Ratiometric Monitoring of Thorium Contamination in Natural Water Using a Dual-Emission Luminescent Europium Organic Framework

Traditional analytical methods of
thorium contamination suffer
from several disadvantages such as time-consuming procedures and an
equipment-intensive nature, leading to substantial challenges in rapid
and on-site monitoring of thorium concentrations in complex natural
water systems. We report here the first case of a luminescent metal
organic framework based probe (ThP-1) for highly sensitive
and selective self-calibrated sensing of Th4+ contamination
in natural fresh water media with a notably facilitated detection
procedure. The detection limit of ThP-1 was determined
to be 24.2 μg/L, much lower than the thorium contamination standard
of 246 μg/L in drinking water defined by the World Health Organization.
Importantly, the detection procedure based on the rarely reported
self-calibration manner is greatly beneficial in improving the detection
accuracy. The self-calibrated luminescence evolution process shows
a great anti-interference ability capable of detecting thorium contamination
in a wide concentration range from 24.2 μg/L to 300 mg/L, which
can not be achieved directly by the traditional methods. The Th4+-selective luminescence response originates from the selective
uptake and efficient enrichment of Th4+ by the host framework
of ThP-1 through inner-sphere coordination, which is
further confirmed by batch experiments, X-ray absorption spectroscopic
study, and DFT calculations.