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Synthesis of FePt nanoparticles with controlled shape and magnetic alignment has become an important goal in developing nanocrystal arrays for applications in information storage, permanent-magnet nanocomposites, and catalysis. FePt alloys are chemically stable owing to the spin–orbit coupling and the hybridization between Fe 3d and Pt 5d states, and their magnetic properties can be tuned by simply controlling the atomic ratio of Fe and Pt in the alloy structure. Recent syntheses have shown that spherical FePt nanoparticles are readily made by simultaneous reduction of platinum acetylacetonate ([Pt(acac)2]) and thermal decomposition of iron pentacarbonyl ([Fe(CO)5]). [1a,5] Thermal annealing results in hard magnetic FePt nanoparticle assemblies with coercivity reaching 30 kOe. These small FePt nanoparticles are also very active in formic acid oxidation under fuel cell reaction conditions. Despite these synthetic progresses, aligning these nanoparticles magnetically has constantly been a problem, and the magnetic easy axes of the nanocrystals in the assemblies are randomly oriented in three dimensions. Previous work on the synthesis and selfassembly of FePt nanocubes suggests that elongated nanocrystals may be used to achieve texture and magnetic alignment. This controlled alignment of FePt nanoparticles is essential for the fabrication of single-particle recording media with ultrahigh density, magnetic nanocomposites with maximum energy product, and magnetotransport devices with optimum magnetoresistivity. Herein we report a general strategy for synthesizing FePt nanowires (NWs) and nanorods (NRs). We refer to the onedimensional nanostructures with a length of 100 nm or longer as NWs, and those below 100 nm as NRs. The diameters of both nanostructures are controlled to be 2–3 nm. The nanostructures were synthesized by reduction of [Pt(acac)2] and thermal decomposition of [Fe(CO)5] in a mixture of oleylamine (OAm) and octadecene (ODE) at 160 8C with the length readily tuneable. Our synthesis is fundamentally different from the very recent report on the preparation of FePt nanorods, for which the reaction was performed in oleic acid and oleylamine in a closed autoclave reaction system without stirring, and offers much better control of both the dimensions and composition of the NWs/NRs. Owing to the structure confinement in the elongated shapes, these NWs and NRs show partial structural and magnetic alignment in thermally annealed self-assemblies. This study indicates that well-controlled NWs or NRs are likely the future choice for controlling texture and magnetic alignment in self-assembled nanomagnet arrays to support high-density magnetic information and as building blocks for fabricating highly sensitive magnetotransport devices. The length control of the FePt NWs/NRs was realized by tuning the volume ratio of OAm/ODE, reaching from over 200 nm for NWs down to 20 nm for NRs. For example, FePt NWs with a length of over 200 nm were made when only OAmwas used as both surfactant and solvent, while an OAm/ ODE ratio of 3:1 gave FePt NWs of length 100 nm, and a 1:1 volume ratio of OAm/ODE led to FePt NRs of length 20 nm. Notably, using a greater proportion of ODE (OAm/ODE 1:3) led to the formation of spherical FePt nanoparticles of diameter 3 nm (see Figure S1 in the Supporting Information). With the amount of [Pt(acac)2] fixed (see the Experimental Section), the compositions of these FePt nanostructures were controlled by varying the amount of [Fe(CO)5] added to the reaction mixture and were measured by energy-dispersive spectroscopy (EDS). For example, for the FePt NWs of length 200 nm, using 0.15 mL [Fe(CO)5] led to about 55% Fe in the final product, while using 0.1 mL [Fe(CO)5] yielded the product with about 45% Fe. Note that CoPt NWs can also be made by reduction of [Pt(acac)2] and decomposition of [Co2(CO)8] under similar reaction conditions (see Figure S2 in the Supporting Information). Transmission electron microscope (TEM) images of the representative NWs and NRs are given in Figure 1. The images in Figure 1a–c show NWs of length 200 nm and NRs of length 50 nm and 20 nm. The diameter of these NWs and NRs is about 2–3 nm. Figure 1d is a high-resolution TEM (HRTEM) image of two single NWs of empirical formula Fe55Pt45. In one NW, the lattice fringes are oriented approximately 558 from the wire-growth direction. The interfringe distance was measured to be 0.214 nm, which is close to the lattice spacing of the (111) planes (0.22 nm) in the facecentered cubic (fcc) FePt structure. This result indicates that the [100] direction is parallel (or perpendicular) to the wiregrowth direction, which is further confirmed by the image showing the lattice fringe in the second NW with clearly discernible (100) planes (0.198 nm interfringe spacing). The synthesis and TEM analyses imply that OAm, a common organic surfactant, induces the one-dimensional growth of FePt under the current synthetic conditions. It is likely that OAm self-organizes into an elongated reversemicelle-like structure within which the FePt nuclei are formed. This type of formation is similar to what has been proposed in the synthesis of Au NRs in the presence of [*] C. Wang, Dr. Y. Hou, J. Kim, Prof. S. Sun Department of Chemistry Brown University Providence, RI 02912 (USA) Fax: (+1)401-863-9046 E-mail: yanglong_hou@brown.edu ssun@brown.edu

