Simultaneous synthesis of polyaniline nanorods and magnetite nanoparticles via self-assembly method

In this work, polyaniline (PANI) nanorods and magnetite (Fe₃O₄) nanoparticles have been synthesised by using ammonium persulphate as oxidant via in-situ chemical oxidative polymerisation of aniline in presence of excess of organic sulphonic acid. The resulting PANI/Fe₃O₄ nanocomposites materials were characterised using X-ray diffraction, UV-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sampling magnetometer and thermogravimetric analysis. Spectroscopic results indicated the successful formation of PANI/Fe₃O₄ nanocomposites. As obtained, PANI/Fe₃O₄ nanocomposites have Fe₃O₄ particle size in the range of 3.2–7?nm. Morphologies of PANI/Fe₃O₄ nanocomposites were found to be dependent on the molar ratio of aniline to organic acid. Under certain polymerisation conditions, PANI rods like structures were obtained. PANI/Fe₃O₄ nanocomposites have superparamagnetism and higher thermal stability.     

Effect of the preparation route,PEG and annealing on the phase stability of Fe3O4 nanoparticles and their magnetic properties

Fe₃O₄ nanoparticles are synthesised via two different methods: (1) co-precipitation of Fe²⁺ and Fe³⁺ ions and (2) oxidative alkaline hydrolysis of Fe²⁺ ions under atmospheric pressure using different protective agents (PEG 200 and PEG 3000) and urea as a base. The preparation method and the polyethylene glycol (PEG) used are concurrently affecting the phase stability of the formation of the iron oxides: the co-precipitation method using PEG 200 (E4a) or PEG 3000 (E4b) leads to the formation of different ratios of Fe₂O₃ and Fe₃O₄, whereas the oxidative hydrolysis of Fe²⁺ using PEG 200 gives Fe₃O₄ (E2) powder as a major product. The average crystallites size of E4a and E4b is almost identical, i.e. around 19?nm but the saturation magnetisation of E4b is three times larger than that of E4a. The sample E2 shows the highest saturation magnetisation value 74?emu/g, with an average crystallites size of 71?nm. Transmission electron microscopy analysis confirmed that the E2 sample shows the presence of needles crystals with typical sizes around 10 and 50?nm and its selected area diffraction (SAD) shows a typical diffraction of the spinel structure of magnetite. On the other hand, E4b sample shows elongated nanoparticles with typical sizes around 24?nm and its SAD confirmed the presence of a mixture of Fe₂O₃ and Fe₃O₄ as many dispersed spots were obtained.     

Investigation of structural,optical, magnetic,and electrical properties of PMMA doped with magnetite nanoparticles

Journal of Materials Science: Materials in Electronics - This research deals with structural, optical, electrical, and magnetic properties of nanocomposite composed of polymethyl methacrylate...     

Characterisation and intrinsic magnetic resonance properties of nickel nanoparticles

Nickel nanoparticles have been extensively characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM) and confocal micro-Raman spectroscopy. AFM underestimates the particle size compared to SEM measurements. It is shown that Raman spectroscopy can detect the nanometre-thick NiO layer on the particles having frequency shifts of the modes indicative of phonon confinement. The magnetic properties of the particles are studied by ferromagnetic resonance (FMR) of magnetic field aligned particles. The alignment is achieved by suspending the particles in the liquid crystal MBBA and freezing the liquid in a 0.4 T DC magnetic field. The in-field solidification locks the direction of maximum magnetisation of the particles parallel to the direction of the applied DC magnetic field. This removes the effects of dynamical particle fluctuations of the nanoparticles on the magnetic properties allowing a study of the intrinsic magnetic properties of the magnetic nanoparticles. The intensity of the FMR signal decreased with lowering temperature for the particles frozen in the liquid in a 0.4 T DC magnetic field. The effect is suggested to be due to a reduction of the microwave skin depth with lowering temperature.     

Characterization and magnetic properties of conducting poly(N-vinylcarbazole)-capped magnetite nanocomposite Langmuir-Schaefer films

Functionalized poly(N-vinylcarbazole) (PVK) has been synthesized by an oxidative polymerization with capped magnetite nanoparticles (CMPs, 10, 20, and 30%) for the preparation of conducting polymer composites that possess both electrical and magnetic properties. Spectroscopic studies reveal the successful functionalization of the nanoparticles into the PVK matrix. I-V characteristics of the composite films show an increase in the conductivity of the PVK film due to the presence of CMPs. The magnetization data exhibit an appreciable hysteresis loop at room temperature. The composite samples reveal an ordered semi-conducting behavior.     

