QUANTUM-CHEMICAL SIMULATION OF INTERACTIONS OF SURFACE AGENTS WITH ZNS AND CDS QUANTUM DOTS

Quantum dots (QDs) are nanoscale semiconductor particles. They are promising objects of research in nanotechnology and materials science due to their special physical and chemical properties. An important role in the application of the QD is played by the modification of their surface by specific substances to increase stability, change optical and magnetic properties, and give the particles improved characteristics. Therefore, the study of the interaction between QD and surface agents (SA) is an interesting task. Experimental analysis of such materials is complicated by the cost and complexity of their synthesis. Thus, quantum-chemical simulation methods are used to facilitate the studies. Such methods allow one to assume the molecular structure and physico-chemical properties of a substance with known accuracy. In this work, we used the Hartree-Fock method and density functional theory with different functionals and basis sets to simulate the molecular structure and some properties of SA. Semiempirical approaches were used for modeling the interactions between molecules of SA (thioglycolic, thiopropionic and dihydrolepolic acids) and surface atoms of semiconductor ZnS and CdS QDs. Optimization of the geometry of surfactant molecules and calculations of their IR spectra, calculation of the QD's surface structure were carried out. Then, the energies of donor-acceptor bonds formed between SA’s molecules and QD’s surface atoms were calculated. It was found that the values of donor-acceptor bond energies in the case of surfactant with carboxyl group exceed the interaction energy of QD surface with surfactant with thiol group by 0.3 eV. This effect is explained by the formation of two bonds of oxygen atoms of the carboxyl group and the bidentate coordination of the agent molecules on the QD surface