Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session D10: Focus Session: Physical Chemistry of Nanoscale System III |
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Sponsoring Units: DCP Chair: Yiping Zhao, University of Georgia Room: Baltimore Convention Center 302 |
Monday, March 13, 2006 2:30PM - 3:06PM |
D10.00001: Chemical Imaging and Lasing of Nanoparticle Systems Invited Speaker: Scanned probe microscopy techniques are developed to investigate nanoscale materials and time-domain processes in nanostructured devices. These include apertureless near field microscopy probing of islanded semiconductor films, confocal microscopy ultrafast pump-probe experiments to interrogate stimulated emission processes in ZnO tetrapod species, and single pulse CARS microscopy using phase-shaped ultra-broad-band pulses for rapid spatial and spectral analysis of soft condensed matter. Apertureless near field microscopy studies of InN islands have revealed contrast mechanisms due to the real and imaginary parts of the index of refraction, providing measurements of nanometer size Ga metal islands and InGaN and InN islands on GaN. Pickup of gold nanoparticles permits tip enhancements with resolution of the electric field phase in the images. Ultrafast laser, differential gain experiments on ZnO stimulated emission in nanowires and tetrapods are performed to measure the timescales and ratios of the electron-hole plasma and exciton mechanisms during lasing in nanostructured materials. Two novel types of measurements are addressed, stimulated emission dumping and upconversion probing methods. A single pulse CARS microscopy instrument using an ultrafast laser and phase control with interferometric detection produces complete Raman spectra while spatially scanning. Polymer domains have been analyzed with vibrational spectral sensitivity. The merger of optical techniques with scanned probe methods to investigate nanoscale features is considered in relation to the scientific requirements for measurements and the results for each system. [Preview Abstract] |
Monday, March 13, 2006 3:06PM - 3:18PM |
D10.00002: Spectroscopic Near-Field Imaging of Flat Gold Nanoparticles L.A. Bumm, D.H. Dahanayaka, D.W. Kelle, D.J. Wasielewski, E.S. Day, D.R. White, B.S. Prall, M. Achermann, V.I. Klimov Using a white-light near-field scanning optical microscope (NSOM) we demonstrate near-field imaging and local plasmon spectroscopy of flat gold nanoparticles (FGNPs). These nanoparticles are atomically-flat single crystal plates with well defined shapes ranging from equilateral triangles to regular hexagons, which include intermediate truncated triangle shapes. NSOM images reveal the FGNP plasmon mode structure and its dependence on FGNP size and shape. Moreover, spatially resolved spectroscopy shows position dependent coupling to different plasmon modes. [Preview Abstract] |
Monday, March 13, 2006 3:18PM - 3:30PM |
D10.00003: Characterization of Palladium and Gold Nanoparticles Using X-ray Reflectivity, EXAFS and Electron Microscopy. Yuan Sun, Anatoly Frenkel, Rebecca Isseroff, Cheryl Shonbrun, Michelle Forman, Kwanwoo Shin, Tadanori Koga, Henry White, Miriam Rafailovich, Jonathan Sokolov We compared the characteristics of thiolate Pd and Au nanoparticles synthesized by 1-phase and 2-phase methods. HRTEM showed that the 1-phase Pd particles had an ordered core surrounded by a disordered shell structure while the 2-phase Pd particles appeared to be crystalline throughout; and multiple twinning existed in both the 1-phase and 2-phase Au particles. EXAFS measurements revealed that Pd particles contained large amount of disordered Pd-S compounds while the 1-phase Au particles have a larger fraction of amorphous or defective structures and higher grafting density of thiol chains than the 2-phase Au particles. Lattice expansion was found in the Pd particles, compared with lattice contraction in the Au particles. Only the 2-phase Pd and Au particles spread at the air/water interface and formed Langmuir films, which were deposited onto solid substrates and examined by x-ray reflectivity and EXAFS. [Preview Abstract] |
Monday, March 13, 2006 3:30PM - 4:06PM |
D10.00004: "CARS microscopy - Seeing the invisibles" Invited Speaker: |
Monday, March 13, 2006 4:06PM - 4:18PM |
