Large-scale, rapid synthesis and application in surface-enhanced Raman spectroscopy of sub-micrometer polyhedral gold nanocrystals

Macromolecule-protected sub-micrometer polyhedral gold nanocrystals have been facilely prepared by heating an aqueous solution containing poly (N-vinyl-2-pyrrolidone) (PVP) and HAuCl4 without adding other reducing agents. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), ultraviolet-visible-near-infrared spectroscopy (UV-vis-NIR), and x-ray diffraction (XRD) were employed to characterize the obtained polyhedral gold nanocrystals. It is found that the 10:1 molar ratio of PVP to gold is a key factor for obtaining quasi-monodisperse polyhedral gold nanocrystals. Furthermore, the application of polyhedral gold nanocrystals in surface-enhanced Raman scattering (SERS) was investigated by using 4-aminothiophenol (4-ATP) as a probe molecule. The results indicated that the sub-micrometer polyhedral gold nanocrystals modified on the ITO substrate exhibited higher SERS activity compared to the traditional gold nanoparticle modified film. The enhancement factor (EF) on polyhedral gold nanocrystals was about six times larger than that obtained on aggregated gold nanoparticles (similar to 25 nm).

Synthesis and characterization of rigid-rod sulfonated polyimides bearing sulfobenzoyl side groups as proton exchange membranes

A novel wholly aromatic diamine, 2,2 '-bis(3-sulfobenzoyl)benzidine (2,2 '-BSBB), was successfully prepared by the reaction of 2,2 '-dibenzoylbenzidine (2,2 '-DBB) with fuming sulfuric acid. Copolymerization of 1,4,5,8-naphathlenetetracarboxylic dianhydride with 2,2 '-BSBB and 2,2 '-DBB generated a series of rigid-rod sulfonated polyimides. The synthesized copolymers with the -SO3H group on the side chain of polymers possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. The copolymer membranes exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendent groups. They displayed clear anisotropic membrane swelling in water with negligibly small dimensional changes in the plane direction of the membrane. The proton conductivities of copolymer membranes increased with increasing IEC and temperature, reaching value above 1.25 x 10(-1) S/cm at 20 degrees C, which is higher than that of Nafion (R) 117 at the same measurement condition. They displayed reasonably high proton conductivity due to the higher acidity of benzoyl sulfonic acid group, the larger interchain spacing, which is available for water to occupy, taking their lower water uptake (WU) into account. Consequently, these materials proved to be promising as proton exchange membrane.

Preparation and evaluation of a proton exchange membrane based on oxidation and water stable sulfonated polyimides

A series of novel oxidation and water stable sulfonated polyimides (SPIs) were synthesized from 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), and wholly aromatic diamine 2,2'-bis(3-sulfobenzoyl) benzidine (2,2'-BSBB) for proton exchange membrane fuel cells. These polyimides could be cast into flexible and tough membranes from m-cresol solutions. The copolymer membranes exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendant groups. Moreover, all BTDA-based SPI membranes exhibited much better water stability than those based on the conventional 1,4,5,8-naphthalenecarboxylic dianhydride. The improved water stability of BTDA-based polyimides was attributed to its unique binaphthalimide structure. The SPI membranes with ion exchange capacity (IEC) of 1.36-1.90 mequiv g(-1) had proton conductivity in the range of 0.41 x 10(-1) to 1. 12 x 10(-1) S cm(-1) at 20 degrees C. The membrane with IEC value of 1.90 mequiv g(-1) displayed reasonably higher proton conductivity than Nafion((R)) 117 (0.9 x 10(-1) S cm(-1)) under the same test condition and the high conductivity of 0.184 S cm(-1) was obtained at 80 degrees C. Microscopic analyses revealed that well-dispersed hydrophilic domains contribute to better proton conducting properties. These results showed that the synthesized materials might have the potential to be applied as the proton exchange membranes for PEMFCs.

Electrical characterization of copper phthalocyanine thin-film transistors with fluoride gate insulator

Different fluoride materials are used as gate dielectrics to fabricate copper phthalocyanine (CuPc) thin film. transistors (OTFTs). The fabricated devices exhibit good electrical characteristics and the mobility is found to be dependent on the gate voltage from 10(-3) to 10(-1) cm(2) V(-1)s(-1). The observed noticeable electron injection at the drain electrode is of great significance in achieving ambipolar OTFTs. The same method for formation of organic semiconductors and gate dielectric films greatly simplifies the fabrication process. This provides a convenient way to produce high-performance OTFTs on a large scale and should be useful for integration in organic displays.

