Towards an Atomic-Scale Understanding of the Adsorbate-Driven Formation of High-Index Faces

Preferential adsorption takes place at the step ledge between adjacent crystal faces, which usually serve as active sites for breaking chemical bonds. In this paper, we present a structural model to interpret the habit modification of single crystals in terms of the step geometries relationship between crystal faces. A new series of high index faces parallel to the ledge between adjacent facets can be explicitly determined from the presence of the symmetry operators in the space group. The relative stability of these new faces undergoes a faceting transition, driven by the adsorbate-induced changes of the step configuration. Combined with the chemical bond-geometric approach, our predictions accurately reproduce the tapering evolutions of KDP crystals in the present of metallic ions. The current work provides a new insight on how changes affecting elementary steps on one face are translated into the emergence of a new crystallographic face.

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What catalysis needs from the electron microscopist

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105539 ◽

1988 ◽

Vol 46 ◽

pp. 694-695

Author(s):

Alexis T. Bell

Keyword(s):

Active Sites ◽

Heterogeneous Catalysts ◽

Catalyst Deactivation ◽

Surface Composition ◽

Internal Surface ◽

Active Phase ◽

Atomic Scale ◽

Metal Catalyst ◽

Internal Surface Area ◽

Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

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Seamless Separation of OHad and Had on a Ni-O Catalyst Toward Exceptional Alkaline Hydrogen Evolution

Journal of Materials Chemistry A ◽

10.1039/d1ta07303f ◽

2022 ◽

Author(s):

Jiangtian Li ◽

Deryn Chu ◽

David R Baker ◽

Rongzhong Jiang

Keyword(s):

Hydrogen Evolution ◽

Active Sites ◽

Atomic Scale

A seamless separation of intermediates (OHad and Had) to different active sites at atomic scale is realized on a Ni-O catalyst that is functionalized with low-coordinated oxygen and abundant vacancies....

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The structure and activity of potassium supported on SBA-15 molecular sieve: Density functional theory study

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633613500764 ◽

2014 ◽

Vol 13 (01) ◽

pp. 1350076 ◽

Cited By ~ 2

Author(s):

Bing Liu ◽

Daxi Wang ◽

Zhongxue Wang ◽

Zhen Zhao ◽

Yu Chen ◽

...

Keyword(s):

Density Functional Theory ◽

Lewis Acid ◽

Molecular Sieve ◽

Active Sites ◽

Density Functional ◽

Structural Model ◽

Vibrational Frequencies ◽

Oxygen Molecule ◽

Lewis Base ◽

Functional Theory

The geometries, vibrational frequencies, electronic properties and reactivity of potassium supported on SBA-15 have been theoretically investigated by the density functional theory (DFT) method. The structural model of the potassium supported on SBA-15 was constructed based on our previous work [Wang ZX, Wang DX, Zhao Z, Chen Y, Lan J, A DFT study of the structural units in SBA-15 mesoporous molecular sieve, Comput. Theor. Chem.963, 403, 2011]. This paper is the extension of our previous work. The most favored location of potassium atom was obtained by the calculation of substitution energy. The calculated vibrational frequencies of K /SBA-15 are in good agreement with the experimental results. By analyzing the properties of electronic structure, we found that the O atom of Si - O (2)- K group acts as the Lewis base center and the K atom acts as the Lewis acid center. The reactivity of K /SBA-15 was investigated by calculating the activation of oxygen molecule. The oxygen molecule can be activated by K /SBA-15 with an energy barrier of 103.2 kJ/mol. In the final state, the activated oxygen atoms become new Lewis acid centers, which are predicted to act as the active sites in the catalytic reactions. This study provides a deep insight into the properties of supported potassium catalysts and offers fundamental information for further research.

