CdSe量子点的线性和非线性光学特性

主要从实验和理论两个方面,探讨了强受限尺寸区域内不同尺寸对CdSe量子点线性和非线性光学性质的影响.用吸收光谱研究了量子点尺寸与吸收峰之间的关系,用皮秒Z扫描技术研究了共振和非共振情况下(激发光波长分别为532和1064nm),尺寸与三阶非线性极化率之间的关系.基于电子能量状态理论和局域场增强理论对量子点进行分析,得到了CdSe不同尺寸的三阶非线性效应,研究了尺寸对量子点非线性光学性质的影响.结果表明,由激发态粒子数布局改变和纳米颗粒增大引起的非线性共振增强效应相当,二者共同作用使得三阶极化率增强20倍左右,且用532nm的共振频率激发4.3nm CdSe量子点时,χ⁽³⁾具有最大值2.0×10^-11esu. 关键词： CdSe量子点 三阶非线性 Z扫描')" href="#">Z扫描 量子限域效应     

Nile Red Synchronous Scan Fluorescence Spectroscopy to Follow Matrix Modification in Sol–Gel Derived Media and its Effect on the Peroxidase Activity of cytochrome <Emphasis Type="Italic">c</Emphasis>

The highly solvatochromic dye Nile red is used in conjunction with synchronous scan fluorescence spectroscopy to elucidate changes in the internal environment of cytochrome c, upon incorporation into differently modified sol–gel derived media. Nile red was first studied in a variety of solvents in order to quantify changes in polarity. Matrix modifications involved the addition of several silanes, intended to interact with any unreacted hydroxyl entities left from the matrix forming reaction, while polymers were used to help reduce shrinkage and modify the internal pore environment. Slight unfolding of the protein was observed on incorporation into the sol–gel derived media. During the aging process further changes were monitored by using difference synchronous scan fluorescence spectra and complementary measurements of catalytic activity, expressed as the initial velocity. Combining Nile red synchronous scan fluorescence with cytochrome c activity data lead to a method to elucidate effects linked to protein conformation and those related to the sol–gel derived host. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Electrochemical Determination of Tartrazine in Foods by Voltammetry with a Screen-printed Carbon/Chitosan-MnO2 Microcomposite Electrode

This paper presents a new application for a screen-printed carbon electrode (SPCE) modified with chitosan (Cs) and manganese oxide (II). This new electrode (Cs-Mn_OX/SPCE) was applied in the detection of tartrazine (TZ) by linear scan voltammetry (LSV). The anodic peak current for TZ increased by nearly 500 % compared with Cs/SPCE and unmodified SPCE. The surface of the electrode was characterized by cyclic voltammetry. The detection limit was 0.06 μmol/L. The relative standard deviations (RSDs) were between 1.0 and 6.0 % (n=15). The accuracy of the new method was evaluated with real samples spiked with known quantities of TZ.     

Optical characterization of thermally evaporated thin CdO films

Cadmium Oxide films have been prepared by vacuum evaporation method on a glass substrate at room temperature. Detailed structural, optical, and electrical properties of the films are presented at different annealing temperatures. The crystal structure of the samples was studied by X‐ ray diffraction. The spectral absorption coefficient of the CdO film at the fundamental absorption region (450‐650nm) was determined using the spectral data of transmittance. The direct and indirect band gap energies were determined and found to be 2.33 eV and 1.95 eV respectively. The third order optical nonlinearities χ(3) of CdO films has been measured used the z‐can technique. The real and imaginary parts of χ(3) have been measured at 514 nm and found to be 1.7x10^‐3 esu and 3.0x10^‐3 esu, respectively. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)