Suspensions of metal nanoparticles as a basis for protection of internal surfaces of building structures from biodegradation

•The antimicrobial properties of ZnO, TiO nanoparticles have been studied.•The highest efficiency is shown by zinc oxide nanoparticles.•Antimicrobial properties were studied for 8 test strains of microorganisms.•The efficiency of ZnO nanoparticles depends on the type of microorganism.•The antimicrobial activity of ZnO nanoparticles is manifested already at a concentration of 0.01%. The study objects were nanoparticles of zinc oxide and titanium dioxide. The aim was to investigate the dependence of antimicrobial activity of solutions with nanosize powders of different particle sizes and concentrations. It has been established that nanoparticles of zinc oxide (size 2−4 nm and 5−7 nm) at a suspension concentration varying from 0.01% to 0.25% exhibit effective antifungal and antibacterial properties in relation to the eight types of microorganisms most commonly affecting internal surface of building structures (the concentration of microorganisms decreases by 2–3 orders of magnitude depending on their type). Nanoparticles of titanium (5−15 nm and 10−20 nm) demonstrated low antimicrobial activity.