Pr,Yb,Ho:GdScO_(3)晶体生长及光谱性能

2.7-3.0μm波段激光在很多领域具有重要应用,为探索和发展该波段新型晶体材料,本文采用提拉法生长出Pr,Yb,Ho:GdScO_(3)晶体,通过共掺入Pr3+离子以达到衰减Ho^(3+):^(5)I_(7)能级寿命的目的.采用X射线衍射测试得到了晶体的粉末衍射数据,测量了拉曼光谱,并对晶体的拉曼振动峰进行指认,对Pr,Yb,Ho:GdScO_(3)晶体的透过光谱、发射光谱和荧光寿命进行表征.Yb^(3+)的最强吸收峰在966 nm,吸收峰半峰宽为90 nm;2.7-3.0μm波段最强发射峰在2850 nm,半峰宽为70 nm;Ho^(3+):^(5)I_(6)和^(5)I_(7)能级寿命分别为1094μs和56μs.与Yb,Ho:GdScO_(3)晶体相比,Yb^(3+)的吸收峰和2.7-3.0μm的发射峰半峰宽明显展宽,同时下能级寿命显著减小,计算表明Ho^(3+):^(5)I_(7)与Pr^(3+):^(3)F_(2)+^(3)H_(6)能级之间能实现高效的能量传递.以上结果表明Pr,Yb,Ho:GdScO_(3)晶体是性能更优异的2.7-3.0μm波段激光材料.

Lu^(3+)掺杂Na_(5)Y_(9)F_(32)∶Ho^(3+)/Yb^(3+)/Ce^(3+)单晶体的增强红色上转换发光与光学温度传感性能

采用密封的坩埚下降法技术生长了一系列Lu^(3+)(摩尔分数0、0.6%、1.2%、1.8%)掺杂Na_(5)Y_(9)F_(32)∶Ho^(3+)/Yb^(3+)/Ce^(3+)单晶体。在980 nm LD激发下,观察到单晶体的绿光543 nm(^(5)S_(2)/^(5)F_(4)→^(5)I_(8))、红光656 nm(^(5)F_(5)→^(5)I_(8))以及近红外750 nm(^(5)S_(2)/^(5)F4→^(5)I_(7))上转换发光。从上转换发光强度随激发光强度的变化情况,确定了543 nm、656 nm与750 nm的发光为双光子跃迁过程。研究了Lu^(3+)离子掺杂浓度对其发光强度与荧光寿命的影响情况,随着Lu^(3+)掺杂浓度从0增加到1.8%,单晶体中的656 nm红光逐步增强,543 nm绿光与750 nm近红外光随之减弱,红绿光强度比从0.01增加到了1.55,而543 nm荧光寿命从1.29 ms降低至0.99 ms。Lu^(3+)离子的掺入取代Y^(3+)晶格位,改变了单晶体的局域场环境,导致上转换发光强度的变化。基于随温度变化的上转换红光656 nm(^(5)F5→^(5)I8)与绿光543 nm(^(5)S_(2)/^(5)F4→^(5)I8)的发光强度变化,研究了1.8%Lu^(3+)掺杂Na_(5)Y_(9)F_(32)∶Ho^(3+)/Yb^(3+)/Ce^(3+)单晶体在298~448 K范围内的绝对灵敏度和相对灵敏度最大值分别为0.242%·K^(-1)和0.217%·K^(-1)。

亲水性CIT-NaYF_(4)∶Yb^(3+),Ho^(3+)纳米粒子的制备及其发光性能研究

采用溶剂热法制备了油溶性稀土掺杂上转换纳米粒子NaYF_(4)∶Yb^(3+),Ho^(3+),并利用TEM、XRD、IR、荧光光谱法等考察了反应温度、反应时间、掺杂比等反应条件对纳米粒子形貌、结构、发光性能的影响。结果表明,在反应温度为300℃、反应时间为50 min、稀土离子掺杂比为NaYF_(4)∶20%Yb^(3+),2%Ho^(3+)条件下,制备出的油溶性NaYF_(4)∶Yb^(3+),Ho^(3+)纳米粒子呈标准六方晶型,尺寸均一、单分散性好,平均粒径为31.55 nm。通过表面配体交换法成功将柠檬酸修饰在其表面,转为亲水性CIT-NaYF_(4)∶Yb^(3+),Ho^(3+)纳米粒子。

