Biomimetic Synthesis of Silica with Chitosan‐Mediated Morphology

Abstract

The exquisite siliceous cell wall of diatoms is one of the most outstanding nanostructured artworks created by Mother Nature. Such a complicated hierarchical structure not only provides the protection for the diatom cell but also has a novel optical property that can improve the efficiency of light in photosynthesis. The physical and chemical properties of frustules have inspired some current research efforts: for instance, various kinds of hybrid inorganicmaterials have been produced successfully through a biomimetic strategy. In the meantime, the siliceous cell wall of the diatom has been employed for a few specific applications. In contrast to the industrial method of producing silica, the biosilica of diatoms is produced in a highly specialized compartment with a flat membrane, termed the silicadeposition vesicles (SDV), combined with a mild acidic environment. A number of biomolecules, such as the peptides of frustulins, pleuralins, silaffins, and long-chain polyamines, are involved in the process via specific interactions. Heretofore, silaffins and polyamines have been widely investigated and it was found that they could induce the formation of spherical silica particles in vitro from certain siliceous precursors. Furthermore, it has been shown that polyamines appear to be essential in silicification because of their cationic character under acidic conditions, and therefore, a few analogues of natural polyamines, as well as some