利用漫反射光谱研究SrAl_2O_4长余辉材料中Dy^(3+)和Eu^(2+)相关陷阱能级北大核心CSCD

在长余辉发光物理机制的研究中,确定发光材料中的缺陷能级是非常重要的。本文通过高温固相法制备了两组SrAl_2O_4∶Dy^(3+)和SrAl_2O_4∶Eu^(2+)样品,并采用漫反射光谱测定了SrAl_2O_4中一系列与Dy^(3+)和Eu^(2+)相关的吸收峰。对于SrAl_2O_4∶Dy^(3+)和SrAl_2O_4∶Eu^(2+),在其吸收谱的较低能量(长波长)和较高能量(短波长)区域内分别存在一组吸收峰。通过这些吸收峰可确定Dy^(3+)和Eu^(2+)掺杂在SrAl_2O_4带隙中引入的陷阱深度。结果表明Dy^(3+)离子能够在SrAl_2O_4中形成浅能级和深能级陷阱,而Eu^(2+)离子仅会形成浅能级陷阱。与文献报道的陷阱相比较,这些陷阱大部分和其它方法测得的数据相一致,小部分则是首次报道,可能是其它方法的测试范围所限而无法测得。我们认为距离导带0.6至1.2eV范围内的Dy^(3+)相关陷阱在SrAl_2O_4∶(Eu^(2+),Dy^(3+))长余辉发光过程中起着关键的作用。     

Pr~(3+)离子激活的新型长余辉发光材料GdY_(1.46)Lu_(0.5)Ga_3Al_2O_(12)∶0.04Pr~(3+)的发光性质研究

通过高温固相法合成了镨掺杂的稀土镓铝石榴石(GdY_(1.46)Lu_(0.5)Ga_3Al_2O_(12)∶0.04Pr~(3+))。利用X射线衍射、荧光光谱、长余辉光谱、荧光衰减曲线和热释光光谱等手段,对样品的发光性质进行了系统的研究。结果表明,在254nm光源的激发下,样品GdY_(1.46)Lu_(0.5)Ga_3Al_2O_(12)∶0.04Pr~(3+)发出黄色的荧光,停止激发后,该样品发出明亮的黄色长余辉。并且,该长余辉能够持续3h以上。     

钬掺杂对SrAl2O4:Eu2+,Dy3+发光性能的影响

首次研究了Ho3+掺杂对SrAl2O4:Eu2+,Dy3+发光性能的影响.采用燃烧合成方法,在600℃条件下,合成Ho3+掺杂的SrAl2O4:Eu2+,Dy3+新型长余辉光致发光材料.X射线衍射分析结果表明,合成的样品为单相SrAl2O4单斜晶系磷石英结构.光致发光光谱测量显示,合成样品的发射光谱是连续宽带谱,峰值位于510nm左右,激发光谱是单峰且峰值位于356nm的连续宽带谱.利用单光子计数系统测量了材料的余辉衰减曲线,结果显示Ho3+的适量掺杂可以明显提高铝酸锶的初始发光亮度.当Ho3+的掺入摩尔比例为0.005时,初始亮度是不掺杂Ho3+时的两倍多.对初始亮度增强的机理做了初步的探讨.     

基于铝酸盐类长余辉材料的Fe3+荧光探针

SrAl_2O_4∶Eu~(2+),Dy~(3+)是常见的长余辉发光材料,具有良好的发光和余辉性能,能够作为荧光共振能量转移(FRET)体系中能量供体,使探针具备在无光源激发条件下的检测能力.但其易发生水解反应而失去光学性能,这限制了其应用.对SrAl_2O_4∶Eu~(2+),Dy~(3+)进行表面修饰改性,并以其为基体制备可利用余辉进行检测的荧光探针具有重要的研究意义.本文利用正硅酸乙酯(TEOS)在酸性条件下的水解缩合在SrAl_2O_4∶Eu~(2+),Dy~(3+)表面包覆SiO_2以提高其耐水性,并通过硅烷偶联剂将其与罗丹明B连接构成一种新型荧光探针.采用扫描电镜、荧光光谱等检测手段对所制备探针进行表征,并分别研究了探针在有、无光源激发条件下的检测性能.结果表明,制备的探针对Fe~(3+)有较特殊的响应,可用于检测溶液中的Fe~(3+).该探针在光源激发下可定量检测溶液中100～500μmol/L浓度范围内的Fe~(3+),在无光源激发条件下可利用自身余辉检测溶液中500μmol/L以上浓度的Fe~(3+).     

