According to Patricia Morris, associate professor of materials science and engineering at Ohio State, the challenge is to design a material that reacts quickly and reliably to a variety of chemicals, including TICs, when incorporated into a sensor.
"These are sensors that a soldier could wear on the battlefield, or a first responder could wear to an accident at a chemical plant," Morris said.
The material under study is nickel oxide, which has unusual electrical properties.
Morris, along with Ohio State doctoral student Elvin Beach, is interested in how nickel oxide's electrical conductance changes when toxic chemicals in the air settle on its surface.
Beach applies a thin coating of the material onto microelectro-mechanical systems (made in a similar fashion to computer chips), with a goal of identifying known toxic substances.
The design works on the same general principle as another, much more familiar sensor.
"The human nose coordinates signals from hundreds of thousands of sensory neurons to identify chemicals," Beach said. "Here, we're using a combination of electrical responses to identify the signature of a toxic chemical," he added.
The key to making the sensor work is how the nickel oxide particles are made.
Beach and Morris have devised a new synthesis method that yields very small particles, which give the sensor a large surface area to capture chemical molecules from the air, and very pure particles, which enable the sensor to detect even very small quantities of a substance.
Each particle of nickel oxide measures only about 50 atoms across, which is equivalent to five nanometers (billionths of a meter).
"Basically, you mix everything together in a pressure vessel, pop it in the oven, rinse it off and it's ready to use," Beach 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 degrees Celsius. 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. (ANI)