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1.
The Ca2MgSi2O7:Eu2+ and Ca2MgSi2O7:Eu2+, Dy3+ long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) techniques. The luminescence properties were investigated using thermoluminescence (TL), photoluminescence (PL), long afterglow, mechanoluminescence (ML), and ML spectra techniques. The crystal structure of sintered phosphors was an akermanite type structure, which belongs to the tetragonal crystallography. TL properties of these phosphors were investigated, and the results were also compared. Under the ultraviolet excitation, the emission spectra of both prepared phosphors were composed of a broad band peaking at 535 nm, belonging to the broad emission band. When the Ca2MgSi2O7:Eu2+ phosphor is co-doped with Dy3+, the PL, afterglow and ML intensity is strongly enhanced. The decay graph indicates that both the sintered phosphors contain fast decay and slow decay process. The ML intensities of Ca2MgSi2O7:Eu2+ and Ca2MgSi2O7:Eu2+, Dy3+ phosphors were proportionally increased with the increase of impact velocity, which suggests that this phosphor can be used as sensors to detect the stress of an object.  相似文献   

2.
CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were synthesized by a sol–gel method under mild conditions (i.e. low temperature and ambient pressure). The as-prepared powders were characterized by transmission electron microscopy (TEM) and analyzed by X-ray diffraction (XRD). The photocatalytic behavior of the TiO2-base surfaces was evaluated by the degradation of nitrogen monoxide gas. It suggested that CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were composed of anatase titania and that CaAl2O4:Eu2+, Nd3+. TiO2 particles were deposited on the surface of CaAl2O4:Eu2+, Nd3+ to form uniform film. CaAl2O4:Eu2+, Nd3+@TiO2 composite powders exhibited higher photocatalytic activity compared with pure TiO2 under visible light. And the result also clearly indicated that the long afterglow phosphor absorbed and stored lights for the TiO2 to remain photocatalytic activity in the dark.  相似文献   

3.
Non-aggregated spherical polystyrene (PS) particles were coated with GdPO4:Tb3+/Ce3+ phosphor layers by a conventional hydrothermal synthesis using poly(vinylpyrrolidone) (PVP) as an additive without further annealing treatment. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), as well as luminescence decay experiments were used to characterise the resulting core-shell structured PS@GdPO4:Tb3+/Ce3+ samples. The results of XRD indicated that the PS particles were successfully coated with the GdPO4:Tb3+/Ce3+ phosphor layers, which could be further verified by the images of FESEM. Under ultraviolet excitation, the PS@GdPO4:Tb3+/Ce3+ phosphors show Tb3+ characteristic emission, i.e. 5D4-7FJ (J = {6, 5, 4, 3}) emission lines with green emission 5D4-7F5 (543 nm) as the most prominent group. The core-shell phosphors so obtained have potential applications in field emission display (FED) and plasma display panels (PDP).  相似文献   

4.
The flower-like phosphors of Sr2MgSi2O7: Eu2+, Dy3+ with high brightness and long afterglow were obtained by sol–gel method. X-ray diffraction pattern (XRD) shows that single-phased Sr2MgSi2O7 phosphor is prepared by sol–gel method under 1250 °C. Scanning electron microscope (SEM) indicates that the phosphor consists of nano-sized whiskers which are detected for the first time in Eu2+ and Dy3+ co-doped long-lasting phosphorescence silicates. Furthermore, the investigation on the mechanism indicates that the internal structure and gas, liquid and solid phase effect play important roles in the formation of flower-like Sr2MgSi2O7: Eu2+, Dy3+ nanostructure. Finally, the optical properties of flower-like Sr2MgSi2O7 nanostructure have been characterized by photoluminescence (PL) spectra.  相似文献   

5.
Fine Eu3+-doped lutetium oxide (Lu2O3:Eu3+) nanophosphor were synthesized using a low-temperature solution-combustion method in a methyl-alcohol solution. The characteristics of the nanophosphors synthesized at various sintering temperatures with different Eu3+ concentrations were analyzed to determine the optimum synthesis conditions. Thermogravimetry/differential thermal analysis showed that Lu2O3:Eu3+ crystallizes completely when the dry powder is sintered at 500 °C. The Lu2O3:Eu3+ crystals had a cubic structure and monoclinic phase. The peak position of the luminescence spectrum did not differ with the concentration of Eu or the sintering temperature or atmosphere, whereas the luminescence intensity was strongly dependent on the concentration and sintering conditions.  相似文献   

