Co-doped Y2O3 Research Articles

Enhanced upconversion emission in Nd, Yb, Er and Ho tetra-doped Y2O3 phosphor

Yb3+, Nd3+, Er3+ and Ho3+ tetra ions doped Y2O3 upconversion phosphors have been prepared by the combustion route. Crystalline phase purity and cubic phase of prepared samples have been confirmed from powder X-ray diffraction study. Absorbance of samples over spectral range 200–1100 nm has been measured by diffuse reflectance spectroscopy. All samples exhibit large band gaps. Scanning electron micrograph analysis reveals spherical morphology of particles and sizes around 200 nm. Upconversion emission has been studied under a 980 nm diode laser excitation with 166 mW laser power. The Ho3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor show very high emission intensity of a green band centred at around 550 nm and another moderate intensity red band centred on 667 nm, while reverse is the case for Er3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor. Er3+, Ho3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor show enhanced high emission intensity in both green and red bands. These two bands are not visible in Nd3+ and Yb3+ co-doped Y2O3 phosphor but show weak upconversion emission at 549, 568 and 799 nm. Owing to the high emission intensity of green band, Ho3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor may find potential applications in medical and security, while Er3+, Ho3+, Nd3+ and Yb3+ co-doped phosphor showing enhanced upconversion in green and red bands may find applications in white light generation.

Exploration of the crystal structures and electronic features of Y2O3:Er and Y2O3:Er,Yb crystals: a first-principles study

The Er3+ doped Y2O3 (Y2O3:Er) and Er3+, Yb3+ co-doped Y2O3 (Y2O3:Er,Yb) have attracted considerable attention due to their outstanding optical properties. However, the crystal structures underlying their electronic features are still unclear. In this paper, we carried out the systematical structural evolutions of Y2O3:Er and Y2O3:Er,Yb via the Crystal Structural AnaLYsis by Particle Swarm Optimization structure search method. Two novel monoclinic structures with P2 space group were uncovered for Y2O3:Er and Y2O3:Er,Yb. Validities of the two ground state structures were verified by the good agreements between the calculated x-ray diffraction patterns and the experimental ones. Phonon dispersion curves were also investigated, and the data showed that the ground state structures of both Y2O3:Er and Y2O3:Er,Yb were dynamically stable. Moreover, the density of states, the band structure and the electronic local function of these two systems were also studied. The impurity Er3+ and Yb3+ ions lead to the transition of electronic feature from the insulator to the semiconductor. The Y–O, Er–O, Yb–O bonds are proved to be covalent bonds. These research results can fill up the vacancy and give instructions in the rare-earth doped laser materials in the future.

Near-infrared photo-responsive Er3+-K+ co-doped Y2O3 phosphors with enhanced UC luminescence

Y2O3: x% Er3+ (x=5, 7, 10, 12, 15) and Y2O3: 10% Er3+，x% K+ (x=0, 1, 3, 5, 7, 10, 15) phosphors were successfully prepared by a low-temperature combustion method. The structure as well as the absorption/emission spectra of phosphors were investigated. The effect of doping concentration of K+ ions on the upconversion (UC) luminescence of Y2O3: 10% Er3+ phosphor was examined and the possible optical transitions were discussed. The results showed that K+ ion doping not only changed the microstructure and crystallinity of the phosphors, but also enhanced its UC luminescence intensity. The Y2O3: 10% Er3+, 7% K+ phosphor exhibit the strongest UC emission intensity. Compared with the Y2O3: 10% Er3+ phosphor, the UC luminescence intensity at 563 nm and 661 nm was enhanced by 67.8 and 27.3 times for the K-codoped samples, respectively. The phosphor with the optimal doping concentration was mixed with a polymer to form a composite film, which was employed for the fabrication of near-infrared (NIR) photo-responsive detection devices. The device exhibited strong photo-current response to NIR light at 980 nm, implying that our work could inspire new design strategy for the development of NIR photo-detection devices.

New Strategy: Molten Salt-Assisted Synthesis to Enhance Lanthanide Upconversion Luminescence.

