形态结构和光电特性对纳米TiO2光催化性能的影响

采用sol-gel法制备了系列纳米TiO2光催化剂,运用X射线衍射、BET比表面测定、紫外漫反射吸收光谱和表面光电压谱等手段对催化剂进行表征,并以乙烯作为光催化反应的指标反应分子,研究了TiO2纳米晶的性质对于光催化活性的影响.随着焙烧温度的升高,TiO2的晶粒逐渐增大,比表面积下降,晶相由锐钛矿向金红石转变,其吸收带边与光伏响应阈值向长波方向移动,氧化－还原能力降低,降解乙烯的转化率迅速下降.     

流动分析法同时测定铬（Ⅵ）及铬（Ⅲ）过程中铈（Ⅳ）氧化剂的影响

以Ｃｅ（Ⅳ）为氧化剂，采用流动分析在线氧化技术，实现了对Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）的同时在线分析，发现Ｃｅ（Ⅳ）氧化剂在测定过程中产生负干扰，在而Ｃｒ（Ⅲ）存在时会使Ｃｒ（Ⅵ）的测定结果偏高，本文提出了一个校正模型，通过数学方法消除上述干扰，所建立的分析方法对Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）分析的平均相对误差不大于６．５％。     

Recent progress in two-photon small molecule fluorescent probes for enzymes

This review aims to provide a summary of the progress in TP small molecule fluorescent probes for enzymes in recent years and displays the main fluorescent mechanisms that have been applied to design probes.     

掺杂ZrO＿2的Pt／Al＿2O＿3表面氧性质及一氧化碳氧化性能研究

用ＴＰＤ－ＭＳ、ＴＰＳＲ－ＭＳ及ＣＯ氧化活性测定等方法研究了Ｐｔ／Ａｌ２Ｏ３和掺杂超细ＺｒＯ２的样品的表面氧脱出－恢复性能、ＣＯ表面氧化性能及催化氧化性能．结果表明，在Ｐｔ／Ａｌ２Ｏ３中掺杂ＺｒＯ２后，样品表面上的氧物种脱出和氧化恢复性能明显提高，脱氧量也明显增大；并发现在ＣＯ－ＴＰＳＲ过程中程脱物ＣＯ２的脱附量大小及峰顶温度次序与对ＣＯ的催化氧化活性也有一致的关系     

Preparation and properties of polyurethane networks based on α,ω-difunctional poly(hexafluoropropylene oxide)

Poly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end linking via urethane groups. The prepolymers were characterized by NMR spectroscopy and GPC. The networks were characterized by determination of the number of network chains from the shear modulus, and were snown to contain both trifunctional crosslinks and difunctional links. The properties of the networks were investigated by a range of techniques. Compared with fully-fluorinated networks formed via triazine cross-links, investigated previously, the urethane-linked networks were more readily prepared but were poorer elastomers, were less thermally stable, and were less resistant to swelling by common polar solvents. © 1995 John Wiley & Sons, Inc.     

Separation and determination of ephedrine alkaloids and tetramethylpyrazine in Ephedra sinica Stapf by gas chromatography-mass spectrometry

A simple, sensitive, and reliable method using gas chromatography (GC)-mass spectrometry (MS) is developed for the simultaneous determination of ephedrine alkaloids and 2,3,5,6-tetramethylpyrazine (TMP) in Ephedra sinica Stapf. The sample is extracted with ethyl ether and submitted to GC-MS for identification and quantitation without derivatization. The column used for GC is an HP-5 (30.0 m x 250 microm x 0.25 microm, 5% phenyl methyl siloxane), and the carrier gas is helium. The detection limits for ephedrine, pseudoephedrine, and TMP are 0.4 ng 0.7 ng, and 0.02 ng (signal-to-noise ratio of 3), respectively. The reproducibility of the total procedure is proved to be acceptable (RSD < 2%), and the recoveries are above 93%.     

对MDTA中测样品热容量的准恒温法的评述

对用调制差热分析（ＭＤＴＡ）准恒温法测样品热容量的情形进行了讨论。通过结合最基本的热传导定律和ＭＤＴＡ模型，指出了目前国际上测量样品热容量的准恒温法只能得到在所测温度范围内的物质热容量平均值，调制温度的幅度越大或调制频率越高，所得到的热容量数据越平滑。在所测温度范围内样品热容量基本不变时，用ＭＤＴＡ准恒温法较好；但当样品热容量在所测温度范围内有明显变化时，用传统差热分析法（ＤＴＡ）更好一些。     

Detection of VX contamination in soil through solid-phase microextraction sampling and gas chromatography/mass spectrometry of the VX degradation product bis(diisopropylaminoethyl)disulfide

A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) sampling and analysis method was developed for bis(diisopropylaminoethyl)disulfide (a degradation product of the nerve agent VX) in soil. A 30-min sampling time with a polydimethylsiloxane-coated fiber and high temperature alkaline hydrolysis allowed detection with 1.0 microg of VX spiked per g of agricultural soil. The method was successfully used in the field with portable GC-MS instrumentation. This method is relatively rapid (less than 1 h), avoids the use of complex preparation steps, and enhances analyst safety through limited use of solvents and decontamination of the soil before sampling.     

Efficient synthesis of isoflavone analogues via a Suzuki coupling reaction

Analogues of 3-aryl-8-isobutyl-5,6,7-trihydroxy-2-methyl-4H-chromen-4-one were synthesized with high yields via the Suzuki coupling reaction of 3-iodo-8-isobutyl-5,6,7-trimethoxy-2-methyl-4H-chromen-4-one with different aryl boronic acids.     

稀土-沸石-TiO2三元体系光催化材料的性能研究

以钛酸丁酯、稀土硝酸盐、斜发沸石为主要原料,用溶胶-凝胶法制备了稀土-沸石-TiO2三元体系的光催化剂.使用IR,TG-DSC,XRD,SEM等手段对样品进行了表征; 以甲基橙为目标物,太阳光为光源,用光解率对光催化剂性能进行了评价.实验表明,随着沸石负载TiO2量的增加,光催化剂的3 h光解率也逐渐提高; 反应体系的温度越高,光解率越大; 当溶液pH约等于5时,光解率达到最大.