlO3/Fe - doped ZnO amount as well as organic dyes on the photocatalytic degradation were also investigated by HPLC techniques. The experimental results indicated that the YAlO3/Fe - doped ZnO composite can effectively utilize visible energy to degrade acid red B and its photocatalytic activity was much superior to that of Fe - doped ZnO composite under the same condition. Results revealed that the AlO3/Fe - doped ZnO showed higher activity and the maximum conversion of acid red B could reach 97.7% within 40 min.%采用溶胶-凝胶、超声分散和溶液沸腾法制备YAlO3/Fe掺杂ZnO复合物,在可见光的照射下,考察了酸性红B降解效果,并利用x-射线衍射(XRD)和扫描电子显微镜(SEM)对光催化剂进行了表征,同时研究了YAlO3的包覆量、YAlO3/Fe掺杂ZnO的量、可见光照射时间、处理温度和处理时间等因素对酸性红B降解率的影响,其降解过程也用HPLC进一步进行验证.结果表明,YAlO3/Fe掺杂ZnO在40 min酸性红B的降解率达到97.7%,表现出更好的光催化活性.

  15. Polymer electrolyte membrane fuel cells based on Nafion and acid-doped PBI:state-of-the-art and recent progress

    2002-01-01

    Based on perfluorosulfonic acid polymer membranes (PFSA,e.g.Nafion),polymer electrolyte membrane fuel cells (PEMFC) operate with hydrogen or purified reformate gas due to the strong poisoning effect of fuel impurities.Consequently,a complicated fuel storage or fuel processing system is needed.Direct methanol fuel cells,on the other hand,suffer from slow anodic kinetics and therefore low power density.The newest technology in the field is the development of temperature-resistant polymer membranes for operation at temperatures higher than 100°C.The high temperature PEMFC exhibits performance compatible with PFSA-based PEM fuel cell but can tolerate up to 3 %(volume fraction) carbon monoxide.The high CO tolerance makes it possible to use the reformed hydrogen directly from a simple methanol reformer without further CO removal.This opens possibility for an integrated reformer-fuel cell system,which is expected to exhibit high power density and simple construction as well as efficient capital and operational cost.

  16. The Anti-Doping Movement.

    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. PMID:26972261

  17. Polarization induced doped transistor

    Xing, Huili (Grace); 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.

  18. Doped Colloidal Artificial Ice

    Libal, A.; Reichhardt, C. J. Olson; Reichhardt, C.

    2015-01-01

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Unlike magnetic artificial spin ices, colloidal and vortex artificial spin ice realizations allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is rai...

  19. The Dope Stops Here

    2007-01-01

    Beijing has been making preparations to present a dope-free Olympics next yearThe China Anti-Doping Agency,set up to replace the 17-year-old China Doping Control Center,was offi- cially unveiled in Beijing on November 12.Between July 27 next year,when the Olympic Village is opened to athletes,and August 24,the last day of the Olympic Games,a total of 4,500 doping tests will be conducted in the build- ing.This number is 25 percent higher than that of the Athens Olympic Games in 2004 and 63 percent higher than at the Sydney Olympics in 2000.

  20. Doped golden fullerene cages

    Baletto, Francesca; Ferrando, Riccardo

    2015-01-01

    A first-principles investigation of the effect of the doping of golden cages of 32 atoms is proposed. It is shown that Ag and Cu doping affects the geometrical stability of the icosahedral fullerene Au-32 cage, where Ag-doping leads to a new, low symmetric, and prolate motif while Cu-doping leads to a lump, incomplete decahedral shape. Most significantly, the HOMO-LUMO gap depends strongly on the cluster geometry while its dependence on the cluster chemical composition seems to be weaker.

  1. Properties, degradation and high temperature fuel cell test of different types of PBI and PBI blend membranes

    Li, Qingfeng; Rudbeck, Hans Christian; Chromik, Andreas;

    2010-01-01

    Polybenzimidazoles (PBIs) with synthetically modified structures and their blends with a partially fluorinated sulfonated aromatic polyether have been prepared and characterized for high temperature proton exchange membrane fuel cells. Significant improvement in the polymer chemical stability in...... to further improve the polymer stability and assist maintaining the membrane integrity. Upon acid doping the membrane swelling was reduced for the modified PBI and their blend membranes, which, in turn, results in enhancement of the mechanical strength, proton conductivity and high temperature fuel...

  2. Photothermal ablation of cancer cells using self-doped polyaniline nanoparticles

    Hong, Yoochan; Cho, Wonseok; Kim, Jeonghun; Hwng, Seungyeon; Lee, Eugene; Heo, Dan; Ku, Minhee; Suh, Jin-Suck; Yang, Jaemoon; Kim, Jung Hyun

    2016-05-01

    Water-stable confined self-doping polyaniline nanocomplexes are successfully fabricated by nano-assembly using lauric acid both as a stabilizer and as a localized dopant. In particular, the colloidal stability of the polyaniline nanocomplexes in neutral pH and the photothermal potential by near-infrared light irradiation are characterized. We demonstrate that confined self-doping polyaniline nanocomplexes as a photothermal nanoagent are preserved in the doped state even at a neutral pH. Finally, confined self-doping polyaniline nanocomplexes aided by lauric acid are successfully applied for the photothermal ablation of cancer cells.

  3. Cathodic electrocrystallization and electrochromic properties of doped rechargeable oxotungstates

    We extend the technique of preparing oxotungstate thin films by cathodic electrocrystallization from metastable acidic solutions to fabricate vanadium- and molybdenum-doped films on platinum and fluorine-doped tin oxide (FTO). By means of cyclic voltammetry, we demonstrate a wider potential interval of highly reversible redox activity for these doped films, as compared to purely tungstate films. Electrochromic behavior in this region is dependent on the nature of the doping element. We characterize the microstructure of these films using scanning tunneling and atomic force microscopy. We also apply Raman and UV-vis spectroscopy to characterize the acidic deposition solutions. In tungstate-vanadate bath, we observe evidence of mixed isopolyanions. We also found some features of less stable mixed anions in the tungstate-molybdate bath, characterized phase composition of these films by means of XRD, and explain the results in the terms of parallel deposition from coexisting molecular precursors.

  4. Cathodic electrocrystallization and electrochromic properties of doped rechargeable oxotungstates

    Laurinavichute, V.K. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation)], E-mail: nika@elch.chem.msu.ru; Vassiliev, S.Yu. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation); Plyasova, L.M.; Molina, I.Yu. [Boreskov Institute of Catalysis, Siberian Division of the Russian Academy of Sciences, Prosp. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Khokhlov, A.A. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation); Pugolovkin, L.V. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation); Boreskov Institute of Catalysis, Siberian Division of the Russian Academy of Sciences, Prosp. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Borzenko, M.I.; Tsirlina, G.A. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation)

    2009-09-30

    We extend the technique of preparing oxotungstate thin films by cathodic electrocrystallization from metastable acidic solutions to fabricate vanadium- and molybdenum-doped films on platinum and fluorine-doped tin oxide (FTO). By means of cyclic voltammetry, we demonstrate a wider potential interval of highly reversible redox activity for these doped films, as compared to purely tungstate films. Electrochromic behavior in this region is dependent on the nature of the doping element. We characterize the microstructure of these films using scanning tunneling and atomic force microscopy. We also apply Raman and UV-vis spectroscopy to characterize the acidic deposition solutions. In tungstate-vanadate bath, we observe evidence of mixed isopolyanions. We also found some features of less stable mixed anions in the tungstate-molybdate bath, characterized phase composition of these films by means of XRD, and explain the results in the terms of parallel deposition from coexisting molecular precursors.

  5. Frode sportiva e doping

    Errede, Pietro

    2009-01-01

    Prima di prendere in esame la pratica del doping dal punto di vista giuridico, l'autore illustra la normativa sulla frode sportiva ed i suoi possibili punti di contatto con il fenomeno doping Segue l'analisi normativa un caso giurisprudenziale degli ultimi anni, il caso Juventus.

  6. Doping and Public Health

    Christiansen, Ask Vest

    http://www.idrottsforum.org/features/aarhus_doping/chrask_doping2007.html INHDR - International Network for Humanistisc Doping Research, med den virtuella adressen www.doping.au.dk , höll sin andra konferens den 15-16 augusti på Aarhus Universitet, med dess Center for Idræt som värdinstitution. En...... rad av världens främsta idrottsvetare och dopningsexperter hade mött upp för att presentera papers till en intresserad och engagerad publik. Temat för konferensen var "Doping and Public Health", och den aspekten behandlades också; dock tolkade flera presentatörer temat på sina egna vis, och hela...

  7. Doped graphene supercapacitors.

    Kumar, Nanjundan Ashok; Baek, Jong-Beom

    2015-12-11

    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. PMID:26574192

  8. Doped graphene supercapacitors

    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.

  9. To dope or not to dope

    Overbye, Marie Birch; Knudsen, Mette Lykke; Pfister, Gertrud Ursula

    2013-01-01

    ’ hypothetical decisions. The most effective deter-rents were related to legal and social sanctions, side-effects and moral considerations. Female athletesand younger athletes evaluated more reasons as deterrents than older, male athletes. When confrontedwith incentives to dope, the type of sport was often a......tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43......, althoughthe fear of social sanctions was almost as great a deterrent.Implications: Anti-doping prevention strategies should be diversified to target specific groups of athletes....

  10. Synthesis and characterization of magnetic nanoparticles of oxides for dual MnFe2O4 bioseparation, stabilized in fatty acid and the system chitosan - Eu(TTA)3(TPPO)2. Studies on the influence of doping with Gd3+, Tb3+, Ho3+ e Eu3+ in structural and magnetic properties

    This work was synthesized and characterized ferrite magnetic nanoparticles manganese, using the chemical coprecipitation method. By varying the heating time under 98°C (0, 10,20,40,60 3 80 minutes), the molar percentage of doping (1, 3, 5, 7, and 10%), gadolinium, europium, terbium and holmium. Magnetic ferrite nanoparticles and manganese ferrite doped with manganese were synthesized by coprecipitation method starting with chloride solutions of metals (iron (III), manganese (II), europium (III), gadolinium (III), terbium (III) and holmium (III)) and NaOH 5mol.L-1 as precipitating agent. The magnetic nanoparticles were characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, magnetization curves, and thermal analysis. Most of manganese ferrite particles showed superparamagnetic behavior. After the characterization it was found that the samples synthesized manganese ferrite with more than 40 minutes heating time, crystal structure showed the characteristic pattern of the inverted manganese ferrite spinel type. The stabilization of the samples in oleic acid nanoparticles produced with a hydrophobic outer layer and facilitated by coating chitosan biopolymer, since this has a positive charge. Among the doped samples there was no significant change in the magnetic behavior. Several techniques for characterizing these materials have been used such as X-ray diffraction spectrum in the infrared region, magnetization curves and thermal analysis. The resins were tested as magnetic material for the separation of biological materials. In this paper, are used as biological targets separation of bovine serum albumin. (author)

  11. Health-enhancing doping controls

    Christiansen, Ask Vest

    2010-01-01

    Editorial published at International Network of Humanistic Doping Research (INHDR) website: http://www.doping.au.dk/en/online-resources/editorials/......Editorial published at International Network of Humanistic Doping Research (INHDR) website: http://www.doping.au.dk/en/online-resources/editorials/...

  12. Thermal, FT–IR and SHG efficiency studies of L-arginine doped KDP crystals

    K D Parikh; D J Dave; B B Parekh; M J Joshi

    2007-04-01

    Potassium dihydrogen phosphate (KDP) is a well known nonlinear optical (NLO) material with different applications. Since most of the amino acids exhibit NLO property, it is of interest to dope them in KDP. In the present study, amino acid L-arginine was doped in KDP. The doping of L-arginine was confirmed by FT–IR and paper chromatography. Thermogravimetry suggested that as the amount of doping increases the thermal stability decreases as well as the value of thermodynamic and kinetic parameters decreases. The second harmonic generation (SHG) efficiency of L-arginine doped KDP crystals was found to be increasing with doping concentration of L-arginine. The results are discussed here.

  13. Doping semiconductor nanocrystals.

    Erwin, Steven C; Zu, Lijun; Haftel, Michael I; Efros, Alexander L; Kennedy, Thomas A; Norris, David J

    2005-07-01

    Doping--the intentional introduction of impurities into a material--is fundamental to controlling the properties of bulk semiconductors. This has stimulated similar efforts to dope semiconductor nanocrystals. Despite some successes, many of these efforts have failed, for reasons that remain unclear. For example, Mn can be incorporated into nanocrystals of CdS and ZnSe (refs 7-9), but not into CdSe (ref. 12)--despite comparable bulk solubilities of near 50 per cent. These difficulties, which have hindered development of new nanocrystalline materials, are often attributed to 'self-purification', an allegedly intrinsic mechanism whereby impurities are expelled. Here we show instead that the underlying mechanism that controls doping is the initial adsorption of impurities on the nanocrystal surface during growth. We find that adsorption--and therefore doping efficiency--is determined by three main factors: surface morphology, nanocrystal shape, and surfactants in the growth solution. Calculated Mn adsorption energies and equilibrium shapes for several nanocrystals lead to specific doping predictions. These are confirmed by measuring how the Mn concentration in ZnSe varies with nanocrystal size and shape. Finally, we use our predictions to incorporate Mn into previously undopable CdSe nanocrystals. This success establishes that earlier difficulties with doping are not intrinsic, and suggests that a variety of doped nanocrystals--for applications from solar cells to spintronics--can be anticipated. PMID:16001066

  14. Recent developments on proton conducting poly(2,5-benzimidazole) (ABPBI) membranes for high temperature polymer electrolyte membrane fuel cells

    Asensio, J.A.; Gomez-Romero, P. [Institut de Ciencia de Materials de Barcelona (ICMAB, CSIC), Campus UAB, E-08193 Bellaterra (Barcelona) (Spain)

    2005-08-01

    Commercial polybenzimidazole (PBI) membranes impregnated with phosphoric acid have become a serious candidate as electrolytes for high temperature PEMFC. Much research effort has been devoted to the study of this proton conducting membrane.[1, 2] On the other hand, PBI is not the simplest nor the cheapest of this family and many other polybenzimidazoles would also be of great interest in this respect. Among them, poly(2,5-benzimidazole) (ABPBI) is one of the best choices [3]. ABPBI is easy to polymerize from a single monomer, even without previous purification, it absorbs more acid than PBI in the same bath concentration, and it has the same thermal stability and high proton conductivity at temperatures up to 200 C. Here we review all the recent developments on the preparation of proton conducting ABPBI membranes, mainly by phosphoric acid impregnation, but also by sulfonation or doping with heteropolyacids to form hybrid organic-inorganic membranes. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  15. Synthesis of boron-doped graphene monolayers using the sole solid feedstock by chemical vapor deposition.

    Wang, Huan; Zhou, Yu; Wu, Di; Liao, Lei; Zhao, Shuli; Peng, Hailin; Liu, Zhongfan

    2013-04-22

    Substitutionally boron-doped monolayer graphene film is grown on a large scale by using a sole phenylboronic acid as the source in a low-pressure chemical vapor deposition system. The B-doped graphene film is a homogeneous monolayer with high crystalline quality, which exhibits a stable p-type doping behavior with a considerably high room-temperature carrier mobility of about 800 cm(2) V(-1) s(-1) . PMID:23463717

  16. Isoelectronic co-doping

    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.

  17. Doping and Fair Play

    Nicolas Eber

    2009-01-01

    The conventional approach to the economic analysis of doping in sport is that athletes are typically involved in a Prisoner’s Dilemma-type interaction (Breivik 1987, Bird and Wagner 1997, Eber and Thépot 1999, Haugen 2004).1 The idea is straightforward: doping being a dominant strategy (i.e., yielding a preferred outcome regardless of the strategy used by the competitor), each athlete finds it optimal to take drugs; this results in a situation of generalized doping although each athlete would...

  18. Marijuana as doping in sports.

    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. PMID:12744713

  19. Methods for Doping Detection.

    Ponzetto, Federico; Giraud, Sylvain; Leuenberger, Nicolas; Boccard, Julien; Nicoli, Raul; Baume, Norbert; Rudaz, Serge; Saugy, Martial

    2016-01-01

    Over the past few years, the World Anti-Doping Agency (WADA) has focused its efforts on detecting not only small prohibited molecules, but also larger endogenous molecules such as hormones, in the view of implementing an endocrinological module in the Athlete Biological Passport (ABP). In this chapter, the detection of two major types of hormones used for doping, growth hormone (GH) and endogenous anabolic androgenic steroids (EAASs), will be discussed: a brief historical background followed by a description of state-of-the-art methods applied by accredited anti-doping laboratories will be provided and then current research trends outlined. In addition, microRNAs (miRNAs) will also be presented as a new class of biomarkers for doping detection. PMID:27348309

  20. Doping - pohledem ekonomie

    Petrisko, Lukáš

    2009-01-01

    My diploma thesis deals with doping and is specially focused on anabolic steroids. It was written in response to § 288 Criminal code, which newly describes production and other handling with hormonal effect as a delict in order to reduce the number of users, both among proffesional and among recreational sportsmen. It shows that sport federations have enough instruments to be able to face doping and that the newly adopted legal ragulation has a negative impact on human health, which is incons...

  1. The Economics of doping

    Berentsen, Aleksander

    2002-01-01

    This paper considers a strategic game in which two players, with unequal prospects of winning the game, decide simultaneously and secretly to use performance-enhancing drugs before they compete. In the mixed strategy equilibrium, the favorite player is more likely to take these drugs than is the underdog, yet, for some parameter values, he is less likely to win the game with doping opportunities than without. The paper then analyzes the anti-doping regulations adopted by the International Oly...

  2. Exploring proton doping in poly-3-methylpyrrole by infrared spectroscopy

    Structural changes induced by electrochemical redox processes or by pH variations on conducting poly-3-methylpyrrole, electrochemically synthesized in NaClO4 acetonitrile solution, have been studied by infrared spectroscopy. With this aim infrared spectra of perchlorate doped poly-3-methylpyrrole films at different oxidation states as well as after immersion in acid (pH = 1) and basic (pH = 12.6) aqueous solutions have been analysed. The existence of proton-doping mechanism in this polymer has been confirmed from the comparative study of spectra of oxidized/reduced and acid/basic treated polymer

  3. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells. PMID:26781285

  4. Doped barium titanate nanoparticles

    T K Kundu; A Jana; P Barik

    2008-06-01

    We have synthesized nickel (Ni) and iron (Fe) ion doped BaTiO3 nanoparticles through a chemical route using polyvinyl alcohol (PVA). The concentration of dopant varies from 0 to 2 mole% in the specimens. The results from X-ray diffractograms and transmission electron micrographs show that the particle diameters in the specimen lie in the range 24–40 nm. It is seen that the dielectric permittivity in doped specimens is enhanced by an order of magnitude compared to undoped barium titanate ceramics. The dielectric permittivity shows maxima at 0.3 mole% doping of Fe ion and 0.6 mole% of Ni ion. The unusual dielectric behaviour of the specimens is explained in terms of the change in crystalline structure of the specimens.

  5. Exploring Knowledge, Attitudes and Abuse Concerning Doping in Sport among Syrian Pharmacy Students

    Mazen El-Hammadi

    2013-09-01

    Full Text Available This study aimed to assess pharmacy students’ knowledge about doping substances used in sport, explore their attitudes toward doping and investigate their misuse of doping drugs. A questionnaire was developed and employed to collect data from bachelor of pharmacy (BPharm students at the International University for Science and Technology (IUST. Two-hundred and eighty students participated in this self-administrated, paper-based survey. Around 90% of the students did not appear to know that narcotics, β-blockers and diuretics were used in sport as doping agents. Additionally, proportions between 60% and 80% considered vitamins, energy drinks and amino acids as substances that possess performance-enhancing effects. The main reason for doping, based on students’ response, was to improve muscular body appearance. The vast majority of students agreed that pharmacists should play a major role in promoting awareness about risks of doping. While students showed negative attitudes toward doping, approximately 15% of them, primarily males, had already tried a doping drug or might do so in the future. More than 60% of the students believed that sports-mates and friends are the most influential in encouraging them to take a doping agent. The study highlights the need to provide pharmacy students with advanced theoretical background and practical training concerning doping. This can be achieved by adopting simple, but essential, changes to the current curricula.

  6. Electrochemical doping of graphene

    Kaverzin, A. A.; Strawbridge, S. M.; Price, A. S.; Withers, F.; Savchenko, A. K.; Horsell, D. W.

    2010-01-01

    The electrical properties of graphene are known to be modified by chemical species that interact with it. We investigate the effect of doping of graphene-based devices by toluene (C6H5CH3). We show that this effect has a complicated character. Toluene is seen to act as a donor, transferring electrons to the graphene. However, the degree of doping is seen to depend on the magnitude and polarity of an electric field applied between the graphene and a nearby electrode. This can be understood in ...

  7. Photocatalysis with chromium-doped TiO2: Bulk and surface doping

    Ould-Chikh, Samy

    2014-04-15

    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:TiO 2 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. It\\'s classified! The photocatalytic properties of TiO2 modified by chromium depend strongly on the preparation method. To clarify this problem, two types of modified titania are discussed: one with CrIII doped in the bulk and one with CrOOH clusters on the TiO2 surface (see picture). Both series show visible-light-driven photo-oxidation activity. However, surface modification appears to be a more efficient strategy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Genetic Doping and Health Damages

    AA Fallahi Fallahi; AA Ravasi Ravasi; DD Farhud Farhud

    2011-01-01

    "nBackground: 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 a...

  9. A Stability Study of Alkali Doped PBI Membranes for Alkaline Electrolyzer Cells

    Jensen, Jens Oluf; Aili, David; Hansen, Martin Kalmar; Li, Qingfeng; Bjerrum, Niels Janniksen; Christensen, Erik

    2014-01-01

    Polybenzimidazole membranes in a linear, a crosslinked and a thermally cured form were subjected to aging in 6 M aqueous KOH at 85 ºC for periods of up to 176 days. The aged membranes were characterized with respect to weight loss, mechanical properties and ionic conductivity. The area specific...

  10. High temperature superconducting with two doping atoms in La-doped Bi-2201 and Y-doped Bi-2212

    Röser, H.P; Huber, F; M. von Schönermark; Nikoghosyan, A

    2009-01-01

    These crystals have two doping patterns given by oxygen excess and doping with an additional atom with projected positions in theCuO2 plane. Both doping elements are necessary for the occurrence of superconductivity. Where the two doping patterns overlap, the point matched locations actas there sonating superconducting pathway and might explain a correlation between Tc and the doping structure.

  11. Wet oxidation of EDTA using metal-doped MCM-41 as catalyst

    Decontaminants like ethylenediaminetetraacetic acid (EDTA), ascorbic acid, and citric acid are widely used in the radioactive decontamination of reactor components. The complexants interfere in the treatment of radioactive effluent and hence it is imperative to oxidatively destroy the complexant to enable easy treatment of radioactive effluent. An attempt has been made to oxidatively destroy EDTA using hydrogen peroxide as oxidant in the presence of metal-doped MCM-41A as catalyst. The reason for using metal-doped MCM-41 as catalyst for the oxidative degradation is because of its larger surface area (∝ 1 000 m2 . g-1) with small pore size (20-100 Aa). Also the metal used has variable valency, which helps in undergoing electron transfer reactions. Metal-doped MCM-41 was synthesized. Results indicate that among the metals chosen for doping MCM-41, the catalytic efficiency in the oxidative degradation decreased in the following order: molybdenum > vanadium > titanium. (orig.)

  12. Doped vanadium oxides phase transitions vapors influence

    N.Y. Shishkin; A.A. Komarov; D.V. Kosov; V.A. Cherkasov; Bashkirov, L. A.; Bardi, U; Y.K. Gunko

    2005-01-01

    The methods of vanadium dioxide synthesis were developed. The first one is based on the decomposition of vanadyl oxalate VOC2O4 obtained by the dissolution of vanadium oxide (V) in ethanedioic acid solution with consequent heating. The second one uses the magnetron sputtering of metallic vanadium with its consequent soft oxidation. Investigations of the transition temperature in vanadium dioxide influence by the material doping and adding MoO3, Bi2O3, SnO2, NiO, CuO, Co3O4 as well as by the pre...

  13. 燃料电池用纳米改性聚苯并咪唑阴离子交换膜的制备%Synthesis of Polybenzimidazole/Nano-Particles Hybrid Anion Conducting Membranes Used for Fuel Cell

    汪称宇; 储富强; 林本才; 冯天英; 袁宁一; 丁建宁

    2016-01-01

    Imidazolium-based ionic liquid (IL) was synthesized from epichlorohydrin and 1 –methyl imidazole,and ionic liquid functionalized graphene oxide (IL–GO) was obtained from IL and graphene oxide (GO). Different content of IL–GO was incorporated into polybenzimidazole (FPBI) to investigate the content effect on the properties of composite membranes. The effect of content of IL–GO on the thermal stability,mechanical strength,ionic conductivity,ion exchange capacity (IEC),water absorption, swelling degree and alkali resistance performance of composite film were investigated. The results show that as the content of IL–GO increases,the properties of the composite membranes,such as proton conductivity,IEC and tensile properties present an increase variation. When IL–GO content is 30%,its tensile stress and tensile elastic modulus reach 77.5 MPa and 1.95 GPa respectively. Under 80℃,its maximum ionic conductivity reach up to 72.3 mS/cm. However,the thermal stability of the composite membranes don’t dramatically change,and the composite membranes show an excellent alkaline stability. This investigation demonstrates that FPBI/IL–GO composite membranes may be promising for alkaline anion exchange membrane fuel cell applications.%以环氧氯丙烷和1–甲基咪唑为原料制备新型离子液体(IL),以IL为原料对氧化石墨烯(GO)进行表面修饰制备离子液体功能化氧化石墨烯(IL–GO),以IL–GO为添加剂制备基于含氟聚苯并咪唑(FPBI)复合膜。研究了IL–GO的含量对复合膜的热稳定性、力学强度、离子电导率、离子交换容量(IEC)、吸水率、溶胀度和耐碱性等性能的影响。研究结果表明,复合膜的IEC、离子电导率和拉伸性能都随着IL–GO含量的增加而增大,当IL–GO含量为30%时其拉伸应力和拉伸弹性模量分别达到77.5 MPa和1.95 GPa,在80℃下,其最大离子电导率可达72.3 mS/cm,然而复合膜的热稳定性并没随着IL–GO含

  14. Doping of carbon foams for use in energy storage devices

    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. Role of mesoscopic morphology in charge transport of doped polyaniline

    A K Mukherjee; Reghu Menon

    2002-02-01

    In doped polyaniline (PANI), the charge transport properties are determined by mesoscopic morphology, which in turn is controlled by the molecular recognition interactions among polymer chain, dopant and solvent. Molecular recognition plays a significant role in chain conformation and charge delocalization. The resistivity of PANI doped by camphor sulfonic acid (CSA)/2-acrylo-amido-1-propane sulfonic acid (AMPSA)/dodecyl benzene sulfonic acid (DBSA) is around 0.02 cm. PANI-CSA and PANI-AMPSA show a metallic positive temperature coefficient of resistivity above 150 K, with a finite value of conductivity at 1.4 K; whereas, PANI-DBSA shows hopping transport at low temperatures. The magnetoresistance is positive (negative) for PANI-CSA (PANIAMPSA); and PANI-DBSA has a large positive MR. The behavior of MR suggests subtle variations in mesoscopic morphology between PANI-CSA and PANI-AMPSA.

  16. Molecular Doping of Graphene

    Wehling, T.O.; K. S. Novoselov; Morozov, S.V.; Vdovin, E. E.; Katsnelson, M. I.; Geim, A. K.; Lichtenstein, A.I.

    2008-01-01

    Graphene, a one-atom thick zero gap semiconductor [1, 2], has been attracting an increasing interest due to its remarkable physical properties ranging from an electron spectrum resembling relativistic dynamics [3-12] to ballistic transport under ambient conditions [1-4]. The latter makes graphene a promising material for future electronics and the recently demonstrated possibility of chemical doping without significant change in mobility has improved graphene's prospects further [13]. However...

  17. Magnetic and electromagnetic properties of Pr doped strontium ferrite/polyaniline composite film

    This paper reported three acid (including hydrochloric acid HCl, p-toluenesulfonic acid PTS and D-camphor-10-acid CSA) doped SrPr0.2Fe11.8O19/PANI composite film and the HCl–PANI film prepared by a sol–gel method and in-situ oxidative polymerization. The characteristics of the film phase structure, surface morphology, conductivity and magnetic and electromagnetic properties were studied by using XRD, XPS, FESEM, four-probe tester, VSM and Vector Network Analyzer. The resistivity of organic acid doped composite films is higher than that of the HCl doped one. The saturation and remanent magnetization of PTS and HCl doped composite films are greater than the CSA-doped one; however, the coercivity of the three acid doped composite films is basically 5546 Oe. The saturation magnetization, remanent magnetization and coercivity of SrPr0.2Fe11.8O19 film are greater than those of the SrPr0.2Fe11.8O19–PANI composite film. In the frequency range of 8–12 GHz, the dielectric loss of HCl–PANI film is the maximum, and the dielectric loss of SrPr0.2Fe11.8O19 film is the minimum; the magnetic loss of the four films is in descending order as SrPr0.2Fe11.8O19 film, PrSrM/(HCl–PANI) composite film, PrSrM/(CSA–PANI) and HCl–PANI film. - Highlights: • Synthesizing three acid doped SrPr0.2Fe11.8O19/PANI composite films. • By sol–gel method and in-situ oxidative polymerization. • With excellent magnetic and electromagnetic properties. • The particular coating structure of PANI and Sr-ferrite. • Great interest for magnetic material and microwave absorbers

  18. Doped Chiral Polymer Metamaterials Project

    National Aeronautics and Space Administration — Doped Chiral Polymer Metamaterials (DCPM) with tunable resonance frequencies have been developed by adding plasmonic inclusions into chiral polymers with variable...

  19. Electrochemical synthesis and characterization of chloride doped polyaniline

    A M Pharhad Hussain; A Kumar

    2003-04-01

    Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl– ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer. But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that, the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic whereas chloride doped polyaniline films were found to be highly hygroscopic.

  20. Dielectric parameters and a.c. conductivity of pure and doped poly (methyl methacrylate) films at microwave frequencies

    Anju Tanwar; K K Gupta; P J Singh; Y K Vijay

    2006-08-01

    Dielectric properties of pure and doped poly (methyl methacrylate) (PMMA) films at microwave frequency, 8.92 GHz, have been studied at 35°C. Iodine, benzoic acid and FeCl3 have been used as dopants. The losses in doped films are found to be larger than in pure PMMA films. The increased losses account for increased a.c. conductivity in doped films. The increase in conductivity is accounted due to creation of additional hopping sites for the charge carriers in doped samples. The dielectric data has also been used to evaluate optical constants, absorption index () and refractive index () of the films.

  1. Hydrothermal synthesis, characterization and luminescent properties of lanthanide-doped NaLaF$_4$ nanoparticles

    JIGMET LADOL; HEENA KHAJURIA; SONIKA KHAJURIA; HAQ NAWAZ SHEIKH

    2016-08-01

    Nanoparticles of sodium lanthanum (III) fluoride-doped and co-doped with Eu$^{3+}/Tb$^{3+}$ were prepared by the hydrothermal method using citric acid as structure-directing agent. Structural aspects and optical properties of synthesized nanoparticles were studied by powder X-ray diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectra (EDS), particle size by dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectrum and photoluminescence (PL) techniques. Nanoparticles consist of well-crystallized hexagonal phase and the average crystallite size for undoped and doped-NaLaF$_4$ nanoparticles are in the range of 20–22 nm. TEM images show that nanoparticles have cylindrical shape and crystalline nature of nanoparticles was confirmed by SAED patterns. Downconversion(DC) luminescent properties of doped NaLaF4 were also investigated and impact of co-doping has been explored.

  2. Direct writing the selective emitter of solar cell with lateral ultrasonic spray laser doping technique

    Song, Jingwei; Wang, Xuemeng; Gong, Li; Lin, Yanghuan; Gao, Xiaodong; Huang, Jiapei; Shen, Hui

    2015-10-01

    In recent years, laser doping of selective emitters has offered an attractive method to improve the performance of silicon solar cell. A simple laser process is presented for the local doping of crystalline silicon solar cells. Here, the doped line has been direct-written by a 532 nm wavelength laser combined with lateral ultrasonic spray using phosphoric acid. The laser doping selective emitter was quantitatively and spatially measured using Kelvin probe force microscopy under external light illumination. By using the exploited system, we could pattern the dielectric layer while simultaneously doping the underlying silicon to easily achieve the selective emitter (n++) in one processing step. With argon as the conveyance gas, the local melted Si was surrounded by the air-argon gas mixture in the entire process, which caused a decrease in oxygen incorporation.

  3. The Ethics of Doping and Anti-Doping

    Møller, Verner

    With every positive drugs test the credibility and veracity of modern elite sport is diminished. In this radical and provocative critique of current anti-doping policy and practice, Verner Møller argues that the fight against doping – promoted as an initiative to cleanse sport of cheats – is at h...

  4. Comparison of Soy Protein Dope with Yeast Protein Dope on the Rheological Properties

    Hayakawa, Isao; Chang, Hung Min; Katoh, Tatsuo

    1984-01-01

    Rheological properties of isolated soybean protein dopes were compared with those of yeart protein dopes in order to find out their application and processing. The elastic properties of soybean protein dope were better than those of yeast protein dope prepared with high protein concentrates because the viscoelastic absorption of soybean protein dope was smaller than that of yeast protein dope and the capacity of water holding was higher than that of yeast protein dope. On the other hand, yeas...

  5. Gene doping in modern sport.

    MAREK SAWCZUK

    2009-01-01

    Full Text Available Background: The subject of this paper is gene doping, which should be understood as "he non-therapeutic use of cells, genes, genetic elements, or of the modulation of gene expression, having the capacity to improve athletic performance". The authors of this work, based on the review of literature and previous research, make an attempt at wider characterization of gene doping and the discussion of related potential threats.Methods: This is a comprehensive survey of literature on the latest applications of molecular biology in medicine. The analysis involves a dozen scientific databases examined in order to find genes used in gene therapy and potentially useful in gene doping. Results: The obtained results enable better recognition of gene doping and indicate genes used in medicine that could be used in gene doping. This paper describes potential effects of their use and associated risk, and predicts the possible developments of gene doping in the future. Conclusion: Gene doping is undoubtedly a part of modern sport. Although WADA included gene doping on the list of banned methods as early as 2004, as previously stated above, it has not managed to develop efficient methods of detection.

  6. Fitness Doping and Body Management

    Thualagant, Nicole

    This PhD thesis examines in a first paper the conceptualization of fitness doping and its current limitations. Based on a review of studies on bodywork and fitness doping it is emphasised that the definition of doping does not provide insights into bodywork of both men and women. Moreover, it is...... argued that the social and a cultural context are missing in the many epidemiological studies on the prevalence of doping. The second paper explores the difficulties of implementing an anti-doping policy, which was originally formulated in an elite sport context, in a fitness context and more......-based fitness centres. Based on a survey in ten Danish club-based fitness centres and on narratives from semi-structured interviews, it is highlighted that the objectives of bodywork differ according to the users’ age and gender. Two different ways of investing in the body are explored in the paper, namely a...

  7. Effect of doping on TSD relaxation in cellulose acetate films

    P K Khare; P L Jain; R K Pandey

    2000-12-01

    Thermally stimulated depolarization current (TSDC) studies have been performed on solution grown cellulose acetate films doped with different concentrations of acrylic acid (AA) prepared at the poling temperatures (40–75°C) with poling fields (10–50 kV/cm). The TSDC spectra of pure and AA doped CA films reveal two relaxation peaks at 80°C and 180 ± 2°C, having activation energies centred around 0.25 and 0.55 eV. The phenomena of the existence of these current maxima have been analyzed and discussed in terms of the molecular motion of the polar side groups and release of the remaining part of the frozen dipoles by their cooperative motion with adjoining segments of the main polymer chain. The peak currents, released charge and activation energies associated with the peaks are affected by AA doping. The effect of doping with acrylic acid on the discharge current indicates the formation of molecular aggregates.

  8. Role Models on Dope

    Christiansen, Ask Vest; Gleaves, John

    2014-01-01

    Compared to football-players cyclists are virtuous role models. Yes, Lance Armstrong, Michael Rasmussen and other riders have doped, and because of this they have received the predicate as the most immoral athletes in the sporting world. But if morality is not only a question of whether a person ...... has enhanced his or hers performances by the use of various drugs (and lied about it), but also is about human beings’ relations and interactions, then cycling isn’t as depraved as we like to tell each other. Football is much worse....

  9. Optical phase-conjugation in erioglaucine dye-doped thin film

    T Geethakrishnan; P K Palanisamy

    2006-02-01

    Optical phase-conjugation (OPC) has been demonstrated in erioglaucine (acid blue 9) dye-doped gelatin films via continuous-wave degenerate four-wave mixing (DFWM) using a low-power He-Ne laser at 633 nm. DFWM and holographic processes are found to contribute to the observed phase-conjugate signal. A maximum phase-conjugate beam reflectivity of about 0.24% has been observed in these dye-doped gelatin films.

  10. Synthesis and characterization of gadolinium-doped nanotubular titania for enhanced photocatalysis

    Graphical abstract: The Gd-doped titania nanotubes showed an increase in photocatalytic activity together with Gd/Ti ratio increase up 0.5%, followed by a rapid fall above 1.0%. - Highlights: • Enhanced Gd-doped titania nanotube photocatalysts have been synthesized. • Uniform Gd-doped titania nanoparticles were employed as raw materials. • Actual gadolinium contents in titania were precisely characterized by ICP-AES. • The distribution of Gd dopant was marked using element mapping. - Abstract: Gadolinium-doped titanium dioxide nanotubes were fabricated with a facile two-step route. Precursors Gd-doped titania nanoparticles were synthesized by a traditional sol–gel method. Hydrothermal process and acid treatment were employed afterwards, and Gd-doped titania nanotubes were finally obtained after calcination. The nominal doping concentration was expressed by Gd/Ti atomic ratio, ranged from 0% to 5.0%. Both the precursors and nanotubes were characterized by X-ray photoelectron spectra, inductively coupled plasma-atomic emission spectrometry, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectrometer, UV–vis diffusion reflection spectra and N2 absorption–desorption experiment. The photocatalytic activities were investigated using methyl orange as the model pollutant. The results indicated that Gd-doped titania nanotubes with nominal Gd/Ti of 0.5% possessed the optimal photocatalytic activity in our study

  11. Superconducting doped topological materials

    Sasaki, Satoshi, E-mail: sasaki@sanken.osaka-u.ac.jp [Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Mizushima, Takeshi, E-mail: mizushima@mp.es.osaka-u.ac.jp [Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Department of Physics, Okayama University, Okayama 700-8530 (Japan)

    2015-07-15

    Highlights: • Studies on both normal- and SC-state properties of doped topological materials. • Odd-parity pairing systems with the time-reversal-invariance. • Robust superconductivity in the presence of nonmagnetic impurity scattering. • We propose experiments to identify the existence of Majorana fermions in these SCs. - Abstract: Recently, the search for Majorana fermions (MFs) has become one of the most important and exciting issues in condensed matter physics since such an exotic quasiparticle is expected to potentially give rise to unprecedented quantum phenomena whose functional properties will be used to develop future quantum technology. Theoretically, the MFs may reside in various types of topological superconductor materials that is characterized by the topologically protected gapless surface state which are essentially an Andreev bound state. Superconducting doped topological insulators and topological crystalline insulators are promising candidates to harbor the MFs. In this review, we discuss recent progress and understanding on the research of MFs based on time-reversal-invariant superconducting topological materials to deepen our understanding and have a better outlook on both the search for and realization of MFs in these systems. We also discuss some advantages of these bulk systems to realize MFs including remarkable superconducting robustness against nonmagnetic impurities.

  12. Doping optimization and surface modification of aluminum doped zinc oxide films as transparent conductive coating

    Aluminum doped zinc oxide (ZnO:Al) films were grown using spray pyrolysis technique. Effect of doping on structural, electrical, optical and morphological properties was studied. Aluminum doping improved the prominence of [002] growth while maintaining the grain size ∼ 48 nm. Using an intermediate Al/Zn atomic ratio in precursor (1.5:100), we could achieve a low resistivity ρ ∼ 7 × 10−4 Ωcm. These films possessed an average visible transmittance ∼ 88%, an optical gap ∼ 3.7 eV and plasma wavelength at 1.87 μm. A simultaneous use of methanol and iso-propanol in the precursor lead to a moderate surface roughness ∼ 12 nm. The films were surface modified using wet chemical etching in diluted hydrochloric acid, for varied time intervals (5 s–15 s) and etchant concentrations (0.125%–1%). The etching experiments could be used to know the building of the film as also to modify the surface for desired optical and morphological properties. - Highlights: ► High conductivity ZnO:Al films prepared by spray pyrolysis. ► Physical properties very competitive as transparent conductor. ► Co-use of methanol and iso-propanol made smoother but compact films. ► Wet chemical etching helped to modify the surface and understand the growth.

  13. Enhancing charge storage of conjugated polymer electrodes with phenolic acids

    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.

  14. Non linear optical studies of Holmium doped glasses

    Holmium doped boric acid glasses were synthesized by the rapid quenching method. Holmium has many transitions in the visible region and so it is a good candidate for saturation studies and possible saturation materials. The glasses were studied for their linear as well as non linear optical properties. The nonlinear behavior is studied using Z-scan set up analyzed by using a NPWE theory. (author)

  15. The Grey Zone in Doping

    Van Thuyne, W

    2006-01-01

    Anti-doping programs seek to preserve what is intrinsically valuable about sport. This intrinsic value is often referred to as “the spirit of sport”, which is the celebration of the human spirit, body and mind and is characterised by values such as ethics, fair play, honesty, health, fun, team work, courage and many others. Doping, which is not only the detection of prohibited substances but also its possession and use, failing or tampering a doping test or refusing a control, is considered a...

  16. Anhydrous phosphoric Acid functionalized sintered mesoporous silica nanocomposite proton exchange membranes for fuel cells.

    Zeng, Jie; He, Beibei; Lamb, Krystina; De Marco, Roland; Shen, Pei Kang; Jiang, San Ping

    2013-11-13

    A novel inorganic proton exchange membrane based on phosphoric acid (PA)-functionalized sintered mesoporous silica, PA-meso-silica, has been developed and investigated. After sintering at 650 °C, the meso-silica powder forms a dense membrane with a robust and ordered mesoporous structure, which is critical for retention of PA and water within the porous material. The PA-meso-silica membrane achieved a high proton conductivity of 5 × 10(-3) to 5 × 10(-2) S cm(-1) in a temperature range of 80-220 °C, which is between 1 and 2 orders of magnitudes higher than a typical membrane Nafion 117 or polybenzimidazole (PBI)/PA in the absence of external humidification. Furthermore, the PA-meso-silica membranes exhibited good chemical stability along with high performance at elevated temperatures, producing a peak power density of 632 mW cm(-2) using a H2 fuel at 190 °C in the absence of external humidification. The high membrane proton conductivity and excellent fuel cell performance demonstrate the utility of PA-meso-silica as a new class of inorganic proton exchange membranes for use in the high-temperature proton exchange membrane fuel cells (PEMFCs). PMID:24125494

  17. Facile hydrothermal preparation of recyclable S-doped graphene sponge for Cu{sup 2+} adsorption

    Zhao, Lianqin; Yu, Baowei [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China); Xue, Fumin [Shandong Provincial Analysis and Tester Center, Shandong Academy of Science, Jinan 250014 (China); Xie, Jingru; Zhang, Xiaoliang; Wu, Ruihan; Wang, Ruijue; Hu, Zhiyan [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China); Yang, Sheng-Tao, E-mail: yangst@pku.edu.cn [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China); Luo, Jianbin, E-mail: luojb1971@163.com [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China)

    2015-04-09

    Graphical abstract: S-doped graphene sponge was prepared via hydrothermal treatment, where S-doped graphene sponge had an adsorption capacity of 228 mg/g for Cu{sup 2+}. - Highlights: • S-doped graphene sponge was prepared by hydrothermal treatment for heavy metal adsorption. • S-doped graphene sponge had a huge adsorption capacity for Cu{sup 2+}, which was 40 times higher than that of active carbon. • S-doped graphene sponge could be easily regenerated by washing with acidic thiourea. - Abstract: Graphene sponge (GS) has been widely employed for water purification, but adsorption capacity loss frequently occurs during the formation of spongy structure. In this study, we reported the hydrothermal preparation of S-doped GS for the removal of Cu{sup 2+} with a huge adsorption capacity of 228 mg/g, 40 times higher than that of active carbon. The adsorption isotherm could be well fitted into the Freundlich model with a K{sub F} value of 36.309 (L/mg){sup 1/n}. The equilibrium adsorption could be fully achieved in the first 5 min. In the thermodynamics study, the negative ΔG indicated that the adsorption was spontaneous and physisorption in nature. The positive ΔH implied that the adsorption was endothermic. The changes of both pH and ionic strength had no apparent influence on the adsorption. S-doped GS could be easily regenerated by washing with acidic thiourea. Moreover, S-doped GS could be used for the adsorption of other heavy metal ions, too. The implication to the applications of S-doped GS in water treatment is discussed.

  18. Facile hydrothermal preparation of recyclable S-doped graphene sponge for Cu2+ adsorption

    Graphical abstract: S-doped graphene sponge was prepared via hydrothermal treatment, where S-doped graphene sponge had an adsorption capacity of 228 mg/g for Cu2+. - Highlights: • S-doped graphene sponge was prepared by hydrothermal treatment for heavy metal adsorption. • S-doped graphene sponge had a huge adsorption capacity for Cu2+, which was 40 times higher than that of active carbon. • S-doped graphene sponge could be easily regenerated by washing with acidic thiourea. - Abstract: Graphene sponge (GS) has been widely employed for water purification, but adsorption capacity loss frequently occurs during the formation of spongy structure. In this study, we reported the hydrothermal preparation of S-doped GS for the removal of Cu2+ with a huge adsorption capacity of 228 mg/g, 40 times higher than that of active carbon. The adsorption isotherm could be well fitted into the Freundlich model with a KF value of 36.309 (L/mg)1/n. The equilibrium adsorption could be fully achieved in the first 5 min. In the thermodynamics study, the negative ΔG indicated that the adsorption was spontaneous and physisorption in nature. The positive ΔH implied that the adsorption was endothermic. The changes of both pH and ionic strength had no apparent influence on the adsorption. S-doped GS could be easily regenerated by washing with acidic thiourea. Moreover, S-doped GS could be used for the adsorption of other heavy metal ions, too. The implication to the applications of S-doped GS in water treatment is discussed

  19. Preparation method and use of visible light responsive nitrogen-doped titanium dioxide nano-tube

    Jiang, Zheng; Zhu, Qingshan; Yang, Fan; Zhang, Yayuan; Li, Hongzhong

    2010-01-01

    The invention discloses a preparation method of a nitrogen-doped titanium dioxide nanotube with response to visible lights, and comprises the following steps: a. metallic titanium or titaniferous compounds are used for preparing a metatitanic acid nanotube with a hydrothermal or solvothermal method; b. the metatitanic acid or titanium dioxide nanotube that is prepared by step a or a commercial metatitanic acid or titanium dioxide nanotube is dispersed in a water solution with nitrogen sources...

  20. Nanocrystal doped matrixes

    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.

  1. The induced synthesis of mixed phase niobate by Cu doping and its photocatalytic property

    Zhang Gaoke, E-mail: gkzhang@whut.edu.cn [School of Resources and Environmental Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan 430070 (China); Gong Jie [School of Resources and Environmental Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan 430070 (China); School of Resources and Environmental Engineering, Wuhan University of Science and Technology, Qingshan District, Wuhan 430081 (China); Gan Huihui; Lue Fan [School of Resources and Environmental Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan 430070 (China)

    2011-10-13

    Highlights: > Cu-doped KNb{sub 3}O{sub 8} photocatalysts were prepared by a simple solid-state method. > Cu doping can induce the formation of mixed phase niobates with KNb{sub 3}O{sub 8} and K{sub 6}Nb{sub 10.8}O{sub 30}. > Cu doping and mixed phase niobates synergistically enhanced the photocatalytic activity. - Abstract: Cu-doped KNb{sub 3}O{sub 8} photocatalysts were prepared using a simple solid-state method. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum. XRD and SEM analyses suggest that Cu doping can induce the formation of the compound K{sub 6}Nb{sub 10.8}O{sub 30} with tungsten-bronze structure and the relative content of K{sub 6}Nb{sub 10.8}O{sub 30} in the Cu-doped samples increased with increasing Cu doping amount. When the Cu doping amount reaches 2 wt.%, the as-prepared sample is mainly composed of K{sub 6}Nb{sub 10.8}O{sub 30}. The photocatalytic properties of the catalysts were evaluated using the degradation of acid red G. The results showed that Cu-doping significantly increased the photocatalytic activity of the KNb{sub 3}O{sub 8} catalyst. The optimum dopant concentration range of Cu was found to be 0.3-1 wt.%. The synergistic effect of Cu doping and mixed phase niobate compounds is responsible for the enhanced photocatalytic activity.

  2. Color stable manganese-doped phosphors

    Lyons, Robert Joseph; Setlur, Anant Achyut; Deshpande, Anirudha Rajendra; Grigorov, Ljudmil Slavchev

    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.

  3. Investigation of Silver Doped Hydroxyapatite

    Dubņika, A; Loča, D; Mālniece, L

    2012-01-01

    Biomaterials based on calcium phosphate ceramics are used as implants in human/animal body due to their excellent biocompatibility. Silver containing materials have a very broad spectrum of antibacterial activity; therefore silver doped hydroxyapatite can be used in medicine as antibacterial implant material. The aim of this work was to synthesize monophasic and biphasic silver doped hydroxyapatite and evaluate the differences in their physical and antibacterial properties.

  4. Gene doping in modern sport.

    MAREK SAWCZUK; AGNIESZKA MACIEJEWSKA; PAWEL CIESZCZYK,

    2009-01-01

    Background: The subject of this paper is gene doping, which should be understood as "he non-therapeutic use of cells, genes, genetic elements, or of the modulation of gene expression, having the capacity to improve athletic performance". The authors of this work, based on the review of literature and previous research, make an attempt at wider characterization of gene doping and the discussion of related potential threats.Methods: This is a comprehensive survey of literature on the latest app...

  5. Genetic Doping and Health Damages

    AA Fallahi Fallahi

    2011-03-01

    Full Text Available "nBackground: 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."nMethods: 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."nConclusion: 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.

  6. XPS analysis of boron doped heterofullerenes

    Schnyder, B.; Koetz, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Muhr, H.J.; Nesper, R. [ETH Zurich, Zurich (Switzerland)

    1997-06-01

    Boron heterofullerenes were generated through arc-evaporation of doped graphite rods in a helium atmosphere. According to mass spectrometric analysis only mono-substituted fullerenes like C{sub 59}B, C{sub 69}B and higher homologues together with a large fraction of higher undoped fullerenes were extracted and enriched when pyridine was used as the solvent. XPS analysis of the extracts indicated the presence of two boron species with significantly different binding energies. One peak was assigned to borid acid. The second one corresponds to boron in the fullerene cage, which is mainly C{sub 59}B, according to the mass spectrum. This boron is in a somewhat higher oxidation state than that of ordinary boron-carbon compounds. The reported synthesis and extraction procedure opens a viable route for production of macroscopic amounts of these compounds. (author) 2 figs., 1 tab., 7 refs.

  7. Porous silica doping by ion bombardment

    A new approach to porous-silica doping is via ion bombardment and exposure of the damaged structure to a controlled atmosphere. As a case study, SiO2 samples, bombarded with Ar2+ in a CO2 ambient and suitably processed, underwent an infrared spectroscopic investigation. The resulting data could be interpreted by assuming the addition of CO2 to the SiO2 skeleton at the diradical silicon defects produced by the bombardment. This addition takes place first via the formation of a carboxylate group, which evolves after heat treatment to an ester-like center, and eventually to a carboxilic acid after exposure to water vapor. Ab initio molecular-dynamics simulations of the interaction between CO2 and a silicon diradical are consistent with the above picture and suggest also the existence of an intermediate, in which tetrahedral carbon is bonded to the two silicon atoms and to two oxygen atoms

  8. Laser doping for ohmic contacts in n-type Ge

    Chiodi, F.; Chepelianskii, A. D.; GARDES C.; Hallais, G.; Bouchier, D.; Débarre, D.

