Synthesis of Uniform Disk-Shaped Copper Telluride Nanocrystals and Cation Exchange to Cadmium Telluride Quantum Disks with Stable Red Emission
journal contributionposted on 16.12.2015, 23:21 authored by Hongbo Li, Rosaria Brescia, Mauro Povia, Mirko Prato, Giovanni Bertoni, Liberato Manna, Iwan Moreels
We present the synthesis of novel disk-shaped hexagonal Cu2Te nanocrystals with a well-defined stoichiometric composition and tunable diameter and thickness. Subsequent cation exchange of Cu to Cd at high temperature (180 °C) results in highly fluorescent CdTe nanocrystals, with less than 1 mol % of residual Cu remaining in the lattice. The procedure preserves the overall disk shape, but is accompanied by a substantial reconstruction of the anion sublattice, resulting in a reorientation of the c-axis from the surface normal in Cu2Te into the disk plane in CdTe nanodisks. The synthesized CdTe nanodisks show a continuously tunable photoluminescence (PL) peak position, scaling with the thickness of the disks. The PL lifetime further confirms that the CdTe PL arises from band-edge exciton recombination; that is, no Cu-related emission is observed. On average, the recombination rate is about 25–45% faster with respect to their spherical quantum dots counterparts, opening up the possibility to enhance the emission rate at a given wavelength by controlling the nanocrystal shape. Finally, with a PL quantum efficiency of up to 36% and an enhanced PL stability under ambient conditions due to a monolayer of CdS formed on the nanocrystal surface during cation exchange, these flat quantum disks form an interesting enrichment to the current family of highly fluorescent, shape-controlled nanocrystals.
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emission rateCdTe PLSubsequent cation exchangeambient conditionsrecombination ratecation exchangeCdTe nanodisks showstoichiometric compositionanion sublatticePL stabilitythicknessPL quantum efficiencyCu 2Tetunable diameterCdTe nanodisksquantum dots counterpartsStable Red EmissionWedisk shapeCadmium Telluride Quantum Disksnanocrystal shapePL lifetimedisk planequantum disks formtunable photoluminescencenanocrystal surfaceCdTe nanocrystalsCation Exchangepeak positionCu 2Te nanocrystals