Belt-like Structures Research Articles

The influence of polyelectrolyte on the synthesis of B4C/BN nanocomposite powders via sol-gel method

In the present study, B4C-BN nanocomposite powders were synthesized by using the sol-gel method. To investigate the effects of polyelectrolyte on phase content, particle size, and final morphology of synthesized powders different amounts of ammonium polycarboxylate were used as a gel dispersing agent and a nitrogen source. Highly crystalline, sub-micron/micron-sized boron carbide particles with varying morphologies including polyhedral-equiaxed, belt-like, needle-like, and complex-shaped hierarchical structures were produced from the polymeric gel containing glycerine, tartaric acid, and citric acid as carbon sources, and boric acid as boron source. With the addition of ammonium polycarboxylate as a polymeric gel network modifier, nanocomposite powders containing micron-sized polyhedral-equiaxed boron carbide particles and boron nitride nanoflakes were obtained. The results indicated that the particles dimensions, crystallinity, and B4C to BN phase ratio of the synthesized powders are directly related to the preliminary formation of borate-ammonium and/or amine complexes in the polymeric gel. The SEM inspections revealed that the size of boron carbide particles tends to increase from 2 μm up to 40 μm as a function of ammonium polycarboxylate content. It was also observed that the average size and thickness of boron nitride nanoflakes within the range of 80 nm to 3 μm and 10–150 nm, respectively. B4C/BN nanocomposite powders were synthesized with up to 32% BN content using a 43 wt% ammonium polycarboxylate additive.

Different micro/nano-scale patterns of surface materials influence osteoclastogenesis and actin structure

The surface topography of a material can influence osteoclast activity. However, the surface structural factors that promote osteoclast activity have not yet been investigated in detail. Therefore, we investigated osteoclastogenesis by testing various defined patterns with different dimensions and shapes. The systematic patterns, made of a cyclo-olefin polymer, were prepared at a micron-, submicron-, and nano-scale with a groove, hole, or pillar shape with a 1:1 pitch ratio. RAW264.7 cells were cultured on these patterns in the presence of the receptor activator of NF-κB ligand (RANKL). Osteoclast formation was induced in the order: pillar > groove ≥ hole. The two-dimensional factors also indicated that submicron-sized patterns strongly induced osteoclast formation. The optimal pillar dimension for osteoclast formation was 500 nm in diameter and 2 µm in height. Furthermore, we observed two types of characteristic actin structure, i.e., belt-like structures with small hollow circles and isolated ring-like structures, which formed on or around the pillars depending on size and height. Furthermore, resorption pits were observed mainly on the top of calcium phosphate-coated pillars. Thus, osteoclasts prefer convex shapes, such as pillars for differentiation and resorption. Our results indicate that osteoclastogenesis can be controlled by designing surfaces with specific morphologies.

Mechanistic insights into the electrospinning fabrication of belt-like structures of BiFeO3 and their photocatalytic properties

One-dimensional fiber and belt-like structures of bismuth ferrite (BiFeO3) have been synthesized using electrospinning process and their mechanistic formation and photocatalytic properties have been investigated towards degradation of various organic pollutants. The X-ray diffraction patterns and micrographs confirmed the crystalline-phase BiFeO3 and their fiber (diameter of ~ 150 nm) and belt morphology (width and thickness of ~ 1 µm and 200 nm, respectively). It is proposed that the formation of belt-like structure could be due to high electrical-pressure mediated buckling instability in the polymer-jet during electrospinning process. These belt-like structures showed relatively enhanced optical absorption (in the range of 400–500 and 600–700 nm) and surface properties (~23.5 m2/g), and thereby it also exhibited the improved photocatalytic degradation of pollutants under sunlight irradiation. These belts have been perceived as a kind of 1D-2D hierarchical structure to understand their photocatalytic mechanism.

