Magnetic Nanoparticle Chains in Gelatin Ferrogels: Bioinspiration from Magnetotactic Bacteria

TL;DR

This study reports a green synthesis of magnetite nanocrystal chains in gelatin, mimicking magnetotactic bacteria, and characterizes their structure and magnetic properties using advanced microscopy and modeling techniques.

Contribution

It introduces a novel, environmentally friendly method to create bioinspired magnetic nanostructures with detailed structural and magnetic characterization.

Findings

Magnetite chains resemble those in magnetotactic bacteria.

Chains exhibit mechanical flexibility and magnetic anisotropy.

Precise magnetic measurements require detailed shape and arrangement data.

Abstract

Inspired by chains of ferrimagnetic nanocrystals (NCs) in magnetotactic bacteria (MTB), the synthesis and detailed characterization of ferrimagnetic magnetite NC chain-like assemblies is reported. An easy green synthesis route in a thermoreversible gelatin hydrogel matrix is used. The structure of these magnetite chains prepared with and without gelatin is characterized by means of transmission electron microscopy, including electron tomography (ET). These structures indeed bear resemblance to the magnetite assemblies found in MTB, known for their mechanical flexibility and outstanding magnetic properties and known to crystallographically align their magnetite NCs along the strongest <111> magnetization easy axis. Using electron holography (EH) and angular dependent magnetic measurements, the magnetic interaction between the NCs and the generation of a magnetically anisotropic material can be shown. The electro- and magnetostatic modeling demonstrates that in order to precisely determine the magnetization (by means of EH) inside chain-like NCs assemblies, their exact shape, arrangement and stray-fields have to be considered (ideally obtained using ET).