纤维状中空结构NaYF4:Yb3+, Er3+上转换材料的 合成及防伪应用

采用水溶性聚合物聚乙烯亚胺(PEI)调介下的水热法,一步合成了具有纤维状中空结构的六方相NaYF4:Yb3+,Er3+上转换荧光材料,并将其作为荧光填料,通过流延成膜法制备了具有上转换荧光性能的壳聚糖/聚乙烯醇(CS/PVA)荧光复合薄膜.探究了PEI配体含量和反应体系pH值对合成的上转换材料的形貌、晶型和荧光性能的影响,以及壳聚糖/聚乙烯醇荧光复合薄膜中荧光填料的最佳掺杂量.研究结果表明,在PEI含量为0.3 g且反应体系pH=5的条件下,合成的产物为具有纤维状中空结构的六方相NaYF4:Yb3+,Er3+.荧光光谱表明,合成的NaYF4:Yb3+,Er3+上转换材料在980 nm激光激发下具有优异的荧光性能.当荧光填料的掺杂质量分数为3.0％时,制备的NaYF4:Yb3+,Er3+/(CS/PVA)荧光复合薄膜具有最佳的透明度和上转换荧光特性.     

微波水热合成六方相NaYF4以及Yb3＋、Er3＋掺杂NaYF4微米管

为了合成单相以及Yb3+、 Er3+掺杂的六方结构NaYF4,采用微波水热的方法,以稀土硝酸盐、氟化钠、柠檬酸、氢氧化钠、乙酸乙酯和水为原料,合成了六方相NaYF4以及Yb3+、Er3+掺杂的六方相NaYF4 (NaYF4 ∶ Yb3+,Er3+)微米管. 利用XRD、SEM对所得样品的物相和形貌进行了表征. 研究了不同反应条件对产物形貌和物相的影响,并提出了NaYF4微米管的形成机理. 研究发现,采用微波加热的方法可以在较低的温度下快速得到单一六方相的NaYF4. 所制备的Yb3+、 Er3+掺杂NaYF4微米管的上转换发光性能与其体材料类似,具有较高的发光强度.     

NaYF4∶Er3+六棱柱的水热合成及上转换发光性能

以氟化钠、硝酸钇、硝酸铒为原料,利用水热法合成NaYF4∶Er3+材料.利用X射线粉末衍射仪(XRD)、场扫描电子显微镜(SEM)、红外吸收(FT-IR)以及发光光谱等手段对产物的物相结构、形貌和荧光性能进行分析.结果表明,NaYF4∶Er3+为六角棱柱晶体,属于六方晶系,具有P63/m(176)空间点群结构.在980nm光激发下,NaYF4∶Er3+展现出强的上转换光,波长在520 nm和539 nm为绿光发射,对应为Er3+离子的2 H11/2→4/I15/2和4S33/2→4/I15/2跃迁发射,而652nm为红光发射,则对应于Er3+离子的4 F9/2→4/I15/2跃迁发射.     

Li+掺杂对NaY(WO4)2:0.07Yb3+/0.025Er3+上转换荧光粉发光性能的影响

采用高温固相法制备一系列不同浓度Li+离子(0.00,0.03,0.05,0.07,0.09和0.11 mol)掺杂NaY(WO4)2:0.07Yb3+/0.025Er3+上转换荧光粉.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、荧光发射光谱及荧光衰减曲线等表征所制备样品物相、形貌及发光性能.结果表明,晶体结晶...     

核壳结构NaYF_4:Yb~(3+)、Er~(3+)/SiO_2颗粒的制备及其光谱性能

以正硅酸乙酯为原料,采用水解法,对100 nm亲水及20 nm亲油的NaYF4:Yb3+、Er3+上转换发光纳米颗粒进行了表面修饰,制备出了NaYF4:Yb3+、Er3+/SiO2核壳结构.研究了反应时间、反应前驱体浓度等工艺条件对包覆效果的影响.结果表明,经过二氧化硅包覆后的亲水及亲油大、小颗粒都可以均匀地分散在亲水溶剂中.在室温下,分别对SiO2壳层包覆前后的NaYF4:Yb3+、Er3+纳米颗粒的上转换发光光谱进行对比研究,发现两种粒子都能在980 nm激光激发下,产生550 nm的绿光及670 nm的红光,且包覆后纳米颗粒的发光位置及整体发光强度与包覆前相比没有受到影响.     

水溶性NaYF4:Yb,Er纳米颗粒的溶剂热合成及其上转换发光性能

稀土上转换发光纳米材料具有极好的生物应用前景,但其应用的前提是能制备出水溶性、发光效率高的稀土纳米材料.以乙二醇为溶剂、稀土氯化物和NaP为反应物,采用简易的溶剂热法一步制备出水溶性的NaYF4:Yb,Er纳米颗粒.NaYF4:Yb,Er样品以粒径为25~40nm的球形颗粒为主,同时含有少量直径为25~40nm、长度为50～100nm的虫状纳米颗粒.该样品具有立方相结构,样品表面上的乙二醇配体使其能够很好地分散于水中.在980nm激光器激发下,NaYF4:Yb,Er纳米颗粒水溶液展现了强的黄绿色上转换发光.因此该样品拥有良好的生物应用潜力.     

