Emerging ultra-narrow-band cyan-emitting phosphor for white LEDs with enhanced color rendition

Phosphor-converted white LEDs rely on combining a blue-emitting InGaN chip with yellow and red-emitting luminescent materials.The discovery of cyan-emitting(470-500 nm)phosphors is a challenge to compensate for the spectral gap and produce full-spectrum white light.Na_(0.5)K_(0.5)Li_(3)SiO_(4):Eu^(2+)(NKLSO:Eu^(2+))phosphor was developed with impressive properties,providing cyan emission at 486 nm with a narrow full width at half maximum(FWHM)of only 20.7 nm,and good thermal stability with an integrated emission loss of only 7% at 150℃.The ultra-narrow-band cyan emission results from the high-symmetry cation sites,leading to almost ideal cubic coordination for UCr_(4)C_(4)-type compounds.NKLSO:Eu^(2+) phosphor allows the valley between the blue and yellow emission peaks in the white LED device to be filled,and the color-rendering index can be enhanced from 86 to 95.2,suggesting great applications in full-spectrum white LEDs.

掺铒氟硫磷酸盐高增益激光光纤

光纤激光器是大功率激光、空间激光通信、引力波探测、地球磁力探测等国家安全与科学前沿领域的迫切和重大需求.稀土离子掺杂的高增益玻璃光纤是光纤激光器的核心工作介质.氟硫磷酸盐(fluoro-sulfo-phosphate,FSP)激光玻璃具有稀土溶解度高、受激发射截面大、光学光谱性质优异等特点,是高增益激光光纤的潜在候选.本文从玻璃形成区、玻璃结构与性质关系、掺稀土玻璃发光与激光角度系统研究了Al F_(3)-R_(2)SO_(4)-RPO_(3)/Zn(PO_(3))_(2)(R=Li、Na、K)系列新型FSP玻璃.结果表明,热力学方法有助于简便快速地确定玻璃形成区,为该类新型激光玻璃设计提供指导.通过固体核磁共振谱、拉曼光谱、差示扫描量热分析、耐久性实验等揭示了Zn(PO_(3))_(2)能够提高FSP玻璃的结构聚合度和阴阳离子相互作用强度,从而增强玻璃的抗析晶稳定性和化学耐久性等,为大尺寸玻璃制备和光纤拉制奠定基础.Er^(3+)/Yb^(3+)共掺FSP激光玻璃典型的Er^(3+):^(4)I_(13/2)→^(4)I_(15/2)跃迁(~1.5μm)的荧光寿命为5.9~7.5 ms,发射截面为8.5×10^(–21)~9.0×10^(–21)cm^(2),光谱品质因子最高为6.4×10^(–23)cm^(2)s,饱和强度最低为1.0×10^(7)W/m^(2),优于部分掺铒磷酸盐、氟磷酸盐激光玻璃.通过组分优化,本文制备了Er^(3+)/Yb^(3+)共掺FSP单模光纤,峰值增益达4.7 d B/cm@1535 nm.基于该光纤实现了阈值约为50 m W、斜率效率为11.3%的光纤激光.

Multi-functional bismuth-doped bioglasses: combining bioactivity and photothermal response for bone tumor treatment and tissue repair

Treatment of large bone defects derived from bone tumor surgery is typically performed in multiple separate operations,such as hyperthermia to extinguish residual malignant cells or implanting bioactive materials to initiate apatite remineralization for tissue repair;it is very challenging to combine these functions into a material.Herein,we report the first photothermal(PT)effect in bismuth(Bi)-doped glasses.On the basis of this discovery,we have developed a new type of Bi-doped bioactive glass that integrates both functions,thus reducing the number of treatment cycles.We demonstrate that Bi-doped bioglasses(BGs)provide high PT efficiency,potentially facilitating photoinduced hyperthermia and bioactivity to allow bone tissue remineralization.The PT effect of Bi-doped BGs can be effectively controlled by managing radiative and non-radiative processes of the active Bi species by quenching photoluminescence(PL)or depolymerizing glass networks.In vitro studies demonstrate that such glasses are biocompatible to tumor and normal cells and that they can promote osteogenic cell proliferation,differentiation,and mineralization.Upon illumination with near-infrared(NIR)light,the bioglass(BG)can efficiently kill bone tumor cells,as demonstrated via in vitro and in vivo experiments.This indicates excellent potential for the integration of multiple functions within the new materials,which will aid in the development and application of novel biomaterials.

