Oxygen-Terminated Polycrystalline Boron-Doped Diamond Superhydrophobic Surface with Excellent Mechanical and Thermal Stabilities.

Superhydrophobic surfaces are of great interest because of their remarkable properties. Due to its maximal hardness and chemical inertness, diamond film has great potential in fabricating robust superhydrophobic surfaces. In the present study, an oxygen-terminated polycrystalline boron-doped diamond (O-PBDD) superhydrophobic surface with micro/nano-hierarchical porous structures is developed. The preparation method is very simple, requiring only sputtering and dewetting procedures. The former involves sputtering gold and copper particles onto the hydrogen-terminated polycrystalline boron-doped diamond (H-PBDD) to form gold/copper films, whereas the latter involves placing the samples in an atmospheric tube furnace to form hierarchical pores. By controlling the etching parameters, the wettability of the O-PBDD surface can be adjusted from hydrophilic to superhydrophobic, which is significantly different to the normal hydrophilicity feature of O-termination diamonds. The water contact angle of the obtained O-PBDD surface can reach 165 ± 5°, which is higher than the superhydrophobic diamond surfaces that are reported in the literature. In addition, the O-PBDD surface exhibits excellent durability; it can maintain satisfactory superhydrophobicity even after high-pressure, high-temperature, and sandpaper friction tests. This work provides a new research direction for fabricating robust superhydrophobic materials with diamond film.

Sinc flexure hinges.

This paper proposes a new type of flexure hinge: the sinc flexure hinge. A theoretical compliance and precision factor model of the sinc flexure hinge is developed based on the transfer matrix method. The finite element simulation is carried out using ANSYS Workbench. The error between the modeling and simulation results obtained is less than 7.0%. The influence of structural parameters on the compliance, precision factor, and compliance-precision ratio is analyzed. The results show that the compliance and precision are contradictory and that the minimum thickness has the most significant influence on performance. Compared with the other seven types of flexure hinges, the sinc flexure hinge delivers a good overall performance. Finally, a sinc flexure hinge is machined and its compliance is measured. The error between the experimental and theoretical values is less than 7.6%. Both the simulation and experimental results verify the effectiveness of the model.

Vertical Diamond p-n Junction Diode with Step Edge Termination Structure Designed by Simulation.

In this paper, diamond-based vertical p-n junction diodes with step edge termination are investigated using a Silvaco simulation (Version 5.0.10.R). Compared with the conventional p-n junction diode without termination, the step edge termination shows weak influences on the forward characteristics and helps to suppress the electric field crowding. However, the breakdown voltage of the diode with simple step edge termination is still lower than that of the ideal parallel-plane one. To further enhance the breakdown voltage, we combine a p-n junction-based junction termination extension on the step edge termination. After optimizing the structure parameters of the device, the depletion regions formed by the junction termination extension overlap with that of the p-n junction on the top mesa, resulting in a more uniform electric field distribution and higher device performance.

Recent Progress on Photoelectrochemical Water Splitting of Graphitic Carbon Nitride (g-CN) Electrodes.

Graphitic carbon nitride (g-CN), a promising visible-light-responsive semiconductor material, is regarded as a fascinating photocatalyst and heterogeneous catalyst for various reactions due to its non-toxicity, high thermal durability and chemical durability, and "earth-abundant" nature. However, practical applications of g-CN in photoelectrochemical (PEC) and photoelectronic devices are still in the early stages of development due to the difficulties in fabricating high-quality g-CN layers on substrates, wide band gaps, high charge-recombination rates, and low electronic conductivity. Various fabrication and modification strategies of g-CN-based films have been reported. This review summarizes the latest progress related to the growth and modification of high-quality g-CN-based films. Furthermore, (1) the classification of synthetic pathways for the preparation of g-CN films, (2) functionalization of g-CN films at an atomic level (elemental doping) and molecular level (copolymerization), (3) modification of g-CN films with a co-catalyst, and (4) composite films fabricating, will be discussed in detail. Last but not least, this review will conclude with a summary and some invigorating viewpoints on the key challenges and future developments.

Identification of a novel germ cell marker MnTdrd from the oriental river prawn Macrobrachium nipponense.

