Directing Energy into a Subwavelength Nonresonant Metasurface across the Visible Spectrum

Group 10 metals (i.e., Ni, Pd, Pt) catalyze a wide range of chemical transformations, but the weak interaction of their nanoparticles with light hinders their development for photocatalytic applications. Conversely, coinage metal nanoparticles (particularly Ag and Au) exhibit intense localized surface plasmon resonances in the visible spectrum but are relatively unreactive, limiting the scope and efficiency of their photochemical processes. Here we demonstrate the design, fabrication, and characterization of a new structure containing a single layer of Pd nanoparticles that absorbs up to >98% of visible light. Furthermore, the wavelength of absorption is controlled throughout the visible range of the electromagnetic spectrum by modulating the thickness of a supporting metal oxide film. We show that the absorbed energy is concentrated in the nanoparticle layer, crucial for energy conversion applications, including photocatalysis and photothermal processes.