Synthesis of Efficiently Green Luminescent CdSe/ZnS Nanocrystals Via Microfluidic Reaction
School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai, 200237, China
Nanoscale Research Letters 2008, 3:134-139 doi:10.1007/s11671-008-9125-5Published: 18 March 2008
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 (λ = 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.