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Electrochimica Acta 06/2013; 100:85-92. · 3.83 Impact Factor
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ABSTRACT: A novel scanning electron microscope (SEM) method is presented for high contrast identification of each layer of pyramidal graphene domains grown on copper. We obtained SEM images by combining the advantages of the high resolution property of the secondary electron signal and the elemental sensitivity of the backscattering electron signal. Through this method, we investigated the difference in the growth mechanisms of mono-layer and few-layer graphene. Due to different lattice mismatches, both the surface adsorption process and the epitaxial growth process existed under the atmospheric growth conditions. Moreover, the copper oxidation process can be easily discovered. It is obvious from the SEM images that the graphene greatly delayed the oxidation process of the copper surface. Finally, the nucleation and growth speed of graphene domains was found to depend on the linear array distribution of surface ledges and terraces of annealed rolled copper foil. This result explains the linear rows of graphene during the growth process and accords with theoretical results.
Nanotechnology 10/2012; 23(47):475705. · 3.98 Impact Factor
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ABSTRACT: The hierarchical photocatalysts of Ag/AgCl@plate-WO₃ have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO₃ nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag⁺-WO₃ suspensions with a Cl⁻ solution added drop-wise was developed to synthesize AgCl@WO₃ composites, which were then photoreduced to form Ag/AgCl@WO₃ nanostructures in situ. WO₃ nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO₃ photocatalysts, and the effects of the WO₃ contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N₂ adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO₃ nanostructures under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO₃ photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO₃ and TiO₂ (P25). The contents and morphologies of the WO₃ substrates in the Ag/AgCl@plate-WO₃ photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.
Nanoscale 07/2012; 4(17):5431-9. · 5.91 Impact Factor
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ABSTRACT: Monodisperse ultrathin SnO₂ nanorods on nitrogen-doped graphene were firstly synthesized by a facile one-step hydrothermal strategy. The uniformed composites with high nitrogen content and ultrathin SnO₂ nanorods of 2.5-4.0 nm in diameter and 10-15 nm in length show a high reversible specific capacity, superior rate capability and outstanding cycling stability (803 mA h g⁻¹) as anode materials for lithium ion batteries, owing to the synergistic effect between GS and SnO₂ and nitrogen-doping, which can greatly decrease the energy barrier for Li penetrating the pyridinic defects and improve the electronic structures. This work opens the door to prepare metal oxide/GS-N composites with superior lithium storage properties and engineering of graphene composites for advanced energy storage.
Nanoscale 07/2012; 4(17):5425-30. · 5.91 Impact Factor
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ABSTRACT: Carbon nanotubes have been the focus of intensive study due to their unique structure-dependent electronic and mechanical
properties. They are thought to have potential applications as catalyst supports in heterogeneous catalysis, high engineering
reinforcements, and molecular wires for the next generation of electronic devices. Good dispersion of carbon nanotubes in
a matrix of composite materials, especially in inorganic materials, indeed is a significant problem due to the strong Van
der Walls force between CNTs and the poor compatibility between the two phases. It is the intention of our research work to
overcome the difficulties regarding incorporation of carbon nanotubes in structural and functional ceramics. The initial step
toward this goal involves coating CNTs with materials that will eliminate the undesirable attractive interactions between
the nanotubes and facilitate their incorporation into composites. In the present study, two new and simple methods named as
heterogeneous coagulation and direct hydrolysis have been developed to attach various inorganic nano particles such as alumina,
zirconia and titania to the surface of carbon nanotubes. These functionalization methods might be new strategies to altering
the electronic properties of nanotubes. We expected that the attachment of metal oxides to nanotube surfaces will promote
better ceramic or other inorganic matrix-CNT adhesion and may lead to the development of homogeneous composites, thereafter
improving mechanical and/or electrical properties.
Journal of Electroceramics 04/2012; 17(1):91-94. · 1.19 Impact Factor
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ABSTRACT: In order to make certain the compaction pressure as well as pre-sintering temperature on the machinability of the zirconia ceramic.
3 mol nano-size 3 mol yttria partially stabilized zirconia (3Y-TZP) powder were compacted at different isostatic pressure and sintered at different temperature. The cylindrical surface was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy.