    2014-01-01

    We achieved ohmic contacts down to 5 K on standard n-doped Ge samples by creating a strongly doped thin Ge layer between the metallic contacts and the Ge substrate. Thanks to the laser doping technique used, Gas Immersion Laser Doping, we could attain extremely large doping levels above the solubility limit, and thus reduce the metal/doped Ge contact resistance. We tested independently the influence of the doping concentration and doped layer thickness, and showed that the ohmic contact impro...

  9. Enhancing photoelectrochemical water splitting by aluminum-doped plate-like WO3 electrodes

    Highlights: • Al-doped plate-like WO3 films were prepared by hydrothermal method in dilute nitric acid solution from Al-W films on the FTO glass substrates. • High photocurrent density was achieved by appropriate amount Al doped plate-like WO3 films. • Efficient charge transfer of Al-doped WO3 plate-like electrodes led to increases of photocurrent. • Al-doped WO3 plate-like electrodes are desirable to become a novel electrode material for water splitting. - ABSTRACT: In the present work, aluminum-doped plate-like tungsten oxide (WO3) photoelectrodes were investigated by photoelectrochemical methods in order to evaluate the possibility of their application in water splitting. The aluminum-doped plate-like WO3 films were prepared by hydrothermal method in nitric acid from a radio frequency (RF) magnetron sputtered aluminum-tungsten layer on fluorine-doped tin oxide (FTO) glass. The crystal structure, composition and morphology of pure and aluminum-doped WO3 were compared using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that aluminum can be doped into WO3 plate-like photoelectrodes by placing radio frequency magnetron sputtered aluminum-tungsten films using a facile hydrothermal method. Plate-like WO3 films doped with 0.77 atom% aluminum showed photocurrent density of 1.14 mA/cm2 at 1.2 V vs. Ag/AgCl, which was 1.3 times higher than that of the pure WO3 (0.87 mA/cm2). Incident photon to current efficiency (IPCE) measurements carried out on photoelectrochemical (PEC) cell with aluminum-doped WO3 plate-like photoelectrodes as anodes demonstrated a significant increase of photoresponse in the intrinsic absorption range. Electrochemical impendence spectroscopy (EIS) showed that aluminum-doped WO3 possessed higher charge transfer rate and electrical conductivity than those of pristine WO3, thus presented a better performance in

  10. Crosslinking of polybenzimidazolemembranes by divinylsulfone post-treatment for high-temperature proton exchange membrane fuel cell applications

    Aili, David; Li, Qingfeng; Christensen, Erik;

    2011-01-01

    Phosphoric acid-doped polybenzimidazole (PBI) has been suggested as a promising electrolyte for proton exchangemembrane fuel cells operating at temperatures up to 200 ◦C. This paper describes the development of a crosslinking procedure for PBI membranes by post-treatment with divinylsulfone. The...... crosslinking chemistry was studied and optimized on a low-molecularweight model system and the results were used to optimize the crosslinking conditions of PBI membranes. The crosslinked membraneswere characterized with respect to chemical and physiochemical properties, showing improved mechanical strength and...... oxidative stability compared with their linear analogues. Fuel cell tests were further conducted in order to demonstrate the feasibility of the crosslinked membranes....

  11. Oxygen reduction on carbon supported platinum catalysts in high temperature polymer electrolytes

    Qingfeng, Li; Hjuler, Hans Aage; Bjerrum, Niels

    2000-01-01

    Oxygen reduction on carbon supported platinum catalysts has been investigated in H3PO4, H3PO4-doped Nafion and polybenzimidazole (PBI) polymer electrolytes in a temperature range up to 190 degrees C. Compared with pure H3PO4, the combination of H3PO4 and polymer electrolytes can significantly...... improve the oxygen reduction kinetics due to increased oxygen solubility and suppressed adsorption of phosphoric acid anions. Further enhancement of the catalytic activity can be obtained by operating the polymer electrolytes at higher temperatures. Efforts have been made to develop a polymer electrolyte...

  12. New electrocatalyst support for high temperature PEM fuel cells (HT-PEMFC)

    Boaventura, M.; Brandao, L.; Mendes, A. [Porto Univ. (PT). Lab. de Engenharia de Processos, Ambiente e Energia (LEPAE)

    2010-07-01

    This work compares the performance of electrocatalysts based on platinum supported in single-wall carbon nanohorns (Pt-SWNH) and supported in carbon black (Pt-carbon black) during high temperature PEM fuel operation. MEAs made of phosphoric acid doped polybenzimidazole (PBI/H{sub 3}PO{sub 4}) were characterized by polarization curves, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), at 160 C. The Pt-SWNH electrocatalyst presented a higher electrochemical surface area (ESA) when compared to Pt-carbon black. However, electrochemical experiments showed a higher ohmic resistance of the Pt-SWNH electrode related to a higher hydrophobic character of the SWNH carbon. (orig.)

  13. Membranes for energy conversion

    Peinemann, K.V.; Pereira Nunes, S. (eds.) [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    2008-07-01

    This volume contains the following chapters: 1. Sulfonated poly(arylether)-type polymers as proton exchange membranes: Synthesis and performance; 2. Polyimide ionomer membranes for PEFCs and DMFCs; 3. Membranes for high temperature PEFC based on acid-doped polybenzimidazoles; 4. Membrane for medium temperature PEFC based on Nafion filled with layered metal phosphates and phosphonates 5. Composite membranes for high temperature direct methanol fuel cells; 6. Dense ceramic membranes for hydrogen separation; 7. Membranes in energy systems with CO{sub 2} capture 8. Palladium membranes for hydrogen separation; 9. Membranes for power generation by pressure retarded osmosis.

  14. Doping dependence of electrical and thermal conductivity of nanoscale polyaniline thin films

    Jin Jiezhu; Wang Qing [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Haque, M A [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States)

    2010-05-26

    We performed simultaneous characterization of electrical and thermal conductivity of 55 nm thick polyaniline (PANI) thin films doped with different levels of camphor sulfonic acids (CSAs). The effect of the doping level is more pronounced on electrical conductivity than on thermal conductivity of PANIs, thereby greatly affecting their ratio that determines the thermoelectric efficiency. At the 60% (the molar ratio of CSA to phenyl-N repeat unit of PANI) doping level, PANI exhibited the maximum electrical and thermal conductivity due to the formation of mostly delocalized structures. Whereas polarons are the charge carriers responsible for the electrical conduction, phonons are believed to play a dominant role in the heat conduction in nanoscale doped PANI thin films.

  15. TiO-Based Organic Hybrid Solar Cells with Mn+ Doping

    Zühal Alparslan

    2011-01-01

    Full Text Available A hybrid solar cell is designed and proposed as a feasible and reasonable alternative, according to acquired efficiency with the employment of TiO2 (titanium dioxide and Mn-doped TiO2 thin films. In the scope of this work, TiO2 (titanium dioxide and Mn:TiO2 hybrid organic thin films are proposed as charge transporter layer in polymer solar cells. Poly(3-hexylthiophene:phenyl-C61-butyric acid methyl ester (P3HT: PCBM is used as active layer. When the Mn-doped TiO2 solar cells were compared with pure TiO2 cells, Mn-doped samples revealed a noteworthy efficiency enhancement with respect to undoped-TiO2-based cells. The highest conversion efficiency was obtained to be 2.44% at the ratio of 3.5% (wt/wt Mn doping.

  16. Superconductivity in doped fullerenes

    While there is not complete agreement on the microscopic mechanism of superconductivity in alkali-metal-doped C sup 0, further research may well lead to the production of analogous materials that lose resistance at even higher temperatures. Carbon 60 is a fascinating and arrestingly beautiful molecule. With 12 pentagonal and 20 hexagonal faces symmetrically arrayed in a soccer-ball-like structure that belongs to the icosahedral point group, I sub h, its high symmetry alone invites special attention. The publication in september 1990 of a simple technique for manufacturing and concentrating macroscopic amounts of this new form of carbon announced to the scientific community that enabling technology had arrived. Macroscopic amounts of C sub 6 sub 0 (and the higher fullerenes, such as C sub 7 sub 0 and C sub 8 sub 4) can now be made with an apparatus as simple as an arc furnace powered with an arc welding supply. Accordingly, chemists, physicists and materials scientists have joined forces in an explosion of effort to explore the properties of this unusual molecular building block. (author). 23 refs., 6 figs

  17. Optical and positron annihilation spectroscopic studies on PMMA polymer doped by rhodamine B/chloranilic acid charge transfer complex: Special relevance to the effect of γ-ray irradiation

    Hassan, H. E.; Refat, Moamen S.; Sharshar, T.

    2016-04-01

    Polymeric sheets of poly (methylmethaclyerate) (PMMA) containing charge transfer (CT) complex of rhodamine B/chloranilic acid (Rho B/CHA) were synthesized in methanol solvent at room temperature. The systematic analysis done on the Rho B and its CT complex in the form of powder or polymeric sheets confirmed their structure and thermal stability. The IR spectra interpreted the charge transfer mode of interaction between the CHA central positions and the terminal carboxylic group. The polymer sheets were irradiated with 70 kGy of γ radiation using 60Co source to study the enhanced changes in the structure and optical parameters. The microstructure changes of the PMMA sheets caused by γ-ray irradiation were analyzed using positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. The positron life time components (τi) and their corresponding intensities (Ii) as well as PADB line-shape parameters (S and W) were found to be highly sensitive to the enhanced disorder occurred in the organic chains of the polymeric sheets due to γ-irradiation.

  18. Doping and thrombosis in sports.

    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. PMID:22198857

  19. Main modern problems of doping in sport

    Rudenko V.P.

    2014-01-01

    Purpose : to identify and substantiate medico-biological, psychological and social problems of doping in sport. Material: Theoretical study is based on analysis of more than 50 scientific and methodical literatures. Results : it was shown that doping is one of the serious problems of modern sport and society in general. Defines important questions regarding anti-doping rules and the anti-doping control in sport. Installed the use of performance enhancing drugs in professional sports for child...

  20. Optoelectronic properties and characteristics of doping superlattices

    Kononenko, V.K.; I. S. Manak; Ushakov, D. V.

    1998-01-01

    Optical and electric properties of doping superlattices, or n-i-p-i crystals, can be varied in a wide range under excitation and through the choice of the thicknesses and doping of the crystal layers. Some basic results concerned the transformation of the electron energy spectrum of doping superlattices are summarized. Parameters and characteristics of doping superlattices related to optoelectronics devices, such as photodetectors, laser diodes, and optical modulators, are presented.

  1. Progress on erbium-doped waveguide components

    Bjarklev, Anders Overgaard; Berendt, Martin Ole; Broeng, Jes; Philipsen, Jacob Lundgreen; Pedersen, Martin Schuster

    The recent development in erbium-doped fiber amplifiers, and fiber lasers is reviewed. Also the latest results on planar erbium-doped waveguide amplifiers and high erbium concentration characterisation methods are presented......The recent development in erbium-doped fiber amplifiers, and fiber lasers is reviewed. Also the latest results on planar erbium-doped waveguide amplifiers and high erbium concentration characterisation methods are presented...

  2. Growth mechanisms for doped clusters

    Structural growth mechanisms for metal doped nanoclusters are investigated in combined experimental and theoretical studies. In particular, silicon, copper and gold clusters incorporating a transition metal dopant atom are investigated: SinX (X=Cu, V), CunSc+ and AunY+ with n < 20. The doped clusters are produced with a dual-target dual-laser vaporization source. Structural information about the doped nanoclusters is provided by infrared multi-photon dissociation spectroscopy. Their size and composition dependent stability is studied with photofragmentation and mass spectrometry. A detailed understanding of the role of the dopant atom in the structural growth and in the electronic structure of the clusters is obtained by comparison with quantum chemical computations using density functional theory. (review)

  3. Nitrogen-doped hydrothermal carbons

    Titirici, Maria-Magdalena; White, Robin J. [Max-Planck-Institute of Colloids and Interfaces, Potsdam (Germany). Dept. of Colloid Chemistry; Zhao, Li [Max-Planck-Institute of Colloids and Interfaces, Potsdam (Germany). Dept. of Colloid Chemistry; National Center for Nanoscience and Technology, Beijing (China)

    2012-07-01

    Nitrogen doped carbon materials are now playing an important role in cutting edge innovations for energy conversion and storage technologies such as supercapacitors and proton exchange membrane fuel cells as well as in catalytic applications, adsorption and CO{sub 2} capture. The production of such materials using benign aqueous based processes, mild temperatures and renewable precursors is of great promise in addressing growing environmental concerns for cleaner power sources at a time of increasing global demand for energy. In this perspective, we show that nitrogen doped carbons prepared using sustainable processes such as ''Hydrothermal Carbonisation'' has advantages in many applications over the conventional carbons. We also summarize an array of synthetic strategies used to create such nitrogen doped carbons, and discuss the application of these novel materials. (orig.)

  4. Amino acids

    Amino acids are organic compounds that combine to form proteins . Amino acids and proteins are the building blocks of life. When proteins are digested or broken down, amino acids are left. The human body uses amino acids ...

  5. Copper doped borate dosimeters revisited

    We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu+ and Cu++) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu+ ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. - Highlights: • The manuscript gives a panoramic overview on copper doped borate dosimeters. • Cu ions activated technique in borate

  6. Copper doped borate dosimeters revisited

    Alajerami, Y.S.M. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Department of Medical Radiography, Al-Azhar University, Gaza Strip, Palestine (Country Unknown); Hashim, S., E-mail: suhairul@utm.my [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Oncology Treatment Centre, Sultan Ismail Hospital, 81100 Johor Bahru (Malaysia); Ghoshal, S.K. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Bradley, D.A. [Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Mhareb, M. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Saleh, M.A. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); National Atomic Energy Commission (NATEC), Sana' a (Yemen)

    2014-11-15

    We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu{sup +} and Cu{sup ++}) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu{sup +} ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. - Highlights: • The manuscript gives a panoramic overview on copper doped borate dosimeters. • Cu ions activated

  7. A simple and rapid ESI-LC-MS/MS method for simultaneous screening of doping agents in urine samples

    Reddy I; Beotra Alka; Jain S; Ahi S

    2009-01-01

    Objective: The use of performance enhancing substances is banned in sports by the World Anti-Doping Agency (WADA). Though most prohibited substances can be detected by GC/MS, inclusion of corticosteroids and designer drugs has made it essential to detect these critical doping agents on LC/MS/MS due to their better separation and detection. Materials and Methods: A common extraction procedure for the isolation of acidic, basic and neutral drugs from urine samples was developed. A total of 2...

  8. Electronegativity and doping in semiconductors

    Schwingenschlögl, Udo

    2012-08-23

    Charge transfer predicted by standard models is at odds with Pauling’s electronegativities but can be reconciled by the introduction of a cluster formation model [Schwingenschlögl et al., Appl. Phys. Lett. 96, 242107 (2010)]. Using electronic structure calculations, we investigate p- and n-type doping in silicon and diamond in order to facilitate comparison as C has a higher electronegativity compared to Si. All doping conditions considered can be explained in the framework of the cluster formation model. The implications for codoping strategies and dopant-defect interactions are discussed.

  9. Extrinsic doping in silicon revisited

    Schwingenschlögl, Udo

    2010-06-17

    Both n-type and p-type doping of silicon is at odds with the charge transfer predicted by Pauling electronegativities and can only be reconciled if we no longer regarding dopant species as isolated atoms but rather consider them as clusters consisting of the dopant and its four nearest neighbor silicon atoms. The process that gives rise to n-type and p-type effects is the charge redistribution that occurs between the dopant and its neighbors, as we illustrate here using electronic structure calculations. This view point is able to explain why conventional substitutional n-type doping of carbon has been so difficult.

  10. Rare earth doped zirconia nanophosphors

    Undoped ZrO2 and single and double doped ZrO2:M (where M = Tb3+ and Eu3+) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS and photoluminescence (PL) spectrophotometry. The SEM micrographs show that resultant nanoparticles have dendritic shape. The CIE coordinates of the double doped ZrO2:Tb3+(1.2%):Eu3+(0.8%) nanophosphor lie in the white light region of the chromaticity diagram and show promise as good phosphor materials for new lighting devices. (author)

  11. Photocatalytic Degradation of Dicofol and Pyrethrum with Boric and Cerous Co-doped TiO2 under Light Irradiation

    GONG Lifen; ZOU Jing; ZENG Jinbin; CHEN Wenfeng; CHEN Xi; WANG Xiaoru

    2009-01-01

    Boric and cerous co-doped nano titanium dioxide (B/Ce co-doped TiO2) was synthesized using a sol-gel tech-nique, which involved the hydrolyzation of tetrabutyl titanate with the addition of boric acid and cerous nitrate. The B/Ce co-doped TiO2 was employed for the photocatalytic degradation of dicofol, cyfluthrin and fenvalerate under light irradiation. XRD, TEM, Fr-IR and UV-Vis DRS methods were used to characterize the crystalline structure. Experimental results showed that only the anatase signal phase was found for B/Ce co-doped TiO2, but multiplicate phases, including anatase, rutile and less brookite phases, were identified both in the pure TiO2 nanoparticles and Ce-doped TiO2 nanoparticles. The band gap value of B/Ce co-doped nano TiO2 was narrower than that of undoped nano TiO2. Compared to undoped TiO2, a stronger absorption in the range of 420 to 850 nm was found for B/Ce co-doped nano TiO2, which presented a higher photocatalytic activity in the degradation of dicofol, cyfluthrin and fenvalerate than both Ce doped nano TiO2 and pure nano TiO2 under the same light irradiation.

  12. Blue to Yellow Photoluminescence Emission and Photocatalytic Activity of Nitrogen Doping in TiO2 Powders

    Gabriela Byzynski

    2015-01-01

    Full Text Available The defects caused by doping are important for understanding the increased photocatalytic activities of TiO2:N in organic reactions and in the evaluation of OH radical production after doping. TiO2:N was therefore synthesized using a modified polymeric method and N doping was performed by calcination with urea. The resulting powders were characterized using field emission scanning electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, Raman spectroscopy, Fourier transformation infrared spectroscopy, and photoluminescence emission spectroscopy (PL. N doping did not alter the morphology of the nanoparticles, and the anatase phase predominated, with the retention of the rutile phase. The band gap values, superficial areas, and crystallite sizes of the powders decreased after doping. The PL results showed an additional energy level in the TiO2:N band gap structure as a result of TiO2 lattice defects caused by doping. At low N contents, the powders showed continuous emissions from the blue region to the yellow region and a high N content shifted the PL emissions to the red region. These results suggest that the use of these powders could increase the efficiencies of solar cells and water-splitting processes. The photocatalytic activity of the powders under UVC illumination was confirmed for different organic dye molecules. The OH radical production did not change extensively after doping, as shown by experiments with terephthalic acid, and higher photocatalytic efficiencies in Rhodamine-B degradation under UVC illumination were achieved using the doped samples.

  13. Tin dioxide sol-gel derived films doped with platinum and antimony deposited on porous silicon

    Savaniu, C.; Arnautu, A.; Cobianu, C.; Craciun, G.; Flueraru, C.; Zaharescu, M.; Parlog, C.; Paszti, F.; Berg, van den A.

    1999-01-01

    SnO2 sol-gel derived thin films doped simultaneously with Pt and Sb are obtained and reported for the first time. The Sn sources were tin(IV) ethoxide or tin(II) ethylhexanoate, while hexachloroplatinic acid (H2PtCl6) and antimony chloride (SbCl3) were used as platinum and antimony sources, respecti

  14. Doping silver nanoparticles in AOT lyotropic lamellarphases

    2001-01-01

    The organic lyotropic liquid crystal with long-range structural order is used as templateto assemble inorganic/organic hybrid by doping pre-fabricated Ag nanoparticles. The lamellar hy-brid with both hydrophilic and hydrophobic particles doped simultaneously is realized for the firsttime. The change of template structure after doping and the stability origin of dual-doped systemare characterized by small angle X-ray scattering and polarized optical microscopy. Results showthat the interaction and space matching between surfactant bilayers and doped particles are

  15. Electronic Structure of Doped Trans-Polyacetylene

    2002-01-01

    The behavior of electronic structures of doped trans-polyacetylene is revealed by a simplemethod. (C24H26)+n is used to simulate p-type doped trans-polyacetylene at various doping concentrations.The electronic structure is calculated by CNDO/2 method. These calculations show that at low doping lev-el, the decrease of electronic energy compensates the increase of elastic energy, thus the bond alternationexists, and the charge carriers are solitons. When doping level is high, the increase of elastic energy islarger than the decrease of electronic energy, the bond alternation disappears, solitons no longer exist,and polyacetylene is in a metalic state.

  16. Doping im Radsport als kollektives Gleichgewicht

    Vöpel, Henning

    2006-01-01

    Der Fall Jan Ullrich hat jüngst bestätigt, was von vielen Experten der Radsportszene schon immer vermutet worden war: Doping im Radsport ist ein flächendeckendes Phänomen. In der sportökonomischen Literatur gibt es verschiedene Modelle, die zeigen, unter welchen Bedingungen Doping eine individuell rationale Strategie sein kann. Formal handelt es sich bei Doping um ein Nash-Gleichgewicht: Wählt mein Konkurrent die Strategie Doping, ist es für mich ebenfalls vorteilhaft zu dopen. Doping ist die...

  17. <> doping threshold in sport contests

    Müller, Daniel

    2013-01-01

    We analyze the doping behavior of heterogeneous athletes in an environment of private information. In a n-player strategic game, modeled as an all-pay auction, each athlete has private information about his actual physical ability and choses the amount of performance-enhancing drugs. The use of doping substances is costly but not further regulated. The main finding of the analysis is the existence of a doping threshold. In our leading case only strong athletes dope. The level of the doping th...

  18. Magnetic and electromagnetic properties of Pr doped strontium ferrite/polyaniline composite film

    Huang, Ying; Li, Yuqing; Wang, Yan, E-mail: wangyan287580632@126.com

    2014-11-15

    This paper reported three acid (including hydrochloric acid HCl, p-toluenesulfonic acid PTS and D-camphor-10-acid CSA) doped SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}/PANI composite film and the HCl–PANI film prepared by a sol–gel method and in-situ oxidative polymerization. The characteristics of the film phase structure, surface morphology, conductivity and magnetic and electromagnetic properties were studied by using XRD, XPS, FESEM, four-probe tester, VSM and Vector Network Analyzer. The resistivity of organic acid doped composite films is higher than that of the HCl doped one. The saturation and remanent magnetization of PTS and HCl doped composite films are greater than the CSA-doped one; however, the coercivity of the three acid doped composite films is basically 5546 Oe. The saturation magnetization, remanent magnetization and coercivity of SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film are greater than those of the SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}–PANI composite film. In the frequency range of 8–12 GHz, the dielectric loss of HCl–PANI film is the maximum, and the dielectric loss of SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film is the minimum; the magnetic loss of the four films is in descending order as SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film, PrSrM/(HCl–PANI) composite film, PrSrM/(CSA–PANI) and HCl–PANI film. - Highlights: • Synthesizing three acid doped SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}/PANI composite films. • By sol–gel method and in-situ oxidative polymerization. • With excellent magnetic and electromagnetic properties. • The particular coating structure of PANI and Sr-ferrite. • Great interest for magnetic material and microwave absorbers.

  19. A systemic model of doping behavior.

    Johnson, Michael B

    2011-01-01

    Human behavior occurs within a system, and as such, so do behaviors in performance-related domains (e.g., athletics, academics). Doping is a performance enhancement behavior that can be problematic because of the negative physical and psychological effects associated with the use of some substances and the common argument that doping is unfair. However, doping continues and may be increasing. Because a firm theoretical or empirical understanding of doping does not exist, this article proposes a conceptual, comprehensive, and innovative systemic model of doping behavior. The model is built from relevant empiricism supporting the idea that contemporary doping behavior is a function of systemic transactions between historical doping practices, the present environment, current antidoping interventions, one's genetic makeup, developmental milestones, social factors, and epigenetics. PMID:21834401

  20. Method of doping organic semiconductors

    Kloc, Christian Leo; Ramirez, Arthur Penn; So, Woo-Young

    2012-02-28

    A method includes the steps of forming a contiguous semiconducting region and heating the region. The semiconducting region includes polyaromatic molecules. The heating raises the semiconducting region to a temperature above room temperature. The heating is performed in the presence of a dopant gas and the absence of light to form a doped organic semiconducting region.

  1. Impurity doping processes in silicon

    Wang, FFY

    1981-01-01

    This book introduces to non-experts several important processes of impurity doping in silicon and goes on to discuss the methods of determination of the concentration of dopants in silicon. The conventional method used is the discussion process, but, since it has been sufficiently covered in many texts, this work describes the double-diffusion method.

  2. Steroid profiling in doping analysis

    Kerkhof, Daniël Henri van de

    2002-01-01

    Profiling androgens in urine samples is used in doping analysis for the detection of abused steroids of endogenous origin. These profiling techniques were originally developed for the analysis of testosterone, mostly by means of the ratio of testosterone to epitestosterone (T/E ratio). A study was p

  3. Effect of Ho-doping on photocatalytic activity of nanosized TiO2 catalyst

    CAI Heshan; LIU Guoguang; Lü Wenying; LI Xiaoxia; YU Lin; LI Daguang

    2008-01-01

    Ho-doped TiO2 nanoparticles with higher photocatalytic activity were prepared by an acid-catalyzed sol-gel method. The photocatalytic decomposition of methyl orange in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of Ho doping on the crystallite sizes, crystal pattern, surface composition, and optical property of the catalysts were investigated by means of techniques such as X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Diffuse Reflectance UV-Vis Spectroscopy (UV-Vis DRS), Fourier Transform Infrared (FT-IR), and Photo-Luminiscence (PL) spectra. Moreover, the modification mechanism of Ho doping was also discussed. The results showed that Ho doping could inhibit phase transformation from anatase to ruffle, suppress the growth of TiO2 grains, cause blue shift of the absorption spectrum edge, accelerate surface hydroxylation, and enhance the separation efficiency of photoinduced electron-hole pairs, which resulted in a significant improvement in the photoreactivity of Ho-doped TiO2. Among them, the Ho-doped TiO2 calcined at 500 ℃ achieved the highest photocatalytic activity.

