Synthesis of vanadium oxide nanostructures with excellent thermochromic properties via sol-gel chemistry in supercritical carbon dioxide

Vanadium oxide VO 2 (M) synthesis was investigated using a simple supercritical CO 2 (scCO 2 ) sol-gel process with vanadium(V) oxytriisopropoxide(VTIP) as the vanadium precursor and acetic acid as catalyst. scCO 2 with different temperatures of 40, 60, 80 and 100 °C under 41.4 MPa was examined on the prepared sol-gels’ chemical constituents by FTIR and morphology by SEM, respectively. 80 °C and 41.4 MPa produced aerogel with smaller size of nanofiber. The calcination conditions were studied in regarding to different atmospheres, time durations and aerogel forms, by the XPS and XRD spectrum of the obtained vanadium oxides. Calcination in N 2 at 500 ºC with vanadium oxides aerogel casted on glass substrate for 15 minute showed best calcination results, with V(IV) of 49.5%, V(V) of 47.1%, and V(III) of 3.4% in the obtained vanadium oxides. The smart glass was manufactured in scCO 2 at 80 °C and 41.4 MPa, by direct synthesis of vanadium oxides aerogel on glass substrate, followed by calcination at 500 ºC in N 2 for 15 min. Phase transition of the obtained vanadium oxides was observed at 65 ºC by DCS analysis. UV-vis-NIR spectrum at temperatures of 23 and 80 ºC were measured. The prepared glass showed excellent regulation efficiency on IR transmittance ( ∆ T IR = 3.72 % ) , and stable luminescence transmittance ( ∆ T lum = 0.03 % ) . This direct scCO 2 sol-gel method shows promising application in manufacturing VO 2 coated smart glass with excellent thermochromic switching properties. • Vanadium oxide VO 2 (M) was synthesized using supercritical CO 2 (scCO 2 ) sol-gel process. • Different scCO 2 temperatures of 40, 60, 80 and 100 °C under 6000 psi was examined. • Calcination conditions were optimized. • The smart glass was manufactured with excellent IR regulation and stable luminescence transmittance.