基于氮掺杂碳量子点的水体氟离子选择性荧光开启检测

Rapid and selective“turn-on”fluorescent detection of fluoride ion in aqueous solution using nitrogen-doped carbon quantum dots

本论文以柠檬酸为碳源、尿素为氮源,通过水热法制备了氮掺杂碳量子点(NCDs),将其作为荧光探针用于检测水体中的氟离子(F^(–)).利用透射电镜(TEM)、X射线光电子能谱(XPS)、红外光谱(FT-IR)、紫外-可见光谱(UV-vis)、荧光光谱等表征手段分析了NCDs的结构和光谱学性质.考察了探针检测氟离子的灵敏度、稳定性和选择性,及其在天然水体样品中的适用性.结果表明,NCDs可在紫外光激发下产生蓝色荧光,且具有较高的荧光量子产率(41%).NCDs富含羧基、羟基等含氧官能团,可与铝离子(Al^(3+))发生反应,这一过程会导致其荧光淬灭;而F^(–)与Al^(3+)的配位反应可置换出与NCDs结合的Al^(3+),使NCDs的荧光恢复,产生荧光“开启”效应.NCDs荧光恢复的程度与F^(–)浓度线性正关系(R2=0.995),表明该方法可用于定量检测F^(–).进一步研究显示,NCDs在检测F^(–)时具有较快的响应时间(约1.0 min)、较宽的线性范围(20—300μmol·L^(-1))、较低的检出限(0.65μmol·L^(-1))和良好的选择性(水体常见阴阳离子对检测过程的影响低于5%).此外,NCDs还具有良好的稳定性,在中性到弱碱性环境(pH 6.0—9.0)中均能有效检出F^(–).在实际水体分析过程中,NCDs显示了良好的F^(–)加标回收率(88.2%—105.0%)和检测精密度(相对标准偏差低于3.0%),表明其具有较好的应用潜能.

Nitrogen-doped carbon quantum dots(NCDs)were synthesized by a facile hydrothermal method using citric acid as the carbon source and urea as the nitrogen source,and were applied as a novel“turn-on”fluorescent probe for the detection of fluoride ions(F^(–))in water.The structural and spectroscopic properties of the NCDs were characterized by transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-vis),and fluorescence spectroscopy.The sensitivity,stability and selectivity of the NCDs probe to detect F^(–)as well as its applicability in natural water samples were investigated.NCDs showed blue fluorescence emission under ultraviolet light irradiation,and had a high fluorescence quantum yield of 41%.The NCDs can react with aluminium ions(Al^(3+))via the surface oxygen-containing groups,which would quench the fluorescence emission of NCDs.Due to the strong coordination affinity,F-can compete with NCDs for Al^(3+)and thus recover the fluorescence of NCDs.There existed a good linear relationship between the recovery ratio of NCDs fluorescence and F-concentration(R2=0.995),suggesting the possibility of NCDs in F-quantification.The NCDs-based fluorescence method for F-detection exhibited a short response time(approximately 1.0 min),wide linear range(20-300μmol·L^(-1)),low detection limit(0.65μmol·L^(-1)),good selectivity(influences of common ions below 5%),and satisfactory stability in environmentally relevant pH range(pH 6.0-9.0).Finally,the proposed method was successfully applied in the analysis of F-in real water samples with high recoveries(88.2%-105.0%)and precision(relative standard deviations lower than 3.0%).