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In this work, we put forward an effective approach by combining both highly transparent and conductive carbon nanotube (CNT) network and poly (3, 4-ethylene dioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) film to co-form-coordinate heterojunctions with silicon, and have developed a hybrid PEDOT:PSS-CNT/n-Si solar cell. The power conversion efficiency (PCE) of the as-designed solar cell can be improved up to 10.2%, which is much higher than the PCE values of both PEDOT:PSS/n-Si (5.5%) and CNT/n-Si (6.1%) solar cells fabricated using the same materials and process. PEDOT:PSS can fill the hundreds nanometer scale pores of the CNT network, both CNT network and PEDOT:PSS patches contact with the silicon concomitantly and form p Synergy -n heterojunctions through seamless contact with n-Si. The PEDOT:PSS-CNT composite film exhibits a much lower sheet resistance and remains high optical transmittance. Once the photo-generated holes are extracted to the PEDOT:PSS-CNT composite film, CNT network can serve as a carrier transport bridge, which is different from the design that inserts an ultrathin polymer between the CNT and Si. Incorporation of the continuous CNT network with PEDOT:PSS jointly in the as-designed simple and explicit structure has generated synergistic effects, which can make full use of the respective merits and then considerably enhance the PCE of hybrid PEDOT:PSS-CNT/n-Si solar cells.

Recent development in epidermal and bionic electronics systems has promoted the increasing demand for supercapcacitors with micrometer-thickness and good compatibility. Here, a highly flexible free-standing epidermal supercapacitor (SC-E) with merely 1 μm thickness and high performance is developed. Single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) hybrid films with unique inner-connected reticulation are adopted as electrodes for ultrathin structure and high electric conductivity. Then, based on two substrates with different surface energies, a stepwise lift-off method is presented to peel off the ultrathin integrated supercapacitor from the substrates nondestructively. As a result of the high conductive hybrid electrodes and the thin electrolyte layer, the as-designed supercapacitors (based on the total mass of two electrodes) achieve a good capacitance of 56 F g−1 and a superhigh power density of 332 kW kg−1, which manifest superior performance in contrast to the other devices fabricated by traditional electrodes. Meanwhile, the ultrashort response time of 11.5 ms enables the epidermal supercapacitor (SC-E) work for high-power units. More importantly, the free-standing structure and outstanding flexibility (105 times bending) endow the SC-E with excellent compatibility to be integrated and work in the next generation of smart and epidermal systems.

It is a great challenge to substantially improve the practical performance of flexible thermoelectric modules due to the absence of air-stable n-type thermoelectric materials with high-power factor. Here an excellent flexible n-type thermoelectric film is developed, which can be conveniently and rapidly prepared based on the as-grown carbon nanotube continuous networks with high conductivity. The optimum n-type film exhibits ultrahigh power factor of ∼1,500 μW m−1 K−2 and outstanding stability in air without encapsulation. Inspired by the findings, we design and successfully fabricate the compact-configuration flexible TE modules, which own great advantages compared with the conventional π-type configuration modules and well integrate the superior thermoelectric properties of p-type and n-type carbon nanotube films resulting in a markedly high performance. Moreover, the research results are highly scalable and also open opportunities for the large-scale production of flexible thermoelectric modules., Thermoelectric modules can generate electricity directly from heat and have applications to waste heat-energy conversion. Here Zhou et al. have fabricated a thermoelectric module based on an air-stable n-type single-walled carbon nanotube sheet which can reach a high power factor of 1500 μWm−1K−2.

Exploiting the superior properties of nanomaterials at macroscopic scale is a key issue of nanoscience. Different from the integration strategy, "additive synthesis" of macroscopic structures from nanomaterial templates may be a promising choice. In this paper, we report the epitaxial growth of aligned, continuous, and catalyst-free carbon nanofiber thin films from carbon nanotube films. The fabrication process includes thickening of continuous carbon nanotube films by gas-phase pyrolytic carbon deposition and further graphitization of the carbon layer by high-temperature treatment. As-fabricated nanofibers in the film have an "annual ring" cross-section, with a carbon nanotube core and a graphitic periphery, indicating the templated growth mechanism. The absence of a distinct interface between the carbon nanotube template and the graphitic periphery further implies the epitaxial growth mechanism of the fiber. The mechanically robust thin film with tunable fiber diameters from tens of nanometers to several micrometers possesses low density, high electrical conductivity, and high thermal conductivity. Further extension of this fabrication method to enhance carbon nanotube yarns is also demonstrated, resulting in yarns with ∼4-fold increased tensile strength and ∼10-fold increased Young's modulus. The aligned and continuous features of the films together with their outstanding physical and chemical properties would certainly promote the large-scale applications of carbon nanofibers.

In order to develop an excellent pseudocapacitor with both high specific capacitance and outstanding stretchability to match with other devices applicable in future wearable and bio-implantable systems, we focus our studies on three vital aspects: Stretchability of hybrid film electrodes, the interface between different components, and the integrated performance in stretchability and electrochemistry of supercapacitors based on single-walled carbon nanotube/polyaniline (SWCNT/PANI) composite films on pre-elongated elastomers. Owing to the moderate porosity, the buckled hybrid film avoids the cracking which occurs in conventional stretchable hybrid electrodes, and both a high specific capacitance of 435 F·g−1 and a high strain tolerance of 140% have been achieved. The good SWCNT/PANI interfacial coupling and the reinforced solid electrolyte penetration structure enable the integrated pseudocapacitors to have stretch-resistant interfaces between different units and maintain a high performance under a stretching of 120% elongation, even after 1,000 cyclic elongations.

We present the influence of a substrate on the properties of well-dispersed individual ZnO nanorods (NRs) with different diameters, especially on the photoluminescence (PL) properties. The studied ZnO NRs were partially supported by the quartz substrate and partially suspended in air. Continuous redshift and intensity decrease of the near band-edge emission (NBE) were observed along the suspended segment of the ZnO NRs due to the increasing temperature under UV laser excitation, suggesting that the presence of the substrate can effectively enhance the heat-sinking capability of ZnO NRs. Based on the PL measurements on individual suspended ZnO NRs with diameters from 86 nm to 2.35 μm, the redshift of NBE along the suspended segment was more obvious for ZnO NRs with a smaller diameter, indicating that the thermal conductive ability increases as diameter increases. Additionally, by combining the experimental and simulation results, we found that the presence of the substrate also quenched the whispering gallery modes (WGMs) of the ZnO NRs with a diameter above about 350 nm due to the symmetry breaking induced by the quartz substrate which has a larger refractive index compared with air. Our studies confirm that the substrate significantly influences the properties of ZnO NRs. To fully utilize the potential properties of nanomaterials for applications in nanodevices, the substrate-induced effects should be considered thoughtfully.

Research interest in ZnO nanostructures derives from their excellent luminescent properties and availability of low cost fabricating and processing, which hold promise for the development of electronic and optoelectronic nanodevices. In this review, we focus on the progress in synthesis, properties and nanodevices of ZnO nanorod (NR) arrays and nanotetrapods (NTPs). Recent work done by the authors are also presented. After a brief introduction to the controlled fabrication methods for the highly-ordered ZnO NR arrays and NTPs, we present some aspects of the fundamental properties, especially optical performance, of ZnO NRs/NTPs. Then, we provide an overview of the applications to functional nanodevices based on individual NR and NTP of ZnO. It is demonstrated that different morphologies of ZnO nanostructures have salient effects on their properties and applications. Although much progress has been achieved in the fundamental and applied investigations of ZnO NRs/NTPs over the past decade, many obstacles still remain, hampering further development in this field. Finally, some longstanding problems that warrant further investigation are addressed.

Single Walled Carbon Nanotube (SWCNT) films were directly synthesized via Floating Catalyst Chemical Vapor Deposition (FCCVD) method. Temperature dependent resistance measurements were carried out on the as-grown and chemical treated SWCNTs films. A "U" shaped curve was obtained for each sample, with a significant variation in the crossover temperatures between the as-grown and treated samples. A heterogeneous model was adopted to interpret the experimental data, revealing the coexistence of anisotropic 1D metallic conduction, conventional metallic conduction and fluctuation assisted tunneling. Our results implied very low barriers, verifying the good intertube and interbundle contacts in the directly synthesized SWCNTs films. We speculated that oxidization and acid treatments would affect the overall configuration of the films, leading to the changes in the temperature dependence of resistance. In addition, Raman and absorption spectra indicated that oxidization and acid process would cause moderate changes in the hole carrier concentration of the films.

