原子吸收光谱法在药物分析中的应用及进展

评述了原子吸收光谱法在药物分析领域中的应用及进展,内容包括测定药物时所利用的各种类型的化学反应。引用文献９１篇。     

Inorganic,Organometallic, and Organic Analogues of Carbenes

This review deals with inorganic, organometallic, and organic compounds, as well as with elements, that on the basis of their electronic structure and their reactions can be regarded formally as analogues of carbenes. These “carbene analogues” include in particular the compounds of monovalent boron, aluminum, nitrogen, and phosphorus; those of divalent silicon, germanium, tin, and lead; atomic oxygen; atomic sulfur; and atomic selenium. The preparation and chemical properties of the carbenes and their analogues are compared.     

Plasma-Induced Synthesis of Organic Compounds From Graphite and Aqueous Solution

Discharge experiments were performed to explore the synthesis between graphite and aqueous solution. It was found that atomic carbon was transferred from anode into the solution by arc-discharge experiments and various kinds of organic compounds were generated by synthetic reactions from graphite and water or ammonia water. Carboxylic acids and amino acids were identified in the products by GC-MS and HPLC analyses. It is well known that graphite can hardly combine with other substances under common conditions. So the reaction not only provided an interesting attempt for the chemical transformation from graphite to organic compounds but also served as a useful reference for the formation of organic compounds from atomic carbon under primitive earth conditions.     

计算分子中原子净电荷的新方法及芳烃亲电取代反应定位效应的定量处理

本文提出一种简捷计算分子中原子净电荷的新方法。用这种方法计算了２３种一元取代苯的原子净电荷。计算所得苯环上碳原子净电荷与其￣（１３）Ｃ－ＮＭＲ化学位移有良好的线性关系。利用苯环上碳原子净电荷及立体参数作为输入参数，应用人工神经网络方法预报２４种一元取代苯硝化反应的邻、间、对位产物产率，结果良好。     

Atomic Force Microscopy for Molecular Structure Elucidation

Using scanning probe microscopy techniques, at low temperatures and in ultrahigh vacuum, individual molecules adsorbed on surfaces can be probed with ultrahigh resolution to determine their structure and details of their conformation, configuration, charge states, aromaticity, and the contributions of resonance structures. Functionalizing the tip of an atomic force microscope with a CO molecule enabled atomic‐resolution imaging of single molecules, and measurement of their adsorption geometry and bond‐order relations. In addition, by using scanning tunneling microscopy and Kelvin probe force microscopy, the density of the molecular frontier orbitals and the electric charge distribution within molecules can be mapped. Combining these techniques yields a high‐resolution tool for the identification and characterization of individual molecules. The single‐molecule sensitivity and the possibility of atom manipulation to induce chemical reactions with the tip of the microscope open up unique applications in chemistry, and differentiate scanning probe microscopy from conventional methods for molecular structure elucidation. Besides being an aid for challenging cases in natural product identification, atomic force microscopy has been shown to be a powerful tool for the investigation of on‐surface reactions and the characterization of radicals and molecular mixtures. Herein we review the progress that high‐resolution scanning probe microscopy with functionalized tips has made for molecular structure identification and characterization, and discuss the challenges it will face in the years to come.     

Atomic oxygen reactions with semifluorinated and n-alkanethiolate self-assembled monolayers

The interaction of atomic oxygen (O(3P)) with semifluorinated self-assembled monolayers (CF-SAMs), two different n-alkanethiolate self-assembled monolayers, and a carbonaceous overlayer derived from an x-ray modified n-alkanethiolate SAM have been studied using in situ x-ray photoelectron spectroscopy. For short atomic oxygen exposures, CF-SAMs remain intact, an effect ascribed to the inertness of C-F and C-C bonds toward atomic oxygen and the well-ordered structure of the CF-SAMs. Following this initial induction period, atomic oxygen permeates through the CF3(CF2)7 overlayer and initiates reactions at the film/substrate interface, evidenced by the formation of sulfonate (RSO3) species and Au2O3. These reactions lead to the desorption of intact adsorbate chains, evidenced by the loss of carbon and fluorine from the film while the C(1s) spectral envelope and the C(1s)/F(1s) ratio remain virtually constant. In contrast, the reactivity of atomic oxygen with alkanethiolate SAMs is initiated at the vacuum/film interface, producing oxygen-containing carbon functional groups. Subsequent reactions of these new species with atomic oxygen lead to erosion of the hydrocarbon film. Experiments on the different hydrocarbon-based films reveal that the atomic oxygen-induced kinetics are influenced by the thickness as well as the structural and chemical characteristics of the hydrocarbon overlayer. Results from this investigation are also discussed in the context of material erosion by AO in low Earth orbit.     

