Green fabrication of ZnO@ZnS binary nanocomposite using Butea monosperma leaf extract: Antibacterial activity and antioxidant enzyme modulation in Spinacia oleracea

Current hot environmental conditions intensely frontier growth and efficiency of leafy vegetables. Investigating the environmental factors such as receptive biochemical and morpho-physiological mechanisms might be an imperative implement for thermo-tolerance of crops. Keeping in mind these facts, the current research had been conducted to evaluate changes in plant growth, as well as antioxidant enzyme modulation in spinach ( Spinacea oleracea L.) under heat associated condition. A green method produced ZnO@ZnS binary nanocomposite had been employed to resolve these issues. Physio-chemical investigations have been done using advanced techniques to confirm the formation of crystalline phase of nanostrucures within a mesoporous composite architecture with average particle sizes. The average size of ZnO, ZnS and ZnO@ZnS lies in the range of 16-18, 3-5 and 18-23 nm, respectively. Pore volumes (Vp) of ZnO, ZnS and ZnO@ZnS have been calculated as 1.9, 12.2 and 0.1 cm 3 g -1 , respectively. Under heat stress, activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (POD), and guaiacol peroxidase (GPX) significantly increased in spinach leaves. In investigation, it has been recorded that ZnO@ZnS treated Spinacia oleracea showed a significant increase (p < 0.05) in antioxidant enzymes, such as SOD, CAT, POD, and GPX and a higher redox regulatory capacity. Additionally, biological evaluation showed concentration dependent antibacterial property against Staphylococcus aureus, Pseudomonas and E. coli with efficient minimum inhibitory concentration (MIC) of ZnO@ZnS which is better than that of ZnO NPs. The antibacterial efficacy and the antioxidant enzyme modulation were measured as an independent biological response. The enhanced performance of the composite is explained by the effect of the modified surface characteristics and the combined physicochemical properties of ZnO and ZnS. These results form the basis for the wide application of green-fabricated ZnO@ZnS nanocomposites as multifunctional platforms for sustainable agricultural and antimicrobial purposes.