Catalytic Enhancement Effect Research Articles

Salen-manganese complex-based nanozyme with enhanced superoxide- and catalase-like activity for wound disinfection and anti-inflammation

Skin wound healing remains a key challenge owing to its vulnerability to pathogen infection, oxidative stress and persistent inflammatory response. Herein, a salen-manganese complex (EUK)-based nanozyme was designed to simultaneously circumvent these barriers. The nanozyme was prepared by the amidation reaction between degradable chito-oligosaccharide (COS) and EUK. Positive charged COS and metallic compounds (EUK) could allow the nanozyme (COS-EUK) synergistic antibacterial activity. Due to the protection and synergistic catalytic enhancement effect provided by COS, superoxide (SOD)- and catalase (CAT)-like capability of COS-EUK was significantly improved compared with EUK. The nanozyme could eradicate not only O2− but also the generated H2O2, further supplying O2 to promote fiber cell proliferation. Moreover, COS-EUK could prevent macrophages from transforming into classically activated macrophages (M1 phenotype), and endow them anti-inflammatory effects. COS-EUK can accelerate bacteria-infected skin wound healing. Thus, COS-EUK provides a promising strategy for bacteria-infected wound healing with great potential in clinical infection.

One-step synthesis of efficient manganese-based oxide catalyst for ultra-rapid CO2 absorption in MDEA solutions

The objective of this study is to develop a promising and feasible technique to significantly increase in the CO2 absorption rate of tertiary amine solutions. Here, for the first time, a manganese-based oxide (MnOx) with four different oxides, including Mn3O4, Mn2O3, MnOOH, and MnO2, is prepared using a one-step synthesis approach, and utilized to catalytically accelerate CO2 absorption in a typical tertiary amine, MDEA solution. The results reveal that the MnOx catalyst improves the CO2 absorption rate and amount as high as 360% and 132%, respectively. The MnOx also outperforms various single manganese-based oxides and their physical mixture, as well as most of the reported catalysts in terms of catalytic enhancement of CO2 absorption in the MDEA solution. The FT-IR analysis is used to confirm the catalytic promotion effect of CO2 absorption, and a catalytic mechanism is proposed. The remarkable catalytic enhancement effect of MnOx might primarily result from both plentiful basic sites and unsaturated Mn sites as well as the synergistic interaction between various oxides. Furthermore, the MnOx also has a favorable effect on CO2 desorption and exhibits outstanding recyclability. This work not only demonstrates a workable strategy for improving the CO2 absorption rate by incorporating a low-cost and high-efficiency solid base catalyst into tertiary amine solutions but also provides guidance for developing more effective catalysts to promote CO2 absorption.

Specific Amino Acid Substitutions in OXA-51-Type β-Lactamase Enhance Catalytic Activity to a Level Comparable to Carbapenemase OXA-23 and OXA-24/40.

The chromosomal blaOXA-51-type gene encodes carbapenem-hydrolyzing class D β-lactamases (CHDLs), specific variants shown to mediate carbapenem resistance in the Gram-negative bacterial pathogen Acinetobacter baumannii. This study aims to characterize the effect of key amino acid substitutions in OXA-51 variants of carbapenem-hydrolyzing class D β-lactamases (CHDLs) on substrate catalysis. Mutational and structural analyses indicated that each of the L167V, W222G, or I129L substitutions contributed to an increase in catalytic activity. The I129L mutation exhibited the most substantial effect. The combination of W222G and I129L substitutions exhibited an extremely strong catalytic enhancement effect in OXA-66, resulting in higher activity than OXA-23 and OXA-24/40 against carbapenems. These findings suggested that specific arrangement of residues in these three important positions in the intrinsic OXA-51 type of enzyme can generate variants that are even more active than known CHDLs. Likewise, mutation leading to the W222M change also causes a significant increase in the catalytic activity of OXA-51. blaOXA-51 gene in A. baumannii may likely continue to evolve, generating mutant genes that encode carbapenemase with extremely strong catalytic activity.

