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1.
Luminescent properties of Pr3+ or Mn2+ singly doped and Pr3+, Mn2+ co-doped LaMgB5O10 are investigated by synchrotron radiation VUV light. When LaMgB5O10:Pr3+ is excited at185 nm, the photon cascade emission between 4f levels of Pr3+ is observed. In the excitation spectra of LaMgB5O10:Mn2+ monitoring the 615 nm emission of Mn2+, several excitation bands in a spectral range from 330 to 580 nm are recorded, among which the most intense band is centered at 412 nm (6A1g4Eg-4A1g). This band has considerable spectra overlap with the 410 nm emission (1S01I6) of Pr3+, which is favorable for energy transfer from Pr3+ to Mn2+. Such energy transfer is observed in the co-doped sample, converting the violet emission (410 nm) of Pr3+ into the red emission (615 nm) of Mn2+. The concentration dependence of transfer efficiency is also investigated.  相似文献   

2.
ZnS and SiO2-ZnS nanophosphors, with or without different concentration of Mn2+ activator ions, were synthesized by using a sol-gel method. Dried gels were annealed at 600 °C for 2 h. Structure, morphology and particle sizes of the samples were determined by using X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The diffraction peaks associated with the zincblende and the wurtzite structures of ZnS were detected from as prepared ZnS powders and additional diffraction peaks associated with ZnO were detected from the annealed powders. The particle sizes of the ZnS powders were shown to increase from 3 to 50 nm when the powders were annealed at 600 °C. An UV-Vis spectrophotometer and a 325 nm He-Cd laser were used to investigate luminescent properties of the samples in air at room temperature. The bandgap of ZnS nanoparticles estimated from the UV-Vis data was 4.1 eV. Enhanced orange photoluminescence (PL) associated with 4T16A1 transitions of Mn2+ was observed from as prepared ZnS:Mn2+and SiO2-ZnS:Mn2+ powders at 600 nm when the concentration of Mn2+ was varied from 2-20 mol%. This emission was suppressed when the powders were annealed at 600 °C resulting in two emission peaks at 450 and 560 nm, which can be ascribed to defects emission in SiO2 and ZnO respectively. The mechanism of light emission from Mn2+, the effect of varying the concentration on the PL intensity, and the effect of annealing are discussed.  相似文献   

3.
ZnS:Cu,Mn phosphors were prepared by conventional solid state reaction with the aid of NaCl-MgCl2 flux at 900 °C. The samples were characterized by X-ray powder diffraction, UV-vis absorbance spectra and photoluminescence spectra. All samples possess cubic structure. Cu has a much stronger effect on the absorption property of ZnS than Mn. Incorporation of Mn into ZnS host only slightly enhances the light absorption, while addition of Cu remarkably increases the ability of absorption due to ground state Cu+ absorption. The emission spectra of the ZnS:Cu,Mn phosphors consist of three bands centered at about 452, 520 and 580 nm, respectively. Introduction of Mn significantly quenches the green luminescence of ZnS:Cu. The excitation energy absorbed by Cu is efficiently transferred to Mn activators non-radiatively and the Mn luminescence can be sensitized by Cu behaving as a sensitizer (energy donor).  相似文献   

4.
ZnS nanoparticles with Mn2+ doping (0.5-20%) have been prepared through a simple chemical method, namely the chemical precipitation method. The structure of the nanoparticles has been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-vis spectrometer. The size of the particles is found to be 3-5 nm range. Photoluminescence spectra were recorded for undoped ZnS nanoparticles using an excitation wavelength of 320 nm, exhibiting an emission peak centered at around 445 nm. However, from the Mn2+-doped samples, a yellow-orange emission from the Mn2+4T1-6A1 transition is observed along with the blue emission. The prepared Mn2+-doped sample shows efficient emission of yellow-orange light with the peak emission 580 nm with the blue emission suppressed. The maximum PL intensity is observed only at the excitation energy of 3.88 eV (320 nm). Increase in stabilizing time up to 48 h in de-ionized water yields the enhancement of emission intensity of doped (4% Mn2+) ZnS. The correlation made through the concentration of Mn2+ versus PL intensity resulted in opposite trend (mirror image) of blue and yellow emissions.  相似文献   

