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Inkjet Printing of Single-Walled Carbon Nanotube/RuO_(2) Nanowire Supercapacitors on Cloth Fabrics and Flexible Substrates

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Nano Research 2010年第8期3卷 594-603页

作者： Pochiang Chen Haitian Chen Jing Qiu chongwu zhou Chemical Engineering Department and Materials Science University of Southern CaliforniaLos AngelesCalifornia 90089USA Department of Electrical Engineering University of Southern CaliforniaLos AngelesCalifornia 90089USA

Single-walled carbon nanotube(SWNT)thin film electrodes have been printed on flexible substrates and cloth fabrics by using SWNT inks and an off-the-shelf inkjet printer,with features of controlled pattern geometry(0.4-6 cm^(2)),location,controllable thickness(20-200 nm),and tunable electrical *** as-printed SWNT films were then sandwiched together with a piece of printable polymer electrolyte to form flexible and wearable supercapacitors,which displayed good capacitive behavior even after 1,000 charge/discharge ***,a simple and efficient route to produce ruthenium oxide(RuO_(2))nanowire/SWNT hybrid films has been developed,and it was found that the knee frequency of the hybrid thin film electrodes can reach 1,500 Hz,which is much higher than the knee frequency of the bare SWNT electrodes(~158 Hz).In addition,with the integration of RuO_(2) nanowires,the performance of the printed SWNT supercapacitor was significantly improved in terms of its specific capacitance of 138 F/g,power density of 96 kW/kg,and energy density of 18.8 Wh/*** results indicate the potential of printable energy storage devices and their significant promise for application in wearable energy storage devices.

关键词： Nanowires carbon nanotubes supercapacitors printed and wearable energy devices

Hybrid Silicon-Carbon Nanostructured Composites as Superior Anodes for Lithium Ion Batteries

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Nano Research 2011年第3期4卷 290-296页

作者： Po-Chiang Chen Jing Xu Haitian Chen chongwu zhou Mork Family Department of Chemical Engineering and Materials Science University of Southern Califomia Los Angeles CA 90089 USA Ming-Hsieh Department of Electrical Engineering University of Southern California Los Angeles CA 90089 USA

We have successfully fabricated a hybrid silicon-carbon nanostructured composite with large area （about 25.5 in^2） in a simple fashion using a conventional sputtering system. When used as the anode in lithium ion batteries, the uniformly deposited amorphous silicon （a-Si） works as the active material to store electrical energy, and the pre-coated carbon nanofibers （CNFs） serve as both the electron conducting pathway and a strain/stress relaxation layer for the sputtered a-Si layers during the intercalation process of lithium ions. As a result, the as-fabricated lithium ion batteries, with deposited a-Si thicknesses of 200 nm or 300 nm, not only exhibit a high specific capacity of 〉2000 mA.h/g, but also show a good capacity retention of over 80% and Coulombic efficiency of 〉98% after a large number of charge/discharge experiments. Our approach offers an efficient and scalable method to obtain silicon-carbon nanostructured composites for application in lithium ion batteries.

关键词： Amorphous silicon carbon nanofibers lithium ion batteries hybrid nanostructured composite

Radio frequency transistors based on ultra-high purity semiconducting carbon nanotubes with superior extrinsic maximum oscillation frequency

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Nano Research 2016年第2期9卷 363-371页

作者： Yu Cao Yuchi Che Hui Gui Xuao Oao chongwu zhou Department of Electrical Engineering University of Southern California Los Angeles CA 90089 USA Department of Chemical Engineering and Materials Science University of Southern California Los Angeles CA 90089 USA

In this paper, we report polyfluorene-separated ultra-high purity semiconducting carbon nanotube radio frequency transistors with a self-aligned T-shape gate structure. Because of the ultra-high semiconducting tube purity and self-aligned T-shape gate structure, these transistors showed an excellent direct current and radio frequency performance. In regard to the direct current characteristics, these transistors showed a transconductance up to 40μS/μm and an excellent current saturation behavior with an output resistance greater than 200 kΩ·μm. In terms of the radio frequency characteristics, an extrinsic maximum oscillation frequency （fmax） of 19 GHz was achieved, which is a record among all kinds of carbon nanotube transistors, and an extrinsic current gain cut-off frequency （fT） of 22 GHz was achieved, which is the highest among transistors based on carbon nanotube networks. Our results take the radio frequency performance of carbon nanotube transistors to a new level and can further accelerate the application of carbon nanotubes for future radio frequency electronics.

