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

Oxygen defects play a crucial role in a variety of functional transition metal oxides, ranging from photocatalytic materials to photoelectric devices. Tungsten oxide (WO3-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 WO3-x structures. Therein, WO3-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 WO3-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 WO2.72 QD@Ag NW (WO2.72 QDs supported on AgNWs) composite compared to those of individual WO2.72 QDs under simulated AM 1.5G light. Furthermore, the WO3-x QD@Ag NW composite exhibits both photocatalytic activity and surface-enhanced Raman scattering (SERS) features, and the WO3-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 WO2.72 QDs upon light irradiation. This work provides new insight into the design of highly efficient transition metal oxide/plasmonic metal nanocomposites for photoelectric devices.