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Flow-less and shape-conformable CNT sheet nanogenerator for self-powered motion sensor
Song, H.,Kim, T.,Im, H.,Ovalle-Robles, R.,Kang, T.,Kim, Y. Royal Society of Chemistry 2016 Nanoscale Vol.8 No.37
<P>A carbon nanotube (CNT) sheet nanogenerator that does not require any liquid or gas flow for power generation is developed on the basis of Coulombic interactions, making the device attractive as a building block for self-powered sensors. The working principle of the CNT nanogenerator is probed in terms of sweeping speed, distance between charged object and nanotube sheet, surface charge, and number of layers of nanotube sheet. The nature of the CNT sheet and its formation process is such that simply winding the CNT sheet stripe n times around a substrate leads to increasing the power n times. For a practical demonstration of the CNT nanogenerator, a self-powered sensor array screen is developed that can read finger movements, just as with a finger command on a smartphone screen.</P>
Aerogel sheet of carbon nanotubes decorated with palladium nanoparticles for hydrogen gas sensing
Kim, Ju Hyeon,Jeon, Jei Gyeong,Ovalle-Robles, Raquel,Kang, Tae June Elsevier 2018 International journal of hydrogen energy Vol.43 No.12
<P><B>Abstract</B></P> <P>In the development of hydrogen sensors, it is required to meet the demands of both high sensor performance as well as the ease of fabrication for mass production. For this purpose we proposed a chemiresistive hydrogen sensors based on an aerogel sheet of carbon nanotubes decorated with palladium nanoparticles (CNT/Pd sheet). The fabrication process is straightforward that a dry-spun CNT aerogel sheet is suspended between concentric electrodes followed by depositing Pd nanoparticles on CNT sheets by thermal evaporation. The present CNT/Pd sheet sensors can detect hydrogen at concentrations as low as 2 ppm at room temperature with a detection range from 2 to 1000 ppm. The aerogel nature of CNT/Pd sheet contributes to low detection limit and broad detection range of the CNT/Pd sensor. Relations between hydrogen concentration and sensor response and response time, and the effects of temperature on sensor performance were investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High performance CNT/Pd sheet hydrogen sensor arrays is fabricated. </LI> <LI> The LOD is 2 ppm at room temperature with a detection range from 2 to 1000 ppm. </LI> <LI> Relations between hydrogen concentration and sensor response and response time were investigated. </LI> <LI> The aerogel nature of CNT/Pd sheet contributes to low detection limit and broad detection range. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ultrastretchable Analog/Digital Signal Transmission Line with Carbon Nanotube Sheets
Lee, Yourack,Joo, Min-Kyu,Le, Viet Thong,Ovalle-Robles, Raquel,Lepró,, Xavier,Lima, Má,rcio D.,Suh, Daniel G.,Yu, Han Young,Lee, Young Hee,Suh, Dongseok American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.31
<P>Stretchable conductors can be used in various applications depending on their own characteristics. Here, we demonstrate simple and robust elastomeric conductors that are optimized for stretchable electrical signal transmission line. They can withstand strains up to 600% without any substantial change in their resistance (<= 10% as is and <= 1% with passivation), and exhibit suppressed charge fluctuations in the medium. The inherent elasticity of a polymeric rubber and the high conductivity of flexible, highly oriented carbon nanotube sheets were combined synergistically, without losing both properties. The nanoscopic strong adhesion between aligned carbon nanotube arrays and strained elastomeric polymers induces conductive wavy folds with microscopic bending of radii on the scale of a few micrometers. Such features enable practical applications such as in elastomeric length-changeable electrical digital and analog signal transmission lines at above MHz frequencies. In addition to reporting basic direct current, alternating current, and noise characterizations of the elastomeric conductors, various examples as a stretchable signal transmission line up to 600% strains are presented by confirming the capability of transmitting audio and video signals, as well as low-frequency medical signals without information distortion.</P>
Lee, Jae Ah,Shin, Min Kyoon,Kim, Shi Hyeong,Kim, Seon Jeong,Spinks, Geoffrey M.,Wallace, Gordon G.,Ovalle-Robles, Raquel,Lima, Má,rcio D.,Kozlov, Mikhail E.,Baughman, Ray H. American Chemical Society 2012 ACS NANO Vol.6 No.1
