Bio-inspired fabrication of silver nanoparticles on nanostructured silica: characterization and application as a highly efficient hydrogenation catalystElectronic supplementary information (ESI) available. See DOI: 10.1039/c3gc40310f

The design and facile green synthesis of supported metal-engineered nanoparticles with efficient catalytic activity has significant industrial importance. A biosynthetic and ecofriendly one-step reduction strategy has been developed through the protein-mediated in vitro biosynthesis of AgNPs on the surface of nanosilica. The as-synthesized silver nanoparticles supported on nanosilica (Ag@Nanosilica) were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDXA) elemental mapping, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The spectroscopic and electron microscopic studies demonstrated that the immobilized protein on the nanosilica surface served as a reducing, capping and stabilising agent, while sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed that the three proteins of 48, 38 and 36 kDa participated in the formation of Ag@Nanosilica material. The formation mechanism of AgNPs on nanosilica explained the origin of the biomineralization of metal nanoparticles in nature. The novel reusable Ag@Nanosilica exhibited enhanced catalytic activity for the hydrogenation of a model compound, namely, 4-nitrophenol. Overall our results will help to understand metal nanoparticle formation in the Earth's crust and aid the design of "green" syntheses of novel nanoreactors. Protein-mediated in vitro biosynthesis of AgNPs on the surface of nanosilica has been developed, and the resultant AgNPs were shown to be efficient catalysts for the hydrogenation of 4-nitrophenol.