Enhancing upconversion of Nd3+ through Yb^(3+)-mediated energy cycling towards temperature sensing

Photon upconversion of lanthanides has been a powerful means to convert low-energy photons into high-energy ones.However,in contrast to the mostly investigated lanthanide ions,it has remained a challenge for the efficient upconversion of Nd^(3+)due to the deleterious concentration quenching effect.Here we report an efficient strategy to enhance the upconversion of Nd^(3+)through the Yb^(3+)-mediated energy cycling in a core-shell-shell nanostructure.Both Nd^(3+)and Yb^(3+)are confined in the interlayer,and the presence of Yb^(3+)in the Nd-sublattice provides a more matched energy for the upconversion transitions occurring at the intermediate state of Nd^(3+)towards much better population at its emissive levels.Moreover,this design also minimizes the possible cross-relaxation processes at both intermediate level and the emissive levels of Nd^(3+)which are the primary factors limiting the upconversion performance for the Nd^(3+)-doped materials.Such energy cycling-enhanced upconversion shows promise in temperature sensing.

One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd^(3+)

Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4f^(n) energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution.Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmann’s law.Despite its simplicity,Boltzmann thermometry with two excited levels allows precise temperature sensing,but only within a limited temperature range.While low temperatures slow down the nonradiative transitions required to generate a measurable population in the higher excitation level,temperatures that are too high favour equalized populations of the two excited levels,at the expense of low relative thermal sensitivity.In this work,we extend the concept of Boltzmann thermometry to more than two excited levels and provide quantitative guidelines that link the choice of energy gaps between multiple excited states to the performance in different temperature windows.By this approach,it is possible to retain the high relative sensitivity and precision of the temperature measurement over a wide temperature range within the same system.We demonstrate this concept using YAl_(3)(BO_(3))_(4)(YAB):Pr^(3+),Gd^(3+)with an excited 6 PJ crystal field and spin-orbit split levels of Gd^(3+)in the UV range to avoid a thermal black body background even at the highest temperatures.This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm.Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr^(3+)−Gd^(3+)couple upon excitation in the visible range.This method allows us to cover a temperature window between 30 and 800 K.

In situ instant generation of an ultrabroadband near-infrared emission center in bismuth-doped borosilicate glasses via a femtosecond laser

Bismuth(Bi)-doped photonic materials, which exhibit broadband near-infrared(NIR) luminescence(1000–1600 nm), are evolving into interesting gain media. However, the traditional methods have shown their limitations in enhancing Bi NIR emission, especially in the microregion. Consequently, the typical NIR emission has seldom been achieved in Bi-doped waveguides, which highly restricts the application of Bi-activated materials.Here, superbroadband Bi NIR emission is induced in situ instantly in the grating region by a femtosecond(fs)laser inside borosilicate glasses. A series of structural and spectroscopic characterizations are summoned to probe the generation mechanism. And we show how this novel NIR emission in the grating region can be enhanced significantly and erased reversibly. Furthermore, we successfully demonstrate Bi-activated optical waveguides.These results present new insights into Bi-doped materials and push the development of broadband waveguide amplification.

Glass crystallization making red phosphor for high-power warm white lighting

Rapid development of solid-state lighting technology requires new materials with highly efficient and stable luminescence,and especially relies on blue light pumped red phosphors for improved light quality.Herein,we discovered an unprecedented red-emitting Mg_(2)AI_(4)Si_(5)0_(18):Eu^(2+)composite phosphor(λex=450 nm,λem=620 nm)via the crystallization of MgO-AI_(2)O_(3)-Sio_(2) aluminosilicate glass.Combined experimental measurement and first-principles calculations verify that Eu^(2+)dopants insert at the vacant channel of Mg_(2)AI_(4)Si_(5)0_(18)crystal with six-fold coordination responsible for the peculiar red emission.Importantly,the resulting phosphor exhibits high internal/external quantum efficiency of 94.5/70.6%,and stable emission against thermal quenching,which reaches industry production.The maximum luminous flux and luminous efficiency of the constructed laser driven red emitting device reaches as high as 274 Im and 54lm W^(-1),respectively.The combinations of extraordinary optical properties coupled with economically favorable and innovative preparation method indicate,that the Mg_(2)AI_(4)Si_(5)0_(18):Eu^(2+)composite phosphor will provide a significant step towards the development of high-power solid-state lighting.

Understanding and tuning blue-to-near-infrared photon cutting by the Tm^(3+)/Yb^(3+) couple

