Adsorption and chemisorption of galactose oxidase on silica surface

Experience accumulated over a number of years in developing of methods of immobilization of galactose oxidase from Fusarium graminearum on parent and modified silica matrices is analyzed. Sturdy adsorption of galactose oxidase on silica surface was observed, such heterogeneous specimens possessed by enhanced biocatalyst stability and activity as compared with enzyme solutions. Covalent immobilization of galactose oxidase was carried out on the amine-containing silicas activated by 2,4-tolylene diisocyanate and cyanuric chloride. It was also shown that in the presence of the substrate (galactose) enzyme chemisorption takes place on the surface on aminecontaining silica matrices. Immobilized preparations were successfully applied for analytical determination of galactose-containing carbohydrates (galactose, lactose, raffinose) in complex mixtures

Carbon Nanoparticles Prepared from Household Waste

The presented paper is concerning the influence of the coffee cake carbonisation condition on the car-bon structure and surface chemical composition. For these the results of some additional measurements, i.e. thermogravimetry, FTIR, etc. are reported, to expose the type of carbon surface groups created by car-bonisation. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3515

Nanocomposites Based on Chitozan and Carbon Nanotubers with Iron Oxides Formed by in situ Precipitation

Composites which contain iron oxide nanoparticles and unmodified or aminated silica were synthesised by in situ precipitation of ferrous salts in chitozan or glucose solution. Nanocomposites based on oxidized or aminated carbon nanotubers were obtained by immobilizing oxide nanoparticles in surface layer during salt precipitation in water dispersion. The metal-containing phase was obtained by the Elmore reaction using different ratios of ferrous ammonium sulfate hexahydrate (FeSO4∙(NH4)2SO4∙6H2O) and ferric chloride hexahydrate (FeCl3∙6H2O). The composites obtained were characterized using FTIR spectroscopy. In addition for selected samples XRD, DSC, and specific surface area measurements were carry out. The analysis results indicate that in situ co-precipitation of iron oxide precursors in chitosan or glucose allows producing Fe3O4 particles with the average size ca. 5-7 nm. The presence of silica leads to particles size decrease which can be controlled, along with iron oxide particles location, by changing the silica surface functional ity. Characteristics and location of iron oxide nanoparticles in nanotubers modified layer are strongly depended from nature of the groups attached to surface. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3536

Особливості хемосорбції диметилкарбонату поверхнею кремнезему

This paper presents the results of studies of dimethyl carbonate interaction with sites of the fumed silica surface. The investigations were performed in a vacuum quartz cuvette using IR spectroscopy method. Chemical interaction of dimethyl carbonate with sites of the dehydrated silica surface was shown to occur at temperature of 200 °C and higher, chemisorption processes take place involving both structural silanol groups and siloxane bridges on the surface.Наведено результати досліджень взаємодії диметилкарбонату з центрами поверхні пірогенного кремнезему, проведених у вакуумній кварцовій кюветі із застосуванням методу ІЧ-спектроскопії. Встановлено, що хімічна взаємодія диметилкарбонату з центрами поверхні дегідратованого кремнезему інтенсивно проходить при підвищенні температури до 200 °С, а процеси хемосорбції відбуваються як по структурним силанольним групам, так і по силоксановим місткам поверхні

Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas

Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM-41 type and bimodal porous materials was studied

Multiband light emission and nanoscale chemical analyses of carbonized fumed silica

Fumed silica with a specific area of 295 m(2)/g was carbonized by successive phenyltrimethoxysilane treatments followed by annealing in inert atmosphere up to 650 degrees C. Emission, excitation, kinetics, and photo-induced bleaching effects were investigated by steady state and time-resolved photoluminescence spectroscopies. The local chemistry was also studied by infrared transmission spectroscopy. Strong ultraviolet and visible photoluminescence was observed in the samples after the chemical treatments/modifications and thermal annealing. It has been shown that ultraviolet photoluminescence in chemically modified fumed silica is associated with phenyl groups, while near ultraviolet and visible emission in annealed samples originated from inorganic pyrolytic carbon precipitates dispersed in the silica host matrix. Two types of emission bands were identified as a function of the annealing temperature: one is in the near UV and the other is in the visible range. Based on the emission/excitation analysis of these two bands, as well as on correlations with the synthesis conditions, a structural-energy concept of light-emitting centers has been proposed. According to this model, the light-emitting centers are associated with carbon clusters that can be bonded or adsorbed on the silica surface. This has been validated by a detailed (S)TEM-electron energy-loss spectroscopy study, confirming the inhomogeneous distribution of nanoscale carbon precipitates at the surface of the silica nanoparticles. These carbon precipitates are mostly amorphous although they possess some degree of graphitization and local order. Finally, the fraction of sp(2) carbon in these nanoclusters has been estimated to be close to 80%. Published by AIP Publishing

Inorganic anion exchanger based on silica with grafted polyhexamethyleneguanidine hydrochloride

Polyhexamethyleneguanidine hydrochloride has been chemically anchored on the surface of amino-containing silica gel preliminarily activated with cyanuric chloride. The possibility of application of the modified adsorbent for extraction and preconcentration V(V), Mo(VI), W(VI) and Cr(VI) anionic forms in acidic media has been demonstrated. Methods of sorption-X-ray fluorescence and sorption-photometric determination of microquantities of these metal-containing anions have been elaborated.Здійснено хімічне закріплення полігексаметиленгуанідинхлориду на поверхні аміновмісного силікагелю, попередньо активованого хлористим ціануром. Показано можливість використання модифікованого адсорбенту для вилучення та передконцентрування аніонних форм V(V), Mo(VI), W(VI) та Cr(VI) у кислотному середовищі, що дозволило розробити методики сорбційно-рентгенофлуоресцентного та сорбційно-фотометричного методів аналізу мікрокількостей металовмісних аніонів.Проведено химическое закрепление гидрохлорида полигексаметиленгуанидина на поверхности аминосодержащего силикагеля, предварительно активированного хлористым циануром. Показана возможность использования модифицированного адсорбента для удаления и предконцентрирования анионных форм V(V), Mo(VI), W(VI) и Cr(VI) в кислой среде, что позволило разработать методику сорбционно-рентгенофлуоресцентного и сорбционно-фотометрического анализа микроколичеств металлосодержащих анионов