Non-disruptive functionalization of carbon nanotubes: Toward enhanced device performance with double-walled hybrid materials

Non-disruptive covalent functionalization of single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) with different azido aryl derivatives and varying degrees of functionalization has been successfully achieved. The synthetic method is based on the reaction of 4-azido-N,N-dimethylaniline and 4-azidobenzonitrile with carbon nanotubes (CNTs) via [2+1] nitrene cycloaddition, yielding fully conjugated hetero-bridged CNTs that preserve the intrinsic π -conjugated system of pristine CNTs. Evidence of covalent functionalization is deduced from different studies, including thermogravimetric analysis, X-Ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The successful incorporation of a non-disruptive ‘open-ring’ aziridine bridge onto the nanotube sidewalls has been demonstrated through various techniques such as Raman, UV-Vis and photoluminescence (PLE) spectroscopies. Finally, the electrical transport properties of the functionalized materials have been studied by fabricating CNT-based devices and acquiring their current vs. voltage characteristics. Our results suggest that the conductance of the functionalized CNTs is mostly preserved in DWCNTs. So treated DWCNTs exhibit electrical conductance of the same order of magnitude as the pristine/control devices. These findings highlight the potential of this synthetic approach to enhance the processability and tailor the properties of DWCNTs for specific applications. Notably, aziridine-functionalized DWCNT-based devices exhibit excellent electrical characteristics, paving the way for systems with promising applications in optoelectronics.