IR luminescence of polyfunctional associates of indocianine green and Ag$_{2}$S quantum dots

In this work, manifestations of IR luminescence sensitization of Indocyanine Green during conjugation with colloidal Ag$_{2}$S quantum dots with an average size of 2.2 and 3.7 nm, passivated with thioglycolic acid molecules (Ag$_{2}$S/TGA QDs) are studied using absorption and luminescence techniques. The possibility of enhancing luminescence in the dye monomer band (820 nm) under excitation at 660 nm by a factor of 6 in the presence of Ag$_{2}$S/TGA QDs (2.2 nm) due to a decrease in the polymethine dye chain movement via coordination interaction with QDs was demonstrated. The way to switch-over from the first therapeutic window of biological tissue transparency (NIR-I, 700–950 nm) to the second (NIR-II, 1000–1700 nm), based on sensitization of IR luminescence of Ag$_{2}$S/TGA QDs with an average size of 3.7 nm in the region of 1040 nm due to of resonance non-radiative transfer of excitation energy from Ag$_{2}$S/TGA (2.2 nm) QDs at 900 nm to Ag$_{2}$S/TGA QDs (3.7 nm) via the J-aggregate of ICG dye, which acts as an exciton bridge.