Co-reporter:Xuemei Zhu, Zhufa Zhou
Journal of Luminescence 2017 Volume 188(Volume 188) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jlumin.2017.05.003
A series of novel tunable green-yellow-red emitting Na2MgSiO4(NMSO): Tb3+, Eu3+ phosphors have been synthesized by a traditional solid state reaction. The PL and PLE properties of NMSO: Tb3+, Eu3+ have been investigated. Under excitation at 376 nm, the phosphors exhibit the characteristic of Tb3+ and Eu3+ emissions with the strongest peaks located at 546 nm (green) and 615 nm (red), respectively. Moreover, the emission intensities of both Tb3+ and Eu3+ remarkably vary with Eu3+ concentration, and the optimized doping concentration of Tb3+ ions and Eu3+ ions were confirmed to 4.00% mol and 0.10% mol, respectively. The dominating energy transfer from Tb3+ to Eu3+ in the NMSO host were investigated and the mechanism was demonstrated to be the resonant type via a non-radiative dipole–dipole interaction. The critical distances between donor-activator was calculated to be 16.76 Å. The hues of the studied phosphors can be tuned in the novel single-phase NMSO host by varying the ratio of Eu3+ to Tb3+ ions. All the results indicating that the phosphor may potentially be used as a tunable green-yellow-red emitting phosphor for UV light-emitting diodes.
Co-reporter:Yuanlin Yao, Zhufa Zhou, Feng Ye
Journal of Alloys and Compounds 2017 Volume 712(Volume 712) pp:
Publication Date(Web):25 July 2017
DOI:10.1016/j.jallcom.2017.04.102
•Sunlight-activated phosphor Ba5Si8O21:Eu2+, Nd3+ was prepared by sol-gel.•PVP/Ba5Si8O21:Eu2+, Nd3+ fiber was prepared by electrospinning for the first time.•The structure, luminescence, morphology of the phosphor and fiber was studied.In this study, a sunlight-activated Ba5Si8O21:Eu2+, Nd3+ (BSEN) persistent luminescent particles were firstly synthesized by sol-gel method, and then combined with polyvinyl pyrrolidone (PVP) to fabricate one-dimensional functional fiber by electrospinning. XRD, photoluminescence, fluorescence microscope, SEM and TEM were used to investigate the crystal structure, the morphology, the luminescent properties and water resistance of BSEN particles and functional fibers. The results show that BSEN owns a monoclinic crystalline and can be effectively and repeatedly excited by both ultraviolet and sunlight. The BSEN particles were water-resistant and uniformly dispersed in the PVP fibers. Both BSEN particles and functional fibers possessed broad excitation spectra from 250 nm to 450 nm with maximum at 341 nm and exhibited a fluorescent and phosphorescent emission band from 365 nm to 650 nm with maximum at around 489 nm with long afterglow up to 240 min. The new functional fiber has potential to be used in flexible coating, textile and optical display.
Co-reporter:Xu Liu;Guangxin Duan;Weifeng Li;Ruhong Zhou
RSC Advances (2011-Present) 2017 vol. 7(Issue 60) pp:37873-37880
Publication Date(Web):2017/07/28
DOI:10.1039/C7RA06442J
The antibacterial activities of tungsten disulfide (WS2) nanosheets against two representative bacterial strains: Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were evaluated by colony-forming unit (CFU) studies. The WS2 samples demonstrate a time and concentration dependent antibacterial activity (retardation of bacterial growth) for both bacterial strains. Morphology analyses reveal that WS2 nanosheets adhere to the bacterial surfaces, resulting in robust inhibition of cell proliferation once a bacterium is fully covered with this nanomaterial. More importantly, the intimate contact of WS2 nanosheets with a bacterium cell membrane can cause serious damage to the membrane integrity, and subsequently the cell death. On the other hand, the reactive oxygen species (ROS) generated by WS2 nanosheets are found to be modest regardless of the WS2 concentration, which is contradictory to the case of its structural analogue, MoS2, where ROS also play a significant role in its antibacterial activity. Taken together, our findings provide a detailed understanding of the antibacterial mechanism of WS2 nanosheets, which might help promote their potential applications in biomedical fields.
