Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata, Mohanpur, Nadia, West Bengal, 741246, India.
Mikrochim Acta. 2019 May 31;186(6):389. doi: 10.1007/s00604-019-3484-8.
The 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 CaF:Tb nanocrystals that were synthesized by a microwave procedure. 4-MBA acts as both a capping agent and a sensitizer for the Tb ions in CaF host matrix. This approach is different from the earlier studies where Ce is generally used as the sensitizer for the Ln 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 Tb ions. The fluorescent nanocrystal probe doped with 2% of Tb 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 abstract Schematic illustration of the use of 4-mercaptobenzoic acid (MBA)-capped CaF:Tb nanocrystals as a fluorescent nanoprobe for the detection of nitroaromatic analytes. The Tb ions show strong green fluorescence via 4-MBA-induced ligand sensitization. The specific π interaction between 4-MBA capped CaF nanocrystals and nitroaromatics leads to reduction in the fluorescence intensity by inhibiting the energy transfer from 4-MBA to Tb ion in CaF nanocrystals.
作者报道了一种基于能量转移的荧光方法，用于检测硝基芳香族污染物。该方法使用通过微波程序合成的巯基苯甲酸（4-MBA）封端的 CaF:Tb 纳米晶体来实现。4-MBA 既可以作为 CaF 基质中 Tb 离子的封端剂，也可以作为敏化剂。这种方法与早期的研究不同，早期的研究通常使用 Ce 作为 Ln 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会改变敏化剂与 Tb 离子之间的能量转移效率。如果用 311nm 的光激发，掺杂有 2%Tb 的荧光纳米晶体探针在 542nm 处显示出绿色发射峰。如果纳米晶体暴露于硝基芳烃化合物（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 2,4,6-三硝基甲苯），则发射会被猝灭。这些分析物还会导致激发最大值的（长波/短波）位移，这有助于使用单个纳米探针识别单个硝基芳烃化合物。各自的检测限（通过应用 3σ/K 标准）分别为 0.86μM、0.83μM、0.78μM、0.36μM、1.5μM 和 1.96μM。
