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

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 x 10(-7) mol L-1 to 1.0 x 10(-4) mol L-1 and a detection limit of 3.7 x 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. (C) 2013 Elsevier B.V. All rights reserved.