Low Oxidation State and Enhanced Magnetic Properties Induced by Raspberry Shaped Nanostructures of Iron Oxide

Abstract

Nanostructures with controlled size, morphology and composition represent a main challenge in materials science because controlling these parameters is fundamental to optimize the subsequent functional properties. Agregated nanostructures, combining both individual and collective properties of nanocrystals, offer interesting perspectives to design new magnetic nanomaterials. In that context, original porous raspberry shaped nanostructures consisting of oriented aggregates of ferrite nanocrystals have been synthesized by an one-pot polyol solvothermal method. Synthesis conditions have been optimized to obtain nanostructures featured by similar sizes of about 250 nm and nanocrystal sizes modulated from 5 to 60 nm, leading to porous structures with tunable specific surface area. Structural and magnetic studies of nanostructures as a function of the nanocrystal size evidenced their low oxidation state and enhanced magnetic properties. Indeed the oriented aggregation of nanocrystals leads to high interface between nanograins reducing significantly their surface oxidation and enhancing their saturation magnetization in comparison to individual nanoparticles of similar sizes. Magnetic moments of each grains are also consequently strongly coupled by dipolar interactions which led to super spin glass effects.

Evidence of the Superparamagnetic State in the Zero-Field Microwave Susceptibility Spectra of Ferrimagnetic Nanoparticles

“…LP are assimilated to a binding between crystallites and the continuity of the crystal planes in one raspberry structure is noticed. This framework has already been observed in the case of iron oxide [Gerber 2015]. The average crystallite size for SP (resp.…”

Design of Fe3–xO4 raspberry decorated graphene nanocomposites with high performances in lithium-ion battery

“…They consist of original orientated aggregates of Fe 3 -x O 4 nanocrystals ( Fig. 1 e) with a mean size of 25 nm, mainly constituted of the magnetite phase (Fe 2.90 O 4, 70% of magnetite) and exhibiting a porous and hollow structure with a BET specific surface area of 27 m 2 /g [41] . The spatial distribution of nanostructures onto the graphene sheets is relatively homogeneous for all nanocomposites, with higher volumetric mass density for the sample with low amount of graphene ( Fig.…”

“…Using a similar approach, porous Fe 3 -x O 4 hollow nanostructures with a raspberry shape, narrow size distribution, well-defined chemical composition and crystalline structure [30] were successfully grown onto few-layer graphene sheets with highly controlled covering density. These nanostructures consist of oriented aggregates of magnetite nanocrystals (nanocrystals with common crystallographic orientations directly combined together to form larger ones) which ensure a nanostructuration, porosity and a low oxidation state of Fe 3 O 4 nanocrystals [41] . The structure of such a composite presents several interests for electrode material such as (i) a high porosity that provides both high electrode/electrolyte interface area and fast Li + diffusion path toward active reaction sites, (ii) a preservation of the magnetite composition at low nanocrystal sizes (as described in ref.…”

Magnetorheology of a magnetic fluid based on Fe3O4immobilized SiO2core–shell nanospheres: experiments and molecular dynamics simulations

“…27 Nevertheless, the Fe 3 O 4 microbeads have higher saturation magnetization compared to g-Fe 2 O 3 nanoparticles. 28 Generally, Fe 3 O 4 is used as the nanosized magnetic material in magnetic uid.…”