Volume 90 Issue 2 | p. 33 | Concentrates
Issue Date: January 9, 2012

Nanoparticles Imaged In Space And Time

Ultrafast electron microscopy maps time-resolved electric fields on and around nanostructures
Department: Science & Technology
Keywords: electron microscopy, ultrafast spectrum imaging, plasmonics, nanoparticles, electron energy gain/loss spectroscopy
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FAST MAPPING
With ultrafast spectrum imaging, researchers can create electric field maps, such as this one for a triangular nanoparticle—red indicates areas on the particle with a strong electric field and blue indicates areas with a weak field.
Credit: Science
In ultrafast spectrum imaging, researchers excite nanoparticles (triangular here) with a laser beam and probe their response in various spots across and around them with an electron beam to create electric field maps (shown); Red indicates areas on the particles with strong fields and blue indicates areas with weak fields.
 
FAST MAPPING
With ultrafast spectrum imaging, researchers can create electric field maps, such as this one for a triangular nanoparticle—red indicates areas on the particle with a strong electric field and blue indicates areas with a weak field.
Credit: Science
[+]Enlarge
Credit: Science
In ultrafast spectrum imaging, researchers excite nanoparticles (triangular here) with a green laser beam and probe their response in various spots with a femtosecond electron beam  to create electric field maps.
 
Credit: Science

A new electron microscopy technique, called ultrafast spectrum imaging, is capable of mapping electric fields across and around nanomaterials over time (Science, DOI: 10.1126/science.1213504). When photons of light strike a metal nanostructure, the object’s electrons oscillate collectively. This wave, known as a plasmon, generates a localized electric field that enables the tiny structure to be used as a photovoltaic component or as a sensor for nearby molecules. Being able to map the electric field, says Philip E. Batson, a physicist at Rutgers University, should enable scientists to design more efficient nanomaterials. A research team led by California Institute of Technology’s Ahmed H. Zewail demonstrated the new method by investigating triangular silver nanoparticles on a graphene surface. After exciting the nanoparticles with a green femtosecond laser beam, the researchers probed the materials’ response with a 10-nm-diameter ultrafast electron beam. They repeated the process at multiple spots on and around the nanoparticles to generate electric field maps. Future improvements to their setup should enable the researchers to resolve electric fields on an atomic scale, they say.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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