Dual-emission LaF3:Tb@DPA-Eu nanoparticles as a ratiometric fluorescence probe for the detection of marbofloxacin

In this work, a facile method for the preparation of dual-emission lanthanide nanoparticles (NPs) was developed. Tb3+-doped LaF3 NPs coated with 2,6-pyridinedicarboxylic acid (DPA) and Eu3+, namely LaF3:[email protected] NPs, could produce characteristic emissions of Tb3+ and Eu3+ under 272 nm excitation, which originated from the absorption of DPA. The LaF3:[email protected] NPs with tunable emission peaks and color could be synthesized by changing the concentration of Eu3+. Additionally, the obtained NPs were comprehensively characterized by various analytical methods. Transmission electron microscopy (TEM) images showed that the average size of the NPs was ~15 nm. Moreover, X-ray diffraction (XRD) analysis revealed that the products were single-phase LaF3, while the doped Tb3+ entered the LaF3 lattice to occupy the La3+ sites. Owing to their excellent water solubility and good optical properties, the LaF3:[email protected] NPs were used as a fluorescence probe for the detection of marbofloxacin (MAR) based on the fluorescence quench. Notably, an effective ratiometric fluorescence method was established. The approach exhibited good sensitivity and selectivity with a linear range of 0.10 ~ 10.0 μM and detection limit of 85 nM. It was successfully employed for the determination of MAR in milk samples with recoveries of 98.1%–106%. Thus, the fluorescence method based on the LaF3:[email protected] NPs developed herein provides a convenient and fast platform for the detection of MAR.