Behavoir of Trapped Bromothymol Blue into Sol-Gel Matrix in Presence of CTAB

Encapsulation of bromothymol blue (BTB) into a polysiloxane network was prepared using sol-gel method without using a catalyst. The co-entrappment of the bromothymol blue (BTB) and surfactant cetyltrimethyl ammonium bromide (CTAB) was used to modify the properties of the sol-gel matrixes which may provide a highly porous materials and made the polysiloxane network an excellent host for sensing molecules. Monolithic disks of trapped BTB were obtained with no leaching. Polarized light microscopy shows that a almost unique particle sizes distributions were formed. The immobilized BTB shows a response for various pH solutions, the feature of absorption spectra of the immobilized BTB was almost the same as that of the solutions.     

Extractive Spectrophotometric Methods for Determination of Clarithromycin in Pharmaceutical Formulations Using Bromothymol Blue and Cresol Red

Two simple and sensitive extractive spectrophotometric methods have been described for the analysis of clarithromycin in pure form and in pharmaceutical formulations. The methods involved formation of yellow colored chloroform extractable ion‐association complexes of clarithromycin with bromothymol blue (BTB) and cresol red (CR) in buffered aqueous solution at pH 4. The extracted complexes showed maximum absorbance at 410 and 415 nm for BTB and CR, respectively. Beer's law is obeyed in the concentration ranges 0.1–20 μg mL^?1 and 2.0–20 μg mL^?1 of clarithromycin with molar absorptivity of 2.01 × 10⁴ and 4.378 × 10³ for BTB and CR, respectively. The composition ratio of the ion‐association complex was clarithromycin: BTB and CR = 1:1 as established by Job's method. The methods have been applied to the determination of drug in commercial formulations. The results of analysis were validated statistically and through recovery studies.     

阴离子表面活性剂－溴化十二烷基二甲基苄基铵－溴百里酚蓝显色反应的分光光度法研究

本文研究了溴化十二烷基二甲基苄基铵－溴百里酚蓝与阴离子表面活性剂显色反应的适宜条件。结果表明，在ｐＨ７．４～８．２范围内阴离子表面活性剂与题示试剂形成１：２：１的绿色离子缔合物，其最大吸收峰位于６１４ｎｍ处。表现摩尔吸光系数分别为：＝３．９９×１０￣４Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１）；＝３．７０×１０￣４Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１）；＝１．７１×１０￣４Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１）。ＳＤＢＳ在０～１９５μｇ／１０ｍＬ，ＳＤＳ在０～１５８μｇ／１０ｍＬ，ＳＬＳ在０～６０μｇ／１０ｍＬ范围内遵守比耳定律。该法用于河水和生活废水中阴离子表面活性剂测定，结果满意。     

Encapsulation of Phenolphthalein pH-Indicator into a Sol-Gel Matrix

Transparent monolithic silica doping with phenolphthalein has been prepared via the acid-catalyzed sol-gel reactions of tetraethylorthosilicate in the presence of phenolphthalein. The immobilized phenolphthalein pH-indicator shows similar behavior as its solution counterpart. The UV/Vis spectra indicate that the phenolphthalein retains its structure during the sol-gel reactions in terms of response to pH. The phenolphthalein can be regarded as uniformly distributed in the silica matrix. This observation has been confirmed using polarized microscopy.     

Spectrophotometric Determination of Trimethoprim in Pure Form and in Pharmaceutical Preparations using Bromothymol Blue,Bromocresol Green and Alizarin Red S

ABSTRACT

Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λ_max.

Beer's law is obeyed in case of BTB in the range 2.9-23.2 μg/ml (CHCl₃), 2.9-20.0 μg/ml (CH₂Cl₂) and 5.0-29.0 μg/ml (ClC₆H₅), in the case of BCG 2.9-27.5 μg/ml (H₂O/alc.), 2.9-18.3 μg/ml (CHCl₃) and 2.9-20.3 μg/ml (CH₂Cl₂) and for ARS in the range 3.0-12.0 μg/ml in H₂O/alc medium.

