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1. CdSe nanocrystal sensitized photon upconverting film

   https://doi.org/10.1039/D1RA06562A  

   Rigsby, Emily M.; Miyashita, Tsumugi; Fishman, Dmitry A.; Roberts, Sean T.; Tang, Ming L. (September 2021, RSC Advances)

   Here, films using CdSe nanocrystal (NC) triplet photosensitizers in conjunction with diphenylanthracene (DPA) emitters were assembled to address several challenges to practical applications for solution-based photon upconversion. By using poly(9-vinylcarbazole) as a phosphorescent host in this film, volatile organic solvents are eliminated, the spontaneous crystallization of the emitter is significantly retarded, and ∼1.5% photon upconversion quantum yield (out of a maximum of 50%) is obtained. Transient absorption spectroscopy on nanosecond-to-microsecond time scales reveals this efficiency is enabled by an exceptionally long triplet lifetime of 3.4 ± 0.3 ms. Ultimately, we find the upconversion efficiency is limited by incomplete triplet–triplet annihilation, which occurs with a rate 3–4 orders of magnitude slower than in solution-phase upconversion systems. 

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2. Colloidal CdSe nanocrystals are inherently defective

   https://doi.org/10.1038/s41467-021-21153-z  

   Goldzak, Tamar; McIsaac, Alexandra R.; Van Voorhis, Troy (February 2021, Nature Communications)

   Abstract Colloidal CdSe nanocrystals (NCs) have shown promise in applications ranging from LED displays to medical imaging. Their unique photophysics depend sensitively on the presence or absence of surface defects. Using simulations, we show that CdSe NCs are inherently defective; even for stoichiometric NCs with perfect ligand passivation and no vacancies or defects, we still observe that the low energy spectrum is dominated by dark, surface-associated excitations, which are more numerous in larger NCs. Surface structure analysis shows that the majority of these states involve holes that are localized on two-coordinate Se atoms. As chalcogenide atoms are not passivated by any Lewis base ligand, varying the ligand should not dramatically change the number of dark states, which we confirm by simulating three passivation schemes. Our results have significant implications for understanding CdSe NC photophysics, and suggest that photochemistry and short-range photoinduced charge transfer should be much more facile than previously anticipated. 

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3. Midinfrared Electroluminescence from CdSe Quantum Dots

   https://doi.org/10.1021/acsnano.4c18113  

   Shen, Xingyu; Guyot-Sionnest, Philippe (February 2025, ACS Nano)
4. Cavity Controlled Upconversion in CdSe Nanoplatelet Polaritons

   https://doi.org/10.1021/acsnano.4c05871  

   Amin, Mitesh; Koessler, Eric_R; Morshed, Ovishek; Awan, Farwa; Cogan, Nicole_M_B; Collison, Robert; Tumiel, Trevor_M; Girten, William; Leiter, Christopher; Vamivakas, A_Nickolas; et al (July 2024, ACS Nano)
5. Release, detection and toxicity of fragments generated during artificial accelerated weathering of CdSe/ZnS and CdSe quantum dot polymer composites

   https://doi.org/10.1039/C8EN00249E  

   Gallagher, Miranda J.; Buchman, Joseph T.; Qiu, Tian A.; Zhi, Bo; Lyons, Taeyjuana Y.; Landy, Kaitlin M.; Rosenzweig, Zeev; Haynes, Christy L.; Fairbrother, D. Howard (January 2018, Environmental Science: Nano)

   Next generation displays and lighting applications are increasingly using inorganic quantum dots (QDs) embedded in polymer matrices to impart bright and tunable emission properties. The toxicity of some heavy metals present in commercial QDs ( e.g. cadmium) has, however, raised concerns about the potential for QDs embedded in polymer matrices to be released during the manufacture, use, and end-of-life phases of the material. One important potential release scenario that polymer composites can experience in the environment is photochemically induced matrix degradation. This process is not well understood at the molecular level. To study this process, the effect of an artificially accelerated weathering process on QD–polymer nanocomposites has been explored by subjecting CdSe and CdSe/ZnS QDs embedded in poly(methyl methacrylate) (PMMA) to UVC irradiation in aqueous media. Significant matrix degradation of QD–PMMA was observed along with measurable mass loss, yellowing of the nanocomposites, and a loss of QD fluorescence. While ICP-MS identified the release of ions, confocal laser scanning microscopy and dark-field hyperspectral imaging were shown to be effective analytical techniques for revealing that QD-containing polymer fragments were also released into aqueous media due to matrix degradation. Viability experiments, which were conducted with Shewanella oneidensis MR-1, showed a statistically significant decrease in bacterial viability when the bacteria were exposed to highly degraded QD-containing polymer fragments. Results from this study highlight the need to quantify not only the extent of nanoparticle release from a polymer nanocomposite but also to determine the form of the released nanoparticles ( e.g. ions or polymer fragments). 

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