ELECTROCHROMETIC STUDIES ON POLAR MULTILAYERS OF LIQUID CRYSTALLINE POLYMERS

Electrochrometic measurements were carried on the Z-type Langmuir-Blodgett films oftwo liquid crystalline polymers: mono-{6-[4-(phenylazo) naphthyloxy] hexyl} (1a) andmono-{6-[4-(anthraquinone-1-azo) naphthyloxy] hexyl} (2a) ester of polymaleic acid. Itwas found that for both polymers, poling fields parallel and antiparalle1 to dipole momentsof the polymer side chains induce red and blue shift in absorption bands, respectively. Forpolymer la blue shift is accompanied by absorbance increase, while red shift by absorbancedecrease;but for polymer 2a only decrease in absorbance is observed. A simple model wasproposed to analyze the results.     

ON THE MECHANISM OF PHOTOSENSITIZING ACTION OF CHLOROPHYLL

Abstract— The paper presents ideas according to which the primary photochemical reaction of chlorophyll and its analogs can be either photooxidation or photoreduction of the pigment sensitizer depending on the reaction conditions. The factors determining the course of the process of photosensitization comprise the nature and state of the pigment and participating reagents, the nature and reaction of the medium, concentration of the oxidant and reductant, their ability to form complexes with the pigment, etc.
The paper presents the results of simple kinetic investigations in which, by means of changing pH of the medium, conditions were created favouring either the primary photo-oxidation or the primary photoreduction of the pigment-sensitizer. These results, as well as the data of experiments on the changes in reagents' concentration show the reality of the above mentioned concepts.
Considerations are presented on the possibility of photochemical interaction of two chlorophyll molecules in vivo during the photosensitization of photosynthesis.     

ON THE NATURE OF CHLOROPHYLL a IN AQUEOUS MICELLAR SYSTEMS

Abstract— Absorption and fluorescence spectra of chlorophyll a in aqueous micellar solutions were studied. Solutions in anionic micelles gave an absorption band at 740 nm, attributable to microcrystal- line chlorophyll a. Solutions in cationic and nonionic micelles do not show this band. The positions of the spectral bands in anionic micelles and the possible structure of microcrystalline form are discussed. A comparison is made of the behaviour of microcrystalline form in hydrocarbon solvents and in micellar solutions.     

脱模溶剂对制备聚苯乙烯表面大孔材料的影响

采用马来酸酐-醋酸乙烯共聚物乳液为模板,分别以水、乙醇和丙酮为脱模溶剂,合成了表面层(厚度为10μm)为大孔结构(孔径为250～400nm)的聚苯乙烯(PS)孔材料.用扫描电子显微镜(SEM)测定了材料表面的微观形貌,SEM照片显示出3种脱模溶剂均能制备PS大孔材料,其中水为脱模溶剂时对PS基材的不利影响最小.用傅立叶红外光谱仪(FTIR)表征了脱模后孔内被固定的特征基团,结果表明,不同的脱模溶剂分别对应不同的孔内基团,即水-羧基、乙醇-酯基及丙酮-酐基.测定了3种脱模溶剂的脱模速率,其顺序为丙酮>>乙醇>水.     

浮游植物体内叶绿素a测定方法的改进

对丙酮萃取分光光度法测定浮游植物体内叶绿素a的方法进行改革。改进法在样品经过冷冻、50℃热丙酮快速提取并放置2h后后进行测定。对改进前后方法测定结果的方法分析表明，方法改进前后测定结果不存在显著性差异。方法改进后简化了操作，提取时间由原来的8-20h缩短为1.5-2.5h。     

ASSOCIATION OF CHLOROPHYLL WITH AMIDES ON PLASTICIZED POLYETHYLENE PARTICLES–III. UNUSUAL SPECTRA OF CHLOROPHYLL a WITH N-METHYLMYRISTAMIDE*

—The absorption spectrum of chlorophyll a, adsorbed with the amphiphilic amide, N-methylmyristamide. to particles of polyethylene swollen with tetradecane, is unusual in that the red band apparently consists of three main components, which by Gaussian deconvolution are located at 664.5, 678 and 687 nm. The last is very narrow, with a band width of only 5-6 nm at half maximum. At low amide concentration, the 744 nm band of chlorophyll hydrate is also observed. Room temperature fluorescence is weak, and indistinctly resolved into bands. However, on gradual cooling to 80 K, the fluorescence intensifies greatly and becomes resolvable into at least eight bands. The circular dichroism spectrum of the red band region shows optical rotatory strength in two narrow bands at 677 and 686 nm which is enormous, compared to that of monomeric chlorophyll or even the 744 nm hydrate. It is suggested that cyclic oligomer structures, in which adjacent chlorophylls are linked through the amide group of N-methylmyristamide, might be responsible for the spectral phenomena. Unsubstituted myristamide and N.N-dimethylmyristamide do not produce these narrow-banded phenomena with chlorophyll at all.     