Indium tin oxide (ITO), as one of the most important transparent conducting oxide, is widely used in electro-optical field. We have developed a simple one-step method to synthesize ITO nanowires at low temperature of 600 degrees C. In detail, mixtures of InN nanowires and SnO powder, with the molar ratio of 10:1, have been used as precursors for the thermal evaporation-deposition of ITO nanowires on silicon/quartz slices. During the growth process, the evaporation temperature is maintained at 600 degrees C, which favors the decomposition of InN and oxidation of In, with a limited incorporation of Sn in the resulting compound (In:Sn approximately 11:1 in atomic ratio). As far as we know, this is the lowest growth temperature reported on the thermal deposition of ITO nanowires. The diameters of the nanowires are about 120 nm and the lengths are up to tens of micrometers. XRD characterization indicates the high crystallization of the nanowires. HRTEM results show the nanowires grow along the [200] direction. The transmittance of the nanowire film on quartz slice is more than 75% in the visible region. Based on photolithography and lift-off techniques, four-terminal measurement was utilized to test the resistivity of individual nanowire (6.11 x 10(-4) omega x cm). The high crystallization quality, good transmittance and low resistivity make as-grown ITO nanowires a promising candidate as transparent electrodes of nanoscale devices.

In this paper, we demonstrate the optical and electrical performance of ZnO nanorod arrays after surface passivation. The material of larger band gaps (HfO2) was chosen for the surface passivation layer through atom layer deposition (ALD), in order to confine the carriers within the core material efficiently. In the case of nanorods with high defects, HfO2 coating treatment not only improved near band edge (NBE) but also greatly enhanced the defect luminescence, while in the case of nanorods with low defects, surface coating suppressed defect luminescence and promoted the NBE emission as well as electrical performance therein. PL investigation at 10 K displayed that after surface coating phonon related emission was confined along c-axis and the exciton emission related to surface states was largely restrained. Therefore, it's suggested that surface passivation of ZnO nanorod arrays decreases the surface defect, enhances the side confinement of nanorod, and thus improves the optical and electrical performance efficiently.

We demonstrate a facile method to synthesize ultrathin vertical ZnO nanowall arrays only through a one-step catalyst fabrication procedure. After being coated with uniformly dispersed gold particles, the substrates were polished gently to create discrete gold nanoparticle alignment as catalyst. The commercial ZnO powder and activated carbon powder with an atom ratio of 1:1 were utilized as source materials, and the whole growth process occurred in a conventional tube furnace chemical vapor deposition (CVD) system. The SEM images confirm that the ZnO nanowall arrays grow vertically along certain tracks made by polishing. The walls are about 17 nm wide, 90 nm high and 1 microm long after 90 min growth. After second growth, the nanowalls become 20 nm wide, 205 nm high, and 2 microm long. AFM images indicate that the alignment of discrete Au particles with certain separations due to polishing plays the key role in realizing vertical ZnO nanowall arrays.

Ultrathin SWCNT transparent and conductive films on flexible and transparent substrates are prepared via repeatedly halving the directly grown SWCNT films and flexible and transparent supercapacitors with excellent performance were fabricated.

An ingenious strategy is put forward to evaluate accurately the thermoelectric performance of carbon nanotube (CNT) thin films, including thermal conductivity, electrical conductivity, and Seebeck coefficient in the same direction. The results reveal that the as-prepared CNT interconnected films and CNT fibers possess enormous potential of thermoelectric applications because of their ultrahigh power factors.