Co-reporter:Yuanlin Yao, Zhufa Zhou
Journal of Luminescence 2016 Volume 179() pp:408-412
Publication Date(Web):November 2016
DOI:10.1016/j.jlumin.2016.07.013
A novel red phosphor Ba2Si4O10: Eu3+ was synthesized by the high-temperature solid state reaction method in air atmosphere. The crystal results reveal that Ba2Si4O10 has two different phases, in which the high-temperature phase belongs to monoclinic system and exhibits better photoluminescence property compared with low-temperature phase. The monoclinic Ba2Si4O10 was obtained at 1250 °C and matched well with the JCPDS Card No. 83-1446. Photoluminescence excitation and emission spectra, fluorescence lifetime and quantum yield are conducted to investigate the luminescent property of Ba2Si4O10: Eu3+ phosphor. The results show that the phosphor can be excited by 393 nm light (7F0→5L6) effectively and emit a strong red emission at 612 nm (5D0→7F2). The optimal concentration of Eu3+ ions in Ba2Si4O10 matrix is 0.02, where the fluorescence lifetime was 1.0837 ms and the quantum yield was up to 31.64%. Additionally, the chromaticity coordinates of the optimal composition Ba1.98Si4O10: 0.02Eu3+ phosphor is calculated to be (0.65, 0.34). These results suggest that Ba2Si4O10: Eu3+ phosphor could be a potential red phosphor for practical application and optical devices.
Co-reporter:Xuemei Zhu, Yuanlin Yao, Zhufa Zhou
Optical Materials 2016 Volume 62() pp:104-109
Publication Date(Web):December 2016
DOI:10.1016/j.optmat.2016.09.054
•A novel green phosphor Na2MgSiO4:Mn2+ was successfully synthesized at 950 °C.•Na2MgSiO4:Mn2+ phosphors showed green emission with the broad-band peak at 520 nm, the optimum Mn2+ concentration was 8 mol%.•The crystal structure, energy transfer and color chromaticity properties of Na2MgSiO4:Mn2+ green emitting phosphors have been investigated in detail.In this paper, a novel green phosphor Na2Mg1-xSiO4:xMn2+ (x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.15, 0.20) was successfully synthesized by a traditional solid-state reaction method at 950 °C. The powder X-ray diffraction (PXRD), the photoluminescence excitation and emission spectra (PL and PLE) were measured to systematically study the as-prepared phosphors. The as-obtained Na2MgSiO4:Mn2+ phosphor shows an intense asymmetric green emission spectra with the broad-band peak at 520 nm due to 4T1(4G) → 6A1(6S) transition of the Mn2+ ion. The optimum Mn2+ concentration in this phosphor was 8 mol%. The MnMn critical distance was calculated to be 13.42 Å. The dipole–dipole interaction dominates in the non-radiative energy transfer between the Mn2+ ions and causes the concentration quenching. The decay curve of the Na2MgSiO4:Mn2+ phosphors were discussed. The CIE chromaticity coordinate values (x = 0.163, y = 0.631) of Na2MgSiO4:0.08Mn2+ phosphor were located in green region and the correlated color temperature was 8643 K. The above results indicate that Na2MgSiO4: Mn2+ as a green component can be a good candidate for near UV-excited w-LEDs.
Co-reporter:Qiru Li;ShanShan Liu;Xingxing Zhang
Ionics 2016 Volume 22( Issue 7) pp:1027-1034
Publication Date(Web):2016 July
DOI:10.1007/s11581-016-1636-y
FePO4·xH2O/graphene oxide (FePO4·xH2O/GO) composites were prepared by a facile chemical precipitation method. Using the as-prepared FePO4·xH2O/GO and LiOH·H2O as precursors and followed by carbothermal reduction, LiFePO4/graphene composites were obtained. Scanning electron microscope (SEM) images indicated that the graphene had very good dispersity and uniformly attached to the LiFePO4 particles. The conductive framework of graphene improved the electrochemical properties of the composites. The composites deliver high initial discharge capacity of 163.4 mAh g−1 as well as outstanding rate performance.
