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

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 Angstroms 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.