NaY(WO4)2:Dy3+荧光粉的制备及其上转换发光性能

利用水热法合成了NaY(WO4)2:Dy3+上转换荧光粉. 通过XRD、SEM表征该荧光粉结构和形貌. 探讨了Dy3+浓度、pH值、反应温度及焙烧温度对NaY(WO4)2:Dy3+晶体结构、形貌及发光性能的影响,得到在Dy3+浓度为0.5%,pH=8,反应温度180℃,800℃焙烧条件下的样品具有最佳上转换发光性能. 利用776 nm近红外光激发NaY(WO4)2:Dy3+,观察到480 nm处的蓝光发射峰以及577 nm处的黄光发射峰. 其中蓝光来自Dy3+离子的4F9/2→6H15/2跃迁,黄光由Dy3+离子4F9/2→6H13/2跃迁产生.     

828 nm近红外光激发下Ho3+掺杂NaYF4的上转换发光性质

采用水热法合成了NaYF4:Ho3+上转换发光材料,用XRD、红外光谱、能谱及荧光光谱等对其进行表征,探讨了掺杂浓度、退火温度对上转换发光特性及晶型的影响. 结果表明,在828 nm近红外光激发下,在Ho含量0.7%(mol)、退火温度900℃时,样品的上转换发光效果最好,退火前样品发射蓝、黄光,700℃退火后,除发射蓝、黄光外,出现绿光的尖锐强峰,且温度越高其发光强度越高;退火温度为400℃时样品为a相和b相的混合相,随温度升高晶型转变为纯b相;Ho3+的上转换发光机制为能级跃迁,绿光、黄光、蓝光分别对应5F4,5S2?5I8, 5I5?5G6和3K8,5F3?5I8跃迁.     

Nd3+/Yb3+/Tm3+共掺杂NaY（WO4）2纳米晶的制备及其上转换发光性能EI北大核心CSCD

采用水热法合成出Nd^3＋/Yb^3＋/Tm^3＋共掺杂NaY（WO4）2纳米晶。通过X射线衍射、扫描电子显微镜、红外光谱、荧光光谱等,对合成样品的晶体结构、形貌和上转换发光性能进行表征。结果表明：合成的样品均为纯四方相的NaY（WO4）2,粒径在50～55 nm之间。利用聚乙二醇（PEG-2000）作为表面活性剂制得的上转换纳米粒子,尺寸小、分散性好并且具有一定的水溶性。在808 nm近红外光激发下,观察到469 nm处的蓝光发射峰以及539 nm处的绿光发射峰,其中蓝光来自Tm^3＋的^1G4→^3H6能级跃迁,绿光由Tm^3＋的^1D2→^3H5跃迁产生。并研究了共掺杂体系中Nd^3＋→Yb^3＋→Tm^3＋的能量传递过程及其上转换发光机理。     

干燥方式对NaY(WO4)2∶Dy3+,Eu3+荧光粉粒度及上转换发光性能的影响

采用水热法合成了Dy3+和Eu3+共掺杂的NaY(WO4)2上转换荧光粉,用XRD, SEM和荧光光谱(PL)等方法对不同干燥方式所得样品的晶体结构、微观形貌、晶粒尺寸及上转换发光性能进行了分析。结果表明,合成样品均为四方白钨矿结构的NaY(WO4)2,空间群为I41/a,掺入Dy3+和Eu3+未改变基质晶格;常规干燥、喷雾干燥、冷冻干燥及真空干燥后荧光粉的尺寸分别为817.91, 486.04, 388.74和349.82 nm,真空干燥的样品分散性最好。在793 nm近红外光激发下,冷冻干燥样品的上转换发光性能最佳,与干燥过程中粉体团聚程度减弱及表面层缺陷减少有关。576 nm处的黄光发射峰来自Dy3+的4F9/2→6H13/2跃迁,595 nm处的橙光、616和655 nm处的红光发射峰分别归属于Eu3+的5D0→7F1, 5D0→7F2和5D0→7F3跃迁。荧光粉的CIE色坐标均位于红光区,表现出良好的红光发射特性,在发光二极管和彩色显示等光电领域具有潜在应用价值。     

