"Bowtie Nanoantennas" Could Shed Light on Molecules, Other Nano-Sized Objects

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.

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 nm wide.

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.

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.

In addition to nano-scale optical imaging, the 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. 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.

Visit www.stanford.edu.