Nanocrystalline CaYAlO4:Tb3+/Eu3+ as promising phosphors for full-color field emission displays

Eu(3+) and/or Tb(3+)-doped CaYAlO(4) phosphor samples were synthesized by Pechini-type sol-gel method. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. For CaYAlO(4):Tb(3+), it is shown that the Tb(3+)-doping concentration has a significant effect on the (5)D(3)/(5)D(4) emission intensity of Tb(3+), which is attributed to the cross relaxation from (5)D(3) to (5)D(4). Under the 4f(8)→ 4f(7)5d excitation of Tb(3+) or low-voltage electron beams excitation, the CaYAlO(4):Tb(3+) phosphors show tunable luminescence from blue to cyan, and then to green with the change of Tb(3+)-doping concentration. The CaYAlO(4):Eu(3+) samples exhibit a reddish-orange emission of Eu(3+) corresponding to (5)D(0,1)→(7)F(0,1,2,3) transitions. Furthermore, a white emission can be realized in the single phase CaYAlO(4) host by reasonably adjusting the doping concentrations of Tb(3+) and Eu(3+) under low-voltage electron beams excitation. Compared with the commercial blue (Y(2)SiO(5):Ce(3+)) and green (ZnO:Zn) phosphors, CaYAlO(4):0.1%Tb(3+) and CaYAlO(4):5%Tb(3+) phosphors have higher CL intensity and stability under continuous electron bombardment. Due to the excellent CL properties and good CIE chromaticity coordinates, the as-prepared Tb(3+)/Eu(3+)-doped CaYAlO(4) nanocrystalline phosphors have potential application in FEDs devices.     

Electrospinning synthesis and luminescence properties of one-dimensional La(9.33)(SiO4)6O2: Ln3+ (Ln = Ce, Eu, Tb) microfibers

One-dimensional La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and low voltage cathodoluminescence (CL) as well as kinetic decay were used to characterize the resulting samples. SEM and TEM results indicated that the diameter of the microfibers annealed at 1000 °C for 3 h was 200-245 nm. The microfibers were further composed of fine and closely linked nanoparticles. La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors showed the characteristic emission of Ce(3+) (5d → 4f), Eu(3+) ((5)D(0)→(7)F(J)) and Tb(3+) ((5)D(3,4)→(7)F(J)) under ultraviolet excitation and low-voltage electron beams (3-5 kV) excitation. An energy transfer from Ce(3+) to Tb(3+) was observed in the La(9.33)(SiO(4))(6)O(2): Ce(3+), Tb(3+) phosphor under ultraviolet excitation and low-voltage electron beam excitation. Luminescence mechanisms were proposed to explain the observed phenomena. Blue, red and green emission can be realized in La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers by changing the doping ions. So the La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors have potential applications in full-color field emission displays.     

YF3:Ln3+ (Ln = Ce, Tb, Pr) submicrospindles: hydrothermal synthesis and luminescence properties

YF(3):Ln(3+) (Ln = Ce, Tb, Pr) microspindles were successfully fabricated by a facile hydrothermal method. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), lifetimes, photoluminescence (PL) and low-voltage cathodoluminescence (CL) were used to characterize the resulting samples. The lengths and diameters of YF(3):0.02Ce(3+) microspindles are around 760 nm and 230 nm, respectively. Adding dilute acid and trisodium citrate (Cit(3-)) are essential for obtaining YF(3) microspindles. A potential formation mechanism for YF(3) microspindles has been presented. PL spectroscopy investigations show that YF(3):Ce(3+) and YF(3):Tb(3+) microcrystals exhibit the characteristic emission of Ce(3+) 5d → 4f and Tb(3+ 5)D(4)→(7)F(J) (J = 6-3) transitions, respectively. In addition, the energy transfer from Ce(3+) to Tb(3+) was investigated in detail for YF(3):Ce(3+), Tb(3+) microspindles. Under the excitation of electron beams, YF(3):Pr(3+) show quantum cutting emission and YF(3):Ce(3+), Tb(3+) phosphors exhibit more intense green emission than the commercial phosphor ZnO:Zn.     

