Highly Sensitive Electrochemical Detection of Baicalein with a New Sensor Based on Multiwalled Carbon Nanotube and Metal–Organic Framework

Baicalein (BA), a natural flavonoid, has a crucial role in treating physical health. The rational fabrication of an electrochemical sensor is key to high-efficiency detection of BA. In this work, a new thiacalix[4]arene-based metal-organic framework (MOF) [Co2TTA(phen)2(H2O)2]·0.5DMA (CoTTA) was synthesized with thiacalix[4]arene-based tetracarboxylic acid (H4TTA), 1,10-phenanthroline (phen), and Co(II) cation (DMA = N,N-dimethylacetamide). In CoTTA, adjacent Co(II) cations were connected by TTA4- anions to yield a three-dimensional (3D) framework. A family of new electrochemical sensors were developed by combining CoTTA with mesoporous carbon (MC), multiwalled carbon nanotube (MWCNT), or reduced graphene oxide (RGO). Among them, CoTTA@MWCNT(1:1)/GCE (GCE = glassy carbon electrode) showed a highly sensitive electrochemical sensing performance for BA with a low limit of determination (LOD, 0.46 nM) under the optimal condition. Moreover, this sensor was successfully used to determine the content of BA in baicalein aluminum capsule with satisfactory results. Further, a possible mechanism involving the electrochemical sensing of BA was proposed.