Hydrogenated amorphous silicon-containing colloids or composite colloids have a silicon-containing shell which surrounds the hollow colloids or composite colloids. The colloids have a spherical geometry. The silicon-containing composite colloids have a spherical geometry and a diameter of between 2 nm and 7 nm in scanning electron micrographs, and the silicon-containing colloids have a spherical geometry with a cavity and a diameter of between 50 and 200 nm in scanning transmission electron micrographs. The cavity is surrounded by a shell with a thickness of between 3 and 10 nm.