Palladium nanoparticles on silica-rich substrates by spontaneous reduction at room temperature

Metallic palladium nanoparticles (< 5 nm) have been spontaneously obtained from an acid solution of palladium chloride salt on silica-rich substrates (sepiolite, microfibrous silica, fumed silica, and milled silica glass) without any additional reduction treatment. Variable proportions of metallic palladium were straightforwardly obtained, depending on the nature of the substrate. The presence of a large amount of silanol groups acting as nucleation centers, seem to be a requisite to obtain small Pd nanoparticles. Additionally, an absorbance maximum associated to a surface plasmon resonance corresponding to the spherical particles of metallic palladium has been identified at a wavelength of 238 nm. The large specific surface of the employed substrates with the palladium nanoparticles suggest that these materials could be used for gas catalysis.