Press-transferred carbon black nanoparticles for class-selective antioxidant electrochemical detection

Carbon black nanoparticles (CBNPs) press imprinted films are proposed for class-selective electrochemical detection of ortho-diphenols (o-diphenols) and mono-phenols (m-phenols) antioxidants. In order to optimize the sensor construction, different surface immobilizations of CBNPs electroactive films on a PMMA support were assayed by using different amounts of CBNPs dispersions. The best sensor in terms of selectivity, sensitivity and stability was obtained when 30 mL of a CBNPs dispersion (0.50 mg/100 mL in 1,2-dichloroethane) were transferred onto PMMA substrates applying a pressure of 4.6 ton. The electrodes were characterized by Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) to explore their electrical properties. The effective transfer of CBNPs on the PMMA support and the CBNPs film conductivity have been evaluated by Atomic Force Microscopy (AFM) confirming that the carbon black film is effectively imprinted on the polymer surface and that retains its good conductivity. X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy have been employed to investigate the CBNPs composition and the CBNPs electrode surface, respectively. CBNPs electrodes exclusively supported the o-diphenols and m-phenols sensing, at low detection potentials (+0.100 and +0.560 V, respectively) and with negligible surface fouling (peak intensity RSDs <12% and oxidation potential <6%, n = 28). Class-selective electrochemical indexes (EIs) for o-diphenols and m-phenols are proposed for the evaluation of the phenols antioxidant contents in complex samples such as olive oils.