Synthesis and luminescence properties of Eu-activated BiF nanoparticles for optical thermometry and fluorescence imaging in rice root.

The luminescence, optical thermometric properties, phytotoxicity, and fluorescence imaging in plant cells of Eu-activated BiF nanoparticles were systematically studied. Under the excitation of near-ultraviolet light, the prepared compounds emitted visible red light arising from the intra-4f transitions of Eu ions. By employing the fluorescence intensity ratio technique, the temperature sensing performance of the synthesized nanoparticles was investigated and the maximum sensitivity was demonstrated to be 3.4 × 10 K at 443 K. Furthermore, the rice root, which was treated with Eu-activated BiF nanoparticles, showed similar primary root elongation and crown root number to the seedlings cultivated in the MS0 medium without nanoparticles, indicating the relatively low phytotoxicity of the resultant samples to the rice root. Additionally, the results of the toxicity-related gene levels and phenotypes also demonstrated the low phytotoxicity of the as-prepared nanoparticles to the plant cells. Ultimately, with the help of the red emission of Eu ions, the studied compounds were found to be accumulated in the division and differentiation regions of the rice root rather than transferred to the above-ground tissues. These results suggest that the Eu-activated BiF nanoparticles may have potential applications in non-invasive optical temperature sensors and fluorescence probes in plant cells.