HETEROJUNCTION DIODES OF POROUS SILICON WITH SOLUBLE POLYANILINE*

Two kinds of heterojunction diodes of porous silicon (PS) with soluble polyaniline (PANI) werefabricated. One is a heterojunction diode of PS with water-soluble copolymer of polyaniline (PAOABSA),Al/PS-PAOABSA/Au cell as rectifying diode. Another is a heterojunction diode of PS with solublepolyaniline doped with DBSA, Al/PS-PANI (DBSA)/Au cell as light emitting diode (LED). The rectifyingcharacteristics of the rectifying diodes were measured as a function of the degree of sulfonation and thicknessof the copolymers, as well as oxidation of PS. The rectifying ratio of the heterojunction can reach 5.0×10~4 at±3 V bias. For the LED, the photoluminescence (PL) and electroluminescence (EL) spectra were measuredand discussed.     

Synthesis and Characterization of Novel Nanophase Hexagonal Poly(2,5‐dimethoxyaniline)

Novel nanophase hexagonal structured polyaniline (PANI) and poly(2,5‐dimethoxyanilines) (PDMA) were synthesized by oxidative polymerization involving the respective anilines and a mixture of ferric chloride and ammonium persulfate. The morphological, spectral and electrochemical characteristics of the polymers were determined from the results of SEM, FTIR, UV‐vis, TGA and cyclic voltammetry experiments. The hexagonal PANI and PDMA nanorods (15–200 nm diameter) exhibited very good thermal stabilities, losing only 10% of their weight on heating to 400 °C. Electrochemical data indicated a pernigraniline state of the polymers with formal potential, E°′, values of 394±6 mV and 400±1 mV, for PANI (conductance, C=0.37×10^?3 S) and PDMA (conductance, C=2.02×10^?3 S), respectively. The pernigraniline state was confirmed by sharp FTIR pernigraniline quinoidic peaks (PANI: 1414 cm^?1; PDMA: 1157 cm^?1), and UV‐vis absorption maxima at 340–370 nm (PANI) and 450–650 nm (PDMA) which are characteristic of charge transfer excitons of the quinoid structures of pernigraniline.     

An investigation of Zn/ZnO:Al/p-Si/Al heterojunction diode by sol–gel spin coating technique

Present study shows the structural, morphological, optical characterization of sol–gel spin coated ZnO:Al film and investigation of device efficiency of Zn/ZnO:Al/p-Si/Al heterojunction diode structure. X-ray diffraction study indicates that film has hexagonal polycrystalline structure with (002) preferential direction. Atomic force microscope and scanning electron microscope images exhibit that surface of ZnO:Al/p-Si consists of homogenously scattered nanoparticles. The surface roughness of ZnO:Al film is found to be 15.24 nm. The band gap value of ZnO:Al film deposited on glass substrate is calculated to be 3.34 eV. The electrical characterization of Zn/ZnO:Al/p-Si/Al heterojunction structure is made by current–voltage (I–V) and capacitance–voltage (C–V) measurements. From these measurements, the heterojunction structure shows a rectifying behavior under a dark condition. The ideality factor and barrier height of Zn/n-ZnO:Al/p-Si/Al structure are calculated as 3.23 and 0.68 eV. The heterojunction structure have diode characteristic with rectification ratio at 64.4 at +2.0 V in the dark. The results suggest that Zn/ZnO:Al/p-Si/Al heterojunction diode can be successfully used in many optoelectronic applications.     

Synthesis and characterization of indenofluorene‐based copolymers containing 2,5‐bis(2‐thienyl)‐N‐arylpyrrole for bulk heterojunction solar cells and polymer light‐emitting diodes

