Core-Shell Cadmium Telluride Quantum Platelets with Absorptions Spanning the Visible Spectrum

CdS and CdSe shells are deposited on wurtzite CdTe quantum platelets (nanoplatelets) by exchanging the initial primary-amine ligation to Cd(OAc)(2) ligation, with subsequent reaction of the Cd(OAc)(2) ligand shell and thiourea or selenourea, respectively. Shell deposition is conducted in a cyclic manner, with 0.21-0.34 monolayers of CdS and 0.99-1.20 monolayers of CdSe being deposited in each cycle. The CdTe quantum platelets having an initial thickness of 1.9 nm are converted to CdTe-CdS and CdTe-CdSe core-shell quantum platelets having maximum thicknesses of 3.0 and 6.3 nm, respectively. The morphologies and wurtzite structure of the initial CdTe quantum platelets are retained upon shell deposition. The absorption spectrum of the CdTe quantum platelets is progressively shifted to lower energy with increasing shell thickness, across the entire visible spectrum. The spectral shifts observed scale with the inverse square of the total core-shell thickness.