Stabilization and Decomposition of Organic Matters by Nano-porous Metals

AbstractNanoporous (np-) metals affect chemical stability of various organic matters much more than their bulk counterparts. Self-assembly monolayers (SAMs) of 4-aminothiophenol are more stable on np-Au fabricated by dealloying Ag-Au alloy than on flat Au, which were elucidated by cyclic voltammetry (CV). The first-principles calculations indicate that atomic defect of Au surface, which is characteristic of ligament surface of np-Au, reduce the binding energy of thiol molecule.The stabilized SAMs on np-Au are also effective for enzyme immobilization. When laccase was immobilized on np-Au surface, its thermal stability was improved compared with nonfixed laccase. The higher stability of immobilized laccase is due to the synergistic effect of reduced conformational flexibility of the enzyme in nanopores and SAMs stability. CV with the working electrode of enzyme-immobilized np-Au revealed that the electron transfer between enzyme and electrode is successfully enhanced by SAMs. These aspects of enzyme-immobilized and SAMs-decorated np-Au can be applied to the electrodes of biofuel cell.Np-metals such as np-Au, np-Pd and np-Ni, on the other hand, remarkably decompose methyl orange (MO, a typical stable azo dye in the textile industry) in an aqueous solution, while MO is highly stable in aqueous solutions which include their bulk counterparts. Ultraviolet-visible light spectroscopy and high-performance liquid chromatography demonstrated that np-Au breaks the azo bond (–N=N–) in MO molecules. Defective surface of ligaments in np-metals plays an important role in this catalytic decomposition of MO

Fabrication of carbon nanotube/NiOx(OH)y nanocomposite by pulsed electrodeposition for supercapacitor applications

Nanocomposite films based on carbon nanotubes (CNTs)/nickel (Ni)-species were fabricated by electrophoretic deposition (EPD) of CNT, followed by pulsed electrodeposition of Ni and annealing in air. NiO/Ni(OH)2 particles with 7 ± 4 nm diameters were uniformly dispersed on the CNT networks. Cyclic voltammetry revealed that the CNT/NiOx(OH)y nanocomposite films had high specific capacitances of 1451, 1158, 998, 896 and 851 F g^{−1} per mass of active Ni species at 1, 10, 30, 50 and 100 mV s^{−1}, respectively, in the potential window of 0.4 V. An annealing time of 1 h (at 523 K) enhanced the pseudocapacity of deposited Ni species by the dehydration of Ni(OH)2 to form NiO. Longer annealing time reduced the capacitance because of sintering and subsequent decrease in surface area of Ni deposits. The capacitance of the fabricated CNT/NiOx(OH)y nanocomposite was maintained after 20, 000 cycles of potential sweeping

Oxygen reduction on bimodal nanoporous palladium-copper catalyst synthesized using sacrificial nanoporous copper

Nanoporous copper (NP-Cu), as a sacrificial support, was used for the synthesis of bimodal nanoporous palladium–copper (BNP-PdCu) for oxygen reduction reaction (ORR) electrodes in fuel cells. The catalytic performance of BNP-PdCu in ORR per electrochemical surface area was enhanced by the dissolution and removal of supporting NP-Cu, which indicates that the intrinsic catalytic properties of palladium are improved by the proposed synthesis strategy including galvanic replacement of copper with palladium, following copper dissolution. Cu remained on Pd surfaces even after dissolution of Cu. Additionally, significant local lattice contraction was observed at the ligament surface. First-principles calculations on the adsorbing oxygen species on Pd show that both lattice contraction and alloying with copper increase the binding energies of oxygen species to the Pd surface. The high ORR activity of the present BNP-PdCu is suggested to be mainly due to the Cu-ligand effect

Antibacterial activity of ultrathin platinum islands on flat gold against Escherichia coli

Nanoporous Au exhibits high antibacterial activity (AA) without releasing reactive oxygen species or metal ions, instead its AA depends on the work function (WF) because cell walls are affected by peculiar electronic states at the surface. Based on this mechanism, a flat surface without nanostructure should show high AA if the WF of the surface is suitably tuned. To verify this, ultrathin Pt islands with high WF was fabricated on flat Au by underpotential deposition (UPD) of copper and subsequent redox replacement with Pt, and the AA of the Pt/Au substrate on Escherichia coli was evaluated. The Pt/Au substrate showed higher AA than Pt and Au surfaces, and a positive relationship between AA and WF was demonstrated. In addition, first principles calculations were performed to investigate the mechanism for the high WF of the Pt/Au substrate. The findings suggest that the high WF of the Pt/Au substrate is at least partly due to charge transfer from Au to Pt

Direction Dependence of Compressive Properties of Mg Processed by Directional Solidification

