Effect of different dopants on the long lasting phosphorescence behavior of CaTiO_3：Pr~（3＋）

In order to improve the luminescence properties of CaTiO3:Pr3+, a series of CaTiO3:Pr3+, such as CaTi0.97Nb0.03O3:Pr3+, Ca0.8Zn0.2TiO3: Pr3+, Ca0.8Zn0.2Ti0.97Nb0.03O3:Pr3+ and B3+-doped Ca0.8Zn0.2Ti0.97Nb0.03O3: Pr3+ were prepared through conventional solid state reaction method. The results of the photoluminescence excitation and emission spectra showed that all the samples emitted red phosphorescence at 612 nm originating from 1D2 to 3H4 emission of Pr3+ under the 337 nm excitation. When examined by the X-ray diffraction (XRD), all the samples presented a predominant phase of CaTiO3 (JCPDS# 42-423) except Zn2+-doped samples which also revealed another phase of Zn2Ti3O8 (JCPDS# 73-579). The results of the afterglow decay curves showed that co-doping Zn2+ ions, Nb5+ ions or adding a small amount of B3+ into Ca0.8Zn0.2Ti0.97Nb0.03O3:Pr3+ were effective in improving the photoluminescence properties of CaTiO3:Pr3+ phosphor. Thermoluminescence results showed that the trap existing in all the samples was the same as in CaTiO3:Pr3+ and doping singly Nb5+ or Zn2+ hardly changed the trap depth but co-doping Nb5+ and Zn2+ could modify the trapping level from 0.63 to 1.26 eV distinctively. In addition, adding a certain amount of B3+ into CTO-PZN could also deepen the trap depth.     

Enhancing the performance of photovoltaic cells by using down-converting KCaGd（PO_4）_2：Eu~（3＋） phosphors

The goal of this work is aimed to improve the power conversion efficiency of single crystalline silicon-based photovoltaic (PV) cells by using the solar spectral conversion principle, which employed a down-converting phosphor to convert a high-energy ultraviolet photon to the less energetic red-emitting photons to improve the spectral response of Si solar cells. In this study, the surface of silicon solar cells was coated with a red-emitting KCaGd(PO4)2:Eu3+ phosphor by using the screen-printing technique. In addition to the investigation on the microstructure using scanning electron microscopy (SEM), we measured the short circuit current (Isc), open circuit voltage (Voc), and power conversion efficiency (η) of spectral-conversion cells and compared with those of bare solar cells as a reference. Preliminary experimental results revealed that in an optimized PV cell, an enhancement of (0.64+0.01)% (from 16.03% to 16.67%) in Δη of a Si-based PV cell was achieved.     

Up-conversion luminescence of Er~（3＋）-doped and Yb~（3＋）/Er~（3＋） co-doped 12CaO·7Al_2O_3 poly-crystals

The optical properties of Er3+-doped and Yb3+/Er3+ co-doped 12CaO·7Al2O3 (C12A7) poly-crystals, synthesized by high temperature solid state method, were investigated in detail. For Er3+-doped and Yb3+/Er3+ co-doped C12A7 poly-crystals, two main emission bands centered around 530/550 nm (green) and 660 nm (red) were observed under 980 nm diode laser excitation via an up-conversion process. The intensity of green up-conversion emission had a strong increase in Er3+ (1.0 mol.%, 1.5 mol.%, 3.0 mol.%), and the intensity ratio of red to green up-conversion emission had an increase in Yb3+ (1.0 mol.%, 2.0 mol.%, 10. 0 mol.%)/Er3+ (fixed at 1.0 mol.%). This detailed study of the up-conversion processes allowed us to identify the dominant up-conversion mechanisms in Er3+-doped and Yb3+/Er3+ co-doped C12A7 poly-crystals.     

