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1.
Silica nanoparticles, prepared by the Stober method, have been doped with Eu 3+, Dy 3+, or processed to result in Au nanoparticles on the silica surface. The luminescence of the rare earth (RE)-doped SiO 2 particles has been studied as a function of the nature of the RE, their concentration and also of the presence of Au nanoparticles at the surface of the SiO 2 nanoparticles. We have shown that the Eu 3+ emission is observable over the experimental conditions examined, whereas it was not possible to observe any emission for Dy 3+ doped materials. No enhancement of the Eu 3+ emission was observed following the adsorption of gold nanoparticles at the surface of the SiO 2 nanoparticle, however an excitation at 250 nm leads to both the emission of the matrix and Eu 3+ showing an energy transfer from the SiO 2 matrix to Eu 3+ ions. 相似文献
2.
Divalent europium activated alkaline earth orthosilicate M 2SiO 4 (M = Ba, Sr, Ca) phosphors were synthesized through solid-state reaction technique and their luminescent properties were
investigated. Photoluminescence emission spectra of Sr 2SiO 4:Eu 2+ phosphor was tuned by substitution of Sr 2+ with 10 mol% Ca 2+ or Mg 2+. Two emission bands originated from the 4f–5d transition of Eu 2+ ion doped into different cation sites in the M 2SiO 4 host lattice were observed under ultraviolet excitation. The Sr 2SiO 4:Eu 2+ phosphor showed a blue and a green broad emission bands peaked around 475 and 555 nm with some variation for different Eu 2+ doping concentration. When 10 mol% of Sr 2+ was substituted by Ca 2+ or Mg 2+, the blue emission band blue-shifted to 460 nm and the green emission band shifted to even longer wavelength. An energy loss
due to energy transfer from one Eu 2+ to another Eu 2+ ion, changing of the crystal field strength and covalence in the host lattice together were assigned for the tuning effect.
With an overview of the excitation spectra and the emission spectra in blue and green-yellow color, these co-doped phosphors
can become a promising phosphor candidate for white light-emitting-diodes (LEDs) pumped by ultraviolet chip. 相似文献
3.
The Ca 2BO 3Cl:Eu 2+ phosphor was synthesized by the general high temperature solid-state reaction and an efficient yellow emission under near-ultraviolet and blue excitation was observed. The emission spectrum shows a single intense broad emission band centered at 573 nm, which corresponds to the allowed f-d transition of Eu 2+. The excitation spectrum is very broad extending from 350 to 500 nm, which is coupled well with the emission of UV LED (350-410 nm) and blue LED (450-470 nm). The measured emission of In-GaN-based Ca 2BO 3Cl:Eu 2+ LED shows white light to the naked eye with a chromatic coordinate of (0.33, 0.36). The Ca 2BO 3Cl:Eu 2+ is a very appropriate yellow-emitting phosphor for white LEDs. 相似文献
4.
Y 2O 3:Eu 3+ nanocrystals were prepared via co-precipitation–solvothermal refluxing–calcination method using three kinds of organic solvents, propylene glycol, 1,3-butanediol and polyethylene glycol and yttrium chloride hexahydrate and europium chloride as starting materials. The Y 2O 3:Eu 3+ nanocrystals with diameter of 20–50 nm prepared by refluxing in polyethylene glycol followed by calcinations at 800–1000 °C exhibited the strongest luminescence at 611 nm under the excitation wavelength of 254 nm than the reference sample prepared via conventional co-precipitation method. The photoluminescence spectra of the samples were recorded at room temperature. The effect of concentration of Eu 3+ (Eu 3+/Y 3+ atomic ratio: 0.01–0.1) on the photoluminescence intensity was also investigated. The samples with the Eu 3+/Y 3+ atomic ratio of 0.07 exhibited the strongest emission at 611 nm and quenching effect was observed above 0.10. 相似文献
5.
