Thiophene derived sky-blue fluorescent probe for the selective recognition of mercuric ion through CHEQ mechanism and...

A vibrant blue organic luminescent material with enhanced photophysical properties is in great demand for the generation of optoelectronic devices and luminescent sensors. In this context, the thiophene-benzimidazole probe TH-IMI was designed and synthesized by a simple condensation reaction. The synthesized probe has shown excellent photophysical properties like high FL intensity, a high quantum yield of 90% in the solution phase, a low optical bandgap of 2.84 eV, positive solvatochromic effect in emission spectra and Disaggregation Caused Quenching Effect (DCQE). Such a high luminescent probe was employed for the recognition of mercuric ions in the solution phase, solid state detection, and in tracking mercury in green gram sprouts. UV-visible absorption and emission spectra, ¹H NMR titration, IR spectroscopic and ESI-MS techniques confirmed that the probe underwent a fluorescence quenching response via the CHEQ effect upon exposure to Hg²⁺. The stoichiometry was found to be 1:1 through Job's plot and has a fast response rate and relatively low limit of detection of about 6.13 × 10^-11 M in a linear range between 0 and 110 µL.