We report a simple approach to conjugate monodisperse Fe3O4 nanoparticles with mPEG molecules via a readily available linker, trichloro-s-triazine (TsT). The mPEG-dopamine coated nanoparticles are stable in buffer at various pH values greater than 7. This approach can be extended to the coupling of various hydrophilic macromolecules to iron oxide nanoparticles.

Uniform Co spherical assemblies were prepared via a facile hydrothermal reduction approach in the presence of surfactants with a yield of 98%. The assembled nanostructures were composed of ordered nanoplatelets with a thickness of ∼20 nm, as characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), and high-resolution TEM (HRTEM). This material exhibits ferromagnetic characteristics and has a high surface area, showing potential applications for catalysts and other related nanodevices.

A rapid ligand-exchange method was developed to transfer high quality hydrophobic magnetite nanocrystals into water-soluble NPs by using protocatechuic acid as a ligand via homogenous reaction. After ligand exchange, the magnetite nanocrystals not only exhibited outstanding stability in water, but also maintained high crystallinity and saturation magnetization. Cell viability experiments demonstrated good biocompatibility of the NPs. For 12 nm magnetite nanoparticles (NPs), the small hydrodynamic size of 14 nm enabled a high T1 relaxivity of 17.8 mM(-1) s(-1) while high saturation magnetization of 77.8 emu g(-1) enabled the NPs to exhibit a high T2 relaxivity of 220 mM(-1) s(-1) in MRI phantom experiments. In vivo MR imaging experiments further confirmed that the NPs were eminent T1 and T2 contrast agents. Moreover, the high quality NPs can be used as excellent magnetic heating agents under an alternating magnetic field. With all those features, including multimodality imaging and magnetic hyperthermia, the NPs can be used as single compound multifunctional agents for various biomedical applications, especially for cancer diagnosis and therapy.

Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rare-earth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.

SmCo5 based magnets with smaller size and larger maximum energy product have been long desired in various fields such as renewable energy technology, electronic industry and aerospace science. However, conventional relatively rough synthetic strategies will lead to either diminished magnetic properties or irregular morphology, which hindered their wide applications. In this article, we present a facile chemical approach to prepare 200 nm single domain SmCo5@Co core/shell magnets with coercivity of 20.7 kOe and saturation magnetization of 82 emu/g. We found that the incorporation of GO sheets is responsible for the generation of the unique structure. The single domain SmCo5 core contributes to the large coercivity of the magnets and the exchange-coupled Co shell enhances the magnetization. This method can be further utilized in the synthesis other Sm-Co based exchange-coupled magnets.

