3,153 research outputs found
Nanoporous plasmonic coatings
No full textThe electrical and optical properties of mesoporous gold are compared to those of thin porous gold films and a simulated thin film made by randomly distributing voids in gold, until the voids fill 76% of film volume. All layers are electrically conducting but in some cases the critical percolation thresholds are close to zero, so conduction is possible at very high void content. Significant qualitative differences are apparent between the properties of mesoporous gold, and very thin sputtered gold containing voids, in plasmonic responses at optical frequencies and in dc resistance, both as a function of fill factor. The mesoporous films have an effective plasma frequency determined by void fill factor and structure, but do not support surface plasmons. In contrast thin porous gold layers display optical features associated with localized and de-localized surface plasmons. Sputtered porous gold is 2-dimensional and its percolation threshold requires a "Swiss-cheese" rather than particle cluster model. Thicker mesoporous layers have critical parameters consistent with very high connectivity, or equivalently large hyper-dimensionality. Our meso-gold samples display various hyper-dimensionalities from 3 to above 10
Observation of Magnetization Processes in Soft Magnetic Composite
No full textA magneto-optical imaging technique has been employed to visualize magnetization processes of soft magnetic composite material. The profiles of reflected light intensity of magneto-optical images at the sample surface were plotted. The results demonstrate that magnetooptical imaging is a sensitive tool to visualize magnetization process. The flux profiles obtained under conditions of perpendicular and tangential magnetizations indicate that the sample behaves as a collection of individual magnetized particles rather than as a uniform and continuous magnetic substance
Mesoporous Gold Sponge
No full textMesoporous gold sponge may be prepared by the removal of aluminium from AuAl2 by an alkaline leach. The
resulting material has nanoscale pores and channels, with a high specific surface area that can be exploited in
electrochemical applications. For example, the material could conceivably serve as the basis of a more sensitive
capacitive sensor or biosensor, as an electrode material for a high efficiency ultracapacitor, as the semi-transparent
current collector in a dye sensitised photovoltaic cell, or as the lithium-storage electrode in a lithium ion cell. The
properties of the sponge may be controlled by varying its density, pore size, and pore size distribution, factors
which are in turn controlled by the microstructure of the precursor compound and the conditions of deposition
Gold nanosphere-antibody conjugates for hyperthermal therapeutic applications
No full textGold nanoparticles can be conjugated with antibodies or other proteins, and the resulting composite particles will selectively attach to various kinds of biological material. Although exploitation of this for staining microscopy specimens is well known, there has recently been interest in attaching gold nanoparticles to live cells for therapeutic reasons. One motivation is that gold nanoparticles display a strong plasmon resonance with light, which can be exploited in principle for an 'in vivo' photothermal therapy. The treatment of cancer by this technique has recently received attention by others, but here we show how gold nanoparticle-based therapies can be developed to target live macrophage cells. We have employed 'active targeting', a scheme in which gold nanoparticles are functionalised with an antibody specific to the target macrophage cell. We describe how to prepare the conjugated particles, demonstrate that they will selectively attach 'in vitro' to their target macrophage cell but not to a non-target cell type and show that their presence renders the target cell susceptible to destruction by a low power laser
A comparison of fatigue crack growth of three alloy steels at elevated temperature
No full textFatigue cracks were grown in alloy steels by the use of a triangular loading waveform with a frequency of 1 Hz and an R-ratio of 0.1, and the crack growth rates were determined. The steel alloys Fe-1%Cr-0.5%Mo and Fe-1.5%Mn-0.8%Ni-0.5%Mo (SA508) were tested at 450 ° C, and Fe-1%Cr-0.5%Mo and Fe-0.5%Cr-0.5%Mo-0.25%V at 550 ° C. Statistical treatment of the results indicated that, over the range of alternating stress intensities applied, the fatigue crack growth rates were very similar for each pair of alloys tested. The use of the Paris Law to describe the rates of fatigue crack growth would have led to an erroneous conclusion in this regard, and a sigmoidal descriptive model is therefore proposed for the growth of fatigue cracks. With the use of a microcomputer, this model is not much more difficult to apply than the Paris Law, and gives a far better description of the results. Finally, a statistical method for the comparison of sets of data on fatigue crack growth is presented and demonstrated. © 1989
Shape Change and Color Gamut in Gold Nanorods, Dumbbells, and Dog Bones
No full textIt is shown here that deviations from prolate ellipsoidal shape have a significant effect on the
optical properties of gold nanorods. Transitions from rods to ‘dumbbell’, or ‘phi’-shaped
particles lead to a shift in the longitudinal plasmon peak in the blue and red directions
respectively. Development of ‘dog-bone’ shapes leads to a red-shift and to the development
of a third peak. A broad and flexible color gamut can be obtained
Thermal stresses and cracking in absorptive solar glazing
No full textThe emerging popularity of absorptive, as opposed to reflective, solar glazing coatings on windows has generated renewed interest in thermally induced cracking of glass structures. Here we analyse the stresses on glass coated with absorptive solar glazing films caused by uneven solar illumination. It is shown that the occasionally reported brittle fracture of such structures can be readily explained as being the result of differential thermal expansion of the glass. The magnitude of the effect is linearly proportional to the shading coefficient of the glass and is also influenced by the manner in which the glass is supported. © 2005 Elsevier Ltd. All rights reserved
Prospects for light-activated nano-devices based on shape-memory polymers
No full textThe recent development of new types of light-activated, conformation-changing polymers has stimulated much interest. These 'smart' materials offer new functionalities and may enable diverse novel devices. One possible application of these substances may be in optically-driven nanoscale actuators, especially in the case of devices in which a plasmon resonance in a precious-metal nanostructure is actively modulated. A one-way or two-way shape memory effect is possible, however, application at the nanoscale will necessitate certain design changes. Nanoscale devices based on these materials could conceivably be used for drug-release or to switch the spectral selectivity of a coating. © 2007 Society of Photo-Optical Instrumentation Engineers
Receiver Windowing Design for Narrowband Interference Mitigation in MB-OFDM UWB System
No full textIn 2005, the WiMedia Alliance working with the European Computer Manufacturers Association (ECMA) announced the establishment of the WiMedia MB-OFDM (Multiband Orthogonal Frequency Division Multiplexing) UWB radio platform as their global UWB standard. It was also chosen as the physical layer (PHY) of high data rate wireless specifications for high speed Wireless USB (W-USB), Bluetooth 3.0 and Wireless High-Definition Media Interface (HDMI). However, due to the low power and wide bandwidth nature of UWB systems, in-band narrowband interference (NBI) may hinder the receiver performance. This thesis presents an analysis of NBI impact on the MB-OFDM system for UWB communication. The intent of our analysis is to provide practical solutions for interference mitigation under different NBI models. In our work, a new receiver windowing for zero padding (ZP) OFDM system is proposed to reduce NBI spreading in the MB-OFDM UWB system. Simulations demonstrate the effectiveness of windowing under different NBI models.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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