STUDIES ON THE ADSORPTION OF ANTIBIOTICS OF THE TETRACYCLINE GROUP ONTO SULFOCATIONITES

The adsorption processes of antibiotics of the tetracyline group (ATG) by several home-made sulfocationites are studied in this paper.The results show that the adsorption may be of nonequivalent normality under certain pH condition.The adsorption mechanism is discussed with infrared spectrometry.It can be concluded that ATG can interact with sulfocationites by ion exchange mechanism or ion-transfer mechanism or both of them.     

Role of palladium in the redox electrochemistry of ferrocene monocarboxylic acid encapsulated within ORMOSIL networks

We report herein the effect of palladium on the redox electrochemistry of ferrocene monocarboxylic acid encapsulated within an organically modified sol-gel glass network (ORMOSIL). It has been found that amount of palladium and its geometrical distribution significantly alter the redox electrochemistry of FcMCA. The geometrical distribution of palladium has been controlled by two methods: (i) palladium is allowed to link within nanostructured network of the ORMOSIL which was subsequently availed from the reactivity of palladium chloride and trimethoxysilane; (ii) palladium powder is encapsulated together FcMCA thus allowing the presence of palladium within the nanoporous domain. The content of palladium is varied by controlling the reaction dynamics of palladium chloride and trimethoxysilane interaction. For this we initially allowed to trigger hydrolysis, condensation and poly-condensation of trimethoxysilane and dimethyldiethoxysilane in acidic medium and subsequently partially dried ORMOSIL film was allowed to interact with palladium chloride. Even with partially dried ORMOSIL derived from trimethoxysilane and dimethyldiethoxysilane undergoes rapid interaction with palladium chloride and the transparent color of ORMOSIL changed to a black colour due to the formation of palladium silicon linkage. The palladium-silicon linkage has been identified by NMR, UV-VIS and transmission electron spectroscopy. The electrochemistry of FcMCA encapsulated within such an ORMOSIL matrix has been studied. Excellent redox electrochemistry of ferrocene monocarboxylic acid having peak potential separation tending to 0 for a multilayered electrode was investigated. The palladium content has been found to affect the redox electrochemistry of ferrocene as well as electrocatalytic efficiency of new ORMOSIL material. The electroanalysis of NADH is reported. The modified electrode is very sensitive to NADH with lowest detection limit of < 1 microM.     

Transparent,thermally stable methyl siloxane hybrid materials using sol-gel synthesized vinyl-methyl oligosiloxane resin

Journal of Sol-Gel Science and Technology - Vinyl-methyl oligosiloxane resin was synthesized by a hydrolytic sol-gel reaction of vinyltriethoxysilane and dimethyldiethoxysilane. Hydrochloric acid...     

Synthesis of polyorganosiloxane oligomers containing terminal malonate groups

Summary Polyorganosiloxane oligomers containing terminal malonate groups have been synthesized by the co-hydrolysis of dimethylethoxysilylmethylmalonic ester and dimethyldiethoxysilane, and their properties have been described.     

Covalent grafting of organoalkoxysilanes on silica surfaces in water-rich medium as evidenced by <Superscript>29</Superscript>Si NMR

This paper addresses two questions related to functionalization of silica particles: (1) is the grafting of hydrophobic organoalkoxysilanes on a silica surface possible in water-rich medium and (2) how to prove the formation of covalent bonds with the surface? Trimethylethoxysilane, dimethyldiethoxysilane and methyltriethoxysilane have been reacted with precipitated silica in water-rich medium (water/ethanol 25/75 v/v) and ²⁹Si MAS NMR was used to answer both questions: ²⁹Si chemical shift values of the organosilicon units in the case of trimethylethoxysilane and dimethyldiethoxysilane clearly distinguished between self-condensation reactions and surface reactions through covalent bonds.     

Synthesis and characterization of hybrid borosiloxane gels as precursors for Si–B–O–C fibers

The sol–gel method has been used for the synthesis of borosilicate gels from mixtures of methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DMDES) and boric acid. The use of boric acid, B(OH)₃ allows the hydrolysis and condensation of hybrid silicon alkoxides without further addition of water or catalyst. The use of difunctional silicon units, –(CH₃)₂SiO– promote the formation, during the sol–gel process, of linear oligomers which facilitate fiber drawing before gelation. Gel characterization performed by FT-IR, XRD, TG-DTA and DCS analysis indicates the formation of a mixed network with incorporation of the boron units via =B-O-Si≡ bridges. The formation of borosiloxane bonds seems favored by the presence of DMDES. SiBOC glasses were obtained after pyrolysis of the borosilicate gels in argon atmosphere at 1000 °C. TG-DTA study indicates that the ceramic yield decreases by increasing the amount of DMDES. Gel fibers were successfully prepared from convenient partially-aged solutions by hand drawing. Pyrolysis of the obtained gel fibers under argon atmosphere at 1000 °C open the possibility to produce SiBOC homogeneous glass fibers with diameter as low as 10 μm.     

