Reduced graphene oxide and carbon nanotubes composite functionalized by azobenzene, characterization and its potential as a curcumin electrochemical sensor

In this study, azobenzene-modified reduced graphene oxide@multiwall carbon nanotubes (Az-rGO@CNTs) was synthesized and characterized by UV-Vis, FT-IR, XRD, FE-SEM, AFM, TEM, EDS, element mapping, BET, and cyclic voltammetry (CV). A glassy carbon electrode (GCE) was modified with Az-rGO@CNTs as an electrochemical sensor for determination of curcumin. Electrochemical impedance spectroscopy (EIS) and CV were used to study the efficiency of the catalyst. Subsequently, various effective parameters on the sensitivity and selectivity of the method, including pH, accumulation potential, and preconcentration time, were optimized. The transfer coefficient, as well as the electron transfer rate constant, were respectively calculated using the Laviron equation as 0.55 and 0.32 s(-1). The linear ranges of the sensor were 0.008-2.0 and 2.0-10.0 mu mol L-1 curcumin with a limit of detection of 0.003 mu mol L-1 using square wave voltammetry (SWV). The repeatability and reproducibility were 2.0% (RSD) and 3.6% (RSD), respectively. The selectivity of the method for determination of curcumin in the presence of different interference species was studied too. Finally, the proposed sensor for determining curcumin was tested with real samples, including plasma, urine, and pharmaceutical compounds.