Controlled synthesis of functional photoluminescent materials are of particular interest due to their fascinating optical properties. Herein, highly uniform SiO 2:xTb 3+spherical nanoparticles are fabricated by a facile sol-gel method. The structure, morphology, compositions, and luminescence properties of As-prepared samples were well investigated using TEM, SEM, EDX, XRD, XPS and luminescence spectroscopy. The PL intensity of SiO 2:xTb 3+spherical nanoparticles is Tb3+ ions concentration dependent achieved a maximum at 3 mol % of Tb3+. Particularly, SiO2:xTb3+spherical nanoparticles exhibit a green emission corresponding to 5D4 → 7 Fj transition (541 nm) of Tb3+. These results show that As-prepared phosphors may find potential application in solid-state lighting fields.
Lanthanides have unique photoluminescence properties, which enables their utilization in diverse applications, such as optical devices [
Cetyltrimethylammonium bromide (CTAB), Ammonia, ethanol, were purchased from Beijing Chemical. Tetraethyl orthosilicate (TEOS) was bought from Aladdin Reagent Database Inc. All chemicals were of analytical grade and were used directly without further purification. Ln(NO3)3 was prepared by dissolving the corresponding Sm2O3 (99.99%) and Tb4O7 (99.99%) powder in dilute HNO3 solution at elevated temperature with ceaseless agitation.
A series of rare earth-doped SiO2 spherical nanoparticles were prepared via a simple CTAB-based sol-gel process. In a typical process, 0.35 g CTAB was dissolved in 5 mL ethanol and 20 ml deionized water. After stirring several minutes, 0.3 ml Ammonia, 2.2 ml TEOS and different amount of Ln(NO3)3 were added into the above solution, respectively. After additional agitation for overnight, the resulting precipitates were collected by centrifugation, washed three times with ethanol, deionized water, and then dried at 60˚C in air for 12 h. The final product was obtained through a heat treatment of the precursor at 600˚C in air for 2 h.
X-ray powder diffraction (XRD) was measured by a Rigaku D/max-B II X-ray diffractometer with Cu Ka radiation. Transmission electron microscopy (TEM) images were obtained with a JEM-2000EX TEM (acceleration voltage of 200 kV). The scanning electron microscope (SEM) images were observed by S-4800, Hitachi. Energy-dispersive spectroscopy (EDS) analysis was performed with an H JEOL JXA 840 EDX system attached to the SEM microscope. The X-ray photoelectron spectra (XPS) were taken using a VG ESCALAB 250 electron energy spectrometer with Mg Ka (1253.6 eV) as the X-ray excitation source. The PL measurements were determined using Jobin Yvon FluoroMax-4 luminescence spectrophotometer (PL) equipped with a 150 W xenon lamp as the excitation source. All the measurements were performed at room temperature.
The morphologies and structures of samples were investigated by the SEM and TEM observations. (
The structure and composition of the as-prepared SiO2:Tb3+ spherical nanoparticles were examined by XRD. As shown in
broad peaks could be observed at 2θ = 24˚ - 25˚ in all samples, which corresponding to the characteristic diffraction peak of pure amorphous SiO2 [
The EDX spectra for SiO2:Tb3+ precursor spherical nanoparticles and SiO2:Tb3+ spherical nanoparticles were demonstrated to
XPS analysis is conducted to get more insight into the chemical composition and electronic structure of the as-prepared SiO2:Tb3+ spheres.
In
of the Tb3+ concentration from 1 mol% to 5 mol%, the PL intensity of the 5D4 " 7FJ (J = 6, 5, 4, 3) transition increased at first, reaching a maximum value at the concentration of 3 mol%, and then decreased with the increasing of Tb3+ content due to the concentration quenching effect [
The decay kinetics behaviors of Tb3+ in SiO2:xTb3+ sphere were investigated. The lifetime decay curves for the 5D4-7F5 transition of Tb3+ (541 nm) at different concentration were measured at room temperature under excitation of 377 nm. As illustrated in
where I and
All the curves can be fitted by a double-exponential procedure, and the lifetime values of Tb3+ in SiO2:Tb3+ can be determined to be 0.37, 0.74, 1.12, 0.69 and 0.32 ms corresponding to the Tb3+ concentration of 1%, 2%, 3%, 4% and 5% respectively. As seen in
In summary, a series of SiO2:xTb3+ spherical nanoparticles with various Tb3+ concentrations were successfully prepared via a simple CTAB-based sol-gel process. The as-synthesized samples present a well-defined spherical morphology. Under ultraviolet excitation, the Tb3+ singly doped SiO2 samples show strong green emission. Furthermore, the luminescence intensity of the As-prepared Tb3+ doped SiO2 spherical nanoparticles exhibited a high PL intensity determined by concentration of Tb3+ and achieved a maximum PL intensity (6.03027 × 106) at 3 mol% Tb3+. These results indicate that the As-prepared Tb3+ doped SiO2 spherical nanoparticles with variable concentration could be a potential phosphor to be used in the display and solid state lighting fields.
This present work was financially supported by the National Natural Science Foundation of China (Grant Nos. 51272085 and 21671078), the Opening Research Funds Projects of the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry and College of Chemistry, Jilin University (2016-06), and Project Supported by Graduate Innovation Fund of Jilin University (2016145). Murad M.A. Abualrejal greatly appreciates Chinese government scholarship 2013.
Abualrejal, M.M. A., Zou, H.F., Chen, J., Song, Y.H. and Sheng, Y. (2017) A Facile Synthesis and Photoluminescence Properties of SiO2:Tb3+ Spherical Nanoparticles. Advances in Nanoparticles, 6, 11-21. https://doi.org/10.4236/anp.2017.62002