In this study, the electrotransport, thermal and structural properties of composite solid electrolytes based on (Csub.2Hsub.5)sub.4NHSOsub.4 plastic phase and silica (1 − ...x)Etsub.4NHSOsub.4−xSiOsub.2, where x = 0.3-0.9) were investigated for the first time. The composites were prepared by mechanical mixing of silica (300 msup.2/g, Rsub.pore = 70Å) and salt with subsequent heating at temperatures near the Etsub.4NHSOsub.4 melting point. Heterogeneous doping is shown to change markedly the thermodynamic and structural parameters of the salt. It is important that, with an increase in the proportion of silica in the composites, the high-temperature disordered I4sub.1/acd phase is stabilized at room temperature, as this determines the properties of the system. Etsub.4NHSOsub.4 amorphization was also observed in the nanocomposites, with an increase in the matrix contents. The enthalpies of the endoeffects of salt melting and phase transitions (160 °C) changed more significantly than the Etsub.4NHSOsub.4 contents in the composites and completely disappeared at x = 0.9. The dependence of proton conductivity on the mole fraction reached a maximum at x = 0.8, which was three or four orders of magnitude higher than the value for pure Etsub.4NHSOsub.4, depending on the composition and the temperature. The maximum conductivity values were close to those for complete pore filling. The conductivity of the 0.2Etsub.4NHSOsub.4-0.8SiOsub.2 composite reached 7 ∗ 10sup.−3 S/cm at 220 °C and 10sup.−4 S/cm at 110 °C.
TiOsub.2/SiOsub.2 composites were synthesized via a simple sol gel method by surface reduction of Tisup.4+ ions to Tisup.3+ using titanium isopropoxide as a TiOsub.2 precursor and rice husks (RHA) as ...a SiOsub.2 source. The silica content and calcination temperature of the materials were evaluated. Thermal, crystallographic and physicochemical aspects suggest that biogenic silica (SiOsub.2) can improve the thermal stability of the anatase phase of TiOsub.2, when the SiOsub.2 content reaches 20%. The Nsub.2 adsorption-desorption isotherms showed that the SiOsub.2-modified samples have uniform pore diameters and a large specific surface area. The XPS analysis showed the surface reduction of Tisup.4+ ions to Tisup.3+ within the TiOsub.2 network via oxygen vacancies after SiOsub.2 introduction, which is beneficial for the photocatalytic reaction. Photocatalytic degradation of sodium diclofenac (SDFC) shows that TiOsub.2/SiOsub.2 composites have better activity compared to commercial P25. Mesoporous TiOsub.2 composite modified with 20 wt% SiOsub.2 showed better photocatalytic mineralization than P25 (83.7% after 2 h instead of 57.3% for P25). The excellent photocatalytic mineralization of the photocatalysts can be attributed to the high anatase crystallinity exhibited by XRD analysis, high specific surface area, surface hydroxyl groups, and the creation of oxygen vacancy, as well as the presence of Tisup.3+ ions.
Mesoporous silica of MCM-41 type with spherical morphology was modified with copper, iron, or manganese as well as pairs of these metals by template ion-exchange (TIE) method. The obtained samples ...were characterized with respect to their structure (XRD), morphology (SEM-EDS), textural parameters (low-temperature Nsub.2 sorption), surface acidity (NHsub.3-TPD), transition metal loadings (ICP-OES), their deposited forms (UV-vis DRS) and reducibility (Hsub.2-TPR). The catalytic performance of monometallic and bimetallic samples in the selective catalytic reduction of NO with ammonia (NHsub.3-SCR) was tested. The best catalytic results presented a bimetallic copper-manganese sample, which was significantly more active than the mechanical mixture of monometallic copper and manganese catalysts. The synergistic cooperation of manganese and copper species is possibly related to charge relocation between them, resulting in activation of the catalyst in oxidation of NO to NOsub.2, which is necessary for the fast NHsub.3-SCR reaction.
The aim. The aim of the research was to study the influence of excipients amount on the technological parameters of the compression mixture and tablets based on dry extract of Origanum vulgare L. ...herb using the method of random balance.
Materials and methods. Objects of the study – Origanum vulgare L. herb dry extract, 8 excipients that have been studied at two quantitative levels. The tablets were prepared by direct compression method. The formulations were designed according to the method of random balance. The technological parameters of the compression mixture and tablets based on Origanum vulgare L. herb dry extract have been studied as a function of quantitative factors: silicon, magnesium carbonate basic, dioxide magnesium aluminometasilicate (Neusilin S1®), isomalt (GalenIQ™720), F-melt® Type C (co-spray dried excipients), sucralose, berry flavor and citric acid.
Results and discussion. The increase in the amount of Neusilin S1®, GalenIQ™720 and F-melt®, and the decrease in the amount of magnesium carbonate basic and silicon dioxide improved the flowability expressed by the Hausner ratio. Results of bulk density and tapped density of the compression mixture depended on the quantities of GalenIQ™720 and F-melt®. All formulations of the prepared tablets had the rapid disintegration and ranging from 6 to 15 minutes. Resistance for crushing and friability tablets’ were improved with a decrease in the amount of silicon dioxide and increase in the amount of Neusilin S1®, F-melt® and sucralose. Higher resistance to moisture of tablets based on Origanum vulgare L. dry extract was obtained by using Neusilin S1®, F-melt® and sucralose on the upper levels.
Conclusions. The tablets based on Origanum vulgare L. herb dry extract were successfully manufactured by direct compression method. The random balance method enabled us to identify the most significant quantitative factors to optimize their composition in the tablets based on the dry extract of Origanum vulgare L. herb.
Silica–metal core–shell nanostructures Jankiewicz, B.J.; Jamiola, D.; Choma, J. ...
Advances in colloid and interface science,
01/2012, Letnik:
170, Številka:
1-2
Journal Article
Recenzirano
Silica–metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and ...biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica–noble metal core–shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica–metal core–shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core–shell nanostructures. Silica–metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed-mediated growth, where metal nanoshells are formed on the modified silica cores with deposited metal nanoparticles. This strategy assures a good control of the nanoshell thickness as well as its surface properties.
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► A brief overview of silica–metal nanostructures is presented. ► Main methods for synthesis of silica particles are reviewed. ► Surface modification of silica particles is discussed. ► Synthesis and applications of silica–metal core–shell particles are reviewed. ► Special emphasis is placed on SiO2–Au and SiO2–Ag core–shell particles.
Hetero-dimeric magnetic nanoparticles of the type Au-Fe.sub.3O.sub.4 have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis ...was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods.
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