PREPARATION AND CHARACTERIZATION OF PVA COATED MAGNETIC NANOPARTICLES

Polyvinyl alcohol coated magnetic particles (PVA ferrofluids) have been synthesized by chemical co-precipitation of Fe(II)/Fe(III) salts in 1.5 mol/L NH4OH solution at 70 degreesC in the presence of PVA. The resultant colloidal particles have core-shell structures, in which the iron oxide crystallites form the cores and PVA chains form the shells. The hydrodynamic diameter of the colloidal particles is in the range of 108 to 155 nm, which increases with increasing PVA concentration from 5 wt% to 20 wt%, The size of the magnetic cores is ca. 5-10 nm, which is relatively independent of PVA concentration. Under transmission electron microscopic (TEM) examination, the magnetic cores exhibit somewhat irregular shapes varying from spherical, oval, to cubic. Magnetometry measurement revealed that the PVA coated magnetic particles are superparamagnetic. The saturation magnetization of 5 wt% and 20 wt% PVA ferrofluids at 300 K is 54 and 49 emu/g, respectively. All the PVA ferrofluids exhibited excellent colloidal stability in pure water and phosphate buffer saline (PBS, pH = 7.4). The ferrofluids can remain stable in above solutions for more than three months at 4 degreesC.

Facile in situ synthesis and characterization of Fe@Si/zeolite Na composites with magnetic core–shell structures from natural materials for enhanced curcumin loading capacity

Curcumin is a natural polyphenol that is used in various traditional medicines.However,its inherent properties,such as its rapid degradation and metabolism,low bioavailability,and short half-life,are serious problems that must be resolved.To this end,a drug carrier incorporating natural magnetic cores in a zeolite framework was developed and applied to the loading of curcumin in ethanol solutions.In this system,curcumin is encapsulated in a zeolite Na(ZNA)magnetic core–shell structure(Fe@Si/ZNA),which can be easily synthesized using an in situ method.Synthesis of Fe_(3)O_(4) nanoparticles was carried out from natural materials using a co-precipitation method.Analysis of the prepared magnetic core–shell structures and composites was carried out using vibrating-sample magnetometery,Fourier transform infrared spectroscopy,transmission electron microscopy,and x-ray diffraction.The cumulative loading of curcumin in the ZNA composite with 9%nanoparticles was found to reach 90.70%with a relatively long half-life of 32.49 min.Stability tests of curcumin loading in the composite showed that adding magnetic particles to the zeolite framework also increased the stability of the composite structure.Adsorption kinetics and isotherm studies also found that the system follows the pseudo-second-order and Langmuir isotherm models.

Engineered magnetic core shell nanoprobes:Synthesis and applications to cancer imaging and therapeutics

Magnetic core shell nanoparticles are composed of a highly magnetic core material surrounded by a thin shell of desired drug, polymer or metal oxide. These magnetic core shell nanoparticles have a wide range of applications in biomedical research, more specifically in tissue imaging, drug delivery and therapeutics. The present review discusses the up-to-date knowledge on the various procedures for synthesis of magnetic core shell nanoparticles along with their applications in cancer imaging, drug delivery and hyperthermia or cancer therapeutics. Literature in this area shows that magnetic core shell nanoparticle-based imaging, drug targeting and therapy through hyperthermia can potentially be a powerful tool for the advanced diagnosis and treatment of various cancers.

Magnetic graphene oxide-anchored Ni/Cu nanoparticles with a Cu-rich surface for transfer hydrogenation of nitroaromatics

