Near-infrared-light mediated ratiometric luminescent sensor for multimode visualized assays of explosives.

The development of a portable and easy-to-use device for the detection of explosives with high sensitivity and selectivity is in high demand for homeland security and public safety. In this study, we demonstrate miniaturized devices depending on the upconversion ratiometric luminescent probe for point-of-care (POC) assay of explosives with the naked-eye. When the PEI-coated upconversion nanoparticles (UCNPs) selectively bonded to 2,4,6-trinitrotoluene (TNT) explosives by the formation of Meisenheimer complex, the formed of UCNP-Meisenheimer complexes show turned visible multicolor upconversion luminescence (UCL) on account of TNT-modulating Förster resonance energy transfer process under near-infrared excitation. With UCL emission at 808 nm as internal standard and ratiometric UCL at 477 nm to that at 808 nm (I477/I808) as output signal, the probe can simultaneously meet the accuracy for TNT explosives quantitative analysis. In addition, this easy-to-use visual technique provides a powerful tool for convenient POC assay of rapid explosives identification.