Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

DOEpatents

Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

2010-07-27

Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

Sacrificial template method of fabricating a nanotube

DOEpatents

Yang, Peidong [Berkeley, CA; He, Rongrui [Berkeley, CA; Goldberger, Joshua [Berkeley, CA; Fan, Rong [El Cerrito, CA; Wu, Yi-Ying [Albany, CA; Li, Deyu [Albany, CA; Majumdar, Arun [Orinda, CA

2007-05-01

Methods of fabricating uniform nanotubes are described in which nanotubes were synthesized as sheaths over nanowire templates, such as using a chemical vapor deposition process. For example, single-crystalline zinc oxide (ZnO) nanowires are utilized as templates over which gallium nitride (GaN) is epitaxially grown. The ZnO templates are then removed, such as by thermal reduction and evaporation. The completed single-crystalline GaN nanotubes preferably have inner diameters ranging from 30 nm to 200 nm, and wall thicknesses between 5 and 50 nm. Transmission electron microscopy studies show that the resultant nanotubes are single-crystalline with a wurtzite structure, and are oriented along the <001> direction. The present invention exemplifies single-crystalline nanotubes of materials with a non-layered crystal structure. Similar "epitaxial-casting" approaches could be used to produce arrays and single-crystalline nanotubes of other solid materials and semiconductors. Furthermore, the fabrication of multi-sheath nanotubes are described as well as nanotubes having multiple longitudinal segments.

Density controlled carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng F [Newton, MA; Tu, Yi [Belmont, MA

2008-12-16

CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the field emission properties of the films are controlled by independently varying the length of CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotube material of the invention is also described.

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility

NASA Astrophysics Data System (ADS)

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J.

2014-07-01

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

PubMed

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J

2014-08-07

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts

DTIC Science & Technology

2012-01-01

12] J. P. Liu, C. X. Guo, C. M. Li et al., “Carbon-decorated ZnO nanowire array: a novel platform for direct electrochemistry of enzymes and...cited. Vertically aligned, high-density ZnO nanowires (NWs) were grown for the first time on c-plane sapphire using binary alloys of Ni/Au or Cu/Au as...deleterious to the ZnO NW array growth. Significant improvement of the Au adhesion on the substrate was noted, opening the potential for direct

Growth of high-aspect ratio horizontally-aligned ZnO nanowire arrays.

PubMed

Soman, Pranav; Darnell, Max; Feldman, Marc D; Chen, Shaochen

2011-08-01

A method of fabricating horizontally-aligned zinc-oxide (ZnO) nanowire (NW) arrays with full control over the width and length is demonstrated. SEM images reveal the hexagonal structure typical of zinc oxide NWs. Arrays of high-aspect ratio horizontal ZnO NWs are fabricated by making use of the lateral overgrowth from dot patterns created by electron beam lithography (EBL). An array of patterned wires are lifted off and transferred to a flexible PDMS substrate with possible applications in several key nanotechnology areas.

Single-crystal gallium nitride nanotubes.

PubMed

Goldberger, Joshua; He, Rongrui; Zhang, Yanfeng; Lee, Sangkwon; Yan, Haoquan; Choi, Heon-Jin; Yang, Peidong

2003-04-10

Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an 'epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200 nm and wall thicknesses of 5-50 nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

PubMed

Cho, Seungho; Jang, Ji-Wook; Lee, Jae Sung; Lee, Kun-Hong

2010-10-01

We report a simple wet-chemical synthesis of ∼5 nm diameter ZnO nanorod arrays at room temperature (20 °C) and normal atmospheric pressure (1 atm) and their optical properties. They were single crystalline in nature, and grew in the [001] direction. These small diameter ZnO nanorod arrays can also be synthesized at 0 °C. Control experiments were also conducted. On the basis of the results, we propose a mechanism for the spontaneous growth of the small diameter ZnO structures. The optical properties of the 5 nm diameter ZnO nanorod arrays synthesized using this method were probed by UV-Visible diffuse reflectance spectroscopy. A clear blue-shift, relative to the absorption band from 50 nm diameter ZnO nanorod arrays, was attributed to the quantum confinement effects caused by the small nanocrystal size in the 5 nm diameter ZnO nanorods.

Making Carbon-Nanotube Arrays Using Block Copolymers: Part 2

NASA Technical Reports Server (NTRS)

Bronikowski, Michael

2004-01-01

Some changes have been incorporated into a proposed method of manufacturing regular arrays of precisely sized, shaped, positioned, and oriented carbon nanotubes. Such arrays could be useful as mechanical resonators for signal filters and oscillators, and as electrophoretic filters for use in biochemical assays. A prior version of the method was described in Block Copolymers as Templates for Arrays of Carbon Nanotubes, (NPO-30240), NASA Tech Briefs, Vol. 27, No. 4 (April 2003), page 56. To recapitulate from that article: As in other previously reported methods, carbon nanotubes would be formed by decomposition of carbon-containing gases over nanometer-sized catalytic metal particles that had been deposited on suitable substrates. Unlike in other previously reported methods, the catalytic metal particles would not be so randomly and densely distributed as to give rise to thick, irregular mats of nanotubes with a variety of lengths, diameters, and orientations. Instead, in order to obtain regular arrays of spaced-apart carbon nanotubes as nearly identical as possible, the catalytic metal particles would be formed in predetermined regular patterns with precise spacings. The regularity of the arrays would be ensured by the use of nanostructured templates made of block copolymers.

Fabrication and Characterization of Vertically Aligned ZnO Nanorod Arrays via Inverted Monolayer Colloidal Crystals Mask

NASA Astrophysics Data System (ADS)

Chen, Cheng; Ding, Taotao; Qi, Zhiqiang; Zhang, Wei; Zhang, Jun; Xu, Juan; Chen, Jingwen; Dai, Jiangnan; Chen, Changqing

2018-04-01

The periodically ordered ZnO nanorod (NR) arrays have been successfully synthesized via a hydrothermal approach on the silicon substrates by templating of the TiO2 ring deriving from the polystyrene (PS) nanosphere monolayer colloidal crystals (MCC). With the inverted MCC mask, sol-gel-derived ZnO seeds could serve as the periodic nucleation positions for the site-specific growth of ZnO NRs. The large-scale patterned arrays of single ZnO NR with good side-orientation can be readily produced. According to the experimental results, the as-integrated ZnO NR arrays showed an excellent crystal quality and optical property, very suitable for optoelectronic applications such as stimulated emitters and ZnO photonic crystal devices.

Fabrication of titanium dioxide nanotube arrays using organic electrolytes

NASA Astrophysics Data System (ADS)

Yoriya, Sorachon

This dissertation focuses on fabrication and improvement of morphological features of TiO2 nanotube arrays in the selected organic electrolytes including dimethyl sulfoxide (DMSO; see Chapter 4) and diethylene glycol (DEG; see Chapter 5). Using a polar dimethyl sulfoxide containing hydrofluoric acid, the vertically oriented TiO2 nanotube arrays with well controlled morphologies, i.e. tube lengths ranging from few microns up to 101 microm, pore diameters from 100 nm to 150 nm, and wall thicknesses from 15 nm to 50 nm were achieved. Various anodization variables including fluoride ion concentration, voltage, anodization time, water content, and reuse of the anodized electrolyte could be manipulated under proper conditions to control the nanotube array morphology. Anodization current behaviors associated with evolution of nanotube length were analyzed in order to clarify and better understand the formation mechanism of nanotubes grown in the organic electrolytes. Typically observed for DMSO electrolyte, the behavior that anodization current density gradually decreases with time is a reflection of a constant growth rate of nanotube arrays. Large fluctuation of anodization current was significantly observed probably due to the large change in electrolyte properties during anodization, when anodizing in high conductivity electrolytes such as using high HF concentration and reusing the anodized electrolyte as a second time. It is believed that the electrolyte properties such as conductivity and polarity play important role in affecting ion solvation and interactions in the solution consequently determining the formation of oxide film. Fabrication of the TiO2 nanotube array films was extended to study in the more viscous diethylene glycol (DEG) electrolyte. The arrayed nanotubes achieved from DEG electrolytes containing either HF or NH4 F are fully separated, freely self-standing structure with open pores and a wide variation of tube-to-tube spacing ranging from < 100 nm

Flexible piezoelectric nanogenerators based on a transferred ZnO nanorod/Si micro-pillar array

NASA Astrophysics Data System (ADS)

Baek, Seong-Ho; Park, Il-Kyu

2017-03-01

Flexible piezoelectric nanogenerators (PNGs) based on a composite of ZnO nanorods (NRs) and an array of Si micro-pillars (MPs) are demonstrated by a transfer process. The flexible composite structure was fabricated by hydrothermal growth of ZnO NRs on an electrochemically etched Si MP array with various lengths followed by mechanically delaminating the Si MP arrays from the Si substrate after embedding them in a polydimethylsiloxane matrix. Because the Si MP arrays act as a supporter to connect the ZnO NRs electrically and mechanically, verified by capacitance measurement, the output voltage from the flexible PNGs increased systematically with the increased density ZnO NRs depending on the length of the Si MPs. The flexible PNGs showed 3.2 times higher output voltage with a small change in current with increasing Si MP length from 5 to 20 μm. The enhancement of the output voltage is due to the increased number of series-connected ZnO NRs and the beneficial effect of a ZnO NR/Si MP heterojunction on reducing free charge screening effects. The flexible PNGs can be attached on fingers as a wearable electrical power source or motion sensor.

Carbon Nanotube Electrode Arrays For Enhanced Chemical and Biological Sensing

NASA Technical Reports Server (NTRS)

Han, Jie

2003-01-01

Applications of carbon nanotubes for ultra-sensitive electrical sensing of chemical and biological species have been a major focus in NASA Ames Center for Nanotechnology. Great progress has been made toward controlled growth and chemical functionalization of vertically aligned carbon nanotube arrays and integration into micro-fabricated chip devices. Carbon nanotube electrode arrays devices have been used for sub-attomole detection of DNA molecules. Interdigitated carbon nanotubes arrays devices have been applied to sub ppb (part per billion) level chemical sensing for many molecules at room temperature. Stability and reliability have also been addressed in our device development. These results show order of magnitude improvement in device performance, size and power consumption as compared to micro devices, promising applications of carbon nanotube electrode arrays for clinical molecular diagnostics, personal medical testing and monitoring, and environmental monitoring.

Controllable synthesis and optical properties of novel ZnO cone arrays via vapor transport at low temperature.

PubMed

Han, Xinhai; Wang, Guanzhong; Jie, Jiansheng; Choy, Wallace C H; Luo, Yi; Yuk, T I; Hou, J G

2005-02-24

Novel ZnO cone arrays with controllable morphologies have been synthesized on silicon (100) substrates by thermal evaporation of metal Zn powder at a low temperature of 570 degrees C without a metal catalyst. Clear structure evolutions were observed using scanning electron microscopy: well-aligned ZnO nanocones, double-cones with growing head cones attached by stem cones, and cones with straight hexagonal pillar were obtained as the distance between the source and the substrates was increased. X-ray diffraction shows that all cone arrays grow along the c-axis. Raman and photoluminescence spectra reveal that the optical properties of the buffer layer between the ZnO cone arrays and the silicon substrates are better than those of the ZnO cone arrays due to high concentration of Zn in the heads of the ZnO cone arrays and higher growth temperature of the buffer layer. The growth of ZnO arrays reveals that the cone arrays are synthesized through a self-catalyzed vapor-liquid-solid (VLS) process.

Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity

NASA Astrophysics Data System (ADS)

Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

2017-02-01

Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

Electro-pumped whispering gallery mode ZnO microlaser array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, G. Y.; State Key Laboratory of Bioelectronics, School of Electronic Science and Engineering, Southeast University, Nanjing 210096; Li, J. T.

2015-01-12

By employing vapor-phase transport method, ZnO microrods are fabricated and directly assembled on p-GaN substrate to form a heterostructural microlaser array, which avoids of the relatively complicated etching process comparing previous work. Under applied forward bias, whispering gallery mode ZnO ultraviolet lasing is obtained from the as-fabricated heterostructural microlaser array. The device's electroluminescence originates from three distinct electron-hole recombination processes in the heterojunction interface, and whispering gallery mode ultraviolet lasing is obtained when the applied voltage is beyond the lasing threshold. This work may present a significant step towards future fabrication of a facile technique for micro/nanolasers.

Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

PubMed Central

2014-01-01

Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

Hydrogen adsorption capacities of multi-walled boron nitride nanotubes and nanotube arrays: a grand canonical Monte Carlo study.

PubMed

Ahadi, Zohreh; Shadman, Muhammad; Yeganegi, Saeed; Asgari, Farid

2012-07-01

Hydrogen adsorption in multi-walled boron nitride nanotubes and their arrays was studied using grand canonical Monte Carlo simulation. The results show that hydrogen storage increases with tube diameter and the distance between the tubes in multi-walled boron nitride nanotube arrays. Also, triple-walled boron nitride nanotubes present the lowest level of hydrogen physisorption, double-walled boron nitride nanotubes adsorb hydrogen better when the diameter of the inner tube diameter is sufficiently large, and single-walled boron nitride nanotubes adsorb hydrogen well when the tube diameter is small enough. Boron nitride nanotube arrays adsorb hydrogen, but the percentage of adsorbed hydrogen (by weight) in boron nitride nanotube arrays is rather similar to that found in multi-walled boron nitride nanotubes. Also, when the Langmuir and Langmuir-Freundlich equations were fitted to the simulated data, it was found that multi-layer adsorptivity occurs more prominently as the number of walls and the tube diameter increase. However, in single-walled boron nitride nanotubes with a small diameter, the dominant mechanism is monolayer adsorptivity.

Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study.

PubMed

Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

2016-04-20

The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C.

Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study

PubMed Central

Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

2016-01-01

The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C. PMID:28773423

Carbon Nanotube Array for Infrared Detection

DTIC Science & Technology

2008-12-05

ctron Transport Charact eri stic s of a Carbon nanotub es/S i He terodimensional He tero structure." Materials Research Society, Spring meeting (2008). 3...From - To) 05-12-2008 Final 27 09 2006-26 09 2008 4 . TITLE AND SUBTITLE 5a . CONTRACT NUMBER Carbon Nanotube Array for Infrared Detection 5b...Distribution is unlimited 13 . SUPPLEMENTARY NOTES 14 . ABSTRACT We explore the basic science issues and device potential of our carbon nanotube-silicon (CNT

ZnO Functionalization of Multi-walled Carbon Nanotubes for Methane Sensing at Single Parts Per Million Concentration Levels

EPA Science Inventory

This paper presents a novel atomic layer deposition (ALD) based ZnO functionalization of surface pre-treated multi-walled carbon nanotubes (MWCNTs) for highly sensitive methane chemoresistive sensors. The temperature optimization of the ALD process leads to enhanced ZnO nanopart...

Photoelectrocatalytic activity of a hydrothermally grown branched Zno nanorod-array electrode for paracetamol degradation.

PubMed

Lin, Chin Jung; Liao, Shu-Jun; Kao, Li-Cheng; Liou, Sofia Ya Hsuan

2015-06-30

Hierarchical branched ZnO nanorod (B-ZnR) arrays as an electrode for efficient photoelectrocatalytic degradation of paracetamol were grown on fluorine-doped tin oxide substrates using a solution route. The morphologic and structural studies show the ZnO trunks are single-crystalline hexagonal wurtzite ZnO with a [0001] growth direction and are densely covered by c-axis-oriented ZnO branches. The obvious enhancement in photocurrent response of the B-ZnR electrode was obtained than that in the ZnO nanoparticle (ZnO NP) electrode. For the photoelectrocatalytic degradation of paracetamol in 20 h, the conversion fraction of the drug increased from 32% over ZnO NP electrode to 62% over B-ZnR arrays with about 3-fold increase in initial reaction rate. The light intensity-dependent photoelectrocatalytic experiment indicated that the superior performance over the B-ZnR electrode was mainly ascribed to the increased specific surface area without significantly sacrificing the charge transport and pollutant diffusion efficiencies. Two aromatic intermediate compounds were observed and eventually converted into harmless carboxylic acids and ammonia. Hierarchical tree-like ZnO arrays can be considered effective alternatives to improve photoelectro degradation rates without the need for expensive additives. Copyright © 2015 Elsevier B.V. All rights reserved.

Nanoindentation study of the mechanical behavior of TiO2 nanotube arrays

NASA Astrophysics Data System (ADS)

Xu, Y. N.; Liu, M. N.; Wang, M. C.; Oloyede, A.; Bell, J. M.; Yan, C.

2015-10-01

Titanium dioxide (TiO2) nanotube arrays are attracting increasing attention for use in solar cells, lithium-ion batteries, and biomedical implants. To take full advantage of their unique physical properties, such arrays need to maintain adequate mechanical integrity in applications. However, the mechanical performance of TiO2 nanotube arrays is not well understood. In this work, we investigate the deformation and failure of TiO2 nanotube arrays using the nanoindentation technique. We found that the load-displacement response of the arrays strongly depends on the indentation depth and indenter shape. Substrate-independent elastic modulus and hardness can be obtained when the indentation depth is less than 2.5% of the array height. The deformation mechanisms of TiO2 nanotube arrays by Berkovich and conical indenters are closely associated with the densification of TiO2 nanotubes under compression. A theoretical model for deformation of the arrays under a large-radius conical indenter is also proposed.

MnO 2 nanotube and nanowire arrays by electrochemical deposition for supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Feng, Jinkui; Wang, Hailong; Lai, Man On; Lu, Li

Highly ordered MnO 2 nanotube and nanowire arrays are successfully synthesized via a electrochemical deposition technique using porous alumina templates. The morphologies and microstructures of the MnO 2 nanotube and nanowire arrays are investigated by field emission scanning electron microscopy and transmission electron microscopy. Electrochemical characterization demonstrates that the MnO 2 nanotube array electrode has superior capacitive behaviour to that of the MnO 2 nanowire array electrode. In addition to high specific capacitance, the MnO 2 nanotube array electrode also exhibits good rate capability and good cycling stability, which makes it promising candidate for supercapacitors.

Augmented Photoelectrochemical Efficiency of ZnO/TiO2 Nanotube Heterostructures

NASA Astrophysics Data System (ADS)

Boda, Muzaffar Ahmad; Shah, Mohammad Ashraf

2017-11-01

ZnO/TiO2 nanotube heterostructures have been fabricated by electrodeposition of ZnO microcrystals over electrochemically anodized TiO2 nanotube arrays. The resulting ZnO/TiO2 nanotube heterostructures showed enhanced photocurrent density of 5.72 mA cm-2, about 1.5 times the value of 3.68 mA cm-2 shown by bare compact TiO2 nanotubes. This enhanced photocurrent density of the ZnO/TiO2 nanotube heterostructures is due to high electron mobility in the ZnO crystals, thereby decreasing the electron-hole recombination process, good interfacial quality between the ZnO and TiO2 structures, and a proposed smooth charge-transfer mechanism due to band bending at the interface. The morphological features of the as-prepared heterostructures were determined by field-emission scanning electron microscopy (FESEM). The crystallinity and phase purity of the samples were confirmed by x-ray diffraction (XRD) analysis. The light absorption properties of the prepared samples were investigated by ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The photoelectrochemical efficiency of bare and ZnO-modified TiO2 nanotube heterostructures was determined by electrochemical analyzer.

Array of aligned and dispersed carbon nanotubes and method of producing the array

DOEpatents

Ivanov, Ilia N [Knoxville, TN; Simpson, John T [Clinton, TN; Hendricks, Troy R [Knoxville, TN

2012-06-19

An array of aligned and dispersed carbon nanotubes includes an elongate drawn body including a plurality of channels extending therethrough from a first end to a second end of the body, where the channels have a number density of at least about 100,000 channels/mm.sup.2 over a transverse cross-section of the body. A plurality of carbon nanotubes are disposed in each channel, and the carbon nanotubes are sufficiently dispersed and aligned along a length of the channels for the array to comprise an average resistivity per channel of about 9700 .OMEGA.m or less.

Array of aligned and dispersed carbon nanotubes and method of producing the array

DOEpatents

Ivanov, Ilia N; Simpson, John T; Hendricks, Troy R

2013-06-11

An array of aligned and dispersed carbon nanotubes includes an elongate drawn body including a plurality of channels extending therethrough from a first end to a second end of the body, where the channels have a number density of at least about 100,000 channels/mm.sup.2 over a transverse cross-section of the body. A plurality of carbon nanotubes are disposed in each channel, and the carbon nanotubes are sufficiently dispersed and aligned along a length of the channels for the array to comprise an average resistivity per channel of about 9700 .OMEGA.m or less.

Arrays of Bundles of Carbon Nanotubes as Field Emitters

NASA Technical Reports Server (NTRS)

Manohara, Harish; Bronkowski, Michael

2007-01-01

Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

Vertically aligned carbon nanotubes for microelectrode arrays applications.

PubMed

Castro Smirnov, J R; Jover, Eric; Amade, Roger; Gabriel, Gemma; Villa, Rosa; Bertran, Enric

2012-09-01

In this work a methodology to fabricate carbon nanotube based electrodes using plasma enhanced chemical vapour deposition has been explored and defined. The final integrated microelectrode based devices should present specific properties that make them suitable for microelectrode arrays applications. The methodology studied has been focused on the preparation of highly regular and dense vertically aligned carbon nanotube (VACNT) mat compatible with the standard lithography used for microelectrode arrays technology.

A simple and transparent well-aligned ZnO nanowire array ultraviolet photodetector with high responsivity

NASA Astrophysics Data System (ADS)

Yin, Lei; Ding, Hesheng; Yuan, Zhaolin; Huang, Wendeng; Shuai, Chunjiang; Xiong, Zhaoxin; Deng, Jianping; Lv, Tengbo

2018-06-01

Well-aligned zinc oxide (ZnO) nanowire arrays were grown on an interdigital patterned fluorine tin oxide (FTO)-coated glass substrate by a facile chemical bath deposition at low temperature. Morphology, crystalline structure, and optical properties of the ZnO nanowire arrays were analyzed in detail. The results revealed that the ZnO nanowires had wurtzite structure, typically ∼40-60 nm in diameter, and ∼700-800 nm in length, a great number of highly uniform and dense nanowires grew vertically on the substrate to form the well-aligned ZnO nanowire arrays, which had very high optical transmission (>86%) in the visible light region. In addition, the performance of ZnO nanowire arrays ultraviolet (UV) photodetector was systematically examined. The photosensitivity (S), responsivity (R), response and decay time of the photodetector were 703 at +0.2 V, 113 A/W at +5 V, 23 s and 73 s respectively. Also, the photoresponse mechanism of the UV photodetector was illuminated in terms of the oxygen adsorption-photodesorption process.

Influence of anodization parameters on the morphology of TiO 2 nanotube arrays

NASA Astrophysics Data System (ADS)

Omidvar, Hamid; Goodarzi, Saba; Seif, Ahmad; Azadmehr, Amir R.

2011-07-01

TiO 2 nanotube arrays can be fabricated by electrochemical anodization in organic and inorganic electrolytes. Morphology of these nanotube arrays changes when anodization parameters such as applied voltage, type of electrolyte, time and temperature are varied. Nanotube arrays fabricated by anodization of commercial titanium in electrolytes containing NH 4F solution and either sulfuric or phosphoric acid were studied at room temperature; time of anodization was kept constant. Applied voltage, fluoride ion concentration, and acid concentrations were varied and their influences on TiO 2 nanotubes were investigated. The current density of anodizing was recorded by computer controlled digital multimeter. The surface morphology (top-view) of nanotube arrays were observed by SEM. The nanotube arrays in this study have inner diameters in range of 40-80 nm.

Quantum dots coupled ZnO nanowire-array panels and their photocatalytic activities.

PubMed

Liao, Yulong; Que, Wenxiu; Zhang, Jin; Zhong, Peng; Yuan, Yuan; Qiu, Xinku; Shen, Fengyu

2013-02-01

Fabrication and characterization of a heterojunction structured by CdS quantum dots@ZnO nanowire-array panels were presented. Firstly, ZnO nanowire-array panels were prepared by using a chemical bath deposition approach where wurtzite ZnO nanowires with a diameter of about 100 nm and 3 microm in length grew perpendicularly to glass substrate. Secondly, CdS quantum dots were deposited onto the surface of the ZnO nanowire-arrays by using successive ion layer absorption and reaction method, and the CdS shell/ZnO core heterojunction were thus obtained. Field emission scanning electron microscopy and transmission electron microscope were employed to characterize the morphological properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. X-ray diffraction was adopted to characterize the crystalline properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. Methyl orange was taken as a model compound to confirm the photocatalytic activities of the CdS shell/ZnO core heterojunction. Results indicate that CdS with narrow band gap not only acts as a visible-light sensitizer but also is responsible for an effective charge separation.

Efficiency improvement of silicon solar cells enabled by ZnO nanowhisker array coating

PubMed Central

2012-01-01

An efficient antireflection coating is critical for the improvement of silicon solar cell performance via increased light coupling. Here, we have grown well-aligned ZnO nanowhisker (NW) arrays on Czochralski silicon solar cells by a seeding-growth two-step process. It is found that the ZnO NWs have a great effect on the macroscopic antireflection effect and, therefore, improves the solar cell performance. The ZnO NW array-coated solar cells display a broadband reflection suppression from 500 to 1,100 nm, and the minimum reflectance smaller than 3% can easily be achieved. By optimizing the time of ZnO NW growth, it has been confirmed that an increase of 3% relatively in the solar cell efficiency can be obtained. These results are quite interesting for the application of ZnO nanostructure in the fabrication of high-efficiency silicon solar cells. PMID:22704578

Surface modification of oxygen-deficient ZnO nanotubes by interstitially incorporated carbon: a superior photocatalytic platform for sustainable water and surface treatments

NASA Astrophysics Data System (ADS)

Ninnora Meethal, Bhabhina; Ramanarayanan, Rajita; Swaminathan, Sindhu

2018-05-01

An interesting architecture of robust, highly reproducible, template-free synthesis of phase pure carbon-incorporated short ZnO nanotubes through polymer assisted sol-gel method is presented here. These nanotubes exhibit enormous surface oxygen vacancies and mid bandgap levels confirmed by X-ray photoelectron spectroscopy. These carbon-modified nanotubes exhibit encouraging results in photocatalytic studies, as there is a 16% greater degradation of contaminant dye than in the pristine ZnO nanotube. The reactive oxygen species generated from the photocatalysts were experimentally confirmed and quantified. Super hydrophilic nature renders these nanotubes suitable for antifogging application as observed from contact angle measurements. Characterisation and mechanism of a competent material with improved photoresponse, promising greater energy efficiency and anti-fog have been described in this investigation.

Antibacterial activity and inflammation inhibition of ZnO nanoparticles embedded TiO2 nanotubes.

PubMed

Yao, Shenglian; Feng, Xujia; Lu, Jiaju; Zheng, Yudong; Wang, Xiumei; Volinsky, Alex A; Wang, Lu-Ning

2018-06-15

Titanium (Ti) with nanoscale structure on the surface exhibits excellent biocompatibility and bone integration. Once implanted, the surgical implantation may lead to bacterial infection and inflammatory reaction, which cause the implant failure. In this work, irregular and nanorod-shaped ZnO nanoparticles were doped into TiO 2 nanotubes (TNTs) with inner diameter of about 50 nm by electro-deposition. The antibacterial properties of ZnO incorporated into TiO 2 nanotubes (TNTs/ZnO) were evaluated using Staphylococcus aureus (S. aureus). Zn ions released from the nanoparticles and the morphology could work together, improving antibacterial effectiveness up to 99.3% compared with the TNTs. Macrophages were cultured on the samples to determine their respective anti-inflammatory properties. The proliferation and viability of macrophages were evaluated by the CCK-8 method and Live&Dead stain, and the morphology of the cells was observed by scanning electron microscopy. Results indicated that TNTs/ZnO has a significant inhibitory effect on the proliferation and adhesion of macrophages, which could be used to prevent chronic inflammation and control the inflammatory reaction. Besides, the release of Zn ions from the ZnO nanoparticles is a long-term process, which could be beneficial for bone integration. Results demonstrate that ZnO deposited into TNTs improved the antibacterial effectiveness and weakened the inflammatory reaction of titanium-based implants, which is a promising approach to enhance their bioactivity.

Antibacterial activity and inflammation inhibition of ZnO nanoparticles embedded TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Yao, Shenglian; Feng, Xujia; Lu, Jiaju; Zheng, Yudong; Wang, Xiumei; Volinsky, Alex A.; Wang, Lu-Ning

2018-06-01

Titanium (Ti) with nanoscale structure on the surface exhibits excellent biocompatibility and bone integration. Once implanted, the surgical implantation may lead to bacterial infection and inflammatory reaction, which cause the implant failure. In this work, irregular and nanorod-shaped ZnO nanoparticles were doped into TiO2 nanotubes (TNTs) with inner diameter of about 50 nm by electro-deposition. The antibacterial properties of ZnO incorporated into TiO2 nanotubes (TNTs/ZnO) were evaluated using Staphylococcus aureus (S. aureus). Zn ions released from the nanoparticles and the morphology could work together, improving antibacterial effectiveness up to 99.3% compared with the TNTs. Macrophages were cultured on the samples to determine their respective anti-inflammatory properties. The proliferation and viability of macrophages were evaluated by the CCK-8 method and Live&Dead stain, and the morphology of the cells was observed by scanning electron microscopy. Results indicated that TNTs/ZnO has a significant inhibitory effect on the proliferation and adhesion of macrophages, which could be used to prevent chronic inflammation and control the inflammatory reaction. Besides, the release of Zn ions from the ZnO nanoparticles is a long-term process, which could be beneficial for bone integration. Results demonstrate that ZnO deposited into TNTs improved the antibacterial effectiveness and weakened the inflammatory reaction of titanium-based implants, which is a promising approach to enhance their bioactivity.

Periodically striped films produced from super-aligned carbon nanotube arrays.

PubMed

Liu, Kai; Sun, Yinghui; Liu, Peng; Wang, Jiaping; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

2009-08-19

We report a novel way to draw films from super-aligned carbon nanotube arrays at large drawing angles. The obtained super-aligned carbon nanotube films have a periodically striped configuration with alternating thinner and thicker film sections, and the width of the stripes is equal to the height of the original arrays. Compared with ordinary uniform films, the striped films provide a better platform for understanding the mechanism of spinning films from arrays because carbon nanotube junctions are easily observed and identified at the boundary of the stripes. Further studies show that the carbon nanotube junctions are bottleneck positions for thermal conduction and mechanical strength of the film, but do not limit its electrical conduction. These films can be utilized as striped and high-degree polarized light emission sources. Our results will be valuable for new applications and future large-scale production of tunable super-aligned carbon nanotube films.

MOF-5 decorated hierarchical ZnO nanorod arrays and its photoluminescence

NASA Astrophysics Data System (ADS)

Zhang, Yinmin; Lan, Ding; Wang, Yuren; Cao, He; Jiang, Heng

2011-04-01

The strategy to manipulate nanoscale materials into well-organized hierarchical architectures is very important to both material synthesis and nanodevice applications. Here, nanoscale MOF-5 crystallites were successfully fabricated onto ordered hierarchical ZnO arrays based on aqueous chemical synthesis and molecule self-assembly technology guided room temperature diffusion method, which has the advantages of energy saving and simple operation. The structures and morphologies of the samples were performed by X-ray powder diffraction and field emission scanning electronic microscopy. The MOF-5 crystallites have good quality and bind well to the hexagonal-patterned ZnO arrays. The photoluminescence spectrum shows that the emission of hybrid MOF-5-ZnO films displays a blue shift in green emission and intensity reduction in UV emission. This ordered hybrid semiconductor material is expected to exploit the great potentiality in sensors, micro/nanodevices, and screen displays.

Electrochemical properties of Ti3+ doped Ag-Ti nanotube arrays coated with hydroxyapatite

NASA Astrophysics Data System (ADS)

Zhang, Hangzhou; Shi, Xiaoguo; Tian, Ang; Wang, Li; Liu, Chuangwei

2018-04-01

Ag-Ti nanotube array was prepared by simple anodic oxidation method and uniform hydroxyapatite were electrochemically deposited on the nanotubes, and then characterized by SEM, XRD, XPS and EIS. In order to investigate the influence of Ti3+ on the electrochemical deposition of hydroxyapatite on the nanotubes, the Ag-Ti nanotube array self-doped with Ti3+ was prepared by one step reduction method. The experiment results revealed that the Ti3+ can promote the grow rate of hydroxyapatite coatings on nanotube surface. The hydroxyapatite coated Ag-Ti nanotube arrays with Ti3+ exhibit excellent stability and higher corrosion resistance. Moreover, the compact and dense hydroxyapatite coating can also prevent the Ag atom erosion from the Ag-Ti nanotube.

A novel flexible nanogenerator made of ZnO nanoparticles and multiwall carbon nanotube

NASA Astrophysics Data System (ADS)

Sun, Hui; Tian, He; Yang, Yi; Xie, Dan; Zhang, Yu-Chi; Liu, Xuan; Ma, Shuo; Zhao, Hai-Ming; Ren, Tian-Ling

2013-06-01

In this paper, a novel flexible nanogenerator (FNG) made of zinc-oxide (ZnO) nanoparticles (NPs) and multiwall-carbon nanotubes (MW-CNTs) is presented. In this structure, ZnO NPs and MW-CNTs are mixed with polydimethylsiloxane (PDMS) uniformly to form an entire flexible nanogenerator. Serial tests illustrate that the output voltage and power density are as high as 7.5 V and 18.75 μW per cycle, respectively. Furthermore, by foot stamp on the FNG, a peak voltage as high as 30 V can be generated. Comparing to the control samples, it is also proved that adding MW-CNTs into the matrix could significantly enhance the output voltage from 0.8 to 7.5 V. In summary, our work indicates that the realization of flexible nanogenerators made of ZnO NPs and MW-CNTs is technologically feasible, which may bring out some important and interesting applications in energy harvesting.In this paper, a novel flexible nanogenerator (FNG) made of zinc-oxide (ZnO) nanoparticles (NPs) and multiwall-carbon nanotubes (MW-CNTs) is presented. In this structure, ZnO NPs and MW-CNTs are mixed with polydimethylsiloxane (PDMS) uniformly to form an entire flexible nanogenerator. Serial tests illustrate that the output voltage and power density are as high as 7.5 V and 18.75 μW per cycle, respectively. Furthermore, by foot stamp on the FNG, a peak voltage as high as 30 V can be generated. Comparing to the control samples, it is also proved that adding MW-CNTs into the matrix could significantly enhance the output voltage from 0.8 to 7.5 V. In summary, our work indicates that the realization of flexible nanogenerators made of ZnO NPs and MW-CNTs is technologically feasible, which may bring out some important and interesting applications in energy harvesting. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00866e

Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

NASA Astrophysics Data System (ADS)

Filippin, A. Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A.; Borras, Ana

2016-02-01

A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor.

Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

PubMed Central

Filippin, A. Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A.; Borras, Ana

2016-01-01

A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor. PMID:26860367

Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

NASA Astrophysics Data System (ADS)

Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

2015-03-01

Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties.

PubMed

Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

2015-01-01

Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

Generic Synthesis of Carbon Nanotube Branches on Metal Oxide Arrays Exhibiting Stable High-Rate and Long-Cycle Sodium-Ion Storage.

PubMed

Xia, Xinhui; Chao, Dongliang; Zhang, Yongqi; Zhan, Jiye; Zhong, Yu; Wang, Xiuli; Wang, Yadong; Shen, Ze Xiang; Tu, Jiangping; Fan, Hong Jin

2016-06-01

A new and generic strategy to construct interwoven carbon nanotube (CNT) branches on various metal oxide nanostructure arrays (exemplified by V2 O3 nanoflakes, Co3 O4 nanowires, Co3 O4 -CoTiO3 composite nanotubes, and ZnO microrods), in order to enhance their electrochemical performance, is demonstrated for the first time. In the second part, the V2 O3 /CNTs core/branch composite arrays as the host for Na(+) storage are investigated in detail. This V2 O3 /CNTs hybrid electrode achieves a reversible charge storage capacity of 612 mAh g(-1) at 0.1 A g(-1) and outstanding high-rate cycling stability (a capacity retention of 100% after 6000 cycles at 2 A g(-1) , and 70% after 10 000 cycles at 10 A g(-1) ). Kinetics analysis reveals that the Na(+) storage is a pseudocapacitive dominating process and the CNTs improve the levels of pseudocapacitive energy by providing a conductive network. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ice-assisted transfer of carbon nanotube arrays.

PubMed

Wei, Haoming; Wei, Yang; Lin, Xiaoyang; Liu, Peng; Fan, Shoushan; Jiang, Kaili

2015-03-11

Decoupling the growth and the application of nanomaterials by transfer is an important issue in nanotechnology. Here, we developed an efficient transfer technique for carbon nanotube (CNT) arrays by using ice as a binder to temporarily bond the CNT array and the target substrate. Ice makes it an ultraclean transfer because the evaporation of ice ensures that no contaminants are introduced. The transferred superaligned carbon nanotube (SACNT) arrays not only keep their original appearance and initial alignment but also inherit their spinnability, which is the most desirable feature. The transfer-then-spin strategy can be employed to fabricate patterned CNT arrays, which can act as 3-dimensional electrodes in CNT thermoacoustic chips. Besides, the flip-chipped CNTs are promising field electron emitters. Furthermore, the ice-assisted transfer technique provides a cost-effective solution for mass production of SACNTs, giving CNT technologies a competitive edge, and this method may inspire new ways to transfer other nanomaterials.

Soft-solution route to ZnO nanowall array with low threshold power density

NASA Astrophysics Data System (ADS)

Jang, Eue-Soon; Chen, Xiaoyuan; Won, Jung-Hee; Chung, Jae-Hun; Jang, Du-Jeon; Kim, Young-Woon; Choy, Jin-Ho

2010-07-01

ZnO nanowall array (ZNWA) has been directionally grown on the buffer layer of ZnO nanoparticles dip-coated on Si-wafer under a soft solution process. Nanowalls on substrate are in most suitable shape and orientation not only as an optical trap but also as an optical waveguide due to their unique growth habit, V[011¯0]≫V[0001]≈V[0001¯]. Consequently, the stimulated emission at 384 nm through nanowalls is generated by the threshold power density of only 25 kW/cm2. Such UV lasing properties are superior to those of previously reported ZnO nanorod arrays. Moreover, there is no green (defect) emission due to the mild procedure to synthesize ZNWA.

Block Copolymers as Templates for Arrays of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Bronikowski, Michael; Hunt, Brian

2003-01-01

A method of manufacturing regular arrays of precisely sized, shaped, positioned, and oriented carbon nanotubes has been proposed. Arrays of carbon nanotubes could prove useful in such diverse applications as communications (especially for filtering of signals), biotechnology (for sequencing of DNA and separation of chemicals), and micro- and nanoelectronics (as field emitters and as signal transducers and processors). The method is expected to be suitable for implementation in standard semiconductor-device fabrication facilities.

Hydrothermal growth of ZnO nanowire arrays: fine tuning by precursor supersaturation

DOE PAGES

Yan, Danhua; Cen, Jiajie; Zhang, Wenrui; ...

2016-12-20

In this paper, we develop a technique that fine tunes the hydrothermal growth of ZnO nanowires to address the difficulties in controlling their growth in a conventional one-pot hydrothermal method. In our technique, precursors are separately and slowly supplied with the assistance of a syringe pump, through the entire course of the growth. Compared to the one-pot method, the significantly lowered supersaturation of precursors helps eliminating competitive homogeneous nucleation and improves the reproducibility. The supersaturation degree can be readily tuned by the precursor quantity and injection rate, thus forming ZnO nanowire arrays of various geometries and packing densities in amore » highly controllable fashion. The precise control of ZnO nanowire growth enables systematic studies on the correlation between the material's properties and its morphology. Finally, in this work, ZnO nanowire arrays of various morphologies are studied as photoelectrochemical (PEC) water splitting photoanodes, in which we establish clear correlations between the water splitting performance and the nanowires' size, shape, and packing density.« less

Preparation of arrays of long carbon nanotubes using catalyst structure

DOEpatents

Zhu, Yuntian T.; Arendt, Paul; Li, Qingwen; Zhang, Xiefie

2016-03-22

A structure for preparing an substantially aligned array of carbon nanotubes include a substrate having a first side and a second side, a buffer layer on the first side of the substrate, a catalyst on the buffer layer, and a plurality of channels through the structure for allowing a gaseous carbon source to enter the substrate at the second side and flow through the structure to the catalyst. After preparing the array, a fiber of carbon nanotubes may be spun from the array. Prior to spinning, the array can be immersed in a polymer solution. After spinning, the polymer can be cured.

ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells

PubMed Central

2014-01-01

Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm2 illumination, and a remarkable short-circuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as well as the direct contact between ZnO and weaved titanium wires. These results indicate that CdS/ZnO nanostructures on weaved titanium wires would open a novel possibility for applications of low-cost solar cells. PMID:24618047

Ultrahigh density alignment of carbon nanotube arrays by dielectrophoresis.

PubMed

Shekhar, Shashank; Stokes, Paul; Khondaker, Saiful I

2011-03-22

We report ultrahigh density assembly of aligned single-walled carbon nanotube (SWNT) two-dimensional arrays via AC dielectrophoresis using high-quality surfactant-free and stable SWNT solutions. After optimization of frequency and trapping time, we can reproducibly control the linear density of the SWNT between prefabricated electrodes from 0.5 SWNT/μm to more than 30 SWNT/μm by tuning the concentration of the nanotubes in the solution. Our maximum density of 30 SWNT/μm is the highest for aligned arrays via any solution processing technique reported so far. Further increase of SWNT concentration results in a dense array with multiple layers. We discuss how the orientation and density of the nanotubes vary with concentrations and channel lengths. Electrical measurement data show that the densely packed aligned arrays have low sheet resistances. Selective removal of metallic SWNTs via controlled electrical breakdown produced field-effect transistors with high current on-off ratio. Ultrahigh density alignment reported here will have important implications in fabricating high-quality devices for digital and analog electronics.

Embedded arrays of vertically aligned carbon nanotube carpets and methods for making them

DOEpatents

Kim, Myung Jong; Nicholas, Nolan Walker; Kittrell, W. Carter; Schmidt, Howard K.

2015-06-30

According to some embodiments, the present invention provides a system and method for supporting a carbon nanotube array that involve an entangled carbon nanotube mat integral with the array, where the mat is embedded in an embedding material. The embedding material may be depositable on a carbon nanotube. A depositable material may be metallic or nonmetallic. The embedding material may be an adhesive material. The adhesive material may optionally be mixed with a metal powder. The embedding material may be supported by a substrate or self-supportive. The embedding material may be conductive or nonconductive. The system and method provide superior mechanical and, when applicable, electrical, contact between the carbon nanotubes in the array and the embedding material. The optional use of a conductive material for the embedding material provides a mechanism useful for integration of carbon nanotube arrays into electronic devices.

Scalable continuous flow synthesis of ZnO nanorod arrays in 3-D ceramic honeycomb substrates for low-temperature desulfurization

DOE PAGES

Wang, Sibo; Wu, Yunchao; Miao, Ran; ...

2017-07-26

Scalable and cost-effective synthesis and assembly of technologically important nanostructures in three-dimensional (3D) substrates hold keys to bridge the demonstrated nanotechnologies in academia with industrially relevant scalable manufacturing. In this paper, using ZnO nanorod arrays as an example, a hydrothermal-based continuous flow synthesis (CFS) method is successfully used to integrate the nano-arrays in multi-channeled monolithic cordierite. Compared to the batch process, CFS enhances the average growth rate of nano-arrays by 125%, with the average length increasing from 2 μm to 4.5 μm within the same growth time of 4 hours. The precursor utilization efficiency of CFS is enhanced by 9more » times compared to that of batch process by preserving the majority of precursors in recyclable solution. Computational fluid dynamic simulation suggests a steady-state solution flow and mass transport inside the channels of honeycomb substrates, giving rise to steady and consecutive growth of ZnO nano-arrays with an average length of 10 μm in 12 h. The monolithic ZnO nano-array-integrated cordierite obtained through CFS shows enhanced low-temperature (200 °C) desulfurization capacity and recyclability in comparison to ZnO powder wash-coated cordierite. This can be attributed to exposed ZnO {101¯0} planes, better dispersion and stronger interactions between sorbent and reactant in the ZnO nanorod arrays, as well as the sintering-resistance of nano-array configurations during sulfidation–regeneration cycles. Finally, with the demonstrated scalable synthesis and desulfurization performance of ZnO nano-arrays, a promising, industrially relevant integration strategy is provided to fabricate metal oxide nano-array-based monolithic devices for various environmental and energy applications.« less

Scalable continuous flow synthesis of ZnO nanorod arrays in 3-D ceramic honeycomb substrates for low-temperature desulfurization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Sibo; Wu, Yunchao; Miao, Ran

Scalable and cost-effective synthesis and assembly of technologically important nanostructures in three-dimensional (3D) substrates hold keys to bridge the demonstrated nanotechnologies in academia with industrially relevant scalable manufacturing. In this paper, using ZnO nanorod arrays as an example, a hydrothermal-based continuous flow synthesis (CFS) method is successfully used to integrate the nano-arrays in multi-channeled monolithic cordierite. Compared to the batch process, CFS enhances the average growth rate of nano-arrays by 125%, with the average length increasing from 2 μm to 4.5 μm within the same growth time of 4 hours. The precursor utilization efficiency of CFS is enhanced by 9more » times compared to that of batch process by preserving the majority of precursors in recyclable solution. Computational fluid dynamic simulation suggests a steady-state solution flow and mass transport inside the channels of honeycomb substrates, giving rise to steady and consecutive growth of ZnO nano-arrays with an average length of 10 μm in 12 h. The monolithic ZnO nano-array-integrated cordierite obtained through CFS shows enhanced low-temperature (200 °C) desulfurization capacity and recyclability in comparison to ZnO powder wash-coated cordierite. This can be attributed to exposed ZnO {101¯0} planes, better dispersion and stronger interactions between sorbent and reactant in the ZnO nanorod arrays, as well as the sintering-resistance of nano-array configurations during sulfidation–regeneration cycles. Finally, with the demonstrated scalable synthesis and desulfurization performance of ZnO nano-arrays, a promising, industrially relevant integration strategy is provided to fabricate metal oxide nano-array-based monolithic devices for various environmental and energy applications.« less

A novel flexible nanogenerator made of ZnO nanoparticles and multiwall carbon nanotube.

PubMed

Sun, Hui; Tian, He; Yang, Yi; Xie, Dan; Zhang, Yu-Chi; Liu, Xuan; Ma, Shuo; Zhao, Hai-Ming; Ren, Tian-Ling

2013-07-07

In this paper, a novel flexible nanogenerator (FNG) made of zinc-oxide (ZnO) nanoparticles (NPs) and multiwall-carbon nanotubes (MW-CNTs) is presented. In this structure, ZnO NPs and MW-CNTs are mixed with polydimethylsiloxane (PDMS) uniformly to form an entire flexible nanogenerator. Serial tests illustrate that the output voltage and power density are as high as 7.5 V and 18.75 μW per cycle, respectively. Furthermore, by foot stamp on the FNG, a peak voltage as high as 30 V can be generated. Comparing to the control samples, it is also proved that adding MW-CNTs into the matrix could significantly enhance the output voltage from 0.8 to 7.5 V. In summary, our work indicates that the realization of flexible nanogenerators made of ZnO NPs and MW-CNTs is technologically feasible, which may bring out some important and interesting applications in energy harvesting.

Structural, optical, and electrical properties of Ni-doped ZnO nanorod arrays prepared via sonicated sol-gel immersion method

NASA Astrophysics Data System (ADS)

Ismail, A. S.; Mamat, M. H.; Malek, M. F.; Saidi, S. A.; Yusoff, M. M.; Mohamed, R.; Sin, N. D. Md; Suriani, A. B.; Rusop, M.

2018-05-01

Nickel (Ni)-doped zinc oxide (ZnO) nanorod array films were synthesised using sonicated sol-gel immersion method. The FESEM images showed that the Ni-doped ZnO nanorod arrays possess hexagonal shape with average diameter about 120 nm and thickness about 1.10 µm. The Ni-doped ZnO nanorod arrays possess better transmittance properties with 3.27 eV of optical band gap energy and 40 meV of urbach energy. The current-voltage (I-V) measurement indicated that the conductivity of ZnO film slightly improved with Ni-doping. The doped film displayed good humidity sensing performance with sensitivity of 1.21.

Self-organized nitrogen and fluorine co-doped titanium oxide nanotube arrays with enhanced visible light photocatalytic performance.

PubMed

Li, Qi; Shang, Jian Ku

2009-12-01

Self-organized nitrogen and fluorine co-doped titanium oxide (TiONF) nanotube arrays were created by anodizing titanium foil in a fluoride and ammoniate-based electrolyte, followed by calcination of the amorphous nanotube arrays under a nitrogen protective atmosphere for crystallization. TiONF nanotube arrays were found to have enhanced visible light absorption capability and photodegradation efficiency on methylene blue under visible light illumination over the TiO(2) nanotube arrays. The enhancement was dependent on both the nanotube structural architecture and the nitrogen and fluorine co-doping effect. TiONF nanotube arrays promise a wide range of technical applications, especially for environmental applications and solar cell devices.

Carbon Nanotube Nanoelectrode Array for Ultrasensitive DNA Detection

NASA Technical Reports Server (NTRS)

Li, Jun; Koehne, Jessica; Chen, Hua; Cassell, Alan; Ng, Hou Tee; Fan, Wendy; Ye, Qi; Han, Jie; Meyyappan, M.

2003-01-01

A reliable nanoelectrode array based on vertically aligned multi-walled carbon nanotubes (MWNTs) embedded in SiO2 is used for ultrasensitive DNA detection. Characteristic nanoelectrode behavior is observed using low-density MWNT arrays for measuring both bulk and surface immobilized redox species such as K4Fe(CN)6. The open-end of MWNTs present similar properties as graphite edge-plane electrodes with wide potential window, flexible chemical functionalities, and good biocompatibility. Oligonucleotide probes are selectively functionalized at the open ends cf the nanotube array and specifically hybridized with oligonucleotide targets. The guanine groups are employed as the signal moieties in the electrochemical measurements. Ru(bpy)3(2+) mediator is used to further amplify the guanine oxidation signal. The hybridization of subattomoles of PCR amplified DNA targets is detected electrochemically by combining the MWNT nanoelectrode array with the Ru(bpy)32' amplification mechanism. This system provides a general platform of molecular diagnostics for applications requiring ultrahigh sensitivity, high-degree of miniaturization, and simple sample preparations.

