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[Display omitted] • Adhesive forces of a single anisole on G-OH/Gr surface are got via AFM experiments. • Anisole exhibits two types of adhesive forces on G-OH surface. • Hydroxyl group has significant effect on the adhesive force of G-OH to anisole. • Conformational changes of anisole cause two peaks of its force-height curve to G-OH. Measuring and understanding interaction forces between hydroxylated graphene (G-OH) and aromatic compounds is significant for the applications of composites based on G-OH, such as 3D graphene derivatives preparation and wastewater treatment. In this research, the adsorption/separation mechanical behavior of anisole on graphene and G-OH surfaces was investigated by atomic force microscopy (AFM) experiments and molecular dynamics (MD) simulations. The adsorption and separation curves of anisole on graphene and G-OH surfaces were obtained by experiments, and the adhesive forces of a single anisole were achieved by the Poisson statistics method. It is found that there are two types of adhesive forces between anisole and G-OH. For graphene and anisole, two extreme values are got by the adsorption and separation processes, and the adhesive force obtained by the separation process is approximately equal to one type of adhesive force between anisole and G-OH. Furthermore, MD simulation results reveal that the maximum adhesive force of anisole on the G-OH surface depends on its position relative to the hydroxyl group, and anisole has a greater affinity near the hydroxyl group. The position and planar angle of the anisole conformations cause the difference in adhesive forces. [ABSTRACT FROM AUTHOR]

[Display omitted] • Theoretical models are established to analyze the interface mechanical behaviors when a droplet infiltrates the microstructures. • The physical mechanism of compressive stability and excellent wettability on the Salvinia surface is theoretically revealed. • The effects of surface geometry and microstructure characteristics parameters on the compressive stability and wettability of the biomimetic surface are discussed. • The geometric structure relationships for designing highly stable superhydrophobic surfaces are proposed. The surface of Salvinia had superhydrophobicity and kept good compressive stability, which was mainly attributed to the dense microscopic eggbeater structure villi on the surface. By means of force equilibrium, a theoretical model was established to analyze the interface mechanical behaviors when a droplet infiltrates the microstructures. Based on the minimum energy principle, a theoretical model was presented to analyze the process of a droplet spreading on the surface of Salvinia reaching a steady state. Combined with numerical simulations, it was found that the superhydrophobicity and compressive stability of the Salvinia were dependent on the morphological and geometric parameters of the microstructure (edge angle φ , number of branching n , width W and spacing D , etc.). By adjusting these geometrical parameters, the surface of the biomimetic structure can maintain a stable Cassie state at 0.63 kPa pressure, and the apparent contact angle is controllable in the range of 121°−169.8°. The research results provide a theoretical foundation for the structural design of superhydrophobic surfaces with high stability and tunable wettability. [ABSTRACT FROM AUTHOR]

In this study, poly(vinyl chloride) (PVC) was electrospun into fibrous membranes and then reacted with NaN 3 to generate azido-terminated PVC fibrous membranes. A propargyl-terminated poly( N -isopropylacrylamide) (PNIPAAm) was also synthesized and then grafted, through click reactions, onto the azido-terminated PVC fiber surface. Protrusion-, scale-, and joint-like structures of the PNIPAAm grafts on the PVC fibers were formed upon increasing the molecular weight of the PNIPAAm grafts. The PNIPAAm-grafted PVC fibrous mats exhibited completely wetted surfaces at 25 °C because of their high roughness. The static water contact angle of the PNIPAAm-grafted PVC fibrous mats reached 140° when the temperature was increased to 45 °C. This thermoresponsive behavior was significantly greater than that of the PNIPAAm grafted on a flat surface. Temperature-responsive membranes were constructed having a pore size of 1.38 μm and applied as protein valves to block and release an antibody (fluorescein-conjugated AffiniPure goat anti-rabbit IgG). At 25 °C, the collection efficiency remained at 94% for antibody concentrations up to 60 ng/L. As the temperature increased to 45 °C, the collection efficiency decreased abruptly, to 4%, when the antibody concentration was greater than 20 ng/L. Accordingly, this system of PNIPAAm-grafted PVC fibers functioned as a protein valve allowing the capture and concentration of proteins. [ABSTRACT FROM AUTHOR]

