Deflating graphene balloons act as sensors for hard-to-detect gases
With excellent strength, flexibility and electrical conductivity, graphene has a lot of potential in a lot of different areas, and that may extend to the detection of odorless, colorless gases. Scientists have fashioned the nanomaterial into microscopic balloons they say can distinguish between different kinds of these hard-to-detect noble gases, by measuring how long they take to escape through tiny perforations in the surface of the balloons.
Graphene has a lot of attractive properties for material scientists working to develop everything form next-gen computer chips, to advanced solar cells and more sensitive microphones. But the research team behind this new breakthrough, from Delft University of Technology and the University of Duisburg-Essen, looked to leverage two properties in particular.
At just one-atom thick, graphene is incredibly thin, but despite that is able to withstand large amounts of stress, which in the team’s view makes it well suited to the job of filtering and detecting gases. While it is not permeable itself, the team addressed this by making perforations as small as 25 nanometers in bilayer graphene, which was used to create tiny balloons from which pressurized gases can escape.
This was achieved by first using a laser to heat different gases inside the ballon, causing them to expand and then filter through the small perforations. Depending on their mass and molecular velocity, different gases pour out of the balloon at different speeds. This makes the balloons a tool well-suited to the detection of noble gases, which is traditionally quite difficult as they don’t react with other materials.
"Picture a balloon that deflates when you let the air run out," says TU Delft researcher Irek Rosłoń, "We measure the time it takes the balloon to deflate. At such a small scale, this happens very quickly – within around 1/100.000th of a second – and interestingly, the length of time depends strongly on the type of gas and the size of the pores. For example helium, a light gas with high molecular velocity, escapes five times faster than krypton, a heavy and slowly moving gas."
The team hopes to build on this proof-of-concept technology by using this approach to develop new types of sensors that can be used to detect noble gases in industrial settings, or for use as low-cost air quality monitors. Beyond that, they say the work also demonstrates how graphene can used to study gas dynamics on microscopic scales.
The research was published in the journal Nature Communications.