Luminescence Properties Of YVO4 Research Articles

The Synthesis of Nanophosphors YPxV1–xO4 by Spray Pyrolysis and Microwave Methods

За счет редкоземельного допирования фосфаты и ванадаты являются ведущими материалами для синтеза люминофоров благодаря их термостойкости, низкой температуре спекания, химической стабильности. Особый интерес привлекают люминофоры в наноразмерном состоянии. Простой, быстрый и масштабируемый синтез нанолюминофоров высокой химической гомогенности является актуальной задачей. Целью работы являлся синтез порошков смешанных кристаллов ванадат-фосфата иттрия различного состава методами соосаждения под действием микроволнового излучения и спрей-пиролиза, а также сравнительный анализ характеристик полученных образцов.Методами соосаждения под действием микроволнового излучения и спрей-пиролиза в различных режимах синтезированы образцы YVхP1–хO4 разного состава. Данные рентгенофазового анализа в случае синтеза ванадат-фосфата иттрия YVхP1–хO4 методом спрей-пиролиза с последующим отжигом подтверждают образование однофазных нанопорошков. Методами просвечивающей электронной микроскопии и растровой электронной микроскопии выявлены морфологические характеристики образцов. В зависимости от режима отжига образцы представляют собой ограненные либо сферические частицы размером менее 100 нм. Состав образцов YVхP1–хO4, синтезированныхметодом соосаждения под действием микроволнового излучения, сильно зависит от рН раствора прекурсоров.Минимальное содержание примесных фаз достигается при рН, равном 9.Метод спрей-пиролиза позволяет синтезировать нанопорошки ванадат-фосфата иттрия YVхP1–хO4 высокой химической гомогенности с размером частиц менее 100 нм. При синтезе YVхP1–хO4 методом соосаждения под действием микроволнового излучения максимальной химической однородности порошков ванадат-фосфата иттрия удается достигнуть при рН = 9. Однако дисперсия частиц по размеру велика, лежит в интервале 2–60 мкм. ЛИТЕРАТУРА 1. Wu C., Wang Y., Jie W. 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Synthesis and luminescence properties of YVO4: Nd3+, Er3+ and Tm3+ nanoparticles

In this work we report on YVO4 nanocrystalline powders doped with individual ions Nd3+, Er3+ and Tm3+, and their combination. Modified Pechini method allowed obtaining weakly agglomerated single phase nanoparticles with average size of 50 nm. Luminescence properties of single and triply doped YVO4 nanoparticles were studied under selective excitation via individual ions and combined excitation via host material. The obtained results demonstrated intra-centers energy transfer processes for the selective excitation, and set of luminescence bands corresponding to all lanthanides under host excitation in the triply doped system.

Morphology analysis and luminescence properties of YVO4:Sm3+,Eu3+ prepared by molten salt synthesis

A series of red phosphors with rare earth ions (Sm3+, Eu3+) as activator, single and co-doped with YVO4 as the matrix were prepared by molten salt method. By changing the type of molten salt, the phosphors with different morphological characteristics were successfully synthesized, and the luminescence properties of the phosphor were systematically studied. Therein, SEM results showed that using NaCl as a molten salt synthesis of samples, stick with good crystallinity and the growth direction. And under the excitation of 313 nm, YVO4:Eu3+, Sm3+ phosphors which using NaCl as a molten salt showed the most intense luminescence intensity. Meanwhile, the concentration adjustment has been made to obtain the most intense luminescence intensity and regulate the emission color.

An auto-combustion synthesis and luminescence properties of polyhedral YVO4: Ln3+ (Ln = Eu, Sm, Yb/Er, Yb/Tm) microcrystals

Abstract

Luminescence properties of YVO4:Yb,Er nanoparticles dispersed in water

We have synthesized YVO4: Yb, Er nanoparticles in the size range of 100-500 nm, which form aqueous colloidal solutions and are luminescent when excited by femtosecond light pulses at a wavelength of 263 nm. It was established that the luminescence occurs due to the emission of Er3+ ions in characteristic spectral lines at 525 nm and 550 nm. However, an effective quenching channel for metastable levels of Er3+ ions is evident, so that the characteristic luminescence line of Er3+ ions in the 660 nm region is absent. We associate this quenching channel with a large concentration of lattice defects with possible localization of high-frequency quenchers.

Luminescence properties of YVO4: Ln (Ln = Dy3+, Eu3+, Tm3+) for white LED by hydrothermal method

YVO4: Dy3+, Eu3+ / YVO4: Dy3+, Eu3+, Tm3+ phosphors were synthesized by a simple hydrothermal method. The energy transfer from Dy3+ to Eu3+ was determined by photoluminescence (PL) spectra and fluorescence lifetime. The energy transfer mechanism from Dy3+ to Eu3+ was confirmed. The amount of Eu3+ in YVO4: 0.01Dy3+, Eu3+ with strong emission and small size was determined by applied ratio, and finally a white light (0.300, 0.317) output was achieved in YVO4: 0.01Dy3+, 0.01Eu3+, 0.03Tm3+ by adjusting the amount of activator ions. Thus the sample with the above characteristics has a promising application prospect in the light emitting diode (LED).

