In situ oxidation and reduction of cerium dioxide nanoparticles studied by scanning transmission electron microscopy

Abstract

Cerium dioxide nanocubes and truncated octahedra were reduced and oxidized in the scanning transmission electron microscope. The reduction process was stimulated by the electron beam and oxidation was supported by background gases in the microscope environment. High-angle annular dark field imaging is sensitive to local lattice distortions that arise as oxygen vacancies are created and cerium cations reduce enabling high spatial resolution characterization of this process with temporal resolution on the order of seconds. Such measurements enable us to differentiate and infer that the observed behavior between the nanocubes and truncated octahedra may be due to the difference in crystallographic termination of surfaces. In situ measurements taken with different partial pressures of oxygen reveal the cerium oxidation state and the dose rate threshold for the onset of beam reduction are influenced by the environment. Increasing oxygen partial pressure reduces the Ce content and decreases susceptibility to electron beam driven reduction.

Reducing electron beam damage through alternative STEM scanning strategies. Part II -- Attempt towards an empirical model describing the damage process

“…Therefore, a threshold is introduced below which no damage is induced. This type of behaviour has been observed by others but without combining it with diffusion [2,3,4,5]. In Section 2 of this manuscript, we introduce the model.…”

“…(1) where r = r − r 0 and t = t − t 0 (2) With Ei being the integral exponential function, τ the dwell time, r 0 is the position of the incoming beam and t 0 is the time when the electron beam arrives at point r 0 . The derivation of Eq.…”

Efficacy of A Novel Smart Polymeric Nanodrug in the Treatment of Experimental Wounds in Rats

“…The results of the preliminary analysis of the product, as well as the results of experiments that demonstrate its safety and biocompatibility, have been published earlier [23][24][25]. Nanocrystalline CeO 2 was chosen for the development of a medical product for wound healing because it has low toxicity, is highly biocompatible, and can provide electron transfer by the transition of the valence from Ce 3+ to Ce 4+ and back depending on the changing pH value [26][27][28][29]. This is why the medicine is called "smart" and makes CeO 2 a promising agent for use in nanomedicine [30][31][32][33][34][35].…”

Acute Skin Wounds Treated with Mesenchymal Stem Cells and Biopolymer Compositions Alone and in Combination: Evaluation of Agent Efficacy and Analysis of Healing Mechanisms

“…In our previous research, we developed new dressing biomaterials for the treatment of wounds containing polymers, mesenchymal stem cells, and nanoparticles of cerium dioxide (CeO2), and demonstrated their preliminary safety and efficacy [30][31][32][33][34]. We have chosen CeO2 nanoparticles as the metal included in our biomaterials because previous studies have shown that it has low toxicity and high biocompatibility, as well as the ability, depending on the changing pH of the wound, to provide electron transfer through the transition from Ce3+ to Ce4+ valence and vice versa [35][36][37][38]. This allows the wound environment to become stable by neutralizing reactive oxygen species and other free radicals, providing antioxidant, antibacterial, and anti-inflammatory effects.…”