We report an effective and facile method for synthesis of FePt–Au hybrid nanoparticles (HNPs). The typical secondary growth of Au proceeded in the presence of FePt seeds in organic solvents under a specific atmosphere. Interestingly, the type of atmosphere (Ar or Ar–H2) and the size of selected FePt seeds were two major parameters determining the final morphology of FePt–Au HNPs. Enhancement of catalytic activity and stability of FePt–Au HNPs in methanol oxidation were achieved owing to interactions between Au and FePt. The optical properties of the resulting products can be steadily tuned which sheds light on their potential application in optical devices and bioimaging. The novel synthetic strategy offers an important tool towards multifunctional nanomaterials with designed architectures.

Gene therapy is becoming a promising strategy to treat various kinds of genetic and acquired diseases. However, the development of safe, efficient, and targetable gene delivery systems remains a major challenge in gene therapy. The unique material characteristics of magnetic nanoparticles (MNPs), including high surface area, facile surface modification, controllable size, and excellent magnetic properties, make them promising candidates for gene delivery. The engineered MNPs with modifiable functional surfaces and bioactive cores can result in several advantageous diagnostic and therapeutic properties including enhanced magnetic resonance imaging (MRI) signal intensity, long permeation and retention in the circulatory system, specific delivery of therapeutic genes to target sites. In this review, the updated research on the preparation and surface modification of MNPs for gene delivery is summarized.

Cobalt sulfide is a good candidate for both lithium ion batteries (LIBs) and cathodic oxygen reduction reaction (ORR), but low conductivity, poor cyclability, capacity fading, and structural changes hinder its applications. The incorporation of graphene into CO 3 S 4 makes it a promising electrode by providing better electrochemical coupling, enhanced conductivity, fast mobility of ions and electrons, and a stabilized structure due to its elastic nature. With the objective of achieving high-performance composites, herein we report a facile hydrothermal process for growing CO 3 S 4 nanotubes (NTs) on graphene (G) sheets. Electrochemical impedance spectroscopy (EIS) verified that graphene dramatically increases the conductivity of the composites to almost twice that of pristine CO 3 S 4 . Electrochemical measurements indicated that the as-synthesized CO 3 S 4 / G composites exhibit good cyclic stability and a high discharge capacity of 720 mAhg1 up to 100 cycles with 99.9% coulombic efficiency. Furthermore, the composites react with dissolved oxygen in the ORR by fourand two-electron mechanisms in both acidic and basic media with an onset potential close to that of commercial Pt/C. The stability of the composites is much higher than that of Pt/C, and exhibit high methanol tolerance. Thus, these properties endorse CO 3 S 4 /G composites as auspicious candidates for both LIBs and ORR.

Phase-controlled nickel sulfide (Ni3 S4 and NiS1.03 ) nanoparticle (NP)/nitrogen-doped graphene (NG) composites are prepared through a facile one-pot hydrothermal process. The composites show ultrahigh capacity retentions of 98.87% and 95.94% for Ni3 S4 /NG and NiS1.03 /NG electrodes, respectively, as anode materials for lithium ion batteries.

Lithium ion batteries (LIBs) possess energy densities higher than those of the conventional batteries, but their lower power densities and poor cycling lives are critical challenges for their applications to electric vehicles (EVs) or grid stations. The energy and power densities, as well as the life of LIBs are dependent on electrodes where sluggish diffusion control process and structural stability are the main concerns. Here, the lithium storage mechanism of anode materials and the Goodenough diagram to explain the potential of cell and key parameters to determine the performance of an anode are highlighted. The cost reduction parameters and the availability of anode materials for future batteries on the basis of their resources and performances will be discussed. Further, the recent progress on anode nanostructures and solutions to the associated challenges will be outlined. The use of several techniques to determine the dynamic variations in nanostructures including both structural and chemical changes of electrode nanostructures during cycling as well as the limitations for high load applications will be explained. Finally, the concluding remarks will highlight the characteristics for both anode and cathode for better choice of electrode combinations in the full batteries.

