Featured Research

from universities, journals, and other organizations

First Measurement Of The Ability Of A Very Long Molecular Wire To Conduct Electric Current

Date:
March 15, 2009
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
For the first time, researchers have measured the ability of a single, very long molecular wire to carry electric current. Until now, there were only statistical measurements on a collection of wires a few nanometers long. Now, thanks to an ingenious experiment using a scanning tunneling microscope, the researchers have characterized individual polymer chains of known length, up to 20 nanometers long. They confirm what is predicted by theory: the ability to conduct electric current decreases exponentially with the length of the wire.

Single polymer chains as molecular wires.
Credit: Image courtesy of CNRS (Délégation Paris Michel-Ange)

For the first time, researchers from CNRS, the Free University of Berlin and Humboldt University (Berlin) have measured the ability of a single, very long molecular wire to carry electric current. Until now, there were only statistical measurements on a collection of wires a few nanometers long. Now, thanks to an ingenious experiment using a scanning tunneling microscope, the researchers have characterized individual polymer chains of known length, up to 20 nanometers long.

They confirm what is predicted by theory:  the ability to conduct electric current decreases exponentially with the length of the wire. 

Tomorrow's electronic circuits will be made up of individual molecules, connected to each other by means of 'molecular electric wires' (themselves consisting of a single, long molecule). But first, researchers need to understand how electric current flows through this type of wire. On the macroscopic scale, the ability to carry current, called conductance, varies linearly as a function of the length and cross-sectional area of the wire. On the scale of a molecule, this rule is no longer valid.

Consequently, it is necessary to measure the electric current that flows through a single molecular wire connected to two electrodes and determine how it varies as a function of the length of the wire. Until now, all the experimental studies focused on very short wires (a few nanometers long) or were based exclusively on statistical measurements.

At the Free University of Berlin, in collaboration with CNRS's Center for Materials Elaboration and Structural Studies (Centre d’élaboration de matériaux et d’études structurales) (CEMES) in Toulouse and with Humboldt University (Berlin), researchers carried out an ingenious experiment to measure the conductance of a single molecule with a perfectly defined length. First they placed small molecules on a gold surface, which they bonded chemically to each other by means of a surface polymerisation reaction, which brought about the formation of long molecular chains.  

They then selected one of the chains by making images of the surface with a scanning tunneling microscope and chemically bonded one end of the chain to the microscope's metal tip, which thus made up one of the two electrodes, while the other end of the polymer remained in position on the gold surface, making up the second electrode. By moving the tip away from the surface, the researchers gradually lifted up the chain, thus forming a molecular electric wire that became longer as the tip moved away from the surface. The scanning tunneling microscope was used both to measure the length of the selected molecular electric wire (since the resolution of the image is on the atomic scale it can, for example, be used to count the number of monomers) and to measure the current flowing through it. For the first time, the charge transport through a single polymer chain was measured for different lengths (up to 20 nanometers) between the two electrical contacts.

The results are in agreement with theoretical predictions: the current decreases exponentially with the length of the molecular electric wire. After the success of this innovative experiment, it is now up to chemists to come up with more conductive molecules that can be used to develop molecular wires able to carry current over even greater distances.


Story Source:

The above story is based on materials provided by CNRS (Délégation Paris Michel-Ange). Note: Materials may be edited for content and length.


Journal Reference:

  1. Lafferentz et al. Conductance of a Single Conjugated Polymer as a Continuous Function of Its Length. Science, 2009; 323 (5918): 1193 DOI: 10.1126/science.1168255

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "First Measurement Of The Ability Of A Very Long Molecular Wire To Conduct Electric Current." ScienceDaily. ScienceDaily, 15 March 2009. <www.sciencedaily.com/releases/2009/02/090226160934.htm>.
CNRS (Délégation Paris Michel-Ange). (2009, March 15). First Measurement Of The Ability Of A Very Long Molecular Wire To Conduct Electric Current. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2009/02/090226160934.htm
CNRS (Délégation Paris Michel-Ange). "First Measurement Of The Ability Of A Very Long Molecular Wire To Conduct Electric Current." ScienceDaily. www.sciencedaily.com/releases/2009/02/090226160934.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) — British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) — Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) — A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) — Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
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:
from the past week

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