Advanced Heavy Metals Detection Through Electrochemical Sens-ing

This thesis presents an innovative approach to enhancing electrochemical sensing by engineering nanostructured diamond/graphite electrodes through the self-assembly of block copolymers (BCPs) and Sequential Infiltration Synthesis (SIS). Diamond, renowned for its exceptional chemical stability, wide potential window, and low background current, offers a compelling platform for high-performance sensing. However, its flat surface limits adsorption and sensitivity. To overcome this, we introduce a bottom-up nanofabrication strategy combining BCP lithography and SIS to create precisely controlled surface nanostructures that significantly enhance sensing capabilities. The process begins with oxygen plasma treatment to activate the diamond surface, improving polymer film adhesion. A thin film of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is then deposited via spin coating and thermally annealed to induce self-assembly into periodic nanodomains. SIS is subsequently applied, using alternating exposures to metal-organic precursors and oxidizing agents that selectively infiltrate the PMMA domains. This forms hybrid organic–inorganic structures within the BCP template. Following plasma etching, the polymer is removed, leaving behind ordered metal oxide nanostructures that replicate the BCP pattern. To integrate conductivity and further functionality, microelectrodes were patterned on the nanostructured diamond using 50 keV ion implantation followed by thermal annealing to induce graphitization. These graphitic microelectrodes were precisely aligned with the nanopatterned areas to ensure maximal interaction with analytes. Electrochemical performance was evaluated using the cyclic voltammetry technique for the detection of dopamine and heavy metal ions, particularly copper (Cu²⁺) and iron (Fe³⁺), in aqueous media. The results demonstrate a substantial enhancement in sensitivity compared to non-patterned diamond electrodes. The increased surface area and nanostructure-driven adsorption led to improved electron transfer kinetics and higher analyte response. This approach not only boosts signal strength but also ensures robust and reproducible performance across a range of concentrations. This work demonstrates the successful application of SIS on diamond surfaces to enhance electrochemical sensing. The resulting nanostructured electrodes show great promise for biosensing and environmental detection, combining the robustness of diamond with the precision of nanoscale engineering