Three-dimensional aluminum nano funnel-antenna for enhanced absorption of near-ultraviolet light by TiO2

We propose a scheme to enhance near-UV band absorption of a rutile Ti_O2 nanoparticle by embedding Ti_O2 nanoparticle into designed Al three-dimensional (3D) nanostructures. The 3D finite-difference time-domain (FDTD) method was employed to calculate the absorption spectrum of pure rutile TiO₂ nanoparticle and that of TiO₂ mixed with designed Al nanostructures. Our theoretical study has shown that pure rutile TiO₂ has its maximum absorption located in the deep-UV band of about 210 nm. When we embedded the TiO₂ nanoparticle into Al nanostructure, a significant light harvesting effect occurs, and this maximum shifts to the near-UV band at about 340 nm, which is close to the mercury lamp 365 nm line. The maximum enhancement coefficient is more than two hundreds with an optimized Al nanostructure. The result means that Al nanostructures can play an important role in increasing the absorption of TiO₂ in the near-UV region. This phenomenon is attributed to the strong scattering and local field enhancement of light via designed Al nanostructure in the near- UV region. These designs open up a promising way to boost the photocatalytic activity of Ti_O2.