[[abstract]]We have obtained nanometer sized silicon remnants sequestered in glass matrices by terminating the reaction of pure silicon powders dispersed in the viscous melt at a temperature of 1400 °C. Repeated use of this truncated melt‐particle reaction process dilutes the amount and size of silicon remnants, and bulk samples containing nanosize silicon crystallites embedded in a glass matrix were eventually obtained. These quantum dot sized silicon‐in‐glass materials emit greenish luminescence with peak wavelengths from ≊480 to 530 nm, considerably shorter than the reddish luminescence (at about 700–850 nm) observed in porous silicon structures prepared by electrochemical etching techniques; upon complete digestion of Si particles by the melt, the luminescence peaks disappear. Since our silicon‐in‐glass preparation method does not involve etching, the origin of the luminescence is not likely to be due to Si‐O‐H compounds (e.g., siloxene) postulated recently. The location of the luminescence peaks and the observed silicon crystallite size suggest quantum confinement leading to a widened silicon band gap arising from remnants in the glass matrix smaller than the exciton diameter of bulk silicon (10 nm)
