Abstract: The interaction between aluminium(Ⅲ) cation(Al3+) and hydroxyl functionalized carbon dots(CDs) was studied through the fluorescence spectra. Upon the addition of increasing amounts of Al3+ in the range of 0.2~8 μmol/L, the fluorescence of CDs quenched gradually. Further increasing the concentration of Al3+, the quenched fluorescence could be recovered. By employing the dynamic light scattering(DLS) and Zeta potential, we proposed a plausible mechanism for the observed phenomena. At lower concentration of Al3+, Al3+ can easily coordinate with hydroxyl groups on the surface of CDs, the distance among neighboring CDs was then shortened, which causes the aggregation of CDs and quenching of fluorescent CDs. Further increasing the concentration of Al3+, the hydroxyl groups of CDs were completely coordinated with Al3+. In such case, the charges of CDs changed from negative to positive. Owing to the repulsion of the positive charges, the aggregated CDs tend to dissolve and the fluorescence of CDs can be recovered. Although Cr3+ and Fe3+ can also coordinate with hydroxyl groups, our experimental results show that they just have strong fluorescence quenching effects on CDs but no fluorescence recovery phenomena. This is probably ascribed to the fact that Al3+ can form amphoteric hydroxide easily.

Key words: carbon dots, fluorescence, aluminum ions, zeta potential, dynamic light scattering