High-performance carbon black/molybdenum disulfide nanohybrid sensor for cocoa catechins determination using an extraction-free approach

In this work, for the first time, the ability to detect catechins on an effective and regenerable carbon black/molybdenum disulfide nanohybrid screen-printed electrode (SPE-CB/MoS2) is demonstrated. The proposed SPE-CB/MoS2 merges the ability of CB to improve the electrochemical response with the proprieties of MoS2 to totally prevent catechins irreversible polymerization and adsorption onto the electrode surface occurring at both bare and CB-modified SPEs. The MoS2 anti-fouling ability has been demonstrated using both flavanols standards and complex samples thus proved to be an unexpected and useful characteristic. The SPE-CB/MoS2 allowed an improvement of sensitivity (LOD ≤ 0.17 μmol L−1) of 100-folds compared to the bare SPE electrode, showing linear range between 0.12 and 25 μmol L−1 with good determination coefficients (R2 ≥ 0.998). Cocoa powder samples have been analyzed employing the developed hybrid sensor and compared with classical methods for polyphenols evaluation as Folin- Ciocalteu (F.C.), ABTS and an AuNPs based assay. The SPE-CB/MoS2 allow to obtain repeatable and reproducible results which also were significantly correlated with classical methods (r = 0.95–0.97). Noteworthy, after the measurements of 59 cocoa samples the electrode was still active (recovery signal 99%). Using the extraction-free approach with the SPE-CB/MoS2 sensor the whole analysis of cocoa powder catechins required only 15 min.