关键词： carbon nanotube ultra-high purity radio frequency transistors maximum oscillation frequency T-shape gate

Comparative study of gel-based separated arcdischarge, HiPCO, and CoMoCAT carbon nanotubes for macroelectronic applications

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Nano Research 2013年第12期6卷 906-920页

作者： Jialu Zhang Hui Gui Bilu Liu Jia Liu chongwu zhou Department of Electrical Engineering University of Southern California Los Angeles California 90089 USA Department of Material Science University of Southern Califomia Los Angeles California 90089 USA Department of Chemistry University of Southern California Los Angeles California 90089 USA

Due to their excellent electrical properties and compatibility with room-temperature deposition/printing processing, high-purity single-walled semiconducting carbon nanotubes hold great potential for macroelectronic applications such as in thin-film transistors and display back-panel electronics. However, the relative advantages and disadvantages of various nanotubes for macroelectronics remains an open issue, despite the great significance. Here in this paper, we report a com- parative and systematic study of three kinds of mainstream carbon nanotubes （arc-discharge, HiPCO, CoMoCAT） separated using low-cost gel-based column chromatography for thin-film transistor applications, and high performance transistors--which satisfy the requirements for transistors used in active matrix organic light-emitting diode displays--have been achieved. We observe a trade-off between transistor mobility and on/off ratio depending on the nanotube diameter. While arc-discharge nanotubes with larger diameters lead to high device mobility, HiPCO and CoMoCAT nanotubes with smaller diameters can provide high on/off ratios （〉 106） for transistors with comparable dimensions. Furthermore, we have also compared gel-based separated nanotubes with nanotubes separated using the density gradient ultracentrifuge （DGU） method, and find that gel-separated nanotubes can offer purity and thin-film transistor performance as good as DGU-separated nanotubes. Our approach can serve as the critical foundation for future carbon nanotube-based thin-film macroelectronics.

关键词： separated carbonnanotubes thin-film transistors gel-based columnchromatography purity of semiconductingnanotubes diameter-dependence

Uniform,Highly Conductive,and Patterned Transparent Films of a Percolating Silver Nanowire Network on Rigid and Flexible Substrates Using a Dry Transfer Technique

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Nano Research 2010年第8期3卷 564-573页

作者： Anuj R.Madaria Akshay Kumar Fumiaki N.Ishikawa chongwu zhou Department of Electrical Engineering and Center for Energy Nanoscience and Technology University of Southern CaliforniaLos AngelesCalifornia 90089USA

Silver nanowire films are promising alternatives to tin-doped indium oxide(ITO)films as transparent conductive *** this paper,we report the use of vacuum filtration and a polydimethylsiloxane(PDMS)-assisted transfer printing technique to fabricate silver nanowire films on both rigid and flexible substrates,bringing advantages such as the capability of patterned transfer,the best performance among various ITO alternatives(10Ω/sq at 85%transparency),and good adhesion to the underlying substrate,thus eliminating the previously reported adhesion *** addition,our method also allows the preparation of high quality patterned films of silver nanowires with different line widths and shapes in a matter of few minutes,making it a scalable ***,use of an anodized aluminum oxide(AAO)membrane in the transfer process allows annealing of nanowire films at moderately high temperature to obtain films with extremely high conductivity and good *** this transfer technique,we obtained silver nanowire films on a flexible polyethylene terephthalate(PET)substrate with a transparency of 85%,a sheet resistance of 10Ω/sq,with good mechanical *** analysis revealed that the Ag nanowire network exhibits two-dimensional percolation behavior with good agreement between experimentally observed and theoretically predicted values of critical volume。

关键词： Ag nanowire PDMS transfer transparent electrode flexible electronics percolation network

Sensitization of Hydrothermally Grown Single Crystalline TiO2 Nanowire Array with CdSeS Nanocrystals for Photovoltaic Applications

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Nano Research 2011年第12期4卷 1181-1190页

作者： Akshay Kumar Kuan-teh Li Anuj R. Madaria chongwu zhou Department of Electrical Engineering and Center for Energy Nanoscience and Technology University of Southern California Los AngelesCA 90089 USA

An oriented array of electron transporting nanowires, grown directly on a transparent conductor constitutes an optimal architecture for efficient photovoltaic applications. In addition, semiconductor nanocrystals can work as efficient light absorbers because of their tunable optical properties. In this paper, we use an oriented array of TiO2 nanowires grown directly on a transparent conductive electrode and subsequently sensitized with colloidally grown CdSeS nanocrystal quantum dots （QDs）, using an efficient bi-linker assisted methodology, to demonstrate photovoltaic cells. Upon excitation with light, exciton dissociation takes place at the nanowire-nanocrystal interface, after which, electrons are transported to the fluorine-doped tin oxide （FTO） electrode via single-crystalline TiO2 nanowire channels. We demonstrate that an ex situ ligand exchange of QDs followed by sensitization on oxygen-plasma treated TiO2 nanowires results in enhanced loading of QDs, as compared to the in situ ligand exchange approach. An array of 1μm long TiO2 nanowire sensitized with CdSeS nanocrystals exhibits photovoltaic effects with a short-circuit current of 2-3 mA/cm2, an open circuit voltage of 0.6-0.7 V and a fill factor of 52-5%, resulting in devices with efficiencies of up to 0.6%.

