Characterization of Antioxidant Activity of Extracts from Flos Lonicerae

Antioxidants are emerging as prophylactic and therapeutic agents for various diseases. However, little is known about the antioxidant property of the extract from Flos Lonicerae, a medically useful traditional Chinese medicine herb. Here the antioxidant capacity of water, methanolic and 70% ethanolic extracts prepared from Flos Lonicerae to scavenge DPPH radical and reduce Fe³⁺ to Fe²⁺ is evaluated. Chlorogenic acid, a major component of Flos Lonicerae, is identified and further purified from 70% ethanolic extract with HPLC and its antioxidant capacity is also characterized. The content of total phenolic compounds and chlorogenic acid in Flos Lonicerae is determined. The present results demonstrate that all Flos Lonicerae extracts examined here exhibit antioxidant activity and chlorogenic acid is a major contributor to this activity, which implicates that the Flos Lonicerae extract may serve as potential source of natural antioxidants for treatment of some diseases.     

Assessment of electrical and optical properties of heavily Fe-implanted semi-insulating InP

We report total compensation of InP layers n-doped to levels as high as n=2×10¹⁸ cm⁻³ by high temperature (>200°C) MeV Fe implantation and annealing. The electronic density and the active Fe (in the form of the Fe²⁺/Fe³⁺ deep acceptor states) profiles are obtained from the comparison between the current–voltage (I–V) characteristics and the outcome of a numerical simulation. These results are confirmed by photo-induced current transient spectroscopy (PICTS) experiments, which show a correlation between the Fe activation and the background doping concentration. A deeper insight into the properties of the Fe²⁺/Fe³⁺ centers is gained by Fourier transform infrared (FTIR) photoluminescence measurements, showing intense and sharp emission peaks at 3.5 μm, associated with Fe intracenter transitions. The corresponding lifetimes have been studied by time resolved integrated photoluminescence measurements.     

Electron spin resonance and electrical conductivity of vanadate glasses

Electron spin resonance (ESR) and d.c. conductivity were measured for a series of vanadium borophosphate glasses before and after heat treatment. The ESR spectra showed the presence of vanadium in the V⁴⁺ state in all untreated and heat-treated samples free from iron. The variable temperature ESR and d.c. conductivity results obtained on the sample free from iron showed an inflexion at about 140°C. The electrical conductivity was found to decrease on substitution of 1 mol.% V₂O₅ by 1 mol.% Fe₂O₃ which may be due to a decrease in the V⁴⁺/V ratio. However, the electrical conductivity was found to increase on addition of more than 1 mol.% Fe₂O₃ which may be due to possible hopping conduction between Fe²⁺−Fe³⁺, V⁴⁺−Fe³⁺ and Fe²⁺−V⁵⁺. The increase in conductivity in the sample heat treated at 350°C relative to those heat treated at 300°C and 400°C may be due to the variation in the V⁴⁺/V total ratio. The activation energy values for untreated and heat-treated samples were calculated and were found to depend on the variation in the V⁴⁺/V ratio and the microstructure.     

Crystal structure, thermal expansion and electrical conductivity of Nd0.7Sr0.3Fe1−xCoxO3 (0≤x≤0.8)

The crystal structure, thermal expansion and electrical conductivity of the solid solution Nd_0.7Sr_0.3Fe_1−xCo_xO₃ for 0≤x≤0.8 were investigated. All compositions had the GdFeO₃-type orthorhombic perovskite structure. The lattice parameters were determined at room temperature by X-ray powder diffraction (XRPD). The pseudo-cubic lattice constant decreased continuously with x. The average linear thermal expansion coefficient (TEC) in the temperature range from 573 to 973 K was found to increase with x. The thermal expansion curves for all values of x displayed rapid increase in slope at high temperatures. The electrical conductivity increased with x for the entire temperature range of measurement. The calculated activation energy values indicate that electrical conduction takes place primarily by the small polaron hopping mechanism. The charge compensation for the divalent ion on the A-site is provided by the formation of Fe⁴⁺ ions on the B-site (in preference to Co⁴⁺ ions) and vacancies on the oxygen sublattice for low values of x. The large increase in the conductivity with x in the range from 0.6 to 0.8 is attributed to the substitution of Fe⁴⁺ ions by Co⁴⁺ ions. The Fe site has a lower small polaron site energy than Co and hence behaves like a carrier trap, thereby drastically reducing the conductivity. The non-linear behaviour in the dependence of log σT with reciprocal temperature can be attributed to the generation of additional charge carriers with increasing temperature by the charge disproportionation of Co³⁺ ions.     

