Superior antibacterial activity against seed-borne plant bacterial disease agents and enhanced physical properties of novel green synthesized nanostructured ZnO using Thymbra spicata plant extract

Abstract

An easy and eco-friendly approach using Thymbra spicata var. spicata L. (TS) plant extract was developed for the formation of nanostructured ZnO. TS aqueous leaf extract was used for the green synthesis of nanostructured ZnO via the Successive ionic layer adsorption and reaction (SILAR) method. Electron microscope images exhibit the morphological adjustments of the samples with respect to change in TS concentration in the growth solution. The nanostructured ZnO grown by SILAR was observed to be polycrystalline with hexagonal crystal structure. The optical energy bandgap value of the samples varies from 3.21 to 3.09 eV as the content of TS increases from 2.5 to 5.0%. Also, the effect of TS additive to ZnO on electrical properties was investigated. It was determined by Van der Pauw measurements that TS contribution to ZnO significantly increased electrical resistance. In addition, impedance analyzes of the produced films were carried out in the frequency range of 20Hz −1 MHz. Nyquist plots showed the single semicircle for all samples, and the values of capacitance and resistance were calculated. Its antibacterial activities was investigated against economically important Gram-positive (Clavibacter michiganensis subsp. Michiganensis) and negative (Pseudomonas syringae pv. Phaseolicola, Pseudomonas cichorii and Pectobacterium carotovorum subsp. Carotovorum) seed-borne plant bacterial disease agents by using paper disc diffusion assay for the first time. In vitro laboratory screenings of green synthesized nanostructured ZnO have given encouraging results, indicating their potential use in the management of seed-borne bacterial diseases.