Abstract
The sensing and differentiation of explosive molecules is key for both security and environmental monitoring. Single fluorophores are a widely used tool for explosives detection, but a fluorescent array is a more powerful tool for detecting and differentiating such molecules. By combining array elements into a single multichannel platform, faster results can be obtained from smaller amounts of sample. Here, five explosives are detected and differentiated using quantum dots as luminescent probes in a multichannel platform: 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), tetryl (2,4,6-trinitrophenylmethylnitramine), cyclotrimethylenetrinitramine (RDX), and pentaerythritol tetranitrate (PETN). The sharp, variable emissions of the quantum dots, from a single excitation wavelength, make them ideal for such a system. Each color quantum dot is functionalized with a different surface receptor via a facile ligation process. These receptors undergo nonspecific interactions with the explosives, inducing variable fluorescence quenching of the quantum dots. Pattern analysis of the fluorescence quenching data allows for explosive detection and identification with limits-of-detection in the ppb range.
Highlights
Detection of small amounts of explosive material is a key challenge in both the securing of public spaces and vulnerable targets and the environmental monitoring of drinking and waste waters
Previous examples have focused on using electrochemical sensors and colorimetric dyes, and advances in computing power allow for application of machine learning techniques to rapidly classify sensing results with a variety of multivariate statistical techniques.[4−8] The use of nanoparticle-based sensors by Rotello et al for biosensing has introduced another powerful tool to array-based chemical sensing, and the new direction of this work focuses on multichannel sensing; combining elements of the cross-reactive array in a single test with multiple outputs, for example, multiple color channels, to reduce the sample volume required and increase sample throughput.[9−11]
Monitoring of types and levels of explosive in the environment is an active challenge in the security and environmental safety domains,[12,13] with the U.S Environmental Protection Agency (EPA) setting limits on 2,4dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and cyclotrimethylenetrinitramine (RDX) in drinking water (
Summary
Detection of small amounts of explosive material is a key challenge in both the securing of public spaces and vulnerable targets and the environmental monitoring of drinking and waste waters. We report a multichannel nanoparticle array for the detection of explosives in a rapid single fluorometric test It is based on a system of cross-reactive surface functionalities comprised of two macrocyclic (calixarene and cyclodextrin) and two simple (−OH and −OMe) surfaces on multicolored, fluorescent QDs. The system is designed to respond to a range of explosives through supramolecular interactions, such as host−guest binding, electrostatics, and π−π stacking, causing fluorescence quenching of the QDs, to create an analytical fingerprint (Figure 1). The system is designed to respond to a range of explosives through supramolecular interactions, such as host−guest binding, electrostatics, and π−π stacking, causing fluorescence quenching of the QDs, to create an analytical fingerprint (Figure 1) It is tested against five explosives, DNT, TNT, tetryl, RDX, and pentaerythritol tetranitrate (PETN) using single channel analysis, demonstrating 100% specificity. OH and OMe surface functionalities were created to give differential reactivity (Figure 2)
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