Detection of Arsenic(V) by Fluorescence Sensing Based on Chlorin e6-Copper Ion

The high toxicity of arsenic (As) can cause irreversible harm to the environment and human health. In this study, the chlorin e6 (Ce6), which emits fluorescence in the infrared region, was introduced as the luminescence center, and the addition of copper ion (Cu²⁺) and As(V) provoked a regular change in fluorescence at 652 nm, whereas that of As(III) was 665 nm, which was used to optionally detect Cu²⁺, arsenic (As(III), and As(V)). The limit of detection (LOD) values were 0.212 μM, 0.089 ppm, and 1.375 ppb for Cu²⁺, As(III), and As(V), respectively. The developed method can be used to determine Cu²⁺ and arsenic in water and soil with good sensitivity and selectivity. The 1:1 stoichiometry of Ce6 with Cu²⁺ was obtained from the Job plot that was developed from UV-visible spectra. The binding constants for Cu²⁺ and As(V) were established to be 1.248 × 10⁵ M^-1 and 2.35 × 10¹² M^-2, respectively, using B-H (Benesi-Hildebrand) plots. Fluorescence lifetimes, B-H plots, FT-IR, and ¹H-NMR were used to postulate the mechanism of Cu²⁺ fluorescence quenching and As(V) fluorescence restoration and the interactions of the two ions with the Ce6 molecule.