  4. Preparation and characterization of Ce-doped HfO{sub 2} nanoparticles

    Gálvez-Barboza, S. [Centro de Investigación en Química Aplicada, Departamento de Materiales Avanzados, Blvd. Enrique Reyna Hermosillo #140, C.P. 25294 Saltillo, Coahuila (Mexico); Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Industria Metalúrgica # 1062 Parque Industrial, C.P. 25900 Ramos Arizpe, Coahuila (Mexico); González, L.A. [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Industria Metalúrgica # 1062 Parque Industrial, C.P. 25900 Ramos Arizpe, Coahuila (Mexico); Puente-Urbina, B.A.; Saucedo-Salazar, E.M. [Centro de Investigación en Química Aplicada, Departamento de Materiales Avanzados, Blvd. Enrique Reyna Hermosillo #140, C.P. 25294 Saltillo, Coahuila (Mexico); García-Cerda, L.A., E-mail: luis.garcia@ciqa.edu.mx [Centro de Investigación en Química Aplicada, Departamento de Materiales Avanzados, Blvd. Enrique Reyna Hermosillo #140, C.P. 25294 Saltillo, Coahuila (Mexico)

    2015-09-15

    Highlights: • Ce-doped HfO{sub 2} nanoparticles were prepared by a modified solgel method. • Ce-doped HfO{sub 2} nanoparticles have a semispherical shape with sizes between 6 and 11.5 nm. • The samples doped with 10% in weight of Ce directly crystallized in a cubic structure. • A quick, straightforward and effective route for the preparation of Ce-doped nanoparticles. - Abstract: A modified solgel method to synthesize Ce-doped HfO{sub 2} nanoparticles was carried out using a precursor material prepared with cerium nitrate, hafnium chloride, citric acid and ethylene glycol. The obtained precursor material was calcined at 500 and 700 °C for 2 h in air. The influence of the concentration of Ce and the calcination temperature was studied to observe the structural and morphological changes of the obtained materials. For the characterization, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman scattering (RS) were employed. The XRD patterns shown that the Ce-doped HfO{sub 2} undergoes a structural transformation from monoclinic to cubic phase, which is significantly dependent on the Ce content and calcination temperature. TEM images have also confirmed the existence of semispherical nanoparticles with sizes between 6 and 11.5 nm.

  5. Preparation and characterization of Ce-doped HfO2 nanoparticles

    Highlights: • Ce-doped HfO2 nanoparticles were prepared by a modified solgel method. • Ce-doped HfO2 nanoparticles have a semispherical shape with sizes between 6 and 11.5 nm. • The samples doped with 10% in weight of Ce directly crystallized in a cubic structure. • A quick, straightforward and effective route for the preparation of Ce-doped nanoparticles. - Abstract: A modified solgel method to synthesize Ce-doped HfO2 nanoparticles was carried out using a precursor material prepared with cerium nitrate, hafnium chloride, citric acid and ethylene glycol. The obtained precursor material was calcined at 500 and 700 °C for 2 h in air. The influence of the concentration of Ce and the calcination temperature was studied to observe the structural and morphological changes of the obtained materials. For the characterization, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman scattering (RS) were employed. The XRD patterns shown that the Ce-doped HfO2 undergoes a structural transformation from monoclinic to cubic phase, which is significantly dependent on the Ce content and calcination temperature. TEM images have also confirmed the existence of semispherical nanoparticles with sizes between 6 and 11.5 nm

  6. Enhanced nonlinear optical characteristics of copper-ion-doped double crossover DNAs

    Park, Byeongho; Lee, Byung Jic; Dugasani, Sreekantha Reddy; Cho, Youngho; Kim, Chulki; Seo, Minah; Lee, Taikjin; Jhon, Young Min; Choi, Jaebin; Lee, Seok; Park, Sung Ha; Jun, Seong Chan; Yeom, Dong-Il; Rotermund, Fabian; Kim, Jae Hun

    2015-10-01

    The modification of deoxyribonucleic acid (DNA) samples by sequencing the order of bases and doping copper ions opens the possibility for the design of novel nanomaterials exhibiting large optical nonlinearity. We investigated the nonlinear characteristics of copper-ion doped double crossover DNA samples for the first time to the best of our knowledge by using Z-scan and four-wave mixing methods. To accelerate the nonlinear characteristics, we prepared two types of unique DNA nanostructures composed of 148 base pairs doped with copper ions with a facile annealing method. The outstanding third-order nonlinear optical susceptibility of the copper-ion-doped DNA solution, 1.19 × 10-12 esu, was estimated by the conventional Z-scan measurement, whereas the four-wave mixing experiment was also investigated. In the visible spectral range, the copper-ion-doped DNA solution samples provided competent four-wave mixing signals with a remarkable conversion efficiency of -4.15 dB for the converted signal at 627 nm. The interactions between DNA and copper ions contribute to the enhancement of nonlinearity due to structural and functional changes. The present study signifies that the copper-ion-doped double crossover DNA is a potential candidate as a highly efficient novel material for further nonlinear optical applications.

  7. Chemically modified graphene and nitrogen-doped graphene: Electrochemical characterisation and sensing applications

    Highlights: •Characterisation of graphene, N-doped graphene, acid/base functionalised derivatives. •N-doping superior to time-consuming functionalisation procedures. •N-doped graphene with redox or conducting polymer composites characterised. •Electrocatalysis of enzyme cofactors FAD+ and NADH2, by N-doped graphene. -- Abstract: Functionalised graphene (G) and nitrogen doped graphene (NG) nanomaterials are excellent candidates for electrocatalytic sensing of biomolecules and for developing biosensors, due to their unique physicochemical and electronic properties. Electrochemical characterisation and comparison of basic or acidic functionalised G and NG has been carried out, as well as of composite materials based on NG with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and the redox polymer poly(neutral red) by cyclic voltammetry and electrochemical impedance spectroscopy. Electroactive areas and heterogeneous electron transfer constant, of the GCE modified with the graphene derivatives have been evaluated, in order to choose the best material for electrode modification. The NG modified GCE enabled excellent electrocatalytic regeneration of the enzyme cofactors β-nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD), underlining the applicability of NG for the development of new sensitive biosensors

  8. Structure and electrochemical applications of boron-doped graphitized carbon nanofibers

    Yeo, Jae-Seong; Jang, Sang-Min; Miyawaki, Jin; An, Bai; Mochida, Isao; Rhee, Choong Kyun; Yoon, Seong-Ho

    2012-08-01

    Boron-doped graphitized carbon nanofibers (CNFs) were prepared by optimizing CNFs preparation, surface treatment, graphitization and boron-added graphitization. The interlayer spacing (d002) of the boron-doped graphitized CNFs reached 3.356 Å, similar to that of single-crystal graphite. Special platelet CNFs (PCNFs), for which d002 is less than 3.400 Å, were selected for further heat treatment. The first heat treatment of PCNFs at 2800 °C yielded a d002 between 3.357 and 3.365 Å. Successive nitric acid treatment and a second heat treatment with boric acid reduced d002 to 3.356 Å. The resulting boron-doped PCNFs exhibited a high discharge capacity of 338 mAh g-1 between 0 and 0.5 V versus Li/Li+ and 368 mAh g-1 between 0 and 1.5 V versus Li/Li+. The first-cycle Coulombic efficiency was also enhanced to 71-80%. Such capacity is comparable to that of natural graphite under the same charge/discharge conditions. The boron-doped PCNFs also exhibited improved rate performance with twice the capacity of boron-doped natural graphite at a discharge rate of 5 C.

  9. Structure and electrochemical applications of boron-doped graphitized carbon nanofibers

    Boron-doped graphitized carbon nanofibers (CNFs) were prepared by optimizing CNFs preparation, surface treatment, graphitization and boron-added graphitization. The interlayer spacing (d002) of the boron-doped graphitized CNFs reached 3.356 Å, similar to that of single-crystal graphite. Special platelet CNFs (PCNFs), for which d002 is less than 3.400 Å, were selected for further heat treatment. The first heat treatment of PCNFs at 2800 °C yielded a d002 between 3.357 and 3.365 Å. Successive nitric acid treatment and a second heat treatment with boric acid reduced d002 to 3.356 Å. The resulting boron-doped PCNFs exhibited a high discharge capacity of 338 mAh g−1 between 0 and 0.5 V versus Li/Li+ and 368 mAh g−1 between 0 and 1.5 V versus Li/Li+. The first-cycle Coulombic efficiency was also enhanced to 71–80%. Such capacity is comparable to that of natural graphite under the same charge/discharge conditions. The boron-doped PCNFs also exhibited improved rate performance with twice the capacity of boron-doped natural graphite at a discharge rate of 5 C. (paper)

  10. Photocatalytic degradation of phenol in Aqueous Solutions by Fe(III-doped TiO2/UV Process

    R Nabizadeh Nodehi

    2011-01-01

    Full Text Available "n "nBackgrounds and Objectives: Phenol and phenolic compounds are widely used in industry and daily liFe, and are of high interest due to stability in the environment, dissolution ability in water and health problems. In this regard, phenol removal from water is of high importance. The purpose of this study was to investigate the efficiency of photodegradation process for removal of phenol from aqueous system by use of Fe-doped TiO2 nanoparticles prepared by sol-gel method."nMaterials and Methods: Phenol concentrations of 5, 10, 50 and 100 mg/L were prepared and exposed to UV and Fe-doped TiO2, separately and simultaneously. Also the effect of initial phenol concentration, Fe-doped TiO2 loading and pH were studied. Various doses of photocatalist investigated for Fe- doped TiO2 were 0.25, 0.5 and 1 g/L. pH was studied at three ranges, acidic (pH=3, neutral (pH=7 and alkaline (pH=11."nResults: Maximum degradation was obtained at acidic pH, 0.5 g/L of Fe-doped TiO2 for all of phenol concentrations. With increasing initial concentration of phenol, photocatalytic degradation decreased. In comparison with Fe-doped TiO2/UV process, efficiency of UV radiation alone was low in phenol degradation (% 64.5 at 100 mg/l of phenol concentration. Also the amount of phenol adsorbed on the Fe-doped TiO2 was negligible at dark conditions."nConclusion: Results of this study showed that Fe(III- doped TiO2 nanoparticles had an important effect on photocatalytic degradation of high initial phenol concentration when Fe(III-doped TiO2/ UV process applied.

  11. Iron-Doped Carbon Aerogels: Novel Porous Substrates for Direct Growth of Carbon Nanotubes

    Steiner, S. A.; Baumann, T. F.; Kong, J.; Satcher, J. H.; Dresselhaus, M. S.

    2007-02-20

    We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K{sup +}-doped gels that can then be converted to Fe{sup 2+}- or Fe{sup 3+}-doped gels through an ion exchange process, dried with supercritical CO{sub 2} and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH{sub 4} (1000 sccm), H{sub 2} (500 sccm), and C{sub 2}H{sub 4} (20 sccm) at temperatures ranging from 600 to 800 C for 10 minutes, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled ({approx}25 nm in diameter and up to 4 mm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs were grown on Fe-doped CAs pyrolyzed at 800 C treated at CVD temperatures of 700 C.

  12. Studies on L-citrulline doped potassium dihydrogen phosphate- A non linear crystal with significant nonlinear properties

    Potassium Dihydrogen Phosphate (KDP) single crystal is considered as one of the best representative of nonlinear optical crystals. Recently, amino acids having excellent nonlinear optical characteristics are being investigated as prospective dopants to improve the non linear optical characteristics of KDP. The present work is an attempt in this direction and L citrulline, one of the non essential amino acids showing good non linear optical characteristics is used as the dopant for KDP. Good quality crystals of L-citrulline doped KDP crystals were grown by slow evaporation technique. From the powder X-ray diffraction studies of doped KDP crystal, the structure of the doped crystals was determined by direct method and refined by Pawley method employing Topaz version program using the single crystal X-ray data for pure KDP. The lattice parameters for L citrulline doped KDP are a=7.467A0, b=7.467 A0, c=6.977 A0. The crystal falls into the tetragonal crystal system with space group I42 d. The presence of carbon and oxygen, which are primary components of amino acids, in the EDAX spectrum confirms the effectiveness of doping. The absorption spectra of the doped samples show that the crystals are transparent in the entire visible region. The second harmonic generation efficiency of the doped samples was determined by Kurtz powder technique using the Q-switched Nd:YAG laser beam and is found to be 2.2 times that of KDP. The nonlinear optical properties can be well studied by the open aperture Z scan technique. The open aperture curve exhibits a normalized transmittance valley. The nonlinear absorption coefficient β is obtained by theoretical fitting for two photon absorption. It is inferred that doping KDP with L citrulline has enhanced the nonlinearity considerably. This obviously suggests the potentiality of the crystal as an optical power limiter and also for various optical device applications

  13. Fluorine doped vanadium dioxide thin films for smart windows

    Kiri, Pragna [Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); Warwick, Michael E.A. [UCL Energy Institute, Central House, 14 Upper Woburn Place, London, WC1H 0HY (United Kingdom); Ridley, Ian [Bartlett School of Graduate Studies, University College London, Wates House, 22 Gordon Street, WC1H 0QB, London (United Kingdom); Binions, Russell, E-mail: r.binions@ucl.ac.uk [Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London, WC1H 0AJ (United Kingdom)

    2011-12-01

    Thermochromic fluorine doped thin films of vanadium dioxide were deposited from the aerosol assisted chemical vapour deposition reaction of vanadyl acetylacetonate, ethanol and trifluoroacetic acid on glass substrates. The films were characterised with scanning electron microscopy, variable temperature Raman spectroscopy and variable temperature UV/Vis spectroscopy. The incorporation of fluorine in the films led to an increase in the visible transmittance of the films whilst retaining the thermochromic properties. This approach shows promise for improving the aesthetic properties of vanadium dioxide thin films.

  14. Effect of chromia doping of thermal stability of silica fibers

    Zaplatynsky, I.

    1974-01-01

    Commercial silica fibers of the type being evaluated for reusable surface insulation for reentry vehicles were found to be porous and composed of subfibers. The effect on shrinkage and devitrification of soaking such silica fibers in water, acetic acid, chromium acetate, and chromium nitrate solutions was studied. Felted specimens made of chromia-doped fibers shrunk only about one-half as much as those made of untreated fibers after exposure in air for 4 hours at 1300 C. The devitrification rate of fibers given prolonged soaks in chromium nitrate was as low as that of as-received fibers.

  15. Synthesis, structure, magnetic, electrical and electrochemical properties of Al, Cu and Mg doped MnO{sub 2}

    Hashem, Ahmed M., E-mail: ahmedh242@yahoo.com [National Research Centre, Inorganic Chemistry Department, Behoes St., Dokki, Cairo (Egypt); Institute for Complex Materials, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Abuzeid, Hanaa M. [National Research Centre, Inorganic Chemistry Department, Behoes St., Dokki, Cairo (Egypt); Narayanan, N. [Institute for Complex Materials, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Ehrenberg, Helmut [Institute for Complex Materials, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, D-64287 Darmstadt (Germany); Julien, C.M. [Universite Pierre et Marie Curie, Physicochimie des Electrolytes, Colloides et Sciences Analytiques (PECSA), 4 place Jussieu, 75005 Paris (France)

    2011-10-17

    Highlights: {yields} Al, Mg and Cu doped MnO{sub 2} as cathode in Li-ion batteries. {yields} Pure phase MnO{sub 2} for virgin and doped MnO{sub 2} were obtained. {yields} Doping elements improve the electrical conductivity of MnO{sub 2}. {yields} Electrochemical behaviour of MnO{sub 2} improved after doping by Al, Mg and Cu. - Abstract: Pure and doped manganese dioxides were prepared by wet-chemical method using fumaric acid and potassium permanganate as raw materials. X-ray diffraction patterns show that pure and Al, Cu and Mg doped manganese dioxides (d-MnO{sub 2}) crystallized in the cryptomelane-MnO{sub 2} structure. Thermal analysis show that, with the assistance of potassium ions inside the 2 x 2 tunnel, the presence of Al, Cu and Mg doping elements increases the thermal stability of d-MnO{sub 2}. The electrical conductivity of d-MnO{sub 2} increases in comparison with pure MnO{sub 2}, while Al-doped MnO{sub 2} exhibits the lower resistivity. As shown in the magnetic measurements, the value of the experimental effective magnetic moment of Mn ions decreases with introduction of dopants, which is attributed to the presence of a mixed valency of high-spin state Mn{sup 4+}/Mn{sup 3+}. Doped MnO{sub 2} materials show good capacity retention in comparison with virgin MnO{sub 2}. Al-doped MnO{sub 2} shows the best electrochemical results in terms of capacity retention and recharge efficiency.

  16. Chimie Douce Synthesis of Chalcogen-Doped Manganese Oxides

    Chalcogen-doped manganese oxides have been prepared by Chimie Douce redox reaction between permanganate and chalcogen element fine powder under acidic condition (pH = 1). According to powder X-ray diffraction analyses, the S- and Se-doped manganese oxides are crystallized with layered birnessite and tunnel-type α-MnO2 structures, respectively. On the contrary, Te-doped compound was found to be X-ray amorphous. According to EDS analyses, these compounds contain chalcogen dopants with the ratio of chalcogen/manganese = 4-7%. We have investigated the chemical bonding character of these materials with X-ray absorption spectroscopic (XAS) analysis. Mn K-edge XAS results clearly demonstrated that the manganese ions are stabilized in octahedral symmetry with the mixed oxidation states of +3/+4. On the other hand, according to Se K- and Te L1-edge XAS results, selenium and tellurium elements have the high oxidation states of +6, which is surely due to the oxidation of neutral chalcogen element by the strong oxidant permanganate ion. Taking into account their crystal structures and Mn oxidation states, the obtained manganese oxides are expected to be applicable as electrode materials for lithium secondary batteries

  17. Thermal stability of conductivity of polyaniline doped with various acids

    Prokeš, J.; Stejskal, Jaroslav

    Rudolstadt : Thüringisches Institut für Textil und KunststoffForschung e.v, 2004, s. 179-181. [International Symposium on Technologies for Polymer Electronics. Rudolstadt (DE), 28.09.2004-30.09.2004] R&D Projects: GA AV ČR IAA4050313 Institutional research plan: CEZ:AV0Z4050913 Keywords : polyaniline * conducting polymer * conductivity Subject RIV: CD - Macromolecular Chemistry

  18. Freestanding doped silicon nanocrystals synthesized by plasma

    Freestanding silicon nanocrystals (Si NCs) have recently gained great popularity largely due to their easily accessible surface and flexible incorporation into device structures. In the past decade plasmas have been increasingly employed to synthesize freestanding Si NCs. As freestanding Si NCs move closer to applications in a variety of fields such as electronics, thermoelectrics and lithium-ion batteries, doping becomes more imperative. Such a context explains the current great interest in plasma-synthesized doped freestanding Si NCs. In this work we review the synthesis of freestanding doped Si NCs by plasma. Doping-induced structural, electronic, optical and oxidation properties of Si NCs are discussed. We also review the applications of plasma-synthesized doped freestanding Si NCs that have been demonstrated so far. The development of freestanding doped Si NCs synthesized by plasma in the future is envisioned. (review article)

  19. Phosphorous doping a semiconductor particle

    Stevens, Gary Don; Reynolds, Jeffrey Scott

    1999-07-20

    A method (10) of phosphorus doping a semiconductor particle using ammonium phosphate. A p-doped silicon sphere is mixed with a diluted solution of ammonium phosphate having a predetermined concentration. These spheres are dried (16, 18), with the phosphorus then being diffused (20) into the sphere to create either a shallow or deep p-n junction. A good PSG glass layer is formed on the surface of the sphere during the diffusion process. A subsequent segregation anneal process is utilized to strip metal impurities from near the p-n junction into the glass layer. A subsequent HF strip procedure is then utilized to removed the PSG layer. Ammonium phosphate is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirement.

  20. Phosphorus doping a semiconductor particle

    Stevens, G.D.; Reynolds, J.S.

    1999-07-20

    A method of phosphorus doping a semiconductor particle using ammonium phosphate is disclosed. A p-doped silicon sphere is mixed with a diluted solution of ammonium phosphate having a predetermined concentration. These spheres are dried with the phosphorus then being diffused into the sphere to create either a shallow or deep p-n junction. A good PSG glass layer is formed on the surface of the sphere during the diffusion process. A subsequent segregation anneal process is utilized to strip metal impurities from near the p-n junction into the glass layer. A subsequent HF strip procedure is then utilized to removed the PSG layer. Ammonium phosphate is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirement. 1 fig.

  1. Degenerate doping of metallic anodes

    Friesen, Cody A; Zeller, Robert A; Johnson, Paul B; Switzer, Elise E

    2015-05-12

    Embodiments of the invention relate to an electrochemical cell comprising: (i) a fuel electrode comprising a metal fuel, (ii) a positive electrode, (iii) an ionically conductive medium, and (iv) a dopant; the electrodes being operable in a discharge mode wherein the metal fuel is oxidized at the fuel electrode and the dopant increases the conductivity of the metal fuel oxidation product. In an embodiment, the oxidation product comprises an oxide of the metal fuel which is doped degenerately. In an embodiment, the positive electrode is an air electrode that absorbs gaseous oxygen, wherein during discharge mode, oxygen is reduced at the air electrode. Embodiments of the invention also relate to methods of producing an electrode comprising a metal and a doped metal oxidation product.

  2. Photocatalytic degradation of selected herbicides in aqueous suspensions of doped titania under visible light irradiation

    The aim of this work was to study the efficiency of Fe- and N-doped titania suspensions in the photocatalytic degradation of the herbicides RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop, MCPP), (4-chloro-2-methylphenoxy)acetic acid (MCPA), and 3,6-dichloropyridine-2-carboxylic acid (clopyralid, CP) under the visible light (λ ≥ 400 nm) irradiation. The obtained results were compared with those of the corresponding undoped TiO2 (rutile/anatase) and of the most frequently used TiO2 Degussa P25. Computational modeling procedures were used to optimize geometry and molecular electrostatic potentials of MCPP, MCPA and CP and discuss the obtained results. The results indicate that the efficiency of photocatalytic degradation is greatly influenced by the molecular structure of the compound. Lowering of the band gap of titanium dioxide by doping is not always favorable for increasing photocatalytic efficiency of degradation.

  3. Professionalisierung und Doping im Sport

    Wüterich, Christoph

    2004-01-01

    Der Beitrag untersucht Zusammenhänge zwischen der zunehmenden Professionalisierung des Sports und dem Anstieg von Dopingvergehen. Er zeigt, dass im historischen Vergleich beide Phänomene nicht neu sind, dass sich die Probleme aufgrund der steigenden Bedeutung des Leistungssports aber zugespitzt haben. Ausgehend von einer juristischen und sozioökonomischen Analyse der Anreize zu Doping werden Lösungsvorschläge entwickelt. The author analyzes the interdependencies between a growing commercia...

  4. Doping, sundhed og fair konkurrencer

    Møller, Verner; Christiansen, Ask Vest

    Doping er blevet et nøgleord i reportagerne fra international sport. Atleternes præstationer kan først godkendes, når de har afgivet en negativ dopingprøve. Den omfattende kontrol retfærdiggøres som det, der skal sikre fair konkurrencer og en sund sport. Men har man egentlig begreb om det, man vil...

  5. Ideal Strength of Doped Graphene

    Woo, S. J.; Son, Young-Woo

    2012-01-01

    While the mechanical distortions change the electronic properties of graphene significantly, the effects of electronic manipulation on its mechanical properties have not been known. Using first-principles calculation methods, we show that, when graphene expands isotropically under equibiaxial strain, both the electron and hole doping can maintain or improve its ideal strength slightly and enhance the critical breaking strain dramatically. Contrary to the isotropic expansions, the electron dop...

  6. Professional Cycling and the Fight against Doping

    Robeck, Volker

    2014-01-01

    Doping seems to be well-organized and inherent in the system of professional cycling. This paper provides a theoretical approach, by using a multi-task (training and doping) principal-agent (team manager and cyclist) model, to illustrate the information asymmetry and conflicting objectives between both actors. Three settings are used to represent different situations in which the fight against doping takes place with varying intensity. The comparison of the equilibria in eachsetting reveals t...

  7. Main modern problems of doping in sport

    Rudenko V.P.

    2014-04-01

    Full Text Available Purpose : to identify and substantiate medico-biological, psychological and social problems of doping in sport. Material: Theoretical study is based on analysis of more than 50 scientific and methodical literatures. Results : it was shown that doping is one of the serious problems of modern sport and society in general. Defines important questions regarding anti-doping rules and the anti-doping control in sport. Installed the use of performance enhancing drugs in professional sports for children and youth. Given the promising solutions to the problems of doping in Ukraine. Conclusions: Among the problems of modern sport is becoming increasingly important issue of doping. It is an extremely complex because it involves the interrelated medical, legal, political, moral, organizational, social and pedagogical aspects. Socio-pedagogical factors of anti-doping policy in sports scientists comprehensively still not addressed. Certain aspects of anti-doping policy presented in scientific papers, which can be divided into two groups. The first group of papers is devoted to doping in sport as a social event. The second group of papers devoted to the problems of doping control. Today there is a need and objective preconditions for the development and adoption of a General concept, which would be generalized numerical amount of data received and served as a basis for developing an effective anti-doping control at the expense of improvement of legislative and normative-legal base and infrastructure of the anti-doping policy in Ukraine, which should be brought in line with modern international standards.

  8. Moral entrepreneurship and doping cultures in sport

    Stokvis, R.

    2003-01-01

    In this article, the fight against doping has been analyzed as an ongoing process of social definition. It is dependent on the development of power relations within and outside the world of sport. To analyze these dependencies, I identified a variety of important doping cultures in sport and studied the development of the power relations between the supporters of these cultures during the second half of the twentieth century. Doping culture is defined as the typical attitudes and practices re...

