Synthesis of stable near-infrared emitting HgTe/CdS core/shell nanocrystals using dihydrolipoic acid as stabilizer

Abstract

HgTe/CdS core/shell nanocrystals (NCs) with highly-stable near-infrared (NIR) emissions were synthesized by employing dihydrolipoic acid (DHLA) as a stabilizer. This synthetic route was performed using Te powder as the tellurium source to prepare HgTe NCs, and H₂S generated by the reaction of Na₂S–H₂SO₄ as the sulfur source for synthesizing HgTe/CdS core/shell NCs at room temperature. The fluorescence emission peaks of DHLA-capped HgTe/CdS NCs could be facilely tuned from 910 nm to 1200 nm by varying the reflux time at 100 °C, with a maximum photoluminescence quantum yield of 52%. The obtained HgTe/CdS NCs exhibited an NIR stable emission when heated at 75 °C. Correspondingly, these HgTe/CdS core/shell NCs displayed excellent colloidal dispersion stability and long exciton lifetimes that reached up to 47.6 ns in an aqueous medium. The resultant HgTe/CdSe NCs have been successfully used to fabricate NIR emitting thin films on the surface of polymers and to perform fluorescence imaging in a live animal.