Pre-sintering temperature had the obviously influence on the machinability of 3Y-TZP. The cutting surface was smooth, and the integrality of edge was better when the pre-sintering temperature was chosen between 800 degrees C to 900 degrees C. Compaction pressure showed only a weak influence on machinability of 3Y-TZP blanks, but the higher compaction pressure result in the poor surface quality.
The best machinability of pre-sintered zirconia body was found for 800-900 degrees C pre-sintering temperature, and 200-300 MPa compaction pressure.
Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 10/2011; 29(5):534-6, 541.
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ABSTRACT: Flexible single-walled carbon nanotubes/polyaniline (SWNT/PANi) composite films with enhanced thermoelectric properties were prepared via a simple method. Furthermore, these paper-like composite films show good flexibility, which makes them possible to be widely applied in various flexible energy converter devices.
Nanoscale 08/2011; 3(9):3616-9. · 5.91 Impact Factor
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ABSTRACT: Fibrous nanocomposites of carbon nanotubes, graphene-oxide or graphene were prepared by a simple coagulation spinning technique exhibiting synergetic enhancement of mechanical strength, electronic conductivity and electrical actuation performance.
Chemical Communications 07/2011; 47(30):8650-2. · 6.17 Impact Factor
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ABSTRACT: We demonstrate here the synthesis of a hierarchical TiO(2) architecture without any surfactants or templates. Two kinds of structure existed simultaneously, the ordered nanoarrays at bottom provided direct conduction pathway for photo generated electrons, while the upper micro-flowers consisted of nanobelt as building units increased the light harvesting ability as the scattering part. The formation mechanism of the hierarchical architecture has been proposed by studying the morphology evolution processes upon reaction time. The performance of dye-sensitized solar cells based on the obtained hierarchical anatase TiO(2) has been also studied, giving a J(SC) = 12.44 mA cm(-2), V(OC) = 0.64 V, FF = 69.05%, and η = 5.53%, which is superior than commercial TiO(2) (P25). The UV-vis results prove that the obtained morphology is beneficial to light-scattering and thus increases the light harvesting ability. This hierarchical TiO(2) structure offers great potential for the development of high-efficiency DSSCs.
ACS Applied Materials & Interfaces 06/2011; 3(6):2148-53. · 4.53 Impact Factor
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ABSTRACT: Quantum dot sensitized solar cell (QDSSC) was fabricated in a low-temperature process based on graphene-CdSe composite, which was prepared by the procedures of immobilizing CdSe on graphene oxide (GO) and reduction in GO. It was found that the charge separation between excited CdSe and graphene could be tapped to generate photocurrent from photocurrent measurements, which established the ability of graphene to collect and transport electrons. By optimizing the CdSe-to-GO ratio at 4.5:1, the obtained graphene-CdSe-based cells exhibited significantly higher short-circuit photocurrent and energy conversion efficiency (5.8 mA/cm2 and 0.72%, respectively) than the reported values of the C60 or carbon nanotube related QDSSC, demonstrating that the graphene-CdSe composite is an attractive candidate in energy conversion devices.
Applied Physics Letters 03/2011; 98(9):093112-093112-3. · 3.84 Impact Factor
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ABSTRACT: Several kinds of one-dimensional TiO2 nanostructures including nanorod arrays, nanobelt arrays, and fan-shaped rectangular parallelepiped rods were prepared by alkali hydrothermal method. Their morphology and crystalline phase could be controlled by changing the concentration of alkali solution. They were used as photoanodes to assemble front-side illumination dye-sensitized solar cells, and the cell performance was correlated with the nanostructure. The highest conversion efficiency (6.0%) was achieved with highly ordered TiO2 nanorod arrays. We demonstrate that the oriented nanorods with appropriate lengths are beneficial to improve the electron transport property and thus lead to the increase of photocurrent, together enhancing the power conversion efficiency.
12/2010;
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ABSTRACT: SWCNT-reduced graphite oxide hybrid films were prepared by a filtration method. An efficient post-treatment procedure was designed to reduce GO and remove dispersants simultaneously. The sheet resistance decreased significantly after treatment, by a factor of 4-13 times. Films with excellent performance (95.6%, 655 Ω per square) were obtained and had great potential applications.
