毛细管电泳柱上络合分离、间接紫外检测重金属离子

采用弱络合剂乙醇酸,柱上络合,间接紫外检测毛细管区带电泳(CZE)技术对重金属离子Ba2+、Cr3+、Cd2+、Pb2+及可能存在的干扰离子进行了分离研究。通过对背景电解质种类和浓度、缓冲液pH、有机添加剂等的优化,确定了最佳分离体系为含12 mmol/L络合剂乙醇酸的10 mmol/L吡啶溶液作为背景电解质(pH 4.0)。在电压15 kV,压差进样68.95 kPa.s,260 nm间接紫外检测条件下,采用50 cm(45.5 cm)×50μm(I.D.)石英毛细管,重复性实验(n=9):迁移时间RSD≤1.37%,峰高RSD≤1.70%,峰面积RSD≤3.55%;Pb2+、Ba2+和Cd3+的检出限(S/N=3)为0.2 mg/L,Cr3+的检出限为0.08 mg/L;在检出限至10 mg/L范围内,各离子的浓度与峰面积线性相关系数好于0.998。该方法并应用于实际样品的分析。     

用于紫外光谱水质分析的Boosting-偏最小二乘法

为提高水质参数总有机碳(TOC)的紫外吸收光谱分析的预测精度,提出一种基于Boosting理论的迭代式回归建模算法,并根据统计学习理论提出一种新的迭代停止判据,可有效防止过拟合,显著提高模型预测精度。为评估所提算法的性能,分别采用本算法和3种常用的光谱分析方法,即偏最小二乘、主成分回归和人工神经网络,对自行研制的紫外光谱水质分析仪实测的一组数据进行了建模和预测。计算结果表明:相对于其他3种方法,本算法具有生成的模型预测精度高的显著优势。     

铌酸锂多晶粉体的水热合成及表征

铌酸锂(LiNbO₃)晶体由于本身具有的优良性能在许多领域中都获得了广泛的应用.以LiOH·H₂O和Nb₂O₅为原料采用水热合成法成功地合成了铌酸锂多晶粉体,并采用FTIR谱、XRD谱和SEM对产物进行了表征.结果表明,采用水热合成法能够得到结晶完整的四方柱形LiNbO₃多晶粉体.同时考察了反应温度、晶化时间和Li源对水热合成产物的影响.     

UV spectra and excitation delocalization in DNA: influence of the spectral width.

The singlet excited states of the model DNA duplex (dA)10.(dT)10 are studied. Calculations are performed in the exciton theory framework. Molecular dynamics calculations provide the duplex geometry. The dipolar coupling is determined using atomic transition charges. The monomer transition energies are simulated by Gaussian functions resembling the absorption bands of nucleosides in aqueous solutions. Most of the excited states are found to be delocalized over at least two bases and result from the mixing of different monomer states. Their properties are only weakly affected by conformational changes of the double helix. On average, the highest oscillator strength is carried by the upper eigenstates. The duplex absorption spectra are shifted a few nanometers to higher energies with respect to the spectra of noninteracting monomers. The states with larger spatial extent are located close to the maximum of the absorption spectrum.     

TiO2-SiO2复合氧化物结构和红外光谱的量子化学研究

 构建了TiO2-SiO2复合氧化物晶胞结构,采用HyperChem量子化学程序中的从头计算方法以3-21G*基组对其进行了全优化计算,并进行了振动分析,预测了TiO2-SiO2复合氧化物各化学键的红外特征吸收频率. 采用IR谱对TiO2-SiO2复合氧化物进行了表征,通过理论计算与实验数据相结合的方法确定了TiO2-SiO2复合氧化物的分子结构,对其平衡几何构型、IR谱、电子结构和Lewis酸性进行了讨论.     

