Strong Micro-Dielectric Environment Effect on the Band Gaps of (n,m)Single-Walled Carbon Nanotubes

Abstract

The electronic states of carbon nanotubes are one of the most fundamental properties of the nanotubes. We now describe the finding that the band gaps of (n,m)SWNTs are strongly affected by the change in microdielectric environments around the isolated nanotubes. In situ photoluminescence (PL) spectroelectrochemistry of the films containing 15 isolated (n,m)single-walled carbon nanotubes (SWNTs) cast on ITO electrodes in organic solvents including DMSO, acetonitirile, DMF, THF, and chloroform was completed and then the oxidation and reduction potentials, and band gaps (ΔE(electr)) of the (n,m)SWNTs in the solvents were determined. We have discovered that the ΔE(electr) of the (n,m)SWNTs become greater as the solvent dielectric constants decreased, which is in sharp contrast to the optical band gaps (ΔE(opt)) that show virtually no solvent dependence. Such a strong solvent dependence of the electrochemical band gaps is due to the difference in the solvation energy of the charged SWNTs produced during the electrochemical processes. The ΔE(electr) of both mod types of the SWNTs, mod = 1 and mod = 2, linearly increased versus the reciprocal of the tube diameter, which agrees with the theory. Moreover, the states of the π-electrons in the SWNTs were evaluated from the dependence of the band gaps on the diameter of the SWNTs. Furthermore, the states of the π-electrons on the sidewalls of the SWNTs were evaluated using the γ(0) values, a parameter representing the measure of the stability or the degree of delocalization of π-electrons in the sidewall of the SWNTs, and revealed that the γ(0) values of the mod = 1 and mod = 2 SWNTs increased with a decrease in the dielectric constants of the solvents in the range of 38-79. This study has enabled us to understand the essential electronic properties of the carbon nanotubes.

Semiconducting single-walled carbon nanotubes sorting with a removable solubilizer based on dynamic supramolecular coordination chemistry

“…4h, sem-SWNTs with (n,m) ¼ (6,5), (7,5), (7,6), (8,3), (8,4), (8,6), (8,7), (9,4), (9,5), (9,7), (10,2), (10,3), (10,5), (10,6), (11,3), (11,4), (11,6) and (12,2) were found to exist in the solution. In order to evaluate the extraction efficiency for each (n,m) chirality of the tubes, we calculated the relative contents of each SWNT based on the calibrated PL intensity using the method reported by Oyama et al 57 The calibrated contents of the SWNT species deduced from the PL mapping are shown in Supplementary Table 1, in which SWNTs with (n,m) ¼ (7,6), (8,6), (9,4) and (10,2) were enriched for the sample using CP-Zn. We also calculated the calibrated contents for the samples using CP-M (M ¼ Co, Ni and Cu; Supplementary Tables 2-4).…”

“…Not only their structural characteristics, but also opto-electronic properties derived from their diameters and chiral indices, denoted as (n,m)SWNTs, are important for a deep understanding of their fundamental intrinsic properties [1][2][3][4][5][6][7][8][9][10] . Highly purified semiconducting SWNTs (sem-SWNTs) not containing metallic SWNTs (met-SWNTs) are specifically required for electronic devices, such as field-effect transistors [11][12][13][14] and photovoltaic applications 15,16 because the met-SWNTs decrease and reduce the efficiency of their associated devices 17,18 .…”

Determination of the spectroscopic properties of indium bromide

“…This portmanteau was introduced to abbreviate this word, but also because this is a new diagram to be used in the interpretation of laser induced fluorescence. Similar diagrams have been used for Raman scattering on carbon nanotubes [29].…”

<i>In Situ </i>Photoluminescence Spectroelectrochemistry for Determination of Electronic States of Single-Walled Carbon Nanotubes

“…To examine the environmental effect, the oxidation and reduction potentials and band gaps (∆E electr ) of the 15 isolated (n, m)-SWNTs cast on ITO electrodes were determined in six different solvents of water, dimethylsulfoxide (DMSO), acetonitrile, N,N-dimethylformamide (DMF), tetrahydrofuran (THF), and chloroform [34], whose dielectric constants are 78.40, 46.68, 37.50, 36.71, 7.58, and 4.81 respectively [35]. The band gaps obtained was compared with the optical band gaps.…”