Charge separation across the silica nanoparticle/water interface

Aqueous suspensions of silica particles at high concentrations were irradia ted with a short pulse of electrons in the presence of scavengers of OH rad icals. The scavengers were chosen to minimize their adsorption on the parti cle surface. It was found that essentially no holes cross the particle/wate r interface to generate OH radicals. All of the holes that are originally g enerated by the ionizing radiation in the silica remain in the particle; ev en at the smallest size used (7-nm diameter). This is contrasted with elect rons, which were earlier shown to escape the particles into the water, even at much larger particle sizes.