Au/TiO ₂/Au as a plasmonic coupling photocatalyst

The enhanced near-field amplitude of localized surface plasmon resonance in the proximity of metal nanoparticles can boost the photocatalytic activity of the neighboring semiconductor, which has been proven and has attracted wide interest recently. Since the plasmon resonance energy strongly depends on the metal particle size and shape, interparticle spacing, and dielectric property of the surrounding medium, it is available to improve the photocatalytic activity of the neighboring semiconductor by designing and synthesizing targeted metal nanoparticles or assembled nanostructures. In this paper, we propose a Au/TiO ₂/Au nanostructure with the thickness of the middle layer TiO ₂ nanosheets around 5 nm, which satisfies the distance needed for the coupling effect between the opposite and nearly touching Au nanoparticles, and thus, it can be used as a "plasmonic coupling photocatalyst". Compared with the bare TiO ₂ nanosheet films, the photocurrent density of this favorable nanostructure exhibited a significant improvement in the visible region. The three-dimensional finite-difference time domain was used to quantitatively account for the electromagnetic enhancement of this Au/TiO ₂/Au heterostructure and substantiated the plasmonic enchancement photocatalytic mechanism further.