Competitive ion-exchange of manganese and gadolinium in titanate nanotubes

Homogeneous Mn2+ and Gd3+ intercalation of scroll-type trititanate nanotubes using a post-synthesis ion exchange method is reported. Compared to Mn2+, Gd3+ ion-exchange shows larger saturation intercalation levels. Upon co-doping, weak interactions between the dopant ions were found to modify the incorporated concentrations. Electron spin resonance (ESR) measurements, performed at several frequencies, confirmed the homogeneous distribution of Mn2+ and Gd3+. Detailed simulation of ESR spectra identified a large spread of the local structural distortions of the occupied sites as a result of a wide range of curvature radii of the titanate nanotubes. (C) 2016 Elsevier B.V. All rights reserved.