Phosphoric acid-based preparing of chitin nanofibers and nanospheres

Chitin nanofibers and nanospheres were prepared by dissolution of the polymer in phosphoric acid and regeneration in water. Up to 4 % chitin was readily soluble in concentrated phosphoric acid. By varying the dissolution temperatures and times, chitin nanofibers with widths around 20 nm or chitin nanospheres with sizes around 200–500 nm were obtained with yields more than 80 %. Chemical composition analysis showed that the chemical structures of native chitin were essentially remained after the dissolution and regeneration process, and the degree of substitution of phosphorous on chitin chain was less than 1.00 %. Crystalline structure analysis revealed the crystalline structure of native chitin was not altered, but the crystallinity was decreased after regeneration. Our findings offers a facile and green process for most common labs to prepare chitin nanomaterials with tuned morphology in high yields, which may find great applications in the biomedical, pharmaceutical and food industries.