Hydrophilic rare-earth up-conversion nanophosphors(UCNPs)with small sizes and a strong up-conversion luminescence have attracted much interest.Herein the simultaneous control of morphologies and the up-conversion lumi...Hydrophilic rare-earth up-conversion nanophosphors(UCNPs)with small sizes and a strong up-conversion luminescence have attracted much interest.Herein the simultaneous control of morphologies and the up-conversion luminescence intensities was reported for NaYF_(4)∶Yb/Er nanophosphors by a facile hydrothermal procedure with different surfactants.With the change of the surfactants from polyvinylpyrrolidone(PVP)to sodium citrate(CIT),edetate disodium(EDTA)or sodium dodecyl benzenesulfonate(SDBS),the morphology of NaYF_(4)∶Yb/Er nanophosphors transformed from nanoparticles with a diameter of about 70.0 nm to hexagonal nanoblocks with a thickness of about 125.0 nm and a length of about 240.0 nm,nanorods with a diameter of about 700.0 nm and a length of about 2.6μm,or nanowires with a diameter of 250.0 nm and a length of about 3.2μm.Simultaneously,their up-conversion luminescence intensity went down gradually under laser irradiation at a wavelength of 980 nm due to the increase of photobleaching.PVP-capped NaYF_(4)∶Yb/Er nanoparticles exhibited the smallest size and the strongest up-conversion luminescence intensity.Biological experiment results revealed that NaYF_(4)∶Yb/Er nanophosphors exhibited a high biocompatibility and could be used as biological labels with a perfect signal-to-noise ratio for cancer cell imaging.展开更多
Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ （CZTOPN） was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glyc...Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ （CZTOPN） was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti（OC4H9）4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis （TG-DSC）, powder X-ray diffraction （XRD）, and scan election microscopy （SEM）. Results of TG-DSC and XRD reveal that the composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.展开更多
In this work,we report an innovative route for the synthesis of rare-earth doped calcium molybdate(CaMoO4)nanophosphors by using high gravity rotating packed bed(RPB)technology and paraffin liquid as the solvent.The s...In this work,we report an innovative route for the synthesis of rare-earth doped calcium molybdate(CaMoO4)nanophosphors by using high gravity rotating packed bed(RPB)technology and paraffin liquid as the solvent.The significant intensified mass transfer and micromixing of reactants in the RPB reactor are benefiting for homogeneous doping of rare-earth ions in the host materials,leading to nanophosphors with high quantum efficiency.The use of liquid paraffin as the solvent eliminates the safety risks associated with volatile organic compounds,increasing the potential for clean production of nanophosphors.Under excitation of deep ultraviolet(DUV)light,the CaMoO4:Na+,Eu3+nanophosphors exhibit red emission at peak wavelength of 615 nm and quantum yield of up to 35.01%.The CaMoO4:Na+,Tb3+nanophosphors exhibit green emission at peak wavelength of543 nm with quantum yield of up to 30.66%.The morphologies of the nanophosphors are tunable from nanofibers through nanorods to nanodots and the possible mechanism of controlling the formation of different nanostructures is proposed on the basis of experimental results and theoretical analysis of mesoscience.These nanophosphors are highly dispersible in organic solvents and utilized for fabricating fabrication of flexible,freestanding luminescent films based on silicone resin.We also demonstrate the red LEDs consisting of the hybrid films of CaMoO4:Na+,Eu3+nanoparticles as color-converting phosphors and DUV LEDs as illuminators,offering strong potential for future nanophosphors-basedsolid-state lighting systems.展开更多
We have synthesized a series of single-composition emission Na_2Sr_2Al_2PO_4Cl_9:Ce^(3+) phosphor by traditional solid state reactions and novel combustion method. Formation of compound was confirmed by X-ray diffract...We have synthesized a series of single-composition emission Na_2Sr_2Al_2PO_4Cl_9:Ce^(3+) phosphor by traditional solid state reactions and novel combustion method. Formation of compound was confirmed by X-ray diffraction analysis. The photoluminescence(PL) emission spectra were observed at 376 nm when excited around 322 nm for the various concentrations in both cases. The PL emission spectra of phosphors showed strong Ce^(3+)emission due to the 5d → 4f transition of Ce^(3+)ions. The Ce^(3+)emission intensity in Na_2Sr_2Al_2PO_4Cl_9:Ce^(3+) prepared by combustion was higher than that of solid state reactions.展开更多
Cerium and europium codoped yttrium aluminum garnet（YAG：Ce,Eu） nanophosphors were prepared by sol-gel method.We systematically explored the structure,composition,morphology and photoluminescence（PL） properties by...Cerium and europium codoped yttrium aluminum garnet（YAG：Ce,Eu） nanophosphors were prepared by sol-gel method.We systematically explored the structure,composition,morphology and photoluminescence（PL） properties by using X-ray diffraction,scanning electron microscope,high resolution transmission electron microscope,energy dispersive spectrometer,photoluminescence emission and excitation spectra techniques,and focused on clarifying the change of local structure surrounding Ce^3＋ ions by utilizing advanced quantitative ^27Al magic angle spinning nuclear magnetic resonance spectroscopy.The results show that the lattice constant slightly increases as the Ce^3＋ and Eu^3＋ ions incorporate,and the geometric distortion of local structure surrounding Ce^（3＋） activator introduced by the incorporated Eu^（3＋） coactivator causes the variation of crystal field,which results in red shift of Ce^3＋ PL emitting in YAG：Ce,Eu nanophosphor.Furthermore,the YAG：Ce,Eu nanophosphors could exhibit several sharp and narrow ^5D0 → ^7FJ（J = 1-4） emissions of Eu^3＋ ion besides the classic broad ^5d1 → ^4f（^2F（5/2）,^2F（7/2）） emissions of Ce^3＋ ion under near ultraviolet（UV） excitation.展开更多
