Raspberry-derived carbon dots for specific detection of intracellular copper ions

The detection of intracellular copper ions is of significant importance in biomedical research and disease diagnosis. In this study, blue emissive carbon dots (B-CDs) were successfully synthesized using raspberries as a carbon source through a simple hydrothermal method. Transmission electron microscopy (TEM) analysis revealed that the B-CDs had an average particle size of 9.05 nm. Characterization techniques combined with theoretical calculations, confirmed that the fundamental structural unit of B-CDs is a twelve-membered aromatic ring rich in oxygen and nitrogen functional groups. The B-CDs exhibited high selectivity for Cu²⁺ ions, showing a strong linear response in the concentration range of 0 to 150 µM, with a detection limit of 0.39 µM. Zeta potential and hydrodynamic size measurements indicated that the B-CDs interact with Cu²⁺ ions via electrostatic forces. Further studies revealed that the fluorescence quenching of B-CDs in the presence of Cu²⁺ is primarily due to a dynamic quenching process. Moreover, B-CDs were successfully applied to detect intracellular Cu²⁺. These findings not only show significant potential of B-CDs in fluorescence sensing but also provide valuable insights for the design of efficient carbon-based sensors.