n型砷化镓微区光电化学腐蚀过程

在n-GaAs电解液界面,用聚焦He-Ne激光照射, 使n-GaAs表面发生微区光电化学腐蚀, 用计算机控制步进马达, 使试样在X-Y二维方向扫描移动, 能在晶片上得到刻蚀点直径2 μm的刻蚀图案. 研究了激光相对光强, KOH、H_2SO_4、KCl等刻蚀剡的浓度, 光腐蚀的时间, 电极电位等因素对腐蚀点的直径和深度的影响, 通过实验数据找出腐蚀过程的规律, 并用光电化学原理进行解释.     

Photochemical Synthesis and Spectral-Optical Characteristics of ZnO/Cu and ZnO/Ag/Cu Nanoheterostructures

The photoreduction of Cu²⁺ at the surface of ZnO nanoparticles and ZnO/Ag nanostructures was investigated. The spectral characteristics of the obtained ZnO/Cu and ZnO/Ag/Cu composites were studied in relation to the reaction conditions. It was shown that the ZnO/Ag nanoparticles have higher photocatalytic activity in the reduction of Cu²⁺ ions than the individual ZnO particles.     

微波辅助合成发光可调ZnS∶Cu纳米晶

以巯基丙酸(MPA)为稳定剂, 利用微波辐射加热方法制备了水溶性的Cu掺杂的ZnS纳米晶. 通过改变微波条件, 可以在460～572 nm之间实现对ZnS∶Cu纳米晶发射峰位的连续调控. 通过XRD、 UV-Vis、荧光及荧光衰减对ZnS∶Cu纳米晶的结构和发光性质进行了详细探索, 并利用时间分辨荧光光谱对其发光机理进行了初步研究.     

The Conductance- and Capacitance-Frequency Characteristics of the Rectifying Junctions Formed by Sublimation of Organic Pyronine-B on p-Type Silicon

The rectifying junction characteristics of the organic compound pyronine-B film on a p-type Si substrate has been studied. The pyronine-B has been sublimed on the top of p-Si surface. The barrier height and ideality factor values of 0.79±0.04 and 1.13±0.06 eV for this structure have been obtained from the forward bias current-voltage (I-V) characteristics. From the low capacitance-frequency (C-f) characteristics as well as conductance-frequency (G-f) characteristics, the energy distribution of the interface states and their relaxation time have been determined in the energy range of (0.53−E_v)-(0.79−E_v) eV taking into account the forward bias I-V data. The interface state density N_ss ranges from 4.93×10¹⁰ cm⁻² eV⁻¹ in (0.79−E_v) eV to 3.67×10¹³ cm⁻² eV⁻¹ in (0.53−E_v) eV. Furthermore, the relaxation ranges from 3.80×10⁻³ s in (0.53−E_v) eV to 4.21×10⁻⁴ s in (0.79−E_v) eV. It has been seen that the interface state density has an exponential rise with bias from the midgap towards the top of the valence band. The relaxation time shows a slow exponential rise with bias from the top of the valence band towards the midgap.     

High-performance liquid chromatographic determination of Levetiracetam in human plasma: comparison of different sample clean-up procedures

An accurate and precise high-performance liquid chromatographic method using diode array detection for the determination of the novel antiepileptic, Levetiracetam, has been developed. Three clean-up procedures for the analysis of Levetiracetam in human plasma were implemented and evaluated, namely solid-phase extraction, deproteinization by addition of organic solvents and formation of insoluble salts. Adenosine was used as the internal standard for all three sample pretreatment procedures. Among the several cartridges used for solid-phase extraction, the hydrophilic-lypophilic balance (Oasis) HLB) phase provides the best extraction yield of Levetiracetam, together with high precision. With the two other clean-up procedures involving plasma deproteinization by addition of methanol or zinc sulphate, lower sensitivity and precision of the assays were obtained. However, they are cheaper and faster when compared with the solid-phase extraction procedure.     