Yb3 +,Er3 +,Eu3 +-codoped YVO4 material for bioimaging with dual mode excitation

We propose an efficient bioimaging strategy using Yb3+,Er3+,Eu3+-triplet doped YVO4 nanoparticles which were synthesized with polymer as a template. The obtained particles possess nanoscale, uniform, and flexible excitation. The effect of Eu3+ ions on the luminescence properties of YVO4:Yb3+,Er3+,Eu3+ was investigated. The upconversion mechanism of the prepared material was also discussed. The structure and optical properties of the prepared material were characterized by using X-ray diffraction (XRD), Fourier-transform IR spectroscopy (FTIR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) upconversion and photoluminescence spectra. The Commission International de I′Eclairage (CIE) chromaticity coordinates was investigated to confirm the performance of color luminescent emission. The prepared YVO4:Yb3+,Er3+,Eu3+ nanoparticles could be easily dispersed in water by surface modification with cysteine (Cys) and glutathione (GSH). The aqueous dispersion of the modified YVO4:Yb3+,Er3+,Eu3+ exhibits bright upconversion and downconversion luminescence and has been applied for bioimaging of HeLa cells. Our developed material with dual excitation offers a promising advance in bioimaging.

Effect of substrate temperature on structure and luminescence properties of YVO4:Eu3+ thin films grown by PLD

YVO4:Eu3+ thin films were deposited by pulse laser deposition at substrate temperatures of 200, 300 and 400 °C. The oxygen deposition background pressure was also changed from 20 to 85 mTorr at a substrate temperature of 400 °C. The films deposited at the higher temperatures showed a tetragonal phase in consistent with the standard JCPDS card 17-0341. The X-ray diffraction patterns obtained from the 200 °C sample showed only a very small peak at the (200) orientation. The other phosphor thin film showed an improved crystalline structure when the temperature was increased. Scanning electron microscope images indicated larger particles on the surface at the higher temperatures. Atomic force microscopy results showed smooth surfaces with small particles at lower temperatures and an increase in surface roughness at higher temperatures due to the improvement in crystallinity. The photoluminescence showed the typical emission peaks of Eu3+ in the red region at 594 and 618 nm attributed to the 5D0–7F1 and 5D0–7F2 transitions. The peaks at 652 and 699 nm corresponding to the 5D0–7F3 and 5D0–7F4 transitions were also observed. The spectra showed an increase in PL intensity when the deposition temperature and oxygen pressure were increased.

The effect of urea:nitrate ratio on the structure and luminescence properties of YVO4:Dy3+ phosphors

YVO4:Dy3+ phosphor has been successfully synthesised using combustion method. The dependence of the properties of YVO4:Dy3+ phosphor upon urea:nitrate concentration was investigated. The single tetragonal phase was observed by x-ray diffraction spectra. A highly crystalline YVO4:Dy3+ sample was obtained when increasing the ratio of the urea to 2. The estimated crystalline sizes from the Scherrer’s formula were found to be 20, 38, 33, 30, and 27nm for the sample prepared with the ratio of 1, 2, 2.5, 3 and 4, respectively. The formation of agglomerated particles was observed by Scanning electron microscope images and it was observed that when increasing the concentration of urea further, flake-like particles formed. The diffuse reflectance spectra of YVO4:Dy3+ with various ratios of urea indicated that the determined optical band gap was ranging from 3.3 to 2.3eV. Luminescence properties of YVO4:Dy3+ showed that the phosphor emit yellow colour at 573nm and blue colour at 482nm corresponding to 4F9/2→6H13/2 and 4F9/2→6H15/2 transitions, respectively. A very weak band at 663nm which correspond to the 4F9/2→6H11/2 transition was also observed. It was found that the Photoluminescent emission intensity increased with an increase in the ratio of urea and reached a maximum at 2 then decreased when increasing the ratio of urea further.

