Inorganic nanotubes and fullerene-like nanoparticles

A Molecular Dynamics Study on the Defect Formation and Mechanical Behavior of Molybdenum Disulfide under Irradiation

Due to its appealing characteristics, molybdenum disulfide (MoS2) presents a promising avenue for the exploration of lubrication protection materials in high-energy irradiation scenarios. Herein, we present a comprehensive investigation into the defect behavior of multilayer MoS2 under argon (Ar) atom irradiation leveraging molecular dynamics simulations. We have demonstrated the energy shifts and structural evolution in MoS2 upon irradiation, including the emergence of Frenkel defects and intricate defect clusters. The structural damage exhibits an initial increase followed by a subsequent decrease as the incident kinetic energy increases, ultimately peaking at 2.5 keV. Moreover, we investigated the effect of postannealing on defect recovery and conducted the uniaxial tensile and interlayer shearing simulation in order to provide valuable insights for the defect evolution and its impact on mechanical and tribological properties. Furthermore, we have proposed the optimal annealing temperature. The current study reveals the atomic mechanisms underlying irradiation-induced damage on the structural integrity and mechanical performance of MoS2, thereby providing crucial guidance for its vital application in nuclear reactors and aerospace industries.

One-pot solvothermal preparation of the porous NiS2//MoS2 composite catalyst with enhanced low-temperature hydrodesulfurization activity

The simple preparation of mesoporous NiS2//MoS2 composite catalyst through a one-pot solvothermal method is presented. The improvement of the specific surface area (220 m2/g) and the construction of the porous structure are realized by this method in the case of no support. The organics acts as a microscopic binder contribute to uniform stacking of MoS2 with NiS2 clusters. The composite structure including NiS2 and MoS2 was obtained (proved by XRD, XPS, TEM, IR, UV-vis and RAMAN) and changed the microelectronic environment of the active metal surface (DFT calculation). The mesoporous NiS2//MoS2 catalyst (Ni1Mo1-200) showed an excellent hydrodesulfurization performance of dibenzothiophene (DBT conversion: 78 % at 260 °C) and a high ratio of direct desulfurization pathway (SDDS/HYD = 16.6) at a low reaction temperature. By combining the characterization and theoretical calculation results, the advantages of this NiS2//MoS2 composite structure in synergistic catalysis was further confirmed.

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.

Toward Edge Engineering of Two-Dimensional Layered Transition-Metal Dichalcogenides by Chemical Vapor Deposition

The manipulation of edge configurations and structures in atomically-thin transition metal dichalcogenides (TMDs) for versatile functionalization has attracted intensive interest in recent years. The chemical vapor deposition (CVD) approach has shown promise for TMD edge engineering of atomic edge configurations (1H, 1T or 1T'-zigzag or armchair edges) as well as diverse edge morphologies (1D nanoribbons, 2D dendrites, 3D spirals, etc.). These edge-rich TMD layers offer versatile candidates for probing the physical and chemical properties and exploring potential applications in electronics, optoelectronics, catalysis, sensing, and quantum technologies. In this Review, we present an overview of the current state-of-the-art in the manipulation of TMD atomic edges and edge-rich structures using CVD. We highlight the vast range of distinct properties associated with these edge configurations and structures and provide insights into the opportunities afforded by such edge-functionalized crystals. The objective of this Review is to motivate further research and development efforts to use CVD as a scalable approach to harness the benefits of such crystal-edge engineering.

Environmental Applications of Sorbents, High-Flux Membranes of Carbon-Based Nanomaterials

Carbon-based nanomaterials have unique and controllable properties, making it possible to find and treat environmental challenges. There are several environmental applications for carbon-based nanoparticles: sorbents, membranes, antimicrobial agents, and sensors. According to this review, carbon-based nanomaterials have a variety of environmental benefits. This article also looks at prospective uses of nanomaterials in environmental systems, utilizing carbonaceous nanoparticles as a guide for their physical, chemical, and electrical properties.