  9. Thermal Diffusion Doping of Single Crystal Diamond

    Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Blanchard, James P.; Zhou, Weidong; Gong, Shaoqin; Ma, Zhenqiang

    2014-01-01

    With the best overall electronic and thermal properties, single-crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors faces doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion-implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstr...

  10. Psychogenic urine retention during doping controls

    Elbe, Anne-Marie; Schlegel, Marius M.; Brand, Ralf

    2012-01-01

    Psychogenic urine retention during doping controls (PURD) refers to an athlete's inability to urinate during a doping control. This paper reports PURD to occur quite frequently in elite athletes, investigates the relationship to the clinical disorder of paruresis (PAR), and investigates its...... and pencil study involving 222 German-speaking athletes from various sports. The results indicate that 60% of these athletes have experienced psychogenic urine retention during doping controls, with only 39% of them showing symptoms of paruresis. PURD impacts athlete recovery and self-perception of...... professionalism and athletic excellence. Suggestions for psychological interventions and recommendations for improving the doping control system are given....

  11. Doping in Sport and Competition Design

    Nicolas EBER; Jacques THÉPOT

    1999-01-01

    We develop a game-theoretic model of doping which focuses on the economic aspects of competitive sports. According to the model, incentives for athletes to use doping increase when (i) the efficiency of the drug test system is low, (ii) the number of competitions during one season is high, (iii) the spread of prizes from sports events is large, (iv) the perceived health cost is low. Implication for anti-doping policy are derived. We also discuss the optimal (anti-doping) competition design.

  12. Chemical approaches for doping nanodevice architectures

    O’Connell, John; Biswas, Subhajit; Duffy, Ray; Holmes, Justin D.

    2016-08-01

    Advanced doping technologies are key for the continued scaling of semiconductor devices and the maintenance of device performance beyond the 14 nm technology node. Due to limitations of conventional ion-beam implantation with thin body and 3D device geometries, techniques which allow precise control over dopant diffusion and concentration, in addition to excellent conformality on 3D device surfaces, are required. Spin-on doping has shown promise as a conventional technique for doping new materials, particularly through application with other dopant methods, but may not be suitable for conformal doping of nanostructures. Additionally, residues remain after most spin-on-doping processes which are often difficult to remove. In situ doping of nanostructures is especially common for bottom-up grown nanostructures but problems associated with concentration gradients and morphology changes are commonly experienced. Monolayer doping has been shown to satisfy the requirements for extended defect-free, conformal and controllable doping on many materials ranging from traditional silicon and germanium devices to emerging replacement materials such as III–V compounds but challenges still remain, especially with regard to metrology and surface chemistry at such small feature sizes. This article summarises and critically assesses developments over the last number of years regarding the application of gas and solution phase techniques to dope silicon-, germanium- and III–V-based materials and nanostructures to obtain shallow diffusion depths coupled with high carrier concentrations and abrupt junctions.

  13. Boron doping of silicon using excimer lasers

    The use of lasers in the doping of semiconductors has been investigated extensively these last years both for photovoltaic and microelectronic applications. In this work, doping of single-crystal silicon in BCl3 ambients using a pulsed UV laser has been studied as a function of laser wavelength and fluence in order to investigate the effects of photochemical decomposition of the BCl3 gas and the effects of thermal decomposition of adsorbed layers on the doping process. Different parameters involved in the process (laser energy density, number of pulses per frame, BCl3 gas pressure) were investigated. The electrical characteristics of the doped layers are discussed

  14. Kilohertz laser ablation for doping helium nanodroplets

    Mudrich, M; Müller, S; Dvorak, M; Buenermann, O; Stienkemeier, F

    2007-01-01

    A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam-depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the non-volatile DNA basis Guanine is found to be efficient and a number of oligomers are detected.

  15. Chemical approaches for doping nanodevice architectures.

    O'Connell, John; Biswas, Subhajit; Duffy, Ray; Holmes, Justin D

    2016-08-26

    Advanced doping technologies are key for the continued scaling of semiconductor devices and the maintenance of device performance beyond the 14 nm technology node. Due to limitations of conventional ion-beam implantation with thin body and 3D device geometries, techniques which allow precise control over dopant diffusion and concentration, in addition to excellent conformality on 3D device surfaces, are required. Spin-on doping has shown promise as a conventional technique for doping new materials, particularly through application with other dopant methods, but may not be suitable for conformal doping of nanostructures. Additionally, residues remain after most spin-on-doping processes which are often difficult to remove. In situ doping of nanostructures is especially common for bottom-up grown nanostructures but problems associated with concentration gradients and morphology changes are commonly experienced. Monolayer doping has been shown to satisfy the requirements for extended defect-free, conformal and controllable doping on many materials ranging from traditional silicon and germanium devices to emerging replacement materials such as III-V compounds but challenges still remain, especially with regard to metrology and surface chemistry at such small feature sizes. This article summarises and critically assesses developments over the last number of years regarding the application of gas and solution phase techniques to dope silicon-, germanium- and III-V-based materials and nanostructures to obtain shallow diffusion depths coupled with high carrier concentrations and abrupt junctions. PMID:27418239

  16. Synthesis of CuO and ZnO Nanoparticles and CuO doped ZnO Nanophotocatalysts

    Nanocrystalline copper oxide (CuO) particles were precipitated by using different sources of copper salts and oxalic acids. Dicelike and flower-like structures were obtained. The particle sizes of all samples, were in the range of 10-30 nm. 0.5 % CuO doped ZnO (CuO-ZnO) nanophotocatalysts were prepared. No significant changes in morphology were observed between the undoped and doped ZnO except for a higher surface area obtained for CuO doped ZnO. The doping of CuO on ZnO also resulted in enhanced photo activity of ZnO in the photodegradation of methyl orange dye. (author)

  17. Effect of doped and undoped POMA on the morphology and miscibility of blends with Poly(vinylidene fluoride (PVDF

    I.S. Rocha

    1999-04-01

    Full Text Available The effect of the addition of small amounts of doped and undoped poly(o-methoxyaniline (POMA on the morphology of melt crystallized PVDF was investigated by means of polarized light optical microscopy. Undoped POMA (POMA-EB inhibits nucleation and growth of non ringed spherulites, partially formed by the polar gphase, whereas POMA doped with toluene sulfonic acid (POMA-TSA favors this process. Moreover, the doping of POMA increases the miscibility between the components of the PVDF/POMA blends, resulting in more homogeneous films. A possible cause of this miscibility increase and for the favoring of the polar gphase, is the higher polarity of the POMA chains as a result of the doping.

  18. Effect of structure on the photocatalytic activity of Pt-doped TiO2 nanotubes

    Highly ordered TiO2 nanotubes with different tube length were fabricated by anodization using C2H2O4.2H2O containing 0.5 wt.% NH4F (electrolyte A) and anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B), respectively. Then cathodic reduction method was used to dope Pt in TiO2 nanotubes in chloroplatinic acid. The results indicated that cathodic reduction could efficiently platinize TiO2 nanotubes. Pt-doped TiO2 nanotubes with the longer length had the higher photocatalytic activity for degrading methyl orange under UV and visible irradiation. The longer tube length has a positive effect on the photocatalytic activity of Pt-doped TiO2 nanotubes. Besides, as the content of anatase further decreases, the photocatalytic activity drops gradually due to the reduction reaction in the surface area.

  19. Transmittance and Reflectance Spectra of Doped-Polyanisidine-Derived Film in the Visible Light Region

    Polyanisidine (PAnis) powder was synthesized using a standard procedure. It was doped with Hydrochloric (HCl) and Perchloric (HClO4) Acids. The air-dried PAnis powder was then diluted using Dimethyl Formamide (DMF) as solvent and was spread out in a SiOx transparent glass substrate. An amorphous and semi-transparent film was fabricated seen in a polarizing microscope. The spectral analysis was carried out in the visible region from 400 nm to 700 nm. For HCl-doped sample, the high intensity region in the transmittance spectra occurred at the green portion while the high intensity region for the reflectance spectra was seen at the violet portion. Lastly, for the HClO4-doped sample, the peak intensities are at 536 nm and 516 nm for the transmittance and the reflectance spectra, respectively

  20. Photodegradation of ibuprofen by TiO2 co-doping with urea and functionalized CNT irradiated with visible light - Effect of doping content and pH.

    Yuan, Ching; Hung, Chung-Hsuang; Li, Huei-Wen; Chang, Wei-Hsian

    2016-07-01

    Ibuprofen (IBP) is one kind of non-steroidal anti-inflammatory drugs (NSAIDs), which are classified as Pharmaceuticals and Personal Care Products (PPCPs). IBP possesses bioactive property and the substantial use of IBP results in a harmful impact on bioreceptors even in small concentrations. Accordingly, the treatment of these wastewaters is important before discharging them into the ecosystem. The photodegradation of IBP with TiO2 co-doped with functionalized CNTs (CNT-COOH and CNT-COCl) and urea, named as N-doping CNT/TiO2, irradiated with visible light of 410 nm was investigated in this study. The titanium tetrachloride was used as the precursor of Ti. The N-doping CNT-COCl/TiO2 photocatalysts exhibited a better crystalline structure and smaller crystal size than the N-doping CNT-COOH/TiO2 photocatalyst. It might largely ascribe to strong binding between acyl chloride functional group and TiO2. About 85.0%-86.0% of IBP was degraded with N-doping CNT/TiO2 within 120 min at natural condition, which obeyed the pseudo first order reaction and the rate constant was 4.45 × 10(-3)-1.22 × 10(-2) min(-1) and 5.03 × 10(-3)-1.47 × 10(-2) min(-1) for N-doping CNT-COOH/TiO2 and N-doping CNT-COCl/TiO2, respectively. The best IBP degradation of 87.9%-89.0% was found at pH 5, which indicated superoxide radicals (O2(-)) played a key role. The optimal pH was majorly dominated by the nature of IBP and N-doping CNT/TiO2. A successful synergy effect of TiO2 and dopants was exhibited and this mainly attributed to the strong binding strength by functional group of acyl chloride (COCl) and carboxylic acid (COOH). In summary, IBP could be effectively photodegraded by the fabricated N-doping CNT/TiO2 photocatalysts. PMID:27145421

  1. Acid Rain.

    Openshaw, Peter

    1987-01-01

    Provides some background information on acid deposition. Includes a historical perspective, describes some effects of acid precipitation, and discusses acid rain in the United Kingdom. Contains several experiments that deal with the effects of acid rain on water quality and soil. (TW)

  2. Pyrolytic synthesis of boron-doped graphene and its application as electrode material for supercapacitors

    Highlights: • Boron-doped graphene was prepared by pyrolysis of graphene oxide with boric acid at 900 °C under an argon atmosphere. • The boron doping content reached the highest value of 4.7% after 3 h of pyrolysis at 900 °C. • The BG-900-3h electrode exhibited the highest specific capacitance of 172.5 F g−1 at 0.5 A g−1 and maintained 96.5% of initial capacity after a continuous of 5000 times cycling. -- Abstract: Chemical doping with foreign atoms is an effective approach to intrinsically modify the properties of the carbon materials. Herein, boron-doped graphene (BG) was prepared through pyrolysis of graphene oxide (GO) with boric acid (H3BO3) in an argon atmosphere at 900 °C. Both boron-doping and reduction of GO to graphene were simultaneously achieved under the thermal treatment processing. Namely, at high temperature condition, H3BO3 was converted into boron oxide (B2O3) accompanied by diffusing B2O3 vapor into the graphene nanosheets, then boron atoms can replace the carbon atoms inside the graphene layers and thereby substitutionally doped into the graphene lattice. The boron content in BG increased with prolonging the reaction time and reached the highest value of 4.7% after 3 h of pyrolysis, which in turn affected their electrochemical properties. The as-prepared electrode of BG-900-3h exhibits the highest capacitive behavior (172.5 F g−1, 0.5 A g−1) and superior cycling stability (maintaining 96.5% of initial capacity after 5000 times of cycling). Remarkably, the boron-doping increased the capacitance of BG-900-3h by about 80% compared to pristine graphene. These results imply that the doping of boron into graphene lattice induces remarkable performance enhancement, and thus make the doped materials superior to those of pristine graphene as electrode materials for supercapacitors

  3. Effects of Different Doping Ratio of Cu Doped CdS on QDSCs Performance

    Xiaojun Zhu; Xiaoping Zou; Hongquan Zhou

    2015-01-01

    We use the successive ionic layer adsorption and reaction (SILAR) method for the preparation of quantum dot sensitized solar cells, to improve the performance of solar cells by doping quantum dots. We tested the UV-Vis absorption spectrum of undoped CdS QDSCs and Cu doped CdS QDSCs with different doping ratios. The doping ratios of copper were 1 : 100, 1 : 500, and 1 : 1000, respectively. The experimental results show that, under the same SILAR cycle number, Cu doped CdS quantum dot sensitize...

  4. Synthesis and photoluminescence of Cr-, Ni-, Co-, and Ti-doped ZnSe nanoparticles

    Huy, Bui The [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Nhatrang Institute of Technology and Research Application, 2 Hungvuong, Nhatrang (Viet Nam); Seo, Min-Ho; Kumar, Avvaru Praveen [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Jeong, Hyuk [Department of Chemistry, Sookmyung Women’s University, Seoul 140-742 (Korea, Republic of); Lee, Yong-Ill, E-mail: yilee@changwon.ac.kr [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of)

    2014-03-05

    Highlights: • The chain length, structure of surfactants operated the size nanoparticles. • Ni{sup 2+}, Co{sup 2+}, Cr{sup 3+}, and Ti{sup 3+} did not create any new centers in the structure of ZnSe. • Doping may have influenced the nanoparticles size because of the Zn replacement. • The TM ions change in ligand field caused the influence on fluorescence intensity. -- Abstract: We developed a facile strategy to synthesize transition metal (TM; Ni, Cr, Co, and Ti)-doped ZnSe nanoparticles (NPs) in aqueous media using a chemical co-precipitation method. Co-precipitation was performed in the presence of one of four different surfactants, namely mercaptoacetic acid (MAA), 3-mercaptopropionic acid (MPA), thioglycerol (TGC), or (3-mercaptopropyl) trimethoxysilane (MPTMS). Surface morphology, chemical, and crystalline properties of the TM-doped ZnSe NPs were studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Optical features were characterized by UV–visible and photoluminescence spectroscopies. The influence of various experimental parameters, including the amount of TM and the ratio of precursors, as well as different types of surfactants on the photoluminescence properties of TM-doped ZnSe NPs was investigated systematically. TM-doped ZnSe NPs were excited in the UV region and exhibited photoluminescence in the visible region. Intensity was affected by the concentration of the TM. The results showed that MPA had a stronger influence on photoluminescence than MAA, TGC, and MPTMS. The photoluminescence intensity of TM-doped ZnSe NPs was 30% higher than that of undoped ZnSe NPs.

  5. Radiation-induced doping of conducting polymers

    Conducting polymers have the potential form many applications in electronics. The various patterns of doped regions of conducting polymers should be generated for the applications. Doping of conducting polymers is achieved by contact of the polymer with dopant or electrochemically. By these methods, doping occurs in the entire area exposed to the dopant. It is necessary to combine these doping techniques with lithography for achieving the patterned doping. Radiation-induced doping effects of conducting polymers have been reported. The doping is performed by irradiation of polymers in an atmosphere of gases, which do not react without irradiation, such as CH3Br, SF6, and N2O. If only the irradiated area was doped, patterned doping could be achieved without using lithography technique. We have elucidated the mechanism of the radiation-induced doping. The electrical conductivity was increased by irradiation the gas near the polymer film without irradiating the film itself. This result indicates that dopants were generated upon irradiation in the gas phase and the dopants react with the polymer. Hence, the pattern of doping is blurred by this method. We then developed another method of radiation-induced doping. Solid dopant precursor was coated on the polymer, and irradiation was performed. Figure 1 shows the results for poly(3-octylhitophene)(P3OT) by this method. A film of poly(3-octylthiophene) was prepared by spin coating from a solution of tetrahydrofuran on a quartz plate. The thickness of the film was approximately 100 nm. The polymer film was dried overnight at 80 degree C in a vacuum, and Au electrodes were evaporated on the films for electrical conductivity measurements. Saturated solution of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) in 1-bromopropane was dropped on the film and dried at room temperature in a vacuum. The film was put in a vacuum chamber, which has a 0.2-mm-thick Be window. X rays entered through the Be window, and the films were irradiated

  6. Boron-doped cadmium oxide composite structures and their electrochemical measurements

    Lokhande, B.J., E-mail: bjlokhande@yahoo.com [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Ambare, R.C. [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Mane, R.S. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (India); Bharadwaj, S.R. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2013-08-01

    Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 Ω internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

  7. Thermal curing of PBI membranes for high temperature PEM fuel cells

    Aili, David; Cleemann, Lars N.; Li, Qingfeng;

    2012-01-01

    Phosphoric acid doped polybenzimidazole (PBI) has emerged as one of the most promising electrolyte materials for proton exchange membrane (PEM) fuel cells operating under anhydrous conditions at temperatures of up to 200 °C. The limited long-term durability of the membrane electrode assemblies...... (MEAs) is currently hampering the commercial viability of the technology. In the present study, thermoset PBI membranes were prepared by curing the membranes under inert atmosphere at temperatures of up to 350 °C prior to the acid doping. The systematic membrane characterizations with respect to...... long-term durability of the corresponding fuel cell MEAs. During continuous operation for 1800 h at 160 °C and 600 mA cm−2, the average cell voltage decay rate of the MEA based on the cured membrane was 43 μV h−1. This should be compared with an average cell voltage decay rate of 308 μV h−1 which was...

  8. Composite Membranes of Polyimide and Polybenzimidazole with Ionic Liquid for Gas Separation at Elevated Temperature%高温条件下高分子材料与离子液体气体分离复合膜的合成及特性表征研究

    郝益民

    2015-01-01

    At high temperatures,polybenzimidazole(PBI)and polyimide(PI)with addition[C4 mim][NTf2]are prepared with different composition to fabricate composite polymer membranes. NMR was used to test the purity of PBI and[C4 mim][NTf2]. All membranes were employed to characterize the mechanical stability,tensile strength, thermal stability and morphology using SEM,DMTA,TGA. Results indicate the PBI-[C4 mim][NTf2]composite membranes(at 100~200 ℃)and PI-[C4 mim][NTf2]composite membranes(at 100~300 ℃)are dense and have enough mechanical and thermal stability for gas separation at elevated temperature.%研究了高温条件下用聚苯并咪唑(PBI)、聚酰亚胺(PI)与离子液体1-丁基-3-甲基咪唑双三氟甲烷磺酰亚胺盐([C4 mim][NTf2])制备不同组分的高分子复合膜的合成方法,并用SEM、TGA、DMTA测试了各复合膜的机械稳定性、抗拉强度、热稳定性以及表面形态。实验结果表明,PBI-[C4 mim][NTf2]复合膜在100~200℃,PI-[C4 mim][NTf2]复合膜在100~300℃范围内结构稳定、致密,具有足够的机械及热稳定性,适用于制备在高温下能够保持结构稳定并提供良好气体分离率及经济适用通过率的高分子膜。

  9. Structural and vibrational investigations of Nb-doped TiO{sub 2} thin films

    Uyanga, E., E-mail: uyanga.enkhnaran@gmail.com [Institute of Physics and Technology, Mongolian Academy of Sciences, Enkhtaivan Avenue 54B, Ulaanbaatar 13330 (Mongolia); Frank Laboratory of Neutron Physics, JINR, Dubna 141980 (Russian Federation); Gibaud, A.; Daniel, P. [LUNAM Université, Université du Maine, CNRS UMR 6283, Institut des molécules et matériaux et du Mans–IMMM, Avenue Olivier Messiaen, Le Mans 72085 Cedex 9 (France); Sangaa, D.; Sevjidsuren, G.; Altantsog, P. [Institute of Physics and Technology, Mongolian Academy of Sciences, Enkhtaivan Avenue 54B, Ulaanbaatar 13330 (Mongolia); Beuvier, T. [LUNAM Université, Université du Maine, CNRS UMR 6283, Institut des molécules et matériaux et du Mans–IMMM, Avenue Olivier Messiaen, Le Mans 72085 Cedex 9 (France); Lee, Chih Hao [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Balagurov, A.M. [Frank Laboratory of Neutron Physics, JINR, Dubna 141980 (Russian Federation)

    2014-12-15

    Highlights: • We studied the evolutions of structure for TiO{sub 2} thin film as changes with Nb doping and temperatures. • Up to 800 °C, the grain size of Nb{sub 0.1}Ti{sub 0.9}O{sub 2} is smaller than for pure TiO{sub 2} because doped Nb hinders the growth of the TiO{sub 2} grains. • There was no formation of the rutile phase at high temperature. • Nb doped TiO{sub 2} films have high electron densities at 400–700 °C. • Nb dope extends the absorbance spectra of TiO{sub 2} which leads to the band gap reduce. - Abstract: Acid-catalyzed sol–gel and spin-coating methods were used to prepare Nb-doped TiO{sub 2} thin film. In this work, we studied the effect of niobium doping on the structure, surface, and absorption properties of TiO{sub 2} by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), Raman, and UV–vis absorption spectroscopy at various annealing temperatures. EDX spectra show that the Nb:Ti atomic ratios of the niobium-doped titania films are in good agreement with the nominal values (5 and 10%). XPS results suggest that charge compensation is achieved by the formation of Ti vacancies. Specific niobium phases are not observed, thus confirming that niobium is well incorporated into the titania crystal lattice. Thin films are amorphous at room temperature and the formation of anatase phase appeared at an annealing temperature close to 400 °C. The rutile phase was not observed even at 900 °C (XRD and Raman spectroscopy). Grain sizes and electron densities increased when the temperature was raised. Nb-doped films have higher electron densities and lower grain sizes due to niobium doping. Grain size inhibition can be explained by lattice stress induced by the incorporation of larger Nb{sup 5+} ions into the lattice. The band gap energy of indirect transition of the TiO{sub 2} thin films was calculated to be about 3.03 eV. After niobium doping, it decreased to 2

  10. Photocatalytic activity of tin-doped TiO{sub 2} film deposited via aerosol assisted chemical vapor deposition

    Chua, Chin Sheng, E-mail: cschua@simtech.a-star.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Tan, Ooi Kiang; Tse, Man Siu [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Ding, Xingzhao [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore)

    2013-10-01

    Tin-doped TiO{sub 2} films are deposited via aerosol assisted chemical vapor deposition using a precursor mixture composing of titanium tetraisopropoxide and tetrabutyl tin. The amount of tin doping in the deposited films is controlled by the volume % concentration ratio of tetrabutyl tin over titanium tetraisopropoxide in the mixed precursor solution. X-ray diffraction analysis results reveal that the as-deposited films are composed of pure anatase TiO{sub 2} phase. Red-shift in the absorbance spectra is observed attributed to the introduction of Sn{sup 4+} band states below the conduction band of TiO{sub 2}. The effect of tin doping on the photocatalytic property of TiO{sub 2} films is studied through the degradation of stearic acid under UV light illumination. It is found that there is a 10% enhancement on the degradation rate of stearic acid for the film with 3.8% tin doping in comparison with pure TiO{sub 2} film. This improvement of photocatalytic performance with tin incorporation could be ascribed to the reduction of electron-hole recombination rate through charge separation and an increased amount of OH radicals which are crucial for the degradation of stearic acid. Further increase in tin doping results in the formation of recombination site and large anatase grains, which leads to a decrease in the degradation rate. - Highlights: ► Deposition of tin-doped TiO{sub 2} film via aerosol assisted chemical vapor deposition ► Deposited anatase films show red-shifted in UV–vis spectrum with tin-dopants. ► Photoactivity improves at low tin concentration but reduces at higher concentration. ► Improvement in photoactivity due to bandgap narrowing from Sn{sup 4+} band states ► Maximum photoactivity achieved occurs for films with 3.8% tin doping.

  11. Synthesis, Characterization and Evaluation of the Cytotoxicity of Ni-Doped Zn(Se,S Quantum Dots

    Melissa Cruz-Acuña

    2015-01-01

    Full Text Available Quantum dots (QDs are semiconductor nanocrystals with desirable optical properties for biological applications, such as bioimaging and drug delivery. However, the potential toxicity of these nanostructures in biological systems limits their application. The present work is focused on the synthesis, characterization, and evaluation of the toxicity of water-stable Ni-doped Zn(Se,S QDs. Also, the study of nondoped nanostructures was included for comparison purposes. Ni-doped nanostructures were produced from zinc chloride and selenide aqueous solutions in presence of 3-mercaptopropionic acid and Ni molar concentration of 0.001 M. In order to evaluate the potential cytoxicity of these doped nanostructures, human pancreatic carcinoma cells (PANC-1 were used as model. The cell viability was monitored in presence of Ni-doped Zn(Se,S QDs at concentrations ranging from 0 μg/mL to 500 μg/mL and light excited Ni-doped Zn(Se,S nanostructures were evaluated at 50 μg/mL. Results suggested that Ni-doped Zn(Se,S nanostructures were completely safe to PANC-1 when concentrations from 0 μg/mL to 500 μg/mL were used, whereas non-doped nanostructures evidenced toxicity at concentrations higher than 200 μg/mL. Also, Ni-doped Zn(Se,S QDs under light excitation do not evidence toxicity to PANC-1. These findings suggest strongly that Zn(Se,S nanostructures doped with nickel could be used in a safe manner in light-driving biological applications and drug delivery.

  12. Probing Photocatalytic Characteristics of Sb-Doped TiO2 under Visible Light Irradiation

    Lingjing Luo

    2014-01-01

    Full Text Available Sb-doped TiO2 nanoparticle with varied dopant concentrations was synthesized using titanium tetrachloride (TiCl4 and antimony chloride (SbCl3 as the precursors. The properties of Sb-doped TiO2 nanoparticles were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, fluorescence spectrophotometer, and Uv-vis spectrophotometer. The absorption edge of TiO2 nanoparticles could be extended to visible region after doping with antimony, in contrast to the UV absorption of pure TiO2. The results showed that the photocatalytic activity of Sb-doped TiO2 nanoparticles was much more active than pure TiO2. The 0.1% Sb-doped TiO2 nanoparticles demonstrated the best photocatalytic activity which was better than that of the Degussa P25 under visible light irradiation using terephthalic acid as fluorescent probe. The effects of Sb dopant on the photocatalytic activity and the involved mechanism were extensively investigated in this work as well.

