A luminescent and mesoporous core-shell structured Gd2O3 : Eu(3+)@nSiO2@mSiO2 nanocomposite as a drug carrier

In this paper, Gd(2)O(3) : Eu(3+) nanospheres have been encapsulated with nonporous silica and further layer of ordered mesoporous silica through a simple sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N(2) adsorption/desorption, photoluminescence (PL) spectra, and kinetic decay were used to characterize the sample. The results indicate that the nanocomposite with general 50 nm shell thickness and 270 nm core size shows typical ordered mesoporous characteristics (2.4 nm) and has spherical morphology with a smooth surface and narrow size distribution. Additionally, the obtained inorganic nanocomposite shows the characteristic emission of Eu(3+) ((5)D(0)→(7)F(1-4)) even after the loading of drug molecules. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. Most importantly, the nanocomposite can be used as an effective drug delivery carrier. A typical anticancer drug, doxorubicin hydrochloride (DOX), was used for drug loading, and the DOX release, cytotoxicity, uptake behavior and therapeutic effects were examined. It was found that DOX is shuttled into the cell by the nanocomposite and released inside cells after endocytosis and that the DOX-loaded nanocomposite exhibited greater cytotoxicity than free DOX. These results indicate that core-shell structured Gd(2)O(3) : Eu(3+)@nSiO(2)@mSiO(2) nanocomposite has potential for drug loading and delivery into cancer cells to induce cell death.     

聚苯乙烯包覆Y_2O_3:Eu~(3 )颗粒及表征

采用柠檬酸表面修饰 Y2 O3:Eu3 颗粒 ,苯乙烯乳液聚合的方法 ,制备出核 -壳型的 Y2 O3:Eu3 /聚苯乙烯颗粒 .在 FTIR谱图上 ,羰基伸缩振动峰向低波数位移 ;在 XPS谱图上 ,Y3d5 / 2 的电子结合能向高能方向移动 ,表明柠檬酸和颗粒表面发生键合作用 .说明此过程符合吸附层媒介作用机理 :柠檬酸使颗粒表面变成两亲性 ,从而使苯乙烯可吸附在颗粒表面形成包覆无机核的乳液结构 .EDS谱图表明聚苯乙烯均匀地包覆在颗粒表面     

Preparation of Gd(2)O(3) : Eu(3+) and Gd(2)O(2)S : Eu(3+) phosphor fine particles using an emulsion liquid membrane system

Size- (submicrometer-sized) and morphology- (spherical) controlled composite Gd-Eu oxalate particles were prepared in an emulsion liquid membrane (water-in-oil-in-water emulsion) system. The oxalate particles thus prepared were calcined in air to obtain Gd(2)O(3) : Eu(3+) phosphor particles and in sulfur atmosphere to obtain Gd(2)O(2)S : Eu(3+) phosphor particles. These submicrometer-sized spherical phosphor particles showed photoluminescence properties with emission peak at 614 nm for Gd(2)O(3) : Eu(3+) and 628 nm for Gd(2)O(2)S : Eu(3+).     

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 and surface effect analysis of trivalent europium-doped nanocrystalline La2O2S

La2O2S:Eu3+ nanocrystals (NCs) with a mean size of 18 nm are prepared by gel thermolysis. The morphology of the particles is hexagonal. The surface Eu3+ ions are first detected by time-resolved spectra in the 5D0 --> 7F1 region. Because the symmetry of the sites occupied by surface Eu3+ ions is lower, the 5D0 --> 7F1(E) line, which is doubly degenerate in the bulk crystal, is split, and the fluorescence lifetime becomes shorter. The results of the laser-selective excitation indicate that the degradation of the site symmetry of Eu3+ seems to be abrupt, which means the as-synthesized La2O2S:Eu3+ NCs might be of the La2O2S/La2O(2-x)S(1+x)core-shell structure and the shell are not in a disordered state but a rather pure one.     

