On the nucleation and growth kinetics of PbSe magic-sized clusters

Pranshu Puri and Chenjie Zeng

University of Florida

Magic-sized clusters (MSCs) gained significant interest in the recent decade due to their exceptional stability, size, and shape controllability with atomic precision. The study of nucleation and stepwise growth kinetics of PbSe MSCs remained unexplored to date due to a lack of precise control in their evolution. Herein, we report systematic in-situ UV-vis-NIR studies under different reaction conditions, including solvent, reactants concentration, and temperature, for the identification of critical parameters for the precise evolution of PbSe MSCs. Having precision in evolution provides us with detailed insights about changes in peak position (size of MSC), absorbance at peak position (concentration of specific MSC), and absorbance at 400 nm (concentration of PbSe monomers) during the reaction. Furthermore, the bulk synthesis of eight PbSe MSCs was successfully performed, and they were isolated using appropriate anti-solvents in their indigenous form. The powder X-ray diffraction (PXRD) technique was employed to estimate the sizes of each MSC, which shows that the core diameters of MSCs range from 1 nm to 3 nm. A continuous trend of increasing FWHM for {111}, {200}, and {220} PXRD spectrum peaks with decreasing the size of clusters demonstrates the existence of confinement effects along the series of MSCs. Thus, it was demonstrated that a perpetual supply of monomers is required for the transformation of one PbSe MSC to the next in the series.