Tag Archives: transmission electron microscopy

SINGLE (3D Structure Identification of Nanoparticles by Graphene Liquid Cell Electron Microscopy) and the 3D structures of two individual platinum nanoparticles in solution

It seems to me there’s been an explosion of new imaging techniques lately. This one from the Lawrence Berkelely National Laboratory is all about imaging colloidal nanoparticles (nanoparticles in solution), from a July 20, 2015 news item on Azonano,

Just as proteins are one of the basic building blocks of biology, nanoparticles can serve as the basic building blocks for next generation materials. In keeping with this parallel between biology and nanotechnology, a proven technique for determining the three dimensional structures of individual proteins has been adapted to determine the 3D structures of individual nanoparticles in solution.

A multi-institutional team of researchers led by the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), has developed a new technique called “SINGLE” that provides the first atomic-scale images of colloidal nanoparticles. SINGLE, which stands for 3D Structure Identification of Nanoparticles by Graphene Liquid Cell Electron Microscopy, has been used to separately reconstruct the 3D structures of two individual platinum nanoparticles in solution.

A July 16, 2015 Berkeley Lab news release, which originated the news item, reveals more details about the reason for the research and the research itself,

“Understanding structural details of colloidal nanoparticles is required to bridge our knowledge about their synthesis, growth mechanisms, and physical properties to facilitate their application to renewable energy, catalysis and a great many other fields,” says Berkeley Lab director and renowned nanoscience authority Paul Alivisatos, who led this research. “Whereas most structural studies of colloidal nanoparticles are performed in a vacuum after crystal growth is complete, our SINGLE method allows us to determine their 3D structure in a solution, an important step to improving the design of nanoparticles for catalysis and energy research applications.”

Alivisatos, who also holds the Samsung Distinguished Chair in Nanoscience and Nanotechnology at the University of California Berkeley, and directs the Kavli Energy NanoScience Institute at Berkeley (Kavli ENSI), is the corresponding author of a paper detailing this research in the journal Science. The paper is titled “3D Structure of Individual Nanocrystals in Solution by Electron Microscopy.” The lead co-authors are Jungwon Park of Harvard University, Hans Elmlund of Australia’s Monash University, and Peter Ercius of Berkeley Lab. Other co-authors are Jong Min Yuk, David Limmer, Qian Chen, Kwanpyo Kim, Sang Hoon Han, David Weitz and Alex Zettl.

Colloidal nanoparticles are clusters of hundreds to thousands of atoms suspended in a solution whose collective chemical and physical properties are determined by the size and shape of the individual nanoparticles. Imaging techniques that are routinely used to analyze the 3D structure of individual crystals in a material can’t be applied to suspended nanomaterials because individual particles in a solution are not static. The functionality of proteins are also determined by their size and shape, and scientists who wanted to image 3D protein structures faced a similar problem. The protein imaging problem was solved by a technique called “single-particle cryo-electron microscopy,” in which tens of thousands of 2D transmission electron microscope (TEM) images of identical copies of an individual protein or protein complex frozen in random orientations are recorded then computationally combined into high-resolution 3D reconstructions. Alivisatos and his colleagues utilized this concept to create their SINGLE technique.

“In materials science, we cannot assume the nanoparticles in a solution are all identical so we needed to develop a hybrid approach for reconstructing the 3D structures of individual nanoparticles,” says co-lead author of the Science paper Peter Ercius, a staff scientist with the National Center for Electron Microscopy (NCEM) at the Molecular Foundry, a DOE Office of Science User Facility.

“SINGLE represents a combination of three technological advancements from TEM imaging in biological and materials science,” Ercius says. “These three advancements are the development of a graphene liquid cell that allows TEM imaging of nanoparticles rotating freely in solution, direct electron detectors that can produce movies with millisecond frame-to-frame time resolution of the rotating nanocrystals, and a theory for ab initio single particle 3D reconstruction.”

The graphene liquid cell (GLC) that helped make this study possible was also developed at Berkeley Lab under the leadership of Alivisatos and co-author Zettl, a physicist who also holds joint appointments with Berkeley Lab, UC Berkeley and Kavli ENSI. TEM imaging uses a beam of electrons rather than light for illumination and magnification but can only be used in a high vacuum because molecules in the air disrupt the electron beam. Since liquids evaporate in high vacuum, samples in solutions must be hermetically sealed in special solid containers – called cells – with a very thin viewing window before being imaged with TEM. In the past, liquid cells featured silicon-based viewing windows whose thickness limited resolution and perturbed the natural state of the sample materials. The GLC developed at Berkeley lab features a viewing window made from a graphene sheet that is only a single atom thick.

“The GLC provides us with an ultra-thin covering of our nanoparticles while maintaining liquid conditions in the TEM vacuum,” Ercius says. “Since the graphene surface of the GLC is inert, it does not adsorb or otherwise perturb the natural state of our nanoparticles.”

Working at NCEM’s TEAM I, the world’s most powerful electron microscope, Ercius, Alivisatos and their colleagues were able to image in situ the translational and rotational motions of individual nanoparticles of platinum that were less than two nanometers in diameter. Platinum nanoparticles were chosen because of their high electron scattering strength and because their detailed atomic structure is important for catalysis.

“Our earlier GLC studies of platinum nanocrystals showed that they grow by aggregation, resulting in complex structures that are not possible to determine by any previously developed method,” Ercius says. “Since SINGLE derives its 3D structures from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.”

The next step for SINGLE is to recover a full 3D atomic resolution density map of colloidal nanoparticles using a more advanced camera installed on TEAM I that can provide 400 frames-per-second and better image quality.

“We plan to image defects in nanoparticles made from different materials, core shell particles, and also alloys made of two different atomic species,” Ercius says. [emphasis mine]

“Two different atomic species?”, they really are pushing that biology analogy.

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

3D structure of individual nanocrystals in solution by electron microscopy by Jungwon Park, Hans Elmlund, Peter Ercius, Jong Min Yuk, David T. Limme, Qian Chen, Kwanpyo Kim, Sang Hoon Han, David A. Weitz, A. Zettl, A. Paul Alivisatos. Science 17 July 2015: Vol. 349 no. 6245 pp. 290-295 DOI: 10.1126/science.aab1343

This paper is behind a paywall.

Physics and coral skeletons at the nanoscale

Given that today, Oct. 31, 2013, is Hallowe’en, it seems thematically appropriate to be talking about skeletons, in this case, coral skieleton. An Oct. 29, 2013, news item on Nanowerk profiles the research (Note: A link has been removed),

An international team of scientists, led by physicists from the University of York, has shed important new light on coral skeleton formation.

Their investigations (“Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites”), carried out at the nanoscale, provide valuable new information for scientists and environmentalists working to protect and conserve coral from the threats of acidification and rising water temperatures.

The Oct. 29, 2013 University of York (UK) news release, which originated the news item, describes coral and what the scientists were looking for,

As corals grow, they produce limestone – calcium carbonate – skeletons which build up over time into vast reefs. The skeleton’s role is to help the coral’s upper living biofilm to move towards the light and nutrients.

Understanding the calcification mechanism by which these skeletons are formed is becoming increasingly important due to the potential impact of climate change on this process.

The scientists looked at the smallest building blocks that can be identified – a microstructure called spherulites – by making a thin cross-section less than 100 nanometres in thickness of a skeleton crystal. They then used Transmission Electron Microscopy (TEM) to analyse the crystals in minute detail.

The TEM micrographs revealed three distinct regions: randomly orientated granular, porous nanocrystals; partly oriented nanocrystals which were also granular and porous; and densely packed aligned large needle-like crystals.

