Ultrathin layer photocatalysts

A method for treating an aqueous medium with photocatalytic particles and electromagnetic radiation, the method comprising:

• immersing a plurality of photocatalytic particles into the aqueous medium with each of the photocatalytic particles having an outer layer of semiconductor material covering, at least partially, an inner layer of transparent ceramic material and having a diameter that is larger than the wavelength of the electromagnetic radiation;
• exposing the semiconductor material to the electromagnetic radiation to produce a plurality of electrons and a plurality of holes that remain confined to the photocatalyst layer;
• and
• forming a plurality of hydroxyl radicals with the plurality of electrons within the aqueous medium to initiate a plurality of treatment reactions within the aqueous medium;
• wherein the transparent ceramic material is selected from materials that have structures selected form the group consisting essentially of highly oriented crystalline, semi-crystalline, vitrified and amorphous materials;
• wherein the outer layer has a thickness of less than 5 nanometers;
• wherein the semiconductor material consists essentially of titanium dioxide, cerium dioxide or a solid solution of titanium dioxide and cerium dioxide;
• and
• wherein the photocatalyst layer and the transparent ceramic material form a particle having a specific surface area of less than 0.02 square meters per gram.