Abstract:
Relationships between structures and properties (energy gaps, vertical ionization potentials (IPv), vertical electron affinities (EA v), and ligand binding energies) in small capped CdSe/CdTe nanoparticles (NPs) are poorly understood. We have performed the first systematic density functional theory (DFT) (B3LYP/Lanl2dz) study of the structural (geometries and ligand binding energies) and electronic (HOMO/LUMO energy gaps, IPsv, and EAsv) properties of Cd nSen/CdnTen NPs (n = 6, 9), both bare and capped with NH3, SCH3, and OPH3 ligands. NH3 and OPH3 ligands cause HOMO/LUMO energy destabilization in capped NPs, more pronounced for the LUMOs than for the HOMOs. Orbital destabilization drastically reduces both the IPv and EA v of the NPs compared with the bare species. For SCH 3-capped Cd6X6 NPs, formation of expanded structures was found to be preferable to crystal-like structures. SCH 3 groups cause destabilization of the HOMOs of the capped NPs and stabilization of their LUMOs, which indicates a reduction of the IPv of the capped NPs compared with the bare species. For the Cd9X 9 NPs, similar trends in stabilization/destabilization of frontier orbitals were observed in comparison with the capped Cd6X6 species. Also, pinning of the HOMO energies was observed for the NH 3- and SCH3-capped NPs as a function of a NP size. © 2012 American Chemical Society.
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