A series of Sr_(2)MgSi_(2)O_(7):Tb^(3+)nanophosphors is prepared using a high-temperature solid-state reaction.The x-ray diffraction patterns show that the crystal structure of the sample is not significantly affected...A series of Sr_(2)MgSi_(2)O_(7):Tb^(3+)nanophosphors is prepared using a high-temperature solid-state reaction.The x-ray diffraction patterns show that the crystal structure of the sample is not significantly affected by Tb^(3+)ions.However,the images of the scanning electron microscope illustrate that the average size of nanoparticles becomes larger with the increase of Tb^(3+)concentration.Unlike earlier investigations on down-conversion emission of Tb^(3+)ion excited by deep ultraviolet light,in this work,the photoluminescence characteristics of Sr_(2)MgSi_(2)O_(7)nanophosphors doped with different Tb^(3+)concentrations are analyzed under 374-nm excitations.The intense green emission at 545 nm is observed at an optimal doping concentration of 1.6 mol%.The main reason for the concentration quenching is due to the electric dipole-electric dipole interaction among Tb^(3+)ions.展开更多
In this report, five systems of varied diameters viz. 62 nm, 85 nm, 115 nm, 160 nm and 450 nm of BaMgAl10O17:Eu2+ nanorods are prepared by solution combustion approach and with annealing at different temperature in re...In this report, five systems of varied diameters viz. 62 nm, 85 nm, 115 nm, 160 nm and 450 nm of BaMgAl10O17:Eu2+ nanorods are prepared by solution combustion approach and with annealing at different temperature in reduced atmosphere (N2 + H2). An intense broad blue photoluminescence (PL), corresponding to the electronic transition of Eu2+ from the 4f 6 5d excited state to the 4f 7 ground state, is observed. The blue-shift and enhanced photoluminescence is also observed, and found to be highly dependent on the size of diameter of BaMgAl10O17:Eu2+ nanostructures. The change in decay time and color-coordinates with change in size of diameter of BaMgAl10O17:Eu2+ nanostructure have been analysed and thoroughly discussed.展开更多
The envisaged design and developme nt of individual mate rials to excavate a broader spectrum of desired properties and offer multiple applications are highly necessitating.Keeping this in mind,a series of forsterite-...The envisaged design and developme nt of individual mate rials to excavate a broader spectrum of desired properties and offer multiple applications are highly necessitating.Keeping this in mind,a series of forsterite-structured Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors was synthesized via a solution combustion method using oxalyl dihydrazide as a fuel.The X-ray diffraction patterns confirm the orthorhombic crystal system with a Puma space group.Morphological results clearly show irregularly shaped cluster-like structures with aggregation of the particles.Employing diffuse reflectance spectra,the optical energy band gap of the Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors was estimated and obtained to be~4.12-4.32 eV.The photoluminescence emission spectra exhibit intense peaks at^(5)79,589,610,661,and 707 nm,which are due to characteristic^(5)D_(0)→^(7)F_(0),^(5)D_(0)→^(7)F_(1),^(5)Do→^(7)F_(2),^(5)D_(0)→^(7)F_(3)and^(5)D_(0)→^(7)F_(4)transitions of Eu^(3+)ions,respectively.The Commission International de L'Eclairage color coordinates are gradually tuned from pale red(0.5980,0.4012)to a pure red(0.6385,0.3611)region.Thermoluminescence glow peaks showcase excellent super-linear response at low doses ofγ-irradiations,indicating that the prepared phosphor can be used in thermoluminescent personal dosimetry which is a biological tissue equivalent.The aforementioned results demonstrate that the prepared Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors are considered an excellent candidate for dual applications,i.e.,red component in future generation white-light-emitting diodes(WLEDs)and personal dosimetric applications.展开更多
This review focused on rare earth upconversion nanophosphors (UCNPs), a particular class of emitters whose photoluminescence mechanism is of fundamental difference from that of conventional dyes and semiconductor quan...This review focused on rare earth upconversion nanophosphors (UCNPs), a particular class of emitters whose photoluminescence mechanism is of fundamental difference from that of conventional dyes and semiconductor quantum dots. We in the first section gave a brief summary on a variety of synthetic methodologies developed during the past decades. Instead of presenting an exhaustive reference list, we selected only a few representative examples, illustrating the merits and limits of each involved synthetic route. Then we surveyed the recent progress in the functionalization techniques for these nanomaterials, depicting the modification in microstructures and improvement in properties with respect to the parent nanoparticles. And finally, we emphasized their application in the research fields of biolabeling and energy transfer, narrating their superior performance benefiting from the unique excitation and emission properties.展开更多
Eu3＋ doped Gd2WO6 and Gd2（WO4）3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray dif...Eu3＋ doped Gd2WO6 and Gd2（WO4）3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction （XRD） and field emission scanning electron microscopy （FE-SEM）, respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3＋ 5D0 energy level were calculated, and the concentration quenching of Eu3＋ luminescence in different matrixes were studied. The results indicated that effective Eu3＋：5D0-7F2 red luminescence could be achieved while excited by 395 nm near-UV light and 465 nm blue light in Gd2WO6 host, which was similar to the familiar Gd2（WO4）3：Eu. Therefore, the Gd2WO6：Eu red phosphors might have a potential application for white LED.展开更多