The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Application of the suggested methods to dosage forms is presented and compared with the pharmacopoeial method. The interference from additives and sulfa compounds, especially sulfamethoxazole, has been overcome by extraction into chloroform or methylene chloride.     

Encapsulation of Microbial Cells into Silica Gel

This work deals with changes in microbial phenol degradation and cell proliferation caused by immobilization into silica gel. Mixed microbial culture and the yeast Candida tropicalis were immobilized in silica layers and pieces prepared by mixing of prepolymerized tetraethoxysilane with cell suspension. The phenol degradation rate of cells entrapped in silica gel was compared with those immobilized into an organic polymer-polyurethane. The phenol degradation efficiency decreased in the following order: free cell suspension > cells entrapped into polyurethane foam > cells entrapped into prepolymerized TEOS. Inside the silica there was no growth observed by optical microscope. The immobilization of bacterium Pseudomonas species 2 into silica gel, cells which co-metabolize PCBs with biphenyl, did not result in substantial change of intermediate concentration.     

Encapsulation of Tetraazaannulenato Compounds in Matrix by Sol-Gel Process

The hybrid organic-inorganic catalyst constituted by {5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraaza[14]annulenato} nickel (II), NiTMTAA, encapsulated in an alumina matrix has been prepared. NiTMTAA was synthesized by the reaction of nickel acetate with o-phenylenediamine in the presence of 2,4-pentanedione under argon atmosphere. The alumina hybrid material was obtained by a non hydrolytic sol-gel route, through the condensation of aluminum chloride with diisopropylether in the presence of NiTMTAA. The material has been prepared through precipitation from a gel. Characterization of the alumina hybrid material has been performed by ultra violet-visible spectroscopy, electron spectroscopic imaging, surface area, atomic absorption, infrared spectroscopy, and thermogravimetric analysis. The ultra violet-visible absorption spectrum of the hybrid material has bands characteristic of the NiTMTAA compound showing that the structure of NiTMTAA has been preserved in the hybrid material. The new material has a surface area of 300 m²/g. The electron image was that of a non-crystalline microstructure. Comparison between the leaching of NiTMTAA from NiTMTAA adsorbed on commercial neutral alumina confirm that in the non-hydrolytic materials the NiTMTAA is entrapped and not only adsorbed on the alumina surface. The use of conventional hydrolytic sol-gel process leads to the complete leaching of NiTMTAA from matrix, underlining the importance of the non-hydrolytic alumina gel process in the matrix preparation. The new catalysts prepared were tested for their ability to catalyze the epoxidation of (Z)-cyclooctene using iodosylbenzene as oxygen donor, giving moderate yields in the epoxidation (40%), while the homogeneous NiTMTAA is inactive due to NiTMTAA bleaching. These results emphasize the effect of the non-hydrolytic alumina matrix to prevent chemical degradation of NiTMTAA.     

Encapsulation of Water-Soluble Dye in Spherical Sol-Gel Silica Matrices

The water-soluble, Lithol rubine B, dye was encapsulated into silica microspheres matrices. Encapsulation has been carried out by sol-gel process of W/O microemulsions formed from sodium silicate and dye aqueous solution in cyclohexane medium. The average particle size could be tailored from 1–10 m, depending on the processing parameter such as homogenizing speed in the formation of W/O emulsion, the weight ratio of water to oil, and concentration of sodium silicate solution, etc. The pore size of dye-doped silica microspheres was measured by nitrogen adsorption-desorption isotherms. The leaching behavior of dye entrapped in silica matrices was investigated by UV/VIS and UV diffuse reflectance spectroscopy for the extract and solid powders after immersion for 24 h in water. The doping of GPTS (3-glycidoxypropyltrimethoxysilane) in sodium silicate and dye mixture solution greatly enhanced the stability against leaching of the dye. It was ascribed that GPTS serves simultaneously as an intermediate for the chemical bonding between the dye and silica, and as an agent for the formation of hybrid sol responsible for the shrinkage of pore size.     

