Fuente: WIPO "tomato" Materials (e.g., packaging materials) comprising a fiber substrate (e.g., paper) in a form of a porous network of fibers, and graphene oxide on surfaces of the fibers are provided, wherein the graphene oxide is present in the material at an amount of less than 1 weight % are provided. The materials are characterized by improved properties (e.g., increased oil/water resistance, increased mechanical properties) as compared to the fiber substrate absent the graphene oxide. Methods of improving mechanical properties of a fiber substrate are also provided. Food-packaging materials, methods of making the food-packaging materials and methods of using the food-packing materials are also provided.