New highly selective turn-on fluorescence receptor for the detection of copper (II)

A Simple Isoniazid-Based N-Acylhydrazone Derivative as Potential Fluorogenic Probe for Zn2+ Ions

This study evaluated three isoniazid-based N-acylhydrazone derivatives (HL1, HL2, and HL3) varying their substituting groups (-H, -N(CH₃)₂, and -NO₂) as potential chemosensors for Zn²⁺ ions. To this end, the absorption and emission properties of these derivatives were investigated in the presence of Zn²⁺ ions. Results point to the derivative HL2 as the best chemosensor for Zn²⁺ ions because of its comparatively higher sensitivity. The color of this derivative changed from colorless to strong yellow with zinc addition, as indicated by the shift in UV-vis spectrum. Moreover, HL2 was the only derivative to emit fluorescence in the presence of Zn²⁺ ions, attributable to PET inhibition and bond isomerization promoted by coordination with this metal. LOD, LOQ, and binding constant values for HL2 + Zn²⁺ were 0.43 μmol.l^-1, 0.93 μmol.l^-1, and 5.04 × 10¹² l.mol^-1, respectively. The fluorescence of HL2 with other metal ions (Fe³⁺, Mg²⁺, Na⁺, Cd²⁺, Cu²⁺, Co²⁺, Ni²⁺, Ca²⁺, and K⁺) was also investigated. Zn²⁺ yielded the best result without Cd²⁺ interferences. Job's Plot showed that the stoichiometric ratio of the complex formed by HL2 and Zn²⁺ ions is 2:1 (ligand:metal). The strip test with adsorbed HL2 indicated fluorescence in the presence of zinc ions under 365 nm UV irradiation.

Reversible turn-on fluorescent Cu(ii) sensors: rather dream than reality?

Reversible turn-on fluorescent Cu(ii) sensors are of high interest to understand copper metabolism in biology and medicine. However, they are intrinsically difficult to build, and careful studies are needed to exclude Cu(ii)-induced sensor oxidation.