ИСТИНА

Effective use of carbon dots (CD) in various fields of science and technology requires a more detailed understanding of the mechanisms of formation and change of their photoluminescence as a result of their interaction with the environment. In this study, CD synthesized via a hydrothermal method from citric acid (CA) and ethylenediamine (EDA) in their different ratios are studied in solvents by FTIR spectroscopy, optical absorption spectroscopy and photoluminescence spectroscopy including time-resolved one. Particular attention is paid to the properties of CD with various nitrogen content (Fig.1) in solvents with different values of acidity SA and basicity SB. The analysis of the obtained experimental results demonstrated a significant dependence of the spectral characteristics of PCD photoluminescence on the acidity and basicity of the solvent. It was determined that the reason for this dependence is the formation of hydrogen bonds of varying strength between PCD functional groups and solvent molecules. In this case, in solutions with different acidity and basicity, nitrogen-deficient CD act as basicity centers, i.e. hydrogen bond acceptors. Nitrogen-rich CD in the studied solvents act as acidity centers, i.e. hydrogen bond donors. The obtained results are of extreme importance for the targeted development of CD-based nanosensors and medical agents in various environments. Knowledge of the mechanisms of medium parameters influence on the photoluminescence of carbon nanomaterials allows one to solve many fundamental problems in nanotechnology and material science. The research was carried out at the expense of the grant from the Russian Science Foundation № 22-12-00138-P, https://rscf.ru/en/project/22-12-00138/