Characterization of Porous Nanocomposites Formed by Cobalt Ferrites Dispersed in Sol-Gel Silica Matrix

Composites of cobalt ferrite particles dispersed in a silica matrix (CoFe₂O₄/SiO₂) were prepared by the sol-gel process using tetraethylorthosilicate (TEOS) as a precursor of silica and metallic nitrates as precursors of ferrite. Samples of SiO₂ and CoFe₂O₄/SiO₂ were prepared in monolithic shape, dried at 110^∘C, treated at various temperatures and their characteristics were compared. After the thermal treatment, the surface area of the silica matrix decreased, above 700^∘C it densified, and above 1100^∘C it crystallized. The same heat treatment in the composite led to the crystallization of CoFe₂O₄ particles in the SiO₂ matrix and the increase in particle size, with the consequent increase in magnetization. The presence of particles in the matrix reinforced its structure, avoiding large changes in surface area and porosity and in the structure of the matrix after high temperature thermal treatment.     

Optical Properties and Structural Perfection of Chicago Sky Blue 6B-doped KDP Crystals

KDP crystals doped with Chicago Sky Blue 6B(CSB-6B) were grown by traditional lowering temperature method.The optical properties and structural perfection of KDP crystals were investigated by transmittance spectra and high-resolution X-ray diffraction,respectively.The results indicate that CSB-6B tends to be incorporated into the pyramidal sector of KDP crystals(PyS-KDP) and lead to inclusions parallel to(101) face.Additionally,the transmittance of as-grown KDP crystals decreases as the amount of CSB-6B increases.Moreover,the rocking curves of PyS-KDP suggest that CSB-6B can deteriorate the structural perfection of PyS-KDP.     

Spin Coating of Titanium Ethoxide Solutions

Titanium oxide films are used in anti-reflection interference filters. These layers can be deposited by spinning titanium ethoxide (TEOTi) solutions. By thorough hydrolysis of the TEOTi precursor, optically acceptable coatings can be made even when cured at temperatures below 150°C. The use of acetylacetone to control the reactivity of a TEOTi solution is not suitable when curing the films at 150°C, because at this curing temperature the acetylacetone remains in the coating. A more suitable method to control the reactivity is by adjusting the H⁺ concentration of the solution. Besides the curing temperature the hydrolysis time of the TEOTi solution also has a major influence on the morphology of the final TiO₂ layer.     

基于芴的蓝色电致发光材料研究进展

新型有机及高分子光电材料的制备与器件设计是目前国际上一个十分活跃的领域。与液晶平面显示器相比,有机和高分子电致发光平面显示器（OLED和PLED）具有主动发光、无角度依赖性、对比度好、轻、薄、能耗低等显著特点,具有广阔的应用前景。红、绿、蓝3原色是实现有效全色显示的必备条件。与红光和绿光材料相比,蓝光材料的效率、稳定性和色纯度都与前两者相去甚远。开发好的蓝光材料不仅可以作为OLED或PLED中的发光层,还可作为主体来掺杂制备绿光和白光光源。在蓝光材料中,基于芴的齐聚物和高分子拥有良好的热稳定性、高荧光量子效率和优异的电致发光特性,但其存在电荷注入与传输困难、易发生聚集、C9位易被氧化等缺点,这些缺点正是导致器件效率低、色纯度低、光谱稳定性差的原因。综述了基于芴的蓝光小分子和高分子的研究进展,主要针对含有电子给体、受体的齐聚芴和聚芴的材料设计、合成及电致发光性能,结果表明,既含空穴传输又含电子传输片段的材料比相应的只含电子给体或受体的材料性能更佳。     

Anhydrous Sol-Gel Synthesis of Titania-Doped Siloxane Polymer for Integrated Optics

