Researchers use graphene quantum dots to detect humidity and pressure
Vikas Berry, William H. Honstead professor of chemical engineering, and his research team are using graphene quantum dots to improve electron tunneling-based sensing devices. (Image credit: Kansas State Universitiy)
The latest research from a Kansas State University chemical engineer may help improve humidity and pressure sensors, particularly those used in outer space. Vikas Berry, William H. Honstead professor of chemical engineering, and his research team are using graphene quantum dots to improve sensing devices in a twofold project. The first part involves producing the graphene quantum dots, which are ultrasmall pieces of graphene. Graphene is a single-atom thick sheet of carbon atoms and has superior electrical, mechanical and optical properties. The second part of the project involves incorporating these quantum dots into electron-tunneling based sensing devices. To create the graphene quantum dots, the researchers used nanoscale cutting of graphite to produce graphene nanoribbons. T.S. Sreeprasad, a postdoctoral researcher in Berry's group, chemically cleaved these ribbons into 100 nanometers lateral dimensions. The scientists assembled the quantum dots into a network on a hydroscopic microfiber that was attached to electrodes on its two sides. They placed the assembled quantum dots less than a nanometer apart so they were not completely connected. The assembling of dots is similar to a corn on the cob structure -- the corn kernels are nanoscale quantum dots and the cob is the microfiber. Several researchers applied a potential across the fiber and controlled the distance between the quantum dots by adjusting the local humidity, which changes the current flowing through the dots. "If you reduce the humidity around this device, the water held by this fiber is lost," Berry said. "As a result, the fiber shrinks and the graphenic components residing atop come close to one another in nanometer scale. This increases the electron transport from one dot to the next. Just by reading the currents one can tell the humidity in the environment."