Emulating -- and surpassing -- nature: Using DNA to build nanomaterials with desired properties

ScienceDaily (Oct. 13, 2011) — Nature is a master builder. Using a bottom-up approach, nature takes tiny atoms and, through chemical bonding, makes crystalline materials, like diamonds, silicon and even table salt. In all of them, the properties of the crystals depend upon the type and arrangement of atoms within the crystalline lattice.

Now, a team of Northwestern University scientists has learned how to top nature by building crystalline materials from nanoparticles and DNA, the same material that defines the genetic code for all living organisms.

Using nanoparticles as "atoms" and DNA as "bonds," the scientists have learned how to create crystals with the particles arranged in the same types of atomic lattice configurations as some found in nature, but they also have built completely new structures that have no naturally occurring mineral counterpart.

The basic design rules the Northwestern scientists have established for this approach to nanoparticle assembly promise the possibility of creating a variety of new materials that could be useful in catalysis, electronics, optics, biomedicine and energy generation, storage and conversion technologies.

The new method and design rules for making crystalline materials from nanostructures and DNA will be published Oct. 14 by the journal Science.

"We are building a new periodic table of sorts," said Professor Chad A. Mirkin, who led the research. "Using these new design rules and nanoparticles as 'artificial atoms,' we have developed modes of controlled crystallization that are, in many respects, more powerful than the way nature and chemists make crystalline materials from atoms. By controlling the size, shape, type and location of nanoparticles within a given lattice, we can make completely new materials and arrangements of particles, not just what nature dictates."

Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and professor of medicine, chemical and biological engineering, biomedical engineering and materials science and engineering and director of Northwestern's International Institute for Nanotechnology (IIN).

"Once we have a certain type of lattice," Mirkin said, "the particles can be moved closer together or farther apart by changing the length of the interconnecting DNA, thereby providing near-infinite tunability."

"This work resulted from an interdisciplinary collaboration that coupled synthetic chemistry with theoretical model building," said coauthor George C. Schatz, a theoretician and the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern. "It was the back and forth between synthesis and theory that was crucial to the development of the design rules. Collaboration is a special aspect of research at Northwestern, and it worked very effectively for this project."

In the study, the researchers start with two solutions of nanoparticles coated with single-stranded DNA. They then add DNA strands that bind to these DNA-functionalized particles, which then present a large number of DNA "sticky ends" at a controlled distance from the particle surface; these sticky ends then bind to the sticky ends of adjacent particles, forming a macroscopic arrangement of nanoparticles.

Different crystal structures are achieved by using different combinations of nanoparticles (with varying sizes) and DNA linker strands (with controllable lengths). After a process of mixing and heating, the assembled particles transition from an initially disordered state to one where every particle is precisely located according to a crystal lattice structure. The process is analogous to how ordered atomic crystals are formed.

The researchers report six design rules that can be used to predict the relative stability of different structures for a given set of nanoparticle sizes and DNA lengths. In the paper, they use these rules to prepare 41 different crystal structures with nine distinct crystal symmetries. However, the design rules outline a strategy to independently adjust each of the relevant crystallographic parameters, including particle size (varied from 5 to 60 nanometers), crystal symmetry and lattice parameters (which can range from 20 to 150 nanometers). This means that these 41 crystals are just a small example of the near infinite number of lattices that could be created using different nanoparticles and DNA strands.

Mirkin and his team used gold nanoparticles in their work but note that their method also can be applied to nanoparticles of other chemical compositions. Both the type of nanoparticle assembled and the symmetry of the assembled structure contribute to the properties of a lattice, making this method an ideal means to create materials with predictable and controllable physical properties.

Mirkin believes that, one day soon, software will be created that allows scientists to pick the particle and DNA pairs required to make almost any structure on demand.

The Air Force Office of Scientific Research, the U.S. Department of Energy Office of Basic Energy Sciences and the National Science Foundation supported the research.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

R. J. Macfarlane, B. Lee, M. R. Jones, N. Harris, G. C. Schatz, C. A. Mirkin. Nanoparticle Superlattice Engineering with DNA. Science, 2011; 334 (6053): 204 DOI: 10.1126/science.1210493

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Engineers 'cook' promising new heat-harvesting nanomaterials in microwave oven

ScienceDaily (Sep. 30, 2011) — Waste heat is a byproduct of nearly all electrical devices and industrial processes, from driving a car to flying an aircraft or operating a power plant. Engineering researchers at Rensselaer Polytechnic Institute have developed new nanomaterials that could lead to techniques for better capturing and putting this waste heat to work. The key ingredients for making marble-sized pellets of the new material are aluminum and a common, everyday microwave oven.

