壳聚糖/LaF3 ∶ Eu3+纳米复合粒子的简易合成及发光特性

在水溶液中采用化学共沉淀法制备了壳聚糖/LaF₃ ∶ Eu³⁺纳米复合粒子。通过透射电子显微镜(TEM),X射线衍射(XRD),傅立叶变换近红外(FT-IR)光谱对样品进行了表征。结果表明:所得纳米复合粒子大小在 20 nm左右,粒径均匀,表面包覆的壳聚糖使其易溶于水,并具备了与生物蛋白偶联的多个基团。测量了该纳米复合粒子的激发光谱与发射光谱,详细说明了各发光峰对应能级的跃迁及其发光机理,分析了不同掺杂浓度对其相对发光强度的影响。结果表明:当 Eu³⁺离子掺杂摩尔分数为 10%时,样品的相对发光强度达到最大值。最后介绍了壳聚糖/LaF₃ ∶ Eu³⁺纳米复合粒子与荧光蛋白 FITC偶联的方法,以表明其在生物学中潜在的应用价值。

Facile Synthesis and Spectroscopic Properties of Chitosan/LaF_3:Eu~(3+) Nanocomposite Particles

Lanthanide-based nanocrystals have shown great potential to be used as luminescent materials but their biological applications have been limited because most of the nanocrystals synthesized so far do not be water soluble or biocompatible. When synthesizing lanthanide (Ⅲ)-doped nanocrystals, organic surfactants are often used as ligands to control the particle growth and to stabilize the particles against aggregation, and therefore the nanocrystals are not water soluble. In this paper, we developed a very straightforward method to prepare water soluble chitosan/LaF₃∶Eu³⁺ nanocomposite particles with functional chemical groups on their surfaces. Chitosan is found to cap the nanocrystals during the synthesis process, which renders them water soluble and biocompatible, and provides functional groups such as hydroxyl and amino groups for further attachment of biomolecules. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) absorption spectra. The results shown that the nanocomposite particles have average size of about 20 nm, the sizes of the nanocrystals were calculated from the XRD pattern based on the Debye-Scherrer formula, assuming that the particles are spherical in shape. Further, we exhibited the excitation and emission spectra of these nanocomposite particles and described the luminescent mechanism corresponding to the transition levels. The chitosan/LaF₃∶Eu³⁺ nanocrystals were well dispersed in water and their fluorescent properties were studied. The results showed that the luminescent intensity corresponding to ⁵D₀→⁷F₁ transition of Eu³⁺ ions in the Eu³⁺-doped LaF₃ nanoparticles increased remar-kably with increasing the doping concentration of Eu³⁺ ions and reached a maximum at approximately 10%. Finally, we introduced the coupled way between the chitosan/LaF₃∶Eu³⁺ nanocomposite particles and the fluorescent protein(FITC). The nanocomposite particles are very suitable for use in biological applications, for example, intracellular labelling or measurements, because they are very small in size. The use of this method can be extended to the synthesis of other water soluble and biocompatible lanthanide(Ⅲ)-doped luminescent nanocrystals.