A Sustainable Nanomaterial Based on Gold Nanoparticles and Graphene for Highly Sensitive Electrochemical Sensing of Caffeic Acid in Coffees

Caffeic acid contributes to the flavor and aroma of coffee. Monitoring its levels can be important to guarantee the quality of the coffee produced. An innovative electrochemical sensor for the determination of caffeic acid was developed using banana pulp (Musa sapientum) extract as the precursor for the green synthesis of gold nanoparticles. Microscopic images verified the presence of dispersed gold nanoparticles, with an average diameter of 14.4 ± 2.5 nm on graphene sheets. The electrochemical behavior of caffeic acid demonstrated reversibility, with oxidation and reduction peaks. Under optimized conditions, a calibration curve was developed in 0.1 mol L⁻¹ Britton-Robinson buffer (pH 2.0) with linear range from 0.05 to 10.0 µmol L⁻¹, and a detection limit of 16 nmol L⁻¹. The sensor was effective in coffee samples, and the results were comparable to those obtained using UV–vis spectrometry.