Syntheses and Catalytic Properties of 1-Naphthoate-Copper-Bipy Complex

BackgroundCellobiose dehydrogenase from Phanerochaete chrysosporium (PcCDH) is a key enzyme in lignocellulose depolymerization, biosensors and biofuel cells. For these applications, it should retain important molecular and catalytic properties when recombinantly expressed. While homologous expression is time-consuming and the prokaryote Escherichia coli is not suitable for expression of the two-domain flavocytochrome, the yeast Pichia pastoris is hyperglycosylating the enzyme. Fungal expression hosts like Aspergillus niger and Trichoderma reesei were successfully used to express CDH from the ascomycete Corynascus thermophilus. This study describes the expression of basidiomycetes PcCDH in T. reesei (PcCDHTr) and the detailed comparison of its molecular, catalytic and electrochemical properties in comparison with PcCDH expressed by P. chrysosporium and P. pastoris (PcCDHPp).ResultsPcCDHTr was recombinantly produced with a yield of 600 U L−1 after 4 days, which is fast compared to the secretion of the enzyme by P. chrysosporium. PcCDHTr and PcCDH were purified to homogeneity by two chromatographic steps. Both enzymes were comparatively characterized in terms of molecular and catalytic properties. The pH optima for electron acceptors are identical for PcCDHTr and PcCDH. The determined FAD cofactor occupancy of 70% for PcCDHTr is higher than for other recombinantly produced CDHs and its catalytic constants are in good accordance with those of PcCDH. Mass spectrometry showed high mannose-type N-glycans on PcCDH, but only single N-acetyl-d-glucosamine additions at the six potential N-glycosylation sites of PcCDHTr, which indicates the presence of an endo-N-acetyl-β-d-glucosaminidase in the supernatant.ConclusionsHeterologous production of PcCDHTr is faster and the yield higher than secretion by P. chrysosporium. It also does not need a cellulose-based medium that impedes efficient production and purification of CDH by binding to the polysaccharide. The obtained high uniformity of PcCDHTr glycoforms will be very useful to investigate electron transfer characteristics in biosensors and biofuel cells, which are depending on the spatial restrictions inflicted by high-mannose N-glycan trees. The determined catalytic and electrochemical properties of PcCDHTr are very similar to those of PcCDH and the FAD cofactor occupancy is good, which advocates T. reesei as expression host for engineered PcCDH for biosensors and biofuel cells.

Pervaporation membranes endowed with catalytic properties, based on polymer blends

Toward Phase and Catalysis Control: Tracking the Formation of Intermetallic Nanoparticles at Atomic Scale

Granulated polyamide (PA6) was mechanically mixed with copper oxide and copper acetylacetonate powders and with glass fibres, then extruded and injection moulded to produce three types of composites varying in the glass fibre content. The composites were irradiated with a Nd:YAG laser (λ = 1064 nm) and ArF excimer laser (λ = 193 nm). Next, they were electroless metalised by the use of a commercial metallisation bath and formaldehyde as a reducing agent. The surface of the specimens irradiated with the Nd:YAG laser did not exhibit adequate catalytic properties. The sample containing 30 wt-% of the glass fibres showed the best catalytic properties. However, these properties were still insufficient from the viewpoint of applicability. On the other hand, the specimens irradiated with the ArF laser could effectively be metallised. In this case, improvement of the catalytic and adhesion properties of the composites was observed as the glass fibre content was increased.

