dilute solutions of NCs onto carbon coated gold grids, which were
then placed under a vacuum to preserve them from oxidation. Low resolution
transmission electron microscopy (TEM) measurements were carried out
on a JEOL JEM-1100 transmission electron microscope operating at an
acceleration voltage of 100 kV. High resolution TEM (HRTEM) was performed
with a JEOL JEM-2200FS microscope equipped with a 200 kV field emission
gun, a CEOS spherical aberration corrector in the objective lens,
enabling a spatial resolution of 0.9 Å, and an in column energy
filter. High angle annular dark field images were acquired on the
same microscope in scanning mode (STEM) with a nominal probe size
of 0.2 nm, and an inner cutoff angle of the annular detector of 75
mrad.