Understanding Hyaluronan Receptor (CD44) Interaction, HA-CD44 Activated Potential Targets in Cancer Therapeutics

Cancer is a complex mechanism involving a series of cellular events. The glycoproteins such as hyaluronan (HA) are a significant element of extracellular matrix (ECM), involve in the onset of cancer developmental process. The pivotal roles of HA in cancer progression depend on dysregulated expression in various cancer. HA, also gain attention due to consideration as a primary ligand of CD44 receptor. The CD44, complex transmembrane receptor protein, due to alternative splicing in the transcription process, various CD44 isoforms predominantly exist. The overexpression of distinct CD44 isoforms (CD44v) standard (CD44s) depends on the tumour type and stage. The receptor proteins, CD44 engage in a variety of biological processes, including cell growth, apoptosis, migration, and angiogenesis. HA-CD44 interaction trigger survival pathways that result in cell proliferation, invasion ultimately complex metastasis. The interaction and binding of ligand-receptor HA-CD44 regulate the downstream cytoskeleton pathways involve in cell survival or cell death. Thus, targeting HA, CD44 (variant and standard) isoform, and HA-CD44 binding consider as an attractive and useful approach towards cancer therapeutics. The use of various inhibitors of HA, hyaluronidases (HYALs), and utilizing targeted Nano-delivery of anticancer agents and antibodies against CD44, peptides gives promising results in vitro and in vivo. However, they are in clinical trials with favourable and unfavourable outcomes, which reflects the need for various modifications in targeting agents and a better understanding of potential targets in tumour progression pathways.

Templated Assembly of Nanoparticles into Continuous Arrays

The templated assembly of nanoparticles has been limited so far to yield only discontinuous nanoparticle clusters confined within lithographically patterned cavities. Here, we explored the templated assembly of nanoparticles into continuous 2D structures, using lithographically patterned templates with topographical features sized as the assembled nanoparticles. We found that these features act as nucleation centers, whose exact arrangement determines four possible assembly regimes (i) rotated, (ii) disordered, (iii) closely packed, and (iv) unpacked. These regimes produce structures strikingly different from their geometry, orientation, long-range and short-range orders, and packing density. Interestingly, for templates with relatively distant nucleation centers, these four regimes are replaced with three new ones, which produce large monocrystalline domains that are either (i) uniformly rotated, (ii) uniformly aligned, or (iii) nonuniformly rotated relative to the nucleation lattice. We rationalized our experimental data using a mathematical model, which examines all the alignment possibilities between the nucleation centers and the ideal hexagonal assembly. Our finding provides a new approach for the à la carte obtainment of various nanoscale structures unachievable by natural self-assembly and opens a route for the fabrication of numerous functional nanodevices and nanosystems that could not be realized so far by the standard bottom-up approach.

Exploring High Aspect Ratio Gold Nanotubes as Cytosolic Agents: Structural Engineering and Uptake into Mesothelioma Cells

The generation of effective and safe nanoagents for biological applications requires their physicochemical characteristics to be tunable, and their cellular interactions to be well characterized. Here, the controlled synthesis is developed for preparing high-aspect ratio gold nanotubes (AuNTs) with tailorable wall thickness, microstructure, composition, and optical characteristics. The modulation of optical properties generates AuNTs with strong near infrared absorption. Surface modification enhances dispersibility of AuNTs in aqueous media and results in low cytotoxicity. The uptake and trafficking of these AuNTs by primary mesothelioma cells demonstrate their accumulation in a perinuclear distribution where they are confined initially in membrane-bound vesicles from which they ultimately escape to the cytosol. This represents the first study of the cellular interactions of high-aspect ratio 1D metal nanomaterials and will facilitate the rational design of plasmonic nanoconstructs as cytosolic nanoagents for potential diagnosis and therapeutic applications.

Molecular Insights into the Ligand-Based Six-Proton- and Six-Electron-Transfer Processes Between Tris-ortho-Phenylenediamines and Tris-ortho-Benzoquinodiimines

The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H₂ ) important. A high-spin (hs) Fe^II complex with o-phenylenediamine (opda) ligands, [Fe^II (opda)₃ ]²⁺ (hs-[6R]²⁺ ), was reported showing photochemical H₂ evolution. In addition, a low-spin (ls) [Fe^II (bqdi)₃ ]²⁺ (bqdi: o-benzoquinodiimine) (ls-[0R]²⁺ ) formation by O₂ oxidation of hs-[6R]²⁺ , accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls-[0R][PF₆ ]₂ can be reduced by hydrazine giving ls-[Fe^II (opda)(bqdi)₂ ][PF₆ ]₂ (ls-[2R][PF₆ ]₂ ) and ls-[Fe^II (opda)₂ (bqdi)][PF₆ ]₂ (ls-[4R][PF₆ ]₂ ) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials.

