Tunable giant Goos-Hänchen shift in Au-ReS2-graphene heterostructure.

Enhancing and flexibly controlling the Goos-Hänchen (GH) shift directly is a significant challenge. Here, we report a tunable giant GH shift in a Au-ReS2-graphene heterostructure. The GH shift of this heterostructure demonstrates strong anisotropy and a unique "sign inversion" feature as the graphene reaches a specific thickness. Flexible control and enhancement of the GH shift to the centimeter scale can be achieved by simply rotating the crystallization direction of the heterostructure. Utilizing this feature, we designed an anisotropic refractive index sensor with a high sensitivity of 1.31 × 108 µm/RIU. This marks an order of magnitude improvement over previous research and introduces a rotation-dependent sensitivity adjustment feature. The tunable giant GH shift provides a promising approach for future designs of optical sensing and modulation devices.

Pin-on-Disc Modelling with Mesh Deformation Using Discrete Element Method.

The pin-on-disc test is a standard sliding wear test used to analyse sliding properties, including wear contour and wear volume. In this study, long-term laboratory test performance is compared with a short-term numerical model. A discrete element method (DEM) approach combined with an Archard wear model and a deformable geometry technique is used. The effect of mesh size on wear results is evaluated, and a scaling factor is defined to relate the number of revolutions between the experiment and the numerical model. The simulation results indicate that the mesh size of the disc has a significant effect on the wear contour. The wear depth and wear width follow a normal distribution after experiencing a run-in phase, while the wear volume has a quadratic relation with the number of revolutions. For the studied material combination, the calibration of the wear coefficient shows that the wear volume of the pin-on-disc test accurately matches the simulation results for a minimum of eight revolutions with a wear coefficient lower than 2 × 10-11 Pa-1.

Reducing metal/graphene contact resistance via N, N-dimethylacetamide-assisted clean fabrication process.

Contact resistance (RC) is of great importance for radio frequency (RF) applications of graphene, especially graphene field effect transistors (FETs) with short channel. FETs and transmission line model test structures based on chemical vapor deposition grown graphene are fabricated. The effects of employing traditional lithography solvent (Acetone) and strong solvents for photo resist, such as N, N-Dimethylacetamide (ZDMAC) and N-Methyl pyrrolidone (NMP), are systematically investigated. It was found that ZDMAC and NMP have more proficiency than acetone to remove the photo-resist residues and contaminations attached on graphene surface, enabling clean surface of graphene. However, strong solvents are found to destroy the lattice structure of graphene channel and induce defects in graphene lattice. Clean surface contributes to a significant reduction in theRCbetween graphene channel and metal electrode, and the defects introduced on graphene surface underneath metal electrodes also contribute the reduction ofRC. But defects and deformation of lattice will increase the resistance in graphene channel and lead to the compromise of device performance. To address this problem, a mix wet-chemical approach employing both acetone and ZDMAC was developed in our study to realize a 19.07% reduction ofRC, without an unacceptable mass production of defects.

Stable p-type chemical doping of graphene with reduced contact resistance by single-layer perfluorinated polymeric sulfonic acid.

Recently, graphene has led to unprecedented progress in device performance at the atom limit. A high performance of field-effect transistors requires a low graphene-metal contact resistance. However, the chemical doping methods used to tailor or improve the properties of graphene are sensitive to ambient conditions. Here, we fabricate a single-layer perfluorinated polymeric sulfonic acid (PFSA), also known as Nafion, between the graphene and the substrate as a p-type dopant. The PFSA doping method, without inducing any additional structural defects, reduces the contact resistance of graphene by ∼28.8%, which has a significant impact on practical applications. This reduction can be maintained for at least 67 days due to the extreme stability of PFSA. Effective, uniform and stable, the PFSA doping method provides an efficient way to reduce the contact resistance of graphene applications.

Peptide-Mediated Synthesis of Zeolitic Imidazolate Framework-8 with Controllable Morphology and Size.

Peptides with a sequence of Nap-Ix-GPLGLAG-R4-NH2 (x = 2, 4, and 6, shorted as I2R4, I4R4, and I6R4) were used as capping agents for the synthesis of zeolitic imidazolate framework-8 (ZIF-8) in water. Peptide addition can significantly inhibit the growth of ZIF-8 crystals. The shape and size of ZIF-8 crystals was related closely to the number of isoleucine (Ile, I) residues as well as concentration of the peptide. The shape of ZIF-8 crystals changes from rhomboid dodecahedron to truncated rhombic dodecahedron to cube with the decreasing number of isoleucine residues from six to two. At a peptide concentration of 1.0 mM, the morphology of ZIF-8 crystals was cubic, truncated rhombic dodecahedron, and typical rhombic dodecahedron in the cases of I2R4, I4R4, and I6R4, respectively. Also, the particle size can be regulated from ca. 1.7 µm to <100 nm by controlling the peptide concentration from 0 to 2.0 mM. This work develops a simple and green method for the synthesis of ZIF-8 crystals with controllable shape and size in water, which shows high potential for biomedical and biological applications.

Bionic Design for Reducing Adhesive Resistance of the Ridger Inspired by a Boar's Head.

The main feature of the boar's head used to root around for food is the front part, which is similar to the ridger in terms of function, load, and environment. In this paper, the boar's head was selected as the biological prototype for developing a new ridger. The point cloud of the head was captured by a 3D scanner, and then, the head surface was reconstructed using 3D coordinates. The characteristic curves of the front part of the boar's head were extracted, and then, five cross-sectional curves and one vertical section curve were fitted. Based on the fitted curves, five kinds of bionic ridgers were designed. The penetrating resistances of the bionic ridgers and traditional ridger were tested at different speeds in an indoor soil bin. The test results showed that bionic ridger B had the best penetrating resistance reduction ratio of 16.67% at 4.2 km/h velocity. In order to further evaluate the performance of the best bionic ridger (bionic ridger B), both the bionic ridger and traditional ridger were tested in a field under the same working conditions. The field results indicate that the bionic ridger reduces penetrating resistance by 6.91% compared to the traditional ridger, and the test results validate that the bionic ridger has an effect on reducing penetrating resistance.