APTES-modified RE2O3:Eu3+ luminescent beads: structure and properties

Europium-doped lanthanide oxide RE(2)O(3):Eu(3+) (RE = Y or Gd) luminescent beads, with a spherical shape and a diameter of 150 ± 15 nm, have been modified by reaction with 3-aminopropyltriethoxysilane (APTES), in order to introduce reactive amine groups at their surfaces. The direct silanation has resulted in the formation of a nanometric layer at the surface of the beads, with an optimum grafting rate of 0.055 ± 0.005 mol APTES/mol RE(2)O(3). Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies confirmed the condensation of an organosilane layer, made of cross-linked -O-Si-O-Si- and of groups -O-Si-R (with R = (CH(2))(3)NH(2) or O-Et). Titration of the accessible amine groups has been performed by simultaneously measuring the luminescence of grafted fluorescein isothiocyanate and that of core particles: there are about 2.3 × 10(4) (2.8 × 10(4)) -NH(2) per Y(2)O(3):Eu(3+) (Gd(2)O(3):Eu(3+)) bead. The isoelectronic point was shifted by one pH unit after APTES modification. The surface modification by APTES at least preserved (for Gd(2)O(3):Eu(3+)) or improved (for Y(2)O(3):Eu(3+)) the red emission of the beads.     

Preparation of Y2O3:Eu3+ nanoparticles in reverse micellar systems and their photoluminescence properties

Y2O3:Eu3+ phosphor nanoparticles (4-8 nm in size) with spherical morphology and narrow size distribution were obtained by calcination of composite Y-Eu hydroxide nanoparticles, which were prepared in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane or polyethylene glycol mono-4-nonylphenyl ether (NP-5)/cyclohexane reverse micellar systems. This was achieved by the incorporation of the Y-Eu hydroxide nanoparticles into polyurea (PUA) via in situ polymerization of hexamethylene diisocyanate (HDI) in the reverse micellar solution and subsequent calcination of the resulting PUA materials. The emission intensity of the Y2O3:Eu3+ nanoparticles, prepared in the AOT/isooctane system, was significantly lower than that of the micrometer-size particles prepared in a homogeneous aqueous solution, since the calcined nanoparticles contained Na2SO4 impurity derived from the remaining AOT surfactant. The nanoparticles prepared in the NP-5/cyclohexane system, in contrast, showed higher emission intensity compared to the nanoparticles prepared in the AOT/isooctane system and longer luminescence lifetime compared to the micrometer-size particles prepared in the homogeneous aqueous solution. The photoluminescence intensity of Y2O3:Eu3+, prepared via the proposed process was found to decrease with decreasing the particle size.     

Gd3Ga5O12∶Eu3+发光纳米晶的燃烧合成及性质

以尿素为燃烧剂,乙二醇为分散剂采用燃烧法制备了Gd3Ga5O12∶Eu3+纳米晶。利用X射线衍射、电镜和荧光光谱对前驱体和热处理后样品的结构、形貌和发光性能进行了表征。XRD结果表明:700℃热处理2 h即可获得立方结构Gd3Ga5O12∶Eu3+纳米晶。根据Scherrer公式估算经700℃和900℃热处理2 h获得的纳米晶的一次性粒径分别为28 nm和42 nm。发射光谱和激发光谱的结果表明:特征发射峰来自于5D0-7FJ跃迁,而来自于Eu3+的5D0→7F1的磁偶极跃迁发射最强;宽激发带主要来自于Eu-O电荷迁移带和Gd3Ga5O12基质吸收。发射强度和激发强度随热处理温度的提高而增强。     

Ga2O3 and GaN nanocrystalline film: reverse micelle assisted solvothermal synthesis and characterization

Gallium oxide (beta-Ga2O3) nanoparticles were successfully deposited on quartz glass substrates using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-hexane/ethylene glycol monomethyl ether (EGME) reverse micelle-mediated solvothermal process with different omega values. The mean diameter of Ga2O3 particles was approximately 2-3 nm and found to be approximately independent of omega values of the reverse micelles. However, when the Ga2O3 nanocrystalline films were nitrided at 900 degrees C under flowing NH3 atmosphere for 1 h, the mean diameter of the resulted gallium nitride (wurtzite-GaN) nanoparticles varied from 3-9 nm. Both nanocrystalline films of Ga2O3 and GaN were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence in order to study their chemical and physical properties explicitly.     

