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Indium nitride crystallites were grown viacombination of vapor–liquid–solid (VLS) and vapor–solid (VS) growth mechanisms using Au nanoparticles as catalysts. A surface diffusion model was proposed to interpret the formation mechanism of the InN crystallites. Facets of InN crystallites were tunable with variation of NH3flux. [ABSTRACT FROM AUTHOR]

Abstract: 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 0.4nm 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 78–650K. 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. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Reports a concept of the confined polaron. Two types of polaron in solids; Discussion on intrinsic polarons; Correlation between the polaron and the luminescence spectroscopy in porous silicon.

Iodine-doped multiwall carbon nanotubes (I-MWNTs) were characterized by means of Raman scattering and thermogravimetric analysis. The results show that multiwall carbon nanotubes (MWNTs) can be effectively doped by iodine and exchange electrons with iodine. Iodine atoms form charged polyiodide chains inside tubes of different inner diameter, which is similar to the iodine-doped single-wall carbon nanotubes (I-SWNTs), but can not intercalate into the graphene walls of MWNTs. The Raman scattering behavior of I-MWNTs exhibits some differences from that of I-SWNTs and the low-dimensional conductive hydrocarbon-iodine complex “perylene·I[sub 2.92].” © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a two-dimensional structure of 1-nonanethiol-capped gold nanoparticles. Background on nanoparticles; Methodology; Results and discussion.

Chirality separation of single-wall carbon nanotubes (SWCNTs) is key to enabling applications in single photon sources, optoelectronic devices and bioimaging, and it generally requires multiple separation steps to obtain single chirality species with the desired purity. In this work, we report the use of a novel sodium hyodeoxycholate (SHC) surfactant for separation of single-chirality SWCNTs. The results demonstrated that chirality-selective adsorption and desorption of SWCNTs on a gel column can be achieved readily by modulating the concentrations of the SHC-based mixed surfactants. Through an optimized one-step procedure, single-chirality (6,5) SWCNTs were successfully separated, and the chirality purity was estimated to be 97% by using a spectroscopic approach, exceeding most reported purities for traditional surfactant-based one- or multiple-step separations. Due to the ultrahigh chirality resolution of the present method, the (6,5) SWCNTs can also be effectively separated from different SWCNT materials with various diameter or chirality distributions, even from materials containing very few (6,5) SWCNTs. The high-purity chirality separation demonstrated in this work lays an important foundation for the industrial production and applications of single-chirality SWCNTs. [Display omitted] [ABSTRACT FROM AUTHOR]

Structural control of single-wall carbon nanotubes (SWCNTs) with uniform properties is critical not only for their property modulation and functional design but also for applications in electronics, optics, and optoelectronics. To achieve this goal, various separation techniques have been developed in the past 20 years through which separation of high-purity semiconducting/metallic SWCNTs, single-chirality species, and even their enantiomers have been achieved. This progress has promoted the property modulation of SWCNTs and the development of SWCNT-based optoelectronic devices. Here, the recent advances in the structure separation of SWCNTs are reviewed, from metallic/semiconducting SWCNTs, to single-chirality species, and to enantiomers by several typical separation techniques and the application of the corresponding sorted SWCNTs. Based on the separation procedure, efficiency, and scalability, as well as, the separable SWCNT species, purity, and quantity, the advantages and disadvantages of various separation techniques are compared. Combined with the requirements of SWCNT application, the challenges, prospects, and development direction of structure separation are further discussed. [ABSTRACT FROM AUTHOR]

The intersubband plasmons (ISBPs) of single‐wall carbon nanotubes (SWCNTs) endow SWCNT‐based optoelectronic devices with more functions. However, the structural dependence of the ISBPs of SWCNTs is not fully understood. Here, the effect of electronic types and diameters of SWCNTs on the energy and intensity of their ISBPs is investigated systematically. The results show that the ISBP energy of semiconducting SWCNTs is ≈50–250 meV larger than that of metallic SWCNTs with the same diameters, while the ISBP integral intensity is approximately 1.25 to 4 times stronger. Diameter dependence of ISBPs for both semiconducting and metallic SWCNTs is also observed. With a decrease in diameter, the ISBPs shift to higher energies, while the intensity decreases dramatically. When the diameter is reduced to less than 1 nm, the ISBPs become unobservable. Interestingly, the energy separation between the ISBPs and interband transition S22 (M11) decreases with an increase in diameter. Theoretical calculations show that the structure‐dependent ISBP characteristics are dominated by the electronic states of SWCNTs. Based on the ISBP characteristics of different SWCNTs, high‐performance SWCNT‐based near‐infrared electrochromic devices are fabricated by mixing small‐diameter metallic SWCNTs with semiconducting SWCNTs due to their high conductivity and negligible ISBP signals. [ABSTRACT FROM AUTHOR]

