Two novel colorimetric fluorescent probes: Hg²⁺ and Al³⁺ in the visual colorimetric recognition environment

Two new dual channel Schiff base fluorescent probes, Tri-R6G and Tri-Flu, were synthesized, and can detect Hg²⁺ and Al³⁺, respectively. The two probes were characterized by FTIR, ¹H NMR, ¹³C NMR and HRMS, and their optical properties were detected by UV and FL. Test results showed the probes' detection of Hg²⁺ and Al³⁺ compared to other metal ions (Ag⁺, Co²⁺, Cd²⁺, Mg²⁺, Cu²⁺, Ni²⁺, Ba²⁺, Pb²⁺, Cr³⁺, Al³⁺, Zn²⁺, Hg²⁺, K⁺, Ga²⁺ and Fe³⁺), respectively. Besides, the detection limits were determined to be 1.61 × 10^-8 M and 1.15 × 10^-8 M through the standard curve plot, respectively. The photoelectron transfer (PET) mechanism was guessed by the Job's plot and the infrared titration. Corresponding orbital electron distribution and molecular geometry configurations of the compounds were predicted by density functional theory (DFT). In addition, the prepared test paper changed from white to pink when the target ion was detected. The color changed from colorless to pink in a solution having a concentration of 10^-5 M.