Structural, electronic, and optical absorption properties of TiO2 nanotube adsorbed with Cu n clusters

Abstract

The structural, electronic, and optical absorption properties of TiO2 nanotube (TiO2NT) with Cu n clusters (n =1–4) adsorbed on its surface have been investigated based on density functional theory calculations. The TiO2NT is constructed by rolling up a (101) sheet of anatase TiO2 around the $[\bar 101]$ direction; the ground states of Cun/TiO2NT systems are determined by analyzing the average adsorption energies. Calculation results show that odd-even oscillations occur for the average adsorption energy, the Cu-O bond length, and the amount of transferred electrons, with the increase in Cu n cluster size; and the Cu n /TiO2NTs with odd n’s demonstrate stronger interaction between the Cu n cluster and the TiO2NT. Also, the impurity states introduced by the Cu n cluster to the band gap of TiO2NT cause an obvious redshift of the optical absorption spectrum toward the visible light region, especially for the even n cases.