Abstract: Using the carbon nanotube (CNT) arrays embedded in anodic aluminum oxide (AAO) template as an electrode, large amounts of Ni nanoparticles have been encapsulated into the CNTs by an alternating current (AC) electrodepostion technique. As deposited Ni nanoparticles with a typical size of 50–60 nm randomly nucleated on the CNT walls, thus inhomogeneously distributed in the CNTs. After annealing at 600 ∘C, the nanoparticles transformed into quasi-spherical structures with the diameter increasing to 60–80 nm. The quasi-spherical nanoparticles were aligned in orderly rows along the axis of the CNT channels. Magnetic hysteresis measured at 5 K showed that the coercivity was 450 Oe for the as-deposited sample and 385 Oe for annealed sample, with the applied magnetic field parallel with the CNT’s axis. The structures and magnetic properties were discussed for both as-deposited and annealed samples. [Copyright &y& Elsevier]

Abstract: A new type of flower-like ZnO nanostructure was prepared on a large scale through a very simple solvothermal method. The nanoflowers are assembled by many thin and uniform hexagonal-structured ZnO nanosheets, with a thickness of around 6nm. The growth mechanism of the nanoflowers is discussed based on the reaction conditions. Room-temperature optical measurements reveal that such ZnO nanoflowers have very strong UV bandedge emission with a large Stokes shift and an asymmetrical band profile. This luminescence characteristic may be attributed to the anisotropic energy band structure of the quantum-confined ZnO nanosheets. [Copyright &y& Elsevier]

There is strong demand for higher energy density and flexible lithium ion batteries recently. Unfortunately, electrodes built by conventional methods cannot meet these requirements simultaneously due to the large amount of inactive additives needed for sufficient flexibility. Herein, by utilizing a continuous single‐walled carbon nanotube reticulation and designing an all‐in‐one hierarchical configuration, binder‐free electrodes are fabricated via an in situ integration procedure. The electrode exhibits excellent electrochemical performance against up to 20 000 cycles of bending and high energy density (up to 493 Wh kg−1electrode and 820 Wh L−1electrode). The hierarchical configuration takes full diverse advantages of different carbon nanostructures. The as‐obtained novel binder‐free electrodes exhibit not only good cyclability (up to ≈90% capacity retentions after 1500 cycles) with only 4 wt% additive materials, but also show enhanced kinetic process, in comparison to those of traditional electrodes. Furthermore, based on the as‐designed electrodes, flexible cells are assembled and a practical wearable system is fabricated, manifesting that they can be used in a stable and flexible power supply for smart systems. [ABSTRACT FROM AUTHOR]

We report an innovative method for the fast preparation of wafer-scale uniform single-wall carbon nanotubes (SWCNT) films with controllable density by NaHCO 3 tuning the interaction between amine-functionalized substrates and surfactant-dispersing SWCNTs in aqueous solution. With this technique, a 4-inch SWCNT film with a linear density of ∼30 tubes/μm can be achieved in 1 s, and over 60 tubes/μm within 30 s using a high-concentration SWCNT solution. The SWCNT density changes by less than 8% over a 4-inch area. The electrical uniformity of the as-prepared wafer-scale single-chirality SWCNT film was demonstrated to be within 10.8% for subthreshold swing and 12% for carrier mobility and 13.5% for their on-current, which is the most uniform SWCNT films reported so far fabricated from the surfactant-dispersed SWCNT solution. Further, the photodetectors made by the uniform semiconducting SWCNT films exhibit excellent cascading ability, which linearly amplify the output photovoltages and could produce a photovoltage responsivity of 2.5 × 106 V/W. When three-stage cascading photodetectors are used as optical gate to establish an integrated photoelectric system, a 20-mW/cm2 light illumination produces the current responsivity of 147.3 A/W under a source/drain voltage of −0.1 V. Our present technique lays an important foundation for their applications in integrated circuits. Image 1 [ABSTRACT FROM AUTHOR]

