Argonne National Laboratory has discovered that nanoparticles of gold act unusually when close to the edge of graphene. This could be big for the development of new sensors and quantum devices. Ultrafast electron microscope (UEM) at Argonne’s Center for Nanoscale Materials (CNM) enables the visualization and investigation of phenomena at the nanoscale and on time frames of less than a trillionth of a second.
When gold nanoparticle sat on a flat sheet of graphene, the plasmonic field was symmetric. But when the gold nanoparticle was positioned close to a graphene edge, the plasmonic field concentrated much more strongly near the edge region.
A paper based on the study, “Visualization of plasmonic couplings using ultrafast electron microscopy,” appeared in the June 21 edition of Nano Letters.
Hybrids of graphene and metal plasmonic nanostructures are promising building blocks for applications in optoelectronics, surface-enhanced scattering, biosensing, and quantum information. An understanding of the coupling mechanism in these hybrid systems is of vital importance to its applications. Previous efforts in this field mainly focused on spectroscopic studies of strong coupling within the hybrids with no spatial resolution. Here we report direct imaging of the local plasmonic coupling between single Au nanocapsules and graphene step edges at the nanometer scale by photon-induced near-field electron microscopy in an ultrafast electron microscope for the first time. The proximity of a step in the graphene to the nanocapsule causes asymmetric surface charge density at the ends of the nanocapsules. Computational electromagnetic simulations confirm the experimental observations. The results reported here indicate that this hybrid system could be used to manipulate the localized electromagnetic field on the nanoscale, enabling promising future plasmonic devices.
SOURCES – Argonne Labs, Nanoletters
Written By Brian Wang, Nextbigfuture.com
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