Two novel alternating π‐conjugated copolymers, poly[2,8‐(6,6′,12,12′‐tetraoctyl‐6,12‐dihydroindeno‐[1,2b]fluorene‐ alt‐5(1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole) ( P1 ) and poly[2,8‐(6,6′,12,12′‐tetraoctyl‐6,12‐dihydroindeno‐[1,2b]fluorene‐ alt‐5(1‐(p‐octylphenyl)‐2,5‐di(2‐thienyl)pyrrole) ( P2 ), were synthesized via the Suzuki coupling method and their optoelectronic properties were investigated. The resulting polymers P1 and P2 were completely soluble in various common organic solvents and their weight‐average molecular weights (M_w) were 5.66 × 10⁴ (polydispersity: 1.97) and 2.13× 10⁴ (polydispersity: 1.54), respectively. Bulk heterojunction (BHJ) solar cells were fabricated in ITO/PEDOT:PSS/polymer:PC₇₀BM(1:5)/TiO_x/Al configurations. The BHJ solar cell with P1 :PC₇₀BM (1:5) has a power conversion efficiency (PCE) of 1.12% (J_sc= 3.39 mA/cm², V_oc= 0.67 V, FF = 49.31%), measured using AM 1.5 G solar simulator at 100 mW/cm² light illumination. We fabricated polymer light‐emitting diodes (PLEDs) in ITO/PEDOT:PSS/emitting polymer:polyethylene glycol (PEG)/Ba/Al configurations. The electroluminescence (EL) maxima of the fabricated PLEDs varied from 526 nm to 556 nm depending on the ratio of the polymer to PEG. The turn‐on voltages of the PLEDs were in the range of 3–8 V depending on the ratio of the polymer to PEG, and the maximum brightness and luminance efficiency were 2103 cd/m² and 0.37 cd/A at 12 V, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3169–3177, 2010     

Controlling the electrical characteristics of Au/n‐Si structure with and without (biphenyl‐CoPc) and (OHSubs‐ZnPc) interfacial layers at room temperature

In order to interpret well whether or not the organic or polymer interfacial layer is effective on performance of the conventional Au/n‐Si (metal semiconductor [MS]) type Schottky barrier diodes (SBDs), in respect to ideality factor (n ), leakage current, rectifying rate (RR ), series and shunt resistances (R_s , R_sh ) and surface states (N_ss ) at room temperature, both Au/biphenyl‐CoPc/n‐Si (MPS₁) and Au/OHSubs‐ZnPc/n‐Si (MPS₂) type SBDs were fabricated. The electrical characteristics of these devices have been investigated and compared by using forward and reverse bias current–voltage (I–V ) characteristics in the voltage range of (?4 V)–(4 V) for with and without (biphenyl‐CoPc) and (OHSubs‐ZnPc) interfacial layers at room temperature. The main electrical parameters of these diodes such as reverse saturation current (I₀ ), ideality factor (n ), zero‐bias barrier height (Φ_B0 ), RR , R_s and R_sh were found as 1.14 × 10^?5 A, 5.8, 0.6 eV, 362, 44 Ω and 15.9 kΩ for reference sample (MS), 7.05 × 10^?10 A, 3.8, 0.84 eV, 2360, 115 Ω and 270 kΩ for MPS1 and 2.16 × 10^?7 A, 4.8, 0.7 eV, 3903, 62 Ω and 242 kΩ for MPS₂, respectively. It is clear that all of these parameters considerably change by using an organic interfacial layer. The energy density distribution profile of N_ss was found for each sample by taking into account the voltage dependence of effective barrier height (Φ_e ) and ideality factor, and they were compared. Experimental results confirmed that the use of biphenyl‐CoPc and OHSubs‐ZnPc interfacial layer has led to an important increase in the performance of the conventional of MS type SBD. Copyright © 2015 John Wiley & Sons, Ltd.     

Enhancing dielectric and mechanical behaviors of hybrid polymer nanocomposites based on polystyrene,polyaniline and carbon nanotubes coated with polyaniline

The dielectric and mechanical properties of hybrid polymer nanocomposites of polystyrene/polyaniline/carbon nanotubes coated with polyaniline(PCNTs) have been investigated using impedance analyzer and extensometer. The blends of PS/PANI formed the heterogeneous phase separated morphology in which PCNTs are dispersed uniformly. The incorporation of a small amount of PCNTs into the blend of PS/PANI has remarkably increased the dielectric properties. Similarly, the AC conductivity of PS/PANI is also increased five orders of magnitude from 1.6 × 10~(-10) to 2.0 × 10~(-5) S·cm~(-1) in the hybrid nanocomposites. Such behavior of hybrid nanocomposites is owing to the interfacial polarization occurring due to the presence of multicomponent domains with varying conductivity character of the phases from insulative PS to poor conductor PANI to highly conductive CNTs. Meanwhile, the tensile modulus and tensile strength are also enhanced significantly up to 55% and 160%, respectively, without much loss of ductility for three phase hybrid nanocomposites as compared to the neat PS. Thereby, the hybrid nanocomposites of PS/PANI/_P CNTs become stiffer, stronger and tougher as compared to the neat systems.     

Preparation and characterization of solution processable phthalocyanine‐containing polymers via a combination of RAFT polymerization and post‐polymerization modification techniques

In this work, a benzenedinitrile functionalized monomer, 2‐methyl‐acrylic acid 6‐(3,4‐dicyano‐phenoxy)‐hexyl ester, was successfully polymerized via the reversible addition‐fragmentation chain transfer method. The polymerization behavior conveyed the characteristics of “living”/controlled radical polymerization: the first‐order kinetics, linear increase of number‐average molecular weight with monomer conversion, narrow molecular weight distribution, and successful chain‐extension experiment. The soluble Zn(II) phthalocyanine (Pc)‐containing (ZnPc) polymers were achieved by post‐polymerization modification of the obtained polymers. The Zn(II) phthalocyanine‐functionalized polymer was characterized by FTIR, UV–vis, fluorescence, atomic absorption spectroscopy, and thermogravimetric analysis. The potential application of above ZnPc‐functionalized polymer as electron donor material in bulk heterojunction organic solar cell was studied. The device with ITO/PEDOT:PSS/ZnPc‐Polymer/PC₆₁BM/LiF/Al structure provided a power conversion efficiency of 0.014%, fill factor of 0.24, open circuit voltage (V_oc) of 0.21 V, and short‐circuit current (J_sc) of 0.28 mA/cm². © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 691–698     

Synthesis and properties of new orange red light‐emitting hyperbranched and linear polymers derived from 3,5‐dicyano‐2,4,6‐tristyrylpyridine

Two new orange red light‐emitting hyperbranched and linear polymers, poly(pyridine phenylene)s P1 and P2, were prepared by the Heck coupling reaction. In particular, an A₂ + B₃ approach was developed to synthesize conjugated hyperbranched polymer P2 via one‐pot polycondensation. The polymers were characterized by NMR, Fourier transform infrared, ultraviolet–visible, and elemental analysis. They showed excellent solubility in common solvents such as tetrahydrofuran, CH₂Cl₂, CHCl₃, and N,N‐dimethylformamide and had high molecular weights (up to 6.1 × 10⁵ and 5.8 × 10⁵). Cyclic voltammetry studies revealed that P2 had a low‐lying lowest unoccupied molecular orbital energy level of ?3.22 eV and a highest occupied molecular orbital energy level of ?5.43 eV. The thin film of P2 emitted strong orange‐red photoluminescence at 595 nm. A double‐layer light‐emitting diode fabricated with the configuration of indium tin oxide/P2/tris(8‐hydroxy‐quinoline)aluminum/Al emitted orange‐red light at 599 nm, with a brightness of 662 cd/m² at 7 V and a turn‐on voltage of 4.0 V; its external quantum efficiency was calculated to be 0.19% at 130.61 mA/cm². This indicated that this new electroluminescent polymer (P2) based on 3,5‐dicyano‐2,4,6‐tristyrylpyridine could possibly be used as an orange‐red emitter in polymer light‐emitting displays. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 493–504, 2005     

Electrochemical Oxidation of Methionine Mediated by a Fullerene‐C60 Modified Gold Electrode

The usefulness of a C₆₀‐fullerene modified gold (Au) electrode in mediating the oxidation of methionine in the presence of potassium ions electrolyte has been demonstrated. During cyclic voltammetry, an oxidation peak of methionine appearing at +1.0 V vs. Ag/AgCl was observed. The oxidation current of methionine is enhanced by about 2 times using a C₆₀ modified gold electrode. The current enhancement is significantly dependent on pH, temperature and C₆₀ dosage. Calibration plot reveals linearity of up to 0.1 mM with a current sensitivity of close to 50 mA L mol^?1 and detection limit of 8.2×10^?6 M. The variation of scan rate study shows that the system undergoes diffusion‐controlled process. Diffusion coefficient and rate constant of methionine were determined using hydrodynamic method (rotating disk electrode) with values of 1.11×10^?5 cm² s^?1 and 0.0026 cm s^?1 respectively for unmodified electrode while the values of diffusion coefficient and rate constant of methionine using C₆₀ modified Au electrode are 5.7×10^?6 cm² s^?1 and 0.0021 cm s^?1 respectively.     

Preparation,morphology and electrical conductivity of polyaniline/polyoxyalkylene–montmorillonite exfoliated nanocomposites

Polyaniline (PANI)/organoclay exfoliated nanocomposites containing different organoclay contents (14–50 wt%) were prepared. PANI emeraldine base (EB) and oligomeric PANI (o‐PANI) were intercalated into montmorillonite (MMT) modified by four types of polyoxyalkylene diamine or triamine (organoclay) using N‐methyl pyrolidinone (NMP) as a solvent in the presence of 0.1 M HCl. o‐PANI and EB have been synthesized by oxidative polymerization of aniline using ammonium peroxydisulfate (APS). Infrared absorption spectra (IR) confirm the electrostatic interaction between negatively charged surface of MMT and positively charged sites in PANI. X‐ray diffraction (XRD) studies disclosed that the d₀₀₁ spacing between interlamellar surface disappeared at low content of the organoclay. The morphology of these materials was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrical conductivities of the PANI‐organoclay and o‐PANI‐organoclay nanocomposites were 1.5 × 10^?3–2 × 10^?4 and 9.5 × 10^?7–1.8 × 10^?9 S/cm, respectively depending on the ratio of PANI. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of polyaniline/Au composite nanotubes and their high performance in the detection of NADH

Polyaniline (PANI)/Au composite nanotubes were synthesized and developed as an electrode material for a nicotinamide adenine dinucleotide (NADH) sensor. A MnO₂ self-degradable template method was used to prepare the tube-like PANI nanomaterial. By introducing PANI nanotubes into Au colloid, Au nanoparticles (NPs) were successfully decorated onto the surface of PANI nanotubes through electrostatic effects. The morphology, composition, and optical properties of the resulting products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) absorption spectra, and thermogravimetric analysis (TGA). In addition, the obtained PANI/Au composites were used as catalysts for the electrochemical oxidation of NADH. Cyclic voltammogram (CV) experiments indicated that PANI/Au-modified glassy carbon electrode showed a higher electrocatalytic activity towards the oxidation of NADH in a neutral environment. Differential pulse voltammogram (DPV) results illustrated that the fabricated NADH sensor had excellent anti-interference ability and displayed a wide linear range from 4?×?10^?4 to 8?×?10^?3 M with a detection limit of 0.5?×?10^?7 M.     

Fe3O4@SiO2‐PANI‐Au Nanocomposite Prepared for Electrochemical Determination of Quercetin in Food Samples and Biological Fluids

A new electrochemical sensor based on Fe₃O₄@SiO₂‐PANI‐Au nanocomposite was fabricated for modification of glassy carbon electrode (Fe₃O₄@SiO₂‐PANI‐Au GCE). The Fe₃O₄@SiO₂‐PANI‐Au nanocomposite was characterized by TEM, FESEM‐EDS‐Mapping, XRD, and TGA methods. The Fe₃O₄@SiO₂‐PANI‐Au GC electrode exhibited an acceptable sensitivity, fast electrochemical response, and good selectivity for determination of quercetin. Under optimal conditions, the linear range for quercetin concentrations using this sensor was 1.0×10^?8 to 1.5×10^?5 mol L^?1, and the limit of detection was 3.8×10^?9 mol L^?1. The results illustrated that the offered sensor could be a possible alternative for the measurement of quercetin in food samples and biological fluids.     

Sensitive amperometric pyridoxine sensor based on self‐assembled Prussian blue nanoparticle‐modified poly(o‐phenylenediamine)/glassy carbon electrode

Prussian blue nanoparticles (PBNPs) were prepared by a self‐assembly process on a glassy carbon electrode (GCE) modified with poly(o‐phenylenediamine) (PoPD) film. The stepwise fabrication process of PBNP‐modified PoPD/GCE was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of the modified electrode. The PBNPs/PoPD/GCE showed electrocatalytic activity towards the oxidation of pyridoxine (PN) and was used as an amperometric sensor. The modified electrode exhibited a linear response for PN oxidation over the concentration range 3–38.5 μM with a detection limit of ca 6.10 × 10^?7 M (S/N = 3) and sensitivity of 2.79936 × 10³ mA M^?1 cm^?2 using an amperometric method. The mechanism and kinetics of the catalytic oxidation reaction of PN were investigated using cyclic voltammetry and chronoamperometry. The values of α, k_cat and D were estimated as 0.36, 1.089 × 10² M^?1 s^?1 and 8.9 × 10^?5 cm² s^?1, respectively. This sensor also exhibited good anti‐interference and selectivity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characterization of a wide-bandgap polymer based on perfluorinated and alkylthiolated benzodithiophene with a deep highest occupied molecular orbital level for organic photovoltaics