Patterning of Gd2(WO4)3:Ln3+ (Ln=Eu, Tb) luminescent films by microcontact printing route

Gd(2)(WO(4))(3) doped with Eu(3+) or Tb(3+) thin phosphor films with dot patterns have been prepared by a combinational method of sol-gel process and microcontact printing. This process utilizes a PDMS elastomeric mold as the stamp to create heterogeneous pattern on quartz substrates firstly and then combined with a Pechini-type sol-gel process to selectively deposit the luminescent phosphors on hydrophilic regions, in which a Gd(2)(WO(4))(3):Ln(3+) (Ln=Eu, Tb) precursor solutions were employed as ink. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, as well as low voltage cathodoluminescence (CL) spectra were carried out to characterize the obtained samples. Under ultraviolet excitation and low-voltage electron beams excitation, the Gd(2)(WO(4))(3):Eu(3+) samples exhibit a strong red emission arising from Eu(3+)(5)D(0,1,2)-(7)F(1,2) transitions, while the Gd(2)(WO(4))(3):Tb(3+) samples show the green emission coming from the characteristic emission of Tb(3+) corresponding to (5)D(4)-(7)F(6,5,4,3) transitions. The results show that the patterning of rare earth-doped phosphors through combining microcontact printing with a Pechini-type sol-gel route has potential for field emission displays (FEDs) applications.     

Solvothermal synthesis and characterization of Ln (Eu3+, Tb3+) doped hydroxyapatite

Luminescent Ln (Eu3+, Tb3+) doped hydroxyapatite (Eu:HAp, Tb:HAp) phosphors were successfully fabricated via the cetyltrimethylammonium bromide (CTAB)/n-octane/n-butanol/water microemulsion-mediated solvothermal process. The structure, morphology, and optical properties were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra as well as the kinetic decays, respectively. The XRD results reveal that the obtained Eu:HAp and Tb:HAp show the characteristic peaks of hydroxyapatite in a hexagonal lattice structure. It is observed that the as-prepared luminescent samples exhibit rod-like morphology with well dispersed and non-aggregated size distribution. Upon excitation by UV radiation, the phosphors demonstrate the characteristic 5D 0-7F 1-4 emission lines of Eu3+ and the characteristic 5D4-7F 3-6 emission lines of Tb3+. Moreover, the photoluminescence intensities (PL) of Eu3+ and Tb3+ can be tuned by altering the solvothermal temperature and the doping concentration of Eu3+ and Tb3+.     

Highly uniform and monodisperse beta-NaYF(4):Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu3+ (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to 5D0-3 --> 7FJ (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively. When doped with 5% Tb3+ ions, the strong DC fluorescence corresponding to 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions with 5D4 --> 7F5 (green emission at 544 nm) being the most prominent group that has been observed. In addition, under 980 nm laser excitation, the Yb3+/Er3+- and Yb3+/Tm3+-codoped beta-NaYF4 samples exhibit bright green and whitish blue up-conversion (UC) luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

Uniform hollow Lu2O3:Ln (Ln = Eu3+, Tb3+) spheres: facile synthesis and luminescent properties

Uniform hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) phosphors have been successfully prepared via a urea-assisted homogeneous precipitation method using carbon spheres as templates, followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, kinetic decays, quantum yields (QY), and UV-visible diffuse reflectance spectra were employed to characterize the samples. The results show that hollow Lu(2)O(3):Ln spheres can be indexed to cubic Gd(2)O(3) phase with high purity. The as-prepared hollow Lu(2)O(3):Ln phosphors are confirmed to be uniform in shape and size with diameter of about 300 nm and shell thickness of approximate 20 nm. The possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow Lu(2)O(3):Ln microspheres has been proposed. Upon ultraviolet (UV) and low-voltage electron beams excitation, the hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) spheres exhibit bright red (Eu(3+), (5)D(0)-(7)F(2)) and green (Tb(3+), (5)D(4)-(7)F(5)) luminescence, which may find potential applications in the fields of color display and biomedicine.     

