A single red InGaN-based light-emitting diode with a europium (III) ternary complex as mono-phosphor

A novel europium (III) ternary complex, Eu(TPBDTFA)(3)Phen, was designed and synthesized. Photoluminescence measurements show that the energy absorbed by the organic ligands was efficiently transferred to the central Eu(3+) ions, and the complex exhibits strongly red emission due to the (5)D(0)-(7)F(j) transitions of Eu(3+) ions with appropriate CIE (Commission Internationale de l'Eclairage, International Commission on Illumination) chromaticity coordinates (x=0.66, y=0.33) under 310-420 nm light excitation. The luminescence quantum yield for the Eu(3+) complex is 0.18. Thermogravimetric analysis (TGA) confirms a high thermal stability of the complex with a decomposition temperature of 341 degrees C. All the characteristics indicate that the Eu(3+) complex is a highly efficient red phosphor suitable to be excited by near UV light. An intense red-emitting LED was fabricated by combining the mono-phosphor Eu(TPBDTFA)(3)Phen with a approximately 395 nm emitting InGaN chip.     

Eu(III)-modified properties of thermosensitive core–shell microspheres

We successfully prepared PNIPAM-g-P(NIPAM-co-St) (PNNS) core–shell microsphere by an emulsifier-free emulsion polymerization method. When PNNS with a core–shell structure is interacted with Eu(III), Eu(III) mainly bonds to oxygen of the carbonyl groups of PNNS, forming the novel PNNS-Eu(III) complex. It was found that the complex showed thermosensitive and fluorescent properties at one time. Especially, the maximum emission intensity of Eu(III) in the complex at 614 nm is significantly enhanced in comparison with that of pure Eu(III), demonstrating that there exists an efficient intermolecular energy transfer from the polymer ligand to Eu(III) and then the excited Eu(III) generates the enhanced fluorescence. When the weight ratio of Eu(III) and the PNNS is 8 wt%, the enhancement of the emission fluorescence intensity at 614 nm is highest.     

Ca(9)Lu(PO(4))(7):Eu(2+),Mn(2+): a potential single-phased white-light-emitting phosphor suitable for white-light-emitting diodes

A novel white-light-emitting phosphor Ca(9)Lu(PO(4))(7):Eu(2+),Mn(2+) has been prepared by solid-state reaction. The photoluminescence properties indicate that there is an efficient energy transfer from the Eu(2+) to Mn(2+) ions via a dipole-quadrupole reaction. The obtained phosphor exhibits a strong excitation band between 250 and 430 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Upon excitation of UV light, white light is realized by combining a broad blue-green emission band at 480 nm and a red emission band at 645 nm attributed to the Eu(2+) and Mn(2+) ions. The energy-transfer efficiency and critical distance were also calculated. Furthermore, the phosphors can generate lights from blue-green through white and eventually to red by properly tuning the relative ratio of the Eu(2+) to Mn(2+) ions through the principle of energy transfer. Preliminary studies showed that the phosphor might be promising as a single-phased white-light-emitting phosphor for a UV white-light LED.     

Ce3+,Tb3+,Eu3+共掺杂Sr2MgSi2O7体系的白色发光和能量传递机理

通过正交试验,采用高温固相法制备了Sr2-x-y-zMgSi2O7∶xCe3+,yTb3+,zEu3+系列样品.使用X射线衍射仪和荧光光谱仪表征了样品的物相和发光性质,并讨论了Ce3+-Tb3+-Eu3+共掺杂Sr2MgSi2O7体系中的能量传递过程.实验结果表明,在327 nm波长激发下,所合成荧光粉的发射峰主要位于387 nm(蓝紫)、542nm(绿)和611 nm(红)处;分别以387,542和611 nm为监控波长,所得激发光谱显示荧光粉在327 nm处有最好的激发.在327 nm光激发下,系列样品发光进入白光区.最优化的荧光粉为Sr1.91MgSi2O7∶0.01Ce3+,0.05Tb3+,0.03Eu3+,其色坐标为(0.337,0.313),是一种潜在的发光二极管(LED)用白色荧光粉.     

