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

A electrochemical platform for signal amplification probing chloride ions (Cl⁻) was fabricated based on the composite integrating core-shell structured nitrogen doped porous carbon@Ag-based metal-organic frameworks (NC@Ag-MOF) with polypyrrole (PPy). NC@Ag-MOF was firstly synthesized with NC as the scaffold. Then, PPy was anchored on NC@Ag-MOF by chemical polymerization, so that PPy could be applied to disperse NC@Ag-MOF, and effectively improve the conductivity and stability of Ag-MOF. The composite NC@Ag-MOF-PPy was utilized to modify electrode, which could exhibit 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, NC@Ag-MOF-PPy-modified electrode could display a fairly stable and sharp peak of solid-state AgCl with the peak potentials gradually approaching to zero, which might effectively overcome the background interference caused by electroactive substances. Meanwhile, the oxidation peak currents of solid AgCl can increase linearly for the quantitative of Cl⁻ ions in a broad range of 0.15 µM-250 mM with an low detection limit of 0.10 µM. Furthermore, the feasibility of practical applicability for Cl⁻ ions evaluation was demonstrated in the actual samples of human serum and urine with good consequence. Therefore, these results suggest that NC@Ag-MOF-PPy composite could be a promising candidate for the construction of the electrochemical sensor.