The effect of the size of raw Gd(OH)3 precipitation on the crystal structure and PL properties of Gd2O3:Eu

Our experiments show that cetyltrimethylammonium bromide (CTAB) has an obvious effect on the particle size of the precipitation of Gd(OH)3. Without CTAB, the particle size of the Gd(OH)3 precipitation is about 50 nm, whereas with CTAB, the particle size is less than 5 nm. We propose a mechanism where CTAB micelles work as a catalyst for the nucleation process and result in the precipitation of 5 nm particles. These small particles, after heat treatment at 1073 K, did not result in small Gd2O3 nanoparticles of the same size, but instead, forming crystals of 30-80 nm size in both cubic and monoclinic phases. When monitoring the photoluminescence (PL) peak at 610 nm, we found that the charge transfer state (CTS) absorption amplitude of Eu-O is reduced in the mixed structures. We speculate that the mixed structures modify the surface properties of the Gd2O3:Eu nanoparticles, leading to the reduction of Eu-O CTS absorption.     

Adsorption of dye from wastewater using chitosan-CTAB modified bentonites

Multifunctional magnetic-fluorescent nanohybrids were successfully fabricated by a facile layer-by-layer (LBL) self-assembly of in situ generated Eu, Gd co-doped LaF(3) nanocrystals (LaF(3):Eu:Gd) on the surface of multi-walled carbon nanotubes (MWNTs). Photoluminescence (PL) quenching occurred when LaF(3):Eu:Gd nanoparticles were directly coated on the surface of MWNTs. By growth of a SiO(2) shell spacer between MWNTs and LaF(3):Eu:Gd nanocrystals, we circumvented the PL quenching and achieved the magnetic-fluorescent MWNTs. Moreover, the nanohybrids showed powerful T(1) and T(2)-weighted magnetic resonance imaging (MRI) signal in water and could be used as MRI contrast agents. As a result, the nanohybrids can be expected to act as a promising multimodal MRI/optical imaging probe.     

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.     

立方Gd2O3∶Eu纳米晶及光谱性质

用透射电镜拍摄球形ＣＧｄ２Ｏ３∶Ｅｕ纳米晶,并研究了室温下它的激发和发射光谱。结果表明,９００℃制备的体材料和相应的纳米晶相比,其激发光谱存在明显差异。前者以基质激发带为主导,电荷转移带（ＣＴＢ）很弱,而后者以ＣＴＢ为主。在绝缘体稀土氧化物中,可以忽略纳米效应对Ｅｕ３＋离子的４ｆ４ｆ能级跃迁的激发和发射光谱峰位的影响     

Synthesis of SiO2/Y2O3:Eu core-shell materials and hollow spheres

The SiO₂/Y₂O₃:Eu core-shell materials and hollow spheres were first synthesized by a template-mediated method. X-ray diffraction patterns indicated that the broadened diffraction peaks result from nanocrystals of Y₂O₃:Eu shells and hollow spheres. X-ray photoelectron spectra showed that the Y₂O₃:Eu shells are linked with silica cores by Si-O-Y chemical bond. SEM and TEM observations showed that the size of SiO₂/Y₂O₃:Eu core-shell structure is in the range of 140-180 nm, and the thickness of Y₂O₃:Eu hollow spherical shell is about 20-40 nm. The photoluminescence spectra of SiO₂/Y₂O₃:Eu core-shell materials and Y₂O₃:Eu hollow spheres have better red luminescent properties, and the broadened emission bands came from the size effects of nanocrystals composed of Y₂O₃:Eu shell.     

Highly uniform and monodisperse Gd(2)O(2)S:Ln(3+) (Ln = Eu, Tb) submicrospheres: solvothermal synthesis and luminescence properties

Gd(2)O(2)S:Ln(3+) (Ln = Eu, Tb) submicrospheres were successfully prepared through a facile and mild solvothermal method followed by a subsequent heat treatment. X-ray diffraction (XRD) results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure hexagonal phase of Gd(2)O(2)S. The energy dispersive spectroscopy (EDS), element analysis, and FT-IR results show that the precursors are composed of the Gd, Eu, O, S, C, H, and N elements. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that these spheres are actually composed of randomly aggregated nanoparticles. The formation mechanism for the Gd(2)O(2)S:Ln(3+)(Ln = Eu, Tb) spheres has been proposed on an isotropic growth mechanism. Under ultraviolet excitation, Gd(2)O(2)S:Ln(3+)(Ln = Eu, Tb) spheres show red and green emission corresponding to the (5)D(0)→(7)F(2) transition of the Eu(3+) ions and the (5)D(4)→(7)F(5) transition of the Tb(3+) ions. Furthermore, this synthetic route may have potential applications for fabricating other lanthanide oxysulfides.     

