Graphite sheet as a novel material for the collection and electrochemical sensing of explosive residues

This work presents the use of a graphite sheet (graphite papers) as a new platform for the collection and sensing of explosive residues. This material offers a lightweight, highly conductive, flexible platform that can be cut in several ways, enabling for the collection of explosive residues at the place of interest, without any further sample preparation steps. As a proof-of-concept, the device was utilised for the collection and electrochemical sensing of 2,4,6-trinitrotoluene (TNT) residues. The GS has a remarkable performance for the sensing of TNT within the supporting electrolyte (0.1 mol dm^-3 HCl) resulting in a linear range between 1 and 1300 μmol dm^-3 and detection limit of 0.06 μmol dm^-3 using square-wave voltammetry (SWV). Five surfaces (granite, gloved and bare hands, metal and cash banknotes) were contaminated with traces of TNT and the collection was performed using the graphite sheet (1 cm² square pieces were swiped over the different surfaces). The results obtained using SWV enabled the identification of TNT residues, at quantities of 0.01-0.23 ng (quantification by the measured coulometric charge of the SWV scan), demonstrating that this novel material can be used as a promising device at crime scene investigations.