The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell(Ni/Cu NPs)were successfully synthesized by a liquid-phase thermal decomposition method.The content of copper and nickel in Ni/Cu NPs was controllable by adjusting the ratio of two metal precursors,copper formate(Cuf)and nickel acetate tetrahydrate(Ni(OAc)_(2)·4H_(2)O).Ni/Cu NPs were further anchored on graphene oxide(GO)to prepare a magnetic composite catalyst,called Ni/Cu-GO.The dispersibility of Ni/Cu NPs in solution was enhanced by GO anchoring to prevent the sintering and aggregation during the reaction process,thereby ensuring the catalytic and cycling performance of the catalyst.The catalytic transfer hydrogenation(CTH)reaction of nitroaromatics was investigated when ammonia borane was used as the hydrogen source.Cu dominated the main catalytic role in the reaction,while Ni played a synergistic role of catalysis and providing magnetic properties for separation.The Ni_(7)/Cu_(3)-GO catalyst exhibited the best catalytic performance with the conversion and yield of 99%and 96%,respectively,when 2-methyl-5-nitrophenol was used as the substrate.The Ni_(7)/Cu_(3)-GO catalyst also exhibited excellent cyclic catalytic performance with the 5-amino-2-methylphenol yield of above 90%after six cycles.In addition,the Ni_(7)/Cu_(3)-GO catalyst could be quickly recycled by magnetic separation.Moreover,the Ni_(7)/Cu_(3)-GO catalyst showed good catalytic performance for halogen-containing nitroaromatics without dehalogenation.

Preparation and Characterization of Nano-Sized (Mg_(x)Fe_(1–x)O/SiO₂) (x = 0.1) Core-Shell Nanoparticles by Chemical Precipitation Method

Magnetic core-shell nanoparticles have been widely studied because of their excellent and convenient magnetic and electrical properties.In this present work core-shell magneticnanoparticles (MNPs) were synthesized by simple chemical precipitation method. Firstly Mg(x)Fe(1–x)O (magnesiwuestite) nano powder samples were synthesised by low temperature chemical combustion method. Secondly the as synthesised Mg(x)Fe(1–x)O nanoparticles are used to synthesis magnetic core-shell Nano particles byusing 2-propanol, poly ethylene glycol (PEG), ammonia solution 30 wt%, tetraethyl orthosilicate (TEOS). Separation of the core-shell magnetic nanoparticles from the aqueous suspension using a centrifuge. The synthesised MNPs and core shell MNP were characterized by X-ray diffraction (XRD), Thermal gravimetric-differential thermal analyzer (TG-DTA), Transmission electron microscopy (TEM), scanning electron microscopy (SEM), (EDAX) for structural, thermal and morphological respectively. It is observed that the particle size of spherical sampleis 32.5 nm.

Memory Effect up to Room-temperature in Ni/Ni_2P Core-shell Structured Nanoparticles

Memory effect has been studied in the system using magnetic nanoparticles with Ni nanocore encapsulated by non-magnetic and oxidation-resistant Ni2P nanoshell acquired through surface-phosphatizing Ni nanoparticles. The self-assembled array with interparticle spacing of about 6 nm shows memory effect up to 200 K below its average blocking temperature of 260 K. And reducing the interparticle spacing of the self-assembled array via annealing can further enlarge the temperature range of memory effect up to room-temperature. The memory effect can be understood based on the thermal relaxation theory of single-domain magnetic nanoparticles. Furthermore, the read-write magnetic coding is realized based on the temperature changes, using the memory effect up to room-temperature, which may be useful for future memory devices.

A Comparative Study on the Selected Area Electron Diffraction Pattern of Fe Oxide/Au Core-shell Structured Nanoparticles

The selected area electron diffraction （SAED） pattern of magnetic iron oxide core/gold shell nanoparticles has been studied. For the composite particles with mean size less than 10 nm, their SAED pattern is found to be different from either the pattern of pure Fe oxide nanoparticles or that of pure Au particles. Based on the fact that the ring diameters of these composite particles fit the characteristic relation for the fcc structure, the Au atoms on surfaces of the concerned particles are supposed to pack in a way more tightly than they usually do in pure Au nanoparticles. The driving force for this is the coherency strain which enables the shell material at the heterostructured interface to adapt the lattice parameters of the core.

