Luminescence and energy transfer of color-tunable Lu_2MgAl_4SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+) phosphors

Energy transfer among the co-doped activators is an efficient route to achieve color-tunable emission in inorganic phosphors.Herein,photoluminescence tuning from blue to cyan has been achieved in the Lu_2MgAl_4 SiO_(12);Eu~(2+),Ce~(3+)phosphors by varying the Ce~(3+) concentration with a fixed Eu~(2+)content.With the further introduction of a Mn~(2+)-Si4+couple into the host lattice,the emission color can be tuned to red through the energy transfer of Eu~(2+)and Mn~(2+).The luminescence properties and the energy transfer mechanism were studied in detail.The energy transfer from Eu~(2+)to Ce~(3+)is certified as a dipolequadrupole interaction with the energy transfer efficiency of 41.4% and Eu~(2+)to Mn~(2+)belongs to a dipole-dipole interaction with the energy transfer efficiency of 94.3%.The results imply that this singlephased Lu_2MgAl4 SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+)phosphor has a potential prospect for application in near-UV chip pumped white light emitting diodes.     

铕-M(Zn~(2+),Ca~(2+)等)-均苯四甲酸的合成及荧光光谱性质

合成了均苯四甲酸（PMA）、铕离子（Eu(3+)和常见Ⅱ族离子（Mg~(2+)，Ca~(2+)Sr(2+)、Ba(2+)、Zn(2+)）形成的系列配合物。研究了它们的红外和荧光光谱，讨论了Zn~(2+)含量对配合物发光强度的影响及敏化发光机理，得到了具有潜在应用价值的鲜红色发光材料Eu-Zn-PMA配合物Zn~(2+3+)=4：1）。     

Luminescent Properties of Eu~(3+) and Bi~(3+) and Their Interaction in LaBO_3 and GdBO_3

Under the excitation of UV light and cathode ray,the dependence of the excitation and emission spectraand luminescent lifetime of Eu~(3+)and Bi~(3+)on composition and structure in LABO_3 and GdBO_3 has been stu-died.The results indicate that the emission spectra of Eu~(3+)in LaBO_3 with aragonite structure and in GdBO_3with YBO_3 structure are quite different.Under 254 nm excitation,Eu~(3+)emission is sensitized by Bi~(3+)inGdBO_3 matrix.In other case Eu~(3+)emission is quenched by Bi(3+).     

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.     

SrAl_2O_4:Eu~(2+),Dy~(3+)的发光性质及机理

研究了Eu2＋、Dy3＋共激活的SrAl2O4体系的发光性能和能量传输。结果表明，Dy3＋、Eu2＋共存时，Eu2＋的发光强度远远大于无Dy3＋时的发光强度，证明Dy3＋对Eu2＋的发光有敏化作用。Dy→Eu2＋能量传输的方式为籍助于载流子的能量输运。     

Photostimulated Luminescence and F-centers of Sr_3Ca_2(PO_4)_3X:Eu~(2+)(X=F,Cl,Br)

This paper reports the F-centers and photostimulated luminescence of Eu~(2+)-activated Sr_3Ca_2(PO_4)_3Xcrystals.The influence of various halide ions on the F-centers and their energy level is discussed.The mechanismfor the photostimulated luminescence and valence change of Eu ion in that process have been investigated.     

Optical performance study of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) ternary luminous fiber

In this study, down-conversion fluorescent powder of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+), which were the common three primary colors materials with long afterglow, were synthesized by high temperature solid state method. The blends of rare earth(RE) luminescent materials have been of interest to reinvest the luminescent characteristics of polyethylene terephtahalate(PET) luminous fiber. The scanning electron microscopy(SEM) and an inversion fluorescence microscope were used to characterize the surface morphology and the dispersion of inclusion. Through analysis of microcosmic morphology, three typical dispersions of luminescent particles were summarized. The X-ray diffraction indicated that the phase structure of fiber samples and crystal structure of luminescence materials kept complete after prilling and spinning. From the fluorescence spectra and CIE 1931 coordinates, it could be found that different combinations of luminous fibers were desired to obtain divers colors emission luminous fiber. And the fiber samples were a light sensation which could induct different excitation wavelengths and convert it down to different colors. The afterglow decay curve and its differential curve were summarized indicating the three decay stages. The decay curve and decay rate curve showed that the contents of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) had obvious influence on the afterglow of fiber samples.     

