White Photoluminescence from Carbon-Incorporated Silica Fabricated from Rice Husk

White photoluminescence (PL) from thermally treated rice husk is demonstrated. The strongest PL is obtained after oxidation at 400 °C following carbonization at 600 °C. The PL intensity was strong enough to be detected by the naked eye in daylight under the irradiation of 370 nm light from a light-emitting-diode (LED)-type flashlight. Thermal treatment changes rice husk to silicon oxycarbide but the amorphous structure and cell-wall architecture of the plants are maintained. The origin of PL is speculated to be related to some centers or defects in strained silicon oxycarbide.