Fabrication of 3D-networks of native starch and their application to produce porous inorganic oxide networks through a supercritical route

Herein an effective method for fabrication of three dimensional networks of starch is presented. In this method, the native starch was dissolved in hot water to form solution, resulting in the formation of starch gel after cooled to room temperature. Then the water in the starch gel was exchanged by ethanol, followed by drying with supercritical (SC) CO2 extraction, the nano-networks of starch were prepared. The obtained starch aerogel was composed of starch fibers and presented porous structure. Changing the initial concentration of native starch and controlling the drying conditions could control the microstructure of the starch networks. The resulting starch networks were utilized as a directing template to prepare the hierarchically ordered TiO2 networks. In this process, TiO2 precursor dissolved in SC CO2 diffused onto the surface of starch gel, and reacted with the hydroxyl groups and adsorbed water molecules on the starch surface, to form an organic/inorganic hybrid material. After calcining the composites at 500 °C, the networks composed of anatase TiO2 nanocrystals were produced, which accurately replicated the fine structures of the starch gel and possessed higher BET surface area and total pore volume compared with those of other TiO2 materials templated by some biomaterials or polymer gels.