Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sandia/UNM self-assembly process forms durable nanocrystal arrays and independent nanocrystals

27.04.2004


NOW, SIT UP: Jeff Brinker (left) and Hongyou Fan observe satisfactory fluorescence by their well-trained nanocrystals in water solution. The dark vial holds gold nanocrystals; the orange and green are semiconductor nanocrystals. (Photo by Randy Montoya)


Top image: ordered gold nanocrystal packed inside silica. Electron diffraction pattern (left corner image) and high-resolution image (right corner) confirmed the nanostructure and gold nanocrystals. Bottom image: self-assembled, well-shaped gold nanocrystal/silica arrays.


Possible uses include biological labeling, laser light, catalysts, memory storage, and relief for physicists

A wish list for nanotechnologists might consist of a simple, inexpensive means - actually, any means at all - of self-assembling nanocrystals into robust orderly arrangements, like soup cans on a shelf or bricks in a wall, each separated from the next by an insulating layer of silicon dioxide.

The silica casing could be linked to compatible semiconductor devices. The trapped nanocrystals might function as a laser, their frequency dependent on their size, or as a very fine catalyst with unusually large surface area, or perhaps a memory device tunable by particle size and composition.



Or perhaps the technologist might want to stop nanocrystals from clumping. Agglomeration prevents them from being used as light-emitting tagging mechanisms to track cancer cells in the body and from being used in light-emitting devices needed for solid state lighting.

In this week’s journal Science, researchers at the National Nuclear Security Administration’s Sandia National Laboratories and the University of New Mexico describe a simple, commercially feasible method for doing both these things.

"The paper overcomes barriers to using nanocrystals routinely," said Jeff Brinker, Sandia Fellow and UNM chemical engineering professor, who with Sandia’s Hongyou Fan led the self-assembling effort. "The question in nanotechnology isn’t ’where’s the beef,’ it’s ’where’s the connectors’? How does one make connections from the macroscale to the nanoscale? This question lies at the heart of nanotechnology."

The self-assembly approach developed by the SNL/UNM teams allows nanocrystal arrays to be integrated into devices using standard microelectronic processing techniques, bridging huge gaps in scale.

Said IBM staff researcher Chuck Black at T. J. Watson Research Center in Yorktown Heights, NY, "One thing that’s nice is that these materials are hard materials. Often they come with an organic surfactant layer that makes it difficult to process materials, like a kind of grease. This material is embedded in oxide. It sounds like a neat thing and a new approach." The Sandia/UNM approach scrubs the surfactants with an ozone compound.

"Also, quantum dots can be important for biolabeling and biosensing," said Fan, who initiated the effort to use the nanocrystals for those purposes. "The beauty of our approach is that it makes these quantum dots both water-soluble and biocompatible, two essential qualities if we want to use them for in vivo imaging. The functional organic groups on the quantum dots can link with a variety of peptides, proteins, DNA, antibodies, etc. so that the dots can bind to and help locate targets like cancer cells, a critical issue in biomedicine."

Sandia has applied for a patent on this approach, which should aid attempts at several major universities to identify individual cancer cells before they increase in number.

(Researchers have found that at the nanoscopic realm, changing merely the size of a material changes the frequency it emits when ’pumped’ by outside energy; thus, quantum dots of particular sizes and material will emit at predictable frequencies, which makes them useful adjuncts when bound to molecules created to bind to particular cancer molecules.)

The process uses a simple surfactant (similar to dishwashing soap) to surround the nanocrystals - in this case, made of gold - to make them water soluble. Further processing involving silica causes the gold nanocrystals to arrange themselves within a silica matrix in a lattice - a kind of artificial solid with properties that can be adjusted through control of nanocrystal composition, diameter, properties of the surfactant, and/or stabilizing ligands used in formation of the water soluble nanocrystals.

The robust 3-D solids, which are stable indefinitely, demonstrate the incorporation of nanocrystalline arrays into device architectures.

A further use allows physicists to go beyond modeling to determine how current scales with voltage in nanodevices. "Before," says Brinker, "there was no way to make precisely ordered 3-D nanocrystalline solids, integrate them in devices, and characterize their behavior. There was no theoretical model. How does the current decide which way to hop between crystals?"

The new material can be used as an artificial solid to test out theories. "It should be a dream for physicists; they don’t just have to model anymore," said Brinker.

A kind of choreographed transmission possibility exists with the so-called "coulomb blockade," he said: No current is passed at low voltages because each crystal is separated by a thin (several nanometer thick) layer of silica dioxide, creating an insulator between the stored charges. Each nanocrystal charges separately. "This could be configured into a flash memory," said Brinker, "with a huge number of charges stored in an array of nodes."

Researchers at UNM’s Center for High Technology Materials performed experiments to establish the current/voltage scaling characteristics of the gold/silica arrays as a function of temperature. Sandia researcher Tim Boyle made and provided nanocrystal semiconductor (cadmium selinide) quantum dots.

Neal Singer | Sandia!
Further information:
http://www.sandia.gov/news-center/news-releases/2004/micro-nano/nanotoolcase.html

More articles from Process Engineering:

nachricht Applying electron beams to 3-D objects
23.09.2016 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP

nachricht New process for cell transfection in high-throughput screening
21.03.2016 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

 
Latest News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

New switch decides between genome repair and death of cells

27.09.2016 | Life Sciences

Nanotechnology for energy materials: Electrodes like leaf veins

27.09.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>