关键词： TiO2 nanowire semiconductor nanocrystals solar cells hydrothermal growth

Coaxial Si/anodic titanium oxide/Si nanotube arrays for lithium-ion battery anodes

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Nano Research 2013年第3期6卷 182-190页

作者： Jiepeng Rong Xin Fang Mingyuan Ge Haitian Chen Jing Xu chongwu zhou Mork Family Department of Chemical Engineering and Materials Science University of Southern California Los Angeles California 90089 USA Ming Hsieh Department of Electrical Engineering University of Southern California Los Angeles California 90089 USA These authors contributed equally to this paper.

Silicon （Si） has the highest known theoretical specific capacity （3,590 mAh/g for Li1.5Si4, and 4,200 mAh/g for Li22Si4） as a lithium-ion battery anode, and has attracted extensive interest in the past few years. However, its application is limited by poor cyclability and early capacity fading due to significant volume changes during lithiation and delithiation processes. In this work, we report a coaxial silicon/anodic titanium oxide/silicon （Si-ATO--Si） nanotube array structure grown on a titanium substrate demonstrating excellent electrochemical cyclability. The ATO nanotube scaffold used for Si deposition has many desirable features, such as a rough surface for enhanced Si adhesion, and direct contact with the Ti substrate working as current collector. More importantly, our ATO scaffold provides a rather unique advantage in that Si can be loaded on both the inner and outer surfaces, and an inner pore can be retained to provide room for Si volume expansion. This coaxial structure shows a capacity above 1,500 mAh/g after 100 cycles, with less than 0.05% decay per cycle. Simulations show that this improved performance can be attributed to the lower stress induced on Si layers upon lithiation/delithiation compared with some other recently reported Si-based nanostructures.

关键词： lithium ion battery anodic titanium oxide silicon anode

Scalable preparation of porous silicon nanoparticles and their application for lithium-ion battery anodes

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Nano Research 2013年第3期6卷 174-181页

作者： Mingyuan Ge Jiepeng Rong Xin Fang Anyi Zhang Yunhao Lu chongwu zhou Department of Chemical Engineering and Materials Science University of Southern California 3710 McClintockAve Los Angeles CA 90089 USA Department of Materials Science and Engineering Zhejiang University 38 Zheda Road Hangzhou 310027 China Department of Electrical Engineering University of Southern California 3710 McClintock Ave Los Angeles CA 90089 USA

Nanostructured silicon has generated significant excitement for use as the anode material for lithium-ion batteries; however, more effort is needed to produce nanostructured silicon in a scalable fashion and with good performance. Here, we present a direct preparation of porous silicon nanoparticles as a new kind of nanostructured silicon using a novel two-step approach combining controlled boron doping and facile electroless etching. The porous silicon nanoparticles have been successfully used as high performance lithium-ion battery anodes, with capacities around 1,400 mA.h/g achieved at a current rate of 1 A/g, and 1,000 mA.h/g achieved at 2 A/g, and stable operation when combined with reduced graphene oxide and tested over up to 200 cycles. We attribute the overall good performance to the combination of porous silicon that can accommodate large volume change during cycling and provide large surface area accessible to electrolyte, and reduced graphene oxide that can serve as an elastic and electrically conductive matrix for the porous silicon nanoparticles.

关键词： porous siliconnanoparticles scalable production lithium-ion battery

Single-step flash-heat synthesis of red phosphorus/ graphene flame-retardant composite as flexible anodes for sodium-ion batteries

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Nano Research 2018年第7期11卷 3780-3790页

作者： Yihang Liu Anyi Zhang Chenfei Shen Qingzhou Liu Jiansong Cai Xuan Cao chongwu zhou Ming Hsieh Department of Electrical Engineering University of Southern California Los Angeles California 90089 USA Mork Family Department of Chemical Engineering and Materials Science University of Southern California Los Angeles California 90089 USA

Red phosphorus （RP） has attracted considerable attention as the anode for high-performance Na-ion batteries, owing to its low cost and high theoretical specific capacity of -2,600 mAh/g. In this study, a facile single-step flash-heat treatment was developed to achieve the reduction of graphene oxide （GO） and the simultaneous deposition of RP onto the reduced graphene oxide （rGO） sheets. The resulting RP/rGO composite was shown to be a promising candidate for overcoming the issues associated with the poor electronic conductivity and large volume variation of RP during cycling. The RP/rGO flexible film anode delivered an average capacity of 1,625 mAh/g during 200 cycles at a charge/ discharge current density of 1 A/g. Average charge capacities of 1,786, 1,597, 1,324, and 679 mAh/g at 1, 2, 4, and 6 A/g current densities were obtained in the rate capability tests. Moreover, owing to the RP component, the RP/rGO film presented superior flame retardancy compared to an rGO film. This work thus introduces a highly accessible synthesis method to prepare flexible and safe RP anodes with superior electrochemical performance toward Na-ion storage.

关键词： sodium-ion batteries red phosphorus facile synthesis flexible flame-retardant reduced graphene oxide