A perfluorinated and alkylthiolated benzodithiophene (BDT)-ttTPD-based donor polymer (P2FS-ttTPD) was synthesized via a Stille polymerization, and found to have a number average molecular weight (M_n) of 13,000 g/mol (Đ = 2.3). P2FS-ttTPD has a wide bandgap (1.96 eV) and a deep highest occupied molecular orbital (HOMO) level (−5.70 eV). The perfluorination and alkylthiolation of the polymer backbone lower the polymer's HOMO level significantly. The hole and electron mobilities of P2FS-ttTPD were determined to be 1.12 × 10⁻⁴ and 9.38 × 10⁻⁷ cm²/V s, respectively. Polymer solar cell devices prepared with a P2FS-ttTPD:IT-4F (1:1) blend as the active layer were found to exhibit power conversion efficiencies of 4.15%, a short-circuit current density (J_SC) of 10.29 mA/cm², an open-circuit voltage (V_OC) of 0.97 V, and a fill factor of 41.6%. The (1:1) blend devices were found to exhibit high V_OC and low E_loss values.     

Electrocatalysis of Horseradish Peroxidase Immobilized on Cobalt Nanoparticles Modified ITO Electrode

Abstract

It is the first time that Horseradish peroxidase (HRP) was successively immobilized on the magnetic cobalt nanoparticles modified ITO (indium tin oxide) electrode. Morphologies of electrode surface were featured by the field emission‐scanning electron microscope (FSEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the modified process of electrode. Direct electrochemistry and electrocatalysis of HRP immobilized on nano‐Co/ITO were investigated. The biosensor exhibited high sensitivity, good stability, and excellent electrocatalytic activity to the reduction of H₂O₂. Under the optimized experimental conditions, a calibration curve over 2.0×10^?9～2.0×10^?8 mol l^?1 and 2.0×10^?7～2.0×10^?6 mol l^?1, with a limit of detection of 1.9×10^?9 mol l^?1 was obtained. The apparent Michaelis‐Menten constant (K _M ^app ) for HRP/nano‐Co/ITO electrode was calculated to be 0.79 mmol l^?1, indicating a higher affinity of HRP attached on the modified electrode.     

Electrochemical Characterization of Myoglobin‐Polylysine Films at a Temperature Range of 6–80 °C

This work demonstrated for the first time that myoglobin cross‐linked in polylysine films is electrochemically active at 6 °C. At 6 °C, these protein films exhibited reversible reduction/oxidation peaks which are characteristic of Fe^III/Fe^II redox couple. The estimated current function densities (J=1.6×10^?4 C/V cm²), surface concentrations (Γ_T=0.10 nmol/cm²) and standard electron transfer constant (k_s=13.86 s^?1) at 6 °C for the data taken at a scan rate of 0.1 V/s were similar to those which were obtained at 10, 15 and 23 °C. Basically, this study shows a possible electrocatalytic application of these myoglobin/polylysine films, for example in low temperature sensing applications.     

Photovoltaic performance enhancement using fluorene‐based copolymers containing pyrene units

A set of novel conjugated polyfluorene co‐ polymers, poly[(9,9′‐didecylfluorene‐2,7‐diyl)‐co‐(4,7′‐di‐2‐thienyl‐ 2′,1′,3′‐benzothiadiazole‐5,5‐diyl)‐co‐(pyrene‐1,6‐diyl)], are synthesized via Pd(II)‐mediated polymerization from 2,7‐bis(4′,4′,5′, 5′‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9′‐di‐n‐decylfluorene, 4, 7‐di(2‐bromothien‐5‐yl)‐2,1,3‐benzothiadiazole, and 1,6‐dibromopyrene with a variety of monomer molar ratios. The field‐effect carrier mobilities and optical, electrochemical, and photovoltaic properties of the copolymers are systematically investigated. The hole mobilities of the copolymers are found to be in the range 7.0 × 10^?5 ? 8.0 × 10^?4 cm² V^?1 s^?1 and the on/off ratios were 8 × 10³ ? 7 × 10⁴. Conventional polymer solar cells (PSCs) with the configuration ITO/PEDOT:PSS/polymer:PC₇₁BM/LiF/Al are fabricated. Under optimized conditions, the polymers display power conversion efficiencies (PCEs) for the PSCs in the range 1.99–3.37% under AM 1.5 illumination (100 mW cm^?2). Among the four copolymers, P2, containing a 2.5 mol % pyrene component incorporated into poly[9,9′‐didecylfluorene‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PFDTBT) displays a PCE of 3.37% with a short circuit current of 9.15 mA cm^?2, an open circuit voltage of 0.86 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW cm^?2). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and properties of the conjugated polymers with indenoindene and benzimidazole units for organic photovoltaics

