Factors affecting the size of polymer stabilized Pd nanoparticles

A consistent and reproducible one-step method for the preparation of Pd nanoparticles of mean sizes varying from 1.5 to 15 nm with relative standard deviation of <0.5 is reported. We have shown that the particle size can be controlled by changing the concentrations of the stabilizing polymer (PVP) and precursor salt, the nature of the reducing agent, the reduction temperature, average molecular weight of the stabilizing polymer as well as the initial pH of the solution. Lower reducing temperature and higher pH lead to the formation of smaller particles. Different molecular weights of the PVP have no significant effect on the particle size. It is inferred that the relative nucleation and crystal growth rate are the decisive factors in determination of the particle size and dispersion. Interestingly, the larger Pd nanoparticles show well-defined morphology and shape, which has only recently been reported by us for this colloidal particle unsupported on solid surface.