Sol-gel synthesis of organic-inorganic hybrid materials for planar waveguides and devices has received growing interest due to its low-cost processing and good suitability for doping. Titania is an important optical dopant, but homogeneous incorporation of titania in silica is difficult to be achieved by the conventional sol-gel process (aqueous system) because of the significant difference between the hydrolysis rates of the precursors. In this paper, we report an anhydrous sol-gel process for synthesising titania-doped siloxane polymers. The process consists of a hydrolysis of 3-methacryloxypropyltrimethoxysilane (MPS) with boric acid under anhydrous conditions, and a condensation with dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPhDMS) and titanium ethoxide (TET). Optical characterisations for the produced titania-doped polymer were performed, and results showed that TET doping is useful for reducing the OH concentration of the synthesised polymer and is also effective for improving the optical quality of spin coatings. DMDMS and DPhDMS are favourable in reducing the birefringence and in increasing the thermostability of the material, and the methacryl groups of MPS are UV-polymerizable, which is useful for low cost fabrication of waveguides by photolithographic process. The results of ellipsometry scanning measurements show that titania is homogeneously incorporated in the hybrid matrix, suggesting that the anhydrous sol-gel process is useful for preparation of UV-sensitive titania-doped siloxane polymers for optical applications.     

溴酚蓝-氯化十六烷基吡啶光度法测定水中痕量阴离子表面活性剂

本文研究了溴酚蓝(BPB)与氯化十六烷基吡啶(CPC),阴离子表面活性剂(AS)与CPC形成缔合物的反应.发现在pH=8.0的NH_3·H_2O-NH_4Cl缓冲溶液中,AS能定量置换出CPC-BPB缔合物中的BPB而显色,其最大吸收在590nm处.阴离子表面活性剂十二烷基本磺酸钠(DBSNa)和十二烷基磺酸钠(DSNa)的ε值分别为2.9 ×10_4和3.2×10~4L·mol~(-1)·cm~(-1).在80μg CPC存在下,DBSNa和DSNa浓度分别在0～80μg/25 ml和0～60μg/25ml范围内符合比耳定律.应用此法测定环境水样中的痕量阴离子表面活性剂,结果满意.     

Hydrosilylation of alkenes catalysed by rhodium complexes immobilized on silica via a pyridine group

2-(2-Trimethoxysilylethyl)pyridine, together with 3-methcryloxypropyltrimethoxysilane, was used to prepare a series of rhodium carbonyl complexes bound to silica via a pyridine group. The rhodium complex Rh₂(CO)₄Cl₂ (Rh₂) was used as the starting compound, and the immobilized complexes were prepared by four different routes which yielded both surface-bonded complexes and complexes bonded within the silicate matrix. These complexes were efficient catalysts of hydrosilylation of octene by triethxysilane. All the immobilized complexes were more than their homogeneous analogues and some could be re-used.     

Chemistry of Preparation of Alumina Aerogels in Presence of a Complexing Agent

Transition alumina with both high specific surface area (SSA) and quite important pore volumes deserve some interest in the field of heterogeneous catalysis as such alumina can be used as supports for different active phases, namely those used in hydroprocessing reactions. Alumina has been synthesised by a sol-gel method for which a key parameter, examined in this study, is the introduction of chelating agents such as butan-1,3-diol or acetylacetone (Hacac) in the aluminium-tri-sec butylate (ASB, the chosen Al precursor) solution. The study of the complexation chemistry for a complexing agent/Al alkoxide molar ratio (C) equal to 1, 2 and 3 was carried out. Some species in initial solutions were identified by IR and ²⁷Al NMR spectroscopies, and the dried solids were characterised by the combined use of elemental analysis, XRD and IR spectroscopy. After hydrolysis of the precursor, the dried solids exhibited the boehmitestructure, more or less crystallised whatever the C ratio when butan-1,3-diol was used whereas a formulation Al(acac)(OH)₂ was obtained when Hacac was introduced with a ratio C = 1. It has been shown that the increase in the C ratio up to 2 or 3 induces the precipitation of well-defined Al(acac)₃ particles before hydrolysis. This compound was also present in small quantities in the dried gel for C = 1. After calcination at 500°C, more or less well crystallised -alumina was obtained. Compared to those of the reference alumina, the textural parameters are strongly modified by the use of a complexing agent. Moreover, Hacac has a stronger effect than butane-1,3-diol on the textural characteristics of the support.     