The synthesis and luminescent properties of bonded Eu(III) polymer phosphors for white light-emitting diode

A coordination and copolymerization strategy was adopted to synthesize bonded Eu(III) polymer phosphor poly(MMA-co-Eu(BTZ)₂(Phen)(UA)) (PM-Eu for short) with methyl methacrylate (MMA) as polymer matrix and Eu-complex monomer Eu (BTZ)₂(Phen)(UA) using azodiisobutyronitrile as initiator. The copolymer PM-Eu exhibits thermal stability up to 266°C. It also exhibits wide and strong excitation bands from 230 to 380 nm monitored at 612 nm, matching well with the 365 nm of ultraviolet (UV) chip. PM-Eu displays Eu(III) characteristic peaks at 579, 591, 612, 650, and 700 nm under the excitation of 365 nm of UV light. Meanwhile, it has a fluorescence lifetime of 0.582 ms, and it has a higher quantum yield of 0.672. All the results prove that the polymer PM-Eu can be applied as a red component for fabrication of near UV-based white light-emitting diode (LED).     

Red Emission of Eu(III) Complex Based on 1-(7-(tert-butyl)-9-ethyl-9H- carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione Excited by Blue Light

A new Eu(III) complex, EuL3(phen), was synthesized, where L is the abbreviation of de-protonated 1-(7-(tert-butyl)-9-ethyl-9H-carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione (HL), phen is the abbreviation of 1,10-phenanthroline. The Eu(III) complex was characterized by element analysis, IR, 1H NMR, UV-visible absorption spectroscopy, thermogravimetric anal-ysis (TGA), and photoluminescence measurements (PL). TGA shows that thermal stability of the complex is up to 325 oC. PL measurement indicates that the Eu(III) complex exhibits intense red-emission and extends their excitation bands to visible region. LEDs device was successfully fabricated by precoating complex EuL3(phen) onto 460 nm blue-emitting InGaN chip. The emission of device shows that the complex can act as red phosphor in combination with 460 nm blue-emitting chips. This europium complex based on 1-(7-(tert-butyl)-9-ethyl-9H-carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione is a kind of interesting red-emitting material excited by blue light, which could avoid the damage of excitation by UV light.     

铕(Ⅲ)与对甲基苯甲酸.2,2'-联吡啶配合物的合成.晶体结构及荧光光谱

合成了对甲基苯甲酸铕2,2'-联吡啶的晶体配合物,元素分析表明配合物的化学式为Eu(p-MBA)~3 dipy(p-MBA:对甲基苯甲酸根;dipy:2,2'-联吡啶).用X 射线衍射法测定了配合物的单晶结构,其结构式为Eu~2(p-MBA)~6(dipy) ~ 2, 属单斜晶系,C2/C空间群,晶胞参数:a=1.4086(6),b=1.9115(11),c=2.3077(16)nm;β=96.60(4)~°,V=6.1727nm^3,Z=4对甲基苯甲酸根,2,2'-联吡啶均以双齿配位, 中心铕离子的配位数为八,形成的配位多面体为三角十二面体,两个铕离子通过四个对甲基苯甲酸基桥联,形成双核配合物,利用配合物Eu(p-MBA)~3 dipy在紫外光或可见激发下, 能发出很强荧光的特性,以Eu(Ⅲ)离子为光谱探针,77K 下测得其高分辨激发和发射光谱及时间分辨光谱,光谱数据表明配合物中有两种Eu(Ⅲ)离子格位.     

Application of chelate phosphine oxide ligand in EuIII complex with mezzo triplet energy level, highly efficient photoluminescent, and electroluminescent performances

