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Title: Surface-Mediated Synthesis and Spectroscopic Characterization of Tantalum Clusters on Silica

Abstract

Tantalum clusters were synthesized on the surface of porous silica by treatment of adsorbed Ta(CH{sub 2}Ph){sub 5} in H{sub 2} at temperatures in the range of 523-723 K. The surface species were characterized by UV-vis, far-infrared, and extended X-ray absorption fine-structure (EXAFS) spectroscopies, each of which provided evidence of Ta-Ta bonds similar to those in well-characterized molecular tantalum clusters. The Ta-Ta distance determined by EXAFS spectroscopy was 2.93 Angstroms. The chemistry of the cluster synthesis is similar to that of syntheses of similar tantalum clusters in solution. The supported clusters formed at 523 K are characterized by an EXAFS first-shell Ta-Ta coordination number of nearly 2, indicative of tri-tantalum clusters, although it is expected that a mixture of clusters was present, and reduction in H2 at higher temperatures led to larger tantalum clusters. This is the first example of the surface-mediated synthesis of an early transition metal cluster, and the supported clusters reported here are the first to have been characterized by all three of the spectroscopic methods mentioned above. The similarity of the surface synthesis to that in solution points to opportunities to extend this new class of material to other early transition metal clusters on various supports.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914198
Report Number(s):
BNL-78766-2007-JA
Journal ID: ISSN 0743-7463; LANGD5; TRN: US200804%%329
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Langmuir; Journal Volume: 22
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; TANTALUM; MOLECULAR CLUSTERS; SYNTHESIS; SILICON OXIDES; SUBSTRATES; COORDINATION NUMBER; national synchrotron light source

Citation Formats

Nemana,S., and Gates, B. Surface-Mediated Synthesis and Spectroscopic Characterization of Tantalum Clusters on Silica. United States: N. p., 2006. Web. doi:10.1021/la0609322.
Nemana,S., & Gates, B. Surface-Mediated Synthesis and Spectroscopic Characterization of Tantalum Clusters on Silica. United States. doi:10.1021/la0609322.
Nemana,S., and Gates, B. Sun . "Surface-Mediated Synthesis and Spectroscopic Characterization of Tantalum Clusters on Silica". United States. doi:10.1021/la0609322.
@article{osti_914198,
title = {Surface-Mediated Synthesis and Spectroscopic Characterization of Tantalum Clusters on Silica},
author = {Nemana,S. and Gates, B.},
abstractNote = {Tantalum clusters were synthesized on the surface of porous silica by treatment of adsorbed Ta(CH{sub 2}Ph){sub 5} in H{sub 2} at temperatures in the range of 523-723 K. The surface species were characterized by UV-vis, far-infrared, and extended X-ray absorption fine-structure (EXAFS) spectroscopies, each of which provided evidence of Ta-Ta bonds similar to those in well-characterized molecular tantalum clusters. The Ta-Ta distance determined by EXAFS spectroscopy was 2.93 Angstroms. The chemistry of the cluster synthesis is similar to that of syntheses of similar tantalum clusters in solution. The supported clusters formed at 523 K are characterized by an EXAFS first-shell Ta-Ta coordination number of nearly 2, indicative of tri-tantalum clusters, although it is expected that a mixture of clusters was present, and reduction in H2 at higher temperatures led to larger tantalum clusters. This is the first example of the surface-mediated synthesis of an early transition metal cluster, and the supported clusters reported here are the first to have been characterized by all three of the spectroscopic methods mentioned above. The similarity of the surface synthesis to that in solution points to opportunities to extend this new class of material to other early transition metal clusters on various supports.},
doi = {10.1021/la0609322},
journal = {Langmuir},
number = ,
volume = 22,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}