<P>We report mechanically robust, electrically conductive, free-standing, and transparent hybrid nanomembranes made of densified carbon nanotube sheets that were coated with poly(3,4-ethylenedioxythiophene) using vapor phase polymerization and their performance as supercapacitors. The hybrid nanomembranes with thickness of ∼66 nm and low areal density of ∼15 μg/cm<SUP>2</SUP>exhibited high mechanical strength and modulus of 135 MPa and 12.6 GPa, respectively. They also had remarkable shape recovery ability in liquid and at the liquid/air interface unlike previous carbon nanotube sheets. The hybrid nanomembrane attached on a current collector had volumetric capacitance of ∼40 F/cm<SUP>3</SUP> at 100 V s<SUP>–1</SUP> (∼40 and ∼80 times larger than that of onion-like carbon measured at 100 V s<SUP>–1</SUP> and activated carbon measured at 20 V s<SUP>–1</SUP>, respectively), and it showed rectangular shapes of cyclic voltammograms up to ∼5 V s<SUP>–1</SUP>. High mechanical strength and flexibility of the hybrid nanomembrane enabled twisting it into microsupercapacitor yarns with diameters of ∼30 μm. The yarn supercapacitor showed stable cycling performance without a metal current collector, and its capacitance decrease was only ∼6% after 5000 cycles. Volumetric energy and power density of the hybrid nanomembrane was ∼70 mWh cm<SUP>–3</SUP> and ∼7910 W cm<SUP>–3</SUP>, and the yarn possessed the energy and power density of ∼47 mWh cm<SUP>–3</SUP> and ∼538 W cm<SUP>–3</SUP>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-1/nn203640a/production/images/medium/nn-2011-03640a_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203640a'>ACS Electronic Supporting Info</A></P>
A Reel-Wound Carbon Nanotube Polarizer for Terahertz Frequencies
Kyoung, Jisoo,Jang, Eui Yun,Lima, Má,rcio D.,Park, Hyeong-Ryeol,Robles, Raquel Ovalle,Lepró,, Xavier,Kim, Yong Hyup,Baughman, Ray H.,Kim, Dai-Sik American Chemical Society 2011 NANO LETTERS Vol.11 No.10
<P>Utilizing highly oriented multiwalled carbon nanotube aerogel sheets, we fabricated micrometer-thick freestanding carbon nanotube (CNT) polarizers. Simple winding of nanotube sheets on a U-shaped polyethylene reel enabled rapid and reliable polarizer fabrication, bypassing lithography or chemical etching processes. With the remarkable extinction ratio reaching ∼37 dB in the broad spectral range from 0.1 to 2.0 THz, combined with the extraordinary gravimetric mechanical strength of CNTs, and the dispersionless character of freestanding sheets, the commercialization prospects for our CNT terahertz polarizers appear attractive.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-10/nl202214y/production/images/medium/nl-2011-02214y_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl202214y'>ACS Electronic Supporting Info</A></P>
Lim, Hee‐,Dae,Park, Kyu‐,Young,Song, Hyelynn,Jang, Eui Yun,Gwon, Hyeokjo,Kim, Jinsoo,Kim, Yong Hyup,Lima, Má,rcio D.,Robles, Raquel Ovalle,Lepró,, Xavier,Baughman, Ray H.,Kang, WILEY‐VCH Verlag 2013 Advanced Materials Vol.25 No.9
<P><B>Hierarchical carbon electrodes</B> with highly aligned carbon nanotube (CNT) fibrils are fabricated, and it is demonstrated that these electrodes, with aligned pores, can significantly enhance the cyclability and rate capability of Li−O<SUB>2</SUB> batteries. The highly aligned pore structure enables good accessibility of oxygen to the inner electrode, which leads to a uniform deposition of discharge products on the individual CNTs.</P>
A new catalyst-embedded hierarchical air electrode for high-performance Li–O<sub>2</sub> batteries
Lim, Hee-Dae,Song, Hyelynn,Gwon, Hyeokjo,Park, Kyu-Young,Kim, Jinsoo,Bae, Youngjoon,Kim, Hyungsub,Jung, Sung-Kyun,Kim, Taewoo,Kim, Yong Hyup,Lepró,, Xavier,Ovalle-Robles, Raquel,Baughman, Ray H. The Royal Society of Chemistry 2013 ENERGY AND ENVIRONMENTAL SCIENCE Vol.6 No.12
<P>The Li–O<SUB>2</SUB> battery holds great promise as an ultra-high-energy-density device. However, its limited rechargeability and low energy efficiency remain key barriers to its practical application. Herein, we demonstrate that the ideal electrode morphology design combined with effective catalyst decoration can enhance the rechargeability of the Li–O<SUB>2</SUB> battery over 100 cycles with full discharge and charge. An aligned carbon structure with a hierarchical micro-nano-mesh ensures facile accessibility of reaction products and provides the optimal catalytic conditions for the Pt catalyst. The new electrode is highly reversible even at the extremely high current rate of 2 A g<SUP>−1</SUP>. Moreover, we observed clearly distinct morphologies of discharge products when the catalyst is used. The effect of catalysts on the cycle stability is discussed.</P> <P>Graphic Abstract</P><P>The Li–O<SUB>2</SUB> battery holds great promise as an ultra-high-energy-density device. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3ee41910j'> </P>
Lim, Hee‐,Dae,Song, Hyelynn,Kim, Jinsoo,Gwon, Hyeokjo,Bae, Youngjoon,Park, Kyu‐,Young,Hong, Jihyun,Kim, Haegyeom,Kim, Taewoo,Kim, Yong Hyup,Lepró,, Xavier,Ovalle‐,Robles, Raque WILEY‐VCH Verlag 2014 Angewandte Chemie Vol.126 No.15
<P><B>Abstract</B></P><P>The lithium–oxygen battery has the potential to deliver extremely high energy densities; however, the practical use of Li‐O<SUB>2</SUB> batteries has been restricted because of their poor cyclability and low energy efficiency. In this work, we report a novel Li‐O<SUB>2</SUB> battery with high reversibility and good energy efficiency using a soluble catalyst combined with a hierarchical nanoporous air electrode. Through the porous three‐dimensional network of the air electrode, not only lithium ions and oxygen but also soluble catalysts can be rapidly transported, enabling ultra‐efficient electrode reactions and significantly enhanced catalytic activity. The novel Li‐O<SUB>2</SUB> battery, combining an ideal air electrode and a soluble catalyst, can deliver a high reversible capacity (1000 mAh g<SUP>−1</SUP>) up to 900 cycles with reduced polarization (about 0.25 V).</P>