An Electrochemical Sensor Using a Derivative of β-Cyclodextrin, Spherical Graphite, and Reduced Graphene Oxide for Sensing of Caffeic Acid

Caffeic acid (CA) possesses antibacterial, antiviral, and anticancer effects but may be genotoxic after excessive intake. Therefore, it is greatly important to fabricate an efficient electrochemical sensor for CA sensing. Herein, a derivative of β-cyclodextrin (4-PyS-β-CD) was successfully synthesized by using β-cyclodextrin and 4-mercaptopyridine. Its structure was characterized by 1H NMR. The ternary composite 4-PyS-β-CD/RGO/SG-b was prepared by milling 4-PyS-β-CD, spherical graphite (SG), and reduced graphene oxide (RGO) in a mass ratio of 3:3:1.5. Scanning electron microscopy (SEM) demonstrated that the nanoscale particles of SG, the rod-shaped samples of 4-PyS-β-CD, and the lamellar RGO were dispersed in the ternary composite 4-PyS-β-CD/RGO/SG-b. 4-PyS-β-CD/RGO/SG-b@GCE (GCE = glassy carbon electrode) showed fine electrochemical detection performance for CA with a wide linear range (0.004–35 μM) and a low limit of detection (LOD, 1.17 nM). Satisfactory recoveries of 97.59–100.30% and 97.26–100.21% were achieved for the sensing of CA in caffeic acid tablets and blueberries, respectively, demonstrating its potential practical application. Moreover, the possible sensing mechanism for CA, as well as the multiple synergistic effects among the composites, was also explored.