Omnidirectional antireflective coatings prepared with chitin nanofibers via layer-by-layer self-assembly

Antireflective coatings play an important role in various optical devices. Herein, we developed omnidirectional antireflective coatings fabricated with charged chitin nanofibers (ChNFs) through layer-by-layer (LbL) selfassembly technology. The charged ChNFs were prepared from chitin with modifications of esterification (negatively charged) and esterification followed partial deacetylation (positively charged), respectively, through ultrasonic treatment. The effects of concentration of the ChNF suspensions and number of bilayers on thickness, refractive index and antireflective capacity of the ChNF coatings were investigated. Refractive index of the ChNF coatings can be manipulated by changing concentration of the ChNF suspensions. Thickness of the ChNF coatings depends on number of bilayers and concentration of the ChNF suspensions. The ChNF coating on a glass substrate with 5 bilayers fabricated using the suspensions with concentration 0.1% had a refractive index of 1.36 and yielded 4% gain in transmittance compared to the glass at the wavelength of 550 nm. This work demonstrates that charged ChNFs are promising building blocks to fabricate antireflective coatings on large size substrates with high efficiency and low cost through LbL self-assembly.

Automated summary

Antireflective coatings were fabricated using charged chitin nanofibers (ChNFs) through layer-by-layer self-assembly. The thickness and refractive index of the ChNF coatings could be controlled by adjusting the concentration of the ChNF suspensions and number of bilayers, resulting in improved transmittance. This study demonstrates the potential of charged ChNFs as building blocks for efficient and cost-effective fabrication of antireflective coatings on large size substrates.