Tailored Graphene Micropatterns by Wafer-Scale Direct Transfer for Flexible Chemical Sensor Platform

2D materials, such as graphene, exhibit great potential as functional materials for numerous novel applications due to their excellent properties. The grafting of conventional micropatterning techniques on new types of electronic devices is required to fully utilize the unique nature of graphene. However, the conventional lithography and polymer-supported transfer methods often induce the contamination and damage of the graphene surface due to polymer residues and harsh wet-transfer conditions. Herein, a novel strategy to obtain micropatterned graphene on polymer substrates using a direct curing process is demonstrated. Employing this method, entirely flexible, transparent, well-defined self-activated graphene sensor arrays, capable of gas discrimination without external heating, are fabricated on 4 in. wafer-scale substrates. Finite element method simulations show the potential of this patterning technique to maximize the performance of the sensor devices when the active channels of the 2D material are suspended and nanoscaled. This study contributes considerably to the development of flexible functional electronic devices based on 2D materials.

Individualized Tumor Response Testing for Prediction of Response to Paclitaxel and Cisplatin Chemotherapy in Patients with Advanced Gastric Cancer

The purpose of our study was to determine the most accurate analytic method to define in vitro chemosensitivity, using clinical response as reference standard in prospective clinical trial, and to assess accuracy of adenosine triphosphate-based chemotherapy response assay (ATP-CRA). Forty-eight patients with chemo-naïve, histologically confirmed, locally advanced or metastatic gastric cancer were enrolled for the study and were treated with combination chemotherapy of paclitaxel 175 mg/m2 and cisplatin 75 mg/m2 for maximum of six cycles after obtaining specimen for ATP-CRA. We performed the receiver operator characteristic curve analysis using patient responses by WHO criteria and ATP-CRA results to define the method with the highest accuracy. Median progression free survival was 4.2 months (95% confidence interval [CI]: 3.4-5.0) and median overall survival was 11.8 months (95% CI: 9.7-13.8) for all enrolled patients. Chemosensitivity index method yielded highest accuracy of 77.8% by ROC curve analysis, and the specificity, sensitivity, positive and negative predictive values were 95.7%, 46.2%, 85.7%, and 75.9%. In vitro chemosensitive group showed higher response rate (85.7% vs. 24.1%) (P=0.005) compared to chemoresistant group. ATP-CRA could predict clinical response to paclitaxel and cisplatin chemotherapy with high accuracy in advanced gastric cancer patients. Our study supports the use of ATP-CRA in further validation studies

Photo-Assisted Hydrogen Evolution with Reduced Graphene Oxide Catalyst on Silicon Nanowire Photocathode

The silicon-based photoelectrochemical (PEC) conversion system has recently gained attention owing to its ability to provide cost-efficient and superior photoresponsive behavior with respect to other semiconductor photoelectrodes. Carbon-based co-catalysts have always been the focus of research as alternative metal-free electrocatalysts intended for hydrogen evolution reaction (HER). In particular, reduced graphene oxide (rGO), a representative carbon-derived material, has attracted much attention as a non-metal catalyst for efficient and durable HER. Herein, we deposited rGO on a silicon nanowire (SiNW) structure, which showed the highest reduction in the overpotential for HER up to date. This can be attributed to the synergistic effects of rGO and SiNW with unique anisotropic morphology, facile tuning capabilities, and scalable fabrication methods. Combined with nanostructured photocathode, rGO-deposited SiNW showed better photon to current conversion efficiency of 3.16% (half solar-to-hydrogen conversion efficiency), which is 158 times higher than that of the bare planar Si system. In light of this development, we believe that rGO-SiNW photoelectrodes will pave the way for state-of-the-art highly efficient non-metal catalysts for energy conversion technologies

Development of fouling-resistant RO membranes using PEGA macromer

Reverse osmosis membranes are widely used in many industrial fields including seawater desalination, ultrapure water production, medical and food processing. But the decrease in performance of RO membranes in water reuse and purification systems due to fouling is one of the concerns. In this study we investigated the anti-fouling property of PEGA homopolymer-coated RO membranes. PEGA homopolymer was synthesized by a free radical solution polymerization method. PEGA-coated membrane was prepared via a simple dip-coating method. Glutaraldehyde was used as a cross linker in our experiment. After chemical modification, membrane surface properties were characterized using X-ray photoelectron spectroscopy (XPS), water contact angle measurement, atomic force microscopy (AFM). Surface modified membranes showed lower roughness, more hydrophilicity compared to unmodified RO membranes. Fouling tests were conducted in the cross-flow mode using various foulants, including bovine serum albumin (BSA), humic acid, and E. coli broth. As a result, surface modified membranes exhibited better anti-fouling properties compared to unmodified RO membranes. After physical cleaning, the modified membrane recovered almost 100% of its initial filtration performance.close0

Stable n-type doping of graphene via high-molecular-weight ethylene amines

We demonstrate a stable and strong n-type doping method to tune the electrical properties of graphene via vapor phase chemical doping with various high-molecular-weight ethylene amines. The resulting carrier concentration after doping with pentaethylenehexamine (PEHA) is as high as -1.01 x 10(13) cm(-2), which reduces the sheet resistance of graphene by up to similar to 400% compared to pristine graphene. Our study suggests that the branched structure of the dopant molecules is another important factor that determines the actual doping degree of graphene

N-doped graphene quantum sheets on silicon nanowire photocathodes for hydrogen production

