Hollow Protein Fibers Templated Synthesis of Pt/Pd Nanostructures with Peroxidase-like Activity

A simple, inexpensive, and viable method for growing multiple heterostructured carbon nanotubes (CNTs) over the entire surface of Ni-Al bimetallic nanowires (NWs) in the gas phase was developed. Polymer-templated bimetallic nitrate NWs were produced by electrospinning in the first step, and subsequent calcination resulted in the formation of bimetallic oxide NWs by thermal decomposition. In the second step, free-floating bimetallic NWs were produced by spray pyrolysis in an environment containing hydrogen gas as a reducing gas. These NWs were continuously introduced into a thermal CVD reactor in order to grow CNTs in the gas phase. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectrometry analyses revealed that the catalytic Ni sites exposed in the non-catalytic Al matrix over the entire surface of the bimetallic NWs were seeded to radially grow highly graphitized CNTs, which resembled “foxtail” structures. The grown CNTs were found to have a relatively uniform diameter of approximately10±2 nm and 10 to 15 walls with a hollow core. The average length of the gas-phase-grown CNTs can be controlled between 100 and 1000 nm by adjusting the residence time of the free-floating bimetallic NWs in the thermal CVD reactor.

Atom-stepped surface-regulated Pd nanowires for boosting alcohol oxidation activity

We report the structures of Ag–Cu and Ag–Ni bimetallic clusters and nanowires(NWs), which are well known as effective Ag-based catalysts, by using an effectivesemi-grand-canonical ensemble Monte Carlo method. The metal–metal interactions aremodeled by the second-moment approximation of the tight-binding potentials. Thesimulation results show that the Ag–Cu and Ag–Ni bimetallic nanomaterials, includingclusters and NWs, possess core–shell structures at different compositions, in which the Agatoms lie on the surface, while the Cu or Ni atoms occupy the cores of the clusters andNWs. It is found that the pentagonal multi-shell-type structure can be transformed intocylindrical multi-shell-type structures for Ag–Cu and Ag–Ni bimetallic NWs at 100, 300,and 500 K. On the other hand, with the increase of Ag mole fraction in the Ag–Cuand Ag–Ni bimetallic clusters, the Ag atoms occupy the surface shell first, thenthe interior shell, and finally the central sites of the clusters. It is also foundthat the initial shape, composition, and temperature have little effect on thecore–shell structures of the bimetallic clusters and NWs. The formation of core–shellAg–Cu and Ag–Ni bimetallic clusters and NWs is due to the fact that a single Agimpurity is favorable to be situated in the core of the Cu or Ni clusters and NWs.

First-Principles Study of the Structural, Electronic, and Magnetic Properties of Cu-Fe, Cu-Co, and Cu-Ni Linear and Zigzag Nanowires

The surface of polyacrylonitrile hollow fibers were hydrolyzed and covalently bonded with cholesterol oxidase (COD) via glutaraldehyde. The immobilized amount of the COD increased with the concentration of glutaraldehyde. However, COD immobilized with 10% glutaraldehyde had higher activity than with other concentrations. The stabilities of immobilized COD to pH and temperature were higher than those of native enzyme. The immobilized enzyme retained 80% of initial activity after 15 days when stored at 4 degrees C, which was longer than native COD. After being reused six times, the COD-immobilized hollow fiber retained more than 80% of the activity.

Cooling components in the hot section of a gas turbine are essential to component durability. Common methods of cooling include rib turbulators in internal passages and film cooling on external surfaces. The holes that produce the film cooling are fed from the internal channels often containing ribs. Consequently, there is an interdependence of internal heat transfer and external film cooling. The purpose of this study was to obtain a better understanding of the interaction of ribs and film cooling. To quantify the cooling performance, the surface temperatures were measured, from which overall effectiveness was calculated. For the experiments, additively manufactured test coupons were made of Inconel 718 to match engine Biot numbers. These test coupons had internal feed channels with and without ribs and had both cylindrical holes and meter-diffuser-shaped holes with 15 deg lateral expansion angles and a 1 deg forward expansion angle. A single rectangular channel was one type of feed channel. The other type of feed channel was individual circular channels, with each circular channel supplying an individual film-cooling hole. The experimental results showed that the circular individual channels have 80% higher baseline overall effectiveness than the single rectangular channels without any film cooling. Ribbed turbulators without film cooling also increased the overall effectiveness by 21% for single rectangular channels and by 29% for the circular individual channels compared to the respective non-ribbed channels. While the film cooling increased the overall effectiveness of all geometries, the single rectangular channels had increased overall effectiveness levels by up to twice that of the no film-cooling case. On average, the single rectangular channels had an 80% improvement from film cooling, whereas the individual channel feeds, on average, had only a 50% improvement, given their high baseline effectiveness levels.

