Effects of Bi3+ on down-/up-conversion luminescence,temperature sensing and optical transition properties of Bi3+/Er3+ co-doped YNbO4 phosphors

A series of YNbO₄:Bi³⁺ and YNbO₄:Bi³⁺/Er³⁺ phosphors were prepared by a conventional high temperature solid–state reaction method. The results of XRD and Rietveld refinement confirm that monoclinic phase YNbO₄ samples are achieved. The down-/up-conversion luminescence of Er³⁺ ions was investigated under the excitation of ultraviolet light (327 nm) and near infrared light (980 nm). Under 327 nm excitation, broad visible emission band from Bi³⁺ ions and characteristic green emission peaks from Er³⁺ ions are simultaneously observed, while only strong green emissions from Er³⁺ ions are detected upon excitation of 980 nm. Remarkable emission enhancement is observed in down-/up-conversion luminescence processes by introducing Bi³⁺ ions into Er³⁺-doped YNbO₄ phosphors. Pumped current versus up-conversion emission intensity study shows that two-photon processes are responsible for both the green and the red up-conversion emissions of Er³⁺ ion. Through the study of the temperature sensing property of Er³⁺ ion, it is affirmed that the temperature sensitivity is sensitive to the doping concentration of Bi³⁺ ions. By comparing the experimental values of the radiative transition rate ratio of the two green emission levels of Er³⁺ ions and the theoretical values calculated by Judd-Ofelt (J-O) theory, it is concluded that the temperature sensing property of Er³⁺ ions is greatly affected by the energy level splitting.     

White up-conversion luminescence and highly-sensitive optical temperature sensing in Na3La(VO4)2:Yb,Er,Tm,Ho phosphors

In this work,tunable white up-conversion luminescence was achieved in the Yb³⁺,Er³⁺,Tm³⁺,Ho³⁺ codoped Na₃La(VO₄)₂ phosphors under 980 nm excitation.The emissions of three primary colors are mainly attributed to the ²H_11/2/⁴S_3/2→⁴I_15/2 transitions of Er³⁺,¹G₄→³H₆ transition of Tm³⁺,and_5...     

Luminescent properties of Ce3+-doped transparent oxyfluoride glass ceramics containing BaGdF5 nanocrystals

The transparent oxyfluoride glass ceramics containing Ba Gd F5 nanocrystals were prepared with a composition of 42 Si O2-12Na2O-16Al2O3-24 Ba F2-4Gd2O3-2Ce F3(mol.%) by thermal treatment technology. The typical DSC curve, X-ray diffraction(XRD) and transmission electron microscopy(TEM) patterns were measured. The transmission spectra and luminescent properties were investigated. The decay times of the Gd3+ ions at 312 nm excited with 275 nm for the Ce3+ ions doped glass and glass ceramics specimens and the energy transfer process between Gd3+ ions and Ce3+ ions were also studied. The XRD analysis and the TEM images confirmed the generation of the spherical Ba Gd F5 nanocrystals. Compared with the PG specimen, the intensity of the luminescence spectra of the glass ceramics specimens was apparently enhanced with the heat treatment temperature increasing, and a blue shift in the excitation spectra and the emission spectra of glass ceramics specimens was obviously observed. In the fluorescence decay curves of the Gd3+ ions, it could be obviously observed that the fluorescent intensity decays in the Ce3+ ions doped glass and glass ceramics specimens decreased rapidly with the increase of the heat treatment temperature. In addition, the energy transfer efficiency from Gd3+ions to Ce3+ ions was also calculated.     

Er~(3+)-Yb~(3+)-Na~+:ZnWO_4 phosphors for enhanced visible upconversion and temperature sensing applications

The crystal structure and surface morphology of the Er³⁺/Yb³⁺/Na+:ZnWO₄ phosphors synthesized by solid state reaction method were analyzed by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) analysis.The frequency upconversion(UC) emission study in the developed phosphors was investigated by using 980 nm laser diode excitation.The effect of codoping in the Er³⁺:ZnWO₄ phosphors on the UC emission intensity was studied.The UC emission bands that are exhibited in the blue(490 nm),green(530,552 nm),red(668 nm) and NIR(800 nm) region correspond to the ⁴F_7/2→⁴I_15/2.²H_11/2,⁴S_3/2→⁴I_15/2,⁴F_9/2→⁴I_15/2 and ⁴I9/2→⁴I_15/2 transitions,respectively.The temperature sensing performance of the Er³⁺-Yb³⁺-Na+:ZnWO₄ phosphors was investigated based on the 2 H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 thermally coupled transitions of the Er³⁺ions.The photometric study was also carried out for the developed phosphors.     

