Interpretation of Ostwald ripening of catalytic nanoparticles based on the radial breathing mode in single-walled carbon nanotubes

•Ostwald ripening of catalytic nanoparticles for single-walled carbon nanotubes was explored.•The density of the nanoparticles was adjusted by varying the spin-coating conditions.•This density control affects the determination of the diameter distribution and tube type.•Diameter-selective growth of single-walled carbon nanotubes was successfully achieved.

Catalytic nanoparticle (NP) size is the crucial factor that determines carbon nanotube (CNT) diameter. Therefore, we explored the Ostwald ripening phenomenon of catalytic NPs from the radial breathing modes in resonant Raman spectra of synthesized single-walled CNTs (SWCNTs). SWCNTs were synthesized using chemically derived monodisperse Fe oxide catalytic NPs by a conventional thermal chemical vapor deposition system. The density of the NPs was manipulated by simply adjusting the spin-coating speed and cycle. The diameter distribution and tube type (SWCNTs or multi-walled CNTs) were thereby determined, which can be understood by density-dependent Ostwald ripening of the NPs. As a result, the diameter-selective growth of SWCNTs was successfully achieved, which will be useful for SWCNTs-based electronic applications.