Stability in Air of Silver and Silver Oxide Nanoparticle Shells Deposited Over Silica Spheres Without Using Coupling Agents

The deposition of silver nanoparticles on the surface of silica was carried out using our simple, robust and rapid chemical method without surface modification of silica or added coupling agents. The process was carried out at room temperature using water/methanol mixtures, tetraethyl orthosilicate as Si source and silver nanoparticles (NPs) in a single-pot reaction. Using EDS, XRD, HRTEM and High Angle Annular Dark Field (HAADF) STEM characterization techniques, we have found the coexistence of silver NPs and silver oxides NPs anchored to the surface of sub-micron silica spheres, with Ag NPs predominating sizes around 2-3 nm approximately, and Ag2O NPs sizes over 10 nm.