Microwave-assisted fast synthesis and red-emitting properties of a borotellurate-based phosphor with excellent thermostability

At present,with the increasing application needs of phosphor-converted white light-emitting diode(wLED),the synthetic efficiency and thermal stability of phosphor become urgent problems.Herein,this research reports a microwave-assisted fast synthesis approach to obtain a Sm^(3+)-activated borotellurate Na_(2)Y_(2)TeO_(4)(BO_(3))_(2)(NYTB)red phosphor with high crystallinity,excellent thermostability,and low chromaticity shift.For the NYTB-based phosphor,in contrast to the conventional solid-state synthesis,the microwave-assisted synthesis method involves lower synthesis temperature and shorter processing time.Additionally,the concentration quenching mechanism was determined.The w-LED device packaged with the studied phosphor exhibits a near-standard white light with proper CCT and high Ra parameters.

Luminescent properties and application of Eu^(3+)-activated Gd_2(MoO_4)_3 red-emitting phosphor with pseudo-pompon shape for solid-state lighting

Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescent spectrophotometry, respectively. The as-obtained phosphors were single crystalline phase with orthorhombic unit cell. The particles of the powder samples had the length of 5-12 m and width of 3-7 m with flake shape and large surface area, which is suitable for manufacture of white LEDs. The phosphor could be efficiently excited by the incident light of 348-425 nm, well matched with the output wavelength of near-UV (In,Ga)N chip, and re-emitted an intense red light peaking at 615 nm. By combing this phosphor with a ~395 nm-emitting (In,Ga)N chip, a red LED was fabricated, so that the applicability of this novel phosphor to white LEDs was confirmed. It is considered to be an efficient red-emitting conversion phosphor for solid-state lighting based on (In,Ga)N LEDs.

Red-emitting YAG:Ce,Mn transparent ceramics for warm WLEDs application

A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properties were systematically investigated.These transparent ceramics have average grain sizes of 10–16μm,clean grain boundaries,and excellent transmittance up to 83.4%at 800 nm.Under the excitation of 460 nm,three obvious emission peaks appear at 533,590,and 745 nm,which can be assigned to the transition 5 d→4 f of Ce^3+and 4 T1→6 A1 of Mn^2+.Thus,the Mn^2+–Si4+pairs can effectively modulate the emission spectrum by compensating broad orange-red and red spectrum component to yield high quality warm white light.After the optimized YAG:Ce,Mn transparent ceramic packaged with blue light-emitting diode(LED)chips,correlated color temperature(CCT)as low as 3723 K and luminous efficiency(LE)as high as 96.54 lm/W were achieved,implying a very promising candidate for application in white light-emitting diodes(WLEDs)industry.

Factors affecting afterglow properties of red-emitting phosphor MgSiO_3:Mn^(2+),Nd^(3+) for luminescent fiber

With stable physical properties, the rare-earth silicate phosphor of MgSiO3：Mn2＋,Nd3＋ is one of the suitable luminescent materials used in preparing functional fibers. In order to promote the afterglow properties of red-emitting phosphors, we prepared it by means of solid-state reaction, and the effect of manufacturing elements including H3BO3 and environmental factor of calcining temperature, type of flux on its luminescence property were investigated through evaluating their afterglow properties. The results showed that with the concentration of Nd3＋ increasing, the amounts of H3BO3 doping and calcining temperature, the afterglow time and initial brightness of the rare-earth silicate phosphor increased and then decreased gradually. The afterglow properties of different flux concentration were different from one to another as： H3BO3〉Na＋〉K＋〉No flux.

Properties of red-emitting phosphors Sr_2MgSi_2O_7:Eu^(3+) prepared by gel-combustion method assisted by microwave

Novel red-emitting phosphors Sr2MgSi2O7：Eu3＋ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7：Eu3＋ was composed of two major parts： one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3＋-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3＋. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3＋, respectively. The concen-tration of Eu3＋ （x） had great effect on the emission intensity of Sr2-xMgSi2O7：Eu3＋x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3＋ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li＋ ions.

A Cost-effective Approach for 2-（t-Butyl）-6-methyl-4H-pyrone-A Key Intermediate Toward the Synthesis of Red-emitting Dyes for OLED Applications

In the interest of driving down the cost of DCM-type light emitting materials, we have found a new approach to prepare 2-（t-butyl）-6-methy1-4H-pyrone, which is cost effective and more amenable to large scale production than the reported method. Furthermore, three new DCM-type dyes, N,N-bis-[p-（2-（4-dicyanomethylene-6-t-butyl-4H- pyran-2-yl）-vinyl）-phenyl]-4-t-butyl-aniline （BDCM-BA）, N,N-bis-[p-（2-（4-dicyanomethylene-6-t-butyl-4H-pyran- 2-yl）-vinyl）-phenyl]aniline （BDCM-A） and N,N-bis-[p-（2-（4-dicyanomethylene-6-t-butyl-4H-pyran-2-yl）-vinyl）- phenyl]-4-methoxyl-aniline （BDCM-MA） were synthesized in good yields using 2-（t-butyl）-6-methyl-4H-pyrone as starting material. They can be utilized in OLEDs as nondoped red emitting materials as the result of the restricted concentration quenching effect.

