单分散超顺磁性Fe_3O_4纳米粒子的合成及表征

利用高温裂解法制备了油酸修饰的Fe3O4磁性纳米粒子,采用TEM、VSM、XRD以及FT-IR对粒子的结构和性能进行了表征和分析。结果表明:Fe3O4纳米粒子粒径为2nm,呈单分散性,结晶性能良好,室温下为超顺磁性,饱和磁化强度为11.73emu/g,可应用于磁流体、磁性分离等领域。     

Magnetic Properties of FePt Nanoparticles Prepared by a Micellar Method

FePt nanoparticles with average size of 9 nm were synthesized using a diblock polymer micellar method combined with plasma treatment. To prevent from oxidation under ambient conditions, immediately after plasma treatment, the FePt nanoparticle arrays were in situ transferred into the film-growth chamber where they were covered by an SiO₂ overlayer. A nearly complete transformation of L1₀ FePt was achieved for samples annealed at temperatures above 700 °C. The well control on the FePt stoichiometry and avoidance from surface oxidation largely enhanced the coercivity, and a value as high as 10 kOe was obtained in this study. An evaluation of magnetic interactions was made using the so-called isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Kelly–Henkel plots (ΔM measurement). The ΔM measurement reveals that the resultant FePt nanoparticles exhibit a rather weak interparticle dipolar coupling, and the absence of interparticle exchange interaction suggests no significant particle agglomeration occurred during the post-annealing. Additionally, a slight parallel magnetic anisotropy was also observed. The results indicate the micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media.     

Magnetic Anisotropic Energy Gap and Strain Effect in Au Nanoparticles

We report on the observation of the size effect of thermal magnetization in Au nanoparticles. The thermal deviation of the saturation magnetization departs substantially from that predicted by the Bloch T^3/2-law, indicating the existence of magnetic anisotropic energy. The results may be understood using the uniaxial anisotropy Heisenberg model, in which the surface atoms give rise to polarized moments while the magnetic anisotropic energy decreases as the size of the Au nanoparticles is reduced. There is a significant maximum magnetic anisotropic energy found for the 6 nm Au nanoparticles, which is associated with the deviation of the lattice constant due to magnetocrystalline anisotropy.     

Chemical synthesis of FePt nanoparticles with high alternate current magnetic susceptibility for biomedical applications

The present paper describes ordered alloy FePt nanoparticles with high magnetic susceptibility to alternate current (ac) fields at around room temperature for biomedical applications such as magnetic sensing devices for diagnostics and magnetic hyperthermia for cancer therapy. Since ac magnetic susceptibility takes the maximum value at a temperature near the blocking temperature of magnetic nanoparticles, the blocking temperature of the FePt nanoparticles is required to be adjusted at around room temperature to improve biomedical performances. Ordered alloy FePt has much higher magnetic anisotropy than iron oxides, and it can be the best candidate in the case of their particle size less than 10 nm. The ordered alloy FePt nanoparticles are synthesized by reduction of Fe and Pt organo-metallic compounds with tetraethylene glycol using poly(N-vinyl-2-pyrrolidone) (PVP) as a protective agent. PVP is a water-soluble polymer, and is proper to obtain dispersion into water. Influences of reaction temperature on crystallite size (particle size) and blocking temperature and the relationship between the blocking temperature and the value of ac magnetic susceptibility at around room temperature are investigated. Furthermore, PVP concentration at the synthesis to obtain well dispersed nanoparticle-suspension is examined.     

药物在体内分布及肝靶向性研究

研究了齐墩果酸-乳酸羟基乙酸共聚物-水溶性维生素E-纳米粒(OA-PLGA-TPGS-NPs,即OA-NPs)在小鼠体内的分布及肝靶向性。按超声乳化-溶剂挥发法制备OA-NPs。经小鼠尾静脉给药,采用RP-HPLC法检测齐墩果酸在小鼠血浆、心、肝、脾、肺、肾中的浓度随时间的变化,与齐墩果酸溶液剂(OA-SOLs)组进行比较。OA-NPs组各时间点肝内药物浓度远高于OA-SOLs组,药物持续作用时间明显长于OA-SOLs组;OA-NPs组药物对肝的5个靶向指标值均显著高于OA-SOLs组;OA-NPs组各时间点血、心、肝、脾、肺、肾中药物浓度显著低于OA-SOLs组。OA-NPs可实现肝脏被动靶向,能够提高药物疗效,降低全身毒副作用。     