Application of in-Situ Radiography to Porous Carbon Felt Electrodes in Vanadium Redox Flow Batteries

Porous carbon felts are routinely applied as electrodes in vanadium redox flow batteries. They offer several advantages, such as low cost, low weight, good electron conductivity, and chemical inertness. However, due to their comparatively low activity in catalyzing the vanadium reactions at the anode and cathode side of the battery, an activation treatment is required to enhance the kinetics. In the literature, a heat-treatment at 400 °C in air has been reported as sufficient to introduce more oxygen functional groups at the surface, also improving the wettability of the felt and its contact with the electrolyte significantly. In this context, it is however not clear, which mechanisms are responsible for the observed performance increase. In another approach, bismuth is deposited on the carbon felts to enhance the V2+/3+ reaction in the anolyte. While a better battery performance is indeed observed, the bismuth is assumed to be dissolved and re-deposited during the charge-discharge cycles.The aim of this work is to utilize in-situ X-ray radiography to study both the activation process and the catalytic enhancement effect due to bismuth decoration in more detail. We will highlight the potential of in-situ (synchrotron) radiography for the investigation of electrode/electrolyte interaction, pore filling and electrolyte flow behaviour complementing other more routine characterization techniques nicely [1]. To elucidate the effect of air activation, pristine and heat-treated carbon felts have been brought into contact with water, sulfuric acid and an acidic vanadium solution and ex-situ contact angles determined. This study was complemented by in-situ X-ray radiography, in which an in-house built flow cell served to monitor the electrolyte flow through the porous felt materials (pristine and heat-treated). The effect of the heat-treatment can be clearly discerned in water, see figure 1 (top: pristine felt, bottom: heat-treated felt). In contrast, when the commercial vandium electrolyte was being used, the differences between pristine and heat-treated felt vanished. Consequently, only a negligibly higher pore filling degree was observed for the treated felts, while all felts were flooded in less than 1 minute. [2]Apart from the phenomena described above, we will also highlight the potential of in-situ radiography with respect to Bi-decorated felts during operation. [3][1] L. Eifert, N. Bevilacqua, K. Köble, K. Fahy, L. Xiao, M. Li, K. Duan, A. Bazylak, P.-C. Sui, R. Zeis, ChemSusChem 13 (2020) 3154.[2] M. Gebhard, M. Schnucklake, A. Hilger, M. Röhe, M. Osenberg, U. Krewer, I. Manke, C. Roth, Energy Technol. 8 (2020) 1901214.[3] M. Gebhard, T. Tichter, J. Schneider, J. Mayer, A. Hilger, M. Osenberg, M. Rahn, I. Manke, C. Roth J. Power Sources 478 (2020) 228695. Figure 1

Synthesis and characterization of magnetic cross-linked enzyme aggregate and its evaluation of the alternating magnetic field (AMF) effects in the catalytic activity

A magnetic cross-linked enzyme aggregate (MCLEA) of cellulases and a non-magnetic analogue (CLEA) were synthesized and further investigated. The obtained MCLEA and CLEA showed a high enzyme loading efficiency of 90% and 88%, respectively. However, the MCLEA presented an activity 33% higher than the CLEA one, suggesting a catalytic enhancement effect as a result of magnetic nanoparticle presence in cross-linked cellulase aggregates structure. In addition, MCLEA shows an unusual behavior with highest enzymatic activity at low temperatures near to 37 °C. Lastly, a full factorial design (2x2) with two variables at two levels, frequency (203–420 kHz) and amplitude (3–6 kA m−1), was used in order to better investigate the effects of an alternating magnetic field (AMF) on MCLEA activity. AMF application decreased MCLEA activity, particularly in the highest values of frequency and amplitude, when compared to condition field free. In addition, frequency implied in more significant effects on MCLEA activity when compared to AMF amplitude.

Fabrication of Bimetal CuFe2O4 Oxide Redox-Active Nanocatalyst for Oxidation of Pinene to Renewable Aroma Oxygenates.

