Bio-hydrothermal synthesis of ZnO–ZnFe2O4 nanoparticles using Psidium guajava leaf extract: Role in waste water remediation and plant immunity

Here in, an environmental friendly and chemical free bio-hydrothermal method was developed to synthesize ZnO–ZnFe2O4 nanoparticles (NPs) using Psidium guajava leaf extract. The prepared NPs effectively mediate water remediation process as well as enhance plant immunity. The phase formation, functionality, chemical composition, morphological feature and surface area of the prepared material was analyzed by XRD, XPS, TEM and BET analytical techniques. The average size of the prepared special shaped NPs was found to be 17.8 nm. The synthesized composite material is used for the removal of highly toxic Congo red (CR) and Methylene blue (MB) dyes from water by batch adsorption method. The adsorption processes follow Pseudo-second order kinetics and Langmuir isotherm models. The maximum adsorption capacity was found to be 120.32 mg/g for CR and 90.35 mg/g for MB at the solution pH = 6 and pH = 8 respectively. Strikingly, the fabricated ZnO–ZnFe2O4 NPs enhance the plant immune response and promote plant growth, potentially by preventing transpirational water loss. Specifically, the protein levels of key immune responsive genes including BAK1, FLS2, PR1, MPK3 and MPK6 were elevated for the plants treated with NPs as compared with the control plants. [Display omitted] •A green bio-hydrothermal method is used to synthesize ZnO–ZnFe2O4 NPs.•NPs effectively mediate water remediation process and enhance plant immunity.•Adsorption capacity was found to be 120.32 mg/g for CR and 90.35 mg/g for MB.•ZnO–ZnFe2O4 NPs mediate plant immunity by lowering the bacterial colonization.•NPs elevate the protein levels of key plant immune responsive genes.