YS-TaS2 and YxLa1-xS-TaS2 (0 ≤ x ≤ 1) Nanotubes: A Family of Misfit Layered Compounds

We present the analysis of a family of nanotubes (NTs) based on the quaternary misfit layered compound (MLC) Y_xLa_1-xS-TaS₂. The NTs were successfully synthesized within the whole range of possible compositions via the chemical vapor transport technique. In-depth analysis of the NTs using electron microscopy and spectroscopy proves the in-phase (partial) substitution of La by Y in the (La,Y)S subsystem and reveals structural changes compared to the previously reported LaS-TaS₂ MLC-NTs. The observed structure can be linked to the slightly different lattice parameters of LaS and YS. Raman spectroscopy and infrared transmission measurements reveal the tunability of the plasmonic and vibrational properties. Density-functional theory calculations showed that the Y_xLa_1-xS-TaS₂ MLCs are stable in all compositions. Moreover, the calculations indicated that substitution of La by Sc atoms is electronically not favorable, which explains our failed attempt to synthesize these MLC and NTs thereof.

One-dimensional van der Waals heterostructures

We present the experimental synthesis of one-dimensional (1D) van der Waals heterostructures, a class of materials where different atomic layers are coaxially stacked. We demonstrate the growth of single-crystal layers of hexagonal boron nitride (BN) and molybdenum disulfide (MoS₂) crystals on single-walled carbon nanotubes (SWCNTs). For the latter, larger-diameter nanotubes that overcome strain effect were more readily synthesized. We also report a 5-nanometer-diameter heterostructure consisting of an inner SWCNT, a middle three-layer BN nanotube, and an outer MoS₂ nanotube. Electron diffraction verifies that all shells in the heterostructures are single crystals. This work suggests that all of the materials in the current 2D library could be rolled into their 1D counterparts and a plethora of function-designable 1D heterostructures could be realized.

Engineered Cell-Derived Microparticles Bi2Se3/DOX@MPs for Imaging Guided Synergistic Photothermal/Low-Dose Chemotherapy of Cancer

Cell-derived microparticles, which are recognized as nanosized phospholipid bilayer membrane vesicles, have exhibited great potential to serve as drug delivery systems in cancer therapy. However, for the purpose of comprehensive therapy, microparticles decorated with multiple therapeutic components are needed, but effective engineering strategies are limited and still remain enormous challenges. Herein, Bi2Se3 nanodots and doxorubicin hydrochloride (DOX) co-embedded tumor cell-derived microparticles (Bi2Se3/DOX@MPs) are successfully constructed through ultraviolet light irradiation-induced budding of parent cells which are preloaded with Bi2Se3 nanodots and DOX via electroporation. The multifunctional microparticles are obtained with high controllability and drug-loading capacity without unfavorable membrane surface destruction, maintaining their excellent intrinsic biological behaviors. Through membrane fusion cellular internalization, Bi2Se3/DOX@MPs show enhanced cellular internalization and deepened tumor penetration, resulting in extreme cell damage in vitro without considering endosomal escape. Because of their distinguished photothermal performance and tumor homing target capability, Bi2Se3/DOX@MPs exhibit admirable dual-modal imaging capacity and outstanding tumor suppression effect. Under 808 nm laser irradiation, intravenous injection of Bi2Se3/DOX@MPs into H22 tumor-bearing mice results in remarkably synergistic antitumor efficacy by combining photothermal therapy with low-dose chemotherapy in vivo. Furthermore, the negligible hemolytic activity, considerable metabolizability, and low systemic toxicity of Bi2Se3/DOX@MPs imply their distinguished biocompatibility and great potential for tumor theranostics.