The chelate phosphine oxide ligand bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) was used as a unit neutral ligand to prepare the complex Eu(TTA)(3)(DPEPO) 1 (TTA = 2-thenoyltrifluoroacetonate). Compound 1 has a photoluminescence (PL) quantum yield of 55.3%, which is more than the twice of the PL quantum yield of Eu(TTA)(3)(TPPO)(2) (TPPO = triphenylphosphine oxide). Investigation indicated that DPEPO in 1 has the mezzo first triplet excited energy level (T(1)) between the first singlet excited energy level (S(1)) and T(1) of TTA, which may support one more additional energy transfer routines from the T(1) energy level of DPEPO to that of TTA, and consequently results in the improvement of energy transfer in the Eu(III) complex. DPEPO forms a complex with a more rigid and compact structure that can improve energy transfer between ligands and the center Eu(III) ion, support the higher saturation level by the coordinating ability of the oxygen atom in the ether moiety, and consequently enhance the PL intensity and efficiency of the corresponding Eu(III) complex. The multilayered electroluminescent (EL) device of 1 used as the red dopant exhibited an impressive brightness of 632 cd m(-2) at 25 V. The device had the excellent voltage-independent spectral stability with an emission peak at 615 nm. To the best of our knowledge, this luminescence is the brightest emission among Eu complexes with phosphine oxide ligands. The maximum external quantum yield (eta(ext)) of 2.89% and the maximum current and power efficiency of 4.58 cd A(-1) and 2.05 lm W(-1) were achieved at a low turn-on voltage of 7 V and current density of 0.021 mA cm(-2). These properties demonstrate that the chelate phosphine oxides ligand DPEPO can not only be favorable to form the rigid and compact complex structure and increase the efficiency of devices, but also reduce the ability of the formation of exciplex. DPEPO shows much better performance compared with the ordinary phosphine oxide ligand triphenylphosphine oxide.     

高温固相法合成R_(2-x)(MoO_4)_3∶xEu~(3+)(R=Y,Gd)红色荧光粉的研究

采用高温固相法合成R2-x(MoO4)3∶xEu3+(R=Y,Gd)系列红色荧光粉.研究了煅烧温度、助熔剂的含量和Eu3+的掺杂量对样品发光性能的影响,并对样品的物相组成、激发和发射光谱进行分析.结果表明,样品Gd0.6(MoO4)3∶1.4Eu3+在800℃左右煅烧时呈单斜晶结构,当煅烧温度提高到950℃左右,呈正交斜晶结构;样品Y0.2(MoO4)3∶1.8Eu3+在800℃左右煅烧时已经完全形成了正交结构,当煅烧温度升高到1000℃左右时,其正交结构得到保持,没有发生相变.其中,助熔剂NH4Cl的含量占样品总量的3%,煅烧温度为1000℃,保温3h得到的样品Gd0.6(MoO4)3∶1.4Eu3+和Y0.2(MoO4)3∶1.8Eu3+的发光性能达到最佳.另外,由激发和发射光谱分析表明,该荧光粉可以被近紫外光(395nm)和蓝光(465nm)有效激发,发射峰值位于612nm的红光,对应于Eu3+离子的5 D0→7 F2跃迁,是一种可应用在紫外光和蓝光芯片激发产生白光LED的红色荧光粉.     

Sr_2CeO_4∶Eu~(3+)柠檬酸-凝胶法的合成及发光性质研究

柠檬酸-凝胶方法促使多离子在分子水平上混合,与固相烧结方法相比,能够降低烧结温度和烧结时间。利用这种方法在1000℃下很短的时间得到单相化合物Sr2CeO4。Sr2CeO4是一种发出很强蓝光的基质发光材料。为寻找新的发光体,我们将稀土离子Eu3+掺杂在其中,从荧光光谱上可以看出存在从基质向稀土离子的能量转移。Sr2CeO4∶Eu3+的发光颜色可调谐,当Eu3+离子浓度较小(<0.5mol%)时,体系发出很强的白光;当Eu3+离子浓度较大(>10mol%)时,体系发出很强的红光,并且猝灭浓度高。     

Ligand-passivated Eu:Y2O3 nanocrystals as a phosphor for white light emitting diodes

