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.     

Selectivity in the photodimerization of 6-alkylcoumarins

Coumarin and 6-alkylcoumarins (alkyl = C(1) to C(16)) were photodimerized in homogeneous solvents differing in polarity and in aqueous micellar solutions. The four possible photodimers, syn head-to-head (hh), anti head-to-head, syn head-to-tail (ht), and anti head-to-tail, were identified through a combination of X-ray analysis and NMR spectroscopy. In 6-methylcoumarin the concentration-corrected dimerization (quantum) yield increases with decreasing concentration of the educt; anti-hh was formed exclusively in nonpolar solvents and upon triplet sensitization and was the main product under all conditions except for ionic micellar systems, which direct to preferred syn-hh dimerization. Long alkyl substituents, however, lead to anti-hh in polar solvents and in micelles, too. Predominating ht dimer formation was observed for nonsubstituted coumarin in polar solvents only. Thus, syn/anti and hh/ht selectivity can be steered by varying the 6-alkyl substituent. Syn-hh photodimers of 6-methylcoumarin can be photochemically split into the monomers; they partly proved thermally unstable against acids, bases, methanol, and on SiO(2) surfaces.     

天青Ⅰ为电子媒介体金纳米颗粒修饰葡萄糖生物传感器

用纳米金溶胶与聚乙烯醇缩丁醛(PVB)构成复合固酶基质,采用溶胶凝胶法固定葡萄糖氧化酶(GOx)于铂金电极表面,并在葡萄糖溶液中加入天青Ⅰ作为电子媒介体,制成了新型葡萄糖生物传感器。实验证明,葡萄糖氧化酶吸附在纳米金颗粒表面上稳定且保持其生物活性;而电子媒介体的存在,显著提高了传感器的响应灵敏度。该传感器对葡萄糖响应的线性范围为2.5×10-5～7.5×10-3mol/L;检出限为8.5×10-6mol/L(S/N=3)。该生物传感器用于人体血清中的葡萄糖测定,结果令人满意。     

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.