Selective Response of Mesoporous Silicon to Adsorbants with Nitro Groups

We demonstrate that the electronic structure of mesoporous silicon is affected by adsorption of nitro-based explosive molecules in a compound-selective manner. This selective response is demonstrated by probing the adsorption of two nitro-based molecular explosives (trinitrotoluene and cyclotrimethylenetrinitramine) and a nonexplosive nitro-based arematic molecule (nitrotoluene) on mesoporous silicon using soft X-ray spec- troscopy. The Si atoms strongly interact with adsorbed molecules to form Si-O and Si-N bonds, as evident from the large shifts in emission energy present in the Si L2,3 X-ray emission spectroscopy (XES) measurements. Furthermore, we find that the energy gap of mesoporous silicon changes depending on the adsorbant, as estimated from the Si L2,3 XES and 2p X-ray absorption spectroscopy (XAS) measurements. Our ab initio molecular dynamics calculations of model compounds suggest that these changes are due to spontaneous breaking of the nitro groups upon contacting surface Si atoms. This compound-selective change in electronic structure may provide a powerful tool for the detection and identification of trace quantities of airborne explosive molecules.Comment: 27 pages, 9 figure

Optical chemosensors and reagents to detect explosives

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Travaux de l'Institut Scientifique / Série Zoologie

2,3-Dimethyl-2,3-dinitrobutane (DMNB) is an explosive taggant added to plastic explosives during manufacture making them more susceptible to vapour-phase detection systems. In this study, the formation and detection of gas-phase \[M+H](+), \[M+Li](+), \[M+NH(4)](+) and \[M+Na](+) adducts of DMNB was achieved using electrospray ionisation on a triple quadrupole mass spectrometer. The \[M+H](+) ion abundance was found to have a strong dependence on ion source temperature, decreasing markedly at source temperatures above 50 degrees C. In contrast, the \[M+Na](+) ion demonstrated increasing ion abundance at source temperatures up to 105 degrees C. The relative susceptibility of DMNB adduct ions toward dissociation was investigated by collision-induced dissociation. Probable structures of product ions and mechanisms for unimolecular dissociation have been inferred based on fragmentation patterns from tandem mass (MS/MS) spectra of source-formed ions of normal and isotopically labelled DMNB, and quantum chemical calculations. Both thermal and collisional activation studies suggest that the \[M+Na](+) adduct ions are significantly more stable toward dissociation than their protonated analogues and, as a consequence, the former provide attractive targets for detection by contemporary rapid screening methods such as desorption electrospray ionisation mass spectrometry. Copyright (C) 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd

Towards Graphane Applications in Security: The Electrochemical Detection of Trinitrotoluene in Seawater on Hydrogenated Graphene

With greater security and humanitarian concerns, the pressing need to develop fast and sensitive point-of-care explosives detectors has never been more pronounced. Electrochemical detectors facilitate accurate and swift detection of these explosive traces to provide opportunities for preemptive measures. Sensitivity of the electrode material is one of the many important factors in the development of an effective and efficient electrochemical detector. Herein, we present study on the applicability of graphene and hydrogenated graphene for the detection of TNT in seawater. Graphene was found to display a higher sensitivity than hydrogenated graphene and could be an ideal material for the detection of TNT in seawater. This is likely due to the fact that graphene contains a larger amount of aromatic rings than hydrogenated graphene, enabling larger preconcentration. These finding are of high importance to the application of graphene-based materials for explosives detection