Flower-like ZnO nanorod arrays grown on HF-etched Si (111): constraining relation between ZnO seed layer and Si (111)

NASA Astrophysics Data System (ADS)

Brahma, Sanjaya; Liu, C.-W.; Huang, R.-J.; Chang, S.-J.; Lo, K.-Y.

2015-11-01

We demonstrate the formation of self-assembled homogenous flower-like ZnO nanorods over a ZnO seed layer deposited on a HF-etched Si (111) substrate. The typical flower-like morphology of ZnO nanorod arrays is ascribed to the formation of the island-like seed layer which is deposited by the drop method followed by annealing at 300 °C. The island-like ZnO seed layer consists of larger ZnO grains, and is built by constraining of the Si (111) surface due to pattern matching. Pattern matching of Si with ZnO determines the shape and size of the seed layer and this controls the final morphology of ZnO nanorods to be either flower like or vertically aligned. The high quality of the island-like ZnO seed layer enhances the diameter and length of ZnO nanorods. Besides, while the amorphous layer formed during the annealing process would influence the strained ZnO grain, that subsequent amorphous layer will not block the constraining between the ZnO grain and the substrate.

Self-assembled ordered carbon-nanotube arrays and membranes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Overmyer, Donald L.; Siegal, Michael P.; Yelton, William Graham

2004-11-01

Imagine free-standing flexible membranes with highly-aligned arrays of carbon nanotubes (CNTs) running through their thickness. Perhaps with both ends of the CNTs open for highly controlled nanofiltration? Or CNTs at heights uniformly above a polymer membrane for a flexible array of nanoelectrodes or field-emitters? How about CNT films with incredible amounts of accessible surface area for analyte adsorption? These self-assembled crystalline nanotubes consist of multiple layers of graphene sheets rolled into concentric cylinders. Tube diameters (3-300 nm), inner-bore diameters (2-15 nm), and lengths (nanometers - microns) are controlled to tailor physical, mechanical, and chemical properties. We proposed to explore growthmore » and characterize nanotube arrays to help determine their exciting functionality for Sandia applications. Thermal chemical vapor deposition growth in a furnace nucleates from a metal catalyst. Ordered arrays grow using templates from self-assembled hexagonal arrays of nanopores in anodized-aluminum oxide. Polymeric-binders can mechanically hold the CNTs in place for polishing, lift-off, and membrane formation. The stiffness, electrical and thermal conductivities of CNTs make them ideally suited for a wide-variety of possible applications. Large-area, highly-accessible gas-adsorbing carbon surfaces, superb cold-cathode field-emission, and unique nanoscale geometries can lead to advanced microsensors using analyte adsorption, arrays of functionalized nanoelectrodes for enhanced electrochemical detection of biological/explosive compounds, or mass-ionizers for gas-phase detection. Materials studies involving membrane formation may lead to exciting breakthroughs in nanofiltration/nanochromatography for the separation of chemical and biological agents. With controlled nanofilter sizes, ultrafiltration will be viable to separate and preconcentrate viruses and many strains of bacteria for 'down-stream' analysis.« less

Novel Gas Sensor Based on ZnO Nanorod Circular Arrays for C2H5OH Gas Detection.

PubMed

Jianjiao, Zhang; Hongyan, Yue; Erjun, Guo; Shaolin, Zhang; Liping, Wang; Chunyu, Zhang; Xin, Gao; Jing, Chang; Hong, Zhang

2015-03-01

Novel side-heating gas sensor based on ZnO nanorod circular arrays was firstly fabricated by hydrothermal treatment assisted with a kind of simple dip-coating technique. The structure and morphologies of ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), respectively. XRD result indicates that the obtained ZnO nanorods have good crystalline with the hexagonal wurtzite structure. SEM result indicates that ZnO nanorod arrays are vertically growth on the surface of ceramic tube of side-heating sensor with controlled diameter and length, narrow size distribution and high orientation. The gas sensing properties of ZnO nanorod circular arrays are also evaluated. Comparative to the sensor based on scattered ZnO nanorods responding to 25 ppm H2, CO, C6H5CH3 and C2H5OH gas, respectively, the sensing values of high orientation gas sensor are generally increased by 5%. This novel sensor has good application promising for the fabrication of cost effective and high performance gas sensors.

Renewable Lignosulfonate-Assisted Synthesis of Hierarchical Nanoflake-Array-Flower ZnO Nanomaterials in Mixed Solvents and Their Photocatalytic Performance

NASA Astrophysics Data System (ADS)

Li, Yue; Zuo, Hong-Fen; Guo, Yuan-Ru; Miao, Ting-Ting; Pan, Qing-Jiang

2016-05-01

With the assistance of sodium lignosulfonate, hierarchical nanoflake-array-flower nanostructure of ZnO has been fabricated by a facile precipitation method in mixed solvents. The sodium lignosulfonate amount used in our synthetic route is able to fine-tune ZnO morphology and an abundance of pores have been observed in the nanoflake-array-flower ZnO, which result in specific surface area reaching as high as 82.9 m2 · g-1. The synthesized ZnO exhibits superior photocatalytic activity even under low-power UV illumination (6 W). It is conjectured that both nanoflake-array structure and plenty of pores embedded in ZnO flakes may provide scaffold microenvironments to enhance photocatalytic activity. Additionally, this catalyst can be used repeatedly without a significant loss in photocatalytic activity. The low-cost, simple synthetic approach as well as high photocatalytic and recycling efficiency of our ZnO nanomaterials allows for application to treat wastewater containing organic pollutants in an effective way.

P(VDF-TrFE) ferroelectric nanotube array for high energy density capacitor applications.

PubMed

Li, Xue; Lim, Yee-Fun; Yao, Kui; Tay, Francis Eng Hock; Seah, Kar Heng

2013-01-14

Poly(vinylidene-fluoride-co-trifluoroethylene) (P(VDF-TrFE)) ferroelectric nanotube arrays were fabricated using an anodized alumina membrane (AAM) as a template and silver electrodes were deposited on both the outer and inner sides of the nanotubes by an electroless plating method. The nanotubes have the unique structure of being sealed at one end and linked at the open end, thus preventing electrical shorting between the inner and outer electrodes. Compared with a P(VDF-TrFE) film with a similar overall thickness, the idealized nanotube array has a theoretical capacitance that is 763 times larger due to the greatly enlarged contact area between the electrodes and the polymer dielectric. A capacitance that is 95 times larger has been demonstrated experimentally, thus indicating that such nanotube arrays are promising for realizing high density capacitance and high power dielectric energy storage.

Arrays of Carbon Nanotubes as RF Filters in Waveguides

NASA Technical Reports Server (NTRS)

Hoppe, Daniel; Hunt, Brian; Hoenk, Michael; Noca, Flavio; Xu, Jimmy

2003-01-01

Brushlike arrays of carbon nanotubes embedded in microstrip waveguides provide highly efficient (high-Q) mechanical resonators that will enable ultraminiature radio-frequency (RF) integrated circuits. In its basic form, this invention is an RF filter based on a carbon nanotube array embedded in a microstrip (or coplanar) waveguide, as shown in Figure 1. In addition, arrays of these nanotube-based RF filters can be used as an RF filter bank. Applications of this new nanotube array device include a variety of communications and signal-processing technologies. High-Q resonators are essential for stable, low-noise communications, and radar applications. Mechanical oscillators can exhibit orders of magnitude higher Qs than electronic resonant circuits, which are limited by resistive losses. This has motivated the development of a variety of mechanical resonators, including bulk acoustic wave (BAW) resonators, surface acoustic wave (SAW) resonators, and Si and SiC micromachined resonators (known as microelectromechanical systems or MEMS). There is also a strong push to extend the resonant frequencies of these oscillators into the GHz regime of state-of-the-art electronics. Unfortunately, the BAW and SAW devices tend to be large and are not easily integrated into electronic circuits. MEMS structures have been integrated into circuits, but efforts to extend MEMS resonant frequencies into the GHz regime have been difficult because of scaling problems with the capacitively-coupled drive and readout. In contrast, the proposed devices would be much smaller and hence could be more readily incorporated into advanced RF (more specifically, microwave) integrated circuits.

Amorphous and crystalline TiO2 nanotube arrays for enhanced Li-ion intercalation properties.

PubMed

Guan, Dongsheng; Cai, Chuan; Wang, Ying

2011-04-01

We have employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials. The lengths and pore diameters of TiO2 nanotubes can be finely tuned by varying voltage, electrolyte composition, or anodization time. The as-prepared nanotubes are amorphous and can be converted into anatase nanotubes with heat treatment at 480 degrees C. Rutile crystallites emerge in the anatase nanotube when the annealing temperature is increased to 580 degrees C, resulting in TiO2 nanotubes of mixed phases. The morphological features of nanotubes remain unchanged after annealing. Li-ion insertion performance has been studied for amorphous and crystalline TiO2 nanotube arrays. Amorphous nanotubes with a length of 3.0 microm and an outer diameter of 125 nm deliver a capacity of 91.2 microA h cm(-2) at a current density of 400 microA cm(-2), while those with a length of 25 microm and an outer diameter of 158 nm display a capacity of 533 microA h cm-2. When the 3-microm long nanotubes become crystalline, they deliver lower capacities: the anatase nanotubes and nanotubes of mixed phases show capacities of 53.8 microA h cm-2 and 63.1 microA h cm(-2), respectively at the same current density. The amorphous nanotubes show excellent capacity retention ability over 50 cycles. The cycled nanotubes show little change in morphology compared to the nanotubes before electrochemical cycling. All the TiO2 nanotubes demonstrate higher capacities than amorphous TiO2 compact layer reported in literature. The amorphous TiO2 nanotubes with a length of 1.9 microm exhibit a capacity five times higher than that of TiO2 compact layer even when the nanotube array is cycled at a current density 80 times higher than that for the compact layer. These results suggest that anodic TiO2 nanotube arrays are promising electrode materials for rechargeable Li-ion batteries.

Toward single-chirality carbon nanotube device arrays.

PubMed

Vijayaraghavan, Aravind; Hennrich, Frank; Stürzl, Ninette; Engel, Michael; Ganzhorn, Marc; Oron-Carl, Matti; Marquardt, Christoph W; Dehm, Simone; Lebedkin, Sergei; Kappes, Manfred M; Krupke, Ralph

2010-05-25

The large-scale integration of devices consisting of individual single-walled carbon nanotubes (SWCNT), all of the same chirality, is a critical step toward their electronic, optoelectronic, and electromechanical application. Here, the authors realize two related goals, the first of which is the fabrication of high-density, single-chirality SWCNT device arrays by dielectrophoretic assembly from monodisperse SWCNT solution obtained by polymer-mediated sorting. Such arrays are ideal for correlating measurements using various techniques across multiple identical devices, which is the second goal. The arrays are characterized by voltage-contrast scanning electron microscopy, electron transport, photoluminescence (PL), and Raman spectroscopy and show identical signatures as expected for single-chirality SWCNTs. In the assembled nanotubes, a large D peak in Raman spectra, a large dark-exciton peak in PL spectra as well as lowered conductance and slow switching in electron transport are all shown to be correlated to each other. By comparison to control samples, we conclude that these are the result of scattering from electronic and not structural defects resulting from the polymer wrapping, similar to what has been predicted for DNA wrapping.

Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer

PubMed Central

2014-01-01

Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on. PACS 78.60.Fi; 85.60.Jb; 78.67.Lt; 81.10.Dn PMID:25489284

Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer.

PubMed

Dong, Jing-Jing; Hao, Hui-Ying; Xing, Jie; Fan, Zhen-Jun; Zhang, Zi-Li

2014-01-01

Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on. 78.60.Fi; 85.60.Jb; 78.67.Lt; 81.10.Dn.

Visible diffraction from quasi-crystalline arrays of carbon nanotubes

NASA Astrophysics Data System (ADS)

Butler, Timothy P.; Butt, Haider; Wilkinson, Timothy D.; Amaratunga, Gehan A. J.

2015-08-01

Large area arrays of vertically-aligned carbon nanotubes (VACNTs) are patterned in a quasi-crystalline Penrose tile arrangement through electron beam lithography definition of Ni catalyst dots and subsequent nanotube growth by plasma-enhanced chemical vapour deposition. When illuminated with a 532 nm laser beam high-quality and remarkable diffraction patterns are seen. The diffraction is well matched to theoretical calculations which assume apertures to be present at the location of the VACNTs for transmitted light. The results show that VACNTs act as diffractive elements in reflection and can be used as spatially phased arrays for producing tailored diffraction patterns.

Fabrication of needle-like ZnO nanorods arrays by a low-temperature seed-layer growth approach in solution

NASA Astrophysics Data System (ADS)

Zhang, Haimin; Quan, Xie; Chen, Shuo; Zhao, Huimin

2007-11-01

Uniform, large-scale, and well-aligned needle-like ZnO nanorods with good photoluminescence and photocatalysis properties on Zn substrates, have been successfully fabricated using a simple low-temperature seed-layer growth approach in solution (50 °C). The formation of ZnO seed-layer by the anodic oxidation technique (AOT) plays an important role in the subsequent growth of highly oriented ZnO nanorods arrays. Temperature also proved to be a significant factor in the growth of ZnO nanorods and had a great effect on their optical properties. X-ray diffraction (XRD) analysis, selected-area electron diffraction (SAED) pattern and high-resolution TEM (HRTEM) indicated that the needle-like ZnO nanorods were single crystal in nature and that they had grown up preferentially along the [0001] direction. The well-aligned ZnO nanorods arrays on Zn substrates exhibited strong UV emission at around 380 nm at room temperature. To investigate their potential as photocatalysts, degradation of pentachlorophenol (PCP) in aqueous solution was carried out using photocatalytic processes, with comparison to direct photolysis. After 1 h, the degradation efficiencies of PCP by direct photolysis and photocatalytic processes achieved 57% and 76% under given experimental conditions, respectively. This improved degradation efficiency of PCP illustrates that ZnO nanorods arrays on Zn substrates have good photocatalytic activity. This simple low-temperature seed-layer growth approach in solution resulted in the development of an effective and low-cost fabrication process for high-quality ZnO nanorods arrays with good optical and photocatalytic properties that can be applicable in many fields such as photocatalysis, photovoltaic cells, luminescent sensors, and photoconductive sensors.

Transparent anodic TiO2 nanotube arrays on plastic substrates for disposable biosensors and flexible electronics.

PubMed

Farsinezhad, Samira; Mohammadpour, Arash; Dalrymple, Ashley N; Geisinger, Jared; Kar, Piyush; Brett, Michael J; Shankar, Karthik

2013-04-01

Exploitation of anodically formed self-organized TiO2 nanotube arrays in mass-manufactured, disposable biosensors, rollable electrochromic displays and flexible large-area solar cells would greatly benefit from integration with transparent and flexible polymeric substrates. Such integration requires the vacuum deposition of a thin film of titanium on the desired substrate, which is then anodized in suitable media to generate TiO2 nanotube arrays. However the challenges associated with control of Ti film morphology, nanotube array synthesis conditions, and film adhesion and transparency, have necessitated the use of substrate heating during deposition to temperatures of at least 300 degrees C and as high as 500 degrees C to generate highly ordered open-pore nanotube arrays, thus preventing the use of polymeric substrates. We report on a film growth technique that exploits atomic peening to achieve high quality transparent TiO2 nanotube arrays with lengths up to 5.1 microm at room temperature on polyimide substrates without the need for substrate heating or substrate biasing or a Kauffman ion source. The superior optical quality and uniformity of the nanotube arrays was evidenced by the high specular reflectivity and the smooth pattern of periodic interferometric fringes in the transmission spectra of the nanotube arrays, from which the wavelength-dependent effective refractive index was extracted for the air-TiO2 composite medium. A fluorescent immunoassay biosensor constructed using 5.1 microm-long transparent titania nanotube arrays (TTNAs) grown on Kapton substrates detected human cardiac troponin I at a concentration of 0.1 microg ml(-1).

Chemical growth of ZnO nanorod arrays on textured nanoparticle nanoribbons and its second-harmonic generation performance

NASA Astrophysics Data System (ADS)

Gui, Zhou; Wang, Xian; Liu, Jian; Yan, Shanshan; Ding, Yanyan; Wang, Zhengzhou; Hu, Yuan

2006-07-01

On the basis of the highly oriented ZnO nanoparticle nanoribbons as the growth seed layer (GSL) and solution growth technique, we have synthesized vertical ZnO nanorod arrays with high density over a large area and multi-teeth brush nanostructure, respectively, according to the density degree of the arrangement of nanoparticle nanoribbons GSL on the glass substrate. This controllable and convenient technique opens the possibility of creating nanostructured film for industrial fabrication and may represent a facile way to get similar structures of other compounds by using highly oriented GSL to promote the vertical arrays growth. The growth mechanism of the formation of the ordered nanorod arrays is also discussed. The second-order nonlinear optical coefficient d31 of the vertical ZnO nanorod arrays measured by the Maker fringes technique is 11.3 times as large as that of d36 KH 2PO 4 (KDP).

Carbon Nanotube Array for Infrared Detection

DTIC Science & Technology

2011-09-28

Scientific Progress Technology Transfer 1    Carbon Nanotube Array for Infrared Detection Final Report Jimmy Xu...devices. In contrast to photocarrier generation across a band gap, nature’s bolometers convert infrared radiation into heating of tissues thereby...been investigated. [5, 6] High TCR is, however, not the only important parameter for bolometric sensing. Heat capacity, thermal conductivity

Efficient generation and transportation of energetic electrons in a carbon nanotube array target

NASA Astrophysics Data System (ADS)

Ji, Yanling; Jiang, Gang; Wu, Weidong; Wang, Chaoyang; Gu, Yuqiu; Tang, Yongjian

2010-01-01

Laser-driven energetic electron propagation in a carbon nanotube-array target is investigated using two-dimensional particle-in-cell simulations. Energetic electrons are efficiently generated when the array is irradiated by a short intense laser pulse. Confined and guided transportation of energetic electrons in the array is achieved by exploiting strong transient electromagnetic fields created at the wall surfaces of nanotubes. The underlying mechanisms are discussed in detail. Our investigation shows that the laser energy can be transferred more effectively to the target electrons in the array than that of in the flat foil due to the hole structures in the array.

Significant enhancement of yellow-green light emission of ZnO nanorod arrays using Ag island films

NASA Astrophysics Data System (ADS)

Lin, Chin-An; Tsai, Dung-Sheng; Chen, Cheng-Ying; He-Hau, Jr.

2011-03-01

Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO.Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO. Electronic supplementary information (ESI) available. See DOI: 10.1039/c0nr00732c

The detection of improvised nonmilitary peroxide based explosives using a titania nanotube array sensor.

PubMed

Banerjee, Subarna; Mohapatra, Susanta K; Misra, Mano; Mishra, Indu B

2009-02-18

There is a critical need to develop an efficient, reliable and highly selective sensor for the detection of improvised nonmilitary explosives. This paper describes the utilization of functionalized titania nanotube arrays for sensing improvised organic peroxide explosives such as triacetone triperoxide (TATP). TATP forms complexes with titania nanotube arrays (prepared by anodization and sensitized with zinc ions) and thus affects the electron state of the nanosensing device, which is signaled as a change in current of the overall nanotube material. The response is rapid and a signal of five to eight orders of magnitude is observed. These nanotube array sensors can be used as hand-held miniaturized devices as well as large scale portable units for military and homeland security applications.

Controlled Growth of Parallel Oriented ZnO Nanostructural Arrays on Ga2O3 Nanowires

DTIC Science & Technology

2008-11-01

Controlled Growth of Parallel Oriented ZnO Nanostructural Arrays on Ga2O3 Nanowires Lena Mazeina,* Yoosuf N. Picard, and Sharka M. Prokes Electronics...Manuscript ReceiVed NoVember 6, 2008 ABSTRACT: Novel hierarchical ZnO- Ga2O3 nanostructures were fabricated via a two stage growth process. Nanowires of Ga2O3 ...nanobrushes (NBs) with Ga2O3 as the core and ZnO as the branches self-assembling symmetrically in six equiangular directions around the core

Plasmon-enhanced Electrically Light-emitting from ZnO Nanorod Arrays/p-GaN Heterostructure Devices

PubMed Central

Lu, Junfeng; Shi, Zengliang; Wang, Yueyue; Lin, Yi; Zhu, Qiuxiang; Tian, Zhengshan; Dai, Jun; Wang, Shufeng; Xu, Chunxiang

2016-01-01

Effective and bright light-emitting-diodes (LEDs) have attracted broad interests in fundamental research and industrial application, especially on short wavelength LEDs. In this paper, a well aligned ZnO nanorod arrays grown on the p-GaN substrate to form a heterostructured light-emitting diode and Al nanoparticles (NPs) were decorated to improve the electroluminescence performance. More than 30-folds enhancement of the electroluminescence intensity was obtained compared with the device without Al NPs decoration. The investigation on the stable and transient photoluminescence spectraof the ZnO nanorod arrays before and after Al NPs decoration demonstrated that the metal surface plasmon resonance coupling with excitons of ZnO leads to the enhancement of the internal quantum efficiency (IQE). Our results provide aneffective approach to design novel optoelectronic devices such as light-emitting diodes and plasmonic nanolasers. PMID:27181337

Plasmon-enhanced Electrically Light-emitting from ZnO Nanorod Arrays/p-GaN Heterostructure Devices.

PubMed

Lu, Junfeng; Shi, Zengliang; Wang, Yueyue; Lin, Yi; Zhu, Qiuxiang; Tian, Zhengshan; Dai, Jun; Wang, Shufeng; Xu, Chunxiang

2016-05-16

Effective and bright light-emitting-diodes (LEDs) have attracted broad interests in fundamental research and industrial application, especially on short wavelength LEDs. In this paper, a well aligned ZnO nanorod arrays grown on the p-GaN substrate to form a heterostructured light-emitting diode and Al nanoparticles (NPs) were decorated to improve the electroluminescence performance. More than 30-folds enhancement of the electroluminescence intensity was obtained compared with the device without Al NPs decoration. The investigation on the stable and transient photoluminescence spectraof the ZnO nanorod arrays before and after Al NPs decoration demonstrated that the metal surface plasmon resonance coupling with excitons of ZnO leads to the enhancement of the internal quantum efficiency (IQE). Our results provide aneffective approach to design novel optoelectronic devices such as light-emitting diodes and plasmonic nanolasers.

THz generation by laser coupling to carbon nanotube array

NASA Astrophysics Data System (ADS)

Malik, Rakhee; Uma, R.

2018-01-01

A viable scheme of THz radiation generation by beating of two lasers ( ω1 , k→ 1 ; ω2 , k→ 2 ) in a nanotube array, mounted on a dielectric substrate, is proposed and studied. The free electrons of the nanotubes acquire a large oscillatory velocity and experience a beat frequency ponderomotive force that turns nanotubes into oscillating dipole antennae emitting THz radiation. The THz power peaks in directions where a phase difference between fields due to successive nanotubes is integral multiple of 2 π . The THz power is large when the beat frequency equals ωp/√{2 } (where ωp is the electron plasma frequency) and surface plasmon resonance occurs. For our set of laser and carbon nanotube parameters, the generated THz is about 0.1 kW for CO2 laser power of 10 GW and pulse length of a few picoseconds.

Arrays of horizontal carbon nanotubes of controlled chirality grown using designed catalysts

NASA Astrophysics Data System (ADS)

Zhang, Shuchen; Kang, Lixing; Wang, Xiao; Tong, Lianming; Yang, Liangwei; Wang, Zequn; Qi, Kuo; Deng, Shibin; Li, Qingwen; Bai, Xuedong; Ding, Feng; Zhang, Jin

2017-02-01

The semiconductor industry is increasingly of the view that Moore’s law—which predicts the biennial doubling of the number of transistors per microprocessor chip—is nearing its end. Consequently, the pursuit of alternative semiconducting materials for nanoelectronic devices, including single-walled carbon nanotubes (SWNTs), continues. Arrays of horizontal nanotubes are particularly appealing for technological applications because they optimize current output. However, the direct growth of horizontal SWNT arrays with controlled chirality, that would enable the arrays to be adapted for a wider range of applications and ensure the uniformity of the fabricated devices, has not yet been achieved. Here we show that horizontal SWNT arrays with predicted chirality can be grown from the surfaces of solid carbide catalysts by controlling the symmetries of the active catalyst surface. We obtained horizontally aligned metallic SWNT arrays with an average density of more than 20 tubes per micrometre in which 90 per cent of the tubes had chiral indices of (12, 6), and semiconducting SWNT arrays with an average density of more than 10 tubes per micrometre in which 80 per cent of the nanotubes had chiral indices of (8, 4). The nanotubes were grown using uniform size Mo2C and WC solid catalysts. Thermodynamically, the SWNT was selectively nucleated by matching its structural symmetry and diameter with those of the catalyst. We grew nanotubes with chiral indices of (2m, m) (where m is a positive integer), the yield of which could be increased by raising the concentration of carbon to maximize the kinetic growth rate in the chemical vapour deposition process. Compared to previously reported methods, such as cloning, seeding and specific-structure-matching growth, our strategy of controlling the thermodynamics and kinetics offers more degrees of freedom, enabling the chirality of as-grown SWNTs in an array to be tuned, and can also be used to predict the growth conditions

Copper-encapsulated vertically aligned carbon nanotube arrays.

PubMed

Stano, Kelly L; Chapla, Rachel; Carroll, Murphy; Nowak, Joshua; McCord, Marian; Bradford, Philip D

2013-11-13

A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites.

Novel iron oxide nanotube arrays as high-performance anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Zhong, Yuan; Fan, Huiqing; Chang, Ling; Shao, Haibo; Wang, Jianming; Zhang, Jianqing; Cao, Chu-nan

2015-11-01

Nanostructured iron oxides can be promising anode materials for lithium ion batteries (LIBs). However, improvement on the rate capability and/or electrochemical cycling stability of iron oxide anode materials remains a key challenge because of their poor electrical conductivities and large volume expansion during cycling. Herein, the vertically aligned arrays of one-dimensional (1D) iron oxide nanotubes with 5.8 wt% carbon have been fabricated by a novel surfactant-free self-corrosion process and subsequent thermal treatment. The as-fabricated nanotube array electrode delivers a reversible capacity of 932 mAh g-1 after 50 charge-discharge cycles at a current of 0.6 A g-1. The electrode still shows a reversible capacity of 610 mAh g-1 even at a very high rate (8.0 A g-1), demonstrating its prominent rate capability. Furthermore, the nanotube array electrode also exhibits the excellent electrochemical cycling stability with a reversible capacity of 880 mAh g-1 after 500 cycles at a current of 4 A g-1. The nanotube array electrode with superior lithium storage performance reveals the promising potential as a high-performance anode for LIBs.

A titania nanotube-array room-temperature sensor for selective detection of hydrogen at low concentrations.

PubMed

Varghese, Oomman K; Mor, Gopal K; Grimes, Craig A; Paulose, Maggie; Mukherjee, Niloy

2004-09-01

A tremendous variation in electrical resistance, from the semiconductor to metallic range, has been observed in titania nanotube arrays at room temperature, approximately 25 degrees C, in the presence of < or = 1000 ppm hydrogen gas. The nanotube arrays are fabricated by anodizing titanium foil in an aqueous electrolyte solution containing hydrofluoric acid and acetic acid. Subsequently, the arrays are coated with a 10 nm layer of palladium by evaporation. Electrical contacts are made by sputtering a 2 mm diameter platinum disk atop the Pd-coated nanotube array. These sensors exhibit a resistance variation of the order of 10(4) in the presence of 100 ppm hydrogen at 25 degrees C. The sensors demonstrate complete reversibility, repeatability, high selectivity, negligible drift and wide dynamic range. The nanoscale geometry of the nanotubes, in particular the points of tube-to-tube contact, is believed to be responsible for the outstanding hydrogen gas sensitivities.

Effects of Functionalization of TiO2 Nanotube Array Sensors with Pd Nanoparticles on Their Selectivity

PubMed Central

Park, Sunghoon; Kim, Soohyun; Park, Suyoung; Lee, Wan In; Lee, Chongmu

2014-01-01

This study compared the responses of Pd-functionalized and pristine titanate (TiO2) nanotube arrays to ethanol with those to acetone to determine the effects of functionalization of TiO2 nanotubes with Pd nanoparticles on the sensitivity and selectivity. The responses of pristine and Pd-functionalized TiO2 nanotube arrays to ethanol gas at 200 °C were ∼2877% and ∼21,253%, respectively. On the other hand, the responses of pristine and Pd-functionalized TiO2 nanotube arrays to acetone gas at 250 °C were ∼1636% and 8746% respectively. In the case of ethanol sensing, the response and recovery times of Pd-functionalized TiO2 nanotubes (10.2 and 7.1 s) were obviously shorter than those of pristine TiO2 nanotubes (14.3 and 8.8 s), respectively. In contrast, in the case of acetone sensing the response and recovery times of Pd-functionalized TiO2 nanotubes (42.5 and 19.7 s) were almost the same as those of pristine TiO2 nanotubes (47.2 and 17.9 s). TiO2 nanotube arrays showed the strongest response to ethanol and Pd functionalization was the most effective in improving the response of TiO2 nanotubes to ethanol among six different types of gases: ethanol, acetone, CO, H2, NH3 and NO2. The origin of the superior sensing properties of Pd-functionalized TiO2 nanotubes toward ethanol to acetone is also discussed. PMID:25166499

Biochips Containing Arrays of Carbon-Nanotube Electrodes

NASA Technical Reports Server (NTRS)

Li, Jun; Meyyappan, M.; Koehne, Jessica; Cassell, Alan; Chen, Hua

2008-01-01

Biochips containing arrays of nanoelectrodes based on multiwalled carbon nanotubes (MWCNTs) are being developed as means of ultrasensitive electrochemical detection of specific deoxyribonucleic acid (DNA) and messenger ribonucleic acid (mRNA) biomarkers for purposes of medical diagnosis and bioenvironmental monitoring. In mass production, these biochips could be relatively inexpensive (hence, disposable). These biochips would be integrated with computer-controlled microfluidic and microelectronic devices in automated hand-held and bench-top instruments that could be used to perform rapid in vitro genetic analyses with simplified preparation of samples. Carbon nanotubes are attractive for use as nanoelectrodes for detection of biomolecules because of their nanoscale dimensions and their chemical properties.

Fringing-field dielectrophoretic assembly of ultrahigh-density semiconducting nanotube arrays with a self-limited pitch

NASA Astrophysics Data System (ADS)

Cao, Qing; Han, Shu-Jen; Tulevski, George S.

2014-09-01

One key challenge of realizing practical high-performance electronic devices based on single-walled carbon nanotubes is to produce electronically pure nanotube arrays with both a minuscule and uniform inter-tube pitch for sufficient device-packing density and homogeneity. Here we develop a method in which the alternating voltage-fringing electric field formed between surface microelectrodes and the substrate is utilized to assemble semiconducting nanotubes into well-aligned, ultrahigh-density and submonolayered arrays, with a consistent pitch as small as 21±6 nm determined by a self-limiting mechanism, based on the unique field focusing and screening effects of the fringing field. Field-effect transistors based on such nanotube arrays exhibit record high device transconductance (>50 μS μm-1) and decent on current per nanotube (~1 μA per tube) together with high on/off ratios at a drain bias of -1 V.

The correlation between radiative surface defect states and high color rendering index from ZnO nanotubes

PubMed Central

2011-01-01

Combined surface, structural and opto-electrical investigations are drawn from the chemically fashioned ZnO nanotubes and its heterostructure with p-GaN film. A strong correlation has been found between the formation of radiative surface defect states in the nanotubes and the pure cool white light possessing averaged eight color rendering index value of 96 with appropriate color temperature. Highly important deep-red color index value has been realized > 95 which has the capability to render and reproduce natural and vivid colors accurately. Diverse types of deep defect states and their relative contribution to the corresponding wavelengths in the broad emission band is suggested. PMID:21878100

Fabrication of heterogeneous nanomaterial array by programmable heating and chemical supply within microfluidic platform towards multiplexed gas sensing application

PubMed Central

Yang, Daejong; Kang, Kyungnam; Kim, Donghwan; Li, Zhiyong; Park, Inkyu

2015-01-01

A facile top-down/bottom-up hybrid nanofabrication process based on programmable temperature control and parallel chemical supply within microfluidic platform has been developed for the all liquid-phase synthesis of heterogeneous nanomaterial arrays. The synthesized materials and locations can be controlled by local heating with integrated microheaters and guided liquid chemical flow within microfluidic platform. As proofs-of-concept, we have demonstrated the synthesis of two types of nanomaterial arrays: (i) parallel array of TiO2 nanotubes, CuO nanospikes and ZnO nanowires, and (ii) parallel array of ZnO nanowire/CuO nanospike hybrid nanostructures, CuO nanospikes and ZnO nanowires. The laminar flow with negligible ionic diffusion between different precursor solutions as well as localized heating was verified by numerical calculation and experimental result of nanomaterial array synthesis. The devices made of heterogeneous nanomaterial array were utilized as a multiplexed sensor for toxic gases such as NO2 and CO. This method would be very useful for the facile fabrication of functional nanodevices based on highly integrated arrays of heterogeneous nanomaterials. PMID:25634814

Self-Ordered Titanium Dioxide Nanotube Arrays: Anodic Synthesis and Their Photo/Electro-Catalytic Applications

PubMed Central

Smith, York R.; Ray, Rupashree S.; Carlson, Krista; Sarma, Biplab; Misra, Mano

2013-01-01

Metal oxide nanotubes have become a widely investigated material, more specifically, self-organized titania nanotube arrays synthesized by electrochemical anodization. As a highly investigated material with a wide gamut of applications, the majority of published literature focuses on the solar-based applications of this material. The scope of this review summarizes some of the recent advances made using metal oxide nanotube arrays formed via anodization in solar-based applications. A general methodology for theoretical modeling of titania surfaces in solar applications is also presented. PMID:28811415

Synthesis of molecular imprinted polymer modified TiO{sub 2} nanotube array electrode and their photoelectrocatalytic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu Na; Chen Shuo; Wang Hongtao

2008-10-15

A tetracycline hydrochloride (TC) molecularly imprinted polymer (MIP) modified TiO{sub 2} nanotube array electrode was prepared via surface molecular imprinting. Its surface was structured with surface voids and the nanotubes were open at top end with an average diameter of approximately 50 nm. The MIP-modified TiO{sub 2} nanotube array with anatase phase was identified by XRD and a distinguishable red shift in the absorption spectrum was observed. The MIP-modified electrode also exhibited a high adsorption capacity for TC due to its high surface area providing imprinted sites. Photocurrent was generated on the MIP-modified photoanode using the simulated solar spectrum andmore » increased with the increase of positive bias potential. Under simulated solar light irradiation, the MIP-modified TiO{sub 2} nanotube array electrode exhibited enhanced photoelectrocatalytic (PEC) activity with the apparent first-order rate constant being 1.2-fold of that with TiO{sub 2} nanotube array electrode. The effect of the thickness of the MIP layer on the PEC activity was also evaluated. - Graphical abstract: A tetracycline hydrochloride molecularly imprinted polymer modified TiO{sub 2} nanotube array electrode was prepared via surface molecular imprinting. It showed improved response to simulated solar light and higher adsorption capability for tetracycline hydrochloride, thereby exhibiting increased PEC activity under simulated solar light irradiation. The apparent first-order rate constant was 1.2-fold of that on TiO{sub 2} nanotube array electrode.« less

Uniform, dense arrays of vertically aligned, large-diameter single-walled carbon nanotubes.

PubMed

Han, Zhao Jun; Ostrikov, Kostya

2012-04-04

Precisely controlled reactive chemical vapor synthesis of highly uniform, dense arrays of vertically aligned single-walled carbon nanotubes (SWCNTs) using tailored trilayered Fe/Al(2)O(3)/SiO(2) catalyst is demonstrated. More than 90% population of thick nanotubes (>3 nm in diameter) can be produced by tailoring the thickness and microstructure of the secondary catalyst supporting SiO(2) layer, which is commonly overlooked. The proposed model based on the atomic force microanalysis suggests that this tailoring leads to uniform and dense arrays of relatively large Fe catalyst nanoparticles on which the thick SWCNTs nucleate, while small nanotubes and amorphous carbon are effectively etched away. Our results resolve a persistent issue of selective (while avoiding multiwalled nanotubes and other carbon nanostructures) synthesis of thick vertically aligned SWCNTs whose easily switchable thickness-dependent electronic properties enable advanced applications in nanoelectronic, energy, drug delivery, and membrane technologies.

Structure and dye-sensitized solar cell application of TiO2 nanotube arrays fabricated by the anodic oxidation method

NASA Astrophysics Data System (ADS)

Ok, Seon-Yeong; Cho, Kwon-Koo; Kim, Ki-Won; Ryu, Kwang-Sun

2010-05-01

Well-ordered TiO2 nanotube arrays were fabricated by the potentiostatic anodic oxidation method using pure Ti foil as a working electrode and ethylene glycol solution as an electrolyte with the small addition of NH4F and H2O. The influence of anodization temperature and time on the morphology and formation of TiO2 nanotube arrays was examined. The TiO2 nanotube arrays were applied as a photoelectrode to dye-sensitized solar cells. Regardless of anodizing temperature and time, the average diameter and wall thickness of TiO2 nanotube arrays show a similar value, whereas the length increases with decreasing reaction temperature. The conversion efficiency is very low, which is due to a morphology breaking of the TiO2 nanotube arrays in the manufacturing process of a photoelectrode.

Enhanced Structural and Luminescent Properties of Carbon-Assisted ZnO Nanorod Arrays on (100) Si Substrate

NASA Astrophysics Data System (ADS)

Yoon, Im Taek; Cho, Hak Dong; Lee, Sejoon; Roshchupkin, Dmitry V.

2018-02-01

We have fabricated as-grown ZnO nanorods (NRs) and carbon-assisted NR arrays on semi-insulating (100)-oriented Si substrates. We compared the structural and luminescent properties of them. High-resolution transmission microscopy, field emission scanning electron microscopy, x-ray diffraction and energy-dispersive x-ray revealed that the as-grown ZnO NRs and carbon-assisted ZnO NRs were single crystals with a hexagonal wurtzite structure, and grew with a c-axis orientation perpendicular to the Si substrate. These measurements show that the carbon-assisted ZnO NRs were better synthesized vertically on an Si substrate compared to the as-grown ZnO NRs. Photoluminescence measurements showed that luminescence intensity of the carbon-assisted ZnO NRs was enhanced compared to the as-grown ZnO NRs. The enhanced luminescence intensity of the carbon-assisted ZnO demonstrates the possible improvement in the performance of photovoltaic nanodevices based on ZnO-like materials. This method can be applied to the fabrication of well-aligned ZnO NRs used widely in optoelectronic devices.

Separating light absorption layer from channel in ZnO vertical nanorod arrays based photodetectors for high-performance image sensors

NASA Astrophysics Data System (ADS)

Ma, Yang; Wu, Congjun; Xu, Zhihao; Wang, Fei; Wang, Min

2018-05-01

Photoconductor arrays with both high responsivity and large ON/OFF ratios are of great importance for the application of image sensors. Herein, a ZnO vertical nanorod array based photoconductor with a light absorption layer separated from the device channel has been designed, in which the photo-generated carriers along the axial ZnO nanorods drive to the external electrodes through nanorod-nanorod junctions in the dense layer at the bottom. This design allows us to enhance the photocurrent with unchanged dark current by increasing the ratio between the ZnO nanorod length and the thickness of the dense layer to achieve both high responsivity and large ON/OFF ratios. As a result, the as-fabricated devices possess a high responsivity of 1.3 × 105 A/W, a high ON/OFF ratio of 790, a high detectivity of 1.3 × 1013 Jones, and a low detectable light intensity of 1 μW/cm2. More importantly, the developed approach enables the integration of ZnO vertical nanorod array based photodetectors as image sensors with uniform device-to-device performance.

Engineered ZnO nanowire arrays using different nanopatterning techniques

NASA Astrophysics Data System (ADS)

Volk, János; Szabó, Zoltán; Erdélyi, Róbert; Khánh, Nguyen Q.

2012-02-01

The impact of various masking patterns and template layers on the wet chemically grown vertical ZnO nanowire arrays was investigated. The nanowires/nanorods were seeded at nucleation windows which were patterned in a mask layer using various techniques such as electron beam lithography, nanosphere photolithography, and atomic force microscope type nanolithography. The compared ZnO templates included single crystals, epitaxial layer, and textured polycrystalline films. Scanning electron microscopy revealed that the alignment and crystal orientation of the nanowires were dictated by the underlying seed layer, while their geometry can be tuned by the parameters of the certain nanopatterning technique and of the wet chemical process. The comparison of the alternative nanolithography techniques showed that using direct writing methods the diameter of the ordered ZnO nanowires can be as low as 30-40 nm at a density of 100- 1000 NW/μm2 in a very limited area (10 μm2-1 mm2). Nanosphere photolithography assisted growth, on the other hand, favors thicker nanopillars (~400 nm) and enables large-area, low-cost patterning (1-100 cm2). These alternative lowtemperature fabrication routes can be used for different novel optoelectronic devices, such as nanorod based ultraviolet photodiode, light emitting device, and waveguide laser.

Structure and properties of nanostructured ZnO arrays and ZnO/Ag nanocomposites fabricated by pulsed electrodeposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopach, V. R.; Klepikova, K. S.; Klochko, N. P., E-mail: klochko-np@mail.ru

We investigate the structure, surface morphology, and optical properties of nanostructured ZnO arrays fabricated by pulsed electrodeposition, Ag nanoparticles precipitated from colloidal solutions, and a ZnO/Ag nanocomposite based on them. The electronic and electrical parameters of the ZnO arrays and ZnO/Ag nanocomposites are analyzed by studying the I–V and C–V characteristics. Optimal modes for fabricating the ZnO/Ag heterostructures with the high stability and sensitivity to ultraviolet radiation as promising materials for use in photodetectors, gas sensors, and photocatalysts are determined.

Nanotube Surface Arrays: Weaving, Bending, and Assembling on Patterned Silicon

NASA Astrophysics Data System (ADS)

Tsukruk, Vladimir V.; Ko, Hyunhyub; Peleshanko, Sergiy

2004-02-01

We report the fabrication of ordered arrays of oriented and bent carbon nanotube on a patterned silicon surface with a micron scale spacing extending over millimeter size surface areas. We suggest that the patterning is controlled by the hydrodynamic behavior of a fluid front and orientation and bending mechanisms are facilitated by the pinned carbon nanotubes trapped by the liquid-solid-vapor contact line. The bending of the pinned nanotubes occurs along the shrinking receding front of the drying microdroplets. The formation of stratified microfluidic layers is vital for stimulating periodic instabilities of the contact line.

Si/Ge double-layered nanotube array as a lithium ion battery anode.

PubMed

Song, Taeseup; Cheng, Huanyu; Choi, Heechae; Lee, Jin-Hyon; Han, Hyungkyu; Lee, Dong Hyun; Yoo, Dong Su; Kwon, Moon-Seok; Choi, Jae-Man; Doo, Seok Gwang; Chang, Hyuk; Xiao, Jianliang; Huang, Yonggang; Park, Won Il; Chung, Yong-Chae; Kim, Hansu; Rogers, John A; Paik, Ungyu

2012-01-24

Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3C rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries. © 2011 American Chemical Society

Graphene quantum dots-carbon nanotube hybrid arrays for supercapacitors

NASA Astrophysics Data System (ADS)

Hu, Yue; Zhao, Yang; Lu, Gewu; Chen, Nan; Zhang, Zhipan; Li, Hui; Shao, Huibo; Qu, Liangti

2013-05-01

Graphene quantum dots (GQDs) have been successfully deposited onto aligned carbon nanotubes (CNTs) by a benign electrochemical method and the capacitive properties of the as-formed GQD/CNT hybrid arrays were evaluated in symmetrical supercapacitors. It was found that supercapacitors fabricated from GQD/CNT hybrid arrays exhibited a high capacitance of 44 mF cm-2, representing a more than 200% improvement over that of bare CNT electrodes.

Graphene quantum dots-carbon nanotube hybrid arrays for supercapacitors.

PubMed

Hu, Yue; Zhao, Yang; Lu, Gewu; Chen, Nan; Zhang, Zhipan; Li, Hui; Shao, Huibo; Qu, Liangti

2013-05-17

Graphene quantum dots (GQDs) have been successfully deposited onto aligned carbon nanotubes (CNTs) by a benign electrochemical method and the capacitive properties of the as-formed GQD/CNT hybrid arrays were evaluated in symmetrical supercapacitors. It was found that supercapacitors fabricated from GQD/CNT hybrid arrays exhibited a high capacitance of 44 mF cm(-2), representing a more than 200% improvement over that of bare CNT electrodes.

Piezo-phototronic effect enhanced photo-detector based on ZnO nano-arrays/NiO structure

NASA Astrophysics Data System (ADS)

Sun, Jingchang; Li, Peida; Gao, Ruixue; Lu, Xue; Li, Chengren; Lang, Yueyi; Zhang, Xiwen; Bian, Jiming

2018-01-01

A photo-detector with n-ZnO nano-arrays/p-NiO film structure was synthesized on flexible Ni foil substrate. In contrast to conventional detectors that detect only the photon energies greater than the band gap of working materials, the visible light with smaller photon energies (3.0 eV) than the band gap of both ZnO (3.3 eV) and NiO (3.7 eV) can be sensitively detected by this detector due to the spatially indirect type-II transition between ZnO nano-arrays and NiO film. The increase in output currents of the photo-detector with illumination density was observed at both forward and reverse bias, and it can be further enhanced by exerting external compressive strain along the c axis of ZnO nano-arrays by piezo-phototronic effect. A maximum enhancement of 1020% of the responsivity (R) was achieved under external compressive strain. The similar behaviors were demonstrated at four different excitation wavelengths (325, 365, 388 and 405 nm), providing compelling evidence that the responses performance of the photo-detector can be effectively enhanced using piezo-phototronic effect. Moreover, the piezo-phototronic effect enhanced performance can be well elucidated by the corresponding energy band diagram.

Fast fabrication of long TiO2 nanotube array with high photoelectrochemical property on flexible stainless steel.

PubMed

Tao, Jie; Wu, Tao; Gao, Peng

2012-03-01

Oriented highly ordered long TiO2 nanotube array films with nanopore structure and high photoelectrochemical property were fabricated on flexible stainless steel substrate (50 microm) by anodization treatment of titanium thin films in a short time. The samples were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoelectrochemical methods, respectively. The results showed that Ti films deposited at the condition of 0.7 Pa Ar pressure and 96 W sputtering power at room temperature was uniform and dense with good homogeneity and high crystallinity. The voltage and the anodization time both played significant roles in the formation of TiO2 nanopore-nanotube array film. The optimal voltage was 60 V and the anodization time is less than 30 min by anodizing Ti films in ethylene glycerol containing 0.5% (w) NH4F and 3% (w) H2O. The growth rate of TiO2 nanotube array was as high as 340 nm/min. Moreover, the photocurrent-potential curves, photocurrent response curves and electrochemical impedance spectra results indicated that the TiO2 nanotube array film with the nanoporous structure exhibited a better photo-response ability and photoelectrochemical performance than the ordinary TiO2 nanotube array film. The reason is that the nanoporous structure on the surface of the nanotube array can separate the photo electron-hole pairs more efficiently and completely than the tubular structure.

Betavoltaic effect in titanium dioxide nanotube arrays under build-in potential difference

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Chen, Ranbin; San, Haisheng; Liu, Guohua; Wang, Kaiying

2015-05-01

We report the fabrication of sandwich-type metal/TiO2 nanotube (TNT) array/metal structures as well as their betavoltaic effects under build-in voltage through contact potential difference. The sandwiched structure is integrated by immobilized TNT arrays on Ti foil with radioisotope 63Ni planar source on Ni substrate (Ni-63Ni/TNT array/Ti). Under irradiation of the 63Ni source with activity of 8 mCi, the structure (TNT diameter ∼ 130 nm, length ∼ 11 μm) presents optimum energy conversion efficiency of 7.30% with open-circuit voltage of 1.54 V and short-circuit current of 12.43 nA. The TNT arrays exhibit a highly potential for developing betavoltaic batteries due to its wide band gap and nanotube array configuration. The TNT-betavoltaic concept offers a facile solution for micro/nano electronics with high efficiency and long life-time instead of conventional planar junction-type batteries.

2D XANES-XEOL mapping: observation of enhanced band gap emission from ZnO nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Guo, Xiaoxuan; Sham, Tsun-Kong

2014-05-01

Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed.Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed. Electronic supplementary information (ESI) available: XEOL spectra with different excitation energies. X-ray attenuation length vs. photon energy. Details of surface defects in ZnO NWs. The second O K-edge and Zn L-edge 2D XANES-XEOL maps. Comparison of the first and second TEY at O K-edge and Zn L-edge scans, respectively. Raman spectra of the ZnO NWs with different IBGE/IDE ratios. See DOI: 10.1039/c4nr01049c

PDMS-based triboelectric and transparent nanogenerators with ZnO nanorod arrays.

PubMed

Ko, Yeong Hwan; Nagaraju, Goli; Lee, Soo Hyun; Yu, Jae Su

2014-05-14

Vertically-grown ZnO nanorod arrays (NRAs) on indium tin oxide (ITO)-coated polyethylene terephthalate (PET), as a top electrode of nanogenerators, were investigated for the antireflective property as well as an efficient contact surface in bare polydimethysiloxane (PDMS)-based triboelectric nanogenerators. Compared to conventional ITO-coated PET (i.e., ITO/PET), the ZnO NRAs considerably suppressed the reflectance from 20 to 9.7% at wavelengths of 300-1100 nm, creating a highly transparent top electrode, as demonstrated by theoretical analysis. Also, the interval time between the peaks of generated output voltage under external pushing forces was significantly decreased from 1.84 to 0.19 s because the reduced contact area of the PDMS by discrete surfaces of the ZnO NRAs on ITO/PET causes a rapid sequence for triboelectric charge generation process including rubbing and separating. Therefore, the use of this top electrode enabled to operate the transparent PDMS-based triboelectric nanogenerator at high frequency of external pushing force. Under different external forces of 0.3-10 kgf, the output voltage and current were also characterized.

