Solid State Photoreduction of Silver on Mesoporous Silica to Enhance Antifungal Activity

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag-0 nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO3, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag-0 nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag-0. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver-silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity.

Automated summary

A solid-state ultraviolet photoreduction process was used to produce Ag-0 nanostructures on mesoporous silica for environmental anti-fouling purposes. The detailed characterization of the materials revealed silica-assisted photo-reduction, leading to the formation of Ag-0 through surface plasmon resonance and morphology changes. The activated silver-silica nanocomposites showed enhanced antimicrobial properties when dispersed in silicon, improving anti-fouling capacity.