Natural Cellulosic Substance Derived Nano-structured Materials

Abstract

When versatile synthetic chemical processes meet natural biological assemblies, a promising shortcut for the design and fabrication of functional materials with tailored structures and properties are lit up. By precisely replicating natural substrates with guest matrices, artificial materials are endowed with the initial biological structures and morphologies. To achieve faithful inorganic/organic replicas of the natural species for the corresponding finest structural details and morphological hierarchies, one effective and practical strategy is to coat the morphologically sophisticated surfaces of the biological structures with ultrathin films accompanied by subsequent removal of the biotemplate. With this process, the morphological hierarchies of initial biological substances can be replicated faithfully from macroscopic down to nanometer scales. And it was successfully applied to natural cellulosic substances such as filter paper, cotton, and cloth to yield the related metal oxide replicas. The hierarchical structure and highly detailed morphologies of the cellulosic substances are precisely memorized in metal oxide films to give macroscopic fossils; and the organic substances are removed by subsequent calcination. The resultant fossils are hierarchical ceramic materials, in which the structures of the original template substance are faithfully inherited. The ceramics are composed of metal oxide nano-tubes, as precise hollow replicas of the template cellulose nanofibers. This approach has been employed to synthesize titania, zirconia, tin oxide, and ITO nanotubular materials. Hierarchical titania nanotube-gold nanoparticle hybrid and polypyrrole composite materials are also achieved with using filter paper as a scaffold. Also, the titania-coated cellulose fibers are employed as a substrate for protein immobilization, resulting in novel bioactive materials. Furthermore, by dissolving the cellulose template instead of calcination, this approach is extended to the design and preparation of bio-inspired polymeric nanotubular materials.