Studies on electrical properties and CO-sensing characteristics of La_（0.9） _（0.1）FeO_3

Semiconducting sensors offer an inexpensive and simple method for monitoring gases. Sensors based on the ABO3-type composite oxides materials have an advantage of high stability. The perovskite structures of these compounds are preserved, when an A-site deficiency of some perovskite structure compounds was formed. However, they exhibit particular physical properties. In this paper, La0.9 0.1FeO3 powder with an orthorhombic perovskite phase was prepared by sol-gel method. The electrical properties and CO-sensing characteristics of the La0.9 0.1FeO3 were also investigated. The results demonstrated that the La0.9 0.1FeO3 was a p-type semiconductor material. Compared with LaFeO3, the conductance of La0.9 0.1FeO3 was better than that of LaFeO3. The sensor based on La0.9 0.1FeO3 showed excellent CO gas-sensing characteristics.     

Preparation and luminescence properties of Ce3＋/Dy3＋-codoped fluorosilicate glass ceramics

The Ce3+and Dy3+ co-doped fluorosilicate glass and glass ceramics containing SrF2 or CeF3 nanocrystals were prepared under re-ducing atmosphere. The precipitated nano-crystalline phase shifted from cubic SrF2 to hexagonal CeF3 gradually with the heat treatment tem-perature increasing from 620 to 680 °C. The glass and glass ceramics emitted white light, deriving from a combination of the Ce3+ blue and the Dy3+ yellow light. The CIE coordinates could be tuned by adjusting the ratio of Ce3+/Dy3+ concentration. The luminescence could be en-hanced significantly by annealing the samples at the temperatures lower than 640 °C.     

Influence of concentration and sintering temperature on luminescence properties of Eu^3＋：SnO2 nanocrystallites

The nanopowders of SnO2 doped with different Eu3+ concentrations were synthesized using the modified Pechini method. The Eu3+ concentrations were high above solubility limit. The average size of crystallites was controlled by the sintering temperatures. The structure and the morphology of obtained powders were examined using the XRD (X-ray diffraction) and TEM (transmission electron microscopy) analyses. The Eu2Sn2O7 phase separation was observed at relatively high concentration of Eu3+ ions. The ZnS:Ag micropowders were mixed with the Eu3+:SnO2 powders and their normalized emission was used to measure a relative efficiency of Eu3+:SnO2. The photoluminescence spectra of mixed powders were measured in function of Eu3+ concentration and average size of nanocrystallites. The reference peak method was used for comparison of intensities of the samples and selection of optimal one. The influence of the average grain size and Eu3+ concen-tration on the phosphor’s efficiency was discussed. The presented results confirmed the rightness of synthesis of the Eu3+:SnO2 in form of nanocrystalites with relatively high Eu3+ concentration.     

Efficient near-infrared quantum cutting by Ce~（3＋）-Yb~（3＋） couple in GdBO_3 phosphors

Ce3+ and Yb3+ co-activated GdBO3 phosphors were prepared by a conventional solid-state reaction method. X-ray powder diffraction, photoluminescent spectra and decay curves were used to characterize their structural and luminescent properties. An efficient near-infrared (NIR) quantum cutting (QC) from the phosphors was observed, which involved the emission of two low-energy NIR photons (around 971 nm) from an absorbed ultra-violet (UV) photon at 358 nm via a cooperative energy transfer (CET) from Ce3+ to Yb3+ ions. The theoretical quantum efficiency was calculated and the maximum efficiency approached up to 164% before reaching the critical concentration quenching threshold. Our results demonstrated that these phosphors might find potential application in improving the efficiency of silicon based solar cells.     

Influences of Nd~（3＋） doping on structure and electrochemical performance of layered Li_（1.05）V_3O_8

Nd3+-doped Li1.05V3O8 was synthesized by liquid-state reactions combined calcination.The influences of Nd3+ doping on physical and electrochemical performances of Li1.05V3O8 were investigated using X-ray diffraction (XRD),cyclic voltammograms,a.c.impedance and galvanostatic charge-discharge tests,etc.Results indicated that Nd3+-doped products had well developed crystal structure of layered LiV3O8 and uniform particle size distribution.Nd3+ doping with a proper amount improved the initial discharge capacity,discharge voltage and ion conductivity of the cathode material to some extent.Nd3+ did not participate in the electrochemical reactions and was beneficial to stability of the crystal structure during cycling.     

