Cathodoluminescence of rare earth implanted Ga2O3 and GeO2 nanostructures

Rare earth (RE) doped gallium oxide and germanium oxide micro- and nanostructures, mostly nanowires, have been obtained and their morphological and optical properties have been characterized. Undoped oxide micro- and nanostructures were grown by a thermal evaporation method and were subsequently doped with gadolinium or europium ions by ion implantation. No significant changes in the morphologies of the nanostructures were observed after ion implantation and thermal annealing. The luminescence emission properties have been studied with cathodoluminescence (CL) in a scanning electron microscope (SEM). Both β-Ga(2)O(3) and GeO(2) structures implanted with Eu show the characteristic red luminescence peak centered at around 610 nm, due to the (5)D(0)-(7)F(2) Eu(3+) intraionic transition. Sharpening of the luminescence peaks after thermal annealing is observed in Eu implanted β-Ga(2)O(3), which is assigned to the lattice recovery. Gd(3+) as-implanted samples do not show rare earth related luminescence. After annealing, optical activation of Gd(3+) is obtained in both matrices and a sharp ultraviolet peak centered at around 315 nm, associated with the Gd(3+) (6)P(7/2)-(8)S(7/2) intraionic transition, is observed. The influence of the Gd ion implantation and the annealing temperature on the gallium oxide broad intrinsic defect band has been analyzed.     

Fabrication of novel luminor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) with core/shell heteronanostructure

A novel polychromic phosphor with core-shell heteronanostructure has been prepared to improve the chromatic index of phosphors. As for the first example, Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+), its synthetic route, structure and optical properties are presented in this paper. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy-dispersive x-ray spectra (EDS) and photoluminescence (PL) were all employed to characterize the composite core-shell phosphors. The XRD, FE-SEM and HR-TEM results indicate that the SiO(2) and YVO(4):Eu(3+) layers have been successfully coated on Y(2)O(3):Eu(3+) nanoparticles and SiO(2) layer, respectively: these layers were further verified by the EDS. The PL showed that the red-emitting phosphor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) possessed the independent luminescent properties of both the core Y(2)O(3):Eu(3+) and the shell YVO(4):Eu(3+). The emissions were dominated by [Formula: see text] or [Formula: see text] transitions of Eu(3+) when excited with different wavelengths. Since this broad-band response to excitation in the range of 225-340?nm gave more red/dark red emissions found at 612, 616 and 620?nm, the novel phosphor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) could have potential biological labeling applications with wide flexibility.     

Enhanced luminescence of lanthanide complexes by silver nanoparticles for ciprofloxacin determination

We present the enhancement of luminescence of europium complex, Eu(3+)-ciprofloxacin (CIP), in the presence of silver nanoparticles (Ag NPs) for the CIP determination. The increment of the luminescence intensity of the Eu(3+)-CIP complex with Ag NPs was obtained due to the transfer of resonance energy to the fluorophores through the interaction of the excited-state fluorophores and surface plasmon electron in the metal nano surface. The luminescence intensity of Eu3+ was enhanced by complexation with CIP at 614 nm after excitation at 373 nm corresponding to the 5D0-7F2 transitions of Eu3+ ion. Based on the above phenomenon, a sensitive and rapid spectrofluorimetric method has been developed for the CIP determination. Linearity of the calibration curve was obtained in the range of 2.0 x 10(-10)-1.0 x 10(-8) g mL(-1) with correlation coefficient of 0.9992. The limit of detection of CIP was found to be 1.9 x 10(-11) g mL(-1) with the relative standard deviation (RSD) of 1.19% for 5 replicate measurements of 5.0 x 10(-7) g mL(-1) of CIP. The present method has been successfully applied for CIP determination in pharmaceutical and biological samples.     

Photoluminescence and raman studies of Y2O3:Eu(3+) nanotubes under high pressure

In this work, the cubic compound Y2O3:Eu(3+) nanotubes with diameter of 70-90 nm and length of 2-3 microm are synthesized by a hydrothermal method. Photoluminescence and Raman spectra of Y2O3:Eu(3+) nanotubes in a diamond anvil cell under high pressure are measured at room temperature. The 5D0 --> 7F(0,1,2) transitions of the Eu(3+) ions exhibit red shifts to higher wavelength with pressure increasing. Above 13.4 GPa, all the Raman active modes disappear. When the pressure is released from 25.6 GPa to ambient pressure, these Raman peaks are not retrieved; this fact indicates that the nanotubes are transformed into amorphous from cubic phase at about 13.4 GPa. It may be related to the collapse of nanotube form under high pressure condition.     

