A colorimetric Pb2+ chemosensor: Rapid naked-eye detection, high selectivity, theoretical insights, and applications

A novel colorimetric chemosensor (MRN1) was designed and synthesized by incorporating the azobenzene disperse dye-based signalling unit and tridentate chelating moiety into a single molecule. MRN1 showed a selective and sensitive colorimetric sensing ability for Pb2+ ion by changing color from light yellow to magenta in an aqueous media. Detailed spectral investigations, mass spectrometry, and comparison (MRN2) studies provided corroborative evidence in support of 1: 1 association between MRN1 and Pb2+. The drastically red-shifted absorption spectrum of MRN1 upon addition of Pb2+ was proposed to be metal-to-ligand charge-transfer (MLCT) and intramolecular charge transfer (ICT) through the experimental results and density functional theory (DFT/TDDFT) calculations. Using this methodology, MRN1 could be used as a practical and visible test strip for Pb2+. MRN1 could also be used as a preliminary sensor for monitoring Pb2+ adsorbed in living Daphnia magna using an optical microscope. (C) 2017 Elsevier B.V. All rights reserved.