Fe3O4 and gamma-Fe2O3 nanoparticles for the adsorption of Co2+ from aqueous solution

The adsorption of Co2+ ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe3O4) and maghemite (gamma-Fe2O3) has been studied. The adsorption of Co2+ ions on the surface of the particles was investigated under different conditions of oxide content, contact time, solution pH, and initial Co2+ ion concentration. It has been found that the equilibrium can be attained in less than 5 min. The maximum loading capacity of Fe3O4 and gamma-Fe2O3 nanoparticles is 5.8 x 10(-5) and 3.7 x 10(-5) mol m(-2), respectively, which are much higher than the previously studied, iron oxides and conventional ion exchange resins. Co2+ ions were also recovered by dilute nitric acid from the loaded gamma-Fe2O3 and Fe3O4 with an efficiency of 86 and 30%, respectively. That has been explained by the different mechanisms by including both the surface and structural loadings of Co2+ ions. The surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles has been found to have the same mechanism of ion exchange reaction between Co2+ in the solution and proton bonded on the particle surface. The conditional equilibrium constants of surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles have been determined to be log K=-3.3+/-0.3 and -3.1+/-0.2, respectively. The structural loading of Co2+ ions into Fe3O4 lattice has been found to be the ion exchange reaction between Co2+ and Fe2+ while that into gamma-Fe2O3 lattice to fill its vacancy. The effect of temperature on the adsorption of Co2+ was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1).     

Thermoluminescence study of persistent luminescence materials: Eu2+- and R3+-doped calcium aluminates, CaAl2O4:Eu2+,R3+

Thermoluminescence properties of the Eu2+-, R3+-doped calcium aluminate materials, CaAl2O4:Eu2+,R3+, were studied above room temperature. The trap depths were estimated with the aid of the preheating and initial rise methods. The seemingly simple glow curve of CaAl2O4:Eu2+ peaking at ca. 80 degrees C was found to correspond to several traps. The Nd3+ and Tm3+ ions, which enhance most the intensity of the high-temperature TL peaks, form the most suitable traps for intense and long-lasting persistent luminescence, too. The location of the 4f and 5d ground levels of the R3+ and R2+ ions were deduced in relation to the band structure of CaAl2O4. No clear correlation was found between the trap depths and the R3+ or R2+ level locations. The traps may thus involve more complex mechanisms than the simple charge transfer to (or from) the R3+ ions. A new persistent luminescence mechanism presented is based on the photoionization of the electrons from Eu2+ to the conduction band followed by the electron trapping to an oxygen vacancy, which is aggregated with a calcium vacancy and a R3+ ion. The migration of the electron from one trap to another and also to the aggregated R3+ ion forming R2+ (or R3+-e-) is then occurring. The reverse process of a release of the electron from traps to Eu2+ will produce the persistent luminescence. The ability of the R3+ ions to trap electrons is probably based on the different reduction potentials and size of the R3+ ions. Hole trapping to a calcium vacancy and/or the R3+ ion may also occur. The mechanism presented can also explain why Na+, Sm3+, and Yb3+ suppress the persistent luminescence.     

配合物EuxM1-x(TTA)3(H2O)2(M=La,Gd)光致发光特性

合成了一系列组成为EuxM1－x(TTA)3(H2O)2(M=La,Gd)的固体配合物,利用红外光谱和荧光光谱研究了配合物结构和发光性质随Eu3＋浓度的变化规律.红外光谱的结果表明,配合物的成份为Eu(TTA)3(H2O)2和M(TTA)3(H2O)2,没有新化合物生成.而荧光光谱的结果显示配合物的发光强度与Eu3＋浓度不成线性关系,其中不发光的M(TTA)3组分对发光有增益作用.对其可能的发光机制进行了探讨.     

