The effects of temperature and carboxylic acid ligand on the growth of nanocrystalline CdSe in a hot paraffin matrix

This paper describes the temperature and the ligand type dependence of the growth kinetics of CdSe nanoparticles synthesized by a version of the hot-matrix method. In this method the composite matrix comprises a non-coordinating solvent (liquid paraffin) and a coordinating ligand (carboxylic acid). As a Cd-precursor serves cadmium carboxylate in situ obtained from CdO and an excess amount of carboxylic acid (stearic or oleic one). The Se-precursor is tributhylphosphine selenide prepared from Se powder and tributhylphosphine (TBP) in the liquid paraffin. The temperature and the carboxylic acid type are varied maintaining constant the precursor amount and the concentration of carboxylic acid in all experiments. It is found that the radius of initial nuclei, the limiting radii of fast and slow growth and the time-constant of the fast growth depend on the temperature and the fatty acid type. The temperature dependence of the rate constant of fast (reaction limited) growth is Arrhenius type. We suppose that the observed difference in the kinetics of growth in the presence of stearic or oleic acid is due to the existence of a double bond in the oleic acid molecule on the particle surface. It leads to steric hindrance between the Cd-oleic monomer and the subsurface layer around the growing nanoparticle.