Currently, many definitions of nanomaterial are used, but the one proposed by European Commission is most widespread: “A natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm–100 nm. In specific cases and where warranted by concerns for the environment, health, safety or competitiveness the number size distribution threshold of 50 % may be replaced by a threshold between 1 and 50%. By derogation from the above, fullerenes, graphene flakes and single wall carbon nanotubes with one or more external dimensions below 1 nm should be considered as nanomaterials.” Nanomaterials must be characterized properly, particularly their size, shape, agglomeration and aggregation, stability, surface characterization (electrokinetic potential, surface chemistry and specific area) and chemical composition.
Silver nanoparticles (AgNPs) are one of the most commonly used engineered nanoproducts, known for their antimicrobial activity. Silver nanoparticles are usually obtained by means of various bottom-up methods. These techniques start with atoms or molecules and build up to nanostructures. In the case of silver nanoparticles, silver salt is reduced using various reagents, and the resulting nanoparticles are stabilized using various polymers or low molecular weight compounds.