Effect of thermal annealing on the kinetics of rehydroxylation of Eu3+:La2O3 nanocrystals

Europium-doped lanthanum oxide (5 mol % Eu(3+):La(2)O(3)) was prepared by calcining europium-doped lanthanum hydroxide (5 mol % Eu(3+):La(OH)(3)) previously synthesized by a simple hydrothermal method. Interestingly, we observed different emission Eu(3+) signatures depending on the phase of the host (lanthanum oxide or hydroxide) by cathodoluminescence. Taking into account that lanthanum oxide easily rehydroxylates in air, for the first time, we report the use of cathodoluminiscence as a novel characterization technique to follow the lanthanum oxide rehydroxylation reaction versus time according to different annealing procedures. Additionally, differential thermal-thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques were used to identify the phases formed from the Eu(3+):La(OH)(3) depending on temperature and to study the evolution of La(2)O(3) to La(OH)(3) versus time. The results showed that the higher the temperature and the longer the annealing time, the higher the resistance to rehydroxylation of the Eu(3+):La(2)O(3) sample.     

Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系光谱性质的研究

根据稀土离子能级的特点,对Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系的光谱性质进行了探讨,发现它们有二类发光性质:Stokes发光和反Stokes发光,研究了发光强度和发射波长与掺杂离子的依赖关系,观察到由能量的共振转移引起的荧光浓度猝灭现象,并取得了最大发光强度时的掺杂离子浓度和一些规律性结果.     

纳米(Y0.95Eu0.05)2O3及其SiO2气凝胶介孔组装体的制备与光致发光

采用尿素溶胶法合成(Y0.95Eu0.05)2O3纳米粉,用超临界干燥技术制备了n-(Y0.95Eu0.05)2O3/SiO2气凝胶介孔组装体。结果表明,当Y3+∶　Eu3+=20∶　1,均相反应时间为4 h,且经680℃、 4 h灼烧热处理后得到的n-(Y0.95Eu0.05)2O3中, 光致发光强度最大（发光峰位于612 nm),以Si与 2Y摩尔比为1∶　7的n-(Y0.95Eu0.05)2O3/SiO2气凝胶介孔组装体,经同样条件热处理后,光致发光强度达不到n-(Y0.95Eu0.05)2O3的红光发射强度,而且峰位出现红移（发光峰在616 nm）。对产生上述发光强度减弱和峰位红移现象进行讨论。     

Judd-Ofelt intensity parameters and spectral properties of Gd2O3:Eu3+ nanocrystals

Three nonequivalent centers of Cs (A, B, and C) in monoclinic phase and C2 and S6 centers in cubic phase were identified in the Gd2O3:Eu3+ nanocrystals with spectral techniques. Size dependence in the spectra indicated that the excitations from both host and charge-transfer band (CTB) for the 5D0 --> 7F2 transition of Eu3+ ions were nearly equal for a larger size of 135 nm of the cubic phase; however, with decreasing the size to or less than 23 nm, the excitations by the CTB dominated. The variation of excitation leading to the symmetry and energy change in the C2 and S6 sites was also observed for larger particle sizes. The Judd-Ofelt intensity parameters Omega(lambda) (lambda = 2, 4) for Gd2O3:Eu3+ nanoparticles were experimentally determined. The parameters Omega(lambda) were found to significantly change with the sizes of Gd2O3:Eu3+ from nanoparticles to bulk material. With decreasing the size from 135 to 15 nm, the quantum efficiencies for 5D0 reduced from 23.6% to 4.6% due to the increasing ratio of surface to volume.     

