Dendrimer-based preparation and luminescence studies of SiO2 fibers doping Eu3+ activator in interstitial sites

Abstract

Luminescent one-dimensional Eu³⁺ doped SiO₂ fibers have been readily prepared by electrospinning method combined with a sol–gel process. In this work, polyvinylpyrrolidone (PVP) as a simple commercial dendrimer not only increased the viscosity of solution but also provided weak hydrogen bonds with silica, which was significant in improving the electrospinability. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the as-obtained samples present fiber-like morphology with uniform size and the diameters of fibers became wider with the increase of Eu³⁺ concentration, from nanoscale to microscale. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) indicated that Eu³⁺ activator ions have been doped into the interstitial sites of SiO₂ fibers through the electrostatic interaction, which would reduce the symmetry of SiO₂ framework. The photoluminescence (PL) properties include the diffuse reflectance, excitation and emission spectra indicated that the obtained SiO₂:Eu³⁺ fibers exhibited typical Eu³⁺ (⁵D₀–⁷F_J) red emission under ultraviolet excitation and the band energy was changed due to the doping of stable Eu³⁺ activator ions. Meanwhile, the concentration quenching effects and decay kinetics behaviors of SiO₂:Eu³⁺ fibers were investigated and the optimal doping concentration and the longest lifetime were both in the composition of 16 mol% Eu³⁺. In addition, the energy-dispersive X-ray spectrum (EDS), thermogravimetry differential thermal analysis (TG-DTA) and the formation mechanism were also displayed in order to better understand the work.