AbstractThe authors report on an energy transfer based fluorometric approach for the detection of nitroaromatic pollutants. This is achieved using 4-mercaptobenzoic acid (4-MBA)-capped CaF2:Tb3+ nanocrystals that were synthesized by a microwave procedure. 4-MBA acts as both a capping agent and a sensitizer for the Tb3+ ions in CaF2 host matrix. This approach is different from the earlier studies where Ce3+ is generally used as the sensitizer for the Ln3+ ions. The use of capping ligand as sensitizer has the feature that binding of nitroaromatics directly to the sensitizer can alter the energy transfer efficiency between the sensitizer and the Tb3+ ions. The fluorescent nanocrystal probe doped with 2% of Tb3+ displays green emission with a peak at 542 nm if photoexcited at 311 nm. The emission is quenched if the nanocrystals are exposed to nitroaromatic compounds such as 4-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol (picric acid), 4-nitrotoluene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene. These analytes also cause a (longwave/shortwave) shift in the excitation maxima which helps in identifying the individual nitroaromatic compound using single nanoprobe. The respective detection limits (by applying the 3σ/K criterion) are 0.86 μM, 0.83 μM, 0.78 μM, 0.36 μM, 1.5 μM, and 1.96 μM. Graphical abstractSchematic illustration of the use of 4-mercaptobenzoic acid (MBA)-capped CaF2:Tb3+ nanocrystals as a fluorescent nanoprobe for the detection of nitroaromatic analytes. The Tb3+ ions show strong green fluorescence via 4-MBA-induced ligand sensitization. The specific π interaction between 4-MBA capped CaF2 nanocrystals and nitroaromatics leads to reduction in the fluorescence intensity by inhibiting the energy transfer from 4-MBA to Tb3+ ion in CaF2 nanocrystals.

中文翻译：

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4-巯基苯甲酸封端的铽（III）掺杂的CaF2纳米晶体：硝基芳香污染物的荧光探针

摘要作者报告了一种基于能量转移的荧光法检测硝基芳香族污染物的方法。这是使用通过微波程序合成的 4-巯基苯甲酸 (4-MBA) 封端的 CaF2:Tb3+ 纳米晶体实现的。4-MBA 既是封端剂，又是 CaF2 宿主基质中 Tb3+ 离子的敏化剂。这种方法与早期的研究不同，早期的研究通常使用 Ce3+ 作为 Ln3+ 离子的敏化剂。使用封端配体作为敏化剂的特点是硝基芳烃直接与敏化剂结合可以改变敏化剂和 Tb3+ 离子之间的能量转移效率。如果在 311 nm 光激发，则掺杂 2% Tb3+ 的荧光纳米晶体探针显示绿色发射，峰值在 542 nm。如果纳米晶体暴露于硝基芳香化合物，如 4-硝基苯酚、2,4-二硝基苯酚、2,4,6-三硝基苯酚（苦味酸）、4-硝基甲苯、2,4-二硝基甲苯和 2,4，则发射被淬灭， 6-三硝基甲苯。这些分析物还会引起激发最大值的（长波/短波）偏移，这有助于使用单个纳米探针识别单个硝基芳族化合物。各自的检测限（通过应用 3σ/K 标准）为 0.86 μM、0.83 μM、0.78 μM、0.36 μM、1.5 μM 和 1.96 μM。图形摘要 使用 4-巯基苯甲酸 (MBA) 封端的 CaF2:Tb3+ 纳米晶体作为用于检测硝基芳香族分析物的荧光纳米探针的示意图。Tb3+ 离子通过 4-MBA 诱导的配体敏化显示出强烈的绿色荧光。