Metal and bimetallic nanoparticles: Flow synthesis, bioactivity and toxicity

Metal nanoparticles are used as additives in commercial products due to their antimicrobial properties. Apart from their high biocidal activity, it is widely observed that silver nanoparticles are toxic. Simultaneously, copper nanoparticles show fungicidal properties, but with limited effectiveness. Hence, it is suggested that a combination of Ag nanoparticles with Cu nanoparticles may decrease the toxic effects of silver while maintaining their high bioactivity.

This paper presents the properties of Ag and Cu metal nanoparticles, and Ag-Cu and Cu-Ag bimetallic nanoparticles, synthesised in a continuous microwave reactor. The size of the metal nanoparticles obtained was in the range of 27-97 nm, and the size of the bimetallic nanoparticles was in the range of 32-184 nm, depending on the microwave irradiation, residence time, pH of the solution and concentrations of the reagents.

Silver nanoparticles of particle size 97 nm revealed the highest antimicrobial activity (MIC = 10 mg/dm³). Simultaneously, silver nanoparticles did not show viral properties, compared to the copper and bimetallic nanoparticles, for which the virus titre was 1.06-1.50 log TCID50/cm³. In contrast to pure metal nanoparticles, the combination of silver and copper in bimetallic systems generated nanoparticles with no genotoxicity (rac(-)/rac(+) < 1.2).