Nanoscale 12/2010; 3(3):904-6. · 5.91 Impact Factor
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ABSTRACT: Well-dispersed, high-quality reduced graphene oxide (RGO) solutions were prepared using an in situ reduction process with lysozyme (lys) as the dispersant. The lys-RGO reaches a concentration as high as 0.22 mg/mL and can remain stable for over six months. Atomic force microscopy indicates that the lys-RGO is effectively exfoliated with an average thickness of about 1 nm. Furthermore, XPS and Raman spectra demonstrate that the presence of lysozyme promotes the chemical reduction of GO and restores the sp2 hybridization in the obtained RGO. The dispersibility effect of lys-RGO solution is pH-sensitive. Zeta potential and UV−vis spectrum analysis indicate that the RGO sheets will aggregate in the pH range of 2.5−7.5 and disperse well at pH 8−12.5. It is found that the dispersibility of the lys-RGO is reversible, and over 80% of the aggregates can be redissolved after pH regulation. This reversible dispersing was attributed to the strong adsorption affinity of lysozyme onto RGO, resulting from the hydrophobic and π−π stacking. This highly dispersed lys-RGO solution has great potential for application in composite materials and biochemical fields.
11/2010;
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ABSTRACT: In this work, flexible single-walled carbon nanotube/polyaniline (SWNT/PANi) composite films have been synthesized through an in situ electrochemical polymerization/degradation process. In addition to their good flexibility and light weight, cyclic voltammetry (CV) tests revealed that free-standing SWNT/PANi composite films also showed good electrochemical properties. Before electrodegradation, the highest specific capacitance, 501.8 F/g, was obtained for SWNT/PANi composite films with 90 electrochemical polymerization cycles. It reached values up to 706.7 F/g after electrodegradation, an increase of 40%, which was attributed to more available charge-transfer channels and increased polycrystalline PANi regions that were produced by the dissolution of off-lying disordered PANi.
10/2010;
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ABSTRACT: To investigate the effect of compaction pressure on the linear shrinkage, sintering property and machinability of the dental zirconia ceramic.
The nano-size zirconia powder was compacted at different isostatic pressure and sintered at different temperature. The linear shrinkage of sintered body was measured and the relative density was tested using the Archimedes method. The cylindrical surface of pre-sintering blanks was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy.
The sintering behaviour depended on the compaction pressure. Increasing compaction pressure led to higher sintering rate and lower sintering temperature. Increasing compaction pressure also led to decreasing linear shrinkage of the sintered bodies, from 24.54% of 50 MPa to 20.9% of 400 MPa. Compaction pressure showed only a weak influence on machinability of zirconia blanks, but the higher compaction pressure resulted in the poor surface quality.
The better sintering property and machinability of dental zirconia ceramic is found for 200-300 MPa compaction pressure.
Shanghai kou qiang yi xue = Shanghai journal of stomatology 10/2010; 19(5):512-6.
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ABSTRACT: RNA was used to exfoliate single-walled carbon nanotubes (SWCNTs) in aqueous solution, and the ratio of it was optimized to obtain the best dispersion state. The obtained homogeneous SWCNT solution with small bundle size was used to prepare flexible transparent conductive films by filtration method. Sodium hydroxide treatment combining short-time acid treatment was used to remove the RNA molecules. After treatment, the sheet resistance of the films decreased significantly, while the change on the transmittance was negligible. Besides, the polyethylene terephthalate substrate would not turn brittle through this treatment process. Flexible films with outstanding performance (190 Omega/sq, 85%) and good stability were obtained after treatment. X-ray photoelectron spectroscopy and scanning electron microscope were used to analyze the role of base and acid treatment in detail.
ACS Nano 08/2010; 4(8):4890-6. · 10.77 Impact Factor
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ABSTRACT: Fibers are promising forms to use carbon nanotubes (CNTs) on the macroscopic scale. Physical and chemical properties of carbon nanotubes, dispersants, and the phase behavior of carbon nanotube suspensions have great impact on the performance of the fibers. In this paper, single-walled carbon nanotube fibers were made by rotating PVA (poly(vinyl alcohol))-based coagulation spinning. Scanning electron microscopy was used to observe the surface and cross section of the fibers. The orientation degree of the fibers was analyzed by polarized Raman spectra. The influence of single-walled carbon nanotube (SWCNT) source materials and different dispersants on the performance of the fibers was investigated systematically for the first time. The results show that purification and acid oxidation of SWCNTs can enhance the fiber strength. Compared to SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfate), SLS (sodium lignosulfonate) is the best dispersant to fabricate carbon nanotube fibers with a higher strength. The performance of the fiber was improved greatly due to the formation of the liquid-crystal phase, and fibers with the strength of 520 MPa were fabricated.
