Colorimetric-SERS Dual-Mode Detection of Organophosphorus Pesticides Using Au-R-Fe3O4 Nanozyme Cascade Platform: A Practical Approach for Chemistry Education

Abstract

Organophosphorus pesticides (OPs) pose significant environmental and health risks due to their persistence and neurotoxicity, yet current detection methods rely on sophisticated instrumentation inaccessible to educational settings. To address this pedagogical gap, we developed a recyclable Au-R-Fe3O4 nanozyme cascade reactor integrating robust peroxidase-like activity and surface-enhanced Raman scattering (SERS) capabilities. This platform enables dual-mode detection of OPs through an innovative enzyme cascade (AChE/ChOx/Au-R-Fe3O4), where OP-induced inhibition of acetylcholinesterase (AChE) modulates colorimetric and SERS signals of oxidized 3,3′,5,5′-tetramethylbenzidine. The magnetic Fe3O4 nanorings facilitated efficient catalyst recovery, maintaining 92% activity after five cycles, demonstrating exceptional operational stability ideal for classroom reuse. The dual-mode Au-R-Fe3O4 sensor achieved detection limits for chlorpyrifos and methyl parathion, reaching 8.56 and 5.24 ng/mL via colorimetry and 0.59 and 0.76 ng/mL via SERS, respectively. Particularly significant for chemical education, this system visually demonstrates enzyme kinetics, nanomaterial properties, and environmental analysis principles in a single integrated experiment. We detail its implementation in undergraduate laboratories, enabling students to explore interfacial catalysis, spectroscopic quantification, and environmental monitoring applications through hands-on experience with cutting-edge nanotechnology.