Optical Response Characteristics of Single-Walled Carbon Nanotube Chirality Exposed to Oxidants with Different Oxidizing Power

Abstract

Semiconductor single-walled carbon nanotubes (SWNTs) have unique characteristics owing to differences in the three-dimensional structure (chirality) expressed by the chiral index (n,m), and many studies on the redox characteristics of chirality have been reported. In this study, we investigated the relationship between the chirality of SWNTs and the oxidizing power of oxidants by measuring the near-infrared (NIR) absorption spectra of two double-stranded DNA-SWNT complexes with the addition of three oxidants with different oxidizing powers. A dispersion was prepared by mixing 0.5 mg of SWNT powder with 1 mg/mL of DNA solution. Different concentrations of hydrogen peroxide (H2O2), potassium hexachloroidylate (IV) (K2IrCl6), or potassium permanganate (KMnO4) were added to the dispersion to induce oxidation. Thereafter, a catechin solution was added to observe if the absorbance of the oxidized dispersion was restored by the reducing action of the catechin. We found that the difference in the oxidizing power had a significant effect on the detection sensitivity of the chiralities of the SWNTs. Furthermore, we revealed a detectable range of oxidants with different oxidizing powers for each chirality.

Numerical Analysis for Light Absorption Spectra of the Base of DNA-Wrapped Single-Walled Carbon Nanotubes

“…As shown in Figure 10 , the adenine- and cytosine-wrapped SWCNTs exhibit significant spectral changes beyond 570 nm compared to bare SWCNTs. This result can be expected to support the explanation of the cause of the absorption spectra change of DNA–SWCNTs shown in the previous research [ 11 ]. The experimental results of the light absorption spectra obscure the intrinsic properties of the structure of DNA–SWCNTs due to the composite effects of solvents.…”

“…These findings are expected to accelerate the study of optical characteristics of base-wrapped DNA–SWCNTs. Furthermore, the previous experimental study showed that the peak of the molar absorbance coefficient was observed near 990 nm [ 11 ]. In the previous study, redox reactions were known to change the light absorption spectra, but the cause had not been identified experimentally.…”

“…To safely and effectively demonstrate the functions of DNA–SWCNTs, it is necessary to understand the physical, chemical, and biological properties of DNA–SWCNTs. Dispersion of SWCNTs is possible not only in single-stranded DNA but also in double-stranded DNA (dsDNA), and research is being conducted to examine the optical absorption spectral characteristics to investigate the properties of DNA–SWCNTs as biosensors [ 11 ]. The difference in the light absorption spectra of ssDNA–SWCNT and dsDNA–SWCNT is believed to be due to the difference in the structure of wrapped ssDNA and dsDNA.…”