Probing the structure and functionalized surface of colloidal AuSe

We report on the synthesis of the less explored AuSe and investigate the influence capping agents; oleylamine (OLA), 1-dodecanethiol (IDDT), and oleic acid (OA) have on its structure and surface. TEM showed long belt-like structures for both OLA and OA-capped materials and nanorods for 1DDT-AuSe. XRD diffractograms and Raman spectra showed the presence of both α- and β-AuSe polymorphs, with the dominance of the α-phase in all three materials. The methylene stretching frequencies in the FTIR spectra confirmed capping by the organic ligands. High-resolution XPS spectra of the Au4f core level showed evidence of the Au + ions. The high total peak area percentage of the Au + ions in OLA-AuSe (90%), 1DDT (23%), and OA (21%) suggests that OLA is the best capping ligand. DFT calculations on the adsorption of the ligands on AuSe showed weak interaction on (001) plane suggesting anisotropic growth along this plane and preference for the α-phase.

Structural transition induced by niobium doping in layered titanium disulfide: The impact on electrocatalytic performance

Transition metal dichalcogenide layered structures have become the focus of special attention for electrochemical applications in recent years. Although various engineering strategies, including size reduction and composition manipulation, have been adopted to modulate the innate electrochemical features of these layered materials, there remains a great deal of work to satisfy the specific requirements for practical applications. In this work, we set forth to provide an insight into the impact of niobium (Nb) doping on the structural features of titanium disulfide (TiS2). In addition, we examine the influence of Nb dopant on the inherent electrochemistry and charge transfer kinetics of TiS2 and its implication for the hydrogen evolution, oxygen reduction and oxygen evolution reaction (HER, ORR, and OER) processes. It has been found that introducing an appropriate amount of Nb atom (>10%) results in the formation of titanium trisulfide (TiS3) belt-like structures on the surface of TiS2 polygonal discs. Nb doping marginally changes the inherent electroactivity of TiS2 through introducing a small trace of reducible species. Furthermore, Nb-doped TiS2 materials show improved electron transfer kinetics when compared to pure TiS2, with the fastest kobs 0 of 5.58 × 10−4 cm s−1 toward [Fe(CN)6]3−/4− redox probe recorded for Ti0.95Nb0.05S2. The same trend is also found in the HER activity of these materials whereby Nb-doped TiS2 materials exhibit better performance in the electrocatalytic hydrogen evolution.

Control synthesis of anatase TiO2 nanobelts via alkali-hydrothermal method for the optimal conditions

TiO2 nanobelts with different synthesis methods have been actively pursued for a long time, however, a systematic study corresponding to the fabrication of TiO2 nanobelts by alkali-hydrothermal method has not been worked out by any research. Here, we systematically study the conditions such as the source of Ti and hydrothermal parameters with the assistance of X-ray diffraction (XRD), scanning electron microscope (SEM), N2-sorption measurement and photochemical tests. The XRD and SEM measurements show that the TiO2 nanobelts exhibit excellent belt-like structures and high crystalline intensity when using tetrabutyl titanate (Ti(OBu)4) as the source of Ti, the volume of 10 mol/L NaOH is 15 mL, the hydrothermal reaction is conducted at 180 °C for 20 h and the heat treatment system is 800 °C for 2 h. The length–diameter ratio of the final obtained sample is about 130 and the specific surface area is 50.4 m2/g.

Single-Crystal MoO3 Micrometer and Millimeter Belts Prepared from Discarded Molybdenum Disilicide Heating Elements

Single-crystal MoO3 micrometer to millimeter even centimeter belts were prepared via a novel route of oxidizing a discarded molybdenum disilicide heating element at 1000 °C for 3 h. The morphology and structure features, and growth mechanism of the products were evidently investigated by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicated that the powdery and fibrous products were typical α-MoO3 belt-like structures which size could develop from micrometer to several millimeter even centimeter in length and up to 0.5 mm in width. It should be formed preferentially along the [001] direction via layer by layer growth to form 1-D single MoO3 belts by vapor-solid mechanism. Thermal and luminescence properties of the products were revealed by thermogravimetric analysis and differential thermal analysis and photoluminescence spectra that the resultant α-MoO3 belts had good thermal stability and characteristics of luminescence with a central peak at 481 nm. The MoO3 belts are of good potential being applied to luminescent and high temperature devices.

