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Synthesis and Surface Chemistry of Cadmium Carboxylate Passivated CdTe Nanocrystals from Cadmium bis(Phenyltellurolate)

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journal contribution
posted on 12.01.2016, 00:00 by Michael P. Campos, Jonathan S. Owen
We report the synthesis of cadmium telluride nanocrystals from cadmium bis(phenyltellurolate) (Cd­(TePh)2) and cadmium alkylcarboxylates (Cd­(O2CR)2, O2CR = oleate, tetradecanoate). Cd­(TePh)2 reacts quantitatively with Cd­(O2CR)2 at 220 °C over 1 h with the concomitant elimination of diphenyl telluride (Ph2Te) and CdTe nanocrystals. The nanocrystal diameter approaches 3.0–3.2 nm at full conversion regardless of changes to the solvent, carboxylate chain length, heating conditions, and reaction concentration. Larger nanocrystals may be grown by slow addition of additional precursors to the crude product mixture. Isolated nanocrystals have carboxylate ligands (2.1–4.7 nm–2) that can be displaced along with excess cadmium ions using low concentrations of N,N,N′,N′-tetramethyl­ethylenediamine (TMEDA) (1.5–280 mM). Using 1H NMR spectroscopy, we measure the extent of the displacement and show that the binding of Cd­(O2CR)2 to CdTe is weaker than to CdSe nanocrystals of similar size. The weaker binding is proposed to arise from a lower polarity and greater stability of reconstructed CdTe surfaces.