Shape controlled synthesis and photoluminescence properties of Eu3+-doped REVO4 nanophosphors

Eu3+-doped REVO4 nanphosphors were controllably synthesized by an EDTA-mediated hydrothermal method at 180 degrees C using RE(NO3)3 and Na3VO4 as precursors. The obtained products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectra (XPS), and photoluminescence spectroscopy (PL). The XRD results showed that the products were pure tetragonal structure and no other impurity phase appeared. The PL studies demonstrated Eu3+ ions doping effectively enhanced luminescent properties of LaxRE(1-x)VO4 and YxRE(1-x)VO4 nanoparticles, but EU3+ ions doping did not enhance luminescent properties of CexRE(1-x)VO4 (x not equal 0) nanoparticles. The prepared phosphors showed well-defined red luminescence due to radiative transitions from 5D0 to 7F(J) (J = 1,2) levels of Eu3+ ions, respectively. Furthermore, we reported Eu3+-doped CexRE(1-x)VO4 (x not equal 0) phases represented a new class of optically inactive materials.     

Fabrication and up-conversion luminescence of Er3+:Y2O3 nanoparticles

Y2O3 nanoparticles doped with different concentrations of Er3+ were prepared by the co-precipitation method. X-ray diffraction and transmission electron microscopy results show that Er3+ dissolves completely in the Y2O3 cubic phase. The Er3+:Y2O3 nanoparticles are homogeneous in size and nearly spherical, and the average diameter of the particles after being calcined at 1,000 degrees C for 2 h is in the range of 40-60 nm. When Er3+:Y2O3 nanoparticles are excited under a 980 nm diode laser, there are two main emission bands: green emission centered at 562 nm corresponding to the 4S3/2/2H11/2 --> 4115/2 radiative transitions and red emission centered at 660 nm corresponding to the 4F9/2 --> 4I15/2 radiative transitions. By changing the doping concentration of Er3+ ions, the up-conversion luminescence can be gradually tuned from green to red.     

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles

Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu³⁺ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca²⁺ with Fe³⁺ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu³⁺ and Fe³⁺ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu³⁺ and Fe³⁺ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu³⁺ and Fe³⁺, and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.     

Characterization and luminescence of Eu3+ ions doped 12CaO 7Al2O3 nanopowders

Eu3+ ions doped 12CaO 7Al2O3 (C12A7) powders with different Eu3+ concentrations were prepared by sol-gel combined with solid state reaction method. The results of XRD and Raman spectra showed that single cubic phase polycrystalline C12A7:Eu3+ powders were prepared. The absorption peaks attributed to f-f transition of Eu3+ ion can be observed, indicating that Eu3+ had been incorporated into C12A7 lattice site. Visible PL peaks around 578, 588, 614 nm were ascribed to 5D0 --> 7FJ (J = 0, 1, 2) transitions of Eu3+ under the excitation of 488 nm line. The PL of C12A7:Eu3+ showed the strongest emission intensity at Eu3+ concentration of 0.5 at%. Two different types of Eu3+ centers were identified by the two lines from 5D0 --> 7F0 transition emission. The doping mechanism of C12A7:Eu3+ might be attributed to Eu3+ ions substitution for two types of Ca2+ lattice sites in C12A7. The temperature dependent PL spectra of Eu-doped C12A7 were measured in the range from 100 to 300 K under the excitation of 488 nm laser line. The PL intensities as a function of temperature were well fitted by using a unified theoretical model, considering thermal activation and nonradiative energy transfer processes.     

Luminescent properties of rare earth ions in one-dimensional oxide nanowires

Rare-earth doped one-dimensional oxide nanowires including LaPO4, La2O3, and Gd2O3 were synthesized by the hydrothermal method. Their luminescent properties including local environments, electronic transitions, energy transfer, and frequency up-conversion luminescence processes were systematically studied. In LaPO4:Eu and La2O3:Eu nanowires, different symmetry sites of Eu3+ ions were identified, which obviously differed from those of the corresponding micrometer-sized particles. This was attributed to crystal field degeneration in the fringe along the length axis. In LaPO4:Eu nanowires, the electronic transition rate of 5D1-sigmaJ7FJ increased approximately 2 times over that of the zero-dimensional nanoparticles and micrometer-sized particles, which was related to the variation of dipole field induced by shape anisotropy. Considering the nonradiative relaxations, meanwhile, the luminescent quantum efficiency for 5D1-sigmaJ7FJ transitions of Eu3+ in nanowires increased 100% over that in nanoparticles and 20% over that in micrometer particles. In Gd2O3:Eu3+, LaPO4:Ce3+, and LaPO4:Tb3+ nanowires and micrometer-sized particles, the electronic transition rate of rare earths had only a little variation. In LaPO4:Ce3+/Tb3+ nanowires, the energy transfer rate of Ce3+--> Tb3+ decreased 3 times compared to that in micrometer rods. Despite this, the brightness for the 5D4-7F5 green emissions of Tb3+ increased several times due to decreased energy transfer from the excited states higher than 5D4 to some defect levels. In Gd2O3:Er3+/Yb3+ nanocrystals, as the shape varied from nanopapers to nanowires, the relative intensity of up-conversion luminescence of 2H(11/2)/4S(3/2)-4I(15/2) and 4F(9/2)-4I(15/2) to the infrared down-conversion luminescence of 4I(13/2)-4I(15/2) increased remarkably, indicating efficient up-conversion luminescence. Our present results indicate that rare-earth-doped oxide nanowires is a type of new and efficient phosphors.     

双微乳液法制备掺杂Fe~(3+)的纳米TiO_2及其光催化性能

为了研究双微乳液法在制备纳米级光催化剂的应用,以TiCl4和NH3.H2O为原料,采用十六烷基三甲基溴化铵-正丁醇-环己烷-水微乳体系制备Fe3+掺杂纳米TiO2,对粉末的晶体结构进行X射线衍射表征,并以其对p-甲酚的降解考察其光催化活性。结果表明,在较小的掺杂量时,Fe3+掺杂量的提高可以提高TiO2的光催化活性,进一步提高掺杂量将引起光催化活性的降低;掺杂Fe3+可导致纳米TiO2的粒径减小;Fe3+的半径较小以及Fe2O3的熔点较低均有利于TiO2从锐钛矿向金红石的相变;当Fe3+掺杂摩尔分数为0.06%,煅烧温度为550℃时,纳米TiO2的光催化活性最高,此时形成TiO2的锐钛矿和金红石相的混晶;乳液中含水量也会影响晶相的组成和粒径大小,随着含水量增加产物中出现了一定比例的金红石相。     

Fabrication of photoluminescent S doped Y2O3:Eu3+ nanobelts

We have successfully fabricated the S doped Y(OH)3 nanobelts with 15-30 microm in length and 50-300 nm in width and S doped Y(OH)3:Eu3+ nanobelts with 4-15 microm in length and 80-500 nm in width (most between 100 and 200 nm) via a similar process for preparation of Y(OH)3 nanotubes. Photoluminescent (PL) nanobelts of S doped Y2O3:Eu3+ were obtained through dehydration of the S doped Y(OH)3:Eu3+ nanobelts at 450 degrees C in N2. The PL properties of the S doped Y2O3:Eu3+ nanobelts have been studied and evidenced that we have successfully synthesized functional S doped Y2O3:Eu3+ nanobelts with interesting photoluminescence properties.     

Aerosol-assisted synthesis of thiol-functionalized mesoporous silica spheres with Fe3O4 nanoparticles

Thiol-functionalized mesoporous silica spheres having Fe3O4 nanoparticles are fabricated in one-pot by aerosol-assisted synthesis. A TEM image shows that Fe3O4 nanoparticles are successfully embedded within the mesoporous silica spheres. SEM images and SAXS profiles reveals that the encapsulating Fe3O4 nanoparticles do not affect the ordering of a mesoporous structure. The spherical morphologies are also well retained. The presence of cage-type mesopores with uniform size is confirmed by N2 adsorption-desorption isotherms and TEM observations. The spray-dried thiol-functionalized particles with Fe3O4 nanoparticles effectively adsorb mercury (II) ions due to their strong interaction to thiol groups embedded in the framework. The particles with the amount of Fe3O4 nanoparticles (3.5 wt%) show a saturated magnetization (over 1.0 emu/g). This magnetic property is useful for practical collection with magnet.     

静电纺丝法制备PAN/Fe3O4磁性纳米纤维

采用化学共沉淀法制备纳米四氧化三铁,选用曲拉通X-100为分散剂,利用静电纺丝法制备PAN/Fe3O4磁性纳米复合材料。X射线衍射仪(XRD)验证了四氧化三铁在复合纳米纤维中的存在。同时使用扫描电镜(SEM)和透射电镜(TEM)对复合纳米纤维的微观形貌和Fe3O4在纤维中的分布进行了观察,利用热重(TGA)对纳米复合材料的热稳定性进行分析;通过磁性实验分析了纳米复合材料的磁性性能。结果表明,所制备PAN/Fe3O4磁性纳米纤维成型良好,且Fe3O4磁性颗粒在纤维中分散均匀,其与PAN是物理复合。纳米复合材料具有一定磁性,并可由磁性颗粒的加入量进行控制。     

Synthesis and luminescence properties of lanthanide (III)-doped YF3 nanoparticles

Synthesis process and luminescence properties of trivalent lanthanide ions (Ln3+) doped YF3 nanoparticles have been investigated. To synthesis Ln(3+)-doped YF3 nanoparticles, the mixture of (YCl3 x nH2O + LnCl3 x nH2O), and NH4F was hydrothermal treated at 180 degrees C in a Teflon-liner auto-clave or heated at higher temperatures (400 degrees C - 600 degrees C) in a stove. The XRD patterns showed that the Ln(3+)-doped orthorhombic YF3 nanoparticles with no second phase have been prepared. The solid solution Y(1-x)Eu(x)F3 (x = 0 - 0.4) nanoparticles have been synthesized. The luminescence concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurred at higher Eu3+ concentrations (30 mol%). The upconversion luminescence of Er(3+)-Yb3+ codoped YF3 nanoparticles under 980 nm excitation has also been observed. With increase of heated temperature, the size of the Er(3+)-Yb3+ codoped YF3 nanoparticles increased gradually, and upconversion luminescence intensity increased significantly.     

Fe3O4磁性纳米颗粒的合成及其调控

利用水解共沉淀法制备了Fe3O4纳米颗粒,研究了温度和pH值对Fe3O4纳米颗粒粒径、形貌的影响关系。研究结果表明,反应温度从30℃升高到90℃,Fe3O4颗粒的粒径从6～8nm增大到10～12nm;同时,Fe3O4颗粒的饱和磁矩也随着Fe3O4颗粒粒径的增加而升高。溶液pH值会影响Fe3O4纳米颗粒的形状,高pH值易使合成的Fe3O4纳米颗粒为四方形,随着pH值的降低,Fe3O4纳米颗粒向球形转变。Fe3O4纳米颗粒的粒径和形状的可控性为进一步合成、调控Fe3O4电磁功能复合材料奠定了良好基础。     

High pressure responsive luminescence of flexible Eu~(3+) doped PVDF fibrous mats

Exploring lanthanide doped materials and their high-pressure optical properties is important from the perspective of designing pressure sensors, piezoelectric materials, scintillators, and optoelectronic devices, just to mention a few. Understanding the high-pressure optical properties of polymeric fibrous mats provides significant advantages in terms of flexibility, tunability, facile processability, and malleability. In this work, we have developed flexible polyvinylidene difluoride(PVDF) fibrous mats doped with an Eu³⁺ source of Eu(NO₃)₃·5H₂O(EN-PF) or Eu₂(SO₄)₃(ES-PF) by a Forcespinning■ method. Microstructural analysis of these two systems indicates that Eu(NO₃)₃·5H₂O and Eu₂(SO₄)₃ are homogeneously distributed and dispersed into the PVDF matrix. Fiber formation promotes a β-phase PVDF. Eu³⁺ doping increases the β-phase. Its fraction is larger for the ES-PF mats. To understand their high-pressure optical properties, their photoluminescence spectra have been taken at various pressures up to 58 GPa in a diamond anvil cell. High-pressure luminescence illustrates a clear change in asymmetry ratio, peak intensity, peak breadth, color coordinate, and color temperature of Eu³⁺ ions from both EN-PF and ES-PF with a different extent of changes. Specifically, Eu³⁺ ions in the ES-PF mats switch from asymmetric to symmetric environment as pressure increases. Those in the EN-PF mats present symmetric environment for all tested pressures. Both of the Eu³⁺ doped PVDF systems present irreversible changes. Therefore,the EN-PF fibrous mats present an opportunity to make pressure induced red-orange-yellow tunable phosphors for multifunctional applications.     