Coated carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng; Wen, Jian; Chen, Jinghua; Huang, Zhongping; Wang, Dezhi

2006-12-12

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

Coated carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng [Newton, MA; Wen, Jian [Newton, MA; Chen, Jinghua [Chestnut Hill, MA; Huang, Zhongping [Belmont, MA; Wang, Dezhi [Wellesley, MA

2008-10-28

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

One-dimensional ZnO nanostructures.

PubMed

Jayadevan, K P; Tseng, T Y

2012-06-01

The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.

Nucleation, Growth Mechanism, and Controlled Coating of ZnO ALD onto Vertically Aligned N-Doped CNTs.

PubMed

Silva, R M; Ferro, M C; Araujo, J R; Achete, C A; Clavel, G; Silva, R F; Pinna, N

2016-07-19

Zinc oxide thin films were deposited on vertically aligned nitrogen-doped carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) from diethylzinc and water. The study demonstrates that doping CNTs with nitrogen is an effective approach for the "activation" of the CNTs surface for the ALD of metal oxides. Conformal ZnO coatings are already obtained after 50 ALD cycles, whereas at lower ALD cycles an island growth mode is observed. Moreover, the process allows for a uniform growth from the top to the bottom of the vertically aligned N-CNT arrays. X-ray photoelectron spectroscopy demonstrates that ZnO nucleation takes place at the N-containing species on the surface of the CNTs by the formation of the Zn-N bonds at the interface between the CNTs and the ZnO film.

Investigations into the impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on growth of ZnO nanowire array

PubMed Central

2012-01-01

The impact of various substrates and zinc oxide (ZnO) ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, indium tin oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, whereas the influence of the seed layers' texture was negligible. PMID:22759838

Fabrication of doped TiO2 nanotube array films with enhanced photo-catalytic activity

NASA Astrophysics Data System (ADS)

Peighambardoust, Naeimeh-Sadat; Khameneh-asl, Shahin; Khademi, Adib

2018-01-01

In the present work, we investigate the N and Fe-doped TiO2 nanotube array film prepared by treating TiO2 nanotube array film with ammonia solution and anodizing in Fe(NO3)3 solution respectively. This method avoided the use of hazardous ammonia gas, or laborious ion implantation process. N and Fe-doped TiO2 nanotube arrays (TiO2 NTs) were prepared by electrochemical anodization process in 0.5 wt % HF aqueous solution. The anodization was performed at the conditions of 20 V and 20 min, Followed by a wet immersion in NH3.H2O (1M) for N-doping for 2 hr and annealing post-treatment at 450 °C. The morphology and structure of the nanotube films were characterized by field emission scanning electron microscope (FESEM) and EDX. UV-vis. illumination test were done to observe photo-enhanced catalysis. The effect of different annealing temperature on the structure and photo-absorption property of the TiO2-TNTs was investigated. The results showed that N-TNTs nanotubes exhibited higher photocatalytic activity compared whit the Fe-doped and pure TNTs, because doping N promoted the separation of the photogenerated electrons and holes.

Laser-assisted simultaneous transfer and patterning of vertically aligned carbon nanotube arrays on polymer substrates for flexible devices.

PubMed

In, Jung Bin; Lee, Daeho; Fornasiero, Francesco; Noy, Aleksandr; Grigoropoulos, Costas P

2012-09-25

We demonstrate a laser-assisted dry transfer technique for assembling patterns of vertically aligned carbon nanotube arrays on a flexible polymeric substrate. A laser beam is applied to the interface of a nanotube array and a polycarbonate sheet in contact with one another. The absorbed laser heat promotes nanotube adhesion to the polymer in the irradiated regions and enables selective pattern transfer. A combination of the thermal transfer mechanism with rapid direct writing capability of focused laser beam irradiation allows us to achieve simultaneous material transfer and direct micropatterning in a single processing step. Furthermore, we demonstrate that malleability of the nanotube arrays transferred onto a flexible substrate enables post-transfer tailoring of electric conductance by collapsing the aligned nanotubes in different directions. This work suggests that the laser-assisted transfer technique provides an efficient route to using vertically aligned nanotubes as conductive elements in flexible device applications.

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter

NASA Astrophysics Data System (ADS)

Pal, Anil Kumar; Bharathi Mohan, D.

2017-10-01

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ˜0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter.

PubMed

Pal, Anil Kumar; Mohan, D Bharathi

2017-10-13

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ∼0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Bioelectrocatalytic application of titania nanotube array for molecule detection.

PubMed

Xie, Yibing; Zhou, Limin; Huang, Haitao

2007-06-15

A bioelectrocatalysis system based on titania nanotube electrode has been developed for the quantitative detection application. Highly ordered titania nanotube array with inner diameter of 60 nm and total length of 540 nm was formed by anodizing titanium foils. The functionalization modification was achieved by embedding glucose oxidases inside tubule channels and electropolymerizing pyrrole for interfacial immobilization. Morphology and microstructure characterization, electrochemical properties and bioelectrocatalytic reactivities of this composite were fully investigated. The direct detection of hydrogen peroxide by electrocatalytic reduction reaction was fulfilled on pure titania nanotube array with a detection limit up to 2.0 x 10(-4)mM. A biosensor based on the glucose oxidase-titania/titanium electrode was constructed for amperometric detection and quantitative determination of glucose in a phosphate buffer solution (pH 6.8) under a potentiostatic condition (-0.4V versus SCE). The resulting glucose biosensor showed an excellent performance with a response time below 5.6s and a detection limit of 2.0 x 10(-3)mM. The corresponding detection sensitivity was 45.5 microA mM(-1)cm(-2). A good operational reliability was also achieved with relative standard deviations below 3.0%. This novel biosensor exhibited quite high response sensitivity and low detection limit for potential applications.

Large-scale horizontally aligned ZnO microrod arrays with controlled orientation, periodic distribution as building blocks for chip-in piezo-phototronic LEDs.

PubMed

Guo, Zhen; Li, Haiwen; Zhou, Lianqun; Zhao, Dongxu; Wu, Yihui; Zhang, Zhiqiang; Zhang, Wei; Li, Chuanyu; Yao, Jia

2015-01-27

A novel method of fabricating large-scale horizontally aligned ZnO microrod arrays with controlled orientation and periodic distribution via combing technology is introduced. Horizontally aligned ZnO microrod arrays with uniform orientation and periodic distribution can be realized based on the conventional bottom-up method prepared vertically aligned ZnO microrod matrix via the combing method. When the combing parameters are changed, the orientation of horizontally aligned ZnO microrod arrays can be adjusted (θ = 90° or 45°) in a plane and a misalignment angle of the microrods (0.3° to 2.3°) with low-growth density can be obtained. To explore the potential applications based on the vertically and horizontally aligned ZnO microrods on p-GaN layer, piezo-phototronic devices such as heterojunction LEDs are built. Electroluminescence (EL) emission patterns can be adjusted for the vertically and horizontally aligned ZnO microrods/p-GaN heterojunction LEDs by applying forward bias. Moreover, the emission color from UV-blue to yellow-green can be tuned by investigating the piezoelectric properties of the materials. The EL emission mechanisms of the LEDs are discussed in terms of band diagrams of the heterojunctions and carrier recombination processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A patterned ZnO nanorod array/gas sensor fabricated by mechanoelectrospinning-assisted selective growth.

PubMed

Wang, Xiaomei; Sun, Fazhe; Huang, Yongan; Duan, Yongqing; Yin, Zhouping

2015-02-21

Micropatterned ZnO nanorod arrays were fabricated by the mechanoelectrospinning-assisted direct-writing process and the hydrothermal growth process, and utilized as gas sensors that exhibited excellent Ohmic behavior and sensitivity response to oxidizing gas NO2 at low concentrations (1-100 ppm).

Polyaniline nanowire array encapsulated in titania nanotubes as a superior electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Xie, Keyu; Li, Jie; Lai, Yanqing; Zhang, Zhi'an; Liu, Yexiang; Zhang, Guoge; Huang, Haitao

2011-05-01

Conducting polymer with 1D nanostructure exhibits excellent electrochemical performances but a poor cyclability that limits its use in supercapacitors. In this work, a novel composite electrode made of polyaniline nanowire-titania nanotube array was synthesized via a simple and inexpensive electrochemical route by electropolymerizing aniline onto an anodized titania nanotube array. The specific capacitance was as high as 732 F g-1 at 1 A g-1, which remained at 543 F g-1 when the current density was increased by 20 times. 74% of the maximum energy density (36.6 Wh kg-1) was maintained even at a high power density of 6000 W kg-1. An excellent long cycle life of the electrode was observed with a retention of ~86% of the initial specific capacitance after 2000 cycles. The good electrochemical performance was attributed to the unique microstructure of the electrode with disordered PANI nanowire arrays encapsulated inside the TiO2 nanotubes, providing high surface area, fast diffusion path for ions and long-term cycle stability. Such a nanocomposite electrode is attractive for supercapacitor applications.

Self-assembled hybrid polymer-TiO2 nanotube array heterojunction solar cells.

PubMed

Shankar, Karthik; Mor, Gopal K; Prakasam, Haripriya E; Varghese, Oomman K; Grimes, Craig A

2007-11-20

Films comprised of 4 microm long titanium dioxide nanotube arrays were fabricated by anodizing Ti foils in an ethylene glycol based electrolyte. A carboxylated polythiophene derivative was self-assembled onto the TiO2 nanotube arrays by immersing them in a solution of the polymer. The binding sites of the carboxylate moiety along the polymer chain provide multiple anchoring sites to the substrate, making for a stable rugged film. Backside illuminated liquid junction solar cells based on TiO2 nanotube films sensitized by the self-assembled polymeric layer showed a short-circuit current density of 5.5 mA cm-2, a 0.7 V open circuit potential, and a 0.55 fill factor yielding power conversion efficiencies of 2.1% under AM 1.5 sun. A backside illuminated single heterojunction solid state solar cell using the same self-assembled polymer was demonstrated and yielded a photocurrent density as high as 2.0 mA cm-2. When a double heterojunction was formed by infiltrating a blend of poly(3-hexylthiophene) (P3HT) and C60-methanofullerene into the self-assembled polymer coated nanotube arrays, a photocurrent as high as 6.5 mA cm-2 was obtained under AM 1.5 sun with a corresponding efficiency of 1%. The photocurrent action spectra showed a maximum incident photon-to-electron conversion efficiency (IPCE) of 53% for the liquid junction cells and 25% for the single heterojunction solid state solar cells.

ZnO nanorod array polydimethylsiloxane composite solid phase micro-extraction fiber coating: fabrication and extraction capability.

PubMed

Wang, Dan; Wang, Qingtang; Zhang, Zhuomin; Chen, Guonan

2012-01-21

ZnO nanorod array coating is a novel kind of solid-phase microextraction (SPME) fiber coating which shows good extraction capability due to the nanostructure. To prepare the composite coating is a good way to improve the extraction capability. In this paper, the ZnO nanorod array polydimethylsiloxane (PDMS) composite SPME fiber coating has been prepared and its extraction capability for volatile organic compounds (VOCs) has been studied by headspace sampling the typical volatile mixed standard solution of benzene, toluene, ethylbenzene and xylene (BTEX). Improved detection limit and good linear ranges have been achieved for this composite SPME fiber coating. Also, it is found that the composite SPME fiber coating shows good extraction selectivity to the VOCs with alkane radicals.

Exploring hierarchical FeS2/C composite nanotubes arrays as advanced cathode for lithium ion batteries

NASA Astrophysics Data System (ADS)

Pan, G. X.; Cao, F.; Xia, X. H.; Zhang, Y. J.

2016-11-01

Rational construction of advanced FeS2 cathode is one of research hotspots, and of great importance for developing high-performance lithium ion batteries (LIBs). Herein we report a facile hydrolysis-sulfurization method for fabrication of FeS2/C nanotubes arrays with the help of sacrificial Co2(OH)2CO3 nanowires template and glucose carbonization. Self-supported FeS2/C nanotubes consist of interconnected nanoburrs of 5-20 nm, and show hierarchical porous structure. The FeS2/C nanotubes arrays are demonstrated with enhanced cycling life and noticeable high-rate capability with capacities ranging from 735 mAh g-1 at 0.25 C to 482 mAh g-1 at 1.5 C, superior to those FeS2 counterparts in the literature. The composite nanotubes arrays architecture plays positive roles in the electrochemical enhancement due to combined advantages of large electrode-electrolyte contact area, good strain accommodation, improved electrical conductivity, and enhanced structural stability.

N- and C-Modified TiO2 Nanotube Arrays: Enhanced Photoelectrochemical Properties and Effect of Nanotubes Length on Photoconversion Efficiency

PubMed Central

Mohamed, Ahmed El Ruby; Barghi, Shahzad

2018-01-01

In this investigation, a new, facile, low cost and environmental-friendly method was introduced to fabricate N- and C-modified TiO2 nanotube arrays by immersing the as-anodized TiO2 nanotube arrays (TNTAs) in a urea aqueous solution with mechanical agitation for a short time and keeping the TNTAs immersed in the solution for 6 h at room temperature. Then, the TNTAs were annealed at different temperatures. The produced N-, C-modified TNTAs were characterized using FESEM, EDX, XRD, XPS, UV-Vis diffuse reflectance spectra. Modified optical properties with narrow band gap energy, Eg, of 2.65 eV was obtained after annealing the modified TNTAs at 550 °C. Modified TNTAs showed enhanced photoelectochemical performance. Photoconversion efficiency (PCE) was increased from 4.35% for pristine (unmodified) TNTAs to 5.18% for modified TNTAs, an increase of 19%. Effect of nanotubes length of modified TNTAs on photoelectrochemical performance was also studied. Photocurrent density and PCE were increased by increasing nanotube length with a maximum PCE of 6.38% for nanotube length of 55 µm. This high PCE value was attributed to: band gap reduction due to C- and N-modification of TNTAs surface, increased surface area of long TNTAs compared with short TNTAs, investigated in previous studies. PMID:29597248

Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azzez, Shrook A., E-mail: shurouq44@yahoo.com; Hassan, Z.; Alimanesh, M.

Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicon substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.

Fabrication and characterization of novel transparent conducting oxide N-CNT doped ZnO for photovoltaic applications

NASA Astrophysics Data System (ADS)

Benyounes, Anas; Abbas, Naseem; Hammi, Maryama; Ziat, Younes; Slassi, Amine; Zahra, Nida

2018-02-01

The present research reports on the electrical and optical properties of N-CNT doped with ZnO, which is considered as wurtzite transparent and conducting oxide semiconductor structure. The thin films of N-doped carbon nanotubes/ZnO were prepared using sol-gel method, then we carried out investigations in optical and electrical point of view to extract their usefulness in photovoltaic applications. For this purpose, ZnO films were doped by several ratios of carbon nanotubes and N-doped carbon nanotubes. The electrical studies were performed over these two kinds of doped ZnO films, the electrical conductivity has found to be more important for ZnO films filled with N-CNTs. This finding is pretty explained by the electronic conduction hold by nitrogen as charge carriers within carbon nanotubes.

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

PubMed Central

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-01-01

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

PubMed

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-03-24

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.

Hot spot dynamics in carbon nanotube array devices.

PubMed

Engel, Michael; Steiner, Mathias; Seo, Jung-Woo T; Hersam, Mark C; Avouris, Phaedon

2015-03-11

We report on the dynamics of spatial temperature distributions in aligned semiconducting carbon nanotube array devices with submicrometer channel lengths. By using high-resolution optical microscopy in combination with electrical transport measurements, we observe under steady state bias conditions the emergence of time-variable, local temperature maxima with dimensions below 300 nm, and temperatures above 400 K. On the basis of time domain cross-correlation analysis, we investigate how the intensity fluctuations of the thermal radiation patterns are correlated with the overall device current. The analysis reveals the interdependence of electrical current fluctuations and time-variable hot spot formation that limits the overall device performance and, ultimately, may cause device degradation. The findings have implications for the future development of carbon nanotube-based technologies.

Enhanced photoelectrochemical property of ZnO nanorods array synthesized on reduced graphene oxide for self-powered biosensing application.

PubMed

Kang, Zhuo; Gu, Yousong; Yan, Xiaoqin; Bai, Zhiming; Liu, Yichong; Liu, Shuo; Zhang, Xiaohui; Zhang, Zheng; Zhang, Xueji; Zhang, Yue

2015-02-15

We have realized the direct synthesis of ZnO nanorods (ZnO NRs) array on reduced graphene layer (rGO), and demonstrated the enhanced photoelectrochemical (PEC) property of the rGO/ZnO based photoanode under UV irradiation compared with the pristine ZnO NRs array. The introduction of the rGO layer resulted in a favorable energy band structure for electron migration, which finally led to the efficient photoinduced charge separation. Such nanostructure was subsequently employed for self-powered PEC biosensing of glutathione in the condition of 0 V bias, with a linear range from 10 to 200 µM, a detection limit of 2.17 µM, as well as excellent selectivity, reproducibility and stability. The results indicated the rGO/ZnO nanostructure is a competitive candidate in the PEC biosensing field. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimization of processing parameters on the controlled growth of ZnO nanorod arrays for the performance improvement of solid-state dye-sensitized solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Yi-Mu, E-mail: ymlee@nuu.edu.t; Yang, Hsi-Wen

2011-03-15

High-transparency and high quality ZnO nanorod arrays were grown on the ITO substrates by a two-step chemical bath deposition (CBD) method. The effects of processing parameters including reaction temperature (25-95 {sup o}C) and solution concentration (0.01-0.1 M) on the crystal growth, alignment, optical and electrical properties were systematically investigated. It has been found that these process parameters are critical for the growth, orientation and aspect ratio of the nanorod arrays, showing different structural and optical properties. Experimental results reveal that the hexagonal ZnO nanorod arrays prepared under reaction temperature of 95 {sup o}C and solution concentration of 0.03 M possessmore » highest aspect ratio of {approx}21, and show the well-aligned orientation and optimum optical properties. Moreover the ZnO nanorod arrays based heterojunction electrodes and the solid-state dye-sensitized solar cells (SS-DSSCs) were fabricated with an improved optoelectrical performance. -- Graphical abstract: The ZnO nanorod arrays demonstrate well-alignment, high aspect ratio (L/D{approx}21) and excellent optical transmittance by low-temperature chemical bath deposition (CBD). Display Omitted Research highlights: > Investigate the processing parameters of CBD on the growth of ZnO nanorod arrays. > Optimization of CBD process parameters: 0.03 M solution concentration and reaction temperature of 95 {sup o}C. > The prepared ZnO samples possess well-alignment and high aspect ratio (L/D{approx}21). > An n-ZnO/p-NiO heterojunction: great rectifying behavior and low leakage current. > SS-DSSC has J{sub SC} of 0.31 mA/cm{sup 2} and V{sub OC} of 590 mV, and an improved {eta} of 0.059%.« less

Facile fabrication of organic/inorganic nanotube heterojunction arrays for enhanced photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Chen, Yingzhi; Li, Aoxiang; Yue, Xiaoqi; Wang, Lu-Ning; Huang, Zheng-Hong; Kang, Feiyu; Volinsky, Alex A.

2016-07-01

Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi) layer were fabricated for photoelectrochemical water splitting. In this arrayed architecture, a PDi layer with a tunable thickness was coated on anodic TiO2 nanotube arrays by physical vapor deposition, which is advantageous for the formation of a uniform layer and an adequate interface contact between PDi and TiO2. The obtained PDi/TiO2 junction exhibited broadened visible light absorption, and an effective interface for enhanced photogenerated electron-hole separation, which is supported by the reduced charge transfer resistance and prolonged excitation lifetime via impedance spectroscopy analysis and fluorescence emission decay investigations. Consequently, such a heterojunction photoanode was photoresponsive to a wide visible light region of 400-600 nm, and thus demonstrated a highly enhanced photocurrent density at 1.23 V vs. a reversible hydrogen electrode. Additionally, the durability of such a photoanode can be guaranteed after long-time illumination because of the geometrical restraint imposed by the PDi aggregates. These results pave the way to discover new organic/inorganic assemblies for high-performance photoelectric applications and device integration.Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi

Backward scattering effect of aligned carbon nanotube arrays

NASA Astrophysics Data System (ADS)

Wu, Pengfei; Ren, Zhifeng; Wang, Michael R.

2009-02-01

In terms of operational bandwidth and speed, photonic components are superior to electronic ones. However, it is difficult to control photons on nanoscale structures for data processing and interconnection. Nanophotonic device using surface plasmon (SP) offers an ideal solution to combine the superior technical advantages of both photonics and electronics on the same chip. The SP wavelength is much shorter than that of the exciting light, allowing the use of SP in various techniques that overcome diffraction limits. In this paper, we report an interesting plasmonic effect, enhanced backward scattering, by using a periodically-aligned carbon nanotube (CNT) array. The CNTs are grown on a transparent glass substrate with an average diameter of 50 nm and a length of about 1 μm. To enhance the conductivity, the CNTs are also coated with 10-nm Au layer by using E-beam CVD technique. By shining a laser beam to the CNT array, we found that the scattering intensity is maximally enhanced at the backward incident direction. The enhanced backward incident scattering is observed by using both periodic and nonperiodic CNT samples. The experimental results suggest that the backward scattering effect is due to the SP excitation and coupling. The proposed technique exploiting aligned carbon-nanotube arrays to manipulate surface plasmon will lead to useful optical features such as optical antennae effects, retro-reflection, switching, wavelength add/drop multiplexing, and may be particularly useful for optical sensing, smart target identification and optical wireless secure communication applications.

Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays

PubMed Central

2011-01-01

Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate) substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices. PMID:27502660

Novel Magnetic Zinc Oxide Nanotubes for Phenol Adsorption: Mechanism Modeling

PubMed Central

Elkady, Marwa F.; Hassan, Hassan Shokry; Amer, Wael A.; Salama, Eslam; Algarni, Hamed; Shaaban, Essam Ramadan

2017-01-01

Considering the great impact of a material’s surface area on adsorption processes, hollow nanotube magnetic zinc oxide with a favorable surface area of 78.39 m2/g was fabricated with the assistance of microwave technology in the presence of poly vinyl alcohol (PVA) as a stabilizing agent followed by sonic precipitation of magnetite nano-particles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs identified the nanotubes’ morphology in the synthesized material with an average aspect ratio of 3. X-ray diffraction (XRD) analysis verified the combination of magnetite material with the hexagonal wurtzite structure of ZnO in the prepared material. The immobilization of magnetite nanoparticles on to ZnO was confirmed using vibrating sample magnetometry (VSM). The sorption affinity of the synthesized magnetic ZnO nanotube for phenolic compounds from aqueous solutions was examined as a function of various processing factors. The degree of acidity of the phenolic solution has great influence on the phenol sorption process on to magnetic ZnO. The calculated value of ΔH0 designated the endothermic nature of the phenol uptake process on to the magnetic ZnO nanotubes. Mathematical modeling indicated a combination of physical and chemical adsorption mechanisms of phenolic compounds on to the fabricated magnetic ZnO nanotubes. The kinetic process correlated better with the second-order rate model compared to the first-order rate model. This result indicates the predominance of the chemical adsorption process of phenol on to magnetic ZnO nanotubes. PMID:29186853

Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization.

PubMed

Ni, Jiahua; Frandsen, Christine J; Noh, Kunbae; Johnston, Gary W; He, Guo; Tang, Tingting; Jin, Sungho

2013-04-01

Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities. Copyright © 2013 Elsevier B.V. All rights reserved.

WIMP detection and slow ion dynamics in carbon nanotube arrays.

PubMed

Cavoto, G; Cirillo, E N M; Cocina, F; Ferretti, J; Polosa, A D

2016-01-01

Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs ([Formula: see text] GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency.

NanoBench: An Individually Addressable Nanotube Array

DTIC Science & Technology

2006-03-25

17 (1999). 5 Cai, L., H. Tabata and T. Kawai, "Probing electrical properties of oriented DNA by conducting atomic force microscopy", Nanotechnology 12...the e-beam hits the other side of the NanoBench. This allows the cells to be kept alive in a biological medium while they are being tested. The key...advantage of the NanoBench is that the e-beam never hits the sample. UHV Technologies Inc. 7 NanoBench: An Individually Addressable Nanotube Array Final

Experimental observation of an extremely dark material made by a low-density nanotube array.

PubMed

Yang, Zu-Po; Ci, Lijie; Bur, James A; Lin, Shawn-Yu; Ajayan, Pulickel M

2008-02-01

An ideal black material absorbs light perfectly at all angles and over all wavelengths. Here, we show that low-density vertically aligned carbon nanotube arrays can be engineered to have an extremely low index of refraction, as predicted recently by theory [Garcia-Vidal, F. J.; Pitarke, J. M.; Pendry, J. B. Phys. Rev. Lett. 1997, 78, 4289-4292] and, combined with the nanoscale surface roughness of the arrays, can produce a near-perfect optical absorption material. An ultralow diffused reflectance of 1 x 10(-7) measured from such arrays is an order-of-magnitude lower compared to commercial low-reflectance standard carbon. The corresponding integrated total reflectance of 0.045% from the nanotube arrays is three times lower than the lowest-ever reported values of optical reflectance from any material, making it the darkest man-made material ever.

Polyaniline nanowire array encapsulated in titania nanotubes as a superior electrode for supercapacitors.

PubMed

Xie, Keyu; Li, Jie; Lai, Yanqing; Zhang, Zhi'an; Liu, Yexiang; Zhang, Guoge; Huang, Haitao

2011-05-01

Conducting polymer with 1D nanostructure exhibits excellent electrochemical performances but a poor cyclability that limits its use in supercapacitors. In this work, a novel composite electrode made of polyaniline nanowire-titania nanotube array was synthesized via a simple and inexpensive electrochemical route by electropolymerizing aniline onto an anodized titania nanotube array. The specific capacitance was as high as 732 F g(-1) at 1 A g(-1), which remained at 543 F g(-1) when the current density was increased by 20 times. 74% of the maximum energy density (36.6 Wh kg(-1)) was maintained even at a high power density of 6000 W kg(-1). An excellent long cycle life of the electrode was observed with a retention of ∼86% of the initial specific capacitance after 2000 cycles. The good electrochemical performance was attributed to the unique microstructure of the electrode with disordered PANI nanowire arrays encapsulated inside the TiO(2) nanotubes, providing high surface area, fast diffusion path for ions and long-term cycle stability. Such a nanocomposite electrode is attractive for supercapacitor applications. © The Royal Society of Chemistry 2011

Fabrication and structural characterization of highly ordered titania nanotube arrays

NASA Astrophysics Data System (ADS)

Shi, Hongtao; Ordonez, Rosita

Titanium (Ti) dioxide nanotubes have drawn much attention in the past decade due to the fact that titania is an extremely versatile material with a variety of technological applications. Anodizing Ti in different electrolytes has proved to be quite successful so far in creating the nanotubes, however, their degree of order is still not nearly as good as nanoporous anodic alumina. In this work, we first deposit a thin layer of aluminum (Al) onto electropolished Ti substrates, using thermal evaporation. Such an Al layer is then anodized in 0.3 M oxalic acid, forming an ordered nanoporous alumina mask on top of Ti. Afterwards, the anodization of Ti is accomplished at 20 V in solutions containing 1 M NaH2PO4 and 0.5% HF or H2SO4, which results in the creation of ordered titania nanotube arrays. The inner pore diameter of the nanotubes can be tuned from ~50 nm to ~75 nm, depending on the anodization voltage applied to Al or Ti. X-ray diffractometry shows the as-grown titania nanotubes are amorphous. Samples annealed at different temperatures in ambient atmosphere will be also reported.

Synthesis of high crystallinity ZnO nanowire array on polymer substrate and flexible fiber-based sensor.

PubMed

Liu, Jinmei; Wu, Weiwei; Bai, Suo; Qin, Yong

2011-11-01

Well aligned ZnO nanowire (NW) arrays are grown on Kevlar fiber and Kapton film via the chemical vapor deposition (CVD) method. These NWs have better crystallinity than those synthesized through the low-temperature hydrothermal method. The average length and diameter of ZnO NWs grown on Kevlar fiber can be controlled from 0.5 to 2.76 μm and 30 to 300 nm, respectively. A flexible ultraviolet (UV) sensor based on Kevlar fiber/ZnO NWs hybrid structure is made to detect UV illumination quantificationally.

Nanoengineered thermal materials based on carbon nanotube array composites

NASA Technical Reports Server (NTRS)

Li, Jun (Inventor); Meyyappan, Meyya (Inventor); Dangelo, Carlos (Inventor)

2010-01-01

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Nanoengineered thermal materials based on carbon nanotube array composites

NASA Technical Reports Server (NTRS)

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites

NASA Technical Reports Server (NTRS)

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Correlation of lattice defects and thermal processing in the crystallization of titania nanotube arrays

NASA Astrophysics Data System (ADS)

Hosseinpour, Pegah M.; Yung, Daniel; Panaitescu, Eugen; Heiman, Don; Menon, Latika; Budil, David; Lewis, Laura H.

2014-12-01

Titania nanotubes have the potential to be employed in a wide range of energy-related applications such as solar energy-harvesting devices and hydrogen production. As the functionality of titania nanostructures is critically affected by their morphology and crystallinity, it is necessary to understand and control these factors in order to engineer useful materials for green applications. In this study, electrochemically-synthesized titania nanotube arrays were thermally processed in inert and reducing environments to isolate the role of post-synthesis processing conditions on the crystallization behavior, electronic structure and morphology development in titania nanotubes, correlated with the nanotube functionality. Structural and calorimetric studies revealed that as-synthesized amorphous nanotubes crystallize to form the anatase structure in a three-stage process that is facilitated by the creation of structural defects. It is concluded that processing in a reducing gas atmosphere versus in an inert environment provides a larger unit cell volume and a higher concentration of Ti3+ associated with oxygen vacancies, thereby reducing the activation energy of crystallization. Further, post-synthesis annealing in either reducing or inert atmospheres produces pronounced morphological changes, confirming that the nanotube arrays thermally transform into a porous morphology consisting of a fragmented tubular architecture surrounded by a network of connected nanoparticles. This study links explicit data concerning morphology, crystallization and defects, and shows that the annealing gas environment determines the details of the crystal structure, the electronic structure and the morphology of titania nanotubes. These factors, in turn, impact the charge transport and consequently the functionality of these nanotubes as photocatalysts.

Preparation of high-aspect-ratio ZnO nanorod arrays for the detection of several organic solvents at room working temperature

NASA Astrophysics Data System (ADS)

Lee, Yi-Mu; Zheng, Min-Ren

2013-11-01

Chemical sensors based on ZnO nanorod arrays were prepared using chemical bath deposition (CBD) to investigate the sensing performance for the detection of several organic solvents with low concentrations (0.1%, 0.5%, 1%, v/v) at room temperature. High quality and high aspect-ratio (value ˜28) ZnO nanorods have a diameter of about 74 nm and average length of 2.1 μm. Nyquist plots and Bode plots of the ZnO sensors under different organic solvents were obtained by electrical impedance spectroscopy (EIS). The sensing properties such as charge-transfer resistance, double-layer capacitance and dielectric parameters were determined from the impedance spectra to explore the charge transport in low-concentration aqueous solutions. The decreasing trend of the charge-transfer resistance (Rct) as decreasing solvent concentrations is observed, and a straight line at low frequency regime indicates adsorption of water molecules on the oxide surface. The sensitivity of the ZnO sensors was calculated from the resistance variation in target solvents and in deionized water. We demonstrated the use of ZnO nanorod arrays as a chemical sensor capable of generating a different response upon exposure to methanol, ethanol, isopropyl alcohol, acetone and water, wherein the methanol sensing exhibited highest sensitivity. In addition, the ZnO sensor also demonstrates good stability and reproducibility for detection of methanol and ethanol.

Highly efficient and completely flexible fiber-shaped dye-sensitized solar cell based on TiO2 nanotube array

NASA Astrophysics Data System (ADS)

Lv, Zhibin; Yu, Jiefeng; Wu, Hongwei; Shang, Jian; Wang, Dan; Hou, Shaocong; Fu, Yongping; Wu, Kai; Zou, Dechun

2012-02-01

A type of highly efficient completely flexible fiber-shaped solar cell based on TiO2 nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm-2) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO2 nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies.A type of highly efficient completely flexible fiber-shaped solar cell based on TiO2 nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm-2) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO2 nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr11532h

High-performance optical projection controllable ZnO nanorod arrays for microweighing sensors.

PubMed

Wang, Hongbo; Jiang, Shulan; Zhang, Lei; Yu, Bingjun; Chen, Duoli; Yang, Weiqing; Qian, Linmao

2018-03-08

Optical microweighing sensors are an essential component of micro-force measurements in physical, chemical, and biological detection fields, although, their limited detection range (less than 15°) severely hinders their wide application. Such a limitation is mainly attributed to the essential restrictions of traditional light reflection and optical waveguide modes. Here, we report a high-performance optical microweighing sensor based on the synergistic effects of both a new optical projection mode and a ZnO nanorod array sensor. Ascribed to the unique configuration design of this sensing method, this optical microweighing sensor has a wide detection range (more than 80°) and a high sensitivity of 90 nA deg -1 , which is much larger than that of conventional microcantilever-based optical microweighing sensors. Furthermore, the location of the UV light source can be adjusted within a few millimeters, meaning that the microweighing sensor does not need repetitive optical calibration. More importantly, for low height and small incident angles of the UV light source, we can obtain highly sensitive microweighing properties on account of the highly sensitive ZnO nanorod array-based UV sensor. Therefore, this kind of large detection range, non-contact, and non-destructive microweighing sensor has potential applications in air quality monitoring and chemical and biological detection.

Drying induced upright sliding and reorganization of carbon nanotube arrays

NASA Astrophysics Data System (ADS)

Li, Qingwen; DePaula, Raymond; Zhang, Xiefei; Zheng, Lianxi; Arendt, Paul N.; Mueller, Fred M.; Zhu, Y. T.; Tu, Yi

2006-09-01

Driven by capillary force, wet carbon nanotube (CNT) arrays have been found to reorganize into cellular structures upon drying. During the reorganization process, individual CNTs are firmly attached to the substrate and have to lie down on the substrate at cell bottoms, forming closed cells. Here we demonstrate that by modifying catalyst structures, the adhesion of CNTs to the substrate can be weakened. Upon drying such CNT arrays, CNTs may slide away from their original sites on the surface and self-assemble into cellular patterns with bottoms open. It is also found that the sliding distance of CNTs increases with array height, and drying millimetre tall arrays leads to the sliding of CNTs over a few hundred micrometres and the eventual self-assembly into discrete islands. By introducing regular vacancies in CNT arrays, CNTs may be manipulated into different patterns.

Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

NASA Astrophysics Data System (ADS)

Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Tan, Dunlin; Zhang, Bowei; Tok, Alfred Iing Yoong; Teo, Edwin Hang Tong

Vertically aligned carbon nanotube (CNT) array is one of the most promising energy dissipating materials due to its excellent temperature invariant mechanical property. However, the CNT arrays with desirable recoverability after compression is still a challenge. Here, we report on the mechanical enhancement of the CNT arrays reinforced by coating with boron nitride (BN) layers. These BN coated CNT (BN/CNT) arrays exhibit excellent compressive strength and recoverability as compared to those of the as-prepared CNT arrays which totally collapsed after compression. In addition, the BN coating also provides better resistance to oxidation due to its intrinsic thermal stability. This work presented here opens a new pathway towards tuning mechanical behavior of any arbitrary CNT arrays for promising potential such as damper, vibration isolator and shock absorber applications.

Conical islands of TiO2 nanotube arrays in the photoelectrode of dye-sensitized solar cells.

PubMed

Kim, Woong-Rae; Park, Hun; Choi, Won-Youl

2015-01-01

Ti conical island structures were fabricated using photolithography and the reactive ion etching method. The resulting conical island structures were anodized in ethylene glycol solution containing 0.25 wt% NH4F and 2 vol% H2O, and conical islands composed of TiO2 nanotubes were successfully formed on the Ti foils. The conical islands composed of TiO2 nanotubes were employed in photoelectrodes for dye-sensitized solar cells (DSCs). DSC photoelectrodes based on planar Ti structures covered with TiO2 nanotubes were also fabricated as a reference. The short-circuit current (J sc) and efficiency of DSCs based on the conical island structures were higher than those of the reference samples. The efficiency of DSCs based on the conical island structures reached up to 1.866%. From electrochemical impedance spectroscopy and open-circuit voltage (V oc) decay measurements, DSCs based on the conical island structures exhibited a lower charge transfer resistance at the counter cathode and a longer electron lifetime at the interface of the photoelectrode and electrolyte compared to the reference samples. The conical island structure was very effective at improving performances of DSCs based on TiO2 nanotubes. Graphical AbstractConical islands of TiO2 nanotube arrays are fabricated by an anodizing process with Ti protruding dots which have a conical shape. The conical islands are applied for use in DSC photoelectrodes. DSCs based on the conical islands of TiO2 nanotube arrays have the potential to achieve higher efficiency levels compared to DSCs based on normal TiO2 nanotubes and TiO2 nanoparticles because the conical islands of TiO2 nanotube arrays enlarge the surface area for dye adsorption.

Electrodeposition of ZnO nanorod arrays on ZnO substrate with tunable orientation and optical properties.

PubMed

Jehl, Z; Rousset, J; Donsanti, F; Renou, G; Naghavi, N; Lincot, D

2010-10-01

The electrodeposition of ZnO nanorods on ZnO:Al films with different orientations is reported. The influence of the total charge exchanged during electrodeposition on the nanorod's geometry (length, diameter, aspect ratio and surface density) and the optical transmission properties of the nanorod arrays is studied on a [0001]-oriented ZnO:Al substrate. The nanorods are highly vertically oriented along the c axis, following the lattice matching with the substrate. The growth on a [1010] and [1120] ZnO:Al-oriented substrate with c axis parallel to the substrate leads to a systematic deviation angle of 55 degrees from the perpendicular direction. This finding has been explained by the occurrence of a minority orientation with the [1011] planes parallel to the surface, with a preferential growth on corresponding [0001] termination. Substrate crystalline orientation is thereby found to be a major parameter in finely tuning the orientation of the nanorod array. This new approach allows us to optimize the light scattering properties of the films.

FeP@C Nanotube Arrays Grown on Carbon Fabric as a Low Potential and Freestanding Anode for High-Performance Li-Ion Batteries.

PubMed

Xu, Xijun; Liu, Jun; Liu, Zhengbo; Wang, Zhuosen; Hu, Renzong; Liu, Jiangwen; Ouyang, Liuzhang; Zhu, Min

2018-06-26

An anode of self-supported FeP@C nanotube arrays on carbon fabric (CF) is successfully fabricated via a facile template-based deposition and phosphorization route: first, well-aligned FeOOH nanotube arrays are simply obtained via a solution deposition and in situ etching route with hydrothermally crystallized (Co,Ni)(CO 3 ) 0.5 OH nanowire arrays as the template; subsequently, these uniform FeOOH nanotube arrays are transformed into robust carbon-coated Fe 3 O 4 (Fe 3 O 4 @C) nanotube arrays via glucose adsorption and annealing treatments; and finally FeP@C nanotube arrays on CF are achieved through the facile phosphorization of the oxide-based arrays. As an anode for lithium-ion batteries (LIBs), these FeP@C nanotube arrays exhibit superior rate capability (reversible capacities of 945, 871, 815, 762, 717, and 657 mA h g -1 at 0.1, 0.2, 0.4, 0.8, 1.3, and 2.2 A g -1 , respectively, corresponding to area specific capacities of 1.73, 1.59, 1.49, 1.39, 1.31, 1.20 mA h cm -2 at 0.18, 0.37, 0.732, 1.46, 2.38, and 4.03 mA cm -2 , respectively) and a stable long-cycling performance (a high specific capacity of 718 mA h g -1 after 670 cycles at 0.5 A g -1 , corresponding to an area capacity of 1.31 mA h cm -2 at 0.92 mA cm -2 ). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical growth of controlled tip shapes of ZnO nanorod arrays on silicon substrate and enhanced photoluminescence emission from nanopyramid arrays compared with flat-head nanorods

NASA Astrophysics Data System (ADS)

Alimanesh, Mahmoud; Hassan, Z.; Zainal, Norzaini

2017-10-01

Zinc oxide (ZnO) nanorod arrays (NRAs) with different morphologies such as; perfect hexagon flat-head, pyramidal, compact pencil, nail-shaped, and high-compact ZnO nanorod thin films, were successfully grown on silicon substrates. These NRAs were formed on substrates using a simple low-temperature electrochemical method without adding any catalyst or template via the precursors of zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and hexamethylenetetramine [HMT; C6H12N4] with an equal molar concentration of 0.025 mol/l. The morphologies of the ZnO nanorods (NRs) could be controlled and transformed successfully in to other morphologies by changing the growth conditions, such as; growth temperature and applied current density. Detailed structural investigations reveal that the synthesized various NRs are single crystalline with wurtzite hexagonal phase and preferentially grow along the c-axis direction. The room temperature photoluminescence spectra show that each spectrum consists of an ultraviolet (UV) band and a relative broad visible light emission and infrared emission peak. The enhanced light emission intensity at UV peak (∼375 nm) is observed significantly from ZnO nanopyramid (NP) arrays because of the conical shape of NP. The photoluminescence intensity of the UV peak from the NPs is found to be 1.5-17 times larger than those from the other various NRs.

Power generation from base excitation of a Kevlar composite beam with ZnO nanowires

NASA Astrophysics Data System (ADS)

Malakooti, Mohammad H.; Hwang, Hyun-Sik; Sodano, Henry A.

2015-04-01

One-dimensional nanostructures such as nanowires, nanorods, and nanotubes with piezoelectric properties have gained interest in the fabrication of small scale power harvesting systems. However, the practical applications of the nanoscale materials in structures with true mechanical strengths have not yet been demonstrated. In this paper, piezoelectric ZnO nanowires are integrated into the fiber reinforced polymer composites serving as an active phase to convert the induced strain energy from ambient vibration into electrical energy. Arrays of ZnO nanowires are grown vertically aligned on aramid fibers through a low-cost hydrothermal process. The modified fabrics with ZnO nanowires whiskers are then placed between two carbon fabrics as the top and the bottom electrodes. Finally, vacuum resin transfer molding technique is utilized to fabricate these multiscale composites. The fabricated composites are subjected to a base excitation using a shaker to generate charge due to the direct piezoelectric effect of ZnO nanowires. Measuring the generated potential difference between the two electrodes showed the energy harvesting application of these multiscale composites in addition to their superior mechanical properties. These results propose a new generation of power harvesting systems with enhanced mechanical properties.

Polyoxometalate-modified TiO2 nanotube arrays photoanode materials for enhanced dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Liu, Ran; Sun, Zhixia; Zhang, Yuzhuo; Xu, Lin; Li, Na

2017-10-01

In this work, we prepared for the first time the TiO2 nanotube arrays (TNAs) photoanode with polyoxometalate(POMs)-modified TiO2 electron-transport layer for improving the performance of zinc phthalocyanine(ZnPc)-sensitized solar cells. The as-prepared POMs/TNAs/ZnPc composite photoanode exhibited higher photovoltaic performances than the TNAs/ZnPc photoanode, so that the power conversion efficiency of the solar cell device based on the POMs/TNAs/ZnPc photoanode displayed a notable improvement of 45%. These results indicated that the POMs play a key role in reducing charge recombination in phthalocyanine-sensitized solar cells, together with TiO2 nanotube arrays being helpful for electron transport. The mechanism of the performance improvement was demonstrated by the measurements of electrochemical impedance spectra and open-circuit voltage decay curves. Although the resulting performance is still below that of the state-of-the-art dye-sensitized solar cells, this study presents a new insight into improving the power conversion efficiency of phthalocyanine-sensitized solar cells via polyoxometalate-modified TiO2 nanotube arrays photoanode.

Study of quantum confinement effects in ZnO nanostructures

NASA Astrophysics Data System (ADS)

Movlarooy, Tayebeh

2018-03-01

Motivation to fact that zinc oxide nanowires and nanotubes with successful synthesis and the mechanism of formation, stability and electronic properties have been investigated; in this study the structural, electronic properties and quantum confinement effects of zinc oxide nanotubes and nanowires with different diameters are discussed. The calculations within density functional theory and the pseudo potential approximation are done. The electronic structure and energy gap for Armchair and zigzag ZnO nanotubes with a diameter of about 4 to 55 Angstrom and ZnO nanowires with a diameter range of 4 to 23 Å is calculated. The results revealed that due to the quantum confinement effects, by reducing the diameter of nanowires and nanotubes, the energy gap increases. Zinc oxide semiconductor nanostructures since having direct band gap with size-dependent and quantum confinement effect are recommended as an appropriate candidate for making nanoscale optoelectronic devices.

Characterizations of low-temperature electroluminescence from ZnO nanowire light-emitting arrays on the p-GaN layer.

PubMed

Lu, Tzu-Chun; Ke, Min-Yung; Yang, Sheng-Chieh; Cheng, Yun-Wei; Chen, Liang-Yi; Lin, Guan-Jhong; Lu, Yu-Hsin; He, Jr-Hau; Kuo, Hao-Chung; Huang, JianJang

2010-12-15

Low-temperature electroluminescence from ZnO nanowire light-emitting arrays is reported. By inserting a thin MgO current blocking layer in between ZnO nanowire and p-GaN, high-purity UV light emission at wavelength 398 nm was obtained. As the temperature is decreased, contrary to the typical GaN-based light emitting diodes, our device shows a decrease of optical output intensity. The results are associated with various carrier tunneling processes and frozen MgO defects.

Surface-restrained growth of vertically aligned carbon nanotube arrays with excellent thermal transport performance.

PubMed

Ping, Linquan; Hou, Peng-Xiang; Liu, Chang; Li, Jincheng; Zhao, Yang; Zhang, Feng; Ma, Chaoqun; Tai, Kaiping; Cong, Hongtao; Cheng, Hui-Ming

2017-06-22

A vertically aligned carbon nanotube (VACNT) array is a promising candidate for a high-performance thermal interface material in high-power microprocessors due to its excellent thermal transport property. However, its rough and entangled free tips always cause poor interfacial contact, which results in serious contact resistance dominating the total thermal resistance. Here, we employed a thin carbon cover to restrain the disorderly growth of the free tips of a VACNT array. As a result, all the free tips are seamlessly connected by this thin carbon cover and the top surface of the array is smoothed. This unique structure guarantees the participation of all the carbon nanotubes in the array in the heat transport. Consequently the VACNT array grown on a Cu substrate shows a record low thermal resistance of 0.8 mm 2 K W -1 including the two-sided contact resistances, which is 4 times lower than the best result previously reported. Remarkably, the VACNT array can be easily peeled away from the Cu substrate and act as a thermal pad with excellent flexibility, adhesive ability and heat transport capability. As a result the CNT array with a thin carbon cover shows great potential for use as a high-performance flexible thermal interface material.

Facile Synthesis of ZnO Nanoparticles on Nitrogen-Doped Carbon Nanotubes as High-Performance Anode Material for Lithium-Ion Batteries

PubMed Central

Li, Haipeng; Liu, Zhengjun; Yang, Shuang; Zhao, Yan; Feng, Yuting; Zhang, Chengwei; Yin, Fuxing

2017-01-01

ZnO/nitrogen-doped carbon nanotube (ZnO/NCNT) composite, prepared though a simple one-step sol-gel synthetic technique, has been explored for the first time as an anode material. The as-prepared ZnO/NCNT nanocomposite preserves a good dispersity and homogeneity of the ZnO nanoparticles (~6 nm) which deposited on the surface of NCNT. Transmission electron microscopy (TEM) reveals the formation of ZnO nanoparticles with an average size of 6 nm homogeneously deposited on the surface of NCNT. ZnO/NCNT composite, when evaluated as an anode for lithium-ion batteries (LIBs), exhibits remarkably enhanced cycling ability and rate capability compared with the ZnO/CNT counterpart. A relatively large reversible capacity of 1013 mAh·g−1 is manifested at the second cycle and a capacity of 664 mAh·g−1 is retained after 100 cycles. Furthermore, the ZnO/NCNT system displays a reversible capacity of 308 mAh·g−1 even at a high current density of 1600 mA·g−1. These electrochemical performance enhancements are ascribed to the reinforced accumulative effects of the well-dispersed ZnO nanoparticles and doping nitrogen atoms, which can not only suppress the volumetric expansion of ZnO nanoparticles during the cycling performance but also provide a highly conductive NCNT network for ZnO anode. PMID:28934141

Facile Synthesis of ZnO Nanoparticles on Nitrogen-Doped Carbon Nanotubes as High-Performance Anode Material for Lithium-Ion Batteries.

PubMed

Li, Haipeng; Liu, Zhengjun; Yang, Shuang; Zhao, Yan; Feng, Yuting; Bakenov, Zhumabay; Zhang, Chengwei; Yin, Fuxing

2017-09-21

ZnO/nitrogen-doped carbon nanotube (ZnO/NCNT) composite, prepared though a simple one-step sol-gel synthetic technique, has been explored for the first time as an anode material. The as-prepared ZnO/NCNT nanocomposite preserves a good dispersity and homogeneity of the ZnO nanoparticles (~6 nm) which deposited on the surface of NCNT. Transmission electron microscopy (TEM) reveals the formation of ZnO nanoparticles with an average size of 6 nm homogeneously deposited on the surface of NCNT. ZnO/NCNT composite, when evaluated as an anode for lithium-ion batteries (LIBs), exhibits remarkably enhanced cycling ability and rate capability compared with the ZnO/CNT counterpart. A relatively large reversible capacity of 1013 mAh·g -1 is manifested at the second cycle and a capacity of 664 mAh·g -1 is retained after 100 cycles. Furthermore, the ZnO/NCNT system displays a reversible capacity of 308 mAh·g -1 even at a high current density of 1600 mA·g -1 . These electrochemical performance enhancements are ascribed to the reinforced accumulative effects of the well-dispersed ZnO nanoparticles and doping nitrogen atoms, which can not only suppress the volumetric expansion of ZnO nanoparticles during the cycling performance but also provide a highly conductive NCNT network for ZnO anode.

