 |
|
The presence of oxygen on carbon nanotubes enhances interaction with ammonia
July 12, 2005Discovery could help in the development of sensors against chemical threats
Single-walled carbon nanotubes (SWNTs), which could play an important role in developing sensors against chemical threats, have enhanced interaction with ammonia because of the presence of oxygen groups on the nanotubes, researchers at Temple University have discovered.
Their findings, "Sensitivity of Ammonia Interaction with Single-Walled Carbon Nanotube Bundles to the Presence of Defect Sites and Functionalities," are reported online July 8 in the Journal of the American Chemical Society.
Eric Borguet, Ph.D., associate professor of chemistry at Temple and the study's lead author, said scientists have shown that in using nanotubes for sensors, their conductivity can be changed by the presence of ammonia.
"Theorists have tried for a long time to explain this interaction, and their calculations have typically shown that the interaction between the carbon nanotubes and ammonia is very weak, and in fact, very few ammonia molecules would stick to the nanotubes at room temperature," said Borguet.
But, he said, the theorists are studying pure nanotubes-often referred to as "perfect" nanotubes-with no oxygen.
Through the use of infrared spectroscopy, Borguet and his collaborators believe they are the first to reveal that the SWNT purification process, which introduces oxygen to the nanotubes, changes the interaction with chemical species such as ammonia.
"It is no longer pure carbon; there are oxygen-containing groups on the purified nanotubes," said Borguet. "And it is the presence of those groups that enhances the interaction between the nanotubes and the ammonia molecules at any temperature.
"We take the nanotubes and heat them up to 500 degrees Kelvin and then cool them down to 94 degrees Kelvin, and we see ammonia sticking, but as we go higher and higher in temperature, the ammonia signal is going down," said Borguet.
"One of the things that is happening as we heat to higher and higher temperatures is we are driving off the oxygen-containing functionality," added Borguet. "Once that oxygen-containing functionality is gone, 'poof,' the ability of the ammonia to stick is gone. But if we re-expose the SWNTs to room temperature and ambient air, the ability to interact comes back."
Borguet said the researchers were not able to detect the oxygen after exposure to air, so the nanotubes may be reoxidizing at a very small level.
He also emphasized that although they are unable to detect the ammonia sticking to the SWNTs at higher temperatures, the lack of detection may be the result of using the infrared spectroscopy technique.
"There may be another technique with a higher sensitivity that can detect the presence of ammonia," Borguet said. "We can't say there is no ammonia, but if there is, it is below our group's detection capability."
Borguet said that this discovery of oxygen impacting the interaction of ammonia with the SWNTs could eventually be important in developing small sensors for Homeland Security.
"Ultimately, you'd like to make a chemical nose, a device that can distinguish between chemicals which might have different hazards associated with them," he said. "You'd like to be able to identify the chemicals and what type of concentration might be present.
"These finding are a step in the right direction," Borguet added. "This could be an important discovery because theorists have all been calculating using 'perfect' nanotubes, but the experiments are not being carried out on 'perfect' nanotubes.
"The theorists can no longer ignore that there is going to be oxygen-containing functionality when looking at the effects of these nanotubes in the future.\\\
Temple University
Eric Borguet, Ph.D., associate professor of chemistry at Temple and the study's lead author, said scientists have shown that in using nanotubes for sensors, their conductivity can be changed by the presence of ammonia.
"Theorists have tried for a long time to explain this interaction, and their calculations have typically shown that the interaction between the carbon nanotubes and ammonia is very weak, and in fact, very few ammonia molecules would stick to the nanotubes at room temperature," said Borguet.
But, he said, the theorists are studying pure nanotubes-often referred to as "perfect" nanotubes-with no oxygen.
Through the use of infrared spectroscopy, Borguet and his collaborators believe they are the first to reveal that the SWNT purification process, which introduces oxygen to the nanotubes, changes the interaction with chemical species such as ammonia.
"It is no longer pure carbon; there are oxygen-containing groups on the purified nanotubes," said Borguet. "And it is the presence of those groups that enhances the interaction between the nanotubes and the ammonia molecules at any temperature.
