Preparation of zwitterionically charged chitin nanofibers through one step chemical modification and their application for antireflective coatings

Chitin nanofibers are widely used in many fields because of their biocompatibility, renewability and excellent mechanical properties. Herein, zwitterionically charged chitin nanofibers (ZC-ChNFs) were prepared from chitin via one step chemical modification (oxalic acid pretreatment) and subsequent ultrasound treatment. Effects of pretreatment time on size of the ZC-ChNFs and pH of ZC-ChNF suspensions on the thickness, porosity, refractive index and antireflective capacity of ZC-ChNF coatings were investigated. It was found that, by adjusting pH of the ZC-ChNF suspension, porosity and refractive index of the ZC-ChNF coatings could be controlled. The ZC-ChNF coatings fabricated with smaller ZC-ChNFs had higher antireflective performance and the transmittance gain of a glass with a ZC-ChNF coating was about 3.5 % at a wavelength of 550 nm compared to the bare glass. The results of this work provide a promising pathway to fabricate antireflective coating with ZC-ChNFs just by controlling the pH of ZC-ChNF suspensions.