SPECTROSCOPIC STUDIES ON QUANTUM DOTS OF PBI2

We report the preparation of PbI2 clusters of sizes less than 30 angstrom by colloidal routes and characterization by optical absorption spectra. We show that the blue-shifted absorption spectra are not due to the presence of I3- ions, as suggested previously, but are characteristic of the clusters present. We also show that similar sized clusters form, though sparingly, on dissolving bulk PbI2 in the solvents. We establish that the stability of a large concentration of these clusters in the colloidal process is due to the presence of excess iodine ions attached to the microcrystallites.