Magnetite nanoparticles stabilized with polymeric bilayer of poly(ethylene glycol) methyl ether-poly(?-caprolactone) copolymers

In this work, we report a synthetic method of water dispersible magnetite nanoparticles having oleic acid and poly(ethylene glycol) methyl ether-poly(?-caprolactone) (mPEG-PCL) amphiphilic block copolymer as polymeric stabilizers. The particles were prepared by coprecipitation of Fe(II) and Fe(III) in NH₄OH and had bilayer surface with hydrophobic inner layer and hydrophilic corona. mPEG-PCL copolymer was synthesized by a ring-opening polymerization of ?-caprolactone using mPEG as a macroinitiator in the presence of stannous octoate catalyst. FTIR and thermogravimetric analysis (TGA) indicated the presence of the copolymer on the particle surface. Roles of reaction parameters, such as stabilizer concentrations and time of ultrasonicating treatment, on percent of magnetite in the complex and its magnetic properties were investigated. Transmission electron microscopy (TEM) showed the average particle size about 9.0 ± 1.1 nm in diameter. Vibrating sample magnetometry (VSM) measurement indicated that the magnetite nanoparticles were superparamagnetic at room temperature. Approximately 6.8 ± 0.5% of indomethacin model drug (68 μg/mg of magnetite) was effectively entrapped on the particles.     

Synthesis of high magnetization hydrophilic magnetite (Fe3O4) nanoparticles in single reaction—Surfactantless polyol process

High magnetization hydrophilic magnetite nanoparticles have been synthesized in two different batches with mean particle sizes of 32.3 and 9.2 nm by inexpensive and surfactant-free facile one-pot modified polyol method. In the synthesis, polyethylene glycol was used as a solvent media and it has been found to play a key role to act as a reducing agent as well as a stabilizer simultaneously. It was shown that the size of the nanoparticles can be effectively controlled by modifying the reaction parameters such as reaction temperature, time and polyol/metal precursor ratio. X-ray diffraction and energy dispersive spectroscopy studies confirm the formation of a pure magnetite phase without the presence of any other phases. Transmission electron microscopy and the Fourier transform infrared spectroscopy results reveal that the particle size and surface adsorption properties are very much dependent on reaction parameters. The magnetic properties of the samples measured by physical property measurement system have shown that the as-synthesized magnetite nanoparticles possess a high magnetization of 85.87 emu/g at 300 K and 91.7 emu/g at 5 K with negligible coercivities. The structural and magnetic characterizations of these polyol coated, hydrophilic, monodisperse, superparamagnetic nanoparticles clearly indicate that they are suitable for biomedical applications.     

Novel mechanistic description of the water granulation process for hydrophilic polymers

The purpose of this study was to investigate the mechanism behind the water granulation of the hydrophilic polymers HEC and HPMC. To gain insight into this process, properties of the polymers, e.g. molecular weight, viscosity, particle size distribution and interaction with water, were related to torque values measured during the granulation process and to the properties of the dried granules. The torque values in the high shear mixer were determined as function of the binder ratio (g added water per g dry polymer). These methods revealed differences in torque behavior between the polymers, indicating that the viscosity and gelling rate were important parameters determining the torque values. Bimodal particle size distributions for both HEC and HPMC were obtained when performing the granulation in the high shear mixer. A novel granulation mechanism is presented relating the water uptake, the viscosity and the gelling rate to the consolidation and coalescence of the granules. Furthermore, the breakage of the granules is suggested to be limited for hydrophilic granules obtained by water granulation.     

丙烯酸系共聚物钠盐分散剂的合成及在农药水分散粒剂中的应用

合成了丙烯酸系共聚物钠盐分散剂,并应用于75%苯磺隆水分散粒剂配方中,对产品的性能进行了评价。结果表明水分散粒剂悬浮率可达到90%以上,崩解时间小于60s,热贮(54±2)℃分解率小于3%,满足水分散粒剂使用的各项技术指标;室内除草药效结果表明自制的样品与国外同类产品对测试杂草靶标的生物活性相当,合成的高分子分散剂适合于所选择农药的水分散粒剂的制备。     

50%乙酰甲胺磷WG的配制

以98％乙酰甲胺磷为原药，硅藻土为载体，进行了50％乙酰甲胺磷WG的配方研究。并对样品的分散性、润湿性、崩解性和稳定性进行测定，从中筛选出最佳配方：乙酰甲胺磷50％，十二烷基苯磺酸钠5％，木质素磺酸钠6％，尿素4％，硅藻土补至100％。实验证明：50％乙酰甲胺磷WG配方，其制剂性能优良。     

Electro-precipitation of magnetite nanoparticles: An electrochemical study

Nanoparticles of magnetites (Fe₃O₄) are synthesized with a new process based on electro-precipitation in ethanol medium. A mechanism pathway is proposed consisting of a Fe(OH)₃ precipitation followed by the reduction of iron hydroxide to magnetite in the presence of hydroxyl ions which are generated at the cathode.     

