Nanosynthesis Techniques of Silica-Coated Nanostructures

Core-shell nanomaterials are fast-emerging hybrid nanocomposites in area of nanotechnology, materials science and biochemistry, which are fast attracting research attention. Nanostructured nanomaterials are utilized in wide industry fields such as electronics, biopharmaceutical, biomedicine, optics and biocatalysis. Owing to the additional exterior shell-coating material, the primary core material’s functionality, biocompatibility, chemical stability and colloidal dispersibility can be greatly enhanced. Silica, in particular, is found to be an excellent exterior shell-coating material, has been widely researched for the synthesis of core-shell nanocomposite materials. So far, there have been numerous publications devoted to silica-coating techniques using hydrophobic silanes, such as tetraethylorthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), via the classic Stober method. Recently, there has been strong interest in the use of water-soluble silanes such as MPTMS (3-(mercaptopropyl)-trimethoxysilane), MPTES (3-(mercaptopropyl-triethoxysilane), MTMS (3-(methyltrimethoxysilane)) and sodium silicate for water-based silica-coating techniques have gained much attention, due to the fast-growing need to focus on process simplicity, large-scale fabrication and environmental-friendly synthesis techniques of silica-based core-shell nanomaterials. Hence, this chapter focuses on the recent development on silica-coating techniques for colloidal nanoparticles, particularly on water-based techniques and morphologies. In summary, we emphasize the importance of advanced nanomaterials in today’s world and envisage there will be more breakthrough research on aqueous silica-coating techniques for silica-encapsulated core-shell nanomaterials.