Preparation of LiFePO4 with inverse opal structure and its satisfactory electrochemical properties

Phase pure, well-crystallized and homogeneous LiFePO₄ powder with inverse opal structure was obtained by calcining the precursors of Li⁺, Fe²⁺ and PO₄³⁻ in the presence of organic template of poly(styrene-methyl methacrylate-acrylic acid) latex micro-spheres under nitrogen atmosphere. The resultant products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), chemical titration, Fourier transform infrared (FTIR) and Land 2001A electrochemical measurement system. Results indicated that after the decomposition of organic template, inverse opal structure and conductive carbon were left in the resultant products. With the large specific surface area resulting from inverse opal structure and with the conductive carbon, the products delivered satisfactory capacity and superior rate capability at room temperature, i.e., over 100 mAh/g at the high current density of 5.9C.     

Color centers and charge state recharge in γ-irradiated Yb:YAP

Gamma-ray irradiation induced color centers and charge state recharge of impurity and doped ion in 10 at.% Yb:YAP have been studied. The change in the additional absorption (AA) spectra is mainly related to the charge exchange of the impurity Fe²⁺, Fe³⁺ and Yb³⁺ ions. Two impurity color center bands at 255 and 313 nm were attributed to Fe³⁺ and Fe²⁺ ions, respectively. The broad AA band centered at 385 nm may be associated with the cation vacancies and F-type center. The transition Yb³⁺ → Yb²⁺ takes place in the process of γ-irradiation. Oxygen annealing and γ-ray irradiation lead to an opposite effect on the absorption properties of the Yb:YAP crystal. In the air annealing process, the transition Fe²⁺ → Fe³⁺ and Yb²⁺ → Yb³⁺ take place and the color centers responsible for the 385 nm band was destroyed.     

普鲁士蓝基HClO荧光纳米探针及其对肿瘤细胞的特异性检测（英文）

次氯酸(HClO)是一种活性氧(ROS),在许多生理和病理过程中起着至关重要的作用。然而,过量的HClO会导致组织损伤、动脉粥样硬化、神经退行性疾病甚至癌症。因此,实时检测肿瘤细胞中HCl O对于探索HClO在肿瘤进展以及免疫治疗中的作用具有重要意义。与目前常用的工艺复杂、水溶性差的有机分子探针不同,本工作简单地将异硫氰酸荧光素(FITC)与中空介孔普鲁士蓝纳米粒子(HMPB)相结合,构建了一种新型的无机亲水荧光纳米探针。由于内滤光效应,HMPB中FITC的荧光有一定程度的猝灭,但通过Fe²⁺-ClO^–氧化还原反应可恢复荧光。体外条件下,加入HClO后, FITC在发射峰(520 nm)处荧光逐渐增强, HClO在5×10^–6～50×10^–6 mol/L范围内呈良好的线性关系,检出限为2.01×10^–6mol/L。此外,在细胞水平上,该纳米探针对癌细胞中的HClO显示出良好的特异检测能力,且灵敏度高。     

Investigating the Characteristics of Cobalt-Substituted MnZn Ferrites by Equivalent Electrical Elements

We investigated the electrical and magnetic properties of cobalt-substituted manganese-zinc soft ferrite by using the equivalent lumped elements acquired from the appropriate equivalent electrical circuit of polycrystalline ferrite. We applied the equivalent lumped circuit, combined with equivalent lumped resistances and capacitance, to determine the effect of microstructure on electrical and magnetic properties of cobalt-substituted manganese-zinc ferrites. Both the hysteresis loss and the eddy-current loss of soft ferrites account for a major proportion of iron loss in high-frequency switching mode power supplies. Replacing a small portion of Fe²⁺ with Co²⁺ remarkably increases the bulk resistivity of the MnZn ferrite and decreases the core loss by lowering eddy-current loss. A longer isothermal duration causes grain growth and forms a larger equivalent capacitance, which leads to a reduction in hysteresis loss. However, excess substitution of Co²⁺ for Fe²⁺ is disadvantageous to magnetic permeability and raises core loss. We measured the dc resistivity by the four-probe method on sintered disks with both sides polished and coated with a thin layer of silver paste as a good contact material. We measured the magnetic permeability by an impedance analyzer at room temperature. The total loss of Mn_0.58Zn_0.37 Co_0.01Fe_2.04O₄ ferrite core does not exceed 420 mW/cm³ at 300 kHz/70 mT.     

