title: Effect of Lanthanide Metal Complexation on the Properties and Electronic Structure of Single-Walled Carbon Nanotube Films.
abstract: We spectroscopically analyze the effect of e-beam deposition of lanthanide metals on the electronic structure and conductivities of films of semiconducting (SC) single-walled carbon nanotubes (SWNTs) in high vacuum. We employ near-infrared and Raman spectroscopy to interpret the changes in the electronic structure of SWNTs on exposure to small amounts of the lanthanides (Ln = Sm, Eu, Gd, Dy, Ho, Yb), based on the behavior of the reference metals (M = Li, Cr) which are taken to exemplify ionic and covalent bonding, respectively. The analysis shows that while the lanthanides are more electropositive than the transition metals, in most cases they exhibit similar conductivity behavior which we interpret in terms of the formation of covalent bis-hexahapto bonds [(η(6)-SWNT)M(η(6)-SWNT), where M = La, Nd, Gd, Dy, Ho]. However, only M = Eu, Sm, Yb show the continually increasing conductivity characteristic of Li, and this supports our contention that these metals provide the first examples of mixed covalent-ionic bis-hexahapto bonds [(η(6)-SWNT)M(η(6)-SWNT), where M = Sm, Eu, Yb].
authors.affiliation: Department of Chemistry, ‡Center for Nanoscale Science and Engineering, and §Department of Chemical Engineering, University of California , Riverside, California 92521, United States.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Moser
authors.affiliation: Department of Chemistry, ‡Center for Nanoscale Science and Engineering, and §Department of Chemical Engineering, University of California , Riverside, California 92521, United States.
authors.forename: Aron
authors.initials: A
authors.lastname: Pekker
authors.affiliation: Department of Chemistry, ‡Center for Nanoscale Science and Engineering, and §Department of Chemical Engineering, University of California , Riverside, California 92521, United States.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Tian
authors.affiliation: Department of Chemistry, ‡Center for Nanoscale Science and Engineering, and §Department of Chemical Engineering, University of California , Riverside, California 92521, United States.
authors.forename: Elena
authors.initials: E
authors.lastname: Bekyarova
authors.affiliation: Department of Chemistry, ‡Center for Nanoscale Science and Engineering, and §Department of Chemical Engineering, University of California , Riverside, California 92521, United States.
authors.forename: Mikhail E
authors.initials: ME
authors.lastname: Itkis
authors.affiliation: Department of Chemistry, ‡Center for Nanoscale Science and Engineering, and §Department of Chemical Engineering, University of California , Riverside, California 92521, United States.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Haddon
keywords: carbon nanotube film; conductivity; lanthanides; optical properties; organometallic