Enhancing Thermal Conductive Performance of Vertically Aligned Carbon Nanotube Array Composite by Pre-Annealing Treatment.

PubMed

Wang, Miao; Chen, Hong-Yuan; Xing, Ya-Juan; Wei, Han-Xing; Li, Qiang; Chen, Ming-Hai; Li, Qing-Wen; Xuan, Yi-Min

2015-04-01

Vertically aligned carbon nanotube (VACNT) array/polymer composite has already been recognized as a promising candidate for advanced thermal pad in thermal management of high-power electronic devices. However, the thermal conductive performance of this composite was limited by the quality of CNTs arrays. In this study, pre-annealing treatment was used to purify CNT arrays and improve thermal conductive performance of VACNT arrays/silicone composite. The thermal conductivity of the composite was enhanced by 34.52% and the thermal interface resistance was also reduced by 65.94% at a pre-annealing temperature of 490 °C for 5 min. The annealing process could remove some amorphous carbon and open the tips of CNTs. As a result, the interfacial compatibility in composite between carbon nanotube and polymer matrix was improved. The cyclic compression and tension performance of VACNT/S160 composite was investigated for further application.

Biochemical Sensors Using Carbon Nanotube Arrays

NASA Technical Reports Server (NTRS)

Meyyappan, Meyya (Inventor); Cassell, Alan M. (Inventor); Li, Jun (Inventor)

2011-01-01

Method and system for detecting presence of biomolecules in a selected subset, or in each of several selected subsets, in a fluid. Each of an array of two or more carbon nanotubes ("CNTs") is connected at a first CNT end to one or more electronics devices, each of which senses a selected electrochemical signal that is generated when a target biomolecule in the selected subset becomes attached to a functionalized second end of the CNT, which is covalently bonded with a probe molecule. This approach indicates when target biomolecules in the selected subset are present and indicates presence or absence of target biomolecules in two or more selected subsets. Alternatively, presence of absence of an analyte can be detected.

Modelling clustering of vertically aligned carbon nanotube arrays.

PubMed

Schaber, Clemens F; Filippov, Alexander E; Heinlein, Thorsten; Schneider, Jörg J; Gorb, Stanislav N

2015-08-06

Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications.

Nanoscale thermocapillarity enabled purification for horizontally aligned arrays of single walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Jin, Sung Hun; Dunham, Simon; Xie, Xu; Rogers, John A.

2015-09-01

Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermos-capillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. Especially for the purpose of selective joule heating over only metallic nanotubes, two representative platforms are proposed and confirmed. One is achieved by selective joule heating associated with thin film transistors with partial gate structure. The other is based on a simple, scalable, large-area scheme through microwave irradiation by using micro-strip dipole antennas of low work-function metals. In this study, based on purified semiconducting SWNTs, we demonstrated field effect transistors with mobility (> 1,000 cm2/Vsec) and on/off switching ratio (~10,000) with current outputs in the milliamp range. Furthermore, as one demonstration of the effectiveness over large area-scalability and simplicity, implementing the micro-wave based purification, on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

Parametrically Optimized Carbon Nanotube-Coated Cold Cathode Spindt Arrays

PubMed Central

Yuan, Xuesong; Cole, Matthew T.; Zhang, Yu; Wu, Jianqiang; Milne, William I.; Yan, Yang

2017-01-01

Here, we investigate, through parametrically optimized macroscale simulations, the field electron emission from arrays of carbon nanotube (CNT)-coated Spindts towards the development of an emerging class of novel vacuum electron devices. The present study builds on empirical data gleaned from our recent experimental findings on the room temperature electron emission from large area CNT electron sources. We determine the field emission current of the present microstructures directly using particle in cell (PIC) software and present a new CNT cold cathode array variant which has been geometrically optimized to provide maximal emission current density, with current densities of up to 11.5 A/cm2 at low operational electric fields of 5.0 V/μm. PMID:28336845

Investigation of the influence of geometric parameters of carbon nanotube arrays on their adhesion properties

NASA Astrophysics Data System (ADS)

Il’ina, M. V.; Konshin, A. A.; Il’in, O. I.; Rudyk, N. N.; Fedotov, A. A.; Ageev, O. A.

2018-03-01

The results of experimental studies of adhesion of carbon nanotube (CNT) arrays with different geometric parameters and orientations using atomic-force microscopy are presented. The adhesion values of CNT arrays were determined, which were from 82 to 1315 nN depending on the parameters of the array. As a result, it was established that the adhesion of a CNT array increases with an increase in branching and disorientation of the array, as well as with the growth of the aspect ratio of CNTs in the array.

Direct selective growth of ZnO nanowire arrays from inkjet-printed zinc acetate precursor on a heated substrate

PubMed Central

2013-01-01

Inkjet printing of functional materials has drawn tremendous interest as an alternative to the conventional photolithography-based microelectronics fabrication process development. We introduce direct selective nanowire array growth by inkjet printing of Zn acetate precursor ink patterning and subsequent hydrothermal ZnO local growth without nozzle clogging problem which frequently happens in nanoparticle inkjet printing. The proposed process can directly grow ZnO nanowires in any arbitrary patterned shape, and it is basically very fast, low cost, environmentally benign, and low temperature. Therefore, Zn acetate precursor inkjet printing-based direct nanowire local growth is expected to give extremely high flexibility in nanomaterial patterning for high-performance electronics fabrication especially at the development stage. As a proof of concept of the proposed method, ZnO nanowire network-based field effect transistors and ultraviolet photo-detectors were demonstrated by direct patterned grown ZnO nanowires as active layer. PMID:24252130

Mechanically and chemically robust sandwich-structured C@Si@C nanotube array Li-ion battery anodes.

PubMed

Liu, Jinyun; Li, Nan; Goodman, Matthew D; Zhang, Hui Gang; Epstein, Eric S; Huang, Bo; Pan, Zeng; Kim, Jinwoo; Choi, Jun Hee; Huang, Xingjiu; Liu, Jinhuai; Hsia, K Jimmy; Dillon, Shen J; Braun, Paul V

2015-02-24

Stability and high energy densities are essential qualities for emerging battery electrodes. Because of its high specific capacity, silicon has been considered a promising anode candidate. However, the several-fold volume changes during lithiation and delithiation leads to fractures and continuous formation of an unstable solid-electrolyte interphase (SEI) layer, resulting in rapid capacity decay. Here, we present a carbon-silicon-carbon (C@Si@C) nanotube sandwich structure that addresses the mechanical and chemical stability issues commonly associated with Si anodes. The C@Si@C nanotube array exhibits a capacity of ∼2200 mAh g(-1) (∼750 mAh cm(-3)), which significantly exceeds that of a commercial graphite anode, and a nearly constant Coulombic efficiency of ∼98% over 60 cycles. In addition, the C@Si@C nanotube array gives much better capacity and structure stability compared to the Si nanotubes without carbon coatings, the ZnO@C@Si@C nanorods, a Si thin film on Ni foam, and C@Si and Si@C nanotubes. In situ SEM during cycling shows that the tubes expand both inward and outward upon lithiation, as well as elongate, and then revert back to their initial size and shape after delithiation, suggesting stability during volume changes. The mechanical modeling indicates the overall plastic strain in a nanotube is much less than in a nanorod, which may significantly reduce low-cycle fatigue. The sandwich-structured nanotube design is quite general, and may serve as a guide for many emerging anode and cathode systems.

Spin-polarized electron emitter: Mn-doped GaN nanotubes and their arrays

NASA Astrophysics Data System (ADS)

Hao, Shaogang; Zhou, Gang; Wu, Jian; Duan, Wenhui; Gu, Bing-Lin

2004-03-01

The influences from the doping magnetic atom, Mn, on the geometry, electronic properties, and spin-polarization characteristics are demonstrated for open armchair gallium nitrogen (GaN) nanotubes and arrays by use of the first-principles calculations. The interaction between dangling bonds of Ga (Mn) and N atoms at the open-end promotes the self-close of the tube mouth and formation of a more stable open semicone top. Primarily owing to hybridization of Mn 3d and N 2p orbitals, one Mn atom introduces several impurity energy levels into the original energy gap, and the calculated magnetic moment is 4μB. The electron spin polarizations in the field emission are theoretically evaluated. We suggest that armchair open GaN nanotube arrays doped with a finite number of magnetic atoms may have application potential as the electron source of spintronic devices in the future.

Controlled growth of c-axis oriented ZnO nanorod array films by electrodeposition method and characterization.

PubMed

Arslan, Andaç; Hür, Evrim; Ilican, Saliha; Caglar, Yasemin; Caglar, Mujdat

2014-07-15

ZnO nanorod array films were deposited from aqueous solution containing different concentrations (1×10(-2) M and 5×10(-3) M) Zn(NO3)2⋅6H2O and C6H12N4 and at different electrodeposition times (i.e., 15 min, 30 min, 60 min, 120 min and 180 min) using chronoamperometry method on p-Si substrate. Surface morphology and crystal structural properties of ZnO films were investigated by XRD and FESEM to select ZnO films which have optimum properties. The highest TC(hkl) value was observed in (002) plane for the film, which is deposited at 1×10(-2) M and 120 min. It is also observed that the highly oriented nanorods in this film are denser. Additionally, the conductivity type was determined by using Mott-Schottky which is electrochemical impedance spectroscopy method (EIS). On the other hand, to investigate the utility of obtained ZnO on p-Si (p-Si/n-ZnO) as supercapacitor electrode active material, the electrochemical storage properties of p-Si/ZnO was studied by electrochemical impedance spectroscopy and repeating chronopotentiometry methods. It is suggested from electrochemical tests results that p-Si/ZnO is a promising electrode materials for supercapacitor applications that required low voltage (<10 V). Rectifiying behavior was observed from the I-V characteristic of nanorod array n-ZnO/p-Si heterojunction diode. The n value, Io and the ϕb were found to be 5.48, 1.93×10(-8) A and 0.75 eV, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

High carrier concentration ZnO nanowire arrays for binder-free conductive support of supercapacitors electrodes by Al doping.

PubMed

Zheng, Xin; Sun, Yihui; Yan, Xiaoqin; Sun, Xu; Zhang, Guangjie; Zhang, Qian; Jiang, Yaru; Gao, Wenchao; Zhang, Yue

2016-12-15

Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. Here, we prepared in situ Al-doped ZnO nanowire arrays by using continuous flow injection (CFI) hydrothermal method to promote the conductivity. This reasonable method offers highly stable precursor concentration for doping that effectively avoid the appearance of the low conductivity ZnO nanosheets. Benefit from this, three orders of magnitude rise of the carrier concentration from 10 16 cm -3 to 10 19 cm -3 can be achieved compared with the common hydrothermal (CH) mothed in Mott-Schottky measurement. Possible effect of Al-doping was discussed by first-principle theory. On this basis, Al-doped ZnO nanowire arrays was developed as a binder-free conductive support for supercapacitor electrodes and high capacitance was triggered. It is owing to the dramatically decreased transfer resistance induced by the growing free-moving electrons and holes. Our results have a profound significance not merely in the controlled synthesis of other doping nanomaterials by co-precipitation method but also in the application of binder-free energy materials or other materials. Copyright © 2016 Elsevier Inc. All rights reserved.

One-reactor plasma assisted fabrication of ZnO@TiO 2 multishell nanotubes: assessing the impact of a full coverage on the photovoltaic performance.

PubMed

Filippin, Alejandro Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Sanchez-Valencia, Juan R; Barranco, Angel; Migdley, Paul A; Anta, Juan A; Borras, Ana

2017-08-29

This paper addresses the fabrication of vertically aligned ZnO@TiO 2 multishell nanotubes by a combined full vacuum-plasma approach at mild temperatures. The growth is carried out within the premises of a one-reactor approach, i.e. minimizing the number of vacuum chambers and sample transferences. In this way, the interface between ZnO and TiO 2 is fully preserved from humidity thus increasing ZnO durability and stability. These nanostructures are studied by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy in STEM (EDX-STEM). High density one-dimensional arrays of these nanotubes formed on FTO substrates are applied as photoanode in a dye-sensitized solar cell (DSC). The evolution of the dye adsorption capacity and solar cells parameters are explored as a function of the crystallinity and thickness of the TiO 2 shell. The results show the critical effect of a full coverage by TiO 2 of ZnO core to explain the mixed results found in the literature.

Annealing effect on the photoluminescence properties of ZnO nanorod array prepared by a PLD-assistant wet chemical method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei Sufeng; Lian Jianshe; Wu Hua, E-mail: weisufeng@gmail.com

2010-11-15

Well-aligned ZnO nanorod arrays were synthesized by a wet chemical method on the glass substrate with ZnO thin film as seed layer prepared by pulsed laser deposition. The effect of annealing temperature on the luminescence characteristics was investigated. As the annealing temperature increased, the photoluminescence properties show a general enhancing tendency. The nanorod array with high ultraviolet emission and negligible visible light emission (designated by the photoluminescence intensity ratio of ultraviolet to visible emission of 66.4) is obtained by annealing the sample at 700 deg. C for 1 h. Based on the results of X-ray photoelectron spectroscopy and photoluminescence spectra,more » the mechanisms of visible emission were discussed. - Research Highlights: {yields} ZnO nanorod array with good crystallography, low defects concentration and good optical property was obtained after annealed at 700 deg. C for 1 h. {yields} The transition from the conduction band to the O{sub i} level may be responsible for the yellow-green emission. {yields} The yellow emission may originate from the presence of Zn(OH){sub 2} on the surface or the band transition from conduction band to V{sub o}Zn{sub i} level. {yields} The transition from the Zn{sub i} level to the level should produce an orange emission or an orange-red emission.« less

Effect of growth time to the properties of Al-doped ZnO nanorod arrays

NASA Astrophysics Data System (ADS)

Ismail, A. S.; Mamat, M. H.; Malek, M. F.; Saidi, S. A.; Yusoff, M. M.; Mohamed, R.; Sin, N. D. Md; Suriani, A. B.; Rusop, M.

2018-05-01

Aluminum (Al)-doped zinc oxide (ZnO) nanorod array films were successfully deposited at different growth time on zinc oxide (ZnO) seed layer coated glass substrate using sol-gel immersion method. The morphology images of the films showed that the thicknesses of the films were increased parallel with the increment of growth period. The surface topology of the films displayed an increment of roughness as the growth period increased. Optical properties of the samples exposed that the percentage of transmittances reduced at higher growth time. Besides, the Urbach energy of the films slightly increased as the immersion time increased. The current-voltage (I-V) measurement indicated that the resistance increased as the immersion time increased owing to the appearance of intrinsic layer on top of the nanorods.

Atomic Layer Deposition of Nickel on ZnO Nanowire Arrays for High-Performance Supercapacitors.

PubMed

Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Wang, Yong-Ping; Liu, Wen-Jun; Ji, Xin-Ming; Devi, Anjana; Jiang, An-Quan; Zhang, David Wei

2018-01-10

A novel hybrid core-shell structure of ZnO nanowires (NWs)/Ni as a pseudocapacitor electrode was successfully fabricated by atomic layer deposition of a nickel shell, and its capacitive performance was systemically investigated. Transmission electron microscopy and X-ray photoelectron spectroscopy results indicated that the NiO was formed at the interface between ZnO and Ni where the Ni was oxidized by ZnO during the ALD of the Ni layer. Electrochemical measurement results revealed that the Ti/ZnO NWs/Ni (1500 cycles) electrode with a 30 nm thick Ni-NiO shell layer had the best supercapacitor properties including ultrahigh specific capacitance (∼2440 F g -1 ), good rate capability (80.5%) under high current charge-discharge conditions, and a relatively better cycling stability (86.7% of the initial value remained after 750 cycles at 10 A g -1 ). These attractive capacitive behaviors are mainly attributed to the unique core-shell structure and the combined effect of ZnO NW arrays as short charge transfer pathways for ion diffusion and electron transfer as well as conductive Ni serving as channel for the fast electron transport to Ti substrate. This high-performance Ti/ZnO NWs/Ni hybrid structure is expected to be one of a promising electrodes for high-performance supercapacitor applications.

Gas Composition Sensing Using Carbon Nanotube Arrays

NASA Technical Reports Server (NTRS)

Li, Jing; Meyyappan, Meyya

2012-01-01

This innovation is a lightweight, small sensor for inert gases that consumes a relatively small amount of power and provides measurements that are as accurate as conventional approaches. The sensing approach is based on generating an electrical discharge and measuring the specific gas breakdown voltage associated with each gas present in a sample. An array of carbon nanotubes (CNTs) in a substrate is connected to a variable-pulse voltage source. The CNT tips are spaced appropriately from the second electrode maintained at a constant voltage. A sequence of voltage pulses is applied and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of the current-voltage characteristics. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas. The CNTs in the gas sensor have a sharp (low radius of curvature) tip; they are preferably multi-wall carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs), to generate high-strength electrical fields adjacent to the tips for breakdown of the gas components with lower voltage application and generation of high current. The sensor system can provide a high-sensitivity, low-power-consumption tool that is very specific for identification of one or more gas components. The sensor can be multiplexed to measure current from multiple CNT arrays for simultaneous detection of several gas components.

Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

PubMed

Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

2013-07-18

We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

Orientation-Controllable ZnO Nanorod Array Using Imprinting Method for Maximum Light Utilization in Dye-Sensitized Solar Cells.

PubMed

Jeong, Huisu; Song, Hui; Lee, Ryeri; Pak, Yusin; Kumaresan, Yogeenth; Lee, Heon; Jung, Gun Young

2015-12-01

We present a holey titanium dioxide (TiO2) film combined with a periodically aligned ZnO nanorod layer (ZNL) for maximum light utilization in dye-sensitized solar cells (DSCs). Both the holey TiO2 film and the ZNL were simultaneously fabricated by imprint technique with a mold having vertically aligned ZnO nanorod (NR) array, which was transferred to the TiO2 film after imprinting. The orientation of the transferred ZNL such as laid, tilted, and standing ZnO NRs was dependent on the pitch and height of the ZnO NRs of the mold. The photoanode composed of the holey TiO2 film with the ZNL synergistically utilized the sunlight due to enhanced light scattering and absorption. The best power conversion efficiency of 8.5 % was achieved from the DSC with the standing ZNL, which represented a 33 % improvement compared to the reference cell with a planar TiO2.

Propagation of three-dimensional bipolar ultrashort electromagnetic pulses in an inhomogeneous array of carbon nanotubes

NASA Astrophysics Data System (ADS)

Fedorov, Eduard G.; Zhukov, Alexander V.; Bouffanais, Roland; Timashkov, Alexander P.; Malomed, Boris A.; Leblond, Hervé; Mihalache, Dumitru; Rosanov, Nikolay N.; Belonenko, Mikhail B.

2018-04-01

We study the propagation of three-dimensional (3D) bipolar ultrashort electromagnetic pulses in an inhomogeneous array of semiconductor carbon nanotubes. The heterogeneity is represented by a planar region with an increased concentration of conduction electrons. The evolution of the electromagnetic field and electron concentration in the sample are governed by the Maxwell's equations and continuity equation. In particular, nonuniformity of the electromagnetic field along the axis of the nanotubes is taken into account. We demonstrate that depending on values of the parameters of the electromagnetic pulse approaching the region with the higher electron concentration, the pulse is either reflected from the region or passes it. Specifically, our simulations demonstrate that after interacting with the higher-concentration area, the pulse can propagate steadily, without significant spreading. The possibility of such ultrashort electromagnetic pulses propagating in arrays of carbon nanotubes over distances significantly exceeding characteristic dimensions of the pulses makes it possible to consider them as 3D solitons.

Double-sided anodic titania nanotube arrays: a lopsided growth process.

PubMed

Sun, Lidong; Zhang, Sam; Sun, Xiao Wei; Wang, Xiaoyan; Cai, Yanli

2010-12-07

In the past decade, the pore diameter of anodic titania nanotubes was reported to be influenced by a number of factors in organic electrolyte, for example, applied potential, working distance, water content, and temperature. All these were closely related to potential drop in the organic electrolyte. In this work, the essential role of electric field originating from the potential drop was directly revealed for the first time using a simple two-electrode anodizing method. Anodic titania nanotube arrays were grown simultaneously at both sides of a titanium foil, with tube length being longer at the front side than that at the back side. This lopsided growth was attributed to the higher ionic flux induced by electric field at the front side. Accordingly, the nanotube length was further tailored to be comparable at both sides by modulating the electric field. These results are promising to be used in parallel configuration dye-sensitized solar cells, water splitting, and gas sensors, as a result of high surface area produced by the double-sided architecture.

Titania nanotube arrays as potential interfaces for neurological prostheses

NASA Astrophysics Data System (ADS)

Sorkin, Jonathan Andrew

Neural prostheses can make a dramatic improvement for those suffering from visual and auditory, cognitive, and motor control disabilities, allowing them regained functionality by the use of stimulating or recording electrical signaling. However, the longevity of these devices is limited due to the neural tissue response to the implanted device. In response to the implant penetrating the blood brain barrier and causing trauma to the tissue, the body forms a to scar to isolate the implant in order to protect the nearby tissue. The scar tissue is a result of reactive gliosis and produces an insulated sheath, encapsulating the implant. The glial sheath limits the stimulating or recording capabilities of the implant, reducing its effectiveness over the long term. A favorable interaction with this tissue would be the direct adhesion of neurons onto the contacts of the implant, and the prevention of glial encapsulation. With direct neuronal adhesion the effectiveness and longevity of the device would be significantly improved. Titania nanotube arrays, fabricated using electrochemical anodization, provide a conductive architecture capable of altering cellular response. This work focuses on the fabrication of different titania nanotube array architectures to determine how their structures and properties influence the response of neural tissue, modeled using the C17.2 murine neural stem cell subclone, and if glial encapsulation can be reduced while neuronal adhesion is promoted.

Peptide Modified ZnO Nanoparticles as Gas Sensors Array for Volatile Organic Compounds (VOCs)

PubMed Central

Mascini, Marcello; Gaggiotti, Sara; Della Pelle, Flavio; Di Natale, Corrado; Qakala, Sinazo; Iwuoha, Emmanuel; Pittia, Paola; Compagnone, Dario

2018-01-01

In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modeled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modeled demonstrated a nice fitting of modeling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability, and discrimination ability of the array was achieved. PMID:29713626

Peptide Modified ZnO Nanoparticles as Gas Sensors Array for Volatile Organic Compounds (VOCs).

PubMed

Mascini, Marcello; Gaggiotti, Sara; Della Pelle, Flavio; Di Natale, Corrado; Qakala, Sinazo; Iwuoha, Emmanuel; Pittia, Paola; Compagnone, Dario

2018-01-01

In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modeled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modeled demonstrated a nice fitting of modeling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability, and discrimination ability of the array was achieved.

Peptide modified ZnO nanoparticles as gas sensors array for volatile organic compounds (VOCs)

NASA Astrophysics Data System (ADS)

Mascini, Marcello; Gaggiotti, Sara; Della Pelle, Flavio; Di Natale, Corrado; Qakala, Sinazo; Iwuoha, Emmanuel; Pittia, Paola; Compagnone, Dario

2018-04-01

In this work a peptide based gas sensor array based of ZnO nanoparticles (ZnONPs) has been realized. Four different pentapeptides molecularly modelled for alcohols and esters having cysteine as a common spacer have been immobilized onto ZnONPs. ZnONPs have been morphologically and spectroscopically characterized. Modified nanoparticles have been then deposited onto quartz crystal microbalances (QCMs) and used as gas sensors with nitrogen as carrier gas. Analysis of the pure compounds modelled demonstrated a nice fitting of modelling with real data. The peptide based ZnONPs had very low sensitivity to water, compared to previously studied AuNPs peptide based gas sensors allowing the use of the array on samples with high water content. Real samples of fruit juices have been assayed; stability of the signal, good repeatability and discrimination ability of the array was achieved.

Thermoacoustic chips with carbon nanotube thin yarn arrays.

PubMed

Wei, Yang; Lin, Xiaoyang; Jiang, Kaili; Liu, Peng; Li, Qunqing; Fan, Shoushan

2013-10-09

Aligned carbon nanotube (CNT) films drawn from CNT arrays have shown the potential as thermoacoustic loudspeakers. CNT thermoacoustic chips with robust structures are proposed to promote the applications. The silicon-based chips can play sound and fascinating rhythms by feeding alternating currents and audio signal to the suspending CNT thin yarn arrays across grooves in them. In additional to the thin yarns, experiments further revealed more essential elements of the chips, the groove depth and the interdigital electrodes. The sound pressure depends on the depth of the grooves, and the thermal wavelength can be introduced to define the influence-free depth. The interdigital fingers can effectively reduce the driving voltage, making the chips safe and easy to use. The chips were successfully assembled into earphones and have been working stably for about one year. The thermoacoustic chips can find many applications in consumer electronics and possibly improve the audiovisual experience.

Superaligned carbon nanotube arrays, films, and yarns: a road to applications.

PubMed

Jiang, Kaili; Wang, Jiaping; Li, Qunqing; Liu, Liang; Li, Changhong; Fan, Shoushan

2011-03-04

A superaligned carbon nanotube (CNT) array is a special kind of vertically aligned CNT array with the capability of being converted into continuous fi lms and yarns. The as-produced CNT fi lms are transparent and highly conductive, with aligned CNTs parallel to the direction of drawing. After passing through volatile solutions or being twisted, CNT fi lms can be further condensed into shrunk yarns. These shrunk yarns possess high tensile strengths and Young’s moduli, and are good conductors. Many applications of CNT fi lms and shrunk yarns have been demonstrated, such as TEM grids, loudspeakers, touch screens, etc.

Transparent TiO 2 nanotube array photoelectrodes prepared via two-step anodization

DOE PAGES

Kim, Jin Young; Zhu, Kai; Neale, Nathan R.; ...

2014-04-04

Two-step anodization of transparent TiO 2 nanotube arrays has been demonstrated with aid of a Nb-doped TiO 2 buffer layer deposited between the Ti layer and TCO substrate. Enhanced physical adhesion and electrochemical stability provided by the buffer layer has been found to be important for successful implementation of the two-step anodization process. As a result, with the proposed approach, the morphology and thickness of NT arrays could be controlled very precisely, which in turn, influenced their optical and photoelectrochemical properties.

Visible-light-driven photoelectrochemical and photocatalytic performances of Cr-doped SrTiO3/TiO2 heterostructured nanotube arrays.

PubMed

Jiao, Zhengbo; Chen, Tao; Xiong, Jinyan; Wang, Teng; Lu, Gongxuan; Ye, Jinhua; Bi, Yingpu

2013-01-01

Well-aligned TiO2 nanotube arrays have become of increasing significance because of their unique highly ordered array structure, high specific surface area, unidirectional charge transfer and transportation features. However, their poor visible light utilization as well as the high recombination rate of photoexcited electron-hole pairs greatly limited their practical applications. Herein, we demonstrate the fabrication of visible-light-responsive heterostructured Cr-doped SrTiO3/TiO2 nanotube arrays by a simple hydrothermal method, which facilitate efficient charge separation and thus improve the photoelectrochemical as well as photocatalytic performances.

Polymer-assisted deposition of films and preparation of carbon nanotube arrays using the films

DOEpatents

Luo, Hongmei; Li, Qingwen; Bauer, Eve; Burrell, Anthony Keiran; McCleskey, Thomas Mark; Jia, Quanxi

2013-07-16

Carbon nanotubes were prepared by coating a substrate with a coating solution including a suitable solvent, a soluble polymer, a metal precursor having a first metal selected from iron, nickel, cobalt, and molybdenum, and optionally a second metal selected from aluminum and magnesium, and also a binding agent that forms a complex with the first metal and a complex with the second metal. The coated substrate was exposed to a reducing atmosphere at elevated temperature, and then to a hydrocarbon in the reducing atmosphere. The result was decomposition of the polymer and formation of carbon nanotubes on the substrate. The carbon nanotubes were often in the form of an array on the substrate.

In-vitro bioactivity and electrochemical behavior of polyaniline encapsulated titania nanotube arrays for biomedical applications

NASA Astrophysics Data System (ADS)

Agilan, P.; Rajendran, N.

2018-05-01

Titania nanotube arrays (TNTA) have attracted increasing attention due to their outstanding properties and potential applications in biomedical field. Fabrication of titania nanotubes on titanium surface enhances the biocompatibility. Polyaniline (PANI) is one of the best conducting polymers with remarkable corrosion resistance and reasonable biocompatibility. In this work, the corrosion resistance and biocompatibility of polyaniline encapsulated TiO2 nanotubes for orthopaedic applications were investigated. The vertically oriented, highly ordered TiO2 nanotubes were fabricated on titanium by electrochemical anodization process using fluoride containing electrolytes. The anodization parameters viz., voltage, pH, time and electrolyte concentration were optimized to get orderly arranged TNTA. Further, the conducting polymer PANI was encapsulated on TNTA by electropolymerization process to enhance the corrosion resistance. The nanostructure of the fabricated TNTA and polyaniline encapsulated titania nanotube arrays (PANI-TNTA) were investigated by HR SEM analysis. The formed phases and functional groups were find using XRD, ATR-FTIR. The hydrophilic surface of TNTA and PANI-TNTA was identified by water contact angle studies. The corrosion behavior of specimens was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies. In-vitro immersion studies were carried out in simulated body fluid solution (Hanks' solution) to evaluate the bioactivity of the TNTA and PANI-TNTA. The surface morphological studies revealed the formation of PANI on the TNTA surface. Formation of hydroxyapatite (HAp) on the surfaces of TNTA and PANI-TNTA enhanced the bioactivity and corrosion resistance.

Core-shell titanium dioxide-titanium nitride nanotube arrays with near-infrared plasmon resonances

NASA Astrophysics Data System (ADS)

Farsinezhad, Samira; Shanavas, Thariq; Mahdi, Najia; Askar, Abdelrahman M.; Kar, Piyush; Sharma, Himani; Shankar, Karthik

2018-04-01

Titanium nitride (TiN) is a ceramic with high electrical conductivity which in nanoparticle form, exhibits localized surface plasmon resonances (LSPRs) in the visible region of the solar spectrum. The ceramic nature of TiN coupled with its dielectric loss factor being comparable to that of gold, render it attractive for CMOS polarizers, refractory plasmonics, surface-enhanced Raman scattering and a whole host of sensing applications. We report core-shell TiO2-TiN nanotube arrays exhibiting LSPR peaks in the range 775-830 nm achieved by a simple, solution-based, low cost, large area-compatible fabrication route that does not involve laser-writing or lithography. Self-organized, highly ordered TiO2 nanotube arrays were grown by electrochemical anodization of Ti thin films on fluorine-doped tin oxide-coated glass substrates and then conformally coated with a thin layer of TiN using atomic layer deposition. The effects of varying the TiN layer thickness and thermal annealing on the LSPR profiles were also investigated. Modeling the TiO2-TiN core-shell nanotube structure using two different approaches, one employing effective medium approximations coupled with Fresnel coefficients, resulted in calculated optical spectra that closely matched the experimentally measured spectra. Modeling provided the insight that the observed near-infrared resonance was not collective in nature, and was mainly attributable to the longitudinal resonance of annular nanotube-like TiN particles redshifted due to the presence of the higher permittivity TiO2 matrix. The resulting TiO2-TiN core-shell nanotube structures also function as visible light responsive photocatalysts, as evidenced by their photoelectrochemical water-splitting performance under light emitting diode illumination using 400, 430 and 500 nm photons.

Highly efficient and completely flexible fiber-shaped dye-sensitized solar cell based on TiO2 nanotube array.

PubMed

Lv, Zhibin; Yu, Jiefeng; Wu, Hongwei; Shang, Jian; Wang, Dan; Hou, Shaocong; Fu, Yongping; Wu, Kai; Zou, Dechun

2012-02-21

A type of highly efficient completely flexible fiber-shaped solar cell based on TiO(2) nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm(-2)) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO(2) nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies. This journal is © The Royal Society of Chemistry 2012

Density-controlled, solution-based growth of ZnO nanorod arrays via layer-by-layer polymer thin films for enhanced field emission

NASA Astrophysics Data System (ADS)

Weintraub, Benjamin; Chang, Sehoon; Singamaneni, Srikanth; Han, Won Hee; Choi, Young Jin; Bae, Joonho; Kirkham, Melanie; Tsukruk, Vladimir V.; Deng, Yulin

2008-10-01

A simple, scalable, and cost-effective technique for controlling the growth density of ZnO nanorod arrays based on a layer-by-layer polyelectrolyte polymer film is demonstrated. The ZnO nanorods were synthesized using a low temperature (T = 90 °C), solution-based method. The density-control technique utilizes a polymer thin film pre-coated on the substrate to control the mass transport of the reactant to the substrate. The density-controlled arrays were investigated as potential field emission candidates. The field emission results revealed that an emitter density of 7 nanorods µm-2 and a tapered nanorod morphology generated a high field enhancement factor of 5884. This novel technique shows promise for applications in flat panel display technology.

Lung Microtissue Array to Screen the Fibrogenic Potential of Carbon Nanotubes

PubMed Central

Chen, Zhaowei; Wang, Qixin; Asmani, Mohammadnabi; Li, Yan; Liu, Chang; Li, Changning; Lippmann, Julian M.; Wu, Yun; Zhao, Ruogang

2016-01-01

Due to their excellent physical and chemical characteristics, multi-wall carbon nanotubes (MWCNT) have the potential to be used in structural composites, conductive materials, sensors, drug delivery and medical imaging. However, because of their small-size and light-weight, the applications of MWCNT also raise health concerns. In vivo animal studies have shown that MWCNT cause biomechanical and genetic alterations in the lung tissue which lead to lung fibrosis. To screen the fibrogenic risk factor of specific types of MWCNT, we developed a human lung microtissue array device that allows real-time and in-situ readout of the biomechanical properties of the engineered lung microtissue upon MWCNT insult. We showed that the higher the MWCNT concentration, the more severe cytotoxicity was observed. More importantly, short type MWCNT at low concentration of 50 ng/ml stimulated microtissue formation and contraction force generation, and caused substantial increase in the fibrogenic marker miR-21 expression, indicating the high fibrogenic potential of this specific carbon nanotube type and concentration. The presented microtissue array system provides a powerful tool for high-throughput examination of the therapeutic and toxicological effects of target compounds in realistic tissue environment. PMID:27510174

Carbon Nanotube Bundle Array Cold Cathodes for THz Vacuum Tube Sources

NASA Astrophysics Data System (ADS)

Manohara, Harish M.; Toda, Risaku; Lin, Robert H.; Liao, Anna; Bronikowski, Michael J.; Siegel, Peter H.

2009-12-01

We present high performance cold cathodes composed of arrays of carbon nanotube bundles that routinely produce > 15 A/cm2 at applied fields of 5 to 8 V/µm without any beam focusing. They have exhibited robust operation in poor vacuums of 10-6 to 10-4 Torr- a typically achievable range inside hermetically sealed microcavities. A new double-SOI process was developed to monolithically integrate a gate and additional beam tailoring electrodes. The ability to design the electrodes for specific requirements makes carbon nanotube field emission sources extremely flexible. The lifetime of these cathodes is found to be affected by two effects: a gradual decay of emission due to anode sputtering, and catastrophic failure because of dislodging of CNT bundles at high fields ( > 10 V/µm).

Exploring doxorubicin localization in eluting TiO2 nanotube arrays through fluorescence correlation spectroscopy analysis.

PubMed

De Santo, Ilaria; Sanguigno, Luigi; Causa, Filippo; Monetta, Tullio; Netti, Paolo A

2012-11-07

Drug elution properties of TiO(2) nanotube arrays have been largely investigated by means of solely macroscopic observations. Controversial elution performances have been reported so far and a clear comprehension of these phenomena is still missing as a consequence of a lack of molecular investigation methods. Here we propose a way to discern drug elution properties of nanotubes through the evaluation of drug localization by Fluorescence Correlation Spectroscopy (FCS) analysis. We verified this method upon doxorubicin elution from differently loaded TiO(2) nanotubes. Diverse elution profiles were obtained from nanotubes filled by soaking and wet vacuum impregnation methods. Impregnated nanotubes controlled drug diffusion up to thirty days, while soaked samples completed elution in seven days. FCS analysis of doxorubicin motion in loaded nanotubes clarified that more than 90% of drugs dwell preferentially in inter-nanotube spaces in soaked samples due to decorrelation in a 2D fashion, while a 97% fraction of molecules showed 1D mobility ascribable to displacements along the nanotube vertical axis of wet vacuum impregnated nanotubes. The diverse drug localizations inferred from FCS measurements, together with distinct drug-surface interaction strengths resulting from diverse drug filling techniques, could explain the variability in elution kinetics.

Hybrid nanostructure heterojunction solar cells fabricated using vertically aligned ZnO nanotubes grown on reduced graphene oxide.

PubMed

Yang, Kaikun; Xu, Congkang; Huang, Liwei; Zou, Lianfeng; Wang, Howard

2011-10-07

Using reduced graphene oxide (rGO) films as the transparent conductive coating, inorganic/organic hybrid nanostructure heterojunction photovoltaic devices have been fabricated through hydrothermal synthesis of vertically aligned ZnO nanorods (ZnO-NRs) and nanotubes (ZnO-NTs) on rGO films followed by the spin casting of a poly(3-hexylthiophene) (P3HT) film. The data show that larger interfacial area in ZnO-NT/P3HT composites improves the exciton dissociation and the higher electrode conductance of rGO films helps the power output. This study offers an alternative to manufacturing nanostructure heterojunction solar cells at low temperatures using potentially low cost materials.

Earth-Abundant Oxygen Evolution Catalysts Coupled onto ZnO Nanowire Arrays for Efficient Photoelectrochemical Water Cleavage

PubMed Central

Jiang, Chaoran; Moniz, Savio J A; Khraisheh, Majeda; Tang, Junwang

2014-01-01

ZnO has long been considered as a model UV-driven photoanode for photoelectrochemical water splitting, but its performance has been limited by fast charge-carrier recombination, extremely poor stability in aqueous solution, and slow kinetics of water oxidation. These issues were addressed by applying a strategy of optimization and passivation of hydrothermally grown 1D ZnO nanowire arrays. The length and diameter of bare ZnO nanowires were optimized by varying the growth time and precursor concentration to achieve optimal photoelectrochemical performance. The addition of earth-abundant cobalt phosphate (Co-Pi) and nickel borate (Ni-B) oxygen evolution catalysts onto ZnO nanowires resulted in substantial cathodic shifts in onset potential to as low as about 0.3 V versus the reversible hydrogen electrode (RHE) for Ni-B/ZnO, for which a maximum photocurrent density of 1.1 mA cm−2 at 0.9 V (vs. RHE) with applied bias photon-to-current efficiency of 0.4 % and an unprecedented near-unity incident photon-to-current efficiency at 370 nm. In addition the potential required for saturated photocurrent was dramatically reduced from 1.6 to 0.9 V versus RHE. Furthermore, the stability of these ZnO nanowires was significantly enhanced by using Ni-B compared to Co-Pi due to its superior chemical robustness, and it thus has additional functionality as a stable protecting layer on the ZnO surface. These remarkable enhancements in both photocatalytic activity and stability directly address the current severe limitations in the use of ZnO-based photoelectrodes for water-splitting applications, and can be applied to other photoanodes for efficient solar-driven fuel synthesis. PMID:25156820

Force sensitive carbon nanotube arrays for biologically inspired airflow sensing

NASA Astrophysics Data System (ADS)

Maschmann, Matthew R.; Dickinson, Ben; Ehlert, Gregory J.; Baur, Jeffery W.

2012-09-01

The compressive electromechanical response of aligned carbon nanotube (CNT) arrays is evaluated for use as an artificial hair sensor (AHS) transduction element. CNT arrays with heights of 12, 75, and 225 µm are examined. The quasi-static and dynamic sensitivity to force, response time, and signal drift are examined within the range of applied stresses predicted by a mechanical model applicable to the conceptual CNT array-based AHS (0-1 kPa). Each array is highly sensitive to compressive loading, with a maximum observed gauge factor of 114. The arrays demonstrate a repeatable response to dynamic cycling after a break-in period of approximately 50 cycles. Utilizing a four-wire measurement electrode configuration, the change in contact resistance between the array and the electrodes is observed to dominate the electromechanical response of the arrays. The response time of the CNT arrays is of the order of 10 ms. When the arrays are subjected to constant stress, mechanical creep is observed that results in a signal drift that generally diminishes the responsiveness of the arrays, particularly at stress approaching 1 kPa. The results of this study serve as a preliminary proof of concept for utilizing CNT arrays as a transduction mechanism for a proposed artificial hair sensor. Such a low profile and light-weight flow sensor is expected to have application in a number of applications including navigation and state awareness of small air vehicles, similar in function to natural hair cell receptors utilized by insects and bats.

Growth of Well-Aligned ZnO Nanorod Arrays and Their Application for Photovoltaic Devices

NASA Astrophysics Data System (ADS)

Yuan, Zhaolin; Yao, Juncai

2017-11-01

We have fabricated well-aligned ZnO nanorod arrays (ZNRAs) on indium tin oxide-coated glass substrates by a facile chemical bath deposition method. We used field-emission scanning electron microscope, x-ray diffraction and UV-Vis absorption spectroscopy to study the morphology, crystalline structure and optical absorption of the fabricated ZNRAs, respectively. The results showed that ZnO nanorods stood almost perpendicularly on the substrate, were about 30-50 nm in diameter and 800-900 nm in length, and were wurtzite-structured (hexagonal) ZnO. In addition, well-aligned ZNRAs exhibited a weak absorption in the visible region and had an optical band gap value of 3.28 eV. Furthermore, a hybrid ZNRAs/polymer photovoltaic device was made, under 1 sun AM 1.5 illumination (light intensity, ˜100 mW/cm2), and the device showed an open circuit voltage ( V oc) of 0.32 V, a short circuit current density ( J sc) of 7.67 mA/cm2, and a fill factor ( FF) of 0.37, yielding an overall power conversion efficiency of 0.91%. Also, the exciton dissociation and transportation processes of charge carriers in the device under illumination were explained according to its current density-voltage ( J- V) curve and the energy level diagram.

Formation of anodic TiO2 nanotube arrays in NaOH added fluoride-ethylene glycol electrolyte for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Tan, Wai Kian; Kawamura, Go; Matsuda, Atsunori; Lockman, Zainovia

2017-07-01

TiO2 nanotube (TNT) arrays were formed by anodizing titanium foil in fluoride-ethylene glycol (EG) electrolyte added to it either water (H2O) or sodium hydroxide (NaOH) as oxidant. In NaOH added fluoride-EG electrolyte, 10 µm long TNT arrays were formed compared to 5 μm long nanotubes in H2O added fluoride-EG electrolyte. When NaOH was added to EG, the electrolyte pH was 9. As the pH of the electrolyte was rather high, surface etching of the nanotubes was reduced resulting in tubes with longer length. Moreover, the addition of NaOH into fluoride-EG resulted in the crystallization of anatase in the as-made TNT arrays. Annealing obviously improved the crystallinity of the oxide. The TNT arrays were then used as a photoanode in a dye-sensitized solar cell (DSSC). A photoconversion efficiency of 2.4 % was recorded with photocurrent of 6.9 mA/cm2.

Detection of the Odor Signature of Ovarian Cancer using DNA-Decorated Carbon Nanotube Field Effect Transistor Arrays

NASA Astrophysics Data System (ADS)

Kehayias, Christopher; Kybert, Nicholas; Yodh, Jeremy; Johnson, A. T. Charlie

Carbon nanotubes are low-dimensional materials that exhibit remarkable chemical and bio-sensing properties and have excellent compatibility with electronic systems. Here, we present a study that uses an electronic olfaction system based on a large array of DNA-carbon nanotube field effect transistors vapor sensors to analyze the VOCs of blood plasma samples collected from patients with malignant ovarian cancer, patients with benign ovarian lesions, and age-matched healthy subjects. Initial investigations involved coating each CNT sensor with single-stranded DNA of a particular base sequence. 10 distinct DNA oligomers were used to functionalize the carbon nanotube field effect transistors, providing a 10-dimensional sensor array output response. Upon performing a statistical analysis of the 10-dimensional sensor array responses, we showed that blood samples from patients with malignant cancer can be reliably differentiated from those of healthy control subjects with a p-value of 3 x 10-5. The results provide preliminary evidence that the blood of ovarian cancer patients contains a discernable volatile chemical signature that can be detected using DNA-CNT nanoelectronic vapor sensors, a first step towards a minimally invasive electronic diagnostic technology for ovarian cancer.

Enhanced performance of ZnO microballoon arrays for a triboelectric nanogenerator.

PubMed

Deng, Weili; Zhang, Binbin; Jin, Long; Chen, Yueqi; Chu, Wenjun; Zhang, Haitao; Zhu, Minhao; Yang, Weiqing

2017-03-01

In recent years, triboelectric nanogenerators (TENGs), harvesting energy from the environment as a sustainable power source, have attracted great attention. Currently, many reports focus on the effect of surface modification on the electrical output performance of the TENG. In this work, we have fabricated vertically grown ZnO microballoon (ZnOMB) arrays on top of pyramid-featured PDMS patterned film, contacted with PTFE film to construct the TENG. The electrical output performances of the designed TENG are presented under external forces with different frequencies. The corresponding output open-circuit voltage with ZnOMBs could reach about 57 V the current density about 59 mA m -2 at 100 Hz, which was about 2.3 times higher than without any ZnO. The global maximum of the instantaneous peak power could reach 1.1 W m -2 when the external load resistance was about 2 MΩ. Furthermore, the electrical output of the fabricated device could light 30 commercial LED bulbs without any rectifier circuits or energy-storage elements. This clearly suggests that this kind of surface modification can dramatically enhance the output performance of the TENG. Moreover, the design of TENG demonstrated here can be applied to various energy harvesting applications.

Enhanced performance of ZnO microballoon arrays for a triboelectric nanogenerator

NASA Astrophysics Data System (ADS)

Deng, Weili; Zhang, Binbin; Jin, Long; Chen, Yueqi; Chu, Wenjun; Zhang, Haitao; Zhu, Minhao; Yang, Weiqing

2017-03-01

In recent years, triboelectric nanogenerators (TENGs), harvesting energy from the environment as a sustainable power source, have attracted great attention. Currently, many reports focus on the effect of surface modification on the electrical output performance of the TENG. In this work, we have fabricated vertically grown ZnO microballoon (ZnOMB) arrays on top of pyramid-featured PDMS patterned film, contacted with PTFE film to construct the TENG. The electrical output performances of the designed TENG are presented under external forces with different frequencies. The corresponding output open-circuit voltage with ZnOMBs could reach about 57 V the current density about 59 mA m-2 at 100 Hz, which was about 2.3 times higher than without any ZnO. The global maximum of the instantaneous peak power could reach 1.1 W m-2 when the external load resistance was about 2 MΩ. Furthermore, the electrical output of the fabricated device could light 30 commercial LED bulbs without any rectifier circuits or energy-storage elements. This clearly suggests that this kind of surface modification can dramatically enhance the output performance of the TENG. Moreover, the design of TENG demonstrated here can be applied to various energy harvesting applications.

Preparation, characterization, and application of titanium nano-tube array in dye-sensitized solar cells

PubMed Central

2012-01-01

The vertically orientated TiO2 nanotube array (TNA) decorated with TiO2 nano-particles was successfully fabricated by electrochemically anodizing titanium (Ti) foils followed by Ti-precursor post-treatment and annealing process. The TNA morphology characterized by SEM and TEM was found to be filled with TiO2 nano-particles interior and exterior of the TiO2 nano-tubes after titanium (IV) n-butoxide (TnB) treatment, whereas TiO2 nano-particles were only found inside of TiO2 nano-tubes upon titanium tetrachloride (TiCl4) treatment. The efficiency in TNA-based DSSCs was improved by both TnB and TiCl4 treatment presumably due to the increase of dye adsorption. PMID:22353282

Highly Transparent and UV-Resistant Superhydrophobic SiO2-Coated ZnO Nanorod Arrays

PubMed Central

2015-01-01

Highly transparent and UV-resistant superhydrophobic arrays of SiO2-coated ZnO nanorods are prepared in a sequence of low-temperature (<150 °C) steps on both glass and thin sheets of PET (2 × 2 in.2), and the superhydrophobic nanocomposite is shown to have minimal impact on solar cell device performance under AM1.5G illumination. Flexible plastics can serve as front cell and backing materials in the manufacture of flexible displays and solar cells. PMID:24495100

Ag Nanoparticle-Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells.

PubMed

Rho, Won-Yeop; Chun, Myeung-Hwan; Kim, Ho-Sub; Kim, Hyung-Mo; Suh, Jung Sang; Jun, Bong-Hyun

2016-06-15

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array-based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array-based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component-Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays-enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency.

Magnetic interactions and reversal mechanisms in Co nanowire and nanotube arrays

NASA Astrophysics Data System (ADS)

Proenca, M. P.; Sousa, C. T.; Escrig, J.; Ventura, J.; Vazquez, M.; Araujo, J. P.

2013-03-01

Ordered hexagonal arrays of Co nanowires (NWs) and nanotubes (NTs), with diameters between 40 and 65 nm, were prepared by potentiostatic electrodeposition into suitably modified nanoporous alumina templates. The geometrical parameters of the NW/NT arrays were tuned by the pore etching process and deposition conditions. The magnetic interactions between NWs/NTs with different diameters were studied using first-order reversal curves (FORCs). From a quantitative analysis of the FORC measurements, we are able to obtain the profiles of the magnetic interactions and the coercive field distributions. In both NW and NT arrays, the magnetic interactions were found to increase with the diameter of the NWs/NTs, exhibiting higher values for NW arrays. A comparative study of the magnetization reversal processes was also performed by analyzing the angular dependence of the coercivity and correlating the experimental data with theoretical calculations based on a simple analytical model. The magnetization in the NW arrays is found to reverse by the nucleation and propagation of a transverse-like domain wall; on the other hand, for the NT arrays a non-monotonic behavior occurs above a diameter of ˜50 nm, revealing a transition between the vortex and transverse reversal modes.