光质对玛咖愈伤组织生长、分化的影响

研究了在组织培养过程中光质对玛咖愈伤组织生长、分化及细胞内糖代谢关键酶的影响. 在红光、黄光和白光下培养25 d, 玛咖愈伤组织的干重明显高于在绿光和蓝光下. 在分化培养基上,红光、黄光和白光条件下玛咖愈伤组织的出芽率达78%~82%,而在绿光和蓝光下出芽率几乎为0. 进一步研究表明,红光、黄光和白光条件下糖代谢中3种关键酶(葡萄糖-6-磷酸酶、己糖激酶、苹果酸脱氢酶)的活性明显高于绿光和蓝光条件下,与愈伤组织生长、分化情况相关联,说明细胞内的糖代谢受光质调节并参与了对愈伤组织生长和分化的调节.     

共沉淀法制备Tm:YbSAG纳米粉体及其发光性能

以聚乙二醇为分散剂,采用共沉淀法制备Tm:Yb3Sc Al4O12纳米粉体。最佳工艺条件为:煅烧温度1 000℃,煅烧时间2 h。通过对样品的扫描电子显微镜分析,得到纳米粉体平均粒径约为90 nm。测试了样品的激发和发射光谱,结果表明:在360 nm处激发峰最强,对应Tm3+的1D2→3H6能级跃迁;最强发射峰位于456 nm处,对应于1G4→3H6能级跃迁。测试了样品的上转换光谱,得到掺杂Tm3+的摩尔分数为2%时样品的发光强度较好,讨论了上转换发光机理,红光和绿光的发射是双光子吸收过程,蓝光发射源于1个三光子吸收过程。     

α-Zn_3(PO_4)_2:Eu~(3+)的合成及发光性质

采用共沉淀法制备了Eu~(3+)掺杂α-Zn_3(PO_4)_2基红色荧光粉,利用XRD和荧光光谱对其晶体结构、发光性能进行了研究。结果表明,样品为纯α-Zn3(PO4)2,晶相为单斜相。样品在612nm波长光监测下得到的激发光谱图主要由一宽峰和一系列尖峰组成,其中396nm处的激发峰强度最大,这说明此荧光粉可被商业化生产的蓝光InGaN LED芯片有效激发。样品在396nm近紫外光激发下,在593nm和612nm处表现出较强的发射峰,分别对应于Eu3+的5D0→7F1磁偶极跃迁和5D0→7F2电偶极跃迁。     

近紫外光激发的颜色可调Sr_2SiO_4:Gd~(3+),Tb~(3+),Eu~(3+)荧光粉的制备及其发光性能研究

采用液相沉淀法制备了近紫外光激发的颜色可调Sr_2SiO_4:0.06Gd~(3+),0.06Tb~(3+)、Sr_2SiO_4:0.06Gd~(3+),0.06Eu~(3+)和Sr_2SiO_4:0.06Gd~(3+),0.03Tb~(3+),0.03Eu~(3+)荧光粉,利用XRD、SEM、荧光光谱以及色坐标分析研究了所制备荧光粉的结构、形貌和发光性能。XRD分析表明,Sr_2SiO_4:0.06Gd~(3+),0.06Tb~(3+)、Sr_2SiO_4:0.06Gd~(3+),0.06Eu~(3+)和Sr_2SiO_4:0.06Gd~(3+),0.03Tb~(3+),0.03Eu~(3+)荧光粉样品属单斜晶系。荧光光谱分析表明,Sr_2SiO_4:Gd~(3+),Tb~(3+),Eu~(3+)的激发光谱包括200~300nm的宽带吸收峰和Tb~(3+)、Eu~(3+)的系列吸收峰。在243nm、354nm紫外光激发下,Sr_2SiO_4:0.06Gd~(3+),0.06Tb~(3+)的发射光谱由Tb~(3+)的~5D_4→~7F6(490nm,蓝绿光)、~5D_4→~7F_5(548nm,绿光)和~5D_4→~7F4(588nm,黄光)跃迁发射峰组成。在243nm、364nm紫外光激发下,Sr_2SiO_4:0.06Gd~(3+),0.06Eu~(3+)的发射光谱由Eu~(3+)的~5D_0→~7F_1(591nm,橙光)、~5D_0→~7F2(614nm,红光)、~5D_0→~7F_3(652nm,红光)跃迁发射峰组成。在243nm、252nm、364nm紫外光激发下,Sr_2SiO_4:0.06Gd~(3+),0.03Tb~(3+),0.03Eu~(3+)的发射光谱由Tb~(3+)的~5D_4→~7F_6(490nm,蓝绿光)、~5D_4→~7F_5 (548nm,绿光)、~5D_4→~7F_4(588nm,黄光)和Eu~(3+)的~5D_0→~7F_1(591nm,橙光)、~5D_0→~7F_2(614nm,红光)、~5D_0→~7F_3(652nm,红光)跃迁发射峰组成。色坐标分析表明,Sr_2SiO_4:0.06Gd~(3+),0.03Tb~(3+),0.03Eu~(3+)是很好的近紫外光激发的三色发光荧光粉。     

