Defect-induced activation of symmetry forbidden infrared resonances in individual metallic nanorods

International audienceWe report on the observation of second-order infrared (IR) plasmon resonances in lithographically prepared gold nanorods investigated by means of far-field microscopic IR spectroscopy. In addition to the fundamental antennalike mode, even and odd higher order resonances are observed under normal incidence of light. The activation of even-order modes under normal incidence is surprising since even orders are dipole-forbidden because of their centrosymmetric charge density oscillation. Performing atomic force microscopy and calculations with the boundary element method, we determine that excitation of even modes is enabled by symmetry breaking by structural deviations of the rods from an ideal, straight shape. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3437093

Nanometer-scale ablation with a table-top soft x-ray laser

Includes bibliographical references (page 3617).Ablation of holes with diameters as small as 82 nm and very clean walls was obtained in poly(methyl methacrylate) focusing pulses from a Ne-like Ar 46.9 nm compact capillary-discharge laser with a freestanding Fresnel zone plate diffracting into third order. These results demonstrate the feasibility of using focused soft x-ray laser beams for the direct nanoscale patterning of materials and the development of new nanoprobes

Validation of walking trails for the Urban Training of chronic obstructive pulmonary disease patients.

Purpose Accessible interventions to train patients with chronic obstructive pulmonary disease (COPD) are needed. We designed urban trails of different intensities (low, moderate and high) in different types of public spaces (boulevard, beach and park). We aimed to validate the trails' design by assessing the physiological response to unsupervised walking trails of: (1) different intensities in COPD patients, and (2) same intensity from different public spaces in healthy adults. Methods On different days and under standardized conditions, 10 COPD patients walked the three intensity trails designed in a boulevard space, and 10 healthy subjects walked the three intensity trails in three different spaces. We measured physiological response and energy expenditure using a gas analyzer. We compared outcomes across trails intensity and/or spaces using mixed-effects linear regression. Results In COPD patients, physiological response and energy expenditure increased significantly according to the trails intensity: mean (SD) peak O2 15.9 (3.5), 17.4 (4.7), and 17.7 (4.4) mL/min/kg (p-trend = 0.02), and MET-min 60 (23), 64 (26), 72 (31) (p-trend<0.01) in low, moderate and high intensity trails, respectively. In healthy subjects there were no differences in physiological response to walking trails of the same intensity across different spaces. Conclusions We validated the trails design for the training of COPD patients by showing that the physiological response to and energy expenditure on unsupervised walking these trails increased according to the predefined trails' intensity and did not change across trails of the same intensity in different public space. Walkable public spaces allow the design of trails that could be used for the training of COPD patients in the community

Ionic liquids at electrified interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules

Optical Properties of Colloidal Silver Nanowires

Silver nanowires are used in many applications, ranging from transparent conductive layers to Raman substrates and sensors. Their performance often relies on their unique optical properties that emerge from localized surface plasmon resonances in the ultraviolet. To tailor the nanowire geometry for a specific application, a correct understanding of the relationship between the wire’s structure and its optical properties is therefore necessary. However, while the colloidal synthesis of silver nanowires typically leads to structures with pentagonally twinned geometries, their optical properties are often modeled assuming a cylindrical cross-section. Here we highlight the strengths and limitations of such an approximation by numerically calculating the optical and electrical response of pentagonally twinned silver nanowires and nanowire networks. We find that our accurate modeling is crucial to deduce structural information from experimentally measured extinction spectra of colloidally synthesized nanowire suspensions and to predict the performance of nanowire-based near-field sensors. On the contrary, the cylindrical approximation is fully capable of capturing the optical and electrical performance of nanowire networks used as transparent electrodes. Our results can help assess the quality of nanowire syntheses and guide in the design of optimized silver nanowire-based devices

On the Optical Properties of Colloidal Silver Nanowires

Silver nanowires are used in many applications, ranging from transparent conductive layers to Raman substrates and sensors. Their performance often relies on their unique optical properties that emerge from localized surface plasmon resonances in the ultraviolet. To tailor the nanowire geometry for a specific application, a correct understanding of the relationship between the wire’s structure and its optical properties is therefore necessary. However, while the colloidal synthesis of silver nanowires typically leads to structures with pentagonally twinned geometries, their optical properties are often modeled assuming a cylindrical cross-section. Here we highlight the strengths and limitations of such an approximation by numerically calculating the optical and electrical response of pentagonally twinned silver nanowires and nanowire networks. We find that our accurate modeling is crucial to deduce structural information from experimentally measured extinction spectra of colloidally synthesized nanowire suspensions and to predict the performance of nanowire-based near-field sensors. On the contrary, the cylindrical approximation is fully capable of capturing the optical and electrical performance of nanowire networks used as transparent electrodes. Our results can help assess the quality of nanowire syntheses and guide in the design of optimized silver nanowire-based devices

Wear studies and cutting tests of Ti-Al-N-C nanocomposite coatings in milling operations - technical communication

New carbon-based nanostructured composite coatings of the material system Ti-Al-N-C were deposited on cemented carbide milling tools, and their feasibility for selected dry high-speed machining operations was assessed. For this purpose, wear studies with instrumented cutting machines in dry cutting tests were carried out in milling operations on Uddeholm hardened steels (AISI H13, and, AISI A2, respectively). The tools were coated in an industrial sputtering machine of the Hauzer HTC 625 type. The new nanocomposite coatings showed a good performance in the dry cutting operations and were benchmarked versus industrial state-of-the-art coatings