Role of boron addition on phase composition, microstructural evolution and mechanical properties of nanocrystalline SiBCN monoliths

Nanocrystalline SiBCN monoliths with the same Si/C/N mole ratio and various boron additions ranged from 0 to 3.0mol were prepared by mechanical alloying plus reactive hot pressing methods. Correction of boron content and microstructural/morphological evolution was investigated in detail by XRD, SEM, TEM and STEM-EDX structure characterization. Except for SiC and BN(C), boron addition contributes to BxC formation. Besides, boron addition promotes the crystallization of SiC, leading to the formation of poor crystallinity of spherical structures in inner SiC. Furthermore, boron addition significantly promotes the grain growth of SiC and BxC and therefore increases the relative volume ratios of BxC/BN(C) and BxC/SiC. Amorphous-like BN(C) changes to belt-like structures as boron addition increases. The new formed BxC effectively contributes to the improvement of Vicker’s hardness while pull-out of BN(C) belt-like structures benefits the fracture toughness.

Morphology and molecular arrangement of perylene-3,4,9,10-(n-pentylester) in thin layers obtained by zone-casting

Liquid-crystalline perylene-3,4,9,10-tetra-(n-pentylester) zone-casted on hydrophilic glass substrates forms characteristic belt-like structures which are observed under optical microscope and atomic force microscope. Polarised Raman scattering spectra reveal the presence of anisotropic alignment of the molecules inside the obtained structures. Moreover, the absorption and fluorescence spectra confirm molecular aggregation in the belt-like structures. The research shows, that the belt-like structures are created by columns of molecules with the edge-on alignment on the glass substrate. Such organisation of the molecules is confirmed by spectroscopic methods. These structures can be interesting from the point of view of organic electronics.

Electrostatics-Driven Hierarchical Buckling of Charged Flexible Ribbons.

We investigate the rich morphologies of an electrically charged flexible ribbon, which is a prototype for many beltlike structures in biology and nanomaterials. Long-range electrostatic repulsion is found to govern the hierarchical buckling of the ribbon from its initially flat shape to its undulated and out-of-plane twisted conformations. In this process, the screening length is the key controlling parameter, suggesting that a convenient way to manipulate the ribbon morphology is simply to change the salt concentration. We find that these shapes originate from the geometric effect of the electrostatic interaction, which fundamentally changes the metric over the ribbon surface. We also identify the basic modes by which the ribbon reshapes itself in order to lower the energy. The geometric effect of the physical interaction revealed in this Letter has implications for the shape design of extensive ribbonlike materials in nano- and biomaterials.

Alternation of aromatic-nonaromatic rings in belt-like structures. The behavior of [6.8](3)cyclacene in magnetic fields.

[6.8]3Cyclacene is an interesting belt-like structure displaying aromatic-non-aromatic alternation, which is useful to gain an understanding of the intramolecular and intermolecular interactions between the anisotropic cones in the magnetic behavior of such rings. From the analysis of certain components in an induced magnetic field and (13)C-NMR shielding under its own principal axis system (PAS), the individual and overall magnetic behavior of each respective aromatic and non-aromatic fragments can be clearly described. Interestingly, the magnetic response of [6.8]3cyclacene suggests a characteristic behavior given by its confinement into a belt-like structure.

Self-Assembly of Hydrosoluble Carbon Nanotubes into Macroscopic Belts

A simple approach for the synthesis of a truly neutral aqueous solution of shortened carbon nanotubes (CNTs) is presented. Upon evaporation of the solvent, the shortened CNTs self-assemble into belt-like macroscopic structures of approximately 3 cm in length. After the annealing process, the macroscopic assembly exhibits a good electrical conductivity of approximately 140 S cm-1 . The possible self-assembly process is also discussed.

