Preparation, characterization and photoluminescence properties of SiO2 and SiO2:Eu3+ submicron rods

SiO2 and Eu3+-doped SiO2 submicron rods were conveniently fabricated via a sol-gel process at room temperature. In this process, citric acid served as a unique structural modifier through hydrolysis of TEOS at alkaline condition to obtain the silica submicron rods. The morphology of the products was sensitive to the conditions, such as stirring, gelation time and the dropping speed of NH4OH. By sampling the products at different reaction times, we discussed the formation and growing mechanism of SiO2:Eu3+ submicron rods in detail. The weak interactions between ammonium citrate crystals and silica species may be the reasons of the rods formation. The obtained silica submicron rods were 5-6 μm in length and 650-750 nm in width and there was no obvious change after doping. Under UV light excitation, the undoped silica submicron rods exhibited blue emission, which may be associated with defect centers in the structures of the products. The Eu3+-doped silica submicron rods exhibited red emission, which was due to the 4f→4f transition of Eu3+. The effect of different doping concentrations of Eu3+ ions on the luminescence was investigated. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), Thermo-gravimetry Analysis (TGA), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Energy-dispersive spectroscopy (EDS) and Photoluminescence spectrum.