Materials Research Express
·
2019
·Vol. 6
·期 12
·125017
·
IF 1.449
Hanyu Yao,Honglie Shen,Quntao Tang
In this paper, Mn doped NaYF4:Er,Yb phosphors were successfully synthesized by a simple solvothermal method. According to the results of x-ray diffraction, scanning electron microscopy and photoluminescence measurement, Mn doping had a remarkable effect on the crystal phase, size, and especially upconversion (UC) properties of these phosphors. Under 980 nanometer (nm) laser excitation, the UC luminescence intensity could be enhanced by increasing Mn concentration. Temperature-dependence measurement of the samples from 300–30 K showed two green emission bands (2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of the Er3+ ion), which meant that the UC phosphors were suitable for temperature sensor by using the fluorescence intensity ratio (FIR) method. The FIR value decreased with temperature, and the experimental data were well fitted with a theoretical function. The higher maximum value of sensitivity (0.0057 K−1) for 20% Mn sample in contrast to that of 0% Mn one (0.0036 K−1) indicated that Mn doped sample had a higher sensitivity for temperature sensing. The results demonstrated that Mn doping would be a good way for optimizing the sensitivity of fluorescence-based temperature sensor.
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Results in Physics
·
2019
·
IF 3.042
Yang Zhou,Xiaoyuan Liu,Ke Wang,Jing Li,Xinglai Zhang,Xin Jin,Xinyue Tang,Xiuhui Zhu,Ruishi Zhang,Xin Jiang,Baodan Liu
Series of “Hopcalite” catalysts for low-temperature CO oxidation are prepared through a facile ultra-sonic spray pyrolysis approach. It has been found that the spray pyrolysis temperature and Cu/Mn atomic ratio in initial precursors show significant impacts on the catalytic activity of Cu-Mn-O catalysts. The catalyst synthesized at 550 °C with Cu/Mn = 1/2 in precursor (Cu1Mn2-550) shows the highest catalytic activity towards CO oxidation (T 100 = 63 °C; E a = 17.04 KJ mol −1 ), owing to the formation of CuMn 2 O 4 phase with poor crystallinity. The synergistic effect of Cu and Mn species in spinel Cu-Mn-O phases attributes to the evaluated catalytic activity compared with those of pure oxides of copper or manganese towards CO oxidation. The results reveal that Cu1Mn2-550 not only provides more defects and vacancies to create more active sites, but also generates more highly active Cu (II) to promote CO oxidation. On the contrary, the decreasing amount of Cu (II) and the higher degree of crystallinity resulting from higher synthesis temperature lead to the deterioration of catalytic activity. Moreover, the phase transformation among the Cu x Mn 3-x O 4 spinels also shows significant effect on CO conversion rate. Finally, the formation mechanism of Cu-Mn-O catalysts and related CO oxidation process are discussed based on series of characterizations.
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NANO
·
2019
·
IF 1.293
Renxin Xu,Huan Yang,Huajun Sun,Jing Zhou,Zhijun Yue,Xinhua Gao
Mg 0 . 2 Mn 0 . 8 Y x Fe 2 − x O 4 ( x = 0 . 0 0 0 , 0.025, 0.050 and 0.075) nanocrystalline is synthesized via hydrothermal technique. Single cubic spinel phase is confirmed by XRD and the formation of Mg 0 . 2 Mn 0 . 8 Y x Fe 2 − x O 4 is verified by EDS. The average size of the nanoferrites is around 80 nm, which is examined by TEM image. Y 3 + substituted Mg-Mn nanoferrites exhibit low saturation magnetization ( M s ) and coercivity ( H c ) . Especially, the nanoferrites with x = 0 . 0 7 5 show the lowest M s and H c of 46.96 emu/g and 12.04 Oe, respectively. The ferrite composites present that the resistivity and the magnetic loss are less than 4 . 5 × 1 0 7 Ω ⋅ cm and 0.7 in the range of 2–18 GHz, respectively. The low coercivity and high resistivity indicate that the addition of Y 3 + contributes to the synthesis of the excellent soft magnetic materials.
