Triphenylamine-based chemosensor and its application in rapid naked eye detection, test strips, bioimaging and complete removal of Hg2+ from water samples

[Display omitted] •The TPA-SB sensor showed rapid absorbance, excellent selectivity, and high sensitivity towards Hg2+ ions.•The TPA-SB sensor could detect Hg2+ ions from colourless to reddish-orange via naked-eye, exhibiting fluorescence OFF response to Hg2+ ions.•The detection limit achieved for Hg2+ ions (0.27 nM).•Low-cost, easy-to-make filter paper strips are developed to detect Hg2+ ions for field application.•Solid-supported TPA-SB@SiO2 was developed and demonstrated for onsite analysis. A new, sensitive and highly selective chemosensor (N, N-diphenyl-4-(E)-(E)-thiophen-2-ylmethylene)hydrazono)methyl) aniline (TPA-SB) for Hg2+ was designed and synthesised by combining the triphenylamine motif and thiophene group. The TPA-SB exhibited a remarkable colour change from light yellow to reddish-orange with Hg2+, which was visible to the naked eye. The detection limit of Hg2+ was 0.27 nM. We fabricated a TPA-SB-coated paper sensor to detect Hg2+ rapidly, with excellent selectivity and sensitivity. Adding KI to TPA-SB-Hg2+ recovered the colour and retained the probe TPA-SB as a reversible sensor for real-time applications in solution and paper matrix. Further, we developed a solid-supported adsorbent (TPA-SB-SiO2) and utilised it for the complete removal (100%) of Hg2+ ions from the mercury-contaminated water. Based on the NMR titration, ESI – MS, Job’s plot and DFT study, probable binding mode and biding ratio (1:1) of TPA-SB with Hg2+ have been proposed. Importantly, we can apply the present sensing system for recognising Hg2+ ions in Escherichia coli cells.