MOF-Derived ZnO Nanoparticles Covered by N-Doped Carbon Layers and Hybridized on Carbon Nanotubes for Lithium-Ion Battery Anodes.

PubMed

Zhang, Hui; Wang, Yunsong; Zhao, Wenqi; Zou, Mingchu; Chen, Yijun; Yang, Liusi; Xu, Lu; Wu, Huaisheng; Cao, Anyuan

2017-11-01

Metal-organic frameworks (MOFs) have many promising applications in energy and environmental areas such as gas separation, catalysis, supercapacitors, and batteries; the key toward those applications is controlled pyrolysis which can tailor the porous structure, improve electrical conductivity, and expose metal ions in MOFs. Here, we present a systematic study on the structural evolution of zeolitic imidazolate frameworks hybridized on carbon nanotubes (CNTs) during the carbonization process. We show that a number of typical products can be obtained, depending on the annealing time, including (1) CNTs wrapped by relatively thick carbon layers, (2) CNTs grafted by ZnO nanoparticles which are covered by thin nitrogen-doped carbon layers, and (3) CNTs grafted by aggregated ZnO nanoparticles. We also investigated the electrochemical properties of those hybrid structures as freestanding membrane electrodes for lithium ion batteries, and the second one (CNT-supported ZnO covered by N-doped carbon) shows the best performance with a high specific capacity (850 mA h/g at a current density of 100 mA/g) and excellent cycling stability. Our results indicate that tailoring and optimizing the MOF-CNT hybrid structure is essential for developing high-performance energy storage systems.

Preparation and photovoltaic properties of perovskite solar cell based on ZnO nanorod arrays

NASA Astrophysics Data System (ADS)

Xu, Yang; Liu, Tian; Li, Zhaosong; Feng, Bingjie; Li, Siqian; Duan, Jinxia; Ye, Cong; Zhang, Jun; Wang, Hao

2016-12-01

A careful control of ZnO nanorod arrays with various densities and thickness were achieved by hydrothermal method. An obvious increase in the ZnO nanorod density is observed as the concentrations of zinc acetate dropped as expected through the surface SEM images. On the other hand, samples with and without TiO2 compact layer were also studied and results had been analyzed to seek for an optimized substrate structure for light absorbing layer and increase the efficiency. What's more, a deep research for the drying temperature for perovskite layer was also conducted. As a result, SEM images discribe a promising surface appearance of perovskite layer which is finely attached onto the nanorod structure. Final power conversion efficiency (PCE) of FTO/ZnO seed layer/ZnO nanorods/perovskite/spiro-OMe-TAD/Au electrode photovoltaic device reached ∼9.15% together with open-circuit voltage of 957 mV, short-circuit current density of 17.8 mA/cm2 and fill factor of 0.537.

A comprehensive biosensor integrated with a ZnO nanorod FET array for selective detection of glucose, cholesterol and urea.

PubMed

Ahmad, Rafiq; Tripathy, Nirmalya; Park, Jin-Ho; Hahn, Yoon-Bong

2015-08-04

We report a novel straightforward approach for simultaneous and highly-selective detection of multi-analytes (i.e. glucose, cholesterol and urea) using an integrated field-effect transistor (i-FET) array biosensor without any interference in each sensor response. Compared to analytically-measured data, performance of the ZnO nanorod based i-FET array biosensor is found to be highly reliable for rapid detection of multi-analytes in mice blood, and serum and blood samples of diabetic dogs.

Directing Stem Cell Differentiation via Electrochemical Reversible Switching between Nanotubes and Nanotips of Polypyrrole Array.

PubMed

Wei, Yan; Mo, Xiaoju; Zhang, Pengchao; Li, Yingying; Liao, Jingwen; Li, Yongjun; Zhang, Jinxing; Ning, Chengyun; Wang, Shutao; Deng, Xuliang; Jiang, Lei

2017-06-27

Control of stem cell behaviors at solid biointerfaces is critical for stem-cell-based regeneration and generally achieved by engineering chemical composition, topography, and stiffness. However, the influence of dynamic stimuli at the nanoscale from solid biointerfaces on stem cell fate remains unclear. Herein, we show that electrochemical switching of a polypyrrole (Ppy) array between nanotubes and nanotips can alter surface adhesion, which can strongly influence mechanotransduction activation and guide differentiation of mesenchymal stem cells (MSCs). The Ppy array, prepared via template-free electrochemical polymerization, can be reversibly switched between highly adhesive hydrophobic nanotubes and poorly adhesive hydrophilic nanotips through an electrochemical oxidation/reduction process, resulting in dynamic attachment and detachment to MSCs at the nanoscale. Multicyclic attachment/detachment of the Ppy array to MSCs can activate intracellular mechanotransduction and osteogenic differentiation independent of surface stiffness and chemical induction. This smart surface, permitting transduction of nanoscaled dynamic physical inputs into biological outputs, provides an alternative to classical cell culture substrates for regulating stem cell fate commitment. This study represents a general strategy to explore nanoscaled interactions between stem cells and stimuli-responsive surfaces.

Chemical modification of TiO2 nanotube arrays for label-free optical biosensing applications

NASA Astrophysics Data System (ADS)

Terracciano, Monica; Galstyan, Vardan; Rea, Ilaria; Casalino, Maurizio; De Stefano, Luca; Sbervegleri, Giorgio

2017-10-01

In this study, we have fabricated TiO2 nanotube arrays by the potentiostatic anodic oxidation of Ti foils in fluoride-containing electrolyte and explored them as versatile devices for biosensing applications. TiO2 nanotubes have been chemically modified in order to bind Protein A as a specific target analyte for the optical biosensing. The obtained structures have been characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, water contact angle, fluorescence microscopy, spectroscopic reflectometry and photoluminescence. Investigations show that the prepared TiO2 nanotubes, 2.5 μm long and 75 nm thick, can be easily and efficiently bio-modified, and the obtained structures are strongly photoluminescent, thus suitable for the label-free biosensing applications in the range of μM, due to their peculiar optical properties.

Effect of Surface and Defect Chemistry on the Photocatalytic Properties of Intentionally Defect-Rich ZnO Nanorod Arrays.

PubMed

Kegel, Jan; Zubialevich, Vitaly Z; Schmidt, Michael; Povey, Ian M; Pemble, Martyn E

2018-05-30

Due to the abundance of intrinsic defects in zinc oxide (ZnO), the material properties are often governed by same. Knowledge of the defect chemistry has proven to be highly important, especially in terms of the photocatalytic degradation of pollutants. Given the fact that defect-free materials or structures exhibiting only one type of defect are extremely difficult to produce, it is necessary to evaluate what influence various defects may have when present together in the material. In this study, intentionally defect-rich ZnO nanorod (NR) arrays are grown using a simple low-temperature solution-based growth technique. Upon changing the defect chemistry using rapid thermal annealing (RTA) the material properties are carefully assessed and correlated to the resulting photocatalytic properties. Special focus is put on the investigation of these properties for samples showing strong orange photoluminescence (PL). It is shown that intense orange emitting NR arrays exhibit improved dye-degradation rates under UV-light irradiation. Furthermore, strong dye-adsorption has been observed for some samples. This behavior is found to stem from a graphitic surface structure (e.g., shell) formed during RTA in vacuum. Since orange-luminescent samples also exhibit an enhancement of the dye adsorption a possible interplay and synergy of these two defects is elucidated. Additionally, evidence is presented suggesting that in annealed ZnO NRs structural defects may be responsible for the often observed PL emission at 3.31 eV. However, a clear correlation with the photocatalytic properties could not be established for these defects. Building on the specific findings presented here, this study also presents some more general guidelines which, it is suggested, should be employed when assessing the photocatalytic properties of defect-rich ZnO.

Synthesis and Investigation of Millimeter-Scale Vertically Aligned Boron Nitride Nanotube Arrays

NASA Astrophysics Data System (ADS)

Tay, Roland; Li, Hongling; Tsang, Siu Hon; Jing, Lin; Tan, Dunlin; Teo, Edwin Hang Tong

Boron nitride nanotubes (BNNTs) have shown potential in a wide range of applications due to their superior properties such as exceptionally high mechanical strength, excellent chemical and thermal stabilities. However, previously reported methods to date only produced BNNTs with limited length/density and insufficient yield at high temperatures. Here we present a facile and effective two-step synthesis route involving template-assisted chemical vapor deposition at a relatively low temperature of 900 degree C and subsequent annealing process to fabricate vertically aligned (VA) BN coated carbon nanotube (VA-BN/CNT) and VA-BNNT arrays. By using this method, we achieve the longest VA-BN/CNTs and VA-BNNTs to date with lengths of over millimeters (exceeding two orders of magnitude longer than the previously reported length of VA-BNNTs). In addition, the morphology, chemical composition and microstructure of the resulting products, as well as the mechanism of coating process are systematically investigated. This versatile BN coating technique and the synthesis of millimeter-scale BN/CNT and BNNT arrays pave a way for new applications especially where the aligned geometry of the NTs is essential such as for field-emission, interconnects and thermal management.

Matrix-assisted energy conversion in nanostructured piezoelectric arrays

DOEpatents

Sirbuly, Donald J.; Wang, Xianying; Wang, Yinmin

2013-01-01

A nanoconverter is capable of directly generating electricity through a nanostructure embedded in a polymer layer experiencing differential thermal expansion in a stress transfer zone. High surface-to-volume ratio semiconductor nanowires or nanotubes (such as ZnO, silicon, carbon, etc.) are grown either aligned or substantially vertically aligned on a substrate. The resulting nanoforest is then embedded with the polymer layer, which transfers stress to the nanostructures in the stress transfer zone, thereby creating a nanostructure voltage output due to the piezoelectric effect acting on the nanostructure. Electrodes attached at both ends of the nanostructures generate output power at densities of .about.20 nW/cm.sup.2 with heating temperatures of .about.65.degree. C. Nanoconverters arrayed in a series parallel arrangement may be constructed in planar, stacked, or rolled arrays to supply power to nano- and micro-devices without use of external batteries.

Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

PubMed

Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

2015-06-10

Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material.

Label-free capture of breast cancer cells spiked in buffy coats using carbon nanotube antibody micro-arrays

NASA Astrophysics Data System (ADS)

Khosravi, Farhad; Trainor, Patrick; Rai, Shesh N.; Kloecker, Goetz; Wickstrom, Eric; Panchapakesan, Balaji

2016-04-01

We demonstrate the rapid and label-free capture of breast cancer cells spiked in buffy coats using nanotube-antibody micro-arrays. Single wall carbon nanotube arrays were manufactured using photo-lithography, metal deposition, and etching techniques. Anti-epithelial cell adhesion molecule (EpCAM) antibodies were functionalized to the surface of the nanotube devices using 1-pyrene-butanoic acid succinimidyl ester functionalization method. Following functionalization, plain buffy coat and MCF7 cell spiked buffy coats were adsorbed on to the nanotube device and electrical signatures were recorded for differences in interaction between samples. A statistical classifier for the ‘liquid biopsy’ was developed to create a predictive model based on dynamic time warping to classify device electrical signals that corresponded to plain (control) or spiked buffy coats (case). In training test, the device electrical signals originating from buffy versus spiked buffy samples were classified with ˜100% sensitivity, ˜91% specificity and ˜96% accuracy. In the blinded test, the signals were classified with ˜91% sensitivity, ˜82% specificity and ˜86% accuracy. A heatmap was generated to visually capture the relationship between electrical signatures and the sample condition. Confocal microscopic analysis of devices that were classified as spiked buffy coats based on their electrical signatures confirmed the presence of cancer cells, their attachment to the device and overexpression of EpCAM receptors. The cell numbers were counted to be ˜1-17 cells per 5 μl per device suggesting single cell sensitivity in spiked buffy coats that is scalable to higher volumes using the micro-arrays.

Modeling and simulation for the field emission of carbon nanotubes array

NASA Astrophysics Data System (ADS)

Wang, X. Q.; Wang, M.; Ge, H. L.; Chen, Q.; Xu, Y. B.

2005-12-01

To optimize the field emission of the infinite carbon nanotubes (CNTs) array on a planar cathode surface, the numerical simulation for the behavior of field emission with finite difference method was proposed. By solving the Laplace equation with computer, the influence of the intertube distance, the anode-cathode distance and the opened/capped CNT on the field emission of CNTs array were taken into account, and the results could accord well with the experiments. The simulated results proved that the field enhancement factor of individual CNT is largest, but the emission current density is little. Due to the enhanced screening of the electric field, the enhancement factor of CNTs array decreases with decreasing the intertube distance. From the simulation the field emission can be optimized when the intertube distance is close to the tube height. The anode-cathode distance hardly influences the field enhancement factor of CNTs array, but can low the threshold voltage by decreasing the anode-cathode distance. Finally, the distribution of potential of the capped CNTs array and the opened CNTs array was simulated, which the results showed that the distribution of potential can be influenced to some extent by the anode-cathode distance, especially at the apex of the capped CNTs array and the brim of the opened CNTs array. The opened CNTs array has larger field enhancement factor and can emit more current than the capped one.

Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.

PubMed

Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song

2013-09-24

We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy.

High voltage generation from lead-free magnetoelectric coaxial nanotube arrays and their applications in nano energy harvesters.

PubMed

Lekha, C S Chitra; Kumar, Ajith S; Vivek, S; Rasi, U P Mohammed; Saravanan, K Venkata; Nandakumar, K; Nair, Swapna S

2017-02-03

Harvesting energy from surrounding vibrations and developing self-powered portable devices for wireless and mobile electronics have recently become popular. Here the authors demonstrate the synthesis of piezoelectric energy harvesters based on nanotube arrays by a wet chemical route, which requires no sophisticated instruments. The energy harvester gives an output voltage of 400 mV. Harvesting energy from a sinusoidal magnetic field is another interesting phenomenon for which the authors fabricated a magnetoelectric energy harvester based on piezoelectric-magnetostrictive coaxial nanotube arrays. Piezoelectric K 0.5 Na 0.5 NbO 3 (KNN) is fabricated as the shell and magnetostrictive CoFe 2 O 4 (CFO) as the core of the composite coaxial nanotubes. The delivered voltages are as high as 300 mV at 500 Hz and at a weak ac magnetic field of 100 Oe. Further tailoring of the thickness of the piezoelectric and magnetic layers can enhance the output voltage by several orders. Easy, single-step wet chemical synthesis enhances the industrial upscaling potential of these nanotubes as energy harvesters. In view of the excellent properties reported here, the lead-free piezoelectric component (KNN) in this nanocomposite should be explored for eco-friendly piezoelectric as well as magnetoelectric power generators in nanoelectromechanical systems (NEMS).

High voltage generation from lead-free magnetoelectric coaxial nanotube arrays and their applications in nano energy harvesters

NASA Astrophysics Data System (ADS)

Lekha, C. S. Chitra; Kumar, Ajith S.; Vivek, S.; Rasi, U. P. Mohammed; Venkata Saravanan, K.; Nandakumar, K.; Nair, Swapna S.

2017-02-01

Harvesting energy from surrounding vibrations and developing self-powered portable devices for wireless and mobile electronics have recently become popular. Here the authors demonstrate the synthesis of piezoelectric energy harvesters based on nanotube arrays by a wet chemical route, which requires no sophisticated instruments. The energy harvester gives an output voltage of 400 mV. Harvesting energy from a sinusoidal magnetic field is another interesting phenomenon for which the authors fabricated a magnetoelectric energy harvester based on piezoelectric-magnetostrictive coaxial nanotube arrays. Piezoelectric K0.5Na0.5NbO3 (KNN) is fabricated as the shell and magnetostrictive CoFe2O4 (CFO) as the core of the composite coaxial nanotubes. The delivered voltages are as high as 300 mV at 500 Hz and at a weak ac magnetic field of 100 Oe. Further tailoring of the thickness of the piezoelectric and magnetic layers can enhance the output voltage by several orders. Easy, single-step wet chemical synthesis enhances the industrial upscaling potential of these nanotubes as energy harvesters. In view of the excellent properties reported here, the lead-free piezoelectric component (KNN) in this nanocomposite should be explored for eco-friendly piezoelectric as well as magnetoelectric power generators in nanoelectromechanical systems (NEMS).

Photoelectrochemical CdSe/TiO2 nanotube array microsensor for high-resolution in-situ detection of dopamine.

PubMed

Qin, Caidie; Bai, Xue; Zhang, Yue; Gao, Kai

2018-05-03

A photoelectrochemical wire microelectrode was constructed based on the use of a TiO 2 nanotube array with electrochemically deposited CdSe semiconductor. A strongly amplified photocurrent is generated on the sensor surface. The microsensor has a response in the 0.05-20 μM dopamine (DA) concentration range and a 16.7 μM detection limit at a signal-to-noise ratio of 3. Sensitivity, recovery and reproducibility of the sensor were validated by detecting DA in spiked human urine, and satisfactory results were obtained. Graphical abstract Schematic of a sensitive photoelectrochemical microsensor based on CdSe modified TiO 2 nanotube array. The photoelectrochemical microsensor was successfully applied to the determination of dopamine in urine samples.

Semiconductor Nanowires and Nanotubes for Energy Conversion

NASA Astrophysics Data System (ADS)

Fardy, Melissa Anne

In recent years semiconductor nanowires and nanotubes have garnered increased attention for their unique properties. With their nanoscale dimensions comes high surface area and quantum confinement, promising enhancements in a wide range of applications. 1-dimensional nanostructures are especially attractive for energy conversion applications where photons, phonons, and electrons come into play. Since the bohr exciton radius and phonon and electron mean free paths are on the same length scales as nanowire diameters, optical, thermal, and electrical properties can be tuned by simple nanowire size adjustments. In addition, the high surface area inherent to nanowires and nanotubes lends them towards efficient charge separation and superior catalytic performance. In thermoelectric power generation, the nanoscale wire diameter can effectively scatter phonons, promoting reductions in thermal conductivity and enhancements in the thermoelectric figure of merit. To that end, single-crystalline arrays of PbS, PbSe, and PbTe nanowires have been synthesized by a chemical vapor transport approach. The electrical and thermal transport properties of the nanowires were characterized to investigate their potential as thermoelectric materials. Compared to bulk, the lead chalcogenide nanowires exhibit reduced thermal conductivity below 100 K by up to 3 orders of magnitude, suggesting that they may be promising thermoelectric materials. Smaller diameters and increased surface roughness are expected to give additional enhancements. The solution-phase synthesis of PbSe nanowires via oriented attachment of nanoparticles enables facile surface engineering and diameter control. Branched PbSe nanowires synthesized by this approach showed near degenerately doped charge carrier concentrations. Compared to the bulk, the PbSe nanowires exhibited a similar Seebeck coefficient and a significant reduction in thermal conductivity in the temperature range 20 K to 300 K. Thermal annealing of the Pb

Planarized arrays of aligned, untangled multiwall carbon nanotubes with Ohmic back contacts

DOE PAGES

Rochford, C.; Limmer, S. J.; Howell, S. W.; ...

2014-11-26

Vertically aligned, untangled planarized arrays of multiwall carbon nanotubes (MWNTs) with Ohmic back contacts were grown in nanopore templates on arbitrary substrates. The templates were prepared by sputter depositing Nd-doped Al films onto W-coated substrates, followed by anodization to form an aluminum oxide nanopore array. The W underlayer helps eliminate the aluminum oxide barrier that typically occurs at the nanopore bottoms by instead forming a thin WO 3 layer. The WO 3 can be selectively etched to enable electrodeposition of Co catalysts with control over the Co site density. This led to control of the site density of MWNTs grownmore » by thermal chemical vapor deposition, with the W also serving as a back electrical contact. As a result, Ohmic contact to MWNTs was confirmed, even following ultrasonic cutting of the entire array to a uniform height.« less

Carbon Nanotube Nanoelectrode Array as an Electronic Chip for Ultrasensitive Label-free DNA Detection

NASA Technical Reports Server (NTRS)

Li, Jun; Koehne, Jessica; Chen, Hua; Cassell, Alan; Ng, Hou Tee; Fan, Wendy; Ye, Qi; Han, Jie; Meyyappan, M.

2003-01-01

A reliable nanoelectrode array based on vertically aligned multi-walled carbon nanotubes (MWNTs) embedded in SiO2 is used for ultrasensitive DNA detection. Characteristic nanoelectrode behavior is observed using low-density MWNT arrays for measuring both bulk and surface immobilized redox species such as K4Fe(CN)6 and ferrocene derivatives. The open-end of MWNTs are found to present similar properties as graphite edge-plane electrodes with wide potential window, flexible chemical functionalities, and good biocompatibility. BRCA1 related oligonucleotide probes with 18 bp are selectively functionalized at the open ends of the nanotube array and specifically hybridized with oligonucleotide targets incorporated with a polyG tag. The guanine groups are employed as the signal moieties in the electrochemical measurements. R(bpy)(sup 2+, sub 3) mediator is used to further amplify the guanine oxidation signal. The hybridization of sub-attomoles of DNA targets is detected electrochemically by combining the MWNT nanoelectrode array with the R(bpy)(sup 2+, sub 3) amplification mechanism. This technique was employed for direct electrochemical detection of label-free PCR amplicon from a healthy donor through specific hybridization with the BRCA1 probe. The detection limit is estimated to be less than 1000 DNA molecules since abundant guanine bases in the PCR amplicon provides a large signal. This system provides a general platform for rapid molecular diagnostics in applications requiring ultrahigh sensitivity, high-degree of miniaturization, and simple sample preparation, and low-cost operation.

Fabrication and characterization of nano-gas sensor arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, H. S., E-mail: hassan.shokry@gmail.com; Kashyout, A. B., E-mail: hady8@yahoo.com; Morsi, I., E-mail: drimanmorsi@yahoo.com

2015-03-30

A novel structures of Nanomaterials gas sensors array constructed using ZnO, and ZnO doped with Al via sol-gel technique. Two structure arrays are developed; the first one is a double sensor array based on doping with percentages of 1% and 5%. The second is a quadrature sensor array based on several doping ratios concentrations (0%, 1%, 5% and 10%). The morphological structures of prepared ZnO were revealed using scanning electron microscope (SEM). X-ray diffraction (XRD) patterns reveal a highly crystallized wurtzite structure and used for identifying phase structure and chemical state of both ZnO and ZnO doped with Al undermore » different preparation conditions and different doping ratios. Chemical composition of Al-doped ZnO nanopowders was performed using energy dispersive x-ray (EDS) analysis. The electrical characteristics of the sensor are determined by measuring the two terminal sensor’s output resistance for O{sub 2}, H{sub 2} and CO{sub 2} gases as a function of temperature.« less

Extremely Black Vertically Aligned Carbon Nanotube Arrays for Solar Steam Generation.

PubMed

Yin, Zhe; Wang, Huimin; Jian, Muqiang; Li, Yanshen; Xia, Kailun; Zhang, Mingchao; Wang, Chunya; Wang, Qi; Ma, Ming; Zheng, Quan-Shui; Zhang, Yingying

2017-08-30

The unique structure of a vertically aligned carbon nanotube (VACNT) array makes it behave most similarly to a blackbody. It is reported that the optical absorptivity of an extremely black VACNT array is about 0.98-0.99 over a large spectral range of 200 nm-200 μm, inspiring us to explore the performance of VACNT arrays in solar energy harvesting. In this work, we report the highly efficient steam generation simply by laminating a layer of VACNT array on the surface of water to harvest solar energy. It is found that under solar illumination the temperature of upper water can significantly increase with obvious water steam generated, indicating the efficient solar energy harvesting and local temperature rise by the thin layer of VACNTs. We found that the evaporation rate of water assisted by VACNT arrays is 10 times that of bare water, which is the highest ratio for solar-thermal-steam generation ever reported. Remarkably, the solar thermal conversion efficiency reached 90%. The excellent performance could be ascribed to the strong optical absorption and local temperature rise induced by the VACNT layer, as well as the ultrafast water transport through the VACNT layer due to the frictionless wall of CNTs. Based on the above, we further demonstrated the application of VACNT arrays in solar-driven desalination.

An Enhanced UV-Vis-NIR an d Flexible Photodetector Based on Electrospun ZnO Nanowire Array/PbS Quantum Dots Film Heterostructure.

PubMed

Zheng, Zhi; Gan, Lin; Zhang, Jianbing; Zhuge, Fuwei; Zhai, Tianyou

2017-03-01

ZnO nanostructure-based photodetectors have a wide applications in many aspects, however, the response range of which are mainly restricted in the UV region dictated by its bandgap. Herein, UV-vis-NIR sensitive ZnO photodetectors consisting of ZnO nanowires (NW) array/PbS quantum dots (QDs) heterostructures are fabricated through modified electrospining method and an exchanging process. Besides wider response region compared to pure ZnO NWs based photodetectors, the heterostructures based photodetectors have faster response and recovery speed in UV range. Moreover, such photodetectors demonstrate good flexibility as well, which maintain almost constant performances under extreme (up to 180°) and repeat (up to 200 cycles) bending conditions in UV-vis-NIR range. Finally, this strategy is further verified on other kinds of 1D nanowires and 0D QDs, and similar enhancement on the performance of corresponding photodetecetors can be acquired, evidencing the universality of this strategy.

Formation of TiO2 nanotube arrays in KOH added fluoride-ethylene glycol (EG) electrolyte and its photoelectrochemical response

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Lockman, Zainovia; Matsuda, Astunori; Kawamura, Go; Tan, Wai Kian; Oo, Than Zaw

2016-07-01

In this study, highly ordered TiO2 nanotube arrays were prepared by anodic oxidation of titanium foil in fluoride -EG electrolyte containing a small amount of potassium hydroxide, KOH at 60 V for 30 min. This electrolyte resulted in the formation of long nanotubes with an average length of 10 µm and diameter of 170 nm. For comparison, TiO2 nanotubes anodized in H2O added EG electrolyte which produces short nanotubes with an average tube length of 5 µm and diameter of 170 nm. It appears that the addition of KOH into the fluoride EG electrolyte accelerated the formation of the TiO2 nanotubes as it is believed that the chemical dissolution at the tips of the nanotubes is suppressed. Highly ordered TiO2 nanotubes anodized in KOH added EG electrolyte exhibited the photocurrent density of 2 mA/cm2, which is significantly higher than H2O added sample (1.5 mA/cm2).

Nanotube antibody biosensor arrays for the detection of circulating breast cancer cells

NASA Astrophysics Data System (ADS)

Shao, Ning; Wickstrom, Eric; Panchapakesan, Balaji

2008-11-01

Recent reports have shown that nanoscale electronic devices can be used to detect a change in electrical properties when receptor proteins bind to their corresponding antibodies functionalized on the surface of the device, in extracts from as few as ten lysed tumor cells. We hypothesized that nanotube-antibody devices could sensitively and specifically detect entire live cancer cells. We report for the first time a single nanotube field effect transistor array, functionalized with IGF1R-specific and Her2-specific antibodies, which exhibits highly sensitive and selective sensing of live, intact MCF7 and BT474 human breast cancer cells in human blood. Those two cell lines both overexpress IGF1R and Her2, at different levels. Single or small bundle of nanotube devices that were functionalized with IGF1R-specific or Her2-specific antibodies showed 60% decreases in conductivity upon interaction with BT474 or MCF7 breast cancer cells in two µl drops of blood. Control experiments with non-specific antibodies or with MCF10A control breast cells produced a less than 5% decrease in electrical conductivity, illustrating the high sensitivity for whole cell binding by these single nanotube-antibody devices. We postulate that the free energy change due to multiple simultaneous cell-antibody binding events exerted stress along the nanotube surface, decreasing its electrical conductivity due to an increase in band gap. Because the free energy change upon cell-antibody binding, the stress exerted on the nanotube, and the change in conductivity are specific to a specific antigen-antibody interaction; these properties might be used as a fingerprint for the molecular sensing of circulating cancer cells. From optical microscopy observations during sensing, it appears that the binding of a single cell to a single nanotube field effect transistor produced the change in electrical conductivity. Thus we report a nanoscale oncometer with single cell sensitivity with a diameter 1000 times

Low-cost silver capped polystyrene nanotube arrays as super-hydrophobic substrates for SERS applications.

PubMed

Lovera, Pierre; Creedon, Niamh; Alatawi, Hanan; Mitchell, Micki; Burke, Micheal; Quinn, Aidan J; O'Riordan, Alan

2014-05-02

In this paper, we describe the fabrication, simulation and characterization of dense arrays of freestanding silver capped polystyrene nanotubes, and demonstrate their suitability for surface enhanced Raman scattering (SERS) applications. Substrates are fabricated in a rapid, low-cost and scalable way by melt wetting of polystyrene (PS) in an anodized alumina (AAO) template, followed by silver evaporation. Scanning electron microscopy reveals that substrates are composed of a dense array of freestanding polystyrene nanotubes topped by silver nanocaps. SERS characterization of the substrates, employing a monolayer of 4-aminothiophenol (4-ABT) as a model molecule, exhibits an enhancement factor of ∼1.6 × 10(6), in agreement with 3D finite difference time domain simulations. Contact angle measurements of the substrates revealed super-hydrophobic properties, allowing pre-concentration of target analyte into a small volume. These super-hydrophobic properties of the samples are taken advantage of for sensitive detection of the organic pollutant crystal violet, with detection down to ∼400 ppt in a 2 μl aliquot demonstrated.

Tunable TiO2 Nanotube Arrays for Flexible Bio-Sensitized Solar Cells

DTIC Science & Technology

2012-08-01

microid extender followed by a colloidal silica /wetted imperial cloth. The foil was then cut into 1- × 2-cm samples. Then, the substrates were...17. Lei, B.; Liao, J.; Wang, R. J.; Su, C.; Kuang, D. Ordered Crystalline Ti02 Nanotube Arrays on Transparent FTO Glass for Efficient Dye...combined with a transparent , Indium Tin Dioxide coated PET film are attractive candidates for efficient, flexible DSSC’s. Flexible solar cells offer

Multidirectional flexible force sensors based on confined, self-adjusting carbon nanotube arrays

NASA Astrophysics Data System (ADS)

Lee, J.-I.; Pyo, Soonjae; Kim, Min-Ook; Kim, Jongbaeg

2018-02-01

We demonstrate a highly sensitive force sensor based on self-adjusting carbon nanotube (CNT) arrays. Aligned CNT arrays are directly synthesized on silicon microstructures by a space-confined growth technique which enables a facile self-adjusting contact. To afford flexibility and softness, the patterned microstructures with the integrated CNTs are embedded in polydimethylsiloxane structures. The sensing mechanism is based on variations in the contact resistance between the facing CNT arrays under the applied force. By finite element analysis, proper dimensions and positions for each component are determined. Further, high sensitivities up to 15.05%/mN of the proposed sensors were confirmed experimentally. Multidirectional sensing capability could also be achieved by designing multiple sets of sensing elements in a single sensor. The sensors show long-term operational stability, owing to the unique properties of the constituent CNTs, such as outstanding mechanical durability and elasticity.

Low temperature preparation of Ag-doped ZnO nanowire arrays for sensor and light-emitting diode applications

NASA Astrophysics Data System (ADS)

Lupan, O.; Viana, B.; Cretu, V.; Postica, V.; Adelung, R.; Pauporté, T.

2016-02-01

Transition metal doped-oxide semiconductor nanostructures are important to achieve enhanced and new properties for advanced applications. We describe the low temperature preparation of ZnO:Ag nanowire/nanorod (NW/NR) arrays by electrodeposition at 90 °C. The NWs have been characterized by SEM, EDX, transmittance and photoluminescence (PL) measurements. The integration of Ag in the crystal is shown. Single nanowire/nanorod of ZnO:Ag was integrated in a nanosensor structure leading to new and enhanced properties. The ultraviolet (UV) response of the nanosensor was investigated at room temperature. Experimental results indicate that ZnO:Ag (0.75 μM) nanosensor possesses faster response/recovery time and better response to UV light than those reported in literature. The sensor structure has been also shown to give a fast response for the hydrogen detection with improved performances compared to pristine ZnO NWs. ZnO:Ag nanowire/nanorod arrays electrochemically grown on p-type GaN single crystal layer is also shown to act as light emitter in LED structures. The emission wavelength is red-shifted compared to pristine ZnO NW array. At low Ag concentration a single UV-blue emission is found whereas at higher concentration of dopant the emission is broadened and extends up to the red wavelength range. Our study indicates that high quality ZnO:Ag NW/NR prepared at low temperature by electrodeposition can serve as building nanomaterials for new sensors and light emitting diodes (LEDs) structures with low-power consumption.

Morphological evolution of TiO2 nanotube arrays with lotus-root-shaped nanostructure

NASA Astrophysics Data System (ADS)

Yu, Dongliang; Song, Ye; Zhu, Xufei; Yang, Ruiquan; Han, Aijun

2013-07-01

TiO2 nanotube arrays (TNAs) with lotus-root-shaped nanostructure have been fabricated by a modified two-step electrochemical anodization method. In the present work, different morphologies formed under different anodizing voltages are investigated in detail by field-emission scanning electron microscope. The results show that the concaves left by the first-step anodization can guide the uniform growth of TNAs in some degree as the second-step anodizing voltage is the same with that in the first step, however, when lower voltages are adopted in the second-step anodization, no guidance can be achieved, and different morphological TNAs with lotus-root-shaped nanostructure are fabricated. And we find that the nanotube diameters are directly proportional to the applied voltage in the second-step anodization. Furthermore, a possible mechanism for the growth of the TiO2 nanotubes with the special morphology is proposed for the first time, which depends on both the oxygen bubble mold and the viscous flow of the barrier oxide from the pore base to the pore wall.

High optical switching speed and flexible electrochromic display based on WO3 nanoparticles with ZnO nanorod arrays' supported electrode

NASA Astrophysics Data System (ADS)

Wang, Mingjun; Fang, Guojia; Yuan, Longyan; Huang, Huihui; Sun, Zhenhua; Liu, Nishuang; Xia, Shanhong; Zhao, Xingzhong

2009-05-01

The electrochromic (EC) property of WO3 nanoparticles grown on vertically self-aligned ZnO nanorods (ZNRs) is reported. An electrochromic character display based on WO3 nanoparticle-modified ZnO nanorod arrays on a flexible substrate has been fabricated and demonstrated. The ZNRs were first synthesized on ZnO-seed-coated In2O3:Sn (ITO) glass (1 cm2 cell) and polyethylene terephthalate (PET) (4 cm2 cell) substrates by a low temperature hydrothermal method, and then amorphous WO3 nanoparticles were grown directly on the surface of the ZNRs by the pulsed laser deposition (PLD) method. The ZNR-based EC device shows high transparence, good electrochromic stability and fast switching speed (4.2 and 4 s for coloration and bleaching, respectively, for a 1 cm2 cell). The good performance of the ZNR electrode-based EC display can be attributed to the large surface area, high crystallinity and good electron transport properties of the ZNR arrays. Its high contrast, fast switching, good memory and flexible characteristics indicate it is a promising candidate for flexible electrochromic displays or electronic paper.

A Photoactivated Gas Detector for Toluene Sensing at Room Temperature Based on New Coral-Like ZnO Nanostructure Arrays.

PubMed

Yeh, Li-Ko; Luo, Jie-Chun; Chen, Min-Chun; Wu, Chih-Hung; Chen, Jian-Zhang; Cheng, I-Chun; Hsu, Cheng-Che; Tian, Wei-Cheng

2016-10-31

A photoactivated gas detector operated at room temperature was microfabricated using a simple hydrothermal method. We report that the photoactivated gas detector can detect toluene using a UV illumination of 2 μW/cm². By ultraviolet (UV) illumination, gas detectors sense toluene at room temperature without heating. A significant enhancement of detector sensitivity is achieved because of the high surface-area-to-volume ratio of the morphology of the coral-like ZnO nanorods arrays (NRAs) and the increased number of photo-induced oxygen ions under UV illumination. The corresponding sensitivity (ΔR/R₀) of the detector based on coral-like ZnO NRAs is enhanced by approximately 1022% compared to that of thin-film detectors. The proposed detector greatly extends the dynamic range of detection of metal-oxide-based detectors for gas sensing applications. We report the first-ever detection of toluene with a novel coral-like NRAs gas detector at room temperature. A sensing mechanism model is also proposed to explain the sensing responses of gas detectors based on coral-like ZnO NRAs.

A Photoactivated Gas Detector for Toluene Sensing at Room Temperature Based on New Coral-Like ZnO Nanostructure Arrays

PubMed Central

Yeh, Li-Ko; Luo, Jie-Chun; Chen, Min-Chun; Wu, Chih-Hung; Chen, Jian-Zhang; Cheng, I-Chun; Hsu, Cheng-Che; Tian, Wei-Cheng

2016-01-01

A photoactivated gas detector operated at room temperature was microfabricated using a simple hydrothermal method. We report that the photoactivated gas detector can detect toluene using a UV illumination of 2 μW/cm2. By ultraviolet (UV) illumination, gas detectors sense toluene at room temperature without heating. A significant enhancement of detector sensitivity is achieved because of the high surface-area-to-volume ratio of the morphology of the coral-like ZnO nanorods arrays (NRAs) and the increased number of photo-induced oxygen ions under UV illumination. The corresponding sensitivity (ΔR/R0) of the detector based on coral-like ZnO NRAs is enhanced by approximately 1022% compared to that of thin-film detectors. The proposed detector greatly extends the dynamic range of detection of metal-oxide-based detectors for gas sensing applications. We report the first-ever detection of toluene with a novel coral-like NRAs gas detector at room temperature. A sensing mechanism model is also proposed to explain the sensing responses of gas detectors based on coral-like ZnO NRAs. PMID:27809222

TiO 2 nanotube arrays for photocatalysis: Effects of crystallinity, local order, and electronic structure

DOE PAGES

Liu, Jing; Hosseinpour, Pegah M.; Luo, Si; ...

2014-11-19

To furnish insight into correlations of electronic and local structure and photoactivity, arrays of short and long TiO₂ nanotubes were synthesized by electrochemical anodization of Ti foil, followed by thermal treatment in O₂ (oxidizing), Ar (inert), and H₂ (reducing) environments. The physical and electronic structures of these nanotubes were probed with x-ray diffraction, scanning electron microscopy, and synchrotron-based x-ray absorption spectroscopy, and correlated with their photocatalytic properties. The photocatalytic activity of the nanotubes was evaluated by monitoring the degradation of methyl orange under UV-VIS light irradiation. Results show that upon annealing at 350 °C all as-anodized amorphous TiO₂ nanotube samplesmore » partially transform to the anatase structure, with variations in the degree of crystallinity and in the concentration of local defects near the nanotubes' surface (~5 nm) depending on the annealing conditions. Degradation of methyl orange was not detectable for the as-anodized TiO₂ nanotubes regardless of their length. The annealed long nanotubes demonstrated detectable catalytic activity, which was more significant with the H₂-annealed nanotubes than with the Ar- and O₂-annealed nanotube samples. This enhanced photocatalytic response of the H₂-annealed long nanotubes relative to the other samples is positively correlated with the presence of a larger concentration of lattice defects (such as Ti 3+ and anticipated oxygen vacancies) and a slightly lower degree of crystallinity near the nanotube surface. These physical and electronic structural attributes impact the efficacy of visible light absorption; moreover, the increased concentration of surface defects is postulated to promote the generation of hydroxyl radicals and thus accelerate the photodegradation of the methyl orange. The information obtained from this study provides unique insight into the role of the near-surface electronic and defect structure

Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites

NASA Technical Reports Server (NTRS)

Li, Jun; Meyyappan, Meyya; Dangelo, Carols

2012-01-01

State-of-the-art integrated circuits (ICs) for microprocessors routinely dissipate power densities on the order of 50 W/cm2. This large power is due to the localized heating of ICs operating at high frequencies and must be managed for future high-frequency microelectronic applications. As the size of components and devices for ICs and other appliances becomes smaller, it becomes more difficult to provide heat dissipation and transport for such components and devices. A thermal conductor for a macro-sized thermal conductor is generally inadequate for use with a microsized component or device, in part due to scaling problems. A method has been developed for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler-composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place, and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Hierarchical core-shell structure of ZnO nanorod@NiO/MoO₂ composite nanosheet arrays for high-performance supercapacitors.

PubMed

Hou, Sucheng; Zhang, Guanhua; Zeng, Wei; Zhu, Jian; Gong, Feilong; Li, Feng; Duan, Huigao

2014-08-27

A hierarchical core-shell structure of ZnO nanorod@NiO/MoO2 composite nanosheet arrays on nickel foam substrate for high-performance supercapacitors was constructed by a two-step solution-based method involving two hydrothermal processes followed by a calcination treatment. Compared to one composed of pure NiO/MoO2 composite nanosheets, the hierarchical core-shell structure electrode displays better pseudocapacitive behaviors in 2 M KOH, including high areal specific capacitance values of 1.18 F cm(-2) at 5 mA cm(-2) and 0.6 F cm(-2) at 30 mA cm(-2) as well as relatively good rate capability at high current densities. Furthermore, it also shows remarkable cycle stability, remaining at 91.7% of the initial value even after 4000 cycles at a current density of 10 mA cm(-2). The enhanced pseudocapacitive behaviors are mainly due to the unique hierarchical core-shell structure and the synergistic effect of combining ZnO nanorod arrays and NiO/MoO2 composite nanosheets. This novel hierarchical core-shell structure shows promise for use in next-generation supercapacitors.

Flexible all-solid-state supercapacitors based on polyaniline orderly nanotubes array.

PubMed

Li, Huihua; Song, Juan; Wang, Linlin; Feng, Xiaomiao; Liu, Ruiqing; Zeng, Wenjin; Huang, Zhendong; Ma, Yanwen; Wang, Lianhui

2017-01-07

Flexible all-solid-state supercapacitors are crucial to meet the growing needs for portable electronic devices such as foldable phones and wearable electronics. As promising candidates for pseudocapacitor electrode materials, polyaniline (PANI) orderly nanotube arrays are prepared via a simple template electrodeposition method. The structures of the final product were characterized using various characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The obtained PANI nanotube film could be directly used as a flexible all-solid-state supercapacitor electrode. Electrochemical results show that the areal capacitance of a PANI nanotube-based supercapacitor with the deposition cycle number of 100 can achieve a maximum areal capacitance of 237.5 mF cm -2 at a scan rate of 10 mV s -1 and maximum energy density of 24.31 mW h cm -2 at a power density of 2.74 mW cm -2 . In addition, the prepared supercapacitor exhibits excellent flexibility under different bending conditions. It retains 95.2% of its initial capacitance value after 2000 cycles at a current density of 1.0 mA cm -1 , which displays its superior cycling stability. Moreover, the prepared flexible all-solid-state supercapacitor can power a light-emitting-diode (LED), which meets the practical applications of micropower supplies.

En route to controlled catalytic CVD synthesis of densely packed and vertically aligned nitrogen-doped carbon nanotube arrays.

PubMed

Boncel, Slawomir; Pattinson, Sebastian W; Geiser, Valérie; Shaffer, Milo S P; Koziol, Krzysztof K K

2014-01-01

The catalytic chemical vapour deposition (c-CVD) technique was applied in the synthesis of vertically aligned arrays of nitrogen-doped carbon nanotubes (N-CNTs). A mixture of toluene (main carbon source), pyrazine (1,4-diazine, nitrogen source) and ferrocene (catalyst precursor) was used as the injection feedstock. To optimize conditions for growing the most dense and aligned N-CNT arrays, we investigated the influence of key parameters, i.e., growth temperature (660, 760 and 860 °C), composition of the feedstock and time of growth, on morphology and properties of N-CNTs. The presence of nitrogen species in the hot zone of the quartz reactor decreased the growth rate of N-CNTs down to about one twentieth compared to the growth rate of multi-wall CNTs (MWCNTs). As revealed by electron microscopy studies (SEM, TEM), the individual N-CNTs (half as thick as MWCNTs) grown under the optimal conditions were characterized by a superior straightness of the outer walls, which translated into a high alignment of dense nanotube arrays, i.e., 5 × 10(8) nanotubes per mm(2) (100 times more than for MWCNTs grown in the absence of nitrogen precursor). In turn, the internal crystallographic order of the N-CNTs was found to be of a 'bamboo'-like or 'membrane'-like (multi-compartmental structure) morphology. The nitrogen content in the nanotube products, which ranged from 0.0 to 3.0 wt %, was controlled through the concentration of pyrazine in the feedstock. Moreover, as revealed by Raman/FT-IR spectroscopy, the incorporation of nitrogen atoms into the nanotube walls was found to be proportional to the number of deviations from the sp(2)-hybridisation of graphene C-atoms. As studied by XRD, the temperature and the [pyrazine]/[ferrocene] ratio in the feedstock affected the composition of the catalyst particles, and hence changed the growth mechanism of individual N-CNTs into a 'mixed base-and-tip' (primarily of the base-type) type as compared to the purely 'base'-type for undoped

Controllable 3D architectures of aligned carbon nanotube arrays by multi-step processes

NASA Astrophysics Data System (ADS)

Huang, Shaoming

2003-06-01

An effective way to fabricate large area three-dimensional (3D) aligned CNTs pattern based on pyrolysis of iron(II) phthalocyanine (FePc) by two-step processes is reported. The controllable generation of different lengths and selective growth of the aligned CNT arrays on metal-patterned (e.g., Ag and Au) substrate are the bases for generating such 3D aligned CNTs architectures. By controlling experimental conditions 3D aligned CNT arrays with different lengths/densities and morphologies/structures as well as multi-layered architectures can be fabricated in large scale by multi-step pyrolysis of FePc. These 3D architectures could have interesting properties and be applied for developing novel nanotube-based devices.

Bio-industrial waste silk fibroin protein and carbon nanotube induced carbonized growth of one dimensional ZnO based bio-nanosheets and their enhanced optoelectronic properties.

PubMed

Saravanan, Adhimoorthy; Huang, Bohr-Ran; Kathiravan, Deepa

2018-06-01

High performance UV/visible photodetectors are successfully fabricated from ZnO/fibroin protein-carbon nanotube (ZFPCNT) composites using a simple hydrothermal method. The as-fabricated ZnO nanorods (ZnO NRs) and ZFPCNT nanostructures were measured under different light illuminations. The measurements showed the UV-light photoresponse of the as-fabricated ZFPCNT nanostructures (55,555) to be approximately 26454% higher than that of the as-prepared ZnO NRs (210). This photodetector can sense photons with energies considerably smaller (2.75 eV) than the band gap of ZnO (3.22 eV). It was observed that the finest distribution of fibroin and CNT into 1D ZnO resulted in rapid electron transportation and hole recombination via carbon/nitrogen dopants from the ZFPCNT. Carbon dopants create new energy levels on the conduction band of the ZFPCNT, which reduces the barrier height to allow for charge carrier transportation under light illumination. Moreover, the nitrogen dopants increase the adsorptivity and amount of oxygen vacancies in the ZFPCNT so that it exhibits fast response/recovery times both in the dark and under light illumination. The selectivity of UV light among the other types of illumination can be ascribed to the deep-level energy traps (ET) of the ZFPCNT. These significant features of ZFPCNT lead to the excellent optical properties and creation of new pathways for the production of low-cost semiconductors and bio-waste protein based UV/visible photodetectors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DFT study of adsorption of picric acid molecule on the surface of single-walled ZnO nanotube; as potential new chemical sensor

NASA Astrophysics Data System (ADS)

Farmanzadeh, Davood; Tabari, Leila

2015-01-01

Using density functional theory (DFT), we have investigated the adsorption of picric acid (PA) molecule on the surface of (8,0) single-walled ZnO nanotube (ZnONT). The results show that the PA molecule can be chemisorbed on the surface of ZnONT with adsorption energies of -82.01 and -75.26 kJ/mol in gas and aqueous phase, respectively. Frontier molecular orbital analysis show that HOMO/LUMO gap of ZnONT reduces from 1.66 and 1.75 eV in the pristine nanotube to 0.83 and 0.72 eV in PA-adsorbed form in gas and aqueous phase, respectively. It suggests that the process can affect the electronic properties of the studied nanotube which would lead to its conductance change upon the adsorption of PA molecule. The modifying effect on the electrical conductance of ZnONT underlies the working mechanism of gas sensors for detecting the PA molecules. Analyses of the adsorption behavior of the electrically charged ZnONT toward PA molecule in the gas phase show that the PA molecule can be strongly adsorbed on the negatively charged ZnONT surface with significant adsorption energy (-135.1 kJ/mol). However, from the HOMO/LUMO gap changes, it can be concluded that the positive ZnONT might sensitively detect the PA molecule in comparison to the negative tube. These results can provide helpful information for experimental investigation to develop novel nanotube-based sensors.

Carbon nanotubes on a substrate

DOEpatents

Gao, Yufei [Kennewick, WA; Liu, Jun [West Richland, WA

2002-03-26

The present invention includes carbon nanotubes whose hollow cores are 100% filled with conductive filler. The carbon nanotubes are in uniform arrays on a conductive substrate and are well-aligned and can be densely packed. The uniformity of the carbon nanotube arrays is indicated by the uniform length and diameter of the carbon nanotubes, both which vary from nanotube to nanotube on a given array by no more than about 5%. The alignment of the carbon nanotubes is indicated by the perpendicular growth of the nanotubes from the substrates which is achieved in part by the simultaneous growth of the conductive filler within the hollow core of the nanotube and the densely packed growth of the nanotubes. The present invention provides a densely packed carbon nanotube growth where each nanotube is in contact with at least one nearest-neighbor nanotube. The substrate is a conductive substrate coated with a growth catalyst, and the conductive filler can be single crystals of carbide formed by a solid state reaction between the substrate material and the growth catalyst. The present invention further provides a method for making the filled carbon nanotubes on the conductive substrates. The method includes the steps of depositing a growth catalyst onto the conductive substrate as a prepared substrate, creating a vacuum within a vessel which contains the prepared substrate, flowing H2/inert (e.g. Ar) gas within the vessel to increase and maintain the pressure within the vessel, increasing the temperature of the prepared substrate, and changing the H2/Ar gas to ethylene gas such that the ethylene gas flows within the vessel. Additionally, varying the density and separation of the catalyst particles on the conductive substrate can be used to control the diameter of the nanotubes.

