Nearly monodisperse Zinc oxide (ZnO) quantum dots (QDs) displayed yellow fluorescence were synthesized using urea as dispersant. In this paper, urea-ZnO QDs were used as fluorescent probe to detect Cr6+ in solution. The emission from the as-synthesized urea-ZnO QDs is selectively quenched when Cr6+ ions were added. Moreover, there are two linear relationships between the quenching of fluorescence intensity and the Cr6+ concentrations ranging from 4 μM to 1000 μM, with the detection limit for Cr6+ at 19.53 nM (on basis of 3σ/slope criterion). The quenching of fluorescence is attributed to aggregation of the QDs and charge transfer between the QDs and Cr6+ by measurements of transmission electron microscopy (TEM) images, UV-visible absorption spectra and fluorescence lifetime.

中文翻译：

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用尿素合成的荧光ZnO量子点，可在宽范围的浓度下选择性检测水中的Cr6 +离子。

使用尿素作为分散剂合成了呈黄色荧光的几乎单分散的氧化锌（ZnO）量子点（QDs）。本文采用尿素-ZnO量子点作为荧光探针检测溶液中的Cr6 +。当添加Cr6 +离子时，选择性地猝灭了合成后的尿素-ZnO QD的发射。此外，荧光强度的猝灭与Cr6 +浓度在4μM至1000μM之间存在两个线性关系，Cr6 +的检出限为19.53 nM（基于3σ/斜率标准）。荧光的猝灭归因于量子点的聚集以及量子点和Cr6 +之间的电荷转移，这是通过测量透射电子显微镜（TEM）图像，紫外可见吸收光谱和荧光寿命来实现的。