Synthesis of Efficiently Green Luminescent CdSe/ZnS Nanocrystals Via Microfluidic Reaction

Quantum dots with emission in the spectral region from 525 to 535 nm are of special interest for their application in green LEDs and white-light generation, where CdSe/ZnS core-shell structured nanocrystals (NCs) are among promising candidates. In this study, triple-ligand system (trioctylphosphine oxide–oleic acid–oleylamine) was designed to improve the stability of CdSe NCs during the early reaction stage. With the precisely controlled reaction temperature (285 C) and residence time (10 s) by the recently introduced microfluidic reaction technology, green luminescent CdSe NCs (k = 522 nm) exhibiting narrow FWHM of PL (30 nm) was reproducibly obtained. After that, CdSe/ZnS core-shell NCs were achieved with efficient luminescence in the pure green spectral region, which demonstrated high PL QY up to 70% and narrow PL FWHM as 30 nm. The strengthened mass and heat transfer in the microchannel allowed the formation of highly luminescent CdSe/ZnS NCs under low reaction temperature and short residence time (T = 120 C, t = 10 s). The successful formation of ZnS layer was evidence of the substantial improvement of PL intensity, being further confirmed by XRD, HRTEM, and EDS study.