Green synthesis of zinc oxide nanoparticles using salvia officials extract

Abstract

The effects of salvia officinalis (an evergreen subshrub with unique pharmacological traits) extract of varying contents (1–3 mL without and with polymers) on the optical characteristics of the zinc oxide nanoparticles (ZnONPs) were assessed. These ZnONPs were prepared using the salvia officinalis extract (SOE) obtained via the Soxhlet apparatus. The hydrothermal method was used to produce the ZnONPs, wherein the SOE was dissolved in the aqueous zinc nitrate solution that yielded the ZnONPs through the oxidation-reduction mechanism. In this green synthesis method of the ZnONPs, the SOE displayed better capping, reducing and stabilizing action than the polymers. The SOE concentration dependent structures, morphologies and optical properties of the as-synthesized ZnONPs were determined. The UV–Vis spectra of the ZnONPs colloidal suspension showed the maximum absorption in the range of 283–317 nm accompanied by a blue shift. The XRD analysis revealed the presence of hexagonal wurtzite structure of the ZnONPs with particle size in the range of 14.08–14.17 nm (SOE with polymer) and 12.07–12.06 nm (SOE without polymer). The EDX spectra verified the existence of Zn and O as basic constituents. The FESEM images of the ZnONPs displayed the threads, plates and flower shaped nanomorphologies. The photoluminescence (PL) peak intensity of the ZnONPs (centered at 500 nm) prepared without polymer was higher than the one obtained with polymer and 1 mL of SOE. That's because phytochemical (flavonoids and phenols) in SOE extracts acts an important role in the reduction and capping, while when polymer added first followed by SOE extracts, polymer plays as a capping and reduction agent of the ZnONPs, but prevents the more reduction of the ZnONPs by SOE extracts. As the SOE content increases (0, 1, 2 and 3 mL) reduction of ZnONPs increases, and the bandgap widdening (range from 4.0 to 4.11 eV in and 4.01–4.18 eV, with and without polymer, respectively). As a result of PL emission increases gradually. The overall attributes of the ZnONPs were sensitive to both SOE and polymer. This green synthesis approach may constitute a basis for the large scale production of the ZnONPs at short time in an easy and environmental amiable way.