Cd-substitution effect on photoexcitation properties of ZnO nanodots surrounded by carbon moiety

The geometrical structure and photoexcitation properties of Zn27-nCdnO27C42 complexes are investigated by density functional theory (DFT) and time-dependent DFT calculations at the PBE0/6-31G*/SDD level of theory. The cohesive energy and frequency analysis indicate that the hybrid materials are energetically stable. In presence of Cd substituting atoms, the energy gap of the ZnO nanodots surrounded by carbon moiety is shown to decrease, as compared to Cd-free complex. In-depth excited state analysis including charge density difference (CDD) mapping and absorption spectrum decomposition is performed to reveal the nature of the dominant excited states and to comprehend the Cd-to-Zn substitution effect on the photoexcitation properties of Zn27-nCdnO27C42. A principal possibility to enhance the intramolecular charge transfer through incorporation of certain number of Cd atoms into the ZnO nanodots is shown. Such Cd-induced modifications in optical properties of semi-spherical Zn27-nCdnO27C42 complexes could potentially enable use of this hybrid material in optoelectronic and photocatalytic applications.