Fluorescence quenching of anthropogenic fulvic acids by Cu(II), Fe(III) and UO(2)(2+)

The quenching of the fluorescence of three anthropogenic fulvic acids (FA) provoked by Cu(II) (pH 6.0), Fe(III) (pH 4.0) and UO₂²⁺ (pH 3.5), was analyzed by a non-linear method and by Stern-Volmer plots. The FA samples were extracted from composted sewage sludges (csFA), composted municipal wastes (mwFA) and composted livestock wastes (lsFA). Synchronous-scan fluorescence (SyF) spectra were collected as a function of metal ion concentration. Spectral data were treated by a self-modeling mixture analysis method (SIMPLISMA) to detect the SyF spectral band with the strongest quenching and to calculate the corresponding quenching profile. The analysis of these profiles by a non-linear method allowed the estimation of conditional stability constants (K) and of the percentage of non-complexing fluorophores. The same quantitative information was obtained by the modified Stern-Volmer equation taking into account the existence of fluorophores that do not participate in the complexation. Good agreement was found between the results of the two procedures. The log K calculated by the non-linear method were (standard deviation in parenthesis): csFA, Cu(II), 4.22 (5); Fe(III), 5.0 (1); UO₂²⁺, 5.2 (2); mwFA, Cu(II), 4.21 (3); Fe(III), 5.6 (2); UO₂²⁺, 4.7 (3); lsFA, Cu(II), 4.51 (8); Fe(III), 5.5 (2); UO₂²⁺, 3.6 (2).     

Trace determination of nitrated polycyclic aromatic hydrocarbons using liquid chromatography with on-line electrochemical reduction and fluorescence detection

An efficient clean-up procedure coupled with a high performance liquid chromatography (HPLC) with on-line electrochemical (EC) reduction and fluorescence detection (FLD) was developed to quantify nitrated polycyclic aromatic hydrocarbons (NPAHs) in the airborne particulate. In this process, NPAHs were extracted ultrasonically followed by analysis by using a reversed phase column with an aqueous eluent containing 70% aqueous acetonitrile and sodium monocholoroacetate as a buffer solution. The extraction efficiencies were above 83% for 1-nitropyrene and 1,3-dinitropyrene (1,3-DNP) 1,6-DNP, and 1,8-DNP, and calibration graphs were linear with very good correlation coefficients (r>0.999) and the detection limits were in the range of 1.0-2.2 pg for dinitropyrenes and nitropyrene. The proposed method provides a relatively simple and convenient procedure for determining the NPAHs samples in airborne particulate.     

Role of structural flexibility in the fluorescence and photochromism of salicylideneaniline: the general scheme of the phototransformations

The mechanism of light-induced transformation in the salicylideneaniline molecule was studied by semiempirical PM3 calculations. The structures and energies of the minima and saddle points (transition states) on the S₀, S₁ and T₁ potential energy hypersurfaces (PESs) were obtained, together with the gradient lines on the PESs. The structure-energy scheme was compared with the experimental findings. According to the results obtained, the following principle processes are observed: fast S₁ excited state intramolecular proton transfer (ESIPT), followed by typical ESIPT fluorescence; the formation of two S₁ twisted intramolecular charge transfer (TICT) structures which quench the ESIPT fluorescence; the diabatic formation of two ground state metastable coloured “post-TICT” structures responsible for photochromism.     

烷基苄基铵对芘的荧光猝灭行为研究

广义的荧光猝灭系指所有能使荧光强度降低的物理和化学过程,但通常涉及的主要有动态猝灭和静态猝灭,二者均遵从Stern-Volmer方程,但由于猝灭作用本质不同,它们在荧光寿命变化、温度效应及吸收光谱等方面表现出差异可资区别.本文通过稳态荧光强度变化和荧光衰减速率的比较研究了具有不同烷基链长的十四烷基苄基二甲基氯化铵(Zeph)和苄基三甲基溴化铵(TMBA)对芘的荧光猝灭,并基于电导实验结果以及猝灭剂全反式构象从理论上计算了Zeph和TMBA的猝灭速率常数,讨论了荧光猝灭的性质和长链分子的构型。     

Fluorescence ratiometric pH sensor prepared from covalently immobilized porphyrin and benzothioxanthene

A fluorescence ratiometric sensor for pH determination is described in this paper. The sensor incorporated the pH-sensitive dye meso-5,10,15,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP) as an indicator and a pH-insensitive dye N-(2-methacryloxyethyl)benzo[k,l]thioxanthene-3,4-dicarboximide (MBTD), a benzothioxanthene derivative, as a reference for fluorescence ratiometric measurement. To prevent leakage of the dyes, both were photocopolymerized with acrylamide, hydroxyethyl methacrylate, and triethylene glycol dimethacrylate on the silanized glass surface. The reproducibility and response time of the prepared sensor were sufficient. Most common coexisting inorganic ions and organic compounds did not interfere with pH sensing. In the acidic pH range from 1.5 to 5.0 the fluorescence intensity ratio of the two dyes varied linearly as a function of pH. The sensing membrane was found to have a lifetime of at least one month. The sensor was applied to the analysis of waste water and artificial samples.     

