TY  - JOUR
A1  - Szczerba, Wojciech
A1  - Zukrowski, Jan
A1  - Przybylski, Marek
A1  - Sikora, Marcin
A1  - Safonova, Olga
A1  - Shmeliov, Aleksey
A1  - Nicolosi, Valeria
A1  - Schneider, Michael
A1  - Granath, Tim
A1  - Oppmann, Maximilian
A1  - Straßer, Marion
A1  - Mandel, Karl
T1  - Pushing up the magnetisation values for iron oxide nanoparticles via zinc doping: X-ray studies on the particle's sub-nano structure of different synthesis routes
JF  - Physical Chemistry Chemical Physics
N2  - The maximum magnetisation (saturation magnetisation) obtainable for iron oxide nanoparticles can be increased by doping the nanocrystals with non-magnetic elements such as zinc. Herein, we closely study how only slightly different synthesis approaches towards such doped nanoparticles strongly influence the resulting sub-nano/atomic structure. We compare two co-precipitation approaches, where we only vary the base (NaOH versus NH\(_3\)), and a thermal decomposition route. These methods are the most commonly applied ones for synthesising doped iron oxide nanoparticles. The measurable magnetisation change upon zinc doping is about the same for all systems. However, the sub-nano structure, which we studied with Mossbauer and X-ray absorption near edge spectroscopy, differs tremendously. We found evidence that a much more complex picture has to be drawn regarding what happens upon Zn doping compared to what textbooks tell us about the mechanism. Our work demonstrates that it is crucial to study the obtained structures very precisely when "playing'' with the atomic order in iron oxide nanocrystals.
KW  - Ferrite
KW  - FE
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187390
VL  - 18
IS  - 36
ER  - 
TY  - JOUR
A1  - Granath, Tim
A1  - Löbmann, Peer
A1  - Mandel, Karl
T1  - Oxidative Precipitation as a Versatile Method to Obtain Ferromagnetic Fe\(_{3}\)O\(_{4}\) Nano‐ and Mesocrystals Adjustable in Morphology and Magnetic Properties
JF  - Particle & Particle Systems Characterization
N2  - Oxidative precipitation is a facile synthesis method to obtain ferromagnetic iron oxide nanoparticles from ferrous salts—with unexplored potential. The concentration of base and oxidant alone strongly affects the particle's structure and thus their magnetic properties despite the same material, magnetite (Fe\(_{3}\)O\(_{4}\)), is obtained when precipitated with potassium hydroxide (KOH) from ferrous sulfate (FeSO\(_{4}\)) and treated with potassium nitrate (KNO\(_{3}\)) at appropriate temperature. Depending on the potassium hydroxide and potassium nitrate concentrations, it is possible to obtain a series of different types of either single crystals or mesocrystals. The time‐dependent mesocrystal evolution can be revealed via electron microscopy and provides insights into the process of oriented attachment, yielding faceted particles, showing a facet‐dependent reactivity. It is found that it is the nitrate and hydroxide concentration that influences the ligand exchange process and thus the crystallization pathways. The presence of sulfate ions contributes to the mesocrystal evolution as well, as sulfate apparently hinders further crystal fusion, as revealed via infrared spectroscopy. Finally, it is found that nitrite, as one possible and ecologically highly relevant reduction product occurring in nature in context with iron, only evolves if the reaction is quantitative.
KW  - colloidal nanostructures
KW  - nanoparticle aggregation
KW  - non‐classical crystallization
KW  - oriented attachment
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224419
VL  - 38
IS  - 3
ER  -