Fe-substituted tobermorites: Synthesis and characterization by Mössbauer spectroscopy and other techniques

The isomorphous substitution of Fe³⁺ for Si⁴⁺ in the tobermorite (Ca₅Si₆H₂O₁₈·4H₂O) structure and its effects on the cation exchange properties of tobermorites were investigated. Fe³⁺- substituted 11Å tobermorites were synthesized under hydrothermal conditions. The cation exchange capacities of these Fe³⁺-substituted tobermorites ranged between 82–122 meq/100g while specific Cs sorption ranged from 420–800 K_d. ⁵⁷Fe Mossbauer Spectroscopy, in addition to other techniques, was used to investigate the Fe-substitution in the tobermorite structure. None of the Mossbauer spectra revealed any absorption line due to Fe²⁺. The observed spectra were fitted to one or more closely overlapping quadrupole doublets. The assignment of Fe³⁺ among the available tetrahedral and octahedral sites was made based on the distinct differences in the observed isomer shifts. The extent of Fe³⁺_IV vs. Fe³⁺_VI site occupancies was determined from the corrected intensities of the respective quadrupole doublets.     

基于FeI2/Ni2+溶液还原制备低成本的高导电性及催化性纸张石墨

采用基于FeI₂/ Ni(NO₃)₂溶液的温和化学法还原制备低成本的纸张型石墨烯, 并对其导电与催化性能进行了研究。研究结果表明: 在pH=1.5, 温度为95℃的条件下处理6 h, 得到电导率高达30231 S/m的纸张型石墨烯, 这是由于作为强路易斯酸的Fe²⁺促进了亲核取代反应, 提高了还原效率, 从而提高了纸张型石墨烯的电导率; 而Ni²⁺通过减少溶液中的H⁺来抑制Fe²⁺的水解, 从而保证Fe²⁺对石墨烯的充分还原以及达到保护环境的目的。此外, 基于此还原工艺制备的纸张型石墨烯在I^-/I^3-电解液中可以获得接近铂电极的电流密度, 表明制备出的纸张型石墨烯具有较好的催化性能,并可以为电子提供快速的传出通道, 使其在太阳能电池中表现出较好的应用前景。     

碳化与氯盐腐蚀作用下钢筋锈蚀物的微结构特征

通过XPS与XRD方法研究了碳化与氯盐腐蚀作用下砂浆内钢筋锈蚀物的组成和微结构特征,阐明了砂浆内钢筋的腐蚀机制。研究结果表明：从氯盐、碳化到氯盐与碳化复合作用,钢筋锈蚀物中Fe的峰值逐渐增强,Fe的氧化物含量增多,钢筋锈蚀越来越严重;在钢筋腐蚀过程中,钢筋表面的FeO和Fe₃O₄等较致密的钝化膜结构会转化为Fe³⁺,且Fe³⁺与水泥的水化产物Ca₂SiO₄形成Fe³⁺-Ca₂SiO₄复盐,随着钢筋腐蚀程度的加剧,Fe³⁺-Ca₂SiO₄复盐含量逐渐减少,而Fe³⁺转化为以Fe₂O₃为主的其他锈蚀物。     

Stabilization of copper sludge by high-temperature CuFe2O4 synthesis process

Copper sludge was stabilized by high-temperature CuFe₂O₄ ferritization technique with different sintering temperature, isothermal time and Fe³⁺/M²⁺ molar ratio. Copper is stabilized by inserting the copper ion into the stable CuFe₂O₄ structure by ferritization. The result indicates that sintering temperature above 800 °C would be proper temperature range for CuFe₂O₄ synthesis. When the Fe³⁺/M²⁺ molar ratio of sludges are above the stoichiometric ratio of 2, copper ion in sludge would be stabilized and hence be kept from leaching out. From the result of relative XRD intensity ratio, the equilibrium of the ferritization reaction could be reached by prolonging the isothermal time to 10 h. Judging by the TCLP results, the optimum ferritization parameters are Fe³⁺/M²⁺ molar ratio equal to 3.5, sintering temperature at 800 °C and isothermal time above 10 h.     