Thermally Conductive Tape Based on Carbon Nanotube Arrays

NASA Technical Reports Server (NTRS)

Kashani, Ali

2011-01-01

To increase contact conductance between two mating surfaces, a conductive tape has been developed by growing dense arrays of carbon nanotubes (CNTs, graphite layers folded into cylinders) on both sides of a thermally conductive metallic foil. When the two mating surfaces are brought into contact with the conductive tape in between, the CNT arrays will adhere to the mating surface. The van der Waals force between the contacting tubes and the mating surface provides adhesion between the two mating surfaces. Even though the thermal contact conductance of a single tube-to-tube contact is small, the tremendous amount of CNTs on the surface leads to a very large overall contact conductance. Interface contact thermal resistance rises from the microroughness and the macroscopic non-planar quality of mating surfaces. When two surfaces come into contact with each other, the actual contact area may be much less than the total area of the surfaces. The real area of contact depends on the load, the surface roughness, and the elastic and inelastic properties of the surface. This issue is even more important at cryogenic temperatures, where materials become hard and brittle and vacuum is used, which prevents any gas conduction through the interstitial region. A typical approach to increase thermal contact conductance is to use thermally conducting epoxies or greases, which are not always compatible with vacuum conditions. In addition, the thermal conductivities of these compounds are often relatively low. The CNTs used in this approach can be metallic or semiconducting, depending on the folding angle and diameter. The electrical resistivity of multiwalled carbon nanotubes (MWCNTs) has been reported. MWCNTs can pass a current density and remain stable at high temperatures in air. The thermal conductivity of a MWCNT at room temperature is measured to be approximately 3,000 W/m-K, which is much larger than that of diamond. At room temperature, the thermal conductance of a 0.3 sq cm

Solution-processed single-wall carbon nanotube transistor arrays for wearable display backplanes

NASA Astrophysics Data System (ADS)

Kang, Byeong-Cheol; Ha, Tae-Jun

2018-01-01

In this paper, we demonstrate solution-processed single-wall carbon nanotube thin-film transistor (SWCNT-TFT) arrays with polymeric gate dielectrics on the polymeric substrates for wearable display backplanes, which can be directly attached to the human body. The optimized SWCNT-TFTs without any buffer layer on flexible substrates exhibit a linear field-effect mobility of 1.5cm2/V-s and a threshold voltage of around 0V. The statistical plot of the key device metrics extracted from 35 SWCNT-TFTs which were fabricated in different batches at different times conclusively support that we successfully demonstrated high-performance solution-processed SWCNT-TFT arrays which demand excellent uniformity in the device performance. We also investigate the operational stability of wearable SWCNT-TFT arrays against an applied strain of up to 40%, which is the essential for a harsh degree of strain on human body. We believe that the demonstration of flexible SWCNT-TFT arrays which were fabricated by all solution-process except the deposition of metal electrodes at process temperature below 130oC can open up new routes for wearable display backplanes.

ZnO nanorod arrays and direct wire bonding on GaN surfaces for rapid fabrication of antireflective, high-temperature ultraviolet sensors

NASA Astrophysics Data System (ADS)

So, Hongyun; Senesky, Debbie G.

2016-11-01

Rapid, cost-effective, and simple fabrication/packaging of microscale gallium nitride (GaN) ultraviolet (UV) sensors are demonstrated using zinc oxide nanorod arrays (ZnO NRAs) as an antireflective layer and direct bonding of aluminum wires to the GaN surface. The presence of the ZnO NRAs on the GaN surface significantly reduced the reflectance to less than 1% in the UV and 4% in the visible light region. As a result, the devices fabricated with ZnO NRAs and mechanically stable aluminum bonding wires (pull strength of 3-5 gf) showed higher sensitivity (136.3% at room temperature and 148.2% increase at 250 °C) when compared with devices with bare (uncoated) GaN surfaces. In addition, the devices demonstrated reliable operation at high temperatures up to 300 °C, supporting the feasibility of simple and cost-effective UV sensors operating with higher sensitivity in high-temperature conditions, such as in combustion, downhole, and space exploration applications.

Enhanced photocatalytic activity of hydrogenated and vanadium doped TiO2 nanotube arrays grown by anodization of sputtered Ti layers

NASA Astrophysics Data System (ADS)

Motola, Martin; Satrapinskyy, Leonid; Čaplovicová, Mária; Roch, Tomáš; Gregor, Maroš; Grančič, Branislav; Greguš, Ján; Čaplovič, Ľubomír; Plesch, Gustav

2018-03-01

TiO2 nanotube (TiNT) arrays were grown on silicon substrate via electrochemical anodization of titanium films sputtered by magnetron. To improve the photocatalytic activity of arrays annealed in air (o-TiNT), doping of o-TiNT with vanadium was performed (o-V/TiNT). These non-doped and doped TiNT arrays were also hydrogenated in H2/Ar atmosphere to r-TiNT and r-V/TiNT samples, respectively. Investigation of composition and morphology by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and X-ray photoelectron spectroscopy (XPS) showed the presence of well-ordered arrays of anatase nanotubes with average diameter and length of 100 nm and 1.3 μm, respectively. In both oxidized and reduced V-doped samples, vanadium is partly dissolved in the structure of anatase and partly deposited in form of oxide on the nanotube surface. Vanadium-doped and reduced samples exhibited higher rates in the photodegradation of organic dyes (compared to non-modified o-TiNT sample) and this is caused by limitation of electron-hole recombination rates and by shift of the energy gap into visible region. The photocatalytic activity was measured under UV, sunlight and visible irradiation, and the corresponding efficiency increased in the order (o-TiNT) < (r-TiNT) < (o-V/TiNT) < (r-V/TiNT). Under visible light, only r-TiNT and r-V/TiNT showed significant photocatalytic activity.

Fabrication of Vertically Aligned Carbon Nanotube or Zinc Oxide Nanorod Arrays for Optical Diffraction Gratings.

PubMed

Kim, Jeong; Kim, Sun Il; Cho, Seong-Ho; Hwang, Sungwoo; Lee, Young Hee; Hur, Jaehyun

2015-11-01

We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications.

Multiwalled Carbon Nanotube/nanofiber Arrays as Conductive and Dry Adhesive Interface Materials

NASA Technical Reports Server (NTRS)

Tong, Tao; Zhao, Yang; Delzeit, Lance; Majumdar, Arun; Kashani, Ali

2004-01-01

We demonstrate the possibility of making conductive and dry adhesive interfaces between multiwalled carbon nanotube (MWNT) and nanofiber (MWNF) arrays grown by chemical vapor deposition with transition-metal as catalyst on highly Boron doped silicon substrates. The maximum observed adhesion force between MWNT and MWNF surfaces is 3.5 mN for an apparent contact area of 2 mm by 4 mm. The minimum contact resistance measured at the same time is approx.20 Omega. Contact resistances of MWNT-MWNT and MWNT-gold interfaces were also measured as pressure forces around several mN were applied at the interface. The resulting minimum contact resistances are on the same order but with considerable variation from sample to sample. For MWNT-MWNT contacts, a minimum contact resistance of approx.1 Omega is observed for a contact area of 2 mm by 1 mm. The relatively high contact resistances, considering the area density of the nanotubes, might be explained by the high cross-tube resistances at the contact interfaces.

ZnO based potentiometric and amperometric nanosensors.

PubMed

Willander, Magnus; Khun, Kimleang; Ibupoto, Zafar Hussain

2014-09-01

The existence of nanomaterials provides the solid platform for sensing applications due to owing of high sensitivity and a low concentration limit of detection. More likely used nanomaterials for sensing applications includes gold nanoparticles, carbon nanotubes, magnetic nanoparticles such as Fe3O4, quantum dots and metal oxides etc. Recently nanomaterial and biological detection becomes an interdisciplinary field and is very much focussed by the researchers. Among metal oxides ZnO is largely considered due to its less toxic nature, biocompatible, cheap and easy to synthesis. ZnO nanomaterial is highly used for the chemical sensing, especially electrochemical sensing due to its fascinating properties such as high surface to volume ratio, atoxic, biosafe and biocompatible. Moreover, ZnO nanostructures exhibit unique features which could expose a suitable nanoenviroment for the immobilization of proteineous material such as enzymes, DNA, antibodies, etc. and in doing so it retains the biological efficiency of the immobilized bio sensitive material. The following review describes the two different coatings (i.e., ionophore and enzyme) on the surface of ZnO nanorods for the chemical sensing of zinc ion detection, thallium (I) ion detection, and L-lactic acid and the measurement of galactose molecules. ZnO nanorods provide the excellent transducing properties in the generation of strong electrical signals. Moreover, this review is very much focused on the applications of ZnO nanostructures in the sensing field.

Multifunctional transparent ZnO nanorod films.

PubMed

Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

2011-03-18

Transparent ZnO nanorod (NR) films that exhibit extreme wetting states (either superhydrophilicity or superhydrophobicity through surface chemical modification), high transmittance, UV protection and antireflection have been prepared via the facile ammonia hydrothermal method. The periodic 1D ZnO NR arrays showed extreme wetting states as well as antireflection properties due to their unique surface structure and prevented the UVA region from penetrating the substrate due to the unique material property of ZnO. Because of the simple, time-efficient and low temperature preparation process, ZnO NR films with useful functionalities are promising for fabrication of highly light transmissive, antireflective, UV protective, antifogging and self-cleaning optical materials to be used for optical devices and photovoltaic energy devices.

Oriented nanotube electrodes for lithium ion batteries and supercapacitors

DOEpatents

Frank, Arthur J.; Zhu, Kai; Wang, Qing

2013-03-05

An electrode having an oriented array of multiple nanotubes is disclosed. Individual nanotubes have a lengthwise inner pore defined by interior tube walls which extends at least partially through the length of the nanotube. The nanotubes of the array may be oriented according to any identifiable pattern. Also disclosed is a device featuring an electrode and methods of fabrication.

Temperature-dependent photoluminescence analysis of ZnO nanowire array annealed in air

NASA Astrophysics Data System (ADS)

Sun, Yanan; Gu, Xiuquan; Zhao, Yulong; Wang, Linmeng; Qiang, Yinghuai

2018-05-01

ZnO nanowire arrays (NWAs) were prepared on transparent conducting fluorine doped tin oxide (FTO) substrates through a facile hydrothermal method, followed by a 500 °C annealing to improve their crystalline qualities and photoelectrochemical (PEC) activities. It was found that the annealing didn't change the morphology, but resulted in a significant reduction of the donor concentration. Temperature-dependent photoluminescence (PL) was carried out for a comprehensive analysis of the effect from annealing. Noteworthy, four dominant peaks were identified from the 10 K spectrum of a 500 °C annealed sample, and they were assigned to FX, D0X, (e, D0) and (e, D0) -1LO, respectively. Of them, the FX emission was only existed below 130 K, while the room-temperature (RT) PL spectrum was dominated by the D0X emission.

The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes

PubMed Central

2011-01-01

In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96. PMID:21711671

The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes.

PubMed

Alvi, N H; Ul Hasan, Kamran; Nur, Omer; Willander, Magnus

2011-02-10

In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

Fabrication of free-standing aligned multiwalled carbon nanotube array for Li-ion batteries

NASA Astrophysics Data System (ADS)

Bulusheva, L. G.; Arkhipov, V. E.; Fedorovskaya, E. O.; Zhang, Su; Kurenya, A. G.; Kanygin, M. A.; Asanov, I. P.; Tsygankova, A. R.; Chen, Xiaohong; Song, Huaihe; Okotrub, A. V.

2016-04-01

We show that a high-temperature CCl4 vapor treatment of vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) grown on silicon substrate allows carefully detach the array from the substrate. Moreover, this procedure partially purifies the VA-MWCNTs from the residual iron catalyst. To improve electrical connectivity of free-standing VA-MWCNTs in an electrochemical cell, the array was placed between the layers of Ni foam. Such assembly demonstrated the better performance in Li-battery as compared to the disordered MWCNTs. After 50 cycles, the specific capacity of VA-MWCNT array synthesized from 0.5 wt% ferrocene solution in toluene was 350 mAh g-1 at a current density of 0.1 A g-1, while the battery with the disordered MWCNTs achieved 197 mAh g-1 only. By the results of electrochemical impedance spectroscopy, the higher capacity of VA-MWCNTs was attributed to larger surface area available for electrolyte and Li ions due to the absence of binder coating.

Electrodeposition synthesis of MnO{sub 2}/TiO{sub 2} nanotube arrays nanocomposites and their visible light photocatalytic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xuyao; Zhou, Xiaosong, E-mail: zxs801213@163.com; Li, Xiaoyu, E-mail: lixiaoyu@iga.ac.cn

2014-11-15

Highlights: • MnO{sub 2}/TiO{sub 2} nanotube arrays nanocomposites are prepared by electrodeposition. • MnO{sub 2}/TiO{sub 2} exhibits high visible light photocatalytic activity. • The results of XRD show the depositions are attributed to α-MnO{sub 2}. • A photocatalytic mechanism is discussed under visible light irradiation. - Abstract: MnO{sub 2}/TiO{sub 2} nanotube arrays nanocomposite photocatalysts have been synthesized through an electrodeposition method. X-ray powder diffraction analysis and X-ray photoelectron spectroscopy measurements reveal that the products of electrodeposition method are MnO{sub 2}. Scanning electron microscopy measurements suggest that the depositions are deposited on the surface or internal of the nanotube. UV–vis lightmore » absorbance spectra demonstrate the excellent adsorption properties of MnO{sub 2}/TiO{sub 2} over the whole region of visible light, which enables this novel photocatalytic material to possess remarkable activity in the photocatalytic degradation of acid Orange II under visible light radiation. Moreover, a possible photocatalytic mechanism is discussed.« less

Electrochemical biosensor for Mycobacterium tuberculosis DNA detection based on gold nanotubes array electrode platform.

PubMed

Torati, Sri Ramulu; Reddy, Venu; Yoon, Seok Soo; Kim, CheolGi

2016-04-15

The template assisted electrochemical deposition technique was used for the synthesis of gold nanotubes array (AuNTsA). The morphological structure of the synthesized AuNTsA was observed by scanning electron microscopy and found that the individual nanotubes are around 1.5 μm in length with a diameter of 200 nm. Nanotubes are vertically aligned to the Au thick film, which is formed during the synthesis process of nanotubes. The electrochemical performance of the AuNTsA was compared with the bare Au electrode and found that AuNTsA has better electron transfer surface than bare Au electrode which is due to the high surface area. Hence, the AuNTsA was used as an electrode for the fabrication of DNA hybridization biosensor for detection of Mycobacterium Tuberculosis DNA. The DNA hybridization biosensor constructed by AuNTsA electrode was characterized by cyclic voltammetry technique with Fe(CN)6(3-/4-) as an electrochemical redox indicator. The selectivity of the fabricated biosensor was illustrated by hybridization with complementary DNA and non-complementary DNA with probe DNA immobilized AuNTsA electrode using methylene blue as a hybridization indicator. The developed electrochemical DNA biosensor shows good linear range of complementary DNA concentration from 0.01 ng/μL to 100 ng/μL with high detection limit. Copyright © 2015 Elsevier B.V. All rights reserved.

Non-metal doped TiO2 nanotube arrays for high efficiency photocatalytic decomposition of organic species in water

NASA Astrophysics Data System (ADS)

Szkoda, Mariusz; Siuzdak, Katarzyna; Lisowska-Oleksiak, Anna

2016-10-01

Titanium dioxide is a well-known photoactive semiconductor with a variety of possible applications. The procedure of pollutant degradation is mainly performed using TiO2 powder suspension. It can also be exploited an immobilized catalyst on a solid support. Morphology and chemical doping have a great influence on TiO2 activity under illumination. Here we compare photoactivity of titania nanotube arrays doped with non-metal atoms: nitrogen, iodine and boron applied for photodegradation of organic dye - methylene blue and terephtalic acid. The doped samples act as a much better photocatalyst in the degradation process of methylene blue and lead to the formation of much higher amount of hydroxyl radicals (•OH) than undoped TiO2 nanotube arrays. The use of a catalyst active under solar light illumination in the form of thin films on a stable substrate can be scaled up for an industrial application.

Preparation of electrochemically active silicon nanotubes in highly ordered arrays

PubMed Central

Grünzel, Tobias; Lee, Young Joo; Kuepper, Karsten

2013-01-01

Summary Silicon as the negative electrode material of lithium ion batteries has a very large capacity, the exploitation of which is impeded by the volume changes taking place upon electrochemical cycling. A Si electrode displaying a controlled porosity could circumvent the difficulty. In this perspective, we present a preparative method that yields ordered arrays of electrochemically competent silicon nanotubes. The method is based on the atomic layer deposition of silicon dioxide onto the pore walls of an anodic alumina template, followed by a thermal reduction with lithium vapor. This thermal reduction is quantitative, homogeneous over macroscopic samples, and it yields amorphous silicon and lithium oxide, at the exclusion of any lithium silicides. The reaction is characterized by spectroscopic ellipsometry for thin silica films, and by nuclear magnetic resonance and X-ray photoelectron spectroscopy for nanoporous samples. After removal of the lithium oxide byproduct, the silicon nanotubes can be contacted electrically. In a lithium ion electrolyte, they then display the electrochemical waves also observed for other bulk or nanostructured silicon systems. The method established here paves the way for systematic investigations of how the electrochemical properties (capacity, charge/discharge rates, cyclability) of nanoporous silicon negative lithium ion battery electrode materials depend on the geometry. PMID:24205460

Research of influence of the underlayer material on the growth rate of carbon nanotube arrays for manufacturing non-volatile memory elements with high speed

NASA Astrophysics Data System (ADS)

Klimin, V. S.; Il'ina, M. V.; Il'in, O. I.; Rudyk, N. N.; Ageev, O. A.

2017-11-01

This experimental work is devoted to the regimes of obtaining arrays of carbon nanotubes. Arrays of perpendicular nanotubes perpendicular to the surface were obtained by the method of Plasma-enhanced chemical vapor deposition. In this paper, geometric and electronic parameters of carbon nanotubes were investigated depending on the material of the sublayer. The rates of growth of carbon nanotubes on various structures were also determined. In the experiments for growth, structures such as Ni-Al-Si, Ni-V-Si, Ni-Ti-Si, Ni-Cr-Si were used. The growth rates for the intensive section were for the Ni-Cr-Si structure, the growth rate is about 1 μm / min, for the Ni-V-Si structure it is 0.55 μm / min. The growth rates for the saturation region for the Ni-Cr-Si structure, the growth rate is about 0.2 μm / min, for the Ni-V-Si structure 0.16 μm / min. The results obtained in this paper can be used to optimize the growth regimes perpendicularly oriented to the substrate carbon nanotubes, which are used as various elements in modern nanoelectronics.

Hierarchical structures of carbon nanotubes and arrays of chromium-capped silicon nanopillars: formation and electrical properties.

PubMed

Koch, Stefan; Joshi, Ravi K; Noyong, Michael; Timper, Jan; Schneider, Jörg J; Simon, Ulrich

2012-09-10

The formation of stochastically oriented carbon-nanotube networks on top of an array of free-standing chromium-capped silicon nanopillars is reported. The combination of nanosphere lithography and chemical vapor deposition enables the construction of nanostructures that exhibit a hierarchical sequence of structural sizes. Metallic chromium serves as an etching mask for Si-pillar formation and as a nucleation site for the formation of carbon nanotubes through the chemical vapor deposition of ethene, ethanol, and methane, respectively, thereby bridging individual pillars from top to top. Iron and cobalt were applied onto the chromium caps as catalysts for CNT growth and the influence of different carbon sources and different gas-flow rates were investigated. The carbon nanotubes were structurally characterized and their DC electrical properties were studied by in situ local- and ex situ macroscopic measurements, both of which reveal their semiconductor properties. This process demonstrates how carbon nanotubes can be integrated into Si-based semiconductors and, thus, this process may be used to form high-surface-area sensors or new porous catalyst supports with enhanced gas-permeation properties. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complex and oriented ZnO nanostructures.

PubMed

Tian, Zhengrong R; Voigt, James A; Liu, Jun; McKenzie, Bonnie; McDermott, Matthew J; Rodriguez, Mark A; Konishi, Hiromi; Xu, Huifang

2003-12-01

Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Xu; Islam, Ahmad E.; Seabron, Eric

2015-04-07

Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that includemore » thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.« less

Fabrication and photoelectrochemical properties of ZnS/Au/TiO2 nanotube array films.

PubMed

Zhu, Yan-Feng; Zhang, Juan; Xu, Lu; Guo, Ya; Wang, Xiao-Ping; Du, Rong-Gui; Lin, Chang-Jian

2013-03-21

A highly ordered TiO(2) nanotube array film was fabricated by an anodic oxidation method. The film was modified by Au nanoparticles (NPs) formed by a deposition-precipitation technique and was covered with a thin ZnS shell prepared by a successive ionic layer adsorption and reaction (SILAR) method. The photoelectrochemical properties of the prepared ZnS/Au/TiO(2) composite film were evaluated by incident photon-to-current conversion efficiency (IPCE), and photopotential and electrochemical impedance spectroscopy (EIS) measurements under white light illumination. The results indicated that the Au NPs could expand the light sensitivity range of the film and suppress the electron-hole recombination, and the ZnS shell could inhibit the leakage of photogenerated electrons from the surface of Au NPs to the ZnS/electrolyte interface. When the 403 stainless steel in a 0.5 M NaCl solution was coupled to the ZnS/Au/TiO(2) nanotube film photoanode under illumination, its potential decreased by 400 mV, showing that the composite film had a better photocathodic protection effect on the steel than that of a pure TiO(2) nanotube film.

Ionization Gas Sensor using Aligned Multiwalled Carbon Nanotubes Array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kermany, A. R.; Mohamed, N. M.; Singh, B. S. M.

2011-05-25

The challenge with current conventional gas sensors which are operating using semiconducting oxides is their size. After the introduction of nanotechnology and in order to reduce the dimension and consequently the power consumption and cost, new materials such as carbon nanotubes (CNTs) are being introduced. From previous works and characterization results, it was proven that the CNTs based gas sensor has better sensitivity, selectivity and faster response time in compared with semiconducting oxides based gas sensors. As in this work, a fabrication and successful testing of an ionization-based gas sensor using aligned Multiwalled CNTs (MWCNTs) as sensing element is discussed,more » in which MWCNTs array and Al film are used as anode and cathode plates respectively with electrode separation ranging from 80 {mu}m to 140 {mu}m. Aligned MWCNTs array was incorporated into a sensor configuration in the gas chamber for testing of gases such as argon, air, and mixed gas of 2%H{sub 2} in air. Obtained results show that among the three gases, argon has the lowest breakdown voltage whilst air has the highest value and the breakdown voltage was found to decrease as the electrode spacing was reduced from 140 {mu}m to 80 {mu}m for all three gases.« less

Development of Amperometric Glucose Biosensor Based on Prussian Blue Functionlized TiO2 Nanotube Arrays

PubMed Central

Gao, Zhi-Da; Qu, Yongfang; Li, Tongtong; Shrestha, Nabeen K.; Song, Yan-Yan

2014-01-01

Amperometric biosensors consisting of oxidase and peroxidase have attracted great attention because of their wide application. The current work demonstrates a novel approach to construct an enzymatic biosensor based on TiO2 nanotube arrays (TiNTs) as a supporting electrode on which Prussian Blue (PB)-an “artificial enzyme peroxidase” and enzyme glucose oxidase (GOx) have been immobilized. For this, PB nanocrystals are deposited onto the nanotube wall photocatalytically using the intrinsic photocatalytical property of TiO2, and the GOx/AuNPs nanobiocomposites are subsequently immobilized into the nanotubes via the electrodeposition of polymer. The resulting electrode exhibits a fast response, wide linear range, and good stability for glucose sensing. The sensitivity of the sensor is as high as 248 mA M−1 cm−2, and the detection limit is about 3.2 μM. These findings demonstrate a promising strategy to integrate enzymes and TiNTs, which could provide an analytical access to a large group of enzymes for bioelectrochemical applications including biosensors and biofuel cells. PMID:25367086

Visible light-harvesting of TiO2 nanotubes array by pulsed laser deposited CdS

NASA Astrophysics Data System (ADS)

Bjelajac, Andjelika; Djokic, Veljko; Petrovic, Rada; Socol, Gabiel; Mihailescu, Ion N.; Florea, Ileana; Ersen, Ovidiu; Janackovic, Djordje

2014-08-01

Titanium dioxide (TiO2) nanotubes arrays, obtained by anodization technique and annealing, were decorated with CdS using pulsed laser deposition method. Their structural, morphological and chemical characterization was carried out by electron microscopy in scanning (SEM) and transmission (TEM) modes, combined with energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). It was demonstrated that the quantity of deposited CdS can be controlled by varying the number of laser pulses. The chemical mapping of the elements of interest was performed using the energy filtered mode of the electron microscope. The results showed that pulse laser deposition is an adequate technique for deposition of CdS inside and between 100 nm wide TiO2 nanotubes. The diffuse reflectance spectroscopy investigation of selected samples proved that the absorption edge of the prepared CdS/TiO2 nanocomposites is significantly extended to the visible range. The corresponding band gaps were determinated from the Tauc plot of transformed Kubelka-Munk function. The band gap reduction of TiO2 nanotubes by pulsed laser deposition of CdS was put in evidence.

On-Chip Sorting of Long Semiconducting Carbon Nanotubes for Multiple Transistors along an Identical Array.

PubMed

Otsuka, Keigo; Inoue, Taiki; Maeda, Etsuo; Kometani, Reo; Chiashi, Shohei; Maruyama, Shigeo

2017-11-28

Ballistic transport and sub-10 nm channel lengths have been achieved in transistors containing one single-walled carbon nanotube (SWNT). To fill the gap between single-tube transistors and high-performance logic circuits for the replacement of silicon, large-area, high-density, and purely semiconducting (s-) SWNT arrays are highly desired. Here we demonstrate the fabrication of multiple transistors along a purely semiconducting SWNT array via an on-chip purification method. Water- and polymer-assisted burning from site-controlled nanogaps is developed for the reliable full-length removal of metallic SWNTs with the damage to s-SWNTs minimized even in high-density arrays. All the transistors with various channel lengths show large on-state current and excellent switching behavior in the off-state. Since our method potentially provides pure s-SWNT arrays over a large area with negligible damage, numerous transistors with arbitrary dimensions could be fabricated using a conventional semiconductor process, leading to SWNT-based logic, high-speed communication, and other next-generation electronic devices.

Ultrasensitive Label-free Electronic Chip for DNA Analysis Using Carbon Nanotube Nanoelectrode Arrays

NASA Technical Reports Server (NTRS)

Li, Jun; Koehne, Jessica; Chen, Hua; Cassell, Alan; Ng, Hou Tee; Ye, Qi; Han, Jie; Meyyappan, M.

2004-01-01

There is a strong need for faster, cheaper, and simpler methods for nucleic acid analysis in today s clinical tests. Nanotechnologies can potentially provide solutions to these requirements by integrating nanomaterials with biofunctionalities. Dramatic improvement in the sensitivity and multiplexing can be achieved through the high-degree miniaturization. Here, we present our study in the development of an ultrasensitive label-free electronic chip for DNA/RNA analysis based on carbon nanotube nanoelectrode arrays. A reliable nanoelectrode array based on vertically aligned multi-walled carbon nanotubes (MWNTs) embedded in a SiO2 matrix is fabricated using a bottom-up approach. Characteristic nanoelectrode behavior is observed with a low-density MWNT nanoelectrode array in measuring both the bulk and surface immobilized redox species. The open-end of MWNTs are found to present similar properties as graphite edge-plane electrodes, with a wide potential window, flexible chemical functionalities, and good biocompatibility. A BRCA1 related oligonucleotide probe with 18 bases is covalently functionalized at the open ends of the MWNTs and specifically hybridized with an oligonucleotide target as well as a PCR amplicon. The guanine bases in the target molecules are employed as the signal moieties for the electrochemical measurements. Ru(bpy)3(2+) mediator is used to further amplify the guanine oxidation signal. This technique has been employed for direct electrochemical detection of label-free PCR amplicon through specific hybridization with the BRCAl probe. The detection limit is estimated to be less than approximately 1000 DNA molecules, approaching the limit of the sensitivity by laser-based fluorescence techniques in DNA microarray. This system provides a general electronic platform for rapid molecular diagnostics in applications requiring ultrahigh sensitivity, high-degree of miniaturization, simple sample preparation, and low- cost operation.

Functionalized ZnO nanowires for microcantilever biosensors with enhanced binding capability.

PubMed

Stassi, Stefano; Chiadò, Alessandro; Cauda, Valentina; Palmara, Gianluca; Canavese, Giancarlo; Laurenti, Marco; Ricciardi, Carlo

2017-04-01

An efficient way to increase the binding capability of microcantilever biosensors is here demonstrated by growing zinc oxide nanowires (ZnO NWs) on their active surface. A comprehensive evaluation of the chemical compatibility of ZnO NWs brought to the definition of an innovative functionalization method able to guarantee the proper immobilization of biomolecules on the nanostructured surface. A noteworthy higher amount of grafted molecules was evidenced with colorimetric assays on ZnO NWs-coated devices, in comparison with functionalized and activated silicon flat samples. ZnO NWs grown on silicon microcantilever arrays and activated with the proposed immobilization strategy enhanced the sensor binding capability (and thus the dynamic range) of nearly 1 order of magnitude, with respect to the commonly employed flat functionalized silicon devices. Graphical Abstract An efficient way to increase the binding capability of microcantilever biosensors is represented by growing zinc oxide nanowires (ZnO NWs) on their active surface. ZnO NWs grown on silicon microcantilever arrays and activated with an innovative immobilization strategy enhanced the sensor binding capability of nearly 1 order of magnitude, with respect to the commonly employed flat functionalized silicon devices.

Investigation on the Plasma-Induced Emission Properties of Large Area Carbon Nanotube Array Cathodes with Different Morphologies

PubMed Central

2011-01-01

Large area well-aligned carbon nanotube (CNT) arrays with different morphologies were synthesized by using a chemical vapor deposition. The plasma-induced emission properties of CNT array cathodes with different morphologies were investigated. The ratio of CNT height to CNT-to-CNT distance has considerable effects on their plasma-induced emission properties. As the ratio increases, emission currents of CNT array cathodes decrease due to screening effects. Under the pulse electric field of about 6 V/μm, high-intensity electron beams of 170–180 A/cm2 were emitted from the surface plasma. The production mechanism of the high-intensity electron beams emitted from the CNT arrays was plasma-induced emission. Moreover, the distribution of the electron beams was in situ characterized by the light emission from the surface plasma. PMID:27502662

Investigation on the Plasma-Induced Emission Properties of Large Area Carbon Nanotube Array Cathodes with Different Morphologies.

PubMed

Liao, Qingliang; Qin, Zi; Zhang, Zheng; Qi, Junjie; Zhang, Yue; Huang, Yunhua; Liu, Liang

2011-12-01

Large area well-aligned carbon nanotube (CNT) arrays with different morphologies were synthesized by using a chemical vapor deposition. The plasma-induced emission properties of CNT array cathodes with different morphologies were investigated. The ratio of CNT height to CNT-to-CNT distance has considerable effects on their plasma-induced emission properties. As the ratio increases, emission currents of CNT array cathodes decrease due to screening effects. Under the pulse electric field of about 6 V/μm, high-intensity electron beams of 170-180 A/cm(2) were emitted from the surface plasma. The production mechanism of the high-intensity electron beams emitted from the CNT arrays was plasma-induced emission. Moreover, the distribution of the electron beams was in situ characterized by the light emission from the surface plasma.

Application of Chemical Doping and Architectural Design Principles To Fabricate Nanowire Co2Ni3ZnO8 Arrays for Aqueous Asymmetric Supercapacitors.

PubMed

Liu, Qi; Yang, Bin; Liu, Jingyuan; Yuan, Yi; Zhang, Hongsen; Liu, Lianhe; Wang, Jun; Li, Rumin

2016-08-10

Electrode materials derived from transition metal oxides have a serious problem of low electron transfer rate, which restricts their practical application. However, chemically doped graphene transforms the chemical bonding configuration to enhance electron transfer rate and, therefore, facilitates the successful fabrication of Co2Ni3ZnO8 nanowire arrays. In addition, the Co2Ni3ZnO8 electrode materials, considered as Ni and Zn ions doped into Co3O4, have a high electron transfer rate and electrochemical response capability, because the doping increases the degree of crystal defect and reaction of Co/Ni ions with the electrolyte. Hence, the Co2Ni3ZnO8 electrode exhibits a high rate property and excellent electrochemical cycle stability, as determined by electrochemical analysis of the relationship between specific capacitance, IR drop, Coulomb efficiency, and different current densities. From the results of a three-electrode system of electrochemical measurement, the Co2Ni3ZnO8 electrode demonstrates a specific capacitance of 1115 F g(-1) and retains 89.9% capacitance after 2000 cycles at a current density of 4 A g(-1). The energy density of the asymmetric supercapacitor (AC//Co2Ni3ZnO8) is 54.04 W h kg(-1) at the power density of 3200 W kg(-1).

Substrate morphology induced self-organization into carbon nanotube arrays, ropes, and agglomerates.

PubMed

Huang, Jia-Qi; Zhang, Qiang; Xu, Guang-Hui; Qian, Wei-Zhong; Wei, Fei

2008-10-29

In this paper, hydrophobic carbon nanotube (CNT) arrays, ropes, and agglomerates were synthesized through self-organization on quartz substrates with different micro-structures under the same growth condition. On a flat substrate, a uniform woven structure was formed which resulted in a synchronous growth into an array. When the substrate with 10 µm round concaves distributed on the surface was adopted, the woven structure was sporadic and a CNT cluster was grown in the concave. With further growth, CNT ropes were self-organized. Subsequently, when the substrate consisting of irregular ∼100 nm gaps was used, the initial woven structure was high density, thus resulting in the formation of CNT agglomerates. Study results showed that CNT arrays grown on the flat substrate were of the highest purity and had a contact angle of 153.8 ± 0.9°. Thus, the self-organization behavior among CNTs was in situ modulated by different substrate morphology without further treatments. This provides us with an additional understanding of the self-organization of CNTs during growth, as well as strategies for the controllable synthesis of CNTs with fixed properties.

Direct electrodeposition of gold nanotube arrays of rough and porous wall by cyclic voltammetry and its applications of simultaneous determination of ascorbic acid and uric acid.

PubMed

Yang, Guangming; Li, Ling; Jiang, Jinhe; Yang, Yunhui

2012-08-01

Gold nanotube arrays of rough and porous wall has been synthesized by direct electrodeposition with cyclic voltammetry utilizing anodic aluminum oxide template (AAO) and polycarbonate membrane (PC) during short time (only 3 min and 2 min, respectively). The mechanism of the direct electrodeposition of gold nanotube arrays by cyclic voltammetry (CV) has been discussed. The morphological characterizations of the gold nanotube arrays have been investigated by scanning electron microscopy (SEM). A simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry (DPV) was constructed by attaching gold nanotube arrays (using AAO) onto the surface of a glassy carbon electrode (GCE). The electrochemical behavior of AA and UA at this modified electrode has been studied by CV and differential pulse voltammetry (DPV). The sensor offers an excellent response for AA and UA and the linear response range for AA and UA were 1.02×10(-7)-5.23×10(-4) mol L(-1) and 1.43×10(-7)-4.64×10(-4) mol L(-1), the detection limits were 1.12×10(-8) mol L(-1) and 2.24×10(-8) mol L(-1), respectively. This sensor shows good regeneration, stability and selectivity and has been used for the determination of AA and UA in real human urine and serum samples with satisfied results. Copyright © 2012 Elsevier B.V. All rights reserved.

Tunable, flexible antireflection layer of ZnO nanowires embedded in PDMS.

PubMed

Kim, Min Kyu; Yi, Dong Kee; Paik, Ungyu

2010-05-18

In this article, we report the fabrication of ordered hybrid structures composed of ZnO nanowires and a polymeric matrix with a polymer precursor infiltrating the nanowire arrays. The antireflective properties of the resulting ZnO nanowire-embedded polydimethylsiloxane composite (ZPC) were investigated at various ZnO nanowire lengths and ZPC bending angles. Interestingly, we found that whereas the antireflective properties showed a strong dependence on the length of the embedded ZnO nanowires in PDMS, the bending of ZPC has little effect on the antireflective properties.

Growth of high-density ZnO nanorods on wood with enhanced photostability, flame retardancy and water repellency

NASA Astrophysics Data System (ADS)

Kong, Lizhuo; Tu, Kunkun; Guan, Hao; Wang, Xiaoqing

2017-06-01

Zinc oxide (ZnO) nanorod arrays were successfully assembled on the wood surface in situ via a two-step process consisting of formation of ZnO seeds and subsequent crystal growth under hydrothermal conditions at a low temperature. The morphology and crystalline structure of the formed ZnO nanorods were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Highly dense and uniform arrays of ZnO nanorods with well-defined hexagonal facets were generated on the wood surface by tuning the concentration of the ZnO growth solution during the hydrothermal treatment. Accelerated weathering tests indicated that the assembled ZnO nanorod arrays were highly protective against UV radiation and greatly enhanced the photostability of the coated wood. Meanwhile, the ZnO nanorod-coated wood can withstand continuous exposure to flame with only minor smoldering in contrast with the pristine wood catching fire easily and burning rapidly. Moreover, when further modified with low-surface-energy stearic acid, the ZnO nanorod decorated wood surface can be transformed into a superhydrophobic surface, with a water contact angle (CA) of ∼154°. Such ZnO nanorod-modified woods with enhanced photostability, flame retardancy and water repellency offer an interesting alternative to conventional wood preservation strategies, highlighting their potential applications in some novel wood products.

Ni nanotube array-based electrodes by electrochemical alloying and de-alloying for efficient water splitting.

PubMed

Teng, Xue; Wang, Jianying; Ji, Lvlv; Lv, Yaokang; Chen, Zuofeng

2018-05-17

The design of cost-efficient earth-abundant catalysts with superior performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is extremely important for future renewable energy production. Herein, we report a facile strategy for constructing Ni nanotube arrays (NTAs) on a Ni foam (NF) substrate through cathodic deposition of NiCu alloy followed by anodic stripping of metallic Cu. Based on Ni NTAs, the as-prepared NiSe2 NTA electrode by NiSe2 electrodeposition and the NiFeOx NTA electrode by dipping in Fe3+ solution exhibit excellent HER and OER performance in alkaline conditions. In these systems, Ni NTAs act as a binder-free multifunctional inner layer to support the electrocatalysts, offer a large specific surface area and serve as a fast electron transport pathway. Moreover, an alkaline electrolyzer has been constructed using NiFeOx NTAs as the anode and NiSe2 NTAs as the cathode, which only demands a cell voltage of 1.78 V to deliver a water-splitting current density of 500 mA cm-2, and demonstrates remarkable stability during long-term electrolysis. This work provides an attractive method for the design and fabrication of nanotube array-based catalyst electrodes for highly efficient water-splitting.

Hierarchical NiCo2 S4 Nanotube@NiCo2 S4 Nanosheet Arrays on Ni Foam for High-Performance Supercapacitors.

PubMed

Chen, Haichao; Chen, Si; Shao, Hongyan; Li, Chao; Fan, Meiqiang; Chen, Da; Tian, Guanglei; Shu, Kangying

2016-01-01

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

From GaN to ZnGa(2)O(4) through a low-temperature process: nanotube and heterostructure arrays.

PubMed

Lu, Ming-Yen; Zhou, Xiang; Chiu, Cheng-Yao; Crawford, Samuel; Gradečak, Silvija

2014-01-22

We demonstrate a method to synthesize GaN-ZnGa2O4 core-shell nanowire and ZnGa2O4 nanotube arrays by a low-temperature hydrothermal process using GaN nanowires as templates. Transmission electron microscopy and X-ray photoelectron spectroscopy results show that a ZnGa2O4 shell forms on the surface of GaN nanowires and that the shell thickness is controlled by the time of the hydrothermal process and thus the concentration of Zn ions in the solution. Furthermore, ZnGa2O4 nanotube arrays were obtained by depleting the GaN core from GaN-ZnGa2O4 core-shell nanowire arrays during the reaction and subsequent etching with HCl. The GaN-ZnGa2O4 core-shell nanowires exhibit photoluminescence peaks centered at 2.60 and 2.90 eV attributed to the ZnGa2O4 shell, as well as peaks centered at 3.35 and 3.50 eV corresponding to the GaN core. We also demonstrate the synthesis of GaN-ZnGa2O4 heterojunction nanowires by a selective formation process as a simple route toward development of heterojunction nanodevices for optoelectronic applications.

A Porous Perchlorate-Doped Polypyrrole Nanocoating on Nickel Nanotube Arrays for Stable Wide-Potential-Window Supercapacitors.

PubMed

Chen, Gao-Feng; Li, Xian-Xia; Zhang, Li-Yi; Li, Nan; Ma, Tian Yi; Liu, Zhao-Qing

2016-09-01

A bottom-up synthetic strategy is developed to fabricate a highly porous wave-superposed perchlorate-doped polypyrrole nanocoating on nickel nanotube arrays. The delicate nanostructure and the unique surface chemistry synergistically endow the obtained electrode with revealable pseudocapacitance, large operating potential window, and excellent cycling stability, which are highly promising for both asymmetric and symmetric supercapacitors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization and synergetic antibacterial properties of ZnO and CeO2 supported by halloysite

NASA Astrophysics Data System (ADS)

Shu, Zhan; Zhang, Yi; Ouyang, Jing; Yang, Huaming

2017-10-01

A novel antibacterial nanocomposite, CeO2-ZnO/HNTs was prepared by a homogeneous co-precipitation method in ethanol solution. ZnO and CeO2 nanoparticles with sizes of approximately 8 and 4 nm, respectively, were dispersively precipitated onto the surface of halloysite nanotubes (HNTs). HNTs served as a template for reducing the agglomeration of ZnO nanoparticles and improving the interface reactions between the nanocomposite and bacteria cells. CeO2 nanoparticles were introduced to suppress the recombination of electron-hole pairs, and narrow the energy gap of ZnO nanoparticles. The synergistic effects of ZnO, CeO2 nanoparticles and HNTs led to the superior antibacterial activity of the CeO2-ZnO/HNTs nanocomposite against gram-negative Escherichia coli.

In situ growth of NiCo2S4 nanotube arrays on Ni foam for supercapacitors: Maximizing utilization efficiency at high mass loading to achieve ultrahigh areal pseudocapacitance

NASA Astrophysics Data System (ADS)

Chen, Haichao; Jiang, Jianjun; Zhang, Li; Xia, Dandan; Zhao, Yuandong; Guo, Danqing; Qi, Tong; Wan, Houzhao

2014-05-01

Self-standing NiCo2S4 nanotube arrays have been in situ grown on Ni foam by the anion-exchange reaction and directly used as the electrode for supercapacitors. The NiCo2S4 nanotube in the arrays effectively reduces the inactive material and increases the electroactive surface area because of the ultrathin wall, which is quite competent to achieve high utilization efficiency at high electroactive materials mass loading. The NiCo2S4 nanotube arrays hybrid electrode exhibits an ultrahigh specific capacitance of 14.39 F cm-2 at 5 mA cm-2 with excellent rate performance (67.7% retention for current increases 30 times) and cycling stability (92% retention after 5000 cycles) at a high mass loading of 6 mg cm-2. High areal capacitance (4.68 F cm-2 at 10 mA cm-2), high energy density (31.5 Wh kg-1 at 156.6 W kg-1) and high power density (2348.5 W kg-1 at 16.6 Wh kg-1) can be achieved by assembling asymmetric supercapacitor with reduced graphene oxide at a total active material mass loading as high as 49.5 mg. This work demonstrates that NiCo2S4 nanotube arrays structure is a superior electroactive material for high-performance supercapacitors even at a mass loading of potential application-specific scale.

Exploring aligned-carbon-nanotubes@polyaniline arrays on household Al as supercapacitors.

PubMed

Huang, Fan; Lou, Fengliu; Chen, De

2012-05-01

Herein, we demonstrate a new approach towards the construction of supercapacitors consisting of carbon nanotubes (CNTs) and conducting polymers (ECPs) with high specific power, high specific energy, and stable cycling performance through a 3D design of a thin film of polyaniline (PANI) on an aligned small carbon nanotube (ACNT) array on household Al foils. The thin-film strategy is used to fully exploit the specific capacitance of PANI, and obtain regular pores, strong interaction between PANI and CNTs, and reduced electrical resistance for the electrodes. A facile process is developed to fabricate a highly flexible supercapacitor using this binder-free composite on household Al foil as the current collector. It exhibits high specific energy of 18.9 Wh kg(-1) , high maximum specific power of 11.3 kW kg(-1) of the active material in an aqueous electrolyte at 1.0 A g(-1) , and excellent rate performance and cycling stability. A high specific energy of 72.4 Wh kg(-1) , a high maximum specific power of 24.9 kW kg(-1) , and a good cycling performance of the active material are obtained in an organic electrolyte. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient fabrication of carbon nanotube micro tip arrays by tailoring cross-stacked carbon nanotube sheets.

PubMed

Wei, Yang; Liu, Peng; Zhu, Feng; Jiang, Kaili; Li, Qunqing; Fan, Shoushan

2012-04-11

Carbon nanotube (CNT) micro tip arrays with hairpin structures on patterned silicon wafers were efficiently fabricated by tailoring the cross-stacked CNT sheet with laser. A blade-like structure was formed at the laser-cut edges of the CNT sheet. CNT field emitters, pulled out from the end of the hairpin by an adhesive tape, can provide 150 μA intrinsic emission currents with low beam noise. The nice field emission is ascribed to the Joule-heating-induced desorption of the emitter surface by the hairpin structure, the high temperature annealing effect, and the surface morphology. The CNT emitters with hairpin structures will greatly promote the applications of CNTs in vacuum electronic devices and hold the promises to be used as the hot tips for thermochemical nanolithography. More CNT-based structures and devices can be fabricated on a large scale by this versatile method. © 2012 American Chemical Society

Synthesis of Hollow Nanotubes of Zn2SiO4 or SiO2: Mechanistic Understanding and Uranium Adsorption Behavior.

PubMed

Tripathi, Shalini; Bose, Roopa; Roy, Ahin; Nair, Sajitha; Ravishankar, N

2015-12-09

We report a facile synthesis of Zn2SiO4 nanotubes using a two-step process consisting of a wet-chemical synthesis of core-shell ZnO@SiO2 nanorods followed by thermal annealing. While annealing in air leads to the formation of hollow Zn2SiO4, annealing under reducing atmosphere leads to the formation of SiO2 nanotubes. We rationalize the formation of the silicate phase at temperatures much lower than the temperatures reported in the literature based on the porous nature of the silica shell on the ZnO nanorods. We present results from in situ transmission electron microscopy experiments to clearly show void nucleation at the interface between ZnO and the silica shell and the growth of the silicate phase by the Kirkendall effect. The porous nature of the silica shell is also responsible for the etching of the ZnO leading to the formation of silica nanotubes under reducing conditions. Both the hollow silica and silicate nanotubes exhibit good uranium sorption at different ranges of pH making them possible candidates for nuclear waste management.

Titania nanotube arrays as interfaces for blood-contacting implantable devices: a study evaluating the nanotopography-associated activation and expression of blood plasma components.

PubMed

Smith, Barbara S; Popat, Ketul C

2012-08-01

The constant exposure of implantable biomaterials such as titanium and titanium alloys to blood-introducesserious and ongoing concerns regarding poor blood-material interactions. To date, all blood-contacting materials have been shown to initiate immunological events in the form of inflammation, thrombosis, fibrosis and infection; potentially leading to complete implant failure. Material surfaces that provide biomimetic cues such as nanoscale architectures have been shown to elicit improved cellular interaction; and thus, may provide possible solutions for enhancing blood-compatibility. However, limited information exists about the thrombogenicityof nanoscalesurface architectures. In this study, we have evaluated the efficacy of titania nanotube arrays as interfaces for blood contacting devices by investigating the thrombogenic effects using whole blood plasma. Thus, platelet/leukocyte adhesion, activation and interaction, morphology, complement activation, contact activation, platelet release reaction, fibrinogen expression and material cytotoxicity were evaluated to determine the in vitro thrombogenicity. The results presented here indicate a decrease in thrombogenic effects of titania nanotube arrays as compared to biomedical grade titanium after 2 hours of contact with whole blood plasma. This work shows the improved blood-compatibility of titania nanotube arrays, identifying this specific nanoarchitecture as a potentially optimal interface for promoting the long-term success of blood contacting biomaterials.

Reconstruction of TiO2/MnO2-C nanotube/nanoflake core/shell arrays as high-performance supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Xiong, Qinqin; Zheng, Cun; Chi, Hongzhong; Zhang, Jun; Ji, Zhenguo

2017-02-01

Construction of electrodes with fast reaction kinetics is of great importance for achieving advanced supercapacitors. Herein we report a facile combined synthetic strategy with atomic layer deposition (ALD) and electrodeposition to rationally fabricate nanotube/nanoflake core/shell arrays. ALD-TiO2 nanotubes are used as the skeleton core for assembly of electrodeposited MnO2-C nanoflake shells forming a core/shell structure. Highly porous architecture and good electrical conductivity are combined in this unique core/shell structure, resulting in fast ion/electron transfer. In tests of electrochemical performance, the TiO2/MnO2-C core/shell arrays are characterized as cathode for asymmetric supecapacitors and exhibit high specific capacitance (880 F g-1 at 2.5 A g-1), excellent rate properties (735 F g-1 at 30 A g-1) and good long-term cycling stability (94.3% capacitance retention after 20 000 cycles). The proposed electrode construction strategy is favorable for fabrication of other advanced supercapacitor electrodes.

Reconstruction of TiO2/MnO2-C nanotube/nanoflake core/shell arrays as high-performance supercapacitor electrodes.

