Jem f200 tem

High-resolution transmission electron
microscopy (HRTEM) was performed on a JEOL JEM-2200FS TEM with Cs
corrector and a JEOL JEM-F200 TEM, both operating at 200 kV. Samples
were made by drop-cast suspensions on the grids. The TEM grids used
were holey carbon-Cu (C200-CU) with 50 μm hole size (200 mesh).
NC sizes were determined by measuring 200 particles using the “polygon
selection” tool of ImageJ, with measurements set to “fit
ellipse”.

STEM-EDS was used in the elemental analysis and mapping of the AuNS in the ultrathin sections. STEM-EDS analysis was performed on samples prepared as described above using a Jeol JEM-F200 TEM (FEG, 200 kV). The instrument was equipped with a high-angle annular dark field detector (HAADF, scanning TEM mode, STEM) and an energy-dispersive X-ray spectrometer (EDS).

X-ray
diffraction (XRD)
measurements were performed on a Bruker AXS D8 Advance diffractometer
using Cu K_α radiation (λ = 154 pm). Specific
surface areas were determined from nitrogen sorption isotherms acquired
at 77 K (Micromeritics ASAP 2020). Diffractograms were recorded in
time intervals of 9 min. Scanning electron microscopy (SEM) measurements
were performed on a Zeiss Gemini Ultra 55 microscope operating at
20 kV. The transmission electron microscopy (TEM) investigations were
performed on a Phillips CM300 UT operated at 300 kV for all samples
except the MgO (111) pristine and annealed samples, which were imaged
with a cold field emission gun JEOL JEM-F200 TEM at 200 kV. The electron
dose received by the samples during the electron beam irradiation
experiments was estimated from in situ measurement of the electron
dose on the fluorescent screen. The TEM samples were prepared by casting
small amounts of the dried metal oxide powders on the carbon grid.