Electrochemical sensor based on phenol formaldehyde amine polymer coated ZnO/GO nanocomposite: An innovative nano-framework for the determination of caffeine

An electrochemical sensor was fabricated by drop-casting ZnO/GO-phenol formaldehyde amine (ZnO/GO-PFA) nanocomposite onto graphite (Gr) electrode for the detection of caffeine. In this concern, the compositional features of the nanocomposite and their morphologies were examined by Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and transition electron microscopy (TEM) techniques. The developed sensor exhibited strong electrocatalytic behaviour towards the oxidation of caffeine in phosphate buffer solution (PBS). EIS studies indicated a significant drop of charge transfer resistance (Rct) and cyclic voltammetry (CV) experiments showed a favourable ionic interaction between ZnO/GO-PFA and caffeine. Differential pulse voltammetry (DPV) exhibited a linearly varied oxidation peak with caffeine concentration range between 5-155 mu M, leading to 0.15 mu M detection limit. The improved surface area of the ZnO/GO in the developed sensor led to remarkable stability and repeatability which is attributed to the growth of controlled sized ZnO nanocrystals on the graphene oxide (GO) sheet. The practical applicability of the developed sensor was tested with urine sample with the recovery rate of more than 97 %, suggesting that the fabricated sensor can find potential application in the electroanalysis of caffeine in drugs and food samples.