Upconversion and Downconversion Quantum Dots for Biomedical and Therapeutic Applications

Three-photon absorption and photoluminescence in films of liquid-crystal polymers with embedded CdSe/ZnS quantum dots

“…Strong restriction in charge carrier movements in the semiconductor nanoparticle significantly changes its electronic and optical properties (Efros, Brus 2021), opening up various ways of their usage in optoelectronics (Litvin et al 2017), photovoltaics (Kirmani et al 2020), laser generation (Jung et al 2021), biomedical applications (Le et al 2023), etc. We should mention the use of the semiconductor QDs for up-conversion, i. e., light emission with wavelength below the excitation wavelength, among their highly promising applications (Rakovich, Donegan 2008). Up-conversion could be used for optical cooling (Ye et al 2021), laser generation (Moon et al 2021), infrared (IR) radiation detection (Zhou et al 2020), bioimaging (Chen, Liang 2014) and therapy (Dutta, Barik 2022). Various mechanisms are responsible for up-converted PL, including population of defect states, phonon-assisted PL, two-and three-photon absorption (Laktaev et al 2022;Wang et al 2023), etc. For many practical applications it would be useful to have a composite of semiconductor QDs and a transparent matrix that immobilizes them.…”