Biomimetic growth of biomorphic CaCO3 with hierarchically ordered cellulosic structures

Biomorphic CaCO3 with different hierarchically ordered micro- and nanostructures was fabricated with natural cellulose substances as the host templates. The fabrication involves two mild sonication processes in which calcium and carbonate ions are sequentially added to the template, together with subsequent calcination in air. The specific pseudo-1D and pseudo-2D structures of the resultant crystalline calcite can be tailored by mimicking both natural and artificially woven cellulosic substances, with the former following the ribbon/tube form of cellulose fiber and the latter following the netlike architectures of the woven cotton cloth. The building block of these structures is a layer of CaCO3 grains grown on the surfaces of each cellulose fiber. By choosing Ca2+, CO32-, or HCO3- ions as the first adsorption species on the cellulose template, we show that the resultant CaCO3 grain size can be fine-tuned in a nanoscopic scale, most probably due to the differences in the nature of ion adsorption on the cellulose molecules and the resultant CaCO3 nucleation and growth. The impact of this new route is that we can precisely predict the morphologies of the final CaCO3 products that were not realized in other chemical approaches.