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

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 MoO 2 and semiconducting WO 3−x is designed to prove the concept. The plasmonic MoO 2 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 × 10 8 ) 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.

High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects

“…Generally, Raman enhancement on a semiconducting material originates from the vibronic coupling between a semiconducting material and an adsorbate. [23][24][25][26][27][28][29][30][31] As shown in Fig. 4, the electronic band structure of ZnO 1Àx is investigated by UV-vis and ultraviolet photoelectron spectroscopy (UPS) as well as density functional theory (DFT) calculations.…”

Flexible Two-Dimensional Vanadium Carbide MXene-Based Membranes with Ultra-Rapid Molecular Enrichment for Surface-Enhanced Raman Scattering

“…The SERS activity of noble-metal-free materials is mainly derived from the charge transfer (CT) between the material and the adsorbed molecule, namely the chemical mechanism (CM). , Compared with noble metal materials, noble-metal-free materials possess more plentiful physical and chemical properties, providing enormous possibilities for the optimization of SERS performances. In recent years, researchers have prepared a series of novel noble-metal-free SERS materials with excellent performances through optimizing the morphology, , stoichiometric ratio, , crystallinity, , and crystal orientation of non-noble metal materials, such as metal oxides, − transition metal dichalcogenides, , metal organic frameworks, , organic semiconductors, , etc. However, these enhancement strategies tend to focus on regulating the physical and chemical properties of noble-metal-free materials, while ignoring the improvement of SERS performances by molecular enrichment.…”

Quantum Effects Enter Semiconductor-Based SERS: Multiresonant MoO3·xH2O Quantum Dots Enabling Direct, Sensitive SERS Detection of Small Inorganic Molecules

“…On the other hand, μ ex resonances are characteristic of semiconductor-based SERS materials, which can be tuned by manipulating the electronic states of the semiconductor. In addition to typical bandgap-related excitonic transitions (VB to CB), previous reports have also acknowledged the contributions of interband CT between the VB state and defective state as a source of μ ex resonance, ,, affording possibilities for the design of resonant CT pathways in wide-gap semiconductors under visible range laser excitation. Because the Raman detection of small inorganic molecules is much more difficult due to their small scattering cross section and the lack of μ mol , it is necessary to induce greater enhancement capacity within the semiconductor via interband energy resonances.…”