New insights into the hydrogen evolution reaction using Ni-ZIF8/67-derived electrocatalysts

Abstract One of the present great challenges is finding nonprecious materials characterized by efficient electrocatalytic behavior in order to substitute the expensive platinum-based materials for the purpose of hydrogen evolution reactions (HERs). In this study, ZIF-67 and ZIF-67 were used as precursors in order to fabricate metallic-doped N-enriched carbon successfully through a simple process of pyrolysis for applying the hydrogen evolution reaction. In addition, nickel was added to these structures in the course of the synthesis procedure. While under high-temperature treatment, Nickel doped ZIF-67 was transformed into metallic NiCo doped N enriched carbon (NiCo/NC), under high-temperature treatments, Ni-doped ZIF-8 changed into metallic NiZn doped N enriched carbon (NiZn/NC). By combining metallic precursors, the following five structures were synthesized: NiCo/NC, Co/NC, NiZn/NC, NiCoZn/NC, as well as CoZn/NC. It is noteworthy that the produced Co/NC shows optimum hydrogen evolution reaction activity along with superior overpotential of 97 mV and the minimum Tafel slope of 60 mV/dec at 10 mA cm. In addition, the superb behavior of hydrogen evolution reaction can be attributable to the numerous active sites, the superior electrical conductivity of carbon, and the firm structure. As a result, the present paper suggests a novel strategy in order to produce nonprecious materials characterized by superb HER efficiency for future scholars

Purification and Partial Characterization of a Thrombin-Like Enzyme (AH144) from Venom of Iranian Snake Agkistrodon Halys

ABSTRACT: The snake venom´s thrombin-like enzymes comprise a number of serine proteases, which are functionally and structurally related to thrombin. Purification and partial characterization of a thrombin-like enzyme from the venom of the Iranian snake, Agkistrodon halys, was the aim of this study. Purification was carried out by a combination of variety of chromatographic methods that included: gel filtration on Sephadex G-50, ion-exchange chromatography on DEAE-Sepharose and HPLC with a C18 column. A trial for the purification of protease resulted in an enzyme with specific activity of 721.2 ( mol/min/mg), which was purified by 72.1 fold. The purified thrombin-like enzyme designated AH144 was found to have a molecular weight of approximately 30.5 kDa. This thrombin-like enzyme had the highest activity at 37 °C and pH 7.5. Enzyme activity increased as its concentration increased, and the purified enzyme did not have any effect on casein. AH144 demonstrated clotting and proteolytic activities in the presence of the human plasma and the synthetic substrate (BApNA), respectively. Data emphasized the possibility of AH144 for quantitative determination of fibrinogen

A novel approach to fabricate high performance nano-SiO2 embedded PES membranes for microfiltration of oil-in-water emulsion

The goal of this study was to determine the desired preparation conditions of polyethersulfone (PES) membrane for the microfiltration of oil-in-water emulsion. Membranes were fabricated via combination of vapor induced phase separation (VIPS) and non-solvent induced phase separation (NIPS) methods. SiO2 nanoparticle were used as the hydrophilicity modification agent in the casting solutions which led to a negative impacts on the permeate flux in high concentrations due to aggregation. The effects of nanoparticle concentration, exposure time and relative humidity on the permeate flux, and their interactions were determined. The morphology of the prepared membranes were studied using FESEM, pore size distribution, contact angle, porosity, and water uptake measurement. Besides, response surface methodology (RSM) and central composite design (CCD) were applied for modeling, statistical analysis and optimization of oil-in-water emulsion microfiltration. The most significant interactions were observed for the exposure time and relative humidity, and a contradictory trend was found for flux variation. The optimum preparation conditions for nanoparticle concentration, exposure time, and humidity were found to be 1%, 33s, and 80%, respectively, where the oil rejection was higher than 98% for all runs. (C) 2015 Elsevier B.V. All rights reserved