title: FTIR study on the formation of TiO2 nanostructures in supercritical CO2.
abstract: TiO(2) nanospherical and fibered structures were obtained via a one-step sol-gel method in supercritical carbon dioxide (scCO(2)) involving polycondensation of the alkoxide monomers titanium isopropoxide (TIP) and titanium butoxide (TBO) with acetic acid (HAc). The resulting materials were characterized by means of electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermal analysis (TGA), and attenuated total reflection Fourier transmission infrared (ATR-FTIR) analysis. Depending on the experimental conditions, TiO(2) anatase nanospheres with a diameter of 20 nm or TiO(2) anatase/rutile nanofibers with a diameter of 10-100 nm were obtained. Fiber formation was enhanced by a higher HAc/Ti ratio and the use of the titanium isopropoxide (TIP) monomer. The mechanism of the microstructure formation was studied using in situ FTIR analysis in scCO(2). The FTIR results indicated that the formation of nanofibers was favored by a titanium hexamer that leads to one-dimensional condensation, while nanospheres were favored by a hexamer that permits three-dimensional condensation.
authors.affiliation: Department of Chemical and Biochemical Engineering, Faculty of Engineering, and Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
authors.forename: Ruohong
authors.initials: R
authors.lastname: Sui
authors.forename: Amin S
authors.initials: AS
authors.lastname: Rizkalla
authors.forename: Paul A
authors.initials: PA
authors.lastname: Charpentier
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D011312:Pressure; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014025:Titanium / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide; C009495:titanium dioxide; D014025:Titanium