The present investigation aims at the luminescence properties of Ca 9Y(VO 4) 7:Eu 3+, Bi 3+ red phosphor materials. The red emission at 613 nm originating from 5D 0– 7F 2 transition of Eu 3+ in Ca 9Y(VO 4) 7 is enhanced strongly with Bi 3+–V 5+ couple as the sensitizer, under excitation either into the 5L 6 state or the 5D 2 state. The energy transfer from Bi 3+–V 5+ to Eu 3+ is discussed. For a fixed Eu 3+ concentration, there is an optimal Bi 3+ concentration with 15 mol%, at which the maximum luminescence intensity of Eu 3+ is achieved. The red emission of Ca 9Y(VO 4) 7:0.8Eu 3+, 0.15Bi 3+ (under 395 nm and 465 nm excitations) is stronger than that of commercial Y 2O 3:Eu 3+ phosphor (under 395 nm and 467 nm excitations). Based on the ratios of the red emission at 613 nm to orange one at 592 nm, it is considered that the symmetry of Eu 3+ site decreases with doping of Bi 3+, leading to more opposite parity components. Lifetime and diffuse reflection spectra measurements indicate that the red emission enhancement is due to the enhanced transition probabilities from the ground state to 5L 6 and 5D 2 states of Eu 3+ in the distorted crystal field. Therefore the present material is a promising red-emitting phosphor for white-light diodes with near-ultraviolet/blue GaN-based chips. 相似文献
6.
A Eu, Dy co-doped SiO 2 matrix xerogel with blue emission was prepared by the sol–gel method. Strong blue emission located between 425 nm and 525 nm with a peak at 486 nm is observed under UV laser excitation at room temperature, which is related to a 4f → 5d energy transition of Eu 2+. Such techniques as FT-IR and TGA–DSC were used to measure the microstructure of the luminescent materials. The influence of Dy 3+ ions on the luminescent property of Eu 2+ was investigated. The emission intensity of Eu, Dy-codoped samples is stronger than that of Eu doped samples. The emission enhancement mechanism relating to Eu 2+ is attributed to an energy transfer involving Dy 3+ → Eu 2+. Using energy transition theory, we speculate that the mechanism may be one of the resonance transfers via multi-polar interactions, and present a possible energy transfer model. The Eu 2+ blue emission intensity reaches the maximum when the Dy 3+ concentration is 0.1 mol%. When the concentration of Dy 3+ is 0.3 mol%, a fluorescence quenching appears which might be related to the overlap part of Eu 2+ excitation and emission levels, and also suggests the existence of Eu 2+ → Eu 2+ energy transfer. 相似文献
7.
Eu 3+-doped (1% and 3%) γ-Ca 3(PO 4) 2 was synthesized by high-pressure and high-temperature experimental method and the samples were characterized by X-ray diffraction. The luminescence properties of samples were investigated by emission and excitation spectra. The excitation spectra of Eu 3+-doped γ-Ca 3(PO 4) 2 showed that samples were mainly attributed to Eu 3+–O 2− charge-transfer band at 270 nm, and some sharp lines were also attributed to Eu 3+ f–f transitions in near-UV regions with the strongest peaks at 395 nm. Under the 395 nm excitation, the intense red emission peak at 611 nm was observed. The strongest line (395 nm) in excitation spectra of those phosphors matched well with the output wavelength of UV InGaN-based light-emitting diodes (LEDs) chip. The luminescent properties suggested that Eu 3+-doped γ-Ca 3(PO 4) 2 might be regarded as a potential red phosphor candidate for near-UV LEDs. 相似文献
8.
CsBr 0.9I 0.1:Eu 2+ crystals were grown by Bridgman technique. Optical absorption spectrum of the unirradiated CsBr 0.9I 0.1:Eu 2+ crystals show absorption bands at 270 nm and 340 nm. Irradiated CsBr 0.9I 0.1:Eu 2+ shows single F band for F(Br −) and F(I −) centers at 730 nm. Conversion of Eu 2+ to Eu 3+ after irradiation is confirmed by optical absorption technique. Sharp and single Photoluminescence (PL) emission band is observed at 440 nm for CsBr 0.9I 0.1:Eu 2+ crystals. Photostimulated Luminescence (PSL) emission band observed for CsBr 0.9I 0.1:Eu 2+ crystals at 442 nm due to excitation at 730 nm shows that the F centers are photostimulable. PSL emission intensity increases linearly with irradiation dose up to 2.5 Krad. 相似文献
9.
