A nanoengineered sensor to detect vibrational modes of warfare agents/explosives using surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) is emerging as a versatile and powerful technique for the detection of various defense related hazardous materials. This work illustrates the level of sensitivity and reproducibility achieved using SERS substrates with structural features engineered at the nanometer scale. Nanostructured substrates show significant sensitivity toward a number of different analytes. Pinacolyl methyl phosphonic acid (PMPA), a nerve-agent degradation product, was detected in less than 30 seconds at 1ppb. Para-nitroaniline, an explosives simulant, was detected in the same amount of time at 10 ppm. Multiple tests showed signal reproduction of PMPA at 100 ppb below a 7% standard deviation. The substrates are small and lightweight. In addition, a portable SERS spectrometer, equipped with a fiber coupling for excitation and detection, can act as the sensor body. On a previous occasion, electrochemically roughened SERS substrates were loaded into this portable spectrometer and deployed in the field for the successful blind detection of buried, defused, landmines. Such a system accommodates multiple substrate technologies, allowing sensing in the vapor and liquid phase as well as via solids extraction, and is compatible with nanoscale substrates.