Noncovalent functionalization of single-walled carbon nanotubes by indocyanine green: Potential nanocomplexes for photothermal therapy

Abstract

Indocyanine green (ICG) is a functional dye with a variety of unique photomechanical, photochemical and photobiological properties. Single-walled carbon nanotubes (SWNTs) are promising new materials being used in biological and medical fields. In this paper, we reveal that ICG can directly dissolve SWNTs without covalent chemical functionalization of the tubes or the use of surfactants in aqueous solution. The ICG-SWNT complexes have been characterized with absorption, fluorescence and Raman spectroscopy. It is demonstrated that ICG molecules that affect nanotubes properties are also altered by the presence of the SWNTs. These results provide an important evidence to better understand the π–π interactions between aromatic molecules and sidewalls of nanotubes. The broad absorption spectrum of ICG-SWNT complexes ranging from the UV to the near-infrared (NIR) regions opens this novel nanosystem to potential applications in the cancer photothermal therapy.