Germ cell-specific genes play an important role in establishing the reproductive system in sexual organisms and have been used as valuable markers for studying gametogenesis and sex differentiation. Previously, we isolated a vasa transcript as a germ cell marker to trace the origin and migration of germ cells in the oriental river prawn Macrobrachium nipponense. Here, we identified a new germ cell-specific marker MnTdrd RNA and assessed its temporal and spatial expression during oogenesis and embryogenesis. MnTdrd transcripts were expressed in high abundance in unfertilized eggs and embryos at cleavage stage and then dropped significantly during late embryogenesis, suggesting that MnTdrd mRNA is maternally inherited. In situ hybridization of ovarian tissue showed that MnTdrd mRNA was initially present in the cytoplasm of previtellogenic oocyte and localized to the perinuclear region as the accumulation of yolk in vitellogenic oocyte. Whole-mount in situ hybridization of embryos showed that MnTdrd-positive signals were only localized in one blastomere until 16-cell stage. In the blastula, there were approximately 16 MnTdrd-positive blastomeres. During embryonized-zoea stage, the MnTdrd-positive cells aggregated as a cluster and migrated to the genital rudiment which would develop into primordial germ cells (PGCs). The localized expression pattern of MnTdrd transcripts resembled that of the previously identified germ cell marker vasa, supporting the preformation mode of germ cell specification. Therefore, we concluded that MnTdrd, together with vasa, is a component of the germ plasm and might have critical roles in germ cell formation and differentiation in the prawn. Thus, MnTdrd can be used as a novel germ cell marker to trace the origin and migration of germ cells.

Polychlorinated Biphenyl Electrochemical Aptasensor Based on a Diamond-Gold Nanocomposite to Realize a Sub-Femtomolar Detection Limit.

Polychlorinated biphenyls (PCBs) with high toxicity, low lethal dose, and bioaccumulation have been inhibited for application in wide fields, and a highly efficient trace detection is thus greatly desirable. In this study, we produce dense Au-nanoparticles by twice sputtering and twice annealing (T-Au-NPs) on boron-doped diamond (BDD). The successful formation of T-Au-NPs/BDD nanocomposites was confirmed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy analysis. Based on T-Au-NPs/BDD, an electronic biosensor with aptamers is fabricated to detect trace polychlorinated biphenyl-77 (PCB-77) by electrochemical impedance. A good linear relationship in the range of femtomolar to micromolar and significantly low detection limit of sub-femtomolar level (0.32 fM) are realized based on the biosensor. The emphasis of this research lies in the key role of the diamond substrate in the biosensor. It is demonstrated that the biosensor has excellent sensitivity, specificity, stability, and recyclability, which are favorable for detecting the trace PCB-77 molecule. It is attributed to the important effect presented by the BDD substrate and the synergistic influence of T-Au-NPs combined with aptamers.

Semiconductor SERS of diamond.

In this work, we report a favorable diamond substrate to realize semiconductor surface-enhanced Raman spectroscopy (SERS) for trace molecular probes with high sensitivity, stability, reproducibility, recyclability and universality. The boron-doped diamond (BDD) with surface hydrogenation or oxygenation has matched energy levels corresponding to the target molecules and plays a critical role in achieving SERS. The enhancement factor based on BDD substrates can reach 104-105, which approaches those obtained with most nanostructured compound semiconductors and is nearly 3-4 orders of magnitude higher than those of state-of-the-art single-element semiconductors (silicon, germanium, and graphene). The mechanism of SERS is determined to be charge transfer with vibronic coupling, which could enhance the molecular polarizability tensor. Because of its unique properties such as chemical inertness, wide bandgap, modulated doping, surface functionalization, biocompatibility, and high thermal conductivity, the single-element semiconductor diamond can serve a high-performance semiconductor SERS platform with applications in broad fields.

Two dimensional monolayer rhombic silicene on the diamond (111) surface.

Two-dimensional rhombic silicene (named r-silicene) bonded on the diamond (111) surface with a (1 × 1) configuration is predicted by density functional theory. The planar structure of r-silicene has P6/mmm symmetry, and it is dynamically and thermodynamically stable on the diamond surface. r-Silicene has a metallic character, which is different to both bulk cubic Si and hexagonal silicene. The hybrid structure of r-silicene/diamond consists of a metallic surface and a wide band gap semiconductor diamond substrate, providing a novel low-dimensional composite based on silicon-diamond to realize high performance nanodevices. Moreover, a similar rhombic configuration of monolayer germanene has been theoretically constructed on the diamond (111) substrate.