金属掺杂聚吡咯碳化物PPY-M的制备及其氧还原反应电催化活性

在Fe³⁺或Co²⁺存在下进行吡咯的聚合反应, 得到金属离子掺杂的聚吡咯, 并在N₂气氛下700℃碳化, 再将该碳化产物在900℃焙烧得到含有不同金属的复合催化剂PPY-M(M为不同的金属)。采用SEM、XRD等对催化剂的结构进行了表征。通过循环伏安和线性电位扫描等电化学手段, 研究了催化剂对氧还原(ORR)的电催化活性及其稳定性。结果表明, 掺杂金属钴的催化剂的活性最好, 在酸性溶液中ORR的起始电位达到0.54 V(vs SCE),电流密度为7.5 mA/mg@-0.3 V(vs SCE); 在碱性溶液中ORR的起始电位为-0.11 V(vs SCE),电流密度为5.7 mA/mg@-0.8 V。Fe或Co掺杂的聚吡咯碳化物对ORR具有较强的电催化活性, 而且制备过程简单、成本低, 有较重要的研究意义。     

纳米铁钴合金/石墨复合材料的微波吸收性能研究

利用氧化石墨的吸附性能将Fe³⁺和Co²⁺吸附到氧化石墨层间制备出Fe³⁺Co²⁺/氧化石墨复合物, 再通过氢气还原制备出纳米铁钴合金/石墨复合材料, 采用XRD和SEM以及磁滞回线测试等手段对其晶体结构、微观形貌以及磁学性能进行表征, 探讨了FeCo合金含量对其微波吸收性能的影响。结果表明: 所制备的产物为石墨和纳米FeCo合金颗粒组成的二元复合材料, FeCo合金分散在石墨表面和层间, 粒径为30~150 nm。纳米铁钴合金/石墨复合材料是典型的软磁性材料, 饱和磁化强度随FeCo合金含量的减小而降低。随着FeCo合金含量的减少, 纳米FeCo/石墨复合材料的介电损耗逐渐增加, 磁损耗逐渐减小。FeCo合金含量适当时, 介电损耗和磁损耗的协同作用使复合材料具有较好的微波吸收性能。     

Effects of adsorbent dose, its particle size and initial arsenic concentration on the removal of arsenic, iron and manganese from simulated ground water by Fe3+ impregnated activated carbon

This paper presents the observations of the study on arsenic removal from a contaminated ground water (simulated) by adsorption onto Fe³⁺ impregnated granular activated carbon (GAC-Fe). Fe²⁺, Fe³⁺ and Mn²⁺ have also been considered along with arsenic species in the water sample. Similar study has also been done with untreated granular activated carbon (GAC) for comparison. The effects of adsorbent dose, particle size of adsorbent and initial arsenic concentration on the removal of As(T), As(III), As(V), Fe²⁺, Fe³⁺ and Mn²⁺ have been discussed. Under the experimental conditions, the optimum adsorbent doses for GAC-Fe and GAC have been found to be 8 g/l and 24 g/l, respectively with an agitation time of 15 h. Particle size of the adsorbents (both GAC and GAC-Fe) has shown negligible effect on the removal of arsenic and Fe species. However, for Mn removal the effect of adsorbent particle size is comparatively more. Percentage removal of As(T), As(V) and As(III) increase with the decrease in initial arsenic concentration (As₀). However, the increase in percentage removal of all the arsenic species with decrease in As₀ are less for higher value of As₀ (3000–500 ppb) than those of the lower value of As₀ (500–10 ppb). The % removal of As(T), As(III), As(V), Fe, and Mn were 95%, 92.4%, 97.6%, 99% and 41.2%, respectively when 8 g/l GAC-Fe was used at the As₀ value of 200 ppb. However, for GAC these values were 55.5%, 44%, 71%, 98% and 97%. The pH and temperature of the study were 7 ± 0.1 and 30 ± 1 °C, respectively.     