Water-soluble,mesoporous Fe3O4: Synthesis,characterization, and properties

Water-soluble, mesoporous Fe₃O₄ nanopowder is successfully prepared by one-step thermal decomposition of an iron-urea complex ([Fe(NH₂CONH₂)₆](NO₃)₃) in triethylene glycol (TEG). The formation of Fe₃O₄ is confirmed from X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and selected area electron diffraction (SAED) measurements. The morphological and structural properties of the Fe₃O₄ nanopowder are characterized by transmission electron microscopy (TEM), nitrogen adsorption–desorption, and thermogravimetric analysis (TGA). Monodisperse, nearly spherical and highly crystalline Fe₃O₄ nanoparticles are obtained by this method. The Fe₃O₄ nanopowder is well dispersed in water and ethanol with a mesoporous structure, average pore size of 3.6 nm, and Brunauner–Emmett–Teller (BET) surface area of 122 m²/g. The room temperature magnetization hysteresis curve exhibits barely measurable values for coercivity and remanence, suggesting that the Fe₃O₄ nanopowder possesses superparamagnetic characteristics.     

Synthesis of chiral hybrid nanotubes of magnetite nanoparticles and conducting polymers

New chiral magnetite nanoparticles with a polymerizable group produced polymer composite films on an electrode surface and the hybrid nanotubes of magnetite nanoparticles and polythiophene from their template-based electropolymerization.     

Synthesis and characterization of chitosan-coated magnetite nanoparticles using a modified wet method for drug delivery applications

Abstract

Immobilizing various chemical functionalities on the surfaces of magnetite nanoparticles extends these applications without affecting the overall magnetic properties of the coated nanoparticles. In this study, magnetite nanoparticles have been prepared in the presence of chitosan using a simple modified wet method. Composition, morphology and magnetic properties of the chitosan-coated nanoparticles were investigated. Results showed the formation of coating with various thicknesses on the surfaces of the superparamagnetic nanoparticles. This in turn reduced the magnetization of the nanoparticles to some extent. The least particle size obtained in the presence of chitosan was 10?nm.     

Low temperature synthesis of monolithic mesoporous magnetite nanoparticles

Magnetite nanoparticles are commonly used for drug delivery, as MRI contrast agents, and as adsorbents for the removal of heavy metal cations from waste water. The smaller the particle sizes the higher the efficiency of these particles in these applications. Different methods have been explored for the preparation of magnetic nanoparticles with this size limitation. Co-precipitation is one of the most versatile methods in this regard, and is characterized by the ability of preparation of a high yield of nanoparticles. Control of the particle size distribution, phase purity and type of porosity of the formed magnetite nanoparticles has been always considered a challenge. In the current study, magnetite mesoporous nanoparticles with an average particle size of 55 nm were prepared in pre-adjusted highly alkaline aqueous media at relatively low temperatures. Phase purity of the deposited magnetite was confirmed by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Scanning (SEM) and transmission electron microscopy (TEM) graphs showed homogenously dispersion of spherical magnetite nanoparticles. Agglomeration of the mesoporous nanoparticles took place forming clusters with unified pore size distribution due to the homogenous particle size distribution. Magnetic susceptibility measurements at room temperature confirmed the magnetization characteristics of the nanoparticles.     

高浓度90%莠去津水分散粒剂的研制

介绍了高浓度90%莠去津水分散粒剂(WG)的制备,并确定了优惠配方,简述了该剂型的特点、配方组成、加工工艺、贮存稳定性以及性能测定。试验结果表明该产品的各项指标符合水分散性粒剂的要求,如悬浮率在90%以上,崩解时间在1min以内,在(54±2)℃下贮存4周后的分解率小于5%,且产品的各项指标均符合水分散粒剂的要求。     