Fluorescent Superparamagnetic Core-Shell Nanostructures: Facile Synthesis of Fe@C-CN_xParticles for Reusable Photocatalysts

Synthesis and characterization of hybrid fluorescent superparamagnetic core-shell particles of Fe@C-CNx composition are presented for the first time. The prepared Fe@C-CNx hybrid nanoparticles were found to possess multifunctionality by exhibiting strong superparamagnetic properties and bright fluorescence emissions at 500 nm after the excitation with light in the UV-visible range. Fe@C-CNx also exhibits photocatalytic activities for organic dye degradation comparable to pure amorphous CNx with reusability through magnetic separation. The combination of magnetic and fluorescent properties of core-shell Fe@C-CNx nanoparticles opens opportunities for their application as sensors and magnet manipulated reusable photocatalysts. Superparamagnetic Fe@C core-shell nanoparticles were used as the template material in the synthesis, where the carbon shell was functionalized through one-step free-radical addition of alkyl groups terminated with carboxylic acid moieties. The method utilizes the organic acyl peroxide of dicarboxylic acid (succinic acid peroxide) as a non-oxidant functional free radical precursor for functionalization. Further, covalently functionalized succinyl-Fe@C core-shell nanoparticles were coated with the amorphous carbon nitride (CNx) generated by an in-situ solution-based chemical reaction of cyanuric chloride with lithium nitride. A detailed physicochemical characterization of the microstructure, magnetic and fluorescence properties of the synthesized hybrid nanoparticles is provided.

Reduced-temperature ordering of FePt nanoparticle assembled films by Fe30Pt70/Fe3O4 core/shell structure

In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine （PEI）-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas （50%Ar2＋30%H2） for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.

Synthesis of High Magnetic Moment CoFe Nanoparticles via Interfacial Diffusion in Core/Shell Structured Co/Fe Nanoparticles

We report the synthesis of high magnetic moment CoFe nanoparticles via the diffusion of Co and Fe in core/shell structured Co/Fe nanoparticles.In an organic solution,Co nanoparticles were coated with a layer of Fe to form a Co/Fe core/shell structure.Further raising the solution temperature led to inter-diffusion of Co and Fe and formation of CoFe alloy nanoparticles.These nanoparticles have high saturation magnetization of up to 192 emu/g CoFe and can be further stabilized by thermal annealing at 600℃.

Preparation and characterization of Fe/SiO_2 core/shell nanocomposites

In a simple ethanol-water system,the magnetic α-Fe nanoparticles(with an average diameter of 10-40 nm)were prepared by reduction of Fe2 +using potassium borohydride in the presence of surfactant.Then the shell was formed by hydrolysis-condensation polymerization of tetraethylorthosilicate(TEOS)on the surface of the Fe particles.The samples were characterized by XRD,TEM,SAED,TG-DSC and VSM.The results indicate that a thin film of silica is coated on the surface of Fe particles through a Si-O-Fe bond.The coated shell of silica can effectively protect the Fe cores from being oxidized.

Drug Target Identification Using Affinity Core-Shell Magnetic Nanoparticles and Mass Spectrometry

Affinity core-shell magnetic nanoparticles （MNPs） were prepared for identifying the target proteins of drugs in the cell lysate when used in combination with nano-high-performance liquid chromatography tandem mass spectrometry （HPLC-MS/MS）-based shotgun proteomic analysis. A number of new potential targets of cyclosporine A （CsA） could be identified, owing to the high efficacy of the affinity MNPs in drug target identification. To the best of our knowledge, this is the first time to reveal such an abundant target spectrum of CsA.

Novel Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites:High-efficiency and magnetic recyclable catalysts for organic dye degradation

A facile step-by-step approach is developed for synthesizing the high-efficiency and magnetic recyclable Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites.This method involves coating Fe2O3 nanorods with a uniform silica layer,reduction in 10%H2/Ar atmosphere to transform the Fe2O3 into magnetic Fe3O4,and finally depositing Ag@Ni core-shell nanoparticles on the L-lysine modified surface of Fe3O4@SiO2 nanorods.The fabricated nanocomposites are further characterized by x-ray diffraction,transmission electron microscopy,scanning electron microscope,Fourier transform infrared spectroscopy,and inductively coupled plasma mass spectroscopy.The Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites exhibit remarkably higher catalytic efficiency than monometallic Fe3O4@SiO2@Ag nanocomposites toward the degradation of Rhodamine B（RhB） at room temperature,and maintain superior catalytic activity even after six cycles.In addition,these samples could be easily separated from the catalytic system by an external magnet and reused,which shows great potential applications in treating waste water.

