Smartphone‐Assisted Wireless Ultrasensitive Nitrite Detection in Food Samples via Hierarchical MXene/NiCoMn‐LDH/Sulfide Heterostructure on Flexible Laser‐Induced Graphene Electrode

Designing a smartphone in-built, wireless, ultrasensitive hybrid heterostructure-based sensor is challenging, but it is potentially crucial for achieving efficient electrochemical responses related to real-time food safety monitoring. Herein, the pioneering design of a few-layered MXene-tagged NiCoMn-layered double hydroxide (LDH)/amorphous sulfide (MXe/NiCoMn-LDH/S) hollow spheres were fabricated and tagged onto a laser-induced graphene (LIG) electrode for smartphone-based electrochemical detection of nitrite (NO₂ ^-). Benefiting from the unique structural and compositional advantages of MXe/NiCoMn-LDH/S integrated on a flexible LIG electrode platform, the sensor achieved a linear detection range from 0.90 to 25 µM, and a low detection limit of 0.21 µM, along with a high sensitivity of 11.88 µA µM^-1 cm^-2. Additionally, using the LSV, the sensor demonstrated a wider linear range from 10 to 860 µM with a detection limit of 7.38 µM and sensitivity of 1.15 µA µM^-1 cm^-2. It also demonstrated strong anti-interference capability against various organic and inorganic substances, along with excellent reproducibility, repeatability, and reusability, as well as outstanding stability over 30 days. The proposed point-of-care electrochemical system, featuring a portable and affordable LIG electrode design, along with compact smartphone integrity, highlights its advantages over traditional benchtop potentiostats in real-time water quality monitoring in rural and low-resource areas.