Air-stable near-infrared AgInSe₂ nanocrystals.

We present the synthesis of air-stable AgInSe2 nanocrystals via thermolysis of an Ag-In-thiolate complex followed by an anion exchange reaction. Evolution of the Ag:In:Se ratio with the reaction time demonstrates progressive incorporation of In(3+) in β-Ag2Se seeds. While their lattice stays in the metastable orthorhombic crystal structure, the final AgInSe2 nanocrystal shape can be spherical, pyramidal, or prismatic depending on reaction conditions. These nanocrystals emit from trap states between 800 and 1300 nm, which is a biologically and technologically important near-infrared range, with a photoluminescence quantum yield up to an order of magnitude of 21%. The appearance of a shoulder within the photoluminescence spectra between 845 and 890 nm is correlated to the presence of prismatic nanocrystals.