75%噻吩磺隆WG的配方研究与应用

以96．6％噻吩磺隆为原药,润湿剂、分散剂以及常用的崩解剂、粘结剂为辅料,进行了75％噻吩磺隆的配方研究。并对该产品的各项性能及药效进行了测定,结果表明：该产品悬浮率大于90％,润湿时间小于30s,热贮分解率小于5％,对测试杂草靶标具有好的生物活性。     

Electrophoretic mobility of magnetite particles in high temperature water

Magnetite (Fe₃O₄) is one of the most common oxides forming deposits and particulate phases in industrial high temperature water circuits. Its colloidal characteristics play a principal role in the mechanism of deposit formation and can be used as controlling factors to prevent or minimize deposit formation and damage of industrial pipelines due to under-deposit corrosion. In this study, a high temperature particle electrophoresis technique was employed to measure the zeta potential at the magnetite/water interface—the parameter that controls colloidal stability of particles, their aggregation, and deposition. The measurements were made at temperatures up to 200 °C over a wide range of pH. The isoelectric points of magnetite, at which the deposition of particles is increased, were determined at pH 6.35, 6.00, 5.25, and 5.05 for temperatures 25, 100, 150, and 200 °C, respectively. The observed temperature dependence of zeta potential and the isoelectric pH point of magnetite can help to explain the extent of interactions between the colloidal particles and the steel wall surfaces under hydrothermal conditions, and indicate methods for controlling and mitigating oxide deposition in high temperature water cycles.     

Characterization by electrochemical impedance spectroscopy of magnetite nanoparticles supported on carbon paste electrode

Magnetite nanoparticles were supported on carbon paste electrode and characterized by low scan rate voltammetry and electrochemical impedance spectroscopy (EIS) to obtain mechanistic information related to its oxidation and reduction in acid media.The voltammograms showed only one reduction and one oxidation peak for the supported magnetite, which were attributed to formation of ferrous ion and ferric oxide, respectively. Both peaks are fairly wide, indicating complex mechanisms.Using EIS, a mechanism showing up to three time constants, capacitive all of them, was evidenced, both in anodic and cathodic domain. These were attributed to charge transfer at the highest frequencies, adsorption of generated species at intermediate frequencies, and proton adsorption at low frequencies. Discussion about the nature of the adsorbed species and the concerned mechanism for each domain is developed.     

Redox stability and high-temperature electrical conductivity of magnesium- and aluminium-substituted magnetite

Spinel-type magnetite-based oxides, possessing relatively high electrical conductivity, are considered as promising consumable anode materials for high temperature pyroelectrolysis, a breakthrough low-CO₂ steel technology to overcome the environmental impact of classical extractive metallurgy. The present work was focused on the analysis of phase stability, thermal expansion and high-temperature electrical conductivity in (Fe,Mg,Al)₃O₄ system under oxidizing and mildly reducing conditions. Metastable, nearly single-phase at room temperature (Fe,Mg,Al)₃O₄ ceramics was obtained by sintering at 1753–1773 K for 10 h in argon atmosphere. Thermal expansion and redox induced dimensional changes were studied on heating, using TG, XRD and dilatometry. The results revealed that magnesium improves the tolerance against oxidative decomposition and minimizes unfavorable dimensional changes in ceramic samples upon thermal cycling. Co-substitution of iron with aluminium and magnesium was proved to be a promising strategy for improvement of refractoriness and phase stability of Fe₃O₄-based spinels at elevated temperatures, without significant reduction in the electrical conductivity.     

Synthesis of magnetite powder from iron ore tailings

Iron ore tailing—a waste material of mineral beneficiation plants, is used as a source of iron for synthesizing magnetite powder. Iron ore tailings containing 15.98% Fe₂O₃, 83.36% SiO₂ and 0.44% Al₂O₃ have been subjected to HCl digestion on a hot plate to extract the entire amount of Fe₂O₃ as FeCl₃. A portion of extracted FeCl₃ solution has been used to convert it to FeCl₂ via metallic iron formation by using NaBH₄ as a reducing reagent. Then, the left out FeCl₃ solution and derived FeCl₂ solutions (from FeCl₃) are mixed in an appropriate molar ratio (2:1) for synthesizing magnetite powder by the addition of alkali solution. The magnetite powder samples have been characterized by means of powder XRD, SEM, vibrating sample magnetometer and laser particle size analyzer. XRD study confirms the formation of magnetite phase. The magnetite particles synthesized in different ways show varying degrees of magnetization behavior which is attributed to the change in their particle size induced by the use of different precipitating reagents.     

