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1.
Different concentrations of Li-doped YBO 3:Eu 3+ phosphors have been prepared by the conventional solid state reaction method and were characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence excitation and emission measurements. An intense reddish orange emission is observed under UV excitation and the emitted radiation was dominated by an orange peak at 594 nm resulted from the 5D 0 → 7F 1 transitions of Eu 3+ ions. The brightness of the YBO 3:Eu 3+ phosphor was found greatly improved with Li-doping accompanied by slight improvement in the purity of the color which might be attributed to improvement in crystallinity, grain sizes and creation of oxygen vacancies with Li-doping. The observed results have been discussed in comparison with similar reported works. 相似文献
2.
ZnS nanoparticles of varying concentrations were incorporated into Eu3+ doped ZrO2/PEG composite system through non-hydrolytic sol–gel method. The presence of the nanoparticles was confirmed by XRD and TEM analyses. The elemental composition of the prepared sample was verified using EDX analysis. Different vibrational modes of the composite system were found out by FTIR spectra. Thermal stability of the as-prepared sample was measured using TGA and DTA analyses. The optical bandgap of the composite system was calculated from the absorption spectrum. The excitation spectrum shows the broad excitation bands of the sensitizer (ZnS) and Host (ZrO2/PEG) as well as the characteristic excitation peaks of the activator (Eu3+). The emission spectra reveal that the characteristic emission of Eu3+ can be obtained using 392 nm as well as the excitation wavelength of the sensitizer (275 nm). The CIE chromaticity analysis shows a change in the emission colour of the co-doped samples from yellow to reddish orange corresponding to a change in the excitation wavelength from 392 to 275 nm. These results suggest the applicability of the as-synthesized composite system as a potential candidate in various optoelectronic devices. 相似文献
3.
Gd–La codoped TiO 2 nanoparticles with diameter of 10 nm were successfully synthesized via a sol–gel method. The photocatalytic activity of the Gd–La codoped TiO 2 nanoparticles evaluated by photodegrading methyl orange has been significantly enhanced compared to that of undoped or Gd or La monodoped TiO 2. Ti 4+ may substitute for La 3+ and Gd 3+ in the lattices of rare earth oxides to create abundant oxygen vacancies and surface defects for electron trapping and dye adsorption, accelerating the separation of photogenerated electron–hole pairs and methyl orange photodegradation. The formation of an excitation energy level below the conduction band of TiO 2 from the binding of electrons and oxygen vacancies decreases the excitation energy of Gd–La codoped TiO 2, resulting in versatile solar photocatalysts. The results suggest that Gd–La codoped TiO 2 nanoparticles are promising for future solar photocatalysts. 相似文献
4.
Pristine orange peel was chemically modified by introducing sulfur groups with the carbon disulfide treatment in alkaline medium. The presence of sulfur groups on orange peel xanthate were identified by FTIR spectroscopic study. Equilibrium isotherms and kinetics were obtained and the effect of various parameters including equilibrium pH, contact time, temperature and initial ion concentration on adsorption of Pb 2+ were studied by batch experiments. The maximum adsorption capacity of orange peel xanthate was 204.50 mg g −1, which was found to increase by about 150% compared to that of pristine orange peel. The adsorption process can attain equilibrium within 20 min, and kinetics was found to be best-fit pseudo-second-order equation. Temperature has little effect on the adsorption capacity of orange peel xanthate. In addition, the adsorption mechanism was suggested to be complexation. 相似文献
5.
A robust aluminophosphate glass matrix containing substantial amounts of Cu 2O and SnO has been prepared by the melt-quenching technique, and the luminescent properties have been assessed. The as-prepared material exhibits tunable luminescence by variation of excitation wavelength, in connection with the distinct excitation/emission properties of Cu + ions and twofold-coordinated Sn centers in the host. Under excitation of both Cu + and Sn species at 300 nm, the co-doped material exhibits a bright whitish luminescence, whereas excitation at 360 nm produces an intense orange emission arising merely from Cu + ions. Thus, white light generation is deemed realizable by combination of cool-bluish emission intrinsic to Sn centers with the warm-orange emission from Cu + ions. The optical properties of the material after heat treatment have been also investigated. Results indicate the chemical reduction of ionic copper via Sn 2+ ultimately producing Cu nanoparticles as evidenced by the surface plasmon resonance. Consequently, the excitation-wavelength dependent photoluminescence bands appear suppressed in relation to Cu + basically and show a dip attributed to light reabsorption by the plasmonic Cu particles. 相似文献
6.