Photoluminescence enhancement of YAG：Ce~（3＋） phosphor prepared by co-precipitation-rheological phase method

YAG:Ce3+ phosphor was prepared by a novel co-precipitation-rheological phase method.The resulting YAG:Ce3+ phosphor was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and photoluminescent emission spectra.By using acetic acid as solvent,YAG:Ce3+ powder with small particle size(≤2 μm) was obtained at a relatively lower sintering temperature of 1400 oC.With the content of acetic acid increasing,small particles dissolved and disappeared,but larger particles grew up and changed its shape from spherical to partially rectangular.Meanwhile,the emission intensity of the sample prepared by co-precipitation-rheological phase method was about 43% higher than that of the sample prepared by co-precipitation method.It was assumed that the significant improvement of luminescence was mainly because the rheological phase presented a better diffusion environment,and therefore,a better homogeneity of activators of Ce3+.     

Photoluminescence properties of Ce3+ doped YSiO2N blue-emitting phosphors

Oxonitridosilicate phosphors with compositions of Y 1-x Ce x SiO 2 N (x=0-0.1) were synthesized by a new synthetic route based on a solid state reaction among YSi, CeSi, SiO 2 and Y 2 O 3 compounds at high temperature and high pressure. The photoluminescence properties dependent on Ce concentration and temperature were investigated. Concentration quenching occurred when the doped Ce 3+ concentration was more than 3 mol.%. The emission spectra showed red shifts from 430 to 447 nm with the increased Ce concentration from 0.5 mol.% to 10 mol.%. The quenching temperature was estimated as ～380 K. The chromaticity coordinates of the excitation and emission spectra were stable against the temperature. This study showed these YSiO 2 N:Ce 3+ phosphors the potential applications in the three-RGB phosphor-converted white LEDs.     

Effects of gadolinium on proliferation, differentiation and calcification of primary mouse osteoblasts in vitro

To evaluate the effects of Gd on proliferation, differentiation and mineralization function of primary osteoblasts (OBs) in vitro, we tested cell viability by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, cell differentiation by alkaline phosphatase (ALP) activity assay, synthesis of type ? collagen, and oil red O and alizarin red S (ARS) stain assays. The results indicated that effects of Gd on the proliferation, osteogenic differentiation, mineralization function and adipocytic transdifferentiation of primary OBs de-pended on concentration and incubation time, but were not dose-dependent. It was suggested that the effect of Gd on bone metabolism was complicated, and concentration and culture time were key factors for switching the biological effects of Gd from damage to protection.     

Enhancement of luminescence and afterglow in Ca0.8Zn0.2TiO3:Pr3+ by Nb5+ substitution for Ti4+

Nb5+ doped Ca0.8Zn0.2TiO3:Pr3+ red long afterglow phosphors were synthesized by solid-state reaction methods. X-ray diffraction, photoluminescence spectroscopy and thermally stimulated spectrometry were used to investigate the effects of Nb5+ content on the crystal characteristics and luminescent properties of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+ phosphors. The results showed that the addition of a small quantity of Nb5+ had negligible effect on the crystal characteristics of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+, but it could change the trapping parameters (the depth of trap, frequency factors and the concentration of trapped charges at t=0) of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+ phosphors, and then led to the enhance-ment of red fluorescence and phosphorescence at 612 nm originating from 1D2→3H4 transition of Pr3+. Both of the red fluorescence intensity and afterglow time reached the largest values in the sample of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+ with x=0.05. The afterglow time of Ca0.8Zn0.2Ti0.95Nb0.05O3:Pr3+ phosphors lasted for over 24 min (≥1 mcd/m2) when the excited source was cut off.     

