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

Abstract

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-SBcoated paper sensor to detect Hg2+ rapidly, with excellent selectivity and sensitivity. Adding KI to TPA-SBHg2+ 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.