5.
The water-soluble Mn2+-doped ZnS quantum dots (Mn:ZnS d-dots) were synthesized by using thioglycolic acid (TGA) as stabilizer in aqueous solutions in air, and characterized by X-ray powder diffraction (XRD), UV-vis absorption spectra and photoluminescence (PL) emission spectroscopy. The sizes of Mn:ZnS d-dots were determined to be about 2 nm using XRD measurements and the UV-vis absorption spectra. It was found that the Mn2+4T1 → 6A1 emission intensity of Mn:ZnS d-dots significantly increased with the increase of Mn2+ concentration, and showed a maximum when Mn2+ doping content was 1.5%. If Mn2+ concentration continued to increase, namely more than 1.5%, the Mn2+4T1 → 6A1 emission intensity would decrease. In addition, the effects of TGA/(Zn + Mn) molar ratio on PL were investigated. It was found that the peak intensity ratio of Mn2+4T1 → 6A1 emission to defect-states emission showed a maximum when the TGA/(Zn + Mn) molar ratio was equal to 1.8.  相似文献   

6.
Cysteine stabilized ZnS and Mn2+-doped ZnS nanoparticles were synthesized by a wet chemical route. Using the ZnS:Mn2+ nanoparticles as seeds, silica-coated ZnS (ZnS@Si) and ZnS:Mn2+ (ZnS:Mn2+@Si) nanocomposites were formed in water by hydrolysis and condensation of tetramethoxyorthosilicate (TMOS). The influence of annealing in air, formier gas, and argon at 200-1000 °C on the chemical stability of ZnS@Si and ZnS:Mn2+@Si nanoparticles with and without silica shell was examined. Silica-coated nanoparticles showed an improved thermal stability over uncoated particles, which underwent a thermal combustion at 400 °C. The emission of the ZnS@Si and ZnS:Mn2+@Si passed through a minimum in photoluminescence intensity when annealed at 600 °C. Upon annealing at higher temperatures, ZnS@Si conserved the typical emission centered at 450 nm (blue). ZnS:Mn2+@Si yielded different high intensity emissions when heated to 800 °C depending on the gas employed. Emissions due to the Mn2+ at 530 nm (green; Zn2SiO4:Mn2+), 580 nm (orange; ZnS:Mn2+@Si), and 630 nm (red; ZnS:Mn2+@Si) were obtained. Therefore, with a single starting product a set of different colors was produced by adjusting the atmosphere wherein the powder is heated.  相似文献   

7.
The SrS:Ce/ZnS:Mn phosphor blends with various combination viz 75:25, 50:50 and 25:75 were assign to generate the white-light emission using near-UV and blue-light emitting diodes (LED) as an excitation source. The SrS:Ce exhibits strong absorption at 427 nm and the corresponding intense emission occurs at 480 and 540 nm due to electron transition from 5d(2D)−4f(2F5/2, 7/2) of Ce3+ ion as a result of spin-orbit coupling. The ZnS:Mn excited under same wavelength shows broad emission band with λmax=582 nm originates due to 3d (4G−6S) level of Mn2+. Photoluminescence studies of phosphor blend excited using near-UV to blue light confirms the emitted radiation varies from cool to warm white light in the range 430-600 nm, applicable to LED lightings. The CIE chromaticity coordinate values measured using SrS:Ce/ZnS:Mn phosphor blend-coated 430 nm LED pumped phosphors in the ratio 75:25, 50:50 and 25:75 are found to be (0.235, 0.125), (0.280, 0.190) and (0.285, 0.250), respectively.  相似文献   

8.
Tb3+:NaGd(WO4)2 (Tb:NGW) phosphors with different Tb3+ concentrations have been synthesized by a mild hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation and emission spectra and decay curve were used to characterize the Tb:NGW phosphors. XRD analysis confirmed the formation of NGW with scheelite structure. SEM study showed that the obtained Tb:NGW phosphors appeared to be nearly spherical and their sizes ranged from 1 to 1.5 μm. The excitation spectra of these systems showed an intense broad band with maximum at 270 nm related to the O→W ligand-to-metal charge-transfer state. Photoluminescence spectra indicated the phosphors emitted strong green light centered at 545 nm under UV light excitation. Analysis of the photoluminescence spectra with different Tb3+ concentrations revealed that the optimum dopant concentration for Tb3+ is about 15 at% of Tb3+ ions in Tb:NGW phosphors.  相似文献   