Near-infrared luminescent Nd~(3+)/Yb~(3+)-codoped metal-organic framework for ratiometric temperature sensing in physiological range

Self-calibrating luminescent thermometry employing luminescence within the optical transparency windows provides a promising prospect for temperature measurement in the biological fields.In this work,a new Nd~(3+)/Yb~(3+)-codoped metal-organic framework Nd_(0.95)Yb_(0.05)BPTC showing threedimensional anionic network,obtained by reacting ligand [1,1'-biphenyl]-3,3',5,5'-tetracarboxylic acid(H_4BPTC) with Nd~(3+) and Yb~(3+) ions under solvothermal conditions,is reported.Upon 808 nm photoexcitation,Nd_(0.95)Yb_(0.05)BPTC simultaneously emits the characteristic near-infrared luminescence of Nd~(3+) and Yb~(3+) ions based on the efficient energy transfer from Nd~(3+) to Yb~(3+) ions.In addition,the emission intensity ratio of Yb~(3+) and Nd~(3+) shows good exponential-like response to temperature in the physiological range of 293-323 K.The feature properties of Nd_(0.95)Yb_(0.05)BPTC include near-infrared absorption and emission,favorable temperature sensitivity and accurate temperature uncertainty,as well as good chemical stability,making such system useful in biomedical applications.     

Upconversion multicolor tuning of NaY(WO4)2:Tb3+ with Eu3+ doping

A series of Tb~(3+) and Eu~(3+) co-doped NaY(WO_4)_2 phosphors were synthesized by hydrothermal reactions.The crystal structure,morphology,upconversion luminescent properties,the energy transfer from Tb~(3+) to Eu~(3+)ions and the ~5 D_4→ ~7 F_5 transition of the Tb~(3+) ion in NaY(WO_4)_2:Tb~(3+),Eu~(3+) phosphors were investigated in details.The results indicate that all the synthesized samples are of pure tetragonal phase NaY(WO_4)2.Furthermore,the micrometer-sized needle spheres and excellent dispersion of the particles are obtained by adding polyethylene glycol(PEG-2000) as the surfactant.Phosphors of NaY(WO_4)_2:Tb~(3+),Eu~(3+) exhibit the492 nm blue emission peak,546 nm green emission peak,595 nm orange emission peak and 616 nm red emission peak under 790 nm excitation.The energy transfer from Tb~(3+) to Eu~(3+) is a resonant transfer,in which electric dipole-dipole interaction plays a leading role.By adjusting the doping concentration of Eu~(3+) in NaY(WO_4)_2: 1.0 mol%Tb~(3+),xmol%Eu~(3+) phosphors,the emitting color of UC phosphors can be tuned from green to red.     

Photoluminescence properties of Tm~(3+)/Tb~(3+)/Sm~(3+)tri-doped Na_5Y_9F_(32)single crystal with high thermal stability for white light-emitting diodes

A novel Tm~(3+)/Tb~(3+)/Sm~(3+)tri-doped Na_5 Y_9 F_(32) single crystal was synthesized by a modified Bridgman method for the propose of white light emitting diodes.The fluorescence spectra of various Sm~(3+)ion concentrations and fixed 0.4 mol% Tm~(3+) and 0.5 mol% Tb~(3+) were measured and studied systematically excited by near-ultraviolet light of 355 nm.The Sm3+ion concentration takes apparent effect on the relative intensity of peaks in the visible region and the color coordinate combining from these emission bands.A near pure white light emission with color coordinates(0.3295,0.3057) and color temperature(5657 K) can be obtained when the concentrations of Tm~(3+),Tb~(3+) and Sm~(3+) ions are 0.4 mol%,0.5 mol%and 0.8 mol%,respectively.Furthermore,the practical down-conversion internal quantum yield was measured by integrating spheres at about 14.39%.The tri-doped Na_5 Y_9 F_(32) single crystal shows a high thermal stability inferring from the temperature dependent emission in which the integrated emission intensities are reduced only by～3% with the increase of temperature from 280 to 450 K.The present results demonstrate that the Tm~(3+)/Tb~(3+)/Sm~(3+)tri-doped Na_5 Y_9 F_(32) single crystal may provide a promising candidate for white light-emitting diodes,luminescent materials and fluorescent display devices.     

