Tag Archives: Anatoli Melechko

Ditch toxic ammonia and grow your vertically aligned carbon nanofibers with ambient air say scientists and their high school colleagues

Ditching the ammonia used in the processing of vertically aligned carbon nanofibers is both healthier, occupationally and environmentally, and more profitable as it paves the way to easier manufacturing. Scientists at North Carolina State University (NCSU) working alongside high school students have demonstrated their new technique, according to a March 24, 2014 news item on Nanowerk,

Researchers from North Carolina State University have demonstrated that vertically aligned carbon nanofibers (VACNFs) can be manufactured using ambient air, making the manufacturing process safer and less expensive. VACNFs hold promise for use in gene-delivery tools, sensors, batteries and other technologies.

The March 24, 2014 NCSU news release (also on EurekAlert), which originated the news item, features an image illustrating VACNFs and more details about the research,

Researchers have shown they can grow vertically-aligned carbon nanofibers using ambient air, rather than ammonia gas. Click to enlarge image. (Image free for use. Credit: Anatoli Melechko.)

Researchers have shown they can grow vertically-aligned carbon nanofibers using ambient air, rather than ammonia gas. Click to enlarge image. (Image free for use. Credit: Anatoli Melechko.)

Conventional techniques for creating VACNFs rely on the use of ammonia gas, which is toxic. And while ammonia gas is not expensive, it’s not free.

“This discovery makes VACNF manufacture safer and cheaper, because you don’t need to account for the risks and costs associated with ammonia gas,” says Dr. Anatoli Melechko, an adjunct associate professor of materials science and engineering at NC State and senior author of a paper on the work. “This also raises the possibility of growing VACNFs on a much larger scale.”

In the most common method for VACNF manufacture, a substrate coated with nickel nanoparticles is placed in a vacuum chamber and heated to 700 degrees Celsius. The chamber is then filled with ammonia gas and either acetylene or acetone gas, which contain carbon. When a voltage is applied to the substrate and a corresponding anode in the chamber, the gas is ionized. This creates plasma that directs the nanofiber growth. The nickel nanoparticles free carbon atoms, which begin forming VACNFs beneath the nickel catalyst nanoparticles. However, if too much carbon forms on the nanoparticles it can pile up and clog the passage of carbon atoms to the growing nanofibers.

Ammonia’s role in this process is to keep carbon from forming a crust on the nanoparticles, which would prevent the formation of VACNFs.

“We didn’t think we could grow VACNFs without ammonia or a hydrogen gas,” Melechko says. But he tried anyway.

The researchers had some unlikely collaborators who inspired them to try a new approach (from the news release),

Melechko’s team tried the conventional vacuum technique, using acetone gas. However, they replaced the ammonia gas with ambient air – and it worked. The size, shape and alignment of the VACNFs were consistent with the VACNFs produced using conventional techniques.

“We did this using the vacuum technique without ammonia,” Melechko says. “But it creates the theoretical possibility of growing VACNFs without a vacuum chamber. If that can be done, you would be able to create VACNFs on a much larger scale.”

Melechko also highlights the role of two high school students involved in the work: A. Kodumagulla and V. Varanasi, who are lead authors of the paper. [emphases mine] “This discovery would not have happened if not for their approach to the problem, which was free from any preconceptions,” Melechko says. “I think they’re future materials engineers.”

Kudos to the students! Dr. Melechko should also be lauded for his flexible attitude towards collaboration and research and for his acknowledgment of the students both in this news release and in the published paper where they have lead author status.

Here’s a link to and a citation for the paper,

Aerosynthesis: Growth of Vertically-aligned Carbon Nanofibres with Air DC Plasma by A. Kodumagulla, V. Varanasi, R. C. Pearce, W. C. Wu, D. K. Hensley, J. B. Tracy, T. E. McKnight and A. V. Melechko. Nanomaterials and Nanotechnology DOI: 10.5772/58449

This is an open access paper in an open access journal.

Can you deflate your spike-studded balloon?

Researchers at North Carolina State University have developed a means for embedding carbon nanofiber spikes (or needles)  into an elastic-like membrane to create a studded balloon that could potentially be used for drug delivery according to a Jan. 15, 2013 news item on ScienceDailyOnline,

The research community is interested in finding new ways to deliver precise doses of drugs to specific targets, such as regions of the brain. One idea is to create balloons embedded with nanoscale spikes that are coated with the relevant drug. Theoretically, the deflated balloon could be inserted into the target area and then inflated, allowing the spikes on the balloon’s surface to pierce the surrounding cell walls and deliver the drug. The balloon could then be deflated and withdrawn.

But to test this concept, researchers first needed to develop an elastic material that is embedded with these aligned, nanoscale needles. That’s where the NC State [North Carolina State University] research team came in.

