The next step in optimizing the performance of MOF-based SERS substrates in terms of matching the focal volume of probing laser beam with the thickness of the prepared structure. Phan-Quang et al explored this dependence by using a multilayer of Ag nanocubes coated with ZIF-8 were prepared by drop-casting. In this work SEM topography measurements were combined with SERS hyperspectral imaging of infiltrated 4-MBT analyte. As it can be seen in In Figure , thin assemblies under-utilize the focal volume of the laser beam, while thicknesses greater than 1 µm no longer contribute to the signal output. Now, even when the full focal volume of the laser is being employed, the distribution of metallic nanostructures in it is also important. Copyright 2018, The Royal Society of Chemistry. (e) SEM and hyperspectral images and schemes (left) for thickness optimization of the SERS substrates (right). Reproduced with permission from Phan-Quang et al. Copyright 2019, American Chemical Society. (f) (i) Single core-shell Au@MOF-5 NPs with controllable shell thicknesses. (ii) CO2 detection capacity for the different MOF-5 shell thicknesses. Reproduced with permission from He et al. Copyright 2013, Wiley-VCH Verlag GmbH & Co. KGaA. (g) SERS response towards CO2 detection of Ag nanocubes encapsulated within ZIF-8 and the different control experiments employing just a N2 flow, pre-synthesized ZIF-8 nanoparticles as modification for the Ag nanocubes and bare nanocubes assembly. Reproduced with permission from Lee et al. Copyright 2017, American Chemical Society.