Visual and Real-Time Monitoring of Cd 2+ in Water, Rice, and Rice Soil with Test Paper Based on [2 + 2] Lanthanide Clusters.

Cadmium ions (Cd 2+ ) are highly toxic to animal and human health, especially through the drinking of Cd 2+ -contaminated water and eating Cd 2+ -contaminated rice. Therefore, accurate detection of Cd 2+ in water, rice, and rice soil is urgent. In this work, two [2 + 2] lanthanide clusters of Tb 2 Tb 2 and Eu 2 Eu 2 were synthesized and characterized in detail. Interestingly, Tb2Tb2 is a rapid sensor for Cd 2+ through luminescence "turn-off". Further studies show that Tb2Tb2 is a highly sensitive and selective sensor toward Cd 2+ in water, rice supernatants, and rice soil supernatants, with a very short response time of 20 s. The limit of detection (LOD) in the above three real samples is as low as 0.0112, 1.1240, and 0.1124 ppb, respectively, which is lower than the national standards for food safety in China (GB 2762-2022). More interestingly, a portable sensing device of test paper based on Tb2Tb2 is developed with a facile method, which shows visible, highly sensitive, and selective sensing toward Cd 2+ in real samples of water, rice supernatants, and rice soil supernatants. Tb2Tb2 and its sensing device of test paper are an on-site analysis sensor for potentially non-expert users, especially for people in remote rural areas.