Characterization of Ag nanoparticles on Si wafer prepared using Tollen's reagent and acid-etching

Ag nanoparticles on SiO₂/Si surfaces synthesized using the Tollen's reagent and a subsequent acid-etching were characterized using X-ray photoelectron spectroscopy (XPS). Combining the reduction of the Tollen's reagent and the chemical etching, one can create naked Ag nanoparticles with various sizes in the size range below ∼10 nanometers (nm). The reduced particle size by the chemical etching was identified using positive core level shifts with increasing etching time. Ag nanoparticles smaller than ∼3 nm undergo a reversible oxidation and reduction cycle by reacting with H₂O₂/H₂O and a subsequent heating under vacuum to 150 °C, which was not found for the bulk counterparts and larger particles, demonstrating unique chemical properties of nanoparticles compared to the bulk counterparts.