Manipulating Hot-Electron Injection in Metal Oxide Heterojunction Array for Ultrasensitive Surface-Enhanced Raman Scattering

ACS Appl Mater Interfaces. 2021 Nov 3;13(43):51618-51627. doi: 10.1021/acsami.1c11977. Epub 2021 Oct 21.

Abstract

Efficient photoinduced charge transfer (PICT) resonance is crucial to the surface-enhanced Raman scattering (SERS) performance of metal oxide substrates. Herein, we venture into the hot-electron injection strategy to achieve unprecedented enhanced PICT efficiency between substrates and molecules. A heterojunction array composed of plasmonic MoO2 and semiconducting WO3-x is designed to prove the concept. The plasmonic MoO2 generates intense localized surface plasmon resonance under illumination, which can generate near-field Raman enhancement as well as accompanied plasmon-induced hot-electrons. The hot-electron injection in direct interfacial charge transfer and plasmon-induced charge transfer process can effectively promote the PICT efficiency between substrates and molecules, achieving a record Raman enhancement factor among metal oxide substrates (2.12 × 108) and the ultrasensitive detection of target molecule down to 10-11 M. This work demonstrates the possibility of hot-electron manipulation to realize unprecedented Raman enhancement in metal oxides, offering a cutting-edge strategy to design high-performance SERS substrates.

Keywords: direct interfacial charge transfer; heterojunction array; localized surface plasmon resonance; photoinduced charge transfer; plasmon-induced charge transfer; surface-enhanced Raman scattering.