Lanthanide-doped upconversion luminescent materials (LUCMs) have attracted much attention in diverse practical applications because of their superior features. However, the relatively weak luminescence intensity and low efficiency of LUCMs are the bottleneck problems that seriously limit their development. Unfortunately, most of the current major strategies of luminescence enhancement have some inherent shortcomings in their implementation. Here, a new and simple strategy of molten salt-assisted synthesis is proposed to enhance lanthanide upconversion luminescence for the first time. As a proof-of-concept, a series of rare earth oxides with obvious luminescence enhancement are prepared by a one-step method, utilizing molten NaCl as the high-temperature reaction media and rare earth chlorides as the precursors. The enhancement factors at different reaction temperatures are systematically investigated by taking Yb3+ /Er3+ co-doped Y2 O3 as an example, which can be enhanced up to more than six times. In addition, the molten salts are extended to all alkali chlorides, indicating that it is a universal strategy. Finally, the potential application of obtained UCL materials is demonstrated in near-infrared excited upconversion white light-emitting diodes (WLEDs) and other monochromatic LEDs.

Enhanced green up/down-conversion emissions through phase transformation in Ho3+/Yb3+ co-doped Y2O3:ZrO2 phosphors in presence of Na+ ions

This study reports the intense green upconversion and downconversion emissions from Ho3+/Yb3+/Na+ co-doped Y2O3:ZrO2 phosphor prepared by traditional solid-state reaction technique for fixed concentration of Ho3+/Yb3+ ions and different concentrations of Na+ ion. The phosphor samples exhibit a multiphase crystalline structure in the absence of Na+ ions. However, with co-doping of Na+ ions (at 20 mol%), it almost turns into Y4Zr3O12 with single rhombohedral phase. When Na + ions are present in the sample, the SEM image reveals a growth in particle size. The UV–Vis–NIR measurements show an enhancement in the absorbance of doped REs ions (Ho3+/Yb3+) on Na+ co-doping. The Ho3+/Yb3+ co-doped Y2O3:ZrO2 phosphor shows an intense green upconversion (UC) emission at 549 nm due to Ho3+ ions on the excitation with 980 nm radiation. In the presence of Na + ions, a modification of the crystallinity, growth in crystallite size (particle size) and an increase in the asymmetry of the crystalline structure around the REs ions led to an enhancement in the intensity of the UC emission almost about ∼8.5 times. The Log-Log plot demonstrates the involvement of two photons in the UC process. The lifetime of the 5F4/5S2 level decreases with increasing the concentration of Na + ion. Thus, the prepared phosphor could be an excellent candidate for source of green light, finger printing, optoelectronic devices etc.

Effect of Y:Zn ratio on microstructure and emission of Er3+/Yb3+ codoped Y2O3–ZnO ceramic phosphors

In this study, Er3+/Yb3+ codoped Y2O3–ZnO ceramic phosphors were prepared by sol–gel method. The samples had two emission bands, namely, green (535 nm) and red (660 nm), which are attributed to Er3+: 2H11/2(4S3/2) → 4I15/2 and Er3+: 4F9/2 → 4I15/2 radiative transitions, respectively. The samples exhibited green- and red-emission intensity enhancement by 1.728 and 2.286 times that of the pure Y2O3 host, respectively and by 514.468 and 214.341 times that of the pure ZnO host. The emission intensities are first enhanced by lattice expansion. With the change of Y:Zn ratio, the high surface energy is converted into low crystal surface resulting in the change of asymmetry crystal field for matrix. When the intensity of the asymmetric crystal field reaches maximum, both emissions are further boosted. When the high surface energy transforms into crystal surface energy, the microstructure changes into a compact mesoporous structure. Consequently, the chemical stability of the samples improves significantly, and the final emission band of the three samples with mesoporous structures is continuously red.

A simple and fast strategy for rare earth doped phosphors prepared by 980 nm laser thermal effect

The phosphors synthesize by the sol-gel method show low cost and good homogeneity, but it also requires furnace annealing at high-temperatures. This report uses a 980 nm laser annealing strategy to replace the furnace annealing in the sol-gel combustion synthesis. The fast laser annealing can improve the preparation efficiency of rare earth doped phosphor. Er3+/Li+ co-doped Y2O3 nanocrystals are synthesized by laser annealing strategy. The structures and spectral properties of the phosphors prepared by laser annealing are studied. The phosphors prepared by laser annealing have the same crystal structure and spectral properties as those organized by furnace annealing. In addition, phosphors can be heated into crystals using a high-power 980 nm laser. Under 980 nm excitation, the crystal prepared by laser annealing shows a much stronger fluorescence intensity than phosphors.

