The Decompositions of Fluorescent Defects and Pristine Structure in (6,5) Carbon Nanotubes Using Various Oxidants

Abstract

Fluorescent quantum defects in single-wall carbon nanotubes (SWCNTs) are outstanding candidates as fluorophores for in vivo biomedical imaging applications such as image-guided surgeries and single-cell tracking. Their longer wavelength emission in the short-wave infrared penetrates biological tissues deeper than visible and NIR light. In addition, fluorescent quantum defects can enhance fluorescence brightness by a factor of ~9 compared to the pristine SWCNT emission. Besides their exceeding optical properties, the degradations of SWCNTs in biological and environmental systems are also of importance, but still not well understood yet. This study utilizes sodium hypochlorite (NaClO) and hydrogen peroxide (H2O2) to examine the chemical decompositions of pristine and defect-containing SWCNTs. We found that the oxidation rate of NaClO is ~5 times faster than that of H2O2, showing an obvious oxidant-dependent degradation kinetics. It is also worth mentioning that when using NaClO as the oxidant, the oxidation rate is significantly increased under acidic conditions, probably due to the increased concentration of hypochlorous acid (HOCl). In contrast, H2O2 prefers to oxidize the pristine structure. It is also found that SWCNT coating materials including SDS, SC, and ssDNA might protect the surface structures, especially the defects, from oxidant attacks. We believe our study will lead to a better understanding of the SWCNT degradation, providing valuable insights for future clinical applications.