Biomass-derived carbon dots-based dual-mode platform for rapid fluorescence detection and portable visual screening of tetracycline

Tetracycline (TC) has been the focus of considerable public concern due to its potential to induce liver function abnormalities, renal damage, suppression of bone growth, and a range of human health hazards. Therefore, the accurate detection of trace amounts of TC is of particular importance. In this work, biomass-derived carbon dots (Fa-CDs) were successfully synthesized by a sustainable hydrothermal treatment of Fatsia japonica leaves (Fa). The chemical composition and structure of the Fa-CDs were comprehensively characterized via UV–vis, FL, FT-IR, TEM, and XPS. The obtained Fa-CDs maintained excellent photoluminescence properties and good stability. Notably, the Fa-CDs displayed a specific and ultrafast (approximately 10 s) response to TC, enabling the development of a label-free fluorescence sensor for rapid and environmentally sustainable TC detection. Mechanistic investigations revealed that the fluorescence quenching behavior in the sensing platform primarily involved static quenching coupled with the inner filter effect (IFE). The sensor exhibited outstanding analytical performance, demonstrating a wide linear dynamic range (0–80 μM, R 2  = 0.999) and an ultralow detection limit (26 nM). Real-sample analysis yielded excellent recovery rates (95.4 %–104.0 %), confirming both the practical utility of the Fa-CDs nanoprobes and the reliability of the developed fluorescence sensing platform. Moreover, smartphone-assisted visual screening of TC was successfully achieved in both solution-phase systems and paper-based platforms. This study developed an environmentally friendly, sustainable, and easy-to-implement synthesis strategy for CDs, successfully constructing a dual-mode detection platform for TC that integrates rapid fluorescence sensing and visual screening capabilities.