Investigation of the emission mechanism in milled SrAl₂O₄:Eu, Dy using optical and synchrotron X-ray spectroscopy

There currently exists much debate as to the active state related to the "long afterglow" effect in europium doped oxide materials. Redox couples that consist of Eu(+/2+) and Eu(2+/3+) are discussed, but no common answer is currently accepted. Here, we present a comparison of the optical properties of a commercially available SrAl(2)O(4):Eu, Dy phosphor, as a function of nanoparticle size reduction via dry mechanical milling. X-ray and optical spectroscopic data indicate a significant decrease in phosphorescence efficiency and an increase in laser stimulated emission efficiency as near surface Eu(2+) ions are oxidized to Eu(3+) as a consequence of increased exposure during the milling process. These results show evidence only for Eu(2+/3+) oxidation states, suggesting the mechanism related to long afterglow effect does not arise from Eu(+) species. We also suggest that size reduction, as a rule, cannot be universally applied to improve optical properties of nanostructures.     

不同尺寸COM、COD对阳离子表面活性剂CTAB的吸附性质差异

为比较研究不同纳微米尺寸的一水草酸钙(COM)和二水草酸钙(COD)晶体对阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)的吸附差异, 探讨抑制剂对结石形成的抑制机理, 本研究测定了各浓度CTAB下不同尺寸COM或COD对CTAB的吸附量; 采用XRD和FT-IR表征吸附前后晶体是否发生晶相改变; 采用Zeta电位仪测定吸附后晶体表面的Zeta电位随CTAB浓度的变化。结果发现, 随着c(CTAB)浓度升高, 3 μm和10 μm的COM、COD晶体的吸附曲线由上升段和平台段组成, 而小尺寸的50 nm、100 nm、1 μm的COM、COD晶体的吸附曲线为直线型。随着晶体尺寸的增大, COM和COD晶体的吸附量依次降低。当尺寸相同时, COM对CTAB的吸附量要大于COD, 归因于CTAB更容易选择吸附在COM表面负电荷的区域。上述结果表明, 草酸钙晶体对阳离子表面活性剂的吸附量与比表面积和晶体的晶面结构有关。晶体尺寸越小, 比表面积越大, 晶面暴露的草酸根密度越大, CTAB的吸附量越大, 导致晶体表面Zeta电位绝对值增大, 静电排斥力增强, 从而抑制尿微晶的聚集, 有利于抑制草酸钙结石的形成。     

Luminescence study on Eu(3+) doped Y(2)O(3) nanoparticles: particle size, concentration and core-shell formation effects

Nanoparticles of Eu(3+) doped Y(2)O(3) (core) and Eu(3+) doped Y(2)O(3) covered with Y(2)O(3) shell (core-shell) are prepared by urea hydrolysis for 3?h in ethylene glycol medium at a relatively low temperature of 140?°C, followed by heating at 500 and 900?°C. Particle sizes determined from x-ray diffraction and transmission electron microscopic studies are 11 and 18?nm for 500 and 900?°C heated samples respectively. Based on the luminescence studies of 500 and 900?°C heated samples, it is confirmed that there is no particle size effect on the peak positions of Eu(3+) emission, and optimum luminescence intensity is observed from the nanoparticles with a Eu(3+) concentration of 4-5?at.%. A luminescence study establishes that the Eu(3+) environment in amorphous Y (OH)(3) is different from that in crystalline Y(2)O(3). For a fixed concentration of Eu(3+) doping, there is a reduction in Eu(3+) emission intensity for core-shell nanoparticles compared to that of core nanoparticles, and this has been attributed to the concentration dilution effect. Energy transfer from the host to Eu(3+) increases with increase of crystallinity.     

Effect of structure, particle size and relative concentration of Eu(3+) and Tb(3+) ions on the luminescence properties of Eu(3+) co-doped Y(2)O(3):Tb nanoparticles

Eu(3+) co-doped Y(2)O(3):Tb nanoparticles were prepared by the combustion method and characterized for their structural and luminescence properties as a function of annealing temperatures and relative concentration of Eu(3+) and Tb(3+) ions. For Y(2)O(3):Eu,Tb nanoparticles annealed at 600 and 1200?°C, variation in the relative intensity of excitation transitions between the (7)F(6) ground state and low spin and high spin 4f(7)5d(1) excited states of Tb(3+) is explained due to the combined effect of distortion around Y(3+)/Tb(3+) in YO(6)/TbO(6) polyhedra and the size of the nanoparticles. Increase in relative intensity of the 285?nm peak (spin-allowed transition denoted as peak B) with respect to the 310?nm peak (spin-forbidden transition denoted as peak A) with decrease of Tb(3+) concentration in the Y(2)O(3):Eu,Tb nanoparticles heated at 1200?°C is explained based on two competing effects, namely energy transfer from Tb(3+) to Eu(3+) ions and quenching among the Tb(3+) ions. Back energy transfer from Tb(3+) to Eu(3+) in these nanoparticles is found to be very poor.     

