Tuning particle wettability opens path for lower-cost waterproofing

Less expensive and hazardous coatings resulting from nanoparticle surface modification could enhance oil recovery and prevent fouling and fogging

Greener alternatives to current materials used for waterproofing, anti-fogging and antifouling could come from research at Swansea University which has shown that the way nanoparticles behave in contact with water can be tuned by adding chemical compounds to their surfaces and altering the structures of these compounds. The resulting particles, which could also be used to improve recovery of oil from established reserves, are cheap, non-toxic and can be used as coatings.

The research was carried out by the Energy Safety Research Institute at Swansea, and has been published in the open access journal ACS Omega. Centred around work carried out by Wafaa Al-Shatty and directed by Dr Shirin Alexander and Prof Andrew Baron, the paper focuses on the behaviour of aluminium oxide nanoparticles whose surfaces were coated with linear and branched carboxylic acids.

Al-Shatty found that nanoparticles whose surfaces had exposed methoxy (–OCH3) functional groups were extremely hydrophilic; a droplet of water on the surface of a material coated with these particles tends to spread out flat. By contrast, particles with “spiky” (highly branched) hydrocarbons made a coating that exhibited superhydrophobic behaviour – water droplets sit proud of the surface and tend to slide off.

Changing the functional groups on the particles’ surface tunes the behaviour of water on a material coated with the particles

It’s the latter type which may have industrial applications, the researchers say. Currently, superhydrophobic coatings – which are the basis of antifouling and waterproofing treatments – tend to be based on expensive and hazardous fluorocarbons. The tuned aluminium oxide nanoparticles are nonhazardous and can be applied to surfaces via spray-or spin-coating.

“They also are able to reduce the interfacial tension of various oils-water emulsions by behaving as surface active agents [surfactants],” noted Shirin Alexander; making oil-water emulsions and understanding their stability is crucial in enhanced oil recovery techniques used in producing oil from wells which have been exploited for long periods. The team is now looking at improving the durability of nanoparticles coatings on various surfaces, and on techniques for applying them to large areas.