Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanotubes Surprise Again: Ideal Photon Emission

08.09.2003


Carbon nanotubes, recently created cylinders of tightly bonded carbon atoms, have dazzled scientists and engineers with their seemingly endless list of special abilities – from incredible tensile strength to revolutionizing computer chips. In today’s issue of Science, two University of Rochester researchers add another feat to the nanotubes’ list: ideal photon emission.



"The emission bandwidth is as narrow as you can get at room temperature," says Lukas Novotny, professor of optics at Rochester and co-author of the study. Such a narrow and steady emission can make such fields as quantum cryptography and single-molecule sensors a practical reality.

The emission profile came as a surprise to Todd Krauss, assistant professor of chemistry at the University, and Novotny. They had set out to simply define the emission, or fluorescence, of a single carbon nanotube. By using a technique called confocal microscopy, the team illuminated a single nanotube with a strongly focused laser beam. The tube absorbed the light from the laser and then re-emitted light at new frequencies that carried information about the tube’s physical characteristics and its surroundings.


The light emitted from the nanotube was in precise, discrete wavelengths, unlike most objects like molecules that radiate into a broader (i.e. more "fuzzy") range of wavelengths at room temperature.

But a greater surprise was in store for the team.

"The emission wasn’t just perfectly narrow, it was steady as far as we could measure," says Krauss. In a strange quirk of quantum physics, molecules usually emit their photons for a certain time and then cease, only to resume again later, like a telegraph signal. The tubes that Krauss and Novotny measured, however, remained steady beacons to the limits of their instruments’ sensitivity. "This is very exciting because for any application in quantum optics, you want a steady and precise photon emitter," says Novotny.

Narrow emissions and a complete absence of blinking have tempting implications for single photon emitters--devices needed to dependably release a single photon on command. The U.S. Department of Defense is very interested in developing quantum cryptography, a theoretically unbreakable method of coding information, which necessitates a reliable way to deliver single photons on demand.

Other applications come in the form of sensors so sensitive they can detect a single molecule of a substance. For example, when a biological molecule such as a protein binds to a nanotube, the nanotube’s perfect emission changes, revealing the presence and characteristics of the molecule. Detecting the change would be impossible if it weren’t for the remarkably steady nature of the nanotube emission, because a researcher wouldn’t know for certain if a sudden change in the emission was just a blink, or was meant to indicate the presence of the target molecule.

Until just a few months ago, determining the emission characteristics of a nanotube was impossible. Carbon nanotubes cannot be made individually-rather they come as a jumble like a pile of spaghetti. Trying to measure the photon emission of a tube in the jumble is impossible because the tube will pass the photons it absorbs to other tubes instead of re-emitting them in its telltale fashion. What scientists end up with is a sort of average of what the collection of tubes will emit--not the emission characteristics of a single tube. Only within the past few months have researchers figured out how to remove a single nanotube from the pile of spaghetti in order to study its properties as an individual.

Krauss and Novotny are now devising experiments to test the steadiness of the nanotube fluorescence beyond the range of the initial experiments, and are pursuing studies aimed at determining the ultimate minimum possible emission bandwidth at ultracold temperatures.

This work was funded by the National Science Foundation, the U.S. Department of Energy, the Research Corporation, and the New York State Office of Science and Academic Research.

Jonathan Sherwood | University of Rochester
Further information:
http://www.rochester.edu/pr/News/NewsReleases/scitech/Krauss-Novotny.html

More articles from Physics and Astronomy:

nachricht Water without windows: Capturing water vapor inside an electron microscope
13.12.2017 | Okinawa Institute of Science and Technology (OIST) Graduate University

nachricht Columbia engineers create artificial graphene in a nanofabricated semiconductor structure
13.12.2017 | Columbia University School of Engineering and Applied Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>