Bimetallic alloy nanoparticles (NPs) exhibit unique optical and catalytic properties that are dependent on their morphology and composition. In this paper, a general and facile way was developed to prepare Ag-related bimetallic alloy NPs with hollow/porous structures, including AgAu, AgPd, and AgPt. The formation of the alloy structures is evidenced by high-resolution transmission electron microscopy (TEM), scanning transmission electron microscopy−energy-dispersive X-ray analysis (STEM-EDX) mapping, and ultraviolet−visible−near-infrared (UV−vis−NIR) absorption spectra. AgM alloy NPs exhibit peroxidase-like activity. A unique composition dependence is found and can be used to tailor the catalytic activity. In addition to the recent discoveries about peroxidase mimetics on Fe3O4 NPs and sheetlike FeS nanostructures, our findings suggest a new type of candidate as peroxidase mimics. Furthermore, for noble metals, apart from size and shape, tailoring the composition poses another effective way to tune the ca...

Heterostructures of side-to-side biaxial ZnS/Zn2SnO4 (ZTO) nanowires have been fabricated via a simple one-step thermal evaporation process. Structural characterization by high-resolution transmission electron microscopy and electron diffraction indicates that both the face-centered cubic spinel ZTO subsection and the wurtzite ZnS subsection of the heterostructure are well crystallized with a distinct interface along the heterostructure axial direction. Based on detailed analysis of the growth process of biaxial ZnS/ZTO nanowire heterostructures, there are two dominating stages: a vapor-liquid-solid (VLS) controlled growth of ZTO sub-nanowire and a self-assembly growth of ZnS sub-nanowire onto the preformed ZTO base nanowire. A growth model of the heterostructures is proposed. The presented method would be flexible and feasible for the synthesis of other nano-heterostructures with non-oxide/oxide interface to meet the growing demands of nanoscale science and technology. (C) 2009 Elsevier B.V. All rights reserved.

Great interest in single-walled carbon nanotubes (SWCNTs) derives from their remarkable electrical, thermal, optical, and mechanical properties together with their lower density, which promise extensive and unique applications. Much progress has been achieved in the fundamental and applied investigations of SWCNTs over the past decade. At the same time, many obstacles still remain, hampering further development in this field. To clarify the emerging problems and to provide a comprehensive understanding of the field, we review the recent progress of research on the synthesis, structure, and properties of SWCNTs, in particular the SWCNT non-woven film, SWCNT rings, boron-nitrogen (B-N) co-doped SWCNTs (BCN-SWNTs), and individual SWCNTs. Some long-standing problems and topics warranting further investigations in the near future are addressed.

Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks, but their potential has not been fully realized in composite materials due to weakness at the interfaces. Here we demonstrate that through load-transfer-favored three-dimensional architecture and molecular level couplings with polymer chains, true potential of CNTs can be realized in composites as initially envisioned. Composite fibers with reticulate nanotube architectures show order of magnitude improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. The molecular level couplings between nanotubes and polymer chains results in drastic differences in the properties of thermoset and thermoplastic composite fibers, which indicate that conventional macroscopic composite theory fails to explain the overall hybrid behavior at nanoscale.

A simple and facile method was developed to fabricate alloyed Pt−Ag nanoislands on Au nanorods (denoted as Au@Pt−Ag NRs). The island growth mode of Pt on the Au rod was employed to guide the growth behavior of Pt−Ag alloys. The formation of the Pt−Ag alloy was confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), UV−visible absorption spectra, and electrochemical characterization. The alloy compositions can be tuned within the broad miscibility gap from Ag9Pt91 to Ag83Pt17 by controlling the ratios of PtCl42−/Ag+. The Au@Pt−Ag NRs show tunable surface plasmon resonance (SPR) and enhanced catalytic activity for methanol electro-oxidation, pointing to a potential future of nanometerized Pt−Ag alloys in fuel cells and other related fields. Apart from Pt−Ag, this strategy may be applied to the formation of Pt-related bimetallic (trimetallic) systems.

