The Surface Chemistry of Colloidal HgSe Nanocrystals, toward Stoichiometric Quantum Dots by Design

Abstract

The prevalent structure of binary semiconductor nanocrystals is a crystallite enriched in metal cations and terminated by anionic surface species that are classified as X-type ligands. Here, we demonstrate that HgSe NCs synthesized from selenourea and mercury chloride in oleylamine have a stoichiometry close to that of bulk HgSe and feature a surface terminated by oleylammonium chloride: a combination of composition and ligand capping that preserves charge neutrality. We demonstrate that oleylammonium chloride can be formed as a side product of the formation of HgSe in the particular reaction mixture used. We complement the experimental work with a detailed investigation by density functional theory of a [HgSe]55 model system. This analysis confirms that the combination of a stoichiometric HgSe nanocrystal and alkylammonium chloride ligands forms a stable structure. Moreover, DFT predicts that stoichiometric HgSe nanocrystals prefer binding of methylammonium chloride over binding of mercury chloride. We t...