A novel strategy for controllable emissions from Eu3+ or Sm3+ ions co-doped SrY2O4:Tb3+ phosphors

Trivalent rare-earth (RE) ions (Eu(3+), Tb(3+) and Sm(3+)) activated multicolor emitting SrY(2)O(4) phosphors were synthesized by a sol-gel process. The structural and morphological studies were performed by the measurements of X-ray diffraction profiles and scanning electron microscope (SEM) images. The pure phase of SrY(2)O(4) appeared after annealing at 1300 °C and the doping of RE ions did not show any effect on the structural properties. From the SEM images, the closely packed particles were observed due to the roughness of each particle tip. The photoluminescence (PL) analysis of individual RE ions activated SrY(2)O(4) phosphors exhibits excellent emission properties in their respective regions. The Eu(3+) co-activated SrY(2)O(4):Tb(3+) phosphor creates different emissions by controlling the energy transfer from Tb(3+) to Eu(3+) ions. Based on the excitation wavelengths, multiple (green, orange and white) emissions were obtained by Sm(3+) ions co-activated with SrY(2)O(4):Tb(3+) phosphors. The decay measurements were carried out for analyzing the energy transfer efficiency and the possible ways of energy transfer from donor to acceptor. The cathodoluminescence properties of these phosphors show similar behavior as PL properties except the energy transfer process. The obtained results indicated that the energy transfer process was quite opposite to the PL properties. The calculated CIE chromaticity coordinates of RE ions activated SrY(2)O(4) phosphors confirmed the red, green, orange and white emissions.     

The fabrication of one-dimensional Ca4Y6(SiO4)6O: Ln3+ (Ln=Eu, Tb) phosphors by electrospinning method and their luminescence properties

One-dimensional Ca(4)Y(6)(SiO(4))(6)O: Ln(3+) (Ln=Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD) pattern and high-resolution transmission electron microscopy (HRTEM) confirmed that the fibers were composed of hexagonal Ca(4)Y(6)(SiO4)(6)O phase. Thermogravimetric and differential scanning calorimetry (TG-DSC) results showed that the Ca(4)Y(6)(SiO4)(6)O phase began to crystallize at 740°C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated that the diameter of as-prepared microfibers ranged from 390 to 900 nm and the diameter of the microfibers annealed at 1000°C ranged from to 120 to 260 nm. Under ultraviolet and low-voltage electron beams (3-5 kV) excitation, the Ca(4)Y(6)(SiO(4))(6)O: Ln(3+) (Ln=Eu, Tb) samples showed the red and green emission, corresponding to (5)D(0)→(7)F(2) transition of Eu(3+) and (5)D(4)→(7)F(5) transition of Tb(3+), respectively.     

Luminescence of Tb3+ and Eu3+ doped amorphous zinc benzoates

The Tb(3+) and Eu(3+) doped amorphous zinc benzoate were prepared. Their infrared absorption, emission and excitation spectra were measured. The luminescence mechanisms of Tb(3+) and Eu(3+) in the amorphous substrate were discussed. The bonding modes of OCO group to Zn(2+) ion have two of symmetric and asymmetric bridging bidentate. The energy of the S(1) pi,pi* excited state of benzene ring can be transferred to Tb(3+) and Eu(3+) ion, and results in characteristic emission from the 5D(4)-->(7)F(j) of Tb(3+) and 5D(0)-->(7)F(j) of Eu(3+), respectively.     

Facile synthesis and multicolor luminescent properties of uniform Lu2O3:Ln (Ln=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanospheres

Multicolor Lu(2)O(3):Ln (Ln=Eu(3+), Tb(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu(2)O(3) phase with high purity. The SEM images show the obtained Lu(2)O(3):Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu(2)O(3):Ln (Ln=Eu(3+) and Tb(3+)) NCs exhibit bright red (Eu(3+), (5)D(0)→(7)F(2)), and green (Tb(3+), (5)D(4)→(7)F(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu(2)O(3):Ln (Ln=Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) NCs display the typical up-conversion (UC) emissions of green (Er(3+), (4)S(3/2),(2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow-green (Ho(3+), (5)F(4), (5)S(2)→(5)I(8)), respectively.     

