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One-Step Synthesis of Cagelike Hollow Silica Spheres …
Certainly propagation of a combustion front through an aerogel material, assuming it is non-combustible, would be stifled due to the tortuosity of the nanoporous network. To your point regarding helium, it is true that it is in diminishing supply with some questionable economics regarding its pricing in place, however aerogels of the density and size required for your application are also currently rare. I would be concerned about having carbon-based aerogels be the matrix material for this application, as they can burn. But there are other low-density aerogels that are non-flammable and structurally sound that may be interesting candidates, for example, methyltrimethoxysilane-based silica aerogels. I’m still not convinced that the math regarding lift works out favorably, but perhaps instead of a solid aerogel sphere/form you could use a hollow form with a wall that’s a few centimeters thick–this would potentially stifle combustion from the outside of the vessel but not chock the vessel full with unnecessary weight in the form of unneeded aerogel.
Both reactions showed that the copper ions of the copper silicate structure migrated to the surface of the silica spheres during heat treatment or nitridation to form CuO and Cu3N nanoparticles, respectively. New morphologies of CuO on SiO2 and Cu3N on SiO2 composites were thus synthesized from the CuSiO3 precursor. Although the temperature during nitridation was much lower than during thermal decomposition, the obtained Cu3N nanoparticles were much larger than the CuO nanoparticles. Extraction of the Cu ions from the silicate network is apparently strongly favored when supported by a chemical reaction. Although a Cu3N nanoparticle size of 31 nm was determined from the XRD experiment, the particles appear to be much larger in the TEM micrographs. This indicates that the larger particles observed by TEM are in fact composed of smaller nanoparticles.
Synthesis of hollow silica spheres SBA-16 with large …
After the nitridation reaction of the hollow CuSiO3 spheres with ammonia at 350 °C for 1 h, hollow silica spheres with Cu3N nanoparticles on the surface were produced without losing the hollow morphology of the CuSiO3 precursor. The nanotubes on the surface of the spheres were again retained. XRD analysis of the brown product () showed the presence of cubic Cu3N nanocrystals and amorphous silica as well as complete conversion from CuSiO3 to Cu3N on SiO2. The crystallite size of Cu3N crystals was 31 nm. The BET surface area was 159 m2/g and the pore size distribution from the adsorption branch of the isotherm was centered at 3–4 nm ().
In summary, the monodisperse hollow silica spheres with controlled surface morphology are prepared via one-pot polymerization under mild condition in aqueous solution. The PS spheres are subsequently, even synchronously, ‘dissolved’ during condensation of TEOS without thermal treatment. This biomimetic “green” process is facile, cost-efficient, environmentally friendly and energy saving. It is very useful for large-scale production especially in industry applications. The effects of surface charge on the polycondensation of TEOS shed light on the nucleation mechanism of silica and give more information for the preparation of silica based materials in the future. The enhanced drug loading and release of raspberry-like hollow silica spheres indicate that they may have promising biomedical applications such as drug delivery.
Synthesis of Hollow Silica by Stöber Method with …
The influence of template solution concentration and solvent and dispersant on the formation of silica hollow spheres is studied and reported in detail.
TEM () images clearly show that the morphology of the CuO on SiO2 composite is almost the same as that of the starting CuSiO3. The high magnification TEM image revealed that CuO nanoparticles are spread on the shell of the hollow silica spheres.
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Synthesis of Hollow Silica by Stöber ..
To demonstrate the application of the unique hollow spheres in drug delivery, a peptide labelled with FITC (VTAMEPGQCG-Lys-FITC) was used as a model drug and the release profiles conducted in PBS buffer solutions were displayed in . The loading capacities of raspberry-like and smooth hollow spheres were 0.024 mg and 0.0146 mg model drug per mg of spheres, respectively. The drug release profiles () showed raspberry-like hollow silica spheres (shown in ) released more drugs than smooth surface of hollow silica spheres (shown in ) due to their larger surface area. The loading of drugs on the hollow silica spheres does not need further surface modification. The peptide can be absorbed on the surface of silica spheres by electrostatic interactions and hydrogen bonding. Because APTES has been incorporated in the silica coating on PS core and it has aminopropyl groups, the surface of the synthesized silica spheres exhibits functional hydroxyl- and amino-groups. After the raspberry-like hollow silica spheres were loaded with the FITC labeled peptide, they were also examined using a fluorescence microscope (). The green fluorescence dots confirmed the success of drug loading. Some larger dots should be aggregation of several silica spheres in the aqueous solution.
Fabrication of hollow silica–alumina composite spheres and ..
Heat treatment of the blue hollow CuSiO3 spheres at 700 °C in air led to the formation of the black CuO on the SiO2 composite through disintegration of the copper silicate. Temperatures below 700 °C did not result in the formation of CuO nanoparticles. The XRD pattern is clear evidence for the formation of monoclinic CuO nanocrystals (). The crystallite size of the CuO crystals was 10 nm. The surface area and average pore size of CuO on SiO2 was 181 m2/g and 3 nm, respectively (). The much lower surface area, compared with CuO@SiO2(A) or CuO@SiO2(B) (), is due to the different preparation method of the hollow silica spheres, where no template for mesopores, i.e. no surfactant, was involved.
Hollow silica spheres: synthesis and mechanical …
The samples were further analyzed by thermal gravimetric analysis (TGA) to verify the presence of PS cores and evaluate their removal (). The weight-loss below 300 °C is attributed to the evaporation of physically adsorbed water and residual solvent. The decomposition of PS cores is located in the region from 300 to 560 °C (), according to the TGA curve of pure PS core (). The decomposition of silica bonded groups such as –OH and/or unhydrolyzed –OR occurs at the region from 420 to 600 °C ()., The BET surface areas of raspberry-like and smooth hollow spheres were determined to be 439.53 and 311.42 m2/g respectively.
One-pot synthesis of mesoporous silica hollow spheres …
The possibility of chemically converting metal silicate nanostructures into new chemical entities offers many options for the synthesis of new functional materials. For example, Jin et al. reported the synthesis of nickel-hollow silica sphere composites by hydrogen reduction of Ni3Si2O5(OH)4 at elevated temperatures. The hollow nanospheres exhibited high catalytic activity and good selectivity in acetone hydrogenation reactions.
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