Charge Separation across the Silica Nanoparticle/Water Interface

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