Electron-Induced Radiation Chemistry in Environmental Transmission Electron Microscopy

In-situ environmental transmission electron microscopy (E-TEM) provides sub-Angstrom spatiotemporal information on nanoscale chemical transformations. However, the high-energy electron probe can significantly affect the surrounding medium's chemistry and induce side reactions within the area of interest. Radiolysis, or the dissociation of molecules under electron beam irradiation, has become an increasingly important consideration in in-situ nanomaterials characterization. While numerous studies have explored this phenomenon in liquid-cell TEM, there are no reported extensions to gas phase TEM thus far. Herein, we present a generalized computational model to elucidate radiation chemistry in both gas and liquid E-TEM. Our model reveals that gas phase E-TEM produces radiolytic species with lower reactivity than in the liquid phase. However, these radiolysis species can accumulate to levels that interfere with desired reactions, especially at higher pressures. We verify our model by studying the radiation-promoted oxidation of aluminum nanocubes and the disproportionation of carbon monoxide, where we find increasing the electron beam dose rate increases the rate of AlOx production and deposited carbon, respectively. Additionally, we propose guidelines to control the production of radiolysis species within these closed-cell in-situ nanoreactors. Taken together, these findings should pave the way for nanoscale control of chemical reactions in E-TEM.