Extraction kinetics of cerium(IV) from sulfuric acid medium by the primary amine N1923 using a constant interfacial area cell with laminar flow

BACKGROUND: Thermodynamic studies on Ce(IV) extraction with primary amine N1923 demonstrate that primary amine N1923 is an excellent extractant for separation of Ce(IV) from Re(III). In order to clarify the mechanism of extraction and to optimize the parameters in practical extraction systems used in the rare earth industry, the extraction kinetics was investigated using a constant interfacial area cell with laminar flow in the present work.RESULTS: The data indicate that the rate constant (k(ao).) becomes constant when stirring speed exceeds 250 rpm. The apparent forward extraction rate is calculated to be 10(-1.70). The activation energy (E.) was calculated to be 20.5 kJ/mol from the slope of log kao against 1000/T. The minimum bulk concentration of the extractant necessary to saturate the interface (C-min) is lower than 10(-5) mol L-1.CONCLUSION: Studies of interfacial tension and the effects of stirring rate and specific interfacial area on the extraction rate show that the extraction rate is kinetically controlled, and a mass transfer model has been proposed. The rate equation has been obtained as: -d[Ce(IV)]/dt = 10(-1.70)[Ce(IV)] [(RNH3)(2)SO4](1.376). The rate-controlling step has been evaluated from analysis of the experimental results.

Preparation and electrical-magnetic properties of polyaniline doped with ionic ferrocenesulfonic acid

Conducting polyamline with electrical conductivity of 2.34 x 10(-1) S cm(-1) was obtained using ferrocenesulfonic acid as dopant. After the ferrocenesulfonic acid was oxidized with FeCl3, though the electrical conductivity of the doped polyaniline decreased by 1-2 orders of magnitude, the magnetic susceptibility (chi) increased with the increase of the oxidation degree of ferrocenesulfonic acid. EPR spectra showed not only a signal with a g value of around 2, but also a so-called half-field signal with a g value of about 4 even at room temperature. Coexistence of ferromagnetic intrachain interactions and antiferromagnetic interchain interactions in the materials has been suggested.

Sulfonated poly(arylene-co-naphthalimide)s synthesized by copolymerization of primarily sulfonated monomer and fluorinated naphthalimide dichlorides as novel polymers for proton exchange membranes

A novel sulfonated aromatic dichloride monomer was successfully prepared by the reaction of 2, 5-dichlorobenzophenone with fuming sulfuric acid. Copolymerization of this monomer in the form of sodium salt (1) with N-(4-chloro-2-trifluoromethylphenyl)-5-chloro-1,8-naphthalimide (2) or bis(N-(4-chloro-2-trifluoromethylphenyl)1,4,5,8-naphthalimide (3) generated two series of novel poly(arylene-co-naphthalimide) s I-x and II-x where x represents the content of the sulfonated monomer. The synthesized copolymers with the -SO3H group in the side chains possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. The copolymers exhibited excellent stability toward water and oxidation due to the introduction of the hydrophobic CF3 groups. The sulfonated copolyimides that incorporated with 1,8-naphthalimide (I-x) exhibited better hydrolytic and oxidative stabilities than those with 1,4,5,8-naphthalimide. Copolymer I-50 membrane endured for more than 83 h in Fenton's reagent at room temperature. The mechanical properties of I-50 membrane kept almost unchanged after immersing membrane in boiling water for 196 h. The proton conductivities of copolymer films increased with increasing IEC and temperature, reaching values above 6.8 x 10(-1) S/cm at 80 degrees C.

The direct synthesis of wholly aromatic poly(p-phenylene)s bearing sulfobenzoyl side groups as proton exchange membranes

Sulfonated poly(p-phenylene)s (SPPs) containing sulfonic acid groups in their side chains had been directly synthesized by Ni(0) catalytic coupling of sodium 3-(2,5-dichlorobenzoyl)benzenesulfonate and 2,5-dichlorobenzophenone. The synthesized copolymers possessed high molecular weights revealed by their high viscosity, and the formation of tough and flexible membranes by casting from DMAc solution. The copolymers exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendent groups. Transmission electron microscopic (TEM) analysis revealed that these side-chain type SPP membranes have a microphase-separated structure composed of hydrophilic side-chain domains and hydrophobic polyphenylene main chain domains. The proton conductivities of copolymer membranes increased with the increase of IEC and temperature, reaching values above 3.4 x 10(-1) S/cm at 120 degrees C, which are almost 2-3 times higher than that of Nafion 117 at the same measurement conditions. Consequently, these materials proved to be promising as proton exchange membranes.

Spectroelectrochemical and voltammetric studies of L-DOPA

The electrooxidation of L-dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L-dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E-0 = 228 mV, the apparent electron-transfer number of the electrooxidation reaction an = 0.376 (R = 0.99, SD = 0.26), the standard electrochemical rate constant k(0) (3.93 +/- 0.12) x 10(-)4 cm s(-1) (SD = 1.02 x 10(-2)), and the formation equilibrium constant of the following chemical reaction k(c)= (5.38+/-0.34) x 10(-1) s(-1) (SD = 1.02 x 10(-2)) were also obtained.

