Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers create freestanding nanoparticle films without fillers

10.06.2009
Nanoparticle films are no longer a delicate matter: Vanderbilt physicists have found a way to make them strong enough so they don¹t disintegrate at the slightest touch.
­In the last 25 years, ever since scientists figured out how to create nanoparticles ­ ultrafine particles with diameters less than 100 nanometers ­ they have come up with a number of different methods to mold them into thin films which have a variety of interesting potential applications ranging from semiconductor fabrication to drug delivery, solid state lighting to flexible television and computer displays.

Until now these films have had a common problem: lack of cohesion.
Nanoparticles typically consist of an inorganic core coated with a thin layer of organic molecules. These particles are not very sticky so they don¹t form coherent thin films unless they are encapsulated in a polymer coating or mixed with molecules called chemical ³cross-linkers² that act like glue to stick the nanoparticles together.

³Adding this extra material can complicate the fabrication of nanoparticle films and make them more expensive. In addition, the added material, usually a polymer, can modify the physical properties that make these films so interesting,² says James Dickerson, assistant professor of physics at Vanderbilt, who headed the research group that developed freestanding nanoparticle films without any additives.

The properties of the new films and the method that the researchers use to create them is described in the article ³Sacrificial layer electrophoretic deposition of freestanding multilayered nanoparticle films² published online in the journal Chemical Communications on May 27, 2009.

³Our films are so resilient that we can pick them up with a pair of tweezers and move them around on a surface without tearing,² says Dickerson. ³This makes it particularly easy to put them into microelectronic devices, such as computer chips.²

Dickerson considers the most straightforward applications for his films to be in semiconductor manufacturing to aid in the continued miniaturization of digital circuitry and in the production of flexible television and computer screens.

A key component in the transistors in integrated circuits is an insulating layer that separates the gate, which turns current flow on and off, from the channel through which the current flows. Traditionally, semiconductor manufacturers have used silicon dioxide for this purpose. As transistors have shrunk, however, they have been forced to make this layer thinner and thinner until they reached the point where electrons leak through and sap the power from the device. This has led semiconductor manufacturers to retool their process to use ³high-k² dielectric materials, such as hafnium oxide, because they have much higher electrical resistance.

³We have made high-k nanoparticle films that could be cheaper and more effective than the high-k materials the manufacturers are currently using,² Dickerson says.

In addition, the physicist argues that the films have properties that make them ideal for flexible television and computer screens. They are very flexible and don¹t show any signs of cracking when they are flexed repeatedly. They are also made using a technique called electrophoretic deposition (EPD) that is well suited for creating patterned material and is compatible with fluorescent materials that can form the red, green and blue pixels used in flat panel television screens and computer displays.

EDP is a wet method. Nanoparticles are placed in a solution along with a pair of electrodes. When an electric current is applied, it creates an electrical field in the liquid that attracts the nanoparticles, which coat the electrodes. Using colloids, mixtures with particles 10 to 1,000 times larger than nanoparticles, EDP is widely used to apply coatings to complex metal parts such as automobile bodies, prosthetic devices, appliances and beverage containers. It is only recently that researchers like Dickerson have begun applying the technique to nanoparticles.

³The science of colloidal EDP is well known but the particles are substantially larger than the solvent molecules. Many nanoparticles, however, are about the same size as the solvent molecules, which makes the process considerably more complicated and difficult to control,² Dickerson explains.

To get the method to work, in fact, Dickerson and his colleagues had to invent of new form of EDP, which they call sacrificial layer electrophoretic deposition. They added a spun-cast layer of polymer to the electrodes that serves as a pattern that organizes the nanoparticles as they are deposited.
Then, after the deposition process is completed, they dissolve (sacrifice) the polymer layer to free the nanoparticle film.

According to the researchers, films made in this fashion stick together because the electrical field slams the nanoparticles into the film with sufficient force to pack the particles together tightly enough to allow naturally attractive inter-particle forces to bind the particles together.

So far the Dickerson group has used the technique to make films out of two different types of nanoparticles ­ iron oxide and cadmium selenide ­ and they believe the technique can be used with a wide variety of other nanoparticles.

³The technique is liberating because you can make these films from the materials you want and use them where you want,² Dickerson says.

The co-authors on the paper are graduate students Saad A. Hasan and Dustin W. Kavich. The research was funded by a grant from Vanderbilt University.

David F. Salisbury | Vanderbilt University
Further information:
http://www.vanderbilt.edu/News

More articles from Physics and Astronomy:

nachricht The moon is front and center during a total solar eclipse
24.07.2017 | NASA/Goddard Space Flight Center

nachricht Superluminous supernova marks the death of a star at cosmic high noon
24.07.2017 | Royal Astronomical Society

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

Chances to treat childhood dementia

24.07.2017 | Health and Medicine

Improved Performance thanks to Reduced Weight

24.07.2017 | Automotive Engineering

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>