The electric resistance CoFe[SUB2]O[SUB4] nanocrystals of different sizes, obtained by the coprecipitation method was investigated under pressure up to 20 GPa in a diamond anvil cell at ambient temperature. The experimental results indicate that the phase transition (from the spinel to a tetragonal structure) takes place at 7.5 and 12.5 GPa for 6 and 80 nm, nanocrystals, respectively, in agreement with the prediction of scaling theory of the phase transition of nanocrystals. The relatively low transition pressure for CoFe[SUB2]O[SUB4] is related to the high d-electron coupling between magnetic ions and to the small band gap in CoFe[SUB2]O[SUB4] as compared to the other spinel ferrites. These results are discussed in terms of decreasing band gap with increasing pressure. The smaller the size of nanocrystals, the higher the phase transition pressure. The resistance of CoFe[SUB2]O[SUB4] nanocrystal decreases exponentially under pressure, according to R∝exp(-CP), where C = 0.7634 Gpa[SUP-1] for large nanocrystals (80 nm) and C = 0.5124 Gpa[SUP-1] for CoFe[SUB2]O[SUB4] of 6 nm. [ABSTRACT FROM AUTHOR]

Fe[sub 80]P[sub 20] amorphous alloy, amorphous Fe-P-C, and amorphous Fe-P strengthened with embedded carbon nanotubes were fabricated by the rapid solidification process. Magnetothermal analysis, high-resolution transmission electron microscopy, and x-ray diffraction were employed to investigate the crystallization behavior of these amorphous alloys. Carbon nanotubes embedded in the amorphous matrix increases the apparent crystallization temperature by about 100 K and modifies the crystallization process compared to those of amorphous Fe-P and amorphous Fe-P-C. The role of the added carbon nanotubes will be discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs), also called electrochemical capacitors, often show high power density, excellent charge/discharge rates, and long cycle life. The recent development of flexible and wearable electronic devices requires that their power sources be sufficiently compact and flexible to match these electronic components. Therefore, flexible SCs have attracted much attention to power current advanced electronics that can be flexible and wearable. In the past several years, many different strategies have been developed to programmably construct different nanocarbon materials into bendable electrode architectures. Furthermore, flexible SC devices with simplified configurations have also been designed based on these nanocarbon-based architectures. Here, recent developments in the programmable assembly of bendable architectures based on nanocarbon materials are presented. Additionally, the design of flexible nanocarbon-based SC devices with various configurations is highlighted. The progress made recently paves the way for further development of nanocarbon architectures and corresponding flexible SC devices. Future development and prospects in this area are also analyzed. [ABSTRACT FROM AUTHOR]

The free-standing Si-coated carbon nanofiber (Si/CNF) mat was fabricated for the anode of lithium ion battery through combining electrospun CNF mat with electrodeposited Si layer. Spaghetti or granule-like Si was obtained by varying the deposition conditions. This Si/CNF mat was directly used as an active material and a current collector as well, which involves neither binders nor additional metal substrate. The best performance was achieved in spaghetti-like Si due to its highly porous nature which can accommodate volume expansion and large surface area which benefit the efficient charge transfer both at Si/CNF interface and at the electrode/electrolyte interface. The optimized Si/CNF mat after annealing at 1000 °C delivered a capacity of 870 mA h g −1 at 1st discharge and 730 mA h g −1 at 50th discharge with a capacity retention of 84%, improving the capacity of pure CNF (280 mA h g −1 at the 50th discharge) by almost three times. In addition, corrosion of the current collector no longer exists in our approach. Our X-ray photoemission spectroscopy and electrochemical analysis revealed that the formation of Si–C bond through high temperature annealing can enhance the adhesion between silicon and carbon at the interface which benefits the cyclic performance of anode ultimately. [ABSTRACT FROM AUTHOR]

