Featured Research

from universities, journals, and other organizations

'Loops of light' promising for optical detection of individual molecules

Date:
July 18, 2012
Source:
Katholieke Universiteit Leuven
Summary:
Researchers have developed a new method for manipulating light at the nanoscale in order to optically detect single molecules. By shining circularly polarized light on a gold, square-ring shaped nanostructure, the researchers were able to ‘activate’ the entire surface of the nanostructure, thereby significantly increasing the opportunity for interaction with molecules. The method has a broad range of potential applications in nanoscale photochemistry and could assist in the advancement of technologies for visualising single molecules and multiple-molecule interactions.

Shining circularly polarised light on ring-shaped nanostructures increases the opportunity for interaction with molecules.
Credit: Image courtesy of Katholieke Universiteit Leuven

KU Leuven researcher Ventsislav Valev and an international team of colleagues have developed a new method for manipulating light at the nanoscale in order to optically detect single molecules. By shining circularly polarised light on a gold, square-ring shaped nanostructure, the researchers were able to 'activate' the entire surface of the nanostructure, thereby significantly increasing the opportunity for interaction with molecules. The method has a broad range of potential applications in nanoscale photochemistry and could assist in the advancement of technologies for visualising single molecules and multiple-molecule interactions.

Nanotechnology researchers around the world are exploring ways to optically detect single molecules, but progress can be hindered by the fact that single molecules have extremely weak optical responses. Thus far, scientists have developed a way to use metal nanostructures to focus light into tiny spots called 'hotspots'. The hotspots excite electrons on the surface of the nanostructure, causing them to oscillate coherently. When shone on a molecule, and with the help of these oscillating electrons, the focused light can increase a molecule's optical signal to 100 billion times its normal strength. This signal can then be detected with an optical microscope.

But there are two limitations to the current method: hotspots can become too hot, and they are just spots. That is, the heat from hotspots can melt the nanostructures, thus destroying their ability to channel light effectively, and hotspots produce only a very small cross-section in which interaction with molecules can take place. Additionally, for a single molecule to become detectable, it needs to find the hotspot.

Loops of light

In order to overcome these limitations, Dr. Valev and his colleagues sought out to nanoengineer larger spots. They began by shining circularly polarised light rather than linearly polarised light on the nanostructures and found that this could increase the useful area of these nanostructures. More importantly, when shone on square-ring shaped gold nanostructures, the scientists observed that theentire surface of the nanostructures was successfully activated.

Dr. Valev explains: "Essentially, light is constituted of electric and magnetic fields moving through space. While with linearly polarised light, the fields move in a linear, forward direction, with circularly polarised light, they rotate in a spiral-like motion." The circularly polarised light imparts a sense of rotation on the electron density in ring-shaped gold nanostructures, thus trapping the light in the rings and forming 'loops of light'. The loops of light cause excited electrons to oscillate coherently on the full surface of the square-ringed nanostructures -- rather than in a few concentrated hotspots. This increases the opportunity for interaction with molecules: "The trick is to try to activate the whole surface of the nanostructure so that whenever a molecule attaches, we will be able to see it," says Dr. Valev. "That is precisely what we did."

The method has a broad range of potential applications in nanoscale photochemistry and could assist in the advancement of technologies for visualising single molecules and multiple-molecule interactions. The findings were published in the scientific journal Advanced Materials.


Story Source:

The above story is based on materials provided by Katholieke Universiteit Leuven. Note: Materials may be edited for content and length.


Journal Reference:

  1. V. K. Valev, B. De Clercq, C. G. Biris, X. Zheng, S. Vandendriessche, M. Hojeij, D. Denkova, Y. Jeyaram, N. C. Panoiu, Y. Ekinci, A. V. Silhanek, V. Volskiy, G. A. E. Vandenbosch, M. Ameloot, V. V. Moshchalkov, T. Verbiest. Distributing the Optical Near-Field for Efficient Field-Enhancements in Nanostructures. Advanced Materials, 2012; DOI: 10.1002/adma.201201151

Cite This Page:

Katholieke Universiteit Leuven. "'Loops of light' promising for optical detection of individual molecules." ScienceDaily. ScienceDaily, 18 July 2012. <www.sciencedaily.com/releases/2012/07/120718103832.htm>.
Katholieke Universiteit Leuven. (2012, July 18). 'Loops of light' promising for optical detection of individual molecules. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2012/07/120718103832.htm
Katholieke Universiteit Leuven. "'Loops of light' promising for optical detection of individual molecules." ScienceDaily. www.sciencedaily.com/releases/2012/07/120718103832.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com
Argentina's Tax Evaders Detected, Hunted Down by Drones

Argentina's Tax Evaders Detected, Hunted Down by Drones

AFP (Sep. 30, 2014) Argentina doesn't only have Lionel Messi the footballer, it has now also acquired "Mesi" the drone system which monitors undeclared mansions, swimming pools and soy fields to curb tax evasion in the country. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins