Transparent layer-by-layer coatings based on biopolymers and CeO2 to protect wood from UV light

Wood is a renewable and abundant material with a high aesthetic appeal, but is heavily affected by weathering, particularly by UV-induced degradation in unprotected exposure. Here, we demonstrate a simple coating procedure of spruce wood with UV-protective CeO2 nanoparticles and biopolymers. Using a layer-by-layer approach, multilayers of the nanoparticles and biopolymers (chitosan or cationic starch) were deposited onto the wood surface by a simple dip coating process. The nanoparticle suspensions and biopolymer solutions were characterized by dynamic light scattering and electrophoretic mobility measurements. The coated wood surfaces were visualized by SEM and the successful nanoparticle deposition confirmed by EDX. The streaming potential data correlated strongly with the proposed layered build-up. The established coatings were transparent and did only lead to a minute alteration of the surface color. At the same time, they reduced the amount of UV light induced color change in all CIELAB dimensions.