Colorimetric fluorescence of the 1,10-phenantholineyl-imidazole sensor probe for the selective detection of Zn2+ and Cd2+ ions.

A colorimetric fluorescent probe, 4-(1H-imidazolo[4,5-f][1,10]phenanthroline-2-yl)-N, N-diphenylaniline (PIN), was designed, synthesized and characterized for the sensitive and selective detection of Zn²⁺ and Cd²⁺. The color of the solution changed from blue to yellow visible to the naked eye with the addition of Zn²⁺ and Cd²⁺. The probe PIN showed good anti-interference to Zn²⁺ and Cd²⁺ in the presence of a variety of metal ions, and the fluorescence intensity showed a good linear relationship with the concentrations of Zn²⁺ and Cd²⁺, with detection limits of 34.84 nM and 35.76 nM, respectively. The probe PIN complexed 2:1 with Zn²⁺ and Cd²⁺, and the complexation constants were 1.03 × 10⁴ M^-1 (PIN - Zn²⁺, R² = 0.9971) and 1.50 × 10⁴ M^-1 (PIN - Cd²⁺, R² = 0.9981), respectively. In addition, the PIN could be recovered by EDTA and could be effectively monitored for Zn²⁺ and Cd²⁺ at pH 4-11, with good results in actual water samples. The HepG-2 cells maintained over 95 % of viability after 24 h exposure to PIN, which identified the extremely low toxic of PIN and could be used for in vivo cell imaging.