“We have now developed a way of embedding carbon nanofibers in an elastic silicone membrane and ensuring that the nanofibers are both perpendicular to the membrane’s surface and sturdy enough to impale cells,” says Dr. Anatoli Melechko, an associate professor of materials science and engineering at NC State and co-author of a paper on the work.

For some reason this description brought to mind medieval weapons of war such as this  flail (the ball

Flail-Klassischer-Flegel (Deutsch: Ein mit einem Lederriemen verzierter klassischer Flegel mit kugelförmigem Kopf und Kette als Faustriemen) Credit: Tim Avatar Bartel [downloaded from: http://en.wikipedia.org/wiki/File:Klassischer-Flegel.jpg]

Flail-Klassischer-Flegel (Deutsch: Ein mit einem Lederriemen verzierter klassischer Flegel mit kugelförmigem Kopf und Kette als Faustriemen) Credit: Tim Avatar Bartel [downloaded from: http://en.wikipedia.org/wiki/File:Klassischer-Flegel.jpg]

not the stick. There’s much more about the flail and its use as a weapon in this Wikipedia essay.

As for this nanoscaled balloon studded with carbon nanofibers, the Jan. 15, 2013 North Carolina State University news release, which originated the news item, goes on to describe the technique,

The researchers first “grew” the nanofibers on an aluminum bed, or substrate. They then added a drop of liquid silicone polymer. The polymer, nanofibers and substrate were then spun, so that centrifugal force spread the liquid polymer in a thin layer between the nanofibers – allowing the nanofibers to stick out above the surface. The polymer was then “cured,” turning the liquid polymer into a solid, elastic membrane. Researchers then dissolved the aluminum substrate, leaving the membrane embedded with the carbon nanofibers “needles.”

“This technique is relatively easy and inexpensive,” says Melechko, “so we are hoping this development will facilitate new research on targeted drug-delivery methods.”

The paper, “Transfer of Vertically Aligned Carbon Nanofibers to Polydimethylsiloxane (PDMS) while Maintaining their Alignment and Impalefection Functionality,” is published online in the journal ACS Applied Materials & Interfaces. Lead authors on the paper are Ryan Pearce, a Ph.D. student at NC State, and Justin Railsback, a former NC State student now pursuing a Ph.D. at Northwestern University. Co-authors are Melechko; Dr. Joseph Tracy, an assistant professor of materials science and engineering at NC State; Bryan Anderson and Mehmet Sarac, Ph.D. students at NC State; and Timothy McKnight of Oak Ridge National Laboratory.

It’s very interesting but I wonder how they plan to deflate the balloon and what will happen to the carbon nanofiber needles and balloon membrane after their usage?

Gold unzips your DNA but not in a sexy way

The animation that the scientists from North Carolina have provided makes the gold nanoparticles look downright mean as that DNA definitely does not want to be unzipped but perhaps your mileage varies,

The June 20, 2012 news item on Nanowerk provides more detail,

New research from North Carolina State University finds that gold nanoparticles with a slight positive charge work collectively to unravel DNA’s double helix. This finding has ramifications for gene therapy research and the emerging field of DNA-based electronics.

The research team introduced gold nanoparticles, approximately 1.5 nanometers in diameter, into a solution containing double-stranded DNA. The nanoparticles were coated with organic molecules called ligands. Some of the ligands held a positive charge, while others were hydrophobic – meaning they were repelled by water.

Because the gold nanoparticles had a slight positive charge from the ligands, and DNA is always negatively charged, the DNA and nanoparticles were pulled together into complex packages.

“However, we found that the DNA was actually being unzipped by the gold nanoparticles,” Melechko [Dr. Anatoli Melechko, an associate professor of materials science and engineering at NC State and co-author of the paper] says. The positively-charged ligands on the nanoparticles attached to the DNA as predicted, but the hydrophobic ligands of the nanoparticles became tangled with each other. As this tangling pulled the nanoparticles into clusters, the nanoparticles pulled the DNA apart.

The implications for this ‘unzipping’ are,

“We think gold nanoparticles still hold promise for gene therapy,” says Dr. Yaroslava Yingling, an assistant professor of materials science and engineering at NC State and co-author of the paper. “But it’s clear that we need to tailor the ligands, charge and chemistry of these materials to ensure the DNA’s structural integrity is not compromised.”

The finding is also relevant to research on DNA-based electronics, which hopes to use DNA as a template for creating nanoelectronic circuits. Because some work in that field involves placing metal nanoparticles on DNA, this finding indicates that researchers will have to pay close attention to the characteristics of those nanoparticles – or risk undermining the structural integrity of the DNA.