High temperature enthalpy and heat capacity of GaN

The heat capacity and the heat content of gallium nitride were measured by calvet calorimetry (320-570 K) and by drop calorimetry (670-1270 K), respectively. The temperature dependence of the heat capacity in the form C_pm=49.552+5.440×10⁻³T−2.190×10⁶T⁻²+2.460×10⁸T⁻³ was derived by the least squares method. Furthermore, thermodynamic functions calculated on the basis of our experimental results and literature data on the molar entropy and the heat of formation of GaN are given.     

Spectral and chemical monitoring of cyclo-addition reaction of CO2 with poly(MMA-co-GMA) copolymers

This paper deals with the monitoring cyclo-addition of CO₂ to methyl methacrylate（MMA）-glycidyl methacrylate （GMA） copolymers using spectral（¹H-NMR and FTIR） and chemical（elemental analysis and titration） methods.Thus, poly（MMA-co-GMA）,was first prepared via solution polymerization.The copolymer was then treated with CO₂ gas flow in the presence of cetyltrimethyl ammoniumbromide as a catalyst.In terms of the carbonation reaction time,the terpolymer poly（MMA-co-GMA-co-2-oxo-l,3-dioxolane-4-yl-methyl methacrylate） was prepared in various yield of CO₂ fixation （>90%）.The peak intensity changes in the ¹H-NMR and FTIR spectra provided excellent demonstrative techniques to monitor the carbonation reaction progression.In a comparative analytical viewpoint,the NMR and elemental analysis were recognized to be the most accurate ways to follow the cyclo-addition reaction progression.However,titration was recognized to be the most preferred method,because it is a very inexpensive,facile and available method with a reasonable costaccuracy balance.     

Lindqvist型钼酸盐修饰的碳纳米管二阶非线性光学性质的理论研究

利用密度泛函理论(DFT)方法研究了[Mo₆O₁₉]^2-修饰的单壁碳纳米管的非线性光学(NLO)性质. 结果表明, [Mo₆O₁₉]^2-修饰的单壁碳纳米管作为特殊的有机-无机杂化体系, 具有显著的二阶非线性光学响应. 通过调整[Mo₆O₁₉]^2-与纳米管之间的角度, 体系的稳定性显示出规律性的变化趋势, 且二阶NLO响应发生了变化. 对静场二阶极化率(β_vec)有主要贡献的电子跃迁特征表明, [Mo₆O₁₉]^2-与碳纳米管之间角度的改变影响了分子内的给受体特征. 当角度达到30°时, 化合物显示出最大的β_vec值, 此时杂多阴离子簇为电子受体, 而碳纳米管为电子给体. 此外, 在碳纳米管的端位连接电子给体(如氨基)可有效地增大β_vec值.     

A selective voltammetric method for uric acid detection at Nafion(R)-coated carbon paste electrodes

A square-wave voltammetric method together with Nafion®-coated carbon paste electrodes were used for the selective determination of uric acid in the presence of a high concentration of ascorbic acid. Since the oxidation potential of uric acid is about 200 mV more positive than that of ascorbic acid at the Nafion®-coated carbon paste electrode, the selectivity can be greatly improved simply by applying an electrolysis potential of +0.4 V vs. Ag/AgCl where only ascorbic acid is oxidised. The acceptable tolerance of ascorbic acid concentration for the determination of uric acid is as high as 1.5 mM. With 30 s of electrolysis time, a linear calibration curve is obtained over the 0–50 μM range in 0.05 M citrate buffer solution, pH 4.0, with slope (μA/μM) and correlation coefficient of 0.34 and 0.9984, respectively. The detection limit (3σ) is 0.25 μM. The practical analytical utility is illustrated by selective measurements of uric acid in human urine without any preliminary treatment.     

二氧化碳与环氧化物的调节共聚合反应速率

在二氧化碳和环氧化物共聚时加入特定的调节剂，生成有规定的分子量和端基官能度的产物．这种调节聚合的本质是调节剂所含活泼氢与活性中心之间的链转移反应．根据建议的历程，提出了调节共聚速率方程，计算结果与实验一致．     

氮化铁催化剂的制备及其苯胺催化加氢性能

用α－Ｆｅ２Ｏ３与氨气程序升温还原方法制备出不同温度氮气的氮化铁系列催化剂。通过ＸＲＤ测试对氮化过程中的晶相转变进行了分析。在中压反应装置上考察了氮化铁系列催化剂上苯胺加氢活性以及反应条件对苯胺加氢反应活性的影响。结果表明，在７００℃氮化制香的氮化铁催化剂显示有较高的苯胺加氢活性，在氢压为３．０ＭＰａ，温度为２５０℃，ｎ（Ｈ２）／ｎ（ｏｉｌ）＝１８，液体空速（ＷＨＳＶ）为０．３ｈ＾－１时，该催化剂     

不同分子筛载体对CO加氢产物分布的影响

研究了几种小孔分子筛ＺＳＭ－５，ＨＹ，ＮａＹ及β担载ＺｒＯ２对Ｃ加氢反应的催化作用，并就产物的分布情况与担载ＺｒＯ２的硅铝中孔分子筛进行了对比研究。其中中孔分子筛分别用季铵盐和一级胺为模板剂，在水热条件和常温常压下合成；并用ＢＥＴ，ＸＲＤ，ＳＥＭ等手段表征了它们的孔道和骨架结构。另外，考察了碱金属Ｋ＾２＋，Ｎａ＾２＋对催化剂催化性能的影响。     

以笼烯为接头的球棒式碳纳米管的电子结构

按照Hamada构造一维至三维球棒式碳纳米管,构造了一些球棒式的笼烯接头的具有C₃/C₅旋转轴的单层碳纳米管.在Hückel近似下,利用群论约化定理计算了它们的π电子结构,并对其稳定性进行了探讨.     

石墨烯的制备、功能化及在化学中的应用

石墨烯是最近发现的一种具有二维平面结构的碳纳米材料, 它的特殊单原子层结构使其具有许多独特的物理化学性质. 有关石墨烯的基础和应用研究已成为当前的前沿和热点课题之一. 本文仅就目前石墨烯的制备方法、功能化方法以及在化学领域中的应用作一综述, 重点阐述石墨烯应用于化学修饰电极、化学电源、催化剂和药物载体以及气体传感器等方面的研究进展, 并对石墨烯在相关领域的应用前景作了展望.     

Structure and protonation of some indolizine derivatives studied by ab initio MO calculations

Some gauge invariant atomic orbitals-coupled-perturbed Hartree-Fock (GIAO-CPHF) calculations were performed for seven indolizine derivatives and their monoprotonated forms. Chemical shift, molecular geometry, and charge distribution data are reported for each molecule. The calculations support the results of nuclear magnetic resonance (NMR) spectroscopy measurements showing that protonation occurs preferentially at N1. The good agreement between the calculated and observed ¹³C and ¹⁵N chemical shifts show that such calculations can be used for chemical shift assignment purposes. Cation structures and probable sites for electrophilic reaction or second protonation are also discussed.