This article features the importance of nanomaterial–protein interfaces, with a special interest on two-dimensional (2D) nanomaterials, for next generation sensors and electronics. Graphene, the first isolated and studied 2D nanomaterial, is taken as the material of most interest and then focused on its engineering by heteroatom doping. The success of graphene engineering for sensors widened the search for better and efficient biosensor platforms of other layered materials such as boron nitride and transition metal dichalcogenides. But functionalization of 2D backbones with biomolecules often ends up with the disruption of the biological activities due to various reasons. This has to be fundamentally studied and corrected for the clinical implementation of these materials based novel sensing platforms in point-of-care devices and micro-fluidic chips. At the end, importance of various 2D materials–biomolecule interfaces is discussed, and MoS2 based label-free biosensor is highlighted. A method for the modification of MoS2–biomolecule interaction via covalent functionalization of oxygen functionalities in MoS2 is also proposed.

Developing high energy density supercapacitors is of great importance to the transportation, consumer electronics, and micro-grid energy storage sectors. Recently, the development of high voltage organic electrolyte based supercapacitor devices has been gaining much attention. Among them, there is an on-going intense interest in investigating high capacity lithium ion storage anode materials in hybrid supercapacitors. However, developing high capacity cathode materials for high voltage organic electrolyte supercapacitor devices is rarely investigated. The low electrical double layer capacitances of carbon cathode electrodes, which are widely used in current supercapacitor devices, are often the limiting bottleneck. In this contribution, we investigated the electrochemical energy storage behavior of a polyaniline (PANI)-single wall carbon nanotube (SWCNT) composite material in an organic electrolyte as a supercapacitor cathode. The PANI-SWCNT composite exhibits a high specific capacitance of 503 F/g, of which 58.8% of the total capacitance is attributed to the pseudocapacitive and electrical double layer energy storage. The cycling stability of the PANI-SWCNT composite could be further improved by polydopamine (PDA) modification. The PDA with strong adhesion properties is able to prevent mechanical degradation. The PDA modified PANI-SWCNT shows excellent stability with only 5% degradation after 2000 cycles.

Flexible touch sensors with high sensitivity show promise in biomedical diagnostics and for artificial “electronic skin” for robotics or prosthetic devices. For “electronic skin” applications, there exists a need for low-cost, scalable methods for producing pixels that sense both medium (10–100 kPa) and low pressures (<10 kPa). Here, the “breath figures” (BFs) method, a simple, self-assembly-based method for producing honeycomb-structured porous polymer films, was used to prepare pattern compressible, and microstructured dielectric layers for capacitive pressure sensors. Porous polystyrene BFs films served as molds for structuring polydimethylsiloxane dielectrics. Pressure sensing devices containing the BFs-molded dielectrics consistently gave pressure response with little hysteresis, high sensitivities at lower applied pressures, and improved sensitivity at higher pressures. Analysis of microstructure geometries and pressure sensor performance suggests that structures with higher aspect ratios (height-to-width) produce less hysteresis, and that less uniform, more polydisperse structures yield a more linear pressure response.

This work describes the effects of different atmospheres used during the thermal treatment of hematite films synthesized on transparent conductive substrates of fluorine-doped tin oxide by a newly reported wet chemical route assisted by microwave. The as-synthesized films were subjected to additional thermal treatment at 750 °C for 30 min in different gas flux (air, O2, and N2) to obtain a desirable phase and surface activation. A series of techniques were used to elucidate effects of each atmosphere used during the thermal treatment. The morphology of the films, as analyzed by top-view and cross-sectional scanning electron microscopy images, showed no significant changes and was composed of rods homogeneously distributed over the substrate, which covered the immersed area with a thickness between 98 and 100 nm. The photoelectrochemical response of the N2-hematite films was found to be 80 and 50% more efficient at 1.23 VRHE (reversible hydrogen electrode) than those of films produced in air and an O2 atmosphere. The photocurrent enhancement achieved by treatment in an oxygen-deficient atmosphere was attributed to the improvement of hematite catalytic activity, which produced a hematite–electrolyte interface favorable for water oxidation. Since an increase in the donor density by one order of magnitude was found for the N2-hematite films, a reduction of charge transfer resistance was expected in these films. However, the Nyquist plot analysis showed that the O2-hematite film had a lower charge transfer resistance. As a result, it is impossible to relate the photocurrent enhancement observed in N2-hematite film to electronic changes or vacancy formation, as previously reported in the literature. Indeed, by performing photoelectrochemical measurements in the presence of hole scavengers, it became clear that the major improvement caused by the oxygen-deficient atmosphere was in the catalytic activity efficiency of the hematite films for water oxidation. It was found that the oxygen-deficient atmosphere could improve the overall photoelectrochemical performance of the hematite by acting as a hole scavengers. This finding contrasts with a previous report, in which the use of an oxygen-deficient atmosphere during the phase transformation from akaganeite to hematite was found to enhance the photocurrent density by inducing an increased donor density caused by the formation of vacancies [Y. Ling et al., Angew. Chem., Int. Ed.51, 4074 (2012)].

