Effect of CeO2 Presence on the Electronic Structure and the Activity for Ethanol Oxidation of Carbon Supported Pt

Pt/CeO2/C electrocatalysts in different compositions were prepared and their structural characteristics and activities for ethanol oxidation in alkaline media were evaluated. In the presence of CeO2, an increase in the platinum particle size was observed. XANES measurements indicated that the Pt d-band vacancies increased with increasing CeO2 amounts. For the first time, the decrease in electro activity was described to an electronic effect for high CeO2 contents. The dependence of the activity for ethanol oxidation on CeO2 content went to a maximum, due to the counteracting bifunctional and electronic effects of the metal oxide.

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Tuning the electronic structure of PtRu bimetallic nanoparticles for promoting the hydrogen oxidation reaction in alkaline media

Inorganic Chemistry Frontiers ◽

10.1039/c9qi00942f ◽

2019 ◽

Vol 6 (10) ◽

pp. 2900-2905 ◽

Cited By ~ 6

Author(s):

Chang Long ◽

Kun Wang ◽

Yanan Shi ◽

Zhongjie Yang ◽

Xiaofei Zhang ◽

...

Keyword(s):

Electronic Structure ◽

Oxidation Reaction ◽

Electronic Effect ◽

Bimetallic Nanoparticles ◽

Hydrogen Oxidation ◽

Alkaline Media ◽

Hydrogen Oxidation Reaction

Alloying degree of PtRu bimetallic nanoparticles can be controlled to finely tune electronic effect for enhanced Hydrogen oxidation reaction in alkaline.

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New Insights into the Nature of the Band Gap of CuGeO3 Nanoparticles: Synthesis, Electronic Structure, and Optical and Photocatalytic Properties

10.26434/chemrxiv.8362409.v1 ◽

2019 ◽

Author(s):

Victor Y. Suzuki ◽

Luís Henrique Cardozo Amorin ◽

Natália H. de Paula ◽

Anderson R. Albuquerque ◽

Julio Ricardo Sambrano ◽

...

Keyword(s):

Electronic Structure ◽

Band Gap ◽

Material Design ◽

Photocatalytic Properties ◽

Critical Parameters ◽

Synthetic Approach ◽

Microwave Assisted ◽

Theoretical Approaches ◽

Nanoparticles Synthesis ◽

First Time

We report, for the first time, new insights into the nature of the band gap of <a>CuGeO3 </a>(CGO) nanocrystals synthesized from a microwave-assisted hydrothermal method in the presence of citrate. To the best of our knowledge, this synthetic approach has the shortest reaction time and it works at the lowest temperatures reported in the literature for the preparation of these materials. The influence of the surfactant on the structural, electronic, optical, and photocatalytic properties of CGO nanocrystals is discussed by a combination of experimental and theoretical approaches, and that results elucidates the nature of the band gap of synthetized CGO nanocrystals. We believe that this particular strategy is one of the most critical parameters for the development of innovative applications and that result could shed some light on the emerging material design with entirely new properties.

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Redox Potential - (Electronic) Structure Relationships in 18- and 17-Electron Mononitrile (or Monocarbonyl) Diphosphine Complexes of Re and Fe

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20010139 ◽

2001 ◽

Vol 66 (1) ◽

pp. 139-154 ◽

Cited By ~ 11

Author(s):

M. Fátima C. Guedes Da Silva ◽

Luísa M. D. R. S. Martins ◽

João J. R. Fraústo Da Silva ◽

Armando J. L. Pombeiro

Keyword(s):

