On-Site Ratiometric Analysis of UO with High Selectivity.

Uranyl ions (UO) are recognized as important indicators for monitoring sudden nuclear accidents. However, the interferences coexisting in the complicated environmental matrices impart serious constraints on the reliability of current on-site monitoring methods. Herein, a novel ratiometric method for the highly sensitive and selective detection of UO is reported based on a [Eu(diaminoterephthalic acid)] (Eu-DATP) metal-organic framework. Benefiting from the unique chemical structure of Eu-DATP, energy transfer from DATP to UO was enabled, resulting in the up-regulated fluorescence of UO and the simultaneous down-regulated fluorescence of Eu. The limit of detection reached as low as 2.7 nM, which was almost 2 orders of magnitude below the restricted limit in drinking water set by the United States Environmental Protection Agency (130 nM). The Eu-DATP probe showed excellent specificity to UO over numerous interfering species, as the intrinsic emissions of UO were triggered. This unprecedentedly high selectivity is especially beneficial for monitoring UO in complicated environmental matrices with no need for tedious sample pretreatment, such as filtration and digestion. Then, by facilely equipping a Eu-DATP-based sampler on a drone, remotely controlled sampling and on-site analysis in real water samples were realized. The concentrations of UO were determined to be from 16.5 to 23.5 nM in the river water of the Guangzhou downtown area, which was consistent with the results determined by the gold-standard inductively coupled plasma mass spectrometry. This study presents a reliable and convenient method for the on-site analysis of UO.