Thermoelectric Field-Assisted Raman Scattering and Photocatalysis with GaN-Plasmonic Metal Composites

Abstract

The combination of metallic nanoparticles (NPs) with semiconductors used as surface-enhanced Raman scattering (SERS) substrates have been widely reported. However, the additional enhancements provided by the semiconductors are impressively small and have little effect on the SERS signal compared with that from the metallic NPs alone. Herein, thermoelectric semiconductor material gallium nitride (GaN) and silver nanoparticles (Ag NPs) are combined to create an electric-field-induced SERS (E-SERS) substrate, which further improves the SERS signal intensity by an order of magnitude compared to that without electric field induction. Based on the chemical enhancement induced by the thermoelectric potential, the presented E-SERS substrate realizes the detection over a broad kind of molecules, even with small Raman scattering cross sections.We show that the thermoelectric potential could regulate the charge exchange between GaN and Ag NPs and then shift the Fermi level of the Ag NPs over a wide-ranging distribution, which could increase the resonant electron transition probabilities with the detected molecules. Furthermore, the E-SERS substrate is also realized to monitor and manipulate the plasmon-activated redox reactions. Based on the finite element calculations, a detailed and comprehensive theoretical analysis is conducted to deepen the understanding of the chemical SERS and plasmon-activated photocatalyst mechanism.

Recent Advances and Perspective in Electrically Regulated Surface‐Enhanced Raman Spectroscopy

“…After applying a temperature gradient to this substrate, the formed thermoelectric potential can modulate the charge exchange between GaN and Ag NPs, thus distributing the Fermi energy level of Ag NPs in a wide range and thus improving the probability of resonant electron leap with the detected molecule. [ 42 ] When the Fermi energy level of n‐type GaN is higher than that of Ag, its work function is 4.26 eV. At the heterogeneous interface of Ag/GaN, the energy band of GaN bends upward, leading to the directional transfer of charge from GaN to Ag.…”

“…Schematics of the device used to flex the substrate and a SERS experiment with a flexed FF-PNT/Ag NP substrate. Adapted with permission from ref [42]…”

Ratiometric SERS detection of N2H4 by porous Ag(i)-linked Waugh-type polyoxometalate as an efficient label-free substrate

“…1,2 Coinage metal (Ag, Au and Cu) based functional materials are widely used as SERS substrates due to their unique local surface plasmon resonance (LSPR) characteristics. [3][4][5][6] On the other hand, stable and well-dispersed silver nanoparticles are vital in order to achieve sensitive and cheap SERS substrates. 7 However, the SERS signals fluctuate dramatically due to the uneven SERS substrates (structural or compositional heterogeneity) and the fluctuation of measurement parameters (focusing depth or laser).…”

Synergistic Enhancement Mechanism of High Electron Density and Localized Surface Plasmons for Strong Light‐Matter Interactions

“…[23] Furthermore, the electronic properties including bandgap (for exciton resonance), polarity (for dipole-dipole interaction), and energy level position (for energy level matching) of 2D layered semiconducting materials are easily tunable via doping and nanostructure engineering, which are benefit to optimize their enhancement performances. [22,24,25] Finally, 2D layered semiconducting materials were demonstrated to have obvious selectivity for probe molecules due to their difference in polarity, bandgap and energy level position. [23,26] These irreplaceable advantages of 2D layered semiconducting materials ensure they can serve as promising substrates to enhance the light-matter interactions.…”