A new electron deficient unit, dimethyl‐2H‐benzimidazole (MBI), and dihydroindeno[2,1‐a]indene (ININE) moiety as electron‐rich unit were coupled to synthesize the conjugated polymers containing electron donor–acceptor pair for organic photovoltaics. ININE, MBI, and thiophene (or bithiophene) units were incorporated using Stille and Suzuki polymerization to generate poly(2,7‐(5,5,10,10‐tetrakis(2‐ethylhexyl)‐5,10‐dihydro‐ indeno[2,1‐a]indene)‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2,2‐dimethyl‐2H‐benzimidazole)) (PININEDTMBIs) (or PININEBBTMBIs). In MBI, the sulfur at 2‐position of 2,1,3‐benzothiadiazole (BT) unit was replaced with dialkyl‐substituted carbon, whereas keeping the 1,2‐quinoid form, to improve the solubility of the polymers. The field‐effect hole mobility of PININEBBTMBI was 3.2 × 10^?4 cm²/Vs which was improved as compared to that of PININEDTMBI (2.7 × 10^?5 cm²/Vs) caused by the introduction of bithiophene units. In case of the most efficient polymer, PININEBBTMBI, the device with the configuration of indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS)/polymer:PC₇₁BM(1:4 w/w)/Al, annealed at 100 °C for 10 min demonstrated a open circuit voltage of 0.78 V, a short‐circuit current density of 6.66 mA/cm², and a fill factor of 0.41, leading to the power conversion efficiency of 2.11%, under white‐light illumination (AM 1.5 G, 100 mW/cm²). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Polyoxometalate derived p-n heterojunction for optimized reaction interface and improved HER

MoS₂ is a typical electrocatalyst for hydrogen evolution reaction (HER), but the HER activity is spoilt by intensive adsorption towards H*, which requires further improvement. For n-type MoS₂, the construction of p-n heterojunction with p-type MoO₃ can reverse this situation, because inner electronic field in p-n heterojunction can facilitate H* desorption. Based on this hypothesis, p-n heterojunction is built between MoS₂ and MoO₃ with polyoxometalate compound as precursor. The obtained MoO₃/MoS₂ exhibits excellent HER activity, which only requires 68 mV to obtain 10 mA/cm². With MoO₃/MoS₂ as cathode material and Zn slice as anode, Zn-H⁺ battery is assembled. Its open circuit voltage achieves 1.11 V with short circuit current 151.4 mA/cm². The peak power density of this Zn-H⁺ battery reaches 47.6 mW/cm². When discharge at 10 mA/cm², the specific capacity and energy density reach 728 mAh/g and 759 Wh/kg. In this process, H₂ production rate of Zn-H⁺ battery achieves 364 μmol/h with Faradic efficiency 97.8%. It realizes H₂ production and electricity generation simultaneously.     

Micro-determination of gold using N-cyanoacylacetaldehyde hydrazone

A reliable and rapid procedure for the flotation and micro-determination of Au(III) using N-cyanoacylacetaldehyde hydrazone (CyAH) is proposed. CyAH forms a blue 1:1 complex (K_f=4.1×10⁵ mol^?1l^?1) with Au(III) at pH 3–7. The maximum absorbance is obtained after 7 min; instantaneously by adding 3.3×10^?3 mol/l H₃PO₄ or by heating to 55°C. Beer's law is obeyed for 1–30 ppm of Au(III) with a molar absorptivity of 0.3×10⁴ l mol^?1 cm^?1 at 550 nm.