9.
The effect of the defects due to the charge compensation obtained with the yttrium co-doping to the ZrO2:Yb3+,Er3+ up-converting phosphors was studied. The materials were prepared with the combustion method. The materials purity was analyzed with the FT-IR spectroscopy. The crystal structure was studied with the X-ray powder diffraction and the crystallite sizes were estimated with the Scherrer formula. Up-conversion luminescence was excited at room temperature with an IR-laser at 970 nm. The up-conversion luminescence spectra showed red (650-685 nm) and green emission (520-560 nm) due to the 4F9/24I15/2 and (2H11/2,4S3/2)→4I15/2 transitions of Er3+, respectively. Persistent up-conversion luminescence was observed both in the Yb3+,Er3+ and Y3+,Yb3+,Er3+ doped materials.  相似文献   

10.
In this paper, we present the photoluminescence properties of Pr3+-, Sm3+- and Dy3+-doped germanate glasses and glass ceramics. From the X-ray diffraction measurement, the host glass structure was determined. These glasses have shown strong absorption bands in the near-infrared (NIR) region. Compared to Pr3+-, Sm3+- and Dy3+-doped glasses, their respective glass ceramics have shown stronger emissions due to the Ba2TiGe2O8 crystalline phase. For Pr3+-doped glass and glass ceramic, emission bands centered at 530 nm (3P03H5), 614 nm (3P03H6), 647 nm (3P03F2) and 686 nm (3P03F3) have been observed with 485 nm (3H43P0) excitation wavelength. Of them, 647 nm (3P03F2) has shown bright red emission. Emission bands of 4G5/26H5/2 (565 nm), 4G5/26H7/2 (602 nm) and 4G5/26H9/2 (648 nm) for the Sm3+:glass and glass ceramic, with excitation at 6H5/24F7/2 (405 nm) have been recorded. Of them, 4G5/26H7/2 (602 nm) has shown a bright orange emission. With regard to the Dy3+:glass and glass ceramic, a bright fluorescent yellow emission at 577 nm (4F9/26H13/2) has been observed, apart from 4F9/26H11/2 (667 nm) emission transition with an excitation at 454 nm (6H15/24I15/2) wavelength. The stimulated emission cross-sections of all the emission bands of Pr3+, Sm3+ and Dy3+:glasses and glass ceramics have been computed based on their measured full-width at half-maxima (FWHM, Δλ) and lifetimes (τm).  相似文献   

11.
This paper reports on the absorption, visible and near-infrared luminescence properties of Nd3+, Er3+, Er3+/2Yb3+, and Tm3+ doped oxyfluoride aluminosilicate glasses. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (Ω2, Ω4 and Ω6) have been calculated for all the studied ions. Decay lifetime curves were measured for the visible emissions of Er3+ (558 nm, green), and Tm3+ (650 and 795 nm), respectively. The near infrared emission spectrum of Nd3+ doped glass has shown full width at half maximum (FWHM) around 45 nm (for the 4F3/24I9/2 transition), 45 nm (for the 4F3/24I11/2 transition), and 60 nm (for the 4F3/24I13/2 transition), respectively, with 800 nm laser diode (LD) excitation. For Er3+, and Er3+/2Yb3+ co-doped glasses, the characteristic near infrared emission bands were spectrally centered at 1532 and 1544 nm, respectively, with 980 nm laser diode excitation, exhibiting full width at half maximum around 50 and 90 nm for the erbium 4I13/24I15/2 transition. The measured maximum decay times of 4I13/24I15/2 transition (at wavelength 1532 and 1544 nm) are about 5.280 and 5.719 ms for 1Er3+ and 1Er3+/2Yb3+ (mol%) co-doped glasses, respectively. The maximum stimulated emission cross sections for 4I13/24I15/2 transition of Er3+ and Er3+/Yb3+ are 10.81×10−21 and 5.723×10-21 cm2. These glasses with better thermal stability, bright visible emissions and broad near-infrared emissions should have potential applications in broadly tunable laser sources, interesting optical luminescent materials and broadband optical amplification at low-loss telecommunication windows.  相似文献   