D10.00005: Probe single cyanine dye molecules' photo isomerization. Zih-Hao Chen, Chang-Yeh Lee, Chao-Kuei Lee, Yu-Tsu Chuang, Jui-Hung Hsu Cyanine dyes are interested in the photosensitization, nonlinear optics, and their photophysical and photochemical behaviors. In particular, cyanine molecules, like DiI, plays an important role in single molecule fluorescence investigations. The high photo-stability, good QE, and low inter-system crossing rates, make it an good example for the single molecule investigations. We present the single molecule fluorescence investigation on the DiI molecules. In the investigation, we observe some (but not all) molecules exhibits reversible and quasi-stepwise polarization change. The decay dynamics is also changed correspondingly. Clear on-off blinking behaviors indicate the change in polarization from a single molecule, rather than the background noise, and we speculate it as the photo isomerization of the dye molecule. More detail analysis indicates some isomerization occurred at the singlet excited states, and it takes longer timescale ($>$ ms) than expected. [Preview Abstract] |
Monday, March 13, 2006 4:18PM - 4:30PM |
D10.00006: Conductive probe AFM investigation on monolayer films of colloidal CdSe quantum dots Itaru Kamiya, Ichiro Tanaka, Risa Wada, Masayo Arimoto, Kazuyuki Uno, Tomohiro Hayashi, Masahiko Hara The opto/electronic properties of single quantum dots (QDs) have attracted much attention due to their potential for applications to various future devices. We have been employing conductive probe AFM for measuring quantized energy levels of single QDs prepared by colloidal synthesis [1]. In contrast to measurements on QDs prepared by MBE [2], a difficulty we suffered was interaction between the probe and the colloidal QDs. We have shown that the use of conductive CNT tips can prevent such problems [3]. Here, we show that the use of monolayer films of close-packed colloidal QDs allows us to perform stable conduction measurements even with standard probes. Thin films of 1-2nm of Ti followed by 20nm of Pt were sputtered on Si(001) substrates, whereon monolayer CdSe QD films were prepared by horizontal adsorption. The nearly close-packed QDs are stably attached to the substrate, enabling us to perform local conduction measurement using AFM without tip-QD interaction. We report the film formation, and the conduction features due to the single QDs. [1] I.Tanaka, \textit{et al.}, Surf.Sci. \textbf{532-535}, 801 (2003). [2] I.Tanaka, \textit{et al.}, Appl.Phys.Lett. \textbf{74}, 844 (1999). [3] I.Tanaka, \textit{et al.}, Jpn.J.Appl.Phys. \textbf{44}, L249 (2005). [Preview Abstract] |
Monday, March 13, 2006 4:30PM - 4:42PM |
D10.00007: Ballistic Electron Emission Spectroscopy Studies of Gold Nanocrystals Sameh Dardona, Jianfei Shao, Ryan Price, Robert Whetten, Phillip First We report experimental measurements of ballistic electron emission spectroscopy (BEES) on single gold nanocrystals. Nanocrystals with core diameters from 1 nm to 3 nm were chemically attached to a 10-nm thick gold film that was vapor-deposited on a silicon substrate. Low temperature (77 K) scanning tunneling microscopy and spectroscopy were used to image and identify nanocrystals prior to BEES measurements. A comparison of BEES spectra acquired by tunneling through a nanocrystal with those acquired by tunneling directly to the gold film, shows attenuation of the BEES signal by a factor of typically 4-10. From a simple rate equation, electron relaxation times in these gold nanocrystals are estimated to be of order 10 picoseconds. [Preview Abstract] |
Monday, March 13, 2006 4:42PM - 4:54PM |
D10.00008: Neutron diffraction and thermodynamics of deuterium adsorption in amorphous carbon materials with a uniform pore network. Lillian Frazier, Tom Arnold, Thomas Hansen, Miguel Gonzalez, David Martin y Marreo, Sheng Dai, Zuojain Li, David Beach, John Z. Larese A coordinated thermodynamic and neutron diffraction investigation of the sorption properties of D2 within an amorphous carbon material with a uniform, close-packed network of open pores has been undertaken. The volumetric adsorption studies are used to determine the gas capacity, the heat of adsorption and as a guide to the neutron diffraction experiments. By combining the results of the thermodynamic measurements with the findings in the structural measurements a precise description of structure of the adsorbed phase as a function of gas filling is possible. Because the pores in these carbon materials are unequivocally open these findings have a direct impact on the interpretation of earlier adsorption and diffraction experiments involving carbon nanotubes. [Preview Abstract] |
