(n,m) Abundance Evaluation of Single-Walled Carbon Nanotubes by Fluorescence and Absorption Spectroscopy

Abstract

A methodology that takes into account the (n,m) structure of single-walled carbon nanotubes (SWNTs), through an exciton-exciton resonance model and an electron-phonon interaction model, was employed in order to evaluate the semiconducting (n,m) abundance of two SWNT samples (i.e., Co-MCM-41 and HiPco). This was based on photoluminescence and near-infrared absorption data obtained on aqueous suspensions of individually dispersed SWNTs. In the absence of known (n,m) abundance SWNT samples, we resorted to determining the diameter distribution curves for both samples, which were found to obey an unsymmetrical log-normal distribution, typical for vapor-phase particle growth. Using this log-normal function, we reconstructed the near-infrared E S11 absorption spectrum of the narrow diameter distribution Co-MCM-41 SWNT sample, which in turn enabled us to assess the predictions of these two theoretical models. High spectral reconstruction accuracy was obtained from the electron-phonon interaction model when considering (11,0) and (10,0) zigzag nanotubes, along with (n,m) line widths inversely proportional to their extinction coefficients.

Dislocation theory of chirality-controlled nanotube growth

“…1 predicts a greater length of nearly armchair tubes relative to rather short and slower growing zigzag. To characterize the tube distribution experimentally it is necessary to unbundle the ropes by sonication (24)(25)(26)(27)(28)(29), in the process breaking the tubes into smaller fragments. Because of the fragmentation, greater length translates into a greater number of fragments, i.e., larger abundance.…”

“…1 predicts a greater abundance of nearly armchair tubes compared to small amounts or no zigzag. After considering common CNT growth methods, such as various CVD [high pressure carbon monoxide HiPco (24), cobalt-molybdenum catalyzed CoMoCat (25), cobalt-catalyzed on MCM-41 template Co-MCM-41 (26), and ACCVD using alcohol as feedstock (27)], arc discharge (28), and laser ablation (29), we present a composite plot of the chiral angle distribution in Fig. 3.…”

Carbon Nanotubes for Electronic and Electrochemical Detection of Biomolecules

“…20 different (n, m) nanotubes. [54][55][56] Figure 2a and b show the DOS versus energy graphs for a representative metallic (7,7)-and semiconducting (11,3)-SWNTs, as calculated from tight-binding theory. [57] The sharp spiked features in both met-and sem-SWNTs DOS are called van Hove singularities.…”

“…[57] These family and modality patterns render the electronic transitions of each nanotube different from that of another, and have enabled the scientific community to collectively assign and characterize individual (n, m)-SWNTs via tunable laser resonance Raman spectroscopy (RRS) and photoluminescence excitation (PLE). [56] These electronic transition differences, however, make SWNT sample homogeneity a major issue. For example, even if a SWNT sample has been separated according to type (met-versus sem-) and d t , [64][65][66][67][68][69][70] different chirality and modality nanotubes will contribute significant heterogeneity as the nanotube diameter gets smaller than 1.5−2 nm.…”

“…[32,79] Photoluminescence excitation mapping, in conjunction with reconstruction of near-infrared absorption spectrum from the S E 11 transition, have recently enabled us to evaluate the semiconducting (n, m)-abundance in a narrow d t SWNT sample. [56,59] Charge-transfer or environmentally induced doping progressively red-shifts and quenches the photoluminescence of sem-SWNTs. [80] Rayleigh scattering, [81] transmission electron microscopy, and electron diffraction [82][83][84] have been also used for (n, m)-characterization of individualized SWNTs, suspended over a trench to remove interference from the substrate.…”