Showing papers by "Sishen Xie published in 2006"
TL;DR: The competing growth of a Pd shell on the {110} and {100} facets of Au nanorods (Au NRs) results in the disappearance of unstable facets and the formation of rectangularly shaped Pd/Au bimetallic nanorod that show only four stable side surfaces.
Abstract: In this letter, we report the competing growth of a Pd shell on the {110} and {100} facets of Au nanorods (Au NRs). This results in the disappearance of unstable {110} facets and the formation of rectangularly shaped Pd/Au bimetallic nanorods that show only four stable {100} side surfaces. The energy minimization to a more stable morphology is believed to be the driving force for the formation of the rectangular shape of the Pd shell.
178 citations
TL;DR: X-ray and X-ray diffraction analyses show that the nanoneedles are almost pure ZnO and preferentially aligned in the c-axis direction of the wurtzite structure, which indicates the growth mechanism is the result of the co-effect of the surface tension and diffusion.
Abstract: ZnO nanoneedle arrays have been grown on a large scale with a chemical vapor deposition method at 680 degrees C. Zn powder and O-2 gas are employed as source materials, and catalyst-free Si plates are used as substrates. Energy-dispersive X-ray and X-ray diffraction analyses show that the nanoneedles are almost pure ZnO and preferentially aligned in the c-axis direction of the wurtzite structure. The growth mechanism of ZnO nanoneedle arrays is discussed with the thermodynamic theory and concluded to be the result of the co-effect of the surface tension and diffusion. Photoluminescence spectrum of the as-grown products shows a strong emission band centering at about 484 nm, which originates from oxygen vacancies. Field-emission examination exhibits that the ZnO nanoneedle arrays have a turn-on voltage at about 5.3V/mu m.
83 citations
TL;DR: The experimental results indicated that nonwoven SWNTs exhibited significant enhancement to the cells adhesion and proliferation in at least 3 weeks, which is of significance to in vitro cell amplification in large scale, tissue regeneration, or guided repair, as well as biomedical device application.
Abstract: Carbon nanotubes have attracted intensive interests in biomedical research in recent years. In this study, a novel type of carbon nanotubes material so called nonwoven single-walled carbon nanotubes (SWNTs) with nanotopographic structure and macroscopic volume was used as cell growing scaffold. The morphology and surface chemistry of nonwoven SWNTs were observed and characterized through scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The cells were cultivated in nonwoven SWNTs and in other types of substrate as control. The cells growth behaviors including adhesion, proliferation, and cytoskeletal development was investigated by using cell viability assay and confocal observation. The experimental results indicated that nonwoven SWNTs exhibited significant enhancement to the cells adhesion and proliferation in at least 3 weeks. Numerous and highly organized cytoskeletal structures were observed when the cells were cultured in nonwoven SWNTs. Furthermore, an obvious promotional influence of the cells cultivated in nonwoven SWNTs scaffold upon the proliferation of those growing in the other kind of substrate through cell-cell communication had been found. The results obtained in this work are of significance to in vitro cell amplification in large scale, tissue regeneration, or guided repair, as well as biomedical device application.
72 citations
TL;DR: In this paper, the formation and evolution of the twinned gold (Au) plates with hexagon or triangle shapes has been investigated using X-ray photoelectron spectroscopy (XPS).
Abstract: PVP (poly(vinyl pyrrolidone))-capped micrometer-sized twinned gold (Au) plates with the shape of hexagon or triangle have been successfully synthesized in a large quantity by reducing hydrogen tetrachloroauric acid (HAuCl4·3H2O) using ethylene glycol in the presence of (PVP) molecules at 200°C under the extra condition of autogenous pressure. Clear twin boundaries in thus-obtained Au plates have been observed by scanning electron microscope (SEM). To further elucidate the mechanism of formation of the twinned Au plates, transmission electron microscopy (TEM) has been employed to characterize smaller Au nanoplates obtained simultaneously with the Au microplates, the occurrence of 1/3{422} forbidden reflections in selected area electron diffraction (SAED) can be believed to result from the presence of twinning boundary within the Au (111) plane normal to TEM electron beam. In addition, X-ray photoelectron spectroscopy (XPS) experiment has confirmed that PVP molecules exist on the surface of the Au cores, which may play a very important role in the formation and evolution of the twinned Au plates. A possible growth mechanism has been suggested to explain the Au plate evolution from nanometer to micrometer.