聚合物包覆纳米铁粒子的结构及其磁性能研究进展

纳米铁粒子具有极大的反应活性而被氧化.本文简要综述了聚合物包覆的纳米铁及其磁性能的研究进展.     

Morphological and optical properties of PdxAg1-x alloy nanoparticles

Alloy nanoparticles (NPs) can offer a wide range of opportunities for various applications due to their composition and structure dependent properties such as multifunctionality, electronic heterogeneity, site-specific response, and multiple plasmon resonance bands. In this work, the fabrication of self-assembled Pd_xAg_1-x NPs alloy nanostructures with distinct size, density, shape, and composition is demonstrated via the solid-state dewetting of sputtered Pd/Ag thin films on c-plane sapphire. The initial stage of bilayer dewetting exhibits the nucleation of voids, followed by the expansion of voids and cluster breakdown and finally shape transformation along with the temperature control. Bilayer composition shows a substantial influence on the dewetting such that the overall dewetting is enhanced along with the increased Ag composition, i.e. Pd_0.25Ag_0.75 > Pd_0.5Ag_0.5 > Pd_0.75Ag_0.25. On the other hand, the size and density of NPs can be efficiently controlled by varying the initial thickness of bilayers. Reflectance peaks in UV and near-infrared (NIR) regions and a wide absorption band in the visible region arisen from the surface plasmon resonance are observed in reflectance spectra. The peak intensity depends on the composition of Pd_xAg_1-x NPs and the NIR peaks gradually blue-shift with the size decrement.     

锰锌铁氧体纳米粒子的制备和磁性能研究

以金属离子的硫酸盐溶液和氨水溶液为原料,采用水热法制备了粒径为6～16nm的锰锌铁氧体纳米粒子.采用XRD、TEM、TGA和VSM等方法对产物以及产物的磁性能进行了表征.结果表明,锰锌铁氧体(Mn1-xZnxFe2O4)的居里温度随着锌的相对含量x的增加而单调的降低.锰锌铁氧体的磁化强度先随着锌的相对含量x的增加而增大,当锌的相对含量＞0.6时,磁化强度随着锌的相对含量x的增加而减小.测量了锰锌铁氧体磁流体的饱和磁化强度,计算了锰锌铁氧体(Mn0.4Zn0.6Fe2O4)纳米粒子的磁矩,其值为1.01×10-19A·m2.     

分散的Sm-Co永磁纳米颗粒的机械化学合成及磁性能

通过机械化学合成方法制备了矫顽力分别为2.95×106、2.83×106和8.60×105 A/m的分散的单晶纳米Sm2Co7、SmCo5和Sm2Co17硬磁颗粒。研究了球磨时间、原料配比和退火工艺等对所制备的纳米永磁颗粒的微观组织、结构和磁性能的影响。结果表明,机械化学球磨时间至少是4h或更长时间才能获得Sm-Co硬磁合金粉末。原料经过高能球磨后、未退火时,由于大部分颗粒为非晶结构,矫顽力较低,随着退火温度的上升,矫顽力增大,当退火温度为600℃时,达到最大值为2.83×106 A/m,然后,随着退火温度的进一步升高,矫顽力减小。Sm-Co纳米颗粒的粒径随着退火温度的降低而明显减小。     

金/银合金纳米颗粒的制备及光学吸收特性

以柠檬酸盐为还原剂,通过共还原氯金酸和硝酸银的混合溶液制备出Au／Ag合金纳米颗粒,用透射电子显微镜（TEM）对颗粒的形貌和尺寸进行了表征。300-800nm范围的吸收光谱研究发现,Au／Ag合金纳米颗粒具有单峰等离子体吸收特征,且随着反应液中氯化金和硝酸银的摩尔比的减少,吸收峰将产生蓝移。实验结果表明,Au-Ag合金纳米颗粒的光学吸收特性具有组分可裁剪性,使其在纳米尺度的光学领域具有潜在的应用价值。     

