New Online Portal: Imaging & Microscopy

November 20, 2009

Dear reader,

Effective immediately our news service you are used to find here has been transferred to our new Imaging & Microscopy website www.imaging-git.com.


New World Record in X-ray Microscopy

Oktober 5, 2009

Groundbreaking work by scientists from Switzerland, Finland and Germany has lead to a new world record in X-ray microscopy. For the first time ever, features below 10 nm in width were resolved.
Key to this new world record was doubling of the effective line density of FZP template (Fresnel Zone Plate, a key component of an X-ray microscope) by extremely conformal thin films created through the use of Atomic Layer Deposition (ALD). ALD work was carried out with a Picosun Sunale reactor at the premises of the University of Helsinki’s Laboratory of Inorganic Chemistry.
ALD is a thin film method which enables completely controlled growth of extremely conformal films through its signature self-limiting, sequential surface reactions. ALD produces complex layer structures with atomic level accuracy. ALD processes can be reproduced with stunning accuracy.
The group produced a modified FZP with structures based on the conformal deposition of high refractive index material by ALD onto the sidewalls of a pre-patterned template made from a low refractive index material. This new focusing structure achieves an unprecedented spatial resolution in X-ray microscopy. Line widths of down to 9 nm were successfully resolved.

Original publication:
Vila-Comamala J., Jefimovs K., Raabe J., Pilvi T., Fink R.H., Senoner M., Maassdorf A., Ritala M., David C.: Advanced thin film technology for ultrahigh resolution X.ray microscopy. Ultramicroscopy. 2009 Oct;109(11):1360-4. Epub 2009 Jul 15.

http://www.picosun.com


Cryo-electron Micoscopy Symposium at UCLA

September 24, 2009

The two-day Advanced Electron Microscopy in NanoMedicine Symposium from Friday, Oct. 2—Saturday, Oct. 3 at the California NanoSystems (CNSI) at UCLA brings together researchers from academia and industry to discuss cryo-electron microscopy, or cryoEM, an important new imaging tool with major applications for nanobiology and nanomedicine, particularly for understanding viruses and other macromolecular complexes. Researchers can use cryoEM to visualize a broad range of assemblies and nanometer-scale structures in three dimensions — from molecular to atomic resolution.
Organized by the Electron Imaging Center for Nanomachines (EICN) , a newly established CNSI core lab, the symposium will also serve as a venue for the public unveiling of the top-of-the-line Titan Krios cryoEM and Titan (S)TEM microscopes in the EICN lab.

For more information and to register for the event, visit: http://www.cnsi.ucla.edu/electron-microscopy/

http://www.newsroom.ucla.edu


Simultaneous Nanoscale Imaging of Surface and Bulk Atoms

September 23, 2009
Uranium single atoms (circled) and small crystallites on a carbon support imaged simultaneously using a scanning probe to produce forward scattering through the sample (top) and backward scattering emerging from the surface (bottom). Center panel shows superimposition of the two in red (bulk) and green (surface). Atoms not seen in the lower image are on the bottom surface of the support. Source: Brookhaven National Laboratory

Uranium single atoms (circled) and small crystallites on a carbon support imaged simultaneously using a scanning probe to produce forward scattering through the sample (top) and backward scattering emerging from the surface (bottom). Center panel shows superimposition of the two in red (bulk) and green (surface). Atoms not seen in the lower image are on the bottom surface of the support. Source: Brookhaven National Laboratory

Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, in collaboration with researchers from Hitachi High Technologies Corp., have demonstrated a new scanning electron microscope capable of selectively imaging single atoms on the top surface of a specimen while a second, simultaneous imaging signal shows atoms throughout the sample’s depth. This new tool, located at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), will greatly expand scientists’ ability to understand and ultimately control chemical reactions, such as those of catalysts in energy-conversion devices.
Like all scanning electron microscopes, the new tool probes a sample with an electron beam focused to a tiny spot and detects so-called secondary electrons emitted by the sample to reveal its surface structure and topography. Though this technique has been a workhorse of surface imaging in industrial and academic laboratories for decades, its resolution has left much to be desired because of imperfect focusing due to lens aberrations.
Using a newly developed spherical aberration corrector, the new tool corrects these distortions to create a smaller probe with significantly increased brightness.
The new device also employs specialized electron optics to channel the emitted secondary electrons to the detector. The result is a fourfold improvement in resolution to below one tenth of a nanometer — and thus, the ability to image single atoms.
Additional detectors, located below the sample, detect electrons transmitted through the sample, revealing details about the entire structure at the exact instant the “shutter” snapped to record each pixel of the surface image. This simultaneous imaging allows the scientists to correlate information in the two images to understand precisely what is happening on the surface and throughout the sample at the same time.
Because of its extreme sensitivity, the new microscope must be kept isolated from a range of environmental effects such as variations in temperature, mechanical vibrations, and electromagnetic fields. Even the slightest waft of air could cause distortions in the images.

Original publication:
Zhu Y., Inada H., Nakamura K., Wall J.: Imaging single atoms using secondary electrons with an aberration-corrected microscope. Nat Mater. 2009 Sep 20. [Epub ahead of print]

http://www.bnl.gov


Imaging Collagen with X-rays

September 21, 2009

Coherent X-ray Diffraction patterns of collagen in soft tissues have been measured for the first time by Dr Felisa Berenguer (London Centre for Nanotechnology) with her colleagues. This development opens doors to better understanding of living tissues like skin and bones, as well as the bio-mineralization processes which turn flexible collagen into semi-flexible cartilage and eventually into rigid bones. In a distant future, the understanding of the collagen structure will eventually lead to cures for of bone diseases, notably osteoporosis, or assist ongoing efforts to develop artificial skin.

Dr Berenguer is part of Prof Ian Robinson’s group in the London Centre for Nanotechnology. This group is developing methods of using the coherence properties of these X-rays for imaging materials on the nanoscale. They use new synchrotron X-ray sources with extremely high brightness such as the Diamond Light Source on the Harwell campus near Oxford. While new light lines at the Diamond Light Source are still under construction, the London Centre Nanotechnology operates one of the experimental out-stations of the Advanced Photon Source (APS), an X-ray synchrotron in Chicago, USA. The group is focusing its efforts on X-rays because this type of light has small wavelengths and is strongly penetrating into material. There is thus an opportunity for imaging physical structures in three dimensions with resolution well beyond that of the visible light microscope. The group is also developing phase-contrast methods that are sensitive to nanoscale strains, or the detailed packing arrangement of molecules in biological tissues.

Original publication:
Berenguer de la Cuesta F, Wenger MP, Bean RJ, Bozec L, Horton MA, Robinson IK. : Coherent X-ray diffraction from collagenous soft tissues. Proc Natl Acad Sci U S A. 2009 Aug 24. [Epub ahead of print]

http://www.london-nano.com

Diffraction pattern of collagen obtain by Dr Berenguer and al during the scope of this research. Source: London Centre for Nanotechnology

Diffraction pattern of collagen obtain by Dr Berenguer and al during the scope of this research. Source: London Centre for Nanotechnology


To Increase Imaging Efficiency in Cell Structure Studies

September 17, 2009

Scientists in the National Institute of Biomedical Imaging and Bioengineering (NIBIB) Laboratory of Bioengineering and Physical Science have developed a new technique, BF STEM tomography, that allows researchers to visualize fine details of cell structure three-dimensionally in thick sections, thus providing greater insight into how cells are organized and how they function.

Electron tomography is carried out at the nanoscale on individual cells. Conventionally, high-resolution imaging of biological specimens has been accomplished by cutting cells into thin sections (300 nanometers or less) and imaging each section separately. Although reconstructing an entire structure from thin sections is laborious, thin sections are used because images of thicker sections typically are blurred. Serial BF STEM tomography accomplishes the same work using fewer yet thicker specimen sections, leading to faster reconstruction of intact organelles, intracellular pathogens, and even entire mammalian cells.

