Oxygen defect-induced localized surface plasmon resonance at the WO3−x quantum dot/silver nanowire interface: SERS and photocatalysis

Abstract

Oxygen defects play a crucial role in a variety of functional transition metal oxides, ranging from photocatalytic materials to photoelectric devices. Tungsten oxide (WO_3−x) is a type of transition metal oxide that has rich substoichiometric compositions and possesses oxygen defects. These oxygen defects determine the photon–electron interactions in the WO_3−x structures. Therein, WO_3−x quantum dots (QDs) exhibit fast carrier-transport for photon–electron interactions due to their strong quantum-size effects. Here, we report the use of non-stoichiometric WO_3−x QDs, as a model material, in combination with silver nanowires (Ag NWs) to study photon–electron interactions on the nanoscale. We demonstrate that the incident photon-to-electron conversion efficiency can be increased by 8.5% and that the dye photodegradation performance was improved by 40% in a WO_2.72 QD@Ag NW (WO_2.72 QDs supported on AgNWs) composite compared to those of individual WO_2.72 QDs under simulated AM 1.5G light. Furthermore, the WO_3−x QD@Ag NW composite exhibits both photocatalytic activity and surface-enhanced Raman scattering (SERS) features, and the WO_3−x QDs can be switched between a “photocatalytic state” and a “SERS state” by changing the stoichiometric ratio. The synergistic effects are ascribed to the “plasmonic state” of WO_2.72 QDs upon light irradiation. This work provides new insight into the design of highly efficient transition metal oxide/plasmonic metal nanocomposites for photoelectric devices.