In Liquid Observation and Quantification of Nucleation and Growth of Gold Nanostructures Using in Situ Transmission Electron Microscopy

In situ liquid transmission electron microscopy (TEM) is a powerful technique for observing nanoscale processes in their native liquid environment and in real time. However, the imaging electron beam can have major interferences with the processes under study, altering the experimental outcome. Here, we use in situ liquid TEM to understand the differences between beam-induced and electrodeposition processes that result in nucleation and growth of gold crystallites. Through this study, we find that beam-induced and electrodeposition processes result in crystallites that deposit at different locations within the liquid cell and differ significantly in morphology. Furthermore, we develop a strategy based on increasing the liquid layer thickness for reducing the amount of beam-induced crystallites to negligible levels. Through this optimized system, we study the electrodeposition of gold on carbon electrodes by correlating current time transients and their corresponding time-resolved scanning TEM images. This analysis demonstrates that even when the electron-beam plays a negligible role in gold deposition under optimal conditions, there is a large discrepancy between the amount of deposits observed and the amount measured using the current time transients. This finding sheds light on the heterogeneity of the deposition process and provides insights into designing a new class of in situ liquid TEM systems

Analysis of the Shell Thickness Distribution on NaYF₄/NaGdF₄ Core/Shell Nanocrystals by EELS and EDS

The structure and chemical composition of the shell distribution on NaYF₄/NaGdF₄ core/shell nanocrystals have been investigated with scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDS). The core and shell contrast in the high-angle annular dark-field (HAADF) images combined with the EELS and EDS signals indicate that Gd is indeed on the surface, but for many of the particles, the shell growth was anisotropic