锶含量对稀土Eu掺杂锶钙羟基磷灰石发光性能及取代位置的影响

采用化学共沉淀法制备了一系列Sr含量不同的铕掺杂锶钙羟基磷灰石粉体(Ca_10-x-Sr_x-HAp: Eu), 通过X射线衍射(XRD)、荧光光谱以及发光能量传递等研究了锶含量对稀土掺杂锶钙羟基磷灰石结构、荧光性能和取代位置的影响。XRD分析表明, 掺杂Eu对锶钙羟基磷灰石样品的结构无明显影响, 而Sr含量增加会使得样品的结晶程度和晶面间距增大。光谱分析表明, 在394 nm波长激发下, Ca_10-x-Sr_x-HAp: Eu样品在596 nm和618 nm处的荧光强度随着Sr含量的增加先升高再降低, 最强峰值出现在Ca₃-Sr₇-HAp: Eu样品中。同时, 样品的荧光寿命随着Sr含量增加也出现相同的变化。此外, 随着基体中Sr含量的增加, 样品的电偶极跃迁与磁偶极跃迁强度比值(I_R/I_O)先增加后减小, 而Eu荧光衰减过程中不同格点之间的能量传递参数(f)则先减小后增大, 两者的转折点都出现在Ca₃-Sr₇-HAp: Eu样品中。实验表明: Eu在基质晶格中的取代位置受Sr在基质中含量和位置的影响, 通过Sr/Ca比例的调节则可以使得Eu在基质中取代不同位点的比例变化进而获得可调节的荧光性能。     

Structural and Magnetic Analyses of Magnetic Nanoparticles Coated with Oleate Molecules

Physical and chemical properties of the magnetic nanoparticles coated with oleate have been investigated by means of transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Mossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, infrared spectra (IR) and the contact angle device. The results show that doped Al ions in Fe3O4 nanoparticles are located on the octahedral sites of the spinel structure. Oleate is coated on the magnetic nanoparticles with two layers by chemical absorbing, the outer layer can be washed away. The wetting of the surface of magnetic nanoparticles coated with monolayer has been changed from hydrophilicity to hydrophobicity, and the nanoparticles can be dispersed very well in some organic solutions.     

Eu2+、Dy3+、Li+共掺杂CaSi2O2N2荧光粉的发光性能

采用高温固相反应法制备了一系列白光LED用CaSi2O2N2:0.05Eu2+,xDy3+,xLi+(0≤x≤0.03)荧光粉.利用X射线衍射仪对样品的物相结构进行了分析,结果表明:Dy3+和Li+离子的掺入没有改变CaSi2O2N2:Eu2+荧光粉的主晶相.利用荧光光谱仪对样品的发光性能进行了测试,发现所有样品的激发光谱均覆盖了从近紫外到蓝光的较宽范围,400 nm激发下得到的发射光谱为宽波段的单峰,峰值位于545 nm左右,是Eu2+离子5d-4f电子跃迁引起的.Dy3+离子掺杂可以提高CaSi2O2N2:Eu2+荧光粉的发光强度,Dy3+与Li+共掺杂可进一步提高荧光粉的发光强度,当Dy3+和Li+的掺杂量为1mol%时,荧光粉的发光强度达到最大值,是单掺杂Eu2+的荧光粉发光强度的157%.     

Optical spectroscopy of Eu3+ ions in tetragonal ZrO2 nanocrystals

A facile solvothermal method was introduced to incorporate Eu3+ ions into the monodisperse tetragonal ZrO2 nanocrystals (NCs) with small size of approximately 4 nm. The optical properties for Eu3+ doped ZrO2 NCs were investigated in detail by using the photoluminescence (PL) spectroscopy at room and low temperatures. Intense red emissions from Eu3+ ions could be achieved via the host sensitization, which was found to be much more efficient than the direct excitation of lanthanide ions. Moreover, multiple sites of Eu3+ as well as the host-to-Eu3+ energy transfer were also revealed based on the PL analyses.     

Synthesis of size-controlled Fe3O4@SiO2 magnetic nanoparticles for nucleic acid analysis

We present a systematic study on the preparation, characteration and potential application of Fe3O4 and Fe3O4@SiO2 nanoparticles. Fe3O4 nanoparticles of controllable diameters were successfully synthesized by solvothermal system with tuning pH. The magnetic properties of nanoparticles were measured by vibration sample magnetometer. Fe3O4@ SiO2 nanoparticles were obtained via classic St?ber process. Streptavidin coated Fe3O4@SiO2 nanoparticles were prepared by covalent interaction. The quantity of streptavidin bound to nanoparticles was determined by UV-Vis spectrometer. To evaluate the binding efficiency and capacity of nucleic acid on nanoparticles, the capture of biotinylated oligonucleotide on streptavidin coated Fe3O4@SiO2 nanoparticles at different concentration was estimated by fluorescence detection. Both Fe3O4 and Fe3O4@SiO2 nanoparticles exhibited well crystallization and magnetic properties. The maximal amount of streptavidin immobilized onto the Fe3O4@SiO2 nanoparticles was 29.3 microg/mg. The saturation ratio of biotinylated oligonucleotides captured on streptavidin coated Fe3O4@SiO2 nanoparticles was 5 microM/mg within 20 minutes, indicating that FeO4@SiO2 nanoparticles immobilized by streptavidin were excellent carriers in nucleic acid analysis due to their convenient magnetic-separation property. Therefore, the synthesized Fe3O4 and Fe3O4@SiO2 nanoparticles with controllable size and high magnetic saturation have shown great application potentials in nucleic acid research.     

