Direct observation of spin-injection in tyrosinate-functionalized single-wall carbon nanotubes

In this work, we report on the interaction of a tyrosinate radical with single wall carbon nanotubes (CNT). The tyrosinate radical was formed from tyrosine (ester) by Fenton's reagent and, reacted in situ with carbon nanotubes resulting in novel tyrosinated carbon nanotube derivatives. The covalent attachment of tyrosine on the external surface of the CNTs resulted in the appearance of a free radical, localized in the graphitic surface. The 'electron injection' (delocalization) of the free radical from the tyrosine ring onto the carbon nanotubes was studied and characterized by a combination of electron paramagnetic resonance, Raman and X-ray photoelectron spectroscopies, thermogravimetric analysis, as well as transmission electron and atomic force microscopies. The experiments, complemented by computer simulations, give insight into the formation process and structural details of the produced hybrid structures.