ИСТИНА

At present, the problem of control of the content of various substances in multicomponent media is particularly acute. To date, sensors based on various physical principles are widely used to determine the content of specific substances in media: optical sensors based on changes in absorption or luminescence properties as a result of the interaction of analytes with chromophores or sensor fluorophores, sensors based on the determination of changes in mechanical properties of the sensor for determining the amount of a substance, electrochemical, magnetic and others [1]. Actively studied carbon dots (CDs) with intense and stable luminescence have broad prospects for their use as optical nanosensors in problems of diagnostics of multicomponent media [2]. Such prospects are provided due to CDs properties - the sensitivity of the fluorescence (FL) of CDs to changes in the characteristics of the environment - temperature, pH, the presence of various ions and molecules [3-6] This work is devoted to the study of the photoluminescent properties of water suspensions of two samples of CDs, synthesized by the hydrothermal method, in the presence of this heavy metal nitrates: Fe3+, Cr3+, Cu2+, Pb2+, Zn2+, Ni2+, Ag+. The concentration of each of the cations in the suspension mixture was varied in the range from 0 to 0.3 mM. As can be seen from the obtained FL spectra of CD in water and in all prepared suspension mixtures, in the presence of all studied cations, the FL intensity of CDs decreases. The series of cations were determined according to the degree of quenching of FL of CDs by them. It was found that FL quenching of different cations is caused by the result of the superposition of several factors. It was found that the aggregation of nanoparticles does not have a major contribution to the change of the FL of CDs. The concentration range when static FL of CDs quenching dominates is determined. FL of CDs quenching in the presence of Fe3+ cations is due to the significant contribution of the inner filter effect. This study has been performed at the expense of the grant of RFBR (project № 20-32-70150). G.N. Chugreeva is grateful for the support by Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS” (Project № 21-2-9-25-1). The authors are grateful to A.E. Tomskaya for providing carbon dots. Literature 1. Lee, J.-H.; Kim, J.-Y.; Kim, J.-H.; Kim, S. Enhanced Hydrogen Detection in ppb-Level by Electrospun SnO2-Loaded ZnO Nanofibers. Sensors 2019, 19(3), 726. 2. Molaei, M. J. Carbon quantum dots and their biomedical and therapeutic applications: a review. RSC Adv. 2019, 9(12), 6460–6481. 3. Dolenko, T.; Burikov, S.; Laptinskiy, K.; Rosenholm, J. M.; Shenderova, O.; Vlasov, I. Evidence of Carbon Nanoparticle-Solvent Molecule Interactions in Raman and Fluorescence Spectra. Phys. Status Solidi A 2015, 212, 2512–2518. 4. Laptinskiy, K.; Burikov, S.; Chugreeva, G.; Sarmanova, O.; Tomskaya, A.; Dolenko, T. The influence of the type of ions hydration on photoluminescence of carbon dots in aqueous suspensions. Fuller. Nanotub. Carbon Nanostructures 2021, 29(1), 67-73. 5. Murugesan, P.; Moses, J. A.; Anandharamakrishnan, C. One step synthesis of fluorescent carbon dots from neera for the detection of silver ions. Spectrosc. Lett. 2020, 53(6), 407–415. 6. Sarmanova, O.; Laptinskiy, K.; Khmeleva, M.; Burikov, S.; Dolenko, S.; Tomskaya, A.; Dolenko, T. Development of the fluorescent carbon nanosensor for pH and temperature of liquid media with artificial neural networks. Spectrochim. Acta A 2021, 258, 119861.