Dual functional colorimetric and turn-off fluorescence probe based on pyrrolinone ester hydrazone dye derivative for Cu²⁺ monitoring and pH change

A new, dual function colorimetric chemosensor and turn-off fluorescent probe based on pyrrolinone esters hydrazone dye bearing a terminal thiophene moiety (TPESHD) was designed, synthesized and investigated. The sensor exhibited highly selective and sensitive detection toward Cu2+ in ethanol aqueous solution with detection limit up to 0.63 μM of copper ion. The distinct color change and fluorescence quenching was visible to the naked eye from yellow to purple in case of copper over other metal cations tested (Na+, Mg2+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Ag+, ….etc.). Also, the sensor showed high sensitivity to pH changes in the 7.25–12.5 range and the color of dye was changed from yellow to bluish color. The structure of the synthesized probe was confirmed by elemental analysis, nuclear magnetic resonance spectroscopy, and mass spectra. The dual chemosensor formed a 1:1 complex with Cu2+ and displayed fluorescent quenching. The binding mechanism with copper ions was confirmed by 1HNMR titration, mass spectra and IR spectra. Cellulose acetate/TPESHD based strips for ammonia detection application was fabricated and studied.