Biosourced polysaccharide nanocrystals to template hybrid materials

Chitin crystalline nanorods are found in many natural nanocomposites associated with an inorganic phase, such as CaCO₃ in crustaceans and silica in the skeleton of glass sponges. This organic-inorganic association at the nanoscale under physiological conditions served as inspiration for new synthesis routes for materials compatible with the principles of green chemistry. Furthermore, polysaccharide nanocrystals are renewable organic precursors that are easily prepared from industrial waste biomass. A new family of organic-inorganic hybrid nanocomposites has been synthesized based on a versatile colloidal approach, which allows a high level of control over the texture and morphology of the materials. The hybrid materials can be obtained through sol-gel processing into microparticles by spray drying, fibers by electrospinning, and thin films by spin coating. The characteristics of the silica-chitin nanocomposites can be transferred to their mesoporous counterpart through simple calcination [1,2]. The porous materials have pore diameters in the range of 5-20 nm and specific surface areas of up to 500 m²·g⁻¹. For heterogeneous catalysis applications (selective oxidation), titanium alkoxides have been introduced to form mixed SiO₂-TiO₂ oxides. The dispersion of Ti sites can be tuned through the synthesis conditions [3].