Optoelectronic properties of hollow spheroid (ZnO)_m quantum dots with nanotube (carbon and ZnO) nanocomposites in the solvent phase - A DFT/TD-DFT study

In this work, we study the electronic structure of (ZnO)(m) (m = 16, 30) quantum dots (QDs) with carbon and ZnO nanotubes in the solvent medium using DFT and TD-DFT methods. The structure consists of hollow sphere of (ZnO)(16) and (ZnO)(30) QDs, carbon and ZnO nanotubes and a thiol molecule. The partial density of states (PDOS) has been calculated for all the structures of (ZnO)(m) QDs with nanotubes where the energy gap of each structure is discussed. From the obtained results of PDOS, it is found that the low band gap is found for CNT with (ZnO)(m) QDs in the solvent medium because of the higher degree of unsaturation. The absorption spectra have been also calculated for the QDs with the armchair and zigzag nanotubes, exhibiting blue-shift which is attributed to the stabilization of the surface states. The natural transition orbital (NTO) map has been plotted to identify how the electron - hole travels through structures which is used to study the charge transport property. This result shows that all ZnO NT with (ZnO)(m) QDs possesses better charge transport property. Further, the electrostatic potential (ESP) map has been plotted to confirm the electron rich region in the hybrid structures and it is found that the weak electrostatic potential occurs around this CNT with (ZnO)(16) QD.