Enhanced-quantum yield sulfur/nitrogen co-doped fluorescent carbon nanodots produced from biomass Enteromorpha prolifera: synthesis, posttreatment, applications and mechanism study

Enteromorpha prolifera (E. prolifera), one of the main algae genera for green tide, significantly influences both the coastal ecological environment and seawater quality. How to effectively utilize this waste as reproducible raw resource with credible application mechanism are urgent environmental issues to be solved. Herein, E. prolifera was converted to attractive fluorescent carbon nanodots (CNDs) by one-pot green hydrothermal process. The purity and quantum yields for the as-prepared CNDs can be enhanced upon the post-treatment of ethanol sedimentation. The CNDs can be well dispersed in aqueous medium with uniform spherical morphology, narrow size distribution and average size of 2.75 ± 0.12 nm. The ease synthesis and relatively high quantum yields of the CNDs make E. prolifera inexpensive benefit to the human and nature, such as applications in efficient cell imaging and fiber staining. Furthermore, it was discovered that the fluorescence intensity of the CNDs can be selectively quenched upon Fe(3+) addition, which can be used for specific sensitive assay and removal of Fe(3+) in aqueous medium. More importantly, it was reasonably proposed that the quenching was resulted from the synergistic effects of CNDs aggregation and Fe(3+)-CNDs charge-transfer transitions due to the coordination interactions between Fe(3+) and the oxygenous groups on the CNDs.