Non-pyrolytic synthesis of laccase-like iron based single-atom nanozymes for highly efficient dual-mode colorimetric and fluorescence detection of epinephrine

Single-atom nanozymes have garnered significant attention due to their exceptional atom utilization and ability to establish well-defined structure-activity relationships. However, conventional pyrolytic synthesis methods pose challenges such as high energy consumption and random local environments at the active sites, while achieving non-pyrolytic synthesis of single-atom nanozymes remains a formidable technical hurdle. The present study focuses on the synthesis of laccase-like iron-based single-atom nanozymes (Fe-SAzymes) using a non-pyrolysis method facilitated by microwave irradiation. Under low iron loading conditions, Fe-SAzymes exhibited significantly enhanced laccase activity (12.1 U/mg), surpassing that of laccase by 24-fold. Moreover, Fe-SAzymes demonstrated efficient catalytic oxidation of epinephrine (EP), enabling its colorimetric detection. Owing to the remarkable laccase activity of Fe-SAzymes, the conventional nanozymes EP detection time was reduced from 60 min to 20 min, with an impressive low detection limit as low as 2.95 μM. In addition, an ultra-sensitive fluorescence method for EP detection was developed using the internal filter effect of EP oxidation products and CDs combined with carbon dots probe. The detection limit of fluorescence method was only 0.39 μM. Therefore, an visual, fast, and highly sensitive dual-mode EP detection strategy has great potential in the clinical diagnostic industry.