Featured Research

from universities, journals, and other organizations

New Family Of Molecules For Self-assembly: The Carboranes

Date:
March 26, 2009
Source:
Penn State
Summary:
Researchers have found a way to control the geometry and stability of a new family of self-assembled-monolayer materials, the carboranes. The resulting exceptionally high quality and simplicity of the improved carboranes opens up new capabilities in selective patterning and control, and new possibilities for applications. A tailored carborane film just one-nanometer or two-nanometers in height completely changes the chemical, physical, and biological properties of the surface on which it is applied.

Schematic showing relative dipole orientations for the carboranethiol isomers, M1 and M9. The M1 molecule's dipole is oriented nearly parallel to the surface of the SAM, while the M9 molecule's dipole is oriented perpendicular to the surface of the SAM. The arrows point in the direction of positive charge.
Credit: J. Nathan Hohman, Penn State

To be useful in real-world applications, a self-assembled monolayer (SAM) of molecules on a surface must have a stable and controllable geometry. Researchers at Penn State and the Sigma-Aldrich company have found a way to control geometry and stability by making SAMs out of different carboranethiol isomers, which are cage-like molecules. The research results will be published in the March 2009 issue of the journal ACS Nano.

"Our results allow us to control the chemical and physical properties of the SAM without changing its structure," said team leader Penn State Distinguished Professor of Chemistry and Physics Paul Weiss. "The ability to control these types of properties enables us to create SAMs that, for example, selectively capture biomolecules from complex mixtures. These carboranethiol molecules give us exceptionally high-quality SAMs, largely because of their simplicity. This innovation opens up new capabilities in terms of patterning and control. We are trying to come up with simple and economical means to control the chemistry of a surface all the way from the wafer scale (several centimeters) down to the single-molecule scale (sub-nanometer)."

Using two different carboranethiol isomers, the team built SAMs that have identical geometries, as well as selectable interaction strengths. They found that they could easily control the chemical properties, including chemical resistance and wettabilitity, of the new SAMs. "The beauty of self-assembled monolayers is that with a one-nanometer or two-nanometer-thick film, we completely changed the chemical, physical, and biological properties of the surface," said Weiss.

To build the new SAMs, the researchers performed separate experiments in which they attached one of two, or both, versions of a carboranethiol molecule -- either a meta-9 isomer (M9) or a meta-1 isomer (M1) -- to gold surfaces through sulfur-gold bonds. Each of the carborane cages consists of 10 boron atoms and two carbon atoms. The carbon atoms have an unusual hexa-coordinated structure that gives them a positive charge. As a result, the carborane cages have a dipole moment -- a measure of the separated charge of a molecule that helps determine its interaction with water and other molecules -- that is either nearly parallel to the surface of the SAM (for M1, in which sulfur is attached to a carbon atom in the carborane cage) or nearly perpendicular to the surface of the SAM (for M9, in which sulfur is attached to a boron atom in the carborane cage).

"Both the M1 and M9 molecules form the same structure on the surface of the SAM, but the M1 molecules make the SAM more stable, while the M9 molecules make the SAM more hydrophilic, or wettable," said Weiss. "Each of these properties is beneficial for different applications."

Specifically, the group determined that the M1 molecules interacted more strongly with one another than the M9 molecules interacted with each other due to dipole interactions between the M1 cages. As a result, more energy was required to remove an M1 molecule from the SAM, thus creating a more stable SAM. On the other hand, the M9 SAM, although less stable, was able to become wet more easily than the M1 SAM because the dipole was oriented toward the outside of the SAM.

"Carborane chemistry is so well-understood that there is a lot we can do to exploit these SAMs," said Weiss. "For example, we can add more chemical groups onto selected spots on SAMs to determine the supra-molecular, or overall, properties of a SAM that go beyond the properties of a single molecule."

Weiss, his lab group, and Viktor Balema, a product manager at Sigma-Aldrich Co, plan to continue their work to develop a library of carboranethiols that can be used to make novel nanostructures and nanodevices. This work was supported by the National Science Foundation through its funding of the Center for Nanoscale Science at Penn State, by Penn State's National Nanotechnology Infrastructure Network, and by the Sigma-Aldrich Materials Science Initiative.


Story Source:

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


Journal Reference:

  1. J. Nathan Hohman, Pengpeng Zhang, Elizabeth I. Morin, Patrick Han, Moonhee Kim, Adam R. Kurland, Patrick D. McClanahan, Viktor P. Balema and Paul S. Weiss. Self-Assembly of Carboranethiol Isomers on Au{111}: Intermolecular Interactions Determined by Molecular Dipole Orientations. ACS Nano, 2009; 3 (3): 527 DOI: 10.1021/nn800673d

Cite This Page:

Penn State. "New Family Of Molecules For Self-assembly: The Carboranes." ScienceDaily. ScienceDaily, 26 March 2009. <www.sciencedaily.com/releases/2009/03/090325132504.htm>.
Penn State. (2009, March 26). New Family Of Molecules For Self-assembly: The Carboranes. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2009/03/090325132504.htm
Penn State. "New Family Of Molecules For Self-assembly: The Carboranes." ScienceDaily. www.sciencedaily.com/releases/2009/03/090325132504.htm (accessed October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Gulfstream G500, G600 Unveiling

Gulfstream G500, G600 Unveiling

Flying (Oct. 20, 2014) Watch Gulfstream's public launch of the G500 and G600 at their headquarters in Savannah, Ga., along with a surprise unveiling of the G500, which taxied up under its own power. Video provided by Flying
Powered by NewsLook.com
Japanese Scientists Unveil Floating 3D Projection

Japanese Scientists Unveil Floating 3D Projection

Reuters - Innovations Video Online (Oct. 20, 2014) Scientists in Tokyo have demonstrated what they say is the world's first 3D projection that floats in mid air. A laser that fires a pulse up to a thousand times a second superheats molecules in the air, creating a spark which can be guided to certain points in the air to shape what the human eye perceives as an image. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
What We Know About Microsoft's Rumored Smartwatch

What We Know About Microsoft's Rumored Smartwatch

Newsy (Oct. 20, 2014) Microsoft will reportedly release a smartwatch that works across different mobile platforms, has a two-day battery life and tracks heart rate. Video provided by Newsy
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