Each particle of nickel oxide measures only about 50 atoms across -- that's equivalent to five nanometers (billionths of a meter).
Beach described the synthesis method in very simple terms. "Basically, you mix everything together in a pressure vessel, pop it in the oven, rinse it off and it's ready to use," he said.
Of course, for the process to go smoothly, the researchers have to meet specific conditions of temperature and pressure, and leave the material in the pressure cooker for just the right amount of time. For this study, they set the pressure cooker to around 225 C. They found they can make the particles in as little as 12 hours, but no more than 24 hours.
"Too short a time, and the nickel oxide doesn't form -- too long and it reduces to metallic nickel," Beach explained.
After he removes the nickel oxide from the pressure cooker, he washes it in a common solvent called methyl ethyl ketone to free up the nanoparticles.
At that point, the material is ready to use. Most other synthesis methods require another additional step -- a high-temperature heat treatment.
Starting with a microsensor silicon chip array provided by collaborators at the National Institute of Standards and Technology (NIST), Beach adds a layer of particles using a device called a picoliter drop dispenser. A picoliter is a trillionth of a liter.
He describes the dispenser as a kind of inkjet printer that places a droplet of a liquid suspension containing particles onto a surface -- in this case, the chips.
According to Morris, this is the first time that nickel oxide nanoparticles have been applied in this way.
But to Beach, the most important "first" to c
|Contact: Patricia Morris|
Ohio State University