Jiwoong Suk

Reproducible dry and wet transfer techniques were developed to improve the transfer of large-area monolayer graphene grown on copper foils by chemical vapor deposition (CVD). The techniques reported here allow transfer onto three different classes of substrates: substrates covered with shallow depressions, perforated substrates, and flat substrates. A novel dry transfer technique was used to make graphene-sealed microchambers without trapping liquid inside. The dry transfer technique utilizes a

Mechanical properties of ultrathin membranes consisting of one layer, two overlapped layers, and three overlapped layers of graphene oxide platelets were investigated by atomic force microscopy (AFM) imaging in contact mode. In order to evaluate both the elastic modulus and prestress of thin membranes, the AFM measurement was combined with the finite element method (FEM) in a new approach for evaluating the mechanics of ultrathin membranes. Monolayer graphene oxide was found to have a lower effe

Residual polymer (here, poly(methyl methacrylate), PMMA) left on graphene from transfer from metals or device fabrication processes affects its electrical and thermal properties. We have found that the amount of polymer residue left after the transfer of chemical vapor deposited (CVD) graphene varies depending on the initial concentration of the polymer solution, and this residue influences the electrical performance of graphene field-effect transistors fabricated on SiO2/Si. A PMMA solution wit

Transparent and flexible loudspeakers are realized with large-area monolayer graphene. The acoustic performances are characterized according to the supporting substrate effect and geometrical configurations. The substrate effect on the thermoacoustic sound generation from graphene is studied by controlling the surface porosity of various substrates. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited

Water is one of the most important resources for human survival and development. Efficient wastewater treatment techniques such as coagulation, filtration, ozonation, and reverse osmosis have been studied to remove toxic materials from water. Implementation of adsorption columns has been proven to be an efficient wastewater treatment method, particularly for the removal of organic contaminants. In this study, we present the preparation of an eco-friendly graphene oxide-chitosan (GC) composite hy

The intrinsic electrical conductivity of graphene is one of the key factors affecting the electrical conductance of its assemblies, such as papers, films, powders, and composites. Here, the local electrical conductivity of the individual graphene flakes was investigated using conductive atomic force microscopy (C-AFM). An isolated graphene flake connected to a pre-fabricated electrode was scanned using an electrically biased tip, which generated a current map over the flake area. The current cha

This note presents a simple method to control the speed of the autonomous capillary flow using an array of hydrophobic patterns. The microfluidic system in this note was composed of two planar parallel plates that were separated by spacers. The bottom plate had a hydrophilic microchannel which was surrounded by hydrophobic tracks. The top surface was relatively hydrophobic compared to the bottom plate. These hydrophobic tracks and the hydrophobic patterns in the middle of the microchannels were

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention owing to their synergetic effects with other 2D materials, such as graphene and hexagonal boron nitride, in TMD-based heterostructures. Therefore, it is important to understand the physical properties of TMD-TMD vertical heterostructures for their applications in next-generation electronic devices. However, the conventional synthesis process of TMD-TMD heterostructures has some critical limitations

Graphene powders obtained via the reduction of graphene oxide flakes have been widely used in various applications as they can be synthesized in large quantities with outstanding properties. The electrical conductivity of graphene powders is critical for their uses in fabricating high-performance devices or materials. Here, we investigated the bulk electrical conductivity of reduced graphene oxide (rGO) powders depending on the applied pressure and additional thermal annealing. The electrical co

Abstract Over the past few years, many researchers have been excited with the advent of two-dimensional (2D) materials such as graphene and molybdenum disulfide (MoS 2 ) because of their intriguing physical and chemical properties. Furthermore, they have great potential in various applications including nanoelectronics, flexible or stretchable devices, energy conversion or storage devices, sensors, nanocomposites, and others. In addition to their electrical, mechanical, optical, and thermal prop

Fiber supercapacitors (FSCs) can be used to power future flexible devices such as wearable electronics and smart textiles. Here, highly porous activated graphene (AG) is embedded into graphene fibers to enhance the electrochemical performance of FSCs based on electric double-layer capacitance (EDLC). Wet spinning of AG mixed with graphene oxide (GO) and subsequent chemical reduction of GO to reduced graphene oxide (rGO) enable the fabrication of continuous and conductive graphene fibers. The AG

The production of a large amount of high-quality transition metal dichalcogenides is critical for their use in industrial applications. Here, we demonstrate the scalable exfoliation of bulk molybdenum disulfide (MoS2) powders into single- or few-layer nanosheets using the Taylor-Couette flow. The toroidal Taylor vortices generated in the Taylor-Couette flow provide efficient mixing and high shear stresses on the surfaces of materials, resulting in a more efficient exfoliation of the layered mate