Harvesting electricity from waste heat requires a material that is good at conducting electricity but poor at conducting heat. One of the most promising candidates for this job is zinc oxide, a nontoxic, inexpensive material with a high melting point. While nanoengineering techniques exist for boosting the electrical conductivity of zinc oxide, the material's high thermal conductivity is a roadblock to its effectiveness in collecting and converting waste heat. Because thermal and electrical conductivity are related properties, it's very difficult to decrease one without also diminishing the other.

However, a team of researchers led by Ganpati Ramanath, professor in the Department of Materials Science and Engineering at Rensselaer, in collaboration with the University of Wollongong, Australia, have demonstrated a new way to decrease zinc oxide's thermal conductivity without reducing its electrical conductivity. The innovation involves adding minute amounts of aluminum to zinc oxide, and processing the materials in a microwave oven. The process is adapted from a technique invented at Rensselaer by Ramanath, graduate student Rutvik Mehta, and Theo Borca-Tasciuc, associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering (MANE). This work could open the door to new technologies for harvesting waste heat and creating highly energy efficient cars, aircraft, power plants, and other systems.

"Harvesting waste heat is a very attractive proposition, since we can convert the heat into electricity and use it to power a device -- like in a car or a jet -- that is creating the heat in the first place. This would lead to greater efficiency in nearly everything we do and, ultimately, reduce our dependence on fossil fuels," Ramanath said. "We are the first to demonstrate such favorable thermoelectric properties in bulk-sized high-temperature materials, and we feel that our discovery will pave the way to new power harvesting devices from waste heat."

Results of the study are detailed in a paper published recently by the journal Nano Letters.

To create the new nanomaterial, researchers added minute quantities of aluminum to shape-controlled zinc oxide nanocrystals, and heated them in a $40 microwave oven. Ramanath's team is able to produce several grams of the nanomaterial in a matter of few minutes, which is enough to make a device measuring a few centimeters long. The process is less expensive and more scalable than conventional methods and is environmentally friendly, Ramanath said. Unlike many nanomaterials that are fabricated directly onto a substrate or surface, this new microwave method can produce pellets of nanomaterials that can be applied to different surfaces. These attributes, together with low thermal conductivity and high electrical conductivity, are highly suitable for heat harvesting applications.

"Our discovery could be key to overcoming major fundamental challenges related to working with thermoelectric materials," said project collaborator Borca-Tasciuc. "Moreover, our process is amenable to scaling for large-scale production. It's really amazing that a few atoms of aluminum can conspire to give us thermoelectric properties we're interested in."

This work was a collaborative effort between Ramanath and Shi Xue Dou, a professor at the Institute for Superconducting and Electronic Materials at the University of Wollogong, Australia. Wollongong graduate student Priyanka Jood carried out the work together with Rensselaer graduate students Rutvik Mehta and Yanliang Zhang during Jood's one-year visit to Rensselaer. Co-authors of the paper are Richard W. Siegel, the Robert W. Hunt Professor of Materials Science and Engineering; along with professors Xiaolin Wang and Germanas Peleckis at the University of Wollongong.

This research is funded by support from IBM through the Rensselaer Nanotechnology Center; S3TEC, an Energy Frontier Research Center funded by the U.S. Department of Energy (DoE) Office of Basic Energy Sciences; the Australian Research Council (ARC); and the University of Wollongong.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Rensselaer Polytechnic Institute.

Journal Reference:

Priyanka Jood, Rutvik J. Mehta, Yanliang Zhang, Germanas Peleckis, Xiaolin Wang, Richard W. Siegel, Theo Borca-Tasciuc, Shi Xue Dou, Ganpati Ramanath. Al-Doped Zinc Oxide Nanocomposites with Enhanced Thermoelectric Properties. Nano Letters, 2011; : 110926094633005 DOI: 10.1021/nl202439h

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Engineers 'cook' promising new heat-harvesting nanomaterials in microwave oven

ScienceDaily (Sep. 30, 2011) — Waste heat is a byproduct of nearly all electrical devices and industrial processes, from driving a car to flying an aircraft or operating a power plant. Engineering researchers at Rensselaer Polytechnic Institute have developed new nanomaterials that could lead to techniques for better capturing and putting this waste heat to work. The key ingredients for making marble-sized pellets of the new material are aluminum and a common, everyday microwave oven.