m-4-m型Gemini表面活性剂对铂电极上亚甲蓝吸附溶出伏安行为的影响

在0.050 mol·L-1磷酸盐缓冲溶液(PBS)中(pH=6.4), 亚甲蓝(MB)在铂电极上于-0.2 V产生一对不明显的伏安峰. 当向溶液中加入阳离子型Gemini表面活性剂Br-C16H33N+(CH3)2-C4H8-N+(CH3)2C16H33Br-, Br-C12H25N+(CH3)2-C4H8-N+(CH3)2C12H25Br-或Br-C8H17N+(CH3)2-C4H8-N+(CH3)2C8H17Br-后, 亚甲蓝的氧化峰显著增高, 还原峰降低, 氧化还原峰峰电位均正移, 这和表面活性剂与MB在电极表面的协同吸附有关. 联接基团相同的Gemini表面活性剂, 其影响程度随烷基链的增长而逐渐增强. 增大表面活性剂的浓度, MB的氧化峰先升高后缓慢降低. 如当Br-C16H33N+(CH3)2-C4H8-N+(CH3)2C16H33Br-的浓度为15 μmol·L-1 时, 5 μmol·L-1 MB的氧化峰峰电流达到最大值. 此外,溶液pH值和富集电位等对MB及表面活性剂的吸附亦有影响.     

超临界 CO2 辅助制备 TiO2 外负载火山岩复合体及其光催化降解亚甲基蓝性能

 以钛酸丁酯为前驱体, 封堵的火山岩为载体, 通过超临界 CO₂ 辅助制备了 TiO₂ 外负载火山岩复合体, 并将其用于光催化降解亚甲基蓝反应, 考察了溶液 pH 值及催化剂浓度对反应性能的影响. 结果表明, TiO₂ 外负载火山岩复合体的光催化性能优于纯 TiO₂ 和 TiO₂ 体负载火山岩复合体. 这是由于外负载复合体对亚甲基蓝的高吸附性、小晶粒尺寸的 TiO₂ 颗粒以及吸附和光催化降解间的协同效应. 亚甲基蓝浓度为 1.5 mg/L, 溶液 pH 为 8, 催化剂浓度为 6.8 mg/L 时, 外负载 TiO₂ 火山岩复合体上亚甲基蓝降解速率最高, 且使用后的催化剂仍具有高的光催化活性.     

Influence of the Matrix in the Optical Response of Organic-Inorganic Hybrid Materials Doped with Europium(III)

Eu³⁺-doped siloxane-oxide hybrid nanocomposites have been prepared by hydrolysis and condensation of diethoxydimethylsilane (DEDMS) and different metallic alkoxides, M(OR) _n with M = Ti, Zr, Al and Ta. The luminescent properties of Eu³⁺ have been used to study the environment of the rare earth ion within the matrices. Emission spectra shows that the surrounding of the Eu³⁺ varies with the matrix composition and depends on the nature of the metal introduced as cross-linking agent. In addition, decay curves have been performed and they show different lifetime values for each system. Among the systems under investigation, the one with tantalum presents the most anisotropic surrounding and the lowest coordination number for the rare earth ion, and the one with aluminium, which shows the most symmetrical surrounding, presents a small lifetime value, probably due to the tendency of Al³⁺cation to attract and retain hydroxyl groups, responsible for luminescence quenching.