Rapid, sensitive DNT vapor detection with UV-assisted photo-chemically synthesized gold nanoparticle SERS substrates

We report rapid, sensitive, and direct detection of 2,4-dinitrotoluene (DNT) vapor using tailored gold nanoparticles (Au-NPs) as the SERS substrate. The Au-NPs were synthesized using the UV-assisted photo-chemical reduction method and subsequently formed a monolayer on the glass slide through polymer-mediated self-assembly. The SERS substrate such prepared has high SERS enhancement, high affinity towards DNT vapor, and rapid response to the DNT adsorption/desorption. We systematically studied the effect of the Au-NP size and surface density on the SERS performance such as enhancement factor and response time. With the optimized SERS substrate, an enhancement factor over 5.6 × 10(6) was achieved. Furthermore, real-time detection of DNT vapor with only 0.35 second data acquisition time was demonstrated using a 12 mW laser. Compared to previously reported results, we achieved two orders of magnitude reduction in detection time and more than one order of magnitude reduction in excitation laser power. The detection limit is estimated to be 0.4 attogram, which corresponds to a sub-ppb DNT concentration in air. This work will lead to the development of ultra-fast and ultra-sensitive SERS devices for explosive identification and monitoring.