Synthesis and photoluminescence properties of novel red-emitting Ca_(14)Mg_2(SiO_4)_8:Eu^(3+)/Sm^(3+) phosphors

Novel red-emitting Eu3＋, Sm3＋ singly doped and co-doped Ca14Mg2（SiO4）8 phosphors were prepared by conventional solidstate reaction. Powder X-ray diffraction patterns were employed to confirm phase pttrity. Ca14Mg2（SiO4）8：Eu3＋ phosphors exhibited intense red emission under 394 nm excitation and Ca14Mg2（SiO4）8：Sm3＋ phosphors, excited at 405 nm, also showed strong red emitting at 602 nm. The concentration quenching mechanism of Cal4Mg2（SiOa）s：Eu3＋ was dipole-dipole interaction, while that of CalnMg2（SiOn）8：Sm3＋ was energy migration among nearest neighbor ions. The results indicated that Ca14Mg2（SiOn）8：Eu3＋ and Ca14Mg2（SiOn）s：Sm3＋ were promising red-emitting phosphors for WLEDs. Meanwhile, the effect of co-doping Sm3＋ ions on photoluminescence properties of CalaMg2（SiO4）s：Eu3＋ was studied and energy transfer from Sm3＋ to Eu3＋ was discovered in Eu3＋, Sm3＋ co-doped phosphors.

Eu^(3+)-doped BaLiZn_(3)(BO_(3))_(3):A novel red-emitting phosphor for blue chips excited white LEDs

A series of novel red-emitting BaLiZn_(3)(BO_(3))_(3):Eu^(3+)phosphors were synthesized through the high temperature solid state reaction method.The phase composition,crystal structure,morphology and photo luminescence property of the BaLiZn_(3)(BO_(3))_(3):Eu^(3+)samples were systematically investigated.The phosphor can be efficiently excited by the near ultraviolet light(NUV)of 396 nm and blue light of 466 nm,and give out red light emission at 618 nm corresponding to the electric dipole transition(^(5)D_(0)→^(7)E_(2)).The optimal doping concentration of Eu^(3+)ions in BaLiZn_(3)(BO_(3))_(3)is determined to be about 3 mol%,and the concentration-quenching phenomenon arise from the electric dipole-dipole interaction.The temperature dependent luminescence behavior of BaLiZn_(3)(BO_(3))_(3):0.03 Eu^(3+)phosphor exhibits its good thermal stability,and the activation energy for thermal quenching characteristics is calculated to be 0.1844 eV.The decay lifetime of the BaLiZn_(3)(BO_(3))_(3):0.03 Eu^(3+)is measured to be 1.88 ms.These results suggest that the BaLiZn_(3)(BO_(3))_(3):Eu^(3+)phosphors have the potential application as a red component in white light emitting diodes(WLEDs)with NUV or blue chips.

A red-emitting water-soluble fluorescent probe for biothiol detection with a large Stokes shift

In this work, we presented a fluorescent probe(MCQ-DNBS) for selective and sensitive detection of biothiols based on a methylated chromenoquinoline(MCQ) derivative. Probe MCQ-DNBS was constructed by masking the OH group in MCQ with a common sensing unit, 2,4-dinitrobezensulfonate group(DNBS) for biothiols. Due to the photo-induced electron transfer(PET) process between MCQ and DNBS, this probe was weekly fluorescent. Upon the addition of biothiols(Cys, Hcy and GSH), this probe emitted a strong red fluorescence(λ_(em max)=613 nm) with a large Stokes shift(115 nm). In addition,fluorescence imaging of biothiols in living cells was successfully realized using MCQ-DNBS as a detector.

Enhancing thermal stability and photoluminescence of red-emitting Sr_(2)Si_(5)N_(8):Eu phosphors via boron doping

Surface passivation is a common method to improve the resistance of thermal degradation of nitride phosphors.However,such a surface passivation generally needs extra processes and decreases the photoluminescence property of the phosphors.In this work,both the thermal stability and photoluminescence property of a red phosphor Sr_(2)Si_(5)N_(8):Eu are improved through the addition of BN.The influence of B on the crystal structure and the valence state of active ions was analyzed by experimental characterization.First-principles calculations were applied to analyze the formation energy of N vacancies,which influence the resistance of thermal degradation.Finally,combining with experimental characterization and calculations,the enhancing mechanism of thermal stability and photoluminescence by B was studied.

