硼氮共掺杂石墨烯量子点及对Hg2+的选择性检测

Preparation of B,N-co-Doped Graphene Quantum Dots for Selective Detection of Hg2+ Ion

以柠檬酸、乙二胺和苯硼酸为原料,采用一步水热法制备了高荧光量子产率、长荧光寿命的硼氮共掺杂石墨烯量子点(B,N-GQDs).通过透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FT-IR)、X射线光电子能谱仪(XPS)、紫外-可见分光光度计(UV-Vis)及荧光光谱仪(PL)对量子点进行了表征.结果表明,B,N-GQDs粒径范围为1.46~3.54 nm,平均粒径为(2.34±0.50)nm,具有明显的晶格条纹结构;表面官能团(—OH,—NH和—BOH)的存在,有利于与金属离子结合从而实现对金属离子的检测;在pH=5.0~10.0和NaCl浓度0~1.0 mol/L的酸碱盐环境下,B,N-GQDs具有优异的荧光稳定性.由于B,N-GQD与金属离子具有结合作用,因此它被用作检测金属离子的荧光探针.考察了15种金属离子(K^+、Na^+、Ba^2+、Ni^2+、Zn^2+、Pb^2^+、Li^+、Cu^2+、Ag^+、Mn^2+、Fe^2+、Mg^2+、Fe^3+、Ca^2+和Hg^2+)对B,N-GQDs荧光强度的影响,发现仅Mg^2+、Fe^3+、Ca^2+和Hg^2+对其荧光有猝灭作用.考虑到Hg^2+是重要的有毒污染物,因此灵敏、选择性地检测Hg^2+对人体健康和环境保护至关重要.在单一汞离子体系中,其线性范围为2.0~20.0μmol/L,检测限为0.05μmol/L;在复杂体系(Mg^2+、Fe^3+、Ca^2+和Hg^2+)中,采用掩蔽剂NaF能够实现对Hg^2+浓度的准确测定,其检测误差范围为-4.432%~2.600%.B,N-GQDs有望在多金属离子响应体系中实现对Hg^2+的快速检测.此外,探究了Hg^2+对B,N-GQDs荧光的猝灭机理,当加入Hg^2+后,B,N-GQDs的荧光寿命从原来的12.86 ns缩短为11.34 ns,符合动态猝灭机理.

In this study,we prepared boron-nitrogen co-doped graphene quantum dots(B,N-GQDs)with a high fluorescence quantum yield and long fluorescence lifetime using a one-step hydrothermal method and citric acid,ethylenediamine,and phenylboronic acid as raw materials.We characterized and determined the structure and properties of the B,N-GQDs by TEM,FT-IR,XPS,UV-Vis,and PL spectroscopy.The results show that the particle size range of B,N-GQDs is 1.46—3.54 nm,the average particle size is(2.34±0.50)nm,and there is an obvious lattice fringe structure.To improve the detection of metal ions,it is beneficial to combine B,N-GQDs with metal ions due to the presence of its surface functional groups(—OH,—NH,and—BOH).B,N-GQDs have excellent fluorescence stability in an environment with a pH=5.0—10.0 and an NaCl concentration of 0—1.0 mol/L.Owing to their excellent affinity for interacting with metal ions,we used B,N-GQDs as a fluorescent probe to detect metal ions.Herein,we investigated the effects of fifteen metal ions(K^+,Na^+,Ba^2+,Ni^2+,Zn^2+,Pb^2+,Li^+,Cu^2+,Ag^+,Mn^2+,Fe^2+,Mg^2+,Fe^3+,Ca^2+and Hg^2+)on the fluorescence of B,N-GQDs.We found that its fluorescence was quenched by Mg^2+,Fe3+,Ca2+and Hg^2+.The sensitive and selective detection of Hg^2+is essential for human health and environmental protection as it was one of the most toxic and dangerous pollutants.We obtained a linear relationship be tween the decreased fluorescence intensity of B,N-GQDs and Hg^2+concentrations ranging from 2.0—20.0μmol/L with a detection limit of 0.05μmol/L.In this work,B,N-GQDs served as a multi-metal-ion responsive platform that could be used to directly detect Hg^2+from a complex system(Mg^2+,Fe3+,Ca2+and Hg^2+)by the masking agent NaF,with a detection error in the range of−4.432%to 2.600%.As such,B,N-GQDs provided an original and fascinating fluorescent platform for effectively differentiating and selectively detecting Hg^2+among multi-metal ions.In addition,we investigated the quenching mechanism of Hg^2+on B,N-GQDs fluorescence.When Hg^2+was added,the fluorescence lifetime of B,N-GQDs was shortened from 12.86 ns to 11.34 ns,which accords with the dynamic quenching mechanism.