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  - Hobbs, Christopher
A1  - Jaskaniec, Sonia
A1  - McCarthy, Eoin K.
A1  - Downing, Clive
A1  - Opelt, Konrad
A1  - Güth, Konrad
A1  - Shmeliov, Aleksey
A1  - Mourad, Maurice C. D.
A1  - Mandel, Karl
A1  - Nicolosi, Valeria
T1  - Structural transformation of layered double hydroxides: an in situ TEM analysis
JF  - npj 2D Materials and Applications
N2  - A comprehensive nanoscale understanding of layered double hydroxide (LDH) thermal evolution is critical for their current and future applications as catalysts, flame retardants and oxygen evolution performers. In this report, we applied in situ transmission electron microscopy (TEM) to extensively characterise the thermal progressions of nickel-iron containing (Ni-Fe) LDH nanomaterials. The combinative approach of TEM and selected area electron diffraction (SAED) yielded both a morphological and crystallographic understanding of such processes. As the Ni-Fe LDH nanomaterials are heated in situ, an amorphization occurred at 250 °C, followed by a transition to a heterogeneous structure of NiO particles embedded throughout a NiFe2O4 matrix at 850 °C, confirmed by high-resolution TEM and scanning TEM. Further electron microscopy characterisation methodologies of energy-filtered TEM were utilised to directly observe these mechanistic behaviours in real time, showing an evolution and nucleation to an array of spherical NiO nanoparticles on the platelet surfaces. The versatility of this characterisation approach was verified by the analogous behaviours of Ni-Fe LDH materials heated ex situ as well as parallel in situ TEM and SAED comparisons to that of an akin magnesium-aluminium containing (Mg-Al) LDH structure. The in situ TEM work hereby discussed allows for a state-of-the-art understanding of the Ni-Fe material thermal evolution. This is an important first, which reveals pivotal information, especially when considering LDH applications as catalysts and flame retardants.
KW  - electrocatalysis
KW  - two-dimensional materials
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-320752
VL  - 2
ER  -