Rare-earth-activated, white-emitting phosphors normalCa2−x−ynormalAl2SinormalO7:xnormalCe3+ , ynormalTb3+ were prepared under a weak reducing atmosphere by conventional solid-state reaction and their luminescence properties under 352nm excitation were investigated in detail. normalCa2normalAl2SinormalO7:normalTb3+ shows excitation at short-UV wavelength light λex=241nm . normalCa2normalAl2SinormalO7:normalCe3+ , Tb3+ showed optimal excitation at long-UV light excitation λex=352nm . By incorporation of Ce3+ , an efficient energy transfer from Ce3+ to Tb3+ was found and generated white light under long-UV excitation. The emission spectra consisted of a blue band (∼419nm) and a green band (∼542nm) , the relative intensities of which changed with the rare earth dopant concentration x and y . As a result, the optimal concentration for the best luminescence intensity was obtained in normalCa2normalAl2SinormalO7:0.0075 Ce3+ , 0.030 Tb3+ , and the closest to daylight white emission was found with a composition of normalCa2normalAl2SinormalO7:0.0075 Ce3+ , 0.020 Tb3+ , which has chromaticity coordinates x=0.316 , y=0.336 . This is considered to be a potential white-emitting phosphor for white light-emitting diodes.

BackgroundXiao Yao San (XYS) is an herbal prescription which is used in the treatment of depression for thousands of years from Song dynasty in China (960–1127 A.D.), and is the bestselling and most popular herb formula for treating major depression. This study aimed to assess the chronic antidepressant effects of XYS and fluoxetine in depressed mice induced by chronic unpredictable mild stress (CUMS) and its association with  alterations in glutamate/glutamine cycle and glutamate transporters.MethodsMice in the control and model group were given 0.5 ml physiological saline by intragastric administration. Mice in two treatment groups were given XYS (0.25 g/kg/d) and fluoxetine (2.6 mg/kg/d), respectively. The depressive-like behaviors such as forced swim test (FST), sucrose preference test (SPT) and novelty-suppressed feeding (NSF) test were measured after mice exposed to CUMS for 21 days. Body weight, contents of glutamate and glutamine, glutamine/glutamate ratio that is usually thought to reflect glutamate/glutamine cycle, and the protein and mRNA expressions of glutamate transporters (excitatory amino acid transporter 1–2,GLAST/EAAT1 and GLT-1/EAAT2) were measured. The immunoreactivities of GLAST and GLT-1 in the hippocampus were also investigated.ResultsAfter CUMS exposure, mice exhibited depressive-like behaviors, body weight loss, increased glutamate level, decreased glutamine level, elevated glutamine/glutamate ratio, decreased GLT-1 protein expression and mRNA level, and decreased average optical density (AOD) of GLT-1 in the CA1, CA3 and DG in the hippocampus. These abnormalities could be effectively reversed by XYS or fluoxetine treatment. In addition, the study also found that GLAST expression in the hippocampus could not be altered by 21-d CUMS.ConclusionThe studies indicated that XYS may have therapeutic actions on depression-like behaviors induced by CUMS in mice possibly mediated by modulation of glutamate/glutamine cycle and glutamate transporter GLT-1 in the hippocampus.

The electronic structure of Ca 2 GeO 4 was calculated using the CASTEP code. Ca 2 GeO 4 shows an indirect optical bandgap with a bandgap energy of about 4.0 eV. Ce 3+ -activated Ca 2 GeO 4 phosphors were synthesized by a solid-state reaction method, and their photoluminescence properties were characterized. The excitation band of Ca 2 GeO 4 :Ce 3+ ,Li + ranges from 380 to 520 nm with a maximum intensity appearing at about 465 nm, which matches well with the emission of blue light-emitting diode chips. Through transitions from 5d to 4f ͑ 2 F 5/2 and 2 F 7/2 ͒ in Ce 3+ , Ca 2 GeO 4 :Ce 3+ ,Li + exhibits a broad yellow emission band in the wavelength range of 480-750 nm under 465 nm excitation. Compared to Y 3 Al 5 O 12 :Ce 3+ garnet, Ca 2 GeO 4 :Ce 3+ ,Li + shows a broader bandwidth ͑140 nm͒ and more saturation in red, which is favorable for white light-emitting diode conversion phosphors.Light-emitting diodes ͑LEDs͒ have drawn increasing attention in recent years, especially because Y 3 Al 5 O 12 :Ce 3+ garnet ͑YAG:Ce͒ was used for downconverting the radiation from blue LEDs to generate white light. 1 White LEDs have been greatly developed as a new generation of light source because they can offer benefits such as high brightness, long life, low power consumption, and environmentally-friendly characteristics. 2-5 At present, a crucial problem of white LEDs is that lamps based on YAG:Ce phosphors are inherently limited to a color correlated temperature ͑CCT͒ greater than 4500 K due to a lack of red spectral intensity, which hampers the use of these lamps in many general lighting applications. Blending red phosphors such as ͑Ca,Sr͒S:Eu 2+ and ͑Ba,Sr,Ca͒ 2 Si 5 N 8 :Eu 2+ with YAG:Ce improves performance in CCT, but causes color aberration due to the extreme difference in degradation between different hosts. 6,7 Therefore, in the past decade, attention has focused on developing a yellow-emitting phosphor which has more emission saturation in red than YAG:Ce. Up to now, several such phosphors based on nitride or oxynitride have been reported and have aroused great interest. 8-10 However, compared to oxide-based phosphors, most nitride-based phosphors suffer a relatively complex preparation process. Therefore, it is necessary to develop an oxide-based yellow-emitting phosphor for white LEDs, which is the aim of the present work.To the best of our knowledge, besides aluminate garnets such as YAG:Ce, the only oxide-based yellow-emitting phosphors that can be excited efficiently by blue lights are based on silicates, such as Sr 2 SiO 4 :Eu 2+ and Sr 3 SiO 5 :Ce 3+ ,Li + , in which a large crystal field splitting is observed for Eu 2+ and Ce 3+ , respectively. 11,12 Because Ge and Si are in the same main group of the periodic table, the same result can be expected in an analogous germanate. Therefore, we considered alkaline earth germanates to act as the host lattice for the phosphor. Among these germanates, Ca 2 GeO 4 is a good candidate due to its physical and chemical stability. Cr 4+ -doped Ca 2 GeO 4 single crystals h...

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