Uncovering the optimal pyrolysis temperature of NH2-MIL-88B-derived FeOX/Fe@porous carbon composites for the ultrasensitive electrochemical detection of baicalin in natural plant samples

Baicalin obtained from natural plants has essential medical value, so the development of accurate and sensitive quantitative methods for it is one of the most important tasks. Here, the FeOX/Fe@porous carbon composite (Fe@C) was synthesized by solvothermal method and carbonized at different temperatures under an N2 atmosphere, and an electrochemical sensor designed based on this material was applied to the accurate and rapid determination of baicalin. According to the results of physical and electrochemical characterization, Fe@C at different pyrolysis temperatures exhibited different morphologies and different electrochemical properties, while the Fe@C pyrolyzed at 800 °C had the optimum performance. Compared with NH2-MIL-88B, the pyrolysis greatly reduces the charge transfer internal resistance of the material and has a larger porosity and specific surface area, resulting in an eminent electrochemical signal for the detection of baicalin. The sensor Fe@C-800/GCE not only has a linear range of 4 nM–700 nM with a low limit of detection of 1.16 nM for the detection of baicalin, but also has outstanding repeatability, anti-interference and stability for the detection of baicalin in several natural plant samples and herbal medicines samples. This work presents several pyrolytic NH2-MIL-88B as electrochemical sensors for the detection of baicalin for the first time, providing a novel idea for the application of MOFs derivatives in environmental analysis.