表面活性剂增敏二甲酚橙显色测定磺胺嘧啶

本文利用光度法研究了在氯化十六烷基吡啶(CPC)、十六烷基三甲基溴化铵(CTAB)分别存在下,磺胺嘧啶(SD)和二甲酚橙(XO)的显色反应体系。实验结果表明:在中性介质中XO-SD-CPC、XO-SD-CTAB体系的显色反应快速、灵敏、稳定,吸光度明显增强,SD质量浓度分别在0~5.0 mg.L-10、~2.0 mg.L-1范围内符合比耳定律。两种方法用于片剂中磺胺嘧啶的测定,结果令人满意。     

原子吸收光谱法测定脐橙和蜜桔中微量元素的含量

采用原子吸收光谱仪(AAS),对脐橙的果皮、肉汁和囊瓣外衣中的10种微量元素进行了测定,同时也选择蜜桔进行了对比测定。结果表明,脐橙和蜜桔的果皮、肉汁和囊瓣外衣中含有比较丰富的人体必需的微量元素,且囊瓣外衣和果皮中的微量元素含量大多高于囊瓣中肉汁的微量元素的含量。这为脐橙和蜜桔药效功能的综合开发利用提供科学依据。     

Properties of carbon and iron modified TiO2 photocatalyst synthesized at low temperature and photodegradation of acid orange 7 under visible light

The nanoparticles of TiO₂ modified with carbon and iron were synthesized by sol-gel followed solvothermal method at low temperature. Its chemical composition and optical absorption were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence emission spectroscopy (PL), UV-vis absorption spectroscopy, and electron paramagnetic resonance (EPR). It was found that carbon and iron modification causes the absorption edge of TiO₂ to shift the visible light region. Fe(III) cation could be doped into the matrix of TiO₂, by which could hinder the recombination rate of excited electrons/holes. Superior photocatalytic activity of TiO₂ modified with carbon and iron was observed for the decomposition of acid orange 7 (AO7) under visible light irradiation. The synergistic effects of carbon and iron in modified TiO₂ nanoparticles were responsible for improving visible light photocatalytic activity.     

Fluorescent Color Readout of DNA Hybridization with Thiazole Orange as an Artificial DNA Base

A fluorescent chameleon : A single thiazole orange (TO) dye, when used as an artificial DNA base shows the typical green emission, whereas the interstrand TO dimer exhibits an orange excimer‐type emission inside duplex DNA (see picture).

     

纳米银对表面吸附甲基橙分子的光谱学性质的影响

甲基橙溶液中引入纳米银胶,甲基橙分子的π-π*和n-π*电子跃迁吸收蓝移。随着纳米银胶浓度增加,S2-S0跃迁荧光发射强度不断下降,发射峰红移,而S1-S0跃迁荧光发射强度不断增加。纳米银对pH=2.1的甲基橙溶液的S1-S0跃迁荧光发射强度增强高于pH=6的甲基橙溶液。采用透射电子显微镜、紫外-可见吸收分光光度计和荧光分光光度计等手段从局域场增强、分子间的相互作用和能量传输等方面初步探讨了纳米银胶对表面吸附甲基橙分子光谱学性质影响机制。     

镍-二甲酚橙-溴化十六烷基三甲铵动力学光度法测定镍

研究了Ni2+与二甲酚橙及溴化十六烷基三甲铵形成三元络合物的反应特性，测定了反应级数和表观活化能．基于该络合反应速率较小的特性，采用对数外推法计算机处理数据，建立了停流－动力学测定Ni2+的新方法．大多数元素的干扰均可用动力学方法消除，应用于镍矿等实样中镍的测定，结果满意，其相对标准偏差小于3％。     

钕掺杂提高TiO2光催化活性的机制

采用X射线衍射(XRD), BET吸附, X射线光电子能谱(XPS)表征了溶胶凝胶法制备的Nd掺杂TiO2光催化剂的晶体结构、表面电子结构与化学组成. 以甲基橙为有机底物, 测试Nd掺杂对光催化剂吸附性能和光催化活性的影响. 结果表明, Nd掺杂可阻碍TiO2的晶相转变, 减小光催化剂的晶粒尺寸, 比表面积增大. Nd掺杂提高光催化剂表面三价钛(TiⅢ)的含量及其对甲基橙的吸附能力是其提高TiO2光催化降解甲基橙活性的主要原因. Nd掺杂量为1.2%时, 光催化剂活性最高.     