Empirical evaluation of chemical hardness

Two possible measures of hardness are proposed. An average chemical hardness is calculated separately for acidic and basic reactions of atoms. Differential hardnesses are derived from atomic radii.     

A Global Model of Chemical Vapor Deposition of Silicon Dioxide by Direct-Current Corona Discharges in Dry Air Containing Octamethylcyclotetrasiloxane Vapor

A model of the electron distribution in direct current corona plasmas is combined with a global chemistry model and a two-dimensional transport model to predict the rate of chemical vapor deposition of silicon dioxide on the discharge wire in both positive and negative discharges in dry air containing octamethylcyclotetrasiloxane. The gas-phase chemistry includes reactions to form atomic oxygen (O) and additional global reactions to form gaseous silicon dioxide precursors by the impact reactions of electrons and atomic oxygen with silicone molecules. Surface chemistry is approximated by a single step global reaction from gaseous to solid silicon dioxide. The rate coefficient between atomic oxygen and octamethylcyclotetrasiloxane is estimated from prior experiments to be on the order of 10^–12 cm³/molecule-s. The effects of discharge polarity, current, wire radius and air velocity (Peclet number for mass transfer) on the deposition rate are considered. Deposition rates can be minimized by using positive coronas instead of negative coronas for Peclet number less than 18.5. At higher Peclet numbers, the deposition rate is slightly higher in positive corona discharges, but devices used indoors should continue to use the positive corona in order to minimize the production of ozone. The deposition rate in the positive corona is relatively insensitive to air velocity for velocities from 0.044 to 10 m/s^–1 . However,it may be minimized by operating the corona with the lowest current that provides adequate performance (e.g., particle charging) and the smallest wire that provides adequate mechanical strength.     

A review of electrocatalyst characterization by transmission electron microscopy

At present, the development of highly efficient electrocatalysts with more rational control of microstructures(e.g. particle size, morphology, surface structure, and electronic structure) and chemical composition is needed and remained great challenges. Transmission electron microscopy(TEM) can offer the information about the microstructures and chemical compositions of the electrocatalysts on nano and atomic scale, which enables us to establish the synthesis-structure-performance relationship and further direct the design of new electrocatalysts with high performance. In this minireview paper, a brief introduction on the basic characterization of electrocatalysts with TEM, followed by the studying of dynamic evolution of the electrocatalysts in electrochemical reactions with identical location-TEM, is discussed.     

Analysis of the cleaved topaz (001) surface

We report on the first study of the cleaved (001) topaz surface and the characterization of the chemical composition and atomic arrangement of the surface. We conclude that there is strong evidence for a hydroxyl group termination appropriate for further chemical reactions. The surface itself is easily accessible, atomically flat and suitable for potential technological applications.     

量子化学模型方法在机械力化学中的应用

机械力化学作为一种无需溶剂的绿色化学技术得到广泛关注。然而,机械力化学反应机制需要从原子和分子尺度上深入理解力诱导的化学反应。在过去的20年中,量子化学模型方法在机械力化学机理研究中得到广泛应用,高精度量化计算可得到外力下变形分子的几何结构、能量、过渡态等诸多性质。本文介绍了目前机械力化学领域的主流量子化学模型的基本原理,同时也关注了这些模型方法在软件上的具体实现,并借助典型的案例阐述了量子化学模型在解释机械力化学机理中的作用与价值。     

Production of metal atoms,clusters and complexes in pulsed discharge-excited jets : Studies via mass-resolved laser multiphoton ionization

A pulsed, high-voltage, discharge-excited nozzle source has been developed and exploited to study the possibility of sputtering and entraining various metal atoms into the gas expansion from the discharge electrodes. By appropriate choice of electrode materials, atomic beams of copper, silver, tin and lead have been generated and spectroscopically characterized by 2 + 1 laser multiphoton ionization with mass analysis. Sufficiently high atomic densities are achieved with this nozzle system that metal clustering also takes place, producing dimers such as Ag₂, species of mixed composition such as AgSn and trimers, Ag₃. In addition, chemical reactions have been observed which can be initiated in the discharge and which lead to the formation of metal–ligand complexes when suitable molecules are seeded into the carrier gas. Mass spectral evidence for two such silver complexes is presented.     

