Synthesis and spectral characterization of the phenothiazine-thiosemicarbazide probe for the optical solid-state detection of Hg2+ and Cu2+

Abstract

In this study, a phenothiazine-thiosemicarbazide (PTZDS) probe was synthesized and characterized. The synthesized PTZDS probe exhibited a yellow color, with a native fluorescence emission at λ_emission = 550 nm and λ_excitation = 450 nm. Over other metal ions, the probe exhibited significant selectivity and sensitivity towards Hg²⁺ and Cu²⁺. The probe showed fluorescence quenching along with a minor shift in the absorbance spectra from 400 to 450 nm and 430 nm in the presence of Hg²⁺ and Cu²⁺, respectively. In addition, the color of the synthesized probe remarkedly faded with the addition of Hg²⁺ or Cu²⁺. Fluorescence measurements, infrared spectroscopy (IR), and density functional theory studies were employed to elucidate the binding process in the PTZDS + Cu²⁺ and PTZDS + Hg²⁺ sensor systems. Furthermore, photophysical investigations of the synthesized probe with Hg²⁺ and Cu²⁺ were performed. Finally, the probe was successfully employed as a solid-state thin layer chromatography (TLC) optical sensor for detecting Hg²⁺ and Cu²⁺ ions.