Tuning the size and the photocatalytic performance of gold nanoparticles in situ generated in photopolymerizable glycomonomers

Abstract

Polymer nanocomposites containing gold nanoparticles (Au NPs) in situ photogenerated during the UV-curing process were prepared starting from methacrylated glycomonomers with α-D-glucofuranose or D-mannitol structural units, other mono(di)methacrylates and AuCl₃. The formation of Au NPs inside the polymer matrix was evidenced through UV-vis, TEM and XRD analyses, the mean size of the spherical particles being around 33 nm. By adding methacrylates functionalized with carboxylic, quaternary ammonium or thiol groups (MA-COOH, MA-N⁺, MA-SH) in each formulation, the mean size of gold nanoparticles in the hybrid films (purple/dark-blue, red, green) decreased from 6.4 nm to 1.5 nm (for those stabilized by a gold–thiol bond). The catalytic activity was tested for the photodegradation of methylene blue (MB) and methyl orange (MO) in aqueous phase under visible irradiation conditions, and the catalytic performance of the resulting hybrid films was improved by the size decrease of the Au NPs. The hybrid films prepared with 30 wt% MA-SH were more active than the samples with 10 wt% thiol methacrylate. Thus, the percentage degradation with nanosized Au NPs and 30 wt% photopolymerized MA-SH was about 98% in MB and 94% for MO (after 100 min of visible irradiation). Finally it was proved that the hybrid polymeric films can be reused as photocatalysts with high performance for the removal of dyes from contaminated wastewater.