Continuous synthesis of CdSe(x)Te(1-x) nanocrystals: chemical composition gradient and single-step capping.

A capillary microreactor was firstly utilized to continuously synthesize near-infrared emitting CdSe(x)Te(1-)(x) nanocrystals (NCs). By using trioctylphosphine oxide and trioctylphosphine as the solvents for anion precursor as well as oleic acid and oleylamine as the solvents for cation precursor, high quantum yield zinc-blend CdSe(x)Te(1-)(x) NCs with a chemical composition gradient internal structure and tunable emission from 634 to 783 nm were synthesized. Thus, the nonlinear relationship between the composition and the emission energies were verified. Moreover, a facile single-step capping approach was developed by using the dissolution of cadmium oxide and free element sulfur in oleic acid, and a very thin CdS shell was successfully epitaxial grown around the as-prepared CdSe(x)Te(1-)(x) NCs to enhance the photostability. After the capping process, the core/shell structured CdSe(x)Te(1-)(x)/CdS NCs remained 15-40% of their initial PL intensity after 3h of illumination.