64 citations
TL;DR: In this paper, single-walled carbon nanotubes with perfectly toroidal geometries are fabricated in high yields by a floating chemical vapor deposition process involving the thermal decomposition of acetylene.
Abstract: Rings of bundled single-walled carbon nanotubes with perfectly toroidal geometries (see figure), are fabricated in high yields by a floating chemical vapor deposition process involving the thermal decomposition of acetylene. The nano-tube rings can be grown with varying densities on a wide variety of substrates at relatively low temperatures, which is a significant advantage for nanoelectronics applications.
54 citations
TL;DR: It was revealed by the intensity abnormality of the radial breathing mode (RBM) that the carbon nanotubes have a temperature-dependent density of electronic states, which means that the previously reported temperature coefficients of RBM of carbon Nanotubes are smaller than their "real" ones for the bulk samples of single- or double-walled carbon nanOTubes.
Abstract: Resonant Raman scattering (RRS) spectra of individual carbon nanotubes on a SiO2 substrate have been investigated first in the temperature range of 100-600 K (Phys. Rev. B 2002, 66, 115411). It was revealed by the intensity abnormality of the radial breathing mode (RBM) that the carbon nanotubes have a temperature-dependent density of electronic states. This means that the previously reported temperature coefficients of RBM of carbon nanotubes are smaller than their "real" ones for the bulk samples of single- or double-walled carbon nanotubes. Comparatively, the G line of individual nanotubes shows no observable difference relative to the bulk samples.
53 citations
TL;DR: The anomalous enhancement of the multi-phonon band at a critical size and 1D structure at room temperature is attributable to an enhanced electron- phonon coupling accompanied by phonon-plasmon coupling, i.e., the 'plasphon' proposed by Alexandrov et al in 1981.
Abstract: CuO is the prototype compound of cuprate superconductors, so understanding its electronic structures will facilitate the study of the pairing mechanism and miscellaneous states of high-temperature superconductors. We prepared uniform CuO nanocrystals (7–100 nm) and studied their size-dependent Raman scattering spectra. The relative variation between the two-phonon scattering band (2Bg) and the one-phonon band (Bg) indicates a decreasing electron–phonon coupling with reducing size, which unveils the dominant Frohlich electron–phonon coupling, as indicated by Devreese, but not the small polaron in CuO. Moreover, the anomalous enhancement of the multi-phonon band at a critical size and 1D structure at room temperature is attributable to an enhanced electron–phonon coupling accompanied by phonon–plasmon coupling, i.e., the 'plasphon' proposed by Alexandrov et al in 1981.
51 citations
TL;DR: Based on the experimental results, a growth mechanism has been suggested to elucidate the formation of the small decahedral Au nanoparticles as well as their evolution into perfect large decahed Au particles with the size of several micrometres.
Abstract: Poly(vinyl pyrrolidone)-capped multiple twinned gold (Au) particles with decahedral shape have been synthesized by a simple and convenient solvothermal wet chemical method. In the process, hydrogen tetrachloroauric acid (HAuCl4·3H2O) was reduced by ethylene glycol (EG) to form the multiple twinned Au nanocrystals in the presence of poly(vinyl pyrrolidone) (PVP) molecules at 200 °C under the extra condition of autogenous pressure. The decahedral nanoparticles take up about 10% of the total amount and have the usual size distribution from several tens to hundreds of nanometres. Some larger microsized five-twinned Au particles with perfect decahedral shape have also been observed in the final product. Furthermore, x-ray photoelectron spectroscopy (XPS) measurements verified that PVP molecules are adsorbed on the surface of the Au particles. Based on the experimental results, a growth mechanism has been suggested to elucidate the formation of the small decahedral Au nanoparticles as well as their evolution into perfect large decahedral Au particles with the size of several micrometres.
50 citations
TL;DR: In this article, double-walled carbon nanotubes (DWCNTs) serve as charge trapping centers when present in low density and as electron donors when presented in high density.