  13. Experimental study and theoretical calculation on the conductivity and stability of praseodymium doped tin oxide electrode

    Ti/SnO2-Sb2O4-Pr2O3/PbO2 anodes are prepared by electrodepositing method. The electrodes are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The degradation of phenol experiment and accelerated life test of the electrode are carried out. Futhermore, the formation energy, band structure and density of states (DOS) are calculated by first principles calculations. The results show that Pr doping can change the phase of SnO2 and prevent the spread of the oxygen to the substrate, lower the interfacial resistance. The catalytic degradation of phenol rate is 58.3% when the doping ratio is 100:8. The service life of electrode reaches the maximum of 121 hours under a high current density of 4 A cm−2 in 1 mol L−1 of H2SO4 solution at 60 °C when the doping ratio is 100:8. Moreover, at the same doping ratio, the formation energy and band gap reach the minimums of -15.59 eV and 0.656 eV respectively. The experiments are consistent well with the theories. Thus, we conclude that the praseodymium doped tin oxide electrode is one promising acid-proof anode

  14. Boron-doped MnO{sub 2}/carbon fiber composite electrode for supercapacitor

    Chi, Hong Zhong, E-mail: hzchi@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhu, Hongjie [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Gao, Linhui [Center of Materials Engineering, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

    2015-10-05

    Highlights: • Interstitial ion in MnO{sub 2} lattice. • Porous film composed by interlocking worm-like nanostructure. • Boron-doped birnessite-type MnO{sub 2}/carbon fiber composite electrode. • Enhanced capacitive properties through nonmetal element doping. - Abstract: The boron-doped MnO{sub 2}/carbon fiber composite electrode has been prepared via in situ redox reaction between potassium permanganate and carbon fibers in the presence of boric acid. The addition of boron as dopant results in the increase of growth-rate of MnO{sub 2} crystal and the formation of worm-like nanostructure. Based on the analysis of binding energy, element boron incorporates into the MnO{sub 2} lattice through interstitial mode. The doped electrode with porous framework is beneficial to pseudocapacitive reaction and surface charge storage, leading to higher specific capacitance and superior rate capability. After experienced 1000 cycles, the boron-doped MnO{sub 2} still retain a higher specific capacitance by about 80% of its initial value. The fall in capacitance is blamed to be the combination of the formation of soluble Mn{sup 2+} and the absence of active site on the outer surface.

  15. Boron-doped MnO2/carbon fiber composite electrode for supercapacitor

    Highlights: • Interstitial ion in MnO2 lattice. • Porous film composed by interlocking worm-like nanostructure. • Boron-doped birnessite-type MnO2/carbon fiber composite electrode. • Enhanced capacitive properties through nonmetal element doping. - Abstract: The boron-doped MnO2/carbon fiber composite electrode has been prepared via in situ redox reaction between potassium permanganate and carbon fibers in the presence of boric acid. The addition of boron as dopant results in the increase of growth-rate of MnO2 crystal and the formation of worm-like nanostructure. Based on the analysis of binding energy, element boron incorporates into the MnO2 lattice through interstitial mode. The doped electrode with porous framework is beneficial to pseudocapacitive reaction and surface charge storage, leading to higher specific capacitance and superior rate capability. After experienced 1000 cycles, the boron-doped MnO2 still retain a higher specific capacitance by about 80% of its initial value. The fall in capacitance is blamed to be the combination of the formation of soluble Mn2+ and the absence of active site on the outer surface

  16. Moral entrepreneurship and doping cultures in sport

    R. Stokvis

    2003-01-01

    In this article, the fight against doping has been analyzed as an ongoing process of social definition. It is dependent on the development of power relations within and outside the world of sport. To analyze these dependencies, I identified a variety of important doping cultures in sport and studied

  17. Doping silicon nanocrystals and quantum dots

    Oliva-Chatelain, Brittany L.; Ticich, Thomas M.; Barron, Andrew R.

    2016-01-01

    The ability to incorporate a dopant element into silicon nanocrystals (NC) and quantum dots (QD) is one of the key technical challenges for the use of these materials in a number of optoelectronic applications. Unlike doping of traditional bulk semiconductor materials, the location of the doping element can be either within the crystal lattice (c-doping), on the surface (s-doping) or within the surrounding matrix (m-doping). A review of the various synthetic strategies for doping silicon NCs and QDs is presented, concentrating on the efficacy of the synthetic routes, both in situ and post synthesis, with regard to the structural location of the dopant and the doping level. Methods that have been applied to the characterization of doped NCs and QDs are summarized with regard to the information that is obtained, in particular to provide researchers with a guide to the suitable techniques for determining dopant concentration and location, as well as electronic and photonic effectiveness of the dopant.

  18. Neodymium doped chalcogenide glass fibre laser

    Samson, B.N.; Schweizer, T.; Moore, R C; Hewak, D.W.; Payne, D.N.

    1997-01-01

    We report on laser action in a Neodymium doped Gallium Lanthanum Sulphide glass fibre. Laser action at 1080nm was obtained in a 22mm long multimode glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour

  19. Design and Synthesis of Cross-Linked Copolymer Membranes Based on Poly(benzoxazine and Polybenzimidazole and Their Application to an Electrolyte Membrane for a High-Temperature PEM Fuel Cell

    Hyuk Chang

    2013-01-01

    Full Text Available Elevated-temperature (100~200 °C polymer electrolyte membrane (PEM fuel cells have many features, such as their high efficiency and simple system design, that make them ideal for residential micro-combined heat and power systems and as a power source for fuel cell electric vehicles. A proton-conducting solid-electrolyte membrane having high conductivity and durability at elevated temperatures is essential, and phosphoric-acid-containing polymeric material synthesized from cross-linked polybenzoxazine has demonstrated feasible characteristics. This paper reviews the design rules, synthesis schemes, and characteristics of this unique polymeric material. Additionally, a membrane electrode assembly (MEA utilizing this polymer membrane is evaluated in terms of its power density and lifecycle by an in situ accelerated lifetime test. This paper also covers an in-depth discussion ranging from the polymer material design to the cell performance in consideration of commercialization requirements.

  20. [Cardiovascular alterations associated with doping].

    Thieme, D; Büttner, A

    2015-05-01

    Doping -the abuse of anabolic-androgenic steroids in particular- is widespread in amateur and recreational sports and does not solely represent a problem of professional sports. Excessive overdose of anabolic steroids is well documented in bodybuilding or powerlifting leading to significant side effects. Cardiovascular damages are most relevant next to adverse endocrine effects.Clinical cases as well as forensic investigations of fatalities or steroid consumption in connection with trafficking of doping agents provide only anecdotal evidence of correlations between side effects and substance abuse. Analytical verification and self-declarations of steroid users have repeatedly confirmed the presumption of weekly dosages between 300 and 2000 mg, extra to the fact that co-administration of therapeutics to treat side-effects represent a routine procedure. Beside the most frequent use of medications used to treat erectile dysfunction or estrogenic side-effects, a substantial number of antihypertensive drugs of various classes, i.e. beta-blockers, diuretics, angiotensin II receptor antagonists, calcium channel blockers, as well as ACE inhibitors were recently confiscated in relevant doping cases. The presumptive correlation between misuse of anabolic steroids and self-treatment of cardiovascular side effects was explicitly confirmed by detailed user statements.Two representative fatalities of bodybuilders were introduced to outline characteristic, often lethal side effects of excessive steroid abuse. Moreover, illustrative autopsy findings of steroid acne, thrombotic occlusion of Ramus interventricularis anterior and signs of cardiac infarctions are presented.A potential steroid abuse should be carefully considered in cases of medical consultations of patients exhibiting apparent constitutional modifications and corresponding adverse effects. Moreover, common self-medications -as frequently applied by steroid consumers- should be taken into therapeutic considerations

  1. Dual vortex theory of doped Mott insulators

    Balents, Leon; Sachdev, Subir

    2007-11-01

    We present a general framework for describing the quantum phases obtained by doping paramagnetic Mott insulators on the square lattice. The undoped insulators are efficiently characterized by the projective transformations of various fields under the square lattice space group (the PSG). We show that the PSG also imposes powerful constraints on the doped system, and on the effective action for the vortex and Bogoliubov quasiparticle excitations of superconducting states. This action can also be extended across transitions to supersolid or insulating states at non-zero doping. For the case of a valence bond solid (VBS) insulator, we show that the doped system has the same PSG as that of elementary bosons with density equal to the density of electron Cooper pairs. We also discuss aspects of the action for a d-wave superconductor obtained by doping a "staggered-flux" spin liquid state.

  2. Dual vortex theory of doped Mott insulators

    We present a general framework for describing the quantum phases obtained by doping paramagnetic Mott insulators on the square lattice. The undoped insulators are efficiently characterized by the projective transformations of various fields under the square lattice space group (the PSG). We show that the PSG also imposes powerful constraints on the doped system, and on the effective action for the vortex and Bogoliubov quasiparticle excitations of superconducting states. This action can also be extended across transitions to supersolid or insulating states at non-zero doping. For the case of a valence bond solid (VBS) insulator, we show that the doped system has the same PSG as that of elementary bosons with density equal to the density of electron Cooper pairs. We also discuss aspects of the action for a d-wave superconductor obtained by doping a 'staggered-flux' spin liquid state

  3. Photocatalytic degradation of phenol by iodine doped tin oxide nanoparticles under UV and sunlight irradiation

    Highlights: • A sol–gel method used to synthesize tin oxide nanoparticles. • Nanoparticles of tin oxide doped with different iodine concentrations. • Degradation studies carried up with UV–vis, TOC, HPLC and GC instruments. • 1% iodine doped tin dioxide showed maximum photodegradation efficiency. - Abstract: Iodine doped tin oxide (SnO2:I) nanoparticles were prepared by sol–gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO2:I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO2 nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO2 nanoparticles under similar illumination conditions

  4. Photocatalytic degradation of phenol by iodine doped tin oxide nanoparticles under UV and sunlight irradiation

    Al-Hamdi, Abdullah M.; Sillanpää, Mika [Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli (Finland); Dutta, Joydeep, E-mail: dutta@squ.edu.om [Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 17, 123 Al-Khoudh (Oman)

    2015-01-05

    Highlights: • A sol–gel method used to synthesize tin oxide nanoparticles. • Nanoparticles of tin oxide doped with different iodine concentrations. • Degradation studies carried up with UV–vis, TOC, HPLC and GC instruments. • 1% iodine doped tin dioxide showed maximum photodegradation efficiency. - Abstract: Iodine doped tin oxide (SnO{sub 2}:I) nanoparticles were prepared by sol–gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO{sub 2}:I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO{sub 2} nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO{sub 2} nanoparticles under similar illumination conditions.

  5. Conversion of ethanol to 1,3-butadiene over Na doped ZnxZryOz mixed metal oxides

    Baylon, Rebecca A.; Sun, Junming; Wang, Yong

    2016-01-01

    Despite numerous studies on different oxide catalysts for the ethanol to 1,3-butadiene reaction, few have identified active sites (i.e., type of acidity) correlated to the catalytic performances. In this work, the type of acidity needed for ethanol to 1,3-butadiene conversion has been studied over Zn/Zr mixed oxide catalysts. Specifically, synthesis method, Zn/Zr ratio, and Na doping have been used to control the surface acid-base properties, as confirmed by characterizations such as NH3-TPD and IR-Py techniques. The 2000 ppm Na doped Zn1Zr10Oz-H with balanced base and weak Bronsted acid sites was found to give not only high selectivity to 1,3-butadiene (47%) at near complete ethanol conversion (97%), but also exhibited a much higher 1,3-butadiene productivity than other mixed oxides studied.

  6. Folic Acid

    ... found naturally in some foods, including leafy vegetables, citrus fruits, beans (legumes), and whole grains. Folic acid ... mcg of folic acid every day for good health. But older adults need to be sure they ...

  7. From Impurity Doping to Metallic Growth in Diffusion Doping: Properties and Structure of Silver-Doped InAs Nanocrystals.

    Amit, Yorai; Li, Yuanyuan; Frenkel, Anatoly I; Banin, Uri

    2015-11-24

    Tuning of the electronic properties of presynthesized colloidal semiconductor nanocrystals (NCs) by doping plays a key role in the prospect of implementing them in printed electronics devices such as transistors and photodetectors. While such impurity doping reactions have already been introduced, the understanding of the doping process, the nature of interaction between the impurity and host atoms, and the conditions affecting the solubility limit of impurities in nanocrystals are still unclear. Here, we used a postsynthesis diffusion-based doping reaction to introduce Ag impurities into InAs NCs. Optical absorption spectroscopy and analytical inductively coupled plasma mass spectroscopy (ICP-MS) were used to present a two-stage doping model consisting of a "doping region" and a "growth region", depending on the impurity to NC ratio in the reaction vessel. X-ray absorption fine-structure (XAFS) spectroscopy was employed to determine the impurity location and correlate between the structural and electronic properties for different sizes of InAs NCs and dopant concentrations. The resulting structural model describes a heterogeneous system where the impurities initially dope the NC, by substituting for In atoms near the surface of the NC, until the "solubility limit" is reached, after which the rapid growth and formation of metallic structures are identified. PMID:26390173

  8. Effects of doping concentration on properties of Mn-doped ZnO thin films

    Gao Li; Zhang Jian-Min

    2009-01-01

    This paper reports that the radio frequency magnetron sputtering is used to fabricate ZnO and Mn-doped ZnO thin films on glass substrates at 500 ℃. The Mn-doped ZnO thin films present wurtzite structure of ZnO and have a smoother surface, better conductivity but no ferromagnetism. The x-ray photoelectron spectroscopy results show that the binding energy of Mn_(2p3/2) increases with increasing Mn content slightly, and the state of Mn in the Mn-doped ZnO thin films is divalent. The chemisorbed oxygen in the Mn-doped ZnO thin films increases with increasing Mn doping concentration. The photoluminescence spectra of ZnO and Mn-doped ZnO thin films have a similar ultraviolet emission. The yellow green emissions of 4 wt. % and 10 wt. % Mn-doped thin films are quenched, whereas the yellow green emission occurs because of abundant oxygen vacancies in the Mn-doped ZnO thin films after 20 wt. % Mn doping. Compared with pure ZnO thin film, the bandgap of the Mn-doped ZnO thin films increases with increasing Mn content.

  9. GaAs MESFET with lateral non-uniform doping

    Wang, Y. C.; Bahrami, M.

    1983-01-01

    An analytical model of the GaAs MESFET with arbitrary non-uniform doping is presented. Numerical results for linear lateral doping profile are given as a special case. Theoretical considerations predict that better device linearity and improved F(T) can be obtained by using linear lateral doping when doping density increases from source to drain.

  10. The importance of cooling of urine samples for doping analysis

    Kuenen, J.G.; Konings, W.N.

    2009-01-01

    Storing and transporting of urine samples for doping analysis, as performed by the anti-doping organizations associated with the World Anti-Doping Agency, does not include a specific protocol for cooled transport from the place of urine sampling to the doping laboratory, although low cost cooling fa

  11. The importance of cooling of urine samples for doping analysis

    Kuenen, J. Gijs; Konings, Wil N.

    2010-01-01

    Storing and transporting of urine samples for doping analysis, as performed by the anti-doping organizations associated with the World Anti-Doping Agency, does not include a specific protocol for cooled transport from the place of urine sampling to the doping laboratory, although low cost cooling fa

  12. Screening dynamics in doped titanates

    The time scale for carrier relaxation in semiconductors is on the same order of magnitude as the life time of shallow core hole states (a few femtoseconds). Resonant Inelastic soft X-ray scattering (RIXS) which involves (virtual) excitations of core levels consequently contains information about the time development of the electronic structure on this time scale. In many cases one can treat the scattering in an absorption (SXA) followed-by-emission (SXE) picture, where simply the rates for various processes can be compared with the intermediate core hole state decay rate as an internal open-quotes clockclose quotes. By variation of x (0 xSr1-xTiO3, the amount of Ti d electrons in the system can be controlled. SrTiO3 (x=0) is an insulator with an empty Ti d band. With increasing x, electrons are doped into the Ti d-band, and LaTiO3 (x=1) is a Mott Hubbard insulator with a Ti 3d1 configuration. In this work the authors demonstrate that the rate for Ti 2p core hole screening in LaxSr1-xTiO3 is doping dependent. The screening rate increases with the availability of Ti 3d electrons, and they estimate it to be 3.8 x 1013/sec in La0.05Sr0.95TiO3

  13. Does water dope carbon nanotubes?

    Bell, Robert A.; Payne, Michael C. [Theory of Condensed Matter Group, Cavendish Laboratory, Cambridge (United Kingdom); Mostofi, Arash A. [Department of Materials and Department of Physics, and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, London SW7 2AZ (United Kingdom)

    2014-10-28

    We calculate the long-range perturbation to the electronic charge density of carbon nanotubes (CNTs) as a result of the physisorption of a water molecule. We find that the dominant effect is a charge redistribution in the CNT due to polarisation caused by the dipole moment of the water molecule. The charge redistribution is found to occur over a length-scale greater than 30 Å, highlighting the need for large-scale simulations. By comparing our fully first-principles calculations to ones in which the perturbation due to a water molecule is treated using a classical electrostatic model, we estimate that the charge transfer between CNT and water is negligible (no more than 10{sup −4} e per water molecule). We therefore conclude that water does not significantly dope CNTs, a conclusion that is consistent with the poor alignment of the relevant energy levels of the water molecule and CNT. Previous calculations that suggest water n-dopes CNTs are likely due to the misinterpretation of Mulliken charge partitioning in small supercells.

  14. Structural and electrical characterization of polyanilines synthesized from chemical oxidative polymerization via doping/de-doping/re-doping processes

    Structural characterization of various emeraldine salt (ES) and emeraldine base (EB) polyaniline (PANI) powders synthesized from chemical oxidative polymerization and then via de-doping and re-doping processes is first presented. Partial crystallinity with well-separated x-ray diffraction peaks is observed in the as-prepared ES PANI powder and an amorphous characteristic is identified in the de-doped EB PANI powder. From scanning electron microscopy, both the nanostructures of the as-prepared ES and de-doped EB PANI precipitated powders possess similar morphology. This finding reveals that the de-doping process to remove the counter-ions intercalated between the as-prepared ES PANI chains makes the de-doped EB PANI pieces become soft but does not change the nanostructures significantly. Then, the electrical conductivity perpendicular to the surface of the pressed PANI disc pellets is studied. The re-doped ES PANI pellets possess less electrical conductivity than their as-prepared counterparts, which suggests that during the re-doping process the counter-ions (Cl− or HSO4−) are re-adsorbed predominantly on the surface region of the PANI nanostructures. Besides, the re-doping of larger HSO4− counter-ions (with respect to Cl−) intercalated between the PANI chains increases the d-spacing of (1 0 0) planes and hence reduces the corresponding π–π inter-chain interaction. Finally, from the temperature dependence of the electrical conductivity together with the structural information, the charge carrier hopping mechanisms perpendicular to the surface of the pressed pellets corresponding to various PANI samples are compared and discussed. (paper)

  15. Radon test measurements with Ce-doped yttrium aluminum oxide perovskite scintillator

    F. de Notaristefani

    2002-04-01

    Full Text Available Scintillation properties of a Ce-doped yttrium aluminium oxide perovskite monocrystal optically coupled to a Hamamatsu H5784 photomultiplier are analyzed with a standard bialkali photocathode for radon and radon daughters gamma-ray spectrometry. Tests in water up to 100°C and in acidic solutions of HCl (37%, H2SO4 (48% and HNO3 (65% were performed to simulate environments of geophysical interest, such as geothermal and volcanic areas. Comparative measurements with standard radon sources provided by the National Institute for Metrology of Ionizing Radiations (ENEA confirm the non-hygroscopic properties of the scintillator and small dependence of the light yield on temperature and HNO3.The Ce-doped yttrium aluminum oxide perovskite monocrystal shows high response stability for radon gamma-ray spectrometry in environments with large temperature gradients and high acid concentrations.

  16. Anodic oxidation with doped diamond electrodes: a new advanced oxidation process

    Boron-doped diamond anodes allow to directly produce OH· radicals from water electrolysis with very high current efficiencies. This has been explained by the very high overvoltage for oxygen production and many other anodic electrode processes on diamond anodes. Additionally, the boron-doped diamond electrodes exhibit a high mechanical and chemical stability. Anodic oxidation with diamond anodes is a new advanced oxidation process (AOP) with many advantages compared to other known chemical and photochemical AOPs. The present work reports on the use of diamond anodes for the chemical oxygen demand (COD) removal from several industrial wastewaters and from two synthetic wastewaters with malic acid and ethylenediaminetetraacetic (EDTA) acid. Current efficiencies for the COD removal between 85 and 100% have been found. The formation and subsequent removal of by-products of the COD oxidation has been investigated for the first time. Economical considerations of this new AOP are included

  17. Yb2O3-doped YAG nano-crystallites in silica-based core glass matrix of optical fiber preform

    Yb2O3-doped yttrium aluminium garnet (YAG) nano-crystals within the silicate glass-based optical fiber preforms were obtained through the conventional-modified chemical vapour deposition (MCVD) and solution doping technique. Nano-crystals were developed with soaking of the porous phospho-silica or pure silica core layer in a solution containing the ytterbium, yttrium and other co-dopants, including fluorine using 10-15% fluorosilicic acid, and through post-annealing of the preform at a temperature of around 1450 deg. C. The size, shape and nature of Yb2O3-doped phase-separated nano-crystallites were evaluated from HRTEM images along with the electron diffraction pattern based on the doping levels of phosphorous and fluorine. The size of nano-crystallites was maintained within 6-10 nm when doped with 0.25 mole% of fluorine. X-ray analyses EDX data reveals that the nano-particles are rich in Yb:YAG, and uniformly dispersed into the amorphous silica glass matrix. The novelty of this technique involves the direct synthesis of rare-earth doped phase-separated nano-crystallites within the core region of silica glass preforms. This class of fibers containing the nano-particles with or without Yb:YAG crystalline nature will keep the advantage of the mechanical properties as well as good lasing properties under high power application compared to the Yb:YAG ceramic laser.

  18. IR-doped ruthenium oxide catalyst for oxygen evolution

    Valdez, Thomas I. (Inventor); Narayanan, Sekharipuram R. (Inventor)

    2012-01-01

    A method for preparing a metal-doped ruthenium oxide material by heating a mixture of a doping metal and a source of ruthenium under an inert atmosphere. In some embodiments, the doping metal is in the form of iridium black or lead powder, and the source of ruthenium is a powdered ruthenium oxide. An iridium-doped or lead-doped ruthenium oxide material can perform as an oxygen evolution catalyst and can be fabricated into electrodes for electrolysis cells.

  19. Public opinion on doping in cycling: Differences among population groups

    Van Reeth, Daam; Lagae, Wim

    2013-01-01

    Despite the vast amount of literature available on doping in sports, little is known about how the general public actually thinks about doping. It is even more unclear how public opinion on doping differs within the population. Our questionnaire-based study for Flanders (Belgium), with a focus on doping in cycling, shows a strong disapproval of doping use by all respondents. There are statistically significant differences, though, among the population groups. Cycling fans tend to be less nega...

  20. Chemically modified graphene and nitrogen-doped graphene: electrochemical characterisation and sensing applications

    Prathish, Krishna P.; Barsan, Madalina M.; Geng, Dongsheng; Sun, Xueliang; Brett, Christopher M. A.

    2013-01-01

    Functionalised graphene (G) and nitrogen doped graphene (NG) nanomaterials are excellent candidates for electrocatalytic sensing of biomolecules and for developing biosensors, due to their unique physicochemical and electronic properties. Electrochemical characterisation and comparison of basic or acidic functionalised G and NG has been carried out, as well as of composite materials based on NG with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and the redox polymer poly(neu...

  1. Photoelectrochemical reduction of carbon dioxide using Ge doped GaN nanowire photoanodes

    Yichen Wang

    2015-11-01

    Full Text Available We report on the direct conversion of carbon dioxide (CO2 in a photoelectrochemical cell consisting of germanium doped gallium nitride nanowire anode and copper (Cu cathode. Various products including methane (CH4, carbon monoxide (CO, and formic acid (HCOOH were observed under light illumination. A Faradaic efficiency of ∼10% was measured for HCOOH. Furthermore, this photoelectrochemical system showed enhanced stability for 6 h CO2 reduction reaction on low cost, large area Si substrates.

  2. The selective detection of dopamine at a polypyrrole film doped with sulfonated β-cyclodextrins

    Harley, Claire C.; Rooney, A. Denise; Breslin, Carmel B.

    2010-01-01

    A highly selective dopamine sensor was fabricated by doping polypyrrole with a sulfonated β-cyclodextrin. This composite material enabled the selective sensing of dopamine in the presence of a large excess of ascorbic acid and prevented the regeneration of dopamine through the homogeneous catalytic reaction of the ascorbate anion with the dopamine-o-quinone. A single redox wave, corresponding to the oxidation of dopamine, was observed in dopamine/ascorbate mixtures, giving a truly se...

  3. Green synthesis of boron doped graphene and its application as high performance anode material in Li ion battery

    Sahoo, Madhumita; Sreena, K.P.; Vinayan, B.P.; Ramaprabhu, S., E-mail: ramp@iitm.ac.in

    2015-01-15

    Graphical abstract: Boron doped graphene (B-G), synthesized by simple hydrogen induced reduction technique using boric acid as boron precursor, have more uneven surface as a result of smaller bonding distance of boron compared to carbon, showed high capacity and high rate capability compared to pristine graphene as an anode material for Li ion battery application. - Abstract: The present work demonstrates a facile route for the large-scale, catalyst free, and green synthesis approach of boron doped graphene (B-G) and its use as high performance anode material for Li ion battery (LIB) application. Boron atoms were doped into graphene framework with an atomic percentage of 5.93% via hydrogen induced thermal reduction technique using graphite oxide and boric acid as precursors. Various characterization techniques were used to confirm the boron doping in graphene sheets. B-G as anode material shows a discharge capacity of 548 mAh g{sup −1} at 100 mA g{sup −1} after 30th cycles. At high current density value of 1 A g{sup −1}, B-G as anode material enhances the specific capacity by about 1.7 times compared to pristine graphene. The present study shows a simplistic way of boron doping in graphene leading to an enhanced Li ion adsorption due to the change in electronic states.