Preparation and characterization of TiO_2-SiO_2-Fe_3O_4 core-shell powders in nano scale

TiO2/SiO2/Fe3O4 nanoparticles have bigger specific area which can greatly increase the efficiency of photo-catalysis.The TiO2/SiO2/Fe3O4 particles in nano scale were prepared with reduction method at high temperature in this paper,and their morphology,particle size and magnetic property were characterized by transmission electron microscope(TEM),Xray diffraction(XRD) and magnetometer.The results show that the grain sizes of Fe3O4,SiO2-Fe3O4 and TiO2-SiO2-Fe3O4 particles were 50nm,70nm and 120nm,respectively.With the modification of SiO2,Fe3O4 magnetic cores are protected from oxidation.Moreover,by the addition of TiO2 function layer,TiO2-SiO2-Fe3O4 functional nanoparticles,with the saturation magnetization density of 34.1emu/g,is magnetically recoverable.The processes of this method are so simple that the nanoparticles can be produced in large quantity.

Preparation of core-shell magnetic Fe_3O_4@SiO_2-dithiocarbamate nanoparticle and its application for the Ni^(2+), Cu^(2+) removal

A novel magnetic nanoparticles-based dithiocarbamate absorbent（Fe3O4@SiO2-DTC） with core-shell structure was synthesized under mild conditions and used in aqueous solution Ni2＋ and Cu2＋ ions treatment. The structure, morphology and magnetic properties of the adsorbent were characterized by Xray diffraction（XRD）, fourier transformed infrared spectroscopy（FTIR）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and vibrating sample magnetometer（VSM）.Fe3O4@SiO2-DTC exhibited a typical superparamagnetic with a saturation magnetization value of52.7 emu/g, which could be rapidly separated from aqueous solution under external magnetic field. We investigated the effects of solution p H, adsorption time, and the initial concentration of heavy metal ions on the adsorption of Ni2＋ and Cu2＋. The adsorption equilibrium times of Ni2＋and Cu2＋ on Fe3 O4@SiO2-DTC were reached at 15 min and 90 min, respectively. The adsorption kinetic data were fitted to the pseudosecond-order model, and the adsorption data were consistent with the Frenudlich isotherm model. When the initial concentration of heavy metal ions was 250 mg/L, the maximum adsorption capacity of Ni2＋ and Cu2＋ at room temperature was 235.23 mg/g and 230.49 mg/g, respectively. In addition, we discussed the plausible adsorption mechanism. The results indicated that the adsorption was mainly dominated by chelation.

Fe_(3)O_(4)@SiO_(2)磁性吸附剂的制备及其对Er(Ⅲ)和Ho(Ⅲ)的吸附性能

稀土资源的开采伴随着稀土离子排放,对水资源造成了严重污染。吸附法是处理水相稀土离子污染的一种高效技术,磁性吸附剂能够加速固液分离,具有较大的研究价值。本研究以FeCl_(3)·6H_(2)O、甘醇、醋酸钠、聚乙二醇(PEG2000)等为原料,采用溶剂热法在200℃的条件下制备粒径约为230 nm的Fe_(3)O_(4)磁性纳米颗粒,将其加入正硅酸乙酯中,利用氨水水解聚合,即可形成粒径约为300 nm的Fe_(3)O_(4)@SiO_(2)磁性吸附剂材料。此复合材料为核壳结构,包含Fe_(3)O_(4)和SiO_(2)两种晶型结构。SiO_(2)的包覆未对Fe_(3)O_(4)物相结构产生较大影响,在包覆的同时能够显现出一定的磁性性能。此复合材料对Er(Ⅲ)和Ho(Ⅲ)的最大吸附容量分别达到10.03 mg/g和5.25 mg/g。

