Photocatalytic Enhancements to the Reduction of 4-Nitrophenol by Resonantly Excited Triangular Gold-Copper Nanostructures

The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride serves as a well-established model reaction for assessing the catalytic activity of metal nanoparticles. While many of the studied nanoparticles are plasmonic in nature, there is little understanding of whether significant photocatalytic enhancements to the reaction rate are achievable. Here, we assess the catalytic and photocatalytic properties of highly faceted, substrate-immobilized nanoprism-like AuCu structures synthesized using a vapor phase templated-assembly technique. The so-formed structures have a bimetallic composition which is well-recognized for its catalytic capabilities as well as a strong localized surface plasmon resonance in the visible spectrum which gives rise to enhanced near-fields at the tips of the triangle. Using a dip catalyst modality, the structures are demonstrated as heterogeneous photocatalysts with a 32-fold enhancement to the reaction rate constant when resonantly illuminated with 10 mW/cm² laser light. The study demonstrates the potential of such structures as photocatalysts and validates the reduction of 4-nitrophenol as a reaction useful in assessing the photocatalytic capabilities of plasmonic nanostructures.