聚丙烯酰胺对草酸钙结晶的调控作用

采用扫描电子显微镜(SEM)和X射线粉末衍射(XRD)等方法, 研究了聚丙烯酰胺(PAM)对草酸钙形貌和晶相的调控作用, 讨论了聚丙烯酰胺浓度、溶液pH和草酸钙过饱和度变化对草酸钙结晶的影响. PAM可以诱导二水草酸钙(COD)晶体生成并改变COD和一水草酸钙(COM)晶体的形貌. 加入5.0g/L的PAM后, 不但诱导了30%(w/w)的COD晶体形成, 出现了较为少见的COD聚集体, 而且使得COM晶体的棱角圆钝. 从PAM的分子结构、不同pH条件下PAM的水解差异、PAM中羧基与钙离子相互作用、PAM与COM表面Ca²⁺的络合-离解平衡、静电作用等角度讨论了上述结果, 表明通过改变实验条件, 可制备出不同晶相和形貌的草酸钙晶体.     

Mediation of calcium oxalate crystal growth on human kidney epithelial cells with different degrees of injury

The current study examined the role of injured human kidney tubular epithelial cell (HKC) in the mediation of formation of calcium oxalate (CaOxa) crystals by means of scanning electronic microscopy and X-ray diffraction. HKC was injured using different concentrations of H₂O₂. Cell injury resulted in a significant decrease in cell viability and superoxide dismutase (SOD) concentration and an increase in the level of malondialdehyde (MDA) and expression of osteopontin (OPN). Injured cells not only promote nucleation and aggregation of CaOxa crystals, but also induce the formation of calcium oxalate monohydrate (COM) crystals that strongly adhere to cells. These results imply that injured HKCs promote stone formation by providing more nucleating sites for crystals, promoting the aggregation of crystals, and inducing the formation of COM crystals.     

凝胶体系中混合羧酸钾对草酸钙结晶的调控作用

酒石酸钾(K₂tart)、柠檬酸钾(K₃cit)和乙二胺四乙酸钾(K₂edta)均可用于防治草酸钙(CaOxa) 结石, 但它们各有其优缺点. 本文采用双扩散法比较研究了这3种羧酸钾以不同比例两两混合时对CaOxa结晶的影响, 结果表明, 混合剂或者能够诱导更多的二水草酸钙(COD)和三水草酸钙(COT)晶体, 或者减小一水草酸钙(COM)的尺寸, K₂edta-K₃cit混合剂还能诱导(100)晶面减小、螺旋式生长的COD晶体, 该COD与肾小管细胞膜的粘附力较弱. 这些均有利于抑制草酸钙结石形成, 表明混合剂的防石效果优于单一钾盐.     

Enhanced emissions of Eu(3+) by energy transfer from ZnO quantum dots embedded in SiO(2) glass

SiO(2):Eu(3+) based bulk composites containing ZnO quantum dots were synthesized by an in situ sol-gel process. The quantum dots homogeneously distributed among the SiO(2) glass matrix exhibited a broad ultraviolet emission band centered at 385?nm. The ZnO ultraviolet luminescence intensity decreased monotonically with increasing Eu(3+) doping concentration, while the Eu(3+) visible emission was intensified significantly by the precipitation of ZnO quantum dots, ascribed to the energy transfer from ZnO to Eu(3+). The Eu(3+) luminescence at 612?nm for the sample with 20?mol% ZnO was about ten times stronger than that for the sample without ZnO. The influence of ZnO or Eu(3+) concentration on the energy transfer process is discussed.     

Synthesis and characterisation of BaSo4:Eu thermoluminescence phosphor

Polycrystalline powder samples of BaSO(4) doped with Eu(2+) were prepared by solid-state reaction in different reducing atmospheres. Photoluminescence (PL), thermoluminescence (TL), TL kinetic and dosimetric studies have been carried out in this phosphor. The TL glow curve of BaSO(4):Eu(2+) showed only a single peak at 513 K unlike other phosphors and the TL intensity is about three to four times higher than that of CaSO(4):Dy, which is currently used as the radiation dosemeter for personnel monitoring in India. The TL dose response of the phosphor was found to be linear up to the dose range of 10(3) Gy beyond which saturation sets in. PL and TL spectra showed the characteristic emission of Eu(2+) ion. The TL parameters such as trap depth (E) or the energy required to release the electron or hole from the trap, frequency factor (s) and the order of kinetics (b) are determined by different methods such as isothermal decay, initial rise and variable heating rate.     

