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In this study, we designed shell-dependent Ag@Cu2O core–shell nanoparticles (NPs) for SERS study. Compared to Cu2O NPs, Ag@Cu2O core–shell NPs exhibited high SERS activity because of the localized surface plasmon resonance (LSPR) from Ag core.

The PI-SERS signals of R6G molecules on a MoS2/Au substrate are enhanced at 2.39 GPa by a two-step charge transfer process.

A systematic high pressure study is performed on Mn–N compounds by using the particle swarm optimization methodology.

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As a newly emerging approach for surface-enhanced Raman spectroscopy (SERS), pressure-induced SERS (PI-SERS) has been attracting increasing interest for its applications in Raman signal enhancement at extreme conditions. However, how to efficiently realize the PI-SERS enhancement and elucidate the corresponding mechanism remain open questions. Herein, we demonstrate the PI-SERS enhancement up to 8.04 GPa using monolayer molybdenum disulfide (ML-MoS2) as a SERS substrate and three organic molecules with similar energy levels but different symmetries as probes. The combined theory and experiment results show that a pressure-induced increase in the Fermi level of the ML-MoS2 substrate and a decrease in the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gap of probe molecules lead to a transition from the multiple resonance-related SERS enhancement to charge transfer (CT)-dominated PI-SERS selective enhancement, depending on the incident laser energy and the pressure applied. Such PI-SERS selective enhancement has been discussed in the framework of CT-induced strengthening of electron–phonon coupling, as well as a possible match of the structural symmetries between probe molecules and the substrate. This study provides deep insights into our understanding of PI-SERS enhancement, and the revealed mechanism can be extended to other molecules for SERS at extreme conditions.

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