45 citations
TL;DR: X-ray absorption near-edge structure (XANES) and photoelectron spectroscopy (PES) have been used to investigate single-walled carbon nanotubes (SWNTs) modified by immersion in a HBr solution at room temperature as mentioned in this paper.
37 citations
TL;DR: It is demonstrated that, due to its high sensitivity to the surface elements, NEXAFS spectroscopy is a powerful tool to investigate the adsorption of fibrinogen on SWNT films.
TL;DR: In this paper, the content of magnetic element Ni in the nanowires can be easily adjusted by changing the ingredients of the electrolyte, the deposited current density and the deposited voltage.
Abstract: NixZn1?x alloy nanowires were successfully prepared by the templated electrodeposition technique. The morphology and the microstructures of as-deposited nanowires were examined by scanning electron microscope, x-ray diffraction, transmission electron microscope and electron diffraction. It is demonstrated that the content of magnetic element Ni in the nanowires can be easily adjusted by changing the ingredients of the electrolyte, the deposited current density and the deposited voltage, which is critical to tune the magnetic property of the nanowires. X-ray diffraction and electron diffraction analysis indicate that the NixZn1?x nanowires exhibit different structures with the variation in the quantity of nickel in the nanowires. It is expected that these heterogeneous alloy nanowires will have a potential application in nanoscale giant-magnetoresistance devices.
TL;DR: In this article, a floating catalytic chemical vapor deposition (FCCVD) method was used to bulk prepare the self-looping carbon nanotubes (SWNTs).
Abstract: Rings of single-walled carbon nanotubes (SWNTs) with a high yield of 30-50% have been fabricated through a floating catalytic chemical vapor deposition (FCCVD) method. The SWNT rings, which were characterized as the self-looping nanotube coils, feature a relative small diameter of 100-300 nm and a thin thickness of 1-8 nm. The high yield of the SWNT rings has been ascribed to the unique experimental configuration which could favor the as-synthesized straight SWNTs to bend freely and easily to form the coil-shaped structures. The technique presented here may advance the new understanding to bulk-prepare the nanotube rings. (c) 2006 Elsevier B.V. All rights reserved.
TL;DR: In this article, a single-walled carbon nanotube (SWNT) rings with a diameter of about 100 nm have been prepared by thermally decomposing hydrocarbon in a floating catalyst system.
Abstract: Single-walled carbon nanotube (SWNT) rings with a diameter of about 100 nm have been prepared by thermally decomposing hydrocarbon in a floating catalyst system. These rings appeared to consist mostly of SWNT toroids. High resolution transmission electron microscopy showed that these rings were composed of tens of SWNTs with a tightly packed arrangement. The production of SWNT rings was improved through optimizing various growth parameters, such as growth temperature, sublimation temperature of the catalyst, different gas flows and different catalyst components. The growth mechanism of the SWNT rings is discussed. In the field emission measurements we found that field emission from a halved ring is better than that from a whole SWNT ring, which contributed to the better emission from two opened ends of the nanotubes of the halved SWNT ring.
TL;DR: In this article, a simple aqueous solution route to directly oxidize metallic Zn powder in concentrated NaOH solution with pre-existence of the zincate ions under various temperature conditions in a closed Teflon reactor was proposed.
TL;DR: In this article, anodic anodic aluminium oxide (AAO) was applied to an aluminium sheet patterned with a metallic tantalum mask, which gave rise to the formation of patterned anodic aluminum oxide.
Abstract: Electrochemical anodization was applied to an aluminium (Al) sheet patterned with a metallic tantalum (Ta) mask, which gave rise to the formation of patterned anodic aluminium oxide (AAO). The morphological evolution of the AAO porous structure with anodizing time was characterized by scanning electron microscopy. Lateral anodizing of the Al sheet gradually developed underneath the metallic Ta mask with the increase of anodizing time. This has given us further understanding of the Al anodizing behaviour compared with our previous work with a SiO2 masked Al sheet. By controlling the anodizing time and the size of the metal mask, deep lithography of the Al substrate can be realized, and a mushroom-like Ta–Al microstructure with a high aspect ratio was created on the Al surface after removal of the AAO film. This Ta–Al microstructure has been studied in detail, and it was found to exhibit pronounced hydrophobic properties.
