The synthesis and characterization of a novel silicon-silica nanocomposite material are reported. A self-assembly method allows the encapsulation of silicon nanoclusters within the channels of a periodic mesoporous silica thin film. ne result is the formation of a silicon-silica nanocomposite film with bright, room-temperature photoluminescence in the visible range, and a nanosecond luminescence lifetime. The properties of the nanocomposite material have been studied by several analytical techniques, which collectively show the existence within the channels of non-diamondoid-structure-type silicon nanoclusters with various hydrogenated silicon sites. It is estimated that the silicon nanoclusters in the silica mesoporous films occupy up to 39 % of the accessible pore volume. The nanocomposite film shows improved resistance to air oxidation compared to crystalline silicon. The high loading and chemical stability to oxidation under ambient conditions are important advantages in terms of the development of silicon-based light-emitting diodes from this class of materials.