Abstract: The multi-walled carbon nanotubes (MWNTs) modified by a hydrophilic polymer were prepared with polymerization and blending approaches. The differences of both modified MWNTs were compared by Fourier transform infrared and Raman spectroscopies, thermogravimetric analysis and transmission electron microscopy. Chemical grafting reaction had occurred between MWNTs and polyvinyl pyrrolidone (PVP) after modification with polymerization and blending approaches. Polymerization modification can graft more PVP on the surface of MWNTs compared with blending modification. Polymerization modification of MWNTs belongs to the “grafting from” mechanism, while blending modification belongs to the “grafting to” mechanism. Modified MWNTs exhibit remarkable solubility in water, ethanol and dimethyl formamide. [Copyright &y& Elsevier]

• Texturing effects on nanotribological properties and subsurface damage are studied. • Nanoscale friction and wear behaviour of GaN can be regulated by texture parameter. • Nano-texture can alleviate dislocation development and reduce subsurface damage. • The m -GaN exhibits lower wear and thicker damage layer compared with the c -GaN. Surface nanotribological properties and subsurface damage of flat and textured gallium nitride (GaN) substrates during both linear and circular nanoscratching processes are investigated using molecular dynamics simulation. Results show that the surface texture can remarkably reduce not only the surface friction and wear but also the scratching-induced subsurface damage regardless of the tip radius and penetration depth. Tangential force and friction coefficient decreased with an increase in groove width or depth primarily due to the reduced contact area. The effect of texturing on stress distribution can affect the development of dislocation to alleviate the nanoscale material deformation and removal and thereby reduce surface wear and subsurface damage. Increasing tip radius can reduce the friction coefficient and surface wear, but it promotes subsurface damage. By contrast, increasing tip penetration depth can increase the friction, wear, and subsurface damage for flat and textured GaN substrates. Compared with the c -plane, the m -plane GaN substrate exhibits higher friction but lower material wear, and it has a considerably thicker subsurface damage layer due to the difference in their dislocation networks. This work can provide useful insights into the design of GaN-based material with antifriction and wear properties through the surface texturing treatments. [ABSTRACT FROM AUTHOR]

The proposed selective etching provides a brand-new route for fabricating high-performance 3D architecture substrates with nanogaps towards SERS applications. [Display omitted] • A facile method was proposed to fabricate 3D inverted architecture SERS substrates. • Electrical field distribution of inverted architecture was simulated by FDTD. • The involved selective etching mechanism was addressed. • SERS detection illustrated excellent sensitivity and reproducibility. • The practical applicability of as-prepared SERS substrates was demonstrated. Three-dimensional (3D) plasmonic nanostructures act as excellent surface-enhanced Raman spectroscopy (SERS) substrates for detecting trace analytes. Nevertheless, an efficient 3D architecture and the optimal fabrication route remain to be uncovered to further raise the performance of 3D SERS substrates and expand application horizons. This work reports a cost-effective and flexible route to fabricate 3D inverted silicon (Si) architectures with nanogaps that are difficult to achieve by conventional lithography towards SERS applications. Finite-difference time-domain simulations demonstrated that the distribution of electrical field depended significantly on the architecture and layout of inverted pyramids. Several parameters including volume ratio of HF/HNO 3 mixtures, indentation force and etching time were evaluated to determine optimal fabrication process of inverted Si architecture. Based on an electrochemical dissolution model and molecular dynamic simulations, the rapid selective etching can be ascribed to nanocrystals in amorphous Si (a-Si) regions, and distorted Si beneath a-Si layer. SERS detection illustrated an impressive sensitivity and excellent reproducibility, and the practical applicability of as-prepared SERS substrates was demonstrated by detecting malachite green residues from different water environments as well as fish tissues and scales. The proposed selective etching provides a brand-new route for manufacturing high-performance 3D architecture substrates for SERS applications. [ABSTRACT FROM AUTHOR]

