Detection of 2,4-Dinitrotoluene (DNT) as a Model System for Nitroaromatic Compounds via Molecularly Imprinted Short-Alkyl-Chain SAMs

Abstract

A 2-D molecularly imprinted monolayer (2-D MIM) approach was used to prepare a simple and robust sensor for nitroaromatic compounds with 2,4-dinitrotoluene (DNT) as the model compound, which is a precursor and analog for explosive 2,4,6-trinitrotoluene (TNT). In contrast to studies utilizing long-chain hexadecylmercaptan self-assembled monolayers (SAM)s for sensing, a shorter-chain alkylthiol (i.e., butanethiol SAM) was utilized for DNT detection. The role of the chain length of the coadsorbed alkylthiol was emphasized with a matched template during solution adsorption. Semiempirical PM3 quantum calculations were used to determine the molecular conformation and complexation of the adsorbates. A switching mechanism was invoked on the basis of the ability of the template analyte to alter the packing arrangement of the alkylthiol SAMs near defect sites as influenced by the DNT-ethanol solvent complex. A 2-D MIM was formed on the Au surface electrode of a quartz crystal microbalance (QCM), which was then used to sense various concentrations of the analyte. Interestingly, the 2-D MIM QCM also enabled the selective detection of DNT even in a mixed solution of competing molecules, demonstrating the selectivity figure of merit. Likewise, electrochemical impedance spectroscopy (EIS) data at different concentrations of DNT confirmed the 2-D MIM effectiveness for sensing based on the interfacial conformation and electron-transport properties of the imprinted butanethiol SAM.

Electrochemical Sensor for Explosives Precursors’ Detection in Water

“…Spectroscopic approaches have been the most widely explored [2][3][4][5][6][7], but quartz crystal microbalance (QCM), ion chromatography [8], capillary electrophoresis [9], surface-enhanced Raman scattering (SERS) [10], nanotechnology based-methods (using molecularly imprinted polymers [11], nanotubes, or nanoparticles), and sensor techniques [12][13][14][15][16] have also been largely described. Amongst the different types of sensors developed to address this need, the electrochemical sensors [17][18][19] present the advantages of being fast, inexpensive, and adapted to miniaturization.…”

Construction of imprint sites in mesopores of SBA-15 via thiol-ene click reaction

“…The purpose of these strategies is to prepare the imprinted materials in the optimizing forms that control recognition sites to be situated at the surface or in the proximity of materials surface. In recent years, molecular imprinting self-assembled mono-layers (SAMs) technique, which was called two-dimensional (2D) MIT, has attracted extensive research interest due to its advantages such as construction simplicity, fast template removal, and rapid sensor response time [20][21][22][23][24]. However, this method contains inherent drawbacks.…”

Development of Portable Quartz Crystal Microbalance for Biosensor Applications

“…Although the physical transduction principle is different between the two types of sensor, the biosensing mechanism is the same. These sensors have been extensively studied for applications in security and safety, such as explosive detection, (5)(6)(7)(8)(9)(10) food analysis, (11) and environmental pollution monitoring. (12) The two transducers can be combined with a flow injection analysis system, which makes the measurement more rapid and lessens the amount of analyte required.…”