Recently, a prototype device based on a semiconducting single-walled CNT (SWCNT) with nanofluidic and electronic field effect transistor (FET) functionality has been built. The internal wetting of semiconducting SWCNTs by pure water significantly modifies the FET characteristics. The device has also been utilized to acquire the average speed of water molecules when moving inside a semiconducting SWCNT.

Now, scientists at Arizona State University and Florida International University have investigated these effects in more detail – examining the electronic sensitivity of SWCNTs to internal electrolyte composition. In the systematic study, the researchers looked at the electrical response of a SWCNT when its interior was exposed to aqueous solutions with various ion concentrations, pH and ion species. High sensitivity was observed for the devices made with semiconducting SWCNTs.

Internal advantage

These electronic responses are very different to those recorded when the analyte contacts the external surface of SWCNT. It's likely that this sensitivity is due to the strong interaction between the electrolyte components and the highly curved crystalline inner surface of the carbon nanotube in an extremely confined space.

The work is a continuation of previous studies of single SWCNTs as nanofluidic devices and takes the team a step closer to its goal of a functional nanoelectrofluidic device. In the future, the group plans to use the same device geometry to examine the electronic response of charged small molecules passing through a semiconducting SWCNT.

The researchers presented their results in the journal Nanotechnology.