Optical studies of Y_3(Al,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+) nano-phosphors obtained by the Pechini method

The Y3(AI,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+)(YAGG) nano-phosphors with homogeneous particle-size distribution,low aggregation and average crystalline size of about 65 nm were obtained using a modified Pechini method.Only slight aggregation of the crystallites occurs after post-annealing at 1100℃.The intense Ce~(3+)bands in the excitation spectra of the Ce~(3+),Cr~(3+),Nd~(3+)co-doped materials monitoring the Cr~(3+) emission at 690 nm indicate energy transfer from Ce~(3+) to Cr~(3+).Weak Nd~(3+) lines are observed,as well.In addition,the emission of Nd~(3+)at 1060 nm with excitation of Ce~(3+) and Cr~(3+) confirms the Ce~(3+)/Cr~(3+)to Nd~(3+)energy transfer.The short average luminescence decay times for the Ce~(3+) emission indicate the Ce~(3+)/Cr~(3+)to Nd~(3+)energy transfer.Eventually,the Y_3(AI,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+) nano-phosphors exhibit persistent luminescence originating from the 4f~3→4f~3 transitions of Nd~(3+) which matches well to the first biological window to be used in bioimaging applications.     

Significant enhancement of blue photoluminescence intensity of Dy~(3+) modified Sr_6Ca_4(PO_4)_6F_2:Eu~(2+) phosphors

Blue-emitting phosphors Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+)(SCPF:Eu~(2+)),Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+),Dy~(3+)(SCPF:Eu~(2+),Dy~(3+))and Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+),Dy~(3+),Si~(4+)(SCPF:Eu~(2+),Dy~(3+),Si~(4+)) with apatite structure were successfully synthesized by traditional solid-state reaction under reducing atmosphere.Eu~(2+),Dy~(3+) and Si4+ions occupy the corresponding sites of Sr~(2+),Ca~(2+) and P~(5+).Strong broad blue photo luminescence band is exhibited in SCPF:Eu~(2+),Dy~(3+) phosphor ranging from 400 to 550 nm centered at 455 nm and Dy~(3+) ions are vital in creating traps.Emission intensity of Eu~(2+),Dy~(3+) co-doped SCPF:0.02 Eu~(2+),0.02 Dy~(3+) is about 1.8 times that of SCPF:0.02 Eu~(2+) and electron trap centers serve as energy transporting media.To further elucidate the formation and effect of the specific defect on the luminescence of SCPF:0.02 Eu~(2+),0.02 Dy~(3+) phosphor,the thermoluminescence properties,decay curves and thermal stability studies were performed while the Si~(4+)-P~(5+) charge compensated pho sphor SCPF:0.02 Eu~(2+),0.02 Dy~(3+),0.02 Si~(4+) was prepared as a contrast.All the results of present work indicate that Dy~(3+) co-doping can obviously enhance photoluminescence intensity of SCPF:0.02 Eu~(2+) by the electron traps generated by non-equivalence replacement of Dy~(3+)-Ca~(2+).     

Effect of glass network modifier R2O (R=Li,Na and K) on upconversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxyfluoride glass-ceramics

The effect of glass network modifier R2O (R=Li, Na, K) on upconversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxyfluoride glass-ceramics was investigated. NaYF4 nanocrystals with different sizes were...     

Blue-emitting Sr_(1-x)Ca_xLu_2O_4:Ce~(3+) phosphors for high CRI white LEDs

A broadband blue-emitting Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+),by partially substituting Sr~(2+) with Ca~(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) gradually increases,the emission peak of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_2 O_4:Ce~(3+)(blue),β-sialon:Eu~(2+)(green) and(Sr,Ca)AlSiN_3:Eu~(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_2 O_4:Ce~(3+)is applied as blue phosphor to substitute SrLu_2 O_4:Ce~(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.     