03/2010;
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ABSTRACT: RNA was used to exfoliate single-walled carbon nanotubes (SWCNTs) in aqueous solution, and
the ratio of it was optimized to obtain the best dispersion state. The obtained homogeneous SWCNT solution with
small bundle size was used to prepare flexible transparent conductive films by filtration method. Sodium hydroxide
treatment combining short-time acid treatment was used to remove the RNA molecules. After treatment, the
sheet resistance of the films decreased significantly, while the change on the transmittance was negligible.
Besides, the polyethylene terephthalate substrate would not turn brittle through this treatment process. Flexible
films with outstanding performance (190�/sq, 85%) and good stability were obtained after treatment. X-ray
photoelectron spectroscopy and scanning electron microscope were used to analyze the role of base and acid
treatment in detail.
ACS Nano 01/2010; 4:4890. · 10.77 Impact Factor
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ABSTRACT: Single-walled carbon nanotubes dispersed by pristine DNA and denatured DNA were used to prepare
transparent conductive films on PET substrates by a vacuum filtration and spray coating method.
Transmission electron microscopy (TEM) was used to characterize the dispersion state of SWCNT
solutions. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to investigate
the interaction between SWCNTs and DNA. It was found that both pristine and denatured DNA could
effectively disperse SWCNTs. Acid treatment on SWCNT films degraded and removed DNA
molecules effectively. The sheet resistance of SWCNT-DNA films was reduced by a factor of 2.5–10
times after acid treatment while the change of transmittance was negligible over the visible region.
Films with high performance (95 U/sq, 78%) and good stability have been obtained.
Journal of Materials Chemistry. 01/2010; 20:6903.
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Deliang Chen,
Xianxiang Hou,
Hejing Wen,
Yu Wang,
Hailong Wang,
Xinjian Li,
Rui Zhang,
Hongxia Lu,
Hongliang Xu,
Shaokang Guan, Jing Sun,
Lian Gao
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ABSTRACT: Chemical sensors based on semiconducting metal oxide nanocrystals are of academic and practical significance in industrial processing and environment-related applications. Novel alcohol response sensors using two-dimensional WO(3) nanoplates as active elements have been investigated in this paper. Single-crystalline WO(3) nanoplates were synthesized through a topochemical approach on the basis of intercalation chemistry (Chen et al 2008 Small 4 1813). The as-obtained WO(3) nanoplate pastes were coated on the surface of an Al(2)O(3) ceramic microtube with four Pt electrodes to measure their alcohol-sensing properties. The results show that the WO(3) nanoplate sensors are highly sensitive to alcohols (e.g., methanol, ethanol, isopropanol and butanol) at moderate operating temperatures (260-360 degrees C). For butanol, the WO(3) nanoplate sensors have a sensitivity of 31 at 2 ppm and 161 at 100 ppm, operating at 300 degrees C. For other alcohols, WO(3) nanoplate sensors also show high sensitivities: 33 for methanol at 300 ppm, 70 for ethanol at 200 ppm, and 75 for isopropanol at 200 ppm. The response and recovery times of the WO(3) nanoplate sensors are less than 15 s for all the test alcohols. A good linear relationship between the sensitivity and alcohol concentrations has been observed in the range of 2-300 ppm, whereas the WO(3) nanoparticle sensors have not shown such a linear relationship. The sensitivities of the WO(3) nanoplate sensors decrease and their response times become short when the operating temperatures increase. The enhanced alcohol-sensing performance could be attributed to the ultrathin platelike morphology, the high crystallinity and the loosely assembling structure of the WO(3) nanoplates, due to the advantages of the effective adsorption and rapid diffusion of the alcohol molecules.
Nanotechnology 12/2009; 21(3):035501. · 3.98 Impact Factor
