Low-temperature (150 °C) carbon nanotube growth on a catalytically active iron oxide–graphene nano-structural system

In this work, we report the growth of carbon nanotubes (CNTs) at temperatures as low as 150 °C on an iron oxide–graphene, multicomponent, nano-structural system. A radio-frequency generator and an electrical furnace are separately used to heat the decorated graphene samples in an argon/hydrogen environment without adding any external hydrocarbon source. Few-layer graphene sheets are decorated with iron oxide nanoparticles using a simple one-step process and thoroughly characterized by electron microscopy. The synthesis temperature is varied between 150 and 500 °C, and nanotube’s presence is confirmed by transmission and scanning electron microscopy. We find that, while the graphene decorated with 5 nm iron oxide nanoparticles forms nanotubes at the lowest temperature (150 °C), the decorated samples with larger nanoparticles (15 nm) only initiate nanotube growth at 400 °C or higher, indicating a strong size-dependence on the catalytic activity of these nanoparticles. This low-temperature, facile technique opens the door to a wide range of applications for these novel nanoparticle/graphene-nanotube systems in areas varying from nano-electronics and energy harvesting to bio-nano.