Titan 80 300

The experimental results are obtained using a monochromated Thermo Fisher Scientific Titan 80-300 scanning transmission electron microscope (STEM) operating at a voltage of 80 keV. Near zero-loss electron energy loss spectroscopy (NZ-EELS) is conducted in Ultimono^TM mode and the optimum energy resolution in vacuum for the experimentally captured data is 45 meV. The silver nanowires suspended in isopropyl alcohol is purchased from Sigma-Aldrich and is dropcast on a SiN TEM grid.

4D STEM measurements were carried out using a Gatan K3 direct detection camera located at the end of a Gatan Continuum imaging filter on a TEAM I microscope (aberration-corrected Thermo Fisher Scientific Titan 80-300). The microscope was operated at 300 kV with a probe current of 100 pA. The probe semiangle used for the measurement was 2 mrad. Diffraction patterns were collected using a step size of 1 nm with 514 by 399 scan positions. The K3 camera was used in full-frame electron counting mode with a binning of 4 pixels by 4 pixels and camera length of 1.05 mm. The exposure time for each diffraction pattern was 47 ms.

For negative staining, 3 µL of the purified proteasome samples was applied to glow-discharged EM grids covered by a thin layer of continuous carbon film (0183-F, Ted Pella Inc., Redding, CA, USA). After a 1 min incubation, the grid was “washed off” at an angle with 25 μL of 2% uranyl-acetate solution. After 1 min, excess uranyl-acetate was blotted, and the grid was dried. Observations of the sample were performed with a Titan 80–300 transmition electron microscope (Thermo Fisher Scientific, Waltham, MA, USA).

Electron microscopy was performed at the National Center for Electron Microscopy in the Molecular Foundry at Lawrence Berkeley National Laboratory. Four-dimensional STEM datasets were acquired using a Gatan K3 direct detection camera located at the end of a Gatan Continuum imaging filter on a TEAM I microscope (aberration-corrected Thermo Fisher Scientific Titan 80–300). The microscope was operated in energy-filtered STEM mode at 80 kV with a 10 eV energy filter centred around the zero-loss peak, an indicated convergence angle of 1.71 mrad, and a typical beam current of 45–65 pA depending on the sample. These conditions yield an effective probe size of 1.25 nm (full-width at half-maximum value). Diffraction patterns were collected using a step size of either 0.5 nm or 1 nm with 50 x 50 to 300 x 300 beam positions, covering an area ranging from 25 nm x 25 nm to 300 nm x 300 nm. The K3 camera was used in full-frame electron counting mode with a binning of 4 × 4 pixels and an energy-filtered STEM camera length of 800 mm. Each diffraction pattern had an exposure time of 13 ms, which is the sum of multiple counted frames.

TEM images were first acquired with a JEOL JEM-1400 Plus working
at 120 kV. For imaging, the as-prepared samples were dispersed in
ethanol and supported on a TEM grid. These images verify the size,
morphology, and dispersion of the Bi/C NPs. High-resolution (HR)-TEM
images were taken from the samples before and after the electrocatalytic
experiments with a Titan 80-300 at 300 kV (Thermo Fisher Scientific).
Energy-dispersive X-ray analysis (EDX) elemental maps were acquired
using a 200 kV Talos TEM (Thermo Fisher Scientific).