Photoelectrochemical hydrogen production from solar energy has been attractingmuch attention in the field of renewable energy technology. The realization of cost-effective hydrogen production by water splitting requires electrolysis or photoelectrochemical cells decorated with highly efficient co-catalysts. A critical requirement for catalysts in photoelectrochemical cells is not only the ability to boost the kinetics of a chemical reaction but also to exhibit durability against electrochemical and photoinduced degradation. In the race to replace previous noble-metal catalysts, the design of carbon-based catalysts represents an important research direction in the search for non-precious, environmentally benign, and corrosion-resistant catalysts. Herein, we suggest graphene quantum sheets as a catalyst for the solar-driven hydrogen evolution reaction on Si nanowire photocathodes. The optimum nanostructures of the Si photocathodes exhibit an enhanced photocurrent and a lower overpotential compared to those of a planar Si surface. This significant enhancement demonstrates how graphene quantum sheet catalysts can be used to produce Si nanowire photocathodes as hydrogen evolution reaction catalysts with high activity

Cooperative Conformational Change of a Single Organic Molecule for Ultrafast Rechargeable Batteries

We unveil that the conformational change of a single organic molecule during the redox reaction leads to impressive battery performance for the first time. We propose the model material, a phenoxazin-3-one derivative, as a new redox-active bioinspired single molecule for the Li-ion rechargeable battery. The phenoxazin-3-one cathode delivered a high discharge capacity (298 mAh g(-1)) and fast rate capability (65% capacity retention at 10 C). We elaborate the redox mechanism and reaction pathway of phenoxazin-3-one during Li+-coupled redox reaction. The molecular structure alteration of phenoxazin-3-one during the lithium-coupled electron transfer reaction enables strong pi-pi interaction between 2Li-phenoxazin-3-one and carbon, which was evidenced by operando Raman spectroscopy and density functional theory calculation. Our work provides in-depth understanding about the conformational molecular switch of the single molecule during Li+-coupled redox reaction and insight into the design of a new class of organic electrode materials.N

Effects of Photochemical Oxidation of the Carbonaceous Additives on Li-S Cell Performance

We introduce a simple and easy way to functionalize the surface of various carbonaceous materials through the ultraviolet light/ozone (UV/O-3) plasma where we utilize the zero-, one-, and two-dimensional carbon frameworks. In a general manner, the lamps of a UV/O-3 generator create two different wavelengths (lambda = 185 and 254 nm); the shorter wavelength (lambda = 185 nm) dissociates the oxygen (O-2) in air and the longer wavelength (lambda = 254 nm) dissociates the O-3 and creates the reactive and monoatomic oxygen radical, which tends to incorporate onto the defects of the carbons. By tailoring the association and dissociation of the oxygen with various forms, carbon black, carbon nanofibers, and graphite flakes, chosen as representative models for the zero-, one-, and two-dimensional carbon frameworks, their structure can be oxidized, respectively, which is known as photochemical oxidation. Various carbons have their own distinctive morphology and electron transport properties, which are applicable for the lithium-sulfur (Li-S) cell. We, here, report on the improvement of electrochemical performance of the lithium/sulfur cell through such an efficient functionalization approach.N

Ultrahigh-strength multi-layer graphene-coated Ni film with interface-induced hardening

Graphene-reinforced metal matrix composites exhibit excellent mechanical properties owing to dislocation impedance at the metal-graphene interface. Graphene coated on metal with composites fabricated using powder sintering can be applied as high-strength thin films across various fields (e.g., microelectromechanical systems, flexible electronics). In this study, a bilayer composite of multilayer graphene (MLG)-coated Ni is synthesized using the chemical vapor deposition (CVD) and transfer methods; mechanical properties are investigated using nanoindentation methods. MLG-coated Ni synthesized by CVD exhibits 195% and 470% increases in hardness and Young's modulus, respectively, compared with single-layer Ni. In contrast, the Young modulus and hardness of MLG-coated Ni synthesized via the transfer method can be estimated using the rule of mixture for composite materials. Transmission electron microscopy (TEM) shows that in MLG-coated Ni synthesized by CVD, dislocations are dense and evenly distributed compared with that synthesized by the transfer method, leading to its high mechanical strength. Molecular dynamics (MD) simulations demonstrate that interface-induced hardening is effective in graphene-coated Ni(111) with a strongly coupled interface. Therefore, ultrahigh-strength MLG-coated metal films can be obtained by manipulating the interface property between the MLG and metal, offering the potential for use as a thin film resistor against external force. (C) 2021 Elsevier Ltd. All rights reserved.

Confocal laser scanning microscopy as a real-time quality-assessment tool for industrial graphene synthesis

For the industrial quality control (QC) of the chemical vapor deposition (CVD) graphene, it is essential to develop a method to screen out unsatisfactory graphene films as efficiently as possible. However, previously proposed methods based on Raman spectroscopy or optical imaging after chemical etching are unable to provide non-invasive and fast analysis of large-area graphene films as grown on Cu foil substrates. Here we report that the reflection mode of confocal laser scanning microscopy (CLSM) provides a high-contrast image of graphene on Cu, enabling the real-time evaluation of the coverage and quality of graphene. The reflectance contrast,Rc, was found to be dependent on the incident laser wavelength, of which the maximum was obtained at 405 nm. In addition,Rcdecreases with increasing defect density of graphene. The dependence ofRcon the graphene's quality and laser wavelengths were explained by the tight-binding model calculation based on the Fresnel's interference formula. Thus, we believe that the reflection mode CLSM would be a very powerful quality-assessment tool for the mass production of CVD graphene films grown on Cu.