Tag Archives: visualization

Understanding how carbon nanotubes grow and self-organize is key to better production

This research may help to commercialize use of carbon nanotubes (CNTs), a  ‘magical’ nanoscale material with great promise and great difficulties (standardizing production being one of the main difficulties). A Feb. 10, 2017 news item on phys.org describes how researchers at the Lawrence Livermore National Laboratory (LLNL) and other collaborators have recorded carbon nanotubes self-organizing,

For the first time, Lawrence Livermore National Laboratory scientists and collaborators have captured a movie of how large populations of carbon nanotubes grow and align themselves.

Understanding how carbon nanotubes (CNT) nucleate, grow and self-organize to form macroscale materials is critical for application-oriented design of next-generation supercapacitors, electronic interconnects, separation membranes and advanced yarns and fabrics.

A Feb. 9, 2017 LLNL news release, which originated the news item, provides more information about the research (Note: Links have been removed),

New research by LLNL scientist Eric Meshot and colleagues from Brookhaven National Laboratory (link is external) (BNL) and Massachusetts Institute of Technology (link is external) (MIT) has demonstrated direct visualization of collective nucleation and self-organization of aligned carbon nanotube films inside of an environmental transmission electron microscope (ETEM).

In a pair of studies reported in recent issues of Chemistry of Materials (link is external) and ACS Nano (link is external), the researchers leveraged a state-of-the-art kilohertz camera in an aberration-correction ETEM at BNL to capture the inherently rapid processes that govern the growth of these exciting nanostructures.

Among other phenomena discovered, the researchers are the first to provide direct proof of how mechanical competition among neighboring carbon nanotubes can simultaneously promote self-alignment while also frustrating and limiting growth.

“This knowledge may enable new pathways toward mitigating self-termination and promoting growth of ultra-dense and aligned carbon nanotube materials, which would directly impact several application spaces, some of which are being pursued here at the Laboratory,” Meshot said.

Meshot has led the CNT synthesis development at LLNL for several projects, including those supported by the Laboratory Directed Research and Development (LDRD) program and the Defense Threat Reduction Agency (link is external) (DTRA) that use CNTs as fluidic nanochannels for applications ranging from single-molecule detection to macroscale membranes for breathable and protective garments.

Here’s a link to and a citation for the both of the papers mentioned in the news release,

Measurement of the Dewetting, Nucleation, and Deactivation Kinetics of Carbon Nanotube Population Growth by Environmental Transmission Electron Microscopy by Mostafa Bedewy, B. Viswanath, Eric R. Meshot, Dmitri N. Zakharov, Eric A. Stach, and A. John Hart. Chem. Mater., 2016, 28 (11), pp 3804–3813 DOI: 10.1021/acs.chemmater.6b00798 Publication Date (Web): May 23, 2016

Copyright © 2016 American Chemical Society

Real-Time Imaging of Self-Organization and Mechanical Competition in Carbon Nanotube Forest Growth by Viswanath Balakrishnan, Mostafa Bedewy, Eric R. Meshot, Sebastian W. Pattinson, Erik S. Polsen, Fabrice Laye, Dmitri N. Zakharov, Eric A. Stach, and A. John Hart. ACS Nano, 2016, 10 (12), pp 11496–11504 DOI: 10.1021/acsnano.6b07251 Publication Date (Web): November 23, 2016

Copyright © 2016 American Chemical Society

Both papers are behind a paywall.

The researchers have also provided this image which allows you to appreciate the difference between a ‘scientific’ version of the work and an artistic version,

This transmission electron microscope image shows growth of a dense carbon nanotube population. Courtesy: LLNL

Gold nanoparticle self-assembly visualization at the Argonne National Laboratory (US)

There’s a Mar. 13, 2013 news item on phys.org which seems to have been written by someone who’s very technical,

The self-assembly of gold nanoparticles (Au NPs) coated with specific organic ions in water was observed by Center for Nanoscale Materials staff in the Nanobio Interfaces, Electronic & Magnetic Materials & Devices, and Nanophotonics groups at the Argonne National Laboratory using in situ transmission electron microscopy (TEM) equipped with a liquid cell. The Au NPs formed one-dimensional chains within a few minutes.

The originating March 2013 article is on an Argonne National Laboratory’s Center for Nanoscale Materials page,

The self-assembly of NPs attracts intense attention for its potential application in the fabrication of hybrid systems with collective properties from different types of materials. The observations provided here clearly elucidate the complex mechanism of charged NP self-assembly processes. They also paint a cautionary tale on using TEM in situ cells to imitate self-assembly processes in actual solution environments. [emphasis mine]

The hydrated electrons formed in radiolysis of water decrease the overall positive charge of cetyltrimethylammonium (CTA)-coated Au NPs. The NPs also were coated with negative citrate ions. (With citrate alone, however, the Au NPs remained steady in the liquid cell regardless of electron-beam intensity). The anisotropic attractive interactions, including dipolar and Van der Waals interactions, overcome the repulsion among the NPs and induce the assembly of NPs. The spatial segregation of different sizes of NPs as a result of electric field gradients within the cell was observed as well.

I’m not sure why the observations paint a cautionary tale. Perhaps a reader could enlighten me?

The researchers also provided an image,

Cetyltrimethylammonium-ion-coated gold nanoparticles before (top) and after (bottom) 500 seconds of electron-beam exposure inside a TEM liquid cell at 200 kV. Scale bar: 100 nm. [downloaded from http://nano.anl.gov/news/highlights/2013_gold_nanoparticles.html]

Cetyltrimethylammonium-ion-coated gold nanoparticles before (top) and after (bottom) 500 seconds of electron-beam exposure inside a TEM liquid cell at 200 kV. Scale bar: 100 nm. [downloaded from http://nano.anl.gov/news/highlights/2013_gold_nanoparticles.html]

For anyone who can understand the technical explanations, here’s a citation and a link to the research paper,

In Situ Visualization of Self-Assembly of Charged Gold Nanoparticles by Yuzi Liu, Xiao-Min Lin, Yugang Sun, and Tijana Rajh. J. Am. Chem. Soc., 2013, 135 (10), pp 3764–3767 DOI: 10.1021/ja312620e Publication Date (Web): February 22, 2013

Copyright © 2013 American Chemical Society

The paper is behind a paywall.