Cooling components in the hot section of a gas turbine is essential to component durability. Common methods of cooling include rib turbulators in internal passages and film cooling on external surfaces. The holes that produce the film cooling are fed from the internal channels often containing ribs. Consequently, there is an interdependence of internal heat transfer and external film cooling. The purpose of this study was to obtain a better understanding of the interaction of ribs and film cooling. To quantify the cooling performance the surface temperatures were measured from which overall effectiveness was calculated. For the experiments, additively manufactured test coupons were made of Inconel 718 to match engine Biot numbers. These test coupons had internal feed channels with and without ribs and had both cylindrical holes and meter diffuser shaped holes with 15° lateral expansion angles and a 1° forward expansion angle. A single rectangular channel was one type of feed channel. The other type of feed channels was individual circular channels with each circular channel supplying an individual film-cooling hole. The experimental results showed that the circular individual channels have 80% higher baseline overall effectiveness than the single rectangular channel without any film cooling. Ribbed turbulators without film cooling also increased the overall effectiveness by 21% for single rectangular channel and by 29% for the circular individual channels compared to the respective non-ribbed channels. While the film cooling increased the overall effectiveness of all geometries, the single rectangular channels had increased overall effectiveness levels by up to twice that of the no film-cooling case. On average the single rectangular channels had an 80% improvement from film cooling, whereas the individual channel feeds on average had only a 50% improvement given their high baseline effectiveness levels.

Rhodococcus sp. R14-2, isolated from Chinese Jin-hua ham, produces a novel extracellular cholesterol oxidase (COX). The enzyme was extracted from fermentation broth and purified 53.1-fold based on specific activity. The purified enzyme shows a single polypeptide band on SDS-PAGE with an estimated molecular weight of about 60 kDa, and has a pI of 8.5. The first 10 amino acid residues of the NH2-terminal sequence of the enzyme are A-P-P-V-A-S-C-R-Y-C, which differs from other known COXs. The enzyme is stable over a rather wide pH range of 4.0–10.0. The optimum pH and temperature of the COX are pH 7.0 and 50°C, respectively. The COX rapidly oxidizes 3β-hydroxysteroids such as cholesterol and phytosterols, but is inert toward 3α-hydroxysteroids. Thus, the presence of a 3β-hydroxyl group appears to be essential for substrate activity. The Michaelis constant (Km) for cholesterol is estimated at 55 μM; the COX activity was markedly inhibited by metal ions such as Hg2+ and Fe3+ and inhibitors such as p-chloromercuric benzoate, mercaptoethanol and fenpropimorph. Inhibition caused by p-chloromercuric benzoate, mercuric chloride, or silver nitrate was almost completely prevented by the addition of glutathione. These suggests that -SH groups may be involved in the catalytic activity of the present COX.

In-situ generation of highly active and four-in-one CoFe2O4/H2PPOP nanozyme: Mechanism and its application for fast colorimetric detection of Cr (VI)

Polystyrene@Au@prussian blue nanocomposites with enzyme-like activity and their application in glucose detection

We for the first time report a facile, wet-chemical strategy for the high-yield (approximately 100%) synthesis of ultralong Pt-on-Pd bimetallic nanowires (NWs) with the cores being Pd NWs and the shells being made of dendritic Pt, which exhibit high surface area and enhanced electrocatalytic activity towards methanol oxidation reaction.

Appropriate addition of phosphate salt in food can improve the food quality and taste. However, extensive intake of phosphate salt may lead to some human diseases such as hyperphosphatemia and renal insufficiency. Thus, it is essential to establish a cost-effective, convenient, sensitive, and selective method for monitoring phosphate ion (Pi) to ensure food quality control. In this work, a Co-based metal-organic frameworks (Co-MOF) nanomaterial with dual functions (peroxidase-like activity and specific recognition) was designed for acting as a catalytic chromogenic platform for sensitive detection of Pi. The Co2+ nodes not only provide high enzyme-like activity to catalyze the 3,3′,5,5′--tetramethylbenzidine (TMB) substrate to blue oxTMB (652 nm) but also act as selective sites for Pi recognition. The use of cationic organic ligands (2-methylimidazole) and cationic metal ions (Co2+) endows the Co-MOF with a strong positive surface charge, which is beneficial to the capture of negative-charged Pi and the dramatically suppressed TMB oxidation. When Pi exists, it specifically adsorbs onto the Co-MOF through the Co-O-P bond and the strong electrostatic interaction, leading to the change of surface charge on Co-MOF. The peroxidase-like catalytic activity of Co-MOF is thus restrained, causing a different catalytic effect on TMB oxidation from that without Pi. Based on this principle, a colorimetric assay was established for rapid and sensitive detection of Pi. A good linear relationship was obtained between Pi concentration and the absorbance at 652 nm, with a linear range of 0.009–0.144 mg/L and a detection limit of 5.4 μg/L. The proposed assay was applied to the determination of Pi in actual food samples with recoveries of 92.2–108% and relative standard deviations (RSDs) of 2.7–7.3%, illustrating the promising practicality for actual samples analysis.

Peroxidase-like activity of FeVO4 nanobelts and its analytical application for optical detection of hydrogen peroxide

Catalytic reduction of 4-nitrophenol over graphene supported Cu@Ni bimetallic nanowires

Ultrathin PdPt bimetallic nanowires with enhanced electrocatalytic performance for hydrogen evolution reaction