Abnormal SPR-Mediated Photocatalytic Enhancement of Ag Nanocubes Covered by AgCl Ultra-thin Layer

Abstract

It was theoretically predicted that electric field intensities generated by surface plasmon resonance (SPR) around plasmonic metallic nanostructures could be reduced after covered by wide bandgap semiconductor, thus worsening the SPR-mediated photocatalytic activities. However, we found that the Ag nanocubes (Ag NCs) covered by AgCl demonstrated an abnormal SPR-mediated catalytic enhancement. Herein the PATP-to-DMAB oxidization was used as a model reaction to explore the photocatalytic conversions. It was observed that the Ag NCs covered by AgCl ultra-thin layer (AgCl@Ag NCs) presented better photocatalytic activities than those of individual Ag NCs under 633-nm excitation. To reveal the mechanism behind the superior activities of AgCl@Ag NCs, the PATP-to-DMAB conversions were also carried out in ambient argon (Ar), in which AgCl@Ag NCs demonstrated significantly higher conversions. These results could be interpreted based on the separation of electron–hole pairs in AgCl through SPR effect of Ag, where the electrons in the valence band of AgCl were excited to the empty states of Ag, leaving holes in the semiconductor and resulting in the oxidation of PATP to DMAB. Thus, our findings may provide a novel way to enhance SPR-mediated photocatalytic activities on plasmonic metallic nanostructures by the cover of an ultra-thin layer of wide bandgap semiconductor.