Silver nanoparticles and silver/silica nanocomposites: Impacts on Z. mays L. growth, nutrient uptake and soil health

Abstract

Although silver nanoparticles (Ag NPs) are widely employed in diverse industries, including agriculture, concerns about their adverse effects on plants at higher concentrations prompt exploration of alternatives, such as Ag/SiO2 NCs. Adding nano SiO2 is anticipated to create a complex with Ag+ ions, potentially decreasing their release into the environment and mitigating toxicity. The potential of Ag/SiO2 NCs as plant growth stimulants remains understudied to date. In this context, the study evaluates the impact of Ag/SiO2 NCs on 30-day-old Z. mays plants compared to Ag NPs at 100 and 200 ppm concentrations and on soil health. Soil health analysis revealed that both Ag NPs and Ag/SiO2 NCs supported the proliferation of P-solubilizing and N-fixing bacteria. Bioaccumulation analysis reveals higher Ag content in plants treated with Ag/SiO2 NCs, attributed to reduced agglomeration. Ag NPs exhibited concentration-dependent toxicity as 200 ppm hindered Z. mays growth, chlorophyll levels and absorption of P, Mg and K, whereas 100 ppm was found to be stimulatory. In stark contrast, Ag/SiO2 NCs demonstrated a remarkable capacity to mitigate Ag toxicity. The beneficial impact of Ag/SiO2 NCs on growth metrics, chlorophyll levels, lipid peroxidation, antioxidant enzyme activity and nutrient absorption was observed at both 100 and 200 ppm. However, it was more pronounced at 100 ppm concentration. This suggests that incorporating SiO2 in NCs may counteract the toxic effects of Ag, possibly through the complexation of Ag+ and a slower release mechanism.