Synthesis and photoluminescence properties of wash-board belt-like ZnSe nanostructures

Washboard belt-like zinc selenide (ZnSe) nanostructures are successfully prepared by a simple chemical vapor deposition (CVD) technology without catalyst. The phase compositions, morphologies and optical properties of the nanostructures are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) spectroscop, respectively. A vapor-liquid mechanism is proposed for the formation of ZnSe belt-like structures. Strong PL from the ZnSe nanostructure can be tuned from 462 nm to 440 nm with temperature varying from 1000 °C to 1200 °C, and it is demonstrated that the washboard belt-like ZnSe nanostructures have potential applications in optical and sensory nanotechnology. This method is expected to be applied to the synthesis of other II–VI groups or other group’s semiconducting materials.

Nanoscale characterization of FeNi alloys processed by high-pressure torsion using photoelectron emission microscope

Photoelectron emission microscopy observation is performed on an FeNi alloy processed by high-pressure torsion (HPT) in order to microscopically analyze magnetic domain structure, elemental distribution, and surface morphology. While belt-like magnetic domain structures with widths of 3 to 5 μm are observed at about 2 mm away from the sample disc center, only narrower magnetic domain structure is observed at 1 mm away from the disc center. While these magnetic domain structures are related to a product during the HPT process, they are related neither to inhomogeneity of elemental distribution nor to surface morphology. Therefore, it is suggested that the observed magnetic domains should be originated from an L10 phase. The present analysis indicates that atomic diffusion is significantly enhanced by processing the samples with HPT and post-annealing.

Board-like dibenzo[fg,op]naphthacenes: synthesis, characterization, self-assembly, and liquid crystallinity

We report the synthesis and characterization of a series of board-like (“sanidic”) compounds with dibenzo[fg,op]naphthacene cores. The compounds exhibit good self-assembly into one-dimensional belt-like structures, and also smectic liquid crystal phases typical of rod-like molecules, but with important differences ascribed to their board-like shapes.

Structural and optical properties of ZnO rods hydrothermally formed on polyethersulfone substrates

Various unique ZnO morphologies, such as cigar-like and belt-like structures and microrod and nanorod structures, were formed on flexible polyethersulfone (PES) substrates by using a low temperature hydrothermal route. The structural properties of ZnO depended highly on the precursor concentration. The effect of a thin ZnO seed layer deposited the on PES substrate by using atomic layer deposition on the structural and the optical properties of ZnO hydrothermally grown on the ZnO seed layer/PES substrates was studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements were employed to analyze the characteristics of hydrothermally-grown ZnO. The diameter of the ZnO nanorods grown on the ZnO seed layer/PES substrates increased with increasing precursor concentration from 0.025 to 0.125 M due to the Ostwald ripening process. ZnO hydrothermally-grown on the ZnO seed layer/PES substrates at a low precursor concentration showed better structural properties than ZnO formed without a seed layer. Well-formed ZnO nanorods deposited on the ZnO seed layer/PES substrates showed two PL peaks, one in the ultraviolet and the other in the visible region, whereas horizontally positioned ZnO formed on the PES substrate in the absence of a seed layer emitted only one broad PL peak in the violet region. The ZnO grown on PES substrates in this work can be used as high-quality transparent electrodes for solar cells fabricated on flexible substrates.

In-Doped Gallium Oxide Micro- and Nanostructures: Morphology, Structure, and Luminescence Properties

The influence of indium doping on morphology, structural, and luminescence properties of gallium oxide micro- and nanostructures is reported. Indium-doped gallium oxide micro- and nanostructures have been grown by thermal oxidation of metallic gallium in the presence of indium oxide. The dominant morphologies are beltlike structures, which in many cases are twisted leading to springlike structures, showing that In diffusion in Ga2O3 influences the microstructure shapes. High-resolution transmission electron microscopy has revealed the presence of twins in the belts, and energy-dispersive X-ray spectroscopy in the scanning electron microscopy (SEM) has detected a segregation of indium impurities at the edges of planar structures. These results suggest that indium plays a major role in the observed morphologies and support the assumption of a layer by layer model as growth mechanism. An additional assessment of indium influence on the defect structure has been performed by cathodoluminescence in the SEM, X-ray photoelectron microscopy, and spatially resolved Raman spectroscopy.