Synthesis and properties of novel water‐dispersible polyisocyanates

A series of novel water‐dispersible polyisocyanates (WDPs) were synthesized with hexamethylene diisocyanate isoxyanurates (HDI trimer), dimethylol butanoic acid (DMBA), polyethylene glycol monomethyl ether (MPEG‐600) and 1,4‐cyclohexanedimethanol (CHDM) as materials. Two‐component waterborne polyurethane (2K‐WPU) films based on WDPs were prepared and characterized by ultraviolet‐visible spectrophotometer, thermogravimetric analyzer (TGA), scanning electron microscopy (SEM), and surface contact angle measurement. The effects of molar ratios of DMBA/MPEG and CHDM/MPEG and their amounts on properties of WDPs including the water dispersibility, storage stability, films hardness, and water resistance were also investigated. The results showed that the introduction of CHDM could efficiently improve the storage stability, the hardness and water resistance of 2K‐WPU films due to the rigid cyclic structure and hydrophobicity property of CHDM. It was found that WDPs had excellent storage stability, and the 2K‐WPU displayed short tack‐free times, high hardness, good water resistance, excellent surface appearance and gloss with 3:7:3 of the molar ratio of DMBA/MPEG/CHDM. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44735.     

Synthesis and properties of highly hydrophilic polyurethane based on diisocyanate with ether group

Highly hydrophilic polyurethane elastomers (PUEs) were synthesized from 1,2-bis(isocyanate) ethoxyethane (TEGDI), poly(ethylene oxide-co-propylene oxide) copolyol (EOPO) and 1,4-butane diol/1,1,1-trimethylol propane (75/25) (wt/wt) by a prepolymer method. 4,4′-Diphenylmethane diisocyanate (MDI)-based PUEs were synthesized as a control as well. Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) measurements revealed that the degree of microphase separation of the TEGDI-based PUEs was much weaker than for the MDI-based PUEs. Young's modulus and elongation at break of the TEGDI-based PUEs were quite lower and larger than for the MDI-based PUEs, respectively. This is due to quite weak cohesion force of the hard segment chains in the TEGDI-based PUEs. The degree of swelling of the TEGDI-based PUEs was five times larger than for the MDI-based one. This is associated with the hydrophilic nature of TEGDI and weak cohesion force in the TEGDI-based PUEs.     

Removal of hydrophilic pollutants from water with organic adsorption polymers: Part I. Adsorption behaviour of selected model compounds

The adsorbability of 2-aminonaphthalene-1-sulfonate, diuron, 1-naphthol and natural organic matter (NOM) onto an organic polymer resin and onto activated carbon was investigated. Isotherms with the substances alone and in the presence of dissolved NOM were measured. There was a good adsorbability of diuron and 1-naphthol on both sorbents. At low initial concentrations of the compounds the activated carbon showed higher adsorptivity, whereas for high initial concentrations the polymer resin showed an equal or better adsorption behaviour. 2-Aminonaphthalene-1-sulfonate and the NOM showed favorable adsorption behaviour to activated carbon but was only poorly adsorbed on the polymer resin. In the presence of NOM, the adsorbability of the single compounds decreased significantly on activated carbon. Nearly no influence was found for the adsorption of the pollutants on the resin. For the polymer resin, additionally, the breakthrough behaviour of the substances was investigated. The results obtained in the batch experiments for the single substances were confirmed. However, in the presence of NOM the breakthrough occurred at shorter times for all three substances. Regeneration of the resin with isopropanol proved to be a good cleaning method. A recovery of 92–96% of the substances was reached.     

Highly dispersible carbon composited Fe3O4 nanoparticles in an aqueous solvent via normal pressure liquid reaction

In this study, a simple fabrication of carbon composited Fe₃O₄ nanoparticles was carried out under reflux condition using glucose as a carbon precursor. The carbon composited Fe₃O₄ nanoparticles having a core-shell structure were synthesized in a low-temperature and low-pressure atmosphere instead of in an autoclave. Simple carbonization without inert gas and extra heating was complemented by adding sulfuric acid, which has an important role as a carbonization catalyst. In addition, sulfuric acid also acted as the controller of such surface properties as surface area by an etching effect. The prepared nanoparticles have uniform and continuous carbon layers, which have several functions, such as stable dispersibility and an increase of electron conductivity. carbon composited Fe₃O₄ nanoparticles were investigated with zeta-potential, particle size distribution, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and a vibrating sample magnetometer. The results provide clear evidence that carbon-coated Fe₃O₄ nanoparticles are applicable in electrochemical industrial fields.