Chen Li, Wu Chuanli, Du Pan, Feng Xiaowei, Wu Ping, Cai Chenxin
Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, National and Local Joint Engineering Research Center of Biomedical Functional Materials, College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, PR China.
Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, National and Local Joint Engineering Research Center of Biomedical Functional Materials, College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, PR China.
Talanta. 2017 Mar 1;164:100-109. doi: 10.1016/j.talanta.2016.11.019. Epub 2016 Nov 12.
This work reports a facile electrolyzing method to synthesize boron-doped graphene quantum dots (BGQDs) and uses the BGQDs as a fluorescent probe to determine Fe ion levels in water samples. The BGQDs were produced by oxidizing graphite in an aqueous borax solution at pH 7; then, the borate solution was filtered with BGQDs, and the borate was dialyzed from the filtrate, leaving a solution of BGQDs in water. The amount of the B in the BGQDs can be adjusted by changing the concentration of borax used for the electrolyte. The excitation wavelength- and B amount-dependent fluorescence characteristics of BQGDs were studied. The fluorescence intensity of the BGQDs is measurable in real time, and its quenching is very sensitive to the concentration of Fe ions in the system but not to other possible coexisting metal ions. The fluorescence quenching mechanism of Fe ions to BGQDs is studied and explained based on electrochemical voltammetry and DFT simulations. The analytical signal, which is defined as F/F, where F and F are the fluorescence intensities of the BGQDs before and after interaction with Fe ions, respectively, displays a good linear relationship in the Fe ion concentration range of 0.01-100µm with a correlation coefficient of 0.999 and a limit of detection (LOD) of ~(0.005±0.001) μM. The LOD value is much lower than the water quality standards for Fe ions (0.3ppm, ~5.36µm) in drinking water suggested by the WHO (World Health Organization) and EPA (U.S. Environmental Protection Agency), implying that this method has great potential for applications in real sample assays. For example, the determination of the Fe ion levels in three water samples (tap water, groundwater, and lake water) gives approximately the same results as those determined by the EPA-recommended AAS (atomic adsorption spectroscopy) method.
本工作报道了一种简便的电解方法来合成硼掺杂石墨烯量子点（BGQDs），并将BGQDs用作荧光探针来测定水样中的铁离子水平。BGQDs是通过在pH值为7的硼砂水溶液中氧化石墨制备的；然后，用BGQDs对硼酸盐溶液进行过滤，并从滤液中透析出硼酸盐，得到BGQDs的水溶液。BGQDs中硼的含量可通过改变用于电解液的硼砂浓度来调节。研究了BQGDs的激发波长和硼含量依赖性荧光特性。BGQDs的荧光强度可实时测量，其猝灭对体系中铁离子的浓度非常敏感，而对其他可能共存的金属离子不敏感。基于电化学伏安法和密度泛函理论（DFT）模拟研究并解释了铁离子对BGQDs的荧光猝灭机理。分析信号定义为F/F，其中F和F分别是BGQDs与铁离子相互作用前后的荧光强度，在铁离子浓度范围为0.01 - 100µm时呈现良好的线性关系，相关系数为0.999，检测限（LOD）约为(0.005±0.001) μM。该LOD值远低于世界卫生组织（WHO）和美国环境保护局（EPA）建议的饮用水中铁离子水质标准（0.3ppm，约5.36µm），这意味着该方法在实际样品分析中具有很大的应用潜力。例如，对三个水样（自来水、地下水和湖水）中铁离子水平的测定结果与EPA推荐的原子吸收光谱法（AAS）测定结果大致相同。
