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Photoluminescence (PL) from mesoporous silica (MS) with the pore size of ∼6 nm and the thickness of walls among pores of ∼1 nm has been studied at room temperature. The heat pretreatment of MS in air at different temperatures and the variation of the excitation wavelengths allow one to shift the PL peak through the whole visible spectral range. The PL is suggested to originate from nonbridging oxygens (red bands), hydrogen-related species (green bands), and water-carbonyl groups (blue bands). The spectroscopic properties of MS are found to be similar to those of surface-oxidized silicon nanocrystals and porous silicon. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]