Highly Efficient Lead Distribution by Magnetic Sewage Sludge Biochar: Sorption Mechanisms and Bench Applications.

Highly efficient magnetic sewage sludge biochar (MSSBC) discloses feasible fabrication process with lower production cost, superior adsorption capacity, usage of waste sewage sludge as resource, selected by external magnetic field and exceptional regeneration property. 2gL-1 MSSBC exhibited a high adsorption capacity of 249.00mgg-1 in 200ppmPb(II) and the lead-MSSBC equilibrium was achieved within one hour, owing to the existence of the copious active sites. The adsorption kinetics was well described by the pseudo-second-order model while the adsorption isotherm could be fitted by Langmuir model. Mechanism study demonstrated the adsorption involved electrostatic attraction, ion exchange, inner-sphere complexation and formation of co-precipitates at the surface of MSSBC. Additionally, adsorption performance maintained remarkable in a broad pH window. These outcomes demonstrated the promising waste resource utilization by a feasible approach that turns the solid waste of sewage sludge into biochar adsorbent with auspicious applications in elimination of Pb(II) from wastewater.

Fatigue reliability based optimal design of planar compliant micropositioning stages.

Conventional compliant micropositioning stages are usually developed based on static strength and deterministic methods, which may lead to either unsafe or excessive designs. This paper presents a fatigue reliability analysis and optimal design of a three-degree-of-freedom (3 DOF) flexure-based micropositioning stage. Kinematic, modal, static, and fatigue stress modelling of the stage were conducted using the finite element method. The maximum equivalent fatigue stress in the hinges was derived using sequential quadratic programming. The fatigue strength of the hinges was obtained by considering various influencing factors. On this basis, the fatigue reliability of the hinges was analysed using the stress-strength interference method. Fatigue-reliability-based optimal design of the stage was then conducted using the genetic algorithm and MATLAB. To make fatigue life testing easier, a 1 DOF stage was then optimized and manufactured. Experimental results demonstrate the validity of the approach.

Adsorption of aromatic organic contaminants by graphene nanosheets: comparison with carbon nanotubes and activated carbon.

Adsorption of two synthetic organic compounds (SOCs; phenanthrene and biphenyl) by two pristine graphene nanosheets (GNS) and one graphene oxide (GO) was examined and compared with those of a coal base activated carbon (HD4000), a single-walled carbon nanotube (SWCNT), and a multi-walled carbon nanotube (MWCNT) in distilled and deionized water and in the presence of natural organic matter (NOM). Graphenes exhibited comparable or better adsorption capacities than carbon nanotubes (CNTs) and granular activated carbon (GAC) in the presence of NOM. The presence of NOM reduced the SOC uptake of all adsorbents. However, the impact of NOM on the SOC adsorption was smaller on graphenes than CNTs and activated carbons. Furthermore, the SOC with its flexible molecular structure was less impacted from NOM preloading than the SOC with planar and rigid molecular structure. The results indicated that graphenes can serve as alternative adsorbents for removing SOCs from water. However, they will also, if released to environment, adsorb organic contaminants influencing their fate and impact in the environment.

Predictive model development for adsorption of aromatic contaminants by multi-walled carbon nanotubes.

In the present study, Quantitative Structure-Activity Relationship (QSAR) and Linear Solvation Energy Relationship (LSER) techniques were used to develop predictive models for adsorption of organic contaminants by multi-walled carbon nanotubes (MWCNTs). Adsorption data for 29 aromatic compounds from literature (i.e., the training data) including some of the experimental results obtained in our laboratory were used to develop predictive models with multiple linear regression analysis. The generated QSAR (r(2) = 0.88), and LSER (r(2) = 0.83) equations were validated externally using an independent validation data set of 30 aromatic compounds. External validation accuracies indicated the success of parameter selection, data fitting ability, and the prediction strength of the developed models. Finally, the combination of training and validation data were used to obtain a combined LSER equation (r(2) = 0.83) that would be used for predicting adsorption of a wide range of low molecular weight aromatics by MWCNTs. In addition, LSER models at different concentrations were generated, and LSER parameter coefficients were examined to gain insights to the predominant adsorption interactions of low molecular weight aromatics on MWCNTs. The molecular volume term (V) of the LSER model was the most influential descriptor controlling adsorption at all concentrations. At higher equilibrium concentrations, hydrogen bond donating (A) and hydrogen bond accepting (B) terms became significant in the models. The results demonstrate that successful predictive models can be developed for the adsorption of organic compounds by CNTs using QSAR and LSER techniques.

