Fig. 1  
Fe NPs were purchased from Nanografi. The TEM results from the Fe NPs can be found in the respective folder. The EELs line scan result to determine the oxide shell thickness can be found in the 
sub-folders "SI-001" and "SI-002". Besides the TEM folder the results of the manually measured Fe NP particles can be found in the excel file "Particle size Fe-NPs nanografi". 
The data particle size was used to create the box charts that are also contained in the folder "Fe_NPs_Nanografi".

TEM images: @USTEM, date 15-02-2023 

