This illustration demonstrates how polymer casting on nanoporous graphene can produce an atomically thin membrane. Image: Piran Kidambi.
This illustration demonstrates how polymer casting on nanoporous graphene can produce an atomically thin membrane. Image: Piran Kidambi.

In a review published earlier this year in Advanced Materials, a team led by Piran Kidambi, assistant professor of chemical and biomolecular engineering at Vanderbilt University, explored new interest in using materials only one atom thick for membrane applications. They explained how the technology has evolved and advanced and how the field is ripe for collaborations. Their technology road map suggested that while two-dimensional (2D) materials and membranes were once separate fields, synergistic opportunities are resulting in exciting new developments at their intersection.

Now, as they report in another paper in Advanced Materials, Kidambi and his team have used this approach to address some of the most critical challenges in membrane research: fabricating high flow-through membranes without compromising filtration performance.

Kidambi and his team initially focused on developing methods to form nanoscale holes directly into graphene, a one-atom-thick sheet of carbon atoms. They did this by reducing the temperature during the synthesis of graphene by chemical vapor deposition, finding that this resulted in the formation of nanoscale holes caused by missing carbon atoms.

"It reminded me of decreasing the temperature while baking a chocolate cake to get a different texture," Kidambi said.

To form a membrane, this atomically thin graphene with nanoscales holes needed to be supported. So the team turned to conventional polymer membrane manufacturing techniques, and spread a thin polymer layer on the nanoporous graphene and then dipped the stack into a water bath.

This dip transformed the polymer into a porous support layer, with graphene on the top, effectively forming an atomically thin membrane. "Continuing on with the baking analogy, this was like dough transforming into porous bread, the support polymer layer."

The team then used these atomically thin membranes to separate salt and small molecules from small proteins.

"Most commercial membranes achieve separation at small size ranges by making a dense polymer layer that is several microns thick with tortuous pores," Kidambi said. "Diffusion across these layers is very slow. Here, we make membranes that are one atom thick and show much higher permeance – up to 100 times greater than the state-of-the-art commercial dialysis membranes – specifically in the low molecular weight cut-off range.

"We think these membranes could offer transformative advances for small molecule separation, fine chemical purification, buffer exchange and a number of other processes including lab-scale dialysis."

This story is adapted from material from Vanderbilt University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.