Although there has been intense research on plasmon-induced charge transfer within metal/semiconductor heterostructures, previous studies have all focused on the surface plasmonic resonance (SPR) of only noble metals. Herein and for the first time, we observe and take into account the plasmonic coupling between SPR of both noble-metal and semiconductor nanostructures. A W18O49/Ag heterostructure composed of metallic Ag nanoparticles (Ag NPs) and semiconducting W18O49 nanowires (W18O49 NWs) is designed and fabricated, which exhibits a broad and strong SPR absorption in the visible wavelength range. This SPR band is attributed to the SPR coupling between the SPR of both Ag NPs and W18O49 NWs. Surface-enhanced Raman scattering (SERS) is then used to reveal the interactions between the metal SPR, semiconductor SPR, and the heterostructure's charge transfer (CT) process, demonstrating that such coupled SPR enhanced the heterostructure's internal CT and SERS signals. Finally, we proposed a new coupled-plasmon-induced charge transfer mechanism to interpret the improved CT efficiency between the SERS substrate and molecules. Our work provides insight for further studies on plasmonic effects and interfacial charge transfer in metal/semiconductor heterostructures.
Keywords: charge transfer; heterostructure; plasmon coupling; surface plasmon resonance; surface-enhanced Raman scattering.