Eu(III)-doped Y(2)O(3) nanocrystals are prepared by microwave synthetic methods as spherical 6.4 ± 1.5 nm nanocrystals with a cubic crystal structure. The surface of the nanocrystal is passivated by acetylacetonate (acac) and HDA on the Y exposed facet of the nanocrystal. The presence of acac on the nanocrystal surface gives rise to a strong S(0) → S(1) (π → π*, acac) and acac → Ln(3+) ligand to metal charge transfer (LMCT) transitions at 270 and 370 nm, respectively, in the Eu:Y(2)O(3) nanocrystal. Excitation into the S(0) → S(1) (π → π*) or acac → Ln(3+) LMCT transition leads to the production of white light emission arising from efficient intramolecular energy transfer to the Y(2)O(3) oxygen vacancies and the Eu(III) Judd-Ofelt f-f transitions. The acac passivant is thermally stable below 400 °C, and its presence is evidenced by UV-vis absorption, FT-IR, and NMR measurements. The presence of the low-lying acac levels allows UV LED pumping of the solid phosphor, leading to high quantum efficiency (～19%) when pumped at 370 nm, high-quality white light color rendering (CIE coordinates 0.33 and 0.35), a high scotopic-to-photopic ratio (S/P = 2.21), and thermal stability. In a LED lighting package luminosities of 100 lm W(-1) were obtained, which are competitive with current commercial lighting technology. The use of the passivant to funnel energy to the lanthanide emitter via a molecular antenna effect represents a new paradigm for designing phosphors for LED-pumped white light.     

Synthesis, characterization and luminescence property of N,N'-di(pyridine N-oxide-2-yl)pyridine-2,6-dicarboxamide and corresponding lanthanide (III) complexes

A new ligand, N,N'-di(pyridine N-oxide-2-yl)pyridine-2,6-dicarboxamide (LH2) and its several lanthanide (III) complexes (La, Eu, Gd, Tb, Y) were synthesized and characterized in detail based on elemental analysis, conductivity measurements, IR, 1H NMR, MS (FAB) and UV spectra and TG-DTA studies. The results indicated that the composition of these binary complexes is [Ln(LH2)(NO3)2.H2O]NO3.nH2O (n=0-1); while the ligand has a good planar structure with strong hydrogen bonds. The fluorescence spectra exhibits that the Tb (III) complex and the Eu (III) complex display characteristic metal-centered fluorescence in solid state while ligand fluorescence is completely quenched. However, the Tb (III) complex displays more effective luminescence than the Eu (III) complex, which is attributed to especial effectivity in transferring energy from the lowest triplet energy level of the ligands (T) onto the excited state (5D4) of Tb (III) than that (5D1) of Eu (III).     

THE IMPORTANCE OF COMPLEX FORMATION IN THE SENSITIZATION OF Eu(III) EMISSION BY OROTIC ACID

Abstract— Orotic acid (I) and 3-methylorotic acid (II) are the only orotic acid derivitives which efficiently sensitire emission from Eu(III) in D₂O solution. This emission is only weakly sensitized by I-methylorotic acid (III), 1,3-dimethylorotic acid (IV), the methyl and isopropyl esters of orotic acid (V) 6-acetyluracil (VI) and not sensitized at all by the bases uracil. thymine and their nucleosides. Substituent groups on either the carboxyl group or the N-l position of the ring thus prevent efficient energy transfer from the excited orotic acid to Eu(III). These structural requirements for efficient energy transfer are the same as the structural requirements for formation of a stable. bidentate. ground state complex between Eu(III) and orotic acid (VII) (Sarpotdar and Burr, 1978).
We, therefore, propose that sensitization of Eu(III) emission by orotic acid at pH 5 is an example of energy transfer within the bidentate complex of Eu(III) and orotic acid. We also propose that the complexed orotic acid is itself excited by eollisional energy transfer from free triplet excited orotic acid (since the concentration of complex measured to be present. 5–7%, is too low to account for the efficiency of the sensitization). We also propose that emission from the excited complexed Eu(III) can be either from the complexed ion or from free Eu(III)* resulting from dissociation of the complex during the lifetime of the excited ion.
The efficiency of Eu(III) sensitized emission is shown to depend on the concentrations of Eu(III). orotic acid and pH with relationships kinetically consistent with the above hypothesis.     