蓝光激发的Na_2ZnSiO_4:Eu~(3+)红色荧光粉的合成及发光特性

以H3BO3作助熔剂,采用溶胶–凝胶法合成了Na2Zn Si O4:Eu3+红色荧光粉。用X射线衍射、荧光光谱分析对样品的结构及发光特性进行了表征,探讨了H3BO3助熔剂添加量和掺Eu3+量对Na2Zn Si O4:Eu3+发光性能的影响。结果表明:所得样品属于单斜晶系,样品的激发光谱主要由一系列线状谱峰组成,激发主峰为465 nm,归属于Eu3+的7F0→5D2特征跃迁。在波长为465 nm蓝光激发下发射红光,发射峰分别为578、591、613、653和701 nm,对应于Eu3+的5D0→7FJ(J=0,1,2,3,4)跃迁,发射主峰位于613 nm(5D0→7F2)处。当Eu3+和H3BO3的摩尔掺杂量分别为5%和0.8%时,样品的荧光发光强度最大。Na2Zn Si O4:Eu3+有望成为蓝光激发的白光发光二极管(w-LED)用红色荧光粉。     

Eu~(3+)掺杂Gd_2TiO_5荧光粉的制备及其发光性质研究

采用溶胶-凝胶法制备了Eu~(3+)掺杂Gd_2TiO_5红色荧光粉,并且用XRD、激发光谱和发射光谱对其结构组成及发光性能进行了表征分析。结果表明,在612nm波长光监测下,荧光粉的激发光谱为一宽带和一系列锐峰,其最佳激发峰出现在467nm处,因此在467nm蓝光激发下,基于Eu3+的5 D0→7F2电偶极跃迁,Gd2TiO5:Eu3+荧光粉发射出强烈的红光。     

钨酸钆镉晶体的光学性能

测试了钨酸钆镉[CdGd2(WO4)4,CGW]晶体在200～700nm波段的透射光谱和反射光谱。结果显示:CGW晶体在可见光区吸收非常小,具有良好的透光性。对测量得到的光谱进行了数学处理,计算得到了描述CGW晶体宏观光学特性的重要物理量,即晶体的折射率n(λ)、消光系数k(λ)和吸收系数α(λ)。用(αE)1/2对E作图,得出了晶体的光学能隙为3.53eV,证明了CGW晶体是间接带隙半导体。     

烧结温度对Er~(3+)/Yb~(3+)共掺氟氧化物粉末上转换发光的影响

采用高温固相法在600～1100 ℃范围内选择6个不同烧结温度制备了系列相同配方的Er~(3+)/Yb~(3+)共掺氟氧化物上转换发光粉末.在室温下对各样品采用波长为980 nm泵浦光激发,肉眼均可观察到峰值位于658 nm、539 nm和523 nm处的上转换红光和绿光,分别对应于Er~(3+)的~4F_(9/2)→~4I_(15/2)和~4S_(3/2)/~2H_(11/2)→~4I_(15/2)能级跃迁,且红光强度大于绿光强度.通过比较,各样品的上转换图谱形状完全相同,而红绿上转换发光强度明显不同,800 ℃烧结制得样品的红绿荧光强度最强.样品的绿色荧光强度与红色荧光强度的比值随烧结温度升高而增加.通过各样品的X射线粉末衍射图谱(XRD)分析其成分结构,发现烧结温度对样品的成分含量有较大影响.通过测量不同烧结温度下制得样品的上转换发光强度与激发功率的变化关系,发现不同烧结温度可改变样品的上转换发光机理.     

Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands

ABSTRACT: We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material.     

Tunable solid‐state fluorescence emission and red upconversion luminescence of novel anthracene‐based fluorophores

Novel, tunable solid‐state emitters based on anthracene groups were synthesised and characterised by spectroscopy and elemental analysis. Their solid‐state photoluminescence properties were studied. These fluorophores display interesting solid‐state emission properties with an emission at wavelengths ranging from 550 to 650 nm when excited by a 325 nm helium–cadmium laser at room temperature. In particular, among them, 1,6‐di(9‐anthryl)hexa‐1,5‐diene‐3,4‐dione, 2‐[4‐(2‐benzoxazolyl)phenyl]‐4,5‐bis[2‐(9‐anthryl)vinyl]‐1H‐imidazole and 2,3‐bis[2‐(9‐anthryl)vinyl]quinoxaline show red, yellow and green emission, respectively, at 650, 584 and 550 nm. The results demonstrated that the luminescent colours can be tuned from red to yellow and green by simply varying molecular structure. Besides, 1,6‐di(9‐anthryl)hexa‐1,5‐diene‐3,4‐dione also exhibited an upconverted red fluorescent emission peak at around 675 nm under femtosecond excitation at 800 nm.     

Er3+掺杂氧氟锗硅酸盐玻璃的频率上转换研究

研究了基质玻璃成分对Er^3 掺杂氧氟锗硅酸盐玻璃上转换光谱和Raman光谱的影响,分析了氧氟锗硅酸盐玻璃中Er^3 的上转换发光机理。结果表明：通过975nm的激光二极管激发,在室温下同时观察到强烈的绿光(529,545nm)和红光(657nm)发射,分别是由于Er^3 的。H11/2→^4I15/2,^4S3/2→^4I15/2,和^4F9/2→^4I15/2跃迁,且均为双光子吸收过程。与545nm的绿光发射相比,657nm的红光发光强度比较微弱。随GeO2浓度的增加,基质玻璃的最大声子能量下降,导致无辐射跃迁几率降低,因此绿光和红光的发光强度都增强,但是其对绿光的影响大于红光。     

铽-樟脑酸-α,α′联吡啶配合物的合成及荧光性能研究

合成了稀土铽-α,α′联吡啶三元配合物,通过元素分析、红外光谱分析,确定了配合物的组成为Tb2(CA)3(dipy)2(CA:樟脑酸根,dipy:α,α′联吡啶),另外,又合成了不同比例铽、钇异核混配三元配合物。在室温下测定了配合物的荧光激发光谱,最佳波长为313 nm,即在313.0 nm光的激发下,测定了四种稀土配合物的发射光谱,发射光谱图显示了Tb3+离子的特征光谱,产生四条谱线,分别是5D4-7F6(490.0 nm),5D4-7F5(544.0 nm),5D4-7F4(584.0 nm),5D4-7F3(620.0nm),最强峰为544 nm处Tb3+离子绿色荧光发射峰。对四种配合物荧光发射峰强度变化的研究表明,钇的掺入并没有降低铽离子的荧光强度,说明不发光稀土离子钇对铽离子的荧光发射有敏化作用。     

白光LED用稀土离子掺杂硼硅酸盐玻璃的发光性能

用熔体淬冷法在空气中制备了稀土(Tm,Dy,Tb,Eu)离子单掺和共掺的硼硅酸盐发光玻璃.研究了制得玻璃的发射光谱和激发光谱特性.结果表明:Eu离子单掺玻璃的发射光谱中出现了Eu2 和Eu3 的特征发射带,证明在此玻璃系统中,有部分Eu3 转化为Eu2 .Eu3 →Eu2 的转化效率与玻璃基质中B2O3的含量和网络调整体的类型有关,并且Eu2 的发射峰随玻璃基质中碱土离子半径的增大而出现红移.Eu/Dy和Tm/Tb/Eu共掺的硼硅酸盐玻璃的发射光谱中出现蓝、黄/绿、红发射带.这些发射带的复合可以使玻璃在紫外光激发下产生白光,并且各发射带的强度比例可以通过改变玻璃基质的组成来调节,表明所制备的稀土离子掺杂硼硅酸盐发光玻璃有可能取代荧光粉应用于制备白光发光器件.     

