Iron–chromium oxide nanoparticles self-assembling into smectic mesophases

Abstract

Organic-coated iron-chromium oxide (chromite) nanoparticles have been prepared by using the thermal decomposition procedure. For this purpose, the substratebimetallic acetatewas treated with oleic acid and dodecylamine as co-ligands in trichloroacetic acid solvent at high temperature (320 C). The main characteristics and behaviors of the obtained nanoparticles were investigated by combined techniques.The size of the obtained nanoparticles was around 11 nm, as estimated by TEM, WAXD and SAXS, which were in good agreement. The bimetallic nature of the nanoparticles was emphasized by X-ray energy dispersive spectrometry (EDX) and their structure was confirmed by WAXD. The Fourier transform infrared (FTIR) spectrum revealed the bands characteristic to metal oxides as well as to the organic components and confirmed the replacement of the acetate with long chain ligands. The co-existence of the organic coatings and metallic core induced a special behavior that was studied by thermogravimetric analysis, differential scanning calorimetry and polarized optical microscopy. The coated bimetallic nanoparticles proved to be thermostable up to 252 C and thermotropic showing a highly organized crystalline smectic mesophase (3D plastic mesophase). The organic part alone, in the absence of the inorganic component, did not develop this self-assembly. The results of the magnetic measurements suggest superparamagnetic behavior of the iron-chromium oxide nanoparticles and a weak ferromagnetic behavior.

Amorphous iron–chromium oxide nanoparticles with long-term stability

“…In our recent work [14], we reported obtaining crystalline iron-chromium oxide NPs starting from a mixed metal complex with a pre-established iron/ chromium ratio.…”

“…Iron-chromium oxide NPs, both in crystalline [10,11,14] and amorphous [4,8] states, were obtained using the same procedures as used to obtain single iron oxide, such as ultrasonic radiation [4,8], hydrothermal methods [10], and thermal decomposition [11,14], using physical mixtures of salts as metals sources. According to previously published reports [4,8], amorphous iron-chromium oxide NPs have been prepared using iron chloride and chromium nitrate in different molar ratios as precursors.…”

Superparamagnetic amorphous iron oxide nanowires self-assembled into ordered layered structures

“…The wide angle region (30- Table 1 shows the diffraction data: 2q values, Bragg distance (d), scattering vector 33 (Q) and wave vectors ratio (Q i /Q 1 ). 34 The NWs sample in paste form was analysed by SAXS using a dedicated holder. This kind of array of values was observed by us previously 34 and describe layered highly ordered materials, namely smectic crystals, a midway between the hard solid-phase crystals and the uid classic liquid crystalline phase.…”

Nanomaterials Developed by Processing Iron Coordination Compounds for Biomedical Application

“…Iron-chromium oxide nanoparticles of 11 nm were obtained using μ 3 -oxo heterotrinuclear (FeCr 2 O) acetate as metals precursor, oleic acid and dodecylamine as surfactants, and trichloroacetic acid as solvent heated at 320°C for 1 h. The molar ratio of iron and chromium in the obtained nanoparticles was similar to the precursor. In this case, the authors also found that the obtained material is self-assembling into smectic crystals [88]. Amorphous iron-chromium oxide nanoparticles of 3.5 nm were prepared by the thermal decomposition of μ 3 -oxo heterotrinuclear (FeCr 2 O) acetate in the presence of dodecylamine, sunflower oil, and trichloroacetic acid at 320°C for 1 h. According to XRD results, the formed nanoparticles remained amorphous even after 2 years.…”