| Light‑triggered shell formation on CdSe quantum dots in glasses |
| Hojeong Lee, Yong Kon Kwon, Jong Heo |
| Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam‑Ro, Pohang, Gyeongbuk 37673, Republic of Korea |
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Received: July 16, 2021; Revised: September 29, 2021 Accepted: November 12, 2021. Published online: January 31, 2022. |
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| ABSTRACT |
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Combination of heat treatment and continuous-wave (CW) laser irradiation at wavelength λ = 532 nm was designed to precipitate quantum dots (QDs) that had Cd-rich core and Zn-rich shell inside a glass matrix. Soda-alumino-silicate glass containing Cd, Zn and Se was heat-treated at 550 °C for 3 h. This glass has a strong absorption band at λ = 513.6 (± 52.7) nm and its photoluminescence spectrum has a strong defect emission centered at λ = ~ 609 nm in addition to the intrinsic CdSe QD emission at λ = ~ 546 nm. Irradiation by a CW laser beam with intensity of 14 W/cm2 for 1 min resulted in a large decrease of the intensity of defect emission. After the initial heat treatment, Cd-rich QDs with an average diameter of ~ 3.15 nm and composition of Cd0.71Zn0.29Se precipitated in the glass. Upon subsequent laser irradiation, a Zn-rich shell of Cd0.23Zn0.77Se formed on the surface of Cd-rich cores. Temperature of the glass during this laser irradiation, estimated using Nd3+ optical thermometry was ~ 637 °C. Cd-rich QD has a band-gap that matches the energy of the laser beam, and therefore converts the photon energy to thermal energy. This thermal energy raises the temperature of the glass and facilitates the diffusion of ions to form Zn-rich shells. |
| Key words:
Glass · Cadmium selenides · Photoluminescence · Optical thermometry |
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