Synthesis of Aqueous CdTe Nanocrystals with High Efficient Blue-Green Emission of Exciton

As one of the most popular nanocrystals （NCs）, aqueous CdTe NCs have very weak green emission under con- ventional synthesis conditions. In this work, we report the first example of blue-emitting CdTe NCs directly synthe- sized in aqueous solution by slowing down the growth rate after nucleation. The key for the synthesis is the optimi- zation of NC growth conditions, namely pH range of 7.5 to 8.5, TGA/Cd ratio of 3.6, Cd/Te ratio of 10, and Te concentration of 2 × 10-5 mol/L, to get a slow growth rate after nucleation. The as-prepared blue-emitting CdTe NCs have small size （as small as 1.9 nm） and bright emission [with 4% photoluminescence quantum yield （PL QY） at 486 nm and 17% PLQY at 500 nm]. Transmission electron microscopy （TEM） images of the as-prepared CdTe show monodispersed NCs which exhibit cubic zinc blend structure. Moreover, time-resolved PL decay and X-ray photoelectron spectroscopy （XPS） results show the as-prepared NCs have better surface modification by ligand, which makes these luminescent small CdTe NCs have higher photoluminescence quantum yield, compared with NCs synthesized under conventional conditions.