Abstract Excessive consumption of synthetic food colourants such as tartrazine (TZ) poses significant health risks, highlighting the need for sensitive detection methods for food safety applications. Here, we report a binder-free electrochemical sensor based on synergistic integration of iron-based metal–organic framework MIL-100(Fe) with multiwalled carbon nanotubes (MWCNTs) on glassy carbon electrode (GCE). The nanocomposite leverages MIL-100's high porosity and accessible Fe 3 ⁺ sites combined with MWCNT's superior conductivity, achieving an 11-fold enlarged electroactive surface area (0.786 cm 2 ) and 19-fold enhanced exchange current density. Under optimized conditions using differential pulse voltammetry (DPV), the sensor exhibited a low detection limit (LOD) of 0.11 μM, a wide linear range (0.9 to 7.5 μM, R 2 = 0.9891), and excellent selectivity over amaranth (AM) and common interferents. Mechanistic studies revealed adsorption-controlled, one-electron/one-proton irreversible oxidation with ultralow charge transfer resistance (0.073 kΩ). The sensor demonstrated robust performance with excellent repeatability (RSD = 2.11%), reproducibility (RSD = 4.11%), and stability (> 98% retention, 14 days). Real-sample analysis of fruit juices and sweets yielded satisfactory recoveries (85.63–118.39%, RSD < 2.17%) without pre-treatment. Monte Carlo (MC) simulations substantiated the selectivity mechanism, revealing stronger TZ adsorption sites relative to AM on the MIL-100(Fe)/MWCNTs nanocomposite. Density functional theory (DFT) calculations yielded valuable insights into the electronic properties and solvation behaviour of the isolated TZ, the MIL-100(Fe) fragment, and their composite (MIL-100(Fe)/TZ) system in aqueous environments. This integrated experimental-computational approach establishes a rational framework for developing next-generation MOF-based electrochemical sensors with predictable performance for food safety monitoring.
Mthiyane et al. (Tue,) studied this question.