New metal disulfide nanotubes

Nanotube Structure of AsPS4-xSex (x = 0, 1)

Single-wall nanotubes of isostructural AsPS4-xSex (x = 0, 1) are grown from solid-state reaction of stoichiometric amounts of the elements. The structure of AsPS4 was determined using single-crystal X-ray diffraction and refined in space group P 1 ¯ . The infinite, single-walled AsPS4 nanotubes have an outer diameter of ≈1.1 nm and are built of corner-sharing PS4 tetrahedra and AsS3 trigonal pyramids. Each nanotube is nearly hexagonal, but the ≈3.4 Å distance between S atoms on adjacent nanotubes allows them to easily slide past one another, resulting in the loss of long-range order. Substituting S with Se disrupted the crystallization of the nanotubes, resulting in amorphous products that precluded the determination of the structure for AsPS3Se. 31P solid-state NMR spectroscopy indicated a single unique tetrahedral P environment in AsPS4 and five different P environments all with different degrees of Se substitution in AsPS3Se. Optical absorption spectroscopy revealed an energy band gap of 2.7 to 2.4 eV for AsPS4 and AsPS3Se, respectively. Individual AsPS4 microfibers showed a bulk conductivity of 3.2 × 10-6 S/cm and a negative photoconductivity effect under the illumination of light (3.06 eV) in ambient conditions. Thus, intrinsic conductivity originates from hopping through empty trap states along the length of the AsPS4 nanotubes.

Recent Developments of Tin (II) Sulfide/Carbon Composites for Achieving High-Performance Lithium Ion Batteries: A Critical Review

The ever-increasing worldwide energy demand and the limited resources of fossil have forced the urgent adoption of renewable energy sources. Additionally, concerns over CO₂ emissions and potential increases in fuel prices have boosted technical efforts to make hybrid and electric vehicles more accessible to the public. Rechargeable batteries are undoubtedly a key player in this regard, especially lithium ion batteries (LIBs), which have high power capacity, a fast charge/discharge rate, and good cycle stability, while their further energy density improvement has been severely limited, because of the relatively low theoretical capacity of the graphite anode material which is mostly used. Among various high-capacity anode candidates, tin (II) sulfide (SnS₂) has been attracted remarkable attention for high-energy LIBs due to its enormous resource and simplicity of synthesis, in addition to its high theoretical capacity. However, SnS₂ has poor intrinsic conductivity, a big volume transition, and a low initial Coulombic efficiency, resulting in a short lifespan. SnS₂/carbon composites have been considered to be a most promising approach to addressing the abovementioned issues. Therefore, this review summarizes the current progress in the synthesis of SnS₂/carbon anode materials and their Li-ion storage properties, with special attention to the developments in Li-based technology, attributed to its immense current importance and promising prospects. Finally, the existing challenges within this field are presented, and potential opportunities are discussed.

Nanotube-Based 1D Heterostructures Coupled by van der Waals Forces

1D van der Waals heterostructures based on carbon nanotube templates are raising a lot of excitement due to the possibility of creating new optical and electronic properties, by either confining molecules inside their hollow core or by adding layers on the outside of the nanotube. In contrast to their 2D analogs, where the number of layers, atomic type and relative orientation of the constituting layers are the main parameters defining physical properties, 1D heterostructures provide an additional degree of freedom, i.e., their specific diameter and chiral structure, for engineering their characteristics. The current state-of-the-art in synthesizing 1D heterostructures are discussed here, in particular focusing on their resulting optical properties, and details the vast parameter space that can be used to design heterostructures with custom-built properties that can be integrated into a large variety of applications. First, the effects of van der Waals coupling on the properties of the simplest and best-studied 1D heterostructure, namely a double-walled carbon nanotube, are described, and then heterostructures built from the inside and the outside are considered, which all use a nanotube as a template, and, finally, an outlook is provided for the future of this research field.

