# 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.

## Key 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.