The physicochemical properties of anode material directly affect the anodic biofilm formation and electron transfer, thus are critical for the power generation of microbial fuel cells (MFCs). In this work, carbon cloth anode was modified with formic acid to enhance the power production of MFCs. Formic acid modification of anode increased the maximum power density of a single-chamber air-cathode MFC by 38.1% (from 611.5 ± 6 mW/m 2 to 877.9 ± 5 mW/m 2 ). The modification generated a cleaner electrode surface and a reduced content of oxygen and nitrogen groups on the anode. The surface changes facilitated bacterial growth on the anode and resulted in an optimized microbial community. Thus, the electron transfer rate on the modified anodes was enhanced remarkably, contributing to a higher power output of MFCs. Anode modification with formic acid could be an effective and simple method for improving the power generation of MFCs. The modification method holds a huge potential for large scale applications and is valuable for the scale-up and commercialization of microbial fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: As a further step in obtaining high performance elevated temperature self-lubrication anti-wear composite coatings on TiAl alloy, a novel Ni–P electroless plating method was adopted to encapsulate the as-received CaF2 in the preparation of precursor NiCr–Cr3C2–CaF2 mixed powders with an aim to decrease its mass loss and increase its compatibility with the metal matrix during a Nd:YAG laser cladding. The microstructure of the coating was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) and the friction and wear behavior of the composite coatings sliding against the hardened 0.45% C steel ring was evaluated using a block-on-ring wear tester at room temperature. It was found that the coating had a unique microstructure consisting of primary dendrites TiC and block Al4C3 carbides reinforcement as well as fine isolated spherical CaF2 solid lubrication particles uniformly dispersed in the NiCrAlTi (γ) matrix. The good friction-reducing and anti-wear abilities of the laser clad composite coating was suggested to the Ni–P electroless plating and the attendant reduction of mass loss of CaF2 and the increasing of it''s wettability with the NiCrAlTi (γ) matrix during the laser cladding process. [Copyright &y& Elsevier]

• Atomic structures of mechanically distorted silicon (protrusion and groove) were characterized. • Distorted microstructure plays an important role in nanomanufacturing process of silicon. • Stress-assisted chemical reactions mechanism on mechanically deformed silicon was revealed. • Enhanced oxide layer dominates the strong suppression in mechanochemical reactions of silicon. Ultra-precision of nanomanufacturing process down to subnanometer level is actually to achieve controllable removal of atomic material, however, which would be strongly impacted by the preconditions of manufactured surfaces. Here, the atomic structures, chemical and mechanical properties of mechanically-driven distorted microstructures on silicon formed in pre-treated process were characterized and their roles in atomic attrition dominated by mechanochemical reactions were revealed at atomic scale. Mechanically deformed silicon depending on applied stress physically behaviors protrusion forming and material removal (groove), which play opposite contributions to the mechanochemical reactions, i.e., atomic attrition suppressed on the protrusion surface but facilitated on the groove surface. Analyzing the mechanochemical reactions with the stress-assisted Arrhenius-type kinetics model and the DMT contact mechanics implies that, compared to the limited effect of the amorphous structure, the enhanced oxide layer at the protrusion surface that increases the energy barrier for mechanochemical reactions plays a more important role in the mechanochemical removal process. The results may help gain a profound insight into the mechanochemical removal mechanism of silicon and provide a wider cognition for regulating the mechanochemical reactions widely existing in scientific and engineering applications. [ABSTRACT FROM AUTHOR]

• Nano abrasive machining of monocrystalline GaN is studied by molecular dynamics simulations. • Deformation of monocrystalline GaN is associated with both the propagation of dislocation and the contact of workpiece/tool. • Dislocation and phase transition are identified in the deformation layer after nano abrasive machining. • Pile-up and elastic recovery of monocrystalline GaN are affected by the stagnation region and slip system. • Effects of cutting velocity, depth of cut and abrasive shape on deformation are systematically investigated. Molecular dynamics simulations are carried out to investigate the nano abrasive machining of monocrystalline gallium nitride (GaN). Effects of the cutting velocity, depth of cut (DOC) and abrasive shape on the atomic strain, stress, temperature, cutting forces, and deformation layer are systematically investigated, aiming at understanding the deformation behaviour of monocrystalline GaN during nano abrasive machining. The results show that the strain, stress and temperature were increased by using the higher cutting velocity, the larger DOC or cub-octahedral abrasive. Being affected by both the average stress and the elasto-plastic deformation zone right ahead the diamond particle, the cutting forces increase with the increase in DOC but decrease under a larger cutting velocity, or when using a cub-octahedral abrasive. The deformation layer in the subsurface is insensitive to the cutting velocity, while impressively shrinks under a larger DOC or cub-octahedral abrasive used. As the stress and temperature rise, the use of higher cutting velocity, larger DOC or cub-octahedral abrasive would facilitate the nucleation of dislocation, phase transition and the development of pile-up. This work can enrich the understanding on the nanoscale deformation mechanism of monocrystalline GaN material during the ultra-precision machining process. [ABSTRACT FROM AUTHOR]