A spectrophotometric determination of the formation constants of the inclusion complexes ofα- andβ-cyclodextrins with the azonium and ammonium tautomers of methyl orange and methyl yellow

The color fading caused by the addition of-cyclodextrin or-cyclodextrin to an aqueous solution of a tautomeric mixture of methyl orange or methyl yellow is studied spectrophotometrically at pH 1.1 and 25.0°C. A model involving 1 : 1 stoichiometry has been used to analyze the spectrophotometric data. The addition of a cyclodextrin shifts the tautomeric mixture towards the side of the ammonium tautomer. An expression allowing the calculation of the tautomeric equilibrium constant of the inclusion complexes is derived. The formation constants of the inclusion complexes of the individual tautomers are determined. Both- and-cyclodextrins bind the ammonium tautomer stronger than the azonium tautomer. The inclusion complexes of-cyclodextrin are more stable than the corresponding ones of-cyclodextrin.     

Amphiphilic copolymers with increased affinity for substrates

The copolymers of methyl quaternized 2-dimethylaminoethyl acrylate and styrene, 2-vinyl naphthalene, acrylic acid iso-octyl ester, or acrylic acid n-butyl ester have been prepared. Studies were made of the binding of a “binding probe,” methyl orange, by the copolymers in aqueous solution. The first binding constants and the thermodynamic parameters in the course of the binding were evaluated. Furthermore, the intensity of fluorescence of a hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate, in the presence of these polymers was investigated. In addition, the fluorescence spectra of monomer and excimer emissions of the polymers with aromatic residues were measured. The excimer/monomer fluorescence intensity ratio was studied in the presence of various additives such as methyl orange, urea, methanol, and NaCl to gain an insight into the nature of microdomains in the polymer. The nature and phenomena of dye binding and hydrophobic fluorescent probe binding with the polymers are discussed. © 1993 John Wiley & Sons, Inc.     

Reactivity of singlet oxygen generated by the photosensitization of tetraphenylporphyrin in liposomes

A hydrophobic porphyrin derivative, tetraphenylporphyrin (TPP), was used as a sensitizer, and an anionic dye, methyl orange (MO), was employed as a substrate of photooxidation. TPP was incorporated into the hydrophobic environment of phosphatidylcholine (PC) bilayer membranes, liposomes. When oxygen was purged out of the liposome suspension by nitrogen bubbling, the degradation of MO was completely inhibited. A specific superoxide scavenger, superoxide dismutase, had no effect on the MO degradation. The replacement of H₂O by D₂O resulted in a 10 times enhancement in the photodegradation of MO. These results suggested that singlet oxygen was generated by the TPP photosensitization and worked as the mediator of the photoreaction from TPP. Trisulphonated TPP,-phenyl-,, -tri(p-sulphonyl)porphyrin (TPPS), is soluble in aqueous solution. The light irradiation to an aqueous solution of TPPS gave rise to the rapid bleaching (decomposition) of the sensitizer itself. On the other hand, TPP in the hydrophobic environment of liposomes was stable during light irradiation and worked as a sensitizer for the continuous photoreaction. Maximum reactivity was observed at the PC/TPP mole ratio of 50. When TPP molecules were incorporated into liposomes at larger concentrations (PC/TPP<50), a part of the excitation energy of the sensitizer molecules was nonradiatively converted into the lattice energy by the resonance between the closely located TPP molecules. This led to lower efficiency for the photoactivation of oxygen. On the other hand, the increase in liposome concentration resulted in the enhancement of the MO binding to lipid membranes and the retardation of MO degradation. Also, the electrostatic attraction and repulsion between the membrane and the substrate influenced the reaction rate greatly. The oxidative degradations of the substrate by singlet oxygen were considered to be much faster in the polar environment than in the less polar environment. The charge transfer or the polarized transition complex of singulet oxygen and MO are presumed to be stabilized in the polar environment. The distribution of substrate between the less polar membrane surface and the polar bulk aqueous solution was another important factor in the photooxidation.