Cavity array, with excellent optical capture capability, has received increasing attention for the surface-enhanced Raman spectroscopy (SERS)-active substrates. Here, we proposed molybdenum disulfide (MoS2) nanocavities growing on pyramid Si (PSi) composed of in situ reduced Au nanoparticles (AuNPs), which can form the multiscale cavities (MSCs), and is facile for the couple of the plasmon. We demonstrated that the PSi/MoS2/Au MSCs can serve as highly sensitive, uniform, and stable SERS substrates for rhodamine 6G (R6G), crystal violet, and adenosine triphosphate detection, benefiting from the synergistic effect of the enhanced light trapping and the effective plasmonic couple. The couple of the plasmon in the MSCs is evidently proved by finite-difference time domain simulation, showing the strong electromagnetic field is located around the cavity wall. Moreover, the excellent hydrophobicity of the PSi/MoS2/AuNPs substrate endows it with the ability for the directional monitoring of organic pollutant in a mixture of oil and water. Finally, we demonstrated the MSCs with outstanding photocatalytic performance could achieve the renewable utilization by self-cleaning, which was attributed to the fast electron transfer and effective light absorption. The proposed PSi/MoS2/AuNPs MSC represents a robust mean using the plasmonic metal/semiconductor heterostructure for high-performance SERS sensors and photodegradation.

Unstable detection environment is one of the biggest interferences for in situ surface-enhanced Raman spectroscopy (SERS) using in real-time monitoring of toxic pollutants, leading to unreliable results. To address this problem, we have designed and prepared a cavity-based particle-in-quasicavity (PIQC) architecture composed of hierarchical ZnO/Ag nanosheets and nanoprotrusions for improving the in situ SERS performance under a liquid environment. Benefitting from the special cascaded optical field mode, the PIQC ZnO/Ag exhibits excellent in situ SERS detectability, with 10–18 M of limit of detection for rhodamine 6G and 12.8% of signal relative standard deviation value. Furthermore, by means of a microfluidic chip, this PIQC structure is proved to have the quantitative analysis feasibility and realizes real-time monitoring of the 3,3′,4,4′-tetrachlorobiphenyl, a representative global environmental hazard, under the flowing environment. The strategy in this paper provides a brand new idea to promote the application of in situ SERS in contaminant monitoring and is also instructive for light control in other optical fields.

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