Preparation of luminescent and mesoporous Eu3+/Tb3+ doped calcium silicate microspheres as drug carriers via a template route

Luminescent and mesoporous Eu(3+)/Tb(3+) doped calcium silicate microspheres (LMCS) were synthesized by using mesoporous silica spheres as the templates. The LMCS and drug-loaded samples were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N(2) adsorption/desorption, and photoluminescence (PL) spectra. The results reveal that the LMCS have uniform spherical morphology with a diameter around 400 nm and the mesopore size of 6 nm. The prepared samples exhibit little cytotoxicity at concentrations below 5 mg mL(-1) via MTT assay. In addition, drug storage/release properties of the LMCS were demonstrated for ibuprofen (IBU). The obtained LMCS can be used to encapsulate drugs and release them. Under excitation by UV light, the IBU-loaded samples still show the characteristic (5)D(0)-(7)F(1-3) emission lines of Eu(3+) and the characteristic (5)D(4)-(7)F(3-6) emission lines of Tb(3+). The PL intensity of Eu(3+) in the drug carrier system increases with the cumulative released amount of IBU, making the drug release able to be tracked or monitored by the change of luminescence of Eu(3+). The LMCS reported here with mesoporous structure, good biocompatibility and luminescent property can be a promising drug delivery carrier.     

LaOF:Eu3+ nanocrystals: hydrothermal synthesis, white and color-tuning emission properties

Uniform LaOF and LaOF : Eu(3+) nanocrystals of the γ-form have been successfully synthesized under mild conditions via a facile hydrothermal method followed a heat treatment of their bastnaesite-type precursor (LaCO(3)F). The synthetic details, investigations into the phase purity and the presence of the oxocarbonate anion CO(3)(2-) proven by IR measurements and EDX, as well as X-ray powder diffraction data, are given. Photoluminescence (PL) and cathodoluminescence (CL) spectra were utilized to characterize the luminescence properties of the LaCO(3)F : Eu(3+) and LaOF : Eu(3+) samples. Under ultraviolet light excitation, the LaCO(3)F : Eu(3+) precursor shows an orange emission of Eu(3+) (dominated by (5)D(0)→(7)F(1)), while the product of heat treatment, LaOF : Eu(3+), shows the characteristic emissions of Eu(3+) ((5)D(J)→(7)F(J')J, J' = 0, 1, 2, 3 transitions). Under the excitation of UV and low-voltage electron beams, the emission color (including white) of LaOF : Eu(3+) can be tuned by adjusting the doping concentration of Eu(3+). The corresponding luminescence mechanisms have been discussed in detail.     

(Ca1-x-yLuy)MoO4∶xEu3+红色荧光粉的化学共沉淀合成与光致发光

使用NH4HCO3-NH3.H2O混合沉淀剂,采用化学共沉淀法合成(Ca1-x-yLuy)MoO4:xEu3+红色荧光粉,通过XRD、EDS、荧光光谱和CIE色度图研究该荧光粉的晶体结构、成分组成及发光性能。结果表明,实验按照理论化学计量比成功合成了(Ca1-x-yLuy)MoO4:xEu3+红色荧光粉,该荧光粉为CaMoO4白钨矿结构;(Ca1-x-yLuy)MoO4:xEu3+具有7F0→5L6(394 nm)和7F0→5D2(465 nm)的强电子吸收,且在613 nm处可发射高强度红光,其色坐标为(0.666 5,0.332 9),明显优于传统的Y2O2S:Eu3+红色荧光粉;此外,当Lu含量为30mol%时,荧光粉发光强度最佳。     

