In this study, the team from the University of Melbourne, Argonne’s Center for Nanoscale Materials in Illinois and the University of Chicago synthesized and studied tiny gold rods with a width 5000 times smaller than the thickness of a human hair.
The work will be published online this week in Nature Nanotechnology.
Professor John Sader from the Department of Mathematics and Statistics, University of Melbourne says that in the same way as a classroom ruler decreases its frequency of vibration when an eraser is attached, nanomechanical mass sensors work by measuring their change in vibration frequency as mass is added.
The sensitivity of such nanomechanical devices is intimately connected to how much energy they displace. So researchers needed to understand how damping (loss of energy) is transferred both to the fluid surroundings and within the nanostructures. With the lower the damping, the purer the mechanical resonance and higher the sensitivity.
It has not previously been possible to determine the rate at which vibrations in metal nanoparticle systems are damped, because of significant variations in the dimensions of the particles that have been studied – which masks the vibrations.
However, by studying a system of bipyramid-shaped gold nanoparticles with highly uniform sizes and shapes, the researchers overcame this limitation.
“Previous measurements of nanomechanical damping have primarily focused on devices where only one- or two-dimensions are nanoscale, such as long nanowires. Our measurements and calculations provide insight into how energy is dissipated in devices that are truly nanoscale in all three-dimensions,” says Professor Sader.
Illuminating these bipyramidal nanoparticle systems with an ultra-fast laser pulse, set them vibrating mechanically at microwave frequencies. These vibrations were long-lived and for the first time damping in these nanoparticle systems could be interrogated and characterized.
Moreover, the researchers separated out the portion of damping that is due to the material itself and that surrounding liquid for which they developed a parameter-free theoretical model that quantitatively explains this fluid damping.
2. FEI company's Titan G2, scanning/transmission electron microscope, sets new performance benchmark with resolution Down to 70 picometers (pm), while extending experimental flexibility for sample manipulation, imaging and analysis.
With Titan G2, users can choose the performance, application and information optimized for their material. We have further extended the minimum accelerating voltage down to 60 kiloVolt (kV), in response to intense research interest in low voltage microscopy results obtained on the first generation Titan family. The broadest available high tension range of 60-300 kV offered by the Titan G2 will allow our customers to make the best choice for each sample."
The Titan G2 60-300 Family offers the choice of second-generation spherical-aberration (Cs) probe and Cs image correction, and in the base configuration, it delivers 80pm specified resolution in both TEM and STEM operation. With the addition of novel FEI proprietary technology modules, such as a high brightness electron source, a monochromator and an environmentallyisolated microscope enclosure (Titan3(tm) G2 60-300), specified resolution improves to 70pm in either STEM or TEM modes.
3. FEI Company (Nasdaq:FEIC), a leading provider of three-dimensional (3D) molecular, cellular and atomic-scale imaging systems, today announced the new Falcon(tm) Direct Electron Detector for its Titan(tm) and Tecnai(tm) transmission electron microscopes (TEMs).
The Falcon is a direct electron detector with improved quantum efficiency, capturing more information from a given electron dose, and accelerating the rate at which the signal-to-noise ratio improves over the exposure period. The unique design of the Falcon detector overcomes the excessive electron beam deterioration that was previously the primary technical challenge in developing a practical direct electron detector.
The Falcon detector offers 4K by 4K resolution and works in tandem with a CCD camera used for surveying and samples that are not dose sensitive. It is available for ordering in the fourth calendar quarter of 2009