Inexpensive, non-toxic nanomaterials developed at the Energy Safety Research Institute at Swansea University (Wales) might replace more expensive and hazardous materials used for waterproofing and antifouling/fogging.
The materials feature tunable wettability and can be applied to a variety of surfaces via spray- or spin-coating. Spray-coated nanomaterials provide both a texture to the surfaces, regardless of the substrate, and the chemical functionality that can alter the surface from superhydrophilic (water wetting) to superhydrophobic (water repelling) based on the choice of tailored functionality.
Schematic of the functionalization of the nanoparticles along with photographic images of the water droplets on spray-coated microscope slides. (Credit: Shirin Alexander/University of Swansea)
Aluminum oxide nanoparticles were synthesized using hydrocarbon linear and branched carboxylic acids (with different surface energies) to demonstrate that hydrophobicity can be readily tuned based on the nature of the chemical functionality. Subtle changes in the organic chain enable control of surface wettability, roughness, surface energy and particle ability to behave as surface active agents.
Nanoparticles whose surfaces had exposed methoxy (–OCH3) functional groups were extremely hydrophilic, while particles with highly branched hydrocarbons formed a superhydrophobic coating. The latter material may be a "green" replacement for costly, hazardous fluorocarbons commonly used for superhydrophobic applications. Since the nanoparticles reduce the interfacial tension of various oils-water emulsions by behaving as surfactants, their use might improve the efficiency of enhanced oil recovery operations.
