title: Oriented attachment explains cobalt ferrite nanoparticle growth in bioinspired syntheses.
abstract: Oriented attachment has created a great debate about the description of crystal growth throughout the last decade. This aggregation-based model has successfully described biomineralization processes as well as forms of inorganic crystal growth, which could not be explained by classical crystal growth theory. Understanding the nanoparticle growth is essential since physical properties, such as the magnetic behavior, are highly dependent on the microstructure, morphology and composition of the inorganic crystals. In this work, the underlying nanoparticle growth of cobalt ferrite nanoparticles in a bioinspired synthesis was studied. Bioinspired syntheses have sparked great interest in recent years due to their ability to influence and alter inorganic crystal growth and therefore tailor properties of nanoparticles. In this synthesis, a short synthetic version of the protein MMS6, involved in nanoparticle formation within magnetotactic bacteria, was used to alter the growth of cobalt ferrite. We demonstrate that the bioinspired nanoparticle growth can be described by the oriented attachment model. The intermediate stages proposed in the theoretical model, including primary-building-block-like substructures as well as mesocrystal-like structures, were observed in HRTEM measurements. These structures display regions of substantial orientation and possess the same shape and size as the resulting discs. An increase in orientation with time was observed in electron diffraction measurements. The change of particle diameter with time agrees with the recently proposed kinetic model for oriented attachment.
authors.affiliation: Department of Physics, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Annalena
authors.initials: A
authors.lastname: Wolff
authors.affiliation: Department of Physics, Bielefeld University, 33615 Bielefeld, Germany ; (USTEM) University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, 1040 Vienna, Austria.
authors.forename: Walid
authors.initials: W
authors.lastname: Hetaba
authors.affiliation: Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Wißbrock
authors.affiliation: (USTEM) University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, 1040 Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Löffler
authors.affiliation: Department of Physics, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Mill
authors.affiliation: Department of Physics, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Eckstädt
authors.affiliation: Institute Advanced Cemarics, Hamburg University of Technology, 21073 Hamburg, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Dreyer
authors.affiliation: Department of Physics, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Inga
authors.initials: I
authors.lastname: Ennen
authors.affiliation: Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Sewald
authors.affiliation: (USTEM) University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, 1040 Vienna, Austria ; Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Schattschneider
authors.affiliation: Department of Physics, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hütten
keywords: bioinspired synthesis; cobalt ferrite nanoparticles; nanoparticle growth; oriented attachment; polypeptide