GdVO_(4):Yb^(3+),Ho^(3+)和GdPO_(4):Yb^(3+),Ho^(3+)荧光粉的上转换发光特性研究

为了探究Yb^(3+),Ho^(3+)分别共掺杂在GdVO_(4)和GdPO_(4)两种基质材料的发光差异性,采用高温固相法制备GdVO_(4):Yb^(3+),Ho^(3+)和GdPO_(4):Yb^(3+),Ho^(3+)上转换发光材料。并采用X射线衍射仪(X-ray diffraction,XRD)、拉曼光谱(Raman spectroscopy,Raman)、扫描电子显微镜(scanning electron microscopy,SEM)和荧光光谱对材料的结构、组成、形貌和上转换发光性能进行测试分析。结果表明,合成样品均是纯相,GdVO_(4):Yb^(3+),Ho^(3+)样品形状为不规则块状;GdPO_(4):Yb^(3+),Ho^(3+)样品为米粒状。在980 nm激发下,两种样品都存在绿光和红光发射。与掺杂相同浓度的GdVO_(4):Yb^(3+),Ho^(3+)相比,GdPO_(4):Yb^(3+),Ho^(3+)样品的红绿比较大,色度坐标更接近红光,在生物成像领域具有更大的应用潜力。

Lu_(2)O_(3):Yb,Tm/MC540纳米材料的制备及研究

以水热反应及后续的高温煅烧过程为合成手段,成功制备了Lu_(2)O_(3):Yb,Tm纳米材料。XRD结果显示所得样品为纯Lu2O3晶相。且SEM结果表明所得样品由不规则形状组成,粒径在100nm左右。随后通过搅拌吸附过程负载部花青(MC540)光敏剂,得到Lu_(2)O_(3):Yb,Tm/MC540纳米材料。然后以肺癌细胞(A-549细胞)为模型,研究了Lu_(2)O_(3):Yb,Tm/MC540纳米材料的抗肿瘤活性。结果表明,在650nm的红光照射下,上述材料对肺癌A-549细胞具有明显的光动力杀伤疗效。

Yb3+/Ho3+/Tm3+三掺杂LiTaO_(3)多晶材料的上转换发光特性

采用高温固相合成法制备了多组Yb^(3+)/Ho^(3+)/Tm^(3+)不同物质的量分数掺杂的LiTaO_(3)多晶材料,测试了双掺Yb^(3+)/Ho^(3+),Yb^(3+)/Tm^(3+)和三掺Yb^(3+)/Ho^(3+)/Tm^(3+)的LiTaO_(3)多晶的X射线衍射图谱、紫外-可见吸收谱和上转换荧光发射谱。X射线衍射(XRD)结果显示,稀土离子掺杂没有改变LiTaO_(3)多晶的物质结构,这表明稀土离子以取代基质离子的方式进入了晶格中。样品的紫外吸收边显示,增加Ho^(3+)或Tm^(3+)物质的量分数会导致吸收边先红移再蓝移。在980 nm泵浦光激发下,可见光区域中出现上转换蓝光(475 nm)、绿光(545 nm)和红光(663 nm和650 nm)发射,通过改变LiTaO_(3)中的激活离子Ho^(3+)-Tm^(3+)物质的量分数,可对上转换荧光色度进行调节,物质的量分数配比为2.0%Yb^(3+)/0.05%Ho^(3+)/0.4%Tm^(3+)的掺杂LiTaO_(3)多晶材料实现了最为接近标准白光的发射。

Upconversion Luminescence Properties of Ho^(3+),Tm^(3+),Yb^(3+) Co-Doped Nanocrystal NaYF_4 Synthesized by Hydrothermal Method

Nanocrystal of upconversion （UC） phosphor Ho^3＋, Tm^3＋ , and Yb^3＋ co-doped NaYF4 was prepared by the hydrothermal method in the presence of the complexing agent EDTA. Under 980 nm diode laser excitation, the impact of different concentrations of Ho^3＋ ion on the UC luminescence intensity was discussed. The law of luminescence intensity versus pump power shows that the 474 nm blue emission, 538 nm green emission, and 642 nm red emission are all due to the two-photon process, while the 450 nm blue emission is a three-photon process. The UC mechanism and processes were also analyzed. The sample was characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. The result shows that Ho^3＋ ,Tm^3＋ , and Yb^3＋ co-doped NaYF4 prepared by the hydrothermal method exhibits a hexagonal nanocrystal.