Chemiluminescence energy transfer reaction for the on-line preparation of peroxymonocarbonate and Eu(II)-dipicolinate complex

In this work, an on-line preparation of peroxymonocarbonate was formed innovatively, which offered a reliable intermediate for further investigation. The forming conditions of on-line peroxymonocarbonate ions were investigated in detail. Meanwhile, the energy transfer chemiluminescent reaction of peroxymonocarbonate and the Eu(II)-dipicolinate complex was studied. Through UV-visible absorption spectra, CL method, ESR spin-trapping technique, and mass spectrum experiments, it can be concluded that peroxymonocarbonate oxidizes Eu(II) to Eu(III), and simultaneously creates radicals. The bond rearrangement within radicals formed the singlet molecular oxygen. The energy originating from the singlet oxygen was accepted by the (Eu(III)dipic)- complex. The excited (Eu(III)dipic)- ions underwent radiative deactivation and emitted the chemiluminescence. The peroxymonocarbonate system was a simple, inexpensive, and relatively nontoxic alternative to other oxidants, and it can be used in a mild, neutral-pH environment.     

d → f energy transfer in a series of Ir(III)/Eu(III) dyads: energy-transfer mechanisms and white-light emission

An extensive series of blue-luminescent iridium(III) complexes has been prepared containing two phenylpyridine-type ligands and one ligand containing two pyrazolylpyridine units, of which one is bound to Ir(III) and the second is pendant. Attachment of {Ln(hfac)(3)} (Ln = Eu, Gd; hfac = anion of 1,1,1,5,5,5,-hexafluoropentanedione) to the second coordination site affords Ir(III)/Ln(III) dyads. Crystallographic analysis of several mononuclear iridium(III) complexes and one Ir(III)/Eu(III) dyad reveals that in most cases the complexes can adopt a folded conformation involving aromatic π stacking between a phenylpyridine ligand and the bis(pyrazolylpyridine) ligand, but in one series, based on CF(3)-substituted phenylpyridine ligands coordinated to Ir(III), the steric bulk of the CF(3) group prevents this and a quite different and more open conformation arises. Quantum mechanical calculations well reproduce these two types of "folded" and "open" conformations. In the Ir(III)/Eu(III) dyads, Ir → Eu energy transfer occurs with varying degrees of efficiency, resulting in partial quenching of the Ir(III)-based blue emission and the appearance of a sensitized red emission from Eu(III). Calculations based on consideration of spectroscopic overlap integrals rule out any significant contribution from F?rster (dipole-dipole) energy transfer over the distances involved but indicate that Dexter-type (exchange) energy transfer is possible if there is a small electronic coupling that would arise, in part, through π stacking between components. In some cases, an initial photoinduced electron-transfer step could also contribute to Ir → Eu energy transfer, as shown by studies on isostructural iridium/gadolinium model complexes. A balance between the blue (Ir-based) and red (Eu-based) emission components can generate white light.     

Excitation Induced Emission Color Change Based on Eu(III)‐Zn(II)‐containing Polymer Complex

A novel polymer P‐1 is prepared by the reaction of the monomer 5,5′‐divinyl‐2,2′‐bipyridine and Salen‐Zn(II) via Heck cross coupling. Interestingly, P‐1 can further incorporate with Eu(TTA)₃·2H₂O to generate copolymer P‐2 with two different metal centers. P‐2 exhibits exceptional dual emissive properties which can be tuned by excitation wavelength. For example, an orange fluorescence can be obtained when P‐2 is excited at 430 nm, whereas a red emission with a huge Stoke shift of 57 nm is observed when it is excited at 345 nm. The high wavelength emission can be attributed to Eu(III) (⁵D₀→⁷F₂), which is lit by an effective photoinduced energy transfer process between P‐1 and the Eu(TTA)₃ complex. The properties of P‐2 have led to a better understanding of the energy transfer process between P‐1 and Eu(TTA)₃ moieties.     