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ELECTROCHIMICA ACTA
·
2019
·
IF 5.383
Qiujun Li,Hua Yao,Feng Liu,Zitao Gao,Yangyi Yang
A new Mn-doped coordination supramolecular network (CSN) was synthesized on nickel foam directly by a simple one-step hydrothermal method . Compared with the pure CSN electrode (∼2.46 C cm −2 at 10 mA cm −2 ), this Mn-doped binder-free electrode showed an ultrahigh areal capacity (∼8.12 C cm −2 at 10 mA cm −2 ). In addition, when the current density increased from 10 mA cm −2 to 50 mA cm −2 , it had a good rate capability with 73.33% capacitance retention. For practicality, an asymmetrical supercapacitor (ASC) was assembled by Activated Carbon (AC) electrode and the Mn-doped CSN electrode. The device not only could achieve a maximum energy density of 3.41 mW h cm −3 at the power density of 44.98 mW cm −3 , but also could exhibit excellent stability after 4000 cycles, with the capacitance retention of 90.14%. The above results indicate that the Mn-doped CSNs are promising electrode materials for supercapacitors in energy storage.
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Water
·
2019
·Vol. 11
·期 11
·2302
·
IF 2.524
Dingyun Yan,Zhe Sun,Jiajie Wang,Lili Wang,Ruijun Pan,Qiang Wu,Xiaowei Liu
Mn(III) oxidation technology has attracted increasing interest in recent years because of its fast decontamination kinetics and second-pollution-free characteristic. Whether it can be used as a pre-oxidation step to enhance conventional coagulation process remains to be evaluated. Herein, an Fe-coagulation/sedimentation process combined with Mn(III) pre-oxidation (Mn(III)+C/S), hypochlorite pre-oxidation (Cl2+C/S), and permanganate pre-oxidation (PM+C/S) was applied to treat simulated micro-polluted raw water. The removal performance of routine water quality indices (turbidity, dissolved organic carbon, total nitrogen, nitrate-nitrogen, ammonia-nitrogen, Pb(II), and Cr(VI)) and the emerging pollutants (acesulfame, carbamazepine, bisphenol S, and nano-ZnO) created by these three processes were researched. The mechanism of how Mn(III) pre-oxidation influences C/S was explored by identifying the transformation products of Mn(III), measuring the timely variation of flocs’ zeta potential and size, and scanning flocs’ micromorphology. Compared to Cl2+C/S and PM+C/S, Mn(III)+C/S exhibited its superiority in removing dissolved organic carbon (72.9%), total nitrogen (31.74%), and emerging pollutants (21.78%–93.49%). The enhanced removal of these contaminants by Mn(III)+C/S found its explanation in the strong oxidation power of Mn(III) and the multiple roles of in-situ formed MnO2(e.g., flocculation core, adsorption co-precipitant, and densification agent). The acute toxicity tests confirmed that water treated by Mn(III)+C/S did not show a significant change in the associated toxicity. The findings of the present study indicate that Mn(III) oxidation technology shows great potential as an alternative to pre-oxidation technology of waterworks.Keywords:pre-oxidation;enhanced coagulation;Mn(III);emerging pollutants;micro-polluted raw water
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MATERIALS RESEARCH BULLETIN
·
2019
·
IF 3.355
Lijun Zhu,Hao Cheng,Jianfeng Ma,Yong Kong,Yong Qin,Sridhar Komarneni
Decolorization of methyl orange (MO) by MnO 2 was investigated with and without small molecules of organic acids such as formic acid. It was found that the decolorization could be significantly improved by MnO 2 with the assistance of organic acids. The effect of various conditions was investigated on MO decolorization by using different crystal types of MnO 2 and changing the types of organic acids. One of the optimum treatment conditions was δ-MnO 2 /formic acid system, which led to the removal efficiency of 90.6% at 30 min. The pseudo-second-order kinetic rate constant of δ-MnO 2 /formic acid was 0.1626. A reasonable decolorization mechanism involving Mn(III) species was proposed and the mechanism was validated by simple detection of ionic species such as, Mn(II) and Mn(III) during the reaction. The δ-MnO 2 /formic acid process designed here may lead to a new advanced oxidation technology based on the in-situ generation of active Mn(III) species and their ability for oxidation.
