采用一步湿化学法合成铜纳米簇(CuNCs),并提出了以CuNCs为荧光探针,荧光分光光度法测定矿泉水和饮料中日落黄含量的方法。将水15.0mL、0.01mol·L^-1 L-半胱氨酸溶液4.0mL和0.1mol·L^-1硝酸铜溶液0.2mL混合,置于15℃水浴中搅拌5min,然后缓慢滴加1.0mol·L^-1氢氧化钠溶液1.00mL,继续在15℃水浴中搅拌反应2.5h,接着将L-半胱氨酸保护的CuNCs浅蓝色溶液透析72h,于60℃干燥72h,得到CuNCs。分取50μL过滤后的样品,与0.33g·L^-1CuNCs溶液0.5mL混合,然后用pH8.0的伯瑞坦-罗宾森缓冲溶液稀释至3.0mL。设置激发波长为370nm,激发、发射的狭缝宽度分别为5,10nm,记录加入日落黄前后体系在490nm处的荧光强度F₀和F。结果显示:日落黄对CuNCs的荧光猝灭主要来自内滤效应;日落黄的浓度在2.00~60.00μmol·L^-1内与体系的荧光强度比值F/F₀呈线性关系,检出限(3s/k)为1.31μmol·L^-1;矿泉水和饮料中日落黄的回收率为95.2%~104%,测定值的相对标准偏差(n=5)为2.1%~3.7%。

Copper nanoclusters (CuNCs) were prepared using one-step wet chemical synthesis method, and a method for the determination of sunset yellow in mineral water and beverage by fluorescence spectroscopy was proposed using CuNCs as fluorescent probe. The mixture containing 15.0 mL of water, 4.0 mL of 0.01 mol·L^-1 L-cysteine solution and 0.2 mL of 0.1 mol·L^-1 copper nitrate solution was placed in 15 ℃ water bath and stirred for 5 min. Then 1.00 mL of 1.0 mol·L^-1 sodium hydroxide solution was added slowly, and the reaction was continued for 2.5h in 15 ℃ water bath. The light blue solution of CuNCs protected by L-cysteine was dialyzed for 72 h, and dried at 60 ℃ for 72h to obtain CuNCs. An aliquot of 50 μL filtered sample was mixed with 0.5 mL of 0.33 g·L^-1 CuNCs solution, and diluted to 3.0 mL with Burritan-Robinson buffer (pH 8.0). The excitation wavelength was set as 370 nm, and the slit widths of excitation and emission were set as 5, 10 nm, respectively. The fluorescence intensities of the system at 490 nm before and after CuNCs addition were recorded. The results showed that the fluorescence of CuNCs was quenched by sunset yellow mainly coming from inner filter effect. Linear relationship between fluorcescence intensity ratio (F/F₀) of the system and concentration of sunset yellow was kept in the range of 2.00-60.00 μmol·L^-1, and the detection limit (3s/k) was 1.31 μmol·L^-1. The recoveries of sunset yellow in mineral water and beverage were in the range of 95.2%-104%, and RSDs (n=5) of the determined values were in the range of 2.0%-3.7%.