Naked Gold Nanoparticles: Synthesis, Characterization, Catalytic Hydrogen Evolution, and SERS

We describe the synthesis of gold nanoparticles upon reduction of Au2O3 by molecular hydrogen. The reaction generates particles that contain no foreign stabilizer other than gold or water species. The reaction readily proceeds at slightly elevated temperatures and somewhat higher than atmospheric pressure of H-2, and these two parameters control the size of the particles produced. The suspensions of particles were analyzed for particle size, size distribution, residual ions, and metal-atom concentrations using TEM, dynamic light scattering, electrophoretic mobility, pH, conductivity, ICP, and UV-vis spectra. The particles were shown to be highly active redox catalysts in the conversion of strongly reducing radicals to hydrogen from water in basic solutions. Surface-enhanced Raman scattering (SERS) spectra of a probe molecule, p-aminothiphenol, adsorbed on the particles surface was determined, and the effects of pH, electron injection, and Au(III) ions on the SERS spectra were measured. These effects are compared with similar results from previously prepared silver particles in an analogous procedure.