β-NaYFa：Yb,Er upconversion nanophosphor （UCNP） is known as one of the most efficient NIR-to-visible upconversion mate- dais, which shows great potential in bioanalytical chemistry and bioimaging. However, its appl...β-NaYFa：Yb,Er upconversion nanophosphor （UCNP） is known as one of the most efficient NIR-to-visible upconversion mate- dais, which shows great potential in bioanalytical chemistry and bioimaging. However, its applications are greatly limited due to its low water dispersibility and thus poor biocompatibility. In this paper, poly（acrylic acid） （PAA）-based ligand exchange strategies are carded out to modify oleic acid-capped hydrophobic β-NaYF4：Yb,Er UCNPs into hydrophilic ones. After efficient surface modification, the presence of free carboxylic acid groups on the surfaces of UCNPs results in high solubility in water, and also allows further conjugation with NH2-containing biomolecules. Facilitated by the covalent linkage between the -COOH groups on UCNPs surfaces and -NHz groups in antigen/antibody, a sensitive immunosensor is constructed by using PAA-functionalized β-NaYFa：Yb,Er UCNPs as biolabels. Through monitoring the upconversion fluorescence intensity or fluorescent imaging of the final immunocomplexes, high sensitivity is achieved for the proposed immunoassay and as low as 0.1 ng/mL goat anti-human immunoglobulin G （IgG） can be detected, which suggests that PAA-modified UCNPs may serve as an ideal candidate for use as bioanalysis and bioimaging probes.展开更多
Gd2O3:Er^3+nanophosphors were fabricated by the combustion method in presence of Na2 ethylene diamine tetra acetic acid(EDTA-Na2)as fuel at not high temperature(≤350℃)within a very short time of 5 min.The added conc...Gd2O3:Er^3+nanophosphors were fabricated by the combustion method in presence of Na2 ethylene diamine tetra acetic acid(EDTA-Na2)as fuel at not high temperature(≤350℃)within a very short time of 5 min.The added concentration of Er^3+ions in Gd2O3 matrix was changed from 0.5 mol%to 5.0 mol%.The X-ray diffraction pattern of samples indicates the monoclinic structure of Gd2O3:Er^3+.The morphology and chemical composition analysis of the Gd2O3:Er^3+samples are characterized by a field emission scanning electron microscope(FESEM)and a Fourier-transform infrared spectrometer(FTIR).The photoluminescence(PL),photo luminescence excitation(PLE)and upconversion(UC)at room temperature of the prepared materials with different concentrations of Er^3+were investigated.The PL of Gd2O3:Er^3+nanomaterials are shown in visible at 545,594,623,648,688 nm under excitation at 275 nm.The emission bands from transitions of Er^3+from 2P3/2 to 4F9/2 are observed,UC luminescent spectra of the Gd2O3:Er^3+/silica nanocomposites under 976 nm excitation show the bands at 548 and 670 nm.The influence of excitation power at 980 nm for transitions were measured and calculated.The results indicate that the upconversion process of Gd2O3:Er^3+/silica is two photons absorption mechanism.The low temperature dependence of UC luminescent intensities of the main bands of Gd2O3:Er^3+was investigated towards development of a nanotemperature sensor in the range of 10-300 K.展开更多
Y1-xEuxBO3 nanophosphors were synthesized by a modified co-precipitation method. The structure of the obtained nanocrystals was determined by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The...Y1-xEuxBO3 nanophosphors were synthesized by a modified co-precipitation method. The structure of the obtained nanocrystals was determined by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The average crystallite size was calculated from the full-width at half-maximum （FWHM） of the diffraction peaks by the Scherrer equation. The average particles size was 25±10 nm. The spectroscopic properties of the Y1-xEuxBO3 nanoborates were characterized by excitation and emission spectra under UV and VUV excitation. In order to improve colour purity, the chromaticity coordinates were also calculated.展开更多
Tb3＋ and Yb3＋ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3：Tb3＋,Yb3＋ nanophosphors were characterized by X-ray diffraction （XRD） and photolumine...Tb3＋ and Yb3＋ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3：Tb3＋,Yb3＋ nanophosphors were characterized by X-ray diffraction （XRD） and photoluminescence （PL） spectra. The XRD results showed that all the prepared nanophosphors could be readily indexed to pure cubic phase of Lu2O3 and indicated good crystallinity. The Tb3＋→Yb3＋ energy transfer mechanisms in the UV-blue region in Lu2O3 nanophosphors were investigated. The experimental results showed that the strong visible emission around 543 nm from Tb3＋ （5D4→7F5） and near-infrared （NIR） emission around 973 nm from Yb3＋ （2F5/2→2F7/2） of Lu2O3：Tb3＋,Yb3＋ nanophosphors were observed under ultraviolet light excitation, respectively. Tb3＋ could be effectively excited up to its 4f75d1 state and relaxed down to the 5D4 level, from which the energy was transferred cooperatively to two neighboring Yb3＋. The Yb3＋ concentration dependent luminescent properties and lifetimes of both the visible and NIR emissions were also studied. The lifetime of the visible emission decreased with the increase of Yb3＋ concentration, verifying the efficient energy transfer from the Tb3＋ to the Yb3＋. Cooperative energy transfer （CET） from Tb3＋ to Yb3＋ was discussed as a possible mechanism for the near-infrared emission. When doped concentrations were 1 mol.% Tb3＋ and 2 mol.% Yb3＋, the intensity of NIR emission was the strongest.展开更多
Novel nanosized Y2WO6：Eu3＋ phosphors were synthesized via a co-precipitation reaction. The crystal structure of Y2WO6：Eu3＋sample was monoclinic phase characterized by using X-ray diffraction （XRD）. The particle ...Novel nanosized Y2WO6：Eu3＋ phosphors were synthesized via a co-precipitation reaction. The crystal structure of Y2WO6：Eu3＋sample was monoclinic phase characterized by using X-ray diffraction （XRD）. The particle size was about 80 nm ob-served by field emission scanning electron microscopy （FE-SEM）. The photoluminescence properties of Y2WO6：Eu3＋nanophos-phors were studied. The results indicated that Eu3＋ 5D0→7F2 red luminescence at 611 nm could be effectively excited by 394 nm near-UV light and 465 nm blue light in Y2WO6 host. The luminescence intensity was the strongest while the Eu3＋doping concentra-tion was 20%. And the chromaticity coordinates of this concentration is （0.651, 0.348）. The energy transfer type between the Eu3＋was determined to be the exchange interaction and the critical energy transfer distance （Dc） was calculated to be about 0.81 ang-strom. The J-O parameters, quantum efficiencies of Eu3＋ 5D0 energy level and Huang-Rhys factor of Y2WO6：Eu3＋nanophosphors were calculated. The calculated values indicated that Y2WO6：Eu3＋had a high capacity for activators and the electron-phonon cou-pling was weak. Therefore, the Y2WO6：Eu3＋nanophosphor is a nice red luminescent material and it may have a potential applica-tion in white LED.展开更多
