A computational study of the effect of an external electric field on the geometry of selected donor–acceptor complexes

To understand the effect of Au and thiol atoms in octane molecule, a structural and charge density analysis has been carried out by high level ab initio quantum chemical calculations using MP2 and B3PW91 methods with the basis sets 6-311G(d,p) and LANL2DZ. The optimized geometries, specifically, the geometry obtained from both levels reveal the effect of S- and Au-atoms in octane molecule. An introduction of sulfur atom in octane molecule lengthen its backbone C–C bond distances, and further adding of Au-atom at the terminals of octane dithiolate stabilizes these distances. The bond densities of the C–C bonds of octane are 1.6 eÅ⁻³, these values are decreased significantly and the charges are largely depleted, when thiol and Au-atoms added in the octane molecule. The presence of negative Laplacian ²ρ(r) at bond critical points of C–C and C–H bonds, indicate, the charges are concentrated in these bonds, confirm that these bonds exhibit an open shell type interaction. The moderate values of density and the negative Laplacian of S–C bonds confirm the covalent character. The positive ²ρ(r) value of Au–S bonds, characterize, the bonding interaction is a closed shell interaction. The combined observed low value of electron density and the positive Laplacian of Au–S bond comprises, the gold and S interaction is not a covalent interaction, but it is a very weak coordination bond interaction. The small positive value of total energy density in Au–S bond indicates, the charges in these bonds are highly depleted and this is further confirmed by the Laplacian of bond characterization.     

原位衰减全反射表面增强红外光谱实验技术

介绍了原位研究电极,溶液界面反应的技术--衰减全反射表面增强红外光谱实验技术(ATR-SEIRAS)的产生背景和工作原理,重点描述了ATR-SEIRAS实验技术的关键:光谱电化学池的构造和薄膜电极的制备.与IRAS相比,ATR-SEIRAS技术可以更容易消除溶剂的背景吸收,获得较高的表面灵敏度,而且允许物质在电极表面自由扩散.与循环伏安相结合,利用ATR-SEIRAS技术可以实时监测电极,溶液界面问的反应.选择了利用ATR-SEIRAS实验技术原位研究功能表面的构造和性质、分子识别和反应中间体的形成等方面的应用实例,分析了ATR-SEIRAS实验技术的研究方向.     

逆流色谱仪器装置的研究进展

逆流色谱是一种快速、高效、无固定相载体的新型液-液分配色谱技术.综述了高速逆流色谱、双向逆流色谱、正交轴逆流色谱、pH-区带精制逆流色谱及螺线型圆盘柱式逆流色谱仪器装置的研究进展,介绍了高速逆流色谱-质谱联用技术、高速逆流色谱.蒸发光散射联用技术、高速逆流色谱.高效液相色谱联用技术及二维逆流色谱技术的发展状况.     

顺序注射在线稀释微量进样技术及其在自动光度法测定水中亚硝酸盐的应用

以测定环境水样中的亚硝酸盐为例,采用顺序注射技术,提出了一种智能化在线微量进样稀释分析系统(SIA系统).将测定过程中分光光度计输出的模拟电压信号,反馈至顺序注射仪,判断是否需要稀释.当获得的电压信号值小于305 mV(约相当于吸光度值0.8)时,SIA系统进入稀释程序,否则,则进入直接测定程序,两种程序均自动完成.直接测定和稀释测定的线性范围分别为1～50μmol·L-1和50～500μmol·L-1NO2-.分别在NO2-浓度水平为10,200μmol·L-1时作精密度试验,测得相对标准偏差(n=11)依次为0.7%和1.0%.该分析系统特别适合于自动分析过程中被测物质浓度变化较大而需要在线稀释的情况.     

一种新的测定微粒的电化学技术

设计了一种由2个石墨电极短路相连组成工作电极的新的电化学池装置.操作时首先通过外力按压使极少量固体微粒粘附在其中一个石墨电极表面上,然后在溶液存在下将微粒夹紧并固定在2个石墨电极表面之间进行电化学测定.电化学转化过程中生成的可溶性物质被封闭在2个石墨电极表面之间而得到测定.用该技术对钯沉积在氧化铝上而组成的催化剂的电化学行为以及黄铁矿的电化学行为进行了研究.结果表明,其兼具可电解粘合剂碳糊电极和固体微粒伏安法(voltammetry of microparticles)技术的优点而避免了各自的缺点:即不使用粘合剂,从而消除了粘合剂中杂质产生的氧化或还原电流的影响;可测定电化学转化过程中生成的可溶性物质;分辨率好、易于操作.     

