Nanotechnology Now





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Ions Control Shape Of Nanofibers Grown On Clear Substrate

The nanofibers lean in different directions depending on where they are located in relation to the chromium grid, because the ions are being drawn to the grid and strike the catalysts at various angles.
The nanofibers lean in different directions depending on where they are located in relation to the chromium grid, because the ions are being drawn to the grid and strike the catalysts at various angles.

Abstract:
"Role of ion flux on alignment of carbon nanofibers synthesized by DC plasma on transparent insulating substrates"

Authors: Ryan C. Pearce, Anatoli V. Melechko, North Carolina State University; Alexei V. Vasenkov, CFDRC; Dale K. Hensley, Michael L. Simpson, Timothy E. McKnight, Oak Ridge National Laboratory

Published: Forthcoming from the ACS journal Applied Materials & Interfaces

Abstract: A key factor to the implementation of devices with vertically aligned carbon nanofibers (VACNFs) is fundamental understanding of how to control fluctuations in the growth direction of the fibers. Here we demonstrate synthesis of VACNF on transparent and insulating substrates by continuous direct current plasma for realization of cellular interface suitable for transmission optical microscopy. To maintain continuous glow discharge above the substrate, a metal grid electrode layer was deposited over silica with windows of exposed silica ranging in size from 200?m to 1mm. This electrode geometry allows for synthesis of VACNFs even within an insulating window. This observation and the observed trends in the alignment of nanofibers in the vicinity of grid electrodes have indicated that the alignment does not correspond to the direction of the electric field at the substrate level, contrary to previously proposed alignment mechanism. Computational modeling of the plasma with this grid cathode geometry has shown that nanofiber alignment trends follow calculated ion flux direction rather than electrical field. The new proposed alignment mechanism is that ion sputtering of the carbon film on a catalyst particle defines the growth direction of the nanofibers. With this development, fiber growth direction can be better manipulated through changes in ionic flux direction, opening the possibility for growth of nanofibers on substrates with unique geometries.

Ions Control Shape Of Nanofibers Grown On Clear Substrate

Raleigh, NC | Posted on August 16th, 2011

Researchers from North Carolina State University, the Oak Ridge National Laboratory and CFD Research Corporation have found a new way to develop straight carbon nanofibers on a transparent substrate. Growing such nanofiber coatings is important for use in novel biomedical research tools, solar cells, water repellent coatings and others. The technique utilizes a charged chromium grid, and relies on ions to ensure the nanofibers are straight, rather than curling - which limits their utility.

"This is the first time, that I know of, where someone has been able to grow straight carbon nanofibers on a clear substrate," says Dr. Anatoli Melechko, an associate professor of materials science and engineering at NC State and co-author of a paper describing the research. "Such nanofibers can be used as gene-delivery tools. And a transparent substrate allows researchers to see how the nanofibers interact with cells, and to manipulate this interaction."

Specifically, the nanofibers can be coated with genetic material and then inserted into the nucleus of a cell - for example, to facilitate gene therapy research. The transparent substrate improves visibility because researchers can shine light through it, creating better contrast and making it easier to see what's going on.

The researchers also learned that ions play a key role in ensuring that the carbon nanofibers are straight. To understand that role, you need to know how the technique works.

The nanofibers are made by distributing nickel nanoparticles evenly on a substrate made of fused silicon (which is pure silicon dioxide). The substrate is then overlaid with a fine grid made of chromium, which serves as an electrode. The substrate and grid are then placed in a chamber at 700 degrees Celsius, which is then filled with acetylene and ammonia gas. The chrome grid is a negatively charged electrode, and the top of the chamber contains a positively charged electrode.

Electric voltage is then applied to the two electrodes, creating an electric field in the chamber that excites the atoms in the acetylene and ammonia gas. Some of the electrons in these atoms break away, creating free electrons and positively charged atoms called ions. The free electrons accelerate around the chamber, knocking loose even more electrons. The positively charged ions are drawn to the negatively charged grid on the floor of the chamber.

Meanwhile, the nickel nanoparticles are serving as catalysts, reacting with the carbon in the acetylene gas (C2H2) to create graphitic carbon nanofibers. The catalyst rides on the tip of the nanofiber that forms beneath it, like a rapidly growing pillar. The term graphitic means that the nanofibers have carbon atoms arranged in a hexagonal structure - like graphite.

One problem with growing carbon nanofibers is that the surface of the catalyst can become obstructed by a carbon film that blocks catalytic action, preventing further nanofibers growth. Here's where those ions come in.

The ions being drawn to the chromium grid are moving very quickly, and they choose the shortest possible route to reach the negatively-charged metal. In their rush to reach the grid, the ions often collide with the nickel catalysts, knocking off the excess carbon - and allowing further nanofibers growth. Video of the process is available here.

Because the ions are being drawn to the chromium grid, the angle at which they strike the catalysts depends on where the catalyst is located relative to the grid. For example, if you are looking down at the grid, a catalyst just to the right of the grid will appear to be leaning right - because ions would have been striking the right side of the catalyst in an attempt to reach the grid. These nanofibers are still straight - they don't curl up - they simply lean in one direction. The bulk of the nanofibers, however, are both straight and vertically aligned.

"This finding gives us an opportunity to create new reactors for creating nanofibers, building in the chromium grid," Melechko says.

