Power of Ultrasound Binds Nanoparticles: Avoiding the Hazards of Air-Borne Particles

There's a new way to join materials together, and it's all about using the power of ultrasound. The findings could help scientists develop new ways to make environments safer for workers that have to worry about the hazards of nanoparticles in the air.

Ultrasound is sound that's so high that it can't be heard by regular means. It's usually used to smash particles apart in water. In this case, though, researchers had ultrasound do just the opposite--bind materials together. More specifically, the researchers wanted to bind nanoparticles.

Nanoparticles can be extremely useful in research. Yet they're difficult to contain because they're invisible to the naked eye and can be easily carried through the air. In addition, they can infiltrate the body, which can create a concern for the safety of industrial workers and the public. Being able to stick nanoparticles to one another could potentially help lessen these dangers.

Ultrasound induces short-lived bubbles, known as cavitation, that create 'hotspots' of thousands of degrees when they collapse. Because this bubble formation is a random and infrequent process, though, scientists have struggled to harness this powerful phenomenon for assembling materials rather than destroying them. The researchers wanted to develop a way to localize cavitation at the nanoparticles' surface. That's when they realized that a phosphate coating on the particles interacts with unstable radicals created at these hotspots to make the nanoparticles weld together.

"Our discovery may help alleviate the loss of platinum from catalytic converters in car exhausts, for example," said David Basset, the new study's co-author, in a news release. "Half of the platinum mined annually worldwide is used to make catalytic converters and up to half of this platinum is lost into the atmosphere during the lifetime of the car. This results from a lack of a better method--up to now--for bonding nanoparticles in a robust and durable manner while still maintaining their activity."

The findings could be huge for industrial processes. In theory, this method could be used to stick nanoparticles together into something that could be handled safely with your fingers without changing its useful properties. This, in turn, could have implications for a range of everyday applications.

The findings are published in the journal Advanced Materials.