Researchers measure carbon nanotube interaction

October 16, 2007
Researchers measure carbon nanotube interaction
An artist's representation of an amine functional group attached to an AFM tip approaching a carbon nanotube surface in toluene solution. Translucent blue shape on the nanotube represents the polarization charge forming on the nanotube as the result of the interaction with the approaching molecule. Chemical force microscopy measures the tiny forces generated by this single functional group interaction. (Illustration by Scott Dougherty, LLNL)

Carbon nanotubes have been employed for a variety of uses including composite materials, biosensors, nano-electronic circuits and membranes.

While they have proven useful for these purposes, no one really knows much about what’s going on at the molecular level. For example, how do nanotubes and chemical functional groups interact with each other on the atomic scale? Answering this question could lead to improvements in future nano devices.

In a quest to find the answer, researchers for the first time have been able to measure a specific interaction for a single functional group with carbon nanotubes using chemical force microscopy – a nanoscale technique that measures interaction forces using tiny spring-like sensors. Functional groups are the smallest specific group of atoms within a molecule that determine the characteristic chemical reactions of that molecule.

A recent report by a team of Lawrence Livermore National Laboratory researchers and colleagues found that the interaction strength does not follow conventional trends of increasing polarity or repelling water. Instead, it depends on the intricate electronic interactions between the nanotube and the functional group.

“This work pushes chemical force microscopy into a new territory,” said Aleksandr Noy, lead author of the paper that appears in the Oct. 14 online issue of the journal, Nature Nanotechnology.

Understanding the interactions between carbon nanotubes (CNTs) and individual chemical functional groups is necessary for the engineering of future generations of sensors and nano devices that will rely on single-molecule coupling between components. Carbon nanotubes are extremely small, which makes it particularly difficult to measure the adhesion force of an individual molecule at the carbon nanotube surface. In the past, researchers had to rely on modeling, indirect measurements and large microscale tests.

But the Livermore team went a step further and smaller to get a more exact measurement. The scientists were able to achieve a true single function group interaction by reducing the probe-nanotube contact area to about 1.3 nanometers (one million nanometers equals one millimeter).

Adhesion force graphs showed that the interaction forces vary significantly from one functionality to the next. To understand these measurements, researchers collaborated with a team of computational chemists who performed ab initio simulations of the interactions of functional groups with the sidewall of a zig-zag carbon nanotube. Calculations showed that there was a strong dependence of the interaction strength on the electronic structure of the interacting molecule/CNT system. To the researchers delight, the calculated interaction forces provided an exact match to the experimental results.

“This is the first time we were able to make a direct comparison between an experimental measurement of an interaction and an ab initio calculation for a real-world materials system,” Noy said. “In the past, there has always been a gap between what we could measure in an experiment and what the computational methods could do. It is exciting to be able to bridge that gap.”

This research opens up a new capability for nanoscale materials science. The ability to measure interactions on a single functional group level could eliminate much of the guess work that goes into the design of new nanocomposite materials, nanosensors, or molecular assemblies, which in turn could help in building better and stronger materials, and more sensitive devices and sensors in the future.

Source: Lawrence Livermore National Laboratory

Explore further: Sugar in your cuppa... not just about a sweet tooth

Related Stories

Researchers build bacteria's photosynthetic engine

July 29, 2015

Nearly all life on Earth depends on photosynthesis, the conversion of light energy into chemical energy. Oxygen-producing plants and cyanobacteria perfected this process 2.7 billion years ago. But the first photosynthetic ...

Are we born racist? Bias expert answers timely questions

July 28, 2015

Rodolfo Mendoza-Denton, PhD, professor of psychology and Richard & Rhoda Goldman distinguished professor of social sciences at the University of California, Berkeley, recently co-edited a book called Are We Born Racist?: ...

Stressed out plants send animal-like signals

July 29, 2015

University of Adelaide research has shown for the first time that, despite not having a nervous system, plants use signals normally associated with animals when they encounter stress.

Insights into catalytic converters

July 24, 2015

Modern catalytic converters for the treatment of exhaust gases in vehicles with a combustion engine have largely contributed to reducing of pollutant emissions. By oxidation or reduction, i.e. the donation or acceptance of ...

Recommended for you

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

Meet the high-performance single-molecule diode

July 29, 2015

A team of researchers from Berkeley Lab and Columbia University has passed a major milestone in molecular electronics with the creation of the world's highest-performance single-molecule diode. Working at Berkeley Lab's Molecular ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.