Goethite Nanorods: Synthesis and Investigation of the Size Effect on Their Orientation within a Magnetic Field by SAXS

Abstract

Goethite is a naturally anisotropic, antiferromagnetic iron oxide. Following its atomic structure, crystals grow into a fine needle shape that has interesting properties in a magnetic field. The needles align parallel to weak magnetic fields and perpendicular when subjected to high fields. We synthesized goethite nanorods with lengths between 200 nm and 650 nm in a two-step process. In a first step we synthesized precursor particles made of akaganeite (β-FeOOH) rods from iron(III)chloride. The precursors were then treated in a hydrothermal reactor under alkaline conditions with NaOH and polyvinylpyrrolidone (PVP) to form goethite needles. The aspect ratio was tunable between 8 and 15, based on the conditions during hydrothermal treatment. The orientation of these particles in a magnetic field was investigated by small angle X-ray scattering (SAXS). We observed that the field strength required to trigger a reorientation is dependent on the length and aspect ratio of the particles and could be shifted from 85 mT for the small particles to about 147 mT for the large particles. These particles could provide highly interesting magnetic properties to nanocomposites, that could then be used for sensing applications or membranes.

Creation of a 3D Goethite–Spongin Composite Using an Extreme Biomimetics Approach

“…There are a number of industrial applications for goethite, which require the use of a variety of methods for its preparation. The most frequently used technique is hydrothermal synthesis [73]; however, other techniques such as sol-gel [74], forced hydrolysis [75], and precipitation methods [76] are also adopted. A particularly interesting approach is the use of an organic matrix for the nucleation and growth of α-FeOOH.…”

A Comprehensive Study of Synthesis and Analysis of Anisotropic Iron Oxide and Oxyhydroxide Nanoparticles

“…Some of the iron hydroxides tend to form ANPs directly during synthesis due to the peculiarities of their crystal structure. Thus, goethite (α-FeOOH) forms needle-like particles [ 20 ], while another oxyhydroxide, akaganeite (β-FeOOH), crystallizes in the form of nanoellipsoids [ 21 ].…”