Coating silver metal-organic frameworks onto nitrogen-doped porous carbons for the electrochemical sensing of cysteine.

Abstract

Nitrogen-doped porous carbons (N-PC) were coated for the first time with silver metal-organic frameworks (Ag-MOF) by the hydrothermal route. The resulted N-PC@Ag-MOF composites present high stability because of the strong interaction between N atoms of N-PC and Ag+ ions of Ag-MOF. It was discovered that the electrodes modified with N-PC@Ag-MOF composites display much higher conductivity than the one modified with Ag-MOF. Especially, they providestable and sharp electrochemical signals of solid-state AgBr at a low potential approaching zero (i.e., 0.02V), which may aid to overcome the drawback of the traditional electroanalysis at high overpotentials with serious interferences from the samples background. More importantly, the yielded AgBr signals selectively decrease induced by cysteine (Cys) through the specific thiol-bromine replacement reactions that transfer AgBr into non-electroactive Ag-Cys. The proposed methodfacilitates the selective detection of Cys with twolinear working ranges of0.10 to 100μM and 100 to 1300μM, respectively. TheN-PC@Ag-MOF-based sensors have beenused for detection of spiked Cys in milk samples with good recovery efficiencies. The developed electroanalysis strategy for probing Cys through the specific thiol-bromine replacement haspotential applications in the food analysis fields. Ag-MOF was coated onto heteroatoms co-doped porous carbons carriers for the selective electroanalysis strategy for cysteine at the potential approaching zero using Br- ions.