DFT/TD-DFT study on the electronic and spectroscopic properties of hollow cubic and hollow spherical (ZnO)m quantum dots interacting with CO, NO2 and SO3 molecules

• Published in: Applied physics. A, Materials science & processing Vol. 124; no. 3; pp. 1 - 13
• Main Authors: Gopalakrishnan, Sankarasubramanian, Shankar, Ramasamy, Kolandaivel, Ponmalai
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2018; Springer Nature B.V
• Subjects: Absorption spectra; Applied physics; Characterization and Evaluation of Materials; Condensed Matter Physics; Density functional theory; Density of states; Energy gap; Energy levels; Machines; Manufacturing; Materials science; Molecular interactions; Molecular orbitals; Nanotechnology; Nitrogen dioxide; Optical and Electronic Materials; Physics; Physics and Astronomy; Processes; Quantum dots; Raman spectra; Spectroscopic analysis; Sulfur trioxide; Surface chemistry; Surfaces and Interfaces; Thin Films; Zinc oxide
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-018-1698-y

Hollow spherical (HS) and hollow cubic (HC) (ZnO) m quantum dots (QDs) were constructed and optimized using density functional theory (DFT) method. CO, NO 2 and SO 3 molecules were used to interact with the HC and HS (ZnO) m QDs at the centre and on the surface of the QDs. The changes in the electronic energy levels of HC and HS (ZnO) m QDs due to the interactions of CO, NO 2 and SO 3 molecules have been studied. The electronic and spectroscopic properties, such as density of states, HOMO–LUMO energy gap, absorption spectra, IR and Raman spectra of HC and HS (ZnO) m QDs have been studied using DFT and Time dependent-DFT (TD-DFT) methods. The interaction energy values show that the SO 3 molecule has strongly interacted with HC and HS (ZnO) m QDs than the CO and NO 2 molecules. The results of the density of states show that the HC QDs have peaks that are very close to each other, whereas the same is found to be broad in the HS QDs. The HOMO–LUMO energy gap is more for the HS QDs than the HC QDs, and also it gets decreased, when the NO 2 and SO 3 molecules interact at the centre of the HC and HS (ZnO) m QDs. The blue and red shifts were observed in the absorption spectra of HS and HC QDs. The natural transition orbital (NTO) plot reveals that the interaction of the molecules on the surface of the QDs reduce the chance of electron–hole recombination; hence the energy gap increases for NO 2 and SO 3 molecular interactions on the surface of the HC and HS (ZnO) m QDs. The vibrational assignments have been made for HC and HS QDs interacting with CO, NO 2 and SO 3 molecules.