Dy3+ activated LaVO4 films synthesized by precursors with different solution concentrations

Using different-solution-concentration precursors with citric acid as chelating agent and polyvinyl alcohol as dispersing media, Dy3+ activated LaVO4 films were deposited on indium tin oxide (ITO) substrates. The scanning electronic microscope (SEM) showed that the compact and crack-free LaVO4:Dy3+ film could be obtained at a suitable solution concentration. The deposited films could absorb the ultra-violet light below 400 nm and were transparent in the visible and infrared region as evidenced by the transmission spectra, and the photolumines-cence spectra exhibited the characteristic emissions of Dy3+ peaking at 484 (blue) and 576 (yellow) nm due to the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2, respectively. The potential application of LaVO4:Dy3+ film in the dye-sensitized solar cell (DSSC) was also discussed.     

Effects of scandium chloride on osteogenic and adipogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells(MSCs)are multi-potent cells that are able to differentiate and mature into various types of cells under a certain microenvironment for cell therapy and tissue regeneration.Scandium(Sc),an important rare earth element,recently has been intensively investigated in biomedical fields as well as industrial engineering,and chloride channels have been proven to be able to affect osteogenic differentiation.Thus,it is significant to investigate effects of ScCl₃on cell activities of MSCs.In this paper,rat bone MSCs(rBMSCs)were co-cultured with various concentrations of ScCl₃(1×10^-8,1×10^-6,and 1×10^-4mol/L)to evaluate their influence on cell proliferation as well as osteogenic and adipogenic differentiation in vitro.The results indicate that ScCl₃promotes the proliferation of rBMSCs initially,which is yet reduced upon ion accumulation.We used immunofluorescence staining,quantitative real time polymerase chain reactions,and assays measuring alkaline phosphatase activity,mineralized deposits,and intracytoplasmic lipids to reveal that rBMSCs treated with ScCl₃at concentrations of 1×10^-8-1×10^-6mol/L can enhance levels of osteogenic differentiation in a dosedependent manner and reduce adipogenic differentiation to a certain degree through Wnt/β-catenin signaling pathway.These results indicate that appropriate concentrations of ScCl₃can improve osteogenic differentiation in the lineage commitment of rBMSCs,and thus,promote bone remodeling.This study implies that ScCl₃ possesses great potentials in the treatment of bone diseases and would provide new strategy of designing composites by SiCl3 doping for biomedical applications in the future.     

Broadband downconversion in YVO4：Tm3＋,Yb3＋ phosphors

An efficient near-infrared (NIR) downconversion (DC) by converting broadband ultraviolet (UV) into NIR was demonstrated in YVO4:Tm3+,Yb3+ phosphors. The phosphors were extensively characterized using various methods such as X-ray diffraction, photoluminescence excitation, photoluminescence spectra and decay lifetime to provide supporting evidence for DC process. Upon UV light varying from 260 to 350 nm or blue light (473 nm) excitation, an intense NIR emission of Yb3+ corresponding to transition of 2F5/2→2F7/2 peaking at 985 nm was generated. The visible emission, the NIR mission and the decay lifetime of the phosphors of various Yb3+ concentrations were investigated. Experimental results showed that the energy transfer from vanadate group to Yb3+ via Tm3+ was very efficient. Application of the broadband DC YVO4:Tm3+,Yb3+ phosphors might greatly enhance response of siliconbased solar cells.     

Synthesis of CaWO4：Eu3＋ phosphor powders via ethylene glycol route and its optical properties

Eu3+ doped CaWO4 with tetragonal system were prepared at comparatively low temperature (125 ?C) in ethylene glycol medium. The phosphor was further investigated by X-ray diffractometer (XRD), photoluminescence spectrophotometer (PL), Fourier transform infra red (FT-IR) spectroscopy and transmission electron microscopy (TEM). XRD analysis indicated a decrease in the unit cell volume of CaWO4 with increasing Eu3+ ion concentration. It indicated the homogeneous substitution of Ca2+ ions in CaWO4 by the Eu3+ ions. TEM images showed that the particle size ranged from 20 to 200 nm and it could extend the application of the nanoparticles. The photoluminescence study showed that the intensity of electric dipole transition (5D0→7F2) at 614 nm dominated over the magnetic dipole transition (5D0→7F1) at 592 nm. The optimum concentration of Eu3+ for the highest luminescence was found to be 20 at.%. The as prepared samples were found to be dis-persible in water and methanol.