Proton conduction and electrochemical glucose sensing property of a newly constructed Cu(II) coordination polymer

Abstract

The assembly between 5-sulfo-1, 2, 4-benzoic acid (H4SBTB) and Cu2+ in the presence of 4, 4´-bipyridine (Bipy) results in a novel ionic coordination polymer with two crystallographically independent hexa-coordinated Cu1 and Cu2 ions, namely, [Cu3(HSBTB)2(Bipy)3(H2O)8]n (1), which consists of an anionic Cu12(C1O1O2)2-Bipy-bridged double-chain and a cationic Cu2-Bipy-bridged mono-chain. With the aid of H-bonds, the anionic Cu12(C1O1O2)2-Bipy-bridged double-chains extend into a 2D supramolecular anionic double-layer, which is further linked by the cationic Cu2-Bipy-bridged mono-chain, resulting in a 3D supramolecular network. The H4SBTB acid exhibits a new coordination mode, i.e. one carboxyl group still remains protonated in 1. The analysis of the solid-state diffuse reflectance UV-Vis-NIR spectrum reveals that the indirect bandgap exists in 1, which was further illustrated by the theoretical calculation on the basis of Density Functional Theory (DFT) using the CASTEP program. The electrochemical studies indicate that the composite membrane of 1 with nafion shows interesting temperature-insensitive proton conduction behavior at pH = 3. Cyclic voltammograms indicate that 1 exhibits electrocatalysis to glucose oxidation in 0.1 M NaOH. The current-time (i-t) response curves reveal that 1 demonstrates sensitive and selective electrochemical oxidation sensing of glucose with an exponential detection range of 0-30 mM. The limit of detection (LOD) was calculated to be 38.74 μM.