Drs. Alioscka Sousa, Martin Hohmann-Marriott, Richard Leapman and colleagues in NIBIB, in collaboration with Dr. Joshua Zimmerberg and colleagues in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), demonstrated feasibility and advantages of BF-STEM tomography in a study of red blood cells infected with Plasmodium falciparum, a parasite that causes malaria. High-resolution 3D reconstructions of entire cells were generated by serially imaging just a few thick sections. The intricate system of red blood cell and parasite membranes, as well as several organelles, can be seen in detail.

Original publication:
Hohmann-Marriott MF, Sousa AA, Azari AA, Glushakova S, Zhang G, Zimmerberg J & Leapman RD.: Nanoscale 3D cellular imaging by axial scanning transmission electron tomography. Nature Methods, Published online: 30 August 2009 | doi:10.1038/nmeth.1367.

http://www.nih.gov


A New Glance on Microscopic Images

September 17, 2009

Atomic force microscopy is well-known even in the public as a versatile tool for the production of images on the nanoscale level. Kelvin probe force microscopy is a special type of this imaging technique named after Lord Kelvin. When brought to the market in 1991, a scientific description of how to interprete the images was delivered. To this, physicist Christine Baumgart, a doctoral student of the nanospintronics group at the research center Forschungszentrum Dresden-Rossendorf (FZD), has now added new features.

Christine Baumgart now discovered what exactly is measured by Kelvin probe force microscopy. It is the electric potential which is needed to move electrons or holes from the inside to the surface of a semiconductor. Her new findings will simplify the microscopic technique itself, and will lead to unambiguous and reproducible results concerning the structure and electronic properties of samples. Also, Kelvin probe force microscopy, which has been used mainly in materials science and semiconductor physics so far, is likely to become more attractive for other areas like biotechnology.

But how exactly does a Kelvin probe force microscope work? The tip is deflected by the electrostatic force between cantilever and sample when moved over the sample. By applying bias to the sample, electrons and holes are moved to the surface of the semiconductor and the electrostatic force decreases. The cantilever moves back to its original position and the applied bias is stored as the signal measured. To be more precise, there is a quantitative relation between the measured Kelvin bias and the difference between the calculated Fermi energy and respective semiconductor band edge independent of the work function of the probing microscope tip. Thus, Christine Baumgart’s novel explanation of how the Kelvin probe force microscope works elucidates why the signal depends on the bias necessary for injecting majority charge carriers towards the interface between insulator and semiconductor.

Original publication:

Baumgart C., Helm M., Schmidt H., (2009): Quantitativ dopant profiling in semiconducters: A Kelvin probe force microscopy model. DOI: 10.1103/PhysRevB.80.085305.

https://www.fzd.de

Schematic drawing of a Kelvin probe force microscopy probe above a doped semiconductor with a thin oxide layer (grey blue atomic layer). Occupied surface states at the interface between the oxide layer and the semiconductor are animated in red and the same number of unscreened dopant atoms is animated in dark blue. Left: The resulting asymmetric electric dipole causes the deflection of the probe. Center: By applying a bias mobile majority charge carriers are injected into the semiconductor (animated in orange) and screen the unscreened ionized dopant atoms. Right:  As a result the electrostatic force onto the cantilever vanishes. The cantilever moves back to its normal position. The applied bias is measured and depends on the concentration of dopant atoms. Picture: Sander Münster, Kunstkosmos

Schematic drawing of a Kelvin probe force microscopy probe above a doped semiconductor with a thin oxide layer (grey blue atomic layer). Occupied surface states at the interface between the oxide layer and the semiconductor are animated in red and the same number of unscreened dopant atoms is animated in dark blue. Left: The resulting asymmetric electric dipole causes the deflection of the probe. Center: By applying a bias mobile majority charge carriers are injected into the semiconductor (animated in orange) and screen the unscreened ionized dopant atoms. Right: As a result the electrostatic force onto the cantilever vanishes. The cantilever moves back to its normal position. The applied bias is measured and depends on the concentration of dopant atoms. Picture: Sander Münster, Kunstkosmos


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