Gas and vapor phase detection of chemical threats on cooled SERS substrates

Detection of airborne chemical threats is an emerging challenge amidst the prevailing tumultuous global milieu. Extensive investigation has showcased the substantial promise of surface-enhanced Raman spectroscopy (SERS) for the on-site identification of hazardous chemicals present in liquid mediums, whether directly from a fluid source or through methodologies such as swab sampling. Nonetheless, exploration into the applicability of SERS for the detection of gas or vapor-phase chemical threats remains severely constrained. In this study, we present the successful realization of sub-parts per million (ppm) detection thresholds via SERS for hydrogen cyanide (HCN) and Tabun (GA) chemical warfare agents, facilitated by a custom-made gas sampling cell integrated with a Peltier cooling mechanism. The cooling regimen, spanning from 20 to -17 °C, verified a 140-fold increase in the SERS signal for 1 ppm HCN, concurrently enabling the detection of HCN and Tabun concentrations as low as 0.25 and 0.5 ppm, respectively. Implementation of temperature modulation and controlled flow routines substantially reduced detection times down to 240 s for HCN, with prospects for further optimization.