Enhanced photodegradation activity of ZnO:Eu~(3+)and ZnO:Eu~(3+)@Au 3D hierarchical structures

In this work the flower-like hierarchical structures(HS) based on 3 D pristine ZnO,ZnO:Eu~(3+)and ZnO:Eu~(3+)@Au were successfully obtained by a template-free solvothermal and deposition-precipitation method.The decolorization/photodegradation of these structures towards model organic dye(rhodamine 6 G) was studied.The synthesized ZnO-based HS were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-vis and photoluminescence(PL) spectroscopies.The proposed synthesis approaches allow to obtain highly crystalline 3 D ZnO,ZnO:Eu~(3+) and ZnO:Eu~(3+)@Au composites.Results of scanning microscopy show that ZnO flower-like HS are assemblies from smaller components,forming larger ones,the whole ZnO structure was approximately 3 μm.Au nanoparticles(size～10 nm)are successfully deposited on ZnO HS surface.Luminescent studies show that ZnO is an ideal matrix for incorporation of Eu~(3+)ions in broad concentration range(Eu~(3+)=1.0 at%-5.0 at%) with an efficient red luminescence.The strong UV emission in ZnO,as well as ZnO;Eu~(3+)HS is observed under 325 nm excitation.Doping of ZnO HS matrix by Eu~(3+)ions leads to the red shift of deep level emission peak(DLE).The PL intensity reaches the maximum up to 5 at% Eu~(3+).The photocatalytic properties of ZnO and ZnO:Eu~(3+)@Au HS were investigated under UV-Vis light irradiation towards rhodamine 6 G.The obtained results demonstrate the synergetic effect of the deposited gold nanoparticles and Eu~(3+)doping on photocatalytic activity of ZnO:Eu~(3+)@Au HS in comparison to pristine ZnO and ZnO:Eu~(3+)HS.     

Synthesis and Luminescence of MeSiO_3:Eu,Bi Luminophors(Me=Mg,Ca,Sr,Ba)

The luminophors of four kinds of alkaline earth meta-silicates doped with Eu~3 and/or Bi~(3 )ion(s)weresynthesized and the luminescence properties of Bi~(3 )and Eu~(3 )ions were studied.The regularities that Me(Ⅱ)ions affect the luminescence of Eu~(3 )ion sensitized by Bi~(3 )ion were investigated.The optimum composition andsynthesis condition were obtained.The absorption and emission peak are situated at 283 and 353nm with theoptimum concentration 0.02 mol of Bi~(3 )in CaSiO_3:Bi.In CaSiO_3:Bi,the optimum concentration of Bi~(3 )is0.007 mol and that of Eu~(3 )is 0.040 mol.For all of the alkaline earth ions concerned in MeSiO_3:Eu,Bi,theBi~(3 )can sensitize the Eu~(3 )and the Me(Ⅱ)ions in host and make a great difference in the adsorption hand ofBi~(3 )ion.by exciting Bi~(3 )ion,the emissions are from both Eu~(3 )and Bi~(3 )ions and the best sensitization effectis achieved when Me(Ⅱ)is Sr.     

Energy transfer mechanism of Sr_4Al_(14)O_(25):Eu~(2+) phosphor

Long lasting blue-green-emitting Sr4Al14O25:Eu2+ phosphors were synthesized by solid-state reactions.The phosphors were investigated by X-ray diffraction(XRD) and fluorescence spectrophotometer.A pure phase of Sr4Al14O25:Eu2+ phosphor was obtained at 1250 °C.There are two different types of Eu emission centers in Sr4Al14O25:Eu2+ phosphor.The effects of the Eu2+ concentration and the reducing temperature on the distribution of Eu2+ among different sites were investigated.The energy transfer mechanism between two different emission centers was elucidated via the investigation of thermal damage influence on the phosphorescence spectra,that is,the energy emitted from an Eu1 emission center could be reabsorbed by an Eu2 emission center.     

Emission tunable of Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35):Eu~(2+),Mn~(2+) oxynitride phosphors via energy transfer for WLEDs

