Ligand and solvent effects in the nonaqueous synthesis of highly ordered anisotropic tungsten oxide nanostructures

Abstract

Tungsten oxide nanoparticles were synthesized by a nonaqueous sol–gel process involving the reaction of tungsten chloride either with benzyl alcohol in the presence of various catechol ligands like 4-tert-butylcatechol, pyrocatechol and nordihydroguaiaretic acid or with 4-tert-butylbenzyl alcohol only. Dependent on the reaction system, organic–inorganic hybrid nanostructures with various morphologies were found, including short-range ordered lamellar structures as well as highly organized anisotropic stacks of tungstite nanoplatelets. In the case of 4-tert-butylbenzyl alcohol, the self-organization reaches two hierarchical levels, where the inorganic nanobuilding blocks, just a few Ångstroms in thickness, form nanocolumns perfectly arranged over a length scale of up to 10 microns. Several of these stacks assemble laterally into polydisperse bundles. The structural details as well as a potential formation mechanism are provided by a combination of XRD, TEM, HRTEM, and IR spectroscopy investigations.