Inhibition of Cladosporium growth on gypsum panels treated with nanosilver particles

Nanosilver particles have recently become an accepted biocide, aimed mostly at combating bacteria and viruses in clinical applications; they have been used in indoor paints against clinically important bacteria, but are not yet utilized in building materials. We carried out accelerated biodeterioration tests to assess the use of nanosilver for protection of gypsum plaster. Gypsum panels with varying concentrations of a nanosilver product were inoculated with the fungus Cladosporium sp., isolated from a mouldy gypsum plaster ceiling, and incubated at 100% RH and 28 °C for 4 wk. Fungal growth (discoloration) on the surface was assessed with the naked eye, by color analysis using the L*a*b* scale, and by scanning electron microscopy with back-scattered electrons. Energy dispersive X-ray spectrometry was used to identify silver particles in the electron micrographs. The results showed that an aqueous solution of 10% nanosilver product (104.27 mg l−1 Ag w/v) reduced discoloration of the gypsum test panels significantly, to only 7.8% of the control value after the 4 wk of incubation, even though the particles were sometimes aggregated and non-homogeneously distributed over the gypsum surface. The results show that incorporation of nanosilver is a viable method for prolonging the effective life of gypsum plaster.