Chitosan films containing visible light absorbing TiO2 nanoparticles and their photoinduced self-cleaning and antimicrobial properties under visible and actinic light irradiation

JULIÁN A. RENGIFO-HERRERA; PAULA A. OSORIO-VARGAS; LUIS PIZZIO

La Serena

Conferencia; 3rd Energy, Efficiency and Environmental Sustainability Conference 2021; 2012

Sol-gel synthesized TiO2 nanoparticles modified with urea exhibited visible light absorption between 400 and 500 nm due to the presence of graphitic carbon nitride (g-C3N4), demonstrating that urea modification of TiO2 does not lead to nitrogen doping as it is often reported in the literature. Urea undergoes thermal condensation reactions catalyzed by the presence of Ti-OH species producing melamine as one of the main byproducts, which at temperatures beyond 300 °C, generates g-C3N4 structures instead interstitial nitrogen doping. This latter was confirmed by DRIFT and XPS measurements. These nanoparticles were successfully immobilized onto chitosan films through casting method. SEM-EDS micrographs, AFM images, and XPS spectra revealed that modified TiO2 was mainly incorporated on the film´s surface. These films exhibited interesting properties to degrade malachite green dye stains under visible light irradiation (λ> 455 nm). It was suggested the participation of visible-light photoinduced hydroxyl radicals (?OH) and singlet oxygen (1O2) as reactive oxygen species (ROS) responsible of dye abatement.On the other hand, under actinic light irradiation (indoor lighting), these photocatalytic films showed a high self-cleaning activity degrading malachite green dye stains after 72 h of continuous irradiation. Furthermore, under the same irradiation conditions, these materials were able to decrease (3 logs) the Staphylococcus aureus cultivability after 3 h of actinic irradiation. Regarding their reusing, films exhibited the ability of photo fade malachite green stains after 5 reusing cycles (15 days) of continuous actinic light exposure.