Proceedings of the 7th International Conference on Theoretical and Applied Nanoscience and Nanotechnology (TANN'23) Ottawa, Canada – June 01-03, 2023 Paper No. 148 DOI: 10.11159/tann23.148 FRET-Enhanced Singlet Oxygen Generation by Nanocomposites Based on Ternary AgInS2/ZnS Quantum Dots and Porphyrin Derivatives Tatiana Oskolkova1, Ekaterina Smirnova1, Lyubov’ Borodina1, Elena Svirshchevskaya2, Andrey Veniaminov1, Anna Orlova1 Center of Information Optical Technology, ITMO University 199034 Saint Petersburg, Russia to.oskolkova@itmo.ru; esmirnova@itmo.ru; lnborodina@itmo.ru; avveniaminov@itmo.ru; a.o.orlova@itmo.ru 2 Department of Immunology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS 117997 Moscow, Russia esvir@mail.ibch.ru 1 Extended Abstract Recently, ternary I-III-VI chalcopyrite-type quantum dots (QDs), such as CuInS2, AgInSe2, and AgInS2, have attracted considerable interest as a less toxic alternative to conventional Cd- and Pb-based binary semiconductor nanocrystals [1]. Due to their non-toxicity and unique photophysical properties, namely, direct bandgap, high photoluminescence quantum yield in the visible and near-infrared regions, and long photoluminescence lifetimes of hundreds of nanoseconds [2], ternary QDs have emerged as promising materials for a wide range of biomedical applications, including bioimaging, biosensing, and photodynamic therapy (PDT) [3]. For example, ternary QDs can be conjugated with conventional PDT molecular agents to expand their excitation range and increase the efficiency of singlet oxygen (SO) generation [4] through the formation of an additional non-radiative energy relaxation channel associated with Förster resonance energy transfer (FRET) [5]. Detailed analysis of the spectrally-resolved dynamics of FRET between ternary QDs and molecular agents can provide insights into the mechanisms of FRET-assisted SO generation and elucidate the optimized parameters for the formation of novel ternary QD-based nanocomposites for PDT. In this study, biocompatible water-soluble nanocomposites based on hydrophilic ternary AgInS2/ZnS QDs and hydrophobic tetraphenylporphyrin (TPP) molecules incorporated into a polymer matrix have been prepared. The analysis of the optical properties of the nanocomposites by steady-state photoluminescence and UV-VIS spectroscopy reveals that an effective sensitization of the TPP emission in the presence of QDs takes place, at the same time, the efficiency of this process decreases with further increase of TPP:QD molar ratio. To explain this phenomenon, we estimate the fraction of nonluminescent aggregates of TPP molecules within the nanocomposite and demonstrate that the TPP of concentration lower than 10-6 M remains completely in the monomeric form in a part of a nanocomposite, while the increase of concentration to 2.5 ∙ 10-6 M causes TPP aggregation, reducing the number of molecular monomers to about 88%. It should be noted that the aggregation of porphyrin molecules leads to the loss of their ability to generate SO due to the increase in the non-radiative rate [6]. Therefore, the nanocomposites with optimized TPP:QD molar ratio value have been used for further FRET efficiency analysis. The photoluminescence kinetics of the nanocomposites has been studied by time-correlated single photon counting fluorescence microscopy (PicoQuant, Germany). Bandpass filters with a full width at half maximum of 10 nm were employed to selectively detect the emission in a wavelength range corresponding to the photoluminescence spectrum of the nanocomposites. With this approach, we analyze the spectrally-resolved FRET dynamics within the nanocomposites taking into account the change in the photoluminescence lifetime of QDs in the presence of TPP. It has been shown that the average efficiency of FRET from the QD radiative transition in the short-wavelength region of the photoluminescence spectrum is approximately 25%, while for the transition corresponding to the peak position of the spectrum this value exceeds 35%. To further evaluate the FRET-mediated enhancement of SO generation, we have tested the formed nanocomposites on Bacillus subtilis bacteria and observed the improved antibacterial activity as compared to the free TPP molecules. This work was supported by the Ministry of Science and Higher Education of the Russian Federation, goszаdanie no. 2019-1080, and by RPMA grant of School of Physics and Engineering of ITMO University. 148-1 References [1] P. M. Allen and M. G. Bawendi, “Ternary I−III−VI Quantum Dots Luminescent in the Red to Near-Infrared,” Journal of the American Chemical Society, vol. 130, no. 29, pp. 9240-9241, 2008. [2] N. Tsolekile, S. Parani, M. C. Matoetoe, S. P. Songca, and O. S. Oluwafemi, “Evolution of ternary I–III–VI QDs: Synthesis, characterization and application,” Nano-Structures & Nano-Objects, vol. 12, pp. 46-56, 2017. [3] W. M. Girma, M. Z. Fahmi, A. Permadi, M. A. Abate, and J. Y. Chang, “Synthetic strategies and biomedical applications of I–III–VI ternary quantum dots,” Journal of Materials Chemistry B, vol. 5, no. 31, pp. 6193-6216, 2017. [4] A. C. S. Samia, X. Chen, and C. 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