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Gullapalli H.,Rice University | Vemuru V.S.M.,Rice University | Kumar A.,Rice University | Botello-Mendez A.,Laboratory for Nanoscience and Nanotechnology Research LINAN | And 4 more authors.
Small | Year: 2010

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real-time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose-based secondary matrix. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Trejo-Valdez M.,National Polytechnic Institute of Mexico | Torres-Martinez R.,Research Center en Ciencia Aplicada | Perea-Lopez N.,Laboratory for Nanoscience and Nanotechnology Research LINAN | Santiago-Jacinto P.,National Autonomous University of Mexico | Torres-Torres C.,Seccion de Estudios de Posgrado e Investigacion
Journal of Physical Chemistry C | Year: 2010

We measured the absorptive and refractive nonlinearities in Au nanoparticles when they are embedded in a TiO2 film and when they are suspended in ethanol. The morphology of the nanoparticles was estimated by using HRTEM microscopy. Different contributions related to electronic polarization and two-photon absorption were observed in the samples using a self-diffraction technique with pulses of 26 ps at 532 nm. Transmittance experiments were performed in order to confirm the mechanisms of optical absorption. The Au nanoparticles were grown by the photoreduction of TiO 2 sol-gel solutions which contain Au3+ ions. The thin films were prepared by using the dip coating technique with fresh UV exposed sol-gel solutions. We observed that when the sample does not present any important nonlinear absorption it is possible to enhance the participation of the nanoparticles in the optical Kerr response of the media. © 2010 American Chemical Society. Source

Villalpando-Paez F.,Massachusetts Institute of Technology | Muramatsu H.,Shinshu University | Kim Y.A.,Shinshu University | Farhat H.,Massachusetts Institute of Technology | And 3 more authors.
Nanoscale | Year: 2010

We measure resonant Raman scattering from 11 individual C 60-derived double-wall carbon nanotubes all having inner semiconducting (6,5) tubes and various outer metallic tubes. The Raman spectra show the radial breathing modes (RBM) of the inner and the outer tubes to be simultaneously in resonance with the same laser energy. We observe that an increase in the RBM frequency of the inner tubes is related to an increase in the RBM frequency of the outer tubes. The Raman spectra also contain a sharp G- feature that increases in frequency as the nominal diameter of the outer metallic tubes decreases. Finally, the one-phonon second-order D-band mode shows a two-way frequency splitting that decreases with decreasing nominal wall-to-wall distance. We suggest that the stress which increases with decreasing nominal wall-to-wall distance is responsible for the hardening that is observed in the frequencies of the RBM, D and G- modes of the inner (6,5) semiconducting tubes. © 2010 The Royal Society of Chemistry. Source

Shimamoto D.,Shinshu University | Muramatsu H.,Shinshu University | Kim Y.J.,Shinshu University | Kim Y.A.,Shinshu University | And 4 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2010

Changes in the optical properties of thermally coalesced single-walled carbon nanotubes (SWCNTs) caused by heat treatment between 1300 and 2800 °C in argon, have been monitored using optical absorption and photoluminescence spectroscopy. For SWNTs heat treated at 1900 °C, we found a complete disapperance of small-diameter tubes (<1.0 nm) as well as the appearance of enlarged, defective tubes. The decreased sp 2/sp 3 ratio for tubes heat treated below 2100 °C suggests that adjacent small-diameter SWNTs transform into energetically stable larger-diameter SWNTs by the presence of structural non sp 2 defects. Copyright © 2010 American Scientific Publishers All rights reserved. Source

Kumar A.,Oceanit Laboratories, Inc. | Gullapalli H.,Rice University | Balakrishnan K.,Rice University | Botello-Mendez A.,Laboratory for Nanoscience and Nanotechnology Research LINAN | And 3 more authors.
Small | Year: 2011

Materials with the ability to harness multiple sources of energy from the ambient environment could lead to new types of energy-harvesting systems. It is demonstrated that nanocomposite films consisting of zinc oxide nanostructures embedded in a common paper matrix can be directly used as energy-conversion devices to transform mechanical and thermal energies to electric power. These mechanically robust and flexible devices can be fabricated over large areas and are capable of producing an output voltage and power up to 80 mV and 50 nW cm -2, respectively. Furthermore, it is shown that by integrating a certain number of devices (in series and parallel) the output voltage and the concomitant output power can be significantly increased. Also, the output voltage and power can be enhanced by scaling the size of the device. This multisource energy-harvesting system based on ZnO nanostructures embedded in a flexible paper matrix provides a simplified and cost-effective platform for capturing trace amounts of energy for practical applications. Nanocomposite films consisting of ZnO nanostructures embedded in common paper are used as energy-conversion devices. The paper matrix makes these devices flexible while retaining their mechanical strength. This composite material can transform multiple sources, such as mechanical and thermal energy, into electric power, to provide a simplified and cost-effective platform for scavenging energy for practical applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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