Steel coils coated with Zn–Mg alloy containing high Mg content develop dark rust when exposed to an extremely limited amount of aqueous environment. To understand the nature of the dark rust and its formation mechanism, the steel is evaluated by the immersion test and high temperature–humidity test followed by critical evaluation with transmission electron microscopy for cross-sectional observation, field-emission scanning electron microscopy for surface morphology observation, Auger electron spectroscopy and glow discharge spectroscopy for identification of chemical composition as a function of depth. The results indicate that the dark rust is formed by precipitation of Mg-based corrosion product on the outermost surface when the steel is exposed to aqueous environment at high temperature. This is due mainly to preferential dissolution of Mg phases by the galvanic action with MgZn2 and Mg2Zn11 composed of the coating layer, and easy precipitation of Mg2+ ion in a form of Mg(OH)2 in a limited volume of the condensed water film on the surface.

Laser metal deposition (LMD) additive manufacturing was used to deposit Inconel 625 matrix composites reinforced with nano-TiC particles. The effects of laser energy input per unit length (E) on the densification level, microstructural features, mircohardness, and wear property were investigated. The relatively low E induced insufficient liquid with higher viscosity, thus inhibiting the melted liquid from spreading out smoothly. As a result, a large number of micropores and reduced densification level of LMD-processed parts were obtained. When the E of 100 kJ/m was properly settled, the obtainable densification level generally approached 98.8%. The TiC reinforcements experienced successive microstructural changes from agglomeration to uniform distribution with coarsening grain, as the applied E increased. The nearly fully dense parts using optimal experimental parameters achieved an increased average microhardness of 330 HV0.2, resultant considerably low coefficient of friction of 0.41 and reduced wear rate of 5.4 × 10−4 mm3/(N m) in dry sliding wear tests.

Molecular dynamics simulations of compression deformation of $\left[ {11\bar 20} \right]$-textured 2-dimensional polycrystalline pure Mg, Mg–0.1 at.%Al, and Mg–1.0 at.%Al models were performed at 5 and 300 K. A $\left\{ {10\bar 11} \right\}$ twin nucleated before formation of a $\left\{ {10\bar 12} \right\}$ twin in the simulations at 5 K, while a $\left\{ {10\bar 11} \right\}$ twin nucleated after formation of a $\left\{ {10\bar 12} \right\}$ twin in the simulations at 300 K. The formation of a $\left\{ {10\bar 11} \right\}$ twin was the result of the glide of pyramidal 〈c + a〉 partial dislocations of ${1 \mathord{\left/ {\vphantom {1 6}} \right. \kern-\nulldelimiterspace} 6}\left\{ {10\bar 11} \right\}\left[ {\bar 2023} \right]$. $\left\{ {10\bar 11} \right\}$ twin formation was suppressed at the sites around the Al atoms because the strong Mg–Al bond suppresses atomic shuffling. However, formation was not suppressed at the sites away from the Al atoms because the effect of strong Mg–Al bond is short range. On the other hand, because $\left\{ {10\bar 12} \right\}$ twinning requires the simultaneous glide of zonal dislocations, Al inevitably suppressed $\left\{ {10\bar 12} \right\}$ twinning.

