基于乙醇和铝离子聚集诱导的铜纳米团簇

金属纳米团簇(MNCs)作为一种新型的纳米材料，具有合成方法简单、光稳定性强、毒性低、生物相容性好以及发光效率高等优点。在本研究中，使用“一锅法”合成谷胱甘肽保护的铜纳米团簇。在激发波长为370 nm时，GS@CuNCs的荧光发射波长在610 nm左右。铜纳米团簇可以通过有溶剂诱导和阳离子诱导两种方法聚集诱导增强其荧光强度。通过测定在不同溶剂(乙醇、甲醇、N, N-二甲基甲酰胺)中铜纳米团簇的荧光强度，探究了溶剂极性对聚集的影响。研究结果表明：在水溶液中铜纳米团簇只发射弱的荧光，随着乙醇含量从0%到85%，其荧光强度逐渐增强。此外，我们开发了一种新的选择性好、灵敏性高的检测铝离子的荧光探针。线性范围为2–20 μmol·L^-1，且检测限(LOD)为33 nmol·L^-1。进一步探究可得，乙醇和铝离子能使GS@CuNCs荧光强度显著增加的机理为聚集诱导荧光增强。

Luminescence Emission of Copper Nanoclusters by Ethanol-induced Aggregation and Aluminum Ion-induced Aggregation

Metal nanoclusters (MNCs), as a new type of nano-material, possess excellent properties such as facile synthesis, strong light stability, low toxicity, excellent biocompatibility, and high luminous efficiency. Aggregation-induced emission (AIE), which can enhance the luminescence properties of MNCs, has resulted in MNCs attracting significant attention. In this thesis, L-glutathione (GSH)-protected copper nanoclusters (GS@CuNCs) were prepared by a "one-pot" method in aqueous solution without additional reducing agents. The GS@CuNCs were characterized by UV-Vis absorption spectroscopy and fluorescence spectroscopy. Upon excitation at 370 nm, the fluorescence spectrum of GS@CuNCs displayed the maximum emission peak at 610 nm. The as-prepared CuNCs generate a striking fluorescence intensity via aggregation-induced emission (AIE). The AIE property of GS@CuNCs was examined for the aggregates in different organic solvents, such as ethanol, methanol, and dimethylformamide. Since the aggregation degree was controlled by the content of organic solvent, we further measured the fluorescence intensity of GS@CuNCs in different volume ratios of a water-ethanol mixture solution. The fluorescence intensity of GS@CuNCs exhibited an approximately 30-fold increase at 85% of ethanol content, as compared to that in aqueous solution. A possible mechanism may be that intramolecular motions are restricted in ethanol, resulting in a significant increase of fluorescence intensity. Moreover, only very weak emissions were recorded for the CuNC dispersion in aqueous solution; however, an apparent luminescence enhancement was observed in both luminescence spectra and by naked eyes under UV light, with a gradual increase in the ethanol content in the water-ethanol mixture from 0% to 85%. Additionally, we developed a new selective and sensitive turn-on fluorescent sensor for the detection of trivalent aluminum ions (Al³⁺) based on cation-induced aggregation methods. Among the 15 types of metal cations studied, only Al³⁺ visibly increased the fluorescence emission of the GS@CuNCs. These results indicated that the GS@CuNCs were highly selective to Al³⁺ than other metal ions, which may result from the electrostatic and coordination interactions between the trivalent aluminum ions and monovalent carboxylic anions from GSH in the CuNCs. The response of the probe to Al³⁺ exhibited a good linear range of 2–20 μmol·L^-1 and the detection limit was 33 nmol·L^-1. Thus, the weak fluorescence intensity of CuNCs was increased markedly by the AIE of Al³⁺, and could construct an interesting fluorescent platform for sensing aluminum ions. The property of AIE of GS@CuNCs may expand the potential applications of nanocluster materials to biosensors and cell imaging.