Large-scale surfactant-free synthesis of WS2 nanosheets: an investigation into the detailed reaction chemistry of colloidal precipitation and their application as an anode material for lithium-ion and sodium-ion batteries

Novel detailed chemistry of WS₂ synthesis.

Synthesis and characterization of quaternary La(Sr)S-TaS2 misfit-layered nanotubes

Misfit-layered compounds (MLCs) are formed by the combination of different lattices and exhibit intriguing structural and morphological characteristics. MLC Sr x La1- x S-TaS2 nanotubes with varying Sr composition (10, 20, 40, and 60 Sr atom %, corresponding to x = 0.1, 0.2, 0.4 and 0.6, respectively) were prepared in the present study and systematically investigated using a combination of high-resolution electron microscopy and spectroscopy. These studies enable detailed insight into the structural aspects of these phases to be gained at the atomic scale. The addition of Sr had a significant impact on the formation of the nanotubes with higher Sr content, leading to a decrease in the yield of the nanotubes. This trend can be attributed to the reduced charge transfer between the rare earth/S unit (La x Sr1- x S) and the TaS2 layer in the MLC which destabilizes the MLC lattice. The influence of varying the Sr content in the nanotubes was systematically studied using Raman spectroscopy. Density functional theory calculations were carried out to support the experimental observations.

2D Single Crystal WSe2 and MoSe2 Nanomeshes with Quantifiable High Exposure of Layer Edges from 3D Mesoporous Silica Template

The design and fabrication of layered transition metal chalcogenides with high exposure of crystal layer edges is one of the key paths to achieve distinctive performances in their catalysis and electrochemistry applications. Two-dimensional WSe₂ and MoSe₂ nanomeshes with orderly arranged nanoholes were synthesized by using a mesoporous silica material KIT-6 with three-dimensional mesoporous structure as a hard template via a nanocasting strategy. Each piece of the nanomesh is a single crystal, and its c axis is always perpendicular to the nanomesh plane. The highly porous structure brings these nanomeshes extremely high exposure of layer edges, and the well-defined nanostructure provides an opportunity to quantitatively estimate the specific length of the crystal layer edges for the WSe₂ and MoSe₂ nanomeshes synthesized in this work, which are estimated to be 3.8 × 10¹⁰ and 6.0 × 10¹⁰ m g^-1, respectively. The formation of a 2D sheet-like nanomesh structure inside a 3D confined pore space should be attributed to the synergistic effect from the crystal self-limitation growth that is caused by their layered crystal structures and the space-limitation effect coming from the unique pore structure of the KIT-6 template. The catalytic activities of the nanomeshes in an electrocatalytic hydrogen evolution reaction were also investigated.

Advanced Materials and Devices for the Regulation and Study of NK Cells

Natural Killer (NK) cells are innate lymphocytes that contribute to immune protection by cytosis, cytokine secretion, and regulation of adaptive responses of T cells. NK cells distinguish between healthy and ill cells, and generate a cytotoxic response, being cumulatively regulated by environmental signals delivered through their diverse receptors. Recent advances in biomaterials and device engineering paved the way to numerous artificial microenvironments for cells, which produce synthetic signals identical or similar to those provided by the physiological environment. In this paper, we review recent advances in materials and devices for artificial signaling, which have been applied to regulate NK cells, and systematically study the role of these signals in NK cell function.

Interlayer expansion of 2D MoS2 nanosheets for highly improved photothermal therapy of tumors in vitro and in vivo

Interlayer-expanded MoS2 (E-MoS2) nanosheets with an interlayer spacing of 0.94 nm are demonstrated to show an high photothermal conversion efficiency of ∼62%. More importantly, such biocompatible E-MoS2 nanosheets show highly improved photothermal therapy (PTT) of tumors in vitro and in vivo under near-infrared light irradiation.

Two-dimensional semiconductor transition metal based chalcogenide based heterostructures for water splitting applications

Recent research and development is focused in an intensive manner to increase the efficiency of solar energy conversion into electrical energy via photovoltaics and photo-electrochemical reactions.