  4. Durability of doped zinc oxide/silver/doped zinc oxide low emissivity coatings in humid environment

    Ando, E. [Research Center, Asahi Glass Co., Ltd., 1150 Hazawa-cho, Kanagawa-ku, Yokohama 221-8755 (Japan)], E-mail: eiichi-ando@agc.co.jp; Miyazaki, M. [Research Center, Asahi Glass Co., Ltd., 1150 Hazawa-cho, Kanagawa-ku, Yokohama 221-8755 (Japan)

    2008-05-30

    The relationship between internal stress of doped zinc oxide films and durability of doped zinc oxide/silver/doped zinc oxide low emissivity (low-e) coatings in humid environment was investigated. Aluminum, titanium, tin, chromium, silicon, gallium, magnesium, boron, barium, and calcium were chosen as a doping element in sputtering targets. Ratios of dopant/zinc in the oxide targets were 4/96-5/95 at.%. Films were formed by radio frequency sputtering. Doping of barium and calcium to the zinc oxide film led to a large increase in the internal stress. Doping of the other elements resulted in decreasing the internal stress. It was concluded that durability of the low-e coatings in humid environment closely correlated with the internal stress of the oxide layers.

  5. Effect of boron doping on optical properties of sol–gel based nanostructured zinc oxide films on glass

    Graphical abstract: Room temperature fine structured UV–vis PL emissions (a) as phonon replicas in 1 at.% boron doped film originated from LO phonon evidenced from Near Grazing Incidence Angle (NGIA) IR spectral study (b). Highlights: ► Sol–gel based boron doped nanostructured ZnO thin films deposited on pure silica glass using crystalline boric acid as boron source. ► Observed first time, room temperature fine structured PL emissions in 1 at.% doped film as phonon replicas originated from LO phonon (both IR and Raman active). ► Boron doping controls the LO phonon energy in addition to visible reflection, band gap and grain size. ► The films possessed mixed crystal phases with hexagonal as major phase. -- Abstract: Boron doped zinc oxide thin films (∼80 nm) were deposited onto pure silica glass by sol–gel dip coating technique from the precursor sol/solution of 4.0 wt.% equivalent oxide content. The boron concentration was varied from 0 to 2 at.% w.r.t. Zn using crystalline boric acid. The nanostructured feature of the films was visualized by FESEM images and the largest cluster size of ZnO was found in 1 at.% boron doped film (B1ZO). The presence of mixed crystal phases with hexagonal as major phase was identified from XRD reflections of the films. Particle size, optical band gap, visible specular reflection, room temperature photoluminescence (PL) emissions (3.24–2.28 eV), infra-red (IR) and Raman active longitudinal optical (LO) phonon vibration were found to be dependent on dopant concentration. For the first time, we report the room temperature fine structured PL emissions as phonon replicas originated from the LO phonon (both IR and Raman active) in 1 at.% boron doped zinc oxide film.

  6. Doped biocompatible layers prepared by laser

    Jelínek, M.; Weiserová, M.; Kocourek, T.; Jurek, K.; Strnad, J.

    2010-03-01

    The contribution deals with KrF laser synthesis and study of doped biocompatible materials with focus on diamond-like carbon (DLC) and hydroxyapatite (HA). Overview of materials used for dopation is given. Experimental results of study of HA layers doped with silver are presented. Films properties were characterized using profilometer, SEM, WDX, XRD and optical transmission. Content of silver in layers moved from 0.06 to 13.7 at %. The antibacterial properties of HA, silver and doped HA layers were studied in vivo using Escherichia coli cells.

  7. Transmutation doping of silicon solar cells

    Wood, R. F.; Westbrook, R. D.; Young, R. T.; Cleland, J. W.

    1977-01-01

    Normal isotopic silicon contains 3.05% of Si-30 which transmutes to P-31 after thermal neutron absorption, with a half-life of 2.6 hours. This reaction is used to introduce extremely uniform concentrations of phosphorus into silicon, thus eliminating the areal and spatial inhomogeneities characteristic of chemical doping. Annealing of the lattice damage in the irradiated silicon does not alter the uniformity of dopant distribution. Transmutation doping also makes it possible to introduce phosphorus into polycrystalline silicon without segregation of the dopant at the grain boundaries. The use of neutron transmutation doped (NTD) silicon in solar cell research and development is discussed.

  8. Alternative medicine and doping in sports

    Benjamin Koh

    2012-01-01

    Full Text Available Athletes are high achievers who may seek creative or unconventional methods to improve performance. The literature indicates that athletes are among the heaviest users of complementary and alternative medicine (CAM and thus may pioneer population trends in CAM use. Unlike non-athletes, athletes may use CAM not just for prevention, treatment or rehabilitation from illness or injuries, but also for performance enhancement. Assuming that athletes’ creative use of anything unconventional is aimed at “legally” improving performance, CAM may be used because it is perceived as more “natural” and erroneously assumed as not potentially doping. This failure to recognise CAMs as pharmacological agents puts athletes at risk of inadvertent doping.The general position of the World Anti-Doping Authority (WADA is one of strict liability, an application of the legal proposition that ignorance is no excuse and the ultimate responsibility is on the athlete to ensure at all times whatever is swallowed, injected or applied to the athlete is both safe and legal for use. This means that a violation occurs whether or not the athlete intentionally or unintentionally, knowingly or unknowingly, used a prohibited substance/method or was negligent or otherwise at fault. Athletes are therefore expected to understand not only what is prohibited, but also what might potentially cause an inadvertent doping violation. Yet, as will be discussed, athlete knowledge on doping is deficient and WADA itself sometimes changes its position on prohibited methods or substances. The situation is further confounded by the conflicting stance of anti-doping experts in the media. These highly publicised disagreements may further portray inconsistencies in anti-doping guidelines and suggest to athletes that what is considered doping is dependent on the dominant political zeitgeist. Taken together, athletes may believe that unless a specific and explicit ruling is made, guidelines are

  9. Sulphur mustard degradation on zirconium doped Ti-Fe oxides

    Stengl, Vaclav, E-mail: stengl@iic.cas.cz [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR v.v.i 250 68 Husinec-Rez (Czech Republic); Grygar, Tomas Matys [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR v.v.i 250 68 Husinec-Rez (Czech Republic); Oplustil, Frantisek; Nemec, Tomas [Military Technical Institute of Protection Brno Veslarska 230, 628 00 Brno (Czech Republic)

    2011-09-15

    Highlights: {yields} New stechiometric materials for sulphur mustard degradation. {yields} High degree of degradation, more then 95% h{sup -1}. {yields} One-pot synthesis procedure. - Abstract: Zirconium doped mixed nanodispersive oxides of Ti and Fe were prepared by homogeneous hydrolysis of sulphate salts with urea in aqueous solutions. Synthesized nanodispersive metal oxide hydroxides were characterised as the Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) microanalysis, and acid-base titration. These oxides were taken for an experimental evaluation of their reactivity with sulphur mustard (chemical warfare agent HD or bis(2-chloroethyl)sulphide). The presence of Zr{sup 4+} dopant tends to increase both the surface area and the surface hydroxylation of the resulting doped oxides in such a manner that it can contribute to enabling the substrate adsorption at the oxide surface and thus accelerate the rate of degradation of warfare agents. The addition of Zr{sup 4+} to the hydrolysis of ferric sulphate with urea shifts the reaction route and promotes formation of goethite at the expense of ferrihydrite. We discovered that Zr{sup 4+} doped oxo-hydroxides of Ti and Fe exhibit a higher degradation activity towards sulphur mustard than any other yet reported reactive sorbents. The reaction rate constant of the slower parallel reaction of the most efficient reactive sorbents is increased with the increasing amount of surface base sites.

  10. Borohydride electro-oxidation by Ag-doped lanthanum chromites

    S Suresh Balaji; A Usha; V V Giridhar

    2014-05-01

    The electrocatalytic activity of Ag-doped lanthanum chromites electrode materials viz., LaCr0.4Ag0.6O3 and LaCr0.7Ag0.3O3 prepared by decomposing the precursor complex is studied. Pure LaCrO3 is synthesized by combustion route using oxalic acid as a fuel. The decomposition behaviour of the assynthesized powder obtained in the latter method is characterized by TGA-DTA and XRD. Both the precursor complex and the as-synthesized powder are calcined at 900°C for 7 and 10 h, respectively. XRD of the final product after calcinations indicated the formation of perovskite phase with minor amounts of impurity phases of component oxides in the Ag-doped lanthanum chromites and pure perovskite phase in the undoped one. The surface morphology of the perovskites is studied by SEM. The electrocatalytic activity of the perovskite powders for borohydride oxidation is studied by using cyclic voltammetry (CV) at a catalyst loading of 0.7 mgcm−2 for both Ag-doped and undoped LaCrO3 coated on glassy carbon substrate. Calibration plots are obtained by plotting the anodic peak current versus concentration of borohydride in the range of 20-100 mM. The sensitivities of the three perovskites towards borohydride oxidation indicated that LaCr0.4Ag0.6O3 is the best among all the perovskites studied giving a value of 1.395 A/mM.

  11. Molecular monolayers for doping silicon: from doping dose control to device applications

    Ye, Liang

    2016-01-01

    The evolution of the semiconductor industry calls for new techniques to address the challenges arising from the downscaling trend known as Moore’s law, which has brought electronic devices into the nano-regime. Monolayer doping (MLD) is an interesting alternative for the currently mostly employed ion implantation to introduce a dopant into silicon. The MLD technique is capable of forming ultra-shallow doping without causing crystal damage to the substrate. It is also capable of doping non-pla...

  12. Doping in elite sport – do the fans care? : public opinion on the consequences of doping scandals

    Solberg, Harry Arne; Hanstad, Dag Vidar; Thøring, Thor Atle

    2010-01-01

    There are indications that commercial stakeholders are reluctant to associate with sports involved in doping scandals. A survey of 925 Norwegian sports consumers supports this reluctance, showing no tolerance for pure doping substances. The majority were in favour of tough responses to athletes and sports involved in doping. Older respondents were more negative towards doping. Those who were strongly interested in sport were more willing than others to accept doping.

  13. Spherical nitrogen-doped hollow mesoporous carbon as an efficient bifunctional electrocatalyst for Zn-air batteries

    Hadidi, Lida; Davari, Elaheh; Iqbal, Muhammad; Purkait, Tapas K.; Ivey, Douglas G.; Veinot, Jonathan G. C.

    2015-12-01

    Materials based upon porous carbon have gained considerable attention due to their high surface area, electric conductivity, thermal and chemical stability, low density, and availability. These superior properties make them ideal for diverse applications. Doping these carbon nanostructures holds promise of designing the properties of these structures and opening the door to practical applications. Herein, we report the preparation of hollow N-doped mesoporous carbon (HMC) spheres fabricated via polymerization and carbonization of dopamine on a sacrificial spherical SiO2 template that is removed upon hydrofluoric acid etching. The morphology and structural features of these HMCs were evaluated using scanning electron microscopy and transmission electron microscopy and the N-doping (7.1 at%) was confirmed by X-ray photoelectron spectroscopy (XPS). The oxygen reduction/evolution reaction (ORR/OER) performance of N-doped HMC was evaluated using rotating disk electrode (RDE) voltammetry in an alkaline electrolyte. N-doped HMC demonstrated a high ORR onset potential of -0.055 V (vs. Hg/HgO) and excellent stability. The outstanding bifunctional activity was implemented in a practical Zn-air battery (ZAB), which exhibited a small charge-discharge voltage polarization of 0.89 V and high stability over repeated cycling.Materials based upon porous carbon have gained considerable attention due to their high surface area, electric conductivity, thermal and chemical stability, low density, and availability. These superior properties make them ideal for diverse applications. Doping these carbon nanostructures holds promise of designing the properties of these structures and opening the door to practical applications. Herein, we report the preparation of hollow N-doped mesoporous carbon (HMC) spheres fabricated via polymerization and carbonization of dopamine on a sacrificial spherical SiO2 template that is removed upon hydrofluoric acid etching. The morphology and structural

  14. Fullerenes doped with metal halides

    The cage-like structure of fullerenes is a challenge to every experimental to put something inside - to dope the fullerenes. In fact, the research team that first identified C60 as a football-like molecule quickly succeeded in trapping metal atoms inside and in shrinking the cage around this atom by photofragmentation. In this paper we report the results of ''shrink-wrapping'' the fullerenes around metal halide molecules. Of special interest is the critical size (the minimum number of carbon atoms) that can still enclose the dopant. A rough model for the space available inside a carbon cage gives good agreement with the measured shrinking limits. (author). 8 refs, 6 figs

  15. Screening dynamics in doped titanates

    Rubensson, J.E.; Luening, J.; Eisebitt, S. [Forschungszentrum Juelich (Germany)] [and others

    1997-04-01

    The time scale for carrier relaxation in semiconductors is on the same order of magnitude as the life time of shallow core hole states (a few femtoseconds). Resonant Inelastic soft X-ray scattering (RIXS) which involves (virtual) excitations of core levels consequently contains information about the time development of the electronic structure on this time scale. In many cases one can treat the scattering in an absorption (SXA) followed-by-emission (SXE) picture, where simply the rates for various processes can be compared with the intermediate core hole state decay rate as an internal {open_quotes}clock{close_quotes}. By variation of x (0 < x < 1) in La{sub x}Sr{sub 1{minus}x}TiO{sub 3}, the amount of Ti d electrons in the system can be controlled. SrTiO{sub 3} (x=0) is an insulator with an empty Ti d band. With increasing x, electrons are doped into the Ti d-band, and LaTiO{sub 3} (x=1) is a Mott Hubbard insulator with a Ti 3d{sup 1} configuration. In this work the authors demonstrate that the rate for Ti 2p core hole screening in La{sub x}Sr{sub 1{minus}x}TiO{sub 3} is doping dependent. The screening rate increases with the availability of Ti 3d electrons, and they estimate it to be 3.8 x 10{sup 13}/sec in La{sub 0.05}Sr{sub 0.95}TiO{sub 3}.

  16. Electrical characterization of proton conducting polymer electrolyte based on bio polymer with acid dopant

    Kalaiselvimary, J.; Pradeepa, P.; Sowmya, G.; Edwinraj, S.; Prabhu, M. Ramesh

    2016-05-01

    This study describes the biodegradable acid doped films composed of chitosan and Perchloric acid with different ratios (2.5 wt %, 5 wt %, 7.5 wt %, 10 wt %) was prepared by the solution casting technique. The temperature dependence of the proton conductivity of complex electrolytes obeys the Arrhenius relationship. Proton conductivity of the prepared polymer electrolyte of the bio polymer with acid doped was measured to be approximately 5.90 × 10-4 Scm-1. The dielectric data were analyzed using Complex impedance Z*, Dielectric loss ɛ', Tangent loss for prepared polymer electrolyte membrane with the highest conductivity samples at various temperature.

  17. Electrical transport and EPR investigations: A comparative study for d.c. conduction mechanism in monovalent and multivalent ions doped polyaniline

    Suresh Kumar Gupta; Vandna Luthra; Ramadhar Singh

    2012-10-01

    A detailed comparative study of electron paramagnetic resonance (EPR) in conjunction with d.c. electrical conductivity has been undertaken to know about the charge transport mechanism in polyaniline (PANI) doped with monovalent and multivalent protonic acids. This work is in continuation of our previous work for further understanding the conduction mechanism in conducting polymers. The results reveal that the polarons and bipolarons are the main charge carriers formed during doping process and these cause increase in electrical conductivity not only by increase in their concentration but also because of their enhanced mobility due to increased inter-chain transport in polyaniline at high doping levels. EPR line asymmetry having Dysonian line shape for highly doped samples shows a marked deviation of amplitudes / ratio from values close to one to much high values as usually observed in metals, thereby support the idea of high conductivity at higher doping levels. The nature of dopant ions and their doping levels control the charge carriers concentration as well as electrical conductivity of polyaniline. The electrical conductivity has also been studied as a function of temperature to know the thermally assisted transport process of these charge carriers at different doping levels which has been found to follow the Mott’s variable range hopping (VRH) conduction model for all the three dopants used. The charge carriers show a change over from 3D VRH to quasi 1D VRH hopping process for multivalent ions at higher doping levels whereas 1D VRH has been followed by monovalent ion for full doping range. These studies collectively give evidence of inter-chain percolation at higher doping levels causing increase in effective mobility of the charge carriers which mainly seems to govern the electrical conduction behaviour in this system.

  18. Doping Scheme of Semiconducting Atomic Chains

    Toshishige, Yamada; Saini, Subhash (Technical Monitor)

    1998-01-01

    Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.

  19. Controlled doping of graphene using ultraviolet irradiation

    Luo Zhengtang [Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong); Pinto, Nicholas J.; Davila, Yarely [Department of Physics and Electronics, University of Puerto Rico at Humacao, Humacao, 00792 (Puerto Rico); Charlie Johnson, A. T. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396 (United States)

    2012-06-18

    The electronic properties of graphene are tunable via doping, making it attractive in low dimensional organic electronics. Common methods of doping graphene, however, adversely affect charge mobility and degrade device performance. We demonstrate a facile shadow mask technique of defining electrodes on graphene grown by chemical vapor deposition (CVD) thereby eliminating the use of detrimental chemicals needed in the corresponding lithographic process. Further, we report on the controlled, effective, and reversible doping of graphene via ultraviolet (UV) irradiation with minimal impact on charge mobility. The change in charge concentration saturates at {approx}2 Multiplication-Sign 10{sup 12} cm{sup -2} and the quantum yield is {approx}10{sup -5} e/photon upon initial UV exposure. This simple and controlled strategy opens the possibility of doping wafer-size CVD graphene for diverse applications.

  20. Controlled doping of graphene using ultraviolet irradiation

    The electronic properties of graphene are tunable via doping, making it attractive in low dimensional organic electronics. Common methods of doping graphene, however, adversely affect charge mobility and degrade device performance. We demonstrate a facile shadow mask technique of defining electrodes on graphene grown by chemical vapor deposition (CVD) thereby eliminating the use of detrimental chemicals needed in the corresponding lithographic process. Further, we report on the controlled, effective, and reversible doping of graphene via ultraviolet (UV) irradiation with minimal impact on charge mobility. The change in charge concentration saturates at ∼2 × 1012 cm-2 and the quantum yield is ∼10-5 e/photon upon initial UV exposure. This simple and controlled strategy opens the possibility of doping wafer-size CVD graphene for diverse applications.

  1. Stabilization of boron carbide via silicon doping.

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping. PMID:25427850

  2. Superconductivity in carrier-doped silicon carbide

    Takahiro Muranaka, Yoshitake Kikuchi, Taku Yoshizawa, Naoki Shirakawa and Jun Akimitsu

    2008-01-01

    Full Text Available We report growth and characterization of heavily boron-doped 3C-SiC and 6H-SiC and Al-doped 3C-SiC. Both 3C-SiC:B and 6H-SiC:B reveal type-I superconductivity with a critical temperature Tc=1.5 K. On the other hand, Al-doped 3C-SiC (3C-SiC:Al shows type-II superconductivity with Tc=1.4 K. Both SiC:Al and SiC:B exhibit zero resistivity and diamagnetic susceptibility below Tc with effective hole-carrier concentration n higher than 1020 cm−3. We interpret the different superconducting behavior in carrier-doped p-type semiconductors SiC:Al, SiC:B, Si:B and C:B in terms of the different ionization energies of their acceptors.

  3. Stabilization of boron carbide via silicon doping

    Proctor, J. E.; Bhakhri, V.; Hao, R.; Prior, T. J.; Scheler, T.; Gregoryanz, E.; Chhowalla, M.; Giulani, F.

    2015-01-01

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  4. Fabrication of Gold Nanoparticles Doped DVB Foams

    The fabrication of gold nanoparticles doped low density DVB foams was researched, which can be used as ICF target materials. By high internal phase emulsion (HIPE) method, gold nanoparticles doped low density DVB foams were prepared, with gold nanoparticles dissolved in inner phase. The results show that the content of Au in the gold nanoparticles doped DVB foam is 3. 19%, the axial direction density of the foam is uniform which indicates none evident settlement of gold nanoparticles. SEM tests show that the gold doped DVB polymer foams have open-celled structure and very uniform aperture, and the average pore size is about 1 μm, which is much smaller than that of pure DVB foams. EDX test shows that Au disperses uniformly in the foams. (authors)

  5. Synthesis of highly thermally stable lanthanum-doped ordered mesoporous alumina

    Highly thermally stable lanthanum-doped ordered mesoporous alumina has been prepared in a sol-gel system with salicylic acid and citric acid as interfacial protectors. When the molar ratio of alumina to lanthanum is 25.5, most La3+ ions in the resulting alumina structure showed tetracoordination. Moreover, the as-obtained sample exhibits a surface area of 305 m2 g-1 when calcined at 400 oC and can maintain an ordered mesostructure with a high surface area of 205 m2 g-1 even when treated at 1000 oC, demonstrating its high thermal stability.

  6. Dual vortex theory of doped Mott insulators

    Balents, Leon; Sachdev, Subir

    2006-01-01

    We present a general framework for describing the quantum phases obtained by doping paramagnetic Mott insulators on the square lattice. The undoped insulators are efficiently characterized by the projective transformations of various fields under the square lattice space group (the PSG). We show that the PSG also imposes powerful constraints on the doped system, and on the effective action for the vortex and Bogoliubov quasiparticle excitations of superconducting states. This action can also ...

  7. Enhanced Casimir effect for doped graphene

    Bordag, M.; Fialkovskiy, I.; Vassilevich, D.

    2016-02-01

    We analyze the Casimir interaction of doped graphene. To this end we derive a simple expression for the finite-temperature polarization tensor with a chemical potential. It is found that doping leads to a strong enhancement of the Casimir force, reaching almost 60 % in quite realistic situations. This result should be important for planning and interpreting Casimir measurements, especially taking into account that the Casimir interaction of undoped graphene is rather weak.

  8. Doped Colloidal ZnO Nanocrystals

    Yizheng Jin; Yuping Ren; MoTao Cao; Zhizhen Ye

    2012-01-01

    Colloidal ZnO nanocrystals are promising for a wide range of applications due to the combination of unique multifunctional nature and remarkable solution processability. Doping is an effective approach of enhancing the properties of colloidal ZnO nanocrystals in well-controlled manners. In this paper, we analyzed two synthetic strategies for the doped colloidal ZnO nanocrystals, emphasizing our understanding on the critical factors associated with the high temperature and nonaqueous approach....

  9. Medicolegal aspects of doping in football

    Graf‐Baumann, T

    2006-01-01

    This article describes the historical background of the medicolegal aspects of doping in sports and especially in football. The definitions of legal terms are explained and the procedure of individual case management as part of FIFA's approach to doping is presented. Finally, three medicolegal problems awaiting urgent solution are outlined: firstly, the difficulties in decision making arising from the decrease of the T/E ratio from 6 to 4; secondly, the therapeutic application of α‐reductase ...

  10. Electronic Strengthening of Graphene by Charge Doping

    Si, Chen; Duan, Wenhui; Liu, Zheng; Liu, Feng

    2012-01-01

    Graphene is known as the strongest 2D material in nature, yet we show that moderate charge doping of either electrons or holes can further enhance its ideal strength by up to ~17%, based on first principles calculations. This unusual electronic enhancement, versus conventional structural enhancement, of material's strength is achieved by an intriguing physical mechanism of charge doping counteracting on strain induced enhancement of Kohn anomaly, which leads to an overall stiffening of zone b...

  11. Detection of Doping with rhGH

    Wu Mou-tian

    2009-01-01

    This presentation reviewed most articles recently pub lished in peer reviewed international scientific journals related to detection doping with rhGH. Four parts were in it: First part was the brief introduction about the background of do ping,special doping with rhGH. Second part summarized the development of "indirect method", markers approach. Third was focused on the development of "direct method", isoform approach. Finally, some potential alternatives have been discussed.

  12. Ultrafast THz Saturable Absorption in Doped Semiconductors

    Turchinovich, Dmitry; Hoffmann, Matthias C.

    2011-01-01

    We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields.......We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields....

  13. Preparation of luminescent CdTe quantum dots doped core-shell nanoparticles and their application in cell recognition

    LI Zhaohui; WANG Kemin; TAN Weihong; LI Jun; FU Zhiying; WANG Yilin; LIU Jianbo; YANG Xiaohai

    2005-01-01

    Based on the reverse microemulsion technique, luminescent quantum dots doped core-shell nanoparticles have been prepared by employing silica as the shell and CdTe quantum dots as the core of the nanoparticles, which have an excellent solubility and dispersibility, especially amine and phosphonate groups have been modified on their surface synchronously. In comparison with CdTe quantum dots, these nanoparticles show superiority in chemical and photochemical stability. The quantum dots doped core-shell nanoparticles were successfully linked with lactobionic acid by amine group on it, which was used to recognize living liver cells.

  14. Fatigue Resistance of Filled NR with PMMA-Wrapped and Rare Earth-Doped Alumina-Siloxane Gel

    2002-01-01

    Poly (methyl methacrylate) (PMMA) was used to wrap alumina-siloxane sol which was produced by water glass, aluminum nitrate and α-methacrylic acid, and as a result, alumina-siloxane gel wrapped by PMMA was obtained. Meanwhile, rare earth ions were employed to dope in the course of reaction, and the formed rare earth doped PMMA microcapsule powder was filled into natural rubber (NR). It is found through the analysis of mechanical properties that Young′s modulus universally improves and a remarkable resistance to fatigue is displayed. Retention rate of tensile strength is twice that of the controlled sample after ten thousand times of extension fatigue.

