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Zhang X.,Shandong University | Zhou G.,Shandong University | Zhou J.,Center for Disease Prevention and Control of Jinan Military Command | Zhou H.,Shandong University | And 2 more authors.
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2015

A single-phase blue-green light emitting phosphor, LaNbTiO6: Er3+, Li+, was synthesized by using a simple and facile sol-gel combustion approach. Its structure and photoluminescence (PL) properties were investigated as a function of Er3+ and Li+ ion concentration. The luminous mechanisms of the Er3+ doping and Er3+/Li+ co-doping in the LaNbTiO6 host were also discussed, including the intra-4f-transitions of Er3+ and the charge compensation of Li+. The incorporation of Li+ ions into LaNbTiO6 lattice further altered the local structure and symmetry of the crystals field around Er3+. Concentration quenching occurred when Er3+ and Li+ reached certain levels. Furthermore, the critical transfer distance of Er3+ → Er3+ in the phosphor was calculated. The absolute quantum efficiencies and the fluorescence decay time of the phosphors were studied. The phosphor produced blue-green light, presenting CIE chromaticity coordinates of (0.211, 0.277) and (0.214, 0.320). © 2014 Elsevier B.V. All rights reserved.


Du Q.,Shandong University | Zhou G.,Shandong University | Zhou J.,Center for Disease Prevention and Control of Jinan Military Command | Zhou H.,Shandong University | And 2 more authors.
Journal of Rare Earths | Year: 2012

CaZrO 3:Sm and CaZrO 3:Sm, Gd nanophosphors were synthesized by a facile and efficient sol-gel combustion method. Their structure and optical properties were studied. The photoluminesce (PL) results showed that the phosphor could be efficiently excited by irradiation at wavelengths in the visible light region (350-430 nm). The CaZrO 3:Sm nanophosphor exhibited strong yellow-green, orange and red emissions with peak wavelength centered at 565 nm ( 4G 5/2→ 6H 5/2), 601 nm ( 4G 5/2→ 6H 7/2) and 645 nm ( 4G 5/2→ 6H 9/2), respectively. The incorporation of Gd 3+ ions could greatly improve the luminescence intensity. The highest emission intensity was observed with 2 mol. Gd 3+ doped CaZrO 3:3 mol. Sm powder. The material had potential application in the development of materials for LED's and other optical devices in the visible region. © 2012 The Chinese Society of Rare Earths.


Zhou J.,Shandong University | Zhou J.,Center for Disease Prevention and Control of Jinan Military Command | Wang R.Q.,Shandong University | Guo W.H.,Shandong University | And 8 more authors.
Communications in Soil Science and Plant Analysis | Year: 2011

The aims of this study were to investigate soil microbial community characteristics and their interrelationships with soil geochemistry under different farmlands in Shouguang, China. The traditional dilution plate counts, BIOLOG system, and fatty acid methyl ester (FAME) analyses were used to assess microbial populations, substrate utilization, and fatty acid profiles. The number of aerobic heterotrophic bacteria varied significantly among untilled land, maize, and mungbean fields. The amounts of actinomycetes, fungal fatty acids, and Gram-positive/Gram-negative bacteria ratios varied greatly among celery, tomato, and aubergine fields. In the tomato field, the soil microbial community characteristics were significantly different from other fields. Principal component analysis of BIOLOG and FAME data revealed differences in the catabolic capability and fatty acid profiles of soil microbial communities among different farmlands. Spearman correlation analyses showed that in these sand clay soils of Shouguang, microbial communities in different farmlands were closely correlated with soil geochemical elements, moisture, and organic matter. © Taylor & Francis Group, LLC.


Du Q.,Shandong University | Zhou G.,Shandong University | Zhou J.,Center for Disease Prevention and Control of Jinan Military Command | Jia X.,Shandong University | Zhou H.,Shandong University
Journal of Alloys and Compounds | Year: 2013

Novel blue-white Y2Zr2O7:Dy3+, Li+ phosphors have been prepared by a facile and efficient sol-gelcombustion method at 800 °C, using ammonium nitrate as a fuel and citric acid as a complexing agent. No additional annealing was required, as crystalline Y2Zr2O7 resulted directly from the combustion reaction. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The photoluminescence properties were measured using an Edinburgh FLS920 at room temperature. Stable blue-white emission from 425 nm to 625 nm has been observed from Y 2Zr2O7:Dy3+ and Y2Zr 2O7:Dy3+, Li+ phosphors. The optimal doping concentration of Dy3+ ions is 2 mol%. Experimental analysis and theoretical calculations reveal that the dipole-quadrupole (d-q) interaction should be the major concentration quenching mechanism of Dy3+ ions emission. Li+ co-doping improves luminescence intensity as well as crystallinity significantly. The incorporation of Li+ ions into Y2Zr2O7 lattice could induce a remarkable increase of photoluminescence intensity by about 2 times. The mechanism of the enhanced emission by Li+ doping was discussed. Both the chromaticity coordinates of Y2Zr2O7:Dy3+ and Y2Zr2O7:Dy3+, Li+ samples were in the near cold-white region. © 2012 Elsevier B.V. All rights reserved.


Yu Z.,Shandong University | Zhou G.,Shandong University | Zhou J.,Center for Disease Prevention and Control of Jinan Military Command | Zhou H.,Shandong University | And 6 more authors.
RSC Advances | Year: 2015

YTiNbO6 phosphors doped with Er3+, Gd3+ were synthesized via a facile sol-gel and combustion approach. The crystal structure and particle morphology were characterized and the phonon energy was investigated in detail. The up-conversion emission excited at 980 nm and down-conversion emission excited at 378 nm of Er3+ with different concentrations were analysed. They both have strong green emission peaks at 522 and 552 nm but the red emission peak at 668 nm only appears in the up-conversion. Furthermore, the Er3+ quenching concentration for up-conversion is higher than that for down-conversion because the up-conversion is a complex multiple stepwise process which includes energy transfer, phonon-assisted energy transfer and excited state absorption that can cover a wider range of Er3+ doping concentrations. Moreover, the influence of co-doped Gd3+ on the morphology and particle size was also explored. Gd3+ had a great effect on the up and down conversion emission intensity as well as the decay time of up-conversion by changing the structure distortion, vibration frequencies and surface defects. © The Royal Society of Chemistry.

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