Biosynthesis, characterization, and determination of antimicrobial activity of gold nanoparticles from reyhan (Ocimum basilicum) aqueous extract

The use of plant species for the biosynthesis of gold nanoparticles (AuNPs) can provide an alternative to the use of various hazardous chemicals commonly used during the synthesis of NPs, thereby reducing the biological effects of the release of these products into the environment. So far, a large number of medicinal plants have been investigated, assuming that medicinal components (functional groups) derived from plants will contribute to the coating formed around the nanoparticles and increase their effectiveness. Metal nanoparticles synthesized with the green approach have different pharmaceutical, medical, and agricultural applications. This work used a green and simple synthesis way for the preparation of potentially bioactive gold nanoparticles (Au NPs). Reyhan (Ocimum basilicum) is a perennial herb from the Lamiaceae family, which usually grows in temperate regions. In this thesis, the synthesis of gold nanoparticles (AuNPs) was carried out by biological synthesis method without using any surfactants, stabilizers, and chemicals except Reyhan (Ocimum basilicum) aqueous extract and Tetrachloroauric acid (HAuCI4.3H2O) solution. Characterization of synthesized AuNPs was performed using UV-Vis, SEM-EDX, XRD, FT-IR, TGA-DTA, AFM, and Zeta potential data. It was detected by UV-Vis data that the synthesized gold naoparticles gave significant plasmon resonance at 542 nm. When the energy distribution spectra of the obtained AuNPs were examined, SEM-EDX analysis confirmed that the crystal structure of the synthesized nanomaterials was in spherical form, the crystal size was around 10-100 nm, and the element composition mostly belonged to the gold nanoparticle. The high resolution and strong XRD pattern revealed that the crystalline AuNPs were produced as a result of the reduction of Au + ions using the leaf extract of Ocimum basilicum (OB). When the XRD data were examined, it was calculated that the average size of the nanoparticles was 40.39 nm according to the Debye-Sherer equation. When XRD and SEM-EDX data were examined, it was seen that the element composition of AuNPs was largely composed of carbon, oxygen, and gold. The surface charges of AuNPs obtained as a result of the zeta potential analysis were found to be (–) 21.2 mV. It was determined that OB-AuNPs synthesized using the extract obtained from the leaves of the Ocimum basilicum plant had more effective inhibition activity on pathogen gram (-) and gram (+) positive bacteria and Candida albicans yeast growth compared to standard antibiotics