Characterization and biological activities of silver nanoparticles obtained by green synthesis from thymus sipyleus Boiss. subsp. rosulans (Borbas) Jalas

In this master thesis, it was aimed to characterize silver nanoparticles synthesized from Thymus sipyleus Boiss. subsp. rosulans (Borbas) Jalas by green synthesis method and to investigate their antioxidant activities. For this purpose, the synthesis of silver nanoparticles was carried out by the green synthesis method. This method has been preferred because it is environmentally friendly, economical and simple. The synthesized silver nanoparticles were characterized using various techniques. It was observed that nanoparticles gave absorbance at 430 nm in UV-Vis absorption spectroscopy. Functional groups were determined by FT-IR analysis and crystal structure was determined by XRD analysis. EDX spectrum analysis revealed the presence of silver in the sample. Using Field Emission Scanning Electron Microscopy (STEM), the nanoparticles were found to be spherical in shape and with an average diameter of 18.28 nm (7.88-26.67 nm). In addition, the zeta potential of the nanoparticles was measured as -39.80 mV. It was determined that silver nanoparticles showed activity in antioxidant activity tests performed using different methods. Total antioxidant activity in silver nanoparticles was determined as 0.10 mmol TE/g. In reducing power determination of silver nanoparticles, CUPRAC and FRAP activities were determined as 74.25 mg TE/g and 35.91 mg TE/g, respectively. Free radical scavenging activities of silver nanoparticles were performed by DPPH and ABTS radical scavenging activity tests. DPPH radical scavenging activity was determined as 6.54 mg TE/g and ABTS radical scavenging activity was determined as 37.82 mg TE/g. In the metal chelation test, however, no activity was detected in the nanoparticle. Total phenolic substance in synthesized AgNPs was determined as 19.36 mg GAE/g extract. According to these findings, the antioxidant activity of silver nanoparticles synthesized by the green synthesis method from Thymus sipyleus subsp. rosulans may offer an advantage in terms of various applications in future studies.