Natural and artificial nanomaterials: biomimetics
المؤلف:
Peter Atkins, Tina Overton, Jonathan Rourke, Mark Weller, and Fraser Armstrong
المصدر:
Shriver and Atkins Inorganic Chemistry ,5th E
الجزء والصفحة:
682
2025-10-15
310
Natural and artificial nanomaterials: biomimetics
Key point: Biological materials can be used as templates in the design of nanoinorganics having specific architectures that mimic the structure of the natural material. The formation mechanisms in fossilization, including those for siliceous woods, offer efficient methods to reproduce morphological hierarchies of original plant matter through the replacement of the organic components by silica. Artificial fossilization processes can be realized by carefully lining the morphologically complex surfaces of the biological structure with inorganic layers followed by removal of the organic template. Natural materials such as wood and eggshell membrane have been used as templates for the preparation of macroporous silica, zeolites, and titanium dioxide from both precursor sol–gel solutions and suspensions of nanocrystals. Unfortunately, morphological replication has been achieved only over the micrometre scale and the nanoscale details of the biological templates have not yet been reproduced. An artificial fossilization process has been developed by taking advantage of a surface sol–gel process that can replicate nanoscale features of biological templates (Box 25.3). The surface sol–gel process consists of two steps. First, metal alkoxides are adsorbed from the solution on to hydroxylated substrate surfaces. Then the adsorbed species are hydrolysed to yield nanometre-thick oxide films. Natural cellulose fibres possess surface –OH groups and provide a template for using the surface sol–gel process. The outer diameter of the TiO2 nanotube varies from 30 to 100 nm, and the thickness of the tube is uniform along its length, with a wall thickness of about 10 nm. The nanotube assembly exhibits the original morphology of interwoven cellulose fibres. The ‘titania paper’ produced in this way records the morphological information of the original paper at the nanoscale and offers a remarkable example of successful biotemplating of metal oxide nanomaterials.
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