•The DA electrochemical sensor was fabricated by overall hierarchical porous carbon.•Sensor can be regenerated with ultrasonic cleaning by removing DA pollutants.•Sensor showed wide linear range and ...low detection limit to DA.
The detection of dopamine (DA) based on electrochemical sensor is of great importance to human diseases diagnosis and treatment. However, such sensors usually faced with the performance deterioration due to serious dopamine fouling. Herein, we fabricated a three-dimensional (3D) porous carbon sheet with hierarchical ordered mesopores by a facile dual-template method, the integrated electrochemical sensor was further discussed in terms of the evolution of porous structure. Results showed that the hierarchical porous structure would provide more mass transport channels and larger active area, resulting in higher sensitivity. In particular, the 3D framework could withstand strong ultrasound cleaning and maintained the superior electrochemical properties with high repeatability after the ultrasonic cleaning for dopamine fouling. The integrated sensor based on 3D porous carbon with high sp2 content presented the excellent performance toward DA detection with wide linear range from 800 nM to 400 μM, low detection limit of 100 nM as well as good selectivity to routine interference substances. It can be said that the constructed 3D hierarchical mesoporous carbon provides the great potential to be a promising material for DA electrochemical sensing platform construction.
Display omitted
Display omitted
•Cr2AlC and (Cr,V)2AlC coatings with a small amount of Cr were prepared by hybrid arc/magnetron sputtering followed by post-annealing.•The hardness and toughness of the Cr2AlC coating ...was enhanced simultaneously when Cr was partially substituted with V.•Cr2AlC had a relatively low COF and wear rate at 900 °C due to the existence of Cr2O3 oxides.•(Cr0.53V0.47)2AlC obtained excellent tribological properties due to the formation of molten V2O5 wrapped (Cr, Al)2O3 hard crystal grains.
Cr2AlC MAX phase coating exhibited excellent oxidation resistance and hot corrosion, but it typically suffered from low hardness and toughness as well as lack of lubrication at high temperature. With a solid solution design on M-site, we demonstrated that the hardness of the Cr2AlC MAX phase coating was enhanced by 34.3% when Cr was partially substituted with V (47 at.%), and the coating toughness was improved simultaneously. Furthermore, according to the high-temperature tribometer test, both the friction coefficient and the wear rate of the coatings at 900 °C against Al2O3 balls were significantly reduced at 47 at.% V. This could be attributed to the formation of a large number of molten V2O5 wrapped (Cr, Al)2O3 hard crystal grains, which not only provided a wide range of liquid-phase lubrication, but also prevented the coating from being apt to wear out. Different from the multi-phase compositing, this study suggested a promising strategy to enhance the combined mechanical and tribological performance of MAX phase coatings by M-site V solid solution for harsh applications at a high temperature of 900 °C.
► Weak carbide former, Al element, was incorporated into DLC films using a hybrid ion beams system comprising an anode-layer ion source and a magnetron sputtering unit. ► The structure disorder of ...the films tended to decrease with Al atoms doping, which resulted in the distinct reduction of the film internal stress and hardness, but the internal stress dropped faster than the hardness. ► The DLC films with low internal stress and high hardness can be acquired by Al incorporation.
Metal incorporation is one of the most effective methods for relaxing internal stress in diamond-like carbon (DLC) films. It was reported that the chemical state of the incorporated metal atoms has a significant influence on the film internal stress. The doped atoms embedding in the DLC matrix without bonding with C atoms can reduce the structure disorder of the DLC films through bond angle distortion and thus relax the internal stress of the films. In present paper, Al atoms, which are inert to carbon, were incorporated into the DLC films deposited by a hybrid ion beams system comprising an anode-layer ion source and a magnetron sputtering unit. The film composition, microstructure and atomic bond structure were characterized using X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. The internal stress, mechanical properties and tribogoical behavior were studied as a function of Al concentration using a stress-tester, nanoindentation and ball-on-disc tribo-tester, respectively. The results indicated that the incorporated Al atoms were dissolved in the DLC matrix without bonding with C atoms and the films exhibited the feature of amorphous carbon. The structure disorder of the films tended to decrease with Al atoms incorporation. This resulted in the distinct reduction of the internal stress in the films. All Al-DLC films exhibited a lower friction coefficient compared with pure DLC film. The formation of the transfer layer and the graphitization induced by friction were expected to contribute to the excellent friction performance.