We demonstrate a promising route to fabricate large scale hexagonally patterned, vertically aligned ZnO nanorod arrays with small diameter. By adding 3-mercaptopropyltriethoxysilane (MPTES) molecules as a connection between catalyst and substrate the large size dispersion resulting from the removal of catalyst pattern is avoided, thus the catalyst particle pattern with tiny size dispersion and regular shape is obtained; the size can be tuned in a large range from 50 nm to 300 nm. Using this technique, ZnO nanorod arrays with tunable spacings and diameters are achieved, which also have uniform shape and length, good crystal quality, and vertical alignment on the substrate. Moreover, a pronounced blue-shift of ultraviolet (UV) luminescence spectra of ZnO nanorods with their diameters decreasing is observed. Combining the temperature-dependent photoluminescence (PL), we suggest that a materially decreased exciton-phonon interaction with the reduced diameter of ZnO nanorods is the main reason for the blue-shift of UV luminescence.

A clear and reliable theoretical investigation on dibromomethane (CHBr,) photodissociation is desired. The calculation must consider: (i) relativistic effects; (ii) the potential energy curves (PECs) of spin-orbit coupling states; (iii) geometry optimization by the method with both static and dynamic electron correlations; (iv) solvent effects oil the photodissociation in the solution. All these have been considered in this study by state-of-the-art quantum chemical calculations. The experimentally observed photodissociation in the gas phase with products of spin-orbit-coupled states, Br(P-2(3/2)) and Br*(P-2(1/2)), was assigned by multi-state second order multiconfigurational perturbation theory in conjunction with spin-orbit interaction through complete active space state interaction (MS-CASPT2/CASSI-SO) PECs. The mechanisms of the experimentally observed photodissociation and photoisomerization in solvent were elucidated by the MS-CASPT2/CASSI-SO method combined with polarized continuum model of the solvent. (C) 2008 Wiley Periodicals, Inc. J Comput Chem 29: 2513-2519, 2008

Single crystalline Au nanorods (Au NRs), synthesized via seed-mediated growth, show unique surface structures. Apart from the oft-observed {100} and {111} facets, unexpectedly, unstable {110} facets dominate in such nanorods due to {110} restricted growth. Unique properties have been suggested for the nanorods. One novel property, we believe, is that the the high-energy {110} endows the nanorod with a high reactivity, thus making the growth to more stable morphologies possible. Herein, by switching the growth to the {110} preference, we successfully obtained thermodynamically more stable morphologies (arrow-headed gold nanorods and gold nano-octahedra) with a high quality and yield. A blockade of selective underpotential deposition of silver is suggested to be responsible for the switching.

Individual zinc oxide tetrapods were designed as multiterminal sensors by the e-beam lithography method. Different from double-terminal sensors, these sensors can give multiple responses to a single signal at the same time. The designed tetrapod devices were employed to detect light with different wavelength. The results indicate that they are remarkable optoelectronic devices, sensitive to ultraviolet light, and have advantages on distinguishing noises and increasing sensitivity. This should be helpful for weak signal measurements of nanodevices.

A highly efficient direct electrodeposition method was used to prepare Co−Cu alloy nanotubes in an anodic alumina template without modification. The morphology and structure of as-prepared Co−Cu nanotubes were examined by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The formation mechanism of the tubular nanostructure is discussed. It was found that the template directed electrodeposition of Co−Cu at a large current density can result in the highly efficient growth of nanotubes and that the growth rate as well as the wall thickness of the nanotubes can be controlled via the current density of electrodeposition. Magnetic measurements of the Co−Cu nanotube array show that the nanotubes are ferromagnetic at room temperature and may find potential applications in the fields of biological separation and drug delivery.

Single-crystal Zn2SnO4 (ZTO) nanowires were synthesized by thermal evaporation of a mixture of Zn and SnO powders at 1000 °C. The ZTO nanowires showed unique periodical structures in contrast to the traditional nanowires. It was found that the yield of the single-crystal ZTO nanowires was strongly dependent on the weight ratio of Zn and SnO in the source mixture. With the decrease of Zn content in the source, twinned ZTO nanowires with alternating (111) twins along the axial direction can be obtained. The formation mechanism of these ZTO nanostructures is discussed. The photoluminescence of the ZTO nanowires was measured.

