Exploration of 3D NiCu-layered double hydroxide flowers tailored on a biomass-derived N-doped carbon stick electrode as a binder-less enzyme-free urea sensing probe

The rational design and construction of highly active, inexpensive, environmentally benign, and easily disposable urea-detecting probes is an appealing idea for the dynamic advancement and extensive practical application of enzyme-free urea sensors (EFUS) in the realm of disease control and prevention. Herein, a facile one-step hydrothermal strategy is employed to anchor three-dimensional (3D) NiCu-layered double hydroxide (NC-LDH) microflowers on naturally tailored low-tortuosity channels of a nitrogen-doped carbon stick electrode (NCSE) acquired by the carbonization of wooden tooth sticks. The comprehensive morphological and spectral analysis portrays the formation of porous 3D flower-like NC-LDH microstructures well-decorated with highly interconnected two-dimensional thin flaky petals. The non-enzymatic urea sensing performances of the distinct as-fabricated NC-LDH@NCSE were examined by electrochemical assessment and among them, the sensing probe with the optimal bimetallic ratio of Ni : Cu-0.875 : 0.125 (dubbed as NC-87) demonstrated remarkable urea detection behaviour ascribed to the ample open morphological feature, synergistic cooperation of the finest bimetallic system and electronically favorable binder-free construction. With solid stability and reproducibility, the NC-87 probe presented two linear ranges of 0.02-0.5 mM and 0.5-5.0 mM with sensitivities of 21 and 3.4 mA mM⁻¹ cm⁻², respectively, with a limit of detection of 0.033 mM (S/N = 3).