Torsional strain engineering of transition metal dichalcogenide nanotubes: anab initiostudy

We study the effect of torsional deformations on the electronic properties of single-walled transition metal dichalcogenide (TMD) nanotubes. In particular, considering forty-five select armchair and zigzag TMD nanotubes, we perform symmetry-adapted Kohn-Sham density functional theory calculations to determine the variation in bandgap and effective mass of charge carriers with twist. We find that metallic nanotubes remain so even after deformation, whereas semiconducting nanotubes experience a decrease in bandgap with twist-originally direct bandgaps become indirect-resulting in semiconductor to metal transitions. In addition, the effective mass of holes and electrons continuously decrease and increase with twist, respectively, resulting in n-type to p-type semiconductor transitions. We find that this behavior is likely due to rehybridization of orbitals in the metal and chalcogen atoms, rather than charge transfer between them. Overall, torsional deformations represent a powerful avenue to engineer the electronic properties of semiconducting TMD nanotubes, with applications to devices like sensors and semiconductor switches.

Torsional moduli of transition metal dichalcogenide nanotubes from first principles

We calculate the torsional moduli of single-walled transition metal dichalcogenide (TMD) nanotubes usingab initiodensity functional theory (DFT). Specifically, considering forty-five select TMD nanotubes, we perform symmetry-adapted DFT calculations to calculate the torsional moduli for the armchair and zigzag variants of these materials in the low-twist regime and at practically relevant diameters. We find that the torsional moduli follow the trend: MS₂> MSe₂> MTe₂. In addition, the moduli display a power law dependence on diameter, with the scaling generally close to cubic, as predicted by the isotropic elastic continuum model. In particular, the shear moduli so computed are in good agreement with those predicted by the isotropic relation in terms of the Young's modulus and Poisson's ratio, both of which are also calculated using symmetry-adapted DFT. Finally, we develop a linear regression model for the torsional moduli of TMD nanotubes based on the nature/characteristics of the metal-chalcogen bond, and show that it is capable of making reasonably accurate predictions.

Magnetic and electronic properties of single-walled Mo2C nanotube: a first-principles study

The structural, electronic, and magnetic properties of single-walled Mo₂C nanotubes are investigated by using first-principles calculations. We establish that single-walled Mo₂C nanotubes can be rolled up from a graphene-like Mo₂C monolayer with H- or T-type phase, i.e. H-Mo₂C and T-Mo₂C nanotubes. The armchair-type T-Mo₂C nanotubes are more energetically stable than H-Mo₂C nanotubes with the same diameter, while zigzag-type H-Mo₂C nanotubes are more energetically stable than T-Mo₂C nanotubes. In particular, (8, 0) H-Mo₂C nanotube are more stable than Mo₂C monolayer due to structural deformation. All Mo₂C nanotubes are magnetic metals, independent of their chirality, and the magnetic moments of Mo atoms in the outer layer are larger than the inner. The ionic and metallic bonds in Mo₂C nanotubes and delocalized electrons around Mo atoms lead to the versatile electronic and magnetic properties in them, endowing them potential applications in catalysts and electronics.

MoSx-coated NbS2 nanoflakes grown on glass carbon: an advanced electrocatalyst for the hydrogen evolution reaction

Recent experimental and theoretical studies have demonstrated that two-dimensional (2D) transition metal dichalcogenide (TMDC) nanoflakes are one of the most promising candidates for non-noblemetal electrocatalysts for hydrogen evolution reaction (HER). However, it is still challenging to optimize their conductivity and enrich active sites for highly efficient electrochemical performance. Herein, we report a chemical vapor deposition (CVD) and thermal annealing two-step strategy to controllably synthesize hybrid electrocatalysts consisting of metallic NbS₂ nanoflake backbones and a highly catalytic active MoS_x nanocrystalline shell on polished commercial glass carbon (GC). In addition, the amount of MoS_x in the hybrids can be easily adjusted. We first demonstrate that a small amount of MoS_x significantly promotes the HER activity of 2D NbS₂ nanoflakes, which is in good agreement with the density functional theory (DFT) calculation results. Moreover, the optimized MoS_x@NbS₂/GC electrocatalyst displays superior HER activity with overpotential of -164 mV at -10 mA cm^-2, a small Tafel slope of 43.2 mV dec^-1, and prominent electrochemical stability. This study provides a new path for enhancing the HER performance of 2D TMDC nanoflakes.