Size influence on optical thermometry of Er3+/Yb3+ Co-doped Y2O3 microspheres: From TCLs and Non-TCLs

Realization and optimization of enhanced/tunable optical luminescence properties is highly demanded for reliable and accurate temperature sensing. In this work, uniform monodisperse spherical Er3+/Yb3+ co-doped Y2O3 microcrystals of four different sizes have been synthesized via homogeneous precipitation by changing the reaction time, and the tuning of luminescence intensity/color was achieved by the controllable particles size. On this basis, by studying the particle size dependence of temperature sensing performance, we found that the behavior of absolute sensitivity (Sa) and relative sensitivity (Sr) have highly size dependence. Interestingly, when different FIR strategies were used (thermally coupled levels (TCLs) and nonthermally coupled levels (non-TCLs)), the sensitivity exhibits the opposite behavior. Importantly, when using the non-TCLs strategy, the maximum Sa value for the smallest phosphors was 1.084 K-1, leading to ∼246 times improvement compared to TCLs-based Sa. The ultrahigh Sa indicated that the Er3+/Yb3+ co-doped Y2O3 phosphors have potential in temperature detection, and the results are of guiding significance to studying the sensitivity of Y2O3 particle size-dependent temperature measurement.

Red light component tuning by n-UV/blue light excitations in Sm3+/Eu3+ co-doped Y2O3–Al2O3–Bi2O3–B2O3–SiO2 glasses for W-LED applications

A series of single (Sm3+, Eu3+) and co-doped (Sm3+- Eu3+) Yttrium alumino bismuth borosilicate (YABiBS) glasses have been prepared by basic melting quench method and the emission properties of synthesized glasses were investigated. To analyze the optical and energy transfer mechanism of these glasses the characterizations viz, absorption and luminescence are done. The absorption spectral data is used to observe the electronic band structure by direct and indirect optical band gaps. Bonding Parameters (β‾,δ) were evaluated to explain the ionic (or) covalent nature of the metal-ligand bonds in the present glass network. Near ultraviolet (n-UV) and blue excitations such as 392 nm, 400 nm, 457 nm, and 488 nm are used to record the emissions of single (Sm3+) and co-doped (Sm3+-Eu3+) glasses to achieve the tuneable emissions. Sm3+ ions show the reddish-orange emission mainly through 4G5/2 → 6H7/2 (597 nm) and Eu3+ ions show the intense red emission of transition 5D0 → 7F2 (612 nm). For the Sm3+-Eu3+ glasses by using different excitations, we will achieve the emission changes from orange to reddish-orange and then to red. Decay curves were analysed to know the process of interaction involved in the energy transfer among co-doped RE3+ ions. CIE coordinates and CCT values for all the prepared glasses by various excitations were calculated.

Energy transfer induced color tunable photoluminescence in Tb3+/Sm3+ co-doped Y2O3 nano-phosphor for warm white LEDs

In this work, the Tb3+/Sm3+ doped and co-doped Y2O3 nano-phosphors have been prepared by solution combustion method. The structural and morphological analyses of Y2O3 nano-phosphors confirm its nano-crystalline structure. The EDS spectra reveal the evidence of Y, Sm, Tb and O elements in the co-doped phosphor. The excitation spectrum of the Tb3+/Sm3+ co-doped nano-phosphor contains the excitation bands due to Tb3+ and Sm3+ ions. The Tb3+ doped nano-phosphor gives intense green (541 nm) and slightly weak blue (483 nm) emissions upon 292 nm excitation. The critical distance and PL intensity per activator ion were calculated to identify the factor responsible for quenching the PL intensity. The PL intensity of green and blue emission bands decreases regularly via doping of Sm3+ ion. This occurs due to energy transfer from Tb3+ to Sm3+ ions. The energy transfer leads to improve the PL intensity of the orange red emission band of Sm3+ ion. The energy transfer has been verified by the lifetime measurements and the energy transfer efficiency is found to increase via doping of Sm3+ ion. The CIE diagrams show wide color tunability from the greenish yellow to reddish orange regions and the color purity of Tb3+ doped nano-phosphor also changes accordingly via Sm3+ doping. The CCT analysis of Tb3+/Sm3+ co-doped nano-phosphors indicates a warm nature of the emitted light. Therefore, the Tb3+/Sm3+ co-doped Y2O3 nano-phosphor may be applied in the field of display devices, color tunable devices and warm white LEDs.

