Exfoliation of Mo₆S_xI_9-x nanowires in common solvents

¹ Department of Physics, University of Dublin, Trinity College, Dublin 2, Ireland
² Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
³ Mo6, Teslova 30, 1000 Ljubljana, Slovenia

Corresponding author: colemaj@tcd.ie

Received: 28 September 2006
Accepted: 27 November 2006
Published online: 31 January 2007

Abstract

We have demonstrated debundling of molydenym-sulphur-iodine nanowires simply by diluting nanowire dispersions in isopropanol. Using atomic-force-microscopy we observe the bundle diameter distribution to decrease dramatically with concentration. Detailed analysis of the data suggests the presence of an equilibrium bundle number density. The population of individual nanowires increases with decreasing concentration until almost half of all dispersed objects are individual nanowires at a concentration of 4 × 10⁻³ mg/ml. The partial concentration of individual nanowires peaks at a concentration of ~7 × 10⁻³ mg/ml. This debundling also occurs spontaneously without the input of sonic energy, suggesting thermodynamic solubility. The absorbance of the nanowire dispersions, measured in the visible region increases linearly with concentration indicating a concentration independent absorption coefficient. However, for the infra-red feature that has been associated with band edge transitions, the absorption coefficient increases with increasing concentration for both stoichiometries. This suggests that this transition may be quenched by the inter-nanowire interactions associated with bundling. Finally, nanowire re-aggregation can be induced by the addition of small quantities of non-solvents.