Cyclacenes: Hoop-Shaped Systems Composed of Conjugated Rings

A carbon nanotube, if it could be cut sideways at the end like a pipe, would yield beltlike structures. These subunits of carbon nanotubes, in their simplest manifestation as the [6](n)cyclacenes, are composed of conjugated six-membered rings that are annelated, that is, made of a series of consecutively fused ring structures. These seemingly simple "one-benzene-thick" slices are of considerable interest as models-for electronic structure and spectroscopic properties, for example-for carbon nanotubes. In the late 1980s Stoddart and co-workers, soon to be followed by other groups, embarked on the synthesis of [6](n)cyclacenes. The necessary curved shape of the belt was achieved with boat-shaped precursors for Diels-Alder reactions, namely, 7-oxanorbornene derivatives. The preferred endo-addition in Diels-Alder reactions assured an efficient synthesis of beltlike systems containing 12 to 18 six-membered rings. However, the removal of the auxiliary oxygen centers to achieve [6](n)cyclacenes as fully conjugated systems has failed so far: they remain an inaccessible target despite some 25 years of synthetic effort. Concurrently, theoretical studies revealed that [6](n)cyclacenes as linearly annelated systems show small energy gaps between triplet and singlet states; they can thus be expected to be unstable species. Angularly annelated systems, on the other hand, were predicted to have large singlet-triplet splittings. Nakamura and co-workers and our laboratory have found ways around the obstacles to create cyclacenes. Nakamura and co-workers prepared the first angular annelated cyclacene by selective reduction of the north and south poles of C(60). We used a cyclic system that is fully conjugated and also adopts a boat conformation: cyclooctatetraene. By following this principle, we synthesized two types of linearly annelated cyclacenes: metal-stabilized four-membered rings alternating with eight-membered rings ([4.8](n)cyclacenes), and six-membered rings alternating with eight-membered rings ([6.8](n)cyclacenes). These new scaffolds, if extended along the molecular axis, would represent as-yet unknown forms of carbon nanotubes and are thus inviting synthetic targets. Calculations show that the incorporation of heteroatoms (S and NH) into these scaffolds is promising, encouraging the synthetic pursuit of thia- and azacyclacenes.

Effects of Oxidation during Synthesis on Structure and Field-Emission Property of Tungsten Oxide Nanowires

We investigated the structure and field-emission property of tungsten oxide nanowires synthesized under different oxidation degrees. We annealed a sputtered tungsten film at 800 °C, controlling the ratio of hydrogen to oxygen (RHO) using Ar/H2 (97/3%) gas in a vacuum furnace. The resulting differences in shape, number density, length, and width of the nanowires were observed by scanning electron microscopy. In the RHO range of 0 to 0.4, beltlike structures were synthesized. In the RHO range of 0.8 to 4, only thin nanowires were synthesized. In this range, length and width did not differ with RHO, but the number density decreased as RHO increased. The sample with a nanowire density of 2 µm-2, annealed with an RHO of 4, showed the highest field-emission property, i.e., a current of 1 mA/cm2 for an electric field of 22 V/µm. We demonstrated their emission by fluorescence imaging and showed that the nanowires are promising candidates for field emitters.

Structural analysis of Er silicide nanowires on Si(001) using three-dimensional medium-energy ion scattering

Er silicide nanostructures were produced by depositing Er on a clean Si(001) substrate. From the off-line observation by scanning electron microscopy, several kinds of nanostructures were observed; nanowires, nanobelts made by a lateral binding of nanowires, and three-dimensional (3D) islands. The 3D islands occupied a major part in those nanostructures, and had slight beltlike structures on their surfaces. The three-dimensional medium-energy ion scattering clearly indicated that the nanostructures were highly epitaxial, and that the nanostructures had a single kind of crystallographic structure of monoclinic $\mathrm{Er}{\mathrm{Si}}_{2}$, deformed from hexagonal.