Green preparation of hollow mesoporous silica nanosphere inside-loaded gold nanoparticles and the catalytic activity

Confined Generation of Homogeneously Dispersed Au and SnO2 Nanoparticles in Layered Silicate as Synergistic Catalysts

With the aid of the confined conversion of layered silicate RUB-15, homogeneously dispersed Au and SnO₂ nanoparticles (NPs) were generated in the confined layer space of RUB-15. The Au-SnO₂/SiO₂ composite was obtained with the structure that ultrafine Au and SnO₂ NPs were supported on SiO₂ lamellas. Benefited by the Sn(II)-assisted in situ reduction strategy, Au NPs were highly uniformed and evenly distributed in/on the RUB-15. This Au-SnO₂/SiO₂ composite was employed as a catalyst to the reduction of 4-nitrophenol showing excellent catalytic activity. The catalytic rate constant at room temperature was calculated to be 6.64 min^-1, which was dramatically higher than that of Au/SiO₂ composite produced by reduction with hydrazine hydrate on the same support of layered silicate RUB-15. The interaction between Au and SnO₂ NPs increased the electron density around Au NPs, which was demonstrated to be an essential factor to the excellent catalytic activity of the Au-SnO₂/SiO₂ composite. The simple and universal synthesis method afforded precise control over the size/spatial arrangement of Au and SnO₂ NPs on SiO₂ lamellas. The high activity of the Au-SnO₂/SiO₂ composite demonstrated that the strategy used in this study has good potential application prospect. Furthermore, this work provided new perspective on the catalysis mechanism to the metal/semiconductor synergistic catalyst system.

Mesoporous Silica Nanoparticles

Integration of nanotechnology and biomedicine has offered great opportunities for the development of nanoscaled therapeutic platforms. Amongst various nanocarriers, mesoporous silica nanoparticles (MSNs) is one of the most developed and promising inorganic materials-based drug delivery system for clinical translations due to their simple composition and nanoporous structure. MSNs possess unique structural features, for example, well-defined morphology, large surface areas, uniform size, controllable structure, flexible pore volume, tunable pore sizes, extraordinarily high loading efficiency, and excellent biocompatibility. Progress in structure control and functionalization may endow MSNs with functionalities that enable medical applications of these integrated nanoparticles such as molecularly targeted drug delivery, multicomponent synergistic therapy, in vivo imaging and therapeutic capability, on-demand/stimuli-responsive drug release, etc. In this chapter, the authors overview MSNs' characteristics and the scientific efforts developed till date involving drug delivery and biomedical applications.