Low-energy electron holographic imaging of gold nanorods supported by ultraclean graphene

TL;DR

This study demonstrates that ultraclean freestanding graphene can support low-energy electron holographic imaging of gold nanorods, revealing organic shells and showcasing potential for biomolecular imaging.

Contribution

It shows that platinum-catalyzed graphene remains ultraclean after exposure and gold deposition, enabling high-resolution holographic imaging of nanostructures.

Findings

Ultraclean graphene supports detailed holographic imaging.

Organic shells around gold nanorods are visible in holography.

Graphene's cleanliness persists after ambient exposure and gold deposition.

Abstract

An ideal support for electron microscopy shall be as thin as possible and interact as little as possible with the primary electrons. Since graphene is atomically thin and made up of carbon atoms arranged in a honeycomb lattice, the potential to use graphene as substrate in electron microscopy is enormous. Until now graphene has hardly ever been used for this purpose because the cleanliness of freestanding graphene before or after deposition of the objects of interest was insufficient. We demonstrate here by means of low-energy electron holographic imaging that freestanding graphene prepared with the Platinum-metal catalysis method remains ultraclean even after re-exposure to ambient conditions and deposition of gold-nanorods from the liquid phase. In the holographic reconstruction of the gold particles the organic shell surrounding the objects is imaged while it is not detectable in SEM images of the very same sample, demonstrating the tremendous potential of low-energy electron holography for the imaging of graphene-supported single biomolecules.