These different regions could be directly correlated to times of the day – at sunset, granular and porous crystals are formed, but as night falls, the calcification process slows down and there is a switch to long aligned needles.

“It has been suspected for some time that the contrast bands seen in crystals in optical images were daily bands. Through our research we have been able to show what the crystals actually contain and the differences between day and night crystals.” [said corresponding author Renée van de Locht,]

I know coral is important but I didn’t know why (from the news release),

Corresponding author Renée van de Locht, a final-year PhD student with the Department of Physics at the University of York, says, “Coral plays a vital role in a variety of eco-systems and supports around 25 per cent of all marine species. In addition, it protects coastlines from wave erosion and plays a key role in the fisheries and tourism industries. However, the fundamental principles of coral’s skeleton formation are still not fully understood.

While the researchers are concerned about climate change and ocean acidification, there are other agendas being pursued as well (from the news release),

The York researchers are now turning their attention to looking directly at the effects of acidification. Their latest research is looking at five-day old coral larvae and compares a population from a normal seawater environment with another in an acidic environment.

The aim is to investigate the nanoscale impacts of the different environments at an early growth stage to assess how these could affect the whole colony and the bigger reef.

The coral research at York is also part of a much larger project looking at the hard and soft matter interface called the MIB – Interface between Materials and Biology – project. Nature has created materials that combine mineral (hard) and organic (soft) components in a way that provides properties that are extremely well suited to function – for example in bone, egg or mollusc shells. The collaborative project aims to develop a working understanding of how this control is worked out in natural systems, so that the same techniques can be used to develop new materials with specially tailored properties.

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

Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites by Renée van de Locht, Andreas Verch, Martin Saunders, Delphine Dissard, Tim Rixen, Aurélie Moya, and Roland Kröger. Journal of Structural Biology, Volume 183, Issue 1, July 2013, Pages 57–65 DOI:10.1016/j.jsb.2013.05.005

The paper is behind a paywall which includes a rental option, as well as, the option of paying for the paper outright. You can also try accessing the paper here at ResearchGate which requires that you register for a free account.

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.

 

All about the University of Calgary and its microscopy and imaging facility

A July 24, 2012 news item on Nanowerk features the the equipment and capabilities of …

The Calgary Microscopy and Imaging Facility (MIF) is a world-class university-wide facility housing transmission electron microscopy (TEM), scanning electron microscopy (SEM), advanced light microscopy, atomic force microscopy (AFM), including single cell force spectroscopy (SCFS), and advanced image processing for three-dimensional electron and light microscopy, directed by Professor Matthias Amrein.

Single cell force spectroscopy at the MIF has now attracted high profile research with three NanoWizard® AFM systems from JPK [Instruments], one of which is equipped with the CellHesion® module. Describing the work of the Calgary group, Professor Amrein says “While we do some work for the energy sector (to predict behaviour of nanoparticles injected into oil reservoirs) our main focus is medicine. We delve into very fundamental problems such as “how does a malaria red blood cell attach itself to a blood vessel” or “how does binding of a ligand to a cell surface receptor or contact of a crystalline surface with the plasma membrane drive lipid sorting and how will this lead to signalling” but then immediately apply it to a practical problem such as “how does contact of uric acid crystals with dendritic cells cause gout in affected joints and how can we prevent this occurrence?” We want to understand disease processes at a very fundamental level so we know how to intervene in the best possible way. For example, a chronic inflammatory disease such as gout or arteriosclerosis may be triggered by a very specific interaction of a particle (uric acid crystals, cholesterol crystals, amyloid plaque, …. ) and specific cell (dendritic cell, macrophage, T-cell, …). Understanding this interaction will lead to targeted treatment “block the interaction” rather than the non-specific dampening of inflammation such as by corticosteroids with its many well-documented side effects and limited efficacy.”

It’s always nice to get some information about activities in microscopy, etc. in Canada although I’m not sure what occasioned the news item/release.