A series of Eu~(2+)doped and Eu~(2+)/Mn~(2+) co-doped Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35)(MSAON) phosphors were synthesized by solid-state reaction at a lower temperature of 1500℃.The crystal morphology and structure of MSAON host were characterized by SEM,TEM and XRD.The quantum yield(QY) for Eu~(2+)doped MSAON phosphors was measured as high as 62%,indicating the excellent luminous efficiency.For the Eu~(2+)/Mn~(2+)co-doped MSAON phosphor,the photoluminescence spectrum and delay curves reveal the efficient energy transfer(ET) process from Eu2+to Mn~(2+)ions.Meanwhile,the corresponding energy transfer efficiency,critical distance and mechanism are discussed in detail.Temperature-dependent emission spectrum shows the thermal and color stabilities.The emission color of MSAON:Eu~(2+),Mn~(2+)phosphors could be tuned from blue through white to red via varying the concentration of Mn~(2+) ions.White-light-emitting diodes(WLEDs) were successfully fabricated by encapsulating the phosphors in nUV LED(365 nm) devices obtaining white light with color rendering index(CRI) as high as 87.7.The results reveal that the MSAON:Eu~(2+),Mn~(2+)phosphors could have potential application in the field of n-UV WLEDs.     

Broadband near-infrared luminescence and energy transfer of Cr~(3+),Ce~(3+) co-doped Ca_2LuHf_2Al_3O_(12) phosphors

Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca₂LuHf₂Al₃O₁₂:Cr³⁺(CLHA:Cr³⁺) and Ca₂LuHf₂Al₃O₁₂:Ce³⁺,Cr³⁺(CLHA:Ce³⁺,Cr^(³⁺)) phosphors were synthesized by the conventional high-temperature solid state reaction.The CLHA:Cr³⁺phosphor,with a good thermal stability,shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr³⁺content.For co-doped sample,the emission intensity of Cr³⁺can be enhanced by three times due to the energy transfer from Ce³⁺to Cr³⁺,which can be evidenced by a significant overlap between the PLE of Cr³⁺single-doped phosphor and the PL of Ce³⁺single-doped phosphor.In addition,the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay Lifetime and Dexter’s energy transfer formula.The broadband NIR emission peaked at 775 nm of CLHA:Cr³⁺,Ce³⁺phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.     

Tunable luminescence,energy transfer and excellent thermal stability of SrMg_2(PO_4)_2:Ce~(3+),Tb~(3+) phosphors for LEDs

A series of novel SrMg_2(PO_4)_2:Ce~(3+),Tb~(3+)(SMP:Ce~(3+),Tb~(3+)) phosphors with tunable emission spectra were produced via high temperature solid phase method.XRD,fluorescence spectrum and fluorescence lifetime for SMP:Ce~(3+),Tb~(3+)were studied in detail.Under the excitation at 308 nm,SMP:Ce~(3+),Tb~(3+) samples can emit high efficiency tunable blue-green light by controlling the proportion of dopant concentration.Through the spectral overlap and the regular change of fluorescence lifetime,it is proved that there is a significant energy transfer between Ce~(3+) and Tb~(3+) in SMP matrix and the energy transfer mechanism is determined to be an electric dipole-dipole interaction with energy transmission efficiency of 55%.In additional,Commission International de L'Eclairage(CIE) color coordinates and thermal stability were studied.All above findings suggest that SMP:Ce~(3+),Tb~(3+)can be regarded as the potential bluish green phosphor for LED applications.     

Energy transfer from Ce~(3+) to Tb~(3+) and Eu~(3+) in zinc phosphate glasses

Ce3+,Eu3+ and Tb3+ singly doped and Ce3+/Eu3+ and Ce3+/Tb3+ co-doped zinc phosphate glasses were prepared by sintering P2O5,ZnO,Ce2(C2O4)3·10H2O and Eu2O3/Tb4O7 mixtures at 1200 °C in the air for 2 h and then annealing at 450 °C for 10 h.The obtained glasses were homogeneous and transparent.The glasses without Ce3+ were colorless and those with Ce3+ showed slightly yellow.The singly doped glasses showed strong emissions and excitations from doped trivalent rare earth ions.Strong energy transfer from Ce3+ to Tb3+ was observed for Ce3+/Tb3+ coped samples.There were also some very weak evidences for the energy transfer from Ce3+ to Eu3+.     

Tunable emission properties of tri-doped Ca_9LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+) phosphors with warm white emitting based on energy transfer

