Celery Stalk-Derived Carbon Dots for Detection of Copper Ions

Fluorescent carbon dots (CDs) have motivated a significant amount of research because of their properties such as excellent biocompatibility and low toxicity. In this work, water-soluble fluorescent CDs were synthesized from celery stalks by a one-step, low-cost hydrothermal process. The as-prepared CDs had the average size of 3.7 ± 1.1 nm, and they emitted bright blue photoluminescence. The surface functional groups and states were investigated via Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The blue fluorescence of the as-prepared CDs was effectively quenched by Cu²⁺ ions compared to other competing metal ions. Therefore, these CDs are promising probes for the fluorescence detection of Cu²⁺ ions. Moreover, an excellent linear relationship was obtained between the relative fluorescence intensity and the concentration of Cu²⁺ ions in the linear detection range 0-100 µM, and the limit of detection was 0.132 µM.