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以抗坏血酸为碳源,通过微波法直接在水溶液中制备了碳量子点( CQDs),利用透射电子显微镜、紫外吸收光谱、荧光光谱、傅里叶红外光谱及X射线衍射粉末仪对其进行表征,讨论了Cr(Ⅳ)对CQDs的荧光猝灭效应,并将其应用于Cr(Ⅳ)的测定。实验表明,在pH值为4．50的醋酸-醋酸钠缓冲溶液中,控制CQDs浓度为5．41×10-5 mol/L(以碳计),在常温下与Cr(Ⅳ)反应20 min时,于激发波长335 nm,发射波长440 nm处进行测定,Cr(Ⅳ)质量浓度与体系的荧光猝灭程度呈良好的线性关系,线性相关系数为0．9968,线性范围为2．0~71μg/L。方法检出限为0．003μg/L。实验方法应用于环境水中Cr(Ⅳ)的测定,测得结果与分光光度法基本一致,相对标准偏差(RSD,n=5)为1．8%~2．3%。“,”Carbon quantum dots( CQDs) were directly prepared in water solution by microwave method with ascorbic acid as carbon source. CQDs were characterized by transmission electron microscopy( TEM) , ultraviolet absorption spectrum, fluorescence spectrum, fourier transform infrared spectrum ( FTIR ) and X-ray power diffractometer ( XRD) . The fluorescence quenching effect of Cr( VI) on CQDs was discussed, which was applied to the determi-nation of Cr(VI). In HAc-NaAc buffer solution at pH 4. 50, CQDs reacted with Cr(VI) at room temperature for 20 min with CQDs concentration as 5 . 41 × 10-5 mol/L ( in carbon ) , and the system was determined at excitation wavelength of 335 nm and emission wavelength of 440 nm. The results showed that the mass concentration of Cr ( VI) had good linear relationship with the fluorescence quenching degree of system. The linear correlation coeffi-cient was 0. 996 8, and the linear range was 2. 0-71 μg/L. The detection limit of method was 0. 003 μg/L. The proposed method was applied to the determination of Cr( VI) in environmental water sample, and the results were basically consistent with those obtained by spectrophotometry. The relative standard deviations (RSD, n=5) were between 1 . 8% and 2 . 3%.