Photochemical reaction of vitamin C with silicon nanocrystals: polymerization, hydrolysis and photoluminescence

In this paper, we report on the photochemical reaction of silicon nanocrystals (SiNCs), released from porous silicon (pSi), with L-ascorbic acid (vitamin C, VC) under 254 nm irradiation. Surface-localized positive charges (holes) are proposed to initiate the polymerization of VC in ethanol under UV irradiation. There is no charge transfer from the reducing carbohydrate of VC to SiNCs; the polymerization arises directly from VC rather than from its oxidized product dehydroascorbic acid (DHA). The SiNCs are embedded in the polymer matrix, which preserves their bright photoluminescence (PL). Hydrolysis of the polymer yielded water-dispersible and highly luminescent SiNCs. pH and photostability studies of the SiNC aqueous dispersion indicated that SiNCs were sensitive to basic solutions due to proton-gated emission and to UV (365 nm) irradiation due to enhanced photoblinking. The resulting SiNC/polymer composite may find potential applications in biology and optoelectronic fields.