Lanthanide β-Diketonate Complex Functionalized Poly(ionic liquid)s/SiO₂ Microsphere as a Fluorescent Probe for the Determination of Bovine Hemoglobin

The application of the excellent luminescence properties of lanthanide β-diketonate complex in water systems is the focus of the research in this field. We introduced the lanthanide β-diketonate complex into the framework of polyionic liquid (PIL) and SiO2 to prepare a lanthanide complex hybrid material fluorescent probe SiO2@PIL-Eu(nta)4, which can be used for the detection of bovine hemoglobin in water. Hydrophilic polyionic liquid grafted with SiO2 nanoparticles was the template of the hybrid material. The lanthanide complex was introduced into the prepared spherical polyionic liquid brushes by ion exchange. The obtained products were characterized by Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), ultraviolet–visible (UV–vis) spectroscopy, and luminescence spectroscopy. The PIL matrix improved the fluorescence lifetime and quantum efficiencies of the lanthanide complex. The as-synthesized hybrid material was employed as a fluorescent probe for the bovine hemoglobin detection in an aqueous solution and the limit of detection is 0.0803 mg/mL. The addition of H2O2 can intensify the quenching of the fluorescent probe. In addition, we analyzed and discussed the quenching mechanism of the probe. The bovine hemoglobin can quench the fluorescence of the probe with the inner filter effect. In the presence of both H2O2 and bovine hemoglobin, the structure of the probe is oxidized by the superoxide anion in the system and the fluorescence of the probe is quenched by the mechanism of static quenching.