铝离子与羟基功能化荧光碳点的相互作用

Interaction Between Aluminium(Ⅲ) Cation and Hydroxyl Functionalized Fluorescent Carbon Dots

研究了铝离子（Al^3＋）与表面带有大量羟基的荧光碳点之间的相互作用。当Al^3＋的浓度在0．2-8μmol／L时，碳点的荧光随其浓度的增大而逐渐被猝灭；继续增大Al^3＋的浓度，碳点的荧光逐渐恢复。借助Zeta电位与动态光散射（DLS），初步探讨了二者的作用机理。Al^3＋极易结合碳点表面的羟基，拉近碳点之间的距离引起碳点聚集，从而导致荧光猝灭；当碳点表面的羟基与Al^3＋完全配位后，碳点表面的负电荷转变为正电荷，由于静电排斥作用和空间效应，聚集的碳点重新分散，致使荧光恢复。对比Cr^3＋和Fe^3＋与荧光碳点的作用，发现它们对荧光碳点只有较强的猝灭作用，在高浓度时却未出现碳点荧光恢复的现象，这归因于Al^3＋易形成两性氢氧化物。

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 - 8μmol/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 （DES） 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 resuhs 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.