The microstructural evolution of type 347H heat-resistant austenitic steel during long-term aging at 700–900 °C was investigated by using a transmission microscope, a scanning electron microscope, and electron energy spectrum technology. The microstructural examination showed the typical micrographs of MX carbonitrides and M23C6 carbides after aging. The existence of the Z phase (NbCrN) at the grain boundaries during aging was identified. Meanwhile, the possible precipitation sequence of these particles was also confirmed. In the beginning of aging, fine Nb(C,N) precipitates first, then, M23C6 carbides precipitate along the grain boundaries. Finally, the Z phase is also observed at the grain boundaries. Moreover, the influence of isothermal holding temperature on the precipitation of MX carbonitrides and M23C6 carbides was discussed. The various microstructural characterizations showed that the M23C6 carbides and MX carbonitrides precipitate more easily with the increase of aging temperature. Furthermore, the number and the size of MX particles and M23C6 carbides increase when the isothermal holding time is prolonged.

The joint of dissimilar metals between Mo2FeB2-based cermets and 316L stainless steel was welded by gas tungsten arc welding with no fillers. The weldability was investigated by plate rigid restraint cracking test and transverse rupture strength was measured by the three-point bending test. Microstructure of the weld joint was studied with scanning electron microscope, energy-dispersive spectrometer, X-ray diffractometer and differential scanning calorimeter, etc. Corrosion behavior was investigated by the potentiodynamic polarization test. Results revealed that weld solidification cracking susceptibility existed in the fusion zone. Coarse irregular complex ternary boride phase (M3B2) and hypoeutectic microstructure were formed in weld metal (WM). In heat affected zone (HAZ), a small number of M3B2 grains dissolved into the γ-Fe based binder, with growth and coalescence of the remaining M3B2 grains. Microhardness of HAZ increased slightly and WM presented the highest microhardness in the whole joint. Besides, potentiodynamic polarization test showed that WM had a better corrosion resistance than Mo2FeB2-based cermets, which can be attributed to the higher Cr content and relatively homogenous Mo distribution.

Microwave sintering is a novel and efficient technology for the rapid preparation of metallic materials. In this paper, an investigation has been performed on the distribution of microwave electromagnetic fields in a metallic particle system and its influence on sintering behavior. The results show that the microstructure of the “metallic-void” will induce a nonuniform distribution and focusing effect of electromagnetic fields during microwave processing, which may accelerate the sintering process. However, further study shows that the focusing effect will decline as the neck grows larger, and will also decline from outside to inside within the loosely packed powder system, which will result in the slowdown of the sintering rate. These results were supported by the synchrotron radiation computed tomography experimental observation of the microstructure evolution of metallic powders during an entire uninterrupted microwave sintering process.

In this study, the effects of Sm on the microstructure and corrosion resistance of hot-extruded AZ61 magnesium alloys were investigated by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that uniformly dispersed Al2Sm particles with size of ∼2 μm were discovered in the hot-extruded AZ61 magnesium alloy sample modified with 1.0 wt% Sm, which promoted dynamic recrystallization grain growth during the hot-extruded process, gradually increasing the grain of the alloy as Sm content increased. The morphology of the corroded surface and the corrosion rate of the hot-extruded AZ61 magnesium alloy both were significantly improved after Sm addition. The alloy sample modified with 2.0 wt% Sm after immersion in 3.5 wt% NaCl solution for 12 h showed minimum corrosion rate value, 3.1 mg/cm2 day, which is only 3.7% of the corrosion rate of unmodified alloy (82 mg/cm2 day).

The alloyed layers were produced on Mg by heating the specimens in contact with pure Al powder or Al + Zn powder mixtures. The powder material acting as the source of diffusion elements was held under pressure during heating, and this led to the formation of thick, continuous layers in a short heating time (1 h). The layer formation process took place through partial melting at the substrate/powder interface. The Al-enriched layer was characterized by a eutectic structure composed of an Mg17Al12 intermetallic phase and a solid solution of Al in Mg. The Al/Zn-enriched layers produced from Al + 20% Zn and Al + 40% Zn powder mixtures consisted of Mg17(Al,Zn)12 and Mg5Al2Zn2 and a solid solution of Al and Zn in Mg. The alloyed layers had higher hardness and better wear resistance than the Mg substrate. The results of the polarization measurements show that the Al- and the Al/Zn-enriched layers provide a certain level of protection to Mg against corrosion.