Polyol-mediated synthesis and photoluminescent properties of Ce3+ and/or Tb3+-doped LaPO4 nanoparticles

Rare-earth ion (Ce3+, Tb3+) doped LaPO4 nanoparticles were prepared by the polyol method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, and lifetimes. The results of XRD indicate that the as-prepared nanoparticles are well-crystallized at 160 degrees C and assigned to the monoclinic monazite structure of the LaPO4 phase. The obtained LaPO4:Ce3+, Tb3+ nanoparticles are spherical with narrow size distribution and average size of 20 nm. The doped rare-earth ions show their characteristic emission in LaPO4 nanoparticles, i.e., Ce3+ 5d-4f and Tb3+ 5D4-7FJ (J = 6-3) transitions, respectively. The optimum doping concentration for Tb3+ in La(0.8-x)Ce0.2TbxPO4 nanoparticles is determined to be 15 mol% (x = 0.15). The luminescence decay curves of Ce3+ in LaPO4:Ce3+ and LaPO4:Ce3+, Tb3+ nanoparticles present a single-exponential behavior, and the lifetimes (tau) of Ce3+ decrease with increasing Tb3+ concentrations (at the constant Ce3+ concentration) in LaPO4:Ce3+, Tb3+ nanoparticles due to the energy transfer from Ce3+ to Tb3+. The energy-transfer efficiency from Ce3+ to Tb3+ was calculated, which depends on the doping concentrations of Tb3+ if the concentration of Ce3+ is fixed.     

The Reflection of Cr/Fe Substitution on the Structural,Magnetic and Photoluminescence Features of Zn–Ni Based Ferrite

In this work, we substituted iron by chromium in the nano-spinel ferrite Ni_0.5Zn_0.5Fe₂O₄ (NZF), then we studied how relevant the structure, magnetic, and optical characteristics of the produced samples are changed accordingly. This doping caused a redistribution of Fe, Zn, and Ni ions over tetrahedral and octahedral sites as confirmed from XRD Reitveld analysis. Upon Cr/Fe substitution, a decrease in the lattice parameter occurred accompanied by a decrease in crystallite size of the doped samples. Magnetic measurements indicated the decrease of saturation magnetization by increasing the amount of Cr doping. On the other hand, the coercivity (H _c) increases about six times from Cr content x = 0.0 (28.28 Oe) to x = 1.0 (192.25 Oe). Photoluminescence (PL) measurements at 650 nm excitation showed emission peaks arising from Fe³⁺ transitions, band-to-band transitions, oxygen defect-related emission, and Cr³⁺ transitions that appeared strongly at heavily doped NZF with Cr. The PL intensity quenches strongly with increasing Cr/Fe ratio due to concentration, mobility, and generation of non-radiative center effects. The band gap energy of the Cr-doped NZF system is red shifted until x = 0.5 and the increases (blue shifted) at x = 0.75.     

Ca掺杂EuMnO3体系的磁性和磁卡效应研究

采用传统的高温固相反应法制备了钙钛矿氧化物Eu1-xCaxMnO3(x=0,0.1,0.2,0.3,0.4,0.5)多晶体系样品。通过样品的XRD谱线、磁化强度随温度、外加磁场的变化曲线(M-T、M-H)等数据研究了Ca不同掺杂量对钙钛矿氧化物EuMnO3系列多晶样品的居里温度、磁熵变、磁相变等的影响。结果表明,Eu1-xCaxMnO3(x=0,0.1,0.2,0.3,0.4,0.5)系列陶瓷样品呈现良好的单相性,空间点群为Pnma。低浓度掺杂的样品存在一个TC,高浓度掺杂的样品出现两个磁转变点,且由于双交换相互作用,随着Ca的掺杂,TC逐渐增大,当掺杂量达到0.4时,低温下的TC却明显减小。根据-ΔSM和RCP值可知,Eu0.7Ca0.3MnO3是该组样品中比较适合做磁制冷的材料。通过对Loop曲线的分析可知该组样品经历了由一级相变向二级相变转变的过程。