Dual color tuning in Ce3+-doped oxyfluoride ceramic phosphor plate for white LED application

Ceramic phosphor plates of cerium (Ce³⁺)-doped oxyfluoride were fabricated by the solid-state reaction method. These phosphors exhibit efficient emission, with the novel feature of color tuning by varying both the doping concentration and excitation wavelength. As the Ce³⁺ concentration increases, the excitation spectrum broadens by a factor of 1.6, and the excitation peak wavelength shifts from 390 to 435 nm, and there is a variation in excitation energy of ~ 10%. Luminescence spectrum of low Ce³⁺ concentration samples is tuned from blue to green with the change of excitation wavelength. The emission peak exhibits a shift of 58 nm into the red spectral region, varying the Ce³⁺ concentration from 0.05 to 0.1 mol% ; whereas this shift is only 6 nm when Ce³⁺ content changes from 0.25 to 1 mol%. Photoluminescence (PL) quantum yield has achieved 76%. The crystal structure was examined using X-ray diffraction to explain its possible influence on the redshift luminescence. A proof of concept of white LED was constructed using a 450 nm blue LED chip with an oxyfluoride phosphor plate, showing a luminous efficacy (LE) of 64 lm/W with a color rendering index of 74.     

Anomalous preparation,intense 5D0→7F4 emission and adjustable double center emission of Eu3+ and Eu2+ codoped Ca2Al2SiO7

A series of Eu³⁺/Eu²⁺ codoped Ca₂Al₂SiO₇ were synthesized by traditional solid-state synthesis in reducing atmosphere. In this work, XRD powder diffraction proved that the obtained sample was pure. Photoluminescence properties are characterized by excitation, emission spectra and decay curves. Double center emission is achieved by adjusting excitation wavelength and concentration. Under the 394 nm excitation, the emission spectra Ca₂Al₂SiO₇: Eu phosphors exhibit two bands situated at blue emission of 4f5d-4f transition from Eu²⁺ ion and red emission of 4f-4f transition coming from Eu³⁺ ion. The red and yellow light can be obtained when the concentration of doped europium ions is at 0.5% and 1%, respectively. When the excitation wavelength was 394, 280 and 584 nm, the emission color change from yellow to blue, respectively. The bond energy theory explains Eu²⁺ and Eu³⁺ ion occupy Ca1 site in the Ca₂Al₂SiO₇ lattices. In addition, the spectra show that the abnormal intensity peaks of europium ion at 701 nm can be found. Analysis of the related intensity ⁵D₀-⁷F₂(618 nm) transition peak is similar to that of ⁵D₀-⁷F₄(701 nm) transition peak in the emission spectra with the Judd-Ofelt theory.     

Non-linear optical properties of coloured diamonds: Observations of frequency up conversion and “whispering gallery-like” modes in photoluminescence

Four coloured diamonds, 1.7 MeV e-beam irradiated to a dose of 10¹⁸e per sqcm and annealed around 900–930 °C, were investigated at room temperature using conventional photoluminescence (PL) and excitation spectra, and PL using 514.5 and 785 nm lasers. Interesting new observations are: (i) excitation spectra reveal energy transfer between NV⁰ and NV⁻ centers (ii) frequency up conversion, blue-green emission on excitation in 740–900 nm range, was observed in blue and lemon yellow samples. This appears to be due to two-photon absorption in GR1 centers and energy transfer to N3/H3 centres. (iii) Excitation with 514 nm line of Ar⁺ laser, in pink and purple samples resulted in the appearance of an intense and broad emission at 267 nm with FWHM of 32 nm. This is rather close to 2ν of the exciting line. It is identified as second harmonic generation (SHG) due to a synergistic effect of strain induced birefringence and resonant absorption which facilitated phase matching. The 785 nm excited anti-Stokes PL contained a frequency up converted band in 620 nm region having extensive closely spaced structure like in the case of ‘whispering gallery modes’ due to spheroid inclusions.