Confining conducting polyaniline in a stable inorganic network

Water soluble conducting polyaniline with electrical conductivity of 10(-1)-10(-2) S/cm was prepared employing dopant induced water solubility technology. The water resistance of the conducting film was significantly improved employing,sol-gel hybrids method, especially when the conductive polyaniline loading was below 30 wt%. The reason for the improvement is that the conducting polyaniline chains are confined in a stable inorganic network.

New technique for capillary electrophoresis directly coupled with end-column electrochemiluminescence detection

capillary electrophoresis (CE) is characterized. A 300 mum diameter Pt working electrode was used to directly couple with a 75 mum inner diameter separation capillary without an electric field decoupler. The hydrodynamic cyclic voltammogram (CV) of Ru(bpy)(3)(2+) showed that electrophoretic current did not affect the ECL reaction. The presence of high-voltage (HV) field only resulted in the shift of the ECL detection potential. The distance of capillary to electrode was an important parameter for optimizing detection performance as it determined the characteristics of mass transport toward the electrode and the actual concentration of Ru(bpy)(3)(2+) in the detection region. The optimum distance of capillary to electrode was decided by the inner diameter of the capillary, too. For a 75 mum capillary, the working electrode should be placed away from the capillary outlet at a distance within the range of 20-260 mum. The effects of pH value of ECL solution and molecular structure of analytes on peak height and theoretical plate numbers were discussed. Using the 75 mum capillary, under the optimum conditions, the method provided a linear range for tripropylamine (TPA) between 1 x 10(-10) and 1 X 10(-5) mol/L with correlation coefficient of 0.998. The detection limit (signal-to-noise ratio S/N = 3) was 5.0 x 10(-11) mol/L. The relative standard deviation in peak height for eight consecutive injections was 5.6%. By this new technique lidocaine spiked in a urine sample was determined. The method exhibited the linear range for lidocaine from 5.0 x 10(-8) to 1.0 X 10(-5) mol/L with correlation efficient of 0.998. The limit of detection (S/N = 3) was 2.0 x 10(-1) mol/L.

Design, synthesis and characterization of novel nitrogen-and sulfur-containing polymers with well-defined conjugated length

A series of novel nitrogen- and sulfur-containing conjugated polymers with well-defined conjugation length have been synthesized via an acid-induced self-polycondensation of functional monomers with methylsulfinyl groups. Synthesized polymers exhibit good solubility in common solvents, such as CHCl3, THF, DMF, DMSO, and NMP. With increased numbers of aminophenyl groups, these polymers have shown similar electrical properties to polyaniline (PAn), and these are demonstrated by UV-vis spectroscopy and cyclic voltammetry (CV) measurements on the polymers. The conductivity of preliminarily protonic-doped poly[phenylene sulfide-alt-tetrakis(aniline)] (PPSTEA) is up to 10(-1) S cm(-1).

Anodic voltammetric behavior of medecamycin at a glassy carbon electrode

The anodic voltammetric behavior of medecamycin (MD) in the presence of various electrolytes was studied by linearsweep voltammetry, differential-pulse voltammetry and cyclic voltammetry at a glassy carbon electrode. In phosphate buffer solutions (pH = 9.4), MD is oxidized irreversibly. The peak potential is at about +0.75 V (vs.Ag/AgCl). The height of the peak is linearly increased with the concentration of MD over the range of 5 x 10(-5) similar to 1 x 10(-1) g/L. The method has been used for the direct determination of MD in tablets. The relative standard deviation (n = 10) is 1.8%. The recoveries of MD in urine samples are in the range of 95% similar to 115%.

时间分辨激光荧光光谱技术在免疫分析中的应用

本研究以时间分辨激发荧光光谱分析技术为基础 ,进行稀土离子标记的激光激发的时间分辨荧光免疫分析 (TRFIA)研究。实验以自行合成的二乙三胺五醋酸酐 (DTPAA)为双功能螯合剂。用 Eu3+标记兔抗人 (RAH) Ig G抗体 ,依据解离增强原理 (DEL FIA) ,研究了 Eu3+ -β萘甲酰三氟丙酮 (β- NTA)的荧光分辨体系 ,测定了荧光光谱和荧光寿命 ,建立了铕离子分析检出方法 ,其工作曲线范围为 1× 10 - 7～ 1× 10 - 1 1g· m L- 1 ,检测限为 1× 10 - 1 3g· m L- 1 ,相对标准偏差为 6 .4%。结合 TRFIA方法学研究 ,进行了人血清丙型肝炎病毒抗体 (Anti- HCV)检测。并同酶联免疫法 (EL ISA)对比。取得 TRFIA法阳性检测率明显高于EL ISA法的结果。