Optical properties of nanocrystalline Y2O3:Eu depending on its odd structure

The structure of nanocrystalline Y2O3:Eu prepared by a combustion reaction was analyzed by XRD and high-resolution electron microscopy. Compared with a large-scale particles, 5-nm Y2O3:Eu particles presented as distorted crystallite and rough surfaces. Luminescent and absorption properties of nano-Y2O3:Eu showed remarkably particle size effects. At Y2O3:Eu particle sizes smaller than 10 nm some new results were observed: (a) a red shift of the charge-transfer-state absorption; (b) new emission bands of Eu3+ in the 5D0 --> 7F2 region; (c) luminescent decay of energy level 5D0 of Eu3+ turning to a two-step exponential; and (d) a pronounced increase in quenching concentration and much lower phonon density compared with those of the bulk material. All these phenomena can be attributed to the effect of the softened lattice and surface state of the nanomaterial. The latter was confirmed by stronger excitation by the host absorption after the surface modification.     

纳米Ag@SiO2核壳结构的表面等离子体共振效应对铕配合物的荧光增强作用

分别制备了二氧化硅壳层厚度为10、25和80 nm的三种Ag@SiO₂纳米粒子, 合成了铕与不同比例苯甲酸根(BA)的配合物、铕与1, 10-邻菲罗啉(phen)及2, 2''-联吡啶(bpy)的配合物, 并对其进行表征. 表征结果推测配合物的组成为Eu(BA)_nCl_3-n·2H₂O (n=1, 2, 3)、Eu(phen)Cl₃·2H₂O和Eu(bpy)Cl₃·2H₂O. 配合物的荧光光谱显示, 在加入Ag@SiO₂纳米粒子后, 复合物的荧光强度有不同程度的增加, 这可能是由于表面等离子体共振造成的. 不同硅壳厚度的Ag@SiO₂纳米粒子的荧光增强顺序是25 nm>80 nm>10 nm, 这表明二氧化硅核壳厚度约25 nm时有较强的表面等离子体共振效应. 此外, 在这些复合物中, Eu(phen)Cl₃·2H₂O复合物的增强效果是最强的, 而Eu(BA)_nCl_3-n·2H₂O的增强效果是最弱的. 在三个苯甲酸铕配合物中, Eu(BA)₃·2H₂O的增强效果最弱, 其他两个苯甲酸铕复合物增强效果相对较好. 原因可能是含氮配合物(Eu(phen)Cl₃·2H₂O和Eu(bpy)Cl₃·2H₂O)可以和Ag@SiO₂更好地成键, 而苯甲酸铕配合物和Ag@SiO₂纳米粒子的作用相对较弱. Ag@SiO₂纳米粒子有望应用于增强稀土材料的发光.     

Ag@SiO2@Y2O3:RE3+（RE=Eu,Tb）核壳结构发光材料的制备与性能

采用均相沉淀法制备了Ag@SiO2@(Y,RE)(OH)CO3.H2O(RE=Eu,Tb)核壳结构微球,经过700℃焙烧后成功制备出Ag@SiO2@Y2O3:RE3+(RE=Eu,Tb)核壳结构发光材料。XRD谱图表明Ag核具有结晶良好的面心立方结构;SiO2层为无定型;Y2O3层为立方晶系。FTIR谱图表明核壳之间以化学键相结合。TEM照片表明合成了核壳结构的表面光滑的复合微球,分散良好,大小均匀,Ag核的粒径分布为50±20 nm;SiO2层的厚度为20～30 nm;Y2O3:RE3+(RE=Eu,Tb)层厚度约为125 nm。电子衍射图像表明Ag@SiO2@Y2O3:RE3+(RE=Eu,Tb)为多晶结构。UV-Vis光谱表明表面包覆使Ag离子的等离子体共振吸收峰发生了红移。荧光光谱表明Ag@SiO2@Y2O3:Eu3+具有Eu3+的特征红光发射,Ag@SiO2@Y2O3:Tb3+具有Tb3+的特征绿光发射,但是发光强度均比纯的Y2O3:RE3+有所减弱,说明贵金属的引入对稀土Y2O3:RE3+(RE=Eu,Tb)的发光起到了荧光猝灭的作用。     

Fabrication and characterization of mesoporous Co3O4 core/mesoporous silica shell nanocomposites

