Effects of Size and Porosity on the Hydrophobicity of Hierarchical Nanoparticles.

Hierarchical nanoporous particles combine properties of microporous and mesoporous materials that are widely exploited for energy storage and conversion, separation of gases and liquids, water purification and desalination, fabrication of nanodevices, etc. Hierarchical meso/microporous level-2 and level-3 Menger sponge particles immersed in water were investigated using computer simulation methods to demonstrate a synergetic effect of additional porosity on the wettability of materials. The Menger sponge is an object with a fractal dimension. At each level, the particles are composed of the same structural blocks. The hydrophobicity of the blocks was shown to depend on their size and position in the nanoparticles. The additional porosity decreases the hydrophobicity of the particles due to the partial breaking of hydrogen bonds between water molecules in the pores. This effect can be used to tune and modify the hydrophobicity and wettability of bulky porous materials, nanoparticles, and nanostructured surfaces.