NiAl-LDH/Mo₂C heterostructure for adsorption-enhanced electrochemical sensing of tartrazine in environmental...

The overuse of tartrazine (Tz) in several industries, including beverage, pharmaceutical, and environmental industries, has created a need for high-performance composite materials for tracking synthetic food dyes. Here, for the first time, a NiAl-layered double hydroxide/molybdenum carbide (NiAl-LDH/Mo₂C) composite. A simple two-step synthesis was used as a new electrochemical platform for detecting Tz. Structural characterizations (XRD, FTIR, XPS, HR-SEM, TEM, BET and EDS) verified the successful formation of the composite, i.e., ultrathin LDH nanosheets on Mo₂C, a highly conductive material that increases the number of electroactive sites in a functional electron-transport network. We assume that the double synergistic effect might be responsible for the improved electrochemical sensing performance: first, the positively charged NiAl-LDH layer provides strong electrostatic interactions with the negatively charged tartrazine, resulting in its preferential adsorption and accumulation. Second, the conductivity of Mo₂C domains enhances electron transfer and the electrochemical oxidation of tartrazine. These mechanisms are consistent with the comprehensive structural and electrochemical characterizations presented in this work. Electrochemical tests showed that the composite electrode exhibited improved charge-transfer kinetics and a lower Rct. The NiAl-LDH/Mo₂C-modified SPCE was also able to use DPV for Tz quantification, demonstrating high analytical capabilities with a wide linear working concentration range (0.09-1277 μM) and a low limit of detection (4.3 nM), while preserving selectivity, reusability, and stable performance over a month. The successful measurement of Tz in various commercial products, such as soft drinks, mouthwash, pharmaceutical tablets, and water samples from rivers and taps, with recoveries of 96-118%, confirmed the practical applicability of the study. These findings illustrate the significant potential of the NiAl-LDH/Mo₂C composite as an electrochemically active material, with mechanisms tailored to enhance electrochemical sensitivity for monitoring food and environmental safety.