Harvesting electricity from waste heat requires a material that is good at conducting electricity but poor at conducting heat. One of the most promising candidates for this job is zinc oxide, a nontoxic, inexpensive material with a high melting point. While nanoengineering techniques exist for boosting the electrical conductivity of zinc oxide, the material's high thermal conductivity is a roadblock to its effectiveness in collecting and converting waste heat. Because thermal and electrical conductivity are related properties, it's very difficult to decrease one without also diminishing the other.

However, a team of researchers led by Ganpati Ramanath, professor in the Department of Materials Science and Engineering at Rensselaer, in collaboration with the University of Wollongong, Australia, have demonstrated a new way to decrease zinc oxide's thermal conductivity without reducing its electrical conductivity. The innovation involves adding minute amounts of aluminum to zinc oxide, and processing the materials in a microwave oven. The process is adapted from a technique invented at Rensselaer by Ramanath, graduate student Rutvik Mehta, and Theo Borca-Tasciuc, associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering (MANE). This work could open the door to new technologies for harvesting waste heat and creating highly energy efficient cars, aircraft, power plants, and other systems.

"Harvesting waste heat is a very attractive proposition, since we can convert the heat into electricity and use it to power a device -- like in a car or a jet -- that is creating the heat in the first place. This would lead to greater efficiency in nearly everything we do and, ultimately, reduce our dependence on fossil fuels," Ramanath said. "We are the first to demonstrate such favorable thermoelectric properties in bulk-sized high-temperature materials, and we feel that our discovery will pave the way to new power harvesting devices from waste heat."

Results of the study are detailed in a paper published recently by the journal Nano Letters.

To create the new nanomaterial, researchers added minute quantities of aluminum to shape-controlled zinc oxide nanocrystals, and heated them in a $40 microwave oven. Ramanath's team is able to produce several grams of the nanomaterial in a matter of few minutes, which is enough to make a device measuring a few centimeters long. The process is less expensive and more scalable than conventional methods and is environmentally friendly, Ramanath said. Unlike many nanomaterials that are fabricated directly onto a substrate or surface, this new microwave method can produce pellets of nanomaterials that can be applied to different surfaces. These attributes, together with low thermal conductivity and high electrical conductivity, are highly suitable for heat harvesting applications.

"Our discovery could be key to overcoming major fundamental challenges related to working with thermoelectric materials," said project collaborator Borca-Tasciuc. "Moreover, our process is amenable to scaling for large-scale production. It's really amazing that a few atoms of aluminum can conspire to give us thermoelectric properties we're interested in."

This work was a collaborative effort between Ramanath and Shi Xue Dou, a professor at the Institute for Superconducting and Electronic Materials at the University of Wollogong, Australia. Wollongong graduate student Priyanka Jood carried out the work together with Rensselaer graduate students Rutvik Mehta and Yanliang Zhang during Jood's one-year visit to Rensselaer. Co-authors of the paper are Richard W. Siegel, the Robert W. Hunt Professor of Materials Science and Engineering; along with professors Xiaolin Wang and Germanas Peleckis at the University of Wollongong.

This research is funded by support from IBM through the Rensselaer Nanotechnology Center; S3TEC, an Energy Frontier Research Center funded by the U.S. Department of Energy (DoE) Office of Basic Energy Sciences; the Australian Research Council (ARC); and the University of Wollongong.

Recommend this story on Facebook, Twitter,
and Google +1:

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Rensselaer Polytechnic Institute.

Journal Reference:

Priyanka Jood, Rutvik J. Mehta, Yanliang Zhang, Germanas Peleckis, Xiaolin Wang, Richard W. Siegel, Theo Borca-Tasciuc, Shi Xue Dou, Ganpati Ramanath. Al-Doped Zinc Oxide Nanocomposites with Enhanced Thermoelectric Properties. Nano Letters, 2011; : 110926094633005 DOI: 10.1021/nl202439h

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Looking inside nanomaterials in 3-D

ScienceDaily (May 17, 2011) — Scientists from Denmark, China and USA have developed a new method for revealing 3-D images of the structure inside a material.

