المؤلفون: Pauchard, Ludovic, Giorgiutti-Dauphiné, Frédérique, McIlroy, David

المصدر: Journal of Applied Physics; 4/28/2022, Vol. 131 Issue 16, p1-9, 9p

مصطلحات موضوعية: NANOSTRUCTURES, GEOMETRY

مستخلص: We study nanostructured films made of helical nanowires and nanosprings, which provide remarkable mechanical behavior. When subjected to wetting and drying processes, these films crack like most coatings. However, beyond the great ability of these films to shrink, the cracks partially close when these films are no longer mechanically stressed. While for conventional coatings about 20 % of the crack opening is relieved, more than 80 % of the crack opening is relieved in films of nanosprings when the film is unloaded. We show here that this quasi-reversibility is related to (i) the high compliance of the material, (ii) the low energy consumed by plasticity, and (iii) the high deformability of the film components, e.g., the nanosprings. These results are compared to the case of usual particulate films. [ABSTRACT FROM AUTHOR]

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المؤلفون: Dice, Nathan, Austin, Aaron J., McIlroy, David

المصدر: Journal of Applied Physics; 9/28/2021, Vol. 130 Issue 12, p1-7, 7p

مصطلحات موضوعية: PHASE separation, POLARITONS, PLASMONICS, EUTECTICS, METAMATERIALS, CONDUCTION bands, SURFACE morphology

مستخلص: Novel Au mesostructures with a polyhedron shape, henceforth referred to as pyramids, are produced by annealing in vacuo an Au thin film on a Si(100) substrate. Gold diffusion and incorporation into pyramids is a function of the thickness of the Au film, the annealing temperature, and the vacuum pressure. The Au pyramids have unique surface morphologies due to the presence of channels and plateaus, where channels are cut into the surface of the pyramids and plateaus are the surfaces between adjacent channels. The bulk of the pyramids consists of Au with cavities that are devoid of Au or Si. Normalized energy dispersive spectroscopy of intact regions of the surface are 98.1 wt. % Au and 1.9 wt. % Si, while the bottom of the channels are 85.7 wt. % Au and 14.3 wt. % Si. Therefore, one step in the growth process is the formation of an Au–Si eutectic. The low concentration of Si in the solid regions of the pyramid and its high concentration in the walls of the cavities are indicative of phase separation of the Au–Si eutectic. The pyramids are oriented in the same direction relative to one another and are a consequence of eutectic formation-induced etching of the Si(100) surface. The scattering spectrum (non-specular reflectivity) of the Au pyramids consists of two very strong surface plasmon polariton states that correspond to excitation from the Au d-bands to the sp conduction bands. The surface morphology produces linearly polarized reflected light. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Tantawy, Hesham Ramzy, Kengne, Blaise-Alexis F., McIlroy, David N., Tai Nguyen, Deukhyoun Heo, You Qiang, Aston, D. Eric

المصدر: Journal of Applied Physics; 2015, Vol. 118 Issue 18, p175501-1-175501-11, 11p, 1 Diagram, 3 Charts, 4 Graphs

مصطلحات موضوعية: POLYANILINES, ELECTROMAGNETIC shielding, X-ray photoelectron spectroscopy, RAMAN spectra, POLYMERIZATION

مستخلص: An in-depth analysis of the chemical functionality in HCl-doped polyaniline (PANI) nanopowders is discussed through interpretations of x-ray photoelectron spectra. The distinctions between three PANI sample types, produced under varied synthesis conditions, are compared on the basis correlations between newly collected electron spectra for chemical analysis (or also x-ray photoelectron spectroscopy) and electromagnetic (EM) shielding effectiveness (SE) within two frequency bands (100-1500 MHz and ~2-14GHz). The findings are discussed with reference to previous data analysis of electrical conductivities and Raman and UV-vis spectra analyzed from replicates of the same PANI nanopowders, where only the 8-12GHz range for SE was tested. They further corroborate previous results for limited-solvent conditions that enhance EM shielding. The three nanopowder types show distinctive differences in polaron, bipolaron, and polar lattice contributions. The collective findings describe the chemical connections between controlling and, most importantly, limiting the available solvent for polymerization with simultaneously doping and how it is that the newly developed solvent-limited approach for HCl-PANI nanopowders provides better shielding than traditionally solvent-rich methods by having more extended and perhaps even faster polaron delocalization than other PANI-based products. The maximum oxidation (50%) and doping (49%) levels obtained in the solvent-free nanopowders also produced the highest SE values of 37.3 ± 3.7 dB (MHz band) and 68.6 ± 4.6 dB (GHz band). [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Tantawy, Hesham Ramzy, Kengne, Blaise-Alexis F., McIlroy, David N., Tai Nguyen, Deukhyoun Heo, You Qiang, Aston, D. Eric

المصدر: Journal of Applied Physics; 2015, Vol. 118 Issue 17, p175501-1-175501-11, 11p, 1 Diagram, 3 Charts, 4 Graphs

مصطلحات موضوعية: X-ray photoelectron spectroscopy, ELECTROMAGNETIC shielding, POLYANILINES, RAMAN spectra, ULTRAVIOLET-visible spectroscopy, POLARONS