The influence of different solvents and metal ions （Li^＋, Ba^2＋, Bi^3＋） on the crystallization behaviour, morphology and enhancement in photoluminescence intensity of Dy^3＋ doped CePO4 were investigated. Highly ...The influence of different solvents and metal ions （Li^＋, Ba^2＋, Bi^3＋） on the crystallization behaviour, morphology and enhancement in photoluminescence intensity of Dy^3＋ doped CePO4 were investigated. Highly crystalline luminescent nanophosphors of CePO4：DY^3＋ re-dispersible in polar solvents were successfully prepared via a simple polyol route at 140 ℃. As-prepared Dy^3＋ doped CePO4 nanophosphors prepared in EG and DMF appeared to have crystalline monoclinic phase but exhibited hexagonal phase when prepared in water and water mixed solvents, The hexagonal phase transformed to monoclinic phase after heating at 900 ℃. TEM study revealed different shapes of the synthesized nanophosphors with change of solvents. The luminescence intensity of 4F9/2→6H15/2 at 478 nm （blue） was found to be more prominent than 4F9/2→6H13/2 at 572 nm （yellow）. The introduction of metal ions （Li＋, Ba2＋ and Bi3＋） in CePO4：Dy3＋ led to considerable luminescent enhancement. The nanophosphors were subsequently incorporated in polymer films of PVA which showed the characteristic emissions of Dy3＋. It also served as an effective method to improve the performance of polymer materials and brought about novel properties in them.展开更多
The blue-emitting YPO4 phosphors doped with Yb3＋ were prepared by a simple hydrothermal method. All the products were characterized by XRD and TEM, which revealed that they were zircon structure with leaf-like morpho...The blue-emitting YPO4 phosphors doped with Yb3＋ were prepared by a simple hydrothermal method. All the products were characterized by XRD and TEM, which revealed that they were zircon structure with leaf-like morphology. According to the analysis of photoluminescence spectra, upon ultraviolet （275 nm） excitation, the Yb3＋ doped YPO4 phosphor showed an intense blue emission composed of two main bands at 420 and 620 nm assigned to charge transfer state （CTS） → 2Fs/2 and CTS →ZF7/2, respectively. Moreover, the optimum doping concentration of Yb3＋ in YPO4 phosphor was 1%, which exhibited the maximum emission intensity. The possible physical mechanism of concentration quenching was discussed, and the critical transfer distance determined to be 23.889 A. In particular, the color purity of the as-synthesized Yb3＋ doped YPO4 phosphor was as high as 83%, which made it an excellent candidate for blue-emitting materials.展开更多
To explore the silicate lattice-based nanophosphors, a series of Eu3+-doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) materials were prepared by sol–gel procedure. The metal nitrates and silica powder were used as precurso...To explore the silicate lattice-based nanophosphors, a series of Eu3+-doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) materials were prepared by sol–gel procedure. The metal nitrates and silica powder were used as precursor components for the synthesis of these luminescent materials. Photoluminescence(PL) emission spectra, powder X-ray diffraction(PXRD), energy-dispersive X-ray spectroscopy(EDS), Fourier transform infrared spectroscopy(FTIR) and transmission electron microscopy(TEM)spectroscopic techniques were applied for the characterization of the fabricated materials. Three peaks were observed at 589, 613 and 650–652 nm corresponding to ^(5)D_(0)→^(7)F_(1-3) transition in PL emission spectra. Upon395 nm excitation and at 0.03 mol Eu3+, these nanophosphors displayed optimum photoluminescence with the most intense peak analogous to ^(5)D_(0)→^(7)F_(2)transition of dopant ion. The as-prepared phosphor materials were re-heated at1050 and 1150 ℃ to observe the consequences of higher temperatures on the emission intensity and crystal lattice.XRD analysis confirmed that all the synthesized materials were of crystalline nature, and the crystallinity was observed to be improved by increasing the temperature. In the FTIR spectrum, peaks at 483 and 610 cm^(-1) proved the existence of SiO_(4)group in Ca_(2)Si_(3)O_(8), and the peak centered at 417 cm^(-1) confirmed the presence of MgO6 octahedral in Mg_(2)Si_(3)O_(8) materials. TEM images were used to determine the particle size(13–35 nm) and to study the threedimensional structure of nanophosphor materials. The experimental studies indicate that these materials may be promising as red-emitting nanophosphors for white lightemitting diodes.展开更多
This work presents the synthesis of Y_(2)O_(3):Eu^(3+),χCa^(2+)(χ=0 mol%,1 mol%,3 mol%,5 mol%,7 mol%,9 mol%,11 mol%)nanophosphors with enhanced photoluminescence properties through a facile solution combustion metho...This work presents the synthesis of Y_(2)O_(3):Eu^(3+),χCa^(2+)(χ=0 mol%,1 mol%,3 mol%,5 mol%,7 mol%,9 mol%,11 mol%)nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic,display,and lighting applications.The X-ray diffraction(XRD)patterns of the proposed nanophosphor reveal its structural properties and crystalline nature.The transmission electron microscope(TEM)results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca^(2+).Fourier transform infrared spectroscopy(FTIR)and Raman vibrations also confirm the presence of Y-O vibration and subsequently explain the crystalline nature,structural properties,and purity of the samples.All the synthesized nanophosphors samples emit intense red emission at 613 nm(~5D_(0)→~7 F_(2))under excitation with 235,394 and 466 nm wavelengths of Eu^(3+)ions.The photoluminescence(PL)emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength,respectively.The emission intensity of Y_(2)O_(3):Eu^(3+),χCa^(2+)(5 mol%)is increased 8-fold as compared to Eu:Y_(2)O_(3).Doping with Ca^(2+)ions enhances the emission intensity of Eu:Y_(2)O_(3)nanopho sphors due to an increase in energy transfer in Ca^(2+)→Eu^(3+)through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix.It is also observed that the optical band gap and the lifetime of the~5D_(0)level of Eu^(3+)ions in Y_(2)O_(3):Eu^(3+),xCa^(2+)nanophosphor sample gets changed with a doping conce ntration of Ca^(2+)ions.Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%,respectively.CIE,CCT,and color purity values(>98%)show an improved red-emitting nanophosphor in the warm region of light,which makes this mate rial superior with a specific potential application for UV-based white LEDs with security ink,display devices,and various other optoelectronics devices.展开更多
