The great interest in compounds that present antioxidant capacity has generating the urgent need for analytical methods that could determine the antioxidant potential of these sources. A method based on generation of reactive oxygen species in water from catalyst composed of palygorskita-TiO2 and silver nanoparticles (AgNPs/TiO2-PAL) was developed and applied to antioxidant assays. Silver nanoparticles were synthesized using silver nitrate solution, sodium borohydride reducing agent and Caraia gum as stabilizing agent. Incorporation of AgNPs into the previously synthesized TiO2-PAL was performed. The catalyst AgNPs/TiO2-PAL was characterized by UV-vis spectroscopy, X-ray diffractometry and scanning electron microscopy. The catalyst AgNPs/TiO2-PAL were used to perform an antioxidant activity method which consisted in monitoring the discoloration of acid yellow 73 dye (AY73) in the presence of gallic acid antioxidant comparing to the dye discoloration in the absence of the antioxidant. A microplate reader was used to measure the discoloration of the aqueous solutions of AY73, irradiated by UV light for 60 min. The effect of reactive oxygen species generated by AgNPs/TiO2-PAL based in photocatalytic kinetics of AY73 dye was investigated. The oxidation of AY73 dye by photocatalysis in the system with AgNPs/TiO2-PAL catalysts was carried out mainly by the participation of O2 ·-, HO· and 1O2 species, in this order of importance. The results showed that the synthesis of the AgNPs/TiO2-PAL catalyst was successfully carried out and the application of this material in the development of an innovative methodology for the determination of antioxidant activity was extremely promising.
Keywords: Antioxidant activity; Palygorskite; ROS; Silver nanoparticles; TiO2.