柿子叶制备碳量子点的光谱性质及对Fe^(3+)的荧光探针

Spectroscopic Properties of Carbon Quantum Dots Prepared From Persimmon Leaves and Fluorescent Probe to Fe^(3+) Ions

碳量子点作为碳纳米材料中的新成员,具有较高的光学稳定性、低毒性、良好水溶性、原料来源广泛、制备方法多样等多种优点,在分析检测、生物标记、光催化降解以及环境监测等领域具有广泛的应用前景,对碳量子点的研究引起了国内外学者极大兴趣。水中Fe^(3+)含量的超标会对生活饮用和工业生产造成一定的危害,所以准确快速地检测水中Fe^(3+)的含量,对人体健康具有重要的意义。目前,对Fe^(3+)进行检测的方法有伏安法、荧光光谱法、电化学法以及火焰原子吸收光谱法等,其中荧光光谱法具有快速响应和方法简便的特点,比其他方法更有优势。以柿子叶为碳源,采用水热法制备了发蓝绿色荧光的碳量子点,通过X射线衍射、高分辨透射电子显微镜、傅里叶变换红外光谱、紫外-可见吸收光谱及荧光光谱等技术对碳量子点的结构、微观形态和光谱学性质进行了详细表征。柿子叶制备的碳量子点呈现为分散均匀的球形颗粒,颗粒平均直径大约5.9 nm,碳量子点颗粒表面具有丰富的含氧官能团,在277 nm有明显的紫外吸收,可归因于C=O的n→π^(*)跃迁。碳量子点的发射波长和荧光强度具有明显的激发依赖性,在410 nm光激发下,发射波长峰值为498 nm且荧光峰最强,荧光寿命为4.59 ns。采用多种金属离子对柿子叶制备的碳量子点在荧光传感方面进行了探究,分析发现该碳量子点对金属Fe^(3+)具有极高的选择性,可作为荧光探针检测水中微量的Fe^(3+)含量,其荧光猝灭率F_(0)/F与金属Fe^(3+)浓度在1~120μmol·L^(-1)范围内呈现良好的线性关系(R^(2)=0.992),猝灭常数和最低检出限分别为8.84×10^(3)L·mol和0.21μmol·L^(-1),最低检出限数值明显小于最近一些文献的报导结果。该工作提供了一种原料天然、操作简单、成本低廉的制备工艺,开发了荧光检测水中微量金属铁离子的新方法。

As a new member of carbon nanomaterials,carbon quantum dots(CDs)with many advantages such as high optical stability,low toxicity,superior water solubility,diverse raw materials and preparation approaches,have shown application prospects in the fields of analytical detection,biomarker,photocatalytic degradation and environmental monitoring widely.The investigation on CDs has attracted significant interest.In general,the exceeding content of Fe^(3+)ion in water would be harmful to daily drinking and industrial production.It is of great significance to determine the content of Fe^(3+)in water accurately and quickly.At present,some techniques are used for the detection of Fe^(3+)ions,which include voltammetry,fluorescence spectrum,electrochemical and flame atomic absorption spectrometry.The fluorescence spectrometry has shown the merits of fast response and facile process,which makes it much better than other ways.In this paper,the CDs with bluish-green emission were prepared by hydrothermal treatment of persimmon leaves.The X-ray diffraction,high resolution transmission electron microscopy,Fourier transform infrared spectroscopy,ultraviolet visible absorption spectroscopy and fluorescence spectroscopy were used to characterize CDs’structure,morphology,and spectroscopic properties.The CDs exhibit uniform spherical particles with an average diameter of 5.9 nm and abundant oxygen-containing functional groups on the surface.The UV absorption at 277 nm should be attributed to then→π^(*)transition of theC=O group.CDs’emission wavelength and intensity are closely dependent on the excitation wavelength.Excited with 410 nm long,the emission maxima are 498 nm and it shows the strongest intensity.The fluorescence liFe^(3+)time is about 4.59 ns.Moreover,the as-prepared CDs show high selectivity for Fe^(3+)ion compared to other metal ions,which can be used as a fluorescent probe to detect the trace concentration of Fe^(3+)in water.The dependence of fluorescence quenching rate F_(0)/F with Fe^(3+)concentration has a good linear relationship(R^(2)=0.992),and the quenching constant,and detection limit value is 8.84×10^(3)L·moland 0.21μmol·L^(-1),respectively.The detection limit value of 0.21μmol·L^(-1)is smaller than those reported in recent literature.Consequently,this work provides a preparation process with natural raw materials,simple operation and low-cost,and develops a new pathway for the fluorescence detection of trace metal iron ions in water.