用于汞离子检测和细胞成像的石墨相氮化碳量子点荧光探针

A fluorescent probe using graphite carbon nitride quantum dots for the detection of mercury ion and cell imaging

本文采用一步固相热解法,以尿素作为前体合成了石墨相氮化碳量子点(gCNQDs).利用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和傅里叶变换红外光谱(FT-IR)等技术对g-CNQDs的粒径分布、元素组成、形貌结构和表面官能团进行表征.基于Hg^(2+)淬灭g-CNQDs荧光的现象,构建可用于血样和尿样以及实际水样中Hg2+检测的荧光探针,在2.5~50.0μmol·L^(-1)范围内,Hg^(2+)浓度与g-CNQDs相对荧光强度呈现良好的线性关系,检出限为1.5nmol·L^(-1).在实际样品中检测Hg2+的加标回收率为97.17%~101.13%.g-CNQDs与Hg^(2+)的相互作用机理主要为静态淬灭.该探针也被成功应用于肿瘤细胞成像.

Mercury ion(Hg^(2+))is a highly toxic heavy metal ion.Exposure to mercury may cause damages to brain,kidney and neurological systems.Therefore,there is an urgent need to develop convenient and fast approaches to detect Hg~(2+).So far,fluorescence spectroscopy has been a powerful optical technology that can provide a good flexible,sensitive,and simple detection method.Graphitic carbon nitride quantum dots(g-CNQDs),as a new type of fluorescent materials,have gained tremendous attentions.The gCNQDs emerge as a novel fluorescent probe for biological and environment detection because they show bright fluorescence,good water solubility and biocompatibility,low cost,and low cytotoxicity.In this work,the g-CNQDs were synthesized by one-step solid phase pyrolysis with urea as the precursor.The particle size distribution,elemental composition,morphology and surface functional groups of g-CNQDs were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and Fourier transform infrared spectroscopy(FTIR)etc.The stability of g-CNQDs was investigated in different concentrations of sodium chloride solution,under ultraviolet light and in a refrigerator at 4℃for a long time.The results showed that the prepared probe have excellent stability.The fluorescence intensity of g-CNQDs before and after the addition of common ions and amino acids was investigated,and only mercury ions can quench the fluorescence of g-CNQDs.Based on the phenomenon of Hg^(2+)quenching g-CNQDs fluorescence,a fluorescent probe for the Hg^(2+)detection was constructed.The pH,reaction time and the best concentration of g-CNQDs were optimized.The sample of pH=7.4,fluorescence reaction time of 5min,and concentration of g-CNQDs of 7.5μg·L^(-1)were found to give the best results.The fluorescence intensity of g-CNQDs was linearly proportional to the concentration of Hg^(2+)in the range from 2.5to 50.0μmol·L^(-1)with the limit of 1.5 nmol·L^(-1).The probe was applied to the determination of the concentration of Hg^(2+)in blood samples,urine samples,tap water,lake water and waste water samples.The recoveries of Hg^(2+)in blood and urine samples were 97.41%~99.31%,and in actual water samples were 97.17%~101.13%,indicating that this method can be used for the determination of mercury ions in actual samples.Compared with the reported Hg^(2+)detection methods,the Hg^(2+)fluorescence probe prepared in this study has a lower detection limit and higher sensitivity.The reaction mechanism between Hg^(2+)and g-CNQDs was then studied.The ground state molecules of g-CNQDs reacted with Hg^(2+)to form a new complex,and the reaction mechanism was mainly static quenching.The prepared g-CNQDs showed low cytotoxicity and has been successfully used for tumor cell imaging.