On the role of hydrodynamic forces in vanadium oxide nanoscroll synthesis
Nanostructured vanadium oxides are promising materials for applications as semiconductors, cathode materials in nanoelectronics, in sensor technology and heterogeneous catalysis. Despite the increasing number of publications on nanostructured vanadium oxides, there is still a significant lack of systematic studies focusing on molecular and supramolecular aspects of the material synthesis. In this article, we address the effect of hydrodynamic forces on vanadium oxide gelation and the formation of vanadium oxide lamellar phases and nanoscrolls systematically. Hydrodynamic forces were generated by circulating the reagent mixture in a closed loop. ESR spectra revealed that application of strong hydrodynamic forces resulted in increased V(4+) concentrations in the lamellar material. High V(4+) concentrations are crucial for the defined rolling up of the lamellar, amine-intercalated vanadium oxide layers during hydrothermal treatment to form the nanoscrolls. The electronic properties of the lamellar precursor which are translated into the final nanoscroll product can be controlled by hydrodynamics, thus enabling nanoscroll synthesis with defined physical characteristics and morphology.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (148 K)Download as PowerPoint slideHighlights► Nanoscroll synthesis from precursor gels in a closed loop mixing device. ► Distinct nanoscroll properties depending on aging time and flow turbulences. ► Strong hydrodynamic forces result in increased V(4+) concentrations in lamellar VOx. ► Electronic properties of the lamellar precursor are translated into the final nanoscroll. ► V(4+)-rich nanotubes show better dispersion and a more defined, tubular morphology.
Journal: Catalysis Today - Volume 192, Issue 1, 30 September 2012, Pages 63–66