Tunable luminescence and energy transfer in Y_2BaAl_4SiO_(12):Tb~(3+),Eu~(3+)phosphors for solid-state lighting

Single-phase Y₂BaAl₄SiO₁₂:Tb³⁺,Eu³⁺phosphors with adjustable luminescence were successfully prepared by high-temperature solid-state reaction method.The structural,luminescent properties and ene rgy transfer(ET) process of Y₂BaAl₄SiO₁₂:Tb^(³⁺),Eu³⁺phosphors were syste matically analyzed with the help of X-ray diffraction(XRD),scanning electron microscopy(SEM),excitation spectra,emission spectra and photoluminescence decay curves.Tunable luminescence ranging from green through yellow and definitively to red can be achieved by elevating amounts of Eu³⁺ions in Tb³⁺,Eu³⁺co-doped samples.Besides,the ET mechanism and efficiency were also analyzed and the maximum ET efficiency is 67%.All the results show that Y₂BaAl₄SiO₁₂:Tb³⁺,Eu³⁺phosphors can be used in solid-state lighting.     

La~(3+) doped LiCo_(0.25)Zn_(0.25)Fe_2O_4 spinel ferrite nanocrystals:Insights on structural,optical and magnetic properties

This paper addresses the manipulation of structural,morphology,optical and magnetic properties of LiCo_(0.25)Zn_(0.25)Fe_2 O_4 ferrite via incorporation of different proportions of La~(3+) at the expense of iron ions using a sol-gel method.The samples were characterized using the X-ray diffraction technique(XRD),Fourier transform infrared(FT-IR) spectroscopy,the energy dispersive X-ray spectra(EDX),inductively coupled plasma optical emission spectroscopy(ICP-OES),high resolution scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET) surface area analysis,ultraviolet-diffuse reflectance spectroscopy(UV-DRS),and vibrating sample magnetometer(VSM) technique.The Rietveld refinements of the samples indicate that at higher concentrations of La3+,nanostructures with dual phase,i.e.cubic spinel and orthorhombic LaFeO_3 perovskite with space group(Pbnm) appear.Optical studies show that the energy band gap(E_g) of the bare LiCo_(0.25)Zn_(0.25)Fe_2 O_4 ferrite sample(2.18 eV) reaches up to 2.47 eV at x=0.06 and above this concentration,it drops sharply to 2.00 eV.Although the saturation magnetization and the coercivity of LiCo_(0.25)Zn_(0.25)La_xFe_(2-x)O_4 are lower than that of LiCo_(0.25)Zn_(0.25)Fe_2 O_4 NPs.Overall,the superparamagnetic nature and low values of saturation magnetization and coercivity of LiCo_(0.25)Zn_(0.25)La_xFe_(2-x)O_4 NPs are suitable to be applied in transformers core.     

Crystal growth,structure and laser performance of a new Yb~(3+):KBaY(MoO_4)_3 crystal

A Yb~(3+):KBaY(MoO_4)_3(Yb3+:KBYM) crystal with dimensions of 51 mm × 27 mm x 10 mm was successfully grown by the TSSG method.The characteristics of the crystal structure and probability of good optical properties were analyzed.The absorption and emission spectra of Yb3+:KBYM crystal exhibit broadened bands,with the maximum absorption cross-sections of 1.17 x 10~(-20),1.44 ×10~(-20) and 1.37 x 10-20 cm~2 at976 nm for X-,Y-and Z-polarizations,respectively.The corresponding absorption FWHMs are as wide as 77,46 and 55 nm.The well-known re-absorption effect of Yb3+in the crystal is discussed.Two methods,the Fiichtbauer-Ladenburg method(FL) and reciprocity method(RM) were adopted to compute the emission cross-sections and results show a certain discrepancy but the errors are allowable.The laser potentiality of the Yb3+:KBYM crystal was also evaluated by calculations of minimum inversion fraction β_(min),saturation pump intensity I_(sat),the minimum pump intensity I_(min) and gain cross-sections spectra.Laser experiment was carried out and Watt-level continuous wave laser has been realized.Results indicate that the Yb~(3+):KBYM crystal with a disordered structure may be a potential laser media that can be used to generate tunable and ultrashort pulse laser emissions with high quality beam.     

Rational design of monovalent ions (Li,Na,K) co-doped ZnAl_2O_4:Eu~(3+) nanocrystals enabling versatile robust latent fingerprint visualization

