Towards a quantum-chemical simulation of the cadmium chalcogenide nanoclusters linked with biomolecules: An effect of terminating group upon the core geometry

Ab initio calculations of cadmium chalcogenide nanoclusters with terminating groups (H, O, N, and C atoms bound to the surface sulfur) are considered as a simulation for the species produced in typical synthesis of bio-conjugates with luminescent quantum dots. The Hartree–Fock (HF) method and density functional theory (DFT) are used assuming geometry optimization keeping the tetrahedral symmetry of cadmium chalcogenide cores. The geometry and electronic structure of CdX (X = S, Se, Te) clusters with size up to Cd17 (HF) and Cd4 (DFT) bound with hydrogen and –OH, –NH2, –CH3, and –CH2CH3 groups are calculated and the effects of the terminating groups upon core clusters are discussed.