The mechanism features of colloidal quantum dots (QDs) passivation with thioglycolic acid molecules (TGA) for cases of different luminescent properties is considered using FTIR. This problem is considered based on FTIR spectra analysis for various ionic forms of TGA. Experimental TGA molecules FTIR spectra is interpreted, basing on the data on modeling of TGA vibrational modes, realized in the framework of density functional method (DFT /B3LYP/6-31+G(d)) taking into account the vibrations anharmonicity of every functional group. This approach provides a significant improvement in the agreement between the experimental and calculated data. FTIR spectra of Ag ${}_2$ S/TGA QDs with exciton and recombination luminescence are differ from each other and B “freeB” TGA molecules. The $\nu (S-H)$ TGA peak (2559 cm ${}^{-1}$ ) disappears in FTIR spectra of Ag ${}_2$ S/TGA QD samples. This fact indicates the interactions between TGA thiol group and dangling bonds of Ag ${}_2$ S nanocrystals. Ag ${}_2$ S QDs passivation with TGA molecules leads to emergence ${\nu }_{as}$ (COO ${}^{-}$ ) (1584 cm ${}^{-1}$ ) and ${\nu }_s$ (COO ${}^{-}$ ) (1387 cm ${}^{-1}$ ) peaks. It indicates TGA adsorption in ionic form. For Ag ${}_2$ S/TGA QDs with exciton luminescence we observed (a) significant low-frequency shift of ${\nu }_s$ (COO ${}^{-}$ ) peak from 1388 cm ${}^{-1}$ to 1359 cm ${}^{-1}$ and high-frequency shift of ${\nu }_{as}$ (COO ${}^{-}$ ) peak from 1567 cm ${}^{-1}$ to 1581 cm ${}^{-1}$ ; (b) change in the ratio of intensities of ${\nu }_{as}$ (COO ${}^{-}$ ) and ${\nu }_s$ (COO ${}^{-}$ ) vibrations. This feature is caused by the change in the symmetry of TGA molecules due to passivation of Ag ${}_2$ S quantum dots.For Ag ${}_2$ S/TGA QDs with recombination luminescence, the insignificant high-frequency shift of 7–10 cm ${}^{-1}$ for ${\nu }_{as}$ (COO ${}^{-}$ ) at 1567 cm ${}^{-1}$ and low-frequency shift of 3–5 cm ${}^{-1}$ for ${\nu }_s$ (COO ${}^{-}$ ) at 1388 cm ${}^{-1}$ , probably caused by the interaction of thiol with Ag ${}_2$ S surface is observed. Using FTIR spectra, it was found that IR luminescence photodegradation is also accompanied by changes in the thioglycolic acid molecules, which capped Ag ${}_2$ S QDs. In the case of Ag ${}_2$ S QDs with exciton luminescence, the degradation process is non-reversible. It is accompanied by TGA photodegradation with the formation of $\alpha$ -thiol-substituted acyl radical (S-CH ${}_2$ -CO ${}^{•}$ ) TGA.

Quantum dots are the most exciting representatives of nanomaterials. They are synthesized using advanced methods of nanotechnology pertaining to both inorganic and organic chemistry. Quantum dots possess unique physical and chemical properties; therefore, they are used in very different fields of physics, chemistry, biology, engineering and medicine. It is not surprising that the Nobel Prize in chemistry in 2023 was given for discovery and synthesis of quantum dots. This review addresses modern methods for the synthesis of quantum dots and their optical properties and practical applications. In the beginning, a short insight into the history of quantum dots is given. Many gifted scientists, including chemists and physicists, were engaged in these studies. The synthesis of quantum dots in solid and liquid matrices is described in detail. Quantum dots are well-known owing to their unique optical properties; that is why the attention in the review is focused on the quantum-size effect. The causes for fascinating blinking of quantum dots and techniques for observation of a single quantum dot are considered. The last part of the review describes mportant applications of quantum dots in biology, medicine and quantum technologies. The bibliography includes 772 references.

The size dependences of the absorption and luminescence spectra of ensembles of hydrophilic colloidal Ag2S quantum dots produced by the sol-gel method and dispersed in gelatin are analyzed. By X-ray...