Pure Mg consisting of elongated grains was fabricated by the directional solidification process, and its compressive properties were investigated at room temperature, 473 and 773 K under the conditions where the angle between the long axis direction of the elongated grains and the compression direction was 0, 45 and 90 degree. At room temperature, the specimen at the angle of 45 degree was fractured prior to " ¼ 0:3, although the specimens at the angles of 0 and 90 degree were not fractured even at " ¼ 0:3. In addition, the yield stress at the angle of 45 degree was higher than those at the angles of 0 and 90 degree. The (0002) basal planes were distributed at a tilt of 30-50 degree to the solidification direction. This was responsible for the higher yield stress at the angle of 45 degree. Also, the yield stress at the angle of 0 degree was lower than that at the angle of 90 degree. The lower yield stress at the angle of 0 degree was attributed to twinning. At 473 K, the yield stress at the angle of 45 degree decreased significantly. The large decrease in yield stress at the angle of 45 degree resulted from grain boundary sliding. At 773 K, the yield stresses were almost the same, irrespectively of the loading direction. Thus, compressive properties of the directionally solidified Mg were affected by the loading direction

Electrochemical actuation of nanoporous Ni in NaOH solution

The fabrication of a bilayer-stacked Ni electrochemical actuator is reported. The stacked bilayer sheet composed of bulk and nanoporous Ni deformed when a potential of ± 1 V was applied in aqueous NaOH solution, which is the first report of nanoporous Ni exhibiting actuation characteristics. Actuation is considered to have a strong relationship with the electrical double layer, because cyclic voltammetric measurements suggested that the effect of oxygen adsorption on the surface was minor. The results suggest that nanoporous Ni can be used as an actuator, and it has potential in being applied for commercial use because of its low price and high availability

Inactivation of HeLa cells on nanoporous gold

Nanoporous metals strongly affect organic matter; however, there is a poor understanding of their effects on cells. The present work shows that HeLa cells on nanoporous gold (NPG) were less active than those on flat gold (FG) with no nanoporous structure. Initially, HeLa cells adhered to the NPG over a period of more than 10 h, then the adhered cells subsequently exhibited apoptosis that was not related to anoikis. ELISA analyses showed that the conformational change of fibronectin was more greatly induced by NPG than FG. First-principles calculations and molecular dynamics simulations were performed to investigate the conformational change in the RGD sequence and the integrin signaling. The simulations suggested that the extended form of integrin, with an open headpiece, was not generated owing to the conformational change of RGD, and the outside-in signals could not be intracellularly transmitted via the integrin binding to the fibronectin on NPG, resulting in cell death

SIGMA: Scala Internal Domain-Specific Languages for Model Manipulations

International audienceModel manipulation environments automate model operations such as model consistency checking and model transformation. A number of external model manipulation Domain-Specific Languages (DSL) have been proposed, in particular for the Eclipse Modeling Framework (EMF). While their higher levels of abstraction result in gains in expressiveness over general-purpose languages, their limitations in versatility, performance, and tool support together with the need to learn new languages may significantly contribute to accidental complexities. In this paper, we present Sigma, a family of internal DSLs embedded in Scala for EMF model consistency checking, model-to-model and model-to-text transformations. It combines the benefits of external model manipulation DSLs with general-purpose programming taking full advantage of Scala versatility, performance and tool support. The DSLs are compared to the state-of-the-art Epsilon languages in non-trivial model manipulation tasks that resulted in 20% to 70% reduction in code size and significantly better performance

Mechanical characterization of nanoporous Au modified with self-assembled monolayers

The surface of nanoporous Au was modified with self-assembled monolayers (SAMs) of 6-mercapto-1-hexanol and the hardness tests were performed on the SAM-modified and non-modified nanoporous Au to investigate the effects of SAM modification on the mechanical properties of nanoporous Au. In addition, the origin of the chemomechanical effects was investigated by first principles shear test simulations on an Au–S alloy. The SAM-modified nanoporous Au showed lower hardness than the non-modified nanoporous Au. The loading rate dependence tests showed that the activation volume was low for both, indicating that events of a short range play an important role in deformation of nanoporous Au, regardless of whether the nanoporous Au was modified with SAMs. It was suggested from the simulations that the lower hardness for the SAM-modified nanoporous Au is because movement of dislocation endpoints at the surface is facilitated by chemical effects of Au–S bonding

Clinical characteristics, management strategies and outcomes of patients with recurrent venous thromboembolism in the real world

There is a paucity of data on management strategies and clinical outcomes after recurrent venous thromboembolism (VTE). In a multicenter registry enrolling 3027 patients with acute symptomatic VTE, the current study population was divided into the following 3 groups: (1) First recurrent VTE during anticoagulation therapy (N = 110); (2) First recurrent VTE after discontinuation of anticoagulation therapy (N = 116); and (3) No recurrent VTE (N = 2801). Patients with first recurrent VTE during anticoagulation therapy more often had active cancer (45, 25 and 22%, P < 0.001). Among 110 patients with first recurrent VTE during anticoagulation therapy, 84 patients (76%) received warfarin at recurrent VTE with the median prothrombin time-international normalized ratio (PT-INR) value at recurrent VTE of 1.6, although patients with active cancer had a significantly higher median PT-INR value at recurrent VTE compared with those without active cancer (2.0 versus 1.4, P < 0.001). Within 90 days after recurrent VTE, 23 patients (20.9%) during anticoagulation therapy and 24 patients (20.7%) after discontinuation of anticoagulation therapy died. Active cancer was a major cause of recurrent VTE during anticoagulation therapy as a patient-related factor, while sub-optimal intensity of anticoagulation therapy was a major cause of recurrent VTE during anticoagulation therapy as a treatment-related factor, particularly in patients without active cancer