The paper, "Role of ion flux on alignment of carbon nanofibers synthesized by DC plasma on transparent insulating substrates," is forthcoming from the ACS journal Applied Materials & Interfaces. The paper was co-authored by Ryan Pearce, a Ph.D. student at NC State; Dr. Alexei Vasenkov of CFDRC; and Dale Hensley, Dr. Michael Simpson and Timothy McKnight of Oak Ridge National Laboratory. The research was supported by Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy (processing, analytical microscopy, and experimental design). The device fabrication for cell interfacing was done through a user project at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, and sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

NC State's Department of Materials Science and Engineering is part of the university's College of Engineering.

-shipman-

####

For more information, please click here

Contacts:
Matt Shipman | News Services | 919.515.6386


Dr. Anatoli Melechko
919.515.8636

Copyright © North Carolina State University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Engineering Phase Changes in Nanoparticle Arrays: Scientists alter attractive and repulsive forces between DNA-linked particles to make dynamic, phase-shifting forms of nanomaterials May 25th, 2015

Nanostructures Increase Corrosion Resistance in Metallic Body Implants May 24th, 2015

Iranian Scientists Use Magnetic Field to Transfer Anticancer Drug to Tumor Tissue May 24th, 2015

Laboratories

Engineering Phase Changes in Nanoparticle Arrays: Scientists alter attractive and repulsive forces between DNA-linked particles to make dynamic, phase-shifting forms of nanomaterials May 25th, 2015

Visualizing How Radiation Bombardment Boosts Superconductivity: Atomic-level flyovers show how impact sites of high-energy ions pin potentially disruptive vortices to keep high-current superconductivity flowing May 23rd, 2015

Govt.-Legislation/Regulation/Funding/Policy

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Engineering Phase Changes in Nanoparticle Arrays: Scientists alter attractive and repulsive forces between DNA-linked particles to make dynamic, phase-shifting forms of nanomaterials May 25th, 2015

This Slinky lookalike 'hyperlens' helps us see tiny objects: The photonics advancement could improve early cancer detection, nanoelectronics manufacturing and scientists' ability to observe single molecules May 23rd, 2015

Visualizing How Radiation Bombardment Boosts Superconductivity: Atomic-level flyovers show how impact sites of high-energy ions pin potentially disruptive vortices to keep high-current superconductivity flowing May 23rd, 2015

Nanomedicine

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Nanostructures Increase Corrosion Resistance in Metallic Body Implants May 24th, 2015

Iranian Scientists Use Magnetic Field to Transfer Anticancer Drug to Tumor Tissue May 24th, 2015

New Antibacterial Wound Dressing in Iran Can Display Replacement Time May 22nd, 2015

Discoveries

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Engineering Phase Changes in Nanoparticle Arrays: Scientists alter attractive and repulsive forces between DNA-linked particles to make dynamic, phase-shifting forms of nanomaterials May 25th, 2015

Nanostructures Increase Corrosion Resistance in Metallic Body Implants May 24th, 2015

Iranian Scientists Use Magnetic Field to Transfer Anticancer Drug to Tumor Tissue May 24th, 2015

Materials/Metamaterials

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Engineering Phase Changes in Nanoparticle Arrays: Scientists alter attractive and repulsive forces between DNA-linked particles to make dynamic, phase-shifting forms of nanomaterials May 25th, 2015

Nanostructures Increase Corrosion Resistance in Metallic Body Implants May 24th, 2015

This Slinky lookalike 'hyperlens' helps us see tiny objects: The photonics advancement could improve early cancer detection, nanoelectronics manufacturing and scientists' ability to observe single molecules May 23rd, 2015

Announcements

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Engineering Phase Changes in Nanoparticle Arrays: Scientists alter attractive and repulsive forces between DNA-linked particles to make dynamic, phase-shifting forms of nanomaterials May 25th, 2015

Nanostructures Increase Corrosion Resistance in Metallic Body Implants May 24th, 2015

Iranian Scientists Use Magnetic Field to Transfer Anticancer Drug to Tumor Tissue May 24th, 2015

Energy

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles: Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays May 25th, 2015

Visualizing How Radiation Bombardment Boosts Superconductivity: Atomic-level flyovers show how impact sites of high-energy ions pin potentially disruptive vortices to keep high-current superconductivity flowing May 23rd, 2015

Conversion of Greenhouse Gases to Syngas in Presence of Nanocatalysts in Iran May 22nd, 2015

Sandia researchers first to measure thermoelectric behavior by 'Tinkertoy' materials May 20th, 2015

Research partnerships

Supercomputer unlocks secrets of plant cells to pave the way for more resilient crops: IBM partners with University of Melbourne and UQ May 21st, 2015

Taking control of light emission: Researchers find a way of tuning light waves by pairing 2 exotic 2-D materials May 20th, 2015

Efficiency record for black silicon solar cells jumps to 22.1 percent: Aalto University's researchers improved their previous record by over 3 absolute percents in cooperation with Universitat Politècnica de Catalunya May 18th, 2015

Organic nanoparticles, more lethal to tumors: Carbon-based nanoparticles could be used to sensitize cancerous tumors to proton radiotherapy and induce more focused destruction of cancer cells, a new study shows May 18th, 2015

Solar/Photovoltaic

Efficiency record for black silicon solar cells jumps to 22.1 percent: Aalto University's researchers improved their previous record by over 3 absolute percents in cooperation with Universitat Politècnica de Catalunya May 18th, 2015

Wearables may get boost from boron-infused graphene: Rice U. researchers flex muscle of laser-written microsupercapacitors May 18th, 2015

Random nanowire configurations increase conductivity over heavily ordered configurations May 16th, 2015

ORNL demonstrates first large-scale graphene fabrication May 14th, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project