Spectroscopic studies on quantum dots of PbI₂

Abstract

We report the preparation of PbI₂ clusters of sizes less than 30 Å by colloidal routes and characterization by optical absorption spectra. We show that the blue-shifted absorption spectra are not due to the presence of I⁻₃ 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.