The inventors have developed a low-temperature, cheap, and simple method to render nanostructures mechanically robust. Superheated steam is used to improve the mechanical properties of polyelectrolyte multilayers of nanoparticles. Incorporated nanoparticles include silica, with sizes range from 7nm to 50 nm. Polymeric layers of charged polymers, such as polyallylamine hydrochloride, may be used between nanoparticle layers. Hydrothermal treatment is performed using steam at 120 °C and 20 psi in an autoclave for up to 8 hours.
Small particles are much more soluble due to their small radii of curvature. The steam treatment is thought to dissolve parts of the nanoparticles and redistribute monomeric or oligomeric units at points of contact between the nanoparticles, forming interparticle bridges and providing stability. In addition to improving mechanical robustness, this hydrothermal treatment can also be used to generate surface patterns via self-assembly. Creating these surface textures on substrates such as glass would produce a material which would virtually eliminate reflections and deflect water droplets entirely, creating a robust anti-glare and anti-fogging coating.