Microextrusion Printing of Hierarchically Structured Thick V 2 O 5 Film with Independent from Humidity Sensing Response to Benzene.

The process of V 2 O 5 oxide by the combination of sol-gel technique and hydrothermal treatment using heteroligand [VO(C 5 H 7 O 2 ) 2-x (C 4 H 9 O) x ] precursor was studied. Using thermal analysis, X-ray powder diffraction (XRD) and infra-red spectroscopy (IR), it was found that the resulting product was VO 2 (B), which after calcining at 300 °C (1 h), oxidized to orthorhombic V 2 O 5 . Scanning electron microscopy (SEM) results for V 2 O 5 powder showed that it consisted of nanosheets (~50 nm long and ~10 nm thick) assembled in slightly spherical hierarchic structures (diameter ~200 nm). VO 2 powder dispersion was used as functional ink for microextrusion printing of oxide film. After calcining the film at 300 °C (30 min), it was found that it oxidized to V 2 O 5 , with SEM and atomic force microscopy (AFM) results showing that the film structure retained the hierarchic structure of the powder. Using Kelvin probe force microscopy (KPFM), the work function value for V 2 O 5 film in ambient conditions was calculated (4.81 eV), indicating a high amount of deficiencies in the sample. V 2 O 5 film exhibited selective response upon sensing benzene, with response value invariable under changing humidity. Studies of the electrical conductivity of the film revealed increased resistance due to high film porosity, with conductivity activation energy being 0.26 eV.