One-dimensional (1D) semiconducting oxide nanostructures such as ZnO, SnO2, and In2O3 have been extensively studied due to their excellent optical and electrical properties. Growth of 1D nanostructures with precisely controlled size, phase purity, crystallinity, and chemical composition still presents numerous challenges. In this review, we report the recent progress on the synthesis of binary oxide nanostructures consisting of different oxides through a simple and effective vapor transport approach in our research. By controlling the experimental conditions, this approach enables the synthesis of various multicomponent binary oxide nanowires.

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.

Water molecules adsorbed on a double-walled carbon nanotube (DWCNT) serve as charge trapping centers when present in low density and as electron donors when present in high density. There is a discontinuous change between the low- and high-density regions. H2O molecules are apt to be adsorbed on the outer surface of DWCNTs, and in this case the electrical transport properties are extremely sensitive to environment, which suggests that DWCNTs are hole doped and act as an electric dipole with the inner tube.

Arrays of noble metal nanoparticles show potential applications in (bio-)sensing, optical storage, surface-enhanced spectroscopy, and waveguides. For all such potential devices, controlling the size, morphology, and interparticle spacing of the nanoparticles is very important. Here, we combine seed-mediated growth with nanosphere lithography to study the controllable growth of gold nanoparticles (Au NPs), in which the self-assembly monolayer of polystyrene (PS) on a silicon surface is used to guide the modification of alkanesilanes and the subsequent adsorption of gold seeds; seed-mediated growth is applied to controlling the morphology and size of Au NPs. The size of adsorption region (determining the number of adsorbed gold seeds) is controlled by etching PS microspheres with oxygen plasma or annealing PS microspheres at the glass transition temperature. The size and morphology of the Au NPs are controlled by changing growth conditions. In such a way, we have achieved the dual control of the obtained Au NPs. Preliminary results show that this strategy holds a great promise. This approach can also be extended to a wide range of materials and substrates.

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.

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.

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 5.3 V/microm.

Field emission from single-walled carbon nanotube (SWNT) nonwoven has been investigated under high vacuum with different vacuum gaps. A low turn-on electric field of 1.05 V/μm is required to reach an emission current density of 10 μA/cm2. An emission current density of 10 mA/cm2 is obtained at an operating electric field of 1.88 V/μm. No current saturation is found even at an emission current of 5 mA. With the vacuum gap increasing from 1 to 10 mm, the turn-on field decreases monotonically from 1.21 to 0.68 V/μm, while the field amplification is augmented. The good field-emission behaviour is ascribed to the combined effects of the intrinsic field emission of SWNT and the waved topography of the nonwoven.

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.

By investigating the morphologies and microstructures of the cathode deposits prepared by self-sustained arc discharge between graphite rods, we consider that there are two electron emission mechanisms occurring on the cathode: field emission and thermionic emission. The former occurs mainly on the edge of the growing surface, by which we can explain the formation of the outer hard shell of the cathode deposit; while the latter occurs mainly on the growing surface except for the edge area and it is the main cause for the growth of carbon nanotubes.

A new experimental technique has been presented to investigate the surface-enhanced Raman scattering (SERS) on “individual and untouched” single-walled carbon nanotubes (SWNTs) deposited onto gold or silver film-covered substrate through a direct CVD method. It was found that the radial breathing mode for SERS shows a narrower linewidth than the normal Raman spectroscopy (NRS). Relative to NRS, the SERS spectra also revealed a preferable contribution to some metallic component of the G line. However no obvious difference for D and G′ between SERS and NRS has been revealed, which is different from the previous results on bulk SWNT samples.

Wurtzite InN nanobelts have been synthesized in bulk quantities by means of in situ nitriding indium oxide powders in ammonia flux, with a high yield, high purity and good reproducibility. As-synthesized InN nanobelts have typical widths of 1–5 μm, thickness of 40–50 nm and lengths of tens to hundreds of microns imaged by scanning electron microscopy. Transmission electron microscopy reveals that the synthesized InN nanobelts are single crystalline in [0 0 0 1] orientation and preferentially enclosed by top surfaces ± ( 0 1 1 ¯ 0 ) /side surfaces ± ( 2 1 ¯ 1 ¯ 0 ) . Photoluminescence spectrum of InN nanobelts at room temperature shows a strong emission peak centered at 704 nm (1.76 eV).

