Early reports of colloidal CdSe nanocrystal syntheses described producing neutral, stoichiometric particles composed of equal numbers of metal cations and chalcogenide anions. The field has since learned that the stoichiometry of these materials is not reliably known, and crystallites generally have excess surface-bound Cd<sup>2+</sup> charge balanced by X-type ligands. Surprisingly, the stoichiometric nanocrystal that was once thought to be the product of such reactions has proven challenging to synthesize. For the first time, we report a rational route to charge-neutral, stoichiometric CdSe nanocrystals bound solely by L-type ligands. Thin film transistors made from this material show record mobilities after sintering under vacuum. We also demonstrate rebinding of several Z-type ligands and a relative binding affinity of these complexes that depends on Lewis acidity as well as sterics. These results demonstrate the utility of a nanocrystal model consisting of a neutral stoichiometric core bound by neutral, close-shelled L-type and Z-type ligands. The stoichiometric nanocrystal provides a well characterized starting material for further exploration of surface reactivity, and acts as a valuable synthon for the rational design of future exotic nanocrystal ligand compositions.

First stoichiometric metal chalcogenide nanocrystal

249th National Meeting (2015)

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