Large Colloidal InAs Nanocrystals Synthesized with a Grignard Reagent

Colloidal nanocrystals (NCs) active in the near-infrared (NIR) region are appealing for a variety of applications, such as machine vision, hyperspectral imaging, and medical diagnosis. Among the various classes of NIR-active NCs, InAs stands out as one of the most viable compositions in terms of environmental safety. Yet, the synthesis of InAs NCs often relies on expensive and hazardous As precursors, such as tris-(trimethylsilyl)-arsine. Alternative syntheses have also been developed, mainly exploiting tris-(dimethylamino)-arsine (amino-As) in conjunction with a reducing agent (typically organometallic metal hydrides) as a safer and more economical precursor. However, to date, the colloidal synthesis of large InAs NCs (active in the 1000-1600 nm window) using the amino-As route relies on lengthy continuous-injection approaches. In the present study, we demonstrate that using benzyl magnesium chloride (a commercially available Grignard compound) as the reducing agent enables the synthesis of InAs NCs with optical absorption tunable from 835 nm (≈3 nm NC diameter) to 1180 nm (NC diameter of ≈4.2 nm) via a single hot injection procedure. After a ZnSe shell growth, the resulting InAs@ZnSe core@shell NCs exhibit photoluminescence tunable from 1000 to 1500 nm, with photoluminescence quantum yields of 46%, 16%, and 6% at 1030, 1190, and 1500 nm, respectively. We further demonstrate that the synthesis of InAs NCs is compatible with a variety of commercially available Grignard reagents.