Structural Origin of Visible Luminescence from Silica Based Organic-Inorganic Hybrid Materials

We synthesized a series of n-octadecylsiloxanes having different empirical formulas, that is, R-SiO3/2 (R = C18H37), R-(CH3)SiO2/2, and R-(CH3)(2)SiO1/2. We found that the compound with the formula R-SiO3/2 shows the highest PL emission with a quantum yield of 19 +/- 0.5%, whereas the compound with the formula R-(CH3)(2)SiO1/2 hardly shows the PL output. The present results clearly demonstrate that carbon-related species are not responsible for the PL; rather, the PL emission results from some silicon/oxygen-related defect species. On the basis of the present experimental findings, a structural origin of the PL from silica based organic-inorganic hybrid materials is proposed.