Feasibility Study of Copper Nanoparticle Biosynthesis using Leaf Extract as well as Green and