Silica-Coated and Bare Akaganeite Nanorods: Structural and Magnetic Properties

Abstract

We report on structural and magnetic properties of uniform silica coated akaganeite nanorods with length of L ~ 80 ± 15 nm and diameter D ~ 15 ± 5 nm as well as silica shell thickness of about 5 nm. Unexpected negative difference between field-cooled (FC) and zero-field-cooled (ZFC) magnetization ∆M= M FC -M ZFC < 0, room temperature ferromagnetism and exchange bias effect have been found. The nanorods are investigated by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) measurements. The magnetic measurements were also performed on bare akaganeite nanorods in order to discriminate the effects of silica coating on the magnetic properties. The measured coercivity and exchange bias effect of bare β-FeOOH nanorods are much lower compared with same properties of SiO 2 @β-FeOOH nanorods emphasizing effect of silica coating on the magnetic properties. These results are discussed considering the core-shell structure of akaganeite nanorods i.e. the inner part of the akaganeite nanorod has antiferromagnetic ordering, whereas the nanorod surface exhibits some disorder spin state.

Magnetism Engineering in Antiferromagnetic β-FeOOH Nanostructures via Chemically Induced Lattice Defects

“…13 Most of the previous examples are characterized by large surface-tovolume ratios, where the predominant surface contribution is corroborated by the significantly larger magnetization observed in high fields 12 or the coercivity enhancement upon silica coating. 15 In our case, we have obtained coercive fields on the same order of magnitude (in particular for the Ak-100 sample), despite the much bigger dimensions of the nanostructures herein reported. The higher coercivity of the Ak-100 sample discloses a source of spin disorder in which the inner uncompensated spins are more strongly coupled to each other or to the bulk AFM component.…”

Green Synthesis of Single-Crystalline Akaganeite Nanorods for Peroxidase Mimic Colorimetric Sensing of Ultralow-Level Vitamin B1 and Sulfide Ions

“…Among the iron oxide family, iron­(III) oxy-hydroxide including goethite (α-FeOOH), akaganéite (β-FeOOH), lepidocrocite (γ-FeOOH), and feroxyhyte (δ-FeOOH) nanoparticles (NPs) have emerged as one of the most interesting nanomaterials owing to abundantly available, nontoxic, chemical stability at room temperature, resistant to corrosion, and low cost . Because of the above-mentioned physicochemical properties FeOOH nanostructures, mainly β-FeOOH nanostructures have attracted significant attention in numerous potential applications such as for the removal of pollutants, chemical catalysis, , photocatalysis, − electrocatalysts, , sorption, magnetic devices, − and electrode in lithium batteries. − Among different polymorphs of oxy-hydroxides, β-FeOOH nanostructure is most extensively studied, which exhibits large tunnel-type monoclinic crystal structure framework. In the β-FeOOH monoclinic structure, iron and oxygen ions occupy two and four distinct special crystallographic positions 4i [[x,0,z]] with local symmetry m, respectively.…”

“…In recent years, β-FeOOH NPs with controlled size and shape have attracted vast attention because of their size- and shape-dependent properties and potential applications. Considerable efforts have been devoted to the synthesis of 1D β-FeOOH nanostructures using hydrolysis of iron salt, , chemical reduction/precipitation, , thermal decomposition, ,, microwave-assisted, , and hydrothermal , methods. Generally, the hydrothermal method is the most common approach for the synthesis of β-FeOOH nanorods because of controlled hydrolysis under high temperature and pressure.…”

Characterization of an active ingredient made of nanoscale iron(oxyhydr)oxide for the treatment of hyperphosphatemia

“…8a. Antiferromagnetic materials show paramagnetic behavior at room temperature with linear dependence of the magnetization on the external magnetic eld as shown for akaganéite 72,73 and lepidocrocite. 74 At cryogenic temperatures, these materials can show hysteresis as uncompensated magnetic spins on the surface contribute to the magnetic behavior.…”