The role of 2-ethylhexanoic acid in manipulating the morphology and upconversion of flame-made Y2O3:Yb3+/Ho3+ nanoparticles towards remote temperature sensing

In the flame spray pyrolysis process, 2-ethylhexanoic acid manipulates morphology of Yb3+/Ho3+ co-doped Y2O3 upconversion nanoparticles towards homogeneous and ultrafine but causing upconversion luminescence quenching and thermal sensitivity lowering.

Optically thermometric sensitivities of Er3+/Yb3+ Co-doped hosts with different phonon energy

For Up-conversion (UC) optical thermometers based on luminescence intensity ratio (LIR) technology, the eternal pursuit is achieving high sensitivity to minimize its temperature measurement uncertainty, in which the selection strategy of matrix and dopants is one of the important factors. Phonon energy, as a basic property of matrix, greatly affects the temperature-dependent luminous intensity. Herein, Yb3+/Er3+ co-doped NaYF4 (NY), Y2O3 (YO), KLa(MoO4)2 (KLM), LaNbO4 (LN) and LaPO4 (LP) phosphors were used to be experimental objects because the phonon energy of them has distinct gradient. By comparing the sensitivities of Yb3+-Er3+ co-doped different matrices, it is found that the sensitivity is positively correlated with the matching degree (MD) between phonon energy and energy gap (ΔE) of thermal coupled levels (TCLs). This is because of the stronger mismatch between the energy gap and the effective phonon energy makes the non-radiative thermalization rates slower, thus affecting the rate of LIR change. The above conclusion gives a guidance method for selecting suitable matrix of high-sensitivity fluorescent thermometers.

In vitro assays and nanothermometry studies of infrared-to-visible upconversion of nanocrystalline Er3+,Yb3+ co-doped Y2O3 nanoparticles for theranostic applications

Luminescent spherical, redispersable, and monodisperse Er3+,Yb3+ co-doped Y2O3 nanoparticles were synthesized by homogenous precipitation followed by thermal annealing. Cubic Y2O3 nanoparticles exhibited high colloidal stability in water and biological medium and 90% cell viability toward glioblastoma multiforme cell lines. Confocal microscopy revealed cellular internalization of Y2O3 nanoparticles. Upon excitation at 980 nm, efficient near-infrared to visible upconversion luminescence from Y2O3:Er3+,Yb3+ nanoparticles occurred. The upconversion dynamics was determined by the number of photons, which evidenced that energy transfer by the upconversion mechanism is predominated. On the basis of luminescence nanothermometry studies, the nanoparticles exhibited features of a primary thermometer with high thermal sensitivity (1.27 ± 0.05% K−1 (303 K) and large repeatability (>97%), attesting that it can be used as a contactless optical thermal sensor. This primary thermometer is also successfully applied in a cell culture medium showing that the nanoparticles can operate on biological media. This opens the possibility of the use of Y2O3:Er3+,Yb3+ nanoparticles in the design of a theranostic platform, able to simultaneously monitor temperature and, coupled to photosensitizers, produce reactive oxygen species for cancer therapy.

Development of Er3+, Yb3+ Co-Doped Y2O3 NPs According to Yb3+ Concentration by LP-PLA Method: Potential Further Biosensor.

