单分散Fe3O4纳米颗粒的控制合成和表征

以十八烯为溶剂、乙酰丙酮铁为铁源,并在油酸、油胺的辅助作用下,通过热分解法成功合成了单分散Fe3O4纳米颗粒。讨论了实验参数如反应温度、表面活性剂的量和种类、溶剂、油酸、油胺对单分散Fe3O4纳米颗粒的尺寸及形貌的影响。利用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）和高分辨透射电子显微镜（HRTEM）对所得产物的物相、结构、尺寸和形貌进行了表征分析。通过振动样品磁强计（VSM）表征产物磁性能,表明在室温下,Fe3O4纳米颗粒的饱和磁化强度（Ms）和矫顽力（Hc）分别为74.0 emu/g,72.6 Oe。     

液相热分解纳米铁镍合金的形貌可控合成及其磁学性能研究

以Fe(CO)₅和Ni(HCOO)₂为前驱物,十八烯为溶剂,在表面活性剂和分散剂油酸和油胺的协同作用下,通过前驱体的液相热分解和自合金化,制备铁镍合金纳米颗粒。通过XRD和TEM研究了产物的微观结构,并对产物的磁学性质进行了表征。结果表明,在反应温度为200 ℃,油胺与油酸及甲酸镍的物质的量比为4∶2∶1,反应时间为20 min时可得形貌可控、抗氧化性强的面心立方晶体结构的平面三角形纳米铁镍合金,晶粒尺寸为15~55 nm。磁性测量表明,300 K时三角形形貌铁镍合金的饱和磁化强度为15.5 emu·g^-1,矫顽力趋近于零,呈现超顺磁性;在低温(4.2 K)时,铁镍合金的饱和磁化强度为17.5 emu·g^-1,矫顽力增大明显。     

纳米Fe3O4/聚苯乙烯均匀分散体系的制备及结构

用化学共沉淀法制备了Fe3O4纳米颗粒,以油酸为表面活性剂,苯乙烯为载液,制备了稳定的纳米Fe3O4可聚合磁流体,将可聚合磁流体经自由基引发聚合制成纳米Fe3O4/聚苯乙烯均匀分散体系,用WAXRD研究了Fe3O4纳米粒子的结晶情况;用FTIR研究了油酸表面改性前后Fe3O4粒子表面官能团的变化;用TEM研究了Fe3O4颗粒的粒径大小及其在苯乙烯单体和聚苯乙烯中的分散情况;用DSC和TGA研究了纳米Fe3O4/聚苯乙烯均匀分散体系的玻璃化转变温度(Tg)和热稳定性,结果表明,合成的纳米Fe3O4为立方晶型,平均粒径在10nm左右,油酸分子在Fe3O4表面是化学吸附,经表面处理的Fe3O4超细颗粒在苯乙烯和聚苯乙烯基体中分散较均匀.界面粘结较好,含1.8％Fe3O4纳米颗粒的聚苯乙烯的最大热失重温度比聚苯乙烯提高了13K,Fe3O4/聚苯乙烯复合体系的饱和磁化强度σs为17.43emu/g.     

单分散Fe_3O_4亚微米球的合成与表征

采用溶剂热法制备出具有尺寸可调、分散性好、亲水性和超顺磁性的亚微米Fe3O4磁球,并考察了不同表面活性剂、反应时间和反应温度的影响。分别采用XRD、FE-SEM、FTIR、超导量子干涉仪(SQUID)对其结构、形貌、表面性质及磁性进行了表征。结果表明,产物为立方结构、具有单分散性的Fe3O4亚微米球,粒径在140~360nm可调。所得Fe3O4亚微米球在室温条件下的磁滞回线表现出超顺磁性,矫顽力为零。不同表面活性剂对粒径大小和磁饱和强度有一定的影响,但对其形貌和晶相结构无影响。随着反应时间的延长和反应温度的提高,颗粒粒径有逐渐减小的趋势。     

Fe3O4纳米颗粒的表面改性

通过实验对Fe3O4纳米颗粒表面改性的最佳条件进行了摸索.并根据表面改性的包覆机理对不同酸度,温度和表面活性剂的用量对Fe3O4纳米颗粒的尺寸,磁性和稳定性的影响进行了理论上的分析.     

单分散球形纳米Fe3O4的可控合成和嵌锂性质研究

利用水热法合成出单分散的球形纳米Fe3O4,探讨含十二烷基三甲基溴化铵表面活性剂合成样品形貌和尺寸.测试表明Fe3O4纳米球呈现出优越的倍率性能和循环性能.     

