Microwave-assisted synthesis of nanoscale VO2 structures

Abstract Nanoscaled VO2 structures were made using a fast microwave-assisted synthesis method in acetophenone as solvent, starting from vanadium pentoxide V2O5. Insights in the reaction and purification process were elaborated by attenuated total reflection infrared and nuclear magnetic resonance spectroscopy, which validated the choice of oleyl amine as ligand and acetophenone as solvent. A straightforward heat treatment in inert atmosphere was used to convert the mixture of VOx (M) and VOOH phases to thermochromically active monoclinic VO2 (M) nanomaterials. This conversion process was monitored via in-situ X-ray diffraction and gave insight in the influence of ethanol and tert-butyl hydroperoxide on the crystal structure and morphology, monitored via bright-field transmission electron microscopy. The thermochromic switching was investigated with differential scanning calorimetry showing a latent heat up to 43.34 ​J/g.