Tommaso Nardi

Fe3O4 nanoparticles and nanocomposites with potential application in biomedicine and in communication technologies: Nanoparticle aggregation, interaction, and effective magnetic anisotropy

Magnetite nanoparticles with a size of 5–6 nm with potential impact on biomedicine and information/communication technologies were synthesized by thermal decomposition of Fe(acac)3 and subsequently coated with a silica shell exploiting a water-in-oil synthetic procedure. The as-produced powders (comprised of either Fe3O4 or Fe3O4@silica nanoparticles) were mixed with a photocurable resin obtaining two magnetic nanocomposites with the same nominal amount of magnetic material. The static magnetic properties of the two nanopowders and the corresponding nanocomposites were measured in the 10 K–300 K temperature range. Magnetic measurements are shown here to be able to give unambiguous information on single-particle properties such as particle size and magnetic anisotropy as well as on nanoparticle aggregation and interparticle interaction. A comparison between the size distribution functions obtained from magnetic measurements and from TEM images shows that figures estimated from properly analyzed magnetic me...

A novel synthetic strategy for bioinspired functionally graded nanocomposites employing magnetic field gradients

In order to mimic the complex architecture of many bio-materials and synthesize composites characterized by continuously graded composition and mechanical properties, an innovative synthetic strategy making use of magnetic field gradients and based on the motion of superparamagnetic Fe3O4@SiO2 core–shell nanoparticles is adopted. It is demonstrated that by lowering the viscosity of the system through particle functionalization, and increasing the magnetic force acting on the nanoparticles upon optimization of a simple set-up composed of two permanent magnets in repulsion configuration, the magnephoretic process can be considerably accelerated. Thus, owing to the magnetic responsiveness of the Fe3O4 core and the remarkable mechanical properties of the SiO2 shell, approximately 150 μm thick polymeric films with continuous gradients in composition and characterized by considerable increments in elastic modulus (up to ≈70%) and hardness (up to ≈150%) when going from particle-depleted to particle-enriched regions can be synthesized, even in times as short as 1 hour. The present methods are highly promising for a more efficient magnetic force-based synthesis of inhomogeneous soft materials whose composition is required to be locally tuned to meet the specific mechanical demands arising from non-uniform external loads.

Antibacterial surfaces based on functionally graded photocatalytic Fe3O4@TiO2 core-shell nanoparticle/epoxy composites

Functionally graded epoxy composites with various concentration profiles of Fe3O4@TiO2 core–shell nanoparticles (NPs) were synthetized and characterized, with focus on their antibacterial properties. The NPs consisted of rutile, anatase, magnetite and hematite. Graded composites were produced starting with homogeneous 2 vol% to 12 vol% NPs suspensions using a magnetophorese process, leading to an enrichment of TiO2 at the surface of the composite up to 16 vol% from an initial 4 vol%. Homogeneous composites were also produced as references. Graded composites with an initial 4 vol% of NPs inactivated E. coli bacteria in less than 2 hours under simulated solar light (50 mW cm−2), significantly faster than their homogeneous analogues. During bacterial inactivation the pH decreased from 6.8 to 5.0. Repetitive E. coli inactivation tests on these 4 vol% graded composites were stable up to 8 cycles and 5 min contact between the bacteria and the sample surface was enough to guarantee an adequate bacterial adhesion.

Nanoindentation of Functionally Graded Polymer Nanocomposites: Assessment of the Strengthening Parameters through Experiments and Modeling

NNanoindentation tests were carried out on the surface of polymer nanocomposites exhibiting either graded or homogeneous distributions of Fe3O4@silica core-shell nanoparticles in a photocurable polymeric matrix. The results reveal a complex interplay between graded morphology, indentation depth and calculated modulus and hardness values, which was elucidated through numerical simulations. First, it was experimentally shown how for small (1 µm) indentations, large increases in modulus (up to +40%) and hardness (up to +93%) were obtained for graded composites with respect to their homogeneous counterparts, whereas at a larger indentation depth (20 µm) the modulus and hardness of the graded and homogeneous composites did not substantially differ from each other and from those of the pure polymer. Then, through a Material Point Method approach, experimental nanoindentation tests were successfully simulated, confirming the importance of the indentation depth and of the associated plastic zone as key factors for a more accurate design of graded polymer nanocomposites whose mechanical properties are able to fulfill the requirements encountered during operational life.

Fe 3 O 4 nanoparticles and nanocomposites for applications in biomedicine and the ICTs: Nanoparticle aggregation, interaction and effective magnetic anisotropy

Magnetite nanocomposites containing Fe₃O₄ nanoparticles (NPs) retain high interest and long-lasting appeal as multifunctional materials for sensors and actuators with applications to biomedicine as well as to the area of Information and Communication Technologies (ICTs). Most of the current chemical routes to synthesize ferrimagnetic Fe-oxide NPs provide a quite reproducible output and a well-defined chemical composition and structure. The relatively easy synthesis procedure explains the widespread use of both bare and suitably coated Fe₃O₄ NPs for a variety of applications, especially in the biomedical field. In this work, magnetite nanoparticles with a size of 5-6 nm were synthesized by thermal decomposition of Fe(acac)₃ and subsequently coated with a silica shell exploiting a water-in-oil synthetic procedure. The average radius and size distribution function of as-produced powders, comprised of either bare (Fe₃O₄) or silica-coated (Fe₃O₄@silica) nanoparticles, have been obtained by TEM image analysis. The Fe₃O₄ nanoparticles have a spheroidal shape characterized by a narrow Gaussian bell distribution centered at 5.65 nm ± 0.13 nm; the Fe₃O₄@silica nanoparticles evidenced a log-normal particle size distribution with a mean diameter of 25.61 nm ±8.43 nm, each silica particle typically enclosing more than one magnetic nanoparticle.