Because of their large surface area and conductivity, some inorganic materials have emerged as good candidates for the trace-level detection of pharmaceutical drugs. In the present work, we demonstrate the detection of an anticancer drug (regorafenib, REG) by using an electrochemical sensor based on a nanocomposite material. We synthesized a zirconia-nanoparticle-decorated reduced graphene oxide composite (ZrO₂/rGO) using a one-pot hydrothermal method. Reduction of the graphene oxide supports of the Zr²⁺ ions with hydrazine hydrate helped in preventing the agglomeration of the zirconia nanoparticles and in obtaining an excellent electrocatalytic response of the nanostructure ZrO₂/rGO-based electrochemical sensor. Structural and morphological characterization of the nanostructure ZrO₂/rGO was performed using various analytical methods. A novel regorafenib (REG) electrochemical sensor was fabricated by immobilizing the as-prepared nanostructure ZrO₂/rGO on to a glassy carbon electrode (GCE). The resulting ZrO₂/rGO/GCE could be used for the rapid and selective determination of REG in the presence of ascorbic acid and uric acid. The ZrO₂/rGO/GCE showed a linear response for the REG analysis in the dynamic range 11–343 nM, with a remarkable lower detection limit and limit of quantifications of 17 and 59 nM, respectively. The newly developed sensor was used for the accurate determination of REG in both serum samples and pharmaceutical formulations, with satisfactory results.

In this study we report a one-step procedure for the fabrication of Pd–Ag bimetallic nanoparticles on the surface of a graphene oxide (rGO) support. A controlled reduction of Pd²⁺ and Ag⁺ ions on an rGO support was achieved by using a methyl ammonium borane reducing agent. The fabricated Pd–Ag/rGO bimetallic nanocomposites were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FT-IR). A Pd–Ag/rGO based electrochemical sensor was fabricated by immobilizing the as-prepared Pd–Ag/rGO bimetallic nanocomposites on to a bare glassy carbon electrode (GCE). The resulting Pd–Ag/rGO/GCE electrochemical sensor was proved to be ultrasensitive and selective towards the detection of acetaminophen (APAP) in the presence of etilefrine (ET). The linear dynamic range (LDR) for the detection of APAP was found to be 1.2–30 nM with a good limit of detection (LOD) and the limit of quantification (LOQ) of 3.26 nM and 13 nM, respectively. The newly prepared Pd–Ag/rGO/GCE-modified electrode makes a good analytical tool for the accurate determination of APAP either in its pristine conditions or in the presence of both real human samples and pharmaceutical formulations. The convenient fabrication protocol shown here can be extendable to other types of bimetallic configurations for various electrochemical sensing applications.

The present report demonstrates the development of a Pt–Ni/rGO composite electrochemical sensor for the detection of dopamine.