Three-Dimensional Coral-Like NiFe-Layered Double Hydroxides on Biomass-Derived Nitrogen-Doped Carbonized Wood as a Sensitive Probe for Nonenzymatic Urea Determination
Ameer Farithkhan, S. Abraham John
Abstract
Binder-less, self-standing, disposable, and cost-effective sensing probes are crucial for the development of next-generation nonenzymatic urea sensors (NEUSs). In the present study, three-dimensional (3D) coral-like NiFe-based layered double hydroxide (NF-LDH) microstructures were grown over the naturally inherited porous microchannels of nitrogen-doped carbonized wood (NCW). The microstructural details and chemical composition of the fabricated electrodes were examined by microscopic and spectral methods. The formation of novel 3D coral-like microarchitectures with uniformly enveloped nanoflakes was evidenced from the scanning electron microscopy measurements. Interestingly, NF-LDH exhibited a voltammetric response for urea due to the unique 3D architecture and synergistic influence between catalytically active Ni3+ sites and doped Fe3+ centers. Here, NCW serves as a catalyst-docking platform and electron-conducting medium. Such direct anchoring of catalytically active structures on conductive scaffolds eliminates the electron transfer resistance provoked by stereotypical insulating binders. Furthermore, the growth of the NF-LDH catalyst on NCW was varied with respect to the mole ratio of Ni3+ and Fe3+. Among the different mole ratios, the NF-LDH catalyst modified with Ni/Fe-0.75:0.25 showed the best sensing performance toward urea with a sensitivity of 53 μA mM–1 cm–2, a wide linear range from 0.5 to 8 mM, and a limit of detection of 0.114 mM (S/N = 3) in addition to exceptional stability and reproducibility.