Naked eye and fluorescent detections of Hg ²⁺ ions and Cysteine via J-aggregation and deaggregation of a perylene bisimide derivative

Selective naked eye and fluorescent sensor responses of a 1,6,7,12-tetra(4-tert-butylphenoxy)perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) derivative are reported for the first time toward Hg ²⁺ ions and Cysteine (Cys) via J-aggregation and deaggregation mechanisms. The J-aggregation and deaggregation of PBI induced by Hg ²⁺ and Cys were well established by UV-vis/PL and ¹ H NMR titrations. The 1:1 stoichiometry of PBI-Hg ²⁺ and Cys-Hg ²⁺ /PBI ensembles were elucidated from the jobs plots based on their UV-vis spectral changes. The linear complex formation by PBI-Hg ²⁺ ensemble was confirmed through FT-IR and ¹ H NMR spectral studies and well supported by its reversible nature upon the addition of pentamethyl diethylene triamine (PMDTA). The positive cooperativities of Hg ²⁺ and Cys (with PBI) in PBI-Hg ²⁺ and Cys-Hg ²⁺ /PBI ensembles were evidenced from the Hill plots based on their fluorescence binding isotherms. The detection limits of Hg ²⁺ ions and Cys were calculated as 36.6 and 91.3 nM, respectively, by standard deviations and linear fittings of their Stern-Volmer (K _SV ) constants and relative fluorescence intensity changes, respectively. Furthermore, the sensor properties of PBI were well investigated by K _SV constants, pH values, time effects, and time resolved photoluminescence (TRPL) spectra.