Direct Chirality Recognition of Single-Crystalline and Single-Walled Transition Metal Oxide Nanotubes on Carbon Nanotube Templates

Chirality is a significant structural feature for chemistry, biology, physics, and materials science, and especially determines the electrical, mechanical, and optical properties of diverse tubular structures, such as carbon nanotubes (CNTs). To recognize the chirality of nanotubes, templates are introduced as potential tools to obtain crystalline samples with visible chiral fringes under electron microscopes. However, few efforts show optimistic results, and new understanding is desired to control the sample quality with CNT templates. Here, a synthesis strategy of single-crystalline molybdenum trioxide (α-MoO₃ ) nanotubes (MONTs) on CNT surfaces is reported to build a 1D van der Waals (vdW) heterostructure. The chirality of the MONTs can be directly "seen" and their structural selectivity is revealed. First, the centralized distribution of the chiral angles of the MONTs indicates a preferential orientation due to the anisotropic bending rigidity of the 2D layers. Then, the interlayer mismatching rejects the radial stacking of α-MoO₃ to maintain the single-walled nature. These results provide a spontaneous strategy for the efficient recognition and control of chirality, and open up a new avenue for CNT-based functional 1D vdW heterostructures.

Hierarchical Nanosheet-Based MS2 (M = Re, Mo, W) Nanotubes Prepared by Templating Sacrificial Te Nanowires with Superior Lithium and Sodium Storage Capacity

Hierarchical nanosheet-based nanotubes are very attractive because their unique structure endows them with large surface areas and exposes massive active sites for functional applications. We herein demonstrate a facile one-pot hydrothermal approach to fabricate the hierarchical nanosheet-based MS₂ (M = Re, Mo, W) nanotubes by using Te nanowires as sacrificial templates. The hierarchical nanotubes show tube channels of ∼30 nm and hierarchical channel walls with a tunable thickness of up to ∼50 nm. As exemplified for application in Li-ion and Na-ion batteries, the ReS₂ hierarchical nanotubes exhibit excellent specific capacities (1137 mA h g^-1 for Li-ion batteries and 375 mA h g^-1 for Na-ion batteries at 0.1 A g^-1 after 100 cycles), good cycling stabilities, and high rate capabilities, demonstrating their promising applicability in rechargeable batteries. This work may open up new opportunities for further exploration of new types of hierarchical nanostructures for applications, e.g., in catalysis, energy chemistry, and gas adsorption and separation.

Flatlands in the Holy Land: The Evolution of Layered Materials Research in Israel

The experimental identification of fullerenes in 1985, carbon nanotubes in 1991, inorganic nanotubes in 1992, and graphene in 2004 are cornerstone events that have marked the beginning of the layered nanostructures era of materials science. Nowadays, the synthesis of such low-dimensional systems is a routine practice allowing the controlled fabrication of 0-, 1-, and 2D layered structures of diverse chemical compositions. These systems possess unique physical properties that stem from their structural anisotropy characterized by strong intralayer covalent bonding and weaker interlayer dispersive interactions. This, in turn, results in promising functionality that attracts the attention of scientists from many disciplines including chemists, physicists, material scientists, engineers, as well as life scientists that are interested in both their basic and applied science aspects. Here, a short review of the contribution of the Israeli scientific community to this effort over the past 3 decades, is provided.

Topotactic Growth of Edge-Terminated MoS2 from MoO2 Nanocrystals

Layered transition metal dichalcogenides have distinct physicochemical properties at their edge-terminations. The production of an abundant density of edge structures is, however, impeded by the excess surface energy of edges compared to basal planes and would benefit from insight into the atomic growth mechanisms. Here, we show that edge-terminated MoS₂ nanostructures can form during sulfidation of MoO₂ nanocrystals by using in situ transmission electron microscopy (TEM). Time-resolved TEM image series reveal that the MoO₂ surface can sulfide by inward progression of MoO₂(202̅):MoS₂(002) interfaces, resulting in upright-oriented and edge-exposing MoS₂ sheets. This topotactic growth is rationalized in the interplay with density functional theory calculations by successive O-S exchange and Mo sublattice restructuring steps. The analysis shows that formation of edge-terminated MoS₂ is energetically favorable at MoO₂(110) surfaces and provides a necessary requirement for the propensity of a specific MoO₂ surface termination to form edge-terminated MoS₂. Thus, the present findings should benefit the rational development of transition metal dichalcogenide nanomaterials with abundant edge terminations.

