NMR Investigation of n-Alkylamine Self-Organization Along the Sidewalls of Single-Wall Carbon Nanotubes (SWNTs)
- PDF / 240,753 Bytes
- 2 Pages / 612 x 792 pts (letter) Page_size
- 64 Downloads / 171 Views
HH3.18.1
NMR Investigation of n-Alkylamine SelfOrganization Along the Sidewalls of SingleWall Carbon Nanotubes (SWNTs) †
†, ‡
Sang-Yong Ju, Marcel Utz
O
oxalyl chloride DMF
A
NH4OH
B
LiAlH4
C
OH O Cl
†, §
, and Fotios Papadimitrakopoulos
O
† Institute of Materials Science, University of Connecticut, ‡ Department of Physics, University of Connecticut, § Department of Chemistry, University of Connecticut
19
17
15
13
11
NH2
9 7
20
18
16
14
12
10
8
6 3 5
INTRODUCTION Single wall carbon nanotubes (SWNTs) have drawn considerable attention from the scientific community based on their potentially unique 1 1-D electronic and optical properties as well as mechanical properties. These characteristics result from the one dimensional quantum wire structure of CNTs, which have the spike-like van Hove singularities (vHs) in the electronic density of states. The detailed shape of the density of states function depends sensitively on CNT type semiconducting (sem-) versus metallic (met-)), diameter and chirality. Using the preferential affinity of amines towards sem-SWNTs, our group has been able to attain bulk separation by type based on a differential solubility of SWNTs according to the amine organization interaction on 2 the nanotube surface. It has been argued that stable dispersions of sem-SWNTs with surfactant-amines originate from the organization of the aliphatic chain along the nanotube sidewalls, along with a small amount of zwitterions. The separation of sem-enriched SWNTs assisted by octadecylamine (ODA) had been depicted in the form of either small amount of zwitterionic interaction between carboxylic acid groups of acid-purified SWNTs or the physisorption on the SWNTs sidewall, leaving met-SWNTs in the precipitate. In this report, NMR spectroscopy will be used to characterize the dynamic mobility of different molecular segments along the hydrocarbon chain of physisorped amines in the 3 presence and in the absence of SWNTs. The study by Min Xu et al. reported that α, β and γ-methylene groups adjacent to amine of ODA reacted with multi-wall carbon nanotube (MWNT) treated with thionyl 13 chloride were disappeared in the solid-state C NMR. However, since they used covalent chemistry between carboxylic chloride of MWNT and ODA, the nature of chemical bonding, along the relatively “flat” surface of MWNT than that of SWNT, cannot be applied directly to SWNTs case. Nevertheless, the methylene units in ODA are not well resolved in 1 13 either the H or the C NMR specta. The introduction of a diacetylenic moiety in the chain of surfactant enables us to differentiate the proton and carbon peaks along the backbone due to the magnetic anisotropy of diacetylenic group without resorting to site-specific deuteratation. Moreover, it is reported that the diacetylene-derived amphiphilics showed a nanoscale tubular or complex self-assembled integrity, as well as various assembled forms such as Langmuir-Blodgette monolayer or vesicular bilayer membrane. Therefore, it can be imagined that the diacetylenic amphi
Data Loading...