Monday, March 13, 2006 4:54PM - 5:06PM |
D10.00009: Adsorption properties of amorphous carbon materials with a uniform pore network. Richard E. Cook, Lillian Frazier, Sami Chanaa, Andrea E. Freitag, Sheng Dai, Zuojiang Li, David Beach, John Z. Larese There has been increasing interest in various forms of high surface area carbon materials, such as buckyballs, nanotubes, and carbon black, because of their potential applications as support for catalysts, electrode materials in fuel cells, gas storage devices and as a component of nano-composites. The underlying mechanism for most of these applications involves adsorption and transport of molecules on the carbon surface. Understanding the details of the interaction potential for different adsorbate molecules with these carbon materials is an important step for tailor-making application-specific materials. The adsorption properties of a carbon material with a uniform, close packed pore distribution of approximately 2.5nm were examined using high resolution adsorption isotherms with different adsorbates. By varying the size of the adsorbate molecule we hope to learn about the potential energy surface offered by these materials and gain a keen insight into the role played by the relative surface curvature on the adsorption properties. Volumetric adsorption isotherms of H2, D2, Ar, N2, H2O, CH4, and Xe were recorded and the results will be presented. Thermodynamic properties derived from these adsorption isotherms will also be discussed. [Preview Abstract] |
Monday, March 13, 2006 5:06PM - 5:18PM |
D10.00010: Sonoelectrochemical Approach Towards Nanostructures Clemens Burda, Xiaofeng Qiu We will report on the sonoelectrochemical synthesis of nanostructured semiconductor materials. The talk will focus on the control of the nanostructure size, shape, and composition using sonolectrochemistry as a versatile synthesis tool. The synthesis of targeted nanostructures requires thorough control of the redox chemistry during the growth process. The composition of the product can be controlled by changing the initial metal-ligand concentration. Futhermore, the properties of the novel materials will be discussed. Powder X-ray diffraction of the products confirmed the compositional change in the nanomaterials. Control of the involved sonoelectrochemistry also allows for the formation of highly monodispersed 1-D Nanorods. Qiu, Xiaofeng; Lou, Yongbing; Samia, Anna C. S.; Devadoss, Anando; Burgess, James D.; Dayal, Smita; Burda, Clemens. \textbf{PbTe nanorods by sonoelectrochemistry.} Angewandte Chemie, International Edition (2005), 44(36), 5855-5857. Qiu, Xiaofeng; Burda, Clemens; Fu, Ruiling; Pu, Lin; Chen, Hongyuan; Zhu, Junjie. \textbf{Heterostructured Bi2Se3 Nanowires with Periodic Phase Boundaries.} Journal of the American Chemical Society (2004), 126(50), 16276-16277. [Preview Abstract] |
Monday, March 13, 2006 5:18PM - 5:30PM |
D10.00011: Optical properties of single solution based semiconductor nanowires Masaru Kuno, Vladimir Protasenko The optical properties of solution based nanowires are studied using single molecule microscopy. Particular emphasis is placed on CdSe nanowires with diameters at or below 10 nm and lengths exceeding 1-10 microns. For comparison the bulk exciton Bohr radius is 5.6 nm. These wires therefore exhibit confinement effects as seen by blueshifts, both in the ensemble linear absorption and band edge emission. No deep trap emission is seen. Furthermore, branched nanowires with tripod, v-shape and y-shape morphologies can be made using the same solution based chemistry. In all cases, unusual intrawire spectral heterogeneity is observed in both the spectral position and linewidth. Fluorescence intermittency within the wire is also observed and has been shown to exhibit power law on-time and off-time probability densities. Possible explanations for this intrawire heterogeneity include dielectric contrast effects as well as more intrinsic causes due to zincblende/wurtzite phase admixtures present in the wires. However, such explanations do not explain any of the observed fluorescence dynamics. Complicating these (and other) possible explanations are recent experiments we have conducted, which show that external electric fields can modulate both the spatial position and intensity of the nanowire emission. [Preview Abstract] |
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