Ultrafast synthesis of highly luminescent green- to near infrared-emitting CdTe nanocrystals in aqueous phase

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Abstract
It is commonly observed that the “traditional” aqueous solution route to prepare CdTe nanocrystals (NCs) using thiol ligands as capping reagents is usually very time-consuming and the luminescent properties are poor in the deep red to near infrared (NIR) emission window. Herein, we present an ultrafast and facile aqueous phase route under atmospheric pressure to prepare high-quality green- to NIR-emitting CdTe NCs with mercaptopropionic acid as capping reagent. In contrast to previous reports, red- to NIR-emitting CdTe NCs with emission efficiency up to 50% can be obtained within 1 h reflux time under the optimized experimental conditions. The growth rate is about 100 times faster than those reported previously. The influences of various experimental variables, including Te-to-Cd ratio, ligand-to-Cd ratio, pH value as well as the precursor concentration, on the growth rate and luminescent properties of the obtained CdTe NCs have been systematically investigated. Experimental results indicate that the combination of high pH value and low Te-to-Cd molar ratio plays a crucial role in determining the fast growth rate and the high-quality optical properties of the obtained CdTe NCs. The mechanism for the fast growth rate and the resulting high-quality optical properties is also elucidated.