Asymmetric supercapacitors with high energy density are fabricated using a self-assembled reduced graphene oxide (RGO)/MnO2 (GrMnO2) composite as a positive electrode and a RGO/MoO3 (GrMoO3) composite as a negative electrode in safe aqueous Na2SO4 electrolyte. The operation voltage is maximized by choosing two metal oxides with the largest work function difference. Because of the synergistic effects of highly conductive graphene and highly pseudocapacitive metal oxides, the hybrid nanostructure electrodes exhibit better charge transport and cycling stability. The operation voltage is expanded to 2.0 V in spite of the use of aqueous electrolyte, revealing a high energy density of 42.6 Wh kg−1 at a power density of 276 W kg−1 and a maximum specific capacitance of 307 F g−1, consequently giving rise to an excellent Ragone plot. In addition, the GrMnO2//GrMoO3 supercapacitor exhibits improved capacitance with cycling up to 1000 cycles, which is explained by the development of micropore structures during the repetition of ion transfer. This strategy for the choice of metal oxides provides a promising route for next-generation supercapacitors with high energy and high power densities. [ABSTRACT FROM AUTHOR]

Conventional methods to produce graphene/silicon Schottky junctions inevitably involve graphene transfer and metal deposition, which leads to the techniques being complicated, high-cost, and environmentally unfriendly. It is possible to directly grow hybrid nanocrystalline graphene/graphite transparent electrodes from photoresist on quartz without any catalyst. Due to the source material being photoresist, nanographene/graphite patterns can easily be made on Si/SiO2 structures to form nanographene/silicon Schottky junctions via commercial photolithography and silicon techniques. The obtained Schottky junctions exhibit excellent properties with respect to photodetection, with photovoltage responsivity of 300 V W-1 at a light power of 0.2 μW and photovoltage response time of less than 0.5 s. The devices also exhibit an excellent reliability with the photovoltage deviating less than 1% when cycled over 200 times. [ABSTRACT FROM AUTHOR]

Bottom-upself-assembly is able to constitute a variety of structuresand has been thought to be a promising way for advanced nanofabrication.Droplet evaporation, as the simplest method, has been used in variousself-assemblies. However, the assembled area is not large enough andthe order is still not well controlled. Here we show a facile andcontrollable two-stage droplet evaporation method by adjusting thehumidity and temperature of the evaporating droplet. Taking the highlymonodispersed gold nanorods (GNRs) as an example, large-area, self-assemblymonolayer arrays are reproducibly achieved. To understand the self-assemblymechanism, we adopted simplified models to analyze the interactionsbetween the nanorods. The results show that a metastable state ofsecondary-energy-minimum exists, especially in the latter stage ofthe assembly process, leading to the ordered arrays. A large electrostaticbarrier between the assembled arrays prevents the formation of themultilayer structures and thereby leads to the preferential monolayers.Moreover, we predict possibilities of different types of assembliesof the nanorods, and a schematic phase diagram is finally given. Theresults here may offer a way toward high-quality self-assembled nanoparticlessuperlattices for use in enhanced spectroscopy, sensors, or nanodevices. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotube (CNT) fibers are a novel type of fibrous materials that show potential in polymeric composite fields. In this study, we investigated the interfacial behavior of a single single-walled carbon nanotube (SWCNT) fiber embedded in isotactic polypropylene (iPP) matrix. The SWCNT fibers were found to be able to act as a heterogeneous nucleating agent which inducing the formation of transcrystals around the fiber surface. According to the theory of heterogeneous nucleation, the interfacial free energy difference Δσ of iPP on the SWCNT fibers was determined and compared with that on the conventional fibers. By carefully controlling the crystallizing conditions, three types of α-iPP supra-molecular microstructures with different optical birefringences were obtained. Raman spectra were utilized to investigate the influences of the supra-molecular microstructures of the transcrystalline (tc) layer on the strain transfer efficiency from the matrix to the fibers at a microscopic level. Conventional single-fiber pull-out tests were further employed to compare with the results derived from the Raman tests. [Copyright &y& Elsevier]

As a type of thin film, two dimensional (2D) reticulate architectures built of freestanding single-walled carbon nanotube (SWCNT) bundles are suitable for scalable integration into devices and nanocomposites for many applications. The superior properties of these films, such as optical transparency, unique electrical properties and mechanical flexibility, result not only from the outstanding properties of individual SWCNTs but also from the collective behavior of the individual tubes, with additional properties arising from the tube-tube interactions. In this review, the synthesis, structure and fundamental properties, such as conductivity, transparency, optical nonlinearity and mechanical performance, of 'freestanding SWCNT bundle network' thin films and nanocomposites, as well as their application as supercapacitors are highlighted. Some long-standing problems and topics warranting further investigation in the near future are addressed. [ABSTRACT FROM AUTHOR]