Red-emitting salicylaldehyde Schiff base with AIE behaviour and large Stokes shift

Three salicylaldehyde Schiff base（SSB）, iso-PBP, PBP and EPB, were facilely synthesized and exhibited aggregation-induced emission. The introduction of C= N-N = C moiety in these SSB dyes largely extend the conjugation system and push their emission to yellow to red spectral region. These SSB dyes were negligibly fluorescent in dilute THF solution. In THF/water mixtures with high water fractions, they displayed strong yellow to red fluorescence（up to 617nm） and large Stokes shifts（up to 152 nm）. Single crystal analysis on EBP showed the longer emission of in aggregated state was attributed to the molecular packing effect as compared with that in dilute solution. The bio-imaging application indicated EBP could specifically accumulate in lipid droplets in living cells.

Preparation and Characterization of Red Emitting Phosphor Ba_xCa_(3-x)(PO_4)_2∶Ce, Mn

Red emitting phosphor （BaCa）3 （PO4）2 ： Ce, Mn was prepared by solid state reactions. Effect of chemical component, preparation conditions on the performance of the phosphor was studied by using TGDTG, XRD and phosphor relative brightness meter. It is found that the host （ Bax Ca1-x ） 3 （PO4） 2 is present as a distorted Ca3（PO4）2 structure. Ce^3＋ acts as a sensitiser, and Mn^2＋ is activator. By energy transfer from Ce^3＋ to Mn^2＋, Mn^2＋ is activated and emits red light with wavelength around 650 nm. The phosphor powder shows the highest emitting brightness, when the con- centrations of Ce^3＋and Mn^2＋ are both at 0.15 mol.

Low-Spatial Coherence High-Power Electrically Injected 6xx nm Dual-Emitter Laser

Laser-based displays have attracted much attention owing to large-size screen and full-color gamut compared with other displays such as liquid crystal display and light emitting diode. However, there exists a phenomenon, speckle, limits the applications of laser display because of the high coherence of laser. In this work, we developed an electrically injected 6xx nm dual-emitter laser which combines the low-spatial coherence with the high-power. The output power of the dual-emitter laser exceeds 500 mW under 20?C pulse operation. The single emitter consists of D-shaped section used to obtain more independent spatial modes thus reduces coherence and a stripe area to obtain the high power. The radius of the D-shaped cavity is 500 μm and the length of stripe is 1000 μm. We used the standard photolithography and inductively coupled plasma (ICP) process to fabricate the device. The speckle contrast was measured to be 5%. It exhibits a great potential of reducing speckle from the source directly for laser display.

Large Redshifts in Emission and Excitation from Eu²⁺-Activated Sr₂SiO₄and Ba₂SiO₄Phosphors Induced by Controlling Eu²⁺Occupancy on the Basis on Crystal-Site Engineering

The photoluminescence properties of Eu2+-activated α’-Sr2SiO4 and α’-Ba2SiO4 with a high Eu2+ concentration were investigated. In the case of Sr2-xEuxSiO4, emission was shifted from 585 to 611 nm with increasing the total Eu2+ concentration (x) from 0.1 to 0.8. This trend was similar to that in Ba2-xEuxSiO4, where the emission was shifted from 513 to 545 nm. The large redshifts in both the excitation and emission spectra were discussed in terms of the Eu2+ occupancies on two kinds of M sites and their local structural changes (M: Sr and Ba).

Enhanced red luminescence of Ca_(3)Si_(2−x)M_(x)O_(7):Eu^(3+)(M=Al,P)phosphors via partial substitution of Si^(4+) for applications in white light-emitting diodes

