Semiconductor Nanoparticles in Contact: Quenching of the Photoluminescence from Silicon Nanocrystals by WO3 Nanoparticles Suspended in Solution

Weblike aggregates of Si nanocrystals and tungsten oxide nanoparticles are produced by a laser vaporization controlled condensation technique. XRD, FTIR, and Raman results confirm that the Si nanoparticles have a diamond-like crystalline structure and WO 3 nanoparticles exhibit a monoclinic crystalline structure. Due to the quantum size effect, the band gaps of Si nanocrystals and WO 3 nanoparticles shift to higher energies by 0.68 and 0.55 eV, respectively, from the bulk values. The red emission of Si nanocrystals is quenched by adding successive amounts of the WO 3 nanoparticles to Si nanoparticles suspended in a methanol solution. The quenching follows Stern−Volmer kinetics and the quenching rate constants are 14.1 × 10 6 and 3.2 × 10 6 (Ms) -1 for WO 3 and W 2 O 5, respectively. The quenching mechanism is explained by an electron transfer from the CB of the Si to the CB of the WO 3 nanoparticles.