Green Electrospark Processing of Metal Nanoparticles for Sustainable Crop Protection and Advanced Materials Applications

Electric spark dispersion in liquids is a promising green process for producing metal nanoparticles without chemical reducing agents, stabilizers, or high-temperature bulk reactors. This work summarizes the technological principles and applied potential of electrospark treatment of conductive metal granules in weakly conductive aqueous media for the synthesis of environmentally acceptable nanodispersed systems. In the proposed process, discharge pulses generated by a capacitive thyristor system initiate stochastic plasma channels between metal granules immersed in deionized water. Local temperatures of approximately 8000–12,000 °C, rapid heating, evaporation, condensation, shock-wave effects, and high cooling rates produce colloidal particles of biogenic and functional metals, including Fe, Cu, Zn, Mn, and Ag. The process parameters, namely pulse voltage, current amplitude, capacitance, frequency, chamber configuration, and dispersion-medium temperature, determine the redistribution of stored electrical energy between plasma-channel heating, electrode erosion, liquid heating, shock-wave formation, and undesirable microfraction formation. Experimental characterization by SEM, TEM, XRD, XPS, and thermal analysis confirms the presence of nanoscale fractions with complex metal/oxide phase compositions, including CuO/Cu2O, Mn3O4, Zn/ZnO, and α-Fe/γ-Fe/FeO/Fe3O4, with particle sizes ranging from several to tens of nanometers and high structural defect density. The obtained aqueous colloids demonstrate significant applied value. Ag/Cu nanosuspensions inhibited the growth of phytopathogenic micromycetes, including Penicillium sp. and Alternaria alternata, by 90–97% at low metal concentrations, indicating their suitability as alternative fungicidal preparations. Multicomponent Fe–Cu–Zn–Mn trace-element dispersions tested in winter wheat cultivation improved the ecological and economic profile of crop production and increased profitability by 10–15%. Iron-based nanoparticles additionally showed potential as energetic modifiers of steel microstructure, refining ferrite–pearlite grains and increasing structural homogeneity. The results indicate that electrospark processing is a scalable, reagent-free, and process-controllable platform for sustainable nanoparticle production in agriculture, environmental technologies, and advanced materials engineering. Accordingly, the approach contributes to circular resource use.