Yb,Ho∶GdScO_(3)晶体生长及光谱性能分析

采用提拉法生长出了尺寸为∅30 mm×50 mm的Yb,Ho∶GdScO_(3)晶体。通过X射线衍射得到了晶体的粉末衍射数据,使用GSAS软件进行了全谱拟合,得到了晶体的结构参数。测试了晶体的拉曼光谱,在100~700 cm^(-1)观察到18个拉曼振动峰。对Yb,Ho∶GdScO_(3)晶体的光谱特性进行了表征,并计算了Yb^(3+)的吸收截面,其在940、975 nm处的吸收截面分别为0.31×10^(-20)、0.42×10^(-20) cm^(2)。采用Judd-Ofelt理论计算了Ho^(3+)的跃迁强度参量Ω_(t),Ω_(4)/Ω_(6)值为2.04,并计算了辐射跃迁概率、能级寿命及荧光分支比等光谱参数。结果表明,Yb,Ho∶GdScO_(3)晶体的发光性能良好,是一种有前景的2~3μm激光晶体候选材料。

Tm^(3+)高掺杂的NaYF_(4)纳米颗粒制备与发光性能研究

为了研究Tm^(3+)高掺杂浓度下NaYF_(4)纳米颗粒的上转换发光性能,采用热分解法合成了六方相的NaYF_(4)∶Yb^(3+)/Tm^(3+)(20%/8%)纳米颗粒,并用X射线衍射对其结构进行了表征,用透射电子显微镜对其形貌和大小进行了表征.通过搭建上转换光谱测试系统,研究了在980 nm激光激发下NaYF_(4)∶Yb^(3+)/Tm^(3+)纳米颗粒的上转换发光光谱,并分析了其发光机制.通过计算475,513,650,744,805 nm处发光强度与激发光功率间的依赖关系,证明了其上转换发光过程为双光子过程.

Yb^(3+)和Tm^(3+)共掺透明磷酸盐微晶盐玻璃上转换发光性能

采用熔融冷却法制备了掺杂不同比例Yb^(3+)和Tm^(3+)的磷酸盐玻璃,通过在630℃保温1 h得到透明的微晶玻璃,对样品进行XRD测试,表明析出的晶体为Na_(3.6)Y_(1.8)(PO_(4))_(3),通过Jade6.0计算和TEM分析,其晶粒尺寸均在20~40 nm之间,小于可见光波长,透过率光谱表明,经过热处理之后微晶玻璃仍保持70%以上的透过率。研究了前驱体玻璃和微晶玻璃在980 nm LD泵浦下的上转换荧光光谱,微晶玻璃的上转换效率明显高于前驱体玻璃,在上转换荧光光谱中,475 nm处发射强烈的上转换蓝光,654 nm处发射微弱的红光,795 nm处发射较弱的红外光。随着Yb^(3+)掺杂浓度的增加其上转换效率先增大后减小,Yb^(3+)的掺杂浓度为0.9%时,产生浓度猝灭现象。通过分析上转发光强度与激光器泵浦功率之间的关系,在Yb^(3+)和Tm^(3+)共掺的磷酸盐微晶玻璃中,上转换蓝光、红光和红外光的发射均为双光子过程。解释了Yb^(3+)和Tm^(3+)在磷酸盐微晶玻璃中的上转换发光机制。利用CIE1931计算,可知Yb^(3+)和Tm^(3+)共掺磷酸盐微晶玻璃的上转换发光色度坐标落在了蓝光区域,有望用在光学储存、全色显示、蓝色防伪、蓝光激光玻璃等领域。

Up-conversion photoluminescence characteristics of Yb^(3+):Er^(3+):Tm^(3+) co-doped borosilicate glasses

Yb^3＋：Er^3＋：Tm^3＋co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb^3＋ Er^3＋ and Tm^3＋ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb^3＋ Stark splitting levels to pump Tm^3＋ ions and there exists an optimum pump power. The concentration of the Tm^3＋ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the yb^3＋：Er^3＋：Tm^3＋ co-doped borosilicate glasses.

