A Library of Selenourea Precursors to PbSe Nanocrystals with Size Distributions near the Homogeneous Limit

摘要

We report a tunable library of N,N,N'-trisub-stituted selenourea precursors and their reaction with lead oleate at 60—150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields. Single exponential conversion kinetics can be tailored over 4 orders of magnitude by adjusting the selenourea structure. The wide range of conversion reactivity allows the extent of nucleation ([nanocrystal] = 4.6—56.7 μM) and the size following complete precursor conversion (d = 1.7-6.6 nm) to be controlled. Narrow size distributions (б = 0.5— 2%) are obtained whose spectral line widths are dominated (73—83%) by the intrinsic single particle spectral broadening, as observed using spectral hole burning measurements. The intrinsic broadening decreases with increasing size (fwhm = 320—65 meV, d = 1.6—4.4 nm) that derives from exciton fine structure and exciton—phonon coupling rather than broadening caused by the size distribution.