A unique nanostructure of 3D and vertically aligned and interconnected porous carbon nanosheets (3D-VCNs) is demonstrated by a simple carbonization of agar. The key feature of 3D-VCNs is that they possess numerous 3D channels with macrovoids and mesopores, leading to high surface area of 1750 m 2 g -1 , which play an important role in loading large amount of sulfur, while vertically aligned microporous carbon nanosheets act as the multilayered physical barrier against polysulfides anions and prevent their dissolution in the electrolyte due to strong adsorption during cycling process. As a result, the 3D hybrid (3D-S-VCNs) infiltered with 68.3 wt% sulfur exhibits a high and stable reversible capacity of 844 mAh g -1 at the current density of 837 mA g -1 with excellent Coulombic efficiency ≈100%, capacity retention of ≈80.3% over 300 cycles, and good rate ability (the reversible capacity of 738 mAh g -1 at the high current density of 3340 mA g -1 ). The present work highlights the vital role of the introduction of 3D carbon nanosheets with macrovoids and mesopores in enhancing the performance of LSBs.

S. Guo, Y. Hou, and S. Rehman develop a new class of silicon crosslinked with hierarchical porous carbon spheres usable as an efficient polysulfide reservoir for enhancing the performance of lithium-sulfur batteries. As described on page 3167, the developed hybrid material adsorbs negatively charged polysulfides via both chemical and physical adsorption. Remarkably, the hybrid spheres show a high specific capacity, an excellent rate capability and long cyclability.

Ag(2)O/TNBs were fabricated by depositing Ag(2)O nanoparticles on the surface of TiO(2) nanobelts (TNBs). The disinfection activities of Ag(2)O/TNBs on two representative bacterial types: Gram-negative Escherichia coli ATCC15597 and Gram-positive Bacillus subtilis, were examined under both dark and visible light conditions. Ag(2)O/TNBs exhibited stronger bactericidal activities than Ag(2)O nanoparticles and TNBs under both dark and light conditions. For both cell types, disinfection effects of Ag(2)O/TNBs were greater under light conditions relative to those under dark conditions. The bactericidal mechanisms of Ag(2)O/TNBs under both dark and light conditions were explored. Ag(+) ions released from Ag(2)O/TNBs did not contribute to the bactericidal activity of Ag(2)O/TNBs under dark conditions, whereas the released Ag(+) ions showed bactericidal activity under visible light irradiation conditions. Active species (H(2)O(2), O(2)(-)·, and e(-)) generated by Ag(2)O/TNBs played important roles in the disinfection processes under both dark and visible light irradiation conditions. Without the presence of active species, the direct contact of Ag(2)O/TNBs with bacterial cells had no bactericidal effect.

We develop a facile method for the synthesis of an iron phthalocyanine (FePc) and nitrogen-doped graphene (NG) composite as a novel and efficient non-precious catalyst in the oxygen reduction reaction (ORR). The resulting product exhibits superior ORR catalytic activity, excellent tolerance to methanol crossover, and comparable stability to commercial Pt/C, which leads to the invention of a new non-precious catalyst for ORR in fuel cells.

Nanosized LiFePO4 is a kind of promising material for high performance lithium ion batteries; however, the synthesis of nanosized LiFePO4 still has some challenges in forming an orthorhombic phase in atmospheric liquid phase and protecting the LFP nanoparticles from aggregation, etc. In this work, LiFePO4 nanocrystals were synthesized through a high-temperature (350 °C) liquid-phase reduction method. The size and morphology of nanocrystals can be readily controlled by tuning the ratio of solvents, and the size-dependent behavior of lithium storage performance is also observed. After a carbon-coating surface treatment, rhombic-shaped LiFePO4 nanocrystals display excellent lithium storage properties with high reversible capacities and good cycle life (141.0 mAh g(-1) at 0.5 C after 50 cycles etc.). This method can be extended to prepare LiMnPO4 nanorods by substituting iron source with manganese salt.