Pincushion of Tubule Discovery and Tubular Morphology Landscape Establishment of Block Copolymer Self-Assemblies

Block copolymer (BCP) self-assembly is a versatile technique in the preparation of polymeric aggregates with varieties of morphologies. However, its morphology library is limited. Here, the discovery of pincushion of tubules is reported for the first time, via BCP self-assembly of poly(4-vinylpyridine)-b-polystyrene (P4VP-b-PS) with very high molecular weight (500 kDa) and asymmetry (2 mol% P4VP). The investigation confirms the importance of core-forming block length on morphology control of BCP self-assemblies, especially with respect to tubular structures. The morphology landscape of tubular structures is successfully established, where dumbbell of tubule, tubule, loose clew of tubules, tight clew of tubules, and pincushion of tubules can be prepared by adjusting the core-forming block length. This work therefore expands the structure library of BCP self-assemblies and opens up a new avenue for the further applications of these tubular materials.

Expanding the morphology library of block copolymer self-assemblies with clews of tubules

Clews of tubules are reported via block copolymer self-assembly of P4VP-b-PS with both high asymmetry and very high molecular weight.

Versatile Method to Expand the Morphology Library of Block Copolymer Solution Self-Assemblies with Tubular Structures

Self-assembly of block copolymers (BCPs) in solution is a powerful technology to achieve a broad range of structures, such as spheres, cylinders, vesicles, and other hierarchical structures. However, the BCP self-assembly library is limited, especially with respect to tubular structures. Here we show a versatile strategy to expand the morphology library of block copolymer solution self-assemblies with tubular structures (including tubular dumbbells and tubules) via self-assembly of the most common diblock copolymers P4VP-b-PS BCPs in methanol. No special chemistry is needed in this strategy, which proves the universality of this method. The novelty of the strategy is to keep the BCPs both highly asymmetric and with very high molecular weight. The underlying formation mechanism and kinetics of these tubular structures were elucidated. The prepared tubular structures expand the structure library of BCP solution self-assemblies and open up a new avenue for the further applications of a variety of tubular materials.

Porous hollow Co₃O₄ with rhombic dodecahedral structures for high-performance supercapacitors

Porous hollow Co₃O₄ with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co₃O₄ rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g(-1) and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co₃O₄ with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.

Polymer Composites Reinforced by Nanotubes as Scaffolds for Tissue Engineering

The interest in polymer based composites for tissue engineering applications has been increasing in recent years. Nanotubes materials, including carbon nanotubes (CNTs) and noncarbonic nanotubes, with unique electrical, mechanical, and surface properties, such as high aspect ratio, have long been recognized as effective reinforced materials for enhancing the mechanical properties of polymer matrix. This review paper is an attempt to present a coherent yet concise review on the mechanical and biocompatibility properties of CNTs and noncarbonic nanotubes/polymer composites, such as Boron nitride nanotubes (BNNTs) and Tungsten disulfide nanotubes (WSNTs) reinforced polymer composites which are used as scaffolds for tissue engineering. We also introduced different preparation methods of CNTs/polymer composites, such as in situ polymerization, solution mixing, melt blending, and latex technology, each of them has its own advantages.

Vapor-phase hydrothermal growth of novel segmentally configured nanotubular crystal structure

A new form of nanotubular crystal structure is directly grown by a vapor-phase hydrothermal method via an epitaxial orientated crystal growth mechanism. The as-prepared nanotubes possess a unique multi-tunnel core-shell layered nanotubular structure with droplet shaped polygonal periphery and segmental crystal configuration. They are dimension-tunable and demonstrate superior ion exchange properties in terms of exchange rate and ion accommodating capacity.