12.
This paper reports on the near infrared (730-783 nm) to the visible upconversion emissions at 482 nm (4F9/26H15/2), 576 nm (4F9/26H13/2) and 662 nm (4F9/26H11/2) from the Dy3+doped 53ZrF4-20BaF2-2LaF3-2YF3-3AlF3-19NaF-1DyF3 glasses. We have also carried out a systematic study on the normal emission properties of these glasses in order to understand their performance both as a NIR upconverted visible luminescent and as normal visible fluorescent optical systems of technical importance. With an increase in Dy3+ concentration beyond a particular value (1 mol%), activator-activator interaction becomes a significant cause of concentration quenching in the luminescence properties. The dependence of the emission spectra on the excitation wavelengths has also been examined and 451 nm was found to be the ideal excitation wavelength in the measurement of normal fluorescence spectra. In the case of NIR upconverted visible emission, we have observed that the NIR excitation at 783 nm as the suitable pump wavelength in demonstrating prominent visible emission colours from these glasses. The relevance in undertaking these optical materials lies in their potential for upconversion laser application in the visible wavelength region. The NIR upconversion phenomenon has been explained in terms of energy level schemes due to excited state absorption (ESA) and energy transfer upconversion (ETU) processes.  相似文献   

13.
Using Czochralski (CZ) pulling method, an Er3+/Yb3+-codoped NaY(WO4)2 crystal was prepared. Absorption spectra, emission spectra and excitation spectra of this crystal were measured at room temperature. Some optical parameters, such as intensity parameters, spontaneous emission probabilities and lifetimes, were calculated from absorption spectra with Judd-Ofelt (J-O) theory. Upconversion luminescence excited by a 970 nm diode laser was studied. In this crystal, green upconversion luminescence is particularly intensive. Energy transfer mechanisms that play an important role in upconversion processes were analyzed. Two cross-relaxation processes: 4G11/2 + 4I9/2 → 2H11/2 (or 4S3/2) + 2H11/2 (or 4S3/2), and 4G11/2 + 4I15/2 → 2H11/2 (or 4S3/2) + 2I13/2, which contribute to the intensive green luminescence under 378 nm excitation, were put forward. Background energy transfer 4G11/2(Er3+) + 2F7/2(Yb3+) → 4F9/2(Er3+) + 2F5/2(Yb3+) was also demonstrated.  相似文献   

14.
A phosphor Tb3+-doped ZnWO4 (ZWO:Tb) phosphors were prepared by a hydrothermal method. X-ray powder diffraction (XRD) analysis revealed that the as-obtained sample is pure ZnWO4 phase. The excitation and emission spectra indicated that the phosphor could be well excited by ultraviolet light (272 nm) and emit blue light at about 491 nm and green light at about 545 nm. Significant energy transfer from WO42− groups to Tb3+ ions has been observed. Two approaches to charge compensation are investigated: (a) 2Zn2+ = Tb3+ + M+, where M+ is a monovalent cation like Li+, Na+ and K+ acting as a charge compensator; (b) 3Zn2+ = 2Tb3+ + vacancy. Compared with two charge compensation patterns in the ZnWO4:Tb3+, it has been found that ZnWO4:Tb3+ phosphors used Li+ as charge compensation show greatly enhanced bluish-green emission under 272 nm excitation.  相似文献   

15.
Zinc sulfide semiconductor nanocrystals doped Mn2+ have been synthesized via a solution-based method utilizing optimum dopant concentration (4%) and employing polyvinyl pyrrolidone (PVP) and sodium hexametapolyphosphate (SHMP) as capping agents. UV-vis absorbance spectra for all of the synthesized nanocrystals show an exitonic peak at around 310 nm. The particle size and morphology were characterized by scanning electron microscopy (SEM), FT-IR, X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence spectrum (PL). Diffraction data confirmed that the crystallite size is around 3-5 nm. Room temperature photoluminescence (PL) spectrum for the bare ZnS sample shows a strong band at ∼445 nm. The uncapped and capped(SHMP, PVP) ZnS:Mn2+ samples show a strong and broad band in the ∼580-585 nm range.  相似文献   

16.
In this paper, we present the spectral results of Dy3+ and Pr3+ (1.0 mol%) ions doped Bi2O3-ZnF2-B2O3-Li2O-Na2O glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out. From the DSC thermograms, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures have been evaluated. The direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. The emission spectrum of Dy3+:glass has shown two emission transitions 4F7/26H15/2 (482 nm) and 4F7/26H13/2 (576 nm) with an excitation at 390 nm wavelength and Pr3+:glass has shown a strong emission transition 1D23H4 (610 nm) with an excitation at 445 nm. Upon exposure to UV radiation, Dy3+ and Pr3+ glasses have shown bright yellow and reddish colors, respectively, from their surfaces.  相似文献   