With the expansion of the potential applications of carbon nanotubes (CNT) in biomedical fields, the toxicity and biocompatibility of CNT have become issues of growing concern. Since the immune system often mediates tissue damage during pathogenesis, it is important to explore whether CNT can trigger cytotoxicity through affecting the immune functions. In the current study, we evaluated the influence of CNT on the cytotoxicity mediated by human lymphocytes in vitro. The results showed that while CNT at low concentrations (0.001 to 0.1 mg/ml) did not cause obvious cell death or apoptosis directly, it enhanced lymphocyte-mediated cytotoxicity against multiple human cell lines. In addition, CNT increased the secretion of IFN-c and TNF-a by the lymphocytes. CNT also upregulated the NF-kB expression in lymphocytes, and the blockage of the NF-kB pathway reduced the lymphocyte-mediated cytotoxicity triggered by CNT. These results suggest that CNT at lower concentrations may prospectively initiate an indirect cytotoxicity through affecting the function of lymphocytes. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: We applied X-ray absorption near edge structure (XANES) spectroscopy to investigate the adsorption of proteins onto single-walled carbon nanotubes (SWCNTs). Specific XANES spectral features such as peptide Cn proteins were recognized and found to be affected by the corresponding aromatic structure of SWCNTs. Experimental data combined with first-principle calculation of the investigated nano-complex allow the understanding of adsorption mechanism and reveal that an interface interaction occurs leading to precise structural distortions of proteins. The study also demonstrates that XANES is a powerful tool to characterize structural details of proteins at the interface of complex systems. [Copyright &y& Elsevier]

Abstract: PbTiO3 nanotube arrays have been synthesized via sol–gel template method, and their morphology and structures have been determined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diameter and length of these nanotubes are about 300nm and 50μm, respectively, and their wall thickness is typically several tens of nanometers. XRD data shows that as-prepared PTO nanotubes possess perovskite structure, and electron diffraction demonstrates that they are polycrystalline. Photoluminescence spectrum of PTO nanotubes reveals an intense and wide emission band centered at 505nm. Polarization–electric field (P–E) response curves of PTO nanotube array were measured, and the hysteresis loops illustrate a room temperature ferroelectric characteristic of as-prepared PTO nanotubes. [Copyright &y& Elsevier]

Abstract: A simple and cheap method is proposed to achieve porous ZnO ribbons by oxidation of ZnS ribbons in the air. ZnS has a fully transformation to ZnO at an annealing temperature of 700°C from energy dispersive X-ray spectra and X-ray diffraction patterns. Scanning electron microscopy images indicate that ZnO ribbons keep the original shapes of ZnS, but produce some ordered and uniform pores on their surfaces. The photovoltage spectrum of ZnO/N3 indicates such dye-porous ZnO ribbons may be used in the dye-sensitized solar cells. The porous ZnO ribbons may also find potential applications in catalyst, sensor, and molecular selection. This technique to produce porous ribbons may also be applied to prepare other porous metal oxide ribbons. [Copyright &y& Elsevier]

Abstract: Many applications based on single-walled carbon nanotubes (SWNTs) require chemical modification of carbon nanotube to optimize the functionalities of the device. In this contribution we discuss the properties of SWNTs immersed in a hydrobromic acid (HBr) solution. Changes of atomic and electronic structures of bromine modified SWNTs were investigated using photoelectron spectroscopy (PES). Spectra of SWNTs before and after immersion in the HBr solution exhibit different features. To understand the mechanism of interaction between SWNTs and bromine, we performed density-functional theory calculations to reveal the structural changes, adsorption energy and chemical bonding information of SWNTs interacting with bromine. In addition, based on the Gelius model, from the molecular orbitals (MOs), we calculated ultraviolet photoelectron spectra (UPS) of SWNTs with and without functionalizing and compared them with the experiment. The present study is a first step in the understanding of the functionalization mechanism of carbon nanotubes. [Copyright &y& Elsevier]

Abstract: Structural defects play an important role in the physics of carbon nanototube. However, very few investigations of the structural changes induced by purifying process and other treatments have been performed by means of X-ray absorption near-edge structure (XANES) spectroscopy. We used XANES spectroscopy to detect the presence of defects induced in single-walled carbon nanotubes (SWNTs) by nitric acid treated processes and by an Ar+ ion bombardment. The relationship between the features in XANES spectrum and the structural defects has been discussed systematically. Data also addresses evidence of oxygen effect induced by aging on nanotubes. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