A red-emitting phosphor Ca_(2.91)Si_(2)O_(7):0.09Eu^(3+) with partial Al^(3+)/P^(5+) substitution on Si^(4+) was synthesized via a simple solid-state method,and the effects of the introduction of the M^(3+/5+)(M=Al,P)ions on the crystal structure and photoluminescence performance of Ca_(2.91)Si_(2−x)M_(x)O_(7):0.09Eu^(3+) phosphors were investigated.The X-ray diffraction(XRD),energy-dispersive X-ray spectroscopy(EDS),and X-ray photoelectron spectroscopy(XPS)results revealed that the structure of Ca_(3)Si_(2)O_(7) remained the same after the introduction of Al^(3+) and P^(5+) ions.The characteristic emission of Eu^(3+)-doped Ca_(3)Si_(2−x)M_(x)O_(7) phosphors exhibited two main peaks at 617 nm(red)and 593 nm(orange)under excitation at 394 nm,which originated from the^(5)D_(0)→^(7)F_(2)and^(5)D_(0)→^(7)F_(1) electron transitions of Eu^(3+) ions.After the partial substitution of Al^(3+) and P^(5+),the red emission intensities of the Ca_(2.91)Si_(2)O_(7):0.09Eu^(3+) phosphors were significantly enhanced by 1.88-and 1.42-fold,respectively,which is attributed to the crystal-field effect around Eu^(3+).Meanwhile,the luminescence intensities of the Ca_(2.91)Si_(1.96)Al_(0.04)O_(7):0.09Eu^(3+) and Ca_(2.91)Si_(1.94)P_(0.06)O_(7):0.09Eu^(3+) phosphors at 210℃ were 79.36%and 77.53%of those at 30°C,respectively,indicating their excellent thermal stability.Moreover,the as-prepared Ca_(2.91)Si_(1.96)Al_(0.04)O_(7):0.09Eu^(3+)and Ca_(2.91)Si_(1.94)P_(0.06)O_(7):0.09Eu^(3+) red-emitting phosphors were combined with a near-ultraviolet chip of 395 nm to fabricate red-light-emitting diode(LED)and white(w)-LED devices with excellent chromaticity features.In summary,Al^(3+)/P^(5+)-substituted Ca_(2.91)Si_(2)O_(7):0.09Eu^(3+) can serve as red-emitting phosphors for applications in w-LEDs.

The achievement of red upconversion lasing for highly stable perovskite nanocrystal glasses with the assistance of anion modulation

Perovskite materials have received extensive attention as optical gain media.However,it is tough to realize lasing using such materials on account of the unstable structure of MAPbl_(3)/CsPbl_(3)nanocrystals(NCs),and the propensity for mixed-halogen perovskites to undergo phase decomposition into bromine-rich and iodide-rich regions under intense laser irradiation.To solve this issue,we fabricated CsPbX_(3)(X=Br,I)NCs,which were embedded into a glassy matrix with high stability.In addition,by doping Brions into the CsPbl_(3) NCs to partially replace I^(-) ions,the optical efficiency and the optical gain properties were found to be significantly improved.Here,under 800 nm pulse laser excitation,red random lasing was realized with the assistance of such anion modulation.Moreover,we demonstrate that the perovskite NCs glasses(PNG)show strong water stability after immersion in water for one week,seeding a promise for application in high-definition(HD)displays and photonic devices.

Rational design of a bifunctional fluorescent probe for distinguishing Hcy/Cys from GSH with ideal properties

By pairing two fluoropho res according to their optical prope rties such as absorption spectral overlap and absorptivity,fluorescent quantum yield and emission spectral separation,a bifunctional fluorescent probe,TQBF-NBD,was rationally designed and synthesized to discriminatively sense Hcy/Cys and GSH with good selectivity and sensitivity.It is noted that this probe could work under a single-wave length excitation and displayed a mega-large Stokes shift.TQBF-NBD reacted with Hcy/Cys to give a mixed green-red fluorescence and displayed a red fluorescence upon the treatment with GSH.Distinguishable imaging of intracellular Hcy/Cys from GSH with the help of TQBF-NBD was realized in living cells and zebrafish.

Synthesis and luminescence properties of a novel red Sr_3Bi(PO_4)_3:Sm^(3+) phosphor

A series of Sr3Bi1-x（PO4）3： xSm^3＋phosphors were prepared by solid state method at 1250 ℃ for 4 h. X-ray diffraction （XRD） indicated that the sample was of a pure phase of Sr3Bi（PO4）3. The main excitation peaks were located at 343 （6H5/2→4H9/2）, 360 （6H5/2→4D3/2）, 373 （6H5/2→6p7/2）, 400 （6H5/2→4F7/2）, 414 （6H5/2→6P5/2） and 467 nm （6H5/2→4113/2）. The main emission were located at 563 （4G5/2→6H5/2）, 599 （4G5/2→6H7/2）, 646 （4G5/2→6H9/2） and 708 nm （4G5/2→6H11/2）. The intensest emission was excited by 400 nm. We studied the effect of different doping concentrations of Sm3＋ activator on the luminescence properties and found that the luminescent intensity first increased with Sm3＋ concentration increasing, and then decreased. The luminescent intensity had the best value when x=0.04. The chromaticity coordinates of the sample Sr3Bi0.96（PO4）3：0.04Sm3＋ were （x=0.57, y=0.36）, and the lifetime was 2.12 ms.