Polypyrrole deposited on the core-shell structured nitrogen-doped porous carbon@Ag-MOF for signal amplification detection of chloride ions.

Abstract

An electrochemical platform for signal amplification probing chloride ions (Cl-) is constructed by the composite integrating core-shell structured nitrogen-doped porous carbon@Ag-based metal-organic frameworks (NC@Ag-MOF) with polypyrrole (PPy). It isbased on the signal of solid-state AgCl derived from Ag-MOF, sinceboth NC and PPy have good electrical conductivityand promote the electron transport capacity of solid-state AgCl. NC@Ag-MOF was firstly synthesized with NC as the scaffold and then, PPy was anchored on NC@Ag-MOF by chemical polymerization. The composite NC@Ag-MOF-PPy was utilized to modify theelectrode, which exhibited a higher peak current and lower peak potential during Ag oxidation compared with those of Ag-MOF and NC@Ag-MOF-modified electrodes. More importantly, in the coexistence of chloride (Cl-) ions in solution, theNC@Ag-MOF-PPy-modified electrode displayed a fairly stable and sharp peak of solid-state AgCl with the peak potentials gradually approaching zero, which might effectively overcome the background interference caused by electroactive substances. Theoxidation peak currents of solid-state AgCl increased linearly with the concentrationof Cl- ions in a broad range of 0.15µM-40mM and 40-250mM, with detection limits of 0.10µM and 40mM, respectively. Thepractical applicability for Cl- ions determinationwas demonstrated usinghuman serum and urinesamples. Theresults suggest that NC@Ag-MOF-PPy composite could be a promising candidate for the construction of the electrochemical sensor.