Silver nanoparticles (AgNPs) were synthesized using Aloe vera leaf extract as both reducing and stabilizing agents via microwave irradiation method. The effects of the microwave exposure time and the amount of AgNO3 solution on the mean particle size and concentration of the synthesized AgNPs solution were investigated using response surface methodology. The synthesized AgNPs were characterized by transmission electron microscopy, UV-Vis spectroscopy, and dynamic light scattering. Well-dispersed and spherically fabricated AgNPs with mean particle size (46 nm) and maximum concentration (64 ppm) and zeta potential (+15.5 mV), were obtained at optimal synthesis conditions, using 9 ml of AgNO3 (1 mm) and 0.1 ml of Aloe vera extract during microwave exposure time of 360 s. The antibacterial activity of the synthesized AgNPs was tested using Escherichia coli and Staphylococcus aureus bacteria and the obtained results indicated their significant inhibitory effects against these two Gram-negative and Gram-positive bacteria.

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Aloe vera leaf extract has been obtained and utilized for silver nanoparticles (AgNPs) synthesis by autoclave at 121 °C and 1.5 bar (pressure) for 15 min. The results of GC-MS analysis of A. vera life extract indicated that there were several natural reducing agents such as acetic acid, hexanol and ethyl amine in the A. vera peel. Central composition design and response surface methodology have been used to design the experiment and to evaluate the effect of independent variables on dependent variables, respectively. After extraction of A. vera leaf extract with different concentrations (0.5–5.5% w/v), 0.1 mL of the prepared extract has been added into different amounts of 1 mM AgNO3 solution (9.5–20.5 mL) and placed into the autoclave. The obtained results indicated that the minimum particle size (53.9 nm) and maximum concentration (46.25 ppm) and color (0.851 IU) values for synthesized AgNPs were obtained using 4.69% w/v of A. vera leaf extract and 11.1 mL of AgNO3 solution (1 mM). The zeta potential value of the synthesized AgNPs at obtained optimum conditions was +15.5 mV which indicated the high stability of the synthesized AgNPs. The high antifungal activity of the synthesized AgNPs was evaluated against to Aspergillus flavus and Aspergillus terreus strains.

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