مستخلص: An in-depth analysis of the chemical functionality in HCl-doped polyaniline (PANI) nanopowders is discussed through interpretations of x-ray photoelectron spectra. The distinctions between three PANI sample types, produced under varied synthesis conditions, are compared on the basis correlations between newly collected electron spectra for chemical analysis (or also x-ray photoelectron spectroscopy) and electromagnetic (EM) shielding effectiveness (SE) within two frequency bands (100-1500 MHz and ~2-14GHz). The findings are discussed with reference to previous data analysis of electrical conductivities and Raman and UV-vis spectra analyzed from replicates of the same PANI nanopowders, where only the 8-12GHz range for SE was tested. They further corroborate previous results for limited-solvent conditions that enhance EM shielding. The three nanopowder types show distinctive differences in polaron, bipolaron, and polar lattice contributions. The collective findings describe the chemical connections between controlling and, most importantly, limiting the available solvent for polymerization with simultaneously doping and how it is that the newly developed solvent-limited approach for HCl-PANI nanopowders provides better shielding than traditionally solvent-rich methods by having more extended and perhaps even faster polaron delocalization than other PANI-based products. The maximum oxidation (50%) and doping (49%) levels obtained in the solvent-free nanopowders also produced the highest SE values of 37.3±3.7 dB (MHz band) and 68.6±4.6 dB (GHz band). [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Beaux, Miles F., Hass, Jamie, Bridges, Nathan, Kwon, Nam Hoon, McIlroy, David N.

المصدر: Journal of Applied Physics; Jul2011, Vol. 110 Issue 2, p024313, 4p

مصطلحات موضوعية: NANOWIRES, REYNOLDS number, MICROWAVES, VISCOSITY, NANOSTRUCTURED materials

مستخلص: A process has been developed for post fabrication manipulation of silica nanowire lengths with reproducible mean length target ability by manual grinding in liquid media. The process is based on the relationship between nanowire Reynolds number and the laminar or turbulent motion of nanowires in a media. Mean lengths of nanowires prepared by this process are predicted to be inversely proportional to the density over viscosity of the media used. Experimental results giving the mean length measurements are in very good agreement with the predicted dependence on medium density and viscosity. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Timalsina, Yukta P., Branen, Joshua, Aston, D. Eric, Noren, Kenneth, Corti, Giancarlo, Schumacher, Randi, McIlroy, David N.

المصدر: Journal of Applied Physics; Jul2011, Vol. 110 Issue 1, p014901, 8p, 1 Color Photograph, 2 Diagrams, 2 Charts, 4 Graphs

مصطلحات موضوعية: SILICA, BIOSENSOR research, ELECTRIC current converters, ELECTRIC impedance, IMPEDANCE spectroscopy, ALTERNATING currents

مستخلص: In this study, alternating current impedance spectroscopic analysis of the biofunctionalization process of a vertically-aligned (silica) nanosprings (VANS) surface is presented. The VANS surface is functionalized with a biotinylated immunoglobulin G (B-IgG) layer formed by physisorption of B-IgG from the solution phase. Bovine serum albumin passivation of the B-IgG layer reduces additional surface adsorption by blocking the potential sites of weak bond formation via electrostatic and hydrophobic interactions. As avidin acts as a receptor of biotinylated compounds, avidin conjugated glucose oxidase (Av-GOx) binds to the B-IgG layer via biotin. This avidin-biotin bond is a stable bond with high association affinity (Ka = 1015 M-1) that withstands wide variations in chemistry and pH. An IgG layer without biotin shows no binding to the Av-GOx, indicating that bonding is through the avidin-biotin interaction. Finally, fluoroscein iso-thiocyanate (FITC) labeled biotinylated bovine serum albumin (B-BSA) added to the Av-GOx surface is used to fluorescently label Av-GOx for fluorescent measurements that allow for the correlation of surface binding with impedance measurements. Modeling of impedance spectra measured after the addition of each biological solution indicates that the bimolecular layers behave as insulating layers. The impedance spectra for the VANS-based sensor are compared to simple parallel capacitor sensors, sans VANS, and serve as controls. VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls below 10 kHz. Changes in the magnitudes of the components of the VANS equivalent circuit indicate that the addition of biological layers changes the effective dielectric response of the VANS via the impediment of ionic motion and biomolecule polarization. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Chen, Yunxia, Dorgan, Jr., Brian L., McIlroy, David N., Eric Aston, D.

المصدر: Journal of Applied Physics; 11/15/2006, Vol. 100 Issue 10, p104301, 7p, 1 Diagram, 2 Charts, 4 Graphs

مصطلحات موضوعية: NANOWIRES, SILVER, BENDING (Metalwork), ELASTICITY, SILICON, ATOMIC force microscopy, FINITE element method, BOUNDARY value problems

مستخلص: Nanomechanical bending behavior and elastic modulus of silver nanowires (65–140 nm[nullset_(circle_with_slash-through)]) suspended across silicon microchannels were investigated using digital pulsed force mode (DPFM) atomic force microscopy through coincident imaging and force profiling. Deflection profiles analyzed off-line demonstrate the role of bending nanowire shape and symmetry in experimentally determining boundary conditions, eliminating the need to rely on isolated midpoint bending measurements and the usual assumptions for supported-end behavior. Elastic moduli for as-prepared silver nanowires ranged from 80.4±5.3 to 96.4±12.8 GPa, which met or exceeded the literature values for bulk silver. The calculated moduli were based on classic modeling, both with one-dimensional analytical solutions and three-dimensional finite element analysis. Modeling results indicate that the classic models are accurate as long as the boundary conditions are not arbitrarily assumed but directly confirmed by data analysis. DPFM also facilitated the experimental determination of sample gauge lengths from images and bending profiles. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)