Synthesis and characterization of poly(vinylpyrrolidone)-modified zinc oxide nanoparticles

We have synthesized highly monodisperse wurtzite ZnO nanoparticles using poly(vinylpyrrolidone) (PVP) as the capping molecules. The effect of surface modification on the size, structure, morphology, and optical properties of ZnO nanoparticles was investigated. It was found that many properties of the ZnO nanoparticles could be optimized by simply varying the molar ratio Zn(II)/PVP. The ZnO nanoparticles prepared under the optimum conditions are particularly stable, monodisperse, as well as small in size. The EXAFS result showed a structural contraction in the ZnO nanoparticles relative to the bulk. These nanoparticles exhibit distinct excitonic absorption features, markedly enhanced near-bandedge UV photoluminescence, and significantly reduced defect-induced green emission. The third-order nonlinear optical response of these PVP-capped ZnO nanoparticles in a dilute solution was found to be larger than that of the bulk ZnO by at least 2 orders of magnitude.