Effect of annealing on the luminescence properties of YVO4:Dy3+ phosphor on co-doping Pb2+ ions

Pb2+ co-doped YVO4:Dy3+ phosphors have been synthesized at a relatively low temperature of 120°C via ethylene glycol route. The samples are further annealed at 500 and 900°C. The prepared samples were characterized by XRD, SEM, spectra energy dispersive analysis of X-ray (EDAX) and photoluminescence spectroscopy. XRD patterns of all samples are well indexed with single tetragonal phase of YVO4. The emission intensity of Dy3+ is significantly enhanced on co-doping Pb2+ ions. The highest emission is obtained at 7at.% Pb2+ for 900°C annealed samples. Both emission intensity and decay lifetime increases on annealing the samples from 500 to 900°C. On co-doping Pb2+ into YVO4:Dy3+ phosphors, the emission color falls near the white region and then shift towards yellow region on annealing from 500 to 900°C thereby indicating that annealing temperature play a role on tuning the color of the phosphors. As well as the emission color of the phosphors remain the same even on changing the excitation wavelengths from 280nm, which would serve as potential phosphors for white emission in LED applications.

Effect of synthesis conditions and surrounding medium on luminescence properties of YVO4:Eu3+ nanopowders

Nanocrystalline yttrium vanadate doped with europium ions powders were synthesized via sol-gel method based on decomposition of metal-polymer complex. X-ray diffraction analysis showed that samples had pure tetragonal phase without any impurities. Scanning electron microscopy and static light scattering technique were used to study morphology and size of prepared nanoparticles. Average diameter of the nanoparticles was about 40 nm. The changes in structural and luminescence properties were observed as a function of the first and second calcination temperature. The optimal conditions for synthesis of nanoparticles were determined as T1=500 °C, t1=1 h; T2=950 °C, t2=1.5 h. The effect of different media surrounding the nanoparticles on their luminescence properties and lifetime was investigated and discussed in terms of effective refractive index. It was found that the observed lifetime of YVO4:Eu3+ 5 at.% nanophosphor was decreased from 0.64 ms in air (nmed=1) to 0.45 ms in chalcogenide glass As39S61 (nmed=2.39).

Fabrication and Luminescent Properties of YVO4: Eu3+/MCM-41 Mesoporous Composites

The optical functionalized YVO4: Eu3+/MCM-41 mesoporous composites were prepared by hydrothermal method. The structure, morphology, luminescence properties and fluorescence dynamics were studied systemically. The compared studies of the luminescence properties of YVO4: Eu3+/MCM-41 with YVO4: Eu3+ nanocrystal were performed. The results show that the YVO4: Eu3+/MCM-41 retains high ordered mesoporous structure of MCM-41. In YVO4: Eu3+/MCM-41, the intrinsic excitation bands of Eu3+ disappears and the lifetimes of Eu3+ become short. The luminescent efficiency of YVO4: Eu3+/MCM-41 is higher than ones of the YVO4: Eu3+ nanocrystal.

Lattice defect quenching effects on luminescence properties of Eu3+-doped YVO4 nanoparticles

A room-temperature co-precipitation method was explored to synthesize Eu3+-doped YVO4 precursors as constructed by an aggregation of several primary particles. After calcination treatment, the primary particles underwent an oriented attachment process and grew into the regular square-like nanoparticles (NPs). These square-like NPs exhibited an improvement in quantum yield of luminescence emission, as indicated by greatly enhanced excitation intensity and lifetime. Further studies on these square-like NPs by electron paramagnetic resonance demonstrated a defect structure as characterized by lower valence state vanadium ions and oxygen vacancies that were produced during the growth process in nitrogen atmosphere. The formation of these defect structures was significantly influenced by the calcination atmospheres, which enables us to uncover the relationships between defect structures and luminescence properties of YVO4:Eu3+ nanocrystals.

Synthesis and Luminescence Properties of YVO<sub>4</sub>:Eu <sup>3+</sup> Nanocrystals by a Sol-Gel Method

YVO4:Eu3+ nanocrystals were synthesized using a sol-gel method which citric acid was used as complexing agent and ethylene glycol was used as coupler. In order to study the influence of heat treating temperature and time on structure and luminescence properties of YVO4:Eu3 nanocrystals, the dry gels were heated at 400 oC, 500 oC and 600 oC for 1 h, 600 o C for 3 h, respectively. X-ray diffraction, SEM and luminescence spectra were used to characterize the structure and luminescence properties. The results of XRD indicate that YVO4:Eu3+ nanocrystals with tetragonal zircon were obtained. The average crystallite sizes of the samples increase with the increasing heat treating temperatures. The results of excitation and emission spectra show that the broad excitation band is assigned to charge transfer band of Eu-O and V-O, the emissions peaks are from 5D0-7FJ transitions. The emission intensities increase with increasing heat treating temperature and time. The local environments of Eu3+ ions in the samples prepared at different conditions are discussed.

