Hydrolytic-Peroxidatic Cascade on Bifunctional Nanozymes for Specific Fluorescent Profiling of Aromatic Polyester Microplastics

Abstract Aromatic polyester microplastics are derived from a special type of engineering plastic. Therefore, effective management requires reliable qualitative discrimination and accurate quantitative detection, rather than simply measuring total microplastic concentrations. To address this challenge, we developed a cascading fluorescence sensing platform based on the sequential dual-enzyme mimicry of magnesium–iron layered double oxide (MgFe LDO) nanozymes. MgFe LDO first hydrolyzes aromatic polyesters into terephthalic acid (TPA), which is subsequently hydroxylated via its peroxidase-mimicking activity to generate the fluorescent product 2-hydroxyterephthalic acid. Differences in hydrolysis rate and TPA concentration arising from the structural variation among distinct aromatic polyesters are translated into quantifiable fluorescence signals, enabling the precise detection and specific discrimination of multiple polymers. The bifunctional nanozymes combining hydrolase-like and peroxidase-like activities exhibit reliable performance and adaptability in spiked real-world samples, including rainwater, river water, tap water, and seawater. This work provides a basis for constructing integrated laboratory-based screening platforms for aromatic polyester microplastics using rationally engineered nanozymes.