Degradation of Toxic Organic Contaminants by Graphene Cathode in an Electro‐Fenton System

A novel composite electrode was constructed by pressing graphene and CuO, using a cathode in an electro‐Fenton (EF) system. Cyclic voltammetry, charge/discharge curve and electrochemical impedance spectroscopy (EIS) were used to characterize the composite electrode. The degradation of a toxic organic contaminant, Terramycin, by EF system was studied in an undivided electrolysis cell. The possible degradation products of Terramycin were studied by a Fourier transform‐infrared spectrum, and the findings showed that the structure of Terramycin was damaged. The variations of hydrogen peroxide and the relative content of hydroxyl radical (.OH) during the degradation process were traced by enzyme catalysis method and fluorescence spectrometry. The results showed that the electro‐catalytic degradation of Terramycin occurred by an ·OH radical mechanism. More importantly, this as‐prepared cathode was very stable and could be reused without any catalytic activity decrease, suggesting its potential application in the wastewater treatment

Development of a growth-coupled selection platform for directed evolution of heme biosynthetic enzymes in Corynebacterium glutamicum

Heme is an important tetrapyrrole compound, and has been widely applied in food and medicine industries. Although microbial production of heme has been developed with metabolic engineering strategies during the past 20 years, the production levels are relatively low due to the multistep enzymatic processes and complicated regulatory mechanisms of microbes. Previous studies mainly adopted the strategies of strengthening precursor supply and product transportation to engineer microbes for improving heme biosynthesis. Few studies focused on the engineering and screening of efficient enzymes involved in heme biosynthesis. Herein, a growth-coupled, high-throughput selection platform based on the detoxification of Zinc-protoporphyrin IX (an analogue of heme) was developed and applied to directed evolution of coproporphyrin ferrochelatase, catalyzing the insertion of metal ions into porphyrin ring to generate heme or other tetrapyrrole compounds. A mutant with 3.03-fold increase in kcat/KM was selected. Finally, growth-coupled directed evolution of another three key enzymes involved in heme biosynthesis was tested by using this selection platform. The growth-coupled selection platform developed here can be a simple and effective strategy for directed evolution of the enzymes involved in the biosynthesis of heme or other tetrapyrrole compounds

The tunable wettability in multistimuli-responsive smart graphene surfaces

The tunable wettability of smart graphene films onto stainless steel substrates with a multi-response to different environmental stimuli has been investigated including light irradiation, pH, electric field, and annealing temperature. Conductive graphene film exhibited the controllable transition from water-repellent to water-loving characteristic in response to different environment fields, which primarily resulted from the morpho-chemically synergistic effect as well as the restoration of electronic stucture. Based on the fundamental theories of wettability, mechanisms in switching from hydrophobicity to hydrophilicity for smart graphene surface including thermal chemistry, electrostatic, photo-induced surface chemistry, solvent, and pH methods were presented

Anticorrosive performance of waterborne epoxy coatings containing attapulgite/graphene nanocomposites

Anticorrosive performance of waterborne epoxy coatings containing attapulgite/graphene nanocomposite

First-Principles Investigation on the Tribological Properties of h-BN Bilayer Under Variable Load

Using first-principles method, for h-BN bilayer, we successfully probe the major factors of different low-friction paths in the three-dimensional potential energy surface (3D-PES) under variable loads. By means of the static PES and charge density difference analysis, we demonstrate how electrostatic interactions, with regard for van der Waals contributions at 0 nN, progressively impact the shape of 3D-PES and low-friction paths with increasing the normal load. Herein, the sliding properties of h-BN bilayers have a distinct relative orientation. Especially, the load-induced 3D-PES with variable shape is assigned to the band gap and repulsive van der Waals force. It is noted that the low friction not only is obtained for the commensurate layers under low loads, but also high ones

Synthesis of a new orthorhombic form of diamond in varying-C VN films: Microstructure, mechanical and tribological properties

Synthesis of a new orthorhombic form of diamond in varying-C VN films: Microstructure, mechanical and tribological propertie

Barrier mechanism of multilayers graphene coated copper against atomic oxygen irradiation