A mesoporous Co(3)O(4) core/mesoporous silica shell composite with a variable shell thickness of 10-35 nm was fabricated by depositing silica on Co(3)O(4) superlatticed particles. The Brunauer-Emmett-Teller (BET) surface area of the composite with a shell thickness of ca. 2.0 nm was 238.6 m(2)/g, which varied with the shell thickness, and the most frequent pore size of the shell was ca. 2.0 nm. After the shell was eroded with hydrofluoric acid, mesoporous Co(3)O(4) particles with a pore size of ca. 8.7 nm could be obtained, whose BET surface area was 86.4 m(2)/g. It is proposed that in the formation of the composite the electropositive cetyltrimethylammonium bromide (CTAB) micelles were first adsorbed on the electronegative Co(3)O(4) particle surface, which directed the formation of the mesoporous silica on the Co(3)O(4) particle surface. Electrochemical measurements showed that the core/shell composites exhibited a higher discharge capacity compared with that of the bare Co(3)O(4) particles.     

A Model for Simultaneous Homogeneous and Heterogeneous Nucleation in the Case of Slow Reaction Rate

(Gd(x)Y(1-x))(2)O(3):Eu [x=0, 0.25, 0.5, 0.75, 1.0] phosphor particles with 6 at.% Eu dopant of total concentration were prepared using spray pyrolysis. The effects of composition on the morphology, crystallinity, and photoluminescence characteristics of composite particles were investigated. The morphological control of (Gd(x)Y(1-x))(2)O(3):Eu particles in spray pyrolysis was also attempted by using colloidal and aqueous solutions. The particles prepared from colloidal solutions containing small amounts of Gd or Y hydroxy carbonate sol as seed material had spherical and filled morphology after the post-treatment at high temperature. On the other hand, the (Gd(x)Y(1-x))(2)O(3):Eu particles prepared from aqueous solutions were hollow and porous after post-treatment in all compositions. Particles prepared from colloidal solutions had photoluminescence emission intensities higher than those of particles prepared from aqueous solutions. Copyright 2000 Academic Press.     

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.     

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。     

Photoluminescence of perovskite nanosheets prepared by exfoliation of layered oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion)

Luminescent perovskite nanosheets were prepared by exfoliation of single- or double-layered perovskite oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion). The thickness of the individual nanosheets corresponded to those of the perovskite block in the parent layered compounds. Intense red and green emissions were observed in aqueous solutions with Gd1.4Eu0.6Ti3O10- and La0.7Tb0.3Ta2O7-nanosheets, respectively, under UV illumination with energies greater than the corresponding host oxide band gap. The coincidence of the excitation spectrum and the band gap absorbance indicates that the visible emission results from energy transfer within the nanosheet. The red emission intensity of the Gd1.4Eu0.6Ti3O10-nanosheets was much stronger than that of the La0.90Eu0.05Nb2O7-nanosheets reported previously. The strong emission intensity is a result of a two-step energy transfer cascade within the nanosheet from the Ti-O network to Gd(3+) and then to Eu(3+). The emission intensities of the Gd1.4Eu0.6Ti3O10- and La0.7Tb0.3Ta2O7-nanosheets can be modulated by applying a magnetic field (1.3-1.4 T), which brings about a change in orientation of the nanosheets in solution. The emission intensities increased when the excitation light and the magnetic field directions were perpendicular to each other, and they decreased when the excitation and magnetic field were collinear and mutually perpendicular to the direction of detection of the emitted light.     

水热法制备具有光滑表面的球形Y2O3∶Eu3+发光材料

The spherical Y₂O₃∶Eu³⁺ luminescent particles with size of 0.5～3 μm and smooth surface were synthesized by hydrothermal method. The resulted Y₂O₃∶Eu³⁺ precursors and the calcined particles were characterized by differential thermal analysis (DTA) and thermogravimetric (TG) analysis, X-ray diffraction (XRD), Fourier-transform IR spectroscopy (FTIR), scanning electron microscopy (SEM) and photoluminescence spectra (PL). FTIR, TG-DTA, XRD measurements show that the precursors are crystal with hydroxyl and carbonate group, and the pure cubic yttria is obtained after annealing above 700 ℃. The SEM images indicate that the Y₂O₃∶Eu³⁺ particles are in spherical shape and with smooth surface. PL analysis shows that the particles present characteristic red emission of Eu³⁺.