基金Shanghai Academic Research Leader,China(No.20XD1420200)Shanghai Shuguang Program,China(No.18SG29)。
文摘Hydrophilic rare-earth up-conversion nanophosphors(UCNPs)with small sizes and a strong up-conversion luminescence have attracted much interest.Herein the simultaneous control of morphologies and the up-conversion luminescence intensities was reported for NaYF_(4)∶Yb/Er nanophosphors by a facile hydrothermal procedure with different surfactants.With the change of the surfactants from polyvinylpyrrolidone(PVP)to sodium citrate(CIT),edetate disodium(EDTA)or sodium dodecyl benzenesulfonate(SDBS),the morphology of NaYF_(4)∶Yb/Er nanophosphors transformed from nanoparticles with a diameter of about 70.0 nm to hexagonal nanoblocks with a thickness of about 125.0 nm and a length of about 240.0 nm,nanorods with a diameter of about 700.0 nm and a length of about 2.6μm,or nanowires with a diameter of 250.0 nm and a length of about 3.2μm.Simultaneously,their up-conversion luminescence intensity went down gradually under laser irradiation at a wavelength of 980 nm due to the increase of photobleaching.PVP-capped NaYF_(4)∶Yb/Er nanoparticles exhibited the smallest size and the strongest up-conversion luminescence intensity.Biological experiment results revealed that NaYF_(4)∶Yb/Er nanophosphors exhibited a high biocompatibility and could be used as biological labels with a perfect signal-to-noise ratio for cancer cell imaging.
文摘Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ （CZTOPN） was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti（OC4H9）4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis （TG-DSC）, powder X-ray diffraction （XRD）, and scan election microscopy （SEM）. Results of TG-DSC and XRD reveal that the composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.
基金financial support from the National Key Research and Development Program of China(2017YFB0404302/2017YFB0404300)National Natural Science Foundation of China(21808009,91934303)the Beijing Natural Science Foundation(2182051)。
文摘In this work,we report an innovative route for the synthesis of rare-earth doped calcium molybdate(CaMoO4)nanophosphors by using high gravity rotating packed bed(RPB)technology and paraffin liquid as the solvent.The significant intensified mass transfer and micromixing of reactants in the RPB reactor are benefiting for homogeneous doping of rare-earth ions in the host materials,leading to nanophosphors with high quantum efficiency.The use of liquid paraffin as the solvent eliminates the safety risks associated with volatile organic compounds,increasing the potential for clean production of nanophosphors.Under excitation of deep ultraviolet(DUV)light,the CaMoO4:Na+,Eu3+nanophosphors exhibit red emission at peak wavelength of 615 nm and quantum yield of up to 35.01%.The CaMoO4:Na+,Tb3+nanophosphors exhibit green emission at peak wavelength of543 nm with quantum yield of up to 30.66%.The morphologies of the nanophosphors are tunable from nanofibers through nanorods to nanodots and the possible mechanism of controlling the formation of different nanostructures is proposed on the basis of experimental results and theoretical analysis of mesoscience.These nanophosphors are highly dispersible in organic solvents and utilized for fabricating fabrication of flexible,freestanding luminescent films based on silicone resin.We also demonstrate the red LEDs consisting of the hybrid films of CaMoO4:Na+,Eu3+nanoparticles as color-converting phosphors and DUV LEDs as illuminators,offering strong potential for future nanophosphors-basedsolid-state lighting systems.
文摘We have synthesized a series of single-composition emission Na_2Sr_2Al_2PO_4Cl_9:Ce^(3+) phosphor by traditional solid state reactions and novel combustion method. Formation of compound was confirmed by X-ray diffraction analysis. The photoluminescence(PL) emission spectra were observed at 376 nm when excited around 322 nm for the various concentrations in both cases. The PL emission spectra of phosphors showed strong Ce^(3+)emission due to the 5d → 4f transition of Ce^(3+)ions. The Ce^(3+)emission intensity in Na_2Sr_2Al_2PO_4Cl_9:Ce^(3+) prepared by combustion was higher than that of solid state reactions.
基金Financial support from the NNSF of China(No.51171007 and 51271009)
文摘Cerium and europium codoped yttrium aluminum garnet（YAG：Ce,Eu） nanophosphors were prepared by sol-gel method.We systematically explored the structure,composition,morphology and photoluminescence（PL） properties by using X-ray diffraction,scanning electron microscope,high resolution transmission electron microscope,energy dispersive spectrometer,photoluminescence emission and excitation spectra techniques,and focused on clarifying the change of local structure surrounding Ce^3＋ ions by utilizing advanced quantitative ^27Al magic angle spinning nuclear magnetic resonance spectroscopy.The results show that the lattice constant slightly increases as the Ce^3＋ and Eu^3＋ ions incorporate,and the geometric distortion of local structure surrounding Ce^（3＋） activator introduced by the incorporated Eu^（3＋） coactivator causes the variation of crystal field,which results in red shift of Ce^3＋ PL emitting in YAG：Ce,Eu nanophosphor.Furthermore,the YAG：Ce,Eu nanophosphors could exhibit several sharp and narrow ^5D0 → ^7FJ（J = 1-4） emissions of Eu^3＋ ion besides the classic broad ^5d1 → ^4f（^2F（5/2）,^2F（7/2）） emissions of Ce^3＋ ion under near ultraviolet（UV） excitation.