Superatomic chemistry

Superatoms are atomic clusters with tailored size and composition that mimic the chemistry of atoms in the periodic table. However, unlike the atoms whose chemistry is governed by their valence electron orbitals, the chemistry of superatoms is governed by their highest occupied molecular orbitals. In addition, due to their large size and non-spherical geometry, superatoms can promote unusual reactions and serve as the building blocks of cluster assembled materials with properties very different from conventional materials. This perspective highlights the unique role of superatoms in chemical and material sciences by focusing on superhalogens, which not only possess electron affinities larger than those of halogens but also can be stable when multiply charged. We discuss how these unique features of superhalogens enable noble gas atoms like argon to form chemical bonds at room temperature and zinc to exhibit an oxidation state of +3. The advantages of using superhalogens in the synthesis of water-resistant materials for solar cells, halogen-free electrolytes for solid-state batteries, and multiferroic materials are also discussed.     

Systematic manipulation of surface chemical reaction on the nanoscale: a novel approach for constructing three-dimensional nanostructures

Nanoscale patches, created by nanografting a maleimide-terminated thiol into a self-assembled monolayer, were elaborated by sequential chemical reactions. Each stage in the nanofabrication was followed by atomic force microscopy (AFM), providing a controlled approach to the fabrication of novel three-dimensional (3D) surface nanostructures.     

Hybrid approach for ab initio molecular dynamics simulation combining energy density analysis and short-time Fourier transform: energy transfer spectrogram

We propose a new analysis technique for specifying molecular vibrational modes related with intramolecular and/or intermolecular energy transfer in ab initio molecular dynamics simulation of chemical reaction. The technique combines the short-time Fourier transform method with energy density analysis, which partitions the quantum chemical potential energy in the system into atomic contributions. The image obtained by the combined scheme, termed an energy transfer spectrogram (ETS), enables us to understand the dynamics of energy transfer by time-frequency representation. The time change of the local energy is quite important in chemical reactions. In order to assess the performance of the ETS, its application to the collision reaction between two carbon dioxide molecules is shown.     

Universal and state-resolved imaging of chemical dynamics

We showcase the use of high-resolution ion imaging with complementary state-resolved and "universal" vacuum ultraviolet probes to address a broad range of fundamental problems in chemical reaction dynamics. Examples from our recent work include applications in state-correlated unimolecular reactions, ion pair dissociation dynamics and spectroscopy, crossed-beam reactive scattering, and atomic angular momentum polarization in photodissociation. These studies are all directed to achieving a detailed understanding of atomic and molecular interactions, with particular emphasis on reaction mechanisms outside the scope of transition state theory; on spectroscopy and dynamics of highly excited, transient species; on nonadiabatic reaction mechanisms; and on chemical dynamics in polyatomic systems.     

Theoretical investigation of the mechanisms for the reaction of fused tricyclic dimetallenes containing highly strained E═E (E = C, Si, Ge, Sn, and Pb) double bonds

The potential energy surfaces for the reactions of fused tricyclic dimetallenes that feature a highly strained E═E double bond, Rea-E═E, where E = C, Si, Ge, Sn, and Pb, were studied using density functional theory (B3LYP/LANL2DZ). Three types of chemical reactions (i.e., a self-isomerization reaction, a [2 + 2] cycloaddition with a ketone and a methanol 1,2-addition reaction) were used to determine the reactivity of the Rea-E═E molecules. The theoretical findings reveal that the smaller the singlet-triplet splitting of the Rea-E═E, the lower are its activation barriers and, in turn, the more rapid are its chemical reactions with other chemical molecules. Theoretical observations suggest that the relative reactivity increases in the following order: C═C ? Si═Si < Ge═Ge < Sn═Sn < Pb═Pb. Namely, the smaller the atomic weight of the group 14 atom (E), the smaller is the atomic radius of E and the more stable is its fused tricyclic Rea-E═E to chemical reaction. It is thus predicted that the fused tricyclic Rea-C═C and Rea-Si═Si molecules should be stable and readily synthesized and isolated at room temperature. The computational results show good agreement with the available experimental observations. The theoretical results obtained from this work allow a number of predictions to be made.