Graphene for Super-Resolution Microscopy

On the left: Image of single molecules on the graphene sheet. Such images allow scientists to determine the position and orientation for each molecule. Comparison with the expected image (right) shows excellent agreement. (Source: U. Göttingen)

Researchers at the Uni­versity of Göttingen have developed a new method that takes advantage of the unusual properties of graphene to electro­magnetically interact with fluorescing molecules. This method allows scientists to optically measure extremely small distances, in the order of 1 ångström with high accuracy and repro­ducibility for the first time. This enabled researchers to optically measure the thickness of lipid bilayers, the stuff that makes the membranes of all living cells.

The team around Jörg Enderlein used a single sheet of graphene, just one atom thick (0.34 nm), to modulate the emission of light-emitting molecules when they came close to the graphene sheet. The excellent optical trans­parency of graphene and its capability to modulate through space the molecules’ emission made it an extremely sensitive tool for measuring the distance of single molecules from the graphene sheet. The accuracy of this method is so good that even the slightest distance changes of around 1 ångström can be resolved.

The scientists were able to show this by depo­siting single molecules above a graphene layer. They could then determine their distance by monitoring and evaluating their light emission. This graphene-induced modulation of molecular light emission provides an extremely sensitive and precise ruler for deter­mining single molecule positions in space. They used this method to measure the thickness of single lipid bilayers which are constituted of two layers of fatty acid chain molecules and have a total thickness of only a few nano­meters.

“Our method has enormous potential for super-resolution micro­scopy because it allows us to localise single molecules with nanometer resolution not only laterally as with earlier methods but also with similar accuracy along the third direction, which enables true three-dimen­sional optical imaging on the length scale of macro­molecules,” says researcher Arindam Ghosh. “This will be a powerful tool with numerous appli­cations to resolve distances with sub-nano­meter accuracy in individual molecules, molecular complexes, or small cellular organelles,” adds Enderlein. (Source: U. Göttingen)

Reference: A. Ghosh et al.: Graphene-based metal-induced energy transfer for sub-nanometre optical localization, Nat. Phot., online 2 September 2019; DOI: 10.1038/s41566-019-0510-7

Link: Biophysics & Complex Systems (J. Enderlein), University of Göttingen, Göttingen, Germany

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