长余辉材料Sr_4Al_(14)O_(25)∶Eu~(2+),Nd~(3+)的溶胶凝胶法制备及性能研究

首次研究了以Nd~(3+)离子为辅助激活剂,对Eu~(2+)掺杂的发光材料Sr_4Al_(14)O_(25):Eu~(2+)余辉性能的影响.用溶胶凝胶法合成了Eu~(2+), Nd~(3+)共掺杂的Sr_4Al_(14)O_(25):Eu~(2+),Nd~(3+)发光粉末,并用扫描电镜、X射线衍射计、荧光分光光度计、余辉亮度测试仪、热释光剂量计等手段对粉末样品进行了表征.结果表明,在1350℃得到了单一的Sr_4Al_(14)O_(25)相,粉末颗粒平均粒度在1μm左右.Eu~(2+), Nd~(3+)共掺杂的Sr_4Al_(14)O_(25):Eu~(2+),Nd~(3+)发光粉末有402和485nm两个发射峰,与Eu~(2+)单掺杂的Sr_4Al_(14)O_(25):Eu~(2+)相比,发射峰位置没有变化,但适量的掺杂可以大大提高余辉时间和余辉亮度,余辉时间可达18h以上.最后通过对热释光谱的分析解释了双掺杂发光粉余辉性能增强的原因,适宜深度的陷阱可以有效存储光能,增强余辉的时间和强度.     

荧光-麦秸纤维/PP复合材料的制备及其性能

以麦秸纤维为基础原料,SrAl_2O_4:Eu~(2+),Dy~(3+)荧光粉为添加剂,采用热压工艺制备出荧光秸塑复合材料,研究了SrAl_2O_4:Eu~(2+),Dy~(3+)荧光粉含量对秸塑复合材料性能的影响。利用扫描电子显微镜(SEM)、电子万能力学实验机、荧光光谱仪、同步热分析红外气质仪等表征材料的微观形貌、力学性能、发射光谱及热稳定性,并利用YH-18W台灯测试材料的余辉性能。结果表明,随着SrAl_2O4:Eu~(2+),Dy~(3+)荧光粉添加量的增多,复合材料的力学性能和抗湿胀性能先增后减,均在添加量为15%时性能最优;复合材料的热稳定性和发光强度随着SrAl_2O_4:Eu~(2+),Dy~(3+)荧光粉添加量的增多而增强,荧光粉添加量为20%时,复合材料的发光强度最大,达到435 a.u.。日光灯照射10 min后,随着SrAl_2O_4:Eu~(2+),Dy~(3+)荧光粉添加量的增多,复合材料的余辉初始亮度增强,余辉衰减时间延长。且30 min后添加量20%复合材料的余辉亮度较其他材料更强;但与添加量15%复合材料的发光强度和余辉亮度相差不大,发光强度差值仅为53 a.u.。综合而言,SrAl_2O_4:Eu~(2+),Dy~(3+)荧光粉含量15%的复合材料综合性能最优。     

SrAl2O4:Eu2+,Dy3+发光粉体的长余辉特性研究

采用高温固相合成法制得了SrAl_2O_4:Eu~（2+）,Dy~（3+）长余辉发光材料.X射线衍射分析(XRD)结果表明:该磷光体为SrAl2O4晶体结构,属单斜晶系.其晶格常数为:a=8.4424A,b=8.822A,c=5.1607A,β=93.415°.SrAl2O4:Eu2+,Dy3+发光材料的激发光谱和发射光谱均为宽带谱,激发谱峰位在300～450nm,发射光谱的峰值波长在518nm处.这一结果表明该材料的发光是由Eu2+的4f65d→4f7(8S7/2)宽带跃迁产生的.其余辉衰减由初始的快衰减和其后的慢衰减所组成.通过热释光谱对材料中的陷阱能级进行了分析,该材料中存在两个较深的陷阱能细。苴深度分别为0.38和1.34eV.     

