Magnetic and specific heat properties of YFe3(BO3)4 and ErFe3(BO3)4.

The present paper reports on the specific heat and magnetization of the YFe(3)(BO(3))(4) and ErFe(3)(BO(3))(4) single crystals. In both compounds, antiferromagnetic order of the iron spins evolves at T(N) = 38 K. The experimental data suggest that the magnetic moments are in the basal plane of the trigonal crystal for both compounds.

Unusual field dependence of remanent magnetization in granular CrO2: the possible relevance of piezomagnetism.

We present low field thermoremanent magnetization (TRM) measurements in granular CrO(2) and composites of ferromagnetic (FM) CrO(2) and antiferromagnetic (AFM) Cr(2)O(3). TRM in these samples is seen to display two distinct timescales. A quasi-static part of remanence, appearing only in the low field regime, exhibits a peculiar field dependence.

A new family of 1D exchange biased heterometal single-molecule magnets: observation of pronounced quantum tunneling steps in the hysteresis loops of quasi-linear {Mn2Ni3} clusters.

First members of a new family of heterometallic Mn/Ni complexes [Mn(2)Ni(3)X(2)L(4)(LH)(2)(H(2)O)(2)] (X = Cl: 1; X = Br: 2) with the new ligand 2-{3-(2-hydroxyphenyl)-1H-pyrazol-1-yl}ethanol (H(2)L) have been synthesized, and single crystals obtained from CH(2)Cl(2) solutions have been characterized crystallographically. The molecular structures feature a quasi-linear Mn(III)-Ni(II)-Ni(II)-Ni(II)-Mn(III) core with six-coordinate metal ions, where elongated axes of all the distorted octahedral coordination polyhedra are aligned parallel and are fixed with respect to each other by intramolecular hydrogen bonds. 1 and 2 exhibit quite strong ferromagnetic exchange interactions throughout (J(Mn-Ni) ≈ 40 K (1) or 42 K (2); J(Ni-Ni) ≈ 22 K (1) or 18 K (2)) that lead to an S(tot) = 7 ground state, and a sizable uniaxial magnetoanisotropy with D(mol) values -0.

Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications.

Objectives: To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays.

Methods: Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed.

Bridging charge-orbital ordering and Fermi surface instabilities in half-doped single-layered manganite La(0.5)Sr(1.5)MnO₄.

The single-layered half-doped manganite La(0.5)Sr(1.5)MnO₄ (LSMO), was studied by means of the angle-resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and resistivity measurements.

Robust determination of Young's modulus of individual carbon nanotubes by quasi-static interaction with Lorentz forces.

Young's modulus of an individual multi-wall carbon nanotube has been determined by the method of quasi-static transverse bending due to a Lorentz force observed in situ in a transmission electron microscope. The deflection of the nanotube allows the determination of Young's modulus using Euler-Bernoulli's beam equation. Because we determine the specific dependence of the deflection on the position along the nanotube axis, it is possible to gain insight into the type of mountings and furthermore allows for an estimation of the homogeneity of the nanotube.

Computational fluid dynamics analysis of nasal flow.

Objectives: Standard methods to examine nasal flow are experimental and do not yield locally detailed results. Using the Lattice-Boltzmann method (LBM), we computed nasal air flow and investigated the relationship between nasal obstruction and anatomical conditions. Because of its mathematical structure, the LBM can be immediately applied to various nasal cavities that are characterized by an extremely intricate geometry.

Iron filled carbon nanotubes as novel monopole-like sensors for quantitative magnetic force microscopy.

We present a novel ultrahigh stability sensor for quantitative magnetic force microscopy (MFM) based on an iron filled carbon nanotube. In contrast to the complex magnetic structure of conventional MFM probes, this sensor constitutes a nanomagnet with defined properties. The long iron nanowire can be regarded as an extended dipole of which only the monopole close to the sample surface is involved in the imaging process.

Superconductivity without nesting in LiFeAs.

We have studied the electronic structure of the nonmagnetic LiFeAs (T(c)∼18  K) superconductor using angle-resolved photoemission spectroscopy. We find a notable absence of the Fermi surface nesting, strong renormalization of the conduction bands by a factor of 3, high density of states at the Fermi level caused by a van Hove singularity, and no evidence for either a static or a fluctuating order except superconductivity with in-plane isotropic energy gaps. Our observations suggest that these electronic properties capture the majority of ingredients necessary for the superconductivity in iron pnictides.

In situ observations of fullerene fusion and ejection in carbon nanotubes.

We present in situ experimental observations of fullerenes seamlessly fusing to single-walled carbon nanotubes. The morphing-entry of a fullerene to the interior of a nanotube is also captured. The confined (1D) motion of the newly-encapsulated fullerene within its host attests to the actual change from the exterior to interior.

Carbon Nanotubes Filled with Ferromagnetic Materials.

Carbon nanotubes (CNT) filled with ferromagnetic metals like iron, cobalt or nickel are new and very interesting nanostructured materials with a number of unique properties. In this paper we give an overview about different chemical vapor deposition (CVD) methods for their synthesis and discuss the influence of selected growth parameters. In addition we evaluate possible growth mechanisms involved in their formation.

Tunable band gap in hydrogenated quasi-free-standing graphene.

We show by angle-resolved photoemission spectroscopy that a tunable gap in quasi-free-standing monolayer graphene on Au can be induced by hydrogenation. The size of the gap can be controlled via hydrogen loading and reaches approximately 1.0 eV for a hydrogen coverage of 8%.

Delivery of carboplatin by carbon-based nanocontainers mediates increased cancer cell death.

