Browsing by Author "Hua, Muchuan"

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    Net energy up-conversion processes in CdSe/CdS (core/shell) quantum dots, a possible pathway to towards optical cooling
    (American Physical Society, 2022) Hua, Muchuan; Decca, Ricardo S.; Physics, School of Science
    An investigation of the possibility of optical refrigeration (OR) on zinc-blende cadmium selenide/cadmium sulfide (CdSe/CdS) core/shell structure quantum dots (QDs) has been carried out. Quality samples were synthesized in our laboratory, and significant energy up-conversion photoluminescence (UCPL) was observed in these samples, showing the potential of generating net cooling effects. To better understand and predict the UCPL characteristics of the QDs, a semiempirical model has been developed, showing good agreement with our experimental results. The model takes into account the corresponding quantum yield and cooling efficiency, predicting the possibility of realizing optical refrigeration on a CdSe QD system.
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    Optical refrigeration on CdSe/CdS quantum dots
    (2019-12) Hua, Muchuan; Decca, Ricardo S.; Li, Tongcang; Cheng, Ruihua; Joglekar, Yogesh N.; Liu, Jing
    Optical refrigeration in quantum dots was carried out in this research. Zinc-blende crystalline CdSe/CdS (core/shell structure) QDs with complete surface passivation were synthesized and been used as the cooling substance. Phonon-assisted up-conversion photoluminescence driven by sub-band gap laser excitation was utilized as the cooling mechanism in the QD samples. A net cooling efficiency was predicted by a semi-empirical model developed during the research, within a range of the laser excitation energy, even after taking into account possible parasitic heating processes. To observe the cooling effect, the experiment was carried out in a thermally isolated environment, which temperature was also monitored. By using an optical thermometry technique developed for this research, a maximum temperature drop around 0.68 K was observed in the experiment. This development paves the way to use QDs' cooling in new industrial and fundamental research approaches.