Evolution of photoluminescence across dimensionality in lanthanide silicates

The dehydratation process of layered lanthanide silicates K3[LnSi3O8(OH)2], Ln = Y, Eu, Tb, and Er, and the structural characterization of the obtained small-pore framework K3LnSi3O9, Ln = Y, Eu, Tb, and Er solids, named AV-23, have been reported. The structure of AV-23 has been solved by single-crystal X-ray diffraction (XRD) methods and further characterized by chemical analysis, thermogravimetry, scanning electron microscopy, and 29Si MAS NMR. The photoluminescence (PL), radiance, and lifetime values of AV-23 have been studied and compared with those of AV-22. Both materials have a similar chemical makeup and structures sharing analogous building blocks, hence providing a unique opportunity for rationalizing the evolution of the PL properties of lanthanide silicates across dimensionality. Although Tb-AV-23 contains a single crystallographic Tb(3+) site, PL spectroscopy indicates the presence of Ln(3+) centers in regular framework positions and in defect regions. PL evidence suggests that Eu-AV-23 contains a third type of Ln(3+) environment, namely, Eu(3+) ions replacing K(+) ions in the micropores. The radiance values of the Tb-AV-22 and Tb-AV-23 samples are of the same order of magnitude as those of standard Tb(3+) green phosphors. For the samples K3(Y1-aEraSi3O9), a = 0.005-1, efficient emission and larger 4I13/2 lifetimes (ca. 7 ms) are detected for low Er(3+) content, indicating that the Er(3+)-Er(3+) interactions become significant as the Er(3)+ content increases.     

(Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties

(Zn(1-x-y)Mg(y))(2)GeO(4): xMn(2+) (y = 0-0.30; x = 0-0.035) phosphors with uniform submicrorod morphology were synthesized through a facile hydrothermal process. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the samples. SEM and TEM images indicate that Zn(2)GeO(4):Mn(2+) samples consist of submicrorods with lengths around 1-2 μm and diameters around 200-250 nm, respectively. The possible formation mechanism for Zn(2)GeO(4) submicrorods has been presented. PL and CL spectroscopic characterizations show that pure Zn(2)GeO(4) sample shows a blue emission due to defects, while Zn(2)GeO(4):Mn(2+) phosphors exhibit a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)) under the excitation of UV and low-voltage electron beam. Compared with Zn(2)GeO(4):Mn(2+) sample prepared by solid-state reaction, Zn(2)GeO(4):Mn(2+) phosphors obtained by hydrothermal process followed by high temperature annealing show better luminescence properties. In addition, codoping Mg(2+) ions into the lattice to substitute for Zn(2+) ions can enhance both the PL and CL intensity of Zn(2)GeO(4):Mn(2+) phosphors. Furthermore, Zn(2)GeO(4):Mn(2+) phosphors exhibit more saturated green emission than the commercial FEDs phosphor ZnO:Zn, and it is expected that these phosphors are promising for application in field-emission displays.     

Controllable synthesis and tunable luminescence properties of Y2(WO4)3:Ln3+ (Ln = Eu, Yb/Er, Yb/Tm and Yb/Ho) 3D hierarchical architectures

Yttrium tungstate precursors with novel 3D hierarchical architectures assembled from nanosheet building blocks were successfully synthesized by a hydrothermal method with the assistance of sodium dodecyl benzenesulfonate (SDBS). After calcination, the precursors were easily converted to Y(2)(WO(4))(3) without an obvious change in morphology. The as-prepared precursors and Y(2)(WO(4))(3) were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra, respectively. The results reveal that the morphology and dimensions of the as-prepared precursors can be effectively tuned by altering the amounts of organic SDBS and the reaction time, and the possible formation mechanism was also proposed. Upon ultraviolet (UV) excitation, the emission of Y(2)(WO(4))(3):x mol% Eu(3+) microcrystals can be tuned from white to red, and the doping concentration of Eu(3+) has been optimized. Furthermore, the up-conversion (UC) luminescence properties as well as the emission mechanisms of Y(2)(WO(4))(3):Yb(3+)/Ln(3+) (Ln = Er, Tm, Ho) microcrystals were systematically investigated, which show green (Er(3+), (4)S(3/2), (2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow (Ho(3+), (5)S(2)→(5)I(8)) luminescence under 980 nm NIR excitation. Moreover, the doping concentration of the Yb(3+) has been optimized under a fixed concentration of Er(3+) for the UC emission of Y(2)(WO(4))(3):Yb(3+)/Er(3+).     