锑化镓的光助微刻蚀及其表面氧化物的研究

用电化学和光电化学方法研究锑化镓表面的腐蚀以及锑化镓表面氧化膜的生成和溶解，锑化镓电极在一定电势下生成的氧化膜，用俄歇能谱证明，其主要成分为难溶的氧化锑，此氧化膜的存在抑制了锑化镓的进一步腐蚀，同时亦使锑化镓的半导体光电化学性能大为减弱，通过激光微刻蚀及电子显微镜的观察，在刻蚀剂中添加酒石酸，柠檬酸和氢氟酸等试剂，可使刻蚀形得改善，实验研究了锑化镓的平带电势的测定。     

Luminescent Sensing with Quantum Dots

Summary This review highlights recent advances in the use of quantum dots (QD’s) as luminescent sensors. The bulk of the study concentrates on systems that possess organic ligands bound to the surface of QD’s. These ligands vary from low molecular weight thiols to larger molecules such as maltose binding protein. All have one thing in common: when a target analyte binds to the ligand/receptor, a perturbation of the system occurs, that registers itself as a change in the luminescence intensity of the QD. Two main mechanisms are prevalent in controlling the luminescent intensity in such systems. The first is Photoinduced Electron Transfer (PET) and the second energy transfer. This review looks at current sensors that operate by using these mechanisms. Two component systems are also investigated where a quencher is first added to a solution of the QD, followed by addition of the target analyte that interacts with the quencher to influence the luminescence intensity.     

Light-emitting diode-induced fluorescence detection of native proteins in capillary electrophoresis

A continuous-wave 280 nm light-emitting diode (LED) was used as the excitation source for native fluorescence detection of proteins in CE. The operating current and temperature of the LED were optimized in order to achieve high luminescence power. It was found that a forward current of 30 mA and a temperature of approximately 5 degrees C gave the best S/N. By using a set of two ball lenses to focus light from the LED, we achieved a spot of approximately 200 mum with a power of 0.1-0.2 mW on the detection window. Fluorescence was collected with a ball lens at 90 degrees angle through a bandpass filter onto a photomultiplier tube. In CZE an LOD of 20 nM for conalbumin was reached. In capillary gel electrophoresis all eight proteins from a commercial standard kit were detected with high S/N. For a 10 microg/mL total protein mixture, S/N was better than 3 for all proteins in solution. Further improvement in LOD should be possible on utilization of an LED with higher luminescence power.     

Application of an integrated microchip system with capillary array electrophoresis to optimization of enzymatic reactions

In this work, a combination of complementary metal-oxide semiconductor (CMOS) microchip system with capillary array electrophoresis (CAE) is demonstrated as a system for optimizing conditions for enzymatic reaction. Dimethylacridinone (DDAO)-phosphate substrate and alkaline phosphatase conjugate were selected for the enzymatic reaction, which was applicable to the enzyme-linked immunosorbent assay (ELISA) technique. Laser-induced fluorometry with a miniature semiconductor laser was used to detect the enzymatic products. The speed of the enzymatic reaction between the DDAO-phosphate and the alkaline phosphatase conjugate was investigated as a function of reaction time. The microchip-CAE detection system could determine the pH condition and the concentration of enzyme that are suitable for rapid and low-cost analysis. This result shows the feasibility of using the microchip-CAE system for application to miniaturized screening systems.     

A novel oligothiophene derivative as a hole‐transport with emitting material for OLED

A novel oligothiophene derivative containing the triphenylamine moiety with high glass transition temperature (T_g; 135 °C), 5,5′‐{bis[4‐di(4‐thiophenyl)amino]phenyl}‐2,2′‐bithiophene (TTPA‐dimer) was synthesized by the dimerization of tris[4‐(2‐thienyl)phenyl]amine (TTPA) with a palladium catalysis. Some types of electroluminescent (EL) devices that use the amorphous material for a hole‐ and an electron‐transporting with an emitting layer were fabricated. These devices emitted a bright green‐yellowish light (λ_emi; around 510 nm) with a small full width at half maximum (FWHM) rather than that of Alq₃. The single layer EL device showed a maximum luminance of 221 cd/m² at 8 V (0.06 lm/W at 100 cd/m²). On the other hand, the double layer (TTPA‐dimer/Alq₃) EL device that used Alq₃ as the electron transport material was increased up to 10830 cd/m² at 12 V (0.89 lm/W at 300 cd/m²) and with a lower turn‐on voltage (3.2 V at 0.1 cd/m²) than other types of EL devices. Copyright © 2003 John Wiley & Sons, Ltd.