Probing the degradation of carbon nanotubes in aqueous solution by liquid cell transmission electron microscopy

Understanding the degradation of carbon nanotubes (CNTs) is critically important for their potential biological and environmental applications. In this work, the chemical degradation of CNTs in aqueous solution in the presence of strong oxidizing hydroxyl radicals was directly investigated through liquid cell transmission electron microscopy. The real-time observation on degradation of CNTs revealed three types of degradation behaviors: (Ι) the radial shrinkage of CNTs; (ΙΙ) the rupture of CNTs caused by perforation degradation; (ΙΙΙ) the axial disappearance of CNTs initiated from both end caps of CNTs and newly formed defects. Among them, the axial degradation was found to be predominant based on statistic results. Moreover, the degradation mechanism and its dependence on the structure of CNTs were explicated. This work provides insights to further understand the microscopic mechanisms governing the degradation of CNTs in solution, and will shed the light on the practical applications of CNTs.