钾离子掺杂提高锂离子电池正极锰酸锂性能的微观机制

改善尖晶石锰酸锂的大倍率性能是目前锂离子电池的重点研究方向之一。本研究用高温固相法合成掺K⁺的尖晶石锰酸锂, 研究K⁺提高锰酸锂倍率性能的微观机制。结果表明, 尽管随着电流密度增大, 电极的放电比容量下降, 但掺K⁺提高材料的大倍率性能效果显著, 如最佳掺K⁺量(物质的量分数)1.0%时, 在10C (1C=150 mA·g^-1)下比容量提高了一倍, 远高于0.5C下的1.9%。原因在于掺K⁺后, 首先, 锰酸锂的晶胞体积扩大, Li-O键变长, Li、Mn阳离子混排程度降低, 载流子(Mn³⁺)量增多; 其次, 电极极化和电荷迁移阻抗降低, 提高了材料的充放电可逆性、导电性及锂离子扩散能力; 再者, [Mn₂]O₄骨架更稳定, 减小了电化学过程中内应力变化, 抑制了晶体结构变化和颗粒破碎; 最后, 钾离子掺杂使制备过程中材料团聚, 从而减小电解液与电极的接触面积, 减轻电解液的侵蚀, 抑制锰的溶解。     

疏松多孔CoFe2O4-还原石墨烯电极复合材料的制备与性能

采用原位溶剂热法,以氧化石墨烯（GO）与Co2+、Fe3+为原料制备疏松多孔的纳米CoFe₂O₄-还原氧化石墨烯（CoFe₂O₄-rGO）复合材料。采用XRD、Raman、SEM和HRTEM测试表征了纳米CoFe₂O₄-rGO复合材料的结构与形貌。测试结果表明,纳米CoFe₂O₄-rGO复合材料具有三维结构。自组装的多孔CoFe₂O₄纳米球粒径约为200 nm,在rGO上均匀分散,解决了CoFe₂O₄易团聚的问题。电化学测试结果表明,纳米CoFe₂O₄-rGO复合材料具有较高的比容量及优异的循环和倍率性能,在100 mA·g-1的电流密度下其比容量为1 262 mAh·g-1,50次循环后比容量仍能保持在642 mAh·g-1;并在2 000 mA·g-1的大电流密度下仍具有221 mAh·g-1的比容量。纳米CoFe₂O₄-rGO复合材料拥有更优异的电化学性能的原因在于CoFe₂O₄纳米球在rGO上均匀分布。三维结构增加了Li+储存的活性位点,有效缓解了电极的体积收缩/膨胀效应,提高了纳米CoFe₂O₄-rGO复合材料的导电性。      

Studies of polycrystalline cobalt-substituted lithium ferrites

The lattice constant, density, electrical conductivity, activation energy, carrier concentration, mobility, Seebeck coefficient, and ferromagnetic resonance linewidth were studied on a series of cobalt-substituted lithium ferrites. We have found that all the samples studied have single phase spinel structure. The lattice constant and the density are increased with substituting Co²⁺ contents. All the specimens studied have two regions of different activation energies. In the region below T_a (below 220°C), the conduction is attributed to electron hopping from Fe²⁺ to Fe³⁺; and in the region above T_a (above 220°C), it is attributed to ionic diffusion of Li ion. The change of mobility is caused by the dispersion of ions. The ferromagnetic resonance (F.M.R.) experimental results indicated that cobalt substitution affects linewidths and relaxation frequency, but it does not affect the g-factor     

On the interpretation of Fe Mössbauer spectra from CdTe thin films with substitutions of Fe, In, and Sb

⁵⁷Fe Mössbauer spectra of well characterized CdTe thin films with substitutions of Fe, In and Sb were recorded and interpreted according to the changes in the ionic radii and electronic properties of these substitutions relative to Cd in the CdTe framework. The literature reports of certain correlations among the iron valence, Fe²⁺ or Fe³⁺, and the crystallinity of the films are critically discussed and an explanation of their origin is provided. The Mössbauer results also allow direct understanding of the effect of In and Sb substitutions on the properties of the films.     

High temperature oxidation of Ni–W coatings electroplated on steel

The high-temperature oxidation of Ni–16 at.% W coating electroplated on the steel substrate was studied at 700 and 800 °C in air. Before oxidation, the coating consisted of supersaturated, nanocrystalline Ni grains. During oxidation, oxygen diffused inward, Ni and the substrate elements such as Fe and Cr diffused outward. The outer NiO layer was not pure but had some dissolved ions of W⁶⁺ and Fe³⁺. Some Fe³⁺ ions were dissolved in the inner (NiO+NiWO₄) mixed layer, below which (W, Fe)-supersaturated, unoxidized Ni grains existed. Below these grains, tiny Ni–W–Fe precipitates, which were formed by the outward diffusion of Fe from the substrate, were surrounded by unoxidized (Fe-enriched, Cr-containing) Ni grains. Detailed oxidation mechanism of Ni–16 at.% W coating is proposed.