This rendering shows gas molecules widening the gaps between rows of the team’s graphene nano-ribbons. Nebraska’s Alexander Sinitskii and his colleagues have proposed that this phenomenon partly explains how the nano-ribbons grant sensors an unprecedented boost in sensitivity. Source: Nature Communication/Springer Nature
Adding a specialized form of graphene to gas sensors can imbue these machines with significantly heightened sensitivity compared to traditional counterparts.
Engineers from the University of Nebraska-Lincoln, University of Illinois at Urbana-Champaign, and Russia’s Saratov State Technical University created a new of type of nano-ribbon derived from the 2D honeycomb of carbon atoms, which stand vertically rather than lying flat on a surface.
The scientists integrated a film of the nano-ribbons into the circuity of the gas sensor where it responded about 100 times more sensitively to molecules than did sensors featuring even the best performing carbon-based materials.
“With multiple sensors on a chip, we were able to demonstrate that we can differentiate between molecules that have nearly the same chemical nature,” said Alexander Sinitskii, study author and associate professor of chemistry at the University of Nebraska, in a statement. “For example, we can tell methanol and ethanol apart. So these sensors based on graphene nano-ribbons can be not only sensitive but also selective.”
One factor may have played an important role in these results.
Graphene usually lacks a component called a band gap, which requires electrons to gain energy before jumping from their near orbits around atoms to an outer “conduction band” driving conductivity. This missing feature presented challenges for applying graphene in electronics that require manipulating the material’s conductivity at will.
The team found a way around this obstacle by initially fabricating these ribbons from the bottom up by strategically snapping together molecules on certain types of solid surfaces followed by implementing a novel method that entailed mass producing these ribbons in a liquid solution.
The final step was adding benzene rings, circular molecules containing six atoms of both carbon and hydrogen, placed onto either side of a first-generation nano-ribbon. The rings widened the ribbon reducing its band gap and enhancing its ability to conduct electricity.
Ultimately, the scientists suspect this prototype’s unique performance was partly due to an “unusual” interaction between the ribbons and the gas molecules. These atoms can nudge the vertical rows apart broadening the gaps between nano-ribbons allowing the electrons to jump to conduct electricity.
Findings from this study were published in the journal Nature Communications.