磁性钴纳米粒子的制备和应用

介绍了制备磁性钴纳米粒子的方法 ,尤其是介绍了近年发展起来的高温液相法 ,即高温液相还原法 ,金属盐醇解法和金属有机化合物热分解法 ;同时就制备颗粒尺寸小、粒度分布均匀的钴纳米粒子所采用的两种表面活性剂从理论上给予了说明。最后简单介绍了磁性金属钴纳米粒子的主要应用。     

High yield synthesis and characterization of the structural and magnetic properties of crystalline ErCl3 nanowires in single-walled carbon nanotube templates

Crystalline ErCl₃ nanowires have been fabricated in single-walled carbon nanotubes (SWCNTs) with high yield (∼90%), and the structural and magnetic properties of the resulting ErCl₃ nanowires encapsulated in SWCNTs (ErCl₃@SWCNTs) characterized. Encapsulation under high temperature and vacuum using high quality SWCNTs results in a high filling-ratio of ErCl₃ nanowires in the SWCNTs. The high filling-ratio of ErCl₃ nanowires and the use of highly pure SWCNTs with only a small amount of residual Fe catalyst nanoparticles enabled us to observe the magnetic properties of ErCl₃@SWCNTs. Structure determination based on simulated annealing calculations and high-resolution transmission electron microscope (HRTEM) image simulations revealed that the structure of the ErCl₃ nanowires is unusual with respect to the coordination environment of the Eu³⁺ ions. This work opens up new possibilities to fabricate various metal complex nanowires with high yield and may also be of more general importance in understanding and exploring magnetic properties in low-dimensional magnetic systems.     

Synthesis,self-assembly,and characterization of PEG-coated iron oxide nanoparticles as potential MRI contrast agent

Aim: Investigated the self-assembly and characterization of novel antifouling polyethylene glycol (PEG)-coated iron oxide nanoparticles as nanoprobes for magnetic resonance imaging (MRI) contrast agent. Method: Monodisperse oleic acid-coated superparamagnetic iron oxide cores are synthesized by thermal decomposition of iron oleate. The self-assembly behavior between iron oxide cores and PEG-lipid conjugates in water and their characteristics are confirmed by transmission electron microscope, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. Result: Dynamic light scattering shows superparamagnetic iron oxide nanoparticles coated with PEG are stable in water for pH of 3–10 and ionic strengths up to 0.3 M NaCl, and are protein resistant in physiological conditions. Additionally, in vitro MRI study demonstrates the efficient magnetic resonance imaging contrast characteristics of the iron oxide nanoparticles. Conclusion: The result indicates that the novel antifouling PEG-coated superparamagnetic iron oxide nanoparticles could potentially be used in a wide range of applications such as biotechnology, MRI, and magnetic fluid hyperthermia.     

Size-dependent structural and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

Phase transitions and magnetic properties of shape-memory materials can be tailored by tuning the size of the constituent materials,such as nanoparticles.However,owing to the lack of suitable synthetic methods for size-controlled Heusler nanoparticles,there is no report on the size dependence of their properties and functionalities.In this contribution,we present the first chemical synthesis of size-selected Co-Ni-Ga Heusler nanoparticles.We also report the structure and magnetic properties of the biphasic Co-Ni-Ga nanoparticles with sizes in the range of 30-84 nm,prepared by a SBA-15 nanoporous silicatemplated approach.The particle sizes could be readily tuned by controlling the loading and concentration of the precursors.The fractions and crystallite sizes of each phase of the Co-Ni-Ga nanoparticles are closely related to their particle size.Enhanced magnetization and decreased coercivity are observed with increasing partide size.The Curie temperature (Tc) of the Co-Ni-Ga nanoparticles also depends on their size.The 84 nm-sized particles exhibit the highest Tc (≈ 1,174 K) among all known Heusler compounds.The very high Curie temperatures of the Co-Ni-Ga nanoparticles render them promising candidates for application in high-temperature shape memory alloy-based devices.     