K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS光催化复合材料的制备及其光催化性能研究

上转换材料与光催化剂复合可以产生吸收光谱“红移”的效果,对提高光催化剂的降解效率具有重要意义。为了提高CdS对近红外光的利用率,通过高温固相反应法合成了冰晶石结构上转换发光材料K_(3)ScF_(6)∶Tm^(3+),Yb^(3+),并采用高能球磨法将其与CdS复合制备出一种新型光催化复合材料K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS。采用X射线粉末衍射(XRD)、场发射扫描电镜(SEM)、荧光光谱(PL)和紫外-可见漫反射吸收光谱对其成分、结构和性能进行了系统表征。同时,对不同复合比例下制备的复合催化剂对罗丹明B(RhB)的光降解效率和K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS光催化复合材料的光催化机理进行了研究。结果表明,K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)和CdS的最佳复合比为3.6∶1,上转换发光材料K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)的引入协同促进了CdS的光催化作用,光催化过程中·OH与·O^(2-)均参与了对RhB的降解,并且·OH起主要作用。此外,在最佳复合比下,经过80 min,K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS样品降解率达到99.9%,与未复合的CdS相比,降解率提高了近50倍。所有结果表明K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS光催化复合材料在光催化领域具有潜在的应用价值。

Ho^(3+)和Yb^(3+)共掺杂La_(7)P_(3)O_(18)荧光粉的合成及上转换发光性能

通过高温固相技术合成Ho^(3+)和Yb^(3+)共掺杂La_(7)P_(3)O_(18)上转换荧光粉。XRD结果表明,合成样品是空间群为P21/n的单斜结构的La_(7)P_(3)O_(18)晶体和少量La PO4晶体的混合物。紫外可见漫反射光谱结果证实La_(7)P_(3)O_(18)晶体是一种光学带隙为4.10 e V的间接半导体。经980 nm激光激发,Ho^(3+)和Yb^(3+)共掺杂La_(7)P_(3)O_(18)荧光粉发射出Ho^(3+)离子特征的蓝色(486 nm)、绿色(550 nm)和红色(661 nm)特征峰,其中,661 nm处发射峰在样品上转换发光光谱中占主导地位。此外,随着Ho^(3+)和Yb^(3+)掺杂量的增加,样品上转换发光强度先增大后减小。当Ho^(3+)和Yb^(3+)的掺杂量分别达到1%和10%(摩尔分数)时,样品出现浓度猝灭现象,其机制为电四极-电四极相互作用。泵浦功率和发光强度关系表明,样品的绿光和红光发射均源于双光子吸收过程激发。Ho^(3+)和Yb^(3+)共掺杂La_(7)P_(3)O_(18)晶体上转换发光色坐标位于橙红色区域。

Up-Conversion Properties of Oxy-Fluoride Glasses Co-Doped with Ho^(3+) and Yb^(3+)

Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540 and 650 nm. The up-conversion mechanism and processes were analyzed. The relationship between pumping power and relative intensity of emissions was discussed. From the dependence, it is known that the emissions centered at 540 and 650 nm are both attributed to two-photon process.

Tm^(3+)/Yb^(3+)共掺含LaF_(3)纳米晶锗酸盐微晶玻璃的上转换发光及其温度传感特性

通过传统的熔融淬火技术以及后续热处理法制备了Tm^(3+)/Yb^(3+)共掺含LaF_(3)纳米晶锗酸盐微晶玻璃。通过DTA和XRD研究其热性质和LaF_(3)纳米晶的可控析出。通过透过光谱和上转换发光光谱研究了玻璃的光学性能。利用荧光强度比(FIR)技术研究了微晶玻璃样品在980 nm激光激发下的上转换发光光谱与温度的依赖关系。研究发现,该微晶玻璃样品在313~573 K温度范围内的最大绝对灵敏度Sa和最大相对灵敏度Sr分别为2.6×10^(-4)K^(-1)(573 K)和2.3×10^(-2)K^(-1)(313 K)。结果表明,Tm^(3+)/Yb^(3+)共掺含LaF_(3)纳米晶锗酸盐微晶玻璃在温度传感领域具有潜在的应用前景。

Spectroscopic properties and mechanism of Tm^(3+)/Er^(3+)/Yb^(3+) co-doped oxyfluorogermanate glass ceramics containing BaF_2 nanocrystals

Transparent Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode （LD）, compared with the glass before heat treatment, the Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark- split peaks; X-ray diffraction （XRD） and transmission electron microscope （TEM） results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm^3＋, Er^3＋ and （or） Yb^3＋ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm^3＋, Er^3＋ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.

