β-cyclodextrin-functionalized acetylene black nanocomposite electrode with enhanced host-guest enrichment for ultralow-level detection of niclosamide.

Accurate electrochemical quantification of niclosamide (NA) remains challenging due to its limited aqueous solubility, sluggish electron-transfer kinetics, and the inherently complex multi-electron nitro-reduction pathway. In this work, a β-cyclodextrin/acetylene black composite electrode (β-CD@AB/GCE) is developed to overcome these limitations through the combined benefits of a highly conductive porous carbon network and the strong host-guest inclusion capability of β-cyclodextrin. The composite architecture enhances interfacial preconcentration of NA, promotes favorable molecular orientation for electron transfer, and improves the efficiency of mass and charge transport throughout the porous film. To elucidate the mechanistic origins of these enhancements, a fully coupled multiphysics framework was constructed in COMSOL, integrating charge conservation, mass transport of diluted species, Butler-Volmer kinetics, and Langmuir adsorption dynamics. The model accurately captures experimentally observed behaviors (including potential gradients, ohmic polarization, concentration depletion, and the transition between diffusion-controlled and adsorption-controlled regimes) with excellent agreement between simulations and voltammetric measurements (RMSE = 0.078). Both modeling and experiments reveal that β-CD-mediated enrichment increases interfacial NA concentration by more than an order of magnitude, while the optimized porous microstructure ensures uniform overpotential distribution and efficient charge transfer. The resulting β-CD@AB/GCE sensor exhibits high sensitivity (3.675 µA µM