The authors also discussed two important features of the SERS substrate. Firstly, the response is not affected by humidity conditions. Although no Raman signal from water should be expected (that is actually one of the advantages of Raman spectroscopy over e.g., infrared spectroscopy), water could still saturate the adsorption sites on the substrate, a common issue when employing porous materials for sensing applications. However, the intrinsic hydrophobicity of ZIF-8 micropores makes it a perfect candidate for this application. Secondly, the microporous ZIF-8 layer acts also as sieving membrane and although other aldehydes could also be detected and identified (see Figure ), aldehydes with larger dimensions were excluded from the sensor surface probed by SERS. Even further, the SERS substrate was also proven to be highly selective towards aldehydes, not showing any signal after exposure to other small molecules that could adsorb in the ZIF-8 porous structure, such as alcohols, organic acids, etc. Moreover, to explore the behavior of the GPS@ZIF-8 SERS substrate and to demonstrate its suitability towards early diagnostics of LC, the substrate was exposed to simulated breath from healthy and unhealthy patients, and by Principal Component Analysis (PCA), the GSP@ZIF-8 SERS substrate was demonstrated to be suitable for identifying the VOC signature of each simulated condition. In a subsequent work from the same group, Li et al. demonstrate the synthesis of hollow ZIF-8 structures encapsulating the GSPs, which improved the detection limit and reduced the interference from other molecules present during the SERS experiment. Also employing 4-aminothiophenol as docking agent and internal standard, the authors transferred the SERS substrate to filter paper and integrated it into the breathing valve of a facial mask, thus generating a platform suitable for continuos collection of analytes from exhaled breath (see Figure ). By this approach, SERS spectra were obtained after collecting the exhaled breath of 15 healthy and 10 LC patients (Figure ) and analyzed by Principal Component-linear discriminant analysis (PC-LDA) model, trained with both simulated gas and real samples. The results, highlighted in Figure , showed that the MOF-based SERS substrate allowed for identifying LC patients with an accuracy of 60%. The use of facial masks as noninvasive sample collection platform for point-of-care devices has also proven to be appropriate for the detection of SARS-CoV-2 infection. Thus developing SERS substrates integrated with Pointof-Care (POC) devices represents a promising and versatile platform. An important topic, especially when considering the development of POC devices, is the availability of a facile readout of the result. For example, reactive paper strips might not provide an absolute quantification of the analyte but with a YES-NO answer, confirming its presence with a concentration higher than certain limit. The generation of dual sensors, capable of both identification by naked eye and quantification are highly appealing platforms for POC devices. This was the approach followed by Xia et al., who generated Fluorescence (FL) and SERS bimodal sensor for the detection of benzaldehyde (BA). 134 Figure provides a summary of the synthesis and readout of this FL-SERS dual sensor. As shown, the authors started with plasmonic gold nanorods (GNRs) functionalized with 4mercaptonoaniline (PATP), which were later capped with CdSe/ZnS quantum dots (QDs) by selfassembly, prior functionalization of the QDs with 3-mercaptopropionic acid (MPA). The proximity between GNRs and QDs resulted in FRET quenching of the fluorescence of the QDs. This composite GNRs-QDs was then included in the reaction mixture for the synthesis of NU-901 MOF, generating single-core-shell GNRs-QDs@NU-901, later filtered through cellulose-based paper and dryed, generating the dual FL-SERS substrates. This clever design is an example of how structureperformance relations are paramount when designing MOF-based SERS substrates. The MOF phase act as sieving membrane and preconcentrate the analyte (BA), favoring the Schiff reaction with PATP on the SERS-active surface. At the same time, the addition of BA disassembly the GNRs-QDs which lead to an increase in the fluorescence signal, thus enabling the dual detection of BA in under 5 min.