Synthesis and characterization of CdS nanoparticles stabilized by double-hydrophilic block copolymers

A novel and simple preparation method for single monodisperse CdS nanoparticles with controllable size and stability against oxidation is presented. Double-hydrophilic block copolymers consisting of a solvating poly(ethylene glycol) PEG block and a poly(ethylene imine) PEI binding block have been used as effective stabilizers for the solution synthesis of high-quality US nanoparticles in water and methanol. Absorption, fluorescence spectroscopy, and transmission electron microscopy were employed for characterization, which revealed that the prepared CdS nanoparticles had a well-resolved cubic structure and were monodisperse in size. It was also found that the US nanoparticles; were dispersed in solution as single entities and showed a very good resistance against oxidation for months, according to their polymer shell. The particle size was controllable in the range between 2 and 4 nm by adjusting the polymer concentration and choice of the solvent.