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.     

Optoacoustic detection of a kinetic-cooling effect in the liquid phase

A kinetic-cooling effect in the liquid phase has been observed by the use of pulsed optoacoustic spectroscopy. The magnitude of the optoacoustic signal in an aqueous Eu(3+) solution, as measured from the absorption of pulsed light, was found to decrease when the excitation-laser wavelength was tuned to the transition from the thermally excited (7)F(1) state to the upper electronic (5)D(0) state of Eu(3+) ion. This anomalous optoacoustic phenomenon is attributed to the kinetic-cooling effect.     

Effects of temperature on growth and aggregation of calcium oxalate in presence of various carboxylic acids in silica gel systems

The effect of monocarboxylic acetic acid (HAc), dicarboxylic tartaric acid (H₂tart), and tricarboxylic citric acid (H₃cit) on growth and aggregation of calcium oxalate (CaOxa) crystals was investigated in gel at different temperature. Calcium oxalate dihydrate (COD) crystals were induced under the conditions of low temperature and in the presence of di- and tricarboxylic acids. The calcium oxalate monohydrate (COM) crystals were more rounded and blunt in the presence of H₃cit and H₂tart. If more COD or more COM crystals with round tips and edges can be induced, CaOxa stones can be inhibited.     

Luminescent properties and characterization of one dimensional Gd(2)O(3):Eu(3+) phosphor nano-wire for field emission application

Gd(2)O(3):Eu(3+) nano-wire phosphors embedded in SBA-15 silica templates were synthesized using a combination of the sol-gel method and hydrothermal reactions followed by a sintering process at 1000?°C. The crystal structure of Gd(2)O(3):Eu(3+) was confirmed using x-ray diffraction. Observation using transmission electron microscopy shows that the nano-wire diameters were very uniform in the 7-9?nm range. In comparison with bulk Gd(2)O(3):Eu(3+) materials, we found that the photo-luminescent property of the nano-wire was different. The analysis shows that the main nano-wire emission peaks were at 585, 597, 613 and 620?nm. The CIE value (x = 0.62, y = 0.38) indicates that the nano-wire emitted a pink colour and not red as for the bulk material. The field emission experimental results agreed well with the photo-luminescent analysis results.     

Site-selective hole burning in Eu3+:Y2SiO5

We found that the Eu(3+) ion occupies several distinct sites in Y(2)SiO(5). We were also able to perform hole-burning studies in more than 40 different transitions.     

Eu(3+) doped gadolinium oxysulfide (Gd(2)O(2)S) nanostructures-synthesis and optical and electronic properties

One-dimensional Eu(3+) doped gadolinium oxysulfide (Gd(2)O(2)S:Eu(3+)) nanotubes/nanorods have been synthesized via precursors of Gd(OH)(3) nanostructures using a hydrothermal technique. The blue-shifts in the optical spectra for the Gd(2)O(2)S:Eu(3+) system corresponding to the fundamental absorption and Eu(3+)-X(2-) ligand (X = O/S) charge transfer bands (CTBs) are significant (～0.22-0.36?eV) with respect to the bulk counterpart. The nanotubes are good candidates for investigating the size-induced electrical and optical properties of functional oxysulfides. In order to identify the origin and nature of the electronic transitions observed in the visible region, optical and photo-induced impedance measurements have been extended to the nanotubes in this report.     

Controllable morphology and high photoluminescence of (Y, Gd)(V, P) O4:Eu3+ nanophosphors synthesized by two-step reactions

Multi-ion doped YVO(4):Eu(3+) nanophosphors with high photoluminescence intensity were successfully prepared by a two-step reaction process for the first time, including YVO(4):Eu(3+) seeds synthesized by hydrothermal reaction and co-doping P(5+) and Gd(3+) in a sol-gel process. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and photoluminescence spectroscopy were adopted to detect the structure, grain size, morphology and optical properties of the nanophosphors, respectively. Owning to the template-induced effect of the seeds, the morphology and size of the nanophosphors could be controlled by adjusting the molar ratios between the seeds and doping ions. The size of these nanophosphors increased as P(5+) and Gd(3+) co-doped. However, most of the samples kept approximately spherical morphology and narrow size distribution. The composition-optimized (Y, Gd)(V, P)O(4):Eu(3+) nanophosphors with spherical morphology in the 80-100 nm range exhibit better red emission and superior color saturation under vacuum ultraviolet excitation compared with that of the commercial phosphor (Y, Gd)BO(3):Eu(3+).