Nanostructure of Diatom Silica Surfaces and of Biomimetic Analogues

Abstract

Diatoms generate their cell walls by silica biomineralization. The cell walls are composed of silica and organic macromolecules and show a complex microscopic structure. Analysis of this structure by different atomic force microscopy (AFM) techniques revealed an unexpected nanostructured granular surface. Silaffins, proteins that are posttranslationally modified with long-chain polyamines, and oligo-N-methylpropyleneamines were identified as the main organic constituents of diatom biosilica. 1 Silaffins as well as free propyleneamines of different chain lengths induce rapid precipitation of nanosized particles from silicic acid solutions in vitro. In a biomimetic approach, we reacted aqueous silicic acid solution with tripropylenetetramine in CHCl 3 in a biphasic system. As a result, thin nanostructured silica layers that show a granular nanostructure very similar to that of the diatom cell walls were obtained. This finding may serve as a good model to study the mechanisms that lead to the nanostructure of the diatom cell walls.

Application of AFM in understanding biomineral formation in diatoms

“…As evidenced by the few examples previously published [1,8,31] and shown in this paper, there is continued use for AFM in the study of diatom biomineralization. With the exception of the image of forming ribs in D. brightwellii in Fig.…”

“…Thirty to fifty nm spherical silica particles are present in a variety of diatoms [8,31;Figs. 3 and 5]; however, other morphologies with little or no detectable nanoscale texture are present in the same species (Figs.…”

Possible mechanism of structural incorporation of Al into diatomite during the deposition process I. Via a condensation reaction of hydroxyl groups

“…For example, the size of the nano-silica balls, which are the basic components of the diatom shell [28,29,2], most likely changes with the presence of Al in their framework because of the different sizes of Al and Si. In addition, the surface charge and solid acidity vary before and after Al incorporation into the structure [1,9].…”

Facile preparation of hierarchically porous carbon using diatomite as both template and catalyst and methylene blue adsorption of carbon products

“…It is the most abundant form of silica on earth and is easily obtained at very low cost [9]. Composed of biogenetic amorphous silica and classified as noncrystalline opal-A in mineralogy, diatom shell is characteristic of highly developed porosity and particularly macroporous structure [12][13][14] and thus has been used as the template for the preparation of macroporous materials [15,16]. The sizes of the macropores of diatomite range from nanometric to micrometric domains.…”