Synthesis and Magnetic Properties of Nearly Monodisperse CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>Nanoparticles Through a Simple Hydrothermal Condition

Nearly monodisperse cobalt ferrite (CoFe₂O₄) nanoparticles without any size-selection process have been prepared through an alluring method in an oleylamine/ethanol/water system. Well-defined nanospheres with an average size of 5.5 nm have been synthesized using metal chloride as the law materials and oleic amine as the capping agent, through a general liquid–solid-solution (LSS) process. Magnetic measurement indicates that the particles exhibit a very high coercivity at 10 K and perform superparamagnetism at room temperature which is further illuminated by ZFC/FC curves. These superparamagnetic cobalt ferrite nanomaterials are considered to have potential application in the fields of biomedicine. The synthesis method is possible to be a general approach for the preparation of other pure binary and ternary compounds.     

B掺杂FePt基纳米复合膜的制备与磁学性能研究

利用磁控溅射法将厚度可控的B掺杂到FePt多层膜中,构成FePtB多层膜体系。多层膜结构采用中间层掺杂和底层掺杂等方式组合,由此研究热处理温度与B掺杂对FePtB多层膜体系磁学性能的影响,分析成相过程。另一方面,B层作为中间层掺杂到FePt多层膜样品中构成不同B掺杂浓度的多层膜体系,通过X射线衍射等表征手段研究不同的掺杂浓度对FePt多层膜样品成相及退火温度的影响。实验结果表明,B掺杂的FePt多层膜样品的矫顽力大幅度提高,出现垂直择优取向;随着B层厚度的增加,FePtB多层膜体系的磁有序相比例增加,当B层为14nm时,FePtB多层膜体系展现良好的垂直取向特性。此外,B掺杂降低了FePt多层膜样品的退火温度。     

表面活性剂调节高矫顽力FePt纳米颗粒的合成

在表面活性剂聚乙烯吡咯烷酮(PVP)存在的体系中,通过NaBH4还原前驱体Fe(acac)3和H2PtCl6·6H2O,制备出了单分散的尺寸在3.0 nm左右的FePt纳米颗粒。XRD和TEM表征结果显示,表面活性剂PVP的用量影响FePt纳米颗粒相变,但对颗粒的尺寸无明显作用。由此推测,PVP对FePt纳米颗粒的相变起"催化"作用,适量的PVP诱导纳米颗粒的相变,可以通过改变表面活性剂的用量来调节FePt纳米颗粒的磁性能,当表面活性剂PVP单体与FePt前驱体的摩尔比(PVP/FePt)为7时,制得的FePt纳米颗粒经过500℃保温30 min热处理后,矫顽力高达5.2 kOe。     

纳米微胶囊牛肉香精的制备技术研究

本文研究了以壳聚糖和三聚磷酸钠为载体,采用离子凝胶化法以及喷雾干燥技术制备出装载牛肉香精的壳聚糖-三聚磷酸钠纳米微胶囊,确定了其最佳制备工艺参数并通过透射电镜、动态激光光散射仪和紫外分光光度计对其进行了分析检测,得到了香气稳定、粒径分布较好的纳米微胶囊香精产品。     

Structural and compositional evolution of FePt nanocubes in oganometallic synthesis

In this study, the mechanisms for the formation of FePt nanocubes via pyrolysis of iron pentacarbonate [Fe(CO)₅] and platinum(II) acetylacetonate [Pt(acac)₂] were investigated. The time evolution of the structure, morphology, and composition of the FePt nanocubes was probed by transmission electron microscopy (TEM) at different reaction stages. On the basis of the detailed characterization, we determined the following aspects of the reaction mechanism: (1) The FePt nanocubes are rapidly formed at 160°C to 180°C by the decomposition of the precursors, and the formation of the FePt nanocubes is dominated by the nucleation of Pt-rich species followed by a slow deposition process of Fe atoms. (2) A thin Fe atomic layer is present on the FePt nanocubes, which does not influence their phase transition into a fct structure. (3) The use of Fe(CO)₅ is the key factor leading to the anisotropic growth of the FePt nanocubes, and the Fe(CO)₅/Pt(acac)₂ molar ratio not only determines the composition of the resulting FePt nanocubes but also affects their morphology and structures.     