Gd_2O_2S∶Pr~(3+)荧光粉的合成与发光性能研究

采用Gd(NO_3)_3、Pr_6O_(11)、HNO_3、(NH_4)_2SO_4和NH_3·H_2O为实验原料,通过共沉淀还原法合成了Gd_2O_2S∶Pr~(3+)荧光粉。利用傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)和光致发光(PL)等手段对合成产物进行了表征。结果表明前驱体具有非晶态结构,在空气气氛中800℃煅烧2 h能转化为单相的Gd_2O_2SO_4粉体,该粉体在氩氢混合气氛下800℃煅烧1 h能转化为单相的Gd_2O_2S粉体。Gd_2O_2S粉体呈准球形,粒径大约1μm左右,团聚严重。PL光谱分析表明在303 nm的紫外光激发下,Gd_2O_2S∶Pr~(3+)荧光粉呈绿光发射,主发射峰位于514nm,归属于Pr~(3+)离子的~3P_0-~3H_4跃迁,Pr~(3+)离子的猝灭浓度为1mol%。     

钬掺杂对SrAl_2O_4∶Eu~(2+),Dy~(3+)发光性能的影响

首次研究了Ho3+掺杂对SrAl2O4∶Eu2+,Dy3+发光性能的影响。采用燃烧合成方法,在600℃条件下,合成Ho3+掺杂的SrAl2O4∶Eu2+,Dy3+新型长余辉光致发光材料。X射线衍射分析结果表明,合成的样品为单相SrAl2O4单斜晶系磷石英结构。光致发光光谱测量显示,合成样品的发射光谱是连续宽带谱,峰值位于510nm左右,激发光谱是单峰且峰值位于356nm的连续宽带谱。利用单光子计数系统测量了材料的余辉衰减曲线,结果显示Ho3+的适量掺杂可以明显提高铝酸锶的初始发光亮度。当Ho3+的掺入摩尔比例为0.005时,初始亮度是不掺杂Ho3+时的两倍多。对初始亮度增强的机理做了初步的探讨。     

SrMoO_4:Pr~(3+)红色荧光粉的水热合成及光致发光

采用水热法合成SrMoO_4:Pr~(3+)红色荧光粉,使用X射线衍射(XRD)、场发射环境扫描电镜(FSEM)以及荧光光谱(PL)等手段研究了荧光粉的晶体结构、表观形貌及发光性能。结果表明,SrMoO_4:Pr~(3+)荧光粉为类球形的纯相结构,激发峰为450 nm、473 nm和485 nm,发射峰为606 nm、625 nm和650 nm,在650 nm呈现良好的红光发射,可与蓝光LED芯片匹配。SrMoO_4:Pr~(3+)的发光强度随着Pr~(3+)掺杂量的增大而增强,掺杂量x=0.02时发光强度最强,继续增大Pr~(3+)掺杂量出现浓度猝灭现象。Pr离子的掺入没有改变荧光粉的主晶相,在450 nm激发下样品产生红光发射,其中对应Pr~(3+)的特征跃迁3P_0→3F_2位于650 nm的发射峰最强。SrMoO_4:Pr~(3+)红色荧光粉可被蓝光LED激发产生红光,是一种性能优异的YAG:Ce~(3+)黄色荧光粉的红光补偿粉。     

