The influence of solvent and ligands on characters of ZnS clusters

According to zinc blende and wurtzite structures of ZnS nanocrystals, four clusters (Zn3S3, Zn4S4, (Zn3S3)(2), and (Zn3S3)(3)), were investigated at B3LYP/Lanl2dz theoretical level. In simultaneous consideration of the influence of solvent and ligands, we calculated their Raman and absorption peaks, which are agreement with experimentally reported results. The calculated Raman spectra of Zn3S3, Zn4S4, (Zn3S3)(2), and (Zn3S3)(3) are in the range of 260-310 cm(-1). During the calculation of absorption spectra, time-dependent density-functional theory (TDDFT) is employed. We have found an obvious blue-shift in the calculated wavelengths of the absorption peaks after consideration of the solvent. In solvent environment, the wavelength of absorption peak shifts to red with the increase of the atomic numbers from Zn3S3, to (Zn3S3)(2) and (Zn3S3)(3) clusters, which is induced by the quantum size effect. Since the sizes of the current calculated clusters are much smaller than the experimentally reported nano-sized ZnS nanocrystals, the calculated wavelengths of absorption peak of the four clusters are shorter than the nano-sized ZnS nanocrystals. Through the analysis of S-Zn-ligand structures, we speculate that the main influence of ligands comes from thiol of ligand because all S-Zn-ligand structures have similar Wiberg Bond Index (WBI) values, absorption spectra, and bond length in theory.