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YURI D. GLINKA, SHENG-HSIEN LIN AND YIT-TSONG CHEN, Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, and Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan.
Dispersed photoluminescence (PL) spectra of silica (SiO2) nanoparticles induced by ArF (193 nm) and Nd:YAG (266 nm) lasers have been observed. PL measurements from the composites of silica nanoparticles (the primary particle size 7 and 15 nm) as a function of heat-treatment temperature show that the PL results from hydrogen-related species and thermally produced structural defects. The green PL exhibits a progression with spacings of
630 cm-1 assigned to the bending vibration of 
Si-H on the surface of particles. The spacings increase up to
1200 cm-1 when Si-H and non-bridging oxygen (Si-O·) form interfacial water species. The two-photon (TP) induced PL with an ArF laser excitation has also been studied. The TP-produced excitons can result in a self-trapped exciton recombination (blue band), surface hydrogen-related centers (green band) and bulk non-bridging oxygen hole centers (red band). Relaxation of free TP-produced excitons and energy transfer of the excitons to the surface and bulk defects will be discussed.