BSA-caged metal clusters to exfoliate MoS2 nanosheets towards their hybridized functionalization

Herein, we develop a facile exfoliation and in situ functionalization strategy to produce hybridized Au/MoS2 nanostructures comprised of size-controlled gold nanoparticles (Au NPs) and ultrathin MoS2 nanosheets by using bovine serum albumin (BSA)-caged Au25 clusters as both exfoliating and functionalizing agents. As revealed, BSA molecules are strongly adsorbed on MoS2via their hydrophobic interaction, and this drives the expansion of the BSA molecules that initially protect Au25 cores at pH 4, leading to the effective exfoliation of MoS2 nanosheets together with the epitaxial growth of Au25 cores into 5 nm-sized Au NPs on MoS2 nanosheets due to their reduced surface protection. Upon the addition of H2O2, the resulting Au NPs can further grow to achieve a controlled size from 5 to 30 nm with an increase of the reaction time. It is demonstrated that the hybridized Au/MoS2 nanosheets exhibit a better performance in the photocatalytic degradation of substrates compared to the individual components or their mixture. Moreover, the hybridized Ag/MoS2, Au/WO3 and Au/graphene nanosheets are further produced by the usage of BSA-caged Ag and Au clusters, respectively. Overall, this work reports the first utilization of protein-caged metal clusters for the exfoliation and hybridized functionalization of 2D materials, and this brings more opportunities to exploit unusual properties of hybridized 2D materials for novel applications.

Comparison of X12Y12 (X=Al, B and Y=N, P) fullerene-like nanoclusters toward adsorption of dimethyl ether

Density functional theory (DFT) was used for studying the adsorption of dimethyl ether (DME) onto four nanoclusters: [Formula: see text] ([Formula: see text], B and [Formula: see text], P). The interaction energy along with the adsorption energy was investigated, and it was found that DME molecule has higher binding energies upon adsorption on Al-containing clusters, but on the other hand, it results in higher alteration in the electronic structure of B-containing cluster. Outcomes of charge analysis and frontier molecular orbital confirm higher alteration in the electronic structure of the later clusters, suggesting the possible potential of B[Formula: see text]N[Formula: see text] and B[Formula: see text]P[Formula: see text] as two sensitive sensors for DME. Nevertheless, Al-containing clusters showed much better adsorbent property, judging from their higher adsorption energies. The positive values of charge transfer upon DME adsorption confirm the p-type semiconducting property of all these clusters.

Preparation and Characterization of WS₂@SiO₂ and WS₂@PANI Core-Shell Nanocomposites

Two tungsten disulfide (WS₂)-based core-shell nanocomposites were fabricated using readily available reagents and simple procedures. The surface was pre-treated with a surfactant couple in a layer-by-layer approach, enabling good dispersion of the WS₂ nanostructures in aqueous media and providing a template for the polymerization of a silica (SiO₂) shell. After a Stöber-like reaction, a conformal silica coating was achieved. Inspired by the resulting nanocomposite, a second one was prepared by reacting the surfactant-modified WS₂ nanostructures with aniline and an oxidizing agent in an aqueous medium. Here too, a conformal coating of polyaniline (PANI) was obtained, giving a WS₂@PANI nanocomposite. Both nanocomposites were analyzed by electron microscopy, energy dispersive X-ray spectroscopy (EDS) and FTIR, verifying the core-shell structure and the character of shells. The silica shell was amorphous and mesoporous and the surface area of the composite increases with shell thickness. Polyaniline shells slightly differ in their morphologies dependent on the acid used in the polymerization process and are amorphous like the silica shell. Electron paramagnetic resonance (EPR) spectroscopy of the WS₂@PANI nanocomposite showed variation between bulk PANI and the PANI shell. These two nanocomposites have great potential to expand the use of transition metals dichalcogenides (TMDCs) for new applications in different fields.

Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives

Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS₂, MoSe₂, MoTe₂, WS₂ and WSe₂, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.