基金Project supported by the National Natural Science Foundation of China(Grant No.11004092)the Foundation of Science and Technology Department of Liaoning Province,China(Grant No.201602455)。
文摘A series of Sr_(2)MgSi_(2)O_(7):Tb^(3+)nanophosphors is prepared using a high-temperature solid-state reaction.The x-ray diffraction patterns show that the crystal structure of the sample is not significantly affected by Tb^(3+)ions.However,the images of the scanning electron microscope illustrate that the average size of nanoparticles becomes larger with the increase of Tb^(3+)concentration.Unlike earlier investigations on down-conversion emission of Tb^(3+)ion excited by deep ultraviolet light,in this work,the photoluminescence characteristics of Sr_(2)MgSi_(2)O_(7)nanophosphors doped with different Tb^(3+)concentrations are analyzed under 374-nm excitations.The intense green emission at 545 nm is observed at an optimal doping concentration of 1.6 mol%.The main reason for the concentration quenching is due to the electric dipole-electric dipole interaction among Tb^(3+)ions.
文摘In this report, five systems of varied diameters viz. 62 nm, 85 nm, 115 nm, 160 nm and 450 nm of BaMgAl10O17:Eu2+ nanorods are prepared by solution combustion approach and with annealing at different temperature in reduced atmosphere (N2 + H2). An intense broad blue photoluminescence (PL), corresponding to the electronic transition of Eu2+ from the 4f 6 5d excited state to the 4f 7 ground state, is observed. The blue-shift and enhanced photoluminescence is also observed, and found to be highly dependent on the size of diameter of BaMgAl10O17:Eu2+ nanostructures. The change in decay time and color-coordinates with change in size of diameter of BaMgAl10O17:Eu2+ nanostructure have been analysed and thoroughly discussed.
基金Project supported by the Department of Science&Technology(DST)(Science and Engineering Research Board(SERB)-Core Research Grant(CRG))Government of India(CRG/2020/006446)。
文摘The envisaged design and developme nt of individual mate rials to excavate a broader spectrum of desired properties and offer multiple applications are highly necessitating.Keeping this in mind,a series of forsterite-structured Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors was synthesized via a solution combustion method using oxalyl dihydrazide as a fuel.The X-ray diffraction patterns confirm the orthorhombic crystal system with a Puma space group.Morphological results clearly show irregularly shaped cluster-like structures with aggregation of the particles.Employing diffuse reflectance spectra,the optical energy band gap of the Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors was estimated and obtained to be~4.12-4.32 eV.The photoluminescence emission spectra exhibit intense peaks at^(5)79,589,610,661,and 707 nm,which are due to characteristic^(5)D_(0)→^(7)F_(0),^(5)D_(0)→^(7)F_(1),^(5)Do→^(7)F_(2),^(5)D_(0)→^(7)F_(3)and^(5)D_(0)→^(7)F_(4)transitions of Eu^(3+)ions,respectively.The Commission International de L'Eclairage color coordinates are gradually tuned from pale red(0.5980,0.4012)to a pure red(0.6385,0.3611)region.Thermoluminescence glow peaks showcase excellent super-linear response at low doses ofγ-irradiations,indicating that the prepared phosphor can be used in thermoluminescent personal dosimetry which is a biological tissue equivalent.The aforementioned results demonstrate that the prepared Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors are considered an excellent candidate for dual applications,i.e.,red component in future generation white-light-emitting diodes(WLEDs)and personal dosimetric applications.
基金Project supported by the National Natural Science Foundation of China (20821091, 20971005, 20731160001, and 20931160429)Ministry of Science and Technology of China (2006CB601104)
文摘This review focused on rare earth upconversion nanophosphors (UCNPs), a particular class of emitters whose photoluminescence mechanism is of fundamental difference from that of conventional dyes and semiconductor quantum dots. We in the first section gave a brief summary on a variety of synthetic methodologies developed during the past decades. Instead of presenting an exhaustive reference list, we selected only a few representative examples, illustrating the merits and limits of each involved synthetic route. Then we surveyed the recent progress in the functionalization techniques for these nanomaterials, depicting the modification in microstructures and improvement in properties with respect to the parent nanoparticles. And finally, we emphasized their application in the research fields of biolabeling and energy transfer, narrating their superior performance benefiting from the unique excitation and emission properties.
基金Project supported by the National Natural Science Foundation of China (51002041)High and New Technique Project of Heilongjiang Province, China (GZ09A405)Science and Technology Research Project of Education Bureau of Heilongjiang Province, China (12511139)
文摘Eu3＋ doped Gd2WO6 and Gd2（WO4）3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction （XRD） and field emission scanning electron microscopy （FE-SEM）, respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3＋ 5D0 energy level were calculated, and the concentration quenching of Eu3＋ luminescence in different matrixes were studied. The results indicated that effective Eu3＋：5D0-7F2 red luminescence could be achieved while excited by 395 nm near-UV light and 465 nm blue light in Gd2WO6 host, which was similar to the familiar Gd2（WO4）3：Eu. Therefore, the Gd2WO6：Eu red phosphors might have a potential application for white LED.
基金supported by the National Natural Science Foundation of China (20925519 & 20875021)the Natural Science Foun-dation of Hebei Province (B2009001525 & B2010000202)the China Postdoctoral Science Foundation (20100470985)
文摘β-NaYFa：Yb,Er upconversion nanophosphor （UCNP） is known as one of the most efficient NIR-to-visible upconversion mate- dais, which shows great potential in bioanalytical chemistry and bioimaging. However, its applications are greatly limited due to its low water dispersibility and thus poor biocompatibility. In this paper, poly（acrylic acid） （PAA）-based ligand exchange strategies are carded out to modify oleic acid-capped hydrophobic β-NaYF4：Yb,Er UCNPs into hydrophilic ones. After efficient surface modification, the presence of free carboxylic acid groups on the surfaces of UCNPs results in high solubility in water, and also allows further conjugation with NH2-containing biomolecules. Facilitated by the covalent linkage between the -COOH groups on UCNPs surfaces and -NHz groups in antigen/antibody, a sensitive immunosensor is constructed by using PAA-functionalized β-NaYFa：Yb,Er UCNPs as biolabels. Through monitoring the upconversion fluorescence intensity or fluorescent imaging of the final immunocomplexes, high sensitivity is achieved for the proposed immunoassay and as low as 0.1 ng/mL goat anti-human immunoglobulin G （IgG） can be detected, which suggests that PAA-modified UCNPs may serve as an ideal candidate for use as bioanalysis and bioimaging probes.