The corrosive anions (e.g., Cl
) have been recognized as the origins to cause severe corrosion of anode during seawater electrolysis, while in experiments it is found that natural seawater (~0.41 M ...Cl
) is usually more corrosive than simulated seawater (~0.5 M Cl
). Here we elucidate that besides Cl
, Br
in seawater is even more harmful to Ni-based anodes because of the inferior corrosion resistance and faster corrosion kinetics in bromide than in chloride. Experimental and simulated results reveal that Cl
corrodes locally to form narrow-deep pits while Br
etches extensively to generate shallow-wide pits, which can be attributed to the fast diffusion kinetics of Cl
and the lower reaction energy of Br
in the passivation layer. Additionally, for the Ni-based electrodes with catalysts (e.g., NiFe-LDH) loading on the surface, Br
causes extensive spalling of the catalyst layer, resulting in rapid performance degradation. This work clearly points out that, in addition to anti-Cl
corrosion, designing anti-Br
corrosion anodes is even more crucial for future application of seawater electrolysis.
Dehydrins are late embryogenesis abundant proteins that help regulate abiotic stress responses in plants. Overexpression of the Saussurea involucrata dehydrin gene SiDHN has previously been shown to ...improve water-use efficiency and enhance cold and drought tolerance of transgenic tobacco. To understand the mechanism by which SiDHN exerts its protective function, we transformed the SiDHN gene into tomato plants (Solanum lycopersicum L.) and assessed their response to abiotic stress. We observed that in response to stresses, the SiDHN transgenic tomato plants had increased contents of chlorophyll a and b, carotenoid and relative water content compared with wild-type plants. They also had higher maximal photochemical efficiency of photosystem II and accumulated more proline and soluble sugar. Compared to those wild-type plants, malondialdehyde content and relative electron leakage in transgenic plants were not significantly increased, and H2O2 and O2- contents in transgenic tomato plants were significantly decreased. We further observed that the production of stress-related antioxidant enzymes, including superoxide dismutase, ascorbate peroxidase, peroxidase, and catalase, as well as pyrroline-5-carboxylate synthetase and lipid transfer protein 1, were up-regulated in the transgenic plants under cold and drought stress. Based on these observations, we conclude that overexpression of SiDHN gene can promote cold and drought tolerance of transgenic tomato plants by inhibiting cell membrane damage, protecting chloroplasts, and enhancing the reactive oxygen species scavenging capacity. The finding can be beneficial for the application of SiDHN gene in improving crop tolerance to abiotic stress and oxidative damage.
Friction behavior of self-mated amorphous carbon (a-C) films with hydrogenated surface were investigated by reactive molecular dynamics simulation. Results revealed that compared to the hydrogenated ...a-C (a-C:H) films, hydrogenating the a-C surface only improved the friction property drastically while not deteriorating the intrinsic properties of a-C films. The analysis of interfacial structure demonstrated that being different with a-C:H cases, the competitive relationship between the stress state of H atoms and interfacial passivation caused by H and C-C structural transformation accounted for the evolution of friction coefficient with surface H content. This discloses the friction mechanism of a-C with surface hydrogenated modification and provides an approach to functionalize the carbon-based films with combined tribological and mechanical properties for specific applications.
Display omitted
•Dependence of friction behavior of a-C on surface passivation degree were explored.•The a-C with surface hydrogenated modification exhibited excellent friction property.•Tailoring surface H content obtained better friction property than oil lubrication.•Friction mechanism of a-C with surface modification was different with that of a-C:H.•H stress state and interfacial passivation accounted for the friction behavior.
TiAlN monolithic and Ti/TiAlN multilayer coatings were fabricated on Ti–6Al–4V substrates by a self-designed multisource cathodic arc ion deposition system. The mechanical properties and crack ...evolution of the coatings were focused under scratch tests with different constant loads. Results showed that the multilayer coating exhibited a higher combination of plasticity, crack resistance and load capacity comparing to those of the monolithic coating. Namely, radical cracks, chippings, and lateral cracks were observed in the monolithic coating after scratch test, whereas only radical cracks occurred in the multilayer coating. The surface and cross-sectional morphology of the scratch tracks revealed that bending and shear stress were responsible for the failure of the two coatings. In particular, the ductile Ti layers within the multilayer coatings could coordinate the deformation and enhance the adhesion between the substrate and the brittle TiAlN layers, which further hindered the propagation of cracks, resulting in a higher crack resistance.
