A dual colorimetric and fluorescent sensor for lead ion based on naphthalene hydrazone derivative

• An easy-to-make colorimetric and fluorometric sensor 1 for Pb2+ was obtained.
• The assay carried in aqueous solution with low limit detection as 37 nM mol L−1.
• The high selectivity and sensitivity of 1 for Pb2+ was for 1’s distinctive structure.
• 1−Pb2+ shows longer wavelength absorption and emission and strong fluorescence.

A new compound, 2-boronobenzaldehyde-(2′-hydroxyl-4′-sulfonic acid) naphthalene hydrazone (1), was synthesized and its structure was characterized by proton nuclear magnetic resonance, mass and element analyses. The presence of Pb2+ led 1 to undergo colorimetric and fluorescent changes, which were detectable with the naked eye. Thus, a dual spectral response for Pb2+ detection was introduced. In KH2PO4–NaOH buffer aqueous solution (pH 6.0), 1 exhibited fluorescence enhancement at 568 nm and hyperchromicity at 595 nm upon the addition of Pb2+. The fluorescent intensity change was proportionate to the concentration of Pb2+ with a dynamic working range of 5.0 × 10−7 mol L−1 to 1.0 × 10−4 mol L−1 and a detection limit of 3.7 × 10−8 mol L−1. The fluorometric method was successfully applied for the detection of Pb2+ water of Qianhu Lake and soil in Nanchang university campus. The recoveries were 111–116% for water and 97.6% for soil respectively, determined via the standard addition method.

A 1:1 metal-ligand complex between lead ion and compound 1 was formed which resulted in color change from red to blue and enhancement of fluorescence at 568 nm.Figure optionsDownload as PowerPoint slide