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Stimuli-Responsive Materials Consisting of Rigid Cylindrical Inorganic Low- Dimensional Compound “Imogolite”
Published in Kazuhiro Shikinaka, Functionalization of Molecular Architectures, 2018
To create the functional materials biomimetically, imogolite (henceforth denoted as IG) was used as low-dimensional compound that is a single-walled aluminosilicate rigid cylindrical inorganic polymer with the composition (HO)3Al2O3SiOH [9–14]. IG’s external and internal diameters are approximately 2 and 1 nm, respectively, while its length can range from several tens nanometers to several micrometers. Since IG is a perfectly rigid polyelectrolyte with high aspect ratio [15], it has been used as a constituent of inorganic-organic nanocomposites [16]. The outer and inner surfaces of IG are covered with Al(OH)2 (proton-capturing) and Si(OH) (proton-releasing) groups, respectively. Thus, the charge density of IG surfaces varies with the pH and ionic strength of aqueous media. Consequently, the dispersibility of IGs in water changes drastically with pH; they disperse as thin bundles or even as monofilaments in acidic and relatively low ionic strength aqueous media (pH ≈ 4), resulting in opaque to transparent solutions. Hereafter we exhibit some developments of stimuli-responsive materials of IG in accordance with the structural characteristics of IG, adequately.
Introduction to Nanomaterials and Nanotechnology
Published in Rajendra Kumar Goyal, Nanomaterials and Nanocomposites, 2017
They have two dimensions of particulates in the nanometer scale and the third dimension is significant compared to other two dimensions, that is, they have length of several micrometers (or >100 nm) and diameter of only a few nanometers. Examples include nanotubes, nanofibers, nanorods, or whiskers of metals or oxides, and carbon nanotubes (CNTs) and carbon nanofibers (CNFs). These entities have a very high-surface area and aspect ratio, which are useful in nanocomposites. Imogolite is a naturally occurring 1-D silicate having chemical formula of Al2SiO3(OH)4. Its tubes have an inside diameter of ∼1 nm and outside diameters of ∼2 nm. The internal and outer diameters can be adjusted by varying the silicon/aluminum ratio. The tubes may be up to a few micrometers in length, and both natural and synthesized imogolite tubes form bundles with diameters ranging from 5 to 30 nm due to their high-surface area-to-volume ratio. Figure 1.2b shows the atomic arrangement in a cross section of an imogolite tube. The structure of imogolite consists of aluminum, silicon, oxygen, and (OH)− ions arranged in rings. The (OH)− ions present on the surface allow its functionalization by the organic molecules. They have surface area of ∼1000 ± 100 m2/g and the Mohs hardness of ca. 2–3. Although they have high-aspect ratio, their lower strength and hardness limit their applications for the nanocomposites [1].
Middle–Upper Pleistocene tephras in the Papua New Guinea highlands
Published in Australian Journal of Earth Sciences, 2023
Chartres and Pain (1984) found that tephras are more weathered at lower altitudes, probably because of higher temperatures. They also weather to specific clay minerals that are seldom found in other weathered materials; these are allophane, imogolite and hydrated halloysite (Pain, 1971). Chartres et al. (1985) found that, in the PNG highlands, allophane dominates the soils above 2000 m, gibbsite those between 1200 and 2000 m and halloysite those below 1200 m. Allophane is an important indicator of tephra and can be easily identified in the field using a test developed by Fieldes and Perrott (1966). Parfitt (1975) noted that allophane and gibbsite occur in the younger tephras with increased abundance of metahalloysite in the lower horizons of these profiles where older, more weathered ashfalls are likely to occur.
Persistence and environmental geochemistry transformation of antibiotic-resistance bacteria/genes in water at the interface of natural minerals with light irradiation
Published in Critical Reviews in Environmental Science and Technology, 2022
Hongliang Yin, Yiwei Cai, Guiying Li, Wanjun Wang, Po Keung Wong, Taicheng An
The natural mineral is widespread in environmental system and closely related to bacteria. During the life process of bacteria, a lot of physical-chemistry interactions happened at the interface of environmental minerals. Among these processes, bacteria usually undergo an antibacterial effect posed by some mineral materials, which can hamper passive and active uptake of essential nutrient, disrupt cell envelope or impair efflux of metabolites (Ferris et al., 1987). Some specific minerals such as allophane and imogolite could make antibacterial by chemical sorption of known bacterial element (Ag, Cu, Co, Zn) onto certain crystallographic sites of mineral surface (Malachová et al., 2011; Onodera et al., 2001). It has been reported that the effects of antibacterial are mineralogically different, but they have in common in the presence of Fe-rich phases (e.g., biotite, Fe-smectite, jarosite, magnetite, pyrite, hematite, amphibole, and goethite) (Williams et al., 2011). Besides, nano-minerals may enhance the solubility of toxic element (Williams et al., 2011). When the antibacterial of natural mineral has been revealed, some studies start to synthesize the artificial mineral media or mineral complexes to inhibit the growth ability of bacteria (Lachowicz et al., 1996; Wu et al., 2009).
Mesoscale simulation of aggregation of imogolite nanotubes from potential of mean force interactions
Published in Molecular Physics, 2019
Hejian Zhu, Andrew J. Whittle, Roland J.-M. Pellenq, Katerina Ioannidou
Clay minerals have layered structures at nanoscale, most commonly in the form of some combination of tetrahedral silicate and octahedral alumina layers bonded through sharing of oxygen atoms. The layers constructed from the building blocks come in different sizes and can also foil up to form rolls or tubes. Natural imogolite nanotubes are formed as weathering products of volcanic ash and are tubular in shape with a typical diameter ∼2 nm, and length ∼100 to 400 nm [1] (dimension ratio 1:50 to 1:400). A nanotube consists of an octahedral outer layer and a tetrahedral inner layer, resulting in a thickness of around 5 Å and a chemical formula: . There also exist double-walled varieties, and types with impurities in the form of isomorphous substitutions (IS) [1]. Through doping, one can also control the diameter of the tubes, which makes imogolite a promising candidate material as molecular sieve [2,3]. Imogolite charged in this way can have a convenient length down to ∼10 nm.