Large-scale synthesis of NbS2 nanosheets with controlled orientation on graphene by ambient pressure CVD

We report ambient pressure chemical vapor deposition (CVD) growth of single-crystalline NbS2 nanosheets with controlled orientation. On Si and SiO2 substrates, NbS2 nanosheets grow almost perpendicular to the substrate surface. However, when we apply transferred CVD graphene on SiO2 as a substrate, NbS2 sheets grow laterally lying on the graphene. The NbS2 sheets show the triangular and hexagonal shapes with a thickness of about 20-200 nm and several micrometres in the lateral dimension. Analyses based on X-ray diffraction and Raman spectroscopy indicate that the NbS2 nanosheets are single crystalline 3R-type with a rhombohedral structure of R3m space group. Our findings on the formation of highly aligned NbS2 nanosheets on graphene give new insight into the formation mechanism of NbS2 and would contribute to the templated growth of various layered materials.

Self-Scrolling Nanotubular Structure of Amorphous Vinyl Polymer Containing Tetraphenylthiophene-quinoline Pendant Groups

In this communication, we report a scroll-like nanotubular structure found in an amorphous vinyl polymer of PS-Qu containing fluorescent tetraphenyl-quinoline (TP-Qu) pendant groups. By spin-casting dilute solution of PS-Qu, long nanoribbons with heights in correlated to the molecular width of TP-Qu pendant groups formed. On the contrast, single-, double-, and multiple-walled nanoscrolls are the major structures existing in the products from the slow-evaporation process. Presumably, scrolling of nanoribbons result in the scroll-like nanotubular structures with the resolved layer thickness in dimension close to molecular width of the TP-Qu pendant. Computer simulation on the single PS-Qu chain suggests the existence of a straight-chain backbone, with most of the vicinal 1,3-disubstituted TP-Qu groups positioned in near face-to-face arrangements. Intermolecular distances evaluated from the SAEDs were approached by the molecular dynamic of two straight-chain polymer backbones. Favorable π-π interactions among the vicinal 1,3-disubstitued TP-Qu groups are suggested to be a major factor leading to the straight-chain backbone and the observed nanoribbons and nanoscrolls.

Biocompatible inorganic fullerene-like molybdenum disulfide nanoparticles produced by pulsed laser ablation in water

We report on the synthesis of inorganic fullerene-like molybdenum disulfide (MoS(2)) nanoparticles by pulsed laser ablation (PLA) in water. The final products were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and resonance Raman spectroscopy, etc. Cell viability studies show that the as-prepared MoS(2) nanoparticles have good solubility and biocompatibility, which may show a great potential in various biomedical applications. It is shown that the technique of PLA in water also provides a green and convenient method to synthesize novel nanomaterials, especially for biocompatible nanomaterials.

Synthesis and Characterization of Titanium Dioxide Nanotubes for Photocatalytic Degradation of Aqueous Nitrobenzene in the Presence of Sunlight

TiO2 derived nanotubes were prepared by hydrothermal treatment of TiO2 (anatase) powder in 10 M NaOH aqueous solution. The crystalline structure, band gap, and morphology of the TiO2 nanotubes were determined by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Transmission Electron microscopy (TEM) and N2 adsorption (BET) at 77 K, respectively. It was observed that the surface area of the nanotubes was increased twelve times compared with TiO2 (anatase) powder. The results demonstrated that the photocatalytic activity of TiO2 nanotubes was higher than that of TiO2 (anatase) powder. The photocatalytic activity of the nanotubes was evaluated in presence of sunlight by degradation of aqueous nitrobenzene. Complete degradation of nitrobenzene was obtained in 4 hours using TiO2 nanotubes whereas 85% degradation was observed in case of TiO2 (anatase).

Superconducting tantalum disulfide nanotapes; growth, structure and stoichiometry

Superconducting tantalum disulfide nanowires have been synthesised by surface-assisted chemical vapour transport (SACVT) methods and their crystal structure, morphology and stoichiometry studied by powder X-ray diffraction (PXD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and nanodiffraction. The evolution of morphology, stoichiometry and structure of materials grown by SACVT methods in the Ta-S system with reaction temperature was investigated systematically. High-aspect-ratio, superconducting disulfide nanowires are produced at intermediate reaction temperatures (650 degrees C). The superconducting wires are single crystalline, adopt the 2H polytypic structure (hexagonal space group P6(3)/mmc: a = 3.32(2) A, c = 12.159(2) A; c/a = 3.66) and grow in the <21_1_0> direction. The nanowires are of rectangular cross-section forming nanotapes composed of bundles of much smaller fibres that grow cooperatively. At lower reaction temperatures nanowires close to a composition of TaS(3) are produced whereas elevated temperatures yield platelets of 1T TaS(2).