Monodisperse MFe2O4 (M = Fe, Co, Mn) nanoparticles

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)(3), with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe(3)O(4)) nanoparticles. Similarly, reaction of Fe(acac)(3) and Co(acac)(2) or Mn(acac)(2) with the same diol results in monodisperse CoFe(2)O(4) or MnFe(2)O(4) nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe(3)O(4) can be oxidized to Fe(2)O(3), as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.     

Elastomeric nanoparticle composites covalently bound to Al2O3/GaAs surfaces

This article reports the modification of Al2O3/GaAs surfaces with multifunctional soft materials. Siloxane elastomers were covalently bound to dopamine-modified Al2O3/GaAs semiconductor surfaces using MPt (M = Fe, Ni) nanoparticles. The sizes of the monodisperse FePt and NiPt nanoparticles were less than 5 nm. The surfaces of the nanoparticles as well as the Al2O3/GaAs substrates were modified with allyl-functionalized dopamine that utilized a dihydroxy group as a strong ligand. The immobilization of the elastomers was performed via a hydrosilation reaction of the allyl-functionalized dopamines with the siloxane backbones. X-ray photoelectron spectroscopy (XPS) experiments confirmed the covalent bonding of the siloxane elastomers to the oxide layer on the semiconductor surface. Fourier transform-infrared reflection absorption spectroscopy (FT-IRRAS) measurements revealed that the allyl functional groups are bonded to the siloxane backbones. The FT-IRRAS data also showed that the density of the allyl groups on the surface was lower than that of the siloxane backbones. The mechanical properties of the surface-bound nanocomposites were tested using nanoindentation experiments. The nanoindentation data showed that the soft matrix composed of the elastomeric coating on the surfaces behaves differently from the inner, hard Al2O3/GaAs substrate.     

Luminescent lanthanide selenites and tellurites decorated by MoO4 tetrahedra or MoO6 octahedra: Nd2MoSe2O10, Gd2MoSe3O12, La2MoTe3O12, and Nd2MoTe3O12

Solid state reactions of lanthanide oxide, MoO3 and SeO2 (or TeO2) at high temperature in an evacuated quartz tube lead to four new Ln-Mo-Se(Te)-O quaternary phases with four different types of structures, namely, Nd2MoSe2O10, Gd2MoSe3O12, La2MoTe3O12, and Nd2MoTe3O12. The structure of Nd2MoSe2O10 features a 3D architecture built by the intergrowth of the Nd-Se-O layers with the Nd-Mo-O layers. The structure of Gd2MoSe3O12 contains a 3D network of gadolinium selenite with the MoO6 octahedra occupying the cavities of the structure. The structure of La2MoTe3O12 features a 3D network of La2(Te3O8)2+ with the tunnels along the a axis occupied by the MoO4 tetrahedra. Nd2MoTe3O12 features a 2D layer built by the lanthanide ions interconnected by tellurite groups and ditellurite groups, with the MoO4 tetrahedra as the interlayer pendant groups. Room temperature and low temperature luminescent studies indicate that Nd2MoSe2O10 and Nd2MoTe3O12 exhibit strong luminescence in the near-IR region.     

纳米Eu2O3和Eu3+对人肝细胞HL-7702生长的影响

稀土化合物的生物效应研究已引起人们的大量关注,但纳米稀土氧化物对细胞产生的生物效应报道较少.为了研究纳米稀土氧化物和稀土离子对正常细胞作用后的影响差异,采用MTT比色实验,形态观察和流式细胞术等方法探讨了纳米Eu2O3和Eu3+对体外培养的人肝细胞HL-7702生长的影响.结果发现,较低浓度的纳米Eu2O3对细胞生长没有明显影响,较高浓度(≥800μg·ml-1)的纳米Eu2O3作用肝细胞后,具有明显的毒性作用,出现了凋亡特征;而Eu3+在较低含量,即≤100 μmol·L-1时诱导肝细胞S期细胞比率上升,对肝细胞增殖有较弱的促进作用.     

