Integrating ZnIn ₂ Se ₄ with Biochar Nanocomposites for Heavy Metal Ion Detection and Photocatalytic Degradation of Organic Contaminants

Herein, we present a simple, sustainable hydrothermal method to decorate ZnIn 2 Se 4 nanoparticles onto corn-tuft-derived biochar. The nanocomposite material, hereafter ZnIn 2 Se 4 @biochar, exhibits outstanding photocatalysis and electrochemical sensing of potentially toxic contaminants. The fabrication of the ZnIn 2 Se 4 @biochar was thoroughly investigated using crystallographic, spectroscopic, and microscopy techniques. The optical studies reveal the formation of semiconducting ZnIn 2 Se 4 @biochar with a band gap of ca. 1.49 eV. The morphological investigations indicate the formation of spherical-shaped ZnIn 2 Se 4 nanoparticles with a sufficiently exposed surface for effective surface activities. These include photodegradation of the methylene blue (MB) dye and electrochemical sensing of Pb 2+ and Hg 2+ ions. Photocatalytic degradation investigations suggest that ZnIn 2 Se 4 @biochar exhibits excellent photocatalytic performance toward photodegradation (with 90% degradation in 100 min) of MB. The degradation followed pseudo-first-order kinetics with a high K 1 value of ca. 1.024 × 10 –3 min –1 . The electrochemical investigations using a modified glassy carbon electrode suggest outstanding performance of the developed nanostructure in the trace detection of Pb 2+ and Hg 2+ in an aqueous medium. We obtain a very low detection limit for the trace analysis of Pb 2+ and Hg 2+, ca. 0.0062 ppm (0.018 μM) and 0.0515 ppm (0.190 μM), respectively.