Tubular Hybrids: A Nanoparticle-Molecular Network

We report here a new methodology for the formation of freestanding nanotubes composed of individual gold nanoparticles (NPs) cross-linked by coordination complexes or porphyrin molecules using WS₂ nanotubes (INT-WS₂) as a template. Our method consists of three steps: (i) coverage of these robust inorganic materials with monodispersed and dense monolayers of gold NPs, (ii) formation of a molecular AuNP network by exposing these decorated tubes to solutions containing a ruthenium polypyridyl complex or meso-tetra(4-pyridyl)porphyrin, and (iii) removal of the INT-WS₂ template with a hydrogen peroxide solution. Nanoindentation of the template-free AuNP tubes with atomic force microscopy indicates a radial elastic modulus of 4 GPa. The template-free molecular AuNP tubes are characterized using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy. The methodology provides a convenient and scalable strategy for the realization of molecular AuNP tubes with a defined length and diameter, depending on the dimensions of the template.

Torsional Resonators Based on Inorganic Nanotubes

We study for the first time the resonant torsional behaviors of inorganic nanotubes, specifically tungsten disulfide (WS₂) and boron nitride (BN) nanotubes, and compare them to that of carbon nanotubes. We have found WS₂ nanotubes to have the highest quality factor (Q) and torsional resonance frequency, followed by BN nanotubes and carbon nanotubes. Dynamic and static torsional spring constants of the various nanotubes were found to be different, especially in the case of WS₂, possibly due to a velocity-dependent intershell friction. These results indicate that inorganic nanotubes are promising building blocks for high-Q nanoelectromechanical systems (NEMS).

Single-layer MoS2formation by sulfidation of molybdenum oxides in different oxidation states on Au(111)

The sulfidation pathway from MoO₃to MoS₂on Au(111) revealed by a combination of Scanning Tunneling Microscopy and X-Ray Photoelectron Spectroscopy.

Fracture behaviors of pre-cracked monolayer molybdenum disulfide: A molecular dynamics study

The fracture strength and crack propagation of monolayer molybdenum disulfide (MoS2) sheets with various pre-existing cracks are investigated using molecular dynamics simulation (MDS). The uniaxial tensions of pre-cracked monolayer MoS2 sheets with different crack tips, different locations of crack, different crack lengths and angled cracks are simulated and studied. The results show that the configuration of crack tip can influence significantly the fracture behaviors of monolayer MoS2 sheets while the location of crack does not influence the fracture strength. With the increase of crack length, the fracture strength of monolayer MoS2 sheets reduces almost linearly, and the fracture of monolayer MoS2 sheets is transformed from almost brittle to ductile. By making comparison between the MDS results and the predictions of continuum fracture mechanics theories, including Inglis' model, Griffith's model with and without finite size effect, it is found that MDS results agree well with the predictions of Griffith's model with finite size effect, differ from the predictions of Inglis' model and Griffith's model without finite size effect. Finally, the MDS results of monolayer MoS2 sheets with different angled crack are also analyzed based on the continuum fracture mechanics model.

Structural and chemical analysis of gadolinium halides encapsulated within WS2 nanotubes

The hollow cavities of nanotubes serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of WS2 nanotubes by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is non-trivial due to the presence of multiple high atomic number elements. Therefore, energy dispersive X-ray spectroscopy (EDS) tomography was employed revealing the three dimensional chemical composition. Molecular dynamics simulations of the filling procedure shed light into the mechanics behind the formation of the confined gadolinium halide crystals. The quasi-1D system employed here serves as an example of a TEM-based chemical nanotomography method that could be extended to other materials, including beam-sensitive soft materials.

Interactions of 1D- and 2D-layered inorganic nanoparticles with fibroblasts and human mesenchymal stem cells

AIM

This study investigates the effects of tungsten disulfide nanotubes (WSNTs) and molybdenum disulfide nanoplatelets (MSNPs) on fibroblasts (NIH-3T3) and mesenchymal stem cells (MSCs) to determine safe dosages for potential biomedical applications.

MATERIALS & METHODS

Cytotoxicity of MSNPs and WSNTs (5-300 μg/ml) on NIH-3T3 and MSCs was assessed at 6, 12 or 24 h. MSC differentiation to adipocytes and osteoblasts was assessed following treatment for 24 h.

