Using unmodified Au nanoparticles as colorimetric probes for TNT based on their competitive reactions with melamine

Abstract

Abstract Gold nanoparticles (Au NPs) can serve as visualized colorimetric probes for various targets and modification-free sensing strategies are preferred. The donor–acceptor interaction between the electron-rich melamine (MA) and the electron-deficient trinitrotoluene (TNT) allows formation of a supramolecule in aqueous solution. Melamine alone makes the initially individual reddish Au NPs aggregate into gray/blue Au NP assemblies due to melamine forming multiple ligand sites toward the Au NPs. Interestingly, the preformed supramolecule of MA–TNT disenables aggregation of the Au NPs. Therefore the unmodified Au NPs provide facile colorimetric probes for TNT detection in aqueous solution. Rapid identification of TNT is established by naked eye inspection. By using spectrophotometer tools, quantification of TNT is accomplished with a linear range of 80 μmol L −1 to 1.2 mmol L −1 and a limit of detection (LOD) of 27 μmol L −1 . In contrast to previous strategy with surface-modified Au NPs, here a modification-free sensing strategy for TNT assay has been developed with greater convenience, rapidity, and cost-effectiveness.