PTA尾气组成及浓度分布的研究

通过典型炼厂PTA装置尾气来源及去向分析,对装置排放点尾气组成及浓度分布进行了研究,采用气相色谱/质谱法研究了PTA尾气组成,采用直接进样大口径毛细管柱气相色谱法,测定了PTA尾气中溴甲烷、乙酸甲酯、苯、甲苯、对二甲苯、乙酸。进样量为1 m L时,方法对溴甲烷、乙酸甲酯、苯、甲苯、对二甲苯、乙酸的最低检出浓度分别为0.5、0.5、0.5、0.5、1.5,20 mg/m~3,加标回收率为95.2%~99.4%,相对标准偏差为1.8%~3.9%。采用总烃测定仪和烟气分析仪对总烃、一氧化碳、二氧化碳、氧气等进行了分析。同时采用本法对PTA尾气治理设施处理效率进行了评价,证明方法具有较好的适应性。     

纳米粒子的热分解动力学模型

研究了纳米粒子热分解反应的动力学规律,首次提出了纳米粒子热分解的通用的微分速率方程,导出了纳米粒子热分解通用的动力学微分机理函数;并且用纳米碳酸钙、纳米碳酸锌和纳米氢氧化铜的热分解数据考察了机理函数的适用性.研究结果表明3种纳米粒子热分解过程具有相似的动力学规律和相同的机理函数,其速率方程与纳米粒子瞬时表而积分数的幂成正比,其机型函数为纳米粒子剩余质量分数的2n/3次方.     

Preparation of Monodisperse Iron Oxide Nanoparticles via the Synthesis and Decomposition of Iron Fatty Acid Complexes

Iron fatty acid complexes (IFACs) are prepared via the dissolution of porous hematite powder in hot unsaturated fatty acid. The IFACs are then decomposed in five different organic solvents under reflux conditions in the presence of the respective fatty acid. The XRD analysis results indicate that the resulting NPs comprise a mixture of wustite, magnetite, and maghemite phases. The solvents with a higher boiling point prompt the formation of larger NPs containing wustite as the major component, while those with a lower boiling point produce smaller NPs with maghemite as the major component. In addition, it is shown that unstable NPs with a mixed wustite–magnetite composition can be oxidized to pure maghemite by extending the reaction time or using an oxidizing agent.     

Effect of Ni2+ substitution on structural,magnetic, dielectric and optical properties of mixed spinel CoFe2O4 nanoparticles

Nanoparticles of Co_1−xNi_xFe₂O₄ with x=0.0, 0.10, 0.20, 0.30, 0.40 and 0.50 were synthesized by co-precipitation method. The structural analysis reveals the formation of single phase cubic spinel structure with a narrow size distribution between 13–17 nm. Transmission electron microscope images are in agreement with size of nanoparticles calculated from XRD. The field emission scanning electron microscope images confirmed the presence of nano-sized grains with porous morphology. The X-ray photoelectron spectroscopy analysis confirmed the presence of Fe²⁺ ions with Fe³⁺. Room temperature magnetic measurements showed the strong influence of Ni²⁺ doping on saturation magnetization and coercivity. The saturation magnetization decreases from 91 emu/gm to 44 emu/gm for x=0.0–0.50 samples. Lower magnetic moment of Ni²⁺ (2 µ_B) ions in comparison to that of Co²⁺ (3 µ_B) ions is responsible for this reduction. Similarly, overall coercivity decreased from 1010 Oe to 832 Oe for x=0.0–0.50 samples and depends on crystallite size. Cation distribution has been proposed from XRD analysis and magnetization data. Electron spin resonance spectra suggested the dominancy of superexchange interactions in Co_1−xNi_xFe₂O₄ samples. The optical analysis indicates that Co_1−xNi_xFe₂O₄ is an indirect band gap material and band gap increases with increasing Ni²⁺ concentration. Dispersion behavior with increasing frequency is observed for both dielectric constant and loss tangent. The conduction process predominantly takes place through grain boundary volume. Grain boundary resistance increases with Ni²⁺ ion concentration.     

高纯、单分散二氧化硅纳米粒子的制备

本文以单晶硅粉作为硅源,氨水作为催化剂,制备了二氧化硅纳米粒子.研究了单晶硅粉制备二氧化硅纳米粒子时反应条件对反应产率和粒径的影响,并通过单因素实验法和正交设计法获得了最佳实验条件.通过激光粒度分析仪、电感耦合等离子体-质谱(ICP-MS)、扫描电子显微镜(SEM)等方法对纳米二氧化硅粒子的纯度、形貌、粒径进行了表征,得到了高纯、单分散的二氧化硅纳米粒子.     

