MOF-in-Cavity Structure with Co-Location Effect of Hotspots and Molecules Suitable for Both Ex-Situ and In-Situ SERS Detections

Metal particle-in-cavity (M-PIC) structure is an excellent SERS model with rich cascade hotspot patterns. However, in most cases, the volume hotspots (VHSs) in conventional M-PIC structures are usually only appropriate for liquid- or gas-phase in-situ detection, greatly limiting their application scenarios. To solve this problem, we proposed a MOF particle-in-cavity (MOF-PIC) model and used it as a basis for designing a SERS substrate based on AAO/Ag/Au/ZIF-8 structure. The ZIF-8 particles in this structure act as the electric field modulation units as well as the spatial carriers of the target analytes, effectively realizing the spatial co-enrichment and co-location of the localized electric field and target analytes within the same micro region. Compared with the conventional M-PIC structure, this MOF-PIC structure shows better SERS enhancement, especially in the ex-situ detection scenario. Taking H₂S in solution as an example, the limit of detection of AAO/Ag/Au/ZIF-8 for it is down to 10^-10 M. Based on this, we can easily detect trace H₂S generated during cancer cell culture or beer manufacturing and storage respectively, in both in-situ and ex-situ detection scenarios, which proves that the MOF-PIC model has a good adaptability in various applications.