Remarkable changes in the optical properties of CeO(2) nanocrystals induced by lanthanide ions doping

Highly uniform and well-dispersed CeO(2) and CeO(2):Eu(3+) (Sm(3+), Tb(3+)) nanocrystals were prepared by a nonhydrolytic solution route and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), UV/vis absorption, and photoluminescence (PL) spectra, respectively. The result of XRD indicates that the CeO(2) nanocrystals are well crystallized with a cubic structure. The TEM images illustrate that the average size of CeO(2) nanocrystals is about 3.5 nm in diameter. The absorption spectrum of CeO(2):Eu(3+) nanocrystals exhibits red-shifting with respect to that of the undoped CeO(2) nanocrystals. Under the excitation of 440 nm (or 426 nm) light, the colloidal solution of the undoped CeO(2) nanocrystals shows a very weak emission band with a maximum at 501 nm, which is remarkably enhanced by doping additional lanthanide ions (Eu(3+), Tb(3+), Sm(3+)) in the CeO(2) nanocrystals. The emission band is not due to the characteristic emission of the lanthanide ions but might arise from the oxygen vacancy which is introduced in the fluorite lattice of the CeO(2)nanocrystals to compensate the effective negative charge associated with the trivalent ions.     

Self-assembled 3D architectures of LuBO3:Eu(3+): phase-selective synthesis, growth mechanism, and tunable luminescent properties

Rhombohedral-calcite and hexagonal-vaterite types of LuBO(3):Eu(3+) microparticles with various complex self-assembled 3D architectures have been prepared selectively by an efficient surfactant- and template-free hydrothermal process for the first time. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, photoluminescence, and cathodoluminescence spectra as well as kinetic decays were used to characterize the samples. The pH, temperature, concentration, solvent, and reaction time have a crucial influence on the phase formation, shape evolution, and microstructure. The reaction mechanism is considered as a dissolution/precipitation process; it is proposed that the self-assembly evolution occurs by homocentric layer-by-layer growth. Under UV excitation and low-voltage electron beam excitation, calcite-type LuBO(3):Eu(3+) particles show a strong orange emission corresponding to the (5)D(0)-->(7)F(1) transition of Eu(3+) whereas vaterite-type LuBO(3):Eu(3+) particles exhibit a strong red emission with much higher R/O values (that is, chromatically redder fluorescence than that of crystals grown from a direct solid-state reaction). The tunable luminescent properties have potential applications in fluorescent lamps and field emission displays.     

磷灰石结构荧光粉Ba10(PO4)6F2:Ce3+,Tb3+的合成、发光和能量传递

采用高温固相法合成了系列Ce~(3+)和Ce~(3+)/Tb~(3+)激活的具有磷灰石结构荧光粉Ba_(10)(PO_4)_6F_2。用X射线衍射(XRD)、扫描电镜(SEM)、激发和发射(PLE和PL)光谱对样品进行了表征分析。研究结果表明:所合成的荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)具有氟磷灰石结构,样品微观呈现不规则形貌。荧光粉Ba10-x(PO4)6F2∶x Ce~(3+)的相对发射强度随着x增加而增强,当x=0.09时,荧光强度达到最大。荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的激发光谱为240～330 nm的宽带,发射光谱呈现出Ce~(3+)的5d→4f跃迁紫外光(335和358 nm)发射和Tb~(3+)的4f→4f跃迁绿光(542 nm)发射。光谱特性表明,发光过程中存在Ce~(3+)→Tb~(3+)能量传递,能量传递效率可以达到60%。计算Ce~(3+)和Tb~(3+)的临界距离为0.79 nm,能量传递机理是偶极-偶极交互作用。此外,详细论述了Ce~(3+)和Tb~(3+)之间的能量传递和发光的过程。通过调节Tb~(3+)的掺杂浓度,对荧光粉发光色坐标与Tb~(3+)的掺杂浓度之间的关系也进行了研究,随着Tb~(3+)的掺杂量从0增加0.52,荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的发射光谱色坐标可以从(0.149 4,0.045 1)蓝色区变化到(0.280 1,0.585 3)绿色区。