通过分析山梨酸钾的橙汁溶液的荧光光谱特征,发现山梨酸钾在激发波长为375nm、发射波长为450~510nm范围的光谱图有毛刺,说明橙汁被激发的荧光会干扰山梨酸钾的荧光光谱。构建布谷鸟搜索算法(CS)优化支持向量机(SVM)模型对15个样本进行训练,并预测7个样本的山梨酸钾的浓度。CS-SVM的平均回收率为99.07%,均方误差为1.21×10 -5g/L,结果表明CS-SVM能够精确测定橙汁溶液中山梨酸钾的浓度,CS-SVM训练过程和对预测结果的平均回收率、误差都优于PSO-SVM和GA-SVM。 相似文献
7.
New Eu 2+ and/or Mn 2+ activated Ca 6La 2Na 2(PO 4) 6F 2 phosphors were prepared and their photoluminescence properties upon ultraviolet excitation were investigated. Phosphor Ca 6La 2Na 2(PO 4) 6F 2:Eu 2+,Mn 2+ shows a broad blue emission band and an orange emission band, which originates from Eu 2+ and Mn 2+, respectively. The resonant type energy transfer from Eu 2+ to Mn 2+ was demonstrated, and the energy transfer efficiency was also calculated according to their PL decay curves. Tuning of the content of Mn 2+ can generate the varied hues from blue to white and eventually to orange. Our results demonstrate that the phosphor is promising for producing UV-LED-based white LEDs. 相似文献
8.
High-field electroluminescence (EL) of chemically synthesized ZnS:Mn nanocrystals with a crystallite size of 4 nm was investigated
using a device consisting of glass substrate/indium–tin oxide/ZnS:Mn NC emission layer/Al. For electric fields over ca. 1 MV/cm,
the current was turned on, and orange EL was observed. The maximum luminance was 0.45 cd/m 2 at a DC voltage of 42 V. The EL spectrum comprises a single peak with a peak wavelength of 593 nm, which is ascribed to the
4T 1– 6A 1 transitions of Mn 2+ ions. The excitation mechanism of the Mn 2+ ions is discussed according to a scheme of impact excitation by hot-electrons. 相似文献
9.
In this work, the excitation mechanism of Eu 3+ ions embedded into nanocrystalline TiO 2 film obtained by Low Pressure Hot Target Reactive Sputtering has been investigated by means of photoluminescence, photoluminescence excitation, transmission and surface photovoltage spectroscopy.The strong emission related to europium ions in the visible range has been observed at a non resonant excitation wavelength suggesting an efficient excitation transfer from the matrix to the ions. Based on obtained results, indirect excitation mechanism of europium ions has been confirmed and discussed. Moreover, surface activity strongly depending on environment conditions, has been also observed. 相似文献
10.
A series of La-based metal?organic frameworks (La-MOFs) phosphors have been successfully synthesized by a facile solvothermal method without assistance of any surfactant or template. The results show that the ethanol volume ratio is important to obtain adjustable shape and size of La-MOFs in the synthesis process. The obtained samples possess flake-like architectures with about 3–5 μm in length. Under UV excitation, all the La-MOFs:Tb3+, Eu3+ phosphors exhibit the characteristic emissions of Tb3+ and Eu3+. Moreover, the emitting color of the as-obtained products can be acquired from green, green-yellow, yellow, yellow-orange, orange, to red owing to the efficient energy transfer (ET) between Tb3+ and Eu3+ions. The ET efficiency of the samples was calculated, and the maximum was found about 96.84%. Furthermore, the dipole–quadrupole interaction has been reasonable proved by the energy transfer between Tb3+ and Eu3+. These results indicated that La-MOFs:Tb3+, Eu3+ might be as a novel potential candidate as phosphors for displays and lightings. 相似文献
11.