Alkali metal ions(M~+ = Na~+,Li~+,K~+) co-doped ZnAl_2O_4:Eu~(3+)(5 mol%)(ZAE) nanopowders(NPs) were prepared via solution combustion route using Mimosa pudica(MP) leaves extract as a fuel. PXRD results of co-doped samples enhance the crystallinity and grain growth. Photoluminescence(PL) of the prepared ZAE and ZAE:M~+(M~+ = Na~+, Li~+, K~+) NPs shows intense emission peaks in the range of 550-750 nm and ascribed to ~5D_0→~7F_J(J=0-4) transitions of Eu~(3+) ions, respectively. A 2-fold enhancement in PL intensity was observed in Li~+ co-doped samples. The optimized ZnAl_2O_4:Eu~(3+)(5 mol%), Li~+(1 wt%)(ZAEL)NPs were used to visualize LFPs on various porous, semi-porous and non-porous surfaces through robust powder dusting technique. The visualized latent fingerprints(LFPs) reveal well defined level 1-3 ridge characteristics under several tests such as fingerprint aging and fresh water treatment for various time durations. The obtained results clearly evidence that the prepared NPs are quite useful for multifunctional applications such as advanced forensic and solid state lightning.     

A novel long lasting phosphor Sr5 (PO4)3FxCl1-x:Eu2+,Gd3+prepared in air condition

A series of blue long afterglow mixed halide-phosphate phosphors Sr5 (PO4)3 FxCl1-x:Eu2+,Gd3+were synthesized in air by traditional solid-state reaction route. The crystal structures, photoluminescence...     

S 16924 ((R)-2-[1-[2-(2,3-dihydro-benzo[1,4] dioxin-5-Yloxy)-ethyl]-pyrrolidin-3yl]-1-(4-fluoro-phenyl)-ethanone), a novel, potential antipsychotic with marked serotonin (5-HT)1A agonist properties: I. Receptorial and neurochemical profile in comparison with clozapine and haloperidol

S 16924 showed a pattern of interaction at multiple (>20) native, rodent and cloned, human (h) monoaminergic receptors similar to that of clozapine and different to that of haloperidol. Notably, like clozapine, the affinity of S 16924 for hD2 and hD3 receptors was modest, and it showed 5-fold higher affinity for hD4 receptors. At each of these sites, using a [35S]GTPgammaS binding procedure, S 16924, clozapine and haloperidol behaved as antagonists. In distinction to haloperidol, S 16924 shared the marked affinity of clozapine for h5-HT2A and h5-HT2C receptors. However, an important difference to clozapine (and haloperidol) was the high affinity of S 16924 for h5-HT1A receptors. At these sites, using a [35S]GTPgammaS binding model, both S 16924 and clozapine behaved as partial agonists, whereas haloperidol was inactive. In vivo, the agonist properties of S 16924 at 5-HT1A autoreceptors were revealed by its ability to potently inhibit the firing of raphe-localized serotoninergic neurones, an action reversed by the selective 5-HT1A receptor antagonist, WAY 100,635. In contrast, clozapine and haloperidol only weakly inhibited raphe firing, and their actions were resistant to WAY 100,635. Similarly, S 16924 more potently inhibited striatal turnover of 5-HT than either clozapine or haloperidol. Reflecting its modest affinity for D2 (and D3) autoreceptors, S 16924 only weakly blocked the inhibitory influence of the dopaminergic agonist, apomorphine, upon the firing rate of ventrotegmental area-localized dopaminergic neurones. Further, S 16924 only weakly increased striatal, mesolimbic and mesocortical turnover of dopamine (DA). Clozapine was, similarly, weakly active in these models, whereas haloperidol, in line with its higher affinity at D2 (and D3) receptors, was potently active. In the frontal cortex (FCX) of freely moving rats, S 16924 dose-dependently reduced dialysate levels of 5-HT, whereas those of DA and NAD were dose-dependently increased in the same samples. In contrast, although S 16924 also suppressed 5-HT levels in the striatum and nucleus accumbens, DA levels therein were unaffected. Clozapine mimicked this selective increase in DA levels in the FCX as compared to striatum and accumbens. In contrast, haloperidol modestly increased DA levels in the FCX, striatum and accumbens to the same extent. In distinction to S 16924, clozapine and haloperidol exerted little influence upon 5-HT levels. Finally, the influence of S 16924 upon FCX levels of 5-HT, DA (and NAD) was attenuated by WAY 100,635. In conclusion, S 16924 possesses a profile of interaction at multiple monoaminergic receptors comparable to that of clozapine and distinct to that of haloperidol. In addition, S 16924 is a potent, partial agonist at 5-HT1A receptors. Correspondingly, acute administration of S 16924 decreases cerebral serotoninergic transmission and selectively reinforces frontocortical as compared to subcortical dopaminergic transmission. In line with these actions, S 16924 shows a distinctive profile of activity in functional (behavioral) models of potential antipsychotic activity (companion paper).