New phenanthridine-based multi-functional chemosensor for selective detection of Th and Hg ions in both aqueous and solid state.

A new phenanthridine-based multifunctional chemosensor (L), was synthesised via a green synthetic route and characterised using FT-IR, NMR and HRMS analysis. The sensing application of L towards metal ions in both solution and solid-state was studied using UV-vis and fluorescence spectroscopy, which exhibits dual-sensing behaviour for Th and Hg ions with good recyclability. In aqueous acetonitrile, L showed rapid response for the detection of environmental toxic metal ions and has a very low analytical detection limit of 125.5 pM and 1.94 nM for Th and Hgions respectively, which is remarkably lower than the World Health Organization standard. The cation binding property of the L with Th and Hgions was investigated by Job plot, H NMR titration, HR-MS and DFT calculation. The in-situ formed ensemble L-Hg was further applied in the naked-eye detection of Cys (Cystine) and His (Histidine) over other common amino acids. The utility of L for real-time detection of Hg and Th ions was explored in various sources of environmental water samples, test paper strips, fingerprint imaging, fluorescent ink and smartphone-assisted sensing techniques, demonstrating the promising on-site visualization of the probe in controlling the toxicity levels in wastewater sources without resorting to expensive instruments.