氧化硅-磁性Fe3O4复合纳米粒子的制备及应用

采用溶胶-凝胶法通过正硅酸四乙酯（TEOS）碱催化水解,在Fe₃O₄纳米粒子表面包裹氧化硅。利用生物倒置显微镜、场发射透射电镜、X射线衍射仪、激光粒度仪、振动样品磁强计对氧化硅/Fe₃O₄复合粒子的外貌、粒径及粒径分布、饱和磁化强度、化学成分进行了表征。结果表明,所制得的复合粒子性能良好,粒径在15 nm左右,饱和磁化强度为109 emu/g。用该磁性纳米复合粒子提取质粒DNA和基因组DNA取得良好的效果,可用于食品中致病菌的分析判定和疾病的基因诊断分析。     

Mechanochemical synthesis,structural, magnetic,optical and electrooptical properties of CuFeS2 nanoparticles

The rapid mechanochemical synthesis of nanocrystalline CuFeS₂ particles prepared by high-energy milling for 60?min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS₂ nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38?±?1?nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30?nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS₂ support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5?K to 300?K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS₂ nanoparticles has been detected to be 1.05?eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS₂ nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS₂ with good structural, magnetic, optical and electrooptical properties.     

激光剥离技术制备GaN/metal/Si的结构和光学特性研究

采用激光剥离技术结合金属熔融键合技术将生长在蓝宝石衬底上的GaN外延层转移到Si衬底上.GaN和Si表面分别用电子束蒸发Al/Ti/Au和Ti/Au/In后,在氮气环境下200℃加压实现GaN和Si的键合.采用脉冲宽度30 ns、波长248 nm的准分子脉冲激光透过蓝宝石衬底辐照GaN薄膜,在脉冲激光能量密度为380 mJ/cm2的条件下将蓝宝石衬底剥离下来,实现GaN薄膜向Si衬底的转移.样品截面显微镜和扫描电镜(SEM)照片说明经过键合工艺形成了致密的GaN/Al/Ti/Au/In/Au/Ti/Si结构.对转移衬底后的GaN薄膜进行原子力显微镜(AFM)和光致发光谱(PL)测试,结果表明金属熔融键合和激光剥离工艺没有对GaN薄膜的结构和光学特性带来明显的不利影响.     

Electronic and magnetic properties of ultra-thin epitaxial magnetite films on MgO(001)

The electronic and magnetic properties of epitaxial Fe₃O₄ (001) films on MgO(100) substrates were studied throughout the 2.5- to 30-nm thickness range using conversion electron Mössbauer spectroscopy. Despite the superparamagnetism that was observed for film thickness below 5 nm, the Verwey transition persisted even for the thinnest film. Temperature-dependent Mössbauer measurements between 80 K and 400 K revealed that the activation energy for the magnetic moment fluctuations in the 3-nm magnetite film is higher than the magnetic anisotropy energy by an order of magnitude.     

Worthwhile effects of salt-matrix reduction on shape, morphology and magnetic properties of FeNi nanoparticles

Modification of hydrogen reduction of mechanically alloyed Ni-ferrite led to well dispersed spherical FeNi nanoparticles with superior magnetic properties. The as-milled powder was reduced in hydrogen atmosphere at 600 °C for 1 h. Salt-matrix utilization during the reduction showed itself as a well barrier to the particle sintering and growth. As the results of the modified process, shape of the particles was changed, their size was decreased and their soft magnetic properties were remarkably improved as evidenced by SEM, TEM, XRD and VSM.     

多元醇法制备CoNi纳米粒子的形成机制,尺寸控制及磁性能

采用多元醇法在150～190℃合成了CoNi合金纳米粒子,利用SEM-EDX,XRD和VSM对所制备的CoNi纳米粒子形貌、成分、结构以及磁性能进行了研究,并进一步探讨了形核剂K2PtCl4对CoNi纳米粒子形貌及磁性能的影响。结果表明,在180℃用多元醇法制备的Co40Ni60(inat%)纳米粒子为FCC结构,Co2+要易于Ni2+被还原,导致最初10min内合成的CoNi纳米粒子中含有约78%(原子分数)Co,表现为高饱和磁化强度和高矫顽力,随着反应时间的延长,CoNi纳米粒子的Co含量、饱和磁化强度及矫顽力逐步下降。在150～190℃范围内,随着反应温度的提高,Ni2+的被还原能力增强,高温下合成的CoNi纳米粒子具有较低的饱和磁化强度和较小的矫顽力。形核剂K2PtCl4的加入,并不影响CoNi合金纳米粒子的成分和晶体结构。但是,随着形核剂浓度的增加,CoNi纳米粒子平均直径明显减小,其矫顽力有所增大。通过设计形核剂的浓度,CoNi纳米粒子的直径可以在96～580nm范围内任意控制。