Coating paper with nanoparticles can make paper more durable or even make it waterproof. From Scientific American:
Scientists at the Istituto Italiano di Tecnologia in Genoa, Italy, developed a process to cover any cellulose fiber, like paper or fabric, with a reactive coating. It involves combining the fiber molecules with a nanoparticle solution, creating a polymer matrix.
The cellulose fibers are wetted with an acrylic solution containing manganese ferrite nanoparticles, which are magnetic. When it gets wet, the mixture forms a nano-shell around each individual fiber, rendering the fiber water-repellent. Scientists can change the composition of the nanoparticles to make it more or less magnetically responsive, or to add other attributes, like perhaps fluorescence. Add some colloidal silver, and it could be antibacterial.