利用荧光探针研究聚甲基丙烯酰胺溶液中的疏水微区

利用荧光探针研究聚甲基丙烯酰胺溶液中的疏水微区沈燕清，江鹏飞，吴世康（中国科学院感光化学研究所，北京，１００１０１）关键词荧光探针，疏水微区，聚甲基丙烯酰胺微多相体系研究近年来受到广泛的注意，它不仅是由于长期来已经发现：不同结构的微多相体系如胶束，乳...     

PREPARATION AND CHARACTERIZATION OF SHISH-KEBAB TYPE LIQUID CRYSTALLINE POLY（p-PHENYLENEVINYLENE）

Novel shish-kebab type liquid crystalline poly（p-phenylenevinylene） derivatives were synthesized by Stille coupling reaction from 2,5-bis[（4-n-alkoxyl）benzoyloxy]1,4-dibromobenzene （monomer l） and 1,2-bis（tributylstannyl） ethylene （monomer 2）. The polymers with alkoxy groups are soluble in common organic solvents and exhibit blue fluorescence. Both the cast film and the annealed film have large red-shifts in fluorescence spectra and show yellow fluorescence. The polymers with CN and NO2 groups show poor solubility and green fluorescence. All the polymers possess liquid crystalline smectic phases. The melting point （Tm） of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The polymers are easily aligned under a magnetic field of 10 Tesla. It is found that the conjugated backbone and LC side chain are aligned perpendicular and parallel to the magnetic field, respectively. The polymers show optical dichroism in fluorescence spectra, suggesting that they are available for advance materials with linear optical polarization.     

Synthesis and fluorescent properties of some new unsymmetricbis-benzothiazolyl furans and thiophenes

Summary Some newmono- andbis-benzothiazolyl compounds with furan or thiophene nuclei were synthesized by multistep reactions from the corresponding furan and thiophene aldehydes. The data obtained from emission spectra show a large influence of the benzothiazole rings on the relative quantum efficiency of the compounds under investigation.

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Synthese und Fluoreszenzeigenschaften von neuen unsymmetrischenbis-Benzothiazolylfuranen und thiophenen

Zusammenfassung Einige neuebis-Benzothiazolylverbindungen mit einem Furan- bzw. Thiophenenring wurden in einer mehrstufigen Reaktion dargestellt. Die Fluoreszenzdaten der untersuchten Verbindungen zeigen einen großen Einfluß der Benzothiazolringe auf die relative Fluoreszenzquantenausbeute.

     

1,8-亚乙基萘在三氟化硼乙醚-聚乙二醇中的电化学聚合

在三氟化硼乙醚(BFEE)-聚乙二醇(分子量400,PEG400)混合电解质溶液中,1,8-亚乙基萘直接阳极氧化聚合可以获得自支撑聚(1,8-亚乙基萘)膜.单体在三氟化硼乙醚+10%PEG400中的起始氧化电位为0.95 Vversus SCE,远低于单体在0.1 mol.L-1四氟化硼四丁基胺-乙腈溶液中的起始氧化电位(1.38 VversusSCE).同时PEG400的加入可以有效改善单体在三氟化硼乙醚中的溶解性.UV-Vis,FTIR和1H-NMR确定了1,8-亚乙基萘在4,5位聚合,荧光光谱表明固态及可溶聚(1,8-亚乙基萘)膜是蓝色发光材料.     

稀土长链配合物的合成及其性质研究

通过筛选配体、优化合成条件,设计合成了以Tb3 为中心离子,以苯甲酸、水杨酸、对羟基苯甲酸、对甲基苯甲酸、大茴香酸、间氯苯甲酸、对氨基苯甲酸、磺基水杨酸为第一配体,以十一烯酸为第二配体合成8种铽三元荧光配合物。通过红外光谱分析、紫外光谱分析、元素分析、EDTA配位滴定分析以及电导率的测定确定了铽三元荧光配合物的分子结构和组成,采用热分析仪研究了铽三元荧光配合物的热稳定性能,其热稳定性强弱顺序为:Tb(SSA)(UA).3H2O磺基水杨酸>大茴香酸>对氨基苯甲酸>苯甲酸>水杨酸>对羟基苯甲酸>间氯苯甲酸,同时对产生上述现象的原因进行了初步的理论探讨。