Spectroscopic ultra-trace detection of nitroaromatic gas vapor on rationally designed two-dimensional nanoparticle cluster arrays.

Nanoparticle cluster arrays (NCAs) are engineered two-dimensional plasmonic arrays that provide high signal enhancements for critical sensing applications using surface enhanced Raman spectroscopy (SERS). In this work we demonstrate that rationally designed NCAs are capable of detecting ultra-traces of 2,4-dinitrotoluene (DNT) vapor. NCAs functionalized with a thin film of an aqueous NaOH solution facilitated the detection of DNT vapor at a concentration of at least 10 ppt, even in the presence of an excess of potential interferents, including Diesel fuel, fertilizers, and pesticides. Both in the presence and in the absence of this complex background the SERS signal intensity of the NO(2) stretching mode showed a continuous, concentration dependent response over the entire monitored concentration range (10 ppt-100 ppb). The small size, superb sensitivity, and selectivity, as well as the fast response time of <5 min, make NCAs a valuable photonic sensor platform for ultra-trace nitroaromatic gas vapor detection with potential applications in landmine removal and homeland security.