Aqueous dispersions of ‘green’ silver nanoparticles for eco-applications: Synthesis, structure and biosafety

• Silver nanoparticles (AgNPs) were synthesized successfully using ‘green’ methods. • Only AgNPs prepared using water eucalyptus extract were of irregular shape. • The AgNPs crystal structure referred to functionally centered cubic (FCC) one. • The stability of the AgNPs suspensions without electrolyte was satisfactory. • There was no genotoxic effect of the prepared AgNPs on eucariotic cells. Sustainable agriculture requires the use of intelligent compounds with multifaceted effect on soil and plants. Such conditioners can be hydrogels enriched with nanoparticles, but only those synthesized using ‘green chemistry’ methods. Therefore, the main aim of the study was to synthesize and characterize innovative ‘green’ silver nanoparticles (AgNPs) for agricultural applications. AgNPs were created using water or alcohol extracts of eucalyptus ( Eucalyptus viminalis Labill) and aloe ( Aloë arborescens Mill) as well as tannin to reduce silver ions (Ag + ) to zero valent form (Ag 0 ). The synthesis was conducted under autoclave conditions or at room temperature, in the presence of potassium carbonate. The AgNPs characterization was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS) method, whereas stability of the AgNPs suspensions under various conditions was estimated using turbidimetry. Biosafety of the formed species was determined based on genotoxicity (comet test) and cytotoxicity (study with crystal violet and MTT) assays. The obtained results confirmed the presence of zero valent silver phase in the nanoparticles and showed that their crystallite size was 14–24 nm, with different degrees of polydispersity depending on the synthesis conditions. Hydrodynamic diameter of AgNPs and their aggregates in the aqueous dispersions varied from 6 nm to 103 nm, and the smallest aggregation degree was noted for the nanoparticles synthesized using tannin. All synthesized nanoparticles were biosafe. Thus, they can be applied in agro-industrial processes without damaging the environment.