硅衬底Al2O3∶Tb3+薄膜的制备及其发光性能

采用溶胶凝胶法在硅衬底上制备了Al₂O₃∶Tb³⁺薄膜; 并采用DTA-TG、XRD、SEM、AFM及光致发光光谱对其进行了一系列表征; 分析了Al₂O₃∶Tb³⁺薄膜的发光机理, 探讨了热处理温度和Tb³⁺掺杂浓度对发光性能的影响规律. 研究结果表明, 采用溶胶凝胶法制备工艺, 制备了高发光强度的Al₂O₃∶Tb³⁺薄膜, 薄膜的最佳激发波长为240nm, Tb³⁺的最佳掺杂浓度为5mol%(Tb₂O₃/Al₂O₃=5mol%), 在240nm光激发下, 最强的发射峰出现在544nm附近; 并且制备的Al₂O₃∶Tb³⁺薄膜表面致密、平整且无裂纹产生, 表面粗糙度约为1.3nm, 有利于硅基光电子器件的制备和应用.     

Fabrication of novel luminor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) with core/shell heteronanostructure

A novel polychromic phosphor with core-shell heteronanostructure has been prepared to improve the chromatic index of phosphors. As for the first example, Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+), its synthetic route, structure and optical properties are presented in this paper. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy-dispersive x-ray spectra (EDS) and photoluminescence (PL) were all employed to characterize the composite core-shell phosphors. The XRD, FE-SEM and HR-TEM results indicate that the SiO(2) and YVO(4):Eu(3+) layers have been successfully coated on Y(2)O(3):Eu(3+) nanoparticles and SiO(2) layer, respectively: these layers were further verified by the EDS. The PL showed that the red-emitting phosphor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) possessed the independent luminescent properties of both the core Y(2)O(3):Eu(3+) and the shell YVO(4):Eu(3+). The emissions were dominated by [Formula: see text] or [Formula: see text] transitions of Eu(3+) when excited with different wavelengths. Since this broad-band response to excitation in the range of 225-340?nm gave more red/dark red emissions found at 612, 616 and 620?nm, the novel phosphor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) could have potential biological labeling applications with wide flexibility.     

Biofunctionalization of CeF(3):Tb(3+) nanoparticles

CeF(3):Tb(3+) nanoparticles (short pillar-like morphology with an average length and width of 11 and 5?nm, respectively) were successfully prepared by a polyol process using diethyleneglycol (DEG) as solvent. After being functionalized with a SiO(2)-NH(2) layer, these CeF(3):Tb(3+) nanoparticles can be conjugated with biotin molecules (activated by thionyl chloride) and further with avidin. The as-formed CeF(3):Tb(3+) nanoparticles, CeF(3):Tb(3+) nanoparticles functionalized with amino groups, biotin conjugated amino-functionalized CeF(3):Tb(3+) nanoparticles and biotinylated CeF(3):Tb(3+) nanoparticles bonded with avidin were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), UV/vis absorption spectra and luminescence spectra, respectively. The biofunctionalization of the CeF(3):Tb(3+) nanoparticles has less effect on their luminescence properties, i.e. they still show strong green emission (from Tb(3+), with (5)D(4)-(7)F(5) at 543?nm as the most prominent group), indicative of the great potential for these CeF(3):Tb(3+) nanoparticles to be used as biological fluorescence probes.     

Emission properties of hydrothermal Yb(3+), Er(3+) and Yb(3+), Tm(3+)-codoped Lu2O3 nanorods: upconversion, cathodoluminescence and assessment of waveguide behavior