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We report in this communication a simple, facile surface modification strategy to transfer hydrophobic manganese oxide nanoparticles (MONPs) into water by using polyaspartic acid (PASP). We systematically investigated the effect of the size of PASP-MONPs on MRI of normal liver and found that the particles with a core size of 10 nm exhibited greater enhancement than those with larger core sizes.

A non-viral gene delivery nanovehicle based on Alkyl-PEI2k capped MnO nanoclusters was synthesized via a simple, facile method and used for efficient siRNA delivery and magnetic resonance imaging.

To achieve the applications of graphene, the modulation of its electrical properties is of great significance. The element doping might give a promising approach to produce fascinating properties of graphene. Herein we report a facile chemical doping method to obtain nitrogen-doped (N-doped) few-layer graphene sheets through supercritical (SC) reaction in acetonitrile at temperature as low as 310 °C, using expanded graphite as starting material. X-ray photoelectron spectroscopy analysis revealed that the level of nitrogen-doping (N-doping) increased from 1.57 to 4.56 at % when the reaction time was tuned from 2 to 24 h. Raman spectrum confirmed that the resulting N-doped few-layer graphene by SC reaction maintain high quality without any significant structural defects. Electrical measurements indicated that N-doped few-layer graphene sheets exhibit a typical n-type field-dependent behavior, suggesting the N-doping into the lattice of graphene. This work provides a convenient chemical route to the scalable production of N-doped graphene for potential applications in nanoelectronic devices.

Synthesis of multifunctional magnetic nanoparticles (MFMNPs) is one of the most active research areas in advanced materials. MFMNPs that have magnetic properties and other functionalities have been demonstrated to show great promise as multimodality imaging probes. Their multifunctional surfaces also allow rational conjugations of biological and drug molecules, making it possible to achieve target-specific diagnostics and therapeutics. This review first outlines the synthesis of MNPs of metal oxides and alloys and then focuses on recent developments in the fabrication of MFMNPs of core/shell, dumbbell, and composite hybrid type. It also summarizes the general strategies applied for NP surface functionalization. The review further highlights some exciting examples of these MFMNPs for multimodality imaging and for target-specific drug/gene delivery applications.

Synthesis of multifunctional magnetic nanoparticles (MFMNPs) is one of the most active research areas in advanced materials. MFMNPs that have magnetic properties and other functionalities have been demonstrated to show great promise as multimodality imaging probes. Their multifunctional surfaces also allow rational conjugations of biological and drug molecules, making it possible to achieve target-specific diagnostics and therapeutics. This review first outlines the synthesis of MNPs of metal oxides and alloys and then focuses on recent developments in the fabrication of MFMNPs of core/shell, dumbbell, and composite hybrid type. It also summarizes the general strategies applied for NP surface functionalization. The review further highlights some exciting examples of these MFMNPs for multimodality imaging and for target-specific drug/gene delivery applications.

Fe(3)O(4) nanoprisms, synthesized by a solvothermal process, exhibited crystal plane dependent electrochemical activities, which opens an approach to nanoscale materials with controlled electrochemical properties.

Aqueous dispersed graphene was successfully prepared via using 7,7,8,8-tetracyanoquinodimethane (TCNQ) anion as a stabilizer and expanded graphite as a starting material, which could provide a facile route to produce high quality water-soluble and organic solvent-soluble graphene sheets for various applications.

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.

