Ligand mediated tuning of the electronic energy levels of ZnO nanoparticles

Abstract

The surface capping of nanoparticles is one of the important ways through which one can alter electronic energy levels and hence enable the development of novel nanostructures with desired properties and specific applications. By using the self-consistent-charge density-functional tight-binding (SCC-DFTB) method we envisage the role of the ligand in engineering the electronic structure of ZnO nanoparticles. Significant differences are observed in the electronic structure of ZnO nanoparticles because of the variation of the nanoparticle–ligand bonding interactions. We found that –OH passivated ZnO quantum dots (QDs) are the most stable, followed by –NH₂ passivated QDs, and –SH passivated QDs are the least stable. The study of the HOMO–LUMO gap and excitation spectra show that there is a clear blue shift in the absorption spectra of the QDs as compared to bare ones and the extent of the blue shift sensitively depends on the nature of the passivating ligands. The maximum blue shift occurs in –OH passivated QDs.