Since the activity of several conventional anticancer drugs is restricted by resistance mechanisms and dose-limiting side-effects, the design of nanocarriers seems to be an efficient and promising approach for drug delivery. Their chemical and mechanical stability and their possible multifunctionality render tubular nanomaterials, such as carbon nanotubes (CNTs) and carbon nanofibres (CNFs), promising delivery agents for anticancer drugs. The goal of the present study was to investigate CNTs and CNFs in order to deliver carboplatin in vitro.

Examining the stability of folded graphene edges against electron beam induced sputtering with atomic resolution.

Low energy electron beam irradiation of the edges of graphene can lead to rearrangement of the carbon atomic structure. We demonstrate the ability to distinguish intrinsic edges of graphene from edges formed by back folding based upon atomic structure and their susceptibility to sputtering. We examine how the atomic structure of the edges of graphene and few layer graphene sheets influences their stability under electron beam irradiation at a low electron accelerating voltage of 80 kV using aberration-corrected high-resolution transmission electron microscopy.

Direct low-temperature nanographene CVD synthesis over a dielectric insulator.

Graphene ranks highly as a possible material for future high-speed and flexible electronics. Current fabrication routes, which rely on metal substrates, require post-synthesis transfer of the graphene onto a Si wafer, or in the case of epitaxial growth on SiC, temperatures above 1000 degrees C are required. Both the handling difficulty and high temperatures are not best suited to present day silicon technology.

Interplay of magnetic exchange interactions and Ni-S-Ni bond angles in polynuclear nickel(II) complexes.

The ability of bridging thiophenolate groups (RS(-)) to transmit magnetic exchange interactions between paramagnetic Ni(II) ions is examined. Specific attention is paid to complexes with large Ni-SR-Ni angles. For this purpose, dinuclear [Ni(2)L(1)(mu-OAc)I(2)][I(5)] (2) and trinuclear [Ni(3)L(2)(OAc)(2)][BPh(4)](2) (3), where H(2)L(1) and H(2)L(2) represent 24-membered macrocyclic amino-thiophenol ligands, are prepared and fully characterized by IR- and UV/Vis spectroscopy, X-ray crystallography, static magnetization M measurements and high-field electron spin resonance (HF-ESR).

Self-assembly of neutral hexanuclear circular copper(II) meso-helicates: topological control by sulfate ions.

Bis-pyridylimine ligands with different linking elements are capable of forming unique hexanuclear circular Cu(II) meso-helicates; the self-assembly is controlled by coordination of sulfate ions to the metal centres.

Nanoscale electronic order in iron pnictides.

The charge distribution in RFeAsO1-xFx (R=La,Sm) iron pnictides is probed using As nuclear quadrupole resonance. Whereas undoped and optimally doped or overdoped compounds feature a single charge environment, two charge environments are detected in the underdoped region. Spin-lattice relaxation measurements show their coexistence at the nanoscale.

Dispersion and diameter separation of multi-wall carbon nanotubes in aqueous solutions.

Comparative studies on dispersing of multi-wall carbon nanotubes (CNTs) using two anionic surfactants (sodium dodecyl sulphate, SDS, and sodium dodecyl benzenosulfonate, SDBS) are presented. The studies were conducted on the surfactant concentrations that were close to the critical micelle concentration (CMC). The stability of CNTs suspensions obtained for surfactant solutions at concentrations lower than the CMC was investigated.

Atomic resolution imaging and topography of boron nitride sheets produced by chemical exfoliation.

Here, we present a simple method for preparing thin few-layer sheets of hexagonal BN with micrometer-sized dimensions using chemical exfoliation in the solvent 1,2-dichloroethane. The atomic structure of both few-layer and monolayer BN sheets is directly imaged using aberration-corrected high-resolution transmission electron microscopy. Electron beam induced sputtering effects are examined in real time.

Graphene synthesis on cubic SiC/Si wafers. perspectives for mass production of graphene-based electronic devices.

The outstanding properties of graphene, a single graphite layer, render it a top candidate for substituting silicon in future electronic devices. The so far exploited synthesis approaches, however, require conditions typically achieved in specialized laboratories and result in graphene sheets whose electronic properties are often altered by interactions with substrate materials. The development of graphene-based technologies requires an economical fabrication method compatible with mass production.

Investigating the outskirts of Fe and Co catalyst particles in alumina-supported catalytic CVD carbon nanotube growth.

Using thermal CVD, the synthesis of multi-walled carbon nanotubes exhibiting roots anchored directly onto alpha-alumina supports, rather than the catalyst particle, is reported. At such roots, the alignment of the graphitic planes with the support lattice fringes depends on the support crystal structure and orientation. Surface defects may alter the reactivity of the surface or control the anchoring of supported atoms or nanoparticles.

Thermodynamic properties and neutron diffraction studies of silver ferrite AgFeO2.

We present thermodynamic and neutron scattering data on silver ferrite AgFeO(2). The data imply that strong magnetic frustration Θ/T(N)∼10 and magnetic ordering arise via two successive phase transitions at T(2) = 7 K and T(1) = 16 K. At T View Article and Find Full Text PDF

Examining co-based nanocrystals on graphene using low-voltage aberration-corrected transmission electron microscopy.

We present a method to produce graphene and few layer graphene sheets using solution phase chemistry, which are used as ultrathin support membranes for enhanced imaging of nanomaterials using transmission electron microscopy. We demonstrate this by decorating the surface of the graphene sheets with Co-based nanocrystals (CoCl(2) and hcp Co). Low-voltage aberration-corrected high resolution transmission electron microscopy at 80 kV is used to image the nanocrystals on the thin graphene supports.