Yb(3+) and Ln(3+) (Ln(3+) = Er(3+) or Tm(3+)) codoped Lu(2)O(3) nanorods with cubic Ia3 symmetry have been prepared by low temperature hydrothermal procedures, and their luminescence properties and waveguide behavior analyzed by means of scanning near-field optical microscopy (SNOM). Room temperature upconversion (UC) under excitation at 980 nm and cathodoluminescence (CL) spectra were studied as a function of the Yb(+) concentration in the prepared nanorods. UC spectra revealed the strong development of Er(3+) (4)F(9/2) → (4)I(15/2) (red) and Tm(3+) (1)G(4) → (3)H(6) (blue) bands, which became the pre-eminent and even unique emissions for corresponding nanorods with the higher Yb(3+) concentration. Favored by the presence of large phonons in current nanorods, UC mechanisms that privilege the population of (4)F(9/2) and (1)G(4) emitting levels through phonon-assisted energy transfer and non-radiative relaxations account for these observed UC luminescence features. CL spectra show much more moderate development of the intensity ratio between the Er(3+) (4)F(9/2) → (4)I(15/2) (red) and (2)H(11/2), (4)S(3/2) → (4)I(15/2) (green) emissions with the increase in the Yb(3+) content, while for Yb(3+), Tm(3+)-codoped Lu(2)O(3) nanorods the dominant CL emission is Tm(3+) (1)D(2) → (3)F(4) (deep-blue). Uniform light emission along Yb(3+), Er(3+)-codoped Lu(2)O(3) rods has been observed by using SNOM photoluminescence images; however, the rods seem to be too thin for propagation of light.     

Luminescent properties and characterization of one dimensional Gd(2)O(3):Eu(3+) phosphor nano-wire for field emission application

Gd(2)O(3):Eu(3+) nano-wire phosphors embedded in SBA-15 silica templates were synthesized using a combination of the sol-gel method and hydrothermal reactions followed by a sintering process at 1000?°C. The crystal structure of Gd(2)O(3):Eu(3+) was confirmed using x-ray diffraction. Observation using transmission electron microscopy shows that the nano-wire diameters were very uniform in the 7-9?nm range. In comparison with bulk Gd(2)O(3):Eu(3+) materials, we found that the photo-luminescent property of the nano-wire was different. The analysis shows that the main nano-wire emission peaks were at 585, 597, 613 and 620?nm. The CIE value (x = 0.62, y = 0.38) indicates that the nano-wire emitted a pink colour and not red as for the bulk material. The field emission experimental results agreed well with the photo-luminescent analysis results.     

Photoluminescence and raman studies of Y2O3:Eu(3+) nanotubes under high pressure

In this work, the cubic compound Y2O3:Eu(3+) nanotubes with diameter of 70-90 nm and length of 2-3 microm are synthesized by a hydrothermal method. Photoluminescence and Raman spectra of Y2O3:Eu(3+) nanotubes in a diamond anvil cell under high pressure are measured at room temperature. The 5D0 --> 7F(0,1,2) transitions of the Eu(3+) ions exhibit red shifts to higher wavelength with pressure increasing. Above 13.4 GPa, all the Raman active modes disappear. When the pressure is released from 25.6 GPa to ambient pressure, these Raman peaks are not retrieved; this fact indicates that the nanotubes are transformed into amorphous from cubic phase at about 13.4 GPa. It may be related to the collapse of nanotube form under high pressure condition.     

The two-photon excitation of SiO(2)-coated Y(2)O(3):Eu(3+) nanoparticles by a near-infrared femtosecond laser

In order to improve the photoluminescence property of Eu(3+)-doped nanoparticles, Y(2)O(3):Eu(3+) nanoparticles were synthesized using the Pechini-type sol-gel method, then coated with SiO(2) shells by using the St?ber method for different coating times. The SiO(2)-coated nanoparticles were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, and their photoluminescence spectra were recorded under 800?nm femtosecond laser excitation. The results indicate that a two-photon simultaneous absorption upconversion luminescence is obtained, and their upconversion luminescence intensities are further enhanced after the surfaces of the nanoparticles are coated with different thickness SiO(2) shells. Compared to the upconversion luminescence intensity of non-coated nanoparticles at 611?nm, the upconversion luminescence intensities of SiO(2)-coated Y(2)O(3):Eu(3+) nanoparticles with coating times of 60, 90 and 120?min were enhanced by 3.30, 3.96 and 4.13 times, respectively. This can be attributed to the contributions of the increased amounts of Eu(3+) ions populated at the (5)D(0) level on the surfaces of the nanoparticles because the cooperative ligand fields between the Y(2)O(3) core and non-crystalline SiO(2) shell interfaces activate the 'dormant' Eu(3+) ions near or on the surfaces of the nanoparticles. From a Judd-Ofelt (J-O) theory analysis, the coated shell structures can improve the radiative quantum efficiencies of Eu(3+)-doped nanoparticles. It is therefore concluded that more intense red upconversion luminescence with high radiative quantum efficiencies can enable the SiO(2)-coated Y(2)O(3):Eu(3+) nanoparticles to have the great potential to be used as a fine resolution phosphor.     