In this paper, we discussed recent studies done in our laboratories with a floating catalyst chemical vapor deposition (CVD) method. We can grow single- or double-walled carbon nanotubes (SWNTs/DWNTs) with different kinds of catalysts. Single-walled carbon nanotubes without amorphous carbon coating were prepared by thermally decomposing acetylene (C2H2) at the temperature range of 750–1200 °C with ferrocene as catalyst. While with sulfur promoted ferrocene catalyst, double-walled carbon nanotubes were mass-produced by pyrolizing C2H2 at the temperature range of 900–1100 °C. Furthermore, tunable growth of DWNTs with different diameter was achieved in our experiment. It is found that DWNTs produced at lower carbon partial pressure have much smaller inner tubes, even DWNTs with the smallest inner diameter of 0.4 nm was found in here. As convenient and effective tool, radial breathing mode (RBM) of Raman scattering technique can be used to distinguish SWNTs from DWNTs. In further studies of Raman scattering with DWNTs, the possible match of the inner tubes and the outer tubes according to the RBM bands was assigned, and different chirality types were discussed according to the diameter and chirality dependence of resonant Raman vibration. We also investigated the temperature-dependent frequency shift of resonant Raman spectra of DWNTs in the range of 78–650 K. We found that different RBM peaks, which are relative to different tube diameters, have different temperature coefficient of frequency shift, and the larger diameter carbon nanotubes have more RBM frequency downshift with increasing temperature. It is ascribed to the RBM frequency variation to the temperature dependence of the stretching force constant of C–C bond. Besides, Polarized Raman spectra were preformed on well-aligned SWNTs structure fabricated through post-growth method and found that the angular dependence of Raman intensity is consistent well with the predictions of the resonance Raman theory.

Branching structures in nanometer level are of great importance in developing nanoscale science and functional electrical devices. In this letter, multidimensional magnesium oxide structures with cone-shaped branching have been mass-produced using a simple chemical vapor deposition method. The dominant structures in the product include two-dimensional ‘+’, ‘T’, or ‘Γ’ assemblies, and three-dimensional complex configurations. The results presented here enrich the nanoscale community with new basic materials for the fabrication of functional electrical and chemical sensing devices.

The well-defined silver (Ag) nanowires with five-twinned structure have been prepared by polyol reduction in the presence of poly(vinylpyrrolidone) (PVP K-30, 40 000). The obtained Ag nanowires are nearly monodispersed with an average diameter of 70 nm and length of 6 μm. It is confirmed from the results of thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Fourier transform Raman spectra (FT-Raman) that one monolayer of the PVP molecules might be absorbed on the surface of the Ag nanowires through Ag−O coordination. On the basis of the experimental analysis, the probable spatial conformation of the PVP molecules is supposed to be that the CH skeleton chain of the PVP is close to the surface of the Ag nanowires. The pyrrolidone ring might be tilted on the surface of the Ag nanowires through Ag:O coordination. These results may provide direct evidence for the role of the PVP molecules in the formation of the Ag nanowires.

Double-wall carbon nanotubes (DWCNTs) were synthesized by pyrolyzing C2H2 on the sulfur-promoted floating iron catalyst. Similar to that of SWCNTs, Raman spectra of DWCNTs display two "fingerprint" features of the radial breathing mode (RBM) at the lower frequency range and the splitting tangential mode (TM). However, RBM frequencies of DWCNTs take a wider range and display much richer peaks than those of SWCNTs. The possible match of the inner tubes and the outer tubes according to the RBM bands was assigned, and different chirality types were discussed according to the diameter and chirality dependence of resonant Raman vibration. By changing experimental conditions, we can tunably grow different DWCNTs with various diameter distributions.

We demonstrate that Fe impurities in double-walled carbon nantoubes (DWNTs) may be greatly depressed by improving the experimental setup in a floating catalyst CVD method. In the paper, the effect of different experimental parameters on sample purity has been systematically studied. The possible reasons for the decrease of impurity in the DWNT samples prepared with the improved apparatus are discussed. The process should be helpful for preparing high quality single- or double-walled carbon nanotubes in scale-up applications.