凝胶网络模板法可控制备NaYF_4:Yb~(3+),Er~(3+)稀土上转换纳米颗粒

采用水凝胶空间网孔结构作为纳米级反应容器可控制备了NaYF4:Yb3+,Er3+稀土上转换发光纳米颗粒。通过控制交联剂密度可以改变网络凝胶网孔结构,用不同网孔结构的凝胶模板可以控制合成纳米颗粒。通过XRD、TEM、PL等方法研究了不同凝胶模板对颗粒的尺寸、发光性能的影响。结果表明,利用高分子交联后形成的凝胶网络,可以制得粒径在10 nm左右的NaYF4:Yb3+,Er3+纳米颗粒。随着交联剂浓度的升高,颗粒粒径及荧光强度都有所下降。本研究为稀土上转换发光纳米颗粒的制备提供了工艺简单、绿色环保的新方法。     

PEG修饰YF_3微米晶的溶剂热合成及Y_(1.2)F_3:Yb_(0.18)~(3+)/Er_(0.01)~(3+)上转换荧光性质

采用溶剂热方法,乙醇和乙二醇的混合溶剂中,150℃条件下,反应12h,成功制备了YF3:Yb3+/Er3+晶体,和PEG-6000修饰的YF3:Yb3+/Er3+晶体。通过X射线粉末衍射,扫描电镜(SEM),红外光谱(IR)和荧光分光光度计对样品的组成、结构和荧光性质进行了表征和分析。结论为:YF3:Yb3+/Er3+晶体与YF3标准卡PDF#74-0911相符,而PEG-6000修饰的YF3:Yb3+/Er3+晶体的标准卡为PDF#32-1431,说明PEG的修饰导致晶体结构的变化。室温下,以980nm为激发光源,YF3:Yb3+/Er3+晶体和PEG修饰的YF3:Yb3+/Er3+晶体的荧光发射峰位置均为551nm、666nm和832nm,其分别对应于Er3+离子的4S3/2→4I15/2,4F9/2→4I15/2和4S3/2→4I13/2跃迁。但荧光强度不同。讨论了表面活性剂聚乙二醇的加入对YF3:Yb3+/Er3+晶体形貌,尺寸及荧光性质的影响,并对Yb3+/Er3+上转换发光机理进行了讨论。     

水热法合成NaYF_4∶Er~(3+)/Pr~(3+)上转换发光性能

以氟化钠、硝酸钇、硝酸铒、硝酸镨为原料,采用水热法合成了NaYF4∶Er3+/Pr3+上转换荧光粉。利用X射线粉末衍射(XRD),场发射扫描电子显微镜(SEM)、荧光光谱(PL)等方法对产物的形貌、结构和发光性能进行表征。结果表明,NaYF4∶Er3+/Pr3+粉体外观主要是六边棱柱,属于六方晶系,具有P63/m(176)空间点群结构。在980nm激光激发下表现出了强的上转换发光性能。其中波长520.5nm和539nm位置为绿光发射,在652m位置为红光发射,分别对应的是Er3+离子的2 H11/2→4 I15/2、4 S3/2→4 I15/2跃迁发射和4 F9/2→4 I15/2跃迁发射。Pr3+上电子向Er3+的能量迁移提高了发光强度。     

热处理温度及EDTA对β-NaYF_4:Yb~(3+),Er~(3+)材料结构与性能的影响

采用共沉淀法合成了Yb3+、Er3+共掺杂的NaYF4粉体,重点研究了热处理温度和螯合剂EDTA对所合成粉体的晶相、表面形貌以及上转换发光性能的影响,并利用X射线衍射、扫描电镜及荧光光谱对其结构组成、晶体表面形貌及发光性能进行了研究。结果表明:随着热处理温度的升高,NaYF4:Yb3+,Er3+粉体由立方相向六方相转变,当温度高于600℃时又从六方相逐渐转变为立方相,而且颗粒的尺寸逐渐变大,从近似球形到无规则形状;NaYF4:Yb3+,Er3+发光强度与热处理温度密切相关,热处理温度对于β-NaYF4:Yb3+,Er3+的发光性能有着重要的影响。经过600℃热处理后的粉体具有较高的发光强度;螯合剂EDTA的添加对所合成粉体的发光性能有着明显的影响,螯合剂的添加降低了其发光强度;在1 000℃以内,NaYF4:Yb3+,Er3+具有良好的热稳定性。     

纳米NaYF4:Er3+,Yb3+上转换材料的合成及其性质研究

采用溶胶-凝胶法在水相合成了纳米NaYF_4:Er~(3 ),Yb~(3 )上转换材料,980nm红外激光照射下,肉眼可观察到明亮的上转换发光。实验研究了铒、镱掺杂浓度及焙烧温度对材料合成的影响。所合成的纳米材料呈圆球形、颗粒均匀、分散性好,平均粒径70nm,可应用于生物标记。     

