Interlayer friction between the atomic planes of 2D materials and heterostructures is a promising probe of the physics in their interlayer couplings and superlubricity. However, it is still challenging to measure the interlayer friction between well-defined 2D layers. We propose an approach of thermally assisted mechanical exfoliation and transfer to fabricate various 2D flake-wrapped atomic force microscopy (AFM) tips and to directly measure the interlayer friction between 2D flakes in single-crystalline contact. First, superlubricity between different 2D flakes and layered bulk materials is achieved with a friction coefficient as low as 10. The rotation angle dependence of superlubricity is observed for friction between graphite layers, whereas it is not observed between graphite and h-BN because of the incommensurate contact of the mismatched lattices. Second, the interlayer lateral force map between ReS layers is measured with atomic resolution, showing hexagonal patterns, as further verified by theoretical simulations. The tribological system constructed here offers an experimental platform to study interlayer couplings and friction between 2D flakes and layered bulk materials.

The interaction of two-dimensional (2D) nanomaterials and bacterial membranes has attracted tremendous attention in antibacterial applications. Various peculiarities of 2D nanomaterials may lead to multiple mechanisms of their interactions with membranes. Here, we investigated the interaction between molybdenum disulfide (MoS2) nanosheets and the bacterial membrane by using both theoretical and experimental approaches. Molecular dynamics simulation presented that MoS2 nanosheets can disrupt the structure of the lipid membrane by making dents on its surface and extracting phospholipid molecules to reduce the integrity of the membrane. This is attributed to the combination of the dispersion interaction of lipid tails with S atoms and the electrostatic interactions of lipid head groups with the Mo and S atoms in the lateral edges of the MoS2 nanosheet. Scanning electron microscopy and transmission electron microscopy confirmed the dents and the destruction of the cell membrane, which would lead to the loss of cytoplasm and the death of bacteria. It should be noted that the phenomenon where MoS2 induces a dent is different from the direct insertion of graphene-based nanomaterials, which might be due to the thicker and stiffer structure of MoS2. Therefore, we believe that the molecular interactions of 2D nanomaterials with bacterial membranes should be highly correlated with their structural characteristics. This newly discovered mechanism of MoS2 nanomaterials to disrupt the cell membrane may promote the application of transition metal dichalcogenide (TMD) nanomaterials in designing remarkable antibacterial materials in the near future.

Remarkable recent advances on Au(SR) nanoclusters have led to significant applications in catalysis, sensing, and magnetism. However, the existing synthetic routes are complicated, particularly for the water-soluble Au(SG) nanoclusters. Here, we report a single-step concentration and temperature-controlled method for rapid synthesis of the Au(SG) nanoclusters in as little as 2 h without the need for low-temperature reaction or even stirring. A systematic time-based investigation was carried out to study the effects of volume, concentration, and temperature on the synthesis of these nanoclusters. Further, we discovered for the first time that the Au(SG) nanoclusters exhibit excellent photothermal activities in achieving 100% cell death for MDA-MB-231 breast cancer cells at a power of 10 W/cm using an 808 nm laser source, demonstrating applications toward photothermal therapy.

Electronic structures, spontaneous polarization, dynamical and nonlinear optical (NLO) properties of polar oxide ZnSnO(3) with LiNbO(3) (LN)-type structure have been investigated in the framework of density functional theory. By analyzing the Born effectives of LN-type ZnSnO(3), we find that Z* of Zn atoms show relatively large anomalous behavior. The spontaneous polarization is attributed to the large displacement of Zn atoms because of the mixed ionic-covalent character between the Zn-O bonds. The optical dielectric tensor is nearly the same; however the static dielectric tensor shows strongly anisotropy. Furthermore, the nonlinear optical properties are calculated by using 2n + 1 theorem applied to an electric-field dependent energy functional. The large dielectric constants and NLO susceptibilities indicate that the LN-type ZnSnO(3) would be a candidate as a high-performance dielectric and nonlinear optical material.

Although a number of experiments have been attempted to investigate the lubrication of aqueous copolymer lubricant, which is applied widely in metalworking operations, a comprehensive theoretical investigation at atomistic level is still lacking. This study addresses the influence of loading pressure and copolymer concentration on the structural properties and tribological performance of aqueous copolymer solution of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) at mixed lubrication using a molecular dynamic (MD) simulation. An effective interfacial potential, which has been derived from density functional theory (DFT) calculations, was employed for the interactions between the fluid's molecules and iron surface. The simulation results have indicated that the triblock copolymer is physisorption on iron surface. Under confinement by iron surfaces, the copolymer molecules form lamellar structure in aqueous solution and behave differently from its bulk state. The lubrication performance of aqueous copolymer lubricant increases with concentration, but the friction reduction is insignificant at high loading pressure. Additionally, the plastic deformation of asperity is dependent on both copolymer concentration and loading pressure, and the wear behavior shows a linear dependence of friction force on the number of transferred atoms between contacting asperities.

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Contacting interfaces with physical isolation and weak interactions usually act as barriers for electrical conduction. The electrical contact conductance across interfaces has long been correlated with the true contact area or the "contact quantity". Much of the physical understanding of the interfacial electrical contact quality was primarily based on Landauer's theory or Richardson formulation. However, a quantitative model directly connecting contact conductance to interfacial atomistic structures still remains absent. Here, we measure the atomic-scale local electrical contact conductance instead of local electronic surface states in graphene/Ru(0001) superstructure, via atomically resolved conductive atomic force microscopy. By defining the "quality" of individual atom−atom contact as the carrier tunneling probability along the interatomic electron transport pathways, we establish a relationship between the atomic-scale contact quality and local interfacial atomistic structure. This real-space model unravels the atomic-level spatial modulation of contact conductance, and the twist angle-dependent interlayer conductance between misoriented graphene layers.