Photoinduced Agn0 cluster deposition: Photoreduction of Ag+ ions on a TiO2-coated quartz crystal microbalance monitored in real time

The extent of photoreduction of a metal ion, such as Ag+, occurring on the TiO2 particle surface was monitored in real time in the presence of hole scavengers methanol and ethanol by the quartz crystal microbalance (QCM) technique. Silver cluster deposition on metal-oxide particles that accompanies electron transfer from TiO2 to Ag+(ads) depends on the surface charge of the particles, which also influences the close approach of Ag+ ions to the particle surface. Formaldehyde and acetaldehyde produced, respectively, as intermediates during silver deposition in the presence of the alcohols contributed negligibly to the mass of silver deposited on the TiO2 surface. The QCM technique provides a means to monitor photoadsorption.