A perovskite group of materials (ABO3) has a wide range of applications due to their structural diversity, adaptability including exceptional physical and chemical properties. They can accommodate around 90% of metallic elements of the periodic table at positions A and/or B without destroying the matrix structure. This gives an extraordinary possibility of various combinations and scope of complete or partial substitutions of cations resulting incredible large number of compounds with enhanced properties. These materials have been extensively explored for their magnetic, optical, catalytic and electrical properties. Thermal stability and catalytic properties enable them to serve as promising candidates for the control of environmental pollution. The methods of synthesis greatly influence the catalytic properties of perovskites. They have been exploited as oxidants, reductants and photocatalysts due to their enhanced catalytic properties. In addition to catalytic uses, the role of perovskites has also been explored for sensing and adsorption of various aqueous and gas phase species. This article provides an overview including the techniques for synthesis of perovskite materials, properties favouring the catalytic activities and the environmental applications of perovskites towards remediation of various organic pollutants through adsorption and photocatalytic degradation.

MoS2 and other transition metal dichalcogenides (TMDs) have recently gained a renewed interest due to the interesting electronic, catalytic, and mechanical properties which they possess when down-sized to single or few layer sheets. Exfoliation of the bulk multilayer structure can be achieved by a preliminary chemical Li intercalation followed by the exfoliation due to the reaction of Li with water. Organolithium compounds are generally adopted for the Li intercalation with n-butyllithium (n-Bu-Li) being the most common. Here, the use of three different organolithium compounds are investigated and compared, i.e., methyllithium (Me-Li), n-butyllithium (n-Bu-Li) and tert-butyllithium (t-Bu-Li), used for the exfoliation of bulk MoS2 . Scanning transmission electron microscopy (STEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) are adopted for a comprehensive characterization of all materials under investigation. In addition, catalytic properties towards the hydrogen evolution reaction (HER) and capacitive properties are also tested. Different organolithium compounds exhibit different extent of Li intercalation resulting in different degrees of exfoliation. The inherent electrochemical behavior of MoS2 consisting of significant anodic and cathodic peaks as well as its capacitive behavior and catalytic properties towards hydrogen evolution reaction are strongly connected to the exfoliation compound used. This research significantly contributes to the development of large-scale synthesis of electrocatalytic MoS2 -based materials.

The widespread application of SnO2-based semiconductor gas sensors stems from their exceptional sensitivity and stability in detecting various gases, including volatile organic compounds (VOCs). The fundamental mechanism involves the interaction between the semiconductor material's surface and oxidizing or reducing gases, resulting in a change in electrical resistance. Additionally, the receptor function stands out as a pivotal factor influencing the sensing performance of chemical sensors [1]. Modification of the surface of SnO2 with acidic or basic oxides has been shown to effectively alter its catalytic properties, thereby changing the reaction pathways during ethanol oxidation. This study focuses on an acidic oxide, WO3, which is a promising candidate receptor for improving gas selectivity due to its property of not adsorbing oxygen as well as its high sensitivity to VOC gases. Our previous results demonstrated that similar ethanol consumption rates are observed between neat SnO2 and WO3-loaded SnO2 within the range of 150 to 350℃ during catalytic combustion. Over neat SnO2, dehydrogenation is primarily observed, resulting in CH3CHO being the main product at 150℃, with peak production occurring at 250℃, gradually transitioning to CO2. Furthermore, CO2 generation is initiated at 250℃ and rapidly increases at higher temperatures, attributed to the high catalytic activity of SnO2. Conversely, loading WO3 onto the surface of SnO2 successfully modifies the reaction pathway of ethanol oxidation, with the primary reaction shifting from dehydrogenation to dehydration and selectively generating C2H4 at temperature exceeding 300℃. When materials synthesized by different compositing methods are applied in thick film sensors, the interaction between WO3 and SnO2 significantly influences their sensing properties, with the fine dispersion of WO3 playing a crucial role. Both WO3-loaded and mixed SnO2 exhibited higher responses compared to neat SnO2, with the loaded group showing the highest response to ethanol and acetone. Additionally, 3 mol% WO3-loaded SnO2 demonstrated selective detection properties, with the highest response to 20 ppm acetone at 250℃, which was 22.8 times higher than that of neat SnO2.Efforts have also been made to enhance the gas sensing properties of VOC gases by integrating thermal modulation techniques into miniaturized gas sensors, known as MEMS sensors. These sensors enable operation in a pulse-driven mode [2,3], where the microheater is capable of rapidly heating and cooling the sensor device. Such a driving mode offers selectivity due to the gas adsorption and combustion properties occurring during the heating and cooling phases. By utilizing the pulse-driven mode, it is suggested that during the low-temperature heat-off phase, VOC gases adsorb to the surface of particles, followed by their combustion during the high-temperature heat-on phase. This gas detection model facilitates enhancements in both sensitivity and selectivity, capitalizing on the gas adsorption, diffusion, and catalytic combustion properties on the particle surface. Such developments offer significant improvements in gas detection based on catalytic combustion properties. These insights are crucial for the development of high-performance volatile organic compound gas sensor materials.

