Chitin nanocrystals prepared by TEMPO-mediated oxidation of alpha-chitin.
Chitin nanocrystals dispersed in water were successfully prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation of alpha-chitin in water at pH 10 under specific conditions, followed by ultrasonic treatment. When the amount of NaClO added as co-oxidant in the oxidation was 5.0 mmol/g of chitin, the weight percentage of the water-insoluble fraction in the TEMPO-oxidized chitin was 90%, and its carboxylate content reached 0.48 mmol/g. Since the TEMPO-oxidized chitin thus prepared had a crystallinity as high as that of the original alpha-chitin, the C6 carboxylate groups formed by TEMPO-mediated oxidation can be regarded as being present only on the chitin crystallite surfaces. No N-deacetylation occurred on the TEMPO-oxidized chitins. When the TEMPO-oxidized chitin was subjected to ultrasonic treatment in water, mostly individualized chitin nanocrystals were obtained, and the average nanocrystal length and width were 340 and 8 nm, respectively.
Fan
Yimin
Y
Department of Biomaterials Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
Saito
Tsuguyuki
T
Isogai
Akira
A
D002686:Chitin / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003497:Cyclic N-Oxides / Q000737:chemistry*; D053758:Nanoparticles; D010084:Oxidation-Reduction; D017550:Spectroscopy, Fourier Transform Infrared
D003497:Cyclic N-Oxides; D002686:Chitin; C003959:TEMPO