RESULTS

Only NIH-3T3 cells treated with MSNPs showed dose or time dependent increase in cytotoxicity. Differentiation markers of MSCs in treated groups were unaffected compared with untreated controls.

CONCLUSION

MSNPs and WSNTs at concentrations less than 50 µg/ml are potentially safe for treatment of fibroblasts or MSCs for up to 24 h.

The Importance of CD44 as a Stem Cell Biomarker and Therapeutic Target in Cancer

CD44 is a cell surface HA-binding glycoprotein that is overexpressed to some extent by almost all tumors of epithelial origin and plays an important role in tumor initiation and metastasis. CD44 is a compelling marker for cancer stem cells of many solid malignancies. In addition, interaction of HA and CD44 promotes EGFR-mediated pathways, consequently leading to tumor cell growth, tumor cell migration, and chemotherapy resistance in solid cancers. Accumulating evidence indicates that major HA-CD44 signaling pathways involve a specific variant of CD44 isoforms; however, the particular variant almost certainly depends on the type of tumor cell and the stage of the cancer progression. Research to date suggests use of monoclonal antibodies against different CD44 variant isoforms and targeted inhibition of HA/CD44-mediated signaling combined with conventional radio/chemotherapy may be the most favorable therapeutic strategy for future treatments of advanced stage malignancies. Thus, this paper briefly focuses on the association of the major CD44 variant isoforms in cancer progression, the role of HA-CD44 interaction in oncogenic pathways, and strategies to target CD44-overexpressed tumor cells.

A High-Rate V2 O5 Hollow Microclew Cathode for an All-Vanadium-Based Lithium-Ion Full Cell

V2O5 hollow microclews (V2O5-HMs) have been fabricated through a facile solvothermal method with subsequent calcination. The synthesized V2O5-HMs exhibit a 3D hierarchical structure constructed by intertangled nanowires, which could realize superior ion transport, good structural stability, and significantly improved tap density. When used as the cathodes for lithium-ion batteries (LIBs), the V2O5-HMs deliver a high capacity (145.3 mAh g(-1)) and a superior rate capability (94.8 mAh g(-1) at 65 C). When coupled with a lithiated Li3VO4 anode, the all-vanadium-based lithium-ion full cell exhibits remarkable cycling stability with a capacity retention of 71.7% over 1500 cycles at 6.7 C. The excellent electrochemical performance demonstrates that the V2O5-HM is a promising candidate for LIBs. The insight obtained from this work also provides a novel strategy for assembling 1D materials into hierarchical microarchitectures with anti-pulverization ability, excellent electrochemical kinetics, and enhanced tap density.

High Pressure Vibrational Properties of WS2 Nanotubes

We bring together synchrotron-based infrared and Raman spectroscopies, diamond anvil cell techniques, and an analysis of frequency shifts and lattice dynamics to unveil the vibrational properties of multiwall WS2 nanotubes under compression. While most of the vibrational modes display similar hardening trends, the Raman-active A1g breathing mode is almost twice as responsive, suggesting that the nanotube breakdown pathway under strain proceeds through this displacement. At the same time, the previously unexplored high pressure infrared response provides unexpected insight into the electronic properties of the multiwall WS2 tubes. The development of the localized absorption is fit to a percolation model, indicating that the nanotubes display a modest macroscopic conductivity due to hopping from tube to tube.

The catalytic activity and chemical structure of nano MoS2 synthesized in a controlled environment

The redox synthesis mechanism is, for the first time, revealed in a novel hydrothermal preparation of nano MoS₂ with MoO₃ as precursors. The S-to-Mo ratio plays a key role in influencing the morphology and activity of catalyst MoS₂.

Supracolloidal fullerene-like cages: design principles and formation mechanisms

A vast collection of fascinating supracolloidal fullerene-like cages has been achievedviathe self-assembly of soft three-patch particles designed to mimic non-planar sp²hybridized carbon atoms in fullerenes, through the rational design of patch configuration, size, and interaction.

MoS2 with an intercalation reaction as a long-life anode material for lithium ion batteries

MoS₂ without carbon modification has achieved a long cycling performance by cutting off the terminal discharge voltage to preserve a layered structure.