Biosynthesis and Characterization of Gold Nanoparticles Using Microwave-Assisted Technology from Pomegranate (Punica granatum L.) Leaf Extract Produced by the Method of Supercritical Fluid Extraction (SFE)

The synthesis and characterization of Au nanoparticles produced from Punica granatum L. leaves (PGL) grown in Trabzon province of Turkey were investigated in this study. After the pomegranate leaves were collected, they were dried under suitable conditions and divided into small pieces, and Supercritical Fluid Extraction (SFE) was applied to obtain the extract. The SFE was performed at a pressure of 200 bar, 50 °C for a period of 2.5 h using ethanol modifier at 0.5 mL/min flow rate in this procedure. Twenty milliliters of 0.5 mM HAuCl₄.3H₂O solution was mixed in the microwave device with different volumes of the prepared aqueous solution (0.1 mL and 0.2 mL). After the mixture was exposed to microwaves for 1 to 30 min at a power of 90 W, Au nanoparticles were synthesized. Au nanoparticles produced utilizing green chemistry principles were characterized by UV–Vis, TEM, FTIR, XRD, and Zeta-sizer. The surface plasmon resonance absorption (SPR) spectra were measured using the UV–visible technique to determine the ideal conditions. The TEM images showed that the PGL-AuNPs had a mean size of 23.510 ± 7.009 nm, with sizes ranging from 14.188 to 42.508 nm, and a shape that was triangular, spherical, or elliptical. The reflection peaks appear at 38.21, 44.40, 64.61, and 77.59 corresponding to lattice planes (111), (200), (220), and (311), respectively. The average size of the synthesized gold nanoparticles is 23.24 nm. The Au nanoparticles have an average particle size of 50.76 ± 1101 nm in aqueous medium, a zeta potential of −14.8 ± 0.4 mV, and the polydispersity index for gold nanoparticles is 0.45 ± 0.011, indicating a moderately level of polydispersity. AuNP production was best achieved at 0.5 mM concentration in 0.1 mL pomegranate (P. granatum L.) leaves extract volume. The process utilized for producing the gold nanoparticles allowed for their stability for 2–2.5 months.