Colloidal Synthesis of Ultrathin and Se-Rich V2Se9 Nanobelts as High-Performance Anode Materials for Li-Ion Batteries.

In this study, the one-dimensional (1D) material V2Se9 was successfully synthesized using a colloidal method with VO(acac)2 and Se powder as precursors in a 1-octadecene solvent. The obtained colloidally synthesized V2Se9 (C-V2Se9) has an ultrathin nanobelt shape and a 4.5 times higher surface area compared with the bulk V2Se9, which is synthesized in a solid-state reaction as previously reported. In addition, all surfaces of C-V2Se9 are exposed to Se atoms, which is advantageous for storing Li through the conversion reaction into the Li2Se phase. Herein, the electrochemical performance of the C-V2Se9 anode material is evaluated; thus, the novelty of C-V2Se9 as a Se-rich 1D anode material is verified. The C-V2Se9 electrode exhibits a reversible capacity of 893.21 mA h g-1 and a Coulombic efficiency of 97.82% at the 100th cycle and excellent structural stability. Compared with the bulk V2Se9 electrode, the outstanding electrochemical performance of C-V2Se9 is attributed to its ultrathin nanobelt shape, high surface area, shorter Li diffusion length, and more electrochemically active sites. This work indicates the great potential of the Se-rich 1D material, C-V2Se9, as a post-transition metal dichalcogenide material for high-performance LIBs.

Colloidal synthesis of 1-D van der Waals material Nb2Se9: study of synergism of coordinating agent in a co-solvent system.

Low-dimensional Nb2Se9 nanocrystals were synthesised through a simple one-pot colloidal synthesis with C18 organic solvents (octadecane, oleylalcohol, octadecanethiol, octadecene (ODE), and oleylamine (OLA)) of varied terminal functional groups. The solvent with high reducing power facilitated the nucleation of the nanoparticle, lowering threshold concentration and broadening the concentration spectrum. As a solvent, reducing agent, and capping agent, ODE functions as a primary factor in the synthesis of high-quality Nb2Se9 nanorods. We further discuss the unique adhesion role of ODE under the co-solvent system and demonstrate morphology control through synergism between ODE and OLA, verified by the electrochemical measurements.

Organic Dispersion of Mo3Se3- Single-Chain Atomic Crystals Using Surface Modification Methods.

In this study, single-chain atomic crystals (SCACs), Mo3Se3-, which can be uniformly dispersed, with an atomically thin diameter of ∼0.6 nm were modified to disperse in an organic solvent. Various surfactants were chosen to provide steric hindrance to aqueous-dispersed Mo3Se3- by modifying the surface of Mo3Se3-. The organic dispersions of surface-modified Mo3Se3- SCACs in nonpolar solvent (toluene, benzene, and chloroform) were stable with a uniform diameter of 2 nm, and they have enhanced stability from oxidation (>10 days). With the surfactants that have a polystyrene tail group (PS-NH2), the surface-modified Mo3Se3- SCAC showed high compatibility with a polystyrene polymer matrix. Using the surface-modified Mo3Se3- SCAC, a homogeneous Mo3Se3-/polystyrene/toluene organogel was prepared. More importantly, the Mo3Se3-/polystyrene organogel exhibits significantly enhanced mechanical properties, with the improvement of 202.27% and 279.52% for tensile strength and elongation, respectively, compared with that of the pure organogel. The surface-modified Mo3Se3- had a similar structure with a polymer matrix, and the properties of the polymer can be improved even with a small addition of Mo3Se3-.

One-dimensional van der Waals stacked p-type crystal Ta2Pt3Se8 for nanoscale electronics.

Recently, ternary transition metal chalcogenides Ta2X3Se8 (X = Pd or Pt) have attracted great interest as a class of emerging one-dimensional (1D) van der Waals (vdW) materials. In particular, Ta2Pd3Se8 has been actively studied owing to its excellent charge transport properties as an n-type semiconductor and ultralong ballistic phonon transport properties. Compared to subsequent studies on the Pd-containing material, Ta2Pt3Se8, another member of this class of materials has been considerably less explored despite its promising electrical properties as a p-type semiconductor. Herein, we demonstrate the electrical properties of Ta2Pt3Se8 as a promising channel material for nanoelectronic applications. High-quality bulk Ta2Pt3Se8 single crystals were successfully synthesized by a one-step vapor transport reaction. Scanning Kelvin probe microscopy measurements were used to investigate the surface potential difference and work function of the Ta2Pt3Se8 nanoribbons of various thicknesses. Field-effect transistors fabricated on exfoliated Ta2Pt3Se8 nanoribbons exhibited moderate p-type transport properties with a maximum hole mobility of 5 cm2 V-1 s-1 and an Ion/Ioff ratio of >104. Furthermore, the charge transport mechanism of Ta2Pt3Se8 was analyzed by temperature-dependent transport measurements in the temperature range from 90 to 320 K. To include Ta2Pt3Se8 in a building block for modern 1D electronics, we demonstrate p-n junction characteristics using the electron beam doping method.

High Breakdown Current Density in Quasi-1D van der Waals Layered Material Ta2NiSe7.

We synthesized ternary composition chalcogenide Ta2NiSe7, a quasi-one-dimensional (Q1D) material with excellent crystallinity. To utilize the excellent electrical conductivity property of Ta2NiSe7, the breakdown current density (JBD) according to thickness change through mechanical exfoliation was measured. It was confirmed that as the thickness decreased, the maximum breakdown voltage (VBD) increased, and at 18 nm thickness, 35 MA cm-2 of JBD was measured, which was 35 times higher than that of copper, which is commonly used as an interconnect material. By optimization of the exfoliation process, it is expected that through a theoretical model fitting, the JBD can be increased to about 356 MA cm-2. It is expected that the low-dimensional materials with ternary compositions proposed through this experiment can be used as candidates for current-carrying materials that are required for the miniaturization of various electronic devices.