Luminescence and Preparation of LED Phosphor Ca_8Mg(SiO_4)_4Cl_2∶Eu^(2+)

Calcium magnesium chlorosilicate doped by europium, Ca8Mg（SiO4）4Cl2： Eu^2＋, was prepared by the solid state reaction at high temperature. The compound obtained is pure Ca8Mg（SiO4）4Cl2 phase with cubic structure. Its average particle size is 5 μm, and it has good dispersity and morphological form. The excitation spectrum of Ca8Mg（SiO4）4Cl2： Eu^2＋ is a wide band, which covers from 270 to 480 nm. The emission spectrum is also a wide band peaked at 510 nm. The luminescent intensity reaches to the maximum when the concentration of Eu^2 ＋ is 2%. The wavelength of emission and excitation of the phosphor with various Eu^2 ＋ contents keeps constant. This spectrum range matches violet and blue LED chips very well, and its strong luminescence intensity is suitable for a green phosphor of tricolor phosphor of white light LED.

Synthesis of Y_2O_2S：Eu^（3＋） Phosphor by Microwave Thermal Effectand Its Luminescent Properties

The phosphor Y2O2S:Eu3+ powder crystal has been synthesized by using the microwave thermal method.The data of X-ray powder diffraction showed that the phosphor structure belongs to hexagonal system with lattice parameters a=0.3785 nm,c=0.6590nm.The excitation spectrum of the phosphor is a broad band with peak at λ(ex)= 261 nm.The main emission peak at λ(em)=626nm and the other emission lines peak at 595,617 and 706 nm are assigned to transitions of the Eu3+ respectively.Under 254 nm excitation,the chromatic coordinates of phosphor are x=0.665, y=0.330.The relative luminescent intensity is about 62% compared with the standard phosphor Y2O3:Eu3+.Under 365nm excitation this phosphor gives rise to an intense red light.The phosphor particle size has a medium diameter of 7.3μm.

Preparation and characterization of visible-light-driven europium doped mesoporous titania photocatalyst

pure and different content europium （Eu） doped mesoporous titania were prepared by template method using Eu（NO3）3·6H2O and Ti（OC4H9）4 as precursors and Pluronic P123 as template and characterized with X-ray diffraction （XRD）, N2 adsorption-desorption measure- ments, and ultraviolet-visible diffuse absorption spectra. Their photocatalytic activities were studied by photodegradation phenol in water un- der visible light irradiation. The results showed that Eu doping restrained the growth of grain size and extended the photoabsorption edge of mesoporous titania into the visible light region, which made Eu-doped mesoporous titania possess high photocatalytic activity under visible light. In the experiment condition, the photocatalytic activity of 0.2 mol.% Eu doped mesoporous titania was optimal of all the prepared samples.

Neurotoxicity and brain localization of europium doped Gd2O3 nanotubes in rats after intranasal instillation

Europium doped Gd2O3nanotubes(Gd2O3:Eu3+NTs) were synthesized and characterized. Then,the neurotoxicity and brain localization of Gd2O3:Eu3+NTs were evaluated. All experimental rats were administered by intranasal instillation with 30 μL Gd2O3:Eu3+NTs suspension 3.0 and 15.0 mg/mL respectively every other day for 35 consecutive days, and the rats of control group were administered with an equal volume of physiological saline. The Morris water maze was used to assess the rats’ spatial learning and memory ability. The oxidative stress-related biomarkers and the activity of AChE in striatum and hippocampus were analyzed, and the histopathology of hippocampus and striatum was observed.The brain localization of gadolinium(Gd) was measured. The results showed that the escape latency of the rats in high-dose group prolonged significantly compared with that of control group after treatment of six weeks(p < 0.05), and the swimming time in D quadrant of high-dose group shortened significantly compared with the control group(p < 0.01). In addition, high-dose Gd2O3:Eu3+NTs could decrease the activity of GSH-Px and CAT in hippocampus and the activity of SOD in striatum(p < 0.05). MDA content in hippocampus and striatum of high-dose group increased(p < 0.05). High dose Gd2O3:Eu3+NTs could increase the activity of AChE in hippocampus(p < 0.05) and in striatum(p < 0.001). But there were no significant differences between the low-dose group and control group(p > 0.05). The results of Gd localization in brain showed that the ranking of Gd levels was olfactory bulb > striatum > hippocampus> cerebellum > brain stem > frontal cortex. The pathology results indicated that high dose Gd2O3:Eu3+NTs resulted in degeneration necrosis, nucleus pycnosis, and axons disappearance of the nerve cells at CA1, CA3 and DG area of hippocampus. Therefore, the results implied that Gd2O3:Eu3+NTs have the potential neurotoxicity and a possible danger in causing neurodegenerative disorders after intranasal instillation.

Structural and spectroscopic diagnosis of ZnO/SnO_2 nanocomposite influenced by Eu^(3+)

Europium doped ZnO/SnO2 nanocomposite phosphors were synthesized via room temperature co-precipitation method. In this work structural changes, optical properties and the associated photoluminescence response were investigated for different compositions of ZnO and SnO2 activated with Eu3＋ ions. The prepared samples were systematically characterized by means of X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, field emission scanning electron microscopy for obtaining the structural information about the prepared materials. Diffuse reflectance （DR） UV-Vis spectrometer and photoluminescence （PL） spectroscopy technique were employed for studying the optical properties of prepared materials. XRD results confirmed the presence of both phases, hexagonal ZnO as well as tetragonal SnO2 simultaneously and further using Debye Scherrer＇s and Hall-Williamson relations, crystallite size were estimated and it was found to be in the range of 8-14 nm. The FTIR studies revealed the presence of different stretching and bending modes of Zn-O and Sn-O with an additional stretching and bending vibration of absorbed water （O-H） molecules. FESEM images suggested that the particle size lied in the range of 50 to 70 nm, which were almost spherical in shapes. A long range multi colour emission from blue to red region was observed for the 320 nm excitation wavelength. The observed emission involved sharp emission due to 5D0→7F1 transition that corresponded to the magnetic dipole transition. The study showed that the Eu3＋ doped nanocomposite was more suitable material than singly Eu3＋ doped ZnO and Eu3＋ doped SnO2 with enhanced opto-eleetronic and luminescence properties and potential applications in display devices.

Photocatalytic activity of Eu-doped ZnO prepared by supercritical antisolvent precipitation route:When defects become virtues

The aim of this work is to determine the structural and optical properties of Eu-doped ZnO powders prepared by supercritical antisolvent precipitation route(SAS)and to correlate the physico-chemical features with the photocatalytic activity under UV light.Raman and EPR spectroscopy highlight the introduction of novel defects(mainly singly and doubly ionized oxygen vacancies,and oxygen interstitials)on the Eu-doped ZnO samples,which confer higher hydrophilicity to the doped samples with respect to bare ZnO,as evidenced by FT-IR analysis.Additionally,photoluminescence spectra show that the presence of Eu^(3+) totally quenches the visible light emission typical of bare ZnO,which mainly results from the recombination of photogenerated holes at defective sites.The prepared samples were tested both for the photocatalytic degradation of crystal violet dye(CV)and for the partial oxidation of ferulic acid under UV irradiation.The photocatalytic activity results evidence of a higher ability of Eu-doped photocatalysts to degrade CV and ferulic acid,while higher selectivity values towards vanillin are obtained in the presence of bare ZnO.The higher activity of Eu-doped ZnO photocatalysts is linked to the stabilization of photogenerated holes and to their higher hydrophilicity,both brought by the generation of defective sites induced by the presence of Eu^(3+) ions within the ZnO lattice.