Molecularly Imprinted Silver Nanocomposites for Explosive Taggant Sensing

Eduardo Aznar-Gadea,Rafael Abargues,Andrii Lopatynskyi,Juan P Martínez-Pastor,Vladimir Chegel,Pedro J Rodríguez-Canto

doi:10.1021/acsapm.1c00116

Abstract

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.

Highlights

Sensing explosives has become a strategic priority in homeland security, land mine detection, and military issues and is of interest in forensic research, human health, and environmental cleaning.[1,2] Most military explosives consist of aliphatic and aromatic nitro-containing molecules
We demonstrate the chemosensing capabilities of the Ag-PEI nanocomposite to 3-NT
The results showed that the Ag-PEI molecularly imprinted polymer (MIP) nanocomposite recognizes and selectively targets 3-NT with respect to the other analytes

Summary

■ INTRODUCTION

Sensing explosives has become a strategic priority in homeland security, land mine detection, and military issues and is of interest in forensic research, human health, and environmental cleaning.[1,2] Most military explosives consist of aliphatic and aromatic nitro-containing molecules. The LSPR band shifts to red around 6−7 nm and line width strongly increases from 76 to 96 nm Both effects can be ascribed to the formation of larger NPs at the expense of small ones by the Ostwald ripening mechanism, other than increasing the size dispersion and, eventually, forming nonspherical shapes at the highest temperatures.[41] We observed a very similar tendency in the synthesis of Ag-PEI NIP films, in which the FWHM increases significantly from 73 to 127 nm. This is somehow expected because 3-NT and 4NP have a similar molecular structure (toluene vs phenol) in terms of size and volume

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES