10-10/11 :: October/November 2010

nanotimes News in Brief

Manufacturing Process // A New Family of Bioorganic–inorganic Nanocomposites

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runo Alonso and Emmanuel Belamie from the Charles Gerhardt Institute in Montpellier

(France) have introduced a novel, highly versatile ap- proach to the large-scale synthesis of a new family of bioorganic–inorganic nanocomposites – with a previously unattainable degree of control over the composition and structure of the materials produced.

For their synthesis, the researchers chose to use a sol-gel process, a popular technique for the produc- tion of inorganic network structures. In the first step they needed to generate a sol: a suspension of finely divided nanoscopic particles in a solvent. Their chal- lenge was to obtain co-suspension of the two diffe- rent components, silicon dioxide precursors (siloxane oligomers) and chitin nanorods from shrimp shells (a renewable resource). However, these two compon- ents require different conditions to remain in stable suspensions without uncontrolled precipitation. The researchers produced an alcohol suspension by slow- ly replacing water with ethanol. Through slow remo- val of the solvent, a gel formed. Gels are gelatinous substances; they contain solid but loose, cross-linked, three-dimensional polymer structures.

The sol can be “poured” into a desired mold and dried or it can be spray-dried into spherical particles. This process results in a nanocomposite made of chi- tin rods that are fully embedded in a silicon dioxide

matrix. The mechanism by which this occurs is based on a self-organized aggregation of the chitin mole- cules and weak attractive forces between chitin and siloxane oligomers.

The stability of the alcohol suspensions opens up a wide range of possibilities for the production of materials with controllable volume ratios, spatial arrangements, and morphologies. If a magnetic field is applied during preparation of the material, the chitin rods line up in parallel. If the nanocomposite is heated, the chitin rods can be burned off to leave behind cavities. This forms a highly porous material with interesting properties.

Dr. Bruno Alonso, Dr. Emmanuel Belamie: Chitin– Silica Nanocomposites by Self-Assembly, In: Angewandte Chemie International Edition, Volume 49(2010), Issue 44, October 25, 2010, pages 8201-8204, DOI:10.1002/ anie.201002104:

http://dx.doi.org/10.1002/anie.201002104

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