Synthesis and optical spectroscopy of a hybrid cadmium sulfide-dendrimer nanocomposite

Hybrid nanocomposites of cadmium sulfide (CdS) quantum dots and poly(propyleneimine) dendrimer having a 1,4-diaminobutane core have been produced by colloidal synthesis in degassed methanol at room temperature using third-, fourth-, and fifth-generation (G5.0) dendrimers, and their spectroscopic properties have been investigated. The nanoparticles fluoresced from 375 to 650 nm under near-ultraviolet excitation, and their absorption spectra exhibited a strong blueshift of the band edge compared to that of the bulk CdS. The stability of nanocomposites depended significantly, while the size and spectroscopic properties exhibited a weaker dependence, on the dendrimer generation. Most compact and stable nanoparticles were obtained with G5.0 dendrimers. Average diameter was estimated to be 2.2 +/- 0.3 nm, assuming nanoparticles of spherical shape within an infinite well potential. The room-temperature luminescence has a fast component with 165 +/- 5 ps lifetime and a slow component with a 40 +/- 2 ns lifetime. The luminescence is partially polarized with an initial anisotropy of 0.39 +/- 0.02. (C) 2007 Optical Society of America.