Gold bowties may shed light on molecules and other nano-sized objects

August 30, 2005

One of the great challenges in the field of nanotechnology is optical imaging--specifically, how to design a microscope that produces high-resolution images of the nano-sized objects that researchers are trying to study. For example, a typical DNA molecule is only about three nanometers wide--so tiny that the contours of its surface are obscured by light waves, which are hundreds of nanometers long.

Now, researchers from Stanford University have greatly improved the optical mismatch between nanoscale objects and light by creating the "bowtie nanoantenna," a device 400 times smaller than the width of a human hair that can compress ordinary light waves into an intense optical spot only 20 nanometers wide. These miniature spotlights may one day allow researchers to produce the first detailed images of proteins, DNA molecules and synthetic nano-objects, such carbon nanotube bundles.

"One of our goals is to build a microscope with bowtie antennas that we can scan over a single molecule," says W.E. Moerner, the Harry S. Mosher Professor of Chemistry at Stanford. He and his Stanford colleagues introduced the bowtie nanoantenna earlier this year in a study published in the journal Physical Review Letters that was co-authored by postdoctoral fellow P. James Schuck and graduate student David Fromm in the Department of Chemistry, and Professor Emeritus Gordon Kino and graduate student Arvind Sundaramurthy in the Department of Electrical Engineering.

Golden bowties

The bowtie nanoantenna consists of two triangular pieces of gold, each about 75 nanometers long, whose tips face each other in the shape of a miniature bowtie. The device operates like an antenna for a radio receiver, but instead of amplifying radio waves, the bowtie takes energy from an 830-nanometer beam of near-infrared light and squeezes it into a 20-nanometer gap that separates the two gold triangles. The result is a concentrated speck of light that is a thousand times more intense than the incoming near-infrared beam.

"What you end up with is a very small optical spot that you could scan to make detailed images of molecules and other nano-particles," says Kino, the W.M. Keck Foundation Professor of Electrical Engineering, Emeritus. "Normally we use lenses to focus, but it's not possible to resolve detail in objects smaller than one-half the wavelength of light."

Because the shortest wavelength of visible light is 400 nanometers, a conventional microscope cannot resolve objects 200 nanometers or smaller. "But the bowtie antenna produces an optical spot that's 20-nanometers wide, so we're improving the resolution by a factor of 10," Kino says.

Polymers and sensors

In addition to nano-scale optical imaging, Moerner says that bowties may be useful in photopolymerization, a process that uses light to create synthetic compounds (polymers), which researchers can use to trap nano-particles and place them in specific locations. "It's difficult to put molecules and crystals exactly where you want them when you're working at a nano-scale," Schuck explains.

Bowties also may have applications in Raman spectroscopy, a technique that allows scientists to identify individual molecules by measuring the vibrational energy the molecule emits when exposed to light. "It's analogous to fingerprinting," Schuck explains. "Each molecule has a unique vibrational energy, and bowties have a potential use as biological or chemical sensors that can differentiate molecules."

The Stanford team plans to explore these and other practical applications of bowtie nanoantennas in future experiments. On Aug. 30, Moerner will discuss bowties and other developments in the field of nanophotonics at the annual meeting of the American Chemical Society in Washington, D.C.
-end-
By Mark Shwartz

CONTACT:
Mark Shwartz, News Service: (650) 723-9296, mshwartz@stanford.edu

COMMENT:
W.E. Moerner, Department of Chemistry: (650) 723-1727, wmoerner@stanford.edu
Jim Schuck, Department of Chemistry: (650) 724-4052, pjschuck@stanford.edu

EDITORS NOTE:
Professor W.E. Moerner will discuss nanophotonics and single-molecule biophysics at the annual meeting of the American Chemical Society in Washington, D.C., on Aug. 30 at 8:30 a.m. For more information, visit the ACS website at http://www.chemistry.org.

RELEVANT WEB URLS:
http://www.stanford.edu/group/moerner
http://snf.stanford.edu
http://www.chemistry.org

News Service website: http://www.stanford.edu/news/
Stanford Report (university newspaper): http://news.stanford.edu
Most recent news releases from Stanford: http://www.stanford.edu/dept/news/html/releases.html

To change contact information for these news releases: news-service@lists.stanford.edu
Phone: (650) 723-2558

Stanford University

Related Microscope Articles from Brightsurf:

Microscope lens inspired by lighthouse
Custom-fabricated lenses make it easy to attach high-tech microscopes directly to cell incubators.

Print your own laboratory-grade microscope for US$18
For the first time, labs around the world can 3D print their own precision microscopes, thanks to an open-source design created at Bath.

Novel high-speed microscope captures brain neuroactivities
A research team led by Dr. Kevin Tsia from the University of Hong Kong (HKU); and Professor Ji Na, from the University of California, Berkeley (UC Berkeley) has successfully recorded the millisecond electrical signals in the neurons of an alert mouse with their super high-speed microscope - two-photon fluorescence microscope.

Graphene forms under microscope's eye
Scientists record the formation of foamy laser-induced graphene made with a small laser mounted to a scanning electron microscope.

Hybrid microscope could bring digital biopsy to the clinic
By adding infrared capability to the ubiquitous, standard optical microscope, researchers at the University of Illinois at Urbana-Champaign hope to bring cancer diagnosis into the digital era.

An ultrafast microscope for the quantum world
Processes taking place inside tiny electronic components or in molecules can now be filmed at a resolution of a few hundred attoseconds and down to the individual atom.

SLAP microscope smashes speed records
A new 2-photon microscope captures videos of the brain faster than ever, revealing voltage changes and neurotransmitter release.

New 3D microscope visualises fast biological processes better than ever
Researchers from the European Molecular Biology Laboratory (EMBL) in Heidelberg have combined their expertise to develop a new type of microscope.

Use a microscope as a shovel? UConn researchers dig it
Using a familiar tool in a way it was never intended to be used opens up a whole new method to explore materials, report UConn researchers.

New method gives microscope a boost in resolution
Scientists at the University of W├╝rzburg have been able to boost current super-resolution microscopy by a novel tweak.

Read More: Microscope News and Microscope Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.