As diagnostic biosensors for analyzing fluids from the human body, the development of inorganic NPs is of increasing concern. For one, nanoceramic phosphors have been studied to meet the increasing requirements for biological, imaging, and diagnostic applications. In this study, Y2O3 NPs co-doped with trivalent rare earths (erbium and ytterbium) were obtained using a liquid phase–pulsed laser ablation (LP–PLA) method after getting high density Er, Yb:Y2O3 ceramic targets by Spark plasma sintering (SPS). Most NPs are under 50 nm in diameter and show high crystallinity of cubic Y2O3 structure, containing (222), (440), and (332) planes via HR–TEM. Excitation under a 980 nm laser to a nanoparticle solution showed 525 and 565 nm green, and 660 nm red emissions. The green emission intensity increased and decreased with increasing Yb3+ additive concentration, when the red spectrum continuously strengthened. Utilizing this study’s outcome, we suggest developing technology to mark invisible biomolecules dissolved in a solvent using UC luminescence of Er3+, Yb3+ co-doped Y2O3 NPs by LP–PLA. The LP–PLA method has a potential ability for the fabrication of UC NPs for biosensors with uniform size distribution by laser parameters.

A high-brightness phosphor based on Yb[formula omitted]/Er[formula omitted] codoped Y2O3 micro-crystals and controllable temperature sensing sensitivity via rare earth ions

Non-contact temperature detection technology based on the fluorescence intensity ratio (FIR) of rare earth ions has attracted much attentions due to its high sensitivity and operability. Herein, Yb3+/Er3+:Y2O3 micro-crystals with different rare earth ion concentrations were prepared and studied. Under 980 nm excitation, the influences of rare earth ion concentration on fluorescence intensity and temperature sensing sensitivity are discussed in detail. The prepared Yb3+/Er3+ codoped Y2O3 micro-crystals possess excellent fluorescence properties, its temperature sensing sensitivity is superior and the maximum absolute sensitivity is up to 0.0078 K−1 at 625 K. The strongest fluorescence intensity and highest sensitivity are achieved in 3.0Yb3+/0.3Er3+:Y2O3 and 3.0Yb3+/0.1Er3+:Y2O3 crystals, respectively. So it is necessary to evaluate doping design for better applications. This work may further promote the optical thermometry research and provide a new strategy to increase the temperature detection sensitivity.

Near-infrared emitting Nd3+-Yb3+ codoped Y2O3 nanocrystals for highly sensitive optical thermometry

Rare earth ions activated nanomaterials have been extensively considered as promising candidates for optical thermometry due to their unique photoluminescence characteristics. Nevertheless, thermally coupled levels-based thermometers are suffering from low sensitivity because of the restriction of small energy gap. Herein, the phonon-assisted energy transfer from Yb3+ to Nd3+ in Y2O3 nanoparticles, which makes the near infrared emissions of Nd3+ and Yb3+ ions respond to temperature inversely, is utilized to achieve sensitive temperature measurement via the ratiometric method. When pumped by 980 nm continuous wave laser, the multizone thermometry is performed owing to the different dependence of energy transfer on the temperature. The maximum relative sensitivities achieved in the temperature ranges of 423–773 K and 303–333 K are both approximately 2.3% K−1, which are superior to most previously reported luminescence-based temperature sensors. In addition, it is found that the measurement sensitivity is significantly influenced by the laser-induced heating effect especially at relatively low temperatures. Under the excitation of 980 nm square wave laser, the relative sensitivity is enhanced from 2.3% to 2.9% K−1 in the physiological temperature region. These findings can provide an effective pathway to improving the thermometric behavior and expanding the application of luminescence temperature sensing in various fields.

Synthesis of Yb3+/Ho3+ co-doped Y2O3 nanoparticles and its application to dye sensitized solar cells

In this study, a series of Yb3+/Ho3+ co-doped Y2O3 up-conversion (UC) nanophosphors was fabricated by a homogeneous precipitation method. The photoluminescence emission in the visible regions of the nanophosphors has been investigated under 980 nm IR laser excitation. The nanophosphors exhibited strong visible green and weaker red up-conversion emissions. The effects of various concentrations of Yb3+ (1–4 mol%) on the photoluminescence properties of fabricated nanophosphors was also investigated. The fabricated UC nanophosphors were incorporated in the DSSC and their influence on the photovoltaic performance of the DSSC was characterized by a current-voltage curve, and incident photon to current conversion efficiency. Compared with the DSSC without the UC nanoparticles which had a cell efficiency of 4.27%, the DSSC incorporating Y2O3:Ho3+/ Yb3+ UC nanoparticles showed an enhanced cell efficiency of 4.79%.

