Novel metal-organic gels of bis(benzimidazole)-based ligands with copper(II) for electrochemical selectively sensing of nitrite

Metal-organic gels (MOG), which consist of metal ions connected by organic linker groups, have attracted great interest in varies research areas such as fluorescent sensors, dye absorption and catalysis. Owing to the viscoelastic solid-like characteristic of gel material, the applications of MOG in electrochemical sensing are limited. Herein, we have demonstrated for the first time that MOG were able to serve as novel electrode-modifying materials by employing a simple freeze-drying method, with which the gel micromorphology could also be retained. A commercially available, pyridine group contained organic ligand 2,6-Bis(2-benzimidazolyl) pyridine was selected to form MOG with copper(II) in our work, based on the fact that the pyridine group endows both the ligands and the MOG with high solubility in diverse solvents, which significantly benefits the modification of electrodes. Nitrite was selected as a proof-of-concept target to trial their practical application. Results showed that the oxidation peak currents of nitrite on MOG-modified electrodes were linearly correlated to the logarithm values of its concentrations in the range of 2-150 mu M, while the detection limit of 0.86 mu M was considerably lower than the recommended nitrite level of 0.8 mM by the World Health Organization. Our work has thus helped to demonstrate promising application of MOG material and their composites in the field of electrochemistry. (C) 2017 Elsevier Ltd. All rights reserved.