title: Preparation of zwitterionically charged nanocrystals by surface TEMPO-mediated oxidation and partial deacetylation of α-chitin.
abstract: Zwitterionic nanocrystals were prepared by TEMPO-mediated oxidation, partial deacetylation, and subsequent mechanical disintegration of α-chitin. The pH dependence of the morphology, transparency, and viscosity of the nanocrystals were evaluated. After those reactions, the carboxylate and amino group contents of the chitin derivative were 0.45 and 1.26 mmol/g, respectively. After mechanical treatment, the water dispersion consisted of nanocrystals approximately 250 nm long and 10nm thick. Under acidic and basic conditions, the water dispersions were highly transparent. On the other hand, under neutral conditions, the dispersion was turbid due to the ionic interaction between the cationic and anionic groups on the nanocrystal surface. Although the surface zwitterionic nanocrystals collected from acidic and basic dispersion were randomly oriented due to electrostatic repulsions, nanocrystals formed aggregates in neutral water due to the cationic and anionic interaction between them. Nanocrystals in neutral water had higher viscosity than those in acidic and basic water, since ionic interaction caused nanocrystal networks to form in water.
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-cho, Minami 680-8552, Tottori, Japan. Electronic address: sifuku@chem.tottori-u.ac.jp.
authors: Shinsuke
authors: S
authors: Ifuku
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-cho, Minami 680-8552, Tottori, Japan.
authors: Taishi
authors: T
authors: Hori
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-cho, Minami 680-8552, Tottori, Japan.
authors: Hironori
authors: H
authors: Izawa
authors: Research Center for Bioscience and Technology, Tottori University, 4-101 Koyama-cho, Minami 680-8550, Tottori, Japan.
authors: Minoru
authors: M
authors: Morimoto
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-cho, Minami 680-8552, Tottori, Japan.
authors: Hiroyuki
authors: H
authors: Saimoto
mesh_terms: D000107:Acetylation; D002686:Chitin / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D013499:Surface Properties
chemical_list: D003497:Cyclic N-Oxides; D002686:Chitin; C003959:TEMPO
keywords: Chitin; Deacetylation; Nanocrystal; TEMPO-mediated oxidation; Zwitterion