Li~+共掺杂对掺Er~(3+):TiO_2上转换发光的增强作用·

采用非水性溶胶-凝胶法制备了0.1%Er~(3+)(摩尔分数,下同)、0%～2%Li~+共掺杂TiO_2粉末,在980nm半导体激光器(LD)激发下获得了中心波长526nm、550nm的绿色和663nm的红色上转换发光.Li~+共掺杂对掺Er~(3+):TiO_2的相结构未产生影响,但极大增强了上转换发光强度.随Li~+共掺杂摩尔分数的逐渐增大,绿色和红色上转换发光强度先增大后减小,当Li~+摩尔分数为1%时,上转换发光强度达到最大,绿色和红色上转换发光强度分别比掺Er~(3+):TiO_2提高了约330倍、30倍和60倍.Er~(3+)Li~+共掺杂TiO_2粉末的绿色和红色上转换发光均为双光子吸收过程.Li~+共掺杂不改变Er~(3+)的上转换发光机制,但破坏了Er~(3+)的局部晶体场对称性,影响了Er~(3+)内部4f能级的跃迁几率,导致上转换发光强度增强.     

Effect of structure, particle size and relative concentration of Eu(3+) and Tb(3+) ions on the luminescence properties of Eu(3+) co-doped Y(2)O(3):Tb nanoparticles

Eu(3+) co-doped Y(2)O(3):Tb nanoparticles were prepared by the combustion method and characterized for their structural and luminescence properties as a function of annealing temperatures and relative concentration of Eu(3+) and Tb(3+) ions. For Y(2)O(3):Eu,Tb nanoparticles annealed at 600 and 1200?°C, variation in the relative intensity of excitation transitions between the (7)F(6) ground state and low spin and high spin 4f(7)5d(1) excited states of Tb(3+) is explained due to the combined effect of distortion around Y(3+)/Tb(3+) in YO(6)/TbO(6) polyhedra and the size of the nanoparticles. Increase in relative intensity of the 285?nm peak (spin-allowed transition denoted as peak B) with respect to the 310?nm peak (spin-forbidden transition denoted as peak A) with decrease of Tb(3+) concentration in the Y(2)O(3):Eu,Tb nanoparticles heated at 1200?°C is explained based on two competing effects, namely energy transfer from Tb(3+) to Eu(3+) ions and quenching among the Tb(3+) ions. Back energy transfer from Tb(3+) to Eu(3+) in these nanoparticles is found to be very poor.     

Electrogenerated chemiluminescence sensors using Ru(bpy)3(2+) doped in silica nanoparticles

A novel electrogenerated chemiluminescence (ECL) sensor based on Ru(bpy)3(2+)-doped silica (RuDS) nanoparticles conjugated with a biopolymer chitosan membrane was developed. These uniform RuDS nanoparticles (approximately 40 nm) were prepared by a water-in-oil microemulsion method and were characterized by electrochemical and transmission electron microscopy technology. The Ru(bpy)3(2+)-doped interior maintained its high ECL efficiency, while the exterior nanosilica prevented the luminophor from leaching out into the aqueous solution due to the electrostatic interaction. This is the first attempt to branch out the application of RuDS nanoparticles into the field of ECL, and since a large amount of Ru(bpy)3(2+) was immobilized three-dimensionally on the electrode, the Ru(bpy)3(2+) ECL signal could be enhanced greatly, which finally resulted in the increased sensitivity. This sensor shows a detection limit of 2.8 nM for tripropylamine, which is 3 orders of magnitude lower than that observed at a Nafion-based ECL sensor. Furthermore, the present ECL sensor displays outstanding long-term stability.