Removal of trichloroethylene DNAPL trapped in porous media using nanoscale zerovalent iron and bimetallic nanoparticles: direct observation and quantification.

Direct trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) removal inside pore areas using nanoscale zerovalent iron (NZVI) and bimetallic nanoparticles were first investigated in a water-saturated porous glass micromodel. Effects of nitrate, aqueous ethanol co-solvent, humic substance, and elapsed time on TCE DNAPL removal using NZVI were studied by direct visualization. The removal efficiency was then quantified by directly measuring the remaining TCE DNAPL blobs area using an image analyzer. As ethanol content of co-solvent increased, TCE DNAPL removal by NZVI was also increased implying sequential TCE DNAPL removal mechanisms: as dissolved TCE was degraded by NZVI, TCE dissolution from TCE blobs would be then facilitated and the TCE blob areas would be eventually reduced. The presence of nitrate and humic substance hindered the NZVI reactivity for the TCE DNAPL removal. In contrast, the TCE DNAPL removal efficiency was enhanced using bimetallic nanoparticles in a short-term reaction by generating atomic hydrogen for catalytic hydro-dechlorination. However, all TCE DNAPL removal efficiencies reached the same level after long-term reaction using both NZVI and bimetallic nanoparticles. Direct TCE DNAPL observation clearly implied that TCE blobs existed for long time even though all TCE blobs were fully exposed to NZVI and bimetallic nanoparticles.

Mobilization and deposition of iron nano and sub-micrometer particles in porous media: a glass micromodel study.

Mobilization and deposition of iron nano and sub-micrometer particles (INSMP) in a porous medium were investigated using a water-saturated glass micromodel. The deposition and detachment of INSMP in the micromodel were visualized by taking serial images and experimentally verified by analysis of breakthrough curves. This first visualization study of INSMP fate showed that there were dense aggregations at the pores as the concentration of INSMP increased. The presence of dissolved humic substances (>1 ppm) significantly reduced deposition of suspended particles and enhanced detachment of the deposited particles. The mobility of INSMP in the presence of Pahokee peat fulvic acid standard II (PPFA) was higher than for Pahokee peat humic acid standard I (PPHA) due to the presence of more aromatic groups and the molecular weight in PPFA. Interfacial energy estimation based on the DLVO theory revealed that the adsorption of humic substances onto the INSMP increased the energy barrier and reduced the depth of secondary minimum between particles. The "affinity transition" in the initial deposition of INSMP within the micromodel was observed in the presence of Pahokee peat humic substances.

Aqueous ethanol modified nanoscale zerovalent iron in bromate reduction: synthesis, characterization, and reactivity.

Nanoscale zerovalent iron (NZVI) was evaluated for the reduction of bromate that is a highly persistent and carcinogenic oxyhalid formed as an ozonation byproduct during oxidative disinfection in drinking water treatment Solid-phase NZVI with different surface areas was controllably synthesized using a liquid phase reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and a Brunauer-Emmett-Teller (BET) surface area and porosity analyzer were utilized to characterize particle size, surface morphology, surface area, and corrosion layers formed onto NZVI before and afterthe reduction of bromate. Surface area of synthesized NZVI was found to be influenced strongly by ethanol contents during synthesis with a maximum surface area of 67.51 +/- 0.35 m2/g in a 90% aqueous ethanol; additionally, capsule structures of NZVI with amorphous phase, in which tens of particles with diameters of 2-5 nm were packed into an iron oxide/hydroxide layer, were also synthesized using 100% ethanol as a solvent. Subsequent XRD and TEM results revealed that in a 20 min bromate reduction NZVI mostly converted to Fe2O3 and Fe3O4 corrosion products mixed with iron hydroxides. Compared to bromate reduction using microsized ZVI in a pseudo-first-order kinetic model, NZVI enhanced the reduction efficiency following a second-order kinetic model, with observed second-order rate constants (kobs) of 2.57 x 10(-4) to 2.19 x 10(-3) microg(-1) min(-1) L. Humic acid was found to be the most influencing factorto decrease NZVI reactivity in bromate reduction. However, the effect of sonication pretreatment showed that the bromate reduction efficiency could be enhanced by increasing the actual reactive surface area. Our results suggest that application of NZVI is a viable process for bromate reduction in water treatment.