TechConnect Innovation Program

Controlled metal nanoparticle decorated surfaces

NASA, Virginia, United States

TECHNOLOGY SUMMARY

NASA Langley has created a new class of materials by depositing nanometer-sized metal or metal-oxide particles onto various surfaces. The new process is amenable to depositing most metals and some oxides, with controlled particle size and surface coverage. New hybrid materials will have applications in catalysis, structural composites, optics, etc.

Primary Application Area: Materials & Chemical

Technology Development Status: Prototype

Technology Readiness Level: TRL 4

FIGURES OF MERIT

Value Proposition: The subject technology is at a mid-level TRL for some applications such as a catalyst, and as a nano-material additive (eg. in polymers) will have numerous other possible applications. It is low cost, rapid (seconds-minutes), scalable, and green since it does not require reducing agents or solvents.

SHOWCASE SUMMARY

Organization Type: Academic/Gov Lab

Showcase Booth #: 819

Website: http://www.larc.nasa.gov

GOVT/EXTERNAL FUNDING SOURCES

Government Funding/Support to Date: The subject technology has been under development for various potential NASA applications for four years funded at about $250K per year or about $1M, total.
A rapid, solventless method was developed for the decoration of carbon nanotubes (and other surfaces)with metal nanoparticles. The straightforward two-step process utilizes neither reducing agents nor electric current and
involves the dry mixing of a precursor metal salt (e.g., a metal acetate) with carbon nanotubes (single- or multiwalled)followed by heating in an inert atmosphere.

The procedure should be easily scalable to very large quantities, is generally applicable to various substrates, including carbon (e.g., carbon nano-tubes, carbon nano-fiber, expanded graphite, and carbon black). Many metal salts have been demonstrated (e.g., Ag, Au, Co, Ni, and Pd acetates). At this time, more than 20 different metals have been deposited by this method.

There are many different possible applications ranging from catalysis to control of thermal, optical and dielectric properties in polymeric composites of particular interest for NASA applications.
As a model system, Ag nanoparticle-decorated carbon nanotube samples were prepared under various mixing techniques, metal loading levels, thermal treatment temperatures, and nanotube oxidative acid treatments. These nanohybrids were characterized by a variety of microscopic and spectroscopic techniques. For example, X-ray diffraction and scanning electron microscopy indicated that the average size of the Ag nanoparticles has little to do with the thermal treatment temperature but can be easily controlled by varying the Ag loading. Raman spectroscopy illustrated both the metal-nanotube electronic interactions and the surface enhancement effect from the Ag nano-particle
attachment. High-resolution transmission electron microscopy captured the in situ salt-to-metal conversion events on the nano-tube surface.

To evaluate potential use as a catalyst,we evaluated
deposition of metal(Pd, Pt, Ru) and metal oxide nanoparticles on various substrates using the solvent-
free method (U.S. Patent 7,704,553). The metal nanoparticles were deposited on carbon, boron nitride, silica, and glass substrates.
Samples containing nano palladium on carbon nanotubes were shown to be highly efficient catalysts for so-called “Suzuki coupling reactions”. In this regard, a series of aryl bromides containing various functional groups on phenyl rings including cyano (1a,b), aldehyde (1c), ketone (1e), ester (1h), and nitro (1d) can effectively undergo Suzuki cross coupling reactions providing high yields of the corresponding biphenyl products.

The metal or metal oxide nanoparticles have potential use in electromagnetic applications. To evaluate this application, aligned nanotubes decorated with nanometer dimension metal particles distributed in a polymer matrix. By adjusting concentration and the particle distribution we were able to demonstrate tailorable properties, including increased dielectric constant along with a decreased loss factor. The decoupling and independent control of these fundamental electrical material properties afford a class of materials useful in a variety of applications in electronics and electromagnetic engineering in general.

Primary Sources of Funding: Federal Grant

Looking for: Development / License Partners