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The basic scenario of resistive switching in TiO₂ (Jameson et al., 2007) assumes the formation and electromigration of oxygen vacancies between the electrodes (Baiatu et al., 1990), so that the distribution of concomitant n-type conductivity (Janotti et al., 2010) across the volume can eventually be controlled by an external electric bias, as schematically shown in Figure 1B. Direct observations with transmission electron microscopy (TEM) revealed more complex electroforming processes in TiO₂ thin films. In one of the studies, a continuous Pt filament between the electrodes was observed in a planar Pt/TiO₂/Pt memristor (Jang et al., 2016). As illustrated in Figure 1C, the corresponding switching mechanism was suggested as the formation of a conductive nanofilament with a high concentration of ionized oxygen vacancies and correspondingly reduced Ti³⁺ ions. These ions induce detachment and migration of Pt atoms from the electrode via strong metal–support interactions (Tauster, 1987). Another TEM investigation of a conductive TiO₂ nanofilament revealed it to be a Magnéli phase Ti_nO_2n−1 (Kwon et al., 2010). Supposedly, its formation results from an increase in the concentrations of oxygen vacancies within a local nanoregion above their thermodynamically stable limit. This scenario is schematically shown in Figure 1D. Other hypothesized point defect mechanisms involve a contribution of cation and anion interstitials, although their behavior has been studied more in tantalum oxide (Wedig et al., 2015; Kumar et al., 2016). The plausible origins and mechanisms of memristive switching have been comprehensively reviewed in topical publications devoted to metal oxide memristors (Yang et al., 2008; Waser et al., 2009; Ielmini, 2016) as well as TiO₂ (Jeong et al., 2011; Szot et al., 2011; Acharyya et al., 2014). The resistive switching mechanisms in memristive materials are regularly revisited and updated in the themed review publications (Sun et al., 2019; Wang et al., 2020).

In a small study published in the European Journal of Nutrition in 2020, researchers examined the effects of several food additives, including titanium dioxide, along with artificial sweeteners and cleaning products by testing the fecal samples of 13 people. Titanium dioxide was among the samples that “induced significant shifts in microbiome community structure.”  The growth of the bacterium species belonging to C. leptum, which has been shown to decrease in patients with inflammatory bowel disease, “significantly decreased in the presence of … titanium dioxide” among other additives and sweeteners tested.

Lithopone, a chemical compound with a rich history, emerges as a vital substance in various industries. Comprising barium sulfate and zinc sulfide, this compound boasts unique properties that make it a popular choice in applications such as paints, inks, and plastics. Recognized for its exceptional opacity and brightness, lithopone significantly enhances the covering power of materials in which it is incorporated. Its inert nature and resistance to atmospheric influences contribute to its longevity in diverse formulations. As a white pigment, lithopone plays a pivotal role in achieving vibrant and enduring colors across a spectrum of products, marking it as a cornerstone in the realm of chemical compounds.