Using TEMPO oxidation to tailor deacetylation of carboxyl β-chitin nanofibers from squid pen

2,2,6,6-tetramethylpiperidine-1-oxyl-radical (TEMPO) oxidation is a classical method to obtain carboxyl chitin nanomaterials, but when the traditional TEMPO/NaBr/NaClO (TBN) oxidation system was oxidizing β-chitin, it was only suitable for β-chitin with a degree of deacetylation (DD) of 1%. Herein, the high yield carboxyl β-chitin nanofibers (CO-ChNFs) were successfully prepared from squid pen β-chitin with partially deacetylated (DD: 5–30%) using the TEMPO/NaClO/NaClO 2 (TNN) oxidation system. The results show that the DD of purified β-chitin has a great impact on the yield of CO-ChNFs, and the yield is as high as 98% when the DD of β-chitin was 11%. XRD results showed that β-chitin undergoes slight of β–α transformation after TNN TEMPO oxidation, and the 010 crystal planes are arranged more closely. AFM characterization suggests that thus prepared CO-ChNFs have a diameter of 2–6 nm and a length in the micrometer range. The proposed preparation method breaks through the previous limitation of TEMPO oxidation for β-chitin, and will facilitate the in-depth research and application of carboxyl β-chitin nanofibers. Graphical abstract