Characterization of silicon nanocrystals and photoluminescence quenching in solution

Weblike aggregates of coalesced Si nanocrystals are prepared by the Laser V aporization-Controlled Condensation (LVCC) method. Upon excitation with vis ible or UV light, the Si nanocrystals show red photoluminescence whose mult iexponential time decays are characterized by lifetimes that range from 20 - 80 mu s, depending on the emission wavelength. This red emission can be q uenched with electron acceptors like 1,4-dinitrobenzene and WO3 nanoparticl es. The quenching rate constants obtained from a Stern-Volmer analysis are 7.65 x 10(6) (Ms)(-1) and 14.1 x 10(6) (Ms)(-1) for 1,4-dinitrobenzene and WO3 nanoparticles, respectively. The quenching mechanism appears to proceed via an electron transfer from the CB band of the Si nanocrystals to the qu enchers. (C)1999 Acta Metallurgica Inc.