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Synthesis and applications of nanostructured titania sol–gel films on glass and stainless steel

Nanostructured titania (TiO2) films were deposited on borosilicate glass and AISI 304 stainless steel substrates by sol-gel process and dip-coating technique. For the preparation of two colloidal suspensions or sols (sol 1 and sol 2) titanium isopropoxide was used as a precursor, propanol as a solvent, with addition of nitric acid as a catalyst and acetylacetone for peptization. Both of the prepared sols contained the same amount of mentioned components, the only difference was in the addition of polyethylene glycol (PEG) as organic/polymer additive to sol 2. After preparation of solutions, deposition of coatings by dip-coating technique was made, followed by drying and calcining at the temperature of 550 °C. The deposited films were characterized by X-ray diffraction (XRD), thermal gravimetry (TG), differential scanning calorimetry (DSC), atomic force microscopy (AFM), scanning electron microscopy (SEM) equipped with EDS detector, UV– Vis spectroscopy and glow-discharge optical emission spectrometry (GD-OES). The photocatalytic activity of the coated glass substrates was evaluated by the photocatalytic degradation of Congo red dye (CR) and sulfonamide antibiotic sulfamethazine. Photocatalytic activity of the films was monitored by means of UV/VIS spectrophotometry. Electrochemical corrosion behavior of the coated stainless steel substrates was evaluated in simulated marine environment in 3 wt. % aqueous NaCl solution by electrochemical impedance spectroscopy (EIS) and in 0.5 M aqueous HCl solution by potentiodynamic polarization. The addition of PEG to the TiO2 solution resulted in the changes in the film surface morphology, and affected the ratio of anatase-rutile crystal phases and the investigated properties of TiO2 (photocatalytic activity on glass substrate and corrosion behaviour on stainless steel substrate). The present study shows that sol-gel TiO2 films with smooth surfaces may be applied for corrosion protection, while the films with higher surface roughness can improve the photocatalytic activity.

sol-gel TiO2; characterization; corrosion; EIS; photocatalytic degradation

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