Co-reporter:Feng Ye, Shengjie Dong, Zhe Tian, Sijia Yao, Zhufa Zhou, Shumei Wang
Optical Materials 2015 Volume 45() pp:64-68
Publication Date(Web):July 2015
DOI:10.1016/j.optmat.2015.03.011
•Long-persistent luminescent particles of Ca1.97MgSi2O7:0.01Eu2+, 0.02Dy3+ were synthesized by sol–gel.•One-dimensional Ca2MgSi2O7:Eu2+, Dy3+/PLA composite fibers were fabricated by electrospinning.•The composite fibers have properties of fluorescence and long-persistent luminescence.•The as-prepared one-dimensional fiber has been characterized by fluorescence microscope for the first time and distinct photographs have been obtained.Long-persistent luminescence /polymer (Ca2MgSi2O7:Eu2+, Dy3+/PLA) composite fibers have been fabricated via electrospinning method. The as-prepared one-dimensional fiber has been characterized by fluorescence microscope and distinct photographs have been obtained. The results show that the Ca2MgSi2O7:Eu2+, Dy3+ particles (12 wt%, size 200 nm) are uniformly dispersed in the PLA fibers (diameter 2.5 μm). It was found that the composite fibers have an emission band from 430 nm to 650 nm that peaks at 537 nm and 452 nm. Similarly, its phosphorescent emission spectra have similar features of luminescence (emission band from 430 nm to 650 nm that peaks at 537 nm and 452 nm). The decay curves of the composite fibers present a similar attenuate tendency with Ca2MgSi2O7:Eu2+, Dy3+ pure particles, but with lower intensity. The composite fiber has applications possibility in textile, display, optical detectors, indicator in the dark without electric energy which they never had before.
Co-reporter:Zhe Tian, Zhufa Zhou, Shanshan Liu, Feng Ye, Sijia Yao
Solid State Ionics 2015 Volume 278() pp:186-191
Publication Date(Web):1 October 2015
DOI:10.1016/j.ssi.2015.06.017
•Nb and Ti co-doping LiFePO4/graphene is first synthesized successfully by sol–gel method.•Among all samples, Li0.99Nb0.01Fe0.97Ti0.03PO4/G shows the best rate capability and cycling stability.•Nb and Ti co-doping and graphene coating can enhance LiFePO4 properties greatly.Nanostructured LiFePO4 powder with a narrow size distribution (~ 100 nm) has been obtained using a sol–gel method with graphene as coating, and applied in high efficiency lithium-ion battery cathode. During preparation of LiFePO4 precursor, Nb5 + and Ti4 + were added to get a sufficient and homogenous doping. Through X-ray diffraction (XRD), scanning electron microscope (SEM), charge/discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) characterization, the influence of supervalent metal doping and graphene coating on the structure and performance of LiFePO4 was studied. Li0.99Nb0.01Fe0.97Ti0.03PO4/graphene cathode delivers a discharge capacity (163 mAh g− 1 at 0.1 C) close to the theoretical value with excellent capacity retention (99.1% after 30 cycles) and rate capability (140 mAh g− 1 after discharged at 0.1 C, 2 C, 5 C stepwise). The results indicate that both ion-doping and graphene-coating are effective to improve the electrochemical performance of lithium ion battery.
Co-reporter:Dongchen Wu, Fuwei Mao, Zhihui Yang, Shumei Wang, Zhufa Zhou
Materials Science in Semiconductor Processing 2014 Volume 23() pp:72-77
Publication Date(Web):July 2014
DOI:10.1016/j.mssp.2014.02.040
Silicon and aluminum co-doped titania (TiO2) nanoparticles were fabricated by the sol–gel method. To investigate the effects of silicon and aluminum co-doping on thermal stability, microstructure and photocatalytic activity of TiO2 nanoparticles. Six batches of silicon-aluminum doped samples were characterized by X-ray diffraction (XRD), BET surface area measurement, scanning electron microscopy (SEM) and UV–vis absorption spectra. The photocatalytic activities were evaluated by the degradation of methylene blue (MB) under UV light irradiation. Experimental results revealed that silicon and aluminum co-doping helped to improve the crystal phase transition temperature of titania to 1200 °C and also decrease the particle size at high calcination temperature. A significant blue-shift was observed in the spectrum of UV–vis absorption. Additionally, it was found that silicon and aluminum co-doping exhibited better photocatalytic activity. The formation defects from solid solution reaction between Si4+, Al3+ and TiO2 effectively inhibits the crystal phase transition and grain growth of TiO2 nanoparticles.
Co-reporter:Fuwei Mao;Dongchen Wu;Shumei Wang
Ionics 2014 Volume 20( Issue 12) pp:1665-1669
Publication Date(Web):2014 December
DOI:10.1007/s11581-014-1143-y
In this study, LiFe1 − 3x/2BixPO4/C cathode material was synthesized by sol–gel method. From XRD patterns, it was found that the Bi-doped LiFePO4/C cathode material had the same olivine structure with LiFePO4/C. SEM studies revealed that Bi doping can effectively decrease the particle sizes. It shortened Li+ diffusion distance between LiFePO4 phase and FePO4 phase. The LiFe0.94Bi0.04PO4/C powder exhibited a specific initial discharge capacity of about 149.6 mAh g−1 at 0.1 rate as compared to 123.5 mAh g−1 of LiFePO4/C. EIS results indicated that the charge-transfer resistance of LiFePO4/C decreased greatly after Bi doping.