Lanthanide-based photon-cutting phosphors absorb high-energy photons and‘cut’them into multiple smaller excitation quanta.These quanta are subsequently emitted,resulting in photon-conversion efficiencies exceeding unity.The photon-cutting process relies on energy transfer between optically active lanthanide ions doped in the phosphor.However,it is not always easy to determine,let alone predict,which energy-transfer mechanisms are operative in a particular phosphor.This makes the identification and design of new promising photon-cutting phosphors difficult.Here we unravel the possibility of using the Tm^(3+)/Yb^(3+) lanthanide couple for photon cutting.We compare the performance of this couple in four different host materials.Cooperative energy transfer from Tm^(3+)to Yb^(3+) would enable blue-to-near-infrared conversion with 200% efficiency.However,we identify phonon-assisted cross-relaxation as the dominant Tm^(3+)-to-Yb^(3+) energy-transfer mechanism in YBO_(3),YAG,and Y_(2)O_(3).In NaYF_(4),in contrast,the low maximum phonon energy renders phonon-assisted cross-relaxation impossible,making the desired cooperative mechanism the dominant energy-transfer pathway.Our work demonstrates that previous claims of high photon-cutting efficiencies obtained with the Tm^(3+)/Yb^(3+) couple must be interpreted with care.Nevertheless,the Tm^(3+)/Yb^(3+) couple is potentially promising,but the host material-more specifically,its maximum phonon energy-has a critical effect on the energy-transfer mechanisms and thereby on the photon-cutting performance.

Thermodynamic study on elimination of platinum inclusions in phosphate laser glasses for inertial confinement fusion applications

A new method to calculate the formation enthalpies and free energies of compounds based on standard electromotive force of cation,φ0, and free energies of formation, ΔG2980, or formation enthalpies, ΔH2980, of chloride was proposed. A linear relationship between φ0 and ΔG2980, φ0 and ΔH2980, and ΔG2980 and ΔH2980 was found respectively. The parameters used for thermodynamic calculation were calculated. The calculated values of the formation enthalpies and the free energies of formation of platinum compounds, such as Pt3（PO4）2 and Pt （PO3）2,were given for the first time. The mechanism of eliminating platinum inclusions in phosphate laser glass by POCI3 gas bubbling was interpreted from thermodynamic aspect.

Structural Engineering of Eu^2+-Doped Silicates Phosphors for LED Applications

CONSPECTUS:Phosphor-converted light-emitting diodes(pc-LEDs)are of great importance for their applications in solid-state lighting,backlit display,and near-infrared detection light source.Herein,the main challenges for these emergent pc-LEDs are to achieve full-spectrum lighting,wide color gamut display and broadband high efficiency near-infrared emission,respectively,which depends on the luminescence properties of phosphors used.Owing to the unique 4f-5d transition,Eu^2+is one of the most commonly used activators in luminescent materials for pc-LEDs,and Eu^2+-doped earth-abundant silicates phosphors exhibit outstanding luminescence properties,including multicolor emission,adjustable bandwidth,excellent thermal stability as well as high luminescence efficiency.These attributes motivate scientists to find Eu^2+-doped silicates phosphors that can practically meet the various LED application requirements.Since the traditional trial and error exploration is time-consuming and not necessarily successful,it is necessary to find reliable structural engineering strategies to discover new phosphor systems and also realize purposeful photoluminescence tuning.The adjustable 4f-5d electronic transitions of Eu^2+,the variable crystal structures of the silicate hosts and their coupling effect simultaneously account for the targeted luminescence behaviors and their precise emission color tuning.Thus,we aim at developing Eu^2+-doped silicate phosphors that can solve the application challenges through a comprehensive understanding of Eu^2+photoluminescence mechanism and the structure−property relationships.In this Account,we first illustrate the luminescence theory of Eu^2+in inorganic solids and summarize the research results of the effect originated from centroid shift,crystal field splitting,Stokes shift,and emission bandwidth.On the basis of the factors dominating the variation of luminescence characteristics,several structural strategies to manipulate Eu^2+emission in silicates are proposed,including(1)modify the chemical composition and crystal structure by various substitutions,(2)choose or change a suitable crystallographic site for Eu^2+and(3)control crystalline phase transition by external factors.Meanwhile,we briefly introduce the photoluminescence behaviors of Eu^2+in different silicates controlled by these structural engineering strategies.Second,we outline our recent research progress on blue LED pumped Eu^2+-doped silicate phosphors with emphasis on the design principle and the relationship between the structure and luminescence.The state-of-the-art LED application including full spectrum solid-state lighting,wide color gamut display and near-infrared night-vision technologies are introduced.Finally,we proposed the future research opportunities and challenges.The development of these Eu^2+-doped silicate phosphors exhibiting excellent luminescence performance is highly inspiring,and we expect this Account can be helpful for controlling the photoluminescence by theory-structure−property relationships and guide scientists discover the next generation of Eu^2+-doped phosphors for emerging applications.

Correction:Multi-functional bismuth-doped bioglasses:combining bioactivity and photothermal response for bone tumor treatment and tissue repair

In this originally published article,we have noticed several mistakes.They should be corrected as follows:1.On page 1,the second affiliation(No.5)of the author“Chuanbin Mao”should be deleted as he does not belong to that affiliation.Namely,he should be only listed with(Department of Chemistry and Biochemistry Stephenson Life Sciences Research Center,University of Oklahoma,Norman,OK 73072,USA).