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Metal oxide-based electrochemical sensors, despite their robust redox activity, lack sufficient conductivity to overcome their sluggish kinetics. Herein, we propose a unique self-assembled hybrid configuration based on redox-active Co3O4 hexagons (Co3O4-HX) and the highly conductive, few-layer-thick Ti3C2Tx sheets. The self-assembly approach enabled the compact interfacial formation and moderate intercalation of Ti3C2Tx sheets, allowing the Co3O4/Ti3C2Tx composite (Co3O4–MX) to exhibit a synergetic improvement in the charge-transfer rate and oxidation current response toward isoprenaline (ISPT), a neurotransmitter drug. The hybrid composite when devised as an electrochemical sensor gives rise to a 7.9-fold higher oxidation current response to 0.65 μM ISPT than its pristine Co3O4 counterpart. The improved charge kinetics and generation of a superior oxidation current emphasized the critical role of Ti3C2Tx as an interactive substrate in the Co3O4–MX hybrid. The analytical detection capability assessed via differential pulse voltammetry (DPV) confirmed the sensor's high selectivity and marked stability both in low and high concentration ranges of ISPT ((0.01 to 0.33 μM) and 0.5 to 0.9 μM) with a limit of detection (LOD) of 3 × 10–3 μM (for low concentrations). Importantly, the fabricated sensor could detect ISPT from harsh biological environments such as human urine samples with a recovery rate of 99%. Moreover, the sensor exhibited a stable working response during its prolonged storage of 30 days in an aqueous PBS system. The proposed route of using MXenes as a conductive substrate paves the way for developing a robust metal-oxide-based redox-active hybrid system for the sensitive detection of important therapeutic compounds. [ABSTRACT FROM AUTHOR]

MXenes have emerged as promising electrode materials for supercapacitors based on their metallic conductivity, good hydrophilicity, rich surface chemistry, and excellent mechanical characteristics. However, the strong interlayer van der Waals forces induce significant layer restacking, which restrict complete exposure of MXenes' surface active sites, impeding electron/ion transport and resulting in poor electrochemical performances. Herein, a porous MXene/carbon nanotube (CNT) film was prepared through a simple alkali-induced process. The developed porosity and the introduction of CNTs can effectively suppress the restacking of MXene nanosheets, promoting the effective utilization of the surface active sites of the MXene and facilitating fast ion/electron transportation. Consequently, the porous MXene/CNT film exhibited a high specific capacitance of 401.4 F g-1 at 1 A g-1 and a sustained capacitance of 336.2 F g-1 at an ultrahigh current density of 1000 A g-1, corresponding to an 83.8% capacitance retention. Furthermore, the film electrode demonstrated outstanding cycling stability, with a capacitance retention of 99.0% after 20,000 cycles at 100 A g-1, showing its significant potential for supercapacitor applications. [ABSTRACT FROM AUTHOR]