17.
Spectral-kinetic study of Pr3+ luminescence has been performed for LiLuF4:Pr(0.1 mol%) single crystal upon the excitation within 5-12 eV range at T=8 K. The fine-structure of Pr3+ 4f 2→4f 5d excitation spectra is shown for LiLuF4:Pr(0.1 mol%) to be affected by the efficient absorption transitions of Pr3+ ions into 4f 5d involving 4f 1 core in the ground state. Favourable conditions have been revealed in LiLuF4:Pr(0.1 mol%) for the transformation of UV-VUV excitation quanta into the visible range. Lightly doped LiLuF4:Pr crystals are considered as the promising luminescent materials possessing the efficient Pr3+3P0 visible emission upon UV-VUV excitation. The mechanism of energy transfer between Lu3+ host ion and Pr3+ impurity is discussed.  相似文献   

18.
In this work the preparation, characterization and photoluminescence studies of pure and copper-doped ZnS nanophosphors are reported, which are prepared by using solid-state reaction technique at a temperature of 100 °C. The as-obtained samples were characterized by X-ray diffraction (XRD) and UV-VIS Reflectance spectroscopy. The XRD analysis confirms the formation of cubic phase of undoped as well as Cu2+-doped ZnS nanoparticles. Furthermore it shows that the average size of pure as well as copper-doped samples ranges from 15 to 50 nm. The room-temperature PL spectra of the undoped ZnS sample showed two main peaks centered at around 421 and 450 nm, which are the characteristic emissions of interstitial zinc and sulfur vacancies, respectively. The PL of the doped sample showed a broad-band emission spectrum centered at 465 nm accompanied with shoulders at around 425, 450 and 510 nm, which are the characteristic emission peaks of interstitial zinc, sulfur vacancies and Cu2+ ions, respectively. Our experimental results indicate that the PL spectrum confirms the presence of Cu2+ ions in the ZnS nanoparticles as expected.  相似文献   

19.
The phosphors, Bi3+- activated Gd2O3:Er3+, were prepared by sol-gel combustion method, and their photoluminescent properties were investigated under ultraviolet light excitation. The emission spectrum exhibited sharp peaks at about 520, 535, 545, 550 and 559 nm due to (2H11/2, 4S3/2)→4I15/2 transitions of Er3+ ions. The luminescent intensity was remarkably improved by the incorporation of Bi3+ ions under 340 nm light excitation, which suggested very efficient energy transfer from Bi3+ ions to Er3+ions. The introducing of Bi3+ ions broadened the excitation band of the phosphor, of which a new strong peak occurred ranging from 320 to 360 nm due to the 6s2→6s6p transition of Bi3+ ions. There is significant energy overlap between the emission band of Bi3+ ions and the excitation band of Er3+ ions. Under 340 nm light excitation, Bi3+ absorbed most of the energy and transferred it to Er3+. The energy transfer probability from Bi3+ to Er3+ is strongly dependent on the Bi3+ ion concentration. Also, the sensitization effectiveness was studied and discussed in this paper.  相似文献   

20.
CdS:Mn2+/ZnS and CdS:Mn2+/CdS core–shell nanoparticles were synthesized in aqueous medium via chemical precipitation method in an ambient atmosphere. Polyvinylpyrrolidone (PVP) was used as a capping agent. The effect of the shell (ZnS and CdS) thickness on CdS:Mn2+ nanoparticles was investigated. Inorganically passivated core/shell nanocrystals having a core (CdS:Mn2+) diameter of 4 nm and a ZnS-shell thickness of ∼0.5 nm exhibited improved PL intensity. Optimum concentration of doping ions (Mn2+) was selected through optical study. For all the core–shell samples two emission peaks were observed, the first one is band edge emission in the lower wavelength side due to energy transfer to the Mn2+ ions in the crystal lattice; the second emission is characteristic peak of Mn2+ ions (4T1 → 6A1). The XRD, TEM and PL results showed that the synthesized core–shell particles were of high quality and monodisperse.  相似文献   

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