A Julolidine Aldehyde Dansyl Hydrazine Schiff Base as Fluorescence Chemosensor for Zn²⁺ ions Recognition and its Application

The Schiff base fluorescent probe (Dz-Jul), containing julolidine aldehyde and dansyl hydrazine, was derived using a simple condensation. This chemosensor showed high selectivity towards Zn²⁺ and quick response (170 s) in DMSO/H₂O solutions (8/2, v/v, pH 7.2 buffer). A fluorometric titration determined that Dz-Jul-Zn²⁺ has a binding ratio of 1:1, and the association constant (Ka) is 1.03 × 10⁵ M⁻¹. The Dz-Jul detection limit of Zn²⁺ ions was 15 nM, much lower than the WHO standard (76.0 nM). DFT, ESI mass, and FTIR spectral demonstrated a plausible complexation mode between Dz-Jul and Zn²⁺ ions. In actual water samples, Zn²⁺ has been detected with good detection performance using Dz-Jul. Additionally, Dz-Jul-coated test strips allowed for rapid and qualitative monitoring of Zn²⁺ ions in a visible manner.