Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

Short Communication: Synthesis of Polymer-Embedded Metal Clusters by Thermolysis of Mercaptides—Polymer Blends

Polymer News ◽  
2005 ◽  
Vol 30 (9) ◽  
pp. 296-300
Author(s):  
F. Esposito ◽  
V. Casuscelli ◽  
M. V. Volpe ◽  
G. Carotenuto ◽  
L. Nicolais
Keyword(s):  
Polymer Blends ◽  
Short Communication ◽  
Metal Clusters ◽  
Communication Synthesis

An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

2020 ◽  
Author(s):  
Peter T. Smith ◽  
Sophia Weng ◽  
Christopher Chang
Keyword(s):  
Proton Transfer ◽  
Co2 Reduction ◽  
Iron Porphyrin ◽  
Redox Mediators ◽  
Reservoir Properties ◽  
Proton Reduction ◽  
Electrochemical Co2 Reduction ◽  
Starting Point ◽  
Rate Improvement ◽  
Molecular Catalysts

We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO<sub>2</sub> to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO<sub>2</sub> versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO<sub>2</sub> reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

Host-Guest Interactions on Electrode Surfaces for Immobilization of Molecular Catalysts

2020 ◽  
Author(s):  
Laurent Sévery ◽  
Jacek Szczerbiński ◽  
Mert Taskin ◽  
Isik Tuncay ◽  
Fernanda Brandalise Nunes ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Heterogeneous Systems ◽  
Catalytic Systems ◽  
New Approach ◽  
Molecular Systems ◽  
Electrode Surfaces ◽  
Catalytic Surfaces ◽  
Oxide Electrodes ◽  
The Stability ◽  
Molecular Catalysts

The strategy of anchoring molecular catalysts on electrode surfaces combines the high selectivity and activity of molecular systems with the practicality of heterogeneous systems. The stability of molecular catalysts is, however, far less than that of traditional heterogeneous electrocatalysts, and therefore a method to easily replace anchored molecular catalysts that have degraded could make such electrosynthetic systems more attractive. Here, we apply a non-covalent “click” chemistry approach to reversibly bind molecular electrocatalysts to electrode surfaces via host-guest complexation with surface-anchored cyclodextrins. The host-guest interaction is remarkably strong and allows the flow of electrons between the electrode and the guest catalyst. Electrosynthesis in both organic and aqueous media was demonstrated on metal oxide electrodes, with stability on the order of hours. The catalytic surfaces can be recycled by controlled release of the guest from the host cavities and readsorption of fresh guest. This strategy represents a new approach to practical molecular-based catalytic systems.

Structural reconstruction of germanosilicate frameworks by controlled hydrogen reduction

2019 ◽  
Vol 55 (13) ◽  
pp. 1883-1886 ◽  
Author(s):  
Yue Ma ◽  
Hao Xu ◽  
Xue Liu ◽  
Mingming Peng ◽  
Wenting Mao ◽  
...  
Keyword(s):  
Metal Clusters ◽  
Hydrogen Reduction ◽  
Hydrogen Atmosphere ◽  
Water Washing

Calcined UTL-type germanosilicate was firstly reduced in a hydrogen atmosphere at an appropriate temperature. Then, air-calcination and water-washing procedures were performed to remove the Ge metal clusters or crystals originated from the reduction of skeleton germanium(iv) to yield pure zeolite phase of two daughter structures analogous to IPC-2 and IPC-6.

scholarly journals Heterogenisation of polyoxometalates and other metal-based complexes in metal–organic frameworks: from synthesis to characterisation and applications in catalysis

2021 ◽  
Author(s):  
P. Mialane ◽  
C. Mellot-Draznieks ◽  
P. Gairola ◽  
M. Duguet ◽  
Y. Benseghir ◽  
...  
Keyword(s):  
Metal Organic Frameworks ◽  
Coordination Complexes ◽  
Metal Organic ◽  
Non Covalent Interactions ◽  
Molecular Catalysts ◽  
Covalent Interactions

This review provides a thorough overview of composites with molecular catalysts (polyoxometalates, or organometallic or coordination complexes) immobilised into MOFs via non-covalent interactions.

scholarly journals Structural tuning of heterogeneous molecular catalysts for electrochemical energy conversion

2021 ◽  
Vol 7 (13) ◽  
pp. eabf3989
Author(s):  
Jiong Wang ◽  
Shuo Dou ◽  
Xin Wang
Keyword(s):  
Energy Conversion ◽  
Model Systems ◽  
Structural Variations ◽  
Metal Centers ◽  
Electrochemical Energy Conversion ◽  
Electronic Configurations ◽  
Coordination Spheres ◽  
The Stability ◽  
Molecular Catalysts ◽  
Electrochemical Energy

Heterogeneous molecular catalysts based on transition metal complexes have received increasing attention for their potential application in electrochemical energy conversion. The structural tuning of first and second coordination spheres of complexes provides versatile strategies for optimizing the activities of heterogeneous molecular catalysts and appropriate model systems for investigating the mechanism of structural variations on the activity. In this review, we first discuss the variation of first spheres by tuning ligated atoms; afterward, the structural tuning of second spheres by appending adjacent metal centers, pendant groups, electron withdrawing/donating, and conjugating moieties on the ligands is elaborated. Overall, these structural tuning resulted in different impacts on the geometric and electronic configurations of complexes, and the improved activity is achieved through tuning the stability of chemisorbed reactants and the redox behaviors of immobilized complexes.

Insights into oxygen activation on metal clusters for catalyst design

2021 ◽  
Author(s):  
LiXin Chen ◽  
Zi Wen ◽  
Zhi Wen Chen ◽  
Qing Jiang ◽  
Chandra Veer Singh
Keyword(s):  
Metal Clusters ◽  
Aerobic Oxidation ◽  
Oxygen Activation ◽  
Vital Role ◽  
Catalyst Design ◽  
Activation Mechanism ◽  
Oxidation Reactions

The activation mechanism of O2 molecules plays a vital role in the development of catalysts for aerobic oxidation reactions. To gain insights into the activation mechanism of O2, the square...

Sign in / Sign up

Export Citation Format

Share Document