1,721,157 research outputs found
Dinuclear ruthenium bipyridine complexes with a bis(iminodioxolene)-meta-phenylene ligand: magnetic coupling and mixed valence character of the semiquinonato species
No full textThe dinuclear bis-iminosemiquinonato [Ru(bpy)2(L)2Ru(bpy)2](PF6)2 complex where L is the deprotonated form of N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,3-phenylenediamine (H4L), has been synthesised. For comparison purposes, the mononuclear iminosemiquinonato [Ru(bpy)2L′]PF6 formed by the N-phenyl-o-aminophenol (H2L′) was also investigated. Magnetic investigation evidences that the bis-semiquinonato species is characterised by a moderately strong ferromagnetic interaction (H = JS1·S2, J = −85(5) cm−1). This result is the theoretically expected one and it is contrasting with the antiferromagnetic interaction observed in previously investigated complexes containing the same ligand. It is suggested that the different behaviour is determined by the different coordination requirements occurring in these complexes. The spectroelectrochemical analysis provides a clear evidence of the valence trapped character of the mono-semiquinonato forms of the ligand. The two mixed valence semiquinonato species containing the quinonato-semiquinonato and semiquinonato-catecholato bridging ligand can be described as class II, but show a significantly different electronic coupling. The electronic factors determining this behaviour are discussed
Influence of metal content on size, dispersion, and magnetic properties of iron-cobalt alloy nanoparticles embedded in silica matrix
No full text(FexCo1-x)(y)(SiO2))(1-y) nanocomposites were prepared by a sol-gel method, using tetraethoxysilane and metal acetates as precursors. Two sets of xerogel samples were prepared: in the first set x was kept equal to 0.5 and four y values were selected in the range 0.02-0.2; in the second set y was kept equal to 0.1 and three samples with x equal to 0.4.5. 0.50. and 0.70 were prepared. The samples were characterized by X-ray diffraction, TEM, and HREM to verify the formation of the FeCo alloy nanocrystals and to investigate their Structure, morphology, and composition. All samples contain spherical FeCo alloy nanoparticles uniformly dispersed in the silica matrix with average size increasing with metal content. Magnetic measurements carried out on selected samples show a superparamangetic behavior. with blocking temperature which depends on metal load, as a con-sequence of particle distance variation
In vivo biomedical applications of magnetic resonance and magnetic materials
No full textAn overview on the recent progress in the biomedical application of magnetic materials and on the most used magnetic resonance imaging techniques is presented. After briefly mentioning the basic aspects of Magnetic Resonance Imaging (MRI), some of the most frequently used pulse sequences are illustrated with particular emphasis on those used in Diffusion Tensor Imaging, Magnetic Resonance
Spectroscopy and functional MRI. Then the basis of the Dynamical Nuclear Polarization technique, which allows to perform in vivo molecular imaging of the metabolic
processes, is presented. The physical properties of smart nanosized magnetic materials which can further improve the potential of these diagnostic techniques are
described in the following sections. These magnetic nanoparticles may be used as MRI contrast agents, for the magnetic transport and drug delivery or even for the
therapy of certain pathologies through magnetic fluid hyperthermia. The possible combination of some of these functionalities into just one multifunctional nanoparticle
is also considered
Intermetallic Au3LixM1-x (M = Fe, Ni or Co) nanoalloys: Effect of synthetic conditions on the composition and order-disorder transition
No full textHow does buoyancy of hydrogel microrobots affect their magnetic propulsion in liquids?
No full textGravity compensation is a key requirement for achieving three-dimensional navigation of magnetic microrobots in fluids. Here we present a brief theoretical introduction to the issue of gravity compensation in the case of magnetic pulling propulsion, explicitly highlighting the constraints it introduces. Therefore, we evaluate the advantages that quasi-neutral buoyancy gives to hydrogel microrobots, demonstrating that despite their relatively weak magnetic properties, for certain size/velocity ranges they could be more easily and efficiently propelled than state-of-the-art metal microrobots. Hence, our analysis endorses the adoption of smart polymers, such as stimuli-responsive hydrogels, for developing truly multifunctional magnetic microrobots. © 2013 American Institute of Physics
Modulation of the magnetic properties of gold-spinel ferrite heterostructured nanocrystals
No full textThe rational design of complex nanostructures is of paramount importance to gain control over their chemical and physical properties. Recently, magnetic-plasmonic heterostructured nanocrystals have been recognized as key players in nanomedicine as multifunctional therapeutic-diagnostic tools and in catalysis. Here we show how the properties of gold-iron oxide heterostructured nanocrystals can be tuned by chemical doping of the magnetic subunit. The divalent cations in the iron oxide were substituted with cobalt and manganese to obtain a general formula Au-MFe2O4 (M = Fe, Co, Mn). Magnetic properties of the heterostructures could be tuned, while maintaining well-defined plasmon resonance signatures, confirming the dual magnetic-plasmonic functional capability of these nanostructures. [Figure not available: see fulltext.]
Medical Applications of Magnetic Nanoparticles
No full textThe increased ability in manipulating matter at the nanoscale has paved the way towards the creation of a plethora of novel systems endowed with extremely appealing properties exploitable in a wide number of clinical applications, the two most prominent being, undoubtedly, Magnetic Resonance Imaging (MRI) and Magnetic Fluid Hyperthermia (MFH). In this Chapter, we review a few recent examples to convey to the reader a picture of the promising role magnetic nanoparticles (MNPs) may play in the medicine of the next future. After a general overview of the two techniques, we summarize the physical principles at their base to provide the reader the necessary tools to understand limits and advantages of employing MNPs as contrast agents in MRI and heat mediators in MFH. Among the countless examples of MNP-based materials proposed in the recent years for these applications, we select and report in detail some of the most representative and promising ones to underline the challenges that this branch of the material science must address to interplay with the complexity of the human body. Finally, we try to photograph the state of the art of the clinical applications, which, mainly concerning MFH, is in continuous evolution
Surfactant-assisted route to fabricate CoFe2O4 individual nanoparticles and spherical assemblies
No full textA surfactant-assisted route in aqueous media has been shown to be suitable to prepare either individual primary CoFe2O4 nanocrystals or secondary spherical nanoporous assemblies with a high surface area. The formation of primary nanoparticles or of spherical assemblies is found to be dependent on the presence of the surfactant and on the particle size, but is shown that the nanoparticle-surfactant interface plays a dominant role. The size of the primary CoFe2O4 particles is controlled by the type of salt, the synthesis temperature and the concentration of the precursors. A detailed characterization evidences the shape and size of the primary particles, the way in which the primary particles assemble and their features in terms of morphological, textural and magnetic propertie
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