Transmission Electron Microscopy of Quantum Dots

The 400 mesh carbon-coated Cu grids were glow discharged for 30 s at 0.3 bar and 30 mA on GloQube (Quorum Technologies). To perform transmission electron microscopy (TEM) with negatively stained QD probes, 3 µl of a 100 nm solution with QD probes were applied onto the grids and incubated for 1 min at room temperature. The grid was then immersed in 15 µl of 2% uranyl acetate and, after 30 s, was blotted with filter paper; this step was repeated twice. Finally, the grids were dried in air for 10 min (Douglas et al., 2018 (link)). The samples were loaded into a transmission electron microscope (model JEM-2100Plus, JEOL) and imaged at a magnification of 60,000× and a pixel (px) size of 1.939 Å/px. The particles corresponding to the QDs were measured using the ImageJ program (Schneider et al., 2012 (link)).