端基对侧链型偶氮聚电解质自组装膜内生色团取向的影响

用偏振紫外光谱研究了 4种带有不同端基的侧链型偶氮聚电解质静电逐层自组装膜中偶氮生色团的初始取向 .讨论了不同的端基对偶氮生色团在自组装膜中初始取向的影响 .进一步探讨了偶氮聚电解质自组装膜的结构特点 .研究表明 ,侧链型偶氮聚电解质自组装膜中偶氮生色团普遍存在一定程度的沿面取向 .偶氮生色团所带端基的类型对其在自组装膜中的取向程度有较大的影响 ,这主要取决于偶氮生色团与聚阳离子基底的电荷相互作用和极性相互作用等 .对偶氮生色团在水溶液中能形成H 聚集体的自组装膜来说 ,H 聚集体对生色团取向也有一定的影响 .结果表明 ,在制备需控制生色团取向性的自组装膜时 ,要考虑生色团上的不同端基对取向的影响     

THE EFFECT OF COORDINATING LIGANDS ON THE TRIPLET STATE OF CHLOROPHYLL

Under laser excitation at 457.9 and 514.5 nm, a frozen solution of chlorophyll a in n -octane displays fluorescence peak maxima at 2K that may be assigned to two distinct monomeric chlorophyll species. Using zero-field fluorescence-detected magnetic resonance the triplet state properties of the two chlorophyll species have been assigned to the monoligated and biligated chlorophyll monomer in which water serves as the ligand coordinated to the magnesium metal center. These triplet state properties for chlorophyll in solution are then utilized in interpreting triplet state results for in vivo chlorophylls associated with the light harvesting chlorophyll protein complex. It is shown that the triplet state data are consistent with attachment of the chlorophyll molecule to the protein site with a single ligand coordinated to the chlorophyll metal center.     

电池结构对叶绿素电池光电性质的影响

叶绿素是绿色植物中吸收太阳能进行光合作用的主要色素,它在可见光范围内有很好的吸收特性^[1]。人们为了充分利用太阳能为人类造福开始了光合作用模拟,70年代后以叶绿素为光敏剂的研究成了科学家的热门课题。     

CuO/ZnO/Al2O3合成甲醇催化剂制备方法

ＣｕＯ／ＺｎＯ／Ａｌ２Ｏ３合成甲醇催化剂的制备方法吴晓晖刘金尧刘崇微朱起明（清华大学化学系一碳化工国家重点实验室，北京１０００８４）何菲（天津大学化工系一碳化工国家重点实验室，天津３０００７２）关键词氧化铜，氧化锌，氧化铝，超细粒子，草酸盐胶体...     

A THEORETICAL STUDY OF EXCITONS IN CHLOROPHYLL a PHOTOSYSTEMS ON A PICOSECOND TIMESCALE

Abstract— The creation and decay of singlet excitons in structurally-explicit Chi a photosystems were investigated by numerical integration of the appropriate Master Equations. The antenna chlorophylls were excited by a simulated 6ps Gaussian light pulse. Positions and orientations for the antenna chlorophylls were randomly generated within regions whose size and shape were chosen to be appropriate for the particles observed in freeze-fractured photosynthetic membranes. Among the variables considered were chlorophyll concentration, depth of the trap (i.e. P680 or P700), and the R₀ parameter for Förster transfer. Among the properties considered were antenna fluorescence lifetime; detrapping rates; the instantaneous and integrated quantum yields for antenna fluorescence and intersystem crossing; and the instantaneous and integrated quantum yields for trap fluorescence, intersystem crossing, and photochemistry. A variety of experimental evidence was used as input to the computational model.     

化学需氧量测定方法的探讨

化学需氧量 (ＣＯＤ)是指在一定条件下 ,用强氧化剂处理水样时所消耗的氧化剂的量 ,化学需氧量反映了水中受还原性物质污染的程度 ,是评价水体污染的重要指标之一 ,是水质监测分析中最常测定的项目 ,目前ＣＯＤ值的测定大都采用重铬酸钾硫酸回流法 ,即标准法[1,2 ] ;该方法具有测定结果准确、重现性好等优点 ,但消耗大量的浓硫酸和价格昂贵的硫酸银 ,为了消除氯离子的干扰 ,还需加入毒性很大的硫酸汞加以掩蔽 ,而且分析时间很长 ,因此 ,对区域水质调查中大批样品的测定、水质监督监测及污水处理厂家的验收监测 ,标准法并不适用。为此 ,广大…     

INFLUENCE OF ELECTRIC FIELDS ON FLUORESCENCE QUENCHING OF CHLOROPHYLL a IN NEMATIC LIQUID CRYSTAL MATRIX

Abstract— An electric field enhances the yield of fluorescence of chlorophyll in a liquid crystal solvent. The presented data suggest that the electric field effect is caused by the decrease in the efficiency of fluorescence quenching by ions. Quenching of each polarized component of fluorescence of chlorophyll molecules oriented by the liquid crystal matrix is different. The relative increase in fluorescence yield due to the applied electric field is stronger for a fluorescence component polarized parallel to the direction of liquid crystal orientation than for the perpendicular component.     

光透电极叶绿素夹层电池的研究

报道了光透电极叶绿素夹层电池SnO_2/chla/PVA/SnO_2的光电特性, 讨论了电池发生光电效应的机理, 说明了电池的暗整流作用和光照时电荷分离的结点为chla/PVA. 测量了电池的输出参数并用氢醌等物质对电池进行改进, 使电池短路电流和能量转化率提高一个数量级以上.     

LOW-TEMPERATURE FLUORESCENCE SPECTRA OF CHLOROPHYLL a SOLUTIONS

Abstract Fluorescence and fluorescence polarization spectra of chlorophyll a dissolved in ethanol, n -propanol, EM (ethanol-methanol, 4:1) and EPE (ether, n -pentane, ethanol, 5:5:2) were measured at 77 K. An emission band ('shoulder') between the two usual fluorescence bands appears in such spectra of dilute solutions (concentration ˜ 10^-5 M ) of chlorophyll a (except in EPE). The position, intensity and half-width of this band were calculated using a computer. The correlation between electronic transitions of chlorophyll a and these emission bands is discussed.