"We take the nanotubes and heat them up to 500 degrees Kelvin and then cool them down to 94 degrees Kelvin, and we see ammonia sticking, but as we go higher and higher in temperature, the ammonia signal is going down," said Borguet.
"One of the things that is happening as we heat to higher and higher temperatures is we are driving off the oxygen-containing functionality," added Borguet. "Once that oxygen-containing functionality is gone, 'poof,' the ability of the ammonia to stick is gone. But if we re-expose the SWNTs to room temperature and ambient air, the ability to interact comes back."
Borguet said the researchers were not able to detect the oxygen after exposure to air, so the nanotubes may be reoxidizing at a very small level.
He also emphasized that although they are unable to detect the ammonia sticking to the SWNTs at higher temperatures, the lack of detection may be the result of using the infrared spectroscopy technique.
"There may be another technique with a higher sensitivity that can detect the presence of ammonia," Borguet said. "We can't say there is no ammonia, but if there is, it is below our group's detection capability."
Borguet said that this discovery of oxygen impacting the interaction of ammonia with the SWNTs could eventually be important in developing small sensors for Homeland Security.
"Ultimately, you'd like to make a chemical nose, a device that can distinguish between chemicals which might have different hazards associated with them," he said. "You'd like to be able to identify the chemicals and what type of concentration might be present.
"These finding are a step in the right direction," Borguet added. "This could be an important discovery because theorists have all been calculating using 'perfect' nanotubes, but the experiments are not being carried out on 'perfect' nanotubes.
"The theorists can no longer ignore that there is going to be oxygen-containing functionality when looking at the effects of these nanotubes in the future.\\\
Temple University
Carbon Nanotubes News and Current Carbon Nanotubes Events RSSTrue properties of carbon nanotubes measured
For more than 15 years, carbon nanotubes (CNTs) have been the flagship material of nanotechnology. Researchers have conceived applications for nanotubes ranging from microelectronic devices to cancer therapy. Their atomic structure should, in theory, give them mechanical and electrical properties far superior to most common materials.
Slipping through cell walls, nanotubes deliver high-potency punch to cancer tumors in mice
The problem with using a shotgun to kill a housefly is that even if you get the pest, you'll likely do a lot of damage to your home in the process. Hence the value of the more surgical flyswatter.
Golden Scales: Nanoscale Mass Sensor from Berkeley Can Be Used to Weigh Individual Atoms and Molecules
There's a new "gold standard" in the sensitivity of weighing scales. Using the same technology with which they created the world's first fully functional nanotube radio, researchers with Berkeley Lab and the University of California (UC) at Berkeley have fashioned a nanoelectromechanical system (NEMS) that can function as a scale sensitive enough to measure the mass of a single atom of gold.
'Nanonet' circuits closer to making flexible electronics reality
Researchers have overcome a major obstacle in producing transistors from networks of carbon nanotubes, a technology that could make it possible to print circuits on plastic sheets for applications including flexible displays and an electronic skin to cover an entire aircraft to monitor crack formation.
LLNL researchers peer into water in carbon nanotubes
Researchers have identified a signature for water inside single-walled carbon nanotubes, helping them understand how water is structured and how it moves within these tiny channels.
The fight for the best quantum bit (qubit)
Our results give us, for the first time, the possibility to understand the interaction between just two electrons placed next to each other in a carbon nanotube.
Perfecting a solar cell by adding imperfections
Nanotechnology is paving the way toward improved solar cells. New research shows that a film of carbon nanotubes may be able to replace two of the layers normally used in a solar cell, with improved performance at a lower cost. Researchers have found a surprising way to give the nanotubes the properties they need: add defects.
Secret ingredient: nanoparticles aid bone growth
In the first study of its kind, bioengineers and bioscientists at Rice University and Radboud University in Nijmegen, Netherlands, have shown they can grow denser bone tissue by sprinkling stick-like nanoparticles throughout the porous material used to pattern the bone.
NASA Scientists Pioneer Method for Making Giant Lunar Telescopes
Scientists working at NASA's Goddard Space Flight Center in Greenbelt, Md., have concocted an innovative recipe for giant telescope mirrors on the Moon. To make a mirror that dwarfs anything on Earth, just take a little bit of carbon, throw in some epoxy, and add lots of lunar dust.