A green-emitting phosphor of Eu 2+-activated Sr 5(PO 4) 2(SiO 4) was synthesized by the conventional solid-state reaction. It was characterized by photoluminescence excitation and emission spectra, and lifetimes. In Sr 5(PO 4) 2(SiO 4):Eu 2+, there are at least two distinguishable Eu 2+ sites, which result in one broad emission situating at about 495 nm and 560 nm. The phosphor can be efficiently excited in the wavelength range of 250–440 nm where the near UV (~ 395 nm) Ga(In)N LED is well matched. The dependence of luminescence intensities on temperature was investigated. With the increasing of temperature, the luminescence of the phosphor shows good thermal stability and stable color chromaticity. The luminescence characteristics indicate that this phosphor has a potential application as a white light emitting diode phosphor. 相似文献
10.
Eu 3+-activated novel red phosphors, MLa 2(MoO 4) 4 (M = Ba, Sr and Ca) were synthesized by the conventional solid state method. The excitation and emission spectra indicate that these phosphors can be effectively excited by UV (395 nm) and blue (466 nm) light, and exhibit a satisfactory red performance at 614 nm. Upon excitation with a 466 nm light, our synthesized phosphors have stronger emission intensity than the sulfide red phosphors used in white LEDs. Due to high emission intensity and a good excitation profile, the Eu 3+-doped CaLa 2(MoO 4) 4 phosphor may be a promising candidate in solid-state lighting applications. 相似文献
11.
The Ba 2Mg(PO 4) 2:Eu 2+, Mn 2+ phosphor is synthesized by a co-precipitation method. Crystal phase, morphology, excitation and emission spectra of sample phosphors are analyzed by XRD, SEM and FL, respectively. The results indicate particles synthesized by a co-precipitation method have a smaller size in diameter than that synthesized by conventional solid-state reaction method. Emission spectra of BMP:Eu 2+, Mn 2+ phosphor show a broad blue and a broad yellow emission bands with two peaks at about 456 nm and 575 nm under 380 nm excitation. An overlap between Eu 2+ emission band and Mn 2+ excitation band proves the existence of energy transfer from Eu 2+ to Mn 2+. Emitting color of the BMP:Eu 2+, Mn 2+ phosphor could be tuned by adjusting relative contents of Eu 2+ and Mn 2+ owing to energy transfer formula. Therefore, BMP:Eu 2+, Mn 2+ may be considered as a potential candidate for phosphor for near-UV white LED. 相似文献
12.
Novel α-SiAlON:Eu 2+-based yellow oxynitride phosphors with the formula Sr 0.375−x
Eu
x
2+Si 12−m−n
Al
m+n
O
n
N 16−n
( m = 0.75, n = x = 0.004–0.04) have been prepared by firing the powder mixture of SrSi 2, α-Si 3N 4, AlN, and Eu 2O 3 at 2,000 °C for 2 h under 1 MPa nitrogen atmosphere. The luminescence properties, the dependence of the activator concentration
of Eu 2+ and the thermal stability of Sr-α-SiAlON:Eu 2+ phosphor have been investigated in comparison with Ca-α-SiAlON:Eu 2+ phosphor. Similar to Ca-α-SiAlON:Eu 2+ phosphor, Sr-α-SiAlON:Eu 2+ phosphor has the excitation wavelength ranging from the ultraviolet region to 500 nm, and exhibit intense yellow light. The
strongest luminescence was achieved at about x = 0.02 with the emission peak at 578 nm, slightly shorter than that of Ca-α-SiAlON:Eu 2+ phosphor at 581 nm. Temperature-dependent emission intensity of Sr-α-SiAlON:Eu 2+ phosphor is comparable to that of Ca-α-SiAlON:Eu 2+ phosphor. The results suggest that the different position of the emission peak for Sr- and Ca-α-SiAlON:Eu 2+ depends on the composition and the Stokes shift, and the thermal stability is nearly independent of Sr and Ca or fixed by
the network of (Si, Al)–(O, N) in α-SiAlON at the same Eu 2+ concentration. 相似文献
13.
