One step closer to using nanoporous graphene in smart filters and sensors

April 13, 2018, Catalan Institute of Nanoscience and Nanotechnology

As part of a national research collaboration, Spanish researchers including the ICN2 have made uniformly nanoporous graphene a practicable reality. A major milestone in graphene research, this brings us one step closer to unlocking this material's full potential not only in electronics, but also in filtration and sensing applications. The work is published in Science.

The researchers have successfully synthesised a membrane with pores whose size, shape and density can be tuned with atomic precision at the nanoscale. Engineering pores at the nanoscale in graphene can change its fundamental properties. It becomes permeable or sieve-like, and this change alone, combined with graphene's intrinsic strength and nano-slimness, points to its future use as the most resilient, energy-efficient and selective filter for extremely small substances including greenhouse gases, salts and biomolecules.

But a second, perhaps less intuitive change also takes place when the spacing between pores is similarly reduced to a few atoms. Doing so transforms the graphene from semimetal to semiconductor, opening the door for its use in electronic applications, where it could be used to replace the bulkier, more rigid silicon components used today.

However, while all of this is true in theory, producing such a material requires a precision that current fabrication methods have yet to achieve, and look unlikely ever to do so. The problem is the approach—punching holes or otherwise manipulating a material that a single atom thick is an incredibly fiddly task. In the work described here, the team takes a "bottom up" approach based on the principles of molecular self-assembly and 2-D polymerisation, effectively growing the graphene from scratch with the nanopores already built-in.

Credit: Catalan Institute of Nanoscience and Nanotechnology

For this approach to work, the researcher required a very specific precursor molecule to use as initial building blocks that would behave as intended when subjected to different stimuli. In this work, these precursors were designed and produced by synthetic chemistry specialists at CiQUS, before being taken to the ICN2 for the "bottom-up" assembly of nanoporous graphene.

They were submitted to several rounds of heating at high temperatures while placed on a gold surface, which serves to catalyse the reactions by which the molecules are first polymerised, to form long, lace-like nanoribbons, and then bonded laterally, to create the desired 2-D nanomesh structure complete with evenly spaced, evenly sized pores.

Simulated at the DIPC and tested experimentally at the ICN2, the result is a new kind of graphene that exhibits electrical properties akin to those of silicon, and can also act as a highly selective molecular sieve. Applied in conjunction, these two properties are predicted to allow the development of combined filter and sensor devices, which will not only sort for specific molecules, but will alternatively block or monitor their passage though the nanopores using an electric field. Such electrical readings would provide additional information as to precisely what concentrations of which molecule are passing through the pores and when, something which also points to possible applications in more efficient DNA sequencing.

Indeed, the real-world applications of such a tunable, uniformly nanoporous graphene membrane are manifold. They range from pollution monitoring and mitigation, to water desalinisation, and even applications in biomedicine, where such a slim, flexible, biocompatible membrane could be used to support failing organs like the kidney, one of the body's natural filters.

Explore further: Researchers have fabricated two types of trilayer graphene with different electrical properties

More information: César Moreno et al. Bottom-up synthesis of multifunctional nanoporous graphene, Science (2018). DOI: 10.1126/science.aar2009

Related Stories

New insights on graphene

December 21, 2017

Graphene floating on water does not repel water, as many researchers believe, but rather attracts it. This has been demonstrated by chemists Liubov Belyaeva and Pauline van Deursen and their supervisor Grégory F. Schneider. ...

Scientists move graphene closer to transistor applications

August 29, 2017

Scientists at the U.S. Department of Energy's Ames Laboratory were able to successfully manipulate the electronic structure of graphene, which may enable the fabrication of graphene transistors— faster and more reliable ...

Graphene performs under pressure

November 8, 2017

Scientists at The University of Manchester have fabricated highly miniaturised pressure sensors using graphene membranes which can detect minute changes in pressure with high sensitivity, over a wide range of operating pressures.

Scientists produce dialysis membrane made from graphene

June 29, 2017

Dialysis, in the most general sense, is the process by which molecules filter out of one solution, by diffusing through a membrane, into a more dilute solution. Outside of hemodialysis, which removes waste from blood, scientists ...

Chemical route to electronic devices in graphene

July 25, 2017

Essential electronic components, such as diodes and tunnel barriers, can be incorporated in single graphene wires (nanoribbons) with atomic precision. The goal is to create graphene-based electronic devices with extremely ...

Recommended for you

After a reset, Сuriosity is operating normally

February 23, 2019

NASA's Curiosity rover is busy making new discoveries on Mars. The rover has been climbing Mount Sharp since 2014 and recently reached a clay region that may offer new clues about the ancient Martian environment's potential ...

Study: With Twitter, race of the messenger matters

February 23, 2019

When NFL player Colin Kaepernick took a knee during the national anthem to protest police brutality and racial injustice, the ensuing debate took traditional and social media by storm. University of Kansas researchers have ...

Researchers engineer a tougher fiber

February 22, 2019

North Carolina State University researchers have developed a fiber that combines the elasticity of rubber with the strength of a metal, resulting in a tougher material that could be incorporated into soft robotics, packaging ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.