Titan themis microscope

TEM and HAADF-STEM
images as well as ED and small-angle ED patterns were collected with
the use of JEOL JEM2200FS microscope operating at 200 kV accelerating
voltage. EDX-STEM maps and HAADF-STEM images at different tilt angles
were recorded using an FEI Titan Themis microscope operated at 300
kV equipped with a SuperEDX detector, with the aid of a motorized
dual-axis tomography holder. Captured TEM and electron diffraction
images were compared with the ones simulated in Crystal Maker 10.4.5
and Single Crystal 3.1.5 software, purchased from CrystalMaker Software
Ltd. Electron tomography was carried out in HAADF-STEM mode at 300
kV using a small beam semiconvergence angle of 2.5 mrad, to increase
the depth of field. Images were recorded over a tilt angle range ±
(57–72)° and interval 2–3°. Reconstruction
was done using IMOD with a Back Projection algorithm and SIRT-like
radial filter.^{81 (link)} The tomograms were recorded
on SLs self-assembled on carbon-coated TEM grids as continuous films
or via a microemulsion technique. SEM images were obtained on a FEI
Helios 660 operated at 3–7 kV using immersion mode.

Transmission electron
microscopy (TEM) and high-angle annular dark-field scanning TEM (HAADF-STEM)
images as well as wide- and small-angle electron diffraction (ED)
patterns were collected with the use of JEOL JEM2200FS microscope
operating at a 200 kV accelerating voltage. Energy-dispersive X-ray
(EDX-STEM) maps and HAADF-STEM were recorded using an FEI Titan Themis
microscope operated at 300 kV. SEM images were obtained on a FEI Helios
660 operated at 3 kV using immersion mode.

The sapphire substrate
with as-grown material
was spin-coated with PMMA and baked at 85 °C for 10 min.
The MoS₂/PMMA film was detached from the sapphire substrate
by submerging it in water. Water surface tension promotes the separation
of the grown material from the substrate. Next, the film floating
in water is collected using a TEM grid and heated for 15 min at 85
°C. After the transfer is completed, the TEM grid is left in
acetone overnight and annealed at 250 °C.
For aberration-corrected
scanning transmission electron microscopy (STEM) imaging, an FEI Titan
Themis microscope equipped with double Cs corrector, monochromator,
and Schottky X-field emission gun was operated at an acceleration
voltage of 80 kV. The electron probe current was in the 17–20
pA range. The semiconvergence angle of the probe was 21.2 mrad. High-angle
annular dark field detector (HAADF) was used to capture the images
using short dwell times (8 μs) with 512 × 512 pixels. The
camera length was set to 185 mm which corresponds to the 49–200
mrad collection angle range. Focused ion beam (FIB, Zeiss Nvision40)
was used to prepare the cross-section lamella from the device. For
the low-resolution cross-sectional TEM imaging, a FEI Talos F200 S
G2 microscope was used at 80 kV acceleration voltage.

The hydrodynamic size of the Hb@AuNCs was evaluated by dynamic light scattering (DLS) (Zetasizer Nanoseries nano-ZS, Malvern, UK). The zeta (ζ)-potentials were assessed also using the Zetasizer. The morphology of the Hb@AuNCs was evaluated by scanning transmission electron microscopy (STEM), using a Titan Themis microscope (Thermo Fisher Scientific) operating at 200 kV with a probe of 20 mrad convergence angle and 50 pA current. The microscope was equipped with a high-brightness Schottky emitter (X-FEG), a probe aberration correction system (CEOS DCOR) and a Super-X energy dispersive X-ray (EDX) detector. Annular dark-field (ADF) STEM images were acquired with a collection angle of 31–192 mrad and EDX spectrum images were acquired with a probe current of 250 pA. Colored elemental maps were processed using Velox software, after removal of the background in the spectra (net count maps). The Cliff-Lorimer method were applied for EDX quantification, using the Brown-Powell ionization cross-sections. The samples were prepared by powder dispersion on lacey carbon films supported by copper meshed TEM grids (LC200-Cu, Electron Microscopy Sciences, PA, US).