Coordination of Intercalated Cu2+ Sites in Copper Doped Sodium Titanate Nanotubes and Nanoribbons

Copper doped sodium titanate nanotubes and nanoribbons were prepared via two different doping methods called in situ and ex situ . In the applied in situ method, titanate nanotubes were grown from anatase TiO 2 doped with Cu 2+, while in the ex situ method, titanate nanotubes and nanoribbons were exposed to aqueous solution of Cu 2+ species. By correlating XRD, electron microscopy, magnetic susceptibility, and electron paramagnetic resonance (EPR) measurements, we found that in the samples prepared via the ex situ doping method, sub-10 nm CuO nanoparticles grow on the inner/outer surface of nanotubes/nanoribbons where the Neel transition temperature is strongly suppressed. In fact, they behave as superparamagnets with a blocking temperature of around 50 K. Strong evidence that Cu 2+ species that form complexes between titanate layers coordinate with Na + ions comes from the pulsed EPR data.