微电极的稳态可逆极化曲线

微电极具备一些常规尺寸电极所没有的优点,例如:(1)半径很小的微电极在不对溶液进行搅拌的情况下就具备与高速旋转的圆盘电极类似的性质,即在电位扫描速率较低时,可获得稳态伏安曲线.这一特点使微电极能方便地用于稳态测量.与暂态测量相比,稳态测量精度较高(实验曲线几乎不受充电电流干扰),实验方法较简单,实验结果的数学处理较容易.(2)微电极体系的时间常数(溶液电阻和双层电容的乘积)正比于电极面积的平方根.若在     

Theoretical studies on the reaction mechanism of CH2CH radical with HNCO

The reaction mechanism of CH₂CH radical with HNCO has been investigated systematically by density functional theory (DFT). The geometries and harmonic frequencies of reactants, intermediates, transition states, and products have been optimized with the B3LYP at different levels. At the same time, AIM is performed to calculate the charge density of some bonding critical points and the charges of some atoms. Nine feasible reaction pathways have been investigated. The results indicated that the main pathway is CH₂CH + HNCO → IMA1 → TSA1 → CH₂CH₂ + NCO, which is characterized by hydrogen atom transferring. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

微环电极理论

近几年来,微电极的应用得到迅速发展,但由于混合边界条件的存在,微电极稳态和暂态问题的数学处理极为复杂.过去,微电极上不可逆和准可逆过程主要采用近似方法研究.自文献利用贝塞尔级数处理微盘电极稳态行为以后,两种可用来精确处理微     

Silver nanoparticles embedded temperature-sensitive nanofibrous membrane as a smart free-standing SERS substrate

Silver nanoparticles (AgNPs) embedded temperature-sensitive nanofibrous membrane as SERS substrate is capable of real-time monitoring the reduction of 4-nitrothiophenol into 4-aminothiophenol catalyzed by its embedded AgNPs, and the detected intermediate indicates that the reaction proceeds via a condensation route.     

Preparation and catalytic properties of chitosan bound Schiff base copper complexes

Chitosan, a natural polymer, bound Schiff base copper complexes CT‐She‐Cu, CT‐o‐Bel‐Cu, CT‐m‐Bel‐Cu were prepared and characterize by inductively coupled plasma (ICP), FT‐IR and X‐ray photoelectron spectroscopy (XPS). Their catalytic activity in the oxidation of cyclohexene with molecular oxygen was studied. All the complexes have catalytic activity and the main oxidation products are 2‐cyclohexene‐ol, 2‐cyclohexene‐one and cyclohexene hydroperoxide, which were measured by gas chromatography/mass spectroscopy (GC/MS) and GC/IR. CT‐m‐Bel‐Cu was selected to study the influence of reaction temperature, amount of catalyst and additives such as acid and base on the oxidation of cyclohexene systematically. Copyright © 2004 John Wiley & Sons, Ltd.     

Preparation, characterization and application of pyrene-loaded methoxy poly(ethylene glycol)–poly(lactic acid) copolymer nanoparticles

Pyrene-loaded biodegradable polymer nanoparticles were prepared by incorporating pyrene into the polymer nanoparticles formulated from amphiphilic diblock copolymer, methoxy poly(ethylene glycol)–poly(lactic acid) (MePEG–PLA). Their morphological structure and physical properties were characterized by nuclear magnetic resonance (NMR), dynamic light scattering, fluorescence spectroscopy, transmission electronic microscopy and zeta potential measurements. Further, MePEG–PLA nanoparticles containing pyrene as fluorescent marker were administered intranasally to rats, and the distribution of nanoparticles in the nasal mucosa and the olfactory bulb were visualized by fluorescence microscopy. NMR results confirmed that MePEG–PLA copolymer can form nanoparticles in water, and hydrophilic PEG chains were located on the surface of the nanoparticles. The particle size, zeta potential and pyrene loading efficiency of MePEG–PLA nanoparticles were dependent on the PLA block content in the copolymer. Following nasal administration, the absorption of nanoparticles across the epithelium was rapid, with fluorescence observed in the olfactory bulb at 5 min, and a higher level of fluorescence persisted in the olfactory mucosa than that in the respiratory mucosa. These results show that pyrene could serve as a useful fluorescence probe for incorporation into polymer nanoparticles to study tissue distribution and MePEG–PLA nanoparticles might have a great potential as carriers of hydrophobic drugs.     

Voltammetric and amperometric determination of ascorbic acid at a chemically modified carbon fibre microelectrode

A carbon fibre microelectrode was modified by electrodeposition of a thin copper-heptacyanonitrosylferrate (CuHNF) film on its surface. The film showed the ability to catalyse electrochemical oxidation of ascorbic acid. The catalytic reaction was limited either by diffusion, or by the electrochemical reaction of the catalyst. A linear, cyclic voltammetric response for ascorbic acid was obtained between 5.0 x 10(-5) and 6.0 x 10(-3)M. By amperometric measurements the linear range could be extended to 8.0 x 10(-6)-2.0 x 10(-3)M. The modified electrode showed good stability and reproducibility.     

Anhydrous Sol-Gel Synthesis of Titania-Doped Siloxane Polymer for Integrated Optics

Sol-gel synthesis of organic-inorganic hybrid materials for planar waveguides and devices has received growing interest due to its low-cost processing and good suitability for doping. Titania is an important optical dopant, but homogeneous incorporation of titania in silica is difficult to be achieved by the conventional sol-gel process (aqueous system) because of the significant difference between the hydrolysis rates of the precursors. In this paper, we report an anhydrous sol-gel process for synthesising titania-doped siloxane polymers. The process consists of a hydrolysis of 3-methacryloxypropyltrimethoxysilane (MPS) with boric acid under anhydrous conditions, and a condensation with dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPhDMS) and titanium ethoxide (TET). Optical characterisations for the produced titania-doped polymer were performed, and results showed that TET doping is useful for reducing the OH concentration of the synthesised polymer and is also effective for improving the optical quality of spin coatings. DMDMS and DPhDMS are favourable in reducing the birefringence and in increasing the thermostability of the material, and the methacryl groups of MPS are UV-polymerizable, which is useful for low cost fabrication of waveguides by photolithographic process. The results of ellipsometry scanning measurements show that titania is homogeneously incorporated in the hybrid matrix, suggesting that the anhydrous sol-gel process is useful for preparation of UV-sensitive titania-doped siloxane polymers for optical applications.     

Theoretical study of molecular interaction between tirapazamine enzymatic catalysis metabolites and water

The weakly hydrogen‐bonded complexes, between tirapazamine enzymatic catalysis metabolites and water, have been investigated by density functional theory (DFT), using the B3LYP hybrid functional. The geometries of these complexes have been fully optimized at the B3LYP/6‐31G(d) and B3LYP/6‐311+G(d) levels. The stabilization energies and charge changes of some atoms have been calculated and analyzed. The results indicate that the catalysis metabolites and water can form stable hydrogen‐bonded complexes. Nine complexes are identified. It is important and necessary to add zero‐point vibrational energy (ZPVE) and basis set superposition error (BSSE) corrections for calculating stabilization energy. The results also reveal an important relationship between the relative stabilities of hydrogen‐bonded complexes and the final products of tirapazamine medication. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007