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 100–300nm and a thin thickness of 1–8nm.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. [Copyright &y& Elsevier]

ZnO nanoneedle arrays have been grown on a large scale with a chemical vapor deposition method at 680 °C. Zn powder and O2 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/μm. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption behavior of human fibrinogen (Hfg) on single-walled carbon nanotube (SWNT) films was investigated using scanning electron microscopy (SEM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was shown in the SEM images that fibrinogen was adsorbed strongly on the surface of SWNT when the samples were incubated in the Hfg solutions for 10min. The dependence of adsorption on the concentration of fibrinogen was also investigated and it was found that adsorption increased with increasing concentration. In order to further explore the adsorption of fibrinogen on SWNT surface, NEXAFS spectra were obtained at the N K-edge and the C K-edge. The results confirmed the conclusion regarding the dependence of adsorption on fibrinogen concentration. 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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 1–5μm, thickness of 40–50nm 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 [0001] orientation and preferentially enclosed by top surfaces /side surfaces . Photoluminescence spectrum of InN nanobelts at room temperature shows a strong emission peak centered at 704nm (1.76eV). [Copyright &y& Elsevier]

Abstract: Light-induced difference THz spectroscopy was used to investigate the dielectric response of free-stand single-walled carbon nanotubes (SWCNTs) films in THz region. We observed an enhanced transmission of the peak-signal of THz wave through SWCNTs films under 800 nm pump. In frequency domain, the transparency came from 0.5 to 2.1 THz and the absorption was in 2.1–3.0 THz region. The pump power dependency of the transmission showed this was a nonlinear effect. The dielectric constant response of the SWCNTs films was analyzed theoretically. The analysis suggests that the nonlinear optical properties stem from two factors, which are Drude and Lorentz term for metallic and semiconducting SWCNTs, respectively. [Copyright &y& Elsevier]

Abstract: Ultrafast time-resolved optical transmission in single-walled carbon nanotubes was measured as a function of pump fluence at a temperature of 200K employing degenerate pump–probe experiment. We observed a relaxation dynamics with two components characterized by 0.1 and 1ps, respectively. The signal amplitude of the slow component also shows a crossover from negative to positive when the pump fluence decreased. It is suggested that the fast component is related to the intraband relaxation and the slow component is attributed to two-competing processes. [Copyright &y& Elsevier]

The temperature-dependent Raman shift of double-walled carbon nanotubes (DWNTs) has been investigated in detail. It was found that radial breathing mode (RBM) frequencies of DWNTs have a linear dependence on the sample temperature, but different RBM frequencies correspond to completely different temperature coefficients. The frequency-dependent temperature coefficient has been investigated and attributed to the intershell effect in DWNTs. In comparison, G-band of DWNTs has a nonlinear or second-order polynomial relation with the increased temperature. The deviation from the linear trend has been revealed to be due to the contribution of the third- and fourth-order anharmonic term in the lattice potential energy with pure temperature effect. [Copyright &y& Elsevier]

The microstructural features of silver nanorods with the average length of 50 μm and diameters of around 100 nm have been investigated by means of SEM, X-ray diffraction, and transmission-electron microscopy (TEM). Silver nanorods in general have a pentagonal shape with a remarkable fivefold symmetry as revealed in cross-section observations. The fivefold axis, i.e. the growth direction, normally goes along the [110]-zone axis direction of the basic fcc Ag-structure. The twinning relationships and relevant twin boundaries among the five subunits in the pentagonal nanorod have been examined by high-resolution TEM and selected-area electron diffraction. Defects and stacking faults in this kind of nanorods have been briefly analyzed. [Copyright &y& Elsevier]

Using the organic solvent method, nearly mono-dispersed CdS nanocrystals were obtained in liquid paraffin. The CdS nanocrystals in tetrahedron shape capped with the hydrophobic surfactants in nanometer scale can be assembled to a close-packed mono-layered structure. The CdS nanocrystals with different sizes have been prepared by changing the reaction conditions such as the concentrations of cadmium precursor and sulfur precursor, the initial ratio of Cd:S precursors and the pH value of reaction system. The UV–visible absorption and photoluminescence show the quantum confinement effect clearly. The time-resolved photoluminescence spectra have also been examined. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]