10×-Enhanced Heterogeneous Nanocatalysis on a Nanoporous Gold Disk Array with High-Density Hot Spots.

Certain noble metal nanostructures as heterogeneous photocatalysts have drawn significant attention in the recent past because of their unique optical properties which lead to the excitation of localized surface plasmon resonance (LSPR). The LSPR concentrates electromagnetic fields to the surfaces and its relaxation processes can convert photon energy to energetic charge carriers or heat, which can be subsequently harvested to enhance surface catalysis. Here, we report the catalytic performance of a novel plasmonic nanostructure, disk-shaped nanoporous gold (NPG) nanoparticles or simply NPG disks, using a well-tested reduction pathway of resazurin to resorufin. We show that the catalytic reaction rate of NPG disks is enhanced by 10-fold upon external light illumination because of the excitation of LSPR. The plasmon-enhanced catalytic reaction follows a linear-to-superlinear transition in the rate dependence on the input light power. In addition, the light input results in a room temperature reaction rate equivalent to that of an ambient temperature of 70 °C. Together, the results support that hot charge carriers play the dominant role in the enhancement.