Electrochemical Determination of Caffeine Using Bimetallic Au−Ag Nanoparticles Obtained from Low-cost Green Synthesis

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 of citrus 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 μM with a sensitivity of 0.75 μA/μM, in the caffeine concentration range of 0 μM to 59 μM. The proposed sensor further demonstrated good selectivity and was successfully applied for the detection of caffeine in commercial samples.