Effect of Sr2+ doping on the luminescence properties of YVO4:Eu3+,Sr2+ particles prepared by a solvothermal method

Well-dispersed Eu3+ and Sr2+ co-doped YVO4 luminescent particles (YVO4:Eu3+,Sr2+) on the submicron scale were prepared by a facile solvothermal method at low temperature. The effect of Sr2+ doping on the luminescence of YVO4:Eu3+,Sr2+ particles was investigated by fixing the Eu3+ doping concentration at 7 mol%. It was found that the luminescence intensity of the as-prepared YVO4:Eu3+,Sr2+ particles increased with the Sr2+ doping concentration x to reach a two-fold enhancement when x = 5 %, and then decreased for higher x. We also investigated the effect of thermal annealing on the luminescence properties of the YVO4:Eu3+ and YVO4:Eu3+,Sr2+ particles. A remarkable enhancement in their luminescence properties was observed after annealing at 900 °C in air for 30 min. It was showed that the annealed YVO4:Eu3+,Sr2+ particles exhibited a two-fold stronger emission than the annealed YVO4:Eu3+. This work indicates that Sr2+ doping is beneficial to the luminescence enhancement for both the as-prepared and annealed YVO4:Eu3+,Sr2+ particles.

Template-directed synthesis and luminescence properties of YVO4:Eu hollow microspheres

YVO4:Eu hollow microspheres have been successfully fabricated via a urea-based homogeneous precipitation method in the presence of colloidal melamine formaldehyde resin (MF) microspheres as templates, without heat treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and the kinetic decay were employed to examine the resulting phase formation, morphology and luminescent properties. The XRD result reveals that the doped sample is of high crystallization which is assigned to the pure tetragonal phase of YVO4. Upon excitation by ultraviolet excitation, the YVO4:Eu sample shows strong red light emission.

Synthesis and luminescence properties of YVO4:Eu3+ cobblestone - like microcrystalline phosphors obtained from the mixed solvent - thermal method

Abstract The mixed solvent-thermal method has been developed for the synthesis of YVO 4 :Eu 3+ luminescent materials in the N, N-dimethylformamide (DMF)/ de-ionized water (DIW) solution. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscope (TEM), UV/vis absorption and photoluminescence spectroscopies. The results demonstrate that we have obtained the uniform YVO 4 :Eu 3+ cobblestone - like microcrystalline phosphors in the mixed solution of DMF and DIW, which are different to the as-obtained YVO 4 :Eu 3+ nanoparticles in pure DIW. And the as - prepared YVO 4 :Eu 3+ microcrystalline particles are composed of numerous nanoparticles. The assembling phenomenon of the nanoparticles is strongly affected by the pH value of the solution and the volume ratio of DMF/DIW. Under UV excitation, the samples can emit the bright red light. While, the photoluminescence (PL) intensities of YVO 4 :Eu 3+ show some difference for samples obtained under the different reaction conditions. This is because that different microstructures of samples result in different combinative abilities between the surface and the adsorbed species so as to produce the different quenching abilities to the emission from Eu 3+ ions.

Synthesis and luminescence properties of YVO4:Dy3+ nanorods

Abstract Dy 3+ -doped YVO 4 nanorods were synthesized via a low temperature hydrothermal route in n -propyl alcohol–water mixtures at 150 °C. The structures and optical properties of products were investigated using the X-ray powder diffraction, transmission electron microscopy, and photoluminescence spectroscopy. The results showed that these nanorods might be fabricated through dissolving of small particles and the depositing of components on large particles. The photoluminescence (PL) measurements showed that these nanorods exhibited improved chromaticity compared with YVO 4 :Dy 3+ irregular nanoparticles. It can be ascribed to the perfect crystal structure of nanorods. From PL spectra, it is found that YVO 4 :Dy 3+ nanorods annealed at higher temperature have higher ratio of yellow ( 4 F 9/2 → 6 H 13/2 ) to blue ( 4 F 9/2 → 6 H 15/2 ) emissions, which ascribe to high site symmetry resulting from the crystallite size and crystallization increased.

Morphology control and luminescence properties of YVO4:Eu phosphors prepared by spray pyrolysis

Abstract Starting from nitrate aqueous solutions with citrate acid and polyethylene glycol (PEG) as additives, YVO 4 :Eu phosphors were prepared by a two-step spray pyrolysis (SP) and citrate-gel (CG) methods, respectively. The morphology and luminescence properties of YVO 4 :Eu phosphors prepared from SP method were investigated by changing the concentration of precursor solution, the concentration of PEG and the annealing temperatures, respectively. The emission intensity of the phosphors increased with increasing the annealing temperature and solution concentration due to the increase of the crystallinity and particles size. Certain PEG concentration was necessary for obtaining solid spherical particles, and the optimum emission could be observed when the concentration of PEG was 0.02 g/ml. Compared with the spherical YVO 4 :Eu phosphors prepared by SP method, the CG-derived non-spherical YVO 4 :Eu phosphors showed lower emission intensity when annealed at 1000 and 1200 °C. The optimum concentration for the luminescence of Eu 3+ is determined to be 7 mol % of Y 3+ in YVO 4 host.