Single-walled carbon nanotubes (SWCNTs) have been in the focus of research and technology, covering an unprecedented broad field of science. Their mechanical and electronic properties, which are determined by the local arrangement of their sp2 hybridized carbon atoms, are exceptional. Their character is either insulating, semiconducting or metallic. They are ideal one-dimensional (1D) conductors with unusual transport properties such as e.g. ballistic transport in metallic tubes. On the other hand, semiconducting tubes are a very promising system for nanoelectronics, which have been even successfully, implemented 2013 in a carbon nanotube computer. Additionally, SWCNT exhibit in many aspects properties of 1D quantum systems and are therefore one of the most promising materials to study tuneable correlation effects, including spin interactions. The latter renders SWCNT functionalized by filling to be one of the promising candidates for future spin based quantum computers as well as for biomedical applications. The project “Correlation and Spin Dynamics in Carbon Nanotubes” clearly elucidated the different behaviour of semiconducting and metallic SWCNTs regarding electron correlation and spin dynamics. This was done by using, on the bulk scale, pristine fully separated sets of semiconducting and metallic tubes as well as doped tubes after controlled substitution and filling reactions. This enabled us to modify the electronic transport and magnetic properties of the separated SWCNT in a controlled manner.
Selected highlights of the project cover the first disentanglement of the exact correlated 1D electronic and magnetic structure of SWCNTs as a function of metallicity. With respect to filled SWCNTs we achieved the exact determination and control of the local charge transfer and local magnetic moments and the optimization of the photoluminescence quantum yield towards biocompatible near infrared sensors for ferrocene filled SWCNT. This study was complemented by a detailed analysis of the properties of 1D nanowires of Gd, Eu and ErCl3 nanowires which are modified by the quantum confinement inside SWCNTs. For substitutional doping we made great progress regarding the control of B and N substitution tailoring the bonding environment and doping level. In addition, we were able to determine the underlying adsorption process of nitroxides on metalicity sorted ultrapure nanotubes revealing an unexpected physisorption process and novel reaction kinetics. This is crucial for their application potential as environmental sensors.
Summarizing, in the frame of this project we were able to unravel underlying electron and spin coupling mechanisms in these correlated systems of functionalized purely metallic viz. purely semiconducting SWCNT. These novel results will be a key for assessing the potential of SWCNTs in nanoelectronics, biomedical applications and as environmental sensors.