2-(2,5-二羟基苯基)-5-甲基-2,5-二氢吡咯并[3,4]富勒烯的合成和电子光谱的理论研究

利用丙氨酸和2,5-二羟基苯甲醛所形成的亚胺叶立德与C₆₀发生1,3-偶极环加成反应, 合成并分离、纯化制备了一种新的C₆₀吡咯烷衍生物: 2-(2-5-二羟基苯基)-5-甲基-2,5-二氢吡咯并[3,4]富勒烯. 通过¹H NMR, FT-IR, UV-vis和元素分析确定了其结构, 研究了体系的电化学和荧光性质. 采用密度泛函的方法, 在B3LYP/6-31G水平上对分子的几何构型进行了优化, 得到稳定的几何构型; 运用INDO/S方法计算了化合物的电子光谱, 计算结果434.2 nm与实验值432.0 nm基本一致.     

手性不对称Salen Ni配合物的模板法合成及表征

本文采用过渡金属镍(Ni)作为金属模板合成了2个未见报道的手性不对称Salen Ni配合物，该法具有反应步骤少、纯化处理简单、产率高的显著优点。用¹H NMR、FTIR、UV-Vis、CD光谱及元素分析对配合物进行了详细的表征，证明该模板合成法的可靠性。此外，对该法合成的手性不对称Salen Ni配合物的红外光谱、电子吸收光谱、圆二色光谱的性质做了进一步研究。     

Theoretical Studies on Electronic Spectra and Second-order Nonlinear Optical Properties of Barbituric Acid Derivatives Substituted with Schiff Base

Barbituric acid (BA) is a very important kind of compound in biological chemistry and medicine. It can be applied in abirritative medicine and antioxidants.1 It is an important sort of raw material for organic synthe-sis.2 It predicts the important reactive mechanism for organic synthesis.3 Some investigations for NLO prop-erties of a series of BA derivatives have been reported by Feng and coworkers in the view of theory.4,5 The Schiff base has extensive application in the fields of organi…     

Quantum-chemical study of C<Subscript>n</Subscript>F2<Subscript><Emphasis Type="Italic">n</Emphasis>+2</Subscript> conformers. Structure and IR spectra

Quantum-chemical calculations of the geometrical structure and vibrational spectra of C_nF_2n+2 oligomers (n = 5–8) in the chain and branched conformations are reported. The lengthening of the chain of C_nF_2n+2 does not substantially affect the geometrical parameters of the oligomers. In all cases under study, the most optimal structure of the molecule is a zigzag chain with bond lengths R(C-C) = 1.53 –1.54 and R(C-F) = 1.36 –1.34 ; the chain is rolled into a helix, which makes an angle of 17° with the plane. The IR spectra are sensitive to the structural deficiency of oligomers C_nF_2n+2 associated with the lateral trifluoromethyl groups formed in the chain; the spectra can be used for revealing defects of this type in the structure of polytetrafluoroethylene (PTFE). The possibility of defects associated with the lateral CF₃ groups in the structure of PTFE and its low-temperature modifications is explained based on the calculated total energies of C_nF2 _n+2.Original Russian Text Copyright © 2004 by L. N. Ignatieva, A. Yu. Beloliptsev, S. G. Kozlova, and V. M. BuznikTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 632–643, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

低对称性硫代烃基四氮杂卟啉的合成、表征及电化学性质研究

合成了硫代烃基四氮杂卟啉2,3,7,8,12,13-六(甲硫基)-17,18-一(二噻英)四氮杂卟啉[H₂Pz(dtn)(mt)₆]及其过渡金属配合物MPz(dtn)(mt)₆,由元素分析、质谱、¹HNMR、UV-Vis和IR光谱对其组成和结构进行了表征,通过循环伏安测试结果讨论了H₂Pz(dtn)(mt)₆的电化学性质,证明H₂Pz(dtn)(mt)₆的还原过程为单电子连续传输过程,属于CE机理.研究了H₂Pz(dtn)(mt)₆对正极材料MnO₂在锂离子电池中的修饰作用.结果表明,H₂Pz(dtn)(mt)₆对改善锂离子电池的初始充放电容量和循环次数都有明显的增加.