Influence of Surface Coating on Fluoride Removal by Magnetite

Al(OH)₃- and ZrO(OH)₂-coated magnetites were prepared and used for fluoride removal from aqueous samples. The influence of pH, sorbent mass, and ions such as chloride, sulfate, and phosphate on the removal of fluoride was characterized. The sorption process was highly pH dependent, and the optimal sorption was obtained from pH 4 to 5 for ZrO(OH)₂- and pH 4 to 7 for Al(OH)₃-coated magnetites. The sorption isotherm was well described by the Langmuir equation for the sorbents. The maximum adsorption capacity of ZrO(OH)₂-coated magnetite (57.47?mg-F?g^?1-sorbent) was higher than for Al(OH)₃-coated magnetite (23.87?mg-F?g^?1-sorbent). The ion-exchange reaction occurred in 5?min and more than 99% of fluoride was removed from solution. When the ZrO(OH)₂-coated magnetite was used, the presence of foreign ions negatively affected the fluoride removal. The prepared sorbents showed an excellent performance for the removal of fluoride in water samples.     

Dispersive magnetic solid‐phase extraction of phthalate esters from water samples and human plasma based on a nanosorbent composed of MIL‐101(Cr) metal–organic framework and magnetite nanoparticles before their determination by GC–MS

In this study, a magnetic metal–organic framework was synthesized simply and utilized in the dispersive magnetic solid‐phase extraction of five phthalate esters followed by their determination by gas chromatography with mass spectrometry. First, MIL‐101(Cr) was prepared hydrothermally in water medium without using highly corrosive hydrofluoric acid, utilizing an autoclave oven heat supply. Afterward, Fe₃O₄ nanoparticles were decorated into the matrix of MIL‐101(Cr) to fabricate magnetic MIL‐101 nanocomposite. The nanocomposite was characterized by various techniques. The parameters affecting dispersive magnetic solid‐phase extraction efficiency were optimized and obtained as: a sorbent amount of 15 mg; a sorption time of 20 min; an elution time of 5 min; NaCl concentration, 10% w/v; type and volume of the eluent 1 mL n‐hexane/acetone (1:1 v/v). Under the optimum conditions detection limits and linear dynamic ranges were achieved in the range of 0.08–0.15 and 0.5–200 μg/L, respectively. The intra‐ and interday RSD% values were obtained in the range of 2.5–9.5 and 4.6–10.4, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of the model analytes in water samples, and human plasma in the range of microgram per liter and satisfactory results were obtained.     

Photocatalytic and magnetic titanium dioxide/polystyrene/magnetite composite hybrid polymer particles

Novel multifunctional titanium dioxide (TiO₂)/polystyrene/magnetite composite hybrid polymer particle dispersions with TiO₂ nanoparticles in the surface and magnetite nanoparticles encapsulated inside the polymer matrix were produced by Pickering miniemulsion polymerization in one single step. Whereas TiO₂ nanoparticles were used to impart photocatalytic functionality and colloidal stability, magnetite nanoparticles were incorporated to allow an easy extraction for recovery and reuse of the composite multifunctional particles. The morphology of the composite particles was assessed by scanning transition electron microscopy (STEM) and energy‐dispersive X‐ray spectroscopy (EDX). The paramagnetism of the particles was analyzed using a SQUID magnetometer and their photocatalytic activity was assessed by degrading methylene blue (MB) solutions under UV light and by recovering and reusing of the particles in five consecutive cycles. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3350–3356     

利用天然磁铁矿简易绿色合成磁性Fe3C@C纳米材料

采用改进的溶胶凝胶法,以天然磁铁矿为铁源,开发出一种制备过程简单且环境友好且低成本的磁性Fe₃C@C纳米材料制备策略. 其中,柠檬酸作为多元羧酸络合剂,不但可以有效地溶解不同铁源,例如Fe、Fe₃O₄或天然磁铁矿,形成柠檬酸铁盐络合物;还可以在热解过程中作为碳源,形成包裹碳层. 通过控制高温热解过程可以直接形成特殊的核-壳结构形态. Fe₃C@C纳米材料具有超顺磁性特性(38.09 emu/mg).     