有机修饰氧化硅对抗紫外纳米ZnO的原位表面修饰

以正硅酸乙酯和二甲基二乙氧基硅烷作为共前驱体,通过溶胶-凝胶反应得到有机修饰氧化硅;用有机修饰氧化硅对碱式碳酸锌进行原位表面改性,通过对表面改性碱式碳酸锌进行热处理得到表面改性纳米ZnO;分析了表面改性纳米ZnO的结构和性能.结果表明,经有机修饰氧化硅改性处理的纳米ZnO具有强憎水性,与有机相的相容性较强,光催化活性得...     

Synthesis of Silicon Carbide Whiskers from Substituted Silicon Alkoxides and Rayon Fibres

Silicon carbide whiskers (SiC_W) were synthesized through sol-gel process by impregnating the rayon fibres with sols of methyltriethoxysilane (MTEOS), phenyltriethoxysilane (PTEOS) and dimethyldiethoxysilane (DMDEOS) and pyrolyzing the impregnated rayon fibres at 1400°C in argon atmosphere. The SiC_W synthesized through this method were needle like, straight and their aspect ratio was found to be greater than 100 except in the case where DMDEOS was used as silica source.     

Alkoxy-compounds

Seventeen previously undescribed 2-alkyl (aryl)-5-alkyl-5- -alkoxyethyl-1, 3-dioxanes have been synthesized by the reaction of 2-alkyl-2--alkoxyethylpropane-1, 3-diols with various aldehydes and ketones in presence of sulfocationites KU-1 and KU-2. Some of these compounds are active as plant growth stimulators, and are bactericidal and fungicidal. The dioxanes examined are non-toxic.For part XVI, see [5].     

Hydrocarbon dispersion of nanospherical silica by a sol–gel process. 2. Alkoxysilane copolymerization

The preparation of hydrocarbon dispersions of nanospherical silica-silicone hybrids by copolymerization of tetraethoxysilane (TEOS) and alkylethoxysilanes such as methyltriethoxysilane (MTEOS) and dimethyldiethoxysilane using a sol-gel process was investigated. Particles completely dispersible in hexane with a diameter in the range 10-24 nm were obtained by means of TEOS and MTEOS copolymerization, using ethanol or methanol as a solvent and a terminator. The solubility of the nanospheres was shown to be dependent on the molar ratio of water to silicon, the reaction time, the terminator concentration as well as the stirring condition. The hexane-dispersible particles have hydroxyl and methyl groups on the surface. A higher conversion of organophilic silica-silicon nanoparticles was attained using trimethylchlorosilane as a terminator and a water-to-silicon molar ratio close to 9.     

PREPARATION OF NANOMETER TiO2 ORGANIC SOLUTION-EFFECT OF ORGANIC SILOXANE ON SOL PROPERTIES

A homogeneous longtime stabilized transparent nanometer TiO2 organic solution was obtained by means of the simultaneous hydrolysis and co-polycodensation of tetrabutyltitanate (TBT) and methacryloxypropyltrimethoxysilane (MAPTMS) by the sol-gel process. The particle size of nanometer titanium dioxide was controlled by use of bifunctional silanes, such as diphenyldimethoxysilane (DPDMS), diphenyldiethoxysilane (DPDES) and dimethyldiethoxysilane (DMDES). The effect of TiO2 content in the solution on the refractive index of system was discussed in detail. The result shows that the refractive index of solution increases linearly with TiO2 content. The refractive index of the three hybrid nanorneter materials attained 1.6053, 1.5846 and 1.5346, respectively. The size of nanometer particles was characterized by TEM and the particle diameter thus obtained is in the range of 20-90 nm. FT-IR spectra of the materials show that the TiO-Si bond is formed.     

Proton conductivity of membranes based on the sulfocationites MSC-H and purolite CT-275

The proton conductivity properties of new heterogeneous membranes based on the sulfocationites MSC-H and Purolite CT-275, which are stable in polar media, have been studied. The specific proton conductivity of the membranes were (1–2.3)·10⁻⁴ S/cm at 75–95 °C. The value of the proton conductivity is determined by the exchange capacity of the membranes and the structure of the hydration shell of the transported proton. The latter depends on the temperature, the relative humidity, and the current intensity through the membrane. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 52–57, January–February, 2007.     

Sol–Gel Synthesis of Methyl Modified Optical Silica Coatings and Gels from DDS and TEOS

Methyl modified silica coatings and gels were prepared from dimethyldiethoxysilane and tetraethylorthosilicate via sol–gel processing and spin-coating. The as-synthesized coatings showed not only anti-reflectivity but also hydrophobicity and high laser damage thresholds compared to pure silica coatings without methyl modification. The existence of methyl groups in the framework was demonstrated by IR and NMR spectroscopy. The microstructure of the xerogels obtained were also characterized and will be discussed.     

