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Sesto Fiorentino, Italy

Nachum S.,University of Cambridge | Fleck N.A.,University of Cambridge | Ashby M.F.,University of Cambridge | Colella A.,CSGI | Matteazzi P.,MBN Nanomaterialia spa
Materials Science and Engineering A | Year: 2010

The mechanical properties and electrical resistivity of nanocrystalline copper reinforced by 1. vol.% and 5. vol.% of nano-alumina particles have been measured. The composites were prepared by ball-milling and consolidated by a combination of hot extrusion and HIPing. The uniaxial tensile and compressive strengths are comparable for each composite, and an elastic, ideally plastic response is observed. Shear bands, of width a few microns, accompany plastic deformation. A number of microstructural characterisation tools were used to reveal that grain boundary strengthening and dispersion strengthening are the dominant strengthening mechanisms. Nano-indentation measurements reveal a size effect in hardness. The electrical resistivity is almost double that of pure oxygen free copper and this is mainly ascribed to the presence of dissolved iron. © 2010 Elsevier B.V. Source

Nappini S.,CNR Institute of Materials | Magnano E.,CNR Institute of Materials | Bondino F.,CNR Institute of Materials | Pis I.,CNR Institute of Materials | And 8 more authors.
Journal of Physical Chemistry C | Year: 2015

Magnetic nanoparticles (MNPs) have shown exceptional potential for several biological and clinical applications. However, MNPs must be coated by a biocompatible shell for such applications. The aim of this study is to understand if and how the surface charge and coating can affect the electronic and magnetic properties of CoFe2O4 MNPs. The role of the surface on the total magnetic moment of MNPs is a controversial issue, and several effects can contribute to make it deviate from the bulk value, including the charge, the nature of the coating, and also the synthetic technique. Positively and negatively charged uncoated CoFe2O4 NPs as well as citrate-coated NPs were prepared by soft chemistry synthesis. The electronic properties and cationic distribution of CoFe2O4 NPs were probed by X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD), and X-ray photoemission spectroscopy (XPS) techniques and confirmed by theoretical simulations. The overall magnetic behavior and the hyperthermic properties were evaluated by magnetometry and calorimetric measurements, respectively. The results show that all of the investigated CoFe2O4 NPs have high magnetic anisotropy energy, and the surface charge and coating do not influence appreciably their electronic and magnetic properties. In addition, the citrate shell improves the stability of the NPs in aqueous environment, making CoFe2O4 NPs suitable for biomedical applications. © 2015 American Chemical Society. Source

Jing D.,Syracuse University | He J.,Syracuse University | Bonini M.,National institute for astrophysics | Brucato J.R.,CSGI | Vidali G.,Syracuse University
Journal of Physical Chemistry A | Year: 2013

We studied the formation of deuterated water on an amorphous silicate surface held at low temperature (10 K < T < 40 K). The surface is first characterized by using Ar+ ion bombardment, and preferential sputtering of oxygen is found. Sputtering creates oxygen vacancies in the surface region that can be filled by deposition of atomic oxygen. The conditions used in the experiment are meant to make it relevant to the study of the initial stages of water formation on dust grains in interstellar space. By changing the D/O ratio of atomic beams of deuterium and oxygen at thermal energy and the temperature of the sample during deposition, we show that the routes to the formation of D2O2 can be untangled and, under certain circumstances, the net yield of D2O2 can be suppressed. The formation efficiency for water and other molecules is then estimated. © 2013 American Chemical Society. Source

Stockmann T.J.,University Paris Diderot | Noel J.-M.,University Paris Diderot | Ristori S.,CSGI | Combellas C.,University Paris Diderot | And 3 more authors.
Analytical Chemistry | Year: 2015

Oscillating chemical reactions, encapsulated within artificial vesicles have been demonstrated as a powerful analogy of living cells for the investigation of chemical communication and morphogenesis. However, little is understood with regards to the influence of confinement on the reactivity of such systems. Herein, the effect of confinement on the Belousov-Zhabotinsky (BZ) oscillating reaction in bulk solution, (employing ferroin as a catalyst and malonic acid as the organic substrate) is investigated using scanning electrochemical microscopy (SECM) toward different insulating surfaces such as glass, silanized glass, or PTFE. An unexpected increase in the amplitude of the BZ reaction at a tip-substrate distance of ∼12-15 μm is observed. By simulating different reaction mechanisms, from simple EC' catalysis to more sophisticated Oregonator or even an 11-reaction scheme, it is shown that such behavior reveals the intervention of redox catalysis processes and particularly the short-lived highly reactive radical intermediate BrO2 • indirectly detected at micromolar concentrations. The reinspection of the EC' mechanism shows that the homogeneous catalysis route is confirmed and kinetically characterized from SECM toward an insulating substrate, with promising potentiality in many systems. More specifically to the complex chemical case of BZ reactions, the mechanism is understood from the envelope curves of the oscillations, which are assessed in the absence of the oscillation (absence of organic substrate). © 2015 American Chemical Society. Source

Nappini S.,CSGI | Bonini M.,CSGI | Bombelli F.B.,CSGI | Pineider F.,Consortium for Science and Technology of Materials | And 3 more authors.
Soft Matter | Year: 2011

The paper describes the effect of a low-frequency alternating magnetic field (LF-AMF) on the permeability and release properties of large (LUVs) and giant (GUVs) unilamellar vesicles loaded with citrate coated cobalt ferrite nanoparticles (NPs). The citrate shell allows a high loading of NPs in lipid vesicles without modifying their magnetic properties. The increase of magnetic LUVs permeability upon exposure to LF-AMF has been evaluated as the fluorescence self-quenching of carboxyfluorescein (CF) entrapped inside the liposome aqueous pool. Liposome leakage has been monitored as a function of field frequency, time exposure and concentration of the citrate coated NPs. Confocal Laser Scanning Microscopy (CLSM) experiments performed on magnetic GUVs labeled with the fluorescent probe DiIC 18 and loaded with Alexa 488-C5-maleimide fluorescent dye provided insights on the release mechanism induced by LF-AMF. The results show that LF-AMF strongly affects vesicles permeability, suggesting the formation of pores in the lipid bilayer due to both hyperthermic effects and nanoparticle oscillations in the vesicles pool at the applied frequency. The behaviour of these magnetic vesicles in the presence of LF-AMF makes this system a good candidate for controlled drug delivery. © 2011 The Royal Society of Chemistry. Source

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