Abstract
A novel caffeine sensor was constructed. The sensor is based on a platinum electrode (PtE) modified with polypyrrole (PPY) and green synthesized Ag-Au bimetallic nanoparticles. The work further describes the synthesis of silver nanoparticles (AgNPs), gold nanoparticles (AuNPs), as well as Ag-Au bimetallic nanoparticles (BMNPs) using the extract ofcitrus sinensis(sweet orange) peels. The nanoparticles were used to form nanocomposite material supported on polypyrrole (PPY) and, consequently used to modify PtE using drop-cast method. Synthesized nanomaterials were characterized by FT-IR, UV-Vis, XRD and TEM. Electrochemical characterization of the modified electrodes was conducted using the ferrocyanide/ferricyanide redox probe prepared in PBS. PPY/Ag-AuBMNP modified PtE exhibited faster electron transport properties as well as enhanced catalytic current response as compared to bare-PtE, PtE/AgNPs, PtE/AuNPs, PtE/Ag-AuBMNPs and PtE/PPY. By Square-wave voltammetry (SWV) the PPY/Ag-AuBMNPs modified PtE yielded a detection limit of 2.02 mu M with a sensitivity of 0.75 mu A/mu M, in the caffeine concentration range of 0 mu M to 59 mu M. The proposed sensor further demonstrated good selectivity and was successfully applied for the detection of caffeine in commercial samples.