Waste-to-resource: Utilization of carbon dots derived from proliferating Sargassum aquifolium (Turner) C. Agardh for fluorescent detection of levofloxacin

The recurrent proliferation and blooms of Sargassum have emerged as a major environmental challenge in tropical and temperate coastal regions, with profound implications for ecological balance, economic stability, and societal well-being. Levofloxacin (LVF), a fluoroquinolone antibiotic, is physiologically toxic and its residues and accumulation in the aquatic environment have become a serious threat to ecosystems and human health. This work presents a novel approach for the fluorescent detection of LVF, a common antibiotic in environmental waters, using carbon dots derived from the abundant invasive seaweed Sargassum aquifolium (Turner) C. Agardh. The Sargassum carbon dots (SACD) were prepared by a simple one-step hydrothermal method and can reduce the internal filtering effect (IFE) of LVF, thereby facilitating fluorescence detection of high-concentrations of LVF. SEM and TEM were used to characterize the structure, and SACD exhibited a spherical amorphous carbon with a partial lattice structure. The composition of SACD was further analyzed by using FTIR and XPS after synthesis. This method offers a wide detection range (1 μM–100 μM, R² = 0.998) and low detection limit (0.3 μM) for LVF analysis, exhibiting high recovery rates (103.4 %–113.9 %) in spiked real environmental water samples, demonstrating its potential application performance. The SACD can selectively detect LVF in the presence of the common interfering substances. Therefore, SACD has promising applications in environmental pollutant detection. This study proposes a sustainable approach to utilizing and mitigating the impact of invasive seaweeds, highlighting the potential for converting biological waste into valuable resources for environmental monitoring and protection.