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Interlayer coupling as a unique feature for two-dimensional (2D) materials may influence their thickness-dependent physical properties, especially the bandgap due to quantum confinement effect. Widely-studied 2D materials usually possess strong interlayer coupling such as most of transition metal dichalcogenides (TMDs), PtS2 and so on. However, 2D materials with weak interlayer coupling are rarely referred that mainly focus on ReS2, as well as its counterpart ReSe2. Here we report a new member of weak interlayer coupling 2D materials, germanium disulfide (GeS2). The interlayer interaction in GeS2 is investigated from theory to experiment. By density functional theory calculations, we find that this extraordinarily weak interlayer coupling in GeS2 originates from the weak hybridization of interlayer S atoms. Thickness-dependent Raman spectra of GeS2 flakes exhibit that the Raman peaks remain unchanged when increasing the thickness; and a small first-order temperature coefficient of −0.00857 cm−1·K−1 is obtained from the temperature-dependent Raman spectra. These experimental results further confirm the weak interlayer coupling in GeS2.

Chalcogen elements, such as sulfur (S), selenium (Se), tellurium (Te) and the interchalcogen compounds, have been studied extensively as cathode materials for the next-generation rechargeable lithium/sodium (Li/Na) batteries. The high energy output of the Li/Na-chalcogen battery originates from the two-electron conversion reaction between chalcogen cathode and alkali metal anode, through which both electrodes are able to deliver high theoretical capacities. The reaction also leads to parasitic reactions that deteriorate the chemical environment in the battery, and different cathode-anode combinations show their own features. In this article, we intend to discuss the fundamental conversion electrochemistry between chalcogen elements and alkali metals and its potential influence, either positive or negative, on the performance of batteries. The strategies to improve the conversion electrochemistry of chalcogen cathode are also reviewed to offer insights into the reasonable design of rechargeable Li/Na-chalcogen batteries.

We have fabricated hybrid molecular chain structures formed by electron acceptor compound 1 and electron donor molecules 2 and 3 at the liquid/solid interface of graphite surface. The structural details of the mono-component and the binary assemblies are revealed by high resolution scanning tunneling microscopy (STM). Compound 1 can form two well-ordered lamellar patterns at different concentrations. In the co-adsorption structures, compounds 2 and 3 can insert into the space between molecular chains of compound 1 and form large area well-ordered nanoscale phase separated lamellar structures. The unit cell parameters for the coassemblies can be “flexibly” adjusted to make the electron donors and acceptors perfectly match along the molecular chains. Scanning tunneling spectroscopy (STS) results indicate that the electronic properties of individual molecular donors and acceptors are preserved in the binary self-assembly. These results provide molecular insight into the nanoscale phase separation of organic electron acceptors and donors on surfaces and are helpful for the fabrication of surface supramolecular structures and molecular devices.

Two-dimensional (2D) self-assembly of two 1,3,2-dioxaborine derivatives was investigated by STM. The molecules consist of π system and steric end groups. A droplet of toluene solution containing the molecules was deposited onto HOPG for preparing the assemblies. STM images showed that the molecular structures affect the assembly structure. The dipole-dipole interaction and steric repulsion played important roles in the formation of the self-assembled monolayers.

The composite material of poly-(L-lactide) (PLLA) and carbon nanotubes (CNTs) were prepared. Its surface morphologies and property were worked out by using atomic force microscopy (AFM) and contact angle measurement. Moreover, the prime cytocompatibility was used to investigate the biocompatibility of the composite material containing CNTs and the effects of CNTs on one aspect of cell function, cell affinity. The results obtained indicate that the composite material of PLLA and CNTs possesses good bio-compatibility for both the 3T3 fibroblasts and Oct-1 osteoblast-like cells. The addition of CNTs will greatly affect cell affinity of the material, which may be disadvantage for the cell adhesion.