 Real time detection of G-agents surrogate at extremely low concentration in gas phase  SERS substrates based on Au NPs layers with near optimum inter-particle distances  Citrate coating acts as an effective concentrator of target molecules

Surface-enhanced Raman scattering (SERS) is a powerful spectroscopic technique for selective detection and quantification of molecules at extremely low concentrations. However, practical SERS applications for gaseous chemicals with small cross section is still in its early stages. We herein report a plasmonic-sorbent thin-film platform with integrated Raman internal standard with outstanding SERS sensing capabilities for chemical warfare agents (CWA) simulants. The thin film is constituted of close-packed core−shell Au@Ag nanorods individually encapsulated within a ZIF-8

The development of SERS substrates for chemical detection of specific analytes requires appropriate selection of plasmonic metal and the surface where it is deposited.Here we deposited Ag nanoplates on three substrates: i) conventional SiO 2 /Si wafer, ii) stainless steel mesh and iii) graphite foils. The SERS enhancement of the signal was studied for Rhodamine 6G (R6G) as common liquid phase probe molecule. We conducted a comprehensive study with =532, 633 and 785 nm on all the substrates.The best substrate was investigated, at the optimum laser 785 nm, for gas phase detection of dimethyl methyl phosphonate (DMMP), simulant of the G-series nerve agents, at a concentration of 2.5 ppmV (14 mg/m 3 ). The spectral fingerprint was clearly observed; with variations on the relative intensities of SERS Raman bands compared to bulk DMMP in liquid phase reflects the DMMP-Ag interactions. These interactions were simulated by Density Functional Theory (DFT) calculations and the simulated spectra matched with the experimental one. Finally, we were detected the characteristics DMMP fingerprint with hand-held portable equipment. These results open the way for the application of SERS technique on real scenarios where robust, light-weight, miniaturized and simple to use and cost-effective tools are required by first responders.