In an achievement some see as the "holy grail" of nanoscience, researchers at the U.S. Department of Energy's Brookhaven National Laboratory have for the first time used DNA to guide the creation of three-dimensional, ordered, crystalline structures of nanoparticles (particles with dimensions measured in billionths of a meter).
The ability to engineer such 3-D structures is essential to producing functional materials that take advantage of the unique properties that may exist at the nanoscale - for example, enhanced magnetism, improved catalytic activity, or new optical properties. The research will be published in the January 31, 2008, issue of the journal Nature.
"From previous research, we know that highly selective DNA binding can be used to program nanoparticle interactions," said Oleg Gang, a scientist at Brookhaven's Center for Functional Nanomaterials (CFN), who led the interdisciplinary research team, which includes Dmytro Nykypanchuk and Mathew Maye of the CFN, and Daniel van der Lelie of the Biology Department. "But while theory has intriguingly predicted that DNA can guide nanoparticles to form ordered, 3-D phases, no one has accomplished this experimentally, until now."
As with the group's previous work, the new assembly method relies on the attractive forces between complementary strands of DNA - the molecule made of pairing bases known by the letters A, T, G, and C that carries the genetic code of living things. First, the scientists attach to nanoparticles hair-like extensions of DNA with specific "recognition sequences" of complementary bases. Then they mix the DNA-covered particles in solution. When the recognition sequences find one another in solution, they bind together to link the nanoparticles.
This first binding is necessary, but not sufficient, to produce the organized structures the scientists are seeking. To achieve ordered crystals, the scientists alter the properties of DNA and borrow some techniques known for traditional crystals.
Importantly, they heat the samples of DNA-linked particles and then cool them back to room temperature. "This 'thermal processing' is somewhat similar to annealing used in forming more common crystals made from atoms," explained Nykypanchuk. "It allows the nanoparticles to unbind, reshuffle, and find more stable binding arrangements."
The team also experimented with different degrees of DNA flexibility, recognition sequences, and DNA designs in order to find a "sweet spot" of interactions where a stable, crystalline form would appear.
Results from a variety of analysis techniques, including small angle x-ray scattering at the National Synchrotron Light Source and dynamic light scattering and different types of optical spectroscopies and electron microscopy at the CFN, were combined to reveal the detail of the ordered structures and the underlying processes for their formation. These results indicate that the scientists have indeed found that sweet spot to create 3-D nanoparticle assemblies with long-range crystalline order using DNA. The crystals are remarkably open, with the nanoparticles themselves occupying only 5 percent of the crystal lattice volume, and DNA occupying another 5 percent. "This open structure leaves a lot of room for future modifications, including the incorporation of different nano-objects or biomolecules, which will lead to enhanced nanoscale properties and new classes of applications," said Maye. For example, pairing gold nanoparticles with other metals often improves catalytic activity. Additionally, the DNA linking molecules can be used as a kind of chemical scaffold for adding small molecules, polymers, or proteins.
Furthermore, once the crystal structure is set, it remains stable through repeated heating and cooling cycles, a feature important to many potential applications.
The crystals are also extraordinarily sensitive to thermal expansion - 100 times more sensitive than ordinary materials, probably due to the heat sensitivity of DNA. This significant thermal expansion could be a plus in controlling optical and magnetic properties, for example, which are strongly affected by changes in the distance between particles. The ability to effect large changes in these properties underlies many potential applications such as energy conversion and storage, as well as sensor technology.
The Brookhaven team worked with gold nanoparticles as a model, but they say the method can be applied to other nanoparticles as well. And they fully expect the technique could yield a wide array of crystalline phases with different types of 3-D lattices that could be tailored to particular functions.
"This work is the first step to demonstrate that it is possible to obtain ordered structures. But it opens so many avenues for researchers, and this is why it is so exciting," Gang says.
Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg
The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Materials Sciences
08.12.2016 | Materials Sciences
08.12.2016 | Physics and Astronomy