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Materials Research Express
·
2018
·Vol. 5
·期 6
·066106
·
IF 1.151
Renxin Xu,Huan Yang,Huajun Sun,Yueli Liu,Huan Zhou,Jianchun Liu
Mg0.2Mn0.8HoxFe2−xO4 (x = 0.025, 0.050, 0.075 and 0.100) nanocrystalline is synthesized via a hydrothermal technique. Single phase cubic spinel is confirmed by XRD and the formation of Mg0.2Mn0.8HoxFe2−xO4 is verified by EDS. The average size for the nanoferrites is around 80 nm which is examined by TEM with the presence of agglomerated particles. Ho3+ substituted Mg-Mn nanoferrites exhibit the low saturation magnetization (Ms) and coercivity (Hc). Especially, with x = 0.100, the nanoferrites show the lowest Ms and Hc of 46.850 emu g−1 and 46 Oe, respectively. The ferrite composites present the dielectric dissipation less than 0.37 and the magnetic loss less than 0.46 at 2–18 GHz. The low saturation magnetization, low coercivity and low dielectric dissipation indicate that the addition of Ho3+ contributes to synthesize better soft magnetic materials.
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Journal of Earth Science
·
2019
·Vol. 30
·期 4
·861-869
·
IF 1.784
Zhang Caixiang,Liao Xiaoping,Lü You,Nan Chao
The ligand-stabilized soluble Mn(III) recognized as active intermediate can potentially mediate the attenuation of contaminants. In this study, the abiotic degradation behaviors of methyl parathion in the ligand stabilized Mn(III)-sulfite system were investigated. The results showed that the yield of soluble Mn(III) produced from the redox reaction of MnO 2 and oxalic acid was dependent linearly on the dosage of MnO 2 and caused the decomposition of methyl parathion up to 50.1% in Mn(III)-sulfite system after 30 minutes. The fitted pseudo-first-order reaction constants of methyl parathion degradation increased with the increasing of the amount of produced Mn(III) but was not effected linearly by the addition of sulfite. Other ligands, including pyrophosphate and oxalic acid, acted as effective complexing agents to stabilize soluble Mn(III), and exhibited competitive effect on methyl parathion degradation with sulfite. The formation of Mn(III)-sulfite complexes is the critical step in the system to produce abundant reactive oxygen species identified as SO 3 • - to facilitate methyl parathion degradation. The hydrolysis and oxidation of methyl parathion were acknowledged as two primary transformation mechanisms in Mn(III)-sulfite system. These findings indicate that naturally ligands-stabilized soluble Mn(III) can be generated and could oxidatively decompose organophosphate pesticides such as methyl parathion.
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MATERIALS CHEMISTRY AND PHYSICS
·
2018
·
IF 2.21
Zhixiang Jiang,Yue Zhao,Ping Yang
Wire-in-tube and tube-in-tube structures have been prepared using single-spinneret electrospinning method through adjusting the preparation parameters of precursors and subsequent calcined process. Cobalt ferrite (CoFe 2 O 4 ) samples revealed wire-in-tube morphology using a Co/Fe molar ratio of 1/2. In the case of other a Co/Fe molar ratio, belt and porous fiber morphologies were created. Manganese ferrite (MnFe 2 O 4 ) sample exhibited tube-in-tube structure while nickel ferrite (NiFe 2 O 4 ) sample just exhibited tube structure. Because of no template in electrospun polymer composite nanofibers , the precursor diffusion process during calcination plays an important role for morphology controlling. The magnetic properties of samples were examined. The cobalt ferrite (CoFe 2 O 4 ) wire-in-tube sample revealed the highest saturation magnetization (60 emu/g). After growing with AlOOH on the surface, CoFe 2 O 4 wire-in-tube sample revealed a high efficiency for the removal of Congo red pollutant. These nanostructures are particularly attractive for use in the field of nano-fluidic and nano-energy harvesting devices.