生物磁铁矿的磁各向异性与磁接收器

磁铁矿是分布广泛且非常重要的亚铁磁材料,也广泛分布在生物体中。生物体中的磁铁矿具有完美的晶体结构,大多为超顺磁颗粒或单畴颗粒,且大多呈链状分布,具有明显的磁各向异性。生物体中存在“磁接收器”,生物磁铁矿是“磁接收器”的生物物理基础。本文中,从超顺磁磁铁矿颗粒和单畴磁铁矿颗粒的物理特性出发,主要是从它们的磁各向异性特性的基础上描述了生物磁铁矿和“磁接收器”的工作机制, 即在某些条件下,在外界地磁场强度量级的磁场作用下,超顺磁颗粒或单畴颗粒可以诱导产生足够强的磁场,使邻近的晶体可以相互吸引或排斥, 这些粒子间的相互作用可以改变晶体颗粒束所在的外围机体形状,而神经系统可以探测到单独的粒子束或一列粒子束的扩张或收缩,因此生物体就可以探测到磁场的方向以及强度等磁场参量。     

A Novel Fluorescence Immunoassay Based on Two-time Amplified Fluorescence Signal by Hemin and Magnetic Nanoparticles for the Detection of Antigen

Abstract

A novel, selective, and sensitive magnetic-mimetic enzyme fluorescence immunoassay method for antigen detection has been developed by taking advantage of a magnetic separation process and the amplification feature of the hemin label. This method is based on a twice amplified fluorescence signal. The signal is first amplified due to the ultrasmall size and the high surface-to-volume ratio of the silica-coated magnetite nanoparticles, which enable the nanoparticles to carry much more antibodies. Second, the mimetic enzyme (hemin) as a labeling reagent catalyzes the reaction of p-hydroxyphenyl acetic acid and H₂O₂ can further amplify the fluorescence signal. This protocol was also evaluated for a sandwich-type immunoassay of human IgG, and the calibration graph for human IgG was linear over the range of 0–100 ng mL^?1 with a detection limit of 9.8 ng mL^?1. This method can easily separate magnetic nanoparticles from the solution, which simplified the process and played a promising role for various applications in immunoassay.     

磁性Fe3O4亚微米球固相萃取-HPLC检测水中植物生长调节剂残留

建立了水中2,4-二氯苯氧乙酸(2,4-D)、萘乙酸(NAA)和6-芐基腺嘌呤(6-BA)3种植物生长调节剂残留分析的高效液相色谱方法.采用溶剂热还原法,以乙二醇和FeCl3·6H2O作原料,合成出形貌均一、分散性好、稳定性佳的磁性Fe3O4亚微米球,作为固相萃取材料,以静电吸附作用可以富集水中残留的2,4-D、NAA、6-BA 3种植物生长调节剂.水样经调节pH值和固相萃取净化后,高效液相色谱法测定.3种植物生长调节剂在0.1 ～10 mg/L范围内响应和浓度的线性关系良好,相关系数均大于0.999;2,4-D、NAA、6-BA的检测限分别为0.06、0.02、0.04 mg/L.在测定的自来水、河水和湖水3种水样中,添加回收率范围为73.20％ ～87.21％,相对标准偏差为1.11％ ～7.52％(n=3),为水中的2,4-D、NAA和6-BA残留监控提供了简单、快速、准确的测定方法.     

5-Br-PADAP光度法测钒钛磁铁矿中钒的不确定度评定

5-Br-PADAP光度法是测钒钛磁铁矿中钒的主要方法之一。根据其分析过程的操作步骤确定了其影响因素。建立数学模型,并根据数学模型把不确定度分解为称样质量、溶液含量、钒标准工作曲线和重复测定引入的各不确定度,对影响测量结果的各个分量进行了分析评定和计算。结果表明,钒的标准工作曲线的建立是影响样品分析误差的重要因素。     

Characterization of energy barrier and particle size distribution of lyophilized ferrofluids by magnetic relaxation measurements

The magnetic properties of a ferrofluid are strongly influenced by its particle size distribution. We analyzed a ferrofluid with an unknown particle size distribution as well as fractionated samples of the original material. The ferrofluid in our investigations consists of a mixture of maghemite and magnetite. We investigated these different samples using temperature-dependent magnetorelaxometry method. The evaluation of the Néel relaxation signal allows us a direct determination of the energy barrier distribution, which is one of the most important parameters of such systems of magnetic nanoparticles. The calculated particle volumes were compared with particle sizes determined by transmission electron microscopy.     

Evidence from Mössbauer spectroscopy of neo-formation of magnetite/maghemite in the soils of loess/paleosol sequences in China

Samples of four different loess/paleosol couplets of a loess sequence in Huangling (China) have been studied with ⁵⁷Fe Mössbauer spectroscopy. Each sample was separated into strongly, weakly and very weakly magnetic fractions. The iron mineralogy of the strongly magnetic fractions of both loess and soils consists of magnetite/maghemite and hematite together with some silicates. The soils contain some additional small-particle maghemite. From the spectral behaviour a similarity in terms of morphology and crystal chemistry for hematite throughout the whole section could be inferred. The ratio of iron in magnetite and maghemite to that in hematite differentiates well between the loess and soil samples. These results strongly suggest the neo-formation of magnetite/maghemite in the soils.