Ag nanocluster/DNA hybrids: Functional modules for the detection of nitroaromatic and RDX explosives

Luminescent Ag nanoclusters (NCs) stabilized by nucleic acids are implemented as optical labels for the detection of the explosives picric acid, trinitrotoluene (TNT), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The sensing modules consist of two parts, a nucleic acid with the nucleic acid-stabilized Ag NCs and a nucleic acid functionalized with electron-donating units, including l-DOPA, l-tyrosine and 6-hydroxy-l-DOPA, self-assembled on a nucleic acid scaffold. The formation of donor-acceptor complexes between the nitro-substituted explosives, exhibiting electron-acceptor properties, and the electron-donating sites, associated with the sensing modules, concentrates the explosives in close proximity to the Ag NCs. This leads to the electron-transfer quenching of the luminescence of the Ag NCs by the explosive molecule. The quenching of the luminescence of the Ag NCs provides a readout signal for the sensing process. The sensitivities of the analytical platforms are controlled by the electron-donating properties of the donor substituents, and 6-hydroxy-l-DOPA was found to be the most sensitive donor. Picric acid, TNT, and RDX are analyzed with detection limits corresponding to 5.2 × 10 ^-12 M, 1.0 × 10^-12 M, and 3.0 × 10 ^-12 M, respectively, using the 6-hydroxy-l-DOPA-modified Ag NCs sensing module.