Lithium‐based batteries possessing energy densities much higher than those of the conventional batteries belong to the most promising class of future energy devices. However, there are some fundamental issues related to their electrodes which are big roadblocks in their applications to electric vehicles (EVs). Nanochemistry has advantageous roles to overcome these problems by defining new nanostructures of electrode materials. This review article will highlight the challenges associated with these chemistries both to bring high performance and longevity upon considering the working principles of the various types of lithium‐based (Li‐ion, Li‐air and Li‐S) batteries. Further, the review discusses the advantages and challenges of nanomaterials in nanostructured electrodes of lithium‐based batteries, concerns with lithium metal anode and the recent advancement in electrode nanostructures.

The combination of 1-adamantanecarboxylic acid and tri-alkylphosphine was applied to produce monodisperse FePd nanoparticles by the polyol reduction of palladium acetylacetonate and thermally decomposition of iron pentacarbonyl. Images of high resolution transmission electron microscopy (TEM) and X-ray diffraction (XRD) data indicate a highly monodisperse and crystalline nature of the FePd nanoparticles. Magnetic studies performed by Quantum Design SQUID magnetometer show that FePd (16nm) nanoparticles are superparamagnetic at room temperature.

Here we have designed a strategy to improve the electronic conductivities of polyoxometalates (POMs) via property-oriented organic grafting for use in lithium-ion batteries (LIBs). POMs usually exhibit limited electronic conductivity that hinders their use in electronic applications. Organic grafting of POMs defines a valuable path for improving electronic conductivities of POMs, due to the enhanced metal to ligand charge transfer (MLCT) via d–π electronic interactions, and results in their feasible application in LIBs. Comparative practical and theoretical study of the effect of functional groups revealed that grafting of the remote electron withdrawing group (–SCN) on POMs via organo-imidoylization along with lower values of lowest unoccupied molecular orbitals (LUMO) results in an enhanced performance as Mo6–SCN shows initial discharge capacity of ∼1678 mA h g−1 with ∼85% capacity retention and coulombic efficiency ∼100% after 100 cycles.

In this work, α-Fe2O3 oblique and truncated nanocubes were synthesized in the presence of oleylamine (OAm), acetylacetone (Hacac) and oleic acid (OA) through a facile one-step solvothermal method. The phase of iron oxide was precisely regulated through the volume ratio of OAm/Hacac, and confirmed by X-ray diffraction (XRD) and Raman imaging microscopy. The formation mechanism of α-Fe2O3 nanocrystals was discussed systematically and a schematic illustration of the probable formation of the morphologies in the whole of the synthetic process was also proposed. Furthermore, the truncated nanocubes exposing both the {012} and {104} dominant planes exhibit higher photocatalytic activity toward RhB compared with the oblique nanocubes surrounded by only the {012} dominant facet, which reveals that the high photocatalytic activity is attributed to the exposure of {104} high-index planes. The truncated nanocubes with high catalytic activity may potentially serve as effective and cheap catalysts for photodegradation.

FePt concave nanocubes enclosed by highly active high-index atom steps were synthesized by a facile process. The oleic acid was demonstrated to be the key point for the formation of FePt concave nanocubes. Due to the concave structure, the FePt concave nanocubes exhibit higher electrocatalytic activity than either FePt nanocubes or commercial Pt catalysts in methanol oxidation.

A general one-pot protocol is reported to prepare hollow or porous manganese (Mn) oxide, phosphate, sulfide nanoparticles (NPs) via a controlled ion transfer process.

Graphene has attracted intense interest due to its exceptional physical and chemical properties as well as its wide potential applications. The processability and stability of this two-dimensional material in a variety of solvents have been the prerequisites for its functionalization, which will generate more interesting properties for further applications. In this mini review, we present and discuss the current status of liquid-phase exfoliation of graphene from various types of graphite, followed by a topical summarization of recent progress in the functionalization and applications of graphene.

A field effect enhanced quantum dot resonant tunneling diode is proposed and demonstrated to improve the detection dynamic range for low light imaging application. Using the cross-wire device geometry, a lateral two dimensional electron gas (2DEG) current is formed in the quantum well channel together with the normal resonant tunneling current for quantum dot modulation. A peak photoresponsivity of the order of 1010 A/W and a light detection saturation level up to 105 photons per second at 77 K are achieved when the 2DEG current makes the main photocurrent contribution.

