Valence conversion and site reconstruction in nearinfrared-emitting chromium-activated garnet for simultaneous enhancement of quantum efficiency and thermal stability

Achievement of high photoluminescence quantum efficiency and thermal stability is challenging for near-infrared(NIR)-emitting phosphors.Here,we designed a“kill two birds with one stone”strategy to simultaneously improve quantum efficiency and thermal stability of the NIR-emitting Ca_(3)Y_(2-2x)(ZnZr)_(x)Ge_(3)O_(12):Cr garnet system by chemical unit cosubstitution,and revealed universal structure-property relationship and the luminescence optimization mechanism.The cosubstitution of[Zn^(2+)-Zr^(4+)]for[Y^(3+)-Y^(3+)]played a critical role as reductant to promote the valence transformation from Cr^(4+)to Cr^(3+),resulting from the reconstruction of octahedral sites for Cr^(3+).The introduction of[Zn^(2+)-Zr^(4+)]unit also contributed to a rigid crystal structure.These two aspects together realized the high internal quantum efficiency of 96%and excellent thermal stability of 89%@423 K.Moreover,information encryption with“burning after reading”was achieved based on different chemical resistance of the phosphors to acid.The developed NIR-emitting phosphor-converted light-emitting diode demonstrated promising applications in bio-tissue imaging and night vision.This work provides a new perspective for developing high-performance NIR-emitting phosphor materials.

New strategy for designing orangish-redemitting phosphor via oxygen-vacancyinduced electronic localization

Phosphor-converted white-light-emitting diodes(pc-WLED)have been extensively employed as solid-state lighting sources,which have a very important role in people’s daily lives.However,due to the scarcity of the red component,it is difficult to realize warm white light efficiently.Hence,red-emitting phosphors are urgently required for improving the illumination quality.In this work,we develop a novel orangish-red La_(4)GeO_(8):Bi^(3+) phosphor,the emission peak of which is located at 600 nm under near-ultraviolet(n-UV)light excitation.The full width at half maximum(fwhm)is 103 nm,the internal quantum efficiency(IQE)exceeds 88%,and the external quantum efficiency(EQE)is 69%.According to Rietveld refinement analysis and density functional theory(DFT)calculations,Bi^(3+) ions randomly occupy all La sites in orthorhombic La_(4)GeO_(8).Importantly,the oxygen-vacancy-induced electronic localization around the Bi3+ions is the main reason for the highly efficient orangish-red luminescence.These results provide a new perspective and insight from the local electron structure for designing inorganic phosphor materials that realize the unique luminescence performance of Bi^(3+) ions.

Thermally stable and highly efficient red-emitting Eu^(3+)-doped Cs3GdGe309 phosphors for WLEDs:non-concentration quenching and negative thermal expansion

Red phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes(pc-WLEDs).However,the development of a red phosphor with simultaneous high efficiency,excellent thermal stability and high colour purity is still a challenge.In this work,unique non-concentration quenching in solid-solution Cs_(3)Gd_(1-x)Ge_(3)O_(9):xEu^(3+)(CGGO:xEu^(3+))(x=0.1-1.0)phosphors is successfully developed to achieve a highly efficient red-emitting Cs_(3)EuGe_(3)0_(9)(CEGO)phosphor.Under the optimal 464 nm blue light excitation,CEGO shows a strong red emission at 611 nm with a high colour purity of 95.07%and a high internal quantum efficiency of 94%.Impressively,this red-emitting CEGO phosphor exhibits a better thermal stability at higher temperatures(175-250℃,>90%)than typical red K2SiF6:Mn^(4+)and Y203:Eu^(3+)phosphors,and has a remarkable volumetric negative thermal expansion(coefficient of thermal expansion,a=—5.06×10^(-5)/℃,25-250℃).By employing this red CEGO phosphor,a fabricated pc-WLED emits warm white light with colour coordinates(0.364,0.383),a high colour rendering index(CRI=89.7),and a low colour coordinate temperature(CCT=4508 K).These results indicate that this highly efficient red-emitting phosphor has great potential as a red component for pc-WLEDs,opening a new perspective for developing new phosphor materials.

Highly efficient Fe^(3+)-doped A_(2)BB′O_(6)(A=Sr^(2+),Ca^(2+);B,B′=In^(3+),Sb^(5+),Sn^(4+))broadband nearinfrared-emitting phosphors for spectroscopic analysis

Near-infrared(NIR)-emitting phosphor-converted light-emitting diodes have attracted widespread attention in various applications based on NIR spectroscopy.Except for typical Cr^(3+)-activated NIR-emitting phosphors,next-generation Cr^(3+)-free NIR-emitting phosphors with high efficiency and tunable optical properties are highly desired to enrich the types of NIR luminescent materials for different application fields.Here,we report the Fe^(3+)-activated Sr2−yCay(InSb)1−zSn_(2)zO_(6)phosphors that exhibit unprecedented long-wavelength NIR emission.The overall emission tuning from 885 to 1005 nm with broadened full-width at half maximum from 108 to 146 nm was realized through a crystallographic site engineering strategy.The NIR emission was significantly enhanced after complete Ca^(2+)incorporation owing to the substitution-induced lower symmetry of the Fe^(3+)sites.The Ca_(2)InSbO_(6):Fe^(3+)phosphor peaking at 935 nm showed an ultra-high internal quantum efficiency of 87%.The as-synthesized emission-tunable phosphors demonstrated great potential for NIR spectroscopy detection.This work initiates the development of efficient Fe^(3+)-activated broadband NIR-emitting phosphors and opens up a new avenue for designing NIR-emitting phosphor materials.

一种以上转换和Fe_(3)O_(4)纳米粒子为基础的超灵敏ctDNA检测系统

ctDNA是重要的肿瘤标志物之一,在肿瘤疾病的早期诊断和临床监控方面发挥着重要作用.目前,常用的ct DNA检测方法通常都缺乏足够的灵敏性和特异性,不能满足实际诊疗的需要.因此,我们急需一种新型的、超灵敏的ct DNA检测方法.上转换纳米粒子是一种优异的发光材料,因其独特的发光特性在生物医学方面具有重要应用.因此,我们设计了一种以上转换和Fe_(3)O_(4)纳米粒子为基础的ct DNA检测方法.在该检测系统中,上转换和Fe_(3)O_(4)纳米粒子通过DNA碱基互补配对原则自组装在一起.目标序列可以通过熵驱动链置换(ESDR)反应将连着上转换纳米粒子的核酸链释放出来.经磁性分离后,上清液中上转换纳米粒子在980 nm激光器激发下的荧光强度与目标序列的浓度在1 nmol L^(-1)–100 amol L^(-1)的范围内具有非常好的线性关系,经计算,最低检出浓度为1.6 amol L^(-1).此外,该检测系统在识别单碱基突变、实际细胞和血清样本的检测中均有较好的应用.因此,该检测系统因为其灵敏性和特异性在肿瘤早期诊断、疾病进行过程监控、治疗方法评价和愈后风险评估等方面具有重大应用潜力.