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Structural Modeling and Analysis of Pregnancy-Associated Glycoprotein-1 of Buffalo (Bubalus bubalis)

ISRN Molecular Biology ◽

10.5402/2012/481539 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Jerome Andonissamy ◽

S. K. Singh ◽

S. K. Agarwal

Keyword(s):

Protein Structure ◽

Active Sites ◽

Structural Model ◽

Protein Structures ◽

Structural Modeling ◽

Bubalus Bubalis ◽

High Energy ◽

Docking Studies ◽

Modeling And Analysis ◽

Structural Conformity

The present study was conducted to design and analyze the structural model of buffalo pregnancy-associated glycoprotein-1 (PAG-1) using bioinformatics. Structural modeling of the deduced buffalo PAG-1 protein was done using PHYRE, CONSURF servers and its structure was subsequently constructed using MODELLER 9.9 and PyMOL softwares Buffalo PAG-1 structural conformity was analyzed using PROSA, WHATIF, and 3D-PSSM servers. Designed buffalo PAG-1 protein structure on BLAST analysis retrieved protein structures belonging to aspartic proteinase family. Moreover in silico analysis revealed buffalo PAG-1 protein retained bilobed structure with pepstatin-binding clefts near the active sites by docking studies with pepstatin A using PatchDock server. Structural studies revealed that the amino and carboxy terminal containing aspartic residues are highly conserved and buried within the protein structure. Structural conformity studies showed that more than 90% of the residues lie inside favored and allowed regions. It was also deduced that buffalo PAG-1 possesses low and high energy zones with a very low threshold for proteolysis ascertaining the stableness of the buffalo PAG-1 protein structure. This study depicts the structural conformity and stability of buffalo PAG-1 protein.

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Graphene oxide based dopamine mussel-like cross-linked polyethylene imine nanocomposite coating with enhanced hexavalent uranium adsorption

Journal of Materials Chemistry A ◽

10.1039/c9ta04562g ◽

2019 ◽

Vol 7 (28) ◽

pp. 16902-16911 ◽

Cited By ~ 64

Author(s):

Songwei Li ◽

Peipei Yang ◽

Xianhu Liu ◽

Jiaoxia Zhang ◽

Wei Xie ◽

...

Keyword(s):

Graphene Oxide ◽

Active Sites ◽

Nanocomposite Coating ◽

Polyethylene Imine ◽

Uranium Adsorption ◽

Hexavalent Uranium ◽

Preferential Adsorption ◽

Excellent Stability

GO-pDA-PEI with excellent stability provided enough movement space and active sites for highly preferential adsorption of U(vi).

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A structural model for across membrane coupling between the Qo and Qi active sites of cytochrome bc1

Biochimica et Biophysica Acta (BBA) - Bioenergetics ◽

10.1016/j.bbabio.2010.05.013 ◽

2010 ◽

Vol 1797 (12) ◽

pp. 1842-1848 ◽

Cited By ~ 14

Author(s):

Jason W. Cooley

Keyword(s):

Active Sites ◽

Structural Model ◽

Cytochrome Bc1

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Vectorized magnetometer for space applications using electrical readout of atomic scale defects in silicon carbide

Scientific Reports ◽

10.1038/srep37077 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 27

Author(s):

Corey J. Cochrane ◽

Jordana Blacksberg ◽

Mark A. Anders ◽

Patrick M. Lenahan

Keyword(s):

Solid State ◽

Large Scale ◽

Atomic Scale ◽

Radiation Environment ◽

Optically Pumped ◽

Space Applications ◽

Viable Solution ◽

Jovian System ◽

Induced Changes ◽

Venusian Surface

Abstract Magnetometers are essential for scientific investigation of planetary bodies and are therefore ubiquitous on missions in space. Fluxgate and optically pumped atomic gas based magnetometers are typically flown because of their proven performance, reliability, and ability to adhere to the strict requirements associated with space missions. However, their complexity, size, and cost prevent their applicability in smaller missions involving cubesats. Conventional solid-state based magnetometers pose a viable solution, though many are prone to radiation damage and plagued with temperature instabilities. In this work, we report on the development of a new self-calibrating, solid-state based magnetometer which measures magnetic field induced changes in current within a SiC pn junction caused by the interaction of external magnetic fields with the atomic scale defects intrinsic to the semiconductor. Unlike heritage designs, the magnetometer does not require inductive sensing elements, high frequency radio, and/or optical circuitry and can be made significantly more compact and lightweight, thus enabling missions leveraging swarms of cubesats capable of science returns not possible with a single large-scale satellite. Additionally, the robustness of the SiC semiconductor allows for operation in extreme conditions such as the hot Venusian surface and the high radiation environment of the Jovian system.

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