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Keywords:

  • Fibers;
  • Nanoribbons;
  • Sensors, vapor;
  • Stimuli-responsive materials;
  • Vanadium oxides

Abstract

Macroscopic vanadium oxide fibers have been fabricated by an extrusion process. By varying the shear rate associated with the gel extrusion process we have been able to tune the diameter and transversal geometry of the fibers at macroscopic length scales. At the mesoscopic length scale, small-angle X-ray scattering (SAXS) analysis provides evidence for the possibility of fine tuning the degree of alignment of the V2O5 ribbons inside the fibers; this alignment is clearly improved upon increasing the shear rate. Nitrogen physisorption measurements (Brunauer–Emmett–Teller (BET)) indicate that the as-synthesized fibers exhibit poor mesoporosity, largely due to the presence of remaining poly(vinyl alcohol) (PVA) entities. Microscopically, from XRD measurements, the fiber structure appears to be semi-crystalline. 51V magic angle spinning NMR (MAS NMR) spectroscopy reveals that the local environment of 51V is typical of the structure of a V2O5·1.8 H2O xerogel. We demonstrate here that the alignment of the nanoribbon subunits can be tuned via the shear rate applied during the extrusion process, which provides a good handle for tuning the mechanical and sensing properties of the as-synthesized fibers.