Dual-mode detection of malathion under neutral conditions: Integrated application of specific nanozyme and time-resolved europium probe

Abstract

This study develops a dual-mode colorimetric-fluorescent sensor for malathion detection, capable of functioning directly under neutral conditions. The sensor integrates the highly specific Cu-MIL-53(Fe)-2 nanozyme and a long-lifetime europium-based probe. Unlike traditional acetylcholinesterase catalytic systems, this method utilizes an alkaline hydrolysis strategy to generate thiol groups, which significantly reduces detection costs and avoids the common issues of enzyme instability and false positives associated with conventional biological enzyme systems. Unlike traditional methods relying on acetylcholinesterase inhibition, the hydrolysis process is based on a "multiple condition tandem protection" mechanism, offering higher specificity. The hydrolysis products simultaneously trigger a broad-range visible colorimetric "off" signal and a highly sensitive fluorescent "on" signal, with the two signals cross-verifying each other to greatly enhance detection accuracy. The Cu-MIL-53(Fe)-2 nanozyme demonstrates exclusive peroxidase activity under neutral conditions, effectively solving the issue of conventional nanozymes only working in acidic environments, thus ensuring compatibility with practical detection settings. Its specific enzyme activity also effectively mitigates interference from nonspecific enzyme reactions. Additionally, combining the long-lifetime Eu(PDA)₃ probe with time-resolved properties significantly eliminates background fluorescence interference, enhancing the signal-to-noise ratio. Through this design, the study provides a reliable, cost-effective method for malathion detection with high specificity and precision.