Eu 2+-Mg 2+ co-doped AlON phosphors were prepared by a solid-state reaction route. Their structure and photoluminescence properties were studied. The substitution of Al by Mg favored the formation of pure spinel-type AlON phase and the incorporation of Eu into AlON crystal lattice. Second phase appeared in Eu containing powders. Under ultraviolet excitation at 310 nm, 3% Eu 2+-10% Mg 2+ co-doped phosphors exhibited a strong broad emission band in the wavelength range of 430-620 nm with a maximum at about 490 nm assigned to the typical 4f 65d 1-4f 7 transition of the Eu 2+ ion. Red shift of the emission peak is observed as the increase of Eu 2+ concentration due to interaction between Eu 2+ ions. 相似文献
14.
SrZrO 3:Eu 3+ nanoparticles with a size of about 100 nm were synthesized by a simple gel combustion route and characterized by X-ray diffraction,
scanning electron microscopy, dynamic light scattering, and photoluminescence techniques. Based on the time-resolved emission
data, it was inferred that three different types of Eu 3+ ions were present in the matrix. The first type was a long-lived species (~τ = 6.0 ms) present at symmetric “Sr 2+” sites, observed for excitations at 229 and 393 nm. The second was a short-lived species (τ = 1.0 ms) observed for excitations
at 229, 296, and 393 nm, while for 296-nm excitation, a long-lived species (τ = 4.0 ms) was also observed. This suggested
that Eu 3+ ions can be present at relatively lower symmetric “Zr 4+” sites with two different environments, which differ in the presence of charge-compensating defects. The color coordinates
of the system were evaluated and plotted on a CIE index diagram. 相似文献
15.
A blue-emitting phosphor of NaMg 4(PO 4) 3:Eu 2+, Ce 3+ was prepared by a combustion-assisted synthesis method. The phase formation was confirmed by X-ray powder diffraction measurement. Photoluminescence excitation spectrum measurements show that the phosphor can be excited by near UV light from 230 to 400 nm and presents a dominant luminescence band centered at 424 nm due to the 4f 65d 1 → 4f 7 transition of Eu 2+ ions at room temperature. Effective energy transfer occurs in Ce 3+/Eu 2+ co-doped NaMg 4(PO 4) 3 due to large spectral overlap between the emission of Ce 3+ and excitation of Eu 2+. Co-doping of Ce 3+ enhances the emission intensity of Eu 2+ greatly by transferring its excitation energy to Eu 2+, and Ce 3+ plays a role as a sensitizer. Ce 3+-Eu 2+ co-doped NaMg 4(PO 4) 3 powders can possibly be applied as blue phosphors in the fields of lighting and display. 相似文献
16.
The photoluminescence spectra of titanium dioxide (TiO 2) nanocrystals doped with Eu 3+ (molar ratio Eu 3+/TiO 2 = 0, 1, 2, 4%) are investigated under different excitation wavelengths. An ultraviolet band of emission energy higher than
the energy gap is found for excitation wavelengths larger than 315 nm when the Eu 3+ content is higher than 2%. The new emission band redshifts and its emission intensity is intensified with the increase of
excitation wavelength. The emission mechanism for the new ultraviolet emission band is analyzed. 相似文献
17.
The Y 2O 2S:Eu 3+,Mg 2+,Ti IV ( xEu = 0.028, xMg = 0.086, xTi = 0.03) materials were prepared with the flux fusion method. According to X-ray powder diffraction, the materials had the hexagonal crystal structure. The emission of Y 2O 2S:Eu 3+,Mg 2+,Ti IV was centered at 627 nm ( λexc : 250 nm) due to the 5D 0 → 7F 2 transition of Eu 3+. The excitation spectra ( λem : 627 nm) showed broad bands at 240 and 320 nm due to the O 2− → Eu 3+ and S 2− → Eu 3+ charge transfer transitions, respectively. The latter band can also overlap with the Ti → Eu 3+ energy transfer. In the excitation spectra with synchrotron radiation, in addition to the O 2− → Eu 3+ and S 2− → Eu 3+ charge transfer transitions, excitation over the band gap was observed at 4.8 eV (258 nm). The red persistent luminescence due to the 5D 0 → 7F 2 emission from Eu 3+ residing in the regular Y 3+ site of the host was ca. 10 min with 1 min fluorescent lamp irradiation. In addition, a very broad band was observed at 600 nm probably due to the Ti 3+ emission. 相似文献
18.
A new series of Eu 3+ ions-activated calcium gadolinium tungstate [Ca 2Gd 2W 3O 14] phosphors were synthesized by conventional solid-state reaction method. The X-ray diffraction patterns of the powder samples
indicate that the Eu 3+: Ca 2Gd 2W 3O 14 phosphors are of tetragonal structure. The prepared phosphors were well characterized by scanning electron microscopy (SEM),
energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL), and mechanoluminescence
(ML) spectra. PL spectra of Eu 3+: Ca 2Gd 2W 3O 14 powder phosphors have shown strong red emission at 615 nm ( 5D 0 → 7F 2) with an excitation wavelength λ
exci = 392 nm ( 7F 0 → 5L 6). The energy transfer from tungstate groups to europium ions has also reported. Mechanoluminescence studies of Eu 3+: Ca 2Gd 2W 3O 14 phosphors have also been explained systematically. 相似文献
19.
As one kind of new optoelectronic materials, ZnS:Mn nanoparticles/PVP composite nanofibers are prepared by the electrospinning technique successfully. SEM, XRD, FT-IR spectroscopy, photoluminescence and TEM measurements are employed in the study. By the method of annealing, the effect on the morphology and properties of the composite nanofibers is studied. After annealing treatment, the separating state of the nanofibers is improved obviously, ZnS:Mn nanoparticles are well dispersed in the nanofiber, the PL peak originated from 4T 1→ 6A 1 transition of Mn ions shifts from 605 nm to 599 nm. The existence of orange emission peaks confirms that ZnS:Mn nanoparticles are formed in the fibers. 相似文献
20.
The bulk LiYF4 single crystals with high-quality doped 0.5 mol% Eu3+ and various Gd3+ from 1.5 to 4.5 mol% in size of about Φ 10?×?65 mm were successfully grown by an improved Bridgman method. The X-ray diffraction (XRD) measurement and Rietveld refinement analysis were conducted to verify the structure of the obtained crystal crystals. The spectroscopic properties of the single crystals as change of GdF3 concentration were investigated with the help of absorption, excitation, emission spectra, and decay curves of their fluorescence. The characteristic absorption bands of Gd3+ at 277 nm and Eu3+ at 395 nm were observed in the co-doped samples. Significant enhanced emission intensity of 613 nm was observed as increasing of GdF3 content into Eu3+:LiYF4 single crystal upon excitations of both 277 nm and 395 nm lights. The former was owing to the energy transfer (ET) between Gd3+ and Eu3+, while the latter was due to the change of crystal field environment around Eu3+ by the increasing of GdF3 content. The ET from Gd3+ to Eu3+ ions was further confirmed from the result of the luminescence decay analysis. Besides, the full width half-maximum (FWHM) of 613 nm emission band was estimated to be?~?4.5 nm. The Eu3+/Gd3+ co-doped LiYF4 single crystal with excellent optical and physicochemical properties might has significant applications in red laser and display devices. 相似文献
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