Bio-carbon-derived porous reduced graphene oxide photo- and electrochemical sensor for ultra-sensitive detection of testosterone hormone

In this study, we report the development of a novel bio-carbon-derived porous reduced graphene oxide (BC-rGO) photo- and electrochemical sensor for the ultra-sensitive detection of testosterone hormone. Bio-carbon-derived rGO, synthesized from agricultural waste, offers a sustainable, cost-effective, and environmentally friendly alternative to traditional chemically derived rGO. The effect of different thermal reduction temperatures (100 °C, 200 °C, 300 °C, and 400 °C) on the properties of the synthesized rGO was investigated. The crystallite sizes of BC-rGO1, BC-rGO2, BC-rGO3, and BC-rGO4 were determined to be 65 nm, 54 nm, 48 nm, and 41 nm, respectively, using the X-Ray diffraction (XRD) data. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed the morphology of the prepared rGO nanosheets, showcasing a two-dimensional nanostructure with transparent lamellar structures and abundant folds dispersed throughout the basal plane. To construct the biosensor for testosterone detection, the BC-rGO was initially fabricated by chemical cross-linking and used to modify the Nafion-pretreated glassy carbon electrode (GCE). BC-rGO prepared at 400 °C demonstrated superior sensitivity and selectivity toward testosterone detection, owing to the enhanced surface chemistry facilitated by the bio-carbon-derived material. The sensor's performance was evaluated through both photo- and electrochemical methods, revealing ultra-sensitive detection capabilities for testosterone hormone. Among the fabricated electrodes, Nafion/BC-rGO4 on GCE showed the highest electrochemical response, indicating superior activity in testosterone oxidation. The synergistic effects of BC-derived 2D rGO and testosterone increase the photocatalytic activity of Nafion/BC-rGO@GCE, making it more effective at detecting testosterone than Nafion@GCE. The results demonstrated that the thermal reduction temperature significantly influenced the electrochemical performance of the rGO, with the optimal performance observed at 400 °C. The use of BC-derived rGO not only addresses environmental sustainability but also provides a highly efficient platform for the sensitive and selective detection of testosterone, making it a promising candidate for medical applications.