基金Project supported by the Vietnam National Foundation for Science and Technology Development(NAFOSTED)(103.03-2015.85)
文摘Gd2O3:Er^3+nanophosphors were fabricated by the combustion method in presence of Na2 ethylene diamine tetra acetic acid(EDTA-Na2)as fuel at not high temperature(≤350℃)within a very short time of 5 min.The added concentration of Er^3+ions in Gd2O3 matrix was changed from 0.5 mol%to 5.0 mol%.The X-ray diffraction pattern of samples indicates the monoclinic structure of Gd2O3:Er^3+.The morphology and chemical composition analysis of the Gd2O3:Er^3+samples are characterized by a field emission scanning electron microscope(FESEM)and a Fourier-transform infrared spectrometer(FTIR).The photoluminescence(PL),photo luminescence excitation(PLE)and upconversion(UC)at room temperature of the prepared materials with different concentrations of Er^3+were investigated.The PL of Gd2O3:Er^3+nanomaterials are shown in visible at 545,594,623,648,688 nm under excitation at 275 nm.The emission bands from transitions of Er^3+from 2P3/2 to 4F9/2 are observed,UC luminescent spectra of the Gd2O3:Er^3+/silica nanocomposites under 976 nm excitation show the bands at 548 and 670 nm.The influence of excitation power at 980 nm for transitions were measured and calculated.The results indicate that the upconversion process of Gd2O3:Er^3+/silica is two photons absorption mechanism.The low temperature dependence of UC luminescent intensities of the main bands of Gd2O3:Er^3+was investigated towards development of a nanotemperature sensor in the range of 10-300 K.
基金Project supported by the Polish Ministry of Science and Higher Education (N N204 089838)the Estonian Science Foundation (grant 8893)the European Community Research Infrastructure Action under the FP6 Structuring the European Research Area Programme (through the Integrated Infrastructure Initiative Integrating Activity on Synchrotron and Free Electron Laser Science)
文摘Y1-xEuxBO3 nanophosphors were synthesized by a modified co-precipitation method. The structure of the obtained nanocrystals was determined by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The average crystallite size was calculated from the full-width at half-maximum （FWHM） of the diffraction peaks by the Scherrer equation. The average particles size was 25±10 nm. The spectroscopic properties of the Y1-xEuxBO3 nanoborates were characterized by excitation and emission spectra under UV and VUV excitation. In order to improve colour purity, the chromaticity coordinates were also calculated.
基金Project supported by National Natural Science Foundation of China (10774140, 11047147, 11074245, 11011120083)Knowledge Innovation Project of The Chinese Academy of Sciences (KJCX2-YW-M11)the Natural Science Foundation of Chongqing Municipal Education Commission (KJTD201016, KJ090514)
文摘Tb3＋ and Yb3＋ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3：Tb3＋,Yb3＋ nanophosphors were characterized by X-ray diffraction （XRD） and photoluminescence （PL） spectra. The XRD results showed that all the prepared nanophosphors could be readily indexed to pure cubic phase of Lu2O3 and indicated good crystallinity. The Tb3＋→Yb3＋ energy transfer mechanisms in the UV-blue region in Lu2O3 nanophosphors were investigated. The experimental results showed that the strong visible emission around 543 nm from Tb3＋ （5D4→7F5） and near-infrared （NIR） emission around 973 nm from Yb3＋ （2F5/2→2F7/2） of Lu2O3：Tb3＋,Yb3＋ nanophosphors were observed under ultraviolet light excitation, respectively. Tb3＋ could be effectively excited up to its 4f75d1 state and relaxed down to the 5D4 level, from which the energy was transferred cooperatively to two neighboring Yb3＋. The Yb3＋ concentration dependent luminescent properties and lifetimes of both the visible and NIR emissions were also studied. The lifetime of the visible emission decreased with the increase of Yb3＋ concentration, verifying the efficient energy transfer from the Tb3＋ to the Yb3＋. Cooperative energy transfer （CET） from Tb3＋ to Yb3＋ was discussed as a possible mechanism for the near-infrared emission. When doped concentrations were 1 mol.% Tb3＋ and 2 mol.% Yb3＋, the intensity of NIR emission was the strongest.
基金Project supported by National Natural Science Foundation of China(51002041)Foundation for Young Key Scholars of Higher Education Institution of Heilongjiang Province(1252G032)Foundation for Young Key Scholars of Harbin Normal University(11KXQ-06)for financial support
文摘Novel nanosized Y2WO6：Eu3＋ phosphors were synthesized via a co-precipitation reaction. The crystal structure of Y2WO6：Eu3＋sample was monoclinic phase characterized by using X-ray diffraction （XRD）. The particle size was about 80 nm ob-served by field emission scanning electron microscopy （FE-SEM）. The photoluminescence properties of Y2WO6：Eu3＋nanophos-phors were studied. The results indicated that Eu3＋ 5D0→7F2 red luminescence at 611 nm could be effectively excited by 394 nm near-UV light and 465 nm blue light in Y2WO6 host. The luminescence intensity was the strongest while the Eu3＋doping concentra-tion was 20%. And the chromaticity coordinates of this concentration is （0.651, 0.348）. The energy transfer type between the Eu3＋was determined to be the exchange interaction and the critical energy transfer distance （Dc） was calculated to be about 0.81 ang-strom. The J-O parameters, quantum efficiencies of Eu3＋ 5D0 energy level and Huang-Rhys factor of Y2WO6：Eu3＋nanophosphors were calculated. The calculated values indicated that Y2WO6：Eu3＋had a high capacity for activators and the electron-phonon cou-pling was weak. Therefore, the Y2WO6：Eu3＋nanophosphor is a nice red luminescent material and it may have a potential applica-tion in white LED.