Brown researchers work toward ending cartilage loss
Scientists have long wrestled with how to aid those who suffer cartilage damage and loss. One popular way is to inject an artificial gel that can imitate cartilage's natural ability to act as the body's shock absorber. But that solution is temporary, requiring follow-up injections.
More Carbon Nanotubes News Articles
 | Introduction to Nanoscale Science and Technology (Nanostructure Science and Technology) Nanoscale science and technology is a young, promising field that encompasses a wide range of disciplines including physics, chemistry, biology, electrical engineering, chemical engineering, and materials science. With rapid advances in areas such as molecular electronics, synthetic biomolecular motors, DNA-based self-assembly, and manipulation of individual atoms, nanotechnology has captured the... |
 | Physical Properties of Carbon Nanotubes by R. Saito An introductory textbook for graduate students & researchers from various fields of science who wish to learn about carbon nanotubes. The field is still at an early stage, & progress continues at a rapid... |
 | Carbon Nanotubes: Properties and Applications Since their discovery more than a decade ago, carbon nanotubes (CNTs) have held scientists and engineers in captive fascination, seated on the verge of enormous breakthroughs in areas such as medicine, electronics, and materials science, to name but a few. Taking a broad look at CNTs and the tools used to study them, Carbon Nanotubes: Properties and Applications comprises the efforts of leading... |
 | Carbon Nanotubes: Synthesis, Structure, Properties and Applications This book gives a comprehensive review of the present status of research in this fast moving field by researchers actively contributing to the advances. After a short introduction and a brief review of the relation between carbon nanotubes, graphite and other forms of carbon, the synthesis techniques and growth mechanisms for carbon nanotubes are described. This is followed by reviews on nanotube... |
| Chemistry of Carbon Nanotubes, 3-Volume Set DESCRIPTION: Contrary to all the books published on carbon nanotubes as of today, this interdisciplinary book focuses specifically on the chemistry of carbon nanotubes and related aspects. It brings together inorganic, organic, macromolecular, biological, analytical and theoretical chemists, materials scientists, spectroscopists and microscopists to share information on the methods of synthesis,... | |
 | Carbon Nanotubes: Science and Applications Carbon nanotubes, with their extraordinary mechanical and unique electronic properties, have garnered much attention in the past five years. With a broad range of potential applications including nanoelectronics, composites, chemical sensors, biosensors, microscopy, nanoelectromechanical systems, and many more, the scientific community is more motivated than ever to move beyond basic properties... |
 | Carbon Nanotubes: Advanced Topics in the Synthesis, Structure, Properties and Applications (Topics in Applied Physics) (Topics in Applied Physics) The carbon nanotubes field has evolved substantially since the publication of the bestseller Carbon Nanotubes: Synthesis, Structure, Properties and Applications . The present volume builds on the generic aspects of the aforementioned book, which emphasizes the fundamentals, with the new volume emphasizing areas that have grown rapidly since the first volume, guiding future directions where... |
 | Fabrication of Single Walled Carbon Nanotube (SW-CNT) Cantilevers for Chemical Sensing by Jui Ching Hsu |
 | Carbon Nanotubes: Basic Concepts and Physical Properties by Stephanie Reich, Christian Thomsen, Janina Maultzsch Carbon nanotubes are exceptionally interesting from a fundamental research point of view. Many concepts of one-dimensional physics have been verified experimentally such as electron and phonon confinement or the one-dimensional singularities in the density of states; other 1D signatures are still under debate, such as Luttinger-liquid behavior. Carbon nanotubes are chemically stable, mechanically... |
| Carbon Materials for Catalysis This is the first comprehensive book covering all aspects of the use of carbonaceous materials in heterogeneous catalysis. It covers the preparation and characterization of carbon supports and carbon-supported catalysts; carbon surface chemistry in catalysis; the description of catalytic, photo-catalytic, or electro-catalytic reactions, including the development of new carbon materials such as... |
| © 2008 BrightSurf.com |