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ChemNanoMat
·
2018
·Vol. 4
·期 5
·487-495
·
IF 3.173
Zhinian Li,Shenliang Wang,Wei Hong,Shihui Zou,Liping Xiao,Jie Fan
Graphical Smart screens : An intelligent approach was developed to screen Na−Mn−W/SiO 2 catalysts for the oxidative coupling of methane (OCM). Effective composition regions other than the standard composition were successfully excavated. The wide range of the optimal composition allowed a fluctuation of composition during the reaction, which secured its excellent stability in the OCM reaction. Optimizing the performance and understanding the mechanism of metal oxide catalysts in the oxidative coupling of methane (OCM) is one of the most important projects in industrial catalysis. Here, we report an intelligent approach to screen Na−Mn−W/SiO 2 catalysts for the OCM reaction via ink-jet printing and multidimensional group testing. The ink-jet-printing-assisted (IJP-A) synthetic methodology ensured a fast synthesis of 1536 catalysts that were evaluated in 24 tests via a multidimensional group testing strategy (m-GT). After two-round synthesis-and-screening processes, several excellent groups with different composition space were screened out. Among the excellent catalysts, the OCM performance of Na−Mn−W/SiO 2 catalyst with higher Na, Mn and W content (G3 and G7) was less sensitive to its constituent than that of Na−Mn−W/SiO 2 catalyst with lower Na, Mn and W content (G1). These results indicated the sensitivity of performance to its Na, Mn and W content decreased in larger Na, Mn and W spaces, consistent with the complex homogeneous/heterogeneous reaction mechanism and multi-active sites. A series of Na−Mn−W/SiO 2 formulas with good performance also provide a reasonable explanation to its excellent stability for the OCM reaction. In addition, this intelligent optimization in total space offers a pathway to study the multicomponent metal oxide catalyst in the OCM reaction.
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JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2013
·Vol. 25
·期 2
·754-759
·
IF 1.486
Liu Lu,Huang Miaoliang,Lan Zhang,Wu Jihuai,Shang Guanglu,Liu Guijing,Lin Jianming
Mn-doped CdS quantum dot sensitized solar cells based on SnO 2 microsphere photoelectrodes are prepared with successive ionic layer adsorption and reaction method. It is found that with Mn-doped CdS quantum dot sensitizers, the photovoltaic performance of the cells based on SnO 2 microsphere photoelectrodes can obviously be enhanced. The reasons are owing to the improved light absorption and the expanded light absorption edge by doping Mn in CdS quantum dots. The electrochemical impedance spectroscopy analysis found that the cells with Mn-doped CdS quantum dot sensitized SnO 2 microsphere photoelectrodes can efficiently suppress dark reaction, owing to the increased related resistance. Moreover, it is also found that the Mn-doped CdS quantum dot sensitized SnO 2 microsphere photoelectrode can increase the electron diffusion lifetime in the cell. The power conversion efficiency of the cell with 4 wt% Mn-doped CdS quantum dot sensitizers can attain to 2.80 %, with 53 % enhancement compared with that of the CdS quantum dot sensitized cell (1.83 %).
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LUMINESCENCE
·
2013
·Vol. 29
·期 2
·151-157
·
IF 1.273
Wei Bian,Jing Ma,Qiaoling Liu,Yanli Wei,Yingfu Li,Chuan Dong,Shaomin Shuang
N -acetyl- l -cysteine-capped Mn-doped ZnS quantum dots (QDs) were prepared by hydrothermal methods. It could emit phosphorescence at 583 nm with the excitation wavelength at 315 nm. The phosphorescence intensity of QDs could be quenched dramatically by increasing the concentration of Co 2+ ion. The novel phosphorescence sensor based on N -acetyl- l -cysteine-capped QDs was developed for detecting Co 2+ ion with a linear dynamic range of 1.25 × 10 –6 –3.25 × 10 –5 m . The limit of detection and RSD were 6.0 × 10 –8 m and 2.3%, respectively. Interference experiments showed excellent selectivity over numerous cations such as alkali, alkaline earth and transitional metal ions. The possible quenching mechanism was also examined by phosphorescence decays. The proposed phosphorescence method was further applied to the trace determination of Co 2+ ion in tap and pond water samples with recoveries of 97.75–103.32%. Copyright © 2013 John Wiley & Sons, Ltd.
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