One-step synthesis of white-light-emitting quantum dots at low temperature.
Alloyed Zn(x)Cd(1-x)Se quantum dots (QDs) have been successfully prepared at low temperatures by reacting a mixture of Cd(ClO(4))(2) and Zn(ClO(4))(2) with NaHSe using 3-mercaptopropionic acid as a surface-stabilizing agent. The optical properties and composition of the alloyed QDs were highly dependent on the molar ratio of Zn(2+) to Cd(2+). With an increase in the Zn content, a systematic blue shift in the first exciton absorption and band-edge emission indicated the formation of the alloyed QDs. Moreover, X-ray diffraction peaks of the alloyed QDs systematically shifted to larger angles as the Zn molar fraction of the Zn(x)Cd(1-x)Se QDs was increased. This systematic shift further confirmed the appearance of alloyed QDs. Interestingly, among these alloyed QDs, the Zn(0.93)Cd(0.07)Se QDs exhibited white-light emission with quantum yields of 12%. In addition, we discovered that we could adjust the Zn(0.93)Cd(0.07)Se QD intensity ratio of the band-edge (431 nm) to trap-state (499 nm) emissions by controlling the reaction time. Careful control of the reaction time allowed us to balance the relative strength of the band-edge and trap-state emissions, thereby attaining white-light-emitting QDs. The Zn(0.93)Cd(0.07)Se QDs offer unique advantages, including one-step synthesis, tunable white-light emission, easy manipulation, a low-temperature requirement, and low fabrication costs.
Shen
Chien-Chih
CC
Department of Chemistry, National Sun Yat-sen University, Kaohsiung 804, Taiwan.
Tseng
Wei-Lung
WL
D000497:Alloys / Q000138:chemical synthesis* / Q000737:chemistry; D019187:Cadmium Compounds / Q000737:chemistry*; D008027:Light; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D013696:Temperature; D017967:Zinc Compounds / Q000737:chemistry*
D000497:Alloys; D019187:Cadmium Compounds; D018036:Selenium Compounds; D017967:Zinc Compounds; C058667:cadmium selenide; C044696:zinc selenide