The present report presents results from the fabrication, structural, and optical characteristics of sub-100 nm thermal chemical vapor deposition-grown silicon-oxycarbide (SiCxOy) nanowire (NW) arrays fabricated by e-beam lithography and reactive-ion-etching. The composition of SiCxOy materials follows closely the silicon-oxycarbide stoichiometry [SiCxO2(1−x), (0 < x < 1)] as observed by compositional and structural analysis. The corresponding structural and bonding evolution of SiCxOy are well-correlated with changes in their optical properties, as demonstrated by the linear dependence of their optical gap and refractive index with [Si–C]/[Si–O] bond–area ratio. By virtue of these advantages, properly tailored SiCxOy NWs were fabricated, exhibiting strong room-temperature visible photoluminescence (PL) through engineering of [Si–C]/[Si–O] bonds. The current studies focused on the thermal-oxidation and excitation intensity behavior of SiCxOy NWs revealed their very good stability, as their luminescence characteristics remain unchanged upon annealing in oxygen ambient (250 °C), while the PL intensity dependence on the excitation power-density exhibited a linear increase up to ∼800 W/cm2.

To obtain a floating and magnetically recyclable photocatalyst, nano-scaled Fe3O4 particles are first deposited on the surface of the KH-550 modified cenosphere under a hydrothermal condition. The Fe3O4 coated cenosphere is then loaded with a layer of globular-flower-like SiO2 particles by a precipitation method. The Fe3O4/SiO2 double-layer structured cenosphere is finally immobilized with TiO2 nanoparticles doped with rare earth element Eu3+ to enhance the photoactivity of TiO2 using titanium sulfate, urea, and polyvinylpyrrolidone by a hydrothermal treatment. The as-prepared cenosphere is systematically characterized by various characterization techniques. The properties of photocatalytic degradation of methylene blue dye are also investigated. Results show that after being doped with 0.1% Eu3+ ions in relation to Ti4+ ions, the photocatalytic degradation efficiency for the Fe3O4/SiO2/Eu-doped TiO2 coated cenosphere is significantly improved under both ultraviolet and visible light irradiations. The saturation magnetization of the Fe3O4/SiO2/Eu-doped TiO2 coated cenosphere increases to some degree.

The search for alternative earth abundant semiconducting nanocrystals for sustainable energy applications has brought forth the need for nanoscale syntheses beyond bulk synthesis routes. Of particular interest are metal phosphides and derivative I–V–VI chalcogenides including copper phosphide (Cu3P) and copper thiophosphate (Cu3PS4). Herein, we report a one-pot, solution-based synthesis of Cu3P nanocrystals utilizing an in situ phosphorus source: phosphorus pentasulfide (P2S5) in trioctylphosphine. By injecting this phosphorus source into a copper solution in oleylamine, uniform and size controlled Cu3P nanocrystals with a phosphorous-rich surface are synthesized. The subsequent reaction of the Cu3P nanocrystals with decomposing thiourea forms nanoscale Cu3PS4 particles having p-type conductivity and an effective optical band gap of 2.36 eV. The synthesized Cu3PS4 produces a cathodic photocurrent during photoelectrochemical measurements, demonstrating its application as a light-absorbing material. Our process creates opportunities to explore other solution-based metal-phosphorus systems and their subsequent sulfurization for earth abundant, alternative energy materials.

Nanocolloidal crystals (NCCs) have promising applications in optical and photonic devices. However, it is critical to mechanically reinforce NCCs for device reliability, since as-synthesized NCCs are fragile due to weak interparticle bonding. Thermal sintering is currently the most common reinforcement technique; however, this method could induce serious cracking and is not suitable for temperature-sensitive materials. In this study, by characterizing silica NCCs reinforced through sintering and alumina atomic layer deposition (ALD), we find that the ALD treatment is much more effective for hardening, stiffening, and more importantly toughening NCCs. Thermally sintered NCCs are prone to indentation-induced cracking due to large residual tensile stress, significantly impairing the toughness. In contrast, the ALD treatment toughens NCCs by much over 300%. Our finding provides insights for reinforcing and toughening various nanoparticle-based and nanoporous materials.