Coating silver metal-organic frameworks onto nitrogen-doped porous carbons for the electrochemical sensing of cysteine
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ORIGINAL PAPER
Coating silver metal-organic frameworks onto nitrogen-doped porous carbons for the electrochemical sensing of cysteine Xiurong Zhai 1,2 & Shuai Li 2 & Xi Chen 3 & Yue Hua 2 & Hua Wang 2 Received: 23 April 2020 / Accepted: 27 July 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
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 provide stable and sharp electrochemical signals of solid-state AgBr at a low potential approaching zero (i.e., 0.02 V), 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 method facilitates the selective detection of Cys with two linear working ranges of 0.10 to 100 μM and 100 to 1300 μM, respectively. The N-PC@Ag-MOF-based sensors have been used 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 has potential applications in the food analysis fields. Keywords Electroanalysis . Cysteine . Ag-MOF . Nitrogen-doped porous carbons
Introduction Cysteine (2-amino-3-sulphydrylpropanoic acid) (Cys), an essential amino acid containing thiol group, may exist in some daily foods (i.e., milk) as the high nutritional content [1–3]. It can also act as the physiological regulator for various diseases such as heart disease, rheumatoid arthritis, and AIDS [4]. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04469-3) contains supplementary material, which is available to authorized users. * Hua Wang [email protected] 1
Department of Chemistry and Chemical Engineering, Jining University, Qufu City 273155, Shandong Province, People’s Republic of China
2
Institute of Medicine and Materials Applied Technologies, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu City 273165, Shandong Province, People’s Republic of China
3
Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin City, Heilongjiang Province, People’s Republic of China
Hence, the selective and sensitive detection of Cys levels in a variety of food products like milk is of great significance. Up to date, several analytical methods have been reported for the determination of Cys, such as the high performance liquid chromatography [5], fluorescence spectroscopy [6], flow injection [7], co
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