This study report on the synthesis of spinel CuFe2O4 nanostructures by surfactant-assisted method. The catalysts were characterized by X-ray diffraction (XRD), laser Raman, transition electron microscope (TEM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), hydrogen temperature programmed reduction (H2-TPR), and Brunauer-Teller-Emmett-Teller (BET) surface area techniques. CuFe2O4 was active for pinene oxidation using tertiary butyl hydroperoxide (TBHP) to pinene oxide, verbenol, and verbenone aroma oxygenates. Under optimized reaction conditions, the spinel CuFe2O4 catalyst could afford 80% pinene conversion at a combined verbenol/verbenone selectivity of 76% within the reaction time of 20 h. The changes in catalyst synthesis solvent composition ratios induced significantly varying redox, phases, and textural structure features, which resulted in various catalytic enhancement effect. Characterization results showed the spinel CuFe2O4 catalyst possessing less than 5 wt% impurity phases, Cu(OH)2, and CuO to afford the best catalytic performance. The CuFe2O4 catalyst was recyclable to up to five reaction cycles without loss of its activity. The recyclability of the bimetal CuFe2O4 oxide catalyst was simply rendered by use of an external magnet to separate it from the liquid solution.

Label-free electrochemiluminescent immunosensor for detection of prostate specific antigen based on mesoporous graphite-like carbon nitride

In this paper, mesoporous graphite-like carbon nitride (mpg-C3N4) combined with gold nanoparticles (Au NPs) was conducted to construct a luminol-hydrogen peroxide (H2O2) based electrochemiluminescent (ECL) immunosensor for prostate specific antigen (PSA) detection. The mpg-C3N4 exhibited large specific surface area and high porosity was synthesized from a simple precursor, which possessed abundant active sites to load Au NPs and luminol (mpg-C3N4/Au-luminol). After that, Au NPs linked mpg-C3N4 (mpg-C3N4/Au) could hatch with the primary antibody (Ab1) via Au-NH2 bond, which reinforced the sensitivity of immunosensor. The mpg-C3N4 and Au shows excellent catalytic enhancement effect on the ECL intensity of luminol. Under optimal conditions, the constructed ECL immunosensor exhibited sensitive response to PSA in a wide linear range of 0.001 ~ 15 ng mL−1 with a lower detection limit of 0.927 pg mL−1. Meanwhile, the proposed ECL immunosensor endows the good reproducibility and stability. Therefore, the results could open another avenue for detection of PSA and other biomarkers.

Fe–Ni Nanoparticles: A Multiscale First-Principles Study to Predict Geometry, Structure, and Catalytic Activity

Nanoparticles of iron and nickel are promising candidates as nanosized soft magnetic materials and as catalysts for carbon nanotube synthesis and CO methanation, among others. To understand geometry- and size-dependent properties of these nanoparticles, phase diagram of Fe/Ni alloy nanoparticles was calculated by density functional theory and cluster expansion method. Ground state convex is presented for face-centered cubic (FCC), body-centered cubic (BCC), and icosahedral (ICO) particles. Previous experimental observations were explained by using multiscale model for particles with realistic size (diameter ≥2 nm). At size 1.5 nm, geometry changes from BCC at low X(Ni) to icosahedral at high X(Ni). FCC is stabilized over icosahedral geometry by increasing number of atoms from 561 to 923. In large FCC particles, there is enrichment of Fe atoms from core to shell beneath surface, while surface and core are enriched by Ni atoms. Catalytic enhancement effect in CO methanation was found to be due to Ni incorpo...

Enhanced Catalytic Activity of Self‐Assembled‐Monolayer‐Capped Gold Nanoparticles

An unprecedented substrate-selective catalytic enhancement effect of an alkanethiol-self-assembled monolayer (SAM) on Au nanoparticles (AuNPs) is reported. In the supported 2D-array of AuNPs, the alkanethiol-SAM acts as a protein-like soft reaction space in which the substrate molecules are encapsulated through non-covalent intermolecular hydrophobic interactions, and thus catalytic reactions are accelerated at AuNP surfaces.

