Smartphone-Assisted Electrochemical Sensor for On-Site Detection of Hazardous Metol in Industrial Samples Using Hexagonal Boron Nitride Decorated with Samarium-Doped SnS 2 Nanocomposite

This work reports a rare-earth-modulated samarium-doped tin disulfide/boron nitride (SmSnS 2 @BN) heterostructure for the electrochemical sensing of metol (MTL), in which f-orbital-induced defect states and two-dimensional charge confinement synergistically enhance electrochemical transduction. The SmSnS 2 @BN nanocomposite was employed to modify a glassy carbon electrode and screen printed carbon electrode (SPCE), combining the catalytic activity of Sm-doped SnS 2 with the large surface area and interfacial charge regulation of hexagonal boron nitride. The homogeneous structure and composition of the nanocomposite were confirmed by XRD, XPS, FT-IR, SEM, EDX, and TEM analyses. Electrochemical sensing platform was developed by using both a conventional Autolab potentiostat and a portable PalmSens device. The SmSnS 2 @BN/GCE exhibited enhanced electrocatalytic activity toward MTL oxidation, achieving a wide linear detection range of 0.05–4000 μM, a low limit of detection of (LOD) 0.002 μM (S/N = 3), and a sensitivity of 0.773 μA μM –1 cm –2 . The practical applicability of the sensor was validated through the accurate determination of MTL in real samples, including hair dyes, photographic solutions, and river water, with satisfactory repeatability and reproducibility. These results demonstrate the potential of rare-earth-engineered 2D heterostructures for portable and on-site electrochemical detection of dye-based contaminants.