Density functional theory investigation of Eu(III) complexes with beta-diketonates and phosphine oxides: model complexes of fluorescence compounds for ultraviolet LED devices

The density functional theory was employed to investigate Eu(III) complexes with three beta-diketonates and two phosphine oxides (complex M1: Eu(bdk)3(TPPO)2, complex M2: Eu(bdk)3(TMPO)2, and complex M3: Eu(bdk)3(TPPO)(TMPO)) deemed to be the model complexes of the fluorescence compounds for the ultraviolet LED devices we have recently developed. For each complex, two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference of the energy between two minimum energy points is found to be quite small (less than 1 kcal/mol). Vertical excitation energies and oscillator strengths for each complex at two optimized geometries have been obtained by the time-dependent density functional theory, and the character of the excited states has been investigated. For complex M3, the absorption edge is red-shifted, and the oscillator strengths are relatively large. The efficiency of intersystem crossing and energy transfer from the triplet excited state to the Eu(III) ion is considered by calculating DeltaE(ISC) (the energy difference between the first singlet excited state and the first triplet excited state) and DeltaE(ET) (the difference between the excitation energy of the complex for the first triplet excited state and the emission energy of the Eu(III) ion for 5D to 7F).     

Sensitized near-IR luminescence of Ln(III) complexes with benzothiazole derivatives

Lanthanide complexes with benzothiazole derivatives (Btz-R, R = OCH(3) and OH) and terpyridine (tpy) ligands were synthesized, and their photophysical properties were precisely investigated. The free Btz-OCH(3) ligand in toluene, excited with UV light, produced the normal emission bands around 410 nm, whereas Btz-OH produced a strong excited-state intramolecular proton transfer (ESIPT) band at 510 nm. The Ln(III) complexes (Ln = Nd, Er, and Yb) exhibited sensitized near-IR luminescence when the Btz-R ligands were excited. The sensitized luminescence quantum yields (Phi(Ln)) of the lanthanide complexes were markedly enhanced by ESIPT: for [Nd(Btz-R)(tpy)] in toluene solution, Phi(Ln) = 0.04% for Btz-OCH(3) and 0.39% for Btz-OH. The sensitized luminescence of the Er(III) complexes (Phi(Ln) = 0.002% for Btz-OCH(3) and 0.009% for Btz-OH) was less efficient than that of the Nd(III) complexes. This difference is due to the smaller energy gap between the emitting and ground levels of the Er(III) ion. The rate constants for the energy transfer from Btz-R to Ln(III) were about approximately 10(9) s(-1), as evaluated by the F?rster resonance energy transfer mechanism.     

Emission band shape probes of the mixed-valence excited state properties of polypyridyl-bridged bis-ruthenium(II) complexes

The absorption spectra and emission spectral band shapes of several polypyridine-ligand (PP) bridged bis-ruthenium(II) complexes imply that the Ru(II)/Ru(III) electronic coupling is weak in their lowest energy metal to ligand charge transfer (MLCT) excited states. Many of these PP-bridging ligands contain pyrazine moieties and the weak electronic coupling of the excited states contrasts to the strong electronic coupling inferred for the correlated mixed-valence ground states. Although the bimetallic complexes emit at significantly lower energy than their monometallic analogs, the vibronic contributions to their 77 K emission spectra are much stronger than expected based on comparison to the monometallic analogs (around twofold in some complexes) and this feature is characteristic of bimetallic complexes in which the mixed-valence excited states are electronically localized. The weaker excited state than ground state donor/acceptor electronic coupling in this class of complexes is attributed to PP-mediated super-exchange coupling in which the mediating orbital of the bridging ligand (PP-LUMO) is partly occupied in the MLCT excited states, but is unoccupied in the ground states; therefore, the vertical Ru(III)-PP⁻ (MLCT) energy is larger and the mixing coefficient smaller in these excited states than is found for Ru(II)-PP in the corresponding ground states.     

一种新型的红色荧光粉——Ca4GdO(BO3)3:Eu3+

采用高温固相法制备了一种新型的红色荧光粉——Ca₄GdO(BO₃)₃:Eu³⁺.研究了它在X射线、真空紫外和紫外激发下的发光性能,研究表明,样品无论是在X射线、真空紫外还是在紫外的激发条件下,样品都能发出很强的红光.它的主发射峰在610 nm,而且其它位置的发射峰都很弱;它很容易被254nm、172 nm和X射线所激发而发出很强的红光,因此是一种具有潜在应用价值的红色荧光粉.研究表明Gd³⁺离子与激活剂(Eu³⁺)存在着一种能量传递的过程,而这种能量的传递过程可能跟二次吸收有关.