DFT study of bare and dye‐sensitized TiO₂ clusters and nanocrystals

Abstract

Abstract Structural and electronic properties of bare and dye‐sensitized TiO 2 clusters and nanoparticles with sizes of ≤2 nm have been studied by density functional theory (DFT) calculations. Starting from truncated bulk lattice structures, the degree of structural reorganization, including the formation of TiO surface species, of bare TiO 2 anatase nanocrystals, is found to be sensitive to the quality of the computational method. The electronic structures of optimized 1–2 nm nanoparticles show well‐developed band structures with essentially no electronic bandgap defect states. Significant bandgap broadening due to quantum size effects is observed as the size of the nanocrystals is reduced from 2 nm to 1 nm in diameter, but further bandgap widening is limited by increasingly severe competing surface defect sites as the particles become smaller than ∼1 nm in diameter. The applicability of the TiO 2 nanocrystals in modeling the electronic structure and electronic coupling at dye‐sensitized TiO 2 nanocrystal interfaces has been investigated by attachment of pyridine to one of the nanoparticle models via phosphonic or carboxylic acid anchor groups. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006