Double wall carbon nanotubes (DWCNTs) were mass-produced by pyrolizing C2H2 at the temperature range of 900–1100 °C on a floating iron catalyst with sulfur promoted. Our experiments indicated that the growth of DWCNTs was strongly dependent on the sulfur addition, and without sulfur only single wall carbon nanotubes (SWCNTs) were produced. The outer tube diameters of DWCNTs observed by high resolution electron microscopy (HRTEM) vary from 1.05 to 2.89 nm, and the inner tube diameters vary from 0.40 to 2.19 nm. The effect mechanism of sulfur to the growth of DWCNTs was discussed.

In this Letter, we report the synthesis of cone-shaped 6H–SiC nanorods by an arc-discharge process. The axis of nanorods is preferentially along the 〈1 0 1 0〉 direction. The diameters of the thin tips are about 10–30 nm , and the lengths range from tens of nanometers up to 1 μm . Branched nanostructures are also formed and the branches form 60° or 120° angles with the main nanorods. The formation of gradually enlarged Fe–Al–Si–C droplets and their high-enthalpy have led to the growth of cone-shaped hexagonal structure SiC nanorods by a VLS mechanism.

The structure separation of synthetic single-wall carbon nanotube (SWCNT) mixture species with diameters larger than 1.2 nm still remains a challenge. Here, an NaOH-assisted gel chromatography method is used for the structure separation of the SWCNT mixture with a diameter range of 1.2–1.7 nm, in which NaOH is used to tune the interaction between distinct (n, m) SWCNTs and gel. Incrementally increasing NaOH concentration in SWCNT dispersion selectively enhances the adsorbability of different-structure SWCNTs and enlarges their interaction difference with gel, leading to their structure separation after applying into a gel column system. On this basis, a two-step method is developed for further improving the structure purity of the separated SWCNTs by combining overloading and stepwise elution. These results are well demonstrated by the optical spectra of the separated SWCNTs. This work paves a way for single-chirality separation of large-diameter SWCNTs using gel chromatography technique and is an advanced progress in the structure control of SWCNTs.

Continuous CNT fibers have been directly fabricated in a speed of 50 m/h–400 m/h, based on an improved chemical vapor deposition method. As-prepared fibers are further post-treated by acid. According to the SEM images and Raman spectra, the acid treatment results in the compaction and surface modification of the CNTs in fibers, which are beneficial for the electron and load transfer. Compared to the HNO3 treatment, HClSO3 or H2SO4 treatment is more effective for the improvement of the fibers' properties. After HClSO3 treatment for 2 h, the fibers' strength and electrical conductivity reach up to ~ 2 GPa and ~ 4.3 MS/m, which are promoted by ~ 200% and almost one order of magnitude than those without acid treatment, respectively. The load-bearing status of the CNT fibers are analyzed based on the downshifts of the G ' band and the strain transfer factor of the fibers under tension. The results reveal that acid treatment could greatly enhance the load transfer and inter-bundle strength. With the HClSO3 treatment, the strain transfer factor is enhanced from ~ 3.9% to ~ 53.6%.

In this work, we have presented a freestanding and flexible CNT-based film with sheet resistance of 60 Ω/ and transmittance of 82% treated by nitric acid and chloroauric acid in sequence. Based on modified CNT film as a transparent electrode, we have demonstrated an ultrathin, flexible organic solar cell (OSC) fabricated on 2.5-μm PET substrate. The efficiency of OSC, combined with a composite film of poly (3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PCBM) as an active layer and with a thin layer of methanol soluble biuret inserted between the photoactive layer and the cathode, can be up to 2.74% which is approximate to that of the reference solar cell fabricated with ITO-coated glass (2.93%). Incorporating the as-fabricated ITO-free OSC with pre-stretched elastomer, 50% compressive deformation can apply to the solar cells. The results show that the as-prepared CNT-based hybrid film with outstanding electrical and optical properties could serve as a promising transparent electrode for low cost, flexible and stretchable OSCs, which will broaden the applications of OSC and generate more solar power than it now does.