Synthesis, structure and properties of intercalation compounds containing perfluoroalkyl groups

Synthesis, structure and properties of various layered materials containing perfluoroalkyl groups in their interlayer space were summarized. They were obtained by ion exchange method for layered materials with ion exchange capacity and by silylation technique for those possessing acidic hydroxyl groups. The orientation of perfluoroalkyl groups greatly changed depending on their contents in the layered materials. The nature of the interlayer space of them changed from hydrophilic to hydrophobic and they were well dispersed in appropriate organic solvents. Some of them formed so called nanosheet solution and film samples were prepared from it. Organic molecules were introduced into the intercalation compounds by co-adsorption or exfoliation-restacking methods. The empty space surrounded by perfluoroalky chains where organic molecules are included showed unique properties. The weak interaction between perfluoroalkyl chains and included organic molecules lead the easy diffusion of them in the interlayer space, which caused the aggregation of them or affected the distribution of isomers obtained by photochemical reaction. The low vibrational C-F bonding in perfluoroalky groups reduced radiational quenching, accordingly enhanced the fluorescence from included organic dyes.     

新光敏剂铝酞菁光化反应机制研究

使用ESR波谱技术研究铝酞菁光化反应,以2,2,6.6-四甲基-4-羟基哌啶醇为探针,探测光化反应的中间产物及反应机制,结果表明,反应体系中氮氧自由基的生成依赖于氧的存在,D_2O的增进效应及β-胡萝卜素的抑制效应表明铝酞菁光化反应产生了单线态氧(~1O_2),SOD及细胞色素C的部分抑制效应表明光化反应中有少量超氧阴离子自由基(O_2)生成。     

大气光化学反应研究（Ⅱ）—二氧化硫与异戊烷的光化学反应

研究了SO_2与异戊烷在无氧和有氧体系中的光化学反应,用GC和GC-MS法确证了部分气、液相产物,包括醇、醛、酮、酯和烃类及含硫有机物,探讨了影响光化学反应的因素和反应机理.     

Determination of photoirradiated high polar benzoylureas in tomato by HPLC with luminol chemiluminescence detection

This study reports the first analytical application of luminol chemiluminescence reaction for the sensitive detection of two benzoylurea insecticides (diflubenzuron and triflumuron). Off-line experiments demonstrated that previously irradiated traces of these benzoylurea insecticides largely enhanced the chemiluminescence emission yielded from the oxidation of luminol in methanol:water mixtures, by potassium permanganate in alkaline medium, the enhancement being proportional to the concentration of both pesticides. The two benzoylureas were determined in tomato samples by coupling liquid chromatography with post-column photoderivatization and detection based on this chemiluminescence reaction. Tomato samples were extracted using the QuEChERS method based on extraction with acetonitrile and dispersive solid-phase clean-up using primary and secondary amine (PSA). Interferences due to matrix effect were overcome by using matrix-matched standards. The optimised method was validated with respect to linearity, limits of detection and quantification, precision and accuracy. Under the optimised conditions, calibrations graphs were linear between 0.05 and 0.50 μg mL⁻¹ for diflubenzuron and between 0.10 and 1.00 μg mL⁻¹ for triflumuron. Method detection limits were 0.0025 and 0.0131 μg mL⁻¹ (equivalent to 0.0005 and 0.0026 mg kg⁻¹) and quantification limits were 0.05 and 0.10 μg mL⁻¹ (equivalent to 0.01 and 0.02 mg kg⁻¹) for diflubenzuron and triflumuron, respectively. In both cases, quantification limits were lower than the maximum residue levels (MRLs) established by the European legislation. The relative standard deviation of intra-day precision was below 10% and recoveries were between 79.7% and 94.2% for both pesticides.     

Reduced classical trajectory equations for electronically non-adiabatic transition on photochemical pericyclic reactions

It may be difficult to use the classical trajectory equations (CTE) for the estimation of electronically non-adiabatic transition probabilities in photochemical pericyclic reactions because of many nuclear degrees of freedom. In order to avoid this difficulty, the CTE were reformulated in terms of the reaction path coordinates, and the reduced CTE were derived, in which the system was restricted to move one-dimensionally along the postulated reaction path. As an application, the non-adiabatic decay from the lowest excited state to the ground state was investigated for the conrotatory and disrotatory processes of the photochemical electrocyclic reaction of 1,3-cis-butadiene to form cyclobutene.     

Enhanced decompositions of some cyano complexes during diode array spectrophotometric measurements

Acidic solutions of the Fe(III), Mo(V), W(V) and Mn(IV) cyano complexes are known to decompose photochemically. These reactions do not take place to an appreciable extent when the cyano complexes are subjected to spectrophotometric measurements by means of conventional spectrophotometers, but they do take place when diode array spectrophotometers are used. The reactions are autoaccelerated, at least in the cases of Mo(V), W(V) and Mn(IV), and consist of photoinduced reductions of the metal ion. This effect should be taken into account in all cases where the measured signal has to be used for quantitative purposes, but its significance must be emphasized mainly in the field of kinetic analysis, where it can lead to large errors. The extent of these reactions, and therefore the size of the errors, can be lowered by using UV cut-off filters and by taking discontinuous measurements with suitable integration times. All these possibilities, which are of general application, are discussed.     

Selective photochemical cleavage of an α-ketoamide in a highly functionalised macrolide ascomycin

A novel photochemical amide cleavage reaction of (6S)-methoxyascomycin opening a pathway for the selective cleavage of the pipecolic acid, is described. The scope of this reaction with several analogues carrying suitable protecting groups is examined.     

Use of carbon adsorption traps combined with high resolution gas chromatography – mass spectrometry for the analysis of polar and non-polar C4-C14 hydrocarbons involved in photochemical smog formation

A method has been developed for the collection and analysis of polar and non-polar C₄-C₁₄ hydrocarbons involved in the formation of photochemical smog. Enrichment of hydrocarbons from both polluted and unpolluted areas has been achieved with three-stage traps packed with carbon adsorbents of different surface area; the use of a home-made desorption unit employing cryofocusing then enables the determination of the compounds by HRGC-FID. Two-stage traps filled with graphitic carbon have been used prior to GC-MS identification and quantitation of compounds producing overlapping peaks. The methodology has been tested in the urban area of Rome and in a pine forest, and more than 140 different compounds identified and quantitated. Many of the constituents were found to be oxygenated, either formed by photochemical reactions or of anthropogenic origin.     

Application of photochemical reactions of Se in natural waters by hydride generation atomic fluorescence spectrometry

A simple, sensitive and accurate method for selenium speciation in natural waters is proposed. The principle of this method is based on recently discovered photochemical reactions of Se(IV) and organic selenium in different aqueous solutions. The speciation of all selenium species was performed with hydride generation-atomic fluorescence spectrometry. Only one pre-reduction step is needed in this procedure, which can greatly reduce the risk of contamination, minimize the analytical work and improve the quality of selenium speciation. In this paper, a comparison is made between the proposed method and a previous method [A.G. Cutter, Anal. Chim. Acta 98 (1978) 59]. In this proposed protocol, Se(IV) was directly measured in 3.0 M HCl. Se(IV) + org-Se was measured directly after a UV irradiation (300 nm) for 2.5 h in a 1.0% (v/v) HNO₃-2.0% (v/v) HCl matrix. Total selenium was obtained in another aliquot sample after a UV irradiation in the 3.0 M HCl. No pre-concentration, separation or more sophisticated instruments are required.