PubMed

Xiong, Qinqin; Zheng, Cun; Chi, Hongzhong; Zhang, Jun; Ji, Zhenguo

2017-02-03

Construction of electrodes with fast reaction kinetics is of great importance for achieving advanced supercapacitors. Herein we report a facile combined synthetic strategy with atomic layer deposition (ALD) and electrodeposition to rationally fabricate nanotube/nanoflake core/shell arrays. ALD-TiO 2 nanotubes are used as the skeleton core for assembly of electrodeposited MnO 2 -C nanoflake shells forming a core/shell structure. Highly porous architecture and good electrical conductivity are combined in this unique core/shell structure, resulting in fast ion/electron transfer. In tests of electrochemical performance, the TiO 2 /MnO 2 -C core/shell arrays are characterized as cathode for asymmetric supecapacitors and exhibit high specific capacitance (880 F g -1 at 2.5 A g -1 ), excellent rate properties (735 F g -1 at 30 A g -1 ) and good long-term cycling stability (94.3% capacitance retention after 20 000 cycles). The proposed electrode construction strategy is favorable for fabrication of other advanced supercapacitor electrodes.

Plasmonic Properties of Vertically Aligned Nanowire Arrays

DTIC Science & Technology

2012-01-01

scattering (SERS) applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography...plasmonic nanowires to investigate this SERS effect. Here we used two types of vertical NWs, ZnO NWs, and Si NWs, respectively, to investigate SERS...successfully grow vertically aligned ZnO nanowires by the well-known VLS process. In this way, the ZnO NWs can be arranged in a repeatable hexagonal pattern

Significantly enhanced UV luminescence by plasmonic metal on ZnO nanorods patterned by screen-printing.

PubMed

Zhao, Jun; Cui, Shuyuan; Zhang, Xingang; Li, Wenqing

2018-08-31

A smart synthetic method is conceived to construct large batches of ZnO nanostructures to meet market demand for light-emitting diodes. Utilizing the localized surface plasmon resonance of metal nanoparticles (NPs) facilitates the recombination of electron-hole pairs and the release of photons. Compared to raw ZnO nanorods (NRs), ZnO NRs@HfO 2 @Al NPs show a ∼120× enhancement in ultraviolet (UV) photoluminescence (PL), while ZnO NRs@HfO 2 @Ag NPs show a six-fold enhancement. Because the surface plasmon energy of Al is nearer the ZnO band gap, the PL enhancement of ZnO NRs covered with Al is stronger than that of those covered with Ag. Based on this analysis, three-dimensional graphical ZnO NR arrays were manufactured by screen-printing, a mass production technique. After covering the arrays with layers of HfO 2 and Al NPs, the UV PL intensities of the corresponding substrates were increased by approximately 16×. This indicates the potential to mass-produce highly efficient optoelectronic devices.

Multi-wall carbon nanotube@zeolite imidazolate framework composite from a nanoscale zinc oxide precursor

DOE PAGES

Yue, Yanfeng; Guo, Bingkun; Qiao, Zhenan; ...

2014-07-24

Nanocomposite of multi-walled carbon nanotube@zeolite imidazolate frameworks (MWNT@ZIF) was prepared through a nanotube-facilitated growth based on a nanosized ZnO precursor. The electrically conductive nanocomposite displays a capacity of 380 mAh/g at 0.1 °C in Li–sulfur battery, transforming electrically inactive ZIF into the active one for battery applications.

In situ TEM and analytical STEM studies of ZnO nanotubes with Sn cores and Sn nanodrops

NASA Astrophysics Data System (ADS)

Ortega, Y.; Jäger, W.; Piqueras, J.; Häussler, D.; Fernández, P.

2013-10-01

ZnO nanorods with Sn core regions grown by a thermal evaporation-deposition method from a mixture of SnO2 and ZnS powders as precursors, are used to study the behaviour of liquid metal in the nanotubes' core regions and the formation of liquid metal nanodrops at the tube ends by in situ TEM experiments. The compositions of the core materials and of the nanodrops were assessed by employing HAADF-STEM imaging and spatially resolved EDXS measurements. By applying variable thermal load through changing the electron-beam flux of the electron microscope, melting of the metallic core can be induced and the behaviour of the liquid metal of the nanorods can be monitored locally. Within the nanorod core, melting and reversible thermal expansion and contraction of Sn core material is reproducibly observed. For nanotubes with core material near-tip regions, a nanodrop emerges from the tip upon melting the core material, followed by reabsorption of the melt into the core and re-solidification upon decreasing the heat load, being reminiscent of a ‘soldering nanorod’. The radius of the liquid nanodrop can reach a few tens of nanometres, containing a total volume of 10-20 up to 10-18 l of liquid Sn. In situ TEM confirms that the radius of the nanodrop can be controlled via the thermal load: it increases with increasing temperature and decreases with decreasing temperature. In addition, some phenomena related to structure modifications during extended electron-beam exposure are also described.

Method of making carbon nanotubes on a substrate

DOEpatents

Gao, Yufei; Liu, Jun

2006-03-14

The present invention includes carbon nanotubes whose hollow cores are 100% filled with conductive filler. The carbon nanotubes are in uniform arrays on a conductive substrate and are well-aligned and can be densely packed. The uniformity of the carbon nanotube arrays is indicated by the uniform length and diameter of the carbon nanotubes, both which vary from nanotube to nanotube on a given array by no more than about 5%. The alignment of the carbon nanotubes is indicated by the perpendicular growth of the nanotubes from the substrates which is achieved in part by the simultaneous growth of the conductive filler within the hollow core of the nanotube and the densely packed growth of the nanotubes. The present invention provides a densely packed carbon nanotube growth where each nanotube is in contact with at least one nearest-neighbor nanotube. The substrate is a conductive substrate coated with a growth catalyst, and the conductive filler can be single crystals of carbide formed by a solid state reaction between the substrate material and the growth catalyst. The present invention further provides a method for making the filled carbon nanotubes on the conductive substrates. The method includes the steps of depositing a growth catalyst onto the conductive substrate as a prepared substrate, creating a vacuum within a vessel which contains the prepared substrate, flowing H2/inert (e.g. Ar) gas within the vessel to increase and maintain the pressure within the vessel, increasing the temperature of the prepared substrate, and changing the H2/Ar gas to ethylene gas such that the ethylene gas flows within the vessel. Additionally, varying the density and separation of the catalyst particles on the conductive substrate can be used to control the diameter of the nanotubes.

Cobalt-Doped Black TiO2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment.

PubMed

Yang, Yang; Kao, Li Cheng; Liu, Yuanyue; Sun, Ke; Yu, Hongtao; Guo, Jinghua; Liou, Sofia Ya Hsuan; Hoffmann, Michael R

2018-05-04

TiO 2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO 2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO 2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO 4 electrolyte at 10 mA cm -2 . Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (O v ) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, O v , and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO 2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoO x film on top of Co-Black electrode. The CoO x /Co-Black composite electrode was found to have a lower OER overpotential (352 mV) in comparison to a DSA IrO 2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm -2 .

Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

PubMed

Sun, Hong; Zhao, Peini; Zhang, Fanjun; Liu, Yuliang; Hao, Jingcheng

2015-12-01

Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

Cobalt-Doped Black TiO2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment

PubMed Central

2018-01-01

TiO2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO4 electrolyte at 10 mA cm–2. Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (Ov) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, Ov, and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoOx film on top of Co-Black electrode. The CoOx/Co-Black composite electrode was found to have a lower OER overpotential (352 mV) in comparison to a DSA IrO2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm–2. PMID:29755829

Control of Carbon Nanotube Density and Tower Height in an Array

NASA Technical Reports Server (NTRS)

Delzeit, Lance D. (Inventor); Schipper, John F. (Inventor)

2010-01-01

A method for controlling density or tower height of carbon nanotube (CNT) arrays grown in spaced apart first and second regions on a substrate. CNTs having a first density range (or first tower height range) are grown in the first region using a first source temperature range for growth. Subsequently or simultaneously, CNTs having a second density range (or second tower height range), having an average density (or average tower height) in the second region different from the average density (or average tower height) for the first region, are grown in the second region, using supplemental localized hearing for the second region. Application for thermal dissipation and/or dissipation of electrical charge or voltage in an electronic device are discussed.

Static micro-array isolation, dynamic time series classification, capture and enumeration of spiked breast cancer cells in blood: the nanotube-CTC chip

NASA Astrophysics Data System (ADS)

Khosravi, Farhad; Trainor, Patrick J.; Lambert, Christopher; Kloecker, Goetz; Wickstrom, Eric; Rai, Shesh N.; Panchapakesan, Balaji

2016-11-01

We demonstrate the rapid and label-free capture of breast cancer cells spiked in blood using nanotube-antibody micro-arrays. 76-element single wall carbon nanotube arrays were manufactured using photo-lithography, metal deposition, and etching techniques. Anti-epithelial cell adhesion molecule (anti-EpCAM), Anti-human epithelial growth factor receptor 2 (anti-Her2) and non-specific IgG antibodies were functionalized to the surface of the nanotube devices using 1-pyrene-butanoic acid succinimidyl ester. Following device functionalization, blood spiked with SKBR3, MCF7 and MCF10A cells (100/1000 cells per 5 μl per device, 170 elements totaling 0.85 ml of whole blood) were adsorbed on to the nanotube device arrays. Electrical signatures were recorded from each device to screen the samples for differences in interaction (specific or non-specific) between samples and devices. A zone classification scheme enabled the classification of all 170 elements in a single map. A kernel-based statistical classifier for the ‘liquid biopsy’ was developed to create a predictive model based on dynamic time warping series to classify device electrical signals that corresponded to plain blood (control) or SKBR3 spiked blood (case) on anti-Her2 functionalized devices with ˜90% sensitivity, and 90% specificity in capture of 1000 SKBR3 breast cancer cells in blood using anti-Her2 functionalized devices. Screened devices that gave positive electrical signatures were confirmed using optical/confocal microscopy to hold spiked cancer cells. Confocal microscopic analysis of devices that were classified to hold spiked blood based on their electrical signatures confirmed the presence of cancer cells through staining for DAPI (nuclei), cytokeratin (cancer cells) and CD45 (hematologic cells) with single cell sensitivity. We report 55%-100% cancer cell capture yield depending on the active device area for blood adsorption with mean of 62% (˜12 500 captured off 20 000 spiked cells in 0.1 ml

Optical properties of ordered vertical arrays of multi-walled carbon nanotubes from FDTD simulations.

PubMed

Bao, Hua; Ruan, Xiulin; Fisher, Timothy S

2010-03-15

A finite-difference time-domain (FDTD) method is used to model thermal radiative properties of vertical arrays of multi-walled carbon nanotubes (MWCNT). Individual CNTs are treated as solid circular cylinders with an effective dielectric tensor. Consistent with experiments, the results confirm that CNT arrays are highly absorptive. Compared with the commonly used Maxwell-Garnett theory, the FDTD calculations generally predict larger reflectance and absorbance, and smaller transmittance, which are attributed to the diffraction and scattering within the cylinder array structure. The effects of volume fraction, tube length, tube distance, and incident angle on radiative properties are investigated systematically. Low volume fraction and long tubes are more favorable to achieve low reflectance and high absorbance. For a fixed volume fraction and finite tube length, larger periodicity results in larger reflectance and absorbance. The angular dependence studies reveal an optimum incident angle at which the reflectance can be minimized. The results also suggest that an even darker material could be achieved by using CNTs with good alignment on the top surface.

A simple route to vertical array of quasi-1D ZnO nanofilms on FTO surfaces: 1D-crystal growth of nanoseeds under ammonia-assisted hydrolysis process

PubMed Central

2011-01-01

A simple method for the synthesis of ZnO nanofilms composed of vertical array of quasi-1D ZnO nanostructures (quasi-NRs) on the surface was demonstrated via a 1D crystal growth of the attached nanoseeds under a rapid hydrolysis process of zinc salts in the presence of ammonia at room temperature. In a typical procedure, by simply controlling the concentration of zinc acetate and ammonia in the reaction, a high density of vertically oriented nanorod-like morphology could be successfully obtained in a relatively short growth period (approximately 4 to 5 min) and at a room-temperature process. The average diameter and the length of the nanostructures are approximately 30 and 110 nm, respectively. The as-prepared quasi-NRs products were pure ZnO phase in nature without the presence of any zinc complexes as confirmed by the XRD characterisation. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnO quasi-NRs are high-crystallinity properties in nature. The mechanism of growth for the ZnO quasi-NRs will be proposed. Due to their simplicity, the method should become a potential alternative for a rapid and cost-effective preparation of high-quality ZnO quasi-NRs nanofilms for use in photovoltaic or photocatalytics applications. PACS: 81.07.Bc; 81.16.-c; 81.07.Gf. PMID:22027275

Chemoselectivity-induced multiple interfaces in MWCNT/Fe3O4@ZnO heterotrimers for whole X-band microwave absorption.

PubMed

Wang, Zhijiang; Wu, Lina; Zhou, Jigang; Jiang, Zhaohua; Shen, Baozhong

2014-11-07

A chemoselective route to induce Fe3O4@ZnO core-shell nanoparticles decorating carbon nanotubes to form MWCNT/Fe3O4@ZnO heterotrimers has been developed. Charges are redistributed in the heterotrimers through C-O-Zn, C-O-Fe and Fe-O-Zn bondings, giving rise to multiple electronic phases. The generated significant interfacial polarization and synergetic interaction between dielectric and magnetic absorbers result in the MWCNT/Fe3O4@ZnO heterotrimers with high-performance microwave absorption in an entire X band.

Gas composition sensing using carbon nanotube arrays

NASA Technical Reports Server (NTRS)

Li, Jing (Inventor); Meyyappan, Meyya (Inventor)

2008-01-01

A method and system for estimating one, two or more unknown components in a gas. A first array of spaced apart carbon nanotubes (''CNTs'') is connected to a variable pulse voltage source at a first end of at least one of the CNTs. A second end of the at least one CNT is provided with a relatively sharp tip and is located at a distance within a selected range of a constant voltage plate. A sequence of voltage pulses {V(t.sub.n)}.sub.n at times t=t.sub.n (n=1, . . . , N1; N1.gtoreq.3) is applied to the at least one CNT, and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of a curve I(t.sub.n) for current or a curve e(t.sub.n) for electric charge transported from the at least one CNT to the constant voltage plate. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas.

Synthesis and magnetotransport studies of CrO2 films grown on TiO2 nanotube arrays by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Wang, Xiaoling; Zhang, Caiping; Wang, Lu; Lin, Tao; Wen, Gehui

2018-04-01

The CrO2 films have been prepared on the TiO2 nanotube array template via atmospheric pressure chemical vapor deposition method. And the growth procedure was studied. In the beginning of the deposition process, the CrO2 grows on the cross section of the TiO2 nanotubes wall, forms a nanonet-like layer. And the grain size of CrO2 is very small. With the increase of the deposition time, the grain size of CrO2 also increases, and the nanonet-like layer changes into porous film. With the further increase of the deposition time, all the nanotubes are covered by CrO2 grains and the surface structure becomes polycrystalline film. The average grain size on the surface of the CrO2 films deposited for 1 h, 2 h and 5 h is about 190 nm, 300 nm and 470 nm. The X-ray diffraction pattern reveals that the rutile CrO2 film has been synthesized on the TiO2 nanotube array template. The CrO2 films show large magnetoresistance (MR) at low temperature, which should originate from spin-dependent tunneling through grain boundaries between CrO2 grains. And the tunneling mechanism of the CrO2 films can be well described by the fluctuation-induced tunneling (FIT) model. The CrO2 film deposited for 2 h shows insulator behavior from 5 k to 300 K, but the CrO2 film deposited for 5 h shows insulator-metal transition around 140 K. The reason is briefly discussed.

Nano-engineering of three-dimensional core/shell nanotube arrays for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Grote, Fabian; Wen, Liaoyong; Lei, Yong

2014-06-01

Large-scale arrays of core/shell nanostructures are highly desirable to enhance the performance of supercapacitors. Here we demonstrate an innovative template-based fabrication technique with high structural controllability, which is capable of synthesizing well-ordered three-dimensional arrays of SnO2/MnO2 core/shell nanotubes for electrochemical energy storage in supercapacitor applications. The SnO2 core is fabricated by atomic layer deposition and provides a highly electrical conductive matrix. Subsequently a thin MnO2 shell is coated by electrochemical deposition onto the SnO2 core, which guarantees a short ion diffusion length within the shell. The core/shell structure shows an excellent electrochemical performance with a high specific capacitance of 910 F g-1 at 1 A g-1 and a good rate capability of remaining 217 F g-1 at 50 A g-1. These results shall pave the way to realize aqueous based asymmetric supercapacitors with high specific power and high specific energy.

Microwave purification of large-area horizontally aligned arrays of single-walled carbon nanotubes.

PubMed

Xie, Xu; Jin, Sung Hun; Wahab, Muhammad A; Islam, Ahmad E; Zhang, Chenxi; Du, Frank; Seabron, Eric; Lu, Tianjian; Dunham, Simon N; Cheong, Hou In; Tu, Yen-Chu; Guo, Zhilin; Chung, Ha Uk; Li, Yuhang; Liu, Yuhao; Lee, Jong-Ho; Song, Jizhou; Huang, Yonggang; Alam, Muhammad A; Wilson, William L; Rogers, John A

2014-11-12

Recent progress in the field of single-walled carbon nanotubes (SWNTs) significantly enhances the potential for practical use of this remarkable class of material in advanced electronic and sensor devices. One of the most daunting challenges is in creating large-area, perfectly aligned arrays of purely semiconducting SWNTs (s-SWNTs). Here we introduce a simple, scalable, large-area scheme that achieves this goal through microwave irradiation of aligned SWNTs grown on quartz substrates. Microstrip dipole antennas of low work-function metals concentrate the microwaves and selectively couple them into only the metallic SWNTs (m-SWNTs). The result allows for complete removal of all m-SWNTs, as revealed through systematic experimental and computational studies of the process. As one demonstration of the effectiveness, implementing this method on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

Design of Pd/PANI/Pd sandwich-structured nanotube array catalysts with special shape effects and synergistic effects for ethanol electrooxidation.

PubMed

Wang, An-Liang; Xu, Han; Feng, Jin-Xian; Ding, Liang-Xin; Tong, Ye-Xiang; Li, Gao-Ren

2013-07-24

Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI.

Preparation and UV-Vis photodegradation of gaseous benzene by TiO2 nanotube arrays supporting V2O5 nanoparticles

NASA Astrophysics Data System (ADS)

Zhao, Chunxia; Song, Yanbao; Yang, Yunxia; Chen, Wen; Li, Xiaoyu; Wang, Zongsheng

2015-07-01

TiO2-based catalysts effective in visible radiation for eliminating organic pollutants have attracted intense research activity as a future generation photocatalytic material. However, recombination of electron-hole pairs through trapping/de-trapping as well as the disadvantages of recycling and separation/filtration of powders lead to the limitation of powder TiO2 materials. TiO2 nanotube array films supporting vanadium pentoxide nanoparticles (VTNTs) were synthesized by electrophoresis deposition method with the prepared TiO2 nanotube arrays as the cathode and V2O5 sol as the electrolyte. The results indicate that the formation of Ti-O-V bonds and intimate interaction between host-guest interfaces help to enhance the hybrids’ photodegradation activity of gaseous benzene. Importantly, hybrid film catalysts prepared with 0.05 mol/L V2O5 sol for 10 min electrophoresis deposition perform a 98% conversion rate of benzene and 1028.8 mg/m3CO2 production in 80 min under UV-Vis irradiation.

Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components

PubMed Central

Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

2014-01-01

The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs. PMID:25330053

Hierarchical Carbon Fibers with ZnO Nanowires for Volatile Sensing in Composite Curing (Postprint)

DTIC Science & Technology

2014-07-01

needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a volatile sensor. ZnO nanowires are demonstrated to function as...processing. For this work, we report on the foundational study needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a...array of ZnO nanowires. Zinc oxide nanowires become more conductive in the presence of ethanol – as analyte sorbs to the surface, electron density

Guided growth of large-scale, horizontally aligned arrays of single-walled carbon nanotubes and their use in thin-film transistors.

PubMed

Kocabas, Coskun; Hur, Seung-Hyun; Gaur, Anshu; Meitl, Matthew A; Shim, Moonsub; Rogers, John A

2005-11-01

A convenient process for generating large-scale, horizontally aligned arrays of pristine, single-walled carbon nanotubes (SWNTs) is described. The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on miscut single-crystal quartz substrates. Studies of the growth reveal important relationships between the density and alignment of the tubes, the CVD conditions, and the morphology of the quartz. Electrodes and dielectrics patterned on top of these arrays yield thin-film transistors that use the SWNTs as effective thin-film semiconductors. The ability to build high-performance devices of this type suggests significant promise for large-scale aligned arrays of SWNTs in electronics, sensors, and other applications.

Graphitic carbon nitride (g-C3N4) coated titanium oxide nanotube arrays with enhanced photo-electrochemical performance.

PubMed

Sun, Mingxuan; Fang, Yalin; Kong, Yuanyuan; Sun, Shanfu; Yu, Zhishui; Umar, Ahmad

2016-08-09

Herein, we report the successful formation of graphitic carbon nitride coated titanium oxide nanotube array thin films (g-C3N4/TiO2) via the facile thermal treatment of anodized Ti sheets over melamine. The proportion of C3N4 and TiO2 in the composite can be adjusted by changing the initial addition mass of melamine. The as-prepared samples are characterized by several techniques in order to understand the morphological, structural, compositional and optical properties. UV-vis absorption studies exhibit a remarkable red shift for the g-C3N4/TiO2 thin films as compared to the pristine TiO2 nanotubes. Importantly, the prepared composites exhibit an enhanced photocurrent and photo-potential under both UV-vis and visible light irradiation. Moreover, the observed maximum photo-conversion efficiency of the prepared composites is 1.59 times higher than that of the pristine TiO2 nanotubes. The optical and electrochemical impedance spectra analysis reveals that the better photo-electrochemical performance of the g-C3N4/TiO2 nanotubes is mainly due to the wider light absorption and reduced impedance compared to the bare TiO2 nanotube electrode. The presented work demonstrates a facile and simple method to fabricate g-C3N4/TiO2 nanotubes and clearly revealed that the introduction of g-C3N4 is a new and innovative approach to improve the photocurrent and photo-potential efficiencies of TiO2.

Influence of the morphology of ZnO nanostructures on luminescent and photovoltaic properties

NASA Astrophysics Data System (ADS)

Ibrayev, N. Kh.; Ilyassov, B. R.; Afanasyev, D. A.

2017-03-01

Arrays of ZnO nanorods and nanoplates are synthesized by the hydrothermal and electrochemical methods, respectively. The photoluminescence spectra indicate that the nanoplates have a more defective structure than the nanorods. The obtained ZnO nanostructures are used as the basis to construct dye-sensitized solar cells. The influence of morphology and defectiveness of ZnO nanostructures on the luminescent and photovoltaic properties of the cells is studied.

Thin randomly aligned hierarchical carbon nanotube arrays as ultrablack metamaterials

NASA Astrophysics Data System (ADS)

De Nicola, Francesco; Hines, Peter; De Crescenzi, Maurizio; Motta, Nunzio

2017-07-01

Ultrablack metamaterials are artificial materials able to harvest all the incident light regardless of wavelength, angle, or polarization. Here, we show the ultrablack properties of randomly aligned hierarchical carbon nanotube arrays with thicknesses below 200 nm. The thin coatings are realized by solution processing and dry-transfer deposition on different substrates. The hierarchical surface morphology of the coatings is biomimetic and provides a large effective area that improves the film optical absorption. Also, such a morphology is responsible for the moth-eye effect, which leads to the omnidirectional and polarization-independent suppression of optical reflection. The films exhibit an emissivity up to 99.36% typical of an ideal black body, resulting in the thinnest ultrablack metamaterial ever reported. Such a material may be exploited for thermal, optical, and optoelectronic devices such as heat sinks, optical shields, solar cells, light and thermal sensors, and light-emitting diodes.

Ultra-Low-Power Smart Electronic Nose System Based on Three-Dimensional Tin Oxide Nanotube Arrays.

PubMed

Chen, Jiaqi; Chen, Zhuo; Boussaid, Farid; Zhang, Daquan; Pan, Xiaofang; Zhao, Huijuan; Bermak, Amine; Tsui, Chi-Ying; Wang, Xinran; Fan, Zhiyong

2018-06-04

In this work, we present a high-performance smart electronic nose (E-nose) system consisting of a multiplexed tin oxide (SnO 2 ) nanotube sensor array, read-out circuit, wireless data transmission unit, mobile phone receiver, and data processing application (App). Using the designed nanotube sensor device structure in conjunction with multiple electrode materials, high-sensitivity gas detection and discrimination have been achieved at room temperature, enabling a 1000 times reduction of the sensor's power consumption as compared to a conventional device using thin film SnO 2 . The experimental results demonstrate that the developed E-nose can identify indoor target gases using a simple vector-matching gas recognition algorithm. In addition, the fabricated E-nose has achieved state-of-the-art sensitivity for H 2 and benzene detection at room temperature with metal oxide sensors. Such a smart E-nose system can address the imperative needs for distributed environmental monitoring in smart homes, smart buildings, and smart cities.

Carbon Nanotube Arrays for Intracellular Delivery and Biological Applications

NASA Astrophysics Data System (ADS)

Golshadi, Masoud

Introducing nucleic acids into mammalian cells is a crucial step to elucidate biochemical pathways, modify gene expression in immortalized cells, primary cells, and stem cells, and intoduces new approaches for clinical diagnostics and therapeutics. Current gene transfer technologies, including lipofection, electroporation, and viral delivery, have enabled break-through advances in basic and translational science to enable derivation and programming of embryonic stem cells, advanced gene editing using CRISPR (Clustered regularly interspaced short palindromic repeats), and development of targeted anti-tumor therapy using chimeric antigen receptors in T-cells (CAR-T). Despite these successes, current transfection technologies are time consuming and limited by the inefficient introduction of test molecules into large populations of target cells, and the cytotoxicity of the techniques. Moreover, many cell types cannot be consistently transfected by lipofection or electroporation (stem cells, T-cells) and viral delivery has limitations to the size of experimental DNA that can be packaged. In this dissertation, a novel coverslip-like platform consisting of an array of aligned hollow carbon nanotubes (CNTs) embedded in a sacrificial template is developed that enhances gene transfer capabilities, including high efficiency, low toxicity, in an expanded range of target cells, with the potential to transfer mixed combinations of protein and nucleic acids. The CNT array devices are fabricated by a scalable template-based manufacturing method using commercially available membranes, eliminating the need for nano-assembly. High efficient transfection has been demonstrated by delivering various cargos (nanoparticles, dye and plasmid DNA) into populations of cells, achieving 85% efficiency of plasmid DNA delivery into immortalized cells. Moreover, the CNT-mediated transfection of stem cells shows 3 times higher efficiency compared to current lipofection methods. Evaluating the cell

Heterodoped nanotubes: theory, synthesis, and characterization of phosphorus-nitrogen doped multiwalled carbon nanotubes.

PubMed

Cruz-Silva, Eduardo; Cullen, David A; Gu, Lin; Romo-Herrera, Jose Manuel; Muñoz-Sandoval, Emilio; López-Urías, Florentino; Sumpter, Bobby G; Meunier, Vincent; Charlier, Jean-Christophe; Smith, David J; Terrones, Humberto; Terrones, Mauricio

2008-03-01

Arrays of multiwalled carbon nanotubes doped with phosphorus (P) and nitrogen (N) are synthesized using a solution of ferrocene, triphenyl-phosphine, and benzylamine in conjunction with spray pyrolysis. We demonstrate that iron phosphide (Fe(3)P) nanoparticles act as catalysts during nanotube growth, leading to the formation of novel PN-doped multiwalled carbon nanotubes. The samples were examined by high resolution electron microscopy and microanalysis techniques, and their chemical stability was explored by means of thermogravimetric analysis in the presence of oxygen. The PN-doped structures reveal important morphology and chemical changes when compared to N-doped nanotubes. These types of heterodoped nanotubes are predicted to offer many new opportunities in the fabrication of fast-response chemical sensors.

Fabrication of ordered metallic glass nanotube arrays for label-free biosensing with diffractive reflectance.

PubMed

Chen, Wei-Ting; Li, Shao-Sian; Chu, Jinn P; Feng, Kuei Chih; Chen, Jem-Kun

2018-04-15

In this study, a photoresist template with well-defined contact hole array was fabricated, to which radio frequency magnetron sputtering process was then applied to deposit an alloyed Zr 55 Cu 30 Al 10 Ni 5 target, and finally resulted in ordered metallic glass nanotube (MGNT) arrays after removal of the photoresist template. The thickness of the MGNT walls increased from 98 to 126nm upon increasing the deposition time from 225 to 675s. The wall thickness of the MGNT arrays also increased while the dimensions of MGNT reduced under the same deposition condition. The MGNT could be filled with biomacromolecules to change the effective refractive index. The air fraction of the medium layer were evaluated through static water contact angle measurements and, thereby, the effective refractive indices the transverse magnetic (TM) and transverse electric (TE) polarized modes were calculated. A standard biotin-streptavidin affinity model was tested using the MGNT arrays and the fundamental response of the system was investigated. Results show that filling the MGNT with streptavidin altered the effective refractive index of the layer, the angle of reflectance and color changes identified by an L*a*b* color space and color circle on an a*b* chromaticity diagram. The limit of detection (LOD) of the MGNT arrays for detection of streptavidin was estimated as 25nM, with a detection time of 10min. Thus, the MGNT arrays may be used as a versatile platform for high-sensitive label-free optical biosensing. Copyright © 2017 Elsevier B.V. All rights reserved.

Conformal atomic layer deposition of alumina on millimeter tall, vertically-aligned carbon nanotube arrays.

PubMed

Stano, Kelly L; Carroll, Murphy; Padbury, Richard; McCord, Marian; Jur, Jesse S; Bradford, Philip D

2014-11-12

Atomic layer deposition (ALD) can be used to coat high aspect ratio and high surface area substrates with conformal and precisely controlled thin films. Vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) with lengths up to 1.5 mm were conformally coated with alumina from base to tip. The nucleation and growth behaviors of Al2O3 ALD precursors on the MWCNTs were studied as a function of CNT surface chemistry. CNT surfaces were modified through a series of post-treatments including pyrolytic carbon deposition, high temperature thermal annealing, and oxygen plasma functionalization. Conformal coatings were achieved where post-treatments resulted in increased defect density as well as the extent of functionalization, as characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Using thermogravimetric analysis, it was determined that MWCNTs treated with pyrolytic carbon and plasma functionalization prior to ALD coating were more stable to thermal oxidation than pristine ALD coated samples. Functionalized and ALD coated arrays had a compressive modulus more than two times higher than a pristine array coated for the same number of cycles. Cross-sectional energy dispersive X-ray spectroscopy confirmed that Al2O3 could be uniformly deposited through the entire thickness of the vertically aligned MWCNT array by manipulating sample orientation and mounting techniques. Following the ALD coating, the MWCNT arrays demonstrated hydrophilic wetting behavior and also exhibited foam-like recovery following compressive strain.

Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wei, Xing; Sugri Nbelayim, Pascal; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2017-03-01

A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

Enhanced electrochemical performance of manganese dioxide spheres deposited on a titanium dioxide nanotube arrays substrate

NASA Astrophysics Data System (ADS)

Zhou, He; Zhang, Yanrong

2014-12-01

The deposition of MnO2 spheres on a TiO2 nanotube arrays substrate are achieved via a sequential chemical bath deposition (SCBD) method for an application of anode materials in supercapacitors. The electrochemical performance of the MnO2-TiO2 composite electrode is observed to show a strong dependence on the MnO2 loading mass, which could be adjusted by repeating the SCBD treatment for several cycles. The optimized doses of MnO2 loaded MnO2-TiO2 and MnO2-Ti samples are compared in terms of their areal capacitance studies and the former is of 175 and 101 mF cm-2 at a scan rate of 10 and 100 mV s-1, respectively, which are 1.52-fold and 1.51-fold of that of the latter sample at corresponding scan rates. The enhancement in areal capacitance has been accounted to the progressive effect of the TiO2 tubular substrate on the capacitive behavior of the loaded MnO2 rather than the different MnO2 loading mass on these two substrates. Impedance analysis reveals this enhanced electrochemical activity is owing to the tubular structure of the TiO2 substrate provides an increased reaction area and facilitates the contact of electrolyte with the active MnO2 material. This work justified the suitability of using the TiO2 nanotube arrays for constructing high-performance supercapacitors.

The fabrication of white light-emitting diodes using the n-ZnO/NiO/p-GaN heterojunction with enhanced luminescence.

PubMed

Abbasi, Mazhar Ali; Ibupoto, Zafar Hussain; Hussain, Mushtaque; Nur, Omer; Willander, Magnus

2013-07-13

Cheap and efficient white light-emitting diodes (LEDs) are of great interest due to the energy crisis all over the world. Herein, we have developed heterojunction LEDs based on the well-aligned ZnO nanorods and nanotubes on the p-type GaN with the insertion of the NiO buffer layer that showed enhancement in the light emission. Scanning electron microscopy have well demonstrated the arrays of the ZnO nanorods and the proper etching into the nanotubes. X-ray diffraction study describes the wurtzite crystal structure array of ZnO nanorods with the involvement of GaN at the (002) peak. The cathodoluminescence spectra represent strong and broad visible emission peaks compared to the UV emission and a weak peak at 425 nm which is originated from GaN. Electroluminescence study has shown highly improved luminescence response for the LEDs fabricated with NiO buffer layer compared to that without NiO layer. Introducing a sandwich-thin layer of NiO between the n-type ZnO and the p-type GaN will possibly block the injection of electrons from the ZnO to the GaN. Moreover, the presence of NiO buffer layer might create the confinement effect.

Channel length scaling behavior in transistors based on individual versus dense arrays of carbon nanotubes

NASA Astrophysics Data System (ADS)

Brady, Gerald J.; Jinkins, Katherine R.; Arnold, Michael S.

2017-09-01

Recent advances in the solution-phase sorting and assembly of semiconducting single-walled carbon nanotubes (SWCNTs) have enabled significant gains in the performance of field-effect transistors (FETs) constructed from dense arrays of aligned SWCNTs. However, the channel length (LCH) downscaling behaviors of these arrays, which contain some organizational disorder (i.e., rotational misalignment and non-uniform pitch), have not yet been studied in detail below LCH of 100 nm. This study compares the behaviors of individualized SWCNTs with arrays of aligned, solution-cast SWCNTs in FETs with LCH ranging from 30 to 240 nm. The on-state conductance of both individual and array SWCNTs rises with decreasing LCH. Nearly ballistic transport is observed for LCH < 40 nm in both cases, reaching a conductance of 0.82 Go per SWCNT in arrays, where Go = 2e2/h is the quantum conductance. In the off-state, the off-current and subthreshold swing of the individual SWCNTs remain nearly invariant with decreasing LCH whereas array SWCNT FETs suffer from increasing off-state current and deteriorating subthreshold swing for LCH below 100 nm. We analyze array disorder using atomic force microscopy, which shows that crossing SWCNTs that arise from misoriented alignment raise SWCNTs off of the substrate for large portions of the channel when LCH is small. Electrostatics modeling analysis indicates that these raised SWCNTs are a likely contributor to the deteriorating off-current and subthreshold characteristics of arrays. These results demonstrate that improved inter-SWCNT pitch uniformity and alignment with minimal inter-SWCNT interactions will be necessary in order for solution processed SWCNT arrays to reach subthreshold performance on par with isolated SWCNTs. These results are also promising because they show that arrays of solution-processed SWCNTs can nearly reach ballistic conductance in the on-state despite imperfections in pitch and alignment.

Self-Organized TiO₂-MnO₂ Nanotube Arrays for Efficient Photocatalytic Degradation of Toluene.

PubMed

Nevárez-Martínez, María C; Kobylański, Marek P; Mazierski, Paweł; Wółkiewicz, Jolanta; Trykowski, Grzegorz; Malankowska, Anna; Kozak, Magda; Espinoza-Montero, Patricio J; Zaleska-Medynska, Adriana

2017-03-31

Vertically oriented, self-organized TiO₂-MnO₂ nanotube arrays were successfully obtained by one-step anodic oxidation of Ti-Mn alloys in an ethylene glycol-based electrolyte. The as-prepared samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD), and micro-Raman spectroscopy. The effect of the applied potential (30-50 V), manganese content in the alloy (5-15 wt. %) and water content in the electrolyte (2-10 vol. %) on the morphology and photocatalytic properties was investigated for the first time. The photoactivity was assessed in the toluene removal reaction under visible light, using low-powered LEDs as an irradiation source (λ max = 465 nm). Morphology analysis showed that samples consisted of auto-aligned nanotubes over the surface of the alloy, their dimensions were: diameter = 76-118 nm, length = 1.0-3.4 μm and wall thickness = 8-11 nm. It was found that the increase in the applied potential led to increase the dimensions while the increase in the content of manganese in the alloy brought to shorter nanotubes. Notably, all samples were photoactive under the influence of visible light and the highest degradation achieved after 60 min of irradiation was 43%. The excitation mechanism of TiO₂-MnO₂ NTs under visible light was presented, pointing out the importance of MnO₂ species for the generation of e - and h⁺.

Vertically aligned carbon nanotube arrays as thermal interface material for vibrational structure of piezoelectric transformer

NASA Astrophysics Data System (ADS)

Chen, Lie; Ju, Bin; Feng, Zhihua; Zhao, Yang

2018-07-01

The application and characterization of thermal interface material (TIM) for vibrational structures is investigated in this paper. The vibrating feature during the operation requires unique solution for its thermal management, since the connection between the device and heat dissipater should be able to conduct heat efficiently and impose minimum constraint onto the vibration simultaneously. As a typical vibrational device, piezoelectric transformers (PTs) are discussed in this paper. The PTs have urgent demands for thermal dissipation since their power conversion efficiency decrease rapidly with the rising temperature. A novel method by applying vertically aligned carbon nanotube (VACNT) arrays to the interface between PT and heat dissipater is presented to enhance the performance of piezoelectric transformers. VACNT arrays are one of the excellent TIMs. It can directly establish thermal contact between two surfaces by van der Waals’ forces. In addition, the unique anisotropic character of CNT arrays provides enough flexibility to accommodate the vibration during the operation. Different configurations of TIMs are compared with each other in this work, including CNT arrays, tape of polypropylene (PP) membrane and without heat transfer structure (HTS). The results indicate that the temperature rise is lowest and the efficiency is highest at the same power density while CNT arrays served as the TIM. Almost no significant fretting and wearing damage occurred on PT electrode surface with CNT arrays TIM even after working continuously for 120 days. Meanwhile, the thermo-physical properties of CNT arrays at contact interface are measured by optical transient thermo-reflectance technique.

Electrical device fabrication from nanotube formations

DOEpatents

Nicholas, Nolan Walker; Kittrell, W. Carter; Kim, Myung Jong; Schmidt, Howard K.

2013-03-12

A method for forming nanotube electrical devices, arrays of nanotube electrical devices, and device structures and arrays of device structures formed by the methods. Various methods of the present invention allow creation of semiconducting and/or conducting devices from readily grown SWNT carpets rather than requiring the preparation of a patterned growth channel and takes advantage of the self-controlling nature of these carpet heights to ensure a known and controlled channel length for reliable electronic properties as compared to the prior methods.

Field emission from optimized structure of carbon nanotube field emitter array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chouhan, V., E-mail: vchouhan@post.kek.jp, E-mail: vijaychouhan84@gmail.com; Noguchi, T.; Kato, S.

The authors report a detail study on the emission properties of field emitter array (FEA) of micro-circular emitters of multiwall carbon nanotubes (CNTs). The FEAs were fabricated on patterned substrates prepared with an array of circular titanium (Ti) islands on titanium nitride coated tantalum substrates. CNTs were rooted into these Ti islands to prepare an array of circular emitters. The circular emitters were prepared in different diameters and pitches in order to optimize their structure for acquiring a high emission current. The pitch was varied from 0 to 600 μm, while a diameter of circular emitters was kept constant to bemore » 50 μm in order to optimize a pitch. For diameter optimization, a diameter was changed from 50 to 200 μm while keeping a constant edge-to-edge distance of 150 μm between the circular emitters. The FEA with a diameter of 50 μm and a pitch of 120 μm was found to be the best to achieve an emission current of 47 mA corresponding to an effective current density of 30.5 A/cm{sup 2} at 7 V/μm. The excellent emission current was attributed to good quality of CNT rooting into the substrate and optimized FEA structure, which provided a high electric field on a whole circular emitter of 50 μm and the best combination of the strong edge effect and CNT coverage. The experimental results were confirmed with computer simulation.« less

Formation, transformation and superhydrophobicity of compound surfactant-assisted aligned ZnO nanoplatelets

NASA Astrophysics Data System (ADS)

Xue, Mingshan; Xu, Tao; Xie, Xiaolin; Ou, Junfei; Wang, Fajun; Li, Wen

2015-11-01

Synthesis and understanding of hierarchically nanostructured materials are significant for exploring peculiar functional properties and underlying applications. In this study, the self-assembly formation and detailed transformation process of ZnO nanoplatelets grown by hydrothermal methods with the addition of compound surfactants (CTAB and Tween-20) have been investigated. The initial growth of ZnO nanoplatelets as well as the subsequent formation of bilayer nanorod arrays and divergent nanocone arrays on the surface and side face of these nanoplatelets were found. Compared with the formation of bulk/block crystals without the case of surfactants, the addition of compound surfactants into zinc nitrate solution is responsible for the self-assembly processes of ZnO because of the effective role of CTAB in decreasing the degree of crystallinity and the positive effect of Tween-20 on decreasing the particle size owing to the space hindered effect. As-formed hierarchically micro-nanostructured ZnO exhibits superhydrophobicity without any chemical modification, which can make water droplets suspend on the air film trapped between the nanoplatelet and nanoplatelet as well as between nanocone and nanocone.

Interfacial effects in ZnO nanotubes/needle-structured graphitic diamond nanohybrid for detecting dissolved acetone at room temperature

NASA Astrophysics Data System (ADS)

Kathiravan, Deepa; Huang, Bohr-Ran; Saravanan, Adhimoorthy; Yeh, Chien-Jui; Leou, Keh-Chyang; Lin, I.-Nan

2017-12-01

A high-performance ZnO nanotubes (ZNTs)/needle-structured graphitic diamond (NGD) nanohybrid material was prepared and observed the electrochemical sensing properties of liquid acetone in water. Initially, we synthesized NGD film using bias-enhanced growth (BEG) process. Afterwards, a well-etched ZNTs were spatially grown on the NGD film using simple hydrothermal method, and utilized as sensing material for assemble an electrochemical sensor (via EGFET configuration) operating at room temperature. The systematic investigations depict the ultra-high sensing properties attained from ZNTs grown on NGD film. The NGD film mostly have needle or wire shaped diamond grains, which contributes extremely high electrical conductivity. Furthermore, needle shaped diamond grains cover with multi-layer graphitic material generates conduction channels for ZNTs and leads to enhance the oxygen residuals and species. The material stability and conductivity of NGD as well the defects exist with oxygen vacancies in ZNTs offers superior sensing properties. Thus, the interesting combination of these wide band gap semiconductor materials exhibit high sensor response (89 mV/mL), high stability and long-term reliability (tested after 60 days).

Buckling failure of square ice-nanotube arrays constrained in graphene nanocapillaries.

PubMed

Zhu, YinBo; Wang, FengChao; Wu, HengAn

2016-08-07

Graphene confinement provides a new physical and mechanical environment with ultrahigh van der Waals pressure, resulting in new quasi-two-dimensional phases of few-layer ice. Polymorphic transition can occur in bilayer constrained water/ice system. Here, we perform a comprehensive study of the phase transition of AA-stacked bilayer water constrained within a graphene nanocapillary. The compression-limit and superheating-limit (phase) diagrams are obtained, based on the extensive molecular-dynamics simulations at numerous thermodynamic states. Liquid-to-solid, solid-to-solid, and solid-to-liquid-to-solid phase transitions are observed in the compression and superheating of bilayer water. Interestingly, there is a temperature threshold (∼275 K) in the compression-limit diagram, which indicates that the first-order and continuous-like phase transitions of bilayer water depend on the temperature. Two obviously different physical processes, compression and superheating, display similar structural evolution; that is, square ice-nanotube arrays (BL-VHDI) will bend first and then transform into bilayer triangular AA stacking ice (BL-AAI). The superheating limit of BL-VHDI exhibits local maxima, while that of BL-AAI increases monotonically. More importantly, from a mechanics point of view, we propose a novel mechanism of the transformation from BL-VHDI to BL-AAI, both for the compression and superheating limits. This structural transformation can be regarded as the "buckling failure" of the square-ice-nanotube columns, which is dominated by the lateral pressure.

Buckling failure of square ice-nanotube arrays constrained in graphene nanocapillaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, YinBo; Wang, FengChao, E-mail: wangfc@ustc.edu.cn; Wu, HengAn

Graphene confinement provides a new physical and mechanical environment with ultrahigh van der Waals pressure, resulting in new quasi-two-dimensional phases of few-layer ice. Polymorphic transition can occur in bilayer constrained water/ice system. Here, we perform a comprehensive study of the phase transition of AA-stacked bilayer water constrained within a graphene nanocapillary. The compression-limit and superheating-limit (phase) diagrams are obtained, based on the extensive molecular-dynamics simulations at numerous thermodynamic states. Liquid-to-solid, solid-to-solid, and solid-to-liquid-to-solid phase transitions are observed in the compression and superheating of bilayer water. Interestingly, there is a temperature threshold (∼275 K) in the compression-limit diagram, which indicates thatmore » the first-order and continuous-like phase transitions of bilayer water depend on the temperature. Two obviously different physical processes, compression and superheating, display similar structural evolution; that is, square ice-nanotube arrays (BL-VHDI) will bend first and then transform into bilayer triangular AA stacking ice (BL-AAI). The superheating limit of BL-VHDI exhibits local maxima, while that of BL-AAI increases monotonically. More importantly, from a mechanics point of view, we propose a novel mechanism of the transformation from BL-VHDI to BL-AAI, both for the compression and superheating limits. This structural transformation can be regarded as the “buckling failure” of the square-ice-nanotube columns, which is dominated by the lateral pressure.« less

Vertically Aligned Carbon Nanotube Arrays as Efficient Supports for Faradaic Capacitive Electrodes

NASA Astrophysics Data System (ADS)

Oguntoye, Moses; Holleran, Mary-Kate; Roberts, Katherine; Pesika, Noshir

Supercapacitors are notable for their ability to deliver energy at higher power (compared to batteries) and store energy at higher density (compared to capacitors) as well as exhibit a long cycle life. In our efforts to further the development of supercapacitors, our focus is on using vertically aligned carbon nanotubes (VACNT) as supports for faradaic capacitive electrode materials. The objective is to develop electrodes functioning in an inexpensive aqueous environment with small potential windows, that store energy at a higher density than carbon materials alone. We describe the different approaches explored to overcome the challenges of non-uniform deposition, poor wetting and array collapse. Materials that are electrochemically anchored to VACNT supports include NiCo2O4, VOx, Fe2O3 and Co-Mn mixed oxides. In each case, the specific capacitance obtained using the VACNT arrays as supports is significantly more than that obtained by direct deposition onto current collectors or by using VACNT alone. The ease of VACNT growth and the degree of coating control achievable using electrodeposition means there is much potential in exploring them as supports for capacitive electrode materials.

Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array

NASA Astrophysics Data System (ADS)

Fedoseeva, Yu. V.; Bulusheva, L. G.; Okotrub, A. V.; Kanygin, M. A.; Gorodetskiy, D. V.; Asanov, I. P.; Vyalikh, D. V.; Puzyr, A. P.; Bondar, V. S.

2015-03-01

Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT-ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of CNTs in the hybrid were revealed. We showed that current-voltage characteristics of the CNT-ND cathode are changed depending on the applied field; below ~3 V/µm they are similar to those of the initial CNT array and at the higher field they are close to the ND behavior. Involvement of the NDs in field emission process resulted in blue luminescence of the hybrid surface at an electric field higher than 3.5 V/µm. Photoluminescence measurements showed that the NDs emit blue-green light, while blue luminescence prevails in the CNT-ND hybrid. The quenching of green luminescence was attributed to a partial removal of oxygen-containing groups from the ND surface as the result of the hybrid synthesis.

Shape-coded silica nanotubes for multiplexed bioassay: rapid and reliable magnetic decoding protocols

PubMed Central

He, Bo; Kim, Sung Kyoung; Son, Sang Jun; Lee, Sang Bok

2010-01-01

Aims The recent development of 1D barcode arrays has proved their capabilities to be applicable to highly multiplexed bioassays. This article introduces two magnetic decoding protocols for suspension arrays of shape-coded silica nanotubes to process multiplexed assays rapidly and easily, which will benefit the minimization and automation of the arrays. Methods In the first protocol, the magnetic nanocrystals are incorporated into the inner voids of barcoded silica nanotubes in order to give the nanotubes magnetic properties. The second protocol is performed by trapping the barcoded silica nanotubes onto streptavidin-modified magnetic beads. Results The rapid and easy decoding process was demonstrated by applying the above two protocols to multiplexed assays, resulting in high selectivity. Furthermore, the magnetic bead-trapped barcode nanotubes provided a great opportunity to exclude the use of dye molecules in multiplexed assays by using barcode nanotubes as signals. Conclusion The rapid and easy manipulation of encoded carriers using magnetic properties could be used to develop promising suspension arrays for portable bioassays. PMID:20025466

MoSe2 modified TiO2 nanotube arrays with superior photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Zhang, Yaping; Zhu, Haifeng; Yu, Lianqing; He, Jiandong; Huang, Chengxing

2018-04-01

TiO2 nanotube arrays (TNTs) are first prepared by anodization Ti foils in ethylene glycol electrolyte. Then, MoSe2 deposites electrochemically on TNTs. The as-synthesized MoSe2/TiO2 composite has a much higher photocurrent density of 1.07 mA cm‑2 at 0 V than pure TNTs of 0.38 mA cm‑2, which suggests that the MoSe2/TiO2 composite film has optimum photoelectrocatalysis properties. The electron transport resistances of the MoSe2/TiO2 decreases to half of pure TiO2, at 295.6 ohm/cm2. Both photocurrent-time and Mott-Schottky plots indicate MoSe2 a p-type semiconductor characteristics. MoSe2/TiO2 composite can achieve a maximum 5 orders of magnitude enhancement in carrier density (4.650 × 1027 cm‑3) than that of pure TiO2 arrays. It can be attributed to p-n heterojunction formed between MoSe2 and TiO2, and the composite can be potentially applied in photoelectrochemical, photocatalysis fields.

Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O

NASA Astrophysics Data System (ADS)

Debgupta, Joyashish; Devarapalli, Ramireddy; Rahman, Shakeelur; Shelke, Manjusha V.; Pillai, Vijayamohanan K.

2014-07-01

Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, ``as grown'' CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ~470 μA cm-2) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2O on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers.Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, ``as grown'' CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ~470 μA cm-2) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar

High intensity, plasma-induced electron emission from large area carbon nanotube array cathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao Qingliang; Yang Ya; Qi Junjie

2010-02-15

The plasma-induced electron emission properties of large area carbon nanotube (CNT) array cathodes under different pulse electric fields were investigated. The formation and expansion of cathode plasmas were proved; in addition, the cathodes have higher emission current in the double-pulse mode than that in the single-pulse mode due to the expansion of plasma. Under the double-pulse electric field of 8.16 V/mum, the plasma's expansion velocity is about 12.33 cm/mus and the highest emission current density reached 107.72 A/cm{sup 2}. The Cerenkov radiation was used to diagnose the distribution of electron beams, and the electron beams' generating process was plasma-induced emission.

Fast diffusion of silver in TiO2 nanotube arrays

PubMed Central

Zhang, Wanggang; Liu, Yiming; Zhou, Diaoyu; Wang, Hui

2016-01-01

Summary Using magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10−18 m2/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag. PMID:27547630

Parametric Investigation of the Kinetics of Growth of Carbon-Nanotube Arrays on Iron Nanoparticles in the Process of Chemical Vapor Deposition of Hydrocarbons

NASA Astrophysics Data System (ADS)

Futko, S. I.; Shulitski, B. G.; Labunov, V. A.; Ermolaevaa, E. M.

2015-03-01

On the basis of the kinetic model of synthesis of carbon nanotubes on iron nanoparticles in the process of chemical vapor deposition of hydrocarbons, the parametric dependences of characteristics of arrays of vertically oriented nanotubes on the temperature of their synthesis, the concentration of acetylene in a reactor, and the diameter of the catalyst nanoparticles were investigated. It is shown that the maximum on the temperature dependence of the rate of growth of carbon nanotubes, detected in experiments at a temperature of ~700oC is due to the competing processes of increasing the catalytic activity of iron nanoparticles and decreasing the acetylene concentration because of the signifi cant gas-phase decomposition of acetylene in the reactor before it enters the substrate with the catalyst. Our calculations have shown that the indicated maximum arises near the transition point separating the low-temperature region where multiwall nanotubes are predominantly synthesized from the higher-temperature region of generation of single-wall nanotubes in the process of chemical vapor deposition of hydrocarbons.

Controlling Morphological Parameters of Anodized Titania Nanotubes for Optimized Solar Energy Applications

PubMed Central

Haring, Andrew; Morris, Amanda; Hu, Michael

2012-01-01

Anodized TiO2 nanotubes have received much attention for their use in solar energy applications including water oxidation cells and hybrid solar cells [dye-sensitized solar cells (DSSCs) and bulk heterojuntion solar cells (BHJs)]. High surface area allows for increased dye-adsorption and photon absorption. Titania nanotubes grown by anodization of titanium in fluoride-containing electrolytes are aligned perpendicular to the substrate surface, reducing the electron diffusion path to the external circuit in solar cells. The nanotube morphology can be optimized for the various applications by adjusting the anodization parameters but the optimum crystallinity of the nanotube arrays remains to be realized. In addition to morphology and crystallinity, the method of device fabrication significantly affects photon and electron dynamics and its energy conversion efficiency. This paper provides the state-of-the-art knowledge to achieve experimental tailoring of morphological parameters including nanotube diameter, length, wall thickness, array surface smoothness, and annealing of nanotube arrays.

In situ formation of a ZnO/ZnSe nanonail array as a photoelectrode for enhanced photoelectrochemical water oxidation performance

NASA Astrophysics Data System (ADS)

Wang, Liyang; Tian, Guohui; Chen, Yajie; Xiao, Yuting; Fu, Honggang

2016-04-01

In this study, a ZnO/ZnSe nanonail array was prepared via a two-step sequential hydrothermal synthetic route. In this synthetic process, the ZnO nanorod array was first grown on a fluorine-doped tin oxide (FTO) substrate using a seed-mediated growth approach via the hydrothermal process. Then, the ZnO nanonail array was obtained via in situ growth of ZnSe nano caps onto the ZnO nanorod array via a hydrothermal process in the presence of a Se source. The surface morphology and amount of ZnSe grown on the surface of the ZnO nanorods can be regulated by varying the reaction time and reactant concentration. Compared with pure ZnO nanorods, this unique nanonail array heterostructure exhibits enhanced visible light absorption. The transient photocurrent condition, in combination with steady-state and time-resolved photoluminescence spectroscopy, reveals that the ZnO/ZnSe nanonail array electrode has the highest charge separation rate, highest electron injection efficiency, and highest chemical stability. The photocurrent density of the ZnO/ZnSe nanonail array heterostructure reaches 1.01 mA cm-2 at an applied potential of 0.1 V (vs. Ag/AgCl), which is much higher than that of the ZnO/ZnSe nanorod array (0.71 mA cm-2), the pristine ZnO nanorod array (0.39 mA cm-2), and the ZnSe electrode (0.21 mA cm-2), indicating its significant visible light driven activities for photoelectrochemical water oxidation. This unique morphology of nail-capped nanorods might be important for providing better insight into the correlation between heterostructure and photoelectrochemical activity.In this study, a ZnO/ZnSe nanonail array was prepared via a two-step sequential hydrothermal synthetic route. In this synthetic process, the ZnO nanorod array was first grown on a fluorine-doped tin oxide (FTO) substrate using a seed-mediated growth approach via the hydrothermal process. Then, the ZnO nanonail array was obtained via in situ growth of ZnSe nano caps onto the ZnO nanorod array via a

Influence of the applied potentials difference on structural and conductive properties of CoZnO nanotubes

NASA Astrophysics Data System (ADS)

Ibragimova, M. A.; Kozlovskiy, A. L.; Kenzhina, I. E.; Zdorovets, M. V.

2018-04-01

A series of CoZnO nanotubes was obtained by electrochemical deposition, with different atomic metal coefficients, due to a change in the applied potential difference. A systematic study of the morphology, structural and conductive properties of nanotubes was also carried out. It is established that the samples synthesized at the applied potentials difference of 1.5 and 1.75 V are three-component systems consisting of two oxide phases of ZnO and CoO1.92 cubic system and a phase of a solid solution of substitution Co0.65Zn0.35 of hexagonal type. The samples synthesized at a potential difference of 2.0 V represent an alloy of two oxide phases, ZnO and CoO1.92.

Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C.S.

We report for the first time a rapid preparation of Zn{sub 1−2x}Co{sub x}Ni{sub x}O nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green–orange–red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemicalmore » experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO. - Graphical abstract: Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: optical and electrochemical properties. Co, Ni co-doped ZnO hexagonal nanoparticles with optical and electrocatalytic properties were successfully prepared for the first time using a microwave hydrothermal method at mild conditions. - Highlights: • Co{sup 2+} and Ni{sup 2+} into ZnO lattice obtained a mild and environmentally friendly process. • The heating method strongly influences in the growth and shape of the particles. • Short-range defects generated by the ions insertion affects the photoluminescence. • Doped ZnO nanoparticles improve the electrocatalytic properties of pure oxide.« less

Template-based synthesis and magnetic properties of Mn-Zn ferrite nanotube and nanowire arrays

NASA Astrophysics Data System (ADS)

Guo, Limin; Wang, Xiaohui; Zhong, Caifu; Li, Longtu

2012-01-01

Template-based electrophoretic deposition of Mn-Zn ferrite nanotubes (NTs) and nanowires (NWs) were achieved using anodic alumina oxide (AAO) membranes. The effect of electrophoretic current and deposition time on the morphology of the tubes was investigated. The samples show cubic spinel structure with no preferred orientation. Room-temperature magnetic properties of the Mn-Zn ferrite NT/NW arrays were studied. The magnetic easy axis parallels the NT/NW's channel axis attributing to the large shape anisotropy in this direction, especially for the NTs with a small wall thickness. Magnetocrystalline anisotropy and magnetostatic interactions were found dominant in the samples when applied field was perpendicular to the channel axis.

Controlled Growth of Carbon Nanotubes on Micropatterned Au/Cr Composite Film and Field Emission from Their Arrays

NASA Astrophysics Data System (ADS)

Kamide, Koichi; Araki, Hisashi; Yoshino, Katsumi

2003-12-01

Carbon nanotube (CNT) arrays with a controlled density are prepared on a micropatterned Au/Cr composite film formed on a quartz glass plate by pyrolysis of Ni-phthalocyanine at 800°C. It is clarified from characteristic X-ray analyses for those samples that a catalytic Ni nanoparticle is not contained within the base of the whisker-like CNT in contrast to that of the bamboo-like CNT, suggesting that the growth process of the present novel CNT is incompatible with that of the bamboo-like CNT. In the Au/Cr composite film, both the Cr atomic content of approximately 30% and the presence of the Ni catalyst devoid of a particle-like shape are important factors for the growth of CNTs. Field emission from the novel CNT arrays exhibits a lower turn-on voltage and a higher current density compared with that from the bamboo-like arrays formed on a quartz plate.

Enhanced performance of dye-sensitized solar cell using Bi2Te3 nanotube/ZnO nanoparticle composite photoanode by the synergistic effect of photovoltaic and thermoelectric conversion

NASA Astrophysics Data System (ADS)

Dou, Yuanyao; Wu, Fang; Fang, Liang; Liu, Gaobin; Mao, Caiying; Wan, Kai; Zhou, Miao

2016-03-01

Ultralong and highly crystalline rhombohedral Bi2Te3 nanotubes were fabricated by a two-step solution phase reaction. A novel photoanode architecture has been fabricated by embedding 0-2.5 wt.% Bi2Te3 nanotubes into ZnO nanoparticles. The photocurrent density-voltage (J-V) characteristics reveal that the dye sensitized solar cells (DSSCs) with Bi2Te3/ZnO composite photoanode exhibit significantly enhanced photovoltaic performance. Notably, the DSSC incorporating 1.5 wt.% Bi2Te3 in the ZnO photoanode demonstrates an energy conversion efficiency (η) of 4.27%, which is 44.3% higher than that of the bare ZnO photoanode. The electrochemical impedance spectroscopy (EIS) analysis shows that the Bi2Te3 nanotubes can provide a direct pathway for electron transportation, prolong the lifetime of electrons, suppress the charge recombination and improve the electron collection efficiency. The thermoelectric effect analysis indicates that with the increase of irradiation time, Bi2Te3/ZnO composite photoanode could convert both heat and photon energies to electrical energy simultaneously and slow down the decline of η. The calculated electron density (ns) further proves that the increment of short-circuit current density (Jsc) is attributed to Seebeck effect in the composite photoanode. These results suggest that compositing 1D thermoelectric nano-materials in photoanode is a promising route to improve the performance of DSSCs.

Vertically aligned double wall carbon nanotube arrays adsorbent for pure and mixture adsorption of H2S, ethylbenzene and carbon monoxide, grand canonical Monte Carlo simulation.

PubMed

Tasharrofi, Saeideh; Taghdisian, Hossein; Golchoobi, Abdollah

2018-05-01

In this study, pure and ternary adsorption of hydrogen sulfide (H 2 S), ethylbenzene (EB), and carbon monoxide (CO) on different arrays of zigzag double wall carbon nanotube was investigated using grand canonical Monte Carlo simulations. The internal diameters of nanotube were fixed at 2r = 50.17 Å while nanotube wall distances were different values from d = 0 Å to d = 150 Å. Pure simulation results indicated that adsorption quantity of H 2 S and EB in low pressure ranges of P = 1.9 bar to P = 3.1 bar was at least 100% more than CO adsorption quantities. At high pressure ranges of P = 23.1 bar to P = 38.2 bar H 2 S adsorption was greater than EB and CO by about 200 molecules per unit cell (UC) at low nanotube distances. This was related to smaller kinetic diameter and greater dipole moment of H 2 S compared to EB and CO. At higher nanotube distance the effect of size however disappears and all three gases approach to adsorption quantity of about 800 molecules/UC. Graphical representation of adsorption areas showed that H 2 S and CO form multilayer adsorption around nanotube inner and outer walls while EB fill the whole space uniformly without any congestion around the walls. Ternary adsorption results EB/CO and H 2 S/CO selectivity are greater than EB/H 2 S selectivity. In addition, at smaller nanotube distances H 2 S/CO selectivity is generally higher than EB/CO selectivity, which at higher nanotube distance the order becomes revers suggesting that size dependent effects on adsorption vanishes. Isosteric heat of adsorption shows that the order of EB > H 2 S > CO suggesting that ethylbenzene interaction with nanotube arrays was strongest. Although H 2 S has a greater dipole moment and smaller molecular dimension, EB adsorption at higher nanotube distance is greater than H 2 S by at least 50% probably because EB is less volatile. Copyright © 2018 Elsevier Inc. All rights reserved.

Synthesis and Characterization of Doped ZnO Nanomaterials: Potential Application in Third Generation Solar Cells

NASA Astrophysics Data System (ADS)

Adcock Smith, Echo D.

ZnO nanomaterials are being incorporated into next-generation solar cell designs including dye-sensitized solar cells, multijunction solar cells, and quantum dot sensitized solar cells. ZnO nanorod (NR) arrays and nanoparticles (NP) used in these devices are typically fabricated using chemical vapor deposition and/or high-temperature reaction conditions. These methods are costly, require high energy, pressure or excessive time, but produce repeatable, defined growth that is capable of easily incorporating metal dopants. Less expensive methods of fabrication such as chemical bath deposition (CBD) eliminate the costly steps but can suffer from undefined growth, excessive waste and have a difficult time incorporating dopants into ZnO materials without additives or increased pH. This dissertation presents a novel method of growing cobalt and vanadium doped ZnO nanomaterials through microwave synthesis. The cobalt growth was compared to standard CBD and found to be faster, less wasteful, reproducible and better at incorporating cobalt ions into the ZnO lattice than typical oven CBD method. The vanadium doped ZnO microwave synthesis procedure was found to produce nanorods, nanorod arrays, and nanoparticles simultaneously. Neither the cobalt nor the vanadium growth required pH changes, catalysts or additives to assist in doping and therefore use less materials than traditional CBD. This research is important because it offers a simple, quick way to grow ZnO nanostructures and is the first to report on growing both cobalt and vanadium doped zinc oxide nanorod arrays using microwave synthesis. This synthesis method presented is a viable candidate for replacing conventional growth synthesis which will result in lowering the cost and time of production of photovoltaics while helping drive forward the development of next-generation solar cells.

Electrical properties of 0.4 cm long single walled nanotubes

NASA Astrophysics Data System (ADS)

Yu, Zhen

2005-03-01

Centimeter scale aligned carbon nanotube arrays are grown from nanoparticle/metal catalyst pads[1]. We find the nanotubes grow both with and ``against the wind.'' A metal underlayer provides in-situ electrical contact to these long nanotubes with no post growth processing needed. Using the electrically contacted nanotubes, we study electrical transport of 0.4 cm long nanotubes[2]. Using this data, we are able to determine the resistance of a nanotube as a function of length quantitatively, since the contact resistance is negligible in these long nanotubes. The source drain I-V curves are quantitatively described by a classical, diffusive model. Our measurements show that the outstanding transport properties of nanotubes can be extended to the cm scale and open the door to large scale integrated nanotube circuits with macroscopic dimensions. These are the longest electrically contacted single walled nanotubes measured to date. [1] Zhen Yu, Shengdong Li, Peter J. Burke, ``Synthesis of Aligned Arrays of Millimeter Long, Straight Single-Walled Carbon Nanotubes,'' Chemistry of Materials, 16(18), 3414-3416 (2004). [2] Shengdong Li, Zhen Yu, Christopher Rutherglen, Peter J. Burke, ``Electrical properties of 0.4 cm long single-walled carbon nanotubes'' Nano Letters, 4(10), 2003-2007 (2004).

Analysis of Multiplexed Nanosensor Arrays Based on Near-Infrared Fluorescent Single-Walled Carbon Nanotubes.

PubMed

Dong, Juyao; Salem, Daniel P; Sun, Jessica H; Strano, Michael S

2018-04-24

The high-throughput, label-free detection of biomolecules remains an important challenge in analytical chemistry with the potential of nanosensors to significantly increase the ability to multiplex such assays. In this work, we develop an optical sensor array, printable from a single-walled carbon nanotube/chitosan ink and functionalized to enable a divalent ion-based proximity quenching mechanism for transducing binding between a capture protein or an antibody with the target analyte. Arrays of 5 × 6, 200 μm near-infrared (nIR) spots at a density of ≈300 spots/cm 2 are conjugated with immunoglobulin-binding proteins (proteins A, G, and L) for the detection of human IgG, mouse IgM, rat IgG2a, and human IgD. Binding kinetics are measured in a parallel, multiplexed fashion from each sensor spot using a custom laser scanning imaging configuration with an nIR photomultiplier tube detector. These arrays are used to examine cross-reactivity, competitive and nonspecific binding of analyte mixtures. We find that protein G and protein L functionalized sensors report selective responses to mouse IgM on the latter, as anticipated. Optically addressable platforms such as the one examined in this work have potential to significantly advance the real-time, multiplexed biomolecular detection of complex mixtures.

CdTe quantum-dot-modified ZnO nanowire heterostructure

NASA Astrophysics Data System (ADS)

Shahi, Kanchana; Singh, R. S.; Singh, Ajaya Kumar; Aleksandrova, Mariya; Khenata, Rabah

2018-03-01

The effect of CdTe quantum-dot (QD) decoration on the photoluminescence (PL) behaviour of ZnO nanowire (NW) array is presented in the present work. Highly crystalline and vertically 40-50 nm diameter range and 1 µm in length aligned ZnO NWs are synthesized using low-cost method. The crystallinity and morphology of the NWs are studied by scanning electron microscopy and X-ray powder diffraction methods.Optical properties of the nanowires are studied using photo-response and PL spectroscopy. CdTe QDs are successfully synthesized on ZnO nanowire surface by dip-coating method. ZnO NWs are sensitized with CdTe QDs characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and PL spectroscopy. The highly quenched PL intensity indicates the charge transfer at interface between CdTe QDs and ZnO NWs and is due to the formation of type-II heterostructure between QDs and NWs. Photo-response behaviour of heterostructure of the film is also been incorporated in the present work.

Ophthalmologial Applications of Carbon Nanotube Nanotechology

NASA Technical Reports Server (NTRS)

Loftus, David; Girten, Beverly (Technical Monitor)

2002-01-01

The development of an implantable device consisting of an array of carbon nanotubes on a silicon chip for restoration of vision in patients with macular degeneration and other retinal disorders is presented. The use of carbon nanotube bucky paper for retinal cell transplantation is proposed. This paper is in viewgraph form.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition.

PubMed

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D; Renevier, Hubert; Consonni, Vincent

2017-03-03

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 10 7 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

NASA Astrophysics Data System (ADS)

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D.; Renevier, Hubert; Consonni, Vincent

2017-03-01

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscaleengineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol–gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on themore » macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscaleengineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.« less

Origin of luminescence from ZnO/CdS core/shell nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Wang, Jian; Sham, Tsun-Kong; Yang, Shaoguang

2014-07-01

Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little.Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the

Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs

PubMed Central

Brady, Gerald J.; Way, Austin J.; Safron, Nathaniel S.; Evensen, Harold T.; Gopalan, Padma; Arnold, Michael S.

2016-01-01

Carbon nanotubes (CNTs) are tantalizing candidates for semiconductor electronics because of their exceptional charge transport properties and one-dimensional electrostatics. Ballistic transport approaching the quantum conductance limit of 2G0 = 4e2/h has been achieved in field-effect transistors (FETs) containing one CNT. However, constraints in CNT sorting, processing, alignment, and contacts give rise to nonidealities when CNTs are implemented in densely packed parallel arrays such as those needed for technology, resulting in a conductance per CNT far from 2G0. The consequence has been that, whereas CNTs are ultimately expected to yield FETs that are more conductive than conventional semiconductors, CNTs, instead, have underperformed channel materials, such as Si, by sixfold or more. We report quasi-ballistic CNT array FETs at a density of 47 CNTs μm−1, fabricated through a combination of CNT purification, solution-based assembly, and CNT treatment. The conductance is as high as 0.46 G0 per CNT. In parallel, the conductance of the arrays reaches 1.7 mS μm−1, which is seven times higher than the previous state-of-the-art CNT array FETs made by other methods. The saturated on-state current density is as high as 900 μA μm−1 and is similar to or exceeds that of Si FETs when compared at and equivalent gate oxide thickness and at the same off-state current density. The on-state current density exceeds that of GaAs FETs as well. This breakthrough in CNT array performance is a critical advance toward the exploitation of CNTs in logic, high-speed communications, and other semiconductor electronics technologies. PMID:27617293

Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs.

PubMed

Brady, Gerald J; Way, Austin J; Safron, Nathaniel S; Evensen, Harold T; Gopalan, Padma; Arnold, Michael S

2016-09-01

Carbon nanotubes (CNTs) are tantalizing candidates for semiconductor electronics because of their exceptional charge transport properties and one-dimensional electrostatics. Ballistic transport approaching the quantum conductance limit of 2G 0 = 4e (2)/h has been achieved in field-effect transistors (FETs) containing one CNT. However, constraints in CNT sorting, processing, alignment, and contacts give rise to nonidealities when CNTs are implemented in densely packed parallel arrays such as those needed for technology, resulting in a conductance per CNT far from 2G 0. The consequence has been that, whereas CNTs are ultimately expected to yield FETs that are more conductive than conventional semiconductors, CNTs, instead, have underperformed channel materials, such as Si, by sixfold or more. We report quasi-ballistic CNT array FETs at a density of 47 CNTs μm(-1), fabricated through a combination of CNT purification, solution-based assembly, and CNT treatment. The conductance is as high as 0.46 G 0 per CNT. In parallel, the conductance of the arrays reaches 1.7 mS μm(-1), which is seven times higher than the previous state-of-the-art CNT array FETs made by other methods. The saturated on-state current density is as high as 900 μA μm(-1) and is similar to or exceeds that of Si FETs when compared at and equivalent gate oxide thickness and at the same off-state current density. The on-state current density exceeds that of GaAs FETs as well. This breakthrough in CNT array performance is a critical advance toward the exploitation of CNTs in logic, high-speed communications, and other semiconductor electronics technologies.

Self-Consistent Physical Properties of Carbon Nanotubes in Composite Materials

NASA Technical Reports Server (NTRS)

Pipes, R. B.; Frankland, S. J. V.; Hubert, P.; Saether, E.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

A set of relationships is developed for selected physical properties of single-walled carbon nanotubes (SWCN) and their hexagonal arrays as a function of nanotube size in terms of the chiral vector integer pair, (n,m). Properties include density, principal Young's modulus, and specific Young's modulus. Relationships between weight fraction and volume fraction of SWCN and their arrays are developed for polymeric mixtures.

Theory of Carbon Nanotube (CNT)-Based Electron Field Emitters

PubMed Central

Bocharov, Grigory S.; Eletskii, Alexander V.

2013-01-01

Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules. PMID:28348342

Ultra-fast microwave-assisted hydrothermal synthesis of long vertically aligned ZnO nanowires for dye-sensitized solar cell application.

PubMed

Mahpeykar, S M; Koohsorkhi, J; Ghafoori-Fard, H

2012-04-27

Long vertically aligned ZnO nanowire arrays were synthesized using an ultra-fast microwave-assisted hydrothermal process. Using this method, we were able to grow ZnO nanowire arrays at an average growth rate as high as 200 nm min(-1) for maximum microwave power level. This method does not suffer from the growth stoppage problem at long growth times that, according to our investigations, a normal microwave-assisted hydrothermal method suffers from. Longitudinal growth of the nanowire arrays was investigated as a function of microwave power level and growth time using cross-sectional FESEM images of the grown arrays. Effect of seed layer on the alignment of nanowires was also studied. X-ray diffraction analysis confirmed c-axis orientation and single-phase wurtzite structure of the nanowires. J-V curves of the fabricated ZnO nanowire-based mercurochrome-sensitized solar cells indicated that the short-circuit current density is increased with increasing the length of the nanowire array. According to the UV-vis spectra of the dyes detached from the cells, these increments were mainly attributed to the enlarged internal surface area and therefore dye loading enhancement in the lengthened nanowire arrays.

Vertically-aligned BCN Nanotube Arrays with Superior Performance in Electrochemical capacitors

PubMed Central

Zhou, Junshuang; Li, Na; Gao, Faming; Zhao, Yufeng; Hou, Li; Xu, Ziming

2014-01-01

Electrochemical capacitors (EC) have received tremendous interest due to their high potential to satisfy the urgent demand in many advanced applications. The development of new electrode materials is considered to be the most promising approach to enhance the EC performance substantially. Herein, we present a high-capacity capacitor material based on vertically-aligned BC2N nanotube arrays (VA-BC2NNTAs) synthesized by low temperature solvothermal route. The obtained VA-BC2NNTAs display the good aligned nonbuckled tubular structure, which could indeed advantageously enhance capacitor performance. VA-BC2NNTAs exhibit an extremely high specific capacitance, 547 Fg−1, which is about 2–6 times larger than that of the presently available carbon-based materials. Meanwhile, VA-BC2NNTAs maintain an excellent rate capability and high durability. All these characteristics endow VA-BC2NNTAs an alternative promising candidate for an efficient electrode material for electrochemical capacitors (EC). PMID:25124300

Effect of annealing temperature on the photoluminescence and scintillation properties of ZnO nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurudirek, Sinem V.; Menkara, H.; Klein, Benjamin D. B.

2018-01-01

The effect of the annealing to enhance the photoluminescence (PL) and scintillation properties, as determined by pulse height distribution of alpha particle irradiation, has been investigated for solution grown ZnO nanorods For this investigation the ZnO nanorod arrays were grown on glass for 22 h at 95 ◦ C as a substrate using a solution based hydrothermal technique. The samples were first annealed for different times (30, 60, 90 and 120 min) at 300 ◦ C and then at different temperatures (100 ◦ C–600 ◦ C) in order to determine the optimum annealing time and temperature, respectively. Before annealing, themore » ZnO nanorod arrays showed a broad yellow–orange visible and near-band gap UV emission peaks. After annealing in a forming gas atmosphere, the intensity of the sub-band gap PL was significantly reduced and the near-band gap PL emission intensity correspondingly increased (especially at temperatures higher than 100 ◦ C). Based on the ratio of the peak intensity ratio before and after annealing, it was concluded that samples at 350 ◦ C for 90 min resulted in the best near-band gap PL emission. Similarly, the analysis of the pulse height spectrum resulting from alpha particles revealed that ZnO nanorod arrays similarly annealed at 350 ◦ C for 90 min exhibited the highest scintillation response.« less

Carbon-Nanotube-Based Electrodes for Biomedical Applications

NASA Technical Reports Server (NTRS)

Li, Jun; Meyyappan, M.

2008-01-01

A nanotube array based on vertically aligned nanotubes or carbon nanofibers has been invented for use in localized electrical stimulation and recording of electrical responses in selected regions of an animal body, especially including the brain. There are numerous established, emerging, and potential applications for localized electrical stimulation and/or recording, including treatment of Parkinson s disease, Tourette s syndrome, and chronic pain, and research on electrochemical effects involved in neurotransmission. Carbon-nanotube-based electrodes offer potential advantages over metal macroelectrodes (having diameters of the order of a millimeter) and microelectrodes (having various diameters ranging down to tens of microns) heretofore used in such applications. These advantages include the following: a) Stimuli and responses could be localized at finer scales of spatial and temporal resolution, which is at subcellular level, with fewer disturbances to, and less interference from, adjacent regions. b) There would be less risk of hemorrhage on implantation because nano-electrode-based probe tips could be configured to be less traumatic. c) Being more biocompatible than are metal electrodes, carbon-nanotube-based electrodes and arrays would be more suitable for long-term or permanent implantation. d) Unlike macro- and microelectrodes, a nano-electrode could penetrate a cell membrane with minimal disruption. Thus, for example, a nanoelectrode could be used to generate an action potential inside a neuron or in proximity of an active neuron zone. Such stimulation may be much more effective than is extra- or intracellular stimulation via a macro- or microelectrode. e) The large surface area of an array at a micron-scale footprint of non-insulated nanoelectrodes coated with a suitable electrochemically active material containing redox ingredients would make it possible to obtain a pseudocapacitance large enough to dissipate a relatively large amount of electric charge

Carbon nanotube diameter selection by pretreatment of metal catalysts on surfaces

DOEpatents

Hauge, Robert H [Houston, TX; Xu, Ya-Qiong [Houston, TX; Shan, Hongwei [Houston, TX; Nicholas, Nolan Walker [South Charleston, WV; Kim, Myung Jong [Houston, TX; Schmidt, Howard K [Cypress, TX; Kittrell, W Carter [Houston, TX

2012-02-28

A new and useful nanotube growth substrate conditioning processes is herein disclosed that allows the growth of vertical arrays of carbon nanotubes where the average diameter of the nanotubes can be selected and/or controlled as compared to the prior art.

Interesting properties of ferroelectric Pb(Zr0.5Ti0.5)O3 nanotube array embedded in matrix medium

NASA Astrophysics Data System (ADS)

Adhikari, Rajendra; Fu, Huaxiang

2013-07-01

Finite-temperature first-principles based simulations are used to determine the structural and polarization properties of ferroelectric Pb(Zr0.5Ti0.5)O3 (PZT) nanotube array embedded in matrix medium of different ferroelectric strengths. Various interesting properties are found, including (i) that the system can behave either 3D-like, or 2D-like, or 1D-like; and (ii) the existence of an unusual structural phase in which 180° stripe domain coexists with vortex. Furthermore, we show in PZT tube array that a vortex phase can spontaneously transform into a ferroelectric phase of polarization by temperature alone, without applying external electric fields. Microscopic insights for understanding these properties are provided.

Bias-polarity-dependent UV/visible transferable electroluminescence from ZnO nanorod array LED with graphene oxide electrode supporting layer

NASA Astrophysics Data System (ADS)

Liu, Weizhen; Wang, Wei; Xu, Haiyang; Li, Xinghua; Yang, Liu; Ma, Jiangang; Liu, Yichun

2015-09-01

A simple top electrode preparation process, employing continuous graphene oxide films as electrode supporting layers, was adopted to fabricate a ZnO nanorod array/p-GaN heterojunction LED. The achieved LED demonstrated different electroluminescence behaviors under forward and reverse biases: a yellow-red emission band was observed under forward bias, whereas a blue-UV emission peak was obtained under reverse bias. Electroluminescence spectra under different currents and temperatures, as well as heterojunction energy-band alignments, reveal that the yellow-red emission under forward bias originates from recombinations related to heterointerface defects, whereas the blue-UV electroluminescence under reverse bias is ascribed to transitions from near-band-edge and Mg-acceptor levels in p-GaN.

Carbon Nanotube Interconnect

NASA Technical Reports Server (NTRS)

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2006-01-01

Method and system for fabricating an electrical interconnect capable of supporting very high current densities ( 10(exp 6)-10(exp 10) Amps/sq cm), using an array of one or more carbon nanotubes (CNTs). The CNT array is grown in a selected spaced apart pattern, preferably with multi-wall CNTs, and a selected insulating material, such as SiOw, or SiuNv is deposited using CVD to encapsulate each CNT in the array. An exposed surface of the insulating material is planarized to provide one or more exposed electrical contacts for one or more CNTs.

Fluidic nanotubes and devices

DOEpatents

Yang, Peidong [Berkeley, CA; He, Rongrui [El Cerrito, CA; Goldberger, Joshua [Berkeley, CA; Fan, Rong [El Cerrito, CA; Wu, Yiying [Albany, CA; Li, Deyu [Albany, CA; Majumdar, Arun [Orinda, CA

2008-04-08

Fluidic nanotube devices are described in which a hydrophilic, non-carbon nanotube, has its ends fluidly coupled to reservoirs. Source and drain contacts are connected to opposing ends of the nanotube, or within each reservoir near the opening of the nanotube. The passage of molecular species can be sensed by measuring current flow (source-drain, ionic, or combination). The tube interior can be functionalized by joining binding molecules so that different molecular species can be sensed by detecting current changes. The nanotube may be a semiconductor, wherein a tubular transistor is formed. A gate electrode can be attached between source and drain to control current flow and ionic flow. By way of example an electrophoretic array embodiment is described, integrating MEMs switches. A variety of applications are described, such as: nanopores, nanocapillary devices, nanoelectrophoretic, DNA sequence detectors, immunosensors, thermoelectric devices, photonic devices, nanoscale fluidic bioseparators, imaging devices, and so forth.

Fluidic nanotubes and devices

DOEpatents

Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yiying; Li, Deyu; Majumdar, Arun

2010-01-10

Fluidic nanotube devices are described in which a hydrophilic, non-carbon nanotube, has its ends fluidly coupled to reservoirs. Source and drain contacts are connected to opposing ends of the nanotube, or within each reservoir near the opening of the nanotube. The passage of molecular species can be sensed by measuring current flow (source-drain, ionic, or combination). The tube interior can be functionalized by joining binding molecules so that different molecular species can be sensed by detecting current changes. The nanotube may be a semiconductor, wherein a tubular transistor is formed. A gate electrode can be attached between source and drain to control current flow and ionic flow. By way of example an electrophoretic array embodiment is described, integrating MEMs switches. A variety of applications are described, such as: nanopores, nanocapillary devices, nanoelectrophoretic, DNA sequence detectors, immunosensors, thermoelectric devices, photonic devices, nanoscale fluidic bioseparators, imaging devices, and so forth.

Growing Aligned Carbon Nanotubes for Interconnections in ICs

NASA Technical Reports Server (NTRS)

Li, Jun; Ye, Qi; Cassell, Alan; Ng, Hou Tee; Stevens, Ramsey; Han, Jie; Meyyappan, M.

2005-01-01

A process for growing multiwalled carbon nanotubes anchored at specified locations and aligned along specified directions has been invented. Typically, one would grow a number of the nanotubes oriented perpendicularly to a silicon integrated-circuit (IC) substrate, starting from (and anchored on) patterned catalytic spots on the substrate. Such arrays of perpendicular carbon nanotubes could be used as electrical interconnections between levels of multilevel ICs. The process (see Figure 1) begins with the formation of a layer, a few hundred nanometers thick, of a compatible electrically insulating material (e.g., SiO(x) or Si(y)N(z) on the silicon substrate. A patterned film of a suitable electrical conductor (Al, Mo, Cr, Ti, Ta, Pt, Ir, or doped Si), having a thickness between 1 nm and 2 m, is deposited on the insulating layer to form the IC conductor pattern. Next, a catalytic material (usually, Ni, Fe, or Co) is deposited to a thickness between 1 and 30 nm on the spots from which it is desired to grow carbon nanotubes. The carbon nanotubes are grown by plasma-enhanced chemical vapor deposition (PECVD). Unlike the matted and tangled carbon nanotubes grown by thermal CVD, the carbon nanotubes grown by PECVD are perpendicular and freestanding because an electric field perpendicular to the substrate is used in PECVD. Next, the free space between the carbon nanotubes is filled with SiO2 by means of CVD from tetraethylorthosilicate (TEOS), thereby forming an array of carbon nanotubes embedded in SiO2. Chemical mechanical polishing (CMP) is then performed to remove excess SiO2 and form a flat-top surface in which the outer ends of the carbon nanotubes are exposed. Optionally, depending on the application, metal lines to connect selected ends of carbon nanotubes may be deposited on the top surface. The top part of Figure 2 is a scanning electron micrograph (SEM) of carbon nanotubes grown, as described above, on catalytic spots of about 100 nm diameter patterned by

Fabrication of uniformly dispersed Ag nanoparticles loaded TiO{sub 2} nanotube arrays for enhancing photoelectrochemical and photocatalytic performances under visible light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Junhui; Zhang, Shengsen; Wang, Hongjuan

2014-12-15

Graphical abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method, which exhibited the enhanced photoelectrochemical and photocatalytic performances under visible-light irradiation due to the more effective separation of photo-generated electron–hole pairs and faster interfacial charge transfer. - Highlights: • Highly dispersed Ag nanoparticles (NPs) are successfully prepared by polyol method. • Ag NPs are uniformly loaded on the surface of the TiO{sub 2} nanotube arrays (NTs). • Ag/TiO{sub 2}-NTs exhibit the enhanced photocatalytic activity under visible-light. • The enhanced photocurrent ismore » explained by electrochemical impedance spectroscopy. - Abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method. The as-prepared Ag/TiO{sub 2}-NTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–vis diffusion reflectance spectroscopy. Photoelectrochemical behaviors were investigated via photocurrent response and electrochemical impedance spectroscopy (EIS). Photocatalytic activity of Ag/TiO{sub 2}-NTs was evaluated by degradation of acid orange II under visible light irradiation. The results showed that photocatalytic efficiency of Ag/TiO{sub 2}-NTs is more than 5 times higher than that of pure TiO{sub 2} NTs. Comparing with the electrochemical deposition method, the photocatalytic activity of Ag/TiO{sub 2}-NTs prepared by polyol method has been obviously increased.« less

Single Walled Carbon Nanotube Based Air Pocket Encapsulated Ultraviolet Sensor.

PubMed

Kim, Sun Jin; Han, Jin-Woo; Kim, Beomseok; Meyyappan, M

2017-11-22

Carbon nanotube (CNT) is a promising candidate as a sensor material for the sensitive detection of gases/vapors, biomarkers, and even some radiation, as all these external variables affect the resistance and other properties of nanotubes, which forms the basis for sensing. Ultraviolet (UV) radiation does not impact the nanotube properties given the substantial mismatch of bandgaps and therefore, CNTs have never been considered for UV sensing, unlike the popular ZnO and other oxide nanwires. It is well-known that UV assists the adsorption/desorption characteristics of oxygen on carbon nanotubes, which changes the nanotube resistance. Here, we demonstrate a novel sensor structure encapsulated with an air pocket, where the confined air is responsible for the UV sensing mechanism and assures sensor stability and repeatability over time. In addition to the protection from any contamination, the air pocket encapsulated sensor offers negligible baseline drift and fast recovery compared to previously reported sensors. The air pocket isolated from the outside environment can act as a stationary oxygen reservoir, resulting in consistent sensor characteristics. Furthermore, this sensor can be used even in liquid environments.

Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests

PubMed Central

Kim, Hyun Chan; Song, Sangho; Kim, Jaehwan

2016-01-01

This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm2, thus fitting the 1.8 × 1.8 mm2 haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices. PMID:27649184

CdS/CdSe quantum dot shell decorated vertical ZnO nanowire arrays by spin-coating-based SILAR for photoelectrochemical cells and quantum-dot-sensitized solar cells.

PubMed

Zhang, Ran; Luo, Qiu-Ping; Chen, Hong-Yan; Yu, Xiao-Yun; Kuang, Dai-Bin; Su, Cheng-Yong

2012-04-23

A CdS/CdSe composite shell is assembled onto the surface of ZnO nanowire arrays with a simple spin-coating-based successive ionic layer adsorption and reaction method. The as-prepared photoelectrode exhibit a high photocurrent density in photoelectrochemical cells and also generates good power conversion efficiency in quantum-dot-sensitized solar cells. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Nanotube Tower-Based Supercapacitor

NASA Technical Reports Server (NTRS)

Meyyappan, Meyya (Inventor)

2012-01-01

A supercapacitor system, including (i) first and second, spaced apart planar collectors, (ii) first and second arrays of multi-wall carbon nanotube (MWCNT) towers or single wall carbon nanotube (SWCNT) towers, serving as electrodes, that extend between the first and second collectors where the nanotube towers are grown directly on the collector surfaces without deposition of a catalyst and without deposition of a binder material on the collector surfaces, and (iii) a porous separator module having a transverse area that is substantially the same as the transverse area of at least one electrode, where (iv) at least one nanotube tower is functionalized to permit or encourage the tower to behave as a hydrophilic structure, with increased surface wettability.

Cu-doped ZnO nanorod arrays: the effects of copper precursor and concentration

PubMed Central

2014-01-01

Cu-doped ZnO nanorods have been grown at 90°C for 90 min onto a quartz substrate pre-coated with a ZnO seed layer using a hydrothermal method. The influence of copper (Cu) precursor and concentration on the structural, morphological, and optical properties of ZnO nanorods was investigated. X-ray diffraction analysis revealed that the nanorods grown are highly crystalline with a hexagonal wurtzite crystal structure grown along the c-axis. The lattice strain is found to be compressive for all samples, where a minimum compressive strain of −0.114% was obtained when 1 at.% Cu was added from Cu(NO3)2. Scanning electron microscopy was used to investigate morphologies and the diameters of the grown nanorods. The morphological properties of the Cu-doped ZnO nanorods were influenced significantly by the presence of Cu impurities. Near-band edge (NBE) and a broad blue-green emission bands at around 378 and 545 nm, respectively, were observed in the photoluminescence spectra for all samples. The transmittance characteristics showed a slight increase in the visible range, where the total transmittance increased from approximately 80% for the nanorods doped with Cu(CH3COO)2 to approximately 90% for the nanorods that were doped with Cu(NO3)2. PMID:24855460

Synthesis of reduced graphene oxide intercalated ZnO quantum dots nanoballs for selective biosensing detection

NASA Astrophysics Data System (ADS)

Chen, Jing; Zhao, Minggang; Li, Yingchun; Fan, Sisi; Ding, Longjiang; Liang, Jingjing; Chen, Shougang

2016-07-01

ZnO quantum dots (QDs), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) are always used in sensors due to their excellent electrochemical characteristics. In this work, ZnO QDs were intercalated by rGO sheets with cross-linked MWCNTs to construct intercalation nanoballs. A MWCNTs/rGO/ZnO QDs 3D hierarchical architecture was fabricated on supporting Ni foam, which exhibited excellent mechanical, kinetic and electrochemical properties. The intercalation construction can introduce strong interfacial effects to improve the surface electronic state. The selectively determinate of uric acid, dopamine, and ascorbic acid by an electrode material using distinct applied potentials was realized.

Single-molecule detection of protein efflux from microorganisms using fluorescent single-walled carbon nanotube sensor arrays

NASA Astrophysics Data System (ADS)

Landry, Markita Patricia; Ando, Hiroki; Chen, Allen Y.; Cao, Jicong; Kottadiel, Vishal Isaac; Chio, Linda; Yang, Darwin; Dong, Juyao; Lu, Timothy K.; Strano, Michael S.

2017-05-01

A distinct advantage of nanosensor arrays is their ability to achieve ultralow detection limits in solution by proximity placement to an analyte. Here, we demonstrate label-free detection of individual proteins from Escherichia coli (bacteria) and Pichia pastoris (yeast) immobilized in a microfluidic chamber, measuring protein efflux from single organisms in real time. The array is fabricated using non-covalent conjugation of an aptamer-anchor polynucleotide sequence to near-infrared emissive single-walled carbon nanotubes, using a variable chemical spacer shown to optimize sensor response. Unlabelled RAP1 GTPase and HIV integrase proteins were selectively detected from various cell lines, via large near-infrared fluorescent turn-on responses. We show that the process of E. coli induction, protein synthesis and protein export is highly stochastic, yielding variability in protein secretion, with E. coli cells undergoing division under starved conditions producing 66% fewer secreted protein products than their non-dividing counterparts. We further demonstrate the detection of a unique protein product resulting from T7 bacteriophage infection of E. coli, illustrating that nanosensor arrays can enable real-time, single-cell analysis of a broad range of protein products from various cell types.

A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays.

PubMed

Liao, Yulong; Yuan, Botao; Zhang, Dainan; Wang, Xiaoyi; Li, Yuanxun; Wen, Qiye; Zhang, Huaiwu; Zhong, Zhiyong

2018-04-03

In this paper, a facile method was proposed to load CeO 2 nanoparticles (NPs) on anodic TiO 2 nanotube (NT) arrays, which leads to a formation of CeO 2 /TiO 2 heterojunctions. Highly ordered anatase phase TiO 2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO 2 NTs were used as tiny "nano-containers" to load a small amount of Ce(NO 3 ) 3 solutions. The loaded anodic TiO 2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO 3 ) 3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO 3 ) 3 , cubic crystal CeO 2 NPs were obtained and successfully loaded into the anodic TiO 2 NT arrays. The prepared CeO 2 /TiO 2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO 2 /TiO 2 films, which could be very useful for environmental and energy-related areas.

Facile preparation of branched hierarchical ZnO nanowire arrays with enhanced photocatalytic activity: A photodegradation kinetic model

NASA Astrophysics Data System (ADS)

Ebrahimi, M.; Yousefzadeh, S.; Samadi, M.; Dong, Chunyang; Zhang, Jinlong; Moshfegh, A. Z.

2018-03-01

Branched hierarchical zinc oxide nanowires (BH-ZnO NWs) were fabricated successfully by a facile and rapid synthesis using two-step growth process. Initially, ZnO NWs have been prepared by anodizing zinc foil at room temperature and followed by annealing treatment. Then, the BH- ZnO NWs were grown on the ZnO NWs by a solution based method at very low temperature (31 oC). The BH- ZnO NWs with different aspect ratio were obtained by varying reaction time (0.5, 2, 5, 10 h). Photocatalytic activity of the samples was studied under both UV and visible light. The results indicated that the optimized BH-ZnO NWs (5 h) as a photocatalyst exhibited the highest photoactivity with about 3 times higher than the ZnO NWs under UV light. In addition, it was also determined that photodegradation rate constant (k) for the BH- ZnO NWs surface obeys a linear function with the branch length (l) and their correlation was described by using a proposed kinetic model.

Characteristics of zinc oxide nanorod array/titanium oxide film heterojunction prepared by aqueous solution deposition

NASA Astrophysics Data System (ADS)

Lee, Ming-Kwei; Hong, Min-Hsuan; Li, Bo-Wei

2016-07-01

The characteristics of a ZnO nanorod array/TiO2 film heterojunction were investigated. A TiO2 film was prepared on glass by aqueous solution deposition with precursors of ammonium hexafluorotitanate and boric acid at 40 °C. Then, a ZnO seed layer was prepared on a TiO2 film/glass substrate by RF sputtering. A vertically oriented ZnO nanorod array was grown on a ZnO seed layer/TiO2 film/glass substrate by aqueous solution deposition with precursors of zinc nitrate and hexamethylenetetramine (HMT) at 70 °C. After thermal annealing in N2O ambient at 300 °C, this heterojunction used as an oxygen gas sensor shows much better rise time, decay time, and on/off current ratio than as-grown and annealed ZnO nanorods.

Micropatternable Double-Faced ZnO Nanoflowers for Flexible Gas Sensor.

PubMed

Kim, Jong-Woo; Porte, Yoann; Ko, Kyung Yong; Kim, Hyungjun; Myoung, Jae-Min

2017-09-27

Micropatternable double-faced (DF) zinc oxide (ZnO) nanoflowers (NFs) for flexible gas sensors have been successfully fabricated on a polyimide (PI) substrate with single-walled carbon nanotubes (SWCNTs) as electrode. The fabricated sensor comprises ZnO nanoshells laid out on a PI substrate at regular intervals, on which ZnO nanorods (NRs) were grown in- and outside the shells to maximize the surface area and form a connected network. This three-dimensional network structure possesses multiple gas diffusion channels and the micropatterned island structure allows the stability of the flexible devices to be enhanced by dispersing the strain into the empty spaces of the substrate. Moreover, the micropatterning technique on a flexible substrate enables highly integrated nanodevices to be fabricated. The SWCNTs were chosen as the electrode for their flexibility and the Schottky barrier they form with ZnO, improving the sensing performance. The devices exhibited high selectivity toward NO 2 as well as outstanding sensing characteristics with a stable response of 218.1, fast rising and decay times of 25.0 and 14.1 s, respectively, and percent recovery greater than 98% upon NO 2 exposure. The superior sensing properties arose from a combination of high surface area, numerous active junction points, donor point defects in the ZnO NRs, and the use of the SWCNT electrode. Furthermore, the DF-ZnO NF gas sensor showed sustainable mechanical stability. Despite the physical degradation observed, the devices still demonstrated outstanding sensing characteristics after 10 000 bending cycles at a curvature radius of 5 mm.

Transition-Metal-Doped p-Type ZnO Nanoparticle-Based Sensory Array for Instant Discrimination of Explosive Vapors.

PubMed

Qu, Jiang; Ge, Yuru; Zu, Baiyi; Li, Yuxiang; Dou, Xincun

2016-03-09

The development of portable, real-time, and cheap platforms to monitor ultratrace levels of explosives is of great urgence and importance due to the threat of terrorism attacks and the need for homeland security. However, most of the previous chemiresistor sensors for explosive detection are suffering from limited responses and long response time. Here, a transition-metal-doping method is presented to remarkably promote the quantity of the surface defect states and to significantly reduce the charge transfer distance by creating a local charge reservoir layer. Thus, the sensor response is greatly enhanced and the response time is remarkably shortened. The resulting sensory array can not only detect military explosives, such as, TNT, DNT, PNT, PA, and RDX with high response, but also can fully distinguish some of the improvised explosive vapors, such as AN and urea, due to the huge response reaching to 100%. Furthermore, this sensory array can discriminate ppb-level TNT and ppt-level RDX from structurally similar and high-concentration interfering aromatic gases in less than 12 s. Through comparison with the previously reported chemiresistor or Schottky sensors for explosive detection, the present transition-metal-doping method resulting ZnO sensor stands out and undoubtedly challenges the best. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O.

PubMed

Debgupta, Joyashish; Devarapalli, Ramireddy; Rahman, Shakeelur; Shelke, Manjusha V; Pillai, Vijayamohanan K

2014-08-07

Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, "as grown" CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ∼ 470 μA cm(-2)) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2O on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers.

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

PubMed Central

2013-01-01

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed. PMID:24004518