Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties

We report the preparation of highly monodisperse ZnO nanoparticles using po ly(vinyl pyrrolidone) (PVP) as the capping molecules. The surface-modified ZnO nanoparticles were found to be remarkably stable. The optical absorptio n shows distinct excitonic features. Markedly enhanced near-band-edge ultra violet photoluminescence and significantly reduced defect-related green emi ssion were also observed. We attribute this observation to the nearly perfe ct surface passivation of the ZnO nanoparticles by the PVP molecules. The t hird-order nonlinear optical response of these PVP-capped ZnO nanoparticles in a dilute solution was found to be significantly larger (by at least two orders of magnitude) than that of the bulk ZnO. (C) 2000 American Institut e of Physics. [S0003-6951(00)00420-4].