Biodegradable flexible transparent films with copper iodide and biomass-derived nanocellulose for ultraviolet and high-energy visible light protection

[Display omitted] •Solar energy converted into biomass of plants to obtain nanocellulose (NC) films.•Acid hydrolysis and TEMPO oxidation of cellulose used to prepare NC suspensions.•Nanocellulose films have stable monoclinic structure and high crystallinity.•Successive Ionic Layer Adsorption and Reaction method to deposit CuI film on NC.•Transparent for visible light CuI/NC films block solar ultraviolet radiation.•Transparent CuI/NC films protect against high-energy visible light. In this work we present utilization of solar energy for a creation of biocompatible, biodegradable, and renewable thin film transparent materials that can protect against overabundant ultraviolet (UV) radiation and high energy visible (HEV) light of solar spectrum. From biomass of herbaceous plants Miscanthus × giganteus and Phragmites australis we obtained nanocellulose suspensions NCm through acid hydrolysis and NCp through TEMPO oxidation, respectively. These suspensions transformed into corresponding transparent flexible NCm and NCp nanocellulose films and used as substrates for 0.17 – 0.23 µm thick nanostructured layers of wide band gap semiconductor CuI deposited via wet chemical method Successive Ionic Layer Adsorption and Reaction (SILAR) to obtain promising visibly transparent UV- and HEV-shielding materials CuI/NCm and CuI/NCp. Under this investigation, we compare UV- and HEV-shielding properties of transparent NCm, CuI/NCm, NCp, and CuI/NCp flexible samples depending on structure, surface morphology, chemical composition, optical properties, and thickness. It is shown that the best CuI/NCp sample with 0.23 µm thick CuI film and 8 µm thick NCp substrate has optical transmittance up to 82% for visible light at wavelengths above 500 nm, blocks 65% of high-energy visible radiation, and has excellent sun protection factor (SPF = 112).