Tri-doped Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors were prepared by a high-temperature solid state method.Under UV light excitation,Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+)samples exhibit a broad band ranging from 320 to 500 nm.At 77 K,the emission spectra of Ca_9 LiY_(2/3)(PO_4)7:Ce~(3+)samples present two obvious emission peaks,indicating that Ce~(3+)ions occupy two different kinds of lattice sites(Ca(1/2) and Ca(3)),As a good sensitizer for Tb~(3+),Ce~(3+)ions in Ca_9 LiY_(2/3)(PO_4)_7 lattice can effectively transfer part of energy to Tb~(3+),and the energy trans fer mechanism is determined to be dipole-dipole interaction.Consequently,the emitting color for Ce~(3+) and Tb~(3+) co-doped Ca_9 LiY_(2/3)(PO_4)_7 samples can be tuned from bluish violet to green.In order to further enlarge the emission gamut,Mn~(2+)ions as red emission components were added,forming tri-doped single-phase Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors.The Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors exhibit tunable emission properties through controlling the relative doping concentration of Ce~(3+),Tb~(3+)and Mn~(2+).Especially,Ca_9 LiY_(2/3)(PO_4)_7:0.09 Ce~(3+),0.12 Tb~(3+),0.30 Mn~(2+)can emit warm white light.The sample shows good thermal stability.At 150℃,the emission intensity for Ce~(3+)(360 nm),Tb~(3+)(545 nm) and Mn~(2+)(655 nm) decreases to 63%,69%,and 72% of its initial intensity,respectively.Moreover,the sample obtains good stability after 10 cycles between room temperature and150℃.     

Enhanced afterglow performance of CaAl_2O_4:Eu~(2+),Nd~(3+) phosphors by co-doping Gd~(3+)

In order to effectively improve the afterglow properties of CaAl_2 O_4:Eu~(2+),Nd~(3+) phosphors,a series of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)(x=0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach.Crystalline composition and microstructure were characterized by XRD,TEM,HRTEM,and XPS,luminescence properties were systematically analyzed by fluorescence spectra,afterglow decay curves and TL glow curve.Results show that all of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)phosphors belong to monoclinic CaAl_2 O_4,without other cystalline phase.The blue emission at 442 nm is observed,which is assigned to the 4 f~65 d→4 f~7 transition of Eu~(2+) ions.Doping with appropriate amount of Gd~(3+) ions(x=0.036 mol) significantly improves the afterglow properties of phosphors,but the excessive doping of Gd~(3+) induces the fluorescent quenching.The doping of moderate Gd3+changes the traps states,the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved,thus significantly improving afterglow performance.     

Luminescence tuning of Ce~(3+),Pr~(3+) activated(Y,Gd)AGG system by band gap engineering and energy transfer

Tuning of phosphor luminescence properties,including the emission energy/intensity and thermal stability,is an important way to develop superior luminescent materials for diverse applications.In this work,we discuss the effect of band gap engineering and energy transfer on the luminescence properties of Ce~(3+)or Pr~(3+) doped(Y,Gd)AGG systems,and analyze the underlying reasons for their different phenomena.By using VUV-UV excitation spectra and constructing VRBE schemes,the changes of host band structure,5 d excited level energies and emission thermal stability of Ce~(3+)and Pr~(3+) with the incorporation of Gd~(3+)ions were studied.In addition,the energy transfer dynamics was also investigated in terms of the luminescence decay curves.This work demonstrates a way to tune phosphor luminescence properties by combining band gap engineering and energy transfer tailoring and provides an inspiring discussion on the different results of Ce~(3+)doping on the Ce~(3+)and Pr~(3+)emissions.     

Synthesis and characterization of Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) nanorods via a solvothermal routine

Y2O2S:Eu3+,Mg2+,Ti4+ nanorods were prepared by a solvothermal procedure.Rod-like Y(OH)3 was firstly synthesized by hydrothermal method to serve as the precursor.Y2O2S:Eu3+,Mg2+,Ti4+ powders were obtained by calcinating the precursor at CS2 atmosphere.The Y2O2S:Eu3+,Mg2+,Ti4+ phosphor with diameters of 30-50 nm and lengths up to 200-400 nm inherited the rod-like shape from the precursor after calcined at CS2 atmosphere.The Y2O2S:Eu3+,Mg2+,Ti4+ nanorods showed hexagonal pure phase,good dispersion and exhibite...     

Luminescent and thermometric properties of dual emitting Eu~(2+)/Sm~(3+) co-doped Sr_4La(PO_4)_3O phosphor based on energy transfer

Eu²⁺/Sm³⁺co-doped dual-emitting Sr₄La(PO₄)₃O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu²⁺/Sm³⁺co-doped Sr₄La(PO₄)₃O phosphors were researched and analyzed in detail.The blue emission of Eu²⁺and the red emission of Sm³⁺can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr₄La(PO₄)₃O:Eu²⁺/Sm^(³⁺)phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr₄La(PO₄)₃O:Eu²⁺/Sm³⁺phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu²⁺and Sm³⁺ions.