Abstract

A significant global challenge is presented by the accumulation of agricultural byproducts, demanding innovative strategies for their valorization within a circular bioeconomy. This investigation is centered on the transformation of rice straw, a pervasive lignocellulosic waste, into a high-performance nanomaterial for advanced applications. A novel electrochemical sensor was developed using a composite of iron oxide (Fe₂​O₃​) and rice straw-based carbon dots (RSCD) for the simultaneous detection of dopamine (DPM) and the banned growth promoter, salbutamol (SBT).

The green synthesis of RSCDs was achieved through a facile hydrothermal method utilizing locally collected rice straw. A nanocomposite was then fabricated by integrating these RSCDs with Fe₂​O₃​ nanoparticles. The synergistic effects of the composite were systematically characterized, revealing that the excellent electrocatalytic activity of Fe₂​O₃​ was significantly enhanced by the high conductivity and large active surface area of the RSCDs. By modifying a glassy carbon electrode (GCE) with this composite, a robust sensing platform was created.

Exceptional analytical performance was demonstrated using differential pulse voltammetry (DPV). The critical challenge of resolving overlapping oxidation peaks of DPM and SBT was successfully overcome, enabling highly sensitive and selective simultaneous detection. Impressive detection limits of 0.02 µM for DPM and 0.03 µM for SBT were achieved, with a broad linear range extending from 0.1 to 92 µM. The method's robustness was validated through comprehensive interference studies and successful application in real-world animal urine samples, with recovery rates ranging from 96% to 105%.

This work is positioned at the intersection of plant science, materials engineering, and analytical chemistry. It showcases a scalable and cost-effective pathway to convert plant-based waste into a sophisticated technological tool, directly addressing global needs for sustainable agriculture and food safety monitoring.