Spectroscopic ellipsometry is used to determine the optical properties of the noncrystalline and crystalline Mn1.56Co0.96Ni0.48O4 (MCN) films prepared by chemical solution deposition method in the range of 250–1100 nm. A pronounced difference in the optical functions is found between 500 and 600 °C. Two distinctive peaks, attributed to the critical points of the MCN films, appear in the optical constant spectra for the films annealed at 600 °C while they are not obvious for the films annealed at 500 °C. The presented results are instructive, further understanding the physical properties of transition metal oxides in theory.

Octahedral Fe(3)O(4) nanoparticles, showing ferrimagnetic behavior, were synthesised by a facile route and due to their monodispersity and anisotropic shape the nanoparticles self-assemble to superlattices with well-defined orientation.

It was shown experimentally that charging InAs quantum dots (QDs) embedded in a small-area GaAs/AlAs double-barrier resonant tunneling diode (RTD) effectively modified the carrier transport proper ...

Hard magnetic nanocomposites SmCo5∕Fex (x=0–2.9) are synthesized by a simultaneous calcium reduction of Sm–Co–O and Fe3O4 nanoparticles. The composites consist of nanostructured SmCo5 and Fe with their average grain sizes at 29 and 8nm, respectively. The magnetic properties of the composites can be tuned by controlling Fe composition. SmCo5∕Fe1.5 shows an enhanced remanent magnetization at 56emu∕g (45emu∕g for SmCo5). The largest coercivity value of 11.6kOe is achieved with SmCo5∕Fe0.23. The synthesis represents a general process toward SmCo-based exchange-spring nanocomposites for high performance permanent magnet applications.

92%Pb(Mg1∕3Nb2∕3)O3–8%PbTiO3 (PMNT) thin films have been prepared on Pt∕Ti∕SiO2∕Si substrate with a LaNiO3 buffer layer and on sapphire substrate by a chemical solution deposition method. X-ray diffraction analysis shows that the PMNT thin films on Pt∕Ti∕SiO2∕Si substrate are polycrystalline with (110)-preferential orientation. The optical properties of PMNT thin film in 2.5–12.5μm and 200–1100nm ranges have been investigated using infrared spectroscopic ellipsometry and ultravisible transmission spectra, respectively. The optical constants and thickness of the thin films have been obtained by fitting the measured ellipsometric parameter (Δ and Ψ) data and transmission spectrum with classical infrared and Tauc-Lorentz models. The optical band gap energy of the PMNT thin films on sapphire substrate is derived to be about 4.02eV.

A methodology for self-integrating cobalt particles (10–70nm) into silica nanotubes has been developed during a simple calcination process. Rhombohedral silica nanotubes serve to guide cobalt nanoparticles into one-dimensional alignment. The Co-silica nanotubes prepared by using [Co(NH3)6](HCO3)(CO3)∙2H2O fibers as structure-directing agents have a size of 100–220nm in diameter and up to 30μm in length. Magnetic study shows that the Co-silica nanocomposite exhibits a ferromagnetic characteristic with a large room temperature coercivity of 520Oe. The formation mechanism of Co particle alignment is discussed.

Magnetite nanoparticles were prepared through a solvothermal reduction approach in the presence of ethylene glycol, oleic acid and trioctylphosphine oxide or hexadecylamine. The size of the magnetite nanoparticles can be controlled easily through tailoring surfactants in the system. Transmission electron microscopy images indicate that the average sizes of magnetite nanoparticles are 8 and 11 nm, depending on the surfactant. The far IR spectra further demonstrate that the products are magnetite instead of hematite. Superparamagnetism and the effect of σ-donor and π-acceptor type surfactants on the magnetic properties of the nanoscale materials have been investigated.