Recently, Prof. Zhongping Zhang’s research group in Institute of Intelligent Machines (IIM)，Chinese Academy of Sciences, has made significant progress in using Raman sensor strips to detect the odors of explosive trinitrotoluene (TNT) crystals and residues in the open environment. A paper entitled “Inkjet-Printed Silver Nanoparticle Paper Detects Airborne Species from Crystalline Explosives and Their Ultratrace Residues in Open Environment” was published on Analytical Chemistry (Anal. Chem. 2014, 86, 3338−3345.). 

In this paper, the researchers inkjet printed silver nanoparticles (AgNPs) on cellulose paper and established a Raman spectroscopic approach to detect the odors of explosive trinitrotoluene (TNT) crystals and residues in the open environment. The layer-by-layer printed AgNP paper was modified with p-aminobenzenethiol (PABT) for efficiently collecting airborne TNT via a charge-transfer reaction and for greatly enhancing the Raman scattering of PABT by multiple spectral resonances. Thus, a Raman switch concept by the Raman readout of PABT for the detection of TNT was proposed. The AgNPs paper at different sites exhibited a highly uniform sensitivity to TNT due to the layer-by-layer printing, and the sensitive limit could reach 1.6 × 10−17 g/cm2 TNT. Experimentally, upon applying a beam of near-infrared low-energy laser to slightly heat (but not destruct) TNT crystals, the resulting airborne TNT in the open environment was probed at the height of 5 cm, in which the concentration of airborne species was lower than 10 ppt by a theoretical analysis. Similarly, the odors from 1.4 ppm TNT in soil and 7.2, 2.9, and 5.7 ng/cm2 TNT on clothing, leather, and envelope, respectively, were also quickly sensed for 2 s without destroying these inspected objects. 

Paper link: http://pubs.acs.org/doi/abs/10.1021/ac403409q