Fluorescence sensing of Cu2+ ion and imaging of fungal cell by ultra-small fluorescent carbon dots derived from Acacia concinna seeds

In this work, we explored the use of Acacia concinna seeds (shikakai) as a green precursor for the fabrication of ultra-small fluorescent carbon dots (CDs). The synthesized ultra-small fluorescent CDs sense only Cu2+ ion through strong chelation between Cu2+ ion and organic groups of CDs. As a result, highly selective fluorescence "turn-off" probe was developed for assay of Cu2+ ion, causing remarkable fluorescence intensity quenching, which has ability to sense Cu2+ ion even at 0.0043 mu M (4.3 nM). Furthermore, the ultra-small fluorescent CDs act as biocompatible probes for multicolour imaging of fungal (Penicillium sp.) cells. The practical application of the developed sensor was demonstrated by assaying of Cu2+ ion in spiked water samples, which confirms their significant analytical and bioanalytical applications.