Preparation, Characterization And Analytical Applications Of Rare Earth Fluorescent Probes

Because of the unique electronic shell structures of rare earth ions, the emission wavelengths of rare earth probes will not be influenced by outside environment. In addition, these probes possess excellent optical properties, such as a narrow emission spectrum, photo-chemical stability and long fluorescence lifetime. Therefore, more and more attention has been focused on them and they have exhibited great potentials in analytical fields.In this work, the binary chelate of terbium-phen (1,10-phenanthroline monohydrate) and ternary chelate terbium-KH-570 (γ-methacryloxypropyl trimethoxy silane)-phen (1, 10-phenanthroline monohydrate) were both synthesized in absolute ethanol. Their optical and structure properties were achieved by UV absorption and fluorescence spectra, as well as FIR spectra. Amino-groups were bond with the ternary chelate terbium-KH-570-phen via linking toγ-aminopropyl triethoxy silane.The prepared terbium ternary complex was used as a probe for the determination of herring sperm DNA by time-resolved fluorescence method. The fluorescent intensity of terbium complex increased with the increase of herring sperm DNA, and it expressed a good linear relationship in a region of concentration of herring sperm DNA, which made quantitative determination of herring sperm DNA become impossible.The linear range of herring sperm DNA was 0.300～4.70 mg/L and the detection limit was 0.08 mg/L (3a) with the RSD of 0.8%(3.00 mg/L, n=11).Rare earth ions can co-ordinate with water molecules, which lead to the decrease of fluorescent intensity in aqueous solution. This shortcoming limits their analytical applications. In contrast, rare earth nanoparticles might overcome above shortcoming and offer new thoughts and methods for the further research and application of rare earth probes.Subsequently, Eu3+-doped LaF3 nanoparticles (NPs) were prepared in aqueous solution and organic phase, respectively. The luminescent properties of prepared NPs were studied by fluorescence spectra, and the structures of them were characterized by X-ray diffraction and transmission electronic microscopy. Compared with Eu3+-doped LaF3 nanoparticles prepared in organic phase, the nanoparticles with hydrophilic group and high fluorescent intensity prepared in aqueous solution can be used directly in analytical fields. It is found that the fluorescent intensity of Eu3+-doped LaF3 nanoparticles decreased gradually with the addition of Fe3+. Based on the fluorescence qunching, a new method for the determination of Fe3+ was developed for the first time. The linear range of 5.00×10-6～5.00×10-4 mol/L and a detection limit of 1.25×106 mol/L were obtained with the RSD of 0.5%(5.00×10-5 mol/L, n=11). The method was applied to the determination of Fe3+ in beer sample, the result was agreed with that obtained via photo spectrometric method.