6.
High quality GdTaO4:Eu3+ luminescence films have been successfully prepared through a modified sol-gel process. The films were prepared using inorganic materials as raw materials, and the thermal decomposition and UV assisted technique were introduced to improve the quality of the film and reduce the period for forming the thick film. Results of structural studies by atomic force microscopy (AFM) and X-ray diffraction (XRD) showed that the surface was smooth and the structure was monoclinic with the average grain size of about 55 nm. The emission and excitation spectra of the film were investigated. Related to the transition 5 D07 F1 and 5 D07 F2 of Eu3+ ions, the main luminescence peaks were observed at 591 and 611 nm respectively, and the luminescence peak at 345 nm was detected simultaneously related to the TaO43− emission. Transmission spectrum and decay curve of the luminescence are also presented in this paper.  相似文献   

7.
Fe3+ doped mesoporous TiO2 with ordered mesoporous structure were successfully prepared by the solvent evaporation-induced self-assembly process using P123 as soft template. The properties and structure of Fe3+ doped mesoporous TiO2 were characterized by means of XRD, EPR, BET, TEM, and UV–vis absorption spectra. The characteristic results clearly show that the amount of Fe3+ dopant affects the mesoporous structure as well as the visible light absorption of the catalysts. The photocatalytic activity of the prepared mesoporous TiO2 was evaluated from an analysis of the photodegradation of methyl orange under visible light irradiation. The results indicate that the sample of 0.50%Fe–MTiO2 exhibits the highest visible light photocatalytic activity compared with other catalysts.  相似文献   

8.
Nano-structure pure barium titanate BaTiO3 (BT) and (BT) co-doped with constant concentration of Er3+ ions and different concentrations of Yb3+ ions were prepared using sol–gel method. XRD results confirmed that the pure sample was found to crystallize in tetragonal phase by sintering at 750 °C for 1 h. All major peaks corresponding to perovskite BT phase appeared. Efficient infrared-to-visible up-conversion is reported in the doped samples. The conversion process and results in the generation of visible emissions are discussed. Up-conversion efficiency for red emission predominates in doped samples. Results illustrate the large potential of this class of materials for photonic applications in optoelectronics devices.  相似文献   

9.
Ti3+ and carbon co-doped TiO2 photocatalysts were prepared hydrothermally to introduce the carbon, and followed by simple vacuum activation to achieve the Ti3+ self-doping. The prepared co-doped photocatalysts were characterized by XRD, TEM, UV–Vis absorption spectra, EPR, and XPS. It was found that the co-doped TiO2 has dispersed nanoparticles and a narrower band-gap compared with the un-doped TiO2 and single-doped TiO2. The experimental results displayed that the coke carbon generated on the surface of co-doped TiO2 acts as a photosensitizer and has the photosensitization effect under solar light irradiation. Except for the carbon sensitization effect, the Ti3+ self-doping modification has a synergistic effect which is the reason for the effective photo-degradation of methyl orange under simulated solar light irradiation.  相似文献   

10.
Zinc gallate (ZnGa2O4) nanopowders doped with Cr3+ (1?mo%) were synthesized by the citric acid assisted sol–gel method. The influence of annealing temperature, structural, morphological, and optical properties of ZnGa2O4: Cr3+ (1?mol%) nanosized particles were investigated. The X-ray diffraction (XRD) spectra indicated that the nanoparticles are cubic in structure and the annealing temperature did not influence any c in structure. The average crystallite size of ZnGa2O4: Cr3+ nanoparticles were observed to increase from 11.85 to 30.88?nm as the annealing temperature increased from 600 to 1000?°C. The scanning electron microscopy (SEM) showed nearly spherical nanostructures that change in size with annealing temperature. The high resolution transmission electron microscope (HR-TEM) images show well resolved lattice fringes which is an indications of highly crystalline samples. Ultraviolet–visible (UV–Vis) measurement show decrease in reflectance in visible region and energy band gap was found to decrease with annealing temperature. The photoluminescence (PL) intensity was found to be maximum for sample annealed at high temperature (1000?°C) and least with sample annealed at low temperature (600?°C). An increase in annealing temperature leads significantly increment in PL intensity. The degree of crystallinity also increased with annealing temperature from XRD, SEM, and HR-TEM analysis. The photoluminescence lifetimes, particle size, and emission spectra are comparable with reports on bioimaging applications.  相似文献   

11.
Microwave-induced combustion with glycine, CTAB-assisted hydrothermal process with NaOH and NH3, EDTA assisted-hydrothermal methods have been applied to prepare NiFe2O4 nanoparticles for the first time. Structural and magnetic properties of the products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmison electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and electron spin resonance spectrometry (EPR). TEM measurements showed that morphology of the product depends on the synthesis method employed. The average cystallite size of NiFe2O4 nanoparticles was in the range of 14–59 nm as measured by XRD. The uncoated sample (Method A) had an EPR linewidth of 1973 Oe, the coated samples reached lower values. The magnetic dipolar interactions existing among the Ni ferrite nanoparticles are reduced by the coatings, which could cause the decrease in the linewidth of the EPR signals. Additionally, the linewidth increases with an increase in the size and the size distribution of nanoparticles.  相似文献   

12.
In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.  相似文献   

13.
Properties of the quantum-cutting phosphors are dependent on various factors such as dopant concentration, crystallinity, homogeneity, particle size and surface morphology. Effective control of the above parameters can enhance the quantum-cutting ability of the phosphor material. Nano-sized particles of Y2O3:Tb3+,Yb3+ were prepared with a solution-based co-precipitation method and subsequent calcination. Effective control of the reaction parameters and doping concentration helped to produce uniform nanostructures with high quantum-cutting efficiency up to 181.1 %. The energy transfer mechanism between Tb3+ and Yb3+ was studied by considering their spectroscopic properties and time-resolved spectroscopy. The high efficiency and small particle size of the quantum-cutting phosphor Y2O3:Tb3+,Yb3+ make it a suitable candidate for its application in solar cells.  相似文献   

14.
A mesoporous iron–titanium mixed-oxides@activated carbon(AC) fiber membrane was fabricated by an electrospinning method and applied to the treatment of phenol waste water. The physical and chemical properties of the composite fiber membrane were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, UV–Vis light diffuse reflectance spectroscopy (DRS), Raman spectroscopy, respectively. The results indicate that the composite nanofiber membrane is composed of α-Fe2O3, anatase TiO2 and activated carbon phases with a specific surface area of 231 m2 g–1 and narrow pore size distribution of 3–6 nm. DRS reveals that the composite membrane has high photons absorption from both ultraviolet light and visible light irradiation owing to the combination of Fe2O3, TiO2 and carbon. The prepared nano Fe2O3–TiO2@AC fiber membrane can act as an efficient reusable photocatalyst and adsorbent for 100% remo val of phenol pollutant. This hybrid technique is hopeful to be widely used in the treatment of various organic waste waters.  相似文献   

15.
Novel luminescent bio-based hydrogels comprising cellulose and Y4Si2O7N2:Ce4+ (YC) were prepared in an alkali/urea aqueous system using epichlorohydrin as a cross-linker. The structure, characteristics and properties of the hydrogels were investigated by various techniques, including FTIR spectroscopy, wideangle X-ray diffraction, scanning electron microscopy, etc. The results showed that when the content of YC was less than 0.05 g, the YC particles were tightly embedded in the macro porous of cellulose matrix, which not only supplied cavities for YC immobilization, but also supplied the pore wall to protect the structure and character of YC. Hence, the cellulose–YC hybrid hydrogels exhibited strong cyan fluorescence under a UV lamp. However, excess of YC particles were enshrouded in the cellulose matrix resulted in smaller pores, weaker fluorescence intensity, lower swelling ratio and higher mechanical properties.  相似文献   

16.
Ag+- and Sn2+-substituted KSbTeO6 were prepared by a facile ion-exchange method at ambient temperature. All the samples were characterised by scanning electron microscopy, energy-dispersive spectra, thermogravimetric analysis, powder X-ray diffraction, Raman spectra and UV-VIS diffuse reflectance spectra. Both Sn2+- and Ag+-substituted KSbTeO6 were crystallised in a cubic lattice with the \(Fd\bar 3m\) space group. The band-gap energy of all the samples was deduced from their UV-VIS diffuse reflectance spectral profiles. The visible light-induced photocatalytic oxidation of the methylene blue (MB) dye was examined in the presence of all the as-prepared materials. The Ag+- and Sn2+-substituted KSbTeO6 exhibited a higher photocatalytic activity than the parent KSbTeO6 in degradation of the MB dye under visible light irradiation.  相似文献   

17.
Fluorescence and spectral hole burning properties of Eu3+ ions were studied in nanocrystals-precipitated SnO2-SiO2 glasses. The glasses were prepared to contain various amount of Eu2O3 using the sol-gel method, in which SnO2 nanocrystals were precipitated by heating in air. In the glasses containing Eu2O3 less than 1%, the Eu3+ ions were preferentially doped in the SnO2 nanocrystals and their fluorescence intensities were enhanced by the energy transfer due to the recombination of electrons and holes excited in SnO2 crystals. The SnO2 nanocrystals-precipitated glasses exhibited the persistent spectral holes with the depth of ∼25% of the total fluorescence intensities of the Eu3+ ions. With the increasing Eu2O3 concentration, the amount of SnO2 nanocrystals decreased and the Sn4+ ions formed the random glass structure together with the silica network. This structure change induced the fluorescence intensities and the hole depth to decrease.  相似文献   

18.
TiO2 nanocrystals with diameters 8–10 nm have been prepared through sol–gel method using a mixed template of polyethylene glycol (PEG) and cetytrimethylammonium bromide (CTAB) at low temperature. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution (HR) TEM and fourier transform infrared spectroscopy (FT-IR) etc. XRD analysis showed the TiO2 photocatalysts prepared with mixed template are pure anatase. FTIR spectrum revealed that the cationic surfactant provides CTA+ molecules and bonds to Ti–O to prevent the condensation reaction. PEG plays a dispersant role in controlling the structure of nano-TiO2 particles. CTAB and PEG incorporated with each other to restrain the growth of crystal nucleus and control the size of grain. The self-assembling process has been confirmed by HRTEM. PEG played different role in mixed template from the single template. The photocatalytic activity of samples was determined by using as a model reaction. The results showed that TiO2 photocatalysts with mixed template have higher photocatalytic activity than P25.  相似文献   

19.
Eu3+ ion-doped LaPO4 nanowires or nanorods have been successfully synthesized by a simple hydrothermal method. The influence of varying the hydrothermal and subsequent sintering conditions on the morphology and structure of the LaPO4 host has been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). For comparison, the Eu3+ ions were also doped into monoclinic monazite LaPO4 nanoparticles and perovskite LaAlO3 nanoparticles. The relative intensities of the emission lines of the LaPO4:Eu3+ nanosystems were essentially independent of their shape. The optimal doping concentrations in the monoclinic LaPO4 and perovskite LaAlO3 nanosystems were determined to be about 5.0 and 3.5 mol%, respectively. Under appropriate UV-radiation, the red light emitted from LaAlO3:Eu3+ (3.5 mol%) was brighter than that from LaPO4:Eu3+ (5.0 mol%) nanomaterial, resulting from differences in their spin-orbit couplings and covalence, which indicates that the nanoscale LaAlO3 is a promising host material for rare earth ions. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. Supported by the National Natural Science Foundation of China (Grant Nos. 20873039 & 90606001), Hunan Provincial Natural Science Foundation (No. 07jj4002), and the Students Innovation Training Fund of Hunan University  相似文献   

20.
The aim of the article is to investigate the influence of particle size on titanium dioxide phase transformations. Nanocrystalline titanium dioxide powder was obtained through a hydrothermal procedure in an aqueous media at high pressure (in the range 25–100 atm) and low temperature (≤200 °C). The as-prepared samples were characterized with respect to their composition by ICP (inductive coupled plasma), structure and morphology by XRD (X-ray diffraction), and TEM (transmission electron microscopy), thermal behavior by TG (thermogravimetry) coupled with DSC (differential scanning calorimetry). Thermal behavior of nanostructured TiO2 was compared with three commercial TiO2 samples. The sequence of brookite–anatase–rutile phase transformation in TiO2 samples was investigated. The heat capacity of anatase and rutile in a large temperature range are reported.  相似文献   

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