Strong red emission of pure Y2O3 nanoparticles from oxygen related defects

Y(2)O(3) nanoparticles with strong red luminescence (quantum yield about 25%) was synthesized via simple hydroxylation of yttrium nitrate using hexamethylenetetramine as an additive; the red luminescence is emitted from oxygen-related defects of pure Y(2)O(3) nanoparticles, and is tunable by altering the additive.     

Y_2O_3∶Eu~(3+)薄膜的制备及发光性能的研究

以稀土氧化物为原料,用溶胶-凝胶法制备前驱液,加入适量的聚乙烯醇做成膜物质,用浸渍拉提法在石英玻璃表面上得到均匀的薄膜,然后经过适当的干燥和热处理得到Y2O3∶Eu3+发光薄膜.讨论了Eu3+的掺杂浓度和热处理温度对薄膜发光性能的影响.试验表明:Eu3+的最佳掺杂浓度为8%(摩尔分数),薄膜的发光性能随热处理温度提高而增强,当热处理温度达到700℃后,薄膜的发光性能基本上稳定.同时用原子力显微镜和X射线衍射分析了薄膜的表面形貌和结构.     

Large-scale synthesis of single-crystalline RE2O3 (RE=Y, Dy, Ho, Er) nanobelts by a solid-liquid-phase chemical route

Yttrium-group heavy rare-earth sesquioxide (RE(2)O(3), RE=Y, Dy, Ho, Er) nanobelts were successfully fabricated by thermolysis of solid RE(NO(3))(3)x H(2)O in a dodecylamine/1-octadecene mixed solvent system. The synthetic principle is based on separating the nucleation and growth processes by utilizing the poor solubility of RE(NO(3))(3)chi H(2)O in the solvent mixture and the heat-transportation difference between the liquid and solid. By using dodecylamine, RE(2)O(3) nanobelts can be readily obtained. X-ray diffraction (XRD) analysis shows that the synthesized RE(2)O(3) nanobelts are body-centered cubic and crystalline. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selective-area electron diffraction (SAED), and high-resolution transmission electron microscopy (HR-TEM) demonstrate that the synthesized RE(2)O(3) compounds possess regular geometric structure (beltlike) with perfect crystallinity. Preliminary experimental results prove that the dodecylamine plays a key role in the formation of RE(2)O(3) nanobelts and cannot be replaced by other surfactants. Furthermore, this method can be extended to the synthesis of RE(2)O(3) nanobelt/metal nanocrystal nanocomposites and ABO(3) (A=Y, Dy, Ho, Er; B=Al) and A(3)B(5)O(12) (A=Y, Dy, Ho, Er; B=Al)-type ternary oxide nanobelts, using mixed-metal nitrate salts in the correct stoichiometry instead of single rare-earth nitrates.     

Photoluminescence properties and analysis of spectral structure of Eu3+-doped SrY2O4

The aim of this work is to report on the luminescence properties of SrY2O4 activated by Eu3+ ion. Powder samples were prepared by solid-state reaction. X-ray diffraction powder data, photoluminescence, and high-resolution spectroscopy were carried out. Results revealed that the Eu3+ ions occupied three nonequivalent sites, with one at the Sr site, one at the Y(1) site, and another at the Y(2) site. Their spectra wavelengths for the 7F0-5D0 transition are located at 578.49, 581.86, and 580.63 nm, respectively. The corresponding charge-transfer transitions are located at 248, 257, and 270 nm, respectively, which are also confirmed by theoretical analysis.     

Fabrication and photoluminescence of chemically stable La2O3:Eu3+-La2Sn2O7 core-shell-structured nanoparticles

Core-shell-structured La2O3:Eu3+-La2Sn2O7 nanoparticles were fabricated through SnO2-coating of LaOF:Eu3+ in an aqueous solution and subsequent heat treatments at a higher temperature. The nanoparticles exhibited high chemical stability under an ambient atmosphere and intense red photoluminescence upon irradiation with ultraviolet light.