Large-scale good-quality submicrometer-sized YPO4:Eu3+ hollow spheres were synthesized by utilizing the colloidal spheres of Y(OH)CO3:Eu3+ as a sacrificial template and NH4H2PO4 as a phosphorus ...source, for the first time. The whole process mainly consists of the hydrothermal reaction and acid erosion. The YPO4:Eu3+@Y(OH)CO3:Eu3+ core−shell structures were first obtained after the hydrothermal process. Then, the remaining Y(OH)CO3:Eu3+ was removed by selective dissolution in a dilute nitric acid solution. The YPO4:Eu3+ hollow spheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL). The formation mechanism was also investigated. The obtained YPO4:Eu3+ hollow spheres may have potential applications in cell biology, drug release, and diagnosis, due to high chemical stability and luminescence functionality.
The multi-morphological coordination polymer La(1,3,5-BTC)(H2O)6 has been prepared through simple and mild one-step approaches at room temperature on a large scale (1,3,5-BTC = ...1,3,5-benzenetricarboxylate). The delicate sheaflike, broccolilike, urchinlike, and fanlike hierarchical architectures made of uniform nanorods were obtained through splitting crystal growth. More interestingly, these three dimensional architectures can exhibit tunable white-light emission by codoping Tb3+ and Eu3+.
Uniform Lu2O3:Eu3+ nanorods and nanowires have been successfully prepared through a simple solution-based hydrothermal process followed by a subsequent calcination process without using any ...surfactant, catalyst, or template. On the basis of X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, and Fourier transform infrared spectroscopy results, it can be assumed that the as-obtained precursors have the structure formula of Lu4O(OH)9(NO3), which is a new phase and has not been reported. The morphology of the precursors could be modulated from nanorods to nanowires with the increase of pH value using ammonia solution. The as-formed precursors could transform to cubic Lu2O3:Eu3+ with the same morphology and a slight shrinkage in size after an annealing process. Both the Lu2O3:Eu3+ nanorods and nanowires exhibit the strong red emission corresponding to the 5D0 −7F2 transition of the Eu3+ ions under UV light excitation or low-voltage electron beam excitation.
Highly uniform pancake‐like YBO3 hierarchical architectures have been successfully prepared by a designed two‐step hydrothermal method. Yttrium precursor microprisms were first synthesized according ...to a simple hydrothermal route. Subsequently, nearly monodisperse multilayered YBO3 products with a pancake‐like shape were synthesized at the expense of the precursor during the hydrothermal process. The whole process was carried out under aqueous conditions without the use of any organic solvent, surfactant, or catalyst. The conversion process from the precursor to YBO3 products has been investigated by time‐dependent XRD experiments. Extending this method, other LnBO3 (Ln=Ho, Er, Tm, Yb) samples with well‐defined shape and dimensionality have also been obtained by a similar synthetic process. The luminescence colors of YBO3 samples co‐doped with Eu3+ and Tb3+ under ultraviolet or low‐voltage electron beam excitation can be tuned from red, through yellow and green‐yellow, to green by simply adjusting the relative doping concentrations of the activator ions. This merit of multicolor emissions in the visible region endows materials of this kind with potential application in the fields of light‐display systems and optoelectronic devices.
Micropancakes: Highly uniform and well‐dispersed YBO3 hierarchical architectures with a pancake‐like shape have been successfully prepared by a hydrothermal conversion method (left image). The luminescence colors of the YBO3 samples co‐doped with Eu3+ and Tb3+ can be tuned from red, through yellow and green‐yellow, to green by simply adjusting the relative doping concentrations of the activator ions (right image).
Novel one-dimensional europium benzene-1,3,5-tricarboxylate compressed nanorods have been synthesized on a large scale through direct precipitation in solution phase under moderate conditions without ...the assistance of any surfactant, catalyst, or template. The obtained nanorods have widths of about 50−100 nm, thicknesses of 10−20 nm, and lengths ranging from a few hundred nanometers to several micrometers. X-ray powder diffraction, elemental analysis, Fourier transform infrared studies, and thermogravimetric and differential thermal analysis show that the nanorods have the structural formula of Eu(1,3,5-BTC)·6H2O. Upon UV excitation, these nanorods exhibit a highly efficient luminescence, which comes from the Eu3+ ions. Moreover, Eu2O3 nanorods could also be obtained via a thermal decomposition method using the corresponding complex as a precursor. This synthetic route is promising for the preparation of other one-dimensional crystalline nanomaterials because of its simplicity and the low cost of the starting reagents.
Near-UV convertible Eu(3+)-activated orange oxynitride phosphors have been obtained via a Ce(3+)→ Tb(3+)→ Eu(3+) energy transfer mechanism. The Tb(3+) ions play the role of an energy transfer bridge ...to connect the Ce(3+) and Eu(3+) ion pairs, and an optimal concentration of the Tb(3+) ion is necessary for maximum intensity of the Eu(3+) ion emission.
Uniform YF3:Eu3+ micro-single crystals with diamond-like, truncated octahedral, and octahedral morphologies have been synthesized by adjusting the molar ratio of KF/Y(NO3)3 and the amount of dilute ...HNO3 through a facile hydrothermal route without using any morphology controlling agent. It has been found that the excess K+ ions favor for the formation of {111} facets. The morphological evolution has been presented on the basis of a series of time-dependent experiments, from which a truncating growth mechanism has been proposed. Besides, the investigation on morphology-dependent luminescence properties reveals that the as-obtained truncated octahedral samples exhibit the strongest orange–red emission, while the intensity of diamond-like ones is the lowest.
In this study, CaCl2, NH4Cl, and CaF2 were selected as the flux respectively to assist the preparation of the yellow emitting phosphor of CaSi2O2N2:Eu2+ by the solid-state reaction method. The ...influence of flux nature on the crystalline structure, morphology and photoluminescent behavior of the CaSi2O2N2:Eu2+ was extensively investigated. Results proved that adding flux can significantly enhance the crystallinity and the emission intensity of the resultant powders. Pure and well crystallized CaSi2O2N2:Eu2+ was formed by using CaCl2 flux at a relatively low temperature (1250°C) and gave much enhanced yellow emission intensity than that in other samples (around 1400°C). Further increase of the emission intensity was achieved by the Gd3+ doping. The experimental results showed that the doping of a certain amount of Gd3+ can expand the lattice and improve the absorption and emission intensity of CaSi2O2N2:Eu2+. When the Gd3+ content (x) increases up to 0.04 the luminescence intensity reaches maximum which is about 2 times as that of the phosphor without Gd3+ doping. A white light LED lamp using the optimal phosphor (Ca0.89Eu0.05Gd0.04Si2O2N2) had the color temperature of 5100K with luminous efficiency of 41 lm W-1 and color rendering index of Ra=76, indicating that Ca0.89Gd0.04Si2O2N2:0.05Eu2+ is a good candidate yellow emitting down-conversion phosphor for white LEDs application.
Pseudo-octahedrons of Ba2GdF7 were successfully synthesized through a solution-based method in a hydrothermal environment for the first time. The preferential adsorption of ethylene glycol (EG) ...molecules on the {111} planes contributed to the formation of the octahedral shape. Hydrazine was employed as the alkaline source to adjust the adsorption affinity of EG and the hydrolysis rate of NaBF4 (fluorine supply), thereby controlling the morphology and phase structure. A series of contrast experiments were conducted to investigate the growth mechanism of the Ba2GdF7 nanocrystals. As a proof-of-concept experiment, Eu3+, Tb3+, Dy3+, and Yb3+/Er3+ ions were doped to demonstrate the potential of the Ba2GdF7 crystals as host material for phosphors.