Most solid materials are composed of millions of small crystals, packed together to form a fully dense solid. The orientations, shapes, sizes and relative arrangement of these crystals are important in determining many material properties.

Traditionally, it has only been possible to see the crystal structure of a material by looking at a cut surface, giving just 2-D information. In recent years, x-ray methods have been developed that can be used to look inside a material and obtain a 3-D map of the crystal structure. However, these methods have a resolution limit of around 100nm (one nanometer is 100,000 times smaller than the width of a human hair).

In contrast, the newly developed technique now published in the journal Science, allows 3-D mapping of the crystal structure inside a material down to nanometer resolution, and can be carried out using a transmission electron microscope, an instrument found in many research laboratories.

Samples must be thinner than a few hundred nanometers. However, this limitation is not a problem for investigations of crystal structures inside nanomaterials, where the average crystal size is less than 100 nanometers, and such materials are investigated all over the world in a search for materials with new and better properties than the materials we use today.

For example, nanomaterials have an extremely high strength and an excellent wear resistance and applications therefore span from microelectronics to gears for large windmills. The ability to collect a 3-D picture of the crystal structure in these materials is an important step in being able to understand the origins of their special properties.

An important advantage of such 3-D methods is that they allow the changes taking place inside a material to be observed directly. For example, the mapping may be repeated before and after a heat treatment revealing how the structure changes during heating.

This new technique has a resolution 100 times better than existing non-destructive 3-D techniques and opens up new opportunities for more precise analysis of the structural parameters in nanomaterials.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Risø National Laboratory for Sustainable Energy.

Journal Reference:

H. H. Liu, S. Schmidt, H. F. Poulsen, A. Godfrey, Z. Q. Liu, J. A. Sharon, X. Huang. Three-Dimensional Orientation Mapping in the Transmission Electron Microscope. Science, 2011; 332 (6031): 833 DOI: 10.1126/science.1202202

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Looking inside nanomaterials in 3-D

ScienceDaily (May 17, 2011) — Scientists from Denmark, China and USA have developed a new method for revealing 3-D images of the structure inside a material.

Most solid materials are composed of millions of small crystals, packed together to form a fully dense solid. The orientations, shapes, sizes and relative arrangement of these crystals are important in determining many material properties.

Traditionally, it has only been possible to see the crystal structure of a material by looking at a cut surface, giving just 2-D information. In recent years, x-ray methods have been developed that can be used to look inside a material and obtain a 3-D map of the crystal structure. However, these methods have a resolution limit of around 100nm (one nanometer is 100,000 times smaller than the width of a human hair).

In contrast, the newly developed technique now published in the journal Science, allows 3-D mapping of the crystal structure inside a material down to nanometer resolution, and can be carried out using a transmission electron microscope, an instrument found in many research laboratories.

Samples must be thinner than a few hundred nanometers. However, this limitation is not a problem for investigations of crystal structures inside nanomaterials, where the average crystal size is less than 100 nanometers, and such materials are investigated all over the world in a search for materials with new and better properties than the materials we use today.

For example, nanomaterials have an extremely high strength and an excellent wear resistance and applications therefore span from microelectronics to gears for large windmills. The ability to collect a 3-D picture of the crystal structure in these materials is an important step in being able to understand the origins of their special properties.

An important advantage of such 3-D methods is that they allow the changes taking place inside a material to be observed directly. For example, the mapping may be repeated before and after a heat treatment revealing how the structure changes during heating.

This new technique has a resolution 100 times better than existing non-destructive 3-D techniques and opens up new opportunities for more precise analysis of the structural parameters in nanomaterials.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Risø National Laboratory for Sustainable Energy.

Journal Reference:

H. H. Liu, S. Schmidt, H. F. Poulsen, A. Godfrey, Z. Q. Liu, J. A. Sharon, X. Huang. Three-Dimensional Orientation Mapping in the Transmission Electron Microscope. Science, 2011; 332 (6031): 833 DOI: 10.1126/science.1202202

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here