5. Conclusion
This paper reports a top down preparation method of chitosan nanoparticles and chitosan nanofibers employing direct ultrasonication of deacetylated chitin nanofibers. Pure chitin isolated from crab shells was treated chemically and mechanically to obtain chitin nanofibers. These nanofibers were then deacetylated under alkaline conditions followed by ultrasonic treatment. This process leads to chitin nanofibers were having diameters less than 20 nm and lengths less than 4 μm. Ultrasonication of deacetylated chitin nanofibers resulted in a mixture of chitosan nanoparticles and nanofibers. Chitosan nanoparticles could be isolated using simple gravity filtration and had diameters less than 300 nm. However, these nanoparticles were observed to be made out of much smaller nanoparticles which had diameters less than 25 nm. The prepared chitosan has a degree of deacetylation close to 98% and amorphous in structure. We show that chitosan nanoparticles and nanofibers can be made using direct ultrasonication of deacetylated chitin nanofibers.