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1、现代光分析化学考试题专业：分析化学（分科所） 学号：200820948 姓名：王小梅题目：以你所掌握的知识，说明光化学分析的发展趋势及其在有机、无机、生物、药物食品环境等领域的应用，并举例（1例）说明其当前的研究热点。（by English 3000 words）Spectroscopy covers a very wide area which has been widened further since the mid-1960s by the development of lasers and such techniques as photoelectron spectroscopy a
2、nd other closely related spectroscopies. It occupies a very special position in chemistry, physics and in science ingeneral. It is capable of providing accurate answers to some of the most searching questions, particularly those concerning atomic and molecular structure. For small molecules, it can
3、provide accurate values of bond lengths and bond angles. For larger molecules, details ofconformation can be obtained. Is a molecule planar? If it is non-planar, what is the energy barrier to planarity? Does a methyl group attached to a benzene ring take up the eclipsed or staggered position? Is a c
4、is- or trans- conformation more stable? It also provides techniques that are vital in chemical analysis. What we can call it Analytical spectroscopic chemistry.Analytical spectroscopic chemistry is basically an experimental subject and is concerned with the absorption, emission or scattering of elec
5、tromagnetic radiation by atoms or molecules. It contains Raman Spectroscopy, Fluorometry Phosphorimetry, Chemiluminescence, Flame Emission, Atomic Absorption, Atomic Fluorescence Spectrometry, Emission Spectroscopy, Radiochemical Methods of Analysis, Structural Analysis, and Microwave Spectroscopy.
6、Among this, Emission spectroscopy is conned largely to the visible and ultraviolet regions, where spectra may be produced in an arc or discharge or by laser excitation. Absorption spectroscopy is, generally speaking, a more frequently used technique in all regions of the spectrum and it is for this
7、reason that we shall concentrate rather more on absorption.Sometimes, we can divide the Spectroscopy into Rotational spectroscopy, Vibrational spectroscopy, Electronic spectroscopy, Photoelectron and related spectroscopies ,Lasers and laser spectroscopy. We will give a example of laser spectroscopy.
8、 Such as Femtosecond spectroscopy. Examples of fast chemical processes which occur on a picosecond time scale are the transfer of an electron during a reaction or the breaking of a bond in dissociation. When a chemical bond is broken by photolysis, following the absorption of a quantum of radiation
9、of appropriate energy, there is a smooth change from the bound molecule to the products. For example, the molecule AB may dissociate into A+B, where the A and B are atomic or molecular fragments. The smooth change from reactant to products involves the so-called transition state AB in which the bond
10、 between A and B is weakened as they move apart. Before it became possible to use femtosecond lasers to investigate the structure of such transition states the only means of doing so were indirect. One method involves the use of two intersecting molecular beams, one containing A and the other B, whi
11、ch react to produce AB at the point of intersection. Structure of the transition state may be inferred by changing the states (rotational, vibrational or electronic) of A and/or B. A second method of obtaining evidence regarding the structure of the transition state is to dissociate AB and investiga
12、te the energy states of one or both of the products by, for example, laser induced uorescence.Recently, the applications of analytical spectroscopic chemistry have been used widely in many research field, just like organic chemistry, inorganic chemistry, biology, medicine, food and environment, and
13、so on. There are more and more references about the new trends and applications of analytical spectroscopic chemistry.In organic chemistry field, Transition-metal complexes that exhibit low-lying excited states i.e., metal-to-ligand charge-transfer (MLCT) excitations can make them particularly well-
14、suited for the detection of small molecules with environmental or industrial relevance. Optical sensors built around metal complexes of this type have become increasingly popular. The detection of gases with crystalline platinum salts that can uptake volatile organic compounds (VOCs) has been an are
15、a of interest to some researchers for several years. The reversible change in the unit cell composition results in a perturbation of the PtPt distance, which controls the color of the complexes (“vapochromism”). Many of these compounds also show a dramatic reversible shift in the position and/or int
16、ensity of the luminescence (“vapoluminescence”) that may be excited by light-emitting diodes and detected with inexpensive photodiode array spectrometers.More recently, more references have been reported an alternative to the currently used polymer-supported sensors for luminescence quenching-based oxygen detection that relies on crystalline salts of Ru(phen)32+. Ru(5,6-Me2Phen)3(Cl)2 was synthesized by a standard method and converted to the tfpb salt, which was c
