Activation of CdS nanoparticles by metallic ions and their selective interactions with PAMAM dendrimers

CdS nanoparticles (NPs) in colloidal dispersion were activated by metallic ions [Mn(II) and Cu(II)], employing a simple method under mild conditions. These metallic ions on the surface of the CdS NPs quench the red-shifted defect emission, and efficiently promote near band gap emission; they also enhance the photo stability and dispersability of the suspensions. Taking advantage of the chemical affinity of Mn(II) and Cu(II) for the CdS surface, we carried out a study of the interaction between [CdS-M(II) _n ] NPs and polyamidoamine dendrimers of 1 and 2.5 generations (G₁=8 amino, and G_2.5=32 carboxylic end-groups, respectively). The strong interaction between these two chemical species results in the formation of new [CdS-M(II) _n G _n ] nanocomposites. All colloidal systems were monitored by UV-visible electronic absorption and emission spectroscopies, and electronic paramagnetic resonance. The crystal structures of the nanocomposites, as well as their average diameters (2.0–3.3 nm), were determined by high-resolution transmission electron microscopy images.