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

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+ (D-5(0)-F-7(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.