Rapid, ultrasensitive, highly selective detection of toxic Hg(II) ions in seabass, swordfish and water samples

[Display omitted] •Triphenylamine-thiosemicarbazide molecule provided selective detection of Hg2+ ions.•The probe (TPA–TSC) demonstrated “turn-off” fluorometric response.•TPA–TSC exhibited limit of detection (0.14 nM) among the lowest reported to date.•TPA–TSC successfully detected Hg2+ ions in different samples of water.•TPA–TSC offered a promising method for monitoring mercury pollution in seafood. A novel fluorescent probe bearing triphenylamine, thiophene and thiosemicarbazide (TPA–TSC) was developed, and its distinct features were investigated. TPA–TSC demonstrated excellent selectivity towards Hg2+ ions, with a limit of detection (0.14 nM) among the lowest reported to date. It also exhibited a turn-off response by forming stable complex for a brief period (