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A new protocol for constructing sandwich-like SiO 2 -Ag@TiO 2 hollow spheres (SAT) is introduced, in which SiO 2 acts as an efficient support for the Ag nanoparticles (Ag NPs) immobilization, while TiO 2 maintains its hierarchical structure and prevents the aggregation of Ag NPs during the photocatalytic reaction. As a photocatalytic agent, the inner and outer surfaces of TiO 2 can be fully occupied by pollutants molecules because of its unique structure, which faster boosts the photo-generated electrons to transfer the substrates, leading to an enhanced photocatalytic performance. Compared with Ag NPs deposited on the surface of SiO 2 @TiO 2 (STA), the as-synthesized SAT exhibits a markedly enhanced visible-light and UV light activity than STA for degrading tetracycline and traditional dyes. The excellent photocatalytic performances are ascribed to the enhanced transport paths of photo-generated electrons, reduced recombination probability of e − /h + pairs, and decreased threat of oxidation and corrosion. Especially, the SAT still maintains its photocatalytic efficiency after five consecutive runs even though the sample is recovered under visible-light irradiation, far beyond the reusability of STA under the same conditions. Therefore, the outstanding photocatalytic activity and excellent recyclability make SAT more potential to purify aquatic contaminants and to meet the demands of future environmental issues. [ABSTRACT FROM AUTHOR]

Ongoing research activities are targeted to explore high photocatalytic activity of TiO 2 -based photocatalysts for the degradation of environmental contaminants under UV and visible light irradiation. In this work, we devise a facile, cost-effective technique to in situ synthesize hierarchical SiO 2 @C-doped TiO 2 (SCT) hollow spheres for the first time. This strategy mainly contains the preparation of monodisperse cationic polystyrene spheres (CPS), sequential deposition of inner SiO 2 , the preparation of the sandwich-like CPS@SiO 2 @CPS particles, and formation of outer TiO 2 . After the one-step removal of CPS templates by calcination at 450 °C, hierarchical SiO 2 @C-doped TiO 2 hollow spheres are in situ prepared. The morphology, hierarchical structure, and properties of SCT photocatalyst were characterized by TEM. SEM, STEM Mapping, BET, XRD, UV–vis spectroscopy, and XPS. Results strongly confirm the carbon doping in the outer TiO 2 lattice of SCT hollow spheres. When the as-synthesized SCT hollow spheres were employed as a photocatalyst for the degradation of Rhodamine B under visible-light and ultraviolet irradiation, the SCT photocatalyst exhibits a higher photocatalytic activity than commercial P25, effectively overcoming the limitations of poorer UV activity for many previous reported TiO 2 -based photocatalysts due to doping. [ABSTRACT FROM AUTHOR]

Abstract: Hollow silica spheres with round mesoporous shells were synthesized by core–shell template method, using monodispersed cationic polystyrene particles as core, and TEOS (tetraethoxysilane) as the silica source to form shell. After calcination at 550°C, uniform spheres with a thin shell of silica and hollow interior structures. Transmission electron microscopy results showed that the size of the spheres is about 700nm in diameter with narrow distribution. In addition, the spheres have a high surface area of 183m2/g. The spheres were subsequently used as silver-loading substrates and the silver loaded spheres were tested in antimicrobial study against gram negative bacteria Eschrichia coli in vitro. The hollow silica–Ag spheres proved significantly higher antibacterial efficacy against E. coli as compared to that of the common silica–Ag particles. [Copyright &y& Elsevier]

Silica-based porous materials are popular adsorbents and have achieved marked success. However, one of the main challenges is surface functionalization for obtaining better removal performances. Therefore, in this paper we developed a hollow silica adsorbent with a well-defined morphology via a sodium silicate route. Compared with the conventional silica-based porous adsorbents prepared by the modified Stöber method, the synthesized hollow silica support exhibits many advantages such as low-cost silica source, and using only industrial commodities as starting materials and water as solvent. Excitedly, the resulting matrix can be used as a powerful separation tool to deal with environmental pollution because it is easy to separate from wastewater simply by centrifugation without any modification. The experimental results of absorption and separation on the neutral red indicate that low-cost hollow silica supports can evidently increase dye loading and decrease the rate of dye desorbed in comparison to conventional hollow silica adsorbents obtained via the Stöber method. We exhibit the first example of constructing high ordered macroporous silica adsorbent by using a low-cost silica source. This silica-based macroporous material can be useful as a powerful separation tool to deal with environmental pollution because it is easy to separate simply by centrifugation without any modification. Interestingly, the absorption and separation for neutral red show that it can increase absorbent amount of dye and decrease the rate of dye desorbed in comparison to conventional hollow silica obtained via the Stöber method. [ABSTRACT FROM AUTHOR]

The preparation of hollow silica spheres via the sodium silicate route presents many advantages such as a low-cost silica source, and an environmentally friendly reaction system. Unfortunately, it is extremely hard to prepare the well-defined hollow silica spheres by using sodium silicate as the silica source owing to its rapid, disordered precipitation under the acid catalysis. As a result, we, in this paper, report a facile, economic, one-pot pathway for preparation of the ordered hollow silica spheres by employing a sodium silicate precursor. In this approach, the cationic polystyrene (CPS) templates can be first prepared via emulsifier-free emulsion polymerization by using the cationic monomer vinylbenzyltrimethylammonium chloride, then, the silica shells were attached on the surfaces of CPS particles via electrostatic interaction, finally CPS particles were in situ dissolved and removed by adding toluene to create ordered hollow silica spheres. Some modern techniques and instruments, including the transmission electron microscope, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller theory were employed to monitor and characterize the resulting hollow silica spheres. [ABSTRACT FROM AUTHOR]