Sensing explosive taggants such as 3-nitrotoluene (3-NT) and 2,3-dimethyl-2,3-dinitrobutane has become a strategic priority in homeland security. This work reports the synthesis of a solid-state plasmonic sensor based on a nanocomposite of Ag nanoparticles (NPs) embedded in a molecularly imprinted polymer (MIP) for selective detection of 3-NT, an explosive taggant for 2,4,6-trinitrotoluene. In our approach, the in situ synthesis of Ag NPs and the molecular imprinting with 3-NT as a template take place simultaneously inside the polyethyleneimine (PEI) thin film during the baking step after spin coating. The MIP sensor fabrication is done by a low-cost, fast, and scalable one-step procedure. We demonstrate the chemosensing capabilities of Ag-PEI MIP nanocomposites to 3-NT using the localized surface plasmon resonance band intensity decay as a sensing parameter. The molecular imprinting approach results in an enhancement of specific sensor response to 3-NT, with a limit of detection of 54.8 ng for 3-NT and a sensitivity of 24.0% ± 3.0%. We tested the MIP sensor specificity by comparing the sensor response to several NO2-containing molecules. The Ag-PEI MIP sensor demonstrated a robust, specific molecular recognition toward 3-NT. Because the MIP nanocomposite sensor is easy to prepare, easy to use, and inexpensive, these plasmonic sensors can be easily implemented with portable reading platforms into remote explosive detection and bomb disposal robots.

Chemical sensors based on fluorescent quantum dots have attracted intense interest because of their excellent optical and electronic properties compared to the routinely employed fluorescent organic dyes. This study reports a CdSe QD-polymer-based luminescent chemosensor, which is based on an array containing either green-emitting or red-emitting CdSe QDs embedded in polycaprolactone as a polymer host matrix. We evaluate the sensing capability of the nanocomposites by exposing both sensors to vapors of explosive taggants, explosive-like molecules, and some common solvents. Both nanocomposites exhibit a very fast response time of <30 s. The limit of detection of the sensors for 3-nitrotoluene, 4-nitrotoluene 2,3-dimethyl-2,3-dinitrobutane, and picric acid was found to be 0.055, 2.7, 0.7 and 916.4 ng, respectively. The sensor array constitutes a powerful tool to discriminate between explosive taggants (3-nitrotoluene, 4-nitrotoluene, and 2,3-dimethyl-2,3-dinitrobutane) and shows specific molecular recognition toward picric acid. This type of miniaturized luminescent QD-based nanocomposites might form the basis of a sensing platform technology to perform effective chemical detection and identification of explosive taggants preblast and postblast.