Tunable luminescence from yttrium oxide flowers using asparagine as shape modifier

A series of Eu3+/Nd3+/Yb3+ co-doped Y2O3 flowers with different Nd3+ concentrations are synthesized using asparagine as a complexing ligand by low-temperature hydrothermal synthesis technique. The cubic crystal structure and flower like architecture morphology of the annealed co-doped Y2O3 phosphors at different synthesis temperatures have been confirmed from XRD and FESEM analysis. The photoluminescence study of the developed phosphors has been performed by using excitations at 220 nm, 808 nm and 980 nm, and the responsible mechanisms have been discussed in detail. Dipole-dipole interaction is found responsible for concentration quenching with inter-ionic separation ∼15.27 Å among the Nd3+ ions. Asymmetric ratio is calculated to be 3.01 with respective to Eu3+ ions in co-doped Y2O3 host lattice. The spectral characteristics have been described via nephelauxetic ratio and Judd–Ofelt parameters in co-doped Y2O3 under UV excitation. Two photon process dominates the upconversion luminescence on 808 nm irradiation. CIE color coordinates clearly indicates that co-doped Y2O3 phosphors can be further used for multi-color labeling applications. Moreover, because of the intrinsic magnetic moment of Nd3+ ions, the developed Eu3+/Nd3+/Yb3+ co-doped Y2O3 phosphors exhibit paramagnetic behavior with magnetization value 0.0064 emu/g at 300 K.

Red light emission of Y2O3:Eu3+ nanophosphors and luminescent enhancement by the addition of gadolinium oxide as co-dopant

This work presents the optical and structural properties of rare earth-doped and co-doped yttrium oxide nanophosphors. Europium oxide and gadolinium oxide-doped and co-doped Y2O3 phosphors were synthesized by make use of combustion method followed by annealing to different temperatures in order to obtain much more good crystallinity. The X-ray diffraction and Fourier transform infrared spectroscopy confirms the structural formation and phase purity of the compound. The diffuse reflectance spectra of doped and co-doped Y2O3 powder were analysed. It was found that there appears shifting of absorption edge towards longer wavelength region when compared to pure yttrium powder. The band gap was calculated by make use of Kubelka–Munk function. It was noticed that band gap increases with annealing temperature. The dependence of doping concentration, pH and annealing temperature on photoluminescence properties were studied in a systematic manner. The PL emission intensity was maximum for 6 wt% Eu3+-doped Y2O3 powders that results 5D0–7F2 transition within europium and emits red light at 612 nm under the excitation of 260 nm. In the case of co-dopant, maximum intensity is obtained for 7 wt% Gd3+ under the excitation of 255 nm.

Role of Li+ ions on the surface morphology and thermoluminescence properties of Y2 O3 :Tm3+ nanophosphor.

Y2 O3 :Tm3+ and Li+ co-doped Y2 O3 :Tm3+ nanopowders were synthesized using the solution combustion method for possible application in ultraviolet (UV) light dosimetry. X-ray diffraction revealed the crystallite sizes to be in the range 21-44 nm and 30-121 nm using the Scherrer equation and the W-H plot relationship, respectively. Field emission scanning electron microscopy confirmed that, after co-doping with 4 mol% concentration of Li+ , the particles were spherical in nature with an average size of ~30 nm. Fourier transformed infrared spectroscopy results showed bands at wavenumbers of 556, 1499, 1704, 2342, 2358, 2973, 3433, and 3610 cm-1 that corresponded to the stretching and bending vibrations of Y-O, C=O and O-H. Thermoluminescence (TL) glow peaks for Y2 O3 :Tm3+ nanophosphors observed at 399 and 590 K were attributed to oxygen defects caused using UV irradiation. These oxygen defects firstly resulted in an increased prominent peak TL intensity for up to 270 min of irradiation and then a decrease. This was attributed to the presence of oxygen defect clusters that caused a reduction in recombination centres. The Li+ co-doped sample showed peaks at 356, 430, and 583 K and its intensity sublinearly increased up to 90 min and then thereafter decreased. The TL trapping parameters were calculated using computerized glow curve deconvolution methods. The Li+ co-doped sample exhibited less fading and high trap density under the UV radiation.