The excitation cross sections and optical excitation functions are experimentally determined for transitions arising as a result of population of the 3
S, 3
P, and 3
P° levels in collisions of slow electrons with cadmium atoms. The dependence of cross sections on the principal quantum number of the upper level is obtained for four spectral series of CdI, which is indicative of the absence of significant perturbation of these series. The obtained results are compared with the data of previous studies. 相似文献
12.
The operation characteristics of polymer light-emitting diodes (PLEDs) are strongly dependent on materials, processing and the structure of the device. The device structure developed at Philips Research is presented together with some typical results for brightness, efficiency, response times and stability. The PLEDs typically operate at a voltage of 3–4 V for a brightness of 100 cd m -2 and have an efficiency ranging from 2 cd A -1 for orange emitting polymers (610 nm) up to 16 cd A -1 for green emitting polymers (550 nm). The response time under conditions for display operation is determined by the charge carrier transport properties and amounts to 43 ns. Lifetimes of several thousand hours have been obtained for large orange emitting devices of 8 cm 2 for daylight visibility at room temperature. 相似文献
13.
A convenient method for synthesizing highly photocatalytic activity PANI/TiO 2–Fe 3+ nanocomposite was developed. The effect of calcination temperature on the phase composition of TiO 2 nanopowder was investigated. It was found that higher temperature could promote the formation of rutile phase. The nanocomposite
was characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), infrared spectroscopy (IR) and
X-ray diffraction (XRD). The results indicated that the nanohybrid was composed of TiO 2, Fe 3+ and PANI. The photocatalytic property of the nanocomposite was evaluated by the degradation of methyl orange. In the presence
of this catalyst, the degradation rate of methyl orange of 95.2% and 70.3% could be obtained under the UV and sunlight irradiation
within 30 min, respectively. The apparent rate constant was 5.64 × 10 −2 which is better than that of the Degussa P25. 相似文献
14.
The present paper brings out the results concerning the preparation and optical properties of Sm 3+ and Dy 3+ each ion separately in different concentrations (0.3, 0.5, 1.0 and 1.5 mol.%) and also together doped (x mol.% Dy 3+ + 1.5 mol.% Sm 3+): Li 2O-LiF-B 2O 3-ZnO (where x = 0.5, 1.0 and 1.5 mol.%) glasses by a melt quenching method. Structural and thermal properties have been extensively studied for those glasses by XRD and TG/DTA. The compositional analysis has been carried out from FTIR spectral profile. Optical absorption spectral studies were also carried out. Sm 3+: LBZ glasses have displayed an intense orange emission at 603 nm ( 4G 5/2 → 6H 7/2) with an excitation wavelength at 403 nm and Dy 3+: LBZ glasses have shown two emissions located at 485 nm ( 4F 9/2 → 6H 15/2; blue) and 574 nm ( 4F 9/2 → 6H 13/2; yellow) with an excitation wavelength at 385 nm. Remarkably, it has been identified that the significant increase in the reddish orange emission of Sm 3+ ions and diminished yellow emission pertaining to Dy 3+ ions in the co-doped LBZ glass system under the excitation of 385 nm which relates to Dy 3+ ions. This could be due energy transfer from Dy 3+ to Sm 3+. The non-radiative energy transfer from Dy 3+ to Sm 3+ is explained in terms of their emission spectra, donor lifetime, energy level diagram and energy transfer characteristic factors. These significantly enhanced orange emission exhibited glasses could be suggested as potential optical glasses for orange luminescence photonic devices. 相似文献
15.
LiSr 4?x (BO 3) 3: xSm 3+ and LiSr 3.985?x (BO 3) 3:0.015Sm 3+, xK + phosphors were prepared by solid-state reactions. The phases and luminescent properties of the obtained phosphors were characterized. The results demonstrate that the phosphors particles emit an intensive reddish orange light emission under excitation at 403 nm. LiSr 4?x (BO 3) 3: xSm 3+ phosphor can be efficiently excited by ultraviolet and blue light, and the emission spectrum consists of three emission peaks at 564, 601 and 647 nm. The introduction of the charge compensator K + into the LiSr 4?x (BO 3) 3: xSm 3+ phosphor matrix promotes the increase of the emission intensity, as well as the decrease of the E g value. Results suggest that LiSr 3.97(BO 3) 3:0.015Sm 3+, 0.015 K + is a promising orange–red emitting phosphor for UV LED applications. 相似文献
16.
