Synthesis, Structural Characterization, and Optical Spectroscopy of Close Packed CdSE Nanocrystallites

Abstract

ABSTRACTWe describe a method to synthesize optical quality thin and thick films of close packed CdSe nanocrystallites (quantum dots). The average dot size is tunable from ∼12-150 Å in diameter with ∼3.5% rms size distribution. The identity of each particle and the high monodispersity of the sample are maintained in the films as revealed by small-angle x-ray scattering, transmission electron microscopy, and optical spectroscopy. We use small-angle x-ray diffraction patterns to obtain form factors for the individual dots and to generate radial distribution functions for the densely packed films. We observe the random close packing of dots in the solid state using transmission electron microscopy. Comparing optical spectra of particles close packed in a film with those of nanocrystallites dispersed in alkanes reveals similar optical resonances in absorption while the emission lineshape is modified and its position is red shifted. Differences in film emission are consistent with electronic energy transfer between close packed dots within the inhomogeneous distribution of the sample.