Exposure of photoluminescent porous Si to alkyllithium reagents results in grafting of the alkyl group to the silicon surface by formation of a Si-C bond. The reaction is proposed to proceed by addition of the alkyllithium reagent across a surface Si-Si bond, forming Si-alkyl and Si-Li surface species. The highly reactive Si-Li surface group is readily hydrolyzed by water, resulting in significant surface oxidation. The surface-bound Li can also be replaced with acyl or methyl groups by addition of acetyl chloride, heptanoyl chloride, 4-butylbenzoyl chloride, 3-(chloromethyl)benzoyl chloride, 3-chloropropionyl chloride, or methyl trifluoromethanesulfonate. The acylation or alkylation steps preclude surface oxidation. In all cases, the intensity of photoluminescence from the porous Si samples is reduced after functionalization.