Deciphering the Role of Light Excitation Attributes in Plasmonic Photocatalysis: The Case of Nicotinamide Cofactor Regeneration

Photocatalysis with metal nanoparticles is attractive because of their unique plasmonic properties, such as large absorption cross section, high charge density, spectral tunability, and photostability. As a result, plasmonic photocatalysis has emerged as a distinct area in catalysis for performing different classes of chemical transformations. However, disentangling the exact mechanism in plasmonic photocatalysis is often challenging because of the interference from different plasmon relaxation pathways, which in turn is highly dependent on the catalyst–reactant system. Presently, the field demands a detailed investigation into different factors involved in plasmonic chemistry to gain a better understanding of the complex reaction pathway. Herein, we reveal the critical role of light excitation attributes in the plasmon-driven photoregeneration of the nicotinamide (NADH) cofactor by gold nanorods (AuNRs). The two distinct surface plasmon bands in AuNRs allowed us to study the exclusive role of interband vs intraband transitions in NADH photoregeneration. Also, the choice of reaction is ideal for testing various hypotheses, as it proceeds only in the presence of both light and catalyst. Long-lived hot charge carriers generated through interband transition, in combination with a favorable catalyst–reactant interaction, drive the efficient photoregeneration of the NADH cofactor (∼40%). Our study emphasizes the need for an appropriately chosen catalyst–reactant system and reaction conditions to gain meaningful insights into various factors controlling the product yield and selectivity in plasmonic photocatalysis.