Bulletin of the American Physical Society
2006 Four Corners Section of the APS Fall Meeting
Friday–Saturday, October 6–7, 2006; Logan, Utah
Session H1: Nanoscale Physics |
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Chair: J.R. Dennison, Utah State University Room: Eccles Conference Center Room 216 |
Saturday, October 7, 2006 8:30AM - 9:06AM |
H1.00001: Toward Nanoscale Imaging of Biomolecular Systems Invited Speaker: Biological cells fabricate and assemble molecular building blocks into diverse molecular networks with striking complexity and functionality. As such, they are model integrated nanosystems whose study should yield important information for optimizing specific cellular functions, and for engineering functional synthetic nano-systems. To study biological systems in this context, it is crucial to observe their molecular machinery at work in a physiologically relevant environment. Currently, there are no techniques that can accomplish this.To study these systems at the molecular length scale, we have developed a near-field microscopy technique called tip-enhanced fluorescence microscopy (TEFM) that combines tapping-mode atomic force microscopy (AFM) with confocal fluorescence microscopy. Briefly, a strong axial field is produced at the focus of a laser beam and an AFM probe is positioned into the focus. This creates a localized dipole field at the tip apex, which can strongly excite fluorescence of nearby chromophores. Scanning the illuminated tip over a surface leads to high-fidelity fluorescence images with resolution limited only by the sharpness of the tip. In contrast to AFM, TEFM also provides single-molecule sensitivity and biochemical specificity when combined with fluorescence labeling. We recently demonstrated $\sim$10 nm resolution in TEFM images of quantum dots in air and we are now working to extend its capabilities to liquid imaging and to improve the resolution yet further by attaching carbon nanotubes to the ends of the AFM tips. [Preview Abstract] |
Saturday, October 7, 2006 9:06AM - 9:18AM |
H1.00002: Apertureless SNOM imaging of higher density samples Chun Mu, Chang'An Xie, Jonathan Cox, Ben Mangum, Jordan Gerton Various efforts in optical microscopy have been devoted to overcome the resolution limit imposed by classical light diffraction. Apertureless NSOM (ANSOM) techniques circumvent this limit by placing a sharp atomic force microscope (AFM) tip in the focus of a laser. In our scheme, a green He-Ne laser beam ($\lambda $=543 nm) was introduced into an inverted microscope equipped with a high numerical-aperture objective. A mask was used to produce an axially-polarized evanescent excitation field confined to a near diffraction-limited focus spot. The AFM tip will locally enhance the incident optical intensity. This enhanced field locally excites fluorescence on the sample. High-density quantum dot (QD) samples were dried onto a clean coverslip and then imaged using ANSOM. The fluorescence signal was modulated by a lock-in amplifier to suppress unwanted background from the excitation laser. The technique yielded spatial resolution near 10 nm with an optimized peak-peak oscillation amplitude of $\sim $30 nm. The signal-to-noise ratio (\textit{SNR}) of single QD within high-density ensembles was measured and individual particles were still easily resolved (\textit{SNR} $>$ 5) at a density of 14 QDs/$\mu $m$^{2}$. [Preview Abstract] |
Saturday, October 7, 2006 9:18AM - 9:30AM |
H1.00003: Functionalization and Metalization of Carbon Nanotube Mats Jacob Fluckiger, Dustin Lloyd, Lei Pei, Robert Davis An intriguing mechanical material would be an aluminum / carbon nanotube composite. It could combine the ultra high strength of carbon nanotubes with the ductility and manufacturability of aluminum. We are studying the formation of this metal matrix composite by electroplating aluminum on preformed carbon nanotube structures. In order to induce aluminum growth on the nanotubes, chemical modification of the nanotube surface is required. Surface chemical functionalization was performed by suspension and immersion in a succinic acid bath for the loose nanotubes and nanotube mats respectively. The active surfaces consisting of carboxyl groups should form a stable chemical bonds with the aluminum. Characterization of the chemically functionalized buckypaper by water contact angle and x-ray photo electron spectroscopy (XPS) measurements will be presented. Initial metallization studies will also be presented. [Preview Abstract] |
Saturday, October 7, 2006 9:30AM - 9:42AM |
H1.00004: Preparation of a dense, vertically-aligned carbon nanotube forest from colloidal iron nanoparticles David Hutchison, Richard Vanfleet, Robert Davis, Brian F. Woodfield, Juliana Boerio-Goates We report growth of vertically-aligned carbon nanotube (VACNT) forests from 10nm iron oxide nanoparticles in colloid form instead of the usual sputtering technique. The nanoparticles were suspended in water by sonication and dried onto a 20nm layer of alumina on silicon dioxide. VACNTs were grown by chemical vapor deposition using ethylene, hydrogen, and argon. Dense forests up to heights of 0.5 mm with uniform height have been grown. These structures have been shown by other groups to be useful as field emitters. [Preview Abstract] |
Saturday, October 7, 2006 9:42AM - 9:54AM |
H1.00005: Separation of Single-Walled Carbon Nanotubes by Density using Isopycnic Fractionation Michael Clemens, Tobias Hertel Single-Walled Carbon Nanotubes (SWNT) have attracted a significant amount of attention due in part to their nanoscale size and their optical and electrical properties. Research has shown that these properties can vary drastically with a sub-nanometer difference in SWNT diameters. Recent developments in SWNT synthesis have given rise to research towards the separation and characterization of SWNTs by diameter. I report a separation of SWNTs by diameter, and thus density, through micelle suspension and ultracentrifugation in density gradients prepared with iodixanol and water. The isopycnic layers produced by the ultracentrifugation were extracted using a fractionation method. I measure the degree of separation through absorption spectroscopy and photoluminescence spectroscopy of these fractions. [Preview Abstract] |
Saturday, October 7, 2006 9:54AM - 10:06AM |
H1.00006: The effects of carbon chain length on nano-crystal structure Hiram Conley, Uma Maran, Robert Davis, Peter Stang We have applied 3,6-Bis[\textit{trans}-Pt(Pet$_{3})$ $_{2}$Br]-9,10-bis(didecyloxy)phenanthrene self assembling nanocrystals to various surfaces using Langmuir- Blodgett technique. The long range order of the nanocrystals was then imaged using the atomic force microscope. We observed the formation of lines and mono-layers of the nanocrystals. [Preview Abstract] |
Saturday, October 7, 2006 10:06AM - 10:18AM |
H1.00007: Nanoscale defect architectures and their influence on material properties Branton Campbell Diffraction studies of long-range order often permit one to unambiguously determine the atomic structure of a crystalline material. Many interesting material properties, however, are dominated by nanoscale crystal defects that can't be characterized in this way. Fortunately, advances in x-ray detector technology, synchrotron x-ray source brightness, and computational power make it possible to apply new methods to old problems. Our research group uses multi-megapixel x-ray cameras to map out large contiguous volumes of reciprocal space, which can then be visually explored using graphics engines originally developed by the video-game industry. Here, I will highlight a few recent examples that include high-temperature superconductors, colossal magnetoresistors and piezoelectric materials. [Preview Abstract] |
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