2,404 research outputs found
Plasmonic modes of gold nano-particle arrays on thin gold films
Regular arrays of metal nanoparticles on metal films have tuneable optical
resonances that can be applied for surface enhanced Raman scattering or
biosensing. With the aim of developing more surface selective geometries we
investigate regular gold nanoparticle arrays on 25nm thick gold films, which
allow to excite asymmetric surface plasmon modes featuring a much better field
confinement compared to the symmetric modes used in conventional surface
plasmon resonance setups. By optical extinction spectroscopy we identify the
plasmonic modes sustained by our structures. Furthermore, the role of thermal
treatment of the metal structures is investigated, revealing the role of
modifications in the crystalline structure of gold on the optical properties.Comment: 8 pages, 3 figure
Adsorption of 2,2 '-dithiodipyridine as a tool for the assembly of silver nanoparticles
Silver nanostructured thin films stabilized by 2,2â-dithiodipyridine (2dtpy) were prepared. The Ag nanoparticles
were obtained by treating the complex [Ag(2dtpy)]NO3 with NaBH4 in a methanolâtoluene mixture. The films
were transferred to borosilicate glass slips by a dip-coating method and were found to consist of Ag
nanoparticles possibly linked via 2dtpy molecules. Surface-enhanced Raman scattering (SERS) studies have
offered the possibility of investigating the adsorption modes of 2dtpy at the Ag nanoparticle surfaces in the
fil
Transport in single-molecule transistors: Kondo physics and negative differential resistance
We report two examples of transport phenomena based on sharp features in the
effective density of states of molecular-scale transistors: Kondo physics in
C-based devices, and gate-modulated negative differential resistance
(NDR) in ``control'' devices that we ascribe to adsorbed contamination. We
discuss the need for a statistical approach to device characterization, and the
criteria that must be satisfied to infer that transport is based on single
molecules. We describe apparent Kondo physics in C-based single-molecule
transistors (SMTs), including signatures of molecular vibrations in the Kondo
regime. Finally, we report gate-modulated NDR in devices made without
intentional molecular components, and discuss possible origins of this
property.Comment: 15 pages, 8 figures. To appear in Oct. 2004 issue of Nanotechnology,
proceedings of International Conference on Nanoscale Devices and Systems
Integratio
Single-crystal silver nanowires: Preparation and Surface-enhanced Raman Scattering (SERS) property
Ordered Ag nanowire arrays with high aspect ratio and high density
self-supporting Ag nanowire patterns were successfully prepared using
potentiostatic electrodeposition within the confined nanochannels of a
commercial porous anodic aluminium oxide (AAO) template. X-ray diffraction and
selected area electron diffraction analysis show that the as-synthesized
samples have preferred (220) orientation. Transmission electron microscopy and
scanning electron microscopy investigation reveal that large-area and ordered
Ag nanowire arrays with smooth surface and uniform diameter were synthesized.
Surface-enhanced Raman Scattering (SERS) spectra show that the Ag nanowire
arrays as substrates have high SERS activity.Comment: 5 pages, 4 figure
The doctrine of self-determination
Poverty and underdevelopment plague millions of people in the world today. Interestingly, the 800 million people that are currently living on less than a dollar a day correlate very closely with the 750 million people who were under colonial subjugation in 1945. In an effort to understand how the disparities in development came about, the theory of self-determination will be defined and historically assessed. Through qualitative evaluation of the principle and history of self-determination and case studies on three key regions that have never known genuine self-rule, it will become clear that the doctrine of self-determination only ever existed in rhetoric. Resource trap theory will be applied to those who have been plagued by outside rule and a general assessment of the state of self-determination in the world will be given. Lastly, an argument for what right transcendently will be given based on the current state of affairs and on Kantian ethics
Laser heating of a sintered oxide superconductor
Raman spectroscopy, in which a laser beam serves the dual role of exciting the Raman spectrum and annealing the sample, shows promise as a means of investigating oxygen effects in the oxide superconductors. A technique is described, based on measurements of the ratios of the areas of corresponding peaks in the anti-Stokes and Stokes spectra, whereby the temperature of the illuminated region of the sample can be determined as a function of the power in the incident laser beam. It is found that, for sintered samples of bismuth 2122, a small correction must be made for the departure from thermodynamic equilibrium induced by the pumping effect of the laser beam
Design Principles for Plasmonic Nanoparticle Devices
For all applications of plasmonics to technology it is required to tailor the
resonance to the optical system in question. This chapter gives an
understanding of the design considerations for nanoparticles needed to tune the
resonance. First the basic concepts of plasmonics are reviewed with a focus on
the physics of nanoparticles. An introduction to the finite element method is
given with emphasis on the suitability of the method to nanoplasmonic device
simulation. The effects of nanoparticle shape on the spectral position and
lineshape of the plasmonic resonance are discussed including retardation and
surface curvature effects. The most technologically important plasmonic
materials are assessed for device applicability and the importance of
substrates in light scattering is explained. Finally the application of
plasmonic nanoparticles to photovoltaic devices is discussed.Comment: 29 pages, 15 figures, part of an edited book: "Linear and Non-Linear
Nanoplasmonics
Annotated Bibliography of the Lake Charles, Mobile and Pensacola Harbor Approach Areas
Project 98 is a literature survey of the Lake Charles, Mobile and Pensacola Harbor Approach Areas sponsored by the US Hydrographic Offic
Radiative and non-radiative local density of states on disordered plasmonic films
We present numerical calculations of the Local Density of Optical States
(LDOS) in the near field of disordered plasmonic films. The calculations are
based on an integral volume method, that takes into account polarization and
retardation effects, and allows us to discriminate radiative and non-radiative
contributions to the LDOS. At short distance, the LDOS is dominated by
non-radiative channels, showing that changes in the spontaneous dynamics of
dipole emitters are driven by non-radiative coupling to plasmon modes. Maps of
radiative and non-radiative LDOS exhibit strong fluctuations, but with
substantially different spatial distributions
High-yield TiO(2) nanowire synthesis and single nanowire field-effect transistor fabrication
We report a facile method for synthesizing single-crystal rutile TiO 2 nanowires using atmospheric-pressure, chemical vapor deposition with Ti and TiO as precursors. The synthesis is found to depend critically on the predeposition of a layer of metallic Ti on the Ni catalysts layer. The omission of this step seems previously to have impeded the efficient synthesis of titania nanowires. Single-nanowire field-effect transistors showed the TiO2 nanowires to be n -type semiconductors with conductance activation energy of ???58 meV.open242
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