Abstract
We report on a new sensor strategy that integrates molecularly imprinted polymers (MIPs) with surface enhanced Raman scattering (SERS). The sensor was developed to detect the explosive, 2,4,6-trinitrotoluene (TNT). Micron thick films of sol gel-derived xerogels were deposited on a SERS-active surface as the sensing layer. Xerogels were molecularly imprinted for TNT using non-covalent interactions with the polymer matrix. Binding of the TNT within the polymer matrix results in unique SERS bands, which allow for detection and identification of the molecule in the MIP. This MIP-SERS sensor exhibits an apparent dissociation constant of (2.3 ± 0.3) × 10−5 M for TNT and a 3 μM detection limit. The response to TNT is reversible and the sensor is stable for at least 6 months. Key challenges, including developing a MIP formulation that is stable and integrated with the SERS substrate, and ensuring the MIP does not mask the spectral features of the target analyte through SERS polymer background, were successfully met. The results also suggest the MIP-SERS protocol can be extended to other target analytes of interest.
Highlights
Rapid detection and identification of energetic materials is a priority for military and homeland defense applications with the increased need to avoid potential harm caused by explosive hazards
There are several key challenges to overcome in the development of a hybrid molecularly imprinted polymers (MIPs)-surface enhanced Raman scattering (SERS) sensing platform including: (i) developing a MIP that does not completely mask the spectral features of the target analyte through SERS polymer background; (ii) developing a strategy for MIP integration that enables target interaction within the surface enhanced plasmon field responsible for SERS signal enhancement; (iii) developing a MIP formulation that is stable and truly integrated with the SERS substrate to allow for practical application in the field; and (iv) ensuring that the developed MIP allows for template removal, analyte reintroduction, and provides selectivity for the target analyte components
To assess the selectivity of the integrated MIP-SERS sensor for the target analyte (i.e., TNT) the sensor was challenged by a series of molecules that are structurally similar to the target molecule
Summary
Rapid detection and identification of energetic materials is a priority for military and homeland defense applications with the increased need to avoid potential harm caused by explosive hazards. SERS is an extremely sensitive and selective technique that involves enhancements in the Raman scattering intensities of analytes adsorbed on a roughened metal surface (typically, gold or silver) [29,30]. By employing the developed approach presented here, the MIP will concentrate the target to the SERS-active surface, thereby making the combined approach more highly selective than a SERS-only detection platform and free from errors related to background interference. This integrated MIPs and SERS concept is a novel approach to chemical sensing; reported investigations of this pairing are scarce [31,32]. Sensitivity is determined by the SERS substrate used in this study, while selectivity is provided by both the specific binding interaction of the TNT with the MIP and the unique molecular “fingerprint” provided by the SERS measurement
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