Fabrication and optimization of working electrodes by using nanosilica extracted from rice straw

The current study focuses on optimizing and developing working electrodes by utilizing nanosilica extracted from rice straw to improve the electrochemical detection of toxic arsenic ions in groundwater. Rice straw, an abundant agricultural waste byproduct, was identified as a promising source of silica nanoparticles for fabricating electrochemical sensors. Leveraging the high silica content in rice straw, a sustainable and precipitation method was employed to produce silica nanoparticles. The resultant nanosilica, characterized by XRD, FTIR, SEM, and TEM, exhibited a substantial surface area of 189.64 m²/g and a three-dimensional, interconnected structure, indicating its suitability for electrode development. The nanosilica (200 nm) was chemically processed and further reduced in size using a CryoMill. A novel composite incorporating nanosilica, carbon, and other materials was formulated. To assess the sensing properties, modified electrodes were prepared with varying silica concentrations (5%, 10%, 20%, and 30%) by adjusting the proportions of graphite and nanosilica powders. These mixtures were dispersed in 300 µl of 2-propanol. Cyclic voltammetry (CV) was employed using a modified glassy carbon electrode (GCE, Ø = 5 mm) to detect arsenic ions in groundwater. The electrode modified with 10% silica demonstrated the best sensing performance, with a limit of detection (LOD) calculated at 4.3627 mM. Differential pulse voltammetry (DPV) further confirmed the strong linearity in sensor response (R² = 0.9643). Central composite design by RSM and ANOVA analysis highlighted the 10% silica-modified electrode as offering the optimal response, with excellent correlation between experimental and model-predicted results.