Memory effects with the on-column interface for on-line coupled high performance liquid chromatography-gas chromatography: The Y-interface

When using the on-column interface for on-line high performance liquid chromatography (HPLC)-gas chromatography (GC), there is a memory effect typically equivalent to 0.5–3% of the previous transfer. The shape of peaks distorted as a result of incomplete reconcentration of the initial bands enabled mapping of the distribution of the solute material in the uncoated precolumn and deriving the mechanism which causes the memory effect. The relatively slow transfer of HPLC eluent causes liquid being sucked backwards into the narrow interspace between the transfer line and the precolumn wall. Solvent is evaporated into the passing carrier gas and is replaced by more eluent pulled into this zone, resulting in enrichment of solute material. At the end of the transfer, some of this solute material enters the transfer line and remains there up to the subsequent transfer of an HPLC fraction. This problem is avoided by replacing the on-column injector used as interface by a Y-piece in which the eluent flow from HPLC and the carrier gas are joined. The memory effect was reduced to below 0.02%.     

Simultaneous determination of CFC-11, CFC-12 and CFC-113 in seawater samples using a purge and trap gas-chromatographic system

We have optimized the analytical parameters of a homemade instrument for the simultaneous measurement of the chlorofluorocarbons CCl₂F₂ (CFC-12), CCl₃F (CFC-11) and C₂Cl₃F₃ (CFC-113) in seawater. Seawater samples are flame sealed into 60 ml glass ampoules avoiding any contact with the atmosphere and stored in cold, dark condition until analysis. In the laboratory, after cracking the ampoule in an enclosed chamber filled with ultra-pure nitrogen, the seawater sample is transferred to a stripping chamber, where ultra-pure nitrogen is used to purge the dissolved CFCs from the seawater. The extracted gases are then cryogenically trapped, subsequently the trap is isolated and heated and the CFCs are transferred by a carrier gas stream into a precolumn and then are separated on a gaschromatographic packed column. To separate adequately CFC-12 from N₂O, during the early part of the chromatographic run, the gas stream passes through a molecular sieve, which is then isolated and backflushed. The CFCs are detected on an electron capture detector (⁶³Ni ECD). After a careful choice of the experimental conditions, the performances of the system were evaluated. The detection limits for seawater samples are: 0.0081 pmol kg⁻¹ for CFC-12, 0.0073 pmol kg⁻¹ for CFC-11 and 0.0043 pmol kg⁻¹ for CFC-113. The reproducibility of replicate samples lies within 5% for the three CFCs. The system has been successfully employed for CFC measurements in seawater samples collected in the Ross Sea (Antarctica) in the framework of the Italian Antarctic research project.     

Biomimetic fabrication of hydroxyapatite-coated zirconia-magnesia composite and its application in the separation of proteins

In this work, biomimetic technique was proposed for the first time to prepare chromatographic packings (2HAp-ZM) for protein separation. By mimicking the mineralization procedures in vivo, this type of matrix with hydroxyapatite (HAp) coating and zirconia-magnesia (ZM) composite core was fabricated. Systematic characterizations, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and specific surface area analysis, were carried out to investigate the properties of the material. Results showed that the surface of 2HAp-ZM was composed of bead-like, amorphous or nanocrystalline HAp. The specific surface area, total pore volume, and average pore diameter of the resultant material were 25 m²/g, 0.09 cm³/g, and 14 nm, respectively. Furthermore, 2HAp-ZM exhibited good mechanical stability through repeated testing and its application as stationary phases for protein separation was then studied. Five model proteins (bovine serum albumin, trypsin, lysozyme, ribonuclease A, and cytochrome c) were successfully separated on 2HAp-ZM. Finally, the mass recovery of protein and the dynamic loading capacity were studied; the results were calculated to be no less than 93% and 80 μg/mL of blank column volume, respectively.     

单壁碳纳米管的轴向能带工程

单壁碳纳米管具有优异的电子学特性,是制备新一代高性能集成电路的重要材料.碳纳米管芯片之路存在诸多挑战,包括直径和手性的控制生长方法、金属性和半导体性单壁碳纳米管的分离方法、器件加工与集成方法等.这些课题从本质上讲大多属于化学问题,因此碳纳米管芯片研究为化学家们提供了新的机遇与挑战.过去10年来,我们围绕单壁碳纳米管的轴向能带工程这一研究思路,开展了一系列碳纳米管芯片的基础探索工作,发展了若干有效的单壁碳纳米管局域能带的调控方法,包括温度阶跃生长法、脉冲供料生长法、基底调控法以及形变调控法等.本文系统地阐述了这些局域能带调控方法,为使读者对该领域的研究进展有一个较为全面的了解,文中对其他课题组开展的代表性工作也给予了综述性介绍.