Rice University researchers have found a new way to spontaneously assemble nanoparticles into bag-like sacs. Their 'nanobatons' could be used to clean up oil spills by trapping oil droplets in polluted waters. These nanoparticles could even be more useful for delivering drugs. The researchers found that 'ultraviolet light and magnetic fields could be used to flip the nanoparticles, causing the bags to instantly turn inside out and release their cargo -- a feature that could ultimately be handy for delivering drugs.' This is still a lab project and it's hard to know when real applications could appear. But read more...
You can see on the left several images illustrating this new method of assembling carbon nanotubes. The top row shows scanning electron microscope (SEM) on the left (A) and transmission electron microscope (TEM) on the right (B) of a CNT/Au nanowire hybrid structure. The bottom image shows "how tiny, stick-shaped particles of metal and carbon can trap oil droplets in water by spontaneously assembling into bag-like sacs." (Credit: Rice University) These images have been extracted from this page at Rice University.
This research project has been led by Pulickel Ajayan, Professor in Mechanical Engineering and Materials Science at Rice University. He worked with several members of his research group, including graduate student Fung Suong Ou and postdoctoral researcher Shaijumon Manikoth.
Here is a comment of Ajayan about this technology. "The core of the nanotechnology revolution lies in designing inorganic nanoparticles that can self-assemble into larger structures like a 'smart dust' that performs different functions in the world -- for example, cleaning up pollution. Our approach brings the concept of self-assembling, functional nanomaterials one step closer to reality."
But how did the researchers obtain their results? "The multisegmented nanowires, akin to 'nanoscale batons,' were made by connecting two nanomaterials with different properties, much like an eraser is attached to the end of a wooden pencil. In the study, the researchers started with carbon nanotubes -- hollow tubes of pure carbon. Atop the nanotubes, they added short segments of gold. Ajayan said that by adding various other segments -- like sections of nickel or other materials -- the researchers can create truly multifunctional nanostructures."
This research work has been published online on May 29, 2008 by Nano Letters under the name "Controlled Manipulation of Giant Hybrid Inorganic Nanowire Assemblies." Here is a link to the abstract. "The ultimate goal of nanotechnology is the design and fabrication of nanosize building blocks with multiple functionalities and their assembly into large-scale functional structures that can be controllably manipulated. Here we show that hybrid inorganic multisegmented nanowires, with hydrophobic carbon nanotube tails and hydrophilic metal nanowire heads, allow the assembly and manipulation of massive ordered structures in solution, reminiscent of the organic molecular micellar assembly. Further, properly designed assemblies can be manipulated using external stimuli such as magnetic field and light. The hybrid nanowires can have multiple segments including magnetic components, allowing the assembly to be manipulated by external magnetic field. The assembled structures can also be manipulated by modifying the hydrophobicity of the respective components via chemical functionalization and optical irradiation. This approach brings the concept of environment sensitive self-assembling nanomaterials closer to reality."
And what can we expect from this project? "The team is next preparing to test whether chemical modifications to the "nanobatons" could result in spheres that can both capture and break down oily chemicals. For example, they hope to attach catalysts to the water-hating ends of the nanowires that will cause compounds like trichloroethene, or TCE, to break into nontoxic constituents."
Sources: Rice University news release, May 29, 2008; and various websites
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