Cyclic Voltammetry ◽

Electronic Structure ◽

Binding Sites ◽

Closed Shell ◽

Carbonyl Complexes ◽

Metal Centre ◽

Pt Electrode ◽

Metal Site ◽

Oxidation Potentials ◽

First Time

The organonitrile or carbonyl complexes cis-[ReCl(RCN)(dppe)2] (1) (R = 4-Et2NC6H4 (1a), 4-MeOC6H4 (1b), 4-MeC6H4 (1c), C6H5 (1d), 4-FC6H4 (1e), 4-ClC6H4 (1f), 4-O2NC6H4 (1g), 4-ClC6H4CH2 (1h), t-Bu (1i); dppe = Ph2PCH2CH2PPh2), or cis-[ReCl(CO)(dppe)2] (2), as well as trans-[FeBr(RCN)(depe)2]BF4 (3) (R = 4-MeOC6H4 (3a), 4-MeC6H4 (3b), C6H5 (3c), 4-FC6H4 (3d), 4-O2NC6H4 (3e), Me (3f), Et (3g), 4-MeOC6H4CH2 (3h); depe = Et2PCH2CH2PEt2), novel trans-[FeBr(CO)(depe)2]BF4 (4) and trans-[FeBr2(depe)2] (5) undergo, as revealed by cyclic voltammetry at a Pt-electrode and in aprotic non-aqueous medium, two consecutive reversible or partly reversible one-electron oxidations assigned as ReI → ReII → ReIII or FeII → FeIII → FeIV. The corresponding values of the oxidation potentials IE1/2ox and IIE1/2ox (waves I and II, respectively) correlate with the Pickett's and Lever's electrochemical ligand and metal site parameters. This allows to estimate these parameters for the various nitrile ligands, depe and binding sites (for the first time for a FeIII/IV couple). The electrochemical ligand parameter show dependence on the "electron-richness" of the metal centre. The values of IE1/2ox for the ReI complexes provide some supporting for a curved overall relationship with the sum of Lever's electrochemical ligand parameter. The Pickett parametrization for closed-shell complexes is extended now also to 17-electron complexes, i.e. with the 15-electron ReII and FeIII centres in cis-{[ReCl(dppe)2]}+ and trans-{FeBr(depe)2}2+, respectively.

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Structure-Properties Correlation of Cross-Linked Penicillin G Acylase Crystals

Crystals ◽

10.3390/cryst11040451 ◽

2021 ◽

Vol 11 (4) ◽

pp. 451

Author(s):

Marta Kubiak ◽

Janine Mayer ◽

Ingo Kampen ◽

Carsten Schilde ◽

Rebekka Biedendieck

Keyword(s):

Mechanical Stability ◽

Structural Characteristics ◽

Penicillin G ◽

Bacillus Species ◽

Diffusion Limitations ◽

Small Water ◽

Long Term Stability ◽

Atomic Force ◽

First Time

In biocatalytic processes, the use of free enzymes is often limited due to the lack of long-term stability and reusability. To counteract this, enzymes can be crystallized and then immobilized, generating cross-linked enzyme crystals (CLECs). As mechanical stability and activity of CLECs are crucial, different penicillin G acylases (PGAs) from Gram-positive organisms have proven to be promising candidates for industrial production of new semisynthetic antibiotics, which can be crystallized and cross-linked to characterize the resulting CLECs regarding their mechanical and catalytic properties. The greatest hardness and Young’s modulus determined by indentation with an atomic force microscope were observed for CLECs of Bacillus species FJAT-PGA CLECs (26 MPa/1450 MPa), followed by BmPGA (Priestia megaterium PGA, 23 MPa/1170 MPa) and BtPGA CLECs (Bacillus thermotolerans PGA, 11 MPa/614 MPa). In addition, FJAT- and BtPGA CLECs showed up to 20-fold higher volumetric activities compared to BmPGA CLECs. Correlation to structural characteristics indicated that a high solvent content and low number of cross-linking residues might lead to reduced stability. Furthermore, activity seems to be restricted by small water channels due to severe diffusion limitations. To the best of our knowledge, we show for the first time in this study that the entire process chain for the characterization of diverse industrially relevant enzymes can be performed at the microliter scale to discover the most important relationships and limitations.

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Sol-Gel Synthesis of the Double Perovskite Sr2FeMoO6 by Microwave Technique

Materials ◽

10.3390/ma14143876 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3876

Author(s):

Jesús Valdés ◽

Daniel Reséndiz ◽

Ángeles Cuán ◽

Rufino Nava ◽

Bertha Aguilar ◽

...