The effects of surface spin on magnetic properties of weak magnetic ZnLa0.02Fe1.98O4 nanoparticles

In order to prominently investigate the effects of the surface spin on the magnetic properties, the weak magnetic ZnLa_0.02Fe_1.98O₄ nanoparticles were chosen as studying objects which benefit to reduce as possibly the effects of interparticle dipolar interaction and crystalline anisotropy energies. By annealing the undiluted and diluted ZnLa_0.02Fe_1.98O₄ nanoparticles at different temperatures, we observed the rich variations of magnetic ordering states (superparamagnetism, weak ferromagnetism, and paramagnetism). The magnetic properties can be well understood by considering the effects of the surface spin of the magnetic nanoparticles. Our results indicate that in the nano-sized magnets with weak magnetism, the surface spin plays a crucial rule in the magnetic properties.     

Structural,dielectric and ferromagnetic behavior of (Zn,Co) co-doped SnO2 nanoparticles

Nanoparticles of basic composition Sn_0.94Zn_0.05Co_0.01O₂, Sn_0.92Zn_0.05Co_0.03O₂ and Sn_0.90Zn_0.05Co_0.05O₂ were synthesized by chemical precipitation method. The incorporation of Co and Zn in SnO₂ lattice introduced significant changes in the physical properties of all the three nanocrystals. The average particle size estimated from TEM data decreased from 15.71 to 6.41  nm with enhancement in concentration of oxygen vacancies as Co content is increased from 1 to 5 wt%. Increasing Co content enhanced the Sn:O atomic ratio as a result concentration of oxygen vacancies increased. The dielectric study revealed strong doping dependence. The dielectric parameters (ε′, tanδ and σ_ac) increased with increasing Co content and attained maximum values for 5% (Zn, Co) co-doped SnO₂ nanoparticles. The dielectric loss (ε′′) exhibited dispersion behavior and the Debye’s relaxation peaks observed in dielectric loss factor (tanδ), whose intensities increased with increasing Co content. The variation of dielectric properties and ac conductivity revealed that the dispersion is due to Maxwell-Wagner interfacial polarization and hopping of charge carriers between Sn⁺²/Sn⁺³ and Co⁺²/Co⁺³. The large dielectric constant of all samples made them interesting materials for device application. Magnetization measurements (M (H) loops) revealed enhancement in saturation magnetization with doping which is due to the formation of large amount of induced defects and oxygen vacancies in the samples. The present study clearly reveals doping dependent properties and the oxygen vacancies induced ferromagnetism in Zn, Co co-doped SnO₂ nanoparticles having applications in ultra-high dielectric materials, high frequency devices and spintronics.     

Influence of Nanoparticles and Drop Size Distributions on the Rheology of w/o Pickering Emulsions

The rheological behavior of particle/oil suspensions and w/o Pickering emulsions consisting of water, 1‐dodecene and different fumed silica nanoparticles was investigated. The particles varied in hydrophobicity and specific surface area. The influence of particle concentration and water content on rheology was determined and the emulsion drop size distributions were examined. Emulsions with different drop sizes were created by either varying the particle concentration or the water content. It was found that the particles in the continuous oil phase and not the drop size distribution seem to be the major influencing factor on the Pickering emulsion rheology.     

Microwave combustion synthesis,magneto-optical and electrochemical properties of NiMoO4 nanoparticles for supercapacitor application

Nickel molybdate (NiMoO₄) nanoparticles (NPs) were synthesized by a simplistic one-pot microwave combustion method using urea as the fuel. The produced NPs have been examined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) analysis, scanning electron microscope (SEM), energy dispersive X-ray (EDX), high-resolution transmission electron microscopy (HR-TEM) analysis. Further, optical and electronic properties were determined by UV-Visible and Photoluminescence (PL) analysis, respectively. The magnetic performance of the NiMoO₄ NPs was investigated by vibrating sample magnetometer (VSM) and the surface chemical composition was identified by X-ray photoelectron spectroscopy (XPS). The electrochemical activities of the NiMoO₄ NPs were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD) analysis. From the results, the CV curves indicated the occurrence of redox couples and besides with the EIS data (Nyquist plot), confirmed the supercapacitor nature of the synthesized NiMoO₄. The prepared NiMoO₄ exhibits a high specific capacitance and rateability. This electrode grants a high specific capacitance of 450?F?g^?1 at 2?mA?cm^?2 and the well permanency with a cycling proficiency of 94% after 1000 cycles. These results clearly showed that the synthesized NiMoO₄ NPs have potential application for the forthcoming flexible and lightweight energy storage.