Synthesis of Homogeneous Manganese-Doped Titanium Oxide Nanotubes from Titanate Precursors

TL;DR

This paper introduces a new method to synthesize homogeneously manganese-doped titanium dioxide nanotubes from titanate precursors, analyzing the local environment of Mn2+ ions and their magnetic properties.

Contribution

A novel synthesis route for manganese-doped titanium dioxide nanotubes with controlled doping levels and detailed characterization of Mn2+ ion environments.

Findings

Mn2+ ions occupy two distinct sites in the nanotubes.

The ratio of Mn2+ sites remains constant across doping levels.

No long-range magnetic order observed in the doped nanotubes.

Abstract

We report a novel synthesis route of homogeneously manganese-doped titanium dioxide nanotubes in a broad concentration range. The scroll-type trititanate (H(2)Ti(3)O(7)) nanotubes prepared by hydrothermal synthesis were used as precursors. Mn2+ ions were introduced by an ion exchange method resulting Mn(x)H(2-x)Ti(3)O(7). In a subsequent heat-treatment they were transformed into Mn(y)Ti(1-y)O(2) where y=x/(3+x). The state and the local environment of the Mn2+ ions in the precursor and final products were studied by Electron Spin Resonance (ESR) technique. It was found that the Mn2+ ions occupy two positions: the first having an almost perfect cubic symmetry while the other is in a strongly distorted octahedral site. The ratio of the two Mn2+ sites is independent of the doping level and amounts to 15:85 in Mn(x)H(2-x)Ti(3)O(7) and to 5:95 in Mn(y)Ti(1-y)O(2). SQUID magnetometry does not show long-range magnetic order in the homogeneously Mn2+-doped nanotubes.