Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Oregon scientists offer new insights on controlling nanoparticle stability

10.12.2013
New findings could enhance stabilizing or destabilizing nanoparticles, depending on their uses

University of Oregon chemists studying the structure of ligand-stabilized gold nanoparticles have captured fundamental new insights about their stability.

The information, they say, could help to maintain a desired, integral property in nanoparticles used in electronic devices, where stability is important, or to design them so they readily condense into thin films for such things as inks or catalysts in electronic or solar devices.

In a project — detailed in the Nov. 27 issue of the Journal of Physical Chemistry C — doctoral student Beverly L. Smith and James E. Hutchison, who holds the Lokey-Harrington Chair in Chemistry at the UO, analyzed how nanoparticle size and molecules on their surfaces, called ligands, influence structural integrity under rising temperatures.

They focused on nanoparticles less than two nanometers in diameter — the smallest studied to date — to better understand structural stability of these tiny particles being engineered for use in electronics, medicine and other materials. Whether a nanoparticle needs to remain stable or condense depends on how they are being used. Those used as catalysts in industrial chemical processing or quantum dots for lighting need to remain intact; if they are precursors for coatings in solar devices or for printing ink, nanoparticles need to be unstable so they sinter and condense into a thin mass.

For their experiments, Smith and Hutchison produced gold nanoparticles in four well-controlled sizes, ranging from 0.9 nanometers to 1.5 nanometers, and analyzed ligand loss and sintering with thermogravimetric analysis and differential scanning calorimetry, and examined the resulting films by scanning electron microscopy and X-ray photoelectron spectroscopy. As the nanoparticles were heated at 5 degrees Celsius per minute, from room temperature to 600 degrees Celsius, the nanoparticles began to transform near 150 degrees Celsius.

The researchers found that smaller nanoparticles have better structural integrity than larger-sized particles that have been tested. In other words, Hutchison said, they are less likely to lose their ligands and bind together. "If you have unstable particles, then the property you want is fleeting," he said. "Either the light emission degrades over time and you're done, or the metal becomes inactive and you're done. In that case, you want to preserve the function and keep the particles from aggregating."The opposite is desired for Hutchison and others working in the National Science Foundation-funded Center for Sustainable Materials Chemistry, a multi-universities collaboration led by the UO and Oregon State University. Researchers there are synthesizing nanoparticles as precursors for thin films.

"We want solution precursors that can lead to inorganic thin films for use in electronics and solar industries," said Hutchison, who also is a member of the UO Materials Science Institute.

"In this case, we want to know how to keep our nanoparticles or other precursors stable enough in solution so that we can work with them, using just a tiny amount of additional energy to make them unstable so that they condense into a film -- where the property that you want comes from the extended solid that is generated, not from the nanoparticles themselves."

The research, Hutchison said, identified weak sites on nanoparticles where ligands might pop off. If only a small amount do so, he said, separate nanoparticles are more likely to come together and begin the sintering process to create thin films.

"That's a really stabilizing effect that, in turn, kicks out all these ligands on the outside," he said. "The surface area decreases quickly and the particles get bigger, but now all the extra ligands gets excluded into the film and then, over time, the ligands vaporize and go away."

The coming apart, however, is a "catastrophic failure" if protecting against sintering is the goal. It may be possible to use the findings, he said, to explore ways to strengthen nanoparticles, such as developing ligands that bind in at least two sites or avoiding volatile ligands.

The process, as studied, produced porous gold films. "A next step might be to study how to manipulate the process to get a more dense film if that is desired," Hutchison said. Understanding how nanoparticles respond to certain conditions, such as changing temperatures, he added, may help researchers reduce waste in the manufacturing process.

"Researchers at the University of Oregon are re-engineering the science, manufacturing and business processes behind critical products," said Kimberly Andrews Espy, vice president for research and innovation and dean of the UO Graduate School. "This research analyzing the structural stability of nanoparticles by Dr. Hutchison and his team has the potential to improve the engineering of electronics, medicine and other materials, helping to foster a sustainable future for our planet and its people."

Smith, the paper's lead author, received a master's degree in chemistry in 2009 from the UO. She now is a doctoral student in Hutchison's lab. During the initial stages of the research, she was supported by the NSF's Integrative Graduate Education and Research Traineeship (IGERT) program. Funding from the Air Force Research Laboratory (grant No. FA8650-05-1-5041) to Hutchison also supported the research.

Hutchison also is a member of both the Oregon Nanoscience and Microtechnologies Institute (ONAMI) and Oregon BEST (Oregon Built Environment & Sustainable Technologies Center), which are state signature research initiatives.

About the University of Oregon

The University of Oregon is among the 108 institutions chosen from 4,633 U.S. universities for top-tier designation of "Very High Research Activity" in the 2010 Carnegie Classification of Institutions of Higher Education. The UO also is one of two Pacific Northwest members of the Association of American Universities.

Source: James Hutchison, professor, Department of Chemistry and Biochemistry, 541-346-4228, hutch@uoregon.edu

Follow UO Science on Facebook: http://www.facebook.com/UniversityOfOregonScience

UO Science on Twitter: http://twitter.com/UO_Research

More UO Science/Research News: http://uoresearch.uoregon.edu

Note: The University of Oregon is equipped with an on-campus television studio with a point-of-origin Vyvx connection, which provides broadcast-quality video to networks worldwide via fiber optic network. In addition, there is video access to satellite uplink, and audio access to an ISDN codec for broadcast-quality radio interviews.

Jim Barlow | EurekAlert!
Further information:
http://www.uoregon.edu

More articles from Life Sciences:

nachricht Parallel computation provides deeper insight into brain function
27.03.2017 | Okinawa Institute of Science and Technology (OIST) Graduate University

nachricht Big data approach to predict protein structure
27.03.2017 | Karlsruher Institut für Technologie (KIT)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Big data approach to predict protein structure

27.03.2017 | Life Sciences

Parallel computation provides deeper insight into brain function

27.03.2017 | Life Sciences

Weather extremes: Humans likely influence giant airstreams

27.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>