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 Sechium edule (S. edule) for electrochemical detection of mancozeb (MCZ) in environmental matrices. The phytochemicals in the S. edule 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 (R_p), a 64.4% increase in the effective surface area (A_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 (E⁰) of 0.655 V vs Ag/AgCl, a rate constant (k⁰) 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.