TL;DR: In this paper, a Fe nanowires-filled amorphous carbon nanotubes (FeNW-filled a-CNTs) array was synthesized by sequential growth of electrodeposited Fe wires and subsequent chemical vapour deposition of amorphized CNTs in the nanochannels of alumina template.
Abstract: A Fe nanowires-filled amorphous carbon nanotubes (FeNW-filled a-CNTs) array was synthesized by sequential growth of electrodeposited Fe nanowires and subsequent chemical vapour deposition of amorphous CNTs in the nanochannels of alumina template. Structural characterizations of as-prepared FeNW-filled a-CNTs were carried out via field emission scanning electron microscope (FE-SEM), x-ray diffraction (XRD), elemental mapping, high-resolution transmission electron microscope (HRTEM) and Raman scattering. The formation mechanism of such Fe/C nanoheterostructure was proposed according to the detailed HRTEM analyses. Furthermore, the room temperature magnetic property of the as-prepared FeNW-filled a-CNTs array was also investigated, and obvious anisotropic behaviour in magnetization was observed.
TL;DR: It can be further inferred that the shape of Ni-rich microzones is probably barlike or disklike, from the anisotropy of zero field cooling/field cooling (ZFC/FC) curves as well as the vortex magnetization behavior of the Ni5Zn21 nanowire array.
Abstract: Ni5Zn21 alloy nanowires were fabricated through template-assisted electrochemical deposition method. The morphology and microstructures of as-deposited nanowires were determined by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), electron diffraction (ED), and electron probe microanalysis (EPMA). The accurate composition was measured via induced coupling plasma atomic emission spectroscopy. SEM results show that Ni5Zn21 nanowires are deposited in most of the nanopores of the template, and they are continuous and dense throughout the whole length. The XRD result demonstrates that the nanowires are mainly composed of a cubic gamma phase Ni5Zn21 alloy, but there also exists a trace of Zn-rich eta phase. HRTEM and ED reveal that the alloy nanowires are polycrystalline with the crystallite size of several tens of nanometers. EPMA of a single nanowire illustrates that there exist Ni-rich microzones in as-deposited nanowires. Subsequent magnetic measurements of the array also confirmed the existence of them. In addition, it can be further inferred that the shape of Ni-rich microzones is probably barlike or disklike, from the anisotropy of zero field cooling/field cooling (ZFC/FC) curves as well as the vortex magnetization behavior of the Ni5Zn21 nanowire array. The low-temperature magnetoresistance of the Ni5Zn21 nanowire array was also measured. Giant magnetoresistance instead of anisotropic magnetoresistance is suggested to be responsible for contributing to the magnetoresistance.
TL;DR: In this article, the authors demonstrate that it is feasible to fabricate specific oxide nano-/microstructures from its corresponding nitride counterparts via controlled oxidation manner and vice versa, showing that temperature-dependent Raman scattering in both InN and In2O3 microtubes was measured and obvious downshifts of Raman modes were observed with increasing temperature.
Abstract: Cubic In2O3 microtubes were prepared by thermally oxidizing InN counterparts under controlled conditions Similar to the starting InN sample, the converted In2O3 microtubes are hexagonal in cross section and exhibit helical motifs of both right-handed and left-handed architectures with helical angles of 0°–30° InN microtubes can be retrieved by renitridation of the oxide microtubes This work demonstrates that it is feasible to fabricate specific oxide nano-/microstructures from its corresponding nitride counterparts via controlled oxidation manner and vice versa Temperature-dependent Raman scattering in both InN and In2O3 microtubes was measured and obvious downshifts of Raman modes were observed with increasing temperature
TL;DR: In this paper, X-ray absorption near-edge structure (XANES) spectroscopy was used to detect the presence of defects induced in single-walled carbon nanotubes (SWNTs) by nitric acid treated processes and by an Ar+ ion bombardment.
TL;DR: In this article, the properties of single-walled carbon nanotubes (SWNTs) immersed in a hydrobromic acid (HBr) solution were investigated using photoelectron spectroscopy.