Fe3O4-PMMA复合纳米微球的制备与表征

采用化学共沉淀法合成了超顺磁Fe3O4纳米粒子,并采用油酸和油酸钠对其表面进行修饰,制备了可稳定分散于水中的磁流体。以该磁流体为种子,通过一步乳液聚合制备了表面带有功能化羧基的Fe3O4-聚甲基丙烯酸甲酯复合纳米微球（Fe3O4-PMMA）。利用动态光散射、透射电镜观察、傅里叶红外光谱、热失重分析、振动样品磁强计测试等手段表征了复合微球的尺寸、形态、结构、组成和磁性能。结果表明,复合微球的平均直径约120nm,表面带有羧基功能基团,在室温下具有超顺磁性和较高的饱和磁化强度。     

Trition X-100/C_(10)H_(21)OH/H_2O体系层状液晶中纳米羟基磷灰石粉体的合成

本文以Triton X-100/C10H21OH/H2O体系层状溶致液晶为模板,Ca(NO3)2和(NH4)2HPO4为反应物,在一定的pH条件下,通过三元相图确定了层状液晶单相区域,并合成了羟基磷灰石(HA)纳米颗粒。用傅立叶红外光谱(FTIR),X射线衍射(XRD)和透射电子显微镜(TEM)对产物进行了表征。并考察了不同助表面活性剂浓度和不同表面活性剂浓度对产物的形貌和尺寸的影响。结果表明所制备的HA纳米颗粒平均直径为8~10nm、长度在100nm左右,呈针状。助表面活性剂浓度对HA形貌及尺寸影响不大,但是在一定范围内改变表面活性剂浓度可以起到调控HA纳米颗粒形貌和尺寸的作用。     

沉淀转化法制备多孔片状纳米LaF3

采用实验中所合成的LaPO4纳米棒为前驱体,通过沉淀的转化作用,大面积地制备了单分散的片状纳米LaF3。采用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、BET(Brunauer-Emmett-Teller)测试对片状纳米LaF3的形貌、结构、相组成及表面性质进行了分析。片状纳米LaF3底边长约为40 nm,片的厚度约为35 nm,大小均一,具有多孔结构。通过改变反应溶剂,可以控制LaF3粒子的成核、生长和团聚,从而有效地调控多孔片状纳米LaF3的颗粒尺寸和分散性。对多孔片状纳米LaF3的生长机制进行了研究,结果表明LaPO4和LaF3的溶度积常数差导致了片状纳米LaF3的生成;体系中自身存在的Ostwald ripening作用使片状纳米LaF3出现了多孔结构。     

静电纺丝法制备定向排列的铁氧体纳米纤维

以聚乙烯吡咯烷酮(PVP)和金属硝酸盐为原料,采用改进的静电纺丝法制备了直径均匀、表面光滑、定向排列的Co0.8Zn0.2Fe2O4/PVP纳米纤维前驱体,经热处理后得到定向排列的铁氧体纳米纤维.对前驱体纤维的热分解过程及Co0.8Zn0.2Fe2O4(CZFO)的结构、物相及形貌进行了表征.结果表明,在空气中经550～950℃热处理3 h后均得到纯相、结晶良好的尖晶石型钴锌铁氧体;在2000 r/min转速下收集的复合纤维形貌最佳,直径约300 nm;经750℃热处理后纤维直径约为70 nm,室温下测得饱和磁化强度为66.1 A.m2/kg,矫顽力达到最大值6.6 A/m,表明钴锌尖晶石型铁氧体单畴临界尺寸约为44 nm.与CoFe2O4相比,CZFO的饱和磁化强度升高,矫顽力下降,并且CZFO的纤维与粉末的磁特性有明显的区别.     

Inorganic nanocrystal self-assembly via the inclusion interaction of beta-cyclodextrins: toward 3D spherical magnetite

Synthesis and three-dimensional (3D) assembly of magnetite nanocrystals were realized by a one-pot procedure, in which Fe(acac)3 (acac = acetylacetonate) was partly reduced by hydrazine accompanied with ethylene glycol and spontaneously assembled into spherical nanostructures in the presence of surfactants including beta-cyclodextrin, oleic acid, and oleylamine. The size of the assembled spheres can coarsely be controlled in a limited range (100 nm to 2 microm) by changing the reaction temperature and the concentration of beta-cyclodextrin. X-ray diffraction and far Fourier transform infrared spectroscopy were employed to clarify the structures of magnetite in the assembled spheres. Electron diffraction pattern in a selected-area exhibits a high-crystallinity characteristic of cubic structure magnetite. We found that the formation of spherical magnetite aggregates highly depends on the presence of beta-cyclodextrin, while oleic acid and oleylamine improve the morphology of individual magnetite nanoparticles in the assembled spheres. In addition, the thermal gravimetric analysis and differential thermal analysis were applied to determine the content of magnetite in the products. Magnetic properties were also studied by using a superconducting quantum interference device magnetometer.     

Size-controlled synthesis of magnetite nanoparticles

Monodisperse magnetite nanoparticles have been synthesized by high-temperature solution-phase reaction of Fe(acac)3 in phenyl ether with alcohol, oleic acid, and oleylamine. Seed-mediated growth is used to control Fe3O4 nanoparticle size, and variously sized nanoparticles from 3 to 20 nm have been produced. The as-synthesized Fe3O4 nanoparticles have inverse spinel structure, and their assemblies can be transformed into gamma-Fe2O3 or alpha-Fe nanoparticle assemblies, depending on the annealing conditions. The reported procedure can be used as a general approach to various ferrite nanoparticles and nanoparticle superlattices.     