18 - The use of polymer-graphene composites in catalysis

Structure and composition of perovskite surface in relation to adsorption and catalytic properties

Gold clusters and nanoparticles have attracted continuous attention due to interesting and important electronic, catalytic and optical properties [1,2]. As the chemical environment strongly affects the catalytic properties, an understanding of this is essential to be able to control these properties. In order to study the influence of the ligand shell on the catalytic properties we have studied various gold clusters in interaction with different ligands by performing DFT-D3, SCS-MP2 and CCSD(T) calculations [3,4]. The effect of the ligands to the geometric and electronic structure of the gold clusters is analysed in a systematic way [5,6]. Furthermore as bimetallic gold-palladium catalysts have been found to have improved catalytic properties in various reactions in comparison to the monometallic clusters, the influence of the ligand shell is investigated for small systems.

In the investigation of flow near surfaces with discontinuous changes in the catalytic properties the question arises of the applicability of parabolic boundary and viscous shock layer equations in the neighborhood of the discontinuity. In the present paper, three types of problem are solved in which longitudinal diffusion is taken into account. In the first an insertion with different catalytic properties is placed in the neighborhood of the stagnation point, in the second the discontinuity lines of the catalytic properties are perpendicular to the oncoming flow, while in the third they are parallel. On the main surface and on the insertion surface the heterogeneous catalytic reactions are assumed firstorder reactions with various rate constants whose values vary in a wide range. The data of the solution are compared with the solution obtained using the boundary layer approximation and the regions of influence of the longitudinal diffusion are estimated. In [1–4] a problem similar to the second one was solved by the numerical method of [1] and the Wiener-Hopf method for the case of transition from a noncatalytic to a perfectly catalytic surface and the region of applicability of the boundary layer was estimated [5].

Improved thermostability, acid tolerance as well as catalytic efficiency of Streptomyces rameus L2001 GH11 xylanase by N-terminal replacement

Transition metal dichalcogenides (TMDs) have recently emerged within the group of 2D materials due to their electrical, catalytic and optical properties significantly enhanced and useful when down-sized to single layer. In particular, MoS2 has attracted much attention due to its semiconducting nature with a useful band gap when present as single layer, the enhanced photoluminescence, but also importantly the excellent catalytic properties towards the electrochemical hydrogen evolution. We present here the preparation of thin layers MoS2 nanosheets with enhanced catalytic properties towards the hydrogen evolution reaction by means of an easy and fast electrochemical top-down exfoliation procedure in aqueous solution from a naturally occurring MoS2 crystal. After structural and chemical characterization with STEM, AFM, XPS and Raman spectroscopy electrochemical investigations were performed to test catalytic properties in acidic solution for the electrogeneration of hydrogen and compare it to MoS2 nanosheets obtained through the widely employed chemical Li intercalation/exfoliation. Electrochemically exfoliated MoS2 shows lower Tafel slope than its counterpart obtained with chemical exfoliation.

Effect of rare-earth doping in CeO2 matrix: Correlations with structure, catalytic and visible light photocatalytic properties

Chapter 30 Ecto-nucleotidases—molecular structures, catalytic properties, and functional roles in the nervous system