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

Abstract 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 (NO ₂ ⁻ ). 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.