In the present work, properties of the interlayer breathing modes in twisted MoS2 samples with different structures are carefully examined. The distribution of peak position of the breathing modes is mainly dependent on overall layer numbers, and is only slightly affected by specific structure of the sample. Linear chain model calculation shows quantitatively a markedly decrease in interlayer force on the twisted interface, and slight difference in Raman frequency may mean considerable difference in interlayer force. When one or both of the component layers get too thick, no new breathing modes can be found, indicating that rigidity of the component may affect the coupling efficiency. Our work demonstrates that low-frequency Raman spectroscopy can act as an effective indirect strategy for the detection of interlayer interaction, which is a good complement to existing methods such as AFM technologies.

A polyaniline-graphene oxide (PANI-GO) composite coating was prepared on the 316 stainless steel (SS) by a pulse current codeposition method. Agglomeration of aniline and graphene oxide occurred during the deposition process and formed a compact coating on the SS surface. The compact structure showed an excellent corrosion resistance. The corrosion inhibition efficiency and protection efficiency of the PANI-GO composite coating reached 98.4% and 99.3%, respectively. In addition, the deposition parameters had an obvious effect on the corrosion resistance of PANI-GO composite coatings due to changes of their porosity and wettability.

The nickel hydroxide-graphene oxide (Ni(OH)2-GO) composite coating was facilely formed on the 316 stainless steel (SS) by a pulse current electrodeposition method. The aggregation of Ni(OH)2 particles and GO in the deposition process resulted in the formation of a compact composite coating on the SS substrate. The compact composite coating provided an excellent barrier against corrosion of the SS as the corrosion inhibition efficiency and protection efficiency reached 97.1% and 98.7%, respectively. In addition, the micro-tribological test by AFM demonstrated that the coatings greatly decreased the friction on the SS surface. The lubrication of the coatings strongly depended on their compositions.

Recently, molybdenum disulfide (MoS2) has attracted considerable attention in the field of biomolecular detection owing to its large surface area and remarkable optoelectronic properties. Here, we report on a novel Au-modified monolayer MoS2 sensor that allows rapid, sensitive, and selective detection of DNA molecules. The Au-thiol bond can effectively enhance the DNA adsorption on MoS2. With the increasing concentration of DNA solution, the photoluminescence peak shows a prominent blueshift induced by the decrease of dielectric constant around MoS2. The monolayer MoS2 nanosheet exhibits different photoluminescence properties toward single-strained DNA versus double strained DNA. Thus, the complementary target DNA could be distinguished from mismatched DNA through the photoluminescence spectra of MoS2. The density functional theory calculation of MoS2/DNA systems was performed to explore the detection mechanism. This work could promote the research of novel sensing platform by coupling nanomaterials with biomolecular recognition events.

Few-layer MoS2 has recently gained great attention owing to its remarkable mechanical and photoelectric properties, which are strongly influenced by the interactions and relative orientations between layers. Here, we report on Raman scattering measurements of twisted MoS2 flakes prepared by exfoliation and nondestructive transfer. Thermal annealing treatment can effectively enhance the interlayer coupling of twisted MoS2 and lead to a van der Waals (vdW) interaction between two stacked layers. We have roughly calculated the interlayer coupling force by a diatomic chain model (DCM) and found that the interlayer adhesive force increased by ∼20% compared with no-treatment samples. We additionally found that the non-Bernal stacking structure of MoS2 induces a weakening in the interlayer coupling. This study could promote the development of novel semiconductors, optoelectronic devices, and superlubricity materials.