A selective resonance scattering assay for immunoglobulin G using Cu(II)–ascorbic acid–immunonanogold reaction

In sodium acetate–acetic acid buffer solution, Au, Ag, Pt, Pd, Fe 3O 4, and Cu 2O nanoparticles have catalytic enhancement effect on the reduction of Cu 2+ by ascorbic acid to form large copper particles that exhibit a strong resonance scattering peak at 610 nm. Those nanocatalytic reactions were studied by the resonance scattering spectral technique, and smaller nanogold exhibited stronger catalytic enhancement effect in pH 4.2 sodium acetate–acetic acid buffer solution. The resonance scattering intensity at 610 nm increased linearly with the concentrations of 0.02 to 1.60, 0.040 to 1.20, and 0.12 to 4.70 nM nanogold in sizes of 5, 10, and 15 nm with detection limits of 0.010, 0.030, and 0.10 nM, respectively. An immunonanogold-catalytic resonance scattering bioassay was established, combining the immunonanogold-catalytic effect on CuSO 4–ascorbic acid reaction with the resonance scattering detection technique. As a model, 0.03 to 7.5 ng ml −1 immunoglobulin G can be assayed by this immunonanogold-catalytic resonance scattering bioassay with a detection limit of 0.015 ng ml −1.

Catalytic Enhancement Effect of a Chiral Ligand on the Asymmetric Mannich­-Type Reactions of Menthyl Alkanoates with Aldimines

The lithium enolate of menthyl acetate underwent the Mannich-type reaction with benzaldehyde PMP-imine in toluene to give the corresponding adduct with 70:30 dr. The diastereoselectivity was dramatically improved to 97:3 dr by the addition of chiral 1,2-diphenyl-1,2-dimethoxyethane. The reaction of menthyl isobutyrate with imines was also influenced by a catalytic amount (5 mol%) of a chiral tridentate aminodiether ligand to give the corresponding β-lactams in high enantioselectivities. Matching and mismatching phenomena were observed by the reaction of t.- and D-menthyl isobutyrates.

Ab initio study of the catalytic effect of H 2O on the self-reaction of HO 2

The catalytic enhancement effect of H 2O on the self-reaction of HO 2 has been studied at the G2M//B3LYP/6-311G(d,p) level of theory. The lowest channel producing O 2 ( 1Δ) was also calculated at the CAS(12,12)/6-311G(d,p)//CAS(2,2)/6-31G(d) level. Comparing with the results for the reaction without H 2O, we note that the H 2O molecule catalytically reduces the barrier for O 2 ( 1Δ) formation by 1–3 kcal/mol and those for the formation of the ground state O 2 and O 3 by as much as 6–7 and 4–8 kcal/mol, respectively. Significantly, O 3 formation becomes competitive with the formation of O 2.

A channel flow cell system specifically designed to test the efficiency of redox shuttles in dye sensitized solar cells

The construction and use of a thin layer flow cell test system employing a TiO 2 working electrode, a platinum quasi-reference electrode and the ruthenium dye (H 2-dcbpy)Ru(NCS) 2 (H 2-dcbpy=2,2′-bipyridine-4,4′-dicarboxylic acid) is described. The efficient design enables significant advantages to be gained over presently available procedures for the measurement of photocurrents of dye-sensitized solar cells. The widely used iodide/triiodide redox shuttle system has been investigated over a wide range of conditions. A linear dependence of photocurrent on cation radius was revealed. Under certain conditions, the photocurrent measured in the presence of the Li + cation is five times larger than when the (C 4H 9) 4N + cation is used. Additionally, the addition of low concentrations of cations with small diameters has a significant catalytic enhancement effect on the photocurrent. Other redox shuttles, based on ferrocene, thiocyanate, triiodide and bromide, were tested for their performance in the flow cell and compared to iodide. However, despite some apparent thermodynamic advantages, the photocurrents obtained with these redox shuttles were more than two orders of magnitude lower than those measured with iodide. This finding implies that the efficiency of redox shuttles is limited by kinetic restraints rather than their thermodynamic properties and confirms that the iodide/triiodide system is the dominant redox shuttle.