Graphene has been demonstrated as a protective coating for Cu under ambient condition because of its high impermeability and light-weight oxidation barrier. However, it lacks the research of graphene as a protective coating in space environment. Here, we experimentally and theoretically study the oxidation behavior of graphene-coated Cu in vacuum atomic oxygen (AO) condition. After AO irradiation, the experimental results show multilayer graphene has better anti-oxidation than monolayer graphene. Meanwhile, the calculation results show the oxidation appeared on the graphene's grain boundaries or the film's vacancy defects for the monolayer graphene coated Cu foil. Moreover, the calculation results show the oxidation process proceeds slowly in multilayers because of the matched defects overlaps each other to form a steric hindrance to suppress the O atom diffusion in the vertical direction, and the mismatched defects generates potential energy barriers for interlayer to suppress the O atom diffusion in the horizontal direction. Hence, multilayer graphene films could serve as protection coatings to prevent diffusion of O atom. (C) 2018 Elsevier B.V. All rights reserved

Corrosion and tribocorrosion behaviour of super-thick diamond-like carbon films deposited on stainless steel in NaCl solution

Super-thick diamond-like carbon (DLC) film is a potential protective coating in corrosive environments. In the present work, three kinds of DLC films whose thickness and modulation periods are 4 Iltm and 3, 21 gm and 17 and 21 pm and 7, respectively, were fabricated on stainless steel. The effect of different thickness and modulation periods on corrosion and tribocorrosion behaviour of the DLC-coating stainless steel was investigated in 3.5 wt% NaCI aqueous solution by a ball-on-flat tribometer equipped with a three -electrode electrochemical cell. The DLC-coating stainless steel served as a working electrode, and its OCP and potentiodynamic polarization were monitored before and during rubbing. The wear-corrosion mechanism of the DLC films was investigated by SEM. The results showed that the increasing thickness can prolong significantly lifetime of DLC films in NaCI aqueous solution. In particular, the modulation period has a significant impact on the tribocorrosion resistance of the DLC super -thick films. The study suggested that the increasing thickness of compressive stress layer could suppress film damage by reducing crack propagation rate. Thus, the super-thick DLC film with thickness of 21 pm and 7 periods presented the best tribocorrosion resistance among all studied films. Copyright (C) 2016 John Wiley & Sons, Ltd

First-Principles Investigation on the Tribological Properties of h-BN Bilayer Under Variable Load

Using first-principles method, for h-BN bilayer, we successfully probe the major factors of different low-friction paths in the three-dimensional potential energy surface (3D-PES) under variable loads. By means of the static PES and charge density difference analysis, we demonstrate how electrostatic interactions, with regard for van der Waals contributions at 0 nN, progressively impact the shape of 3D-PES and low-friction paths with increasing the normal load. Herein, the sliding properties of h-BN bilayers have a distinct relative orientation. Especially, the load-induced 3D-PES with variable shape is assigned to the band gap and repulsive van der Waals force. It is noted that the low friction not only is obtained for the commensurate layers under low loads, but also high ones

A feasible multilayer structure design for solid lubricant coatings in a lunar environment

Solid lubricant coatings have received considerable research attention in space applications owing to their remarkably improved tribological characteristics. But their service life is seriously restricted by the harsh environment, such as high vacuum and abrasive wear. In this paper, a novel design of carbon-based multilayer (MoS2/DLC multilayer) coatings was reported to clarify the friction and wear behavior in high vacuum conditions with and without simulated lunar-dust (SLD). Compared with pure DLC or MoS2 coatings, the multilayer coating showed excellent tribological performance with a low friction coefficient of 0.02 and a wear rate of similar to 6.5 x 10(-6) mm(3) N-1 m(-1). What is particularly interesting is that the wear volume of MoS2/DLC multilayer coatings with the increase of time is in accordance with the Archard linear law, regardless of the condition with or without SLD. Moreover, the surface morphology and composition of wear tracks and scars reveal that the long life of carbon-based multilayer coatings cannot be explained solely by excellent mechanical performance, and is also attributed to the formation of ridge layers as third body reservoirs and a tribo-induced composite transfer layer containing SLD nanoparticles and coating materials