Revolutionizing Water Solutions: The Game-Changing Ion Permeability of Graphene

Chemists from Würzburg have managed to govern the movement of halide ions by intentionally creating defects in a bilayer nanographene arrangement. Their findings have been published in Nature. The publication reveals novel opportunities for applications in water filtration and sensor technologies.

Graphene is an extraordinarily thin, adaptable, and durable substance composed solely of carbon. It forms layers that are virtually a single atomic layer of carbon atoms. To achieve the thickness of a human hair, numerous such layers would need to be piled on each other.

A vast number of researchers are devoting significant effort to graphene. There is a substantial rationale for this, as the unique characteristics of the material promise innovative applications, particularly in electronics and energy sectors.

Making graphene passable for different molecules

It is particularly intriguing for scientists to gain control over the permeability of graphene for various materials. “Defects can be intentionally induced in the carbon lattice of graphene. These can be conceptualized as tiny openings that render the lattice permeable to gases,” states chemistry professor Frank Würthner from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

Permeability to other materials, including ions like fluoride, chloride, or bromide, has yet to be observed. “However, this would hold critical scientific significance, especially for applications like water desalination, detection, or purification of mixtures,” the Würzburg professor elucidates.

Defect enables ions to traverse

For the first time, a group led by Frank Würthner has now established a model system featuring a defect that allows the halides fluoride, chloride, and bromide to traverse, while excluding iodide. This was accomplished in a stable double layer that consists of two nanographenes enclosing a cavity. The halide ions that infiltrate are trapped within this cavity, allowing the measurement of the time taken for their ingress.

Chloride, a component of table salt, is prevalent in seawater and plays a vital role in living organisms’ biological processes.

“The validation of high chloride permeability through single-layer nanographene alongside selective binding of halides in a double-layer nanographene advances certain applications,” remarks Dr. Kazutaka Shoyama, who initiated and directed the project with Frank Würthner. Potential applications include water filtration membranes, synthetic receptors, and chloride channels.

Expanding stacks of nanographenes is the next ambition

The Würzburg chemists aim to construct larger stacks of their nanographenes in the next phase. They plan to utilize these to probe the flow of ions—and thus investigate a process that occurs similarly within biological ion channels.

This research was conducted at the Institute of Organic Chemistry and the Center for Nanosystems Chemistry at JMU.