Keyword(s):

Particle Size ◽

Hydrothermal Synthesis ◽

Microwave Radiation ◽

Structural Characteristics ◽

Sol Gel ◽

Synthesis Method ◽

Double Perovskite ◽

Synthesis Methods ◽

X Ray ◽

Sol Gel Synthesis

The effect of microwave radiation on the hydrothermal synthesis of the double perovskite Sr2FeMoO6 has been studied based on a comparison of the particle size and structural characteristics of products from both methods. A temperature, pressure, and pH condition screening was performed, and the most representative results of these are herein presented and discussed. Radiation of microwaves in the hydrothermal synthesis method led to a decrease in crystallite size, which is an effect from the reaction temperature. The particle size ranged from 378 to 318 nm when pH was 4.5 and pressure was kept under 40 bars. According to X-ray diffraction (XRD) results coupled with the size-strain plot method, the product obtained by both synthesis methods (with and without microwave radiation) have similar crystal purity. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques showed that the morphology and the distribution of metal ions are uniform. The Curie temperature obtained by thermogravimetric analysis indicates that, in the presence of microwaves, the value was higher with respect to traditional synthesis from 335 K to 342.5 K. Consequently, microwave radiation enhances the diffusion and nucleation process of ionic precursors during the synthesis, which promotes a uniform heating in the reaction mixture leading to a reduction in the particle size, but keeping good crystallinity of the double perovskite. Precursor phases and the final purity of the Sr2FeMoO6 powder can be controlled via hydrothermal microwave heating on the first stages of the Sol-Gel method.

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Nanostructured TiO2-Based Composites for Light Absorption

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.975.207 ◽

2014 ◽

Vol 975 ◽

pp. 207-212

Author(s):

Dayse I. dos Santos ◽

Olayr Modesto Jr. ◽

Luis Vicente A. Scalvi ◽

Americo S. Tabata

Keyword(s):

Metal Oxide ◽

Light Absorption ◽

Structural Characteristics ◽

Sol Gel ◽

Second Phase ◽

X Ray Diffraction ◽

Two Phase ◽

X Ray ◽

Oxide Powders

Metal oxide nanocomposites were prepared by two different routes: polyol and sol-gel. Characterization by X ray diffraction showed that the first process produces directly a two-phase material, while the sol-gel powder never showed second phase below 600°C. Light spectroscopy of the treated powders indicated similarities for the processed materials. Although the overall material compositions are about the same, different structural characteristics are found for each processing. With the exception of Ti-Zn materials, all the double metal oxide powders showed higher absorbance than either TiO2 powder.

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First-principles study of electronic structure, chemical bonding and elastic properties for new superconductor CaFeAs2

International Journal of Modern Physics B ◽

10.1142/s0217979216502635 ◽

2017 ◽

Vol 31 (02) ◽

pp. 1650263

Author(s):

J. G. Yan ◽

Z. J. Chen ◽

G. B. Xu ◽

Z. Kuang ◽

T. H. Chen ◽

...

Keyword(s):

Electronic Structure ◽

Elastic Properties ◽

Density Of States ◽

First Principles ◽

Elastic Anisotropy ◽

First Principles Calculation ◽

Hard Material ◽

Dirac Cone ◽

First Time ◽

New Superconductor

Using first-principles calculation we investigated the structural, electronic and elastic properties of paramagnetic CaFeAs2. Our results indicated that the density of states (DOS) was dominated predominantly by Fe-3[Formula: see text] states at Fermi levels, and stronger hybridization exists between As1 and As1 atoms. Three hole pockets are formed at [Formula: see text] and Z points, and two electronic pockets are formed at A and E points. The Dirac cone-like bands appear near B and D points. For the first time we calculated the elastic properties and found that CaFeAs2 is a mechanically stable and moderately hard material, it has elastic anisotropy and brittleness, which agrees well with the bonding picture and the calculation of Debye temperature ([Formula: see text]).

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