Deformable hollow hybrid silica/siloxane colloids by emulsion templating

A procedure to obtain hollow colloidal particles has been developed using an emulsion templating technique. Monodisperse silicone oil droplets were prepared by hydrolysis and polymerization of dimethyldiethoxysilane monomer and incorporated in a solid shell using tetraethoxysilane. Hollow shells were obtained by exchange of the core. The formation of the oil droplets was investigated using static light scattering and 29Si solution NMR, and the hollow shells were characterized by electron microscopy and static light scattering. Details on the composition of the shell material were obtained from energy-dispersive X-ray analysis and 29Si solid state NMR, revealing that the shells consist of a hybrid cross-linked network of silica and siloxane units. Confocal microscopy was used to show that the shells are permeable to small dye molecules. The thickness of the coating can be easily varied from a few nanometers upward. Depending on the ratio of shell thickness to particle radius, three types of hollow shells can be distinguished depending on the way in which they buckle upon drying. We designate them as microspheres, microcapsules, and microballoons. As a result of their monodispersity, these particles can be used for making 3D-ordered materials.     

PREPARATION OF NANOMETER TiO2 ORGANIC SOLUTION —EFFECT OF ORGANIC SILOXANE ON SOL PROPERTIES*

A homogeneous longtime stabilized transparent nanometer TiO2 organic solution was obtained by means of the simultaneous hydrolysis and co-polycodensation of tetrabutyltitanate (TBT) and methacryloxypropyltrimethoxysilane (MAPTMS) by the sol-gel process. The particle size of nanometer titanium dioxide was controlled by use of bifunctional silanes, such as diphenyldimethoxysilane (DPDMS), diphenyldiethoxysilane (DPDES) and dimethyldiethoxysilane (DMDES). The effect of TiO2 content in the solution on the refractive index of system was discussed in detail. The result shows that the refractive index of solution increases linearly with TiO2 content. The refractive index of the three hybrid nanometer materials attained 1.6053, 1.5846 and 1.5346, respectively. The size of nanometer particles was characterized by TEM and the particle diameter thus obtained is in the range of 20-90 nm. FT-IR spectra of the materials show that the TiO-Si bond is formed.     

Composition, structure, and properties of pharmacologically active silicon dimethylglycerolates

¹H and ²⁹Si NMR spectroscopy showed that the product of the reaction of dimethyldiethoxysilane with glycerol in the molar ratio 1: 2 is an equilibrium mixture of dimethyldiglyceroxysilane and low-molecular-weight condensation products. The change of viscosity of silicon dimethylglycerolates, synthesized using different excesses of glycerol, versus time was studied by viscosimetry. Composition of products of hydrolysis and condensation of silicon dimethylglycerolates is determined by their concentration in the starting aqueous solutions.     

SYNTHESIS OF POLY(SILPHENYLENE-SILOXANE) THROUGH DEHYDROCARBON POLYCONDENSATION OF 1,4-BIS(DIMETHYLSILYL)BENZENE AND DIALKOXYSILANE

Poly(silphenylene-siloxane)s had been synthesized through dehydrocarbon polycondensation of 1,4- bis(dimethylsilyl)benzene(BDSB)and dialkoxysilane.The polymer composition and structure was characterized by ~(29)Si-NMR.The influence of temperature,B(C_6F_5)_3 concentration and monomer structure on the composition and the microstructure of the copolymers were investigated.It shows that elevating reaction temperature or using substrate (R'O)_2R_2R_1Si with bulk organic group of R_1 or R_2 augments the run n...     

The promoting role of silver on the supported silver salt of dodecatungstosiliticic acid in the methanol-to-hydrocarbon conversion

The conversion of methanol into light olefins has been studied using the silver salt of dodecatungstosilicic acid supported on serosil. Special attention has been paid to the process of the acid sites formation during the initial reaction period and to the role of hydrogen. The significantly higher activity and stability of the supported silver salt compared with the supported free heteropoly acid is explained by a controlled formation process of acidic sites and their additional generation from hydrogen on the metallic silver surface.     

Exergoecological analysis of processing of SO<Subscript>2</Subscript>-containing gases from zinc production

An energy and technological study of processing SO₂-containing metallurgical gases from zinc production to sulfuric acid production using the exergy method of thermodynamic analysis has bean carried out. A real operating installation since 2003 at the KCM-SA, Plovdiv, Bulgaria, has been used as the model scheme. The principal production stages have been analyzed. The absolute and the relative exergy characteristics of the separate stages as well as of the process as a whole have been calculated. The results have been used to evaluate the influence of sulfuric acid production on the environment. The results obtained have been compared with previous studies on similar processes both in zinc and in copper production. The studied installation of sulfuric acid production has good exergoecological indices, defining it as an effective process both in thermotechnical and in ecological aspects.     

A simple synthesis of ketone from carboxylic acid using tosyl chloride as an activator

An effective process for the conversion of carboxylic acid to ketone has been discovered. In this process, carboxylic acid has been activated using p-toluene sulphonyl group. Under the optimized condition, aromatic, aliphatic heteroaromatic carboxylic acids have been proved to be good substrates for this methodology. The byproduct of this reaction can be removed very easily during work up process. Also, one equivalent of organometallic reagent is sufficient to complete this transformation.