Intense up-conversion emissions of yb3＋/Dy3＋ co-doped A12O3 nanopowders prepared by non-aqueous sol-gel method＊

yb3＋/Dy3＋ co-doped A1203 nanopowders have been prepared by the non-aqueous sol-gel method and their up- conversion photoluminescence spectra are measured under excitation by a 980-nm semiconductor laser. The results show that there are comparatively abundant spectra of up-conversion emissions centered at 378, 408, 527 and 543, and 663 nm, corresponding to 4C9/2→ 6H13/2, 4C9/2→ 6Hll/2, 4115/2 → 6H13/2, and 4F9/2 →6Hll/2 transitions of Dy3＋, respectively. Two-photon and three-photon processes are involved in ultraviolet, violet, green, and red up-conversion emissions. The energy transition between Yb3＋ and Dy3＋ is discussed.

Upconversion Properties of LiNbO_3 Single Crystals Co-doped with Ho and Yb

The IR-to-visible upconversion fluorescent crystals, Yb：Ho：LiN-bO3, with a constant Ho^3＋ concentration （0.1 mol%） and different doping concentrations of Yb^3＋ （0.5, 1.5, 2.0, 2.5, 3.0 tool%） are synthesized by Czochralski method in air atmosphere. X-ray diffraction shows that the obtained crystal is a single phase of LiNbO3 and the rare-earth ions occupied the Li^＋ or Nb^5＋ sites instead of the interstitial sites. Under 980 nm excitation, green and red emission bands due to the Ho^3＋ （^5S2, ^5F4）/^5I8 and Ho^3＋ ^5F5/^5I8 energy transitions are observed in these samples, respectively. Power dependence studies on these samples with different Yb^3＋ dopant concentrations indicate that the red and green emissions are based on a two-photon process. The intensities of the red and green upconversion fluorescence increase with Yb3＋ ions of 0-2.0 mol% because of an increased Yb^3＋ sensitization, but decrease at higher concentrations owing to the back-energy transfer between the Yb^3＋ and Ho^3＋ ions.

不同掺杂浓度的NaGdF_4∶Ho^(3+),Tm^(3+),Yb^(3+)发光粉的上转换发光

采用水热法制备了掺杂不同比例Ho3+/Tm3+和不同Yb3+浓度的Na Gd F4∶Ho3+,Tm3+,Yb3+上转换发光粉,对其结构和上转换发光性能进行了表征。XRD研究结果表明:所有的样品均为六方结构Na Gd F4。980 nm红外光激发下,稀土掺杂的Na Gd F4发光粉显示分别来自于Ho3+离子5S2,5F4(Ho)→5I8(Ho)跃迁发射的绿光,5F5(Ho)→5I8(Ho)跃迁发射的红光,5S2,5F4(Ho)→5I7(Ho)跃迁发射的近红外光;来自Tm3+离子1D2(Tm)→3F4(Tm)和1G4(Tm)→3H6(Tm)跃迁发射的蓝光,1G4(Tm)→3F4(Tm)跃迁发射的红光,3H4(Tm)→3H6(Tm)跃迁发射的红外光。研究了Ho3+/Tm3+比例和Yb3+浓度对发光粉上转换发光性能的影响,并讨论了体系的上转换发光机制。计算的发光粉色坐标显示:掺杂Ho3+/Tm3+比例和Yb3+浓度的变化能调控样品上转换发光颜色。

Frequency Up-conversion Luminescence Properties and Mechanism of Tm^(3+) /Er^(3+)/Yb^(3+) Co-doped Oxyfluorogermanate Glasses

Oxyfluoride glasses were developed with composition 60GeO 2 ·10AlF 3 ·25BaF 2 ·（1.95-x）GdF 3 · 3YbF 3 ·0.05TmF 3 ·xErF 3 （x=0.02,0.05,0.08,0.11,0.14,0.17）in mole percent.Intense blue（476 nm）,green（524 and 546 nm）and red（658 nm）emissions which identified from the 1G 4 →3H 6 transition of Tm3＋and the（2H 11/2 ,4S 3/2 ）→4I 15/2 ,4F 9/2 →4I 15/2 transitions of Er3＋,respectively,were simultaneously observed under 980 nm excitation at room temperature.The results show that multicolor luminescence including white light can be adjustably tuned by changing doping concentrations of Er3＋ion or the excitation power.In addition,the energy transfer processes among Tm3＋,Er3＋and Yb3＋ions,and up-conversion mechanisms are discussed.