Silver nanoparticles obtained using cyclodextrin derivatives and pectin as a key component of titanium dioxide-based composites for water purification

This study investigated the effect of β-cyclodextrin (β-CD), its derivatives, and pectin on reducing Ag⁺ ions for the synthesis of silver nanoparticles (AgNPs) and corresponding composites with TiO₂ (TiO₂/Ag), which were evaluated as high-performance photocatalysts for degrading methyl orange (MO) in both model solutions and natural water samples. AgNPs were obtained at a significantly lower molar ratio of Ag:β-CD (9:1) and in the pH range from 5.5 to 7.5. The influence of cyclodextrins on the reduction of Ag⁺ ions to AgNPs in water and on the surface of titanium dioxide was researched. The average particle size of TiO₂/Ag determined from SEM data ranged from 125 nm to 140 nm, depending on the type of reducing agent. When pectin was used, the samples showed less aggregation, with an average particle size of 125-127 nm. The photocatalytic degradation process was monitored by UV-Vis spectroscopy in different types of water media and pH. The best photodegradation results for MO were achieved with samples prepared from silver methacrylate. In this case, complete decolorization of the MO solution occurred within 30 min at pH 2.5 and 70 min at pH 7.5, which is 2.5 times and 3 times faster than with pure TiO₂.