By controlling a mix of clay, water and salt, Norwegian and Brazilian researchers have created nanostructures that might help boost oil production, expand the lifespan of certain foods or that could be used in cosmetics or drugs.
You’ve seen sauce or mayonnaise that separates, or a slippery layer of oil that forms on top of skin cream. Oil and water generally stay separate. It is actually hard work to keep water droplets or oil droplets stable in a substance called an emulsion.
Processed food, medicine and enhanced oil recovery from oil reservoirs all face this challenge. And while a substance called an emulsifier can also be used to keep an emulsion stable, many industries also have the opposite challenge—keeping oil separated from water.
Jon Otto Fossum, an NTNU physicist, has previously worked with controlling the behavior of clay and oil drops using electricity, a find that was published in Nature Communications in 2013. Now he’s branching out into salty water, oil and clay.
- You might also like: Clay can be used for carbon capture
In this latest effort, Fossum led an international group that created two different types of clay-based nanostructures on an oil droplet in water simply by fine-tuning the salinity of the water around the drop. The find was published in an open-access online journal published by Nature called Scientific Reports.
The find builds on two well-known properties of clay in water.
Clay particles repel one another in water that does not contain salt. In this case, the clays form the same kinds of nanostructures that are found in glass materials.
In contrast, clay particles in saline water tend to aggregate and form a kind of gel consisting of a nano-network of clay particles.
“It is possible to design small particles of clay with a micrometer thin gel on an oil droplet in water by fine tuning the salinity of the water around the oil drop,” said Fossum.
- You might also like: Small capsules, big potential
Mechanical strength important
Fossum said the find shows that there are micrometer-thick gel structures formed at specific salt concentrations in water with sufficient mechanical strength to prevent oil droplets in emulsions from merging with one another. Until the team’s research, no one had observed glass or gel nanostructures in nanofluids at fluid-fluid interfaces.
The ability to create micrometer-thick gel structures by controlling salt concentrations could be used to improve the amount of oil recovered from oil reservoirs, Fossum said, or might be able to improve the lifetime of specific food products. The structures might also find a use in medicines or cosmetics, he said.
The international team behind the research is drawn from NTNU, Norway’s largest university, and from Pontifica Universidade Catolica do Rio de Janeiro (PUC-Rio), and Universidade de Sao Paulo (USP), two of Latin America’s top universities.
New technique to grow nanostructures that degrade organic matter when exposed to light
A spot of sunshine is all it could take to get your washing done, thanks to pioneering nano research into self-cleaning textiles.
Researchers at RMIT University in Melbourne, Australia, have developed a cheap and efficient new way to grow special nanostructures — which can degrade organic matter when exposed to light — directly onto textiles.
The work paves the way towards nano-enhanced textiles that can spontaneously clean themselves of stains and grime simply by being put under a light bulb or worn out in the sun.
Dr Rajesh Ramanathan said the process developed by the team had a variety of applications for catalysis-based industries such as agrochemicals, pharmaceuticals and natural products, and could be easily scaled up to industrial levels.
“The advantage of textiles is they already have a 3D structure so they are great at absorbing light, which in turn speeds up the process of degrading organic matter,” he said.
“There’s more work to do to before we can start throwing out our washing machines, but this advance lays a strong foundation for the future development of fully self-cleaning textiles.”
The researchers from the Ian Potter NanoBioSensing Facility and NanoBiotechnology Research Lab at RMIT worked with copper and silver-based nanostructures, which are known for their ability to absorb visible light.
When the nanostructures are exposed to light, they receive an energy boost that creates “hot electrons”. These “hot electrons” release a burst of energy that enables the nanostructures to degrade organic matter.
The challenge for researchers has been to bring the concept out of the lab by working out how to build these nanostructures on an industrial scale and permanently attach them to textiles.
The RMIT team’s novel approach was to grow the nanostructures directly onto the textiles by dipping them into a few solutions, resulting in the development of stable nanostructures within 30 minutes.
When exposed to light, it took less than six minutes for some of the nano-enhanced textiles to spontaneously clean themselves.
“Our next step will be to test our nano-enhanced textiles with organic compounds that could be more relevant to consumers, to see how quickly they can handle common stains like tomato sauce or wine,” Ramanathan said.