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제123회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Stepwise growth of CdS quantum dots in ethylene glycol

2019년 1월 15일 11시 24분 13초
PHYS.P-80 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
4월 19일 (금요일) 11:00~12:30
Physical Chemistry
저자 및
Dong-Won Jeong, Du-Jeon Jang*
Department of Chemistry, Seoul National University, Korea
Colloidal quantum dots (QDs), which have size-dependent band-gap energies with remarkably high quantum yields, have received great attentions. Those intriguing properties are related to the surface states of QDs. Therefore, controlling the surface structure of QDs has been of big importance and varying the types of ligands has been often attempted as means of surface control. Water-dispersive CdS quantum dots have been rapidly synthesized in a polyol solvent of ethylene glycol at 160 °C without using nonpolar organic solvents and their stepwise growth mechanisms have been investigated thoroughly. CdO and 3-mercaptopropionate ions react in water to form cadmium thiolate complexes, which transform gradually into CdS QDs in ethylene glycol at 160 °C. Absorption spectra reveal that the growth rate of CdS QDs in the first step of ≤70 s is noticeably faster than that in the second step of ≥70 s. Static and time-resolved PL spectra suggest that the dominant growth mechanism of CdS QDs switches from the OR growth in the first step to the OA growth in the second step. PL decay profiles have suggested that the fast decay time of 40 ns and the slow decay time of 300 ns are due to the decay times of excitons in internal defects (IDs) and OA-induced defects (OADs), respectively. In the first step, IDs are eliminated by the OR growth to reduce PL and the center of the PL of the slow decay component shifts from 550 nm to 600 nm as ligands dissociate to leave sulfur atoms on the surfaces of CdS QDs. In the second step, the OA growth occurs to enhance the number of OADs, increasing PL at 600 nm. Overall, the two stepwise mechanisms of the OR growth and the OA growth can be well distinguishable in a polyol solvent of ethylene glycol at a high reaction temperature of 160 °C.