Analysis of trace-level metals in environmental samples (e.g., soil, water, and plant samples) is essential for assessing environmental quality and food safety. This dissertation reports a non-toxic, eco-friendly, and cost-effective sensing method, capable of in-situ detection of microgram per liter (μg/L) levels of heavy metal ions in plant and soil solutions using carbon-based electrodes, including carbon fiber electrodes (CFEs) and boron-doped diamond electrodes (BDDs). The electrochemical behaviors of the CFEs and BDDs were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. As proof of principle, the CFEs and BDDs were validated for sensing selected heavy metals in buffer solutions as well as in extracted plant and soil solutions using differential pulse anodic stripping voltammetry (DP-ASV). The ideal pH range for heavy metal detection was also extensively investigated and was found to be between pH 4.0 and pH 5.0. Experimental results confirm that the CFEs were able to simultaneously measure cadmium (Cd), lead (Pb), and mercury (Hg) with a limit of detection (LOD) of 2.10 μg/L in buffer solution with an effective area (Aeff) of 0.123 cm2, showcasing good selectivity and sensitivity. On the other hand, the BDD electrodes showed simultaneous measurement of these metals with an LOD of 17.34 μg/L in buffer solution with Aeff of 0.122 mm2. Besides, BDD offers precise control over the fabrication by utilizing a microfabrication facility. Overall, the integration of these sensors with a microfluidics system lays a better foundation for long-term, in-situ, and stable electrochemical analysis for aqueous environment matrices.
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