The spectroscopic properties of a Dy 3+-doped aluminophosphate glass containing silver and tin were reported. Different oxidation and aggregation states of silver
were obtained by varying silver concentration and glass thermal history. The addition of silver and tin at the lowest concentration
studied results in Dy 3+ ions emission under nonresonant UV excitation in connection with the appearance of an excitation band around 270 nm, which
is associated to isolated Ag + ions and twofold-coordinated Sn centers. The increase in silver and tin concentration leads to a broadening of aforementioned
band and to the presence of charged silver dimers as evidenced by the appearance of an excitation band around 330 nm. The
data indicated that light absorption might take place at ionic silver species and twofold-coordinated Sn centers, followed
by energy transfer to Dy 3+ ions. After heat treatment, ionic silver species were reduced to atomic Ag by tin with the subsequent formation of Ag nanoparticles
(NPs) inside the dielectric host. A quenching effect in Dy 3+ ions luminescence was shown with the presence of the Ag NPs, most notably for excitation of 6H 15/2 → 4F 9/2, 4I 15/2, 4G 11/2 transitions, which were in resonance with the dipole absorption mode of the particles. The silver NPs were believed to provide
radiationless pathways for excitation energy loss in Dy 3+ ions. 相似文献
17.
Ba 2LaV 3O 11:Eu 3+ phosphors were firstly synthesized by the traditional solid-state reaction method at 1100 °C. Their luminescence properties were investigated by photoluminescence excitation and emission spectra. The excitation spectrum shows a broad band centered at about 275 nm in the region from 200 to 370 nm, which is attributed to an overlap of the charge transfer transitions of O 2??→?V 5+ and O 2??→?Eu 3+. The phosphors exhibit the red emissions of Eu 3+ and the emission intensity ratio of 5D 0?→? 7F 2 to 5D 0?→? 7F 1 is dependent on the Eu 3+ concentration due to an environment change about Eu 3+ ions. Concentration quenching occurs at 30 mol% in the phosphors and exchange interaction is its main mechanism. Ba 2LaV 3O 11:Eu 3+ displays tunable CIE color coordinates from yellow orange to red depended on Eu 3+ content, which may have a potential application for illuminating and display devices. 相似文献
18.
A two-dimensional model is suggested of dc glow discharge with parallel electrodes. The model includes equations for electron and ion concentrations, which are related to the Poisson equation for electric potential. The collision ionization and electron-ion recombination are described using empirical relations. Processes of vibrational excitation of N 2 molecules are considered. The vibrational kinetics of nitrogen are described in view of excitation by electron impact, vibrational exchange, and vibrational-translational relaxation. The finite-difference model used for solving kinetic equations is described. Results are obtained for a two-dimensional model of glow discharge in nitrogen at a pressure of 5 torr and an emf of 2000 V. The obtained fields of distribution of electron temperature and populations of vibrational levels of nitrogen are analyzed. The results enable one to estimate the fraction of electric field energy utilized for the excitation of vibrational states. 相似文献
19.
The realization of a monocrystalline nanofilm of Nd 3+-doped fluoride on LiYF 4 substrates by pulsed laser deposition is reported. The film was obtained by laser ablation with 355 nm photons of a bulk LiYF 4 crystal doped with Nd 3+ ions at 1.5% atomic concentration. The measurements of the sample thickness obtained by an in situ interferometric technique, and the film optical characteristics analyzed via laser induced fluorescence spectroscopy upon UV and IR excitation, are presented. Lifetime measurements of the fundamental Nd 3+ ion transition in the film were also performed. All the results were compared with those obtained in a Nd 3+:LiYF 4 bulk crystal. The emission spectra of the deposited film following IR excitation seem to indicate the obtained deposit is Nd 3+:YF 3. 相似文献
20.
Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant a = 5.408 ± 0.011 ?. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn 2+ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn 2+ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn 2+ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour. 相似文献
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