Controlled introduction of diameter modulations in arrayed magnetic iron oxide nanotubes

To date, no large-scale preparative method for arrays of nanotube enables the experimentalist to arbitrarily define changes in the tubes' diameter along their length. To this goal, we start with anodic alumina substrates displaying controlled modulations in pore diameter obtained by alternating "mild" and "hard" electrochemical etching conditions. We then utilize atomic layer deposition (ALD) to coat the internal pore walls with conformal layers of an oxide. Ferromagnetic Fe(3)O(4) tubes of 10 nm wall thickness and 10-30 microm in length are thus prepared, which replicate the modulated silhouette of the template. Their magnetic properties strongly depend on the presence of diameter modulations. Introducing one or several very short segments of large diameter (150 nm) into an otherwise thin tube (70 nm diameter) brings its initially large coercive field down to a value close to the case of a homogeneously thick tube. Theoretical modeling emphasizes the major influence of the magnetostatic interactions between neighboring tubes. They are enhanced locally at the sites of diameter modulations, which directly translates into a reduction in coercive field.

Crystalline nanotubes of gamma-AlOOH and gamma-Al2O3: hydrothermal synthesis, formation mechanism and catalytic performance

Crystalline nanotubes of gamma-AlOOH and gamma-Al(2)O(3) have been synthesized. An anionic surfactant-assisted hydrothermal process yields gamma-AlOOH nanotubes, and appropriate calcination treatment of the gamma-AlOOH nanotubes yields gamma-Al(2)O(3) nanotubes. The nanotubes were characterized by XRD, SEM, TEM, TG-DSC, FTIR and nitrogen adsorption-desorption techniques. Both the gamma-AlOOH and gamma-Al(2)O(3) nanotubes are crystalline, with a representative length of approximately 500 nm and diameters of 20-40 nm. The gamma-Al(2)O(3) nanotubes exhibit a very high mesoporous specific surface area (SSA) of 201.0 m(2) g(-1) and a high mesopore volume of 0.68 cm(3) g(-1) with an average mesopore size of 27.7 nm, as well as a high microporous SSA of 186.0 m(2) g(-1) and a micropore volume of 0.08 cm(3) g(-1) with an average micropore size of 0.53 nm. The formation process was discussed and a possible mechanism was proposed, in which a lamellar phase was first formed by camphorsulfonic anions and Al(III) species, and then rolled up to form the crystalline nanotubes under the hydrothermal condition. The catalytic performance of the obtained gamma- Al(2)O(3) nanotubes was tested by using the dehydration of ethanol to ethylene as a probe reaction and it was shown that the obtained gamma- Al(2)O(3) nanotubes catalyst possesses a higher catalytic activity compared with the gamma- Al(2)O(3) nanoparticles.

One-Dimensional Nanostructures and Devices of II-V Group Semiconductors

The II-V group semiconductors, with narrow band gaps, are important materials with many applications in infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators. Since the first report on trumpet-like Zn(3)P(2) nanowires, one-dimensional (1-D) nanostructures of II-V group semiconductors have attracted great research attention recently because these special 1-D nanostructures may find applications in fabricating new electronic and optoelectronic nanoscale devices. This article covers the 1-D II-V semiconducting nanostructures that have been synthesized till now, focusing on nanotubes, nanowires, nanobelts, and special nanostructures like heterostructured nanowires. Novel electronic and optoelectronic devices built on 1-D II-V semiconducting nanostructures will also be discussed, which include metal-insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, and p-n heterojunction photodiode. We intent to provide the readers a brief account of these exciting research activities.

Synthesis and characterization of indium oxide nanobubbles with ultrathin single crystal shells

Nanobubbles with ultrathin single crystal shells, a new kind of closed nanostructure, have been synthesized from a nonlayered indium oxide semiconductor.