Luminescent Tb-doped Ca-deficient hydroxyapatite/agar for selective adsorption and detection of UO22+ ion

Uranium is a hazardous radioactive pollutant commonly produced from nuclear energy development and nuclear accidents. It has posed a potentially serious threat to the environment and human health. Thus, it is crucial to develop adsorptive sensors for adsorbing and detecting uranium in the environment. Here, we have synthesized a novel eco-friendly luminescent Tb-doped Ca-deficient hydroxyapatite utilizing agar as a template (denoted as "Tb-DEF-HAP/agar ") to sensitively and selectively adsorb and detect UO22+ ion. Ca2+ vacancy defects within the crystal structure of the Tb-DEF-HAP/agar can be tuned by changing the (Tb+Ca)/P molar ratio of the precursors, which adjusts its luminescence performance. The Tb-DEF-HAP/agar shows fluorescence intensity 3.6 times of the Tb-doped HAP synthesized with stoichiometric (Tb+Ca)/P (denoted as "Tb-HAP/agar "). The Tb-DEF-HAP/agar adsorbs and detects UO22+ ion sensitively with an ultra-low limit of detection of 27.2 nM and shows high selectivity over various other tested metal ions. Moreover, we have investigated the luminescent adsorbing and sensing mechanism of the Tb-DEF-HAP/agar as an adsorptive sensor for UO22+ ion. Our work provides new and valuable insights for the future development of excellent biodegradable rare earth (RE) doped HAP-based luminescent adsorptive sensors by tailoring their chemical composition such as (RE+Ca)/P molar ratios.