Synthesis of colloidal upconverting NaYF4: Er3+/Yb3+ and Tm3+/Yb3+ monodisperse nanocrystals

The synthesis, characterization, and spectroscopy of upconverting lanthanide-doped NaYF4 nanocrystals (NCs) is presented. The monodisperse cubic NaYF4 NCs were synthesized via a thermal decomposition reaction of trifluoroacetate precusors in a mixture of technical grade chemicals, octadecene and the coordinating ligand oleic acid. In this straightforward method, the dissolved precursors are added slowly to the reaction solution through a stainless-steel canula resulting in highly luminescent nanocrystals with an almost monodisperse particle size distribution. The NCs were characterized through the use of transmission electron microscopy, selected area electron diffraction, 1H NMR, powder X-ray diffraction, and high-resolution luminescence spectroscopy. The NaYF4 NCs are capable of being of dispersed in nonpolar organic solvents thus forming colloidally stable solutions. The colloids of the Er3+, Yb3+ and Tm3+, Yb3+ doped NCs exhibit green/red and blue upconversion luminescence, respectively, under 980 nm laser diode excitation with low power densities.     

Up-conversion luminescence of the NaYF4:Yb3+,Er3+ nanomaterials prepared with the solvothermal synthesis

Up-converting NaYF₄:Yb³⁺,Er³⁺ (x_Yb: 0.20, x_Er: 0.02) nanomaterials were prepared with a microwave assisted solvothermal synthesis to study how the synthesis parameters affect the structure and up-conversion luminescence of the materials and thus their usability as labels in biomedical applications. The purity of the materials was studied with Fourier transform infra-red (FT-IR) spectroscopy and the particle size and morphology with transmission electron microscopy (TEM). The crystal structure was characterized with X-ray powder diffraction (XPD) and the crystallite sizes were calculated with the Scherrer formula. Up-conversion luminescence and luminescence decays were studied with near infra-red (NIR) laser excitation at 970 nm.The presence of the oleic acid was observed in the FT-IR spectra. The TEM images showed small quasi-spherical nanoparticles as well as long nanorods. The XPD measurements revealed that both cubic and hexagonal forms of NaYF₄ were present in the materials. The crystallite sizes ranged from ca. 20 to over 150 nm for the cubic and hexagonal phases, respectively. The characteristic up-conversion luminescence of Er³⁺ in red (640–685 nm; ⁴F_9/2 → ⁴I_15/2) and green (515–560 nm; ²H_11/2, ⁴S_3/2 → ⁴I_15/2 transitions) wavelengths was observed. The most intense luminescence and the longest luminescence emission lifetime were obtained with the material annealed for 12 h at 177 °C with 1.8 MPa pressure due to the predominance of the well-crystallized hexagonal form of NaRF₄ (R: Y, Yb, Er).     

Synthesis and characterization of upconverting NaYF4:Er3+, Yb3+ nanocrystals via thermal decomposition of stearate precursor

Er3+-Yb3+ codoped hexagonal NaYF4 nanocrystals were prepared via a method of thermal decomposition of stearate precursor. Their crystal structure, morphologies and photoluminescence (PL) properties were characterized by XRD, SEM, and fluorescence spectra. The hexagonal NaYF4:Er3+, Yb3+ nanocrystals could be well dispersed in cyclohexane to form a clear solution. Under 980 nm excitation, the solution of Er3+-Yb3+ codoped NaYF4 nanocrystals emits bright green upconversion fluorescence.     

Optimisation of ligand exchange towards stable water suspensions of crystalline NaYF4: Er3+, Yb3+ nanoluminophors

NaYF4: 2%Er3+, 20%Yb3+ nanoparticles were synthesized through a wet chemical route. In order to transfer the nanoparticles from chloroform to aqueous solution an oleic acid to 3-mercaptopropionic acid ligand exchange process has been performed and optimized. The influence of temperature and atmosphere onto the NaYF4:2%Er3+, 20%Yb3+ nanoparticles water suspensions dispersibility and stability after replacing oleic acid with 3-mercaptopropionic acid ligands has been investigated. The results revealed an improvement of nanoparticles water suspension transparency and luminescence yield after ligand exchange process performed under inert atmosphere and at elevated temperature.     

Er3+/Yb3+ codoped oxyfluoride borosilicate glass ceramic containing NaYF4 nanocrystals for amorphous silicon solar cells

Transparent oxyfluoride borosilicate glass ceramic containing cubic NaYF₄ nanocrystals were successfully fabricated. The cubic NaYF₄ nanocrystals with average size of 30 nm were precipitated in the glass matrix, which was confirmed by the X-ray diffraction and TEM results. In comparison with the as-made glass, significant enhancement of upconversion luminescence is observed in the Er³⁺/Yb³⁺ codoped transparent glass ceramic, which may be due to the variation of coordination environment of Er³⁺ and Yb³⁺ ions after crystallization. The high transparency, intense upconversion luminescence and the simple, low-cost fabrication process make this material exhibiting potential applications in the fields of amorphous silicon solar cells.