Micro-morphological effects on the photocatalytic properties of TiO2 films immobilized onto glass slides

MORALES, JESÚS M.N.; TULLI, FIORELLA; SALAS, ESTEBAN E.; FERNÁNDEZ, JUAN M.; MORÁN VIEYRA, FAUSTINO E.; BORSARELLI, CLAUDIO D.

Viña del Mar

Encuentro; XIV ENCUENTRO LATINOAMERICANO DE FOTOQUIMICA Y FOTOBIOLOGIA; 2019

USACH

Titanium dioxide (TiO2) is the most popular semiconductor utilized in photocatalytic processes, including water-splitting and contaminant degradation.1 The low cost and toxicity, high thermal and chemical stability of TiO2 are still advantages for its use as photocatalyst applying different immobilization strategies , despite the requirement of using UVA illumination sources for photoexcitation of the conductive band (3.1 eV).In this report we present a systematic study of the photocatalytic efficiency of TiO2 thin films prepared by the ?Doctor Blade? technique onto commercial microscope glass slides. For this purpose 1 g of commercial TiO2 powder (Degussa P25 or Hombikat) was homogenized with 100 μL of acetyl acetone, 50 μL of sodium dodecyl sulphate (10 mg mL-1), and different amounts of polyethylene glycol (PEG 20000, 20-100 %w/w TiO2) and latter, were calcinated during 2 h at 450 °C. The immobilized TiO2 were characterized by UV-vis reflectance and ATR-FTIR spectroscopies as well as by optical transmission and fluorescence microscopy.All films were mechanically stable after immersion in a water bath with orbital agitation during 5 h, while the %PEG has not effect on the amount of TiO2 deposited. However, different micro-morphology patterns were observed as a function of the PEG composition. Also, the photocatalytic activity of the films were evaluated by irradiation with a germicidal lamp (λmax 365 nm) and monitoring both the bleaching of adsorbed xanthenic dye Rose Bengal (RB)2 and reaction of the pre-fluorescent probe coumarin (CM) with the photo-generated HO?, to form 7-hydroxicoumarin (7OH-CM), which shows fluorescence at 460 nm.3 The relative quantum yields of RB photobleaching and HO? generation are discussed as function of the surface micro-morphology of the TiO2 films.