High barrier paper-based materials with optical anti-counterfeiting performance

Paper-based packaging materials demonstrate inadequate barrier capabilities due to the porous structure of cellulosic material, especially with respect to oxygen and water vapor, which significantly hindered the application of paper-based packaging materials. In this paper, inspired by the “brick and mortar” biomimetic structure, the monodisperse silicon dioxide nanoparticles (SiO₂ NPs) were used as “brick” to block water vapor, and the polyvinyl alcohol (PVA) and polyacrylate (PA) were utilized as organic barrier layers in the composite paper-based material. Interestingly, photonic crystals exhibiting structural colors can be formed through the self-assembly of SiO₂ NPs (inorganic layer). Attributed to the vibrant structural color would present different hues as the viewing angle changing, and the paper-based material was endowed with exceptional optical anti-counterfeiting properties. Compared with the pristine paper with almost no barrier property, the oxygen transmission rate (OTR) of the coated paper-based composite film was reduced to 0.723 cm³/cm²·24 h·0.1 MPa, and the water vapor transmission rate (WVTR) was reduced to 8.3544 g/m²·24h, which demonstrated the excellent oxygen and water vapor resistance. And the observed color of the paper-based film could be changed by adjusting the particle size of the silica nanospheres and the observation angle to achieve angular anti-counterfeiting. This strategy effectively enhanced the oxygen and water vapor barrier ability of paper matrix composites and gives the materials stable and bright color results in outstanding anti-counterfeiting effects. Therefore, this paper-based material has dual functional advantages, both excellent gas barrier and optical anti-counterfeiting ability, showing great potential in the field of packaging materials.