Monodisperse MFe2O4 (M = Fe, Co, Mn) nanoparticles

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)(3), with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe(3)O(4)) nanoparticles. Similarly, reaction of Fe(acac)(3) and Co(acac)(2) or Mn(acac)(2) with the same diol results in monodisperse CoFe(2)O(4) or MnFe(2)O(4) nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe(3)O(4) can be oxidized to Fe(2)O(3), as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.     

Understanding mercapto ligand exchange on the surface of FePt nanoparticles

Tailoring the surface of nanoparticles is essential for biological applications of magnetic nanoparticles. FePt nanoparticles are interesting candidates owing to their high magnetic moment. Established procedures to make FePt nanoparticles use oleic acid and oleylamine as the surfactants, which make them dispersed in nonpolar solvents such as hexane. As a model study to demonstrate the modification of the surface chemistry, stable aqueous dispersions of FePt nanoparticles were synthesized after ligand exchange with mercaptoalkanoic acids. This report focuses on understanding the surface chemistry of FePt upon ligand exchange with mercapto compounds by conducting X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) studies. It was found that the mercapto end displaces oleylamine on the Pt atoms and the carboxylic acid end displaces the oleic acid on the Fe atoms, thus exposing carboxylate and thiolate groups on the surface that provide the necessary electrostatic repulsion to form stable aqueous dispersions of FePt nanoparticles.     

Metal ion redox potential plays an important role in high-yield synthesis of monodisperse silver nanoparticles

A facile method is developed to prepare monodisperse silver nanoparticles in a much enhanced yield by adding a trace amount of Fe(3+) ions into the reaction of AgNO(3) with oleic acid and oleylamine. We propose that Fe(2+) ions speed up the nucleation and growth of silver nanoparticles due to the electron-transfer between Ag(+) and Fe(2+), in which Fe(2+) is from Fe(3+) reduced by oleylamine.     

Fe3O4-LiMo3Se3 nanoparticle clusters as superparamagnetic nanocompasses

A scaleable chemical approach to functional nanoscale analogues of the magnetic compasses in magnetotactic bacteria is described. LiMo(3)Se(3)-Fe(3)O(4) nanowire-nanoparticle composites were synthesized by a reaction of 3-iodopropionic acid treated LiMo(3)Se(3) nanowire bundles with oleic acid-stabilized Fe(3)O(4) nanoparticles of 2.8, 5.3, and 12.5 nm size in tetrahydrofuran. Transmission electron micrographs show that the composite consists of Fe(3)O(4) nanoparticles attached to the surfaces of the 4-6 nm thick nanowire bundles. UV/vis spectra reveal absorptions from the nanowire (506 nm) and magnetite components (280-450 nm), and IR spectra show characteristic bands for the propionic acid linkers and for the residual oleic acid ligands on the magnetite particles. In the presence of excess oleic acid, the nanocomposites undergo rapid disassembly, suggesting that Fe(3)O(4) nanoparticles are bonded to nanowires via carboxylate groups from the linkers. Ultrasonication of a dispersion of the composite in THF produces individual LiMo(3)Se(3)-Fe(3)O(4) clusters, which are 340 +/- 107 nm long and 20 +/- 5 nm thick, depending on the sonication time and Fe(3)O(4) nanoparticle size. Field cooled and zero-field cooled magnetization measurements reveal that the blocking temperature (T(B) = 100 K) of the clusters with 5.3 nm Fe(3)O(4) is increased as compared to the free nanoparticles (T(B) = 30 K). Directional dipolar interactions in the clusters lead to magnetic anisotropy, which makes it possible to align the clusters in a magnetic field (900 Oe).     

Ambient pressure syntheses of size-controlled corundum-type In2O3 nanocubes

Hydrolysis of In(O-iPr)3 by 10 molar excess of water at 90 degrees C in a surfactant/solvent mixture of oleylamine/oleic acid/trioctylamine provides very small nanoparticles (<5 nm in diameter) of In(O)(OH). Subsequent in situ thermolysis of the formed In(O)(OH) nanoparticles at 350 degrees C and ambient pressure produces monodisperse h-In2O3 nanocubes, which can form an extended two-dimensional array on a flat surface. The size of the In2O3 nanocubes (8, 10, and 12 nm) could be easily controlled by the simple change in the amounts of employed surfactants. The h-In2O3 nanocube samples show blue PL emissions at room temperature due to, presumably, systematic oxygen vacancy.     

Adsorption of surfactants on superfine magnetite

Superfine magnetite particles were obtained by chemical condensation. Their size can be varied by the magnetic field application and a change in the crystallization temperature. The X-ray diffraction and adsorption data suggested an increase in the crystallite size and a decrease in the value of limiting adsorption and specific area of magnetite with an increase in the temperature and magnetic field intensity. The nature of surfactants and solvents has a substantial effect on the adsorption process. The IR spectroscopic and equilibrium adsorption data showed that oleic acid has the highest affinity to the surface among the surfactants studied (stearic, oleic, and linoleic acids and sodium oleate). On going from carbon tetrachloride to hexane, the value of limiting adsorption of oleic acid decreases.