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

TL;DR

A new electrochemical sensor using a ZnCo2O4 and carbon nanotube hybrid is developed for highly sensitive riboflavin detection.

Contribution

Integration of carbon nanotubes with MOF-derived ZnCo2O4 significantly enhances electrochemical sensing of riboflavin.

Findings

The ZnCo2O4/MWCNT hybrid achieved a detection range of 0.01–1.2 µM riboflavin with a low detection limit of 0.2615 nM.

The sensor showed excellent repeatability (RSD = 1.41%) and recovery rates of 93–94% in pharmaceutical samples.

Electron-transfer behavior and charge-transfer resistance were significantly improved by the nanohybrid structure.

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 (Rct = 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.

Electrochemical detection of riboflavin (vitamin B2) on ZnCo2O4/MWCNT modified GCE.

Figures