Optical Properties of Single-walled Carbon Nanotubes and Nanobuds

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Ying Tian Name of the doctoral dissertation Optical properties of single-walled carbon nanotubes and nanobuds Publisher School of Science Unit Department of Applied Physics Series Aalto University publication series DOCTORAL DISSERTATIONS 77/2012 Field of research Nanomaterials, physics Manuscript submitted 12 March 2012 Manuscript revised 7 May 2012 Date of the defence 8 June 2012 Language English Monograph Article dissertation (summary + original articles) Abstract This thesis presents the study of the optical properties of single-walled carbon nanotubes (SWCNTs) and carbon nanobuds by means of optical spectroscopy and electron microscopy. A novel analysis method that is based on optical absorption spectroscopy was developed in order to meet the challenge of accurately and efficiently evaluating the diameter distribution in any bulk SWCNT sample. Properties of SWCNTs that were synthesized both in lab-scale and semi-industrial scale aerosol reactors were investigated in detail by using the proposed method. The results show that the diameter of SWCNTs can be easily altered over a broad range from 1.1 to 1.9 nm in the same reactor by varying the growth conditions. This opens up a new route towards diameter control in the synthesis of SWCNTs. The further application, that of SWCNTs with optimized properties deposited as thin films on a saturable absorber, was also demonstrated in this work.This thesis presents the study of the optical properties of single-walled carbon nanotubes (SWCNTs) and carbon nanobuds by means of optical spectroscopy and electron microscopy. A novel analysis method that is based on optical absorption spectroscopy was developed in order to meet the challenge of accurately and efficiently evaluating the diameter distribution in any bulk SWCNT sample. Properties of SWCNTs that were synthesized both in lab-scale and semi-industrial scale aerosol reactors were investigated in detail by using the proposed method. The results show that the diameter of SWCNTs can be easily altered over a broad range from 1.1 to 1.9 nm in the same reactor by varying the growth conditions. This opens up a new route towards diameter control in the synthesis of SWCNTs. The further application, that of SWCNTs with optimized properties deposited as thin films on a saturable absorber, was also demonstrated in this work. The other important work in this thesis involves the optical properties of carbon nanobuds. Focusing on a freestanding individual nanobud, as opposed to bulk samples of nanobuds, allowed us for the first time to observe the Raman features of a nanobud with Raman spectroscopy. The simultaneous presence of SWCNT and fullerene features in the Raman spectrum is in good agreement with independent TEM and ED investigations of the same nanobud structure, which confirmed the Raman measurement interpretation of the SWCNT chirality assignment (16,11), as well as the presence of fullerenes on the surface of the SWCNT.