基金Project supported by Department of Science and Technology of India
文摘The influence of different solvents and metal ions （Li^＋, Ba^2＋, Bi^3＋） on the crystallization behaviour, morphology and enhancement in photoluminescence intensity of Dy^3＋ doped CePO4 were investigated. Highly crystalline luminescent nanophosphors of CePO4：DY^3＋ re-dispersible in polar solvents were successfully prepared via a simple polyol route at 140 ℃. As-prepared Dy^3＋ doped CePO4 nanophosphors prepared in EG and DMF appeared to have crystalline monoclinic phase but exhibited hexagonal phase when prepared in water and water mixed solvents, The hexagonal phase transformed to monoclinic phase after heating at 900 ℃. TEM study revealed different shapes of the synthesized nanophosphors with change of solvents. The luminescence intensity of 4F9/2→6H15/2 at 478 nm （blue） was found to be more prominent than 4F9/2→6H13/2 at 572 nm （yellow）. The introduction of metal ions （Li＋, Ba2＋ and Bi3＋） in CePO4：Dy3＋ led to considerable luminescent enhancement. The nanophosphors were subsequently incorporated in polymer films of PVA which showed the characteristic emissions of Dy3＋. It also served as an effective method to improve the performance of polymer materials and brought about novel properties in them.
文摘The blue-emitting YPO4 phosphors doped with Yb3＋ were prepared by a simple hydrothermal method. All the products were characterized by XRD and TEM, which revealed that they were zircon structure with leaf-like morphology. According to the analysis of photoluminescence spectra, upon ultraviolet （275 nm） excitation, the Yb3＋ doped YPO4 phosphor showed an intense blue emission composed of two main bands at 420 and 620 nm assigned to charge transfer state （CTS） → 2Fs/2 and CTS →ZF7/2, respectively. Moreover, the optimum doping concentration of Yb3＋ in YPO4 phosphor was 1%, which exhibited the maximum emission intensity. The possible physical mechanism of concentration quenching was discussed, and the critical transfer distance determined to be 23.889 A. In particular, the color purity of the as-synthesized Yb3＋ doped YPO4 phosphor was as high as 83%, which made it an excellent candidate for blue-emitting materials.
文摘To explore the silicate lattice-based nanophosphors, a series of Eu3+-doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) materials were prepared by sol–gel procedure. The metal nitrates and silica powder were used as precursor components for the synthesis of these luminescent materials. Photoluminescence(PL) emission spectra, powder X-ray diffraction(PXRD), energy-dispersive X-ray spectroscopy(EDS), Fourier transform infrared spectroscopy(FTIR) and transmission electron microscopy(TEM)spectroscopic techniques were applied for the characterization of the fabricated materials. Three peaks were observed at 589, 613 and 650–652 nm corresponding to ^(5)D_(0)→^(7)F_(1-3) transition in PL emission spectra. Upon395 nm excitation and at 0.03 mol Eu3+, these nanophosphors displayed optimum photoluminescence with the most intense peak analogous to ^(5)D_(0)→^(7)F_(2)transition of dopant ion. The as-prepared phosphor materials were re-heated at1050 and 1150 ℃ to observe the consequences of higher temperatures on the emission intensity and crystal lattice.XRD analysis confirmed that all the synthesized materials were of crystalline nature, and the crystallinity was observed to be improved by increasing the temperature. In the FTIR spectrum, peaks at 483 and 610 cm^(-1) proved the existence of SiO_(4)group in Ca_(2)Si_(3)O_(8), and the peak centered at 417 cm^(-1) confirmed the presence of MgO6 octahedral in Mg_(2)Si_(3)O_(8) materials. TEM images were used to determine the particle size(13–35 nm) and to study the threedimensional structure of nanophosphor materials. The experimental studies indicate that these materials may be promising as red-emitting nanophosphors for white lightemitting diodes.
基金University Grants Commission(UGC),India for providing research fellowshipDST,New Delhi for fellowship under the Women Scientist Scheme-A with file number SR/WOS-A/CS-52/2018Institute of Eminence(IOE),Banaras Hindu University(BHU),India for financial support。
文摘This work presents the synthesis of Y_(2)O_(3):Eu^(3+),χCa^(2+)(χ=0 mol%,1 mol%,3 mol%,5 mol%,7 mol%,9 mol%,11 mol%)nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic,display,and lighting applications.The X-ray diffraction(XRD)patterns of the proposed nanophosphor reveal its structural properties and crystalline nature.The transmission electron microscope(TEM)results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca^(2+).Fourier transform infrared spectroscopy(FTIR)and Raman vibrations also confirm the presence of Y-O vibration and subsequently explain the crystalline nature,structural properties,and purity of the samples.All the synthesized nanophosphors samples emit intense red emission at 613 nm(~5D_(0)→~7 F_(2))under excitation with 235,394 and 466 nm wavelengths of Eu^(3+)ions.The photoluminescence(PL)emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength,respectively.The emission intensity of Y_(2)O_(3):Eu^(3+),χCa^(2+)(5 mol%)is increased 8-fold as compared to Eu:Y_(2)O_(3).Doping with Ca^(2+)ions enhances the emission intensity of Eu:Y_(2)O_(3)nanopho sphors due to an increase in energy transfer in Ca^(2+)→Eu^(3+)through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix.It is also observed that the optical band gap and the lifetime of the~5D_(0)level of Eu^(3+)ions in Y_(2)O_(3):Eu^(3+),xCa^(2+)nanophosphor sample gets changed with a doping conce ntration of Ca^(2+)ions.Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%,respectively.CIE,CCT,and color purity values(>98%)show an improved red-emitting nanophosphor in the warm region of light,which makes this mate rial superior with a specific potential application for UV-based white LEDs with security ink,display devices,and various other optoelectronics devices.
