Nature-Inspired Vertically Oriented 1D Bi₂S₃ Surface Nanorods for Ultra-Selective Electrochemical Sensing of Mancozeb

The issue of environmental contamination is becoming increasingly critical as industrial and agricultural activities continue to grow. As a result, there is a growing need for fast and accurate methods to detect and determine pesticide residues in environmental samples. This study highlights the development of nature-inspired 1D Bi₂S₃ vertically oriented nanorods on fluorine-doped tin oxide glass (Bi₂S₃-VONs(nat)/FTO) using the vegetal extract of <i>Sechium edule</i> (<i>S. edule</i>) for electrochemical detection of mancozeb (MCZ) in environmental matrices. The phytochemicals in the <i>S. edule</i> extract were utilized to promote the growth and stabilization of Bi₂S₃ VONs. The Bi₂S₃ nanorods synthesized at 2.3 g of Bi(NO₃)₃·5H₂O and pH 3 (2.3Bi₂S₃-VONs(nat)/FTO@pH3) exhibit ∼1.74 ± 0.09 μm vertical length with a high surface roughness (67.5% higher than FTO(bare)). The 2.3Bi₂S₃-VONs(nat)/FTO@pH3 electrode exhibited an 89.2% reduction in charge transfer resistance (<i>R</i>_p), a 64.4% increase in the effective surface area (<i>A</i>_e), and a 68.7% enhancement in the anodic peak current of MCZ compared to the FTO(bare). The detection of MCZ at 2.3Bi₂S₃-VONs(nat)/FTO@pH3 involved a reversible four-electron diffusion-controlled event with a formal potential (<i>E</i>⁰) of 0.655 V vs Ag/AgCl, a rate constant (<i>k</i>⁰) of 0.011 s^-1, and a surface coverage of MCZ ions (Γ*) of 1.126 × 10^-11 mol cm^-2. 2.3Bi₂S₃-VONs(nat)/FTO@pH3 demonstrated a detection limit of 0.0085 μM, a quantification limit of 0.0284 μM, and a sensitivity of 0.1578 μA·μM^-1·cm^-2 within a working range of 0-200 μM. Commonly used pesticides, such as chlorpyrifos, carbendazim, malathion, thiram, ziram, and profenofos, could not interfere with MCZ detection. Only a 16.4% reduction in the peak current was observed up to the 30th run when the same sensing platform was reused. 2.3Bi₂S₃-VONs(nat)/FTO@pH3 could effectively detect MCZ spiked in the environmental matrices, which are comparable to liquid chromatography, with a maximum deviation of 4.1, 4.9, 7.1, and 9.7% recorded for tap water, river water, agricultural runoff, and wastewater, respectively.