“新工科”背景下生物制药专业多学科交叉融合的探索研究——以Fe_(3)O_(4)@SiO_(2)核壳磁性纳米粒子的制备及应用实验为例

“新工科”背景下,多学科交叉融合已成为生物制药专业教学育人的新方式,对培养“明德求真,弘药济世”的卓越应用型工程人才具有重要意义。本文将以Fe_(3)O_(4)@SiO_(2)核壳磁性纳米粒子的制备及应用实验为例,顺应教育部“三全育人”的战略要求,在调动学生科研的积极性和主动性的同时,探索生物制药与有机化学之间的联系,挖掘多学科交叉融合的独特优势,提高学生的科学探究能力和实验操作能力。

Bifunctional luminescent and magnetic core/shell type nanostructures Fe_3O_4@CeF_3:Tb^(3+)/SiO_2

A facile co-precipitation and microemulsion methods were applied to obtain core/shell type nanoparticles. Cerium fluoride doped with terbittrn（Ⅲ） ions supplied intensive green luminescence of the system. Due to the presence of magnetite nanoparticles as cores, the prod- uct was highly sensitive to external magnetic field. Both sorts of nanostructures were encapsulated by silica shell. Such external layer of inert oxide can potentially increase the resistance of prepared nanostructttres to thermal oxidation, aggressive agents, changing ofpH or destructive radiation. Morphology of the product was examined using transmission electron microscopy （TEM）. Formations of the core/shell type nanostructures were clearly seen in the TEM pictures. Powder X-ray diffraction （XRD） confirmed the structure of the products, their nanocrystallinity and amorphous nature of silica shell. Optical properties were investigated by measuring excitation and emission spectra. Such multifunctional luminescent and magnetic nanoparticles coated with easily functionalized silica shell could be applied in many field of science.

Determination of Hydrocortisone in Cosmetics by CdSe/CdS Quantum Dots-Based Fluoroimmunoassay Using Magnetic Fe304/Au Nanoparticles as Solid Carriers

This work demonstrated the feasibility of detecting hydrocortisone in cosmetics using a novel CdSe/CdS quan- tum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe3Oa/Au nanoparticles （MCFN） as solid carriers. Hydrocortisone antigen was labeled with the synthesized core/shell CdSe/CdS quantum dots （QDs） to form the antigen-QDs conjugate. Meanwhile, hydrocortisone antibody was incubated with MCFN and the immobilized antibody was obtained. The immobilized antibody was then mixed sequentially with hydrocortisone and a slightly excess amount of the QDs-labeled hydrocortisone antigen, allowing their competition for binding with the antibody immobilized on MCFN. The bound hydrocortisone and the antigen-QDs conjugates on MCFN were removed subsequently after the mixture was applied to a magnetic force. The analyte concentration was obtained by measuring the fluorescence intensity of the unbound hydrocortisone antigen-QDs conjugates. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.5 to 15000 pg·mL^-1 and a low detection limit of 0.5 pg.mL^- 1. The proposed method was successfully applied to the determination of hydrocortisone in cosmetics with satisfactory results.

锐钛矿型TiO_2/MnFe_2O_4核壳结构复合纳米颗粒的制备及其光催化特性

采用柠檬酸盐前驱体技术，合成了粒径约为20～70nm的尖晶石结构MnFe2O4纳米颗粒，用聚乙烯亚胺（PEI）对MnFe2O4纳米颗粒进行表面处理后，以异丙醇钛为前驱物，采用sol—gel法在纳米MnFe2O4表面包覆锐钛矿型TiO2纳米层形成核壳结构。利用透射电子显微镜（TEM）、X射线衍射仪（XRD）和振动样品磁强计等测试手段对样品的结构、形貌、粒径以及磁学性能等进行了表征。采用罗丹明B的光催化降解反应对所制催化剂的活性进行了评价。结果表明，核壳结构TiO2／MnFe2O4复合纳米颗粒的光催化活性随着壳层厚度的增加而增强，当达到一定厚度以后，其催化活性不随壳层厚度的增加而改变。复合颗粒中TiO2含量达到30wt％，反应时间4h时，TiO2／MnFe2O4磁性光催化剂对罗丹明B的光降解率达到100％，与纯TiO2纳米粉体的催化活性相当，且光催化活性稳定，是一种便于回收、可重复使用的高效光催化剂。