  15. Doping-induced Charge-Density-Wave

    Nomura, Atsushi; Yamaya, Kazuhiko; Takayanagi, Shigeru; Ichimura, Koichi; Matsuura, Toru; Tanda, Satoshi; Hokkaido University Team

    Doping is a useful method for searching new characters in solids, as we can see in the discoveries of impurity semiconductors and high-temperature superconductors. If a Charge-Density-Wave (CDW) is induced in materials which do not exhibit a CDW, new CDW properties might be brought there. TaSe3 exhibits no CDW transition but a superconductivity transition at about 2 K while it has a quasi-one-dimensional chain structure as well as typical CDW conductors, NbSe3, TaS3, and NbS3. Therefore, TaSe3 is one of the suitable materials for the induction of a CDW by doping, and we tried to induce a CDW in TaSe3 by doping Cu. Cu concentration was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The high Cu concentration was consistent with the high value of residual resistance (R (4 . 5 K) / (R (280 K) - R (4 . 5 K))). Single-crystal X-ray diffraction pattern (XRD) showed an expansion of the c-axis in Cu-doped TaSe3. The temperature dependence of the resistivity showed the anomaly at 80-100 K in Cu-doped TaSe3, which was never observed in pure TaSe3. These results suggest that the Cu-doping induces a CDW. We will discuss the relation between the resistivity anomaly and superconductivity.

  16. Fabrication of Pd Doped WO3 Nanofiber as Hydrogen Sensor

    Alireza Nikfarjam

    2013-01-01

    Full Text Available Pd doped WO3 fibers were synthesized by electro-spinning. The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA. Palladium chloride and Polyvinyl pyrrolidone (PVP was dissolved in the sol Pd:WO3 = 10% molar ratio. The prepared sol was loaded into a syringe connected to a high voltage of 18.3 kV and electrospun fibers were collected on the alumina substrates. Scanning electron microscope (SEM, X-ray powder diffraction (XRD and X-ray photoelectron spectroscopy (XPS techniques were used to analyze the crystal structure and chemical composition of the fibers after heat treatment at 500 °C. Resistance-sensing measurements exhibited a sensitivity of about 30 at 500 ppm hydrogen in air, and the response and recovery times were about 20 and 30 s, respectively, at 300 °C. Hydrogen gas sensing mechanism of the sensor was also studied.

  17. Effect of L-Valine on the growth and characterization of Sodium Acid Phthalate (SAP) single crystals

    Nirmala, L. Ruby; Prakash, J. Thomas Joseph

    2013-06-01

    Undoped and amino acid doped good quality single crystals of Sodium Acid Phthalate crystals (SAP) were grown by slow evaporation solution growth technique which are semiorganic in nature. The effect of amino acid (L-Valine) dopant on the growth and the properties of SAP single crystal was investigated. The single crystal X-ray diffraction studies and FT-IR studies were carried out to identify the crystal structure and the presence of functional groups in undoped and L-Valine doped SAP crystals. The transparent nature of the grown crystal was observed using UV-Visible spectrum. The thermal decomposition of the doped SAP crystals was investigated by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The enhancement in the NLO property of the undoped and L-Valine doped SAP crystals using KDP crystal as a reference was studied using SHG measurements. Vickers micro hardness measurements are used for the study of mechanical strength of the grown crystals.

  18. Density functional theory (DFT) study of a new novel bionanosensor hybrid; tryptophan/Pd doped single walled carbon nanotube

    Yoosefian, Mehdi; Etminan, Nazanin

    2016-07-01

    In order to explore a new novel L-amino acid/transition metal doped single walled carbon nanotube based biosensor, density functional theory calculations were studied. These hybrid structures of organic-inorganic nanobiosensors are able to detect the smallest amino acid building block of proteins. The configurations of amine and carbonyl group coordination of tryptophan aromatic amino acid adsorbed on Pd/doped single walled carbon nanotube were compared. The frontier molecular orbital theory, quantum theory atom in molecule and natural bond orbital analysis were performed. The molecular electrostatic potential and the electron density surfaces were constructed. The calculations indicated that the Pd/SWCNT was sensitive to tryptophan suggesting the importance of interaction with biological molecule and potential detecting application. The proposed nanobiosensor represents a highly sensitive detection of protein at ultra-low concentration in diagnosis applications.

  19. Highly efficient sulfated Zr-doped titanoniobate nanoplates for the alcoholysis of styrene epoxide at room temperature

    Zhang, Lihong; Hu, Chenhui; Mei, Weigang; Zhang, Junfeng; Cheng, Liyuan; Xue, Nianhua; Ding, Weiping; Chen, Jing; Hou, Wenhua

    2015-12-01

    Sulfated Zr-doped titanoniobate nanoplates were prepared and evaluated as a solid acid catalyst in the alcoholysis of styrene epoxide at room temperature. Compared with undoped and Zr-doped nanosheets, the resulting sulfated catalyst exhibited an excellent catalytic performance to afford corresponding β-alkoxyalcohols (99% yield with methanol as nucleophile in only 10 min) due to the high dispersion of zirconia species on nanosheets, appropriate Lewis acid strength and amount from the strong interaction between zirconia and sulfate species, and greatly increased surface area arisen from the exfoliation and house-of-cards restacking of nanosheets. The corresponding catalytic mechanism was proposed and discussed. The obtained material may act as a promising catalyst in many acid catalyzed reactions.

  20. Ibotenic acid and thioibotenic acid

    Hermit, Mette B; Greenwood, Jeremy R; Nielsen, Birgitte;

    2004-01-01

    In this study, we have determined and compared the pharmacological profiles of ibotenic acid and its isothiazole analogue thioibotenic acid at native rat ionotropic glutamate (iGlu) receptors and at recombinant rat metabotropic glutamate (mGlu) receptors expressed in mammalian cell lines....... Thioibotenic acid has a distinct pharmacological profile at group III mGlu receptors compared with the closely structurally related ibotenic acid; the former is a potent (low microm) agonist, whereas the latter is inactive. By comparing the conformational energy profiles of ibotenic and thioibotenic acid with...... the conformations preferred by the ligands upon docking to mGlu1 and models of the other mGlu subtypes, we propose that unlike other subtypes, group III mGlu receptor binding sites require a ligand conformation at an energy level which is prohibitively expensive for ibotenic acid, but not for...

  1. Neutron transmutation doping conceptual design

    When silicon is irradiated the objective is to produce number of phosphorus atoms in the target sample in order to obtain a given resistivity after the treatment. The resistivity of the sample is decreased by the transmutation of the silicon, by neutrons, to phosphorus. Irradiation is carried out by thermal neutrons. The silicon doping facility at ETRR-2 had commission for production of 5- inches silicon ingot. The trend in the semiconductors industry is to increase the wafer diameter to increase the number of integrated circuits produced from each wafer which leads to reduce the cost of the product. Hence, it is necessary to upgrade the silicon doping facility to 6-inches diameter. A new neutron transmutation doping conceptual design (NTDCD) has followed to upgrade the silicon doping facility. The new design has main three branches. First, is the mechanical design of the irradiation rig and silicon ingot handling tools. In the new design two graphite blocks are dispensed with to increase the ingot height and reduce the weight for ease the handling the silicon ingot container, safe handling, and to enhance the cooling of the silicon ingot during irradiation. The second branch in the new design is the neutronic analysis and design. The neutronic design, includes the neutron flux measuring in the two positions are available in the thermal column. From the neutronic design the axial resistivity variation can be predicted. Two irradiation methods are proposed. They are based on irradiating two ingots simultaneously in one position. These two methods are explained in the thesis. The axial resistivity variation obtained is (6.21%-8.2%) for 500 mm ingot length irradiated in position (1) using irradiation method (2), and axial resistivity variation (5.56%-12.52%) for position (2) using irradiation method (2). The axial resistivity variation for 400 mm ingot length is (3.82%-4.28%) for position (1) using method (2) and a value between (3.65%-6.2%) has been obtained for

  2. pH-indicators doped polysaccharide LbL coatings for hazardous gases optical sensing.

    Mironenko, A Yu; Sergeev, A A; Voznesenskiy, S S; Marinin, D V; Bratskaya, S Yu

    2013-01-30

    Sensitive layer-by-layer (LbL) coatings for optical detection of gaseous NH(3) and HCl were prepared by self-assembly of oppositely charged polysaccharides (chitosan and λ-carrageenan) followed by doping LbLs with pH-sensitive dyes - bromothymol blue (BTB) and Congo red (CR). It has been shown that CR, being an amphoteric dye, diffuses into LbL films regardless of the charge of the outermost polyelectrolyte layer, and the dye loading increases linearly with the LbL film thickness, whereas BTB diffuses into LbL films only when the outermost layer is positively charged, and linearity between dye loading and film thickness holds only up to 8-12 double layers (DLs) deposited. Formation of dye-doped LbL coatings at the surface of K(+)/Na(+) ion-exchanged glass has allowed fabrication of composite optical waveguide (OWG) gas sensor for detection of ammonia and hydrochloric acid vapors. The response time of BTB-doped composite OWG for ammonia detection was below 1s, and the detection limit was below 1 ppm. CR-doped OWG sensors have shown high sensitivity to HCl vapor but slow relaxation time (up to several hours for 12 DL LbL films). PMID:23218366

  3. Alkaline earth metal doped tin oxide as a novel oxygen storage material

    Alkaline earth metal doped tin oxide (SnO2) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl4·5H2O and A(NO3)2·xH2O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO2 and A-doped SnO2 hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO2 hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m2 g−1 exhibited the considerably high OSC of 457 μmol-O g−1 and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material

  4. Alkaline earth metal doped tin oxide as a novel oxygen storage material

    Dong, Qiang, E-mail: dong@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan); Yin, Shu; Yoshida, Mizuki; Wu, Xiaoyong; Liu, Bin [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan); Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro [Department of Research Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Miyamae cho-7, Kofu 400-8511 (Japan); Sato, Tsugio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan)

    2015-09-15

    Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.

  5. Understanding the doping effects on the structural and electrical properties of ultrathin carbon nanotube networks

    Zhou, Ying, E-mail: y-shuu@aist.go.jp; Shimada, Satoru; Azumi, Reiko [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, 305-8565 Tsukuba (Japan); Saito, Takeshi [Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, 305-8565 Tsukuba (Japan)

    2015-12-07

    Similar to other semiconductor technology, doping of carbon nanotube (CNT) thin film is of great significance for performance improvement or modification. However, it still remains a challenge to seek a stable and effective dopant. In this paper, we unitize several spectroscopic techniques and electrical characterizations under various conditions to investigate the effects of typical dopants and related methods. Nitric acid (HNO{sub 3}) solution, I{sub 2} vapor, and CuI nanoparticles are used to modify a series of ultrathin CNT networks. Although efficient charge transfer is achieved initially after doping, HNO{sub 3} is not applicable because it suffers from severe reliability problems in structural and electrical properties, and it also causes a number of undesired structural defects. I{sub 2} vapor doping at 150 °C can form some stable C-I bonding structures, resulting in relatively more stable but less efficient electrical performances. CuI nanoparticles seem to be an ideal dopant. Photonic curing enables the manipulation of CuI, which not only results in the construction of novel CNT-CuI hybrid structures but also encourages the deepest level of charge transfer doping. The excellent reliability as well as processing feasibility identify the bright perspective of CNT-CuI hybrid film for practical applications.

  6. Effect of Er doping on the structural and magnetic properties of cobalt-ferrite

    Prathapani, Sateesh; Vinitha, M.; Das, D., E-mail: ddse@uohyd.ernet.in [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Jayaraman, T. V. [Department of Mechanical and Materials Engineering, University of Nebraska, Lincoln, Nebraska 68588 (United States)

    2014-05-07

    Nanocrystalline particulates of Er doped cobalt-ferrites CoFe{sub (2−x)}Er{sub x}O{sub 4} (0 ≤ x ≤ 0.04), were synthesized, using sol-gel assisted autocombustion method. Co-, Fe-, and Er- nitrates were the oxidizers, and malic acid served as a fuel and chelating agent. Calcination (400–600 °C for 4 h) of the precursor powders was followed by sintering (1000 °C for 4 h) and structural and magnetic characterization. X-ray diffraction confirmed the formation of single phase of spinel for the compositions x = 0, 0.01, and 0.02; and for higher compositions an additional orthoferrite phase formed along with the spinel phase. Lattice parameter of the doped cobalt-ferrites was higher than that of pure cobalt-ferrite. The observed red shift in the doped cobalt-ferrites indicates the presence of induced strain in the cobalt-ferrite matrix due to large size of the Er{sup +3} compared to Fe{sup +3}. Greater than two-fold increase in coercivity (∼66 kA/m for x = 0.02) was observed in doped cobalt-ferrites compared to CoFe{sub 2}O{sub 4} (∼29 kA/m)

  7. Effects of Doping on Thermal Conductivity of Pyrochlore Oxides for Advanced Thermal Barrier Coatings

    Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

    2006-01-01

    Pyrochlore oxides of general composition, A2B2O7, where A is a 3(+) cation (La to Lu) and B is a 4(+) cation (Zr, Hf, Ti, etc.) have high melting point, relatively high coefficient of thermal expansion, and low thermal conductivity which make them suitable for applications as high-temperature thermal barrier coatings. The effect of doping at the A site on the thermal conductivity of a pyrochlore oxide La2Zr2O7, has been investigated. Oxide powders of various compositions La2Zr2O7, La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 were synthesized by the citric acid sol-gel method. These powders were hot pressed into discs and used for thermal conductivity measurements using a steady-state laser heat flux test technique. The rare earth oxide doped pyrochlores La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 had lower thermal conductivity than the un-doped La2Zr2O7. The Gd2O3 and Yb2O3 co-doped composition showed the lowest thermal conductivity.

  8. Understanding the doping effects on the structural and electrical properties of ultrathin carbon nanotube networks

    Similar to other semiconductor technology, doping of carbon nanotube (CNT) thin film is of great significance for performance improvement or modification. However, it still remains a challenge to seek a stable and effective dopant. In this paper, we unitize several spectroscopic techniques and electrical characterizations under various conditions to investigate the effects of typical dopants and related methods. Nitric acid (HNO3) solution, I2 vapor, and CuI nanoparticles are used to modify a series of ultrathin CNT networks. Although efficient charge transfer is achieved initially after doping, HNO3 is not applicable because it suffers from severe reliability problems in structural and electrical properties, and it also causes a number of undesired structural defects. I2 vapor doping at 150 °C can form some stable C-I bonding structures, resulting in relatively more stable but less efficient electrical performances. CuI nanoparticles seem to be an ideal dopant. Photonic curing enables the manipulation of CuI, which not only results in the construction of novel CNT-CuI hybrid structures but also encourages the deepest level of charge transfer doping. The excellent reliability as well as processing feasibility identify the bright perspective of CNT-CuI hybrid film for practical applications

  9. Simultaneous size and luminescence control of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) microcrystals via Li+ doping

    Lin, Hao; Xu, Dekang; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

    2015-07-01

    Enhancement of upconversion (UC) luminescence is imperative for the applications of UC microcrystals (MCs). In this work, NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping were successfully prepared by a simple hydrothermal process with the assistance of citric acid. The UC luminescence intensities of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) are significantly enhanced via Li+ doping at different concentrations. Compared to Li+-absent sample, UC luminescence intensities of blue emission (477 nm) and red emission (649 nm) in NaYF4:Yb3+/Tm3+ MCs via 15 mol% Li+ doping are improved by 10 and 9 times, respectively; UC luminescence intensities of green emission (538 nm) and red emission (644 nm) in NaYF4:Yb3+/Ho3+ MCs via 15 mol% Li+ doping are improved by 12 and 3 times, respectively. The mechanism of the enhancement via Li+ doping is discussed in details, which may be attributed to the fact that Li+ doping can cause the distortion of the local symmetry around RE ions. Our results indicate that the enhanced UC luminescence of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping may have potential applications in optoelectronic devices such as solar cells and plasma display panel.

  10. Reporting doping in sport: national level athletes' perceptions of their role in doping prevention.

    Whitaker, L; Backhouse, S H; Long, J

    2014-12-01

    This paper qualitatively explores national level athletes' willingness to report doping in sport. Following ethical approval, semi-structured interviews were conducted with nine national level athletes from rugby league (n = 5) and track and field athletics (n = 4). Thematic analysis established the main themes within the data. Contextual differences existed around the role that athletes perceived they would play if they became aware of doping. Specifically, track and field athletes would adopt the role of a whistle-blower and report individuals who were doping in their sport. In comparison, the rugby league players highlighted a moral dilemma. Despite disagreeing with their teammates' actions, the players would adhere to a code of silence and refrain from reporting doping. Taking these findings into account, prevention programs might focus on changing broader group and community norms around doping. In doing so, community members' receptivity to prevention messages may increase. Moreover, developing skills to intervene (e.g., speaking out against social norms that support doping behavior) or increasing awareness of reporting lines could enhance community responsibility for doping prevention. In sum, the findings highlight the need to consider the context of sport and emphasize that a one-size-fits-all approach to anti-doping is problematic. PMID:24673128

  11. Field Evaporation of Grounded Arsenic Doped Silicon Clusters

    Deng, Zexiang; Li, Zhibing; WeiliangWang,

    2014-01-01

    We have investigated field evaporation of grounded arsenic (As) doped silicon (Si) clusters consist of 52 atoms with density functional theory to mimic Si nano structures of hundreds of nanometers long standing on a substrate. Six cluster structures with different As doping concentrations and dopant locations are studied. The critical evaporation electric fields are found to be lower for clusters with higher doping concentrations and doping sites closer to the surface. We attribute the difference to the difference in binding energies corresponding to the different As-doping concentrations and to the doping locations. Our theoretical study could shed light on the stability of nano apexs under high electric field.

  12. Novel base doping profile for improved speed and power

    Rehder, E. M.; Cismaru, C.; Zampardi, P. J.; Welser, R. E.

    2005-01-01

    We have experimentally studied the effect of twonewbase doping profiles on the base transit time of a GaAs npn heterojunction bipolar transistor. The doping in a region close to the collector is reduced either by a doping grade or a stepwise reduction. Quasi-electric fields resulting from these doping gradients increase the minority carrier velocity and the beta of large area transistors. By focusing these doping changes adjacent to the collector, the amount of low-doped base material and t...

  13. [Gastric Acid].

    Ruíz Chávez, R

    1996-01-01

    Gastric acid, a product of parietal cells secretion, full fills multiple biological roles which are absolutely necessary to keep corporal homeostasis. The production of the acid depends upon an effector cellular process represented in the first step by histamine, acetilcholine and gastrin, first messengers of the process. These interact with specific receptors than in sequence activate second messengers -cAMP and the calcium-calmodulin system- which afterwards activate a kinase. An specific protein is then phosphorilated by this enzyme, being the crucial factor that starts the production of acid. Finally, a proton bomb, extrudes the acid towards the gastric lumen. The secretion process mentioned above, is progressive lyactivated in three steps, two of which are stimulators -cephalic and gastric phases- and the other one inhibitor or intestinal phase. These stages are started by mental and neurological phenomena -thought, sight, smell or memory-; by food, drugs or other ingested substances; and by products of digestion. Changes in regulation of acid secretion, in the structure of gastro-duodenal mucosal barrier by a wide spectrum of factors and agents including food, drugs and H. pylori, are the basis of acid-peptic disease, entity in which gastric acid plays a fundamental role. From the therapeutic point of view, so at the theoretical as at the practical levels, t is possible to interfere with the secretion of acid by neutralization of some of the steps of the effector cellular process. An adequate knowledge of the basics related to gastric acid, allows to create strategies for the clinical handling of associated pathology, specifically in relation to peptic acid disease in all of the known clinical forms. PMID:12165790

  14. Optical sensing of HCl with phenol red doped sol-gels

    Wang Enju [Department of Chemistry, St. John' s University, 8000 Utopia Parkway, Jamaica, NY 11439 (United States)]. E-mail: wange@stjohns.edu; Chow, Kwok-Fan [Department of Chemistry, St. John' s University, 8000 Utopia Parkway, Jamaica, NY 11439 (United States); Wang Wenqun [Department of Chemistry, St. John' s University, 8000 Utopia Parkway, Jamaica, NY 11439 (United States); Wong, Crystal [Department of Chemistry, St. John' s University, 8000 Utopia Parkway, Jamaica, NY 11439 (United States); Yee, Cynthia [Department of Chemistry, St. John' s University, 8000 Utopia Parkway, Jamaica, NY 11439 (United States); Persad, Alvin [Department of Chemistry, St. John' s University, 8000 Utopia Parkway, Jamaica, NY 11439 (United States); Mann, Jonathan [Department of Chemistry, Princeton University, Princeton, NJ 08540 (United States); Bocarsly, Andrew [Department of Chemistry, Princeton University, Princeton, NJ 08540 (United States)

    2005-04-08

    A dye doped sol-gel for the sensing of hydrochloric acid in solution and/or gaseous phase is described. The sol-gel is obtained by acidic hydrolysis of tetraethoxysilane (TEOS) and phenyltriethoxysilane (Ph-TriEOS) in the presence of phenol red (PR) and further spin-coating onto glass slides. The sensitive response is based on an increase of the absorption band at 510 nm of phenol red entrapped in the sol-gel casting when exposed to HCl solution or gas, due to protonation of the dye. The detection limit of the sol-gel response to moisturized gaseous HCl is below 12 ppm, and its response to HCl in solution falls in the range of 0.01-6 M. The sol-gel coating has a response time of less than 40 s in steady-state, and life-time of more than a year. Weak acids such as acetic acid, benzoic acid, salicylate acid, citrate acid, and carbonic acid do not interfere the response. The responses in acid solutions are completely reversible. In the gaseous phase, response of HCl appears to be moisture sensitive.

  15. Growth and characterization of pure and lithium doped strontium tartrate tetrahydrate crystals by solution–gel technique

    B Suresh Kumar; M H Rahim Kutty; M R Sudarsana Kumar; K Rajendra Babu

    2007-08-01

    The effect of lithium ion as dopant on the size and transparency of strontium tartrate tetrahydrate (SrC4H4O6.4H2O) crystals are presented in this paper. Growth of single crystals of undoped and lithium doped strontium tartrate tetrahydrate by controlled diffusion of strontium nitrate into the gel charged with tartaric acid at room temperature are narrated. The lithium ion enhances the size and transparency of the doped crystals. The crystal structure of the compound was confirmed by X-ray diffractometry and dopant concentration with ICP–atomic emission spectrometer system. Thermal decomposition of the grown crystals is investigated by TGA and DTA studies. The FTIR spectra of pure and doped crystals are recorded and analysed. Kurtz powder technique has been used to test SHG efficiency of the crystals.

  16. Boron Doped Multi-walled Carbon Nanotubes as Catalysts for Oxygen Reduction Reaction and Oxygen Evolution Reactionin in Alkaline Media

    The boron doped multi-walled carbon nanotubes (B-MWCNTs) were synthesized by thermal annealing multi-walled carbon nanotubes (MWCNTs) in the presence of boric acid. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) results revealed that the structure of MWCNTs does not be destroyed during the doping process, and X-ray photoelectron spectroscopy (XPS) analysis demonstrated the boron atoms were successfully doped in the structure of MWCNTs. The electrocatalytic properties of B-MWCNTs are characterized by rotating disk electrode (RDE) methods. The results demonstrated that the B-MWCNTs catalyzed oxygen reduction reaction (ORR) in alkaline media by a 2 + 2 electron pathway and it showed good catalytic activity for oxygen evolution reaction (OER) as well

  17. Effect of structure on the photocatalytic activity of Pt-doped TiO{sub 2} nanotubes

    Su Yaling, E-mail: ylsu@niglas.ac.cn [Nanjing Institute of Geography and Limnology, State Key Laboratory of Lake Science and Environment, Chinese Academy of Sciences, Nanjing 210008 (China); Deng Yirong [Nanjing Institute of Geography and Limnology, State Key Laboratory of Lake Science and Environment, Chinese Academy of Sciences, Nanjing 210008 (China)

    2011-09-15

    Highly ordered TiO{sub 2} nanotubes with different tube length were fabricated by anodization using C{sub 2}H{sub 2}O{sub 4}.2H{sub 2}O containing 0.5 wt.% NH{sub 4}F (electrolyte A) and anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B), respectively. Then cathodic reduction method was used to dope Pt in TiO{sub 2} nanotubes in chloroplatinic acid. The results indicated that cathodic reduction could efficiently platinize TiO{sub 2} nanotubes. Pt-doped TiO{sub 2} nanotubes with the longer length had the higher photocatalytic activity for degrading methyl orange under UV and visible irradiation. The longer tube length has a positive effect on the photocatalytic activity of Pt-doped TiO{sub 2} nanotubes. Besides, as the content of anatase further decreases, the photocatalytic activity drops gradually due to the reduction reaction in the surface area.

  18. Synthesis of Nb-doped SrTiO3 by a modified glycine-nitrate process

    Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L.R.; Mogensen, Mogens Bjerg

    The objective of the present investigation was to develop a technique to synthesize submicronic particles of Nb-doped strontium titanate with a homogeneous composition. This was achieved by a modified glycine-nitrate process, using Ti-lactate, Nb-oxalate, and Sr(NO3)(2) as starting materials. A...... combination of both citric acid and glycine was needed in order to integrate the useful features of both complexation and combustion natures of citric acid and glycine, respectively. The amount of citric acid, glycine, and nitrates in the starting solution, as well as the source for extra nitrates, and the...

  19. Doping of Semiconducting Atomic Chains

    Toshishige, Yamada; Kutler, Paul (Technical Monitor)

    1997-01-01

    Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.

  20. Growth hormone doping: a review

    Erotokritou-Mulligan I

    2011-07-01

    Full Text Available Ioulietta Erotokritou-Mulligan, Richard IG Holt, Peter H SönksenDevelopmental Origins of Health and Disease Division, University of Southampton School of Medicine, The Institute of Developmental Science, Southampton General Hospital, Southampton, UKAbstract: The use of growth hormone (GH as a performance enhancing substance was first promoted in lay publications, long before scientists fully acknowledged its benefits. It is thought athletes currently use GH to enhance their athletic performance and to accelerate the healing of sporting injuries. Over recent years, a number of high profile athletes have admitted to using GH. To date, there is only limited and weak evidence for its beneficial effects on performance. Nevertheless the “hype” around its effectiveness and the lack of a foolproof detection methodology that will detect its abuse longer than 24 hours after the last injection has encouraged its widespread use. This article reviews the current evidence of the ergogenic effects of GH along with the risks associated with its use. The review also examines methodologies, both currently available and in development for detecting its abuse.Keywords: performance enhancing substance, GH, doping in sport, detection methods