Co-reporter:Lixiu Gong;Shumei Wang;Ben Wang
Journal of Applied Polymer Science 2013 Volume 129( Issue 3) pp:1212-1217
Publication Date(Web):
DOI:10.1002/app.38728
Abstract
Porous ultrahigh-molecular-weight polyethylene (UHMWPE)-based composites filled with surface-modified Ce-doped TiO2 nanoparticles (Ce–TiO2/UHMWPE) were prepared by template dissolution. The composites were characterized by Fourier transform infrared spectroscopy, ultraviolet (UV)–visible spectroscopy, diffuse reflectance spectra, and scanning electron microscopy); the photocatalytic activity was also evaluated by the decomposition of methyl orange under UV exposure. The results demonstrate that the severe aggregation of Ce–TiO2 nanoparticles could be reduced by surface modification via a silane coupling agent (KH570). The Ce–TiO2/UHMWPE porous composites exhibited a uniform pore size. Doping with Ce4+ effectively extended the spectral response from the UV to the visible region and enhanced the surface hydroxyl groups of the TiO2 attached to the matrix. With a degradation rate of 85.3%, the 1.5 vol % Ce–TiO2/UHMWPE sample showed the best photocatalytic activity. The excellent permeability of the porous composites is encouraging for their possible use in wastewater treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Lixiu Gong, Zhufa Zhou, Shumei Wang, Ben Wang
Materials Science in Semiconductor Processing 2013 Volume 16(Issue 2) pp:288-294
Publication Date(Web):April 2013
DOI:10.1016/j.mssp.2012.10.009
BiFeO3@TiO2–Ce composite nanoparticles with a BiFeO3 core and a Ce-doped TiO2 shell structure were fabricated via a sol–gel method. The nanoparticles were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results reveal that core-shell structured BiFeO3@TiO2–Ce nanoparticles show a significant redshift in the UV–vis absorption spectra in comparison with both Ce-TiO2 and BiFeO3@TiO2 nanoparticles. The photocatalytic activities of the samples were tested in the degradation of methyl orange in aqueous solutions under visible light and UV light irradiations. The core-shell structured BiFeO3@TiO2–Ce sample exhibits higher photocatalytic activity, which is attributed to the synergistic effects of BiFeO3 and cerium.
Co-reporter:Feng Ye, Shengjie Dong, Zhe Tian, Sijia Yao, Zhufa Zhou, Shumei Wang
Optical Materials 2013 Volume 36(Issue 2) pp:463-466
Publication Date(Web):December 2013
DOI:10.1016/j.optmat.2013.10.019
Co-reporter:Ben Wang, Shumei Wang, Lixiu Gong, Zhufa Zhou
Ceramics International 2012 Volume 38(Issue 8) pp:6643-6649
Publication Date(Web):December 2012
DOI:10.1016/j.ceramint.2012.05.051
Abstract
A novel ultrasonic irradiation assisted self-combustion method was developed to prepare single-phase Bi1−xSrxFeO3−δ (BSFO) nanoparticles, which were charactered by XRD, SEM, TEM and UV–vis spectra. The results show that structure, as well as magnetic and photocatalytic properties of BSFO are influenced by the particle size and the Sr2+ dopant content. Regarding smaller particles, even if small amount of Sr2+ substitution content change can result in the phase transition from the rhombohedral distorted perovskite to the cubic. The doping of heterovalent Sr2+ ions in BiFeO3 (BFO) nanoparticles improves the ferromagnetic property. As ultrasonication can generate particles with larger surface area and more defections, BSFO nanoparticles exhibit efficient photocatalytic activity as a promising photocatalyst.
Co-reporter:Xinshuang Guo, Zhufa Zhou, Guilin Ma, Shumei Wang, Song Zhao, Qiang Zhang
Ceramics International 2012 Volume 38(Issue 1) pp:713-719
Publication Date(Web):January 2012
DOI:10.1016/j.ceramint.2011.07.062
Abstract
Pore-gradient Al2O3 foams were produced by gelcasting using the epispastic polystyrene (EPS) sphere template. This approach allows the design of porous ceramics with degree of pore connectivity and height of gradient layers via appropriate selection of the sizes and numbers of spheres. The fabrication processing of open-cell porous ceramics limited by polymeric sponge template, sharp cracks at the strut edges and closed pores can be resolved by this approach. To achieve the optimal manufacturing conditions of maintaining integrity of the network, the effects of solid loads, height of the slurry and the pre-removal of the polymeric foam template on the struts of the ceramic foams were studied. The results revealed that 55 vol.% Al2O3 slurries with 0.5 wt.% ammonium polyacrylate kept good fluidity for casting and avoided the inner inordinate shrinkage. Different shrinkage behavior of the top and bottom of the sample was effectively reduced due to approximately same water vapor diffusion areas on the top and bottom. The integrity of dendritic solidification structure maintained perfectly through template pre-removed in dichloromethane compared with direct heating.
Co-reporter:Qiang Zhang, Wenwen Jiang, Zhufa Zhou, Shumei Wang, Xinshuang Guo, Song Zhao, Guilin Ma
Solid State Ionics 2012 Volume 218() pp:31-34
Publication Date(Web):22 June 2012
DOI:10.1016/j.ssi.2012.05.006
In this study, Li4SiO4-coated LiFePO4 cathode material was synthesized by sol–gel method and microwave heating. The structure and electrochemical properties of the prepared cathode at room temperature were investigated. The XRD results indicate that the Li4SiO4 coating modification does not affect the structure of LiFePO4 and the Li4SiO4-coated LiFePO4 cathode material still has olivine structure. The TEM image reveals that the Li4SiO4 coating is a nanoscale amorphous layer. The electrochemical measurements of Li4SiO4-coated LiFePO4 show that the discharge capacity, cycling stability and interfacial resistance are improved by the Li4SiO4 coating. Thus, surface coating with Li4SiO4 is a feasible approach for enhancing the electrochemical performance of LiFePO4.Highlights► Li4SiO4-coated LiFePO4 was prepared by sol-gel method and microwave heating. ► The existence of Li4SiO4 coating effectively enhanced the discharge capacity. ► The Li4SiO4 coating enhanced the cycling performance of LiFePO4.
Co-reporter:Qiang Zhang, Shumei Wang, Zhufa Zhou, Guilin Ma, Wenwen Jiang, Xinshuang Guo, Song Zhao
Solid State Ionics 2011 Volume 191(Issue 1) pp:40-44
Publication Date(Web):2 June 2011
DOI:10.1016/j.ssi.2011.03.025
To further improve the electrochemical performance of LiFePO4/C, Nd doping has been adopted for cathode material of the lithium ion batteries. The Nd-doped LiFePO4/C cathode was synthesized by a novel solid-state reaction method at 750 °C without using inert gas. The Li0.99Nd0.01FePO4/C composite has been systematically characterized by X-ray diffraction, EDS, SEM, TEM, charge/discharge test, electrochemical impedance spectroscopy and cyclic stability. The results indicate that the prepared sample has olivine structure and the Nd3+ and carbon modification do not affect the structure of the sample but improve its kinetics in terms of discharge capacity and rate capability. The Li0.99Nd0.01FePO4/C powder exhibited a specific initial discharge capacity of about 161 mAh g− 1 at 0.1 C rate, as compared to 143 mAh g− 1 of LiFePO4/C. At a high rate of 2 C, the discharge capacity of Li0.99Nd0.01FePO4/C still attained to 115 mAh g− 1 at the end of 20 cycles. EIS results indicate that the charge transfer resistance of LiFePO4/C decreases greatly after Nd doping.Research Highlights► The Nd-doped LiFePO4/C was successfully synthesized without using inert gas. ► C coating and Nd doping are adopted to improve the performance of LiFePO4. ► Nd-doped LiFePO4/C exhibited excellent electrochemical performance.
Co-reporter:Zhufa Zhou 周竹发;Shumei Wang
Journal of Wuhan University of Technology-Mater. Sci. Ed. 2008 Volume 23( Issue 3) pp:309-311
Publication Date(Web):2008 June
DOI:10.1007/s11595-007-3309-1
Nanosized ZrO2 powder was prepared by evaporative decomposition of solution(EDS). The particle size is from 50 nm to 200 nm. This process has such advantages as high purity, precise compositional control, simple procedure and successive auto-operating. In this process, mixed solution of zirconium acetate and yttrium nitrate was atomized to from a fine mist and blown into the hot zone from the bottom of furnace. The solution was rapidly decomposed at 900°C and the powder was collected by a filter system. The powder characteristics can be controlled by adjusting the concentration, droplet volume and decomposition temperature of the solution.
