Carbon nanotube integrated MOF-derived ZnCo2O4: a nanohybrid electrochemical platform for riboflavin sensing

Abstract

Metal–organic framework (MOF) derived spinel metal oxides have attracted significant interest as electrochemical transducers due to their high surface area, rich redox-active sites, and tunable porous architectures. A nanohybrid sensing platform based on MOF-derived ZnCo₂O₄, integrated with multi-walled carbon nanotubes (MWCNT) was developed to enhance electrical conductivity and electron-transfer kinetics for riboflavin (RF) sensing. Structural and physicochemical analyses confirmed the formation of a crystalline spinel ZnCo₂O₄ framework uniformly decorated with MWCNT. XRD confirmed the formation of a single-phase spinel ZnCo₂O₄ with well-defined diffraction peaks, validating the successful MOF to oxide transformation, while BET indicated a high surface area of 198.32 m² g⁻¹. FTIR/Raman verified metal-oxide lattice bonding, whereas the electrochemical impedance spectroscopy demonstrated the significantly reduced charge-transfer resistance (R_ct = 104.4 Ω), indicative of enhanced conductivity using active-site of the nanocomposite. Electrochemical characterization revealed that the ZnCo₂O₄/MWCNT/GCE exhibited significantly higher current response. The sensor displayed a linear detection range of 0.01–1.2 µM (or 10–1200 nM) and a low detection limit of 0.2615 nM, as determined from DPV calibration. Kinetic analysis confirmed a diffusion-controlled electrochemical process of RF on ZnCo₂O₄/MWCNT/GCE, with dynamic electron-transfer behaviour. The electrode also demonstrated excellent repeatability (RSD = 1.41%, n = 4) and storage stability (signal loss = 5.85% over 8 days). The designed sensor was successfully applied to pharmaceutical tablet samples using the standard addition method, yielding recovery values of 93–94%, highlighting its robustness and suitability for precise RF quantification in complex matrices. These results confirm that carbon-nanotube integration significantly reinforces the electrocatalytic activity of MOF-derived ZnCo₂O₄, establishing the ZnCo₂O₄/MWCNT nanohybrid as a highly sensitive, accurate and practical electrochemical platform for RF determination, demonstrates the benefits of CNTs integration on MOF-derived spinel electrodes.