Display omitted
•Dependence of structural property of a-C film on empirical potential was studied.•Compared with Tersoff and REBO, AIREBO gave the most accurate structure and property.•The ...conjugation effect in AIREBO resulted in the rational hybridization structure.•LJ term in AIREBO potential made contribution to the rational density.•Both LJ and Torsion terms in AIREBO dominated the accurate evaluation of stress.
Amorphous carbon (a-C) films were deposited by molecular dynamics simulation using Tersoff, REBO and AIREBO potentials, respectively. The hybridization and the distributions of both bond angles and lengths as a function of the three potentials were analyzed, and the density and residual stress were calculated. Results revealed that comparing with the Tersoff and REBO potentials, the AIREBO potential gave the more reasonable values of density, hybridization ratio and residual stress. This attributed to that in AIREBO potential, the conjugation effect between the different coordinated atoms was corrected by revising the bond order term, which was responsible for the sp3 content; while the introduction of long-range Lennard-Jones (LJ) interaction described the compressed graphite structure correctly following the rational density; in particular, both the LJ and torsion interactions were indispensable for the accurate evaluation of residual stress of a-C films. In addition, the simulation result using AIREBO potential suggested no dependence on the processing methods of atom-by-atom deposition and liquid-quenching method.
The MoS2-Ti composite coatings were deposited by a hybrid high power impulse magnetron sputtering (HIPIMS) source of Ti combined with a direct current magnetron sputtering (DC-MS) source of MoS2. The ...composition, microstructure, mechanical and tribological behaviors of the MoS2-Ti composite coatings were investigated using the various analytical techniques (XPS, SEM, XRD, TEM, nano-indentation, scratch and ball-on-disk test). The results showed that doping Ti using HIPIMS technique enabled MoS2 coatings to grow in the form of a dense amorphous structure. The crystallization degree of the MoS2-Ti composite coatings decreased with the increase of doped titanium content. Ti reacting with O to form titanium oxides in the surface inhibited the oxidation of MoS2. The hardness and adhesion of the composite coatings reached its maximum within a certain range of Ti content. Doped Ti improved the tribological properties of pure MoS2 coatings in the atmospheric environment. The coefficient of friction (COF) decreased with the increase of Ti content. The lowest average COF at 0.04 and the wear rate at 10−7mm3 N−1 m−1 were achieved at the optimum of Ti content at 13.5at.%. The improved tribological property was discussed in terms of the obtained higher hardness and better adhesion of the composite coatings combined with inhibition of MoS2 oxidation.
•MoS2-Ti composite coatings were deposited by a novel hybrid HIPIMS system.•Doping Ti enabled MoS2 coatings to grow into a dense amorphous structure.•Ti reacting with O to form titanium oxides inhibited the oxidation of MoS2.•Doped Ti improved the tribological behavior of pure MoS2 coating in ambient air.•The mechanism was discussed in terms of higher coating hardness and adhesion.
Ab initio molecular dynamics simulation based on density functional theory was performed to investigate (Ti, Cr, or W)-incorporated diamond-like carbon (DLC) films. The structure models were ...generated from liquid quench containing 64 atoms. The dependence of the residual compressive stress, bulk modulus and tetra-coordinated C content on the Ti, Cr, and W concentrations in the range of 1.56 to 7.81 atom % was studied. The present simulation results reveal that the residual stress strongly depends on the incorporated Ti, Cr, and W atoms. With the incorporation of Ti at 1.56 atom %, Cr at 4.69 atom %, and W at 3.13 atom % to DLC films, the compressive stress was reduced by 46.9%, 81.4%, and 82.5%, respectively, without obvious deterioration of the mechanical properties. However, at higher Ti, Cr, and W concentrations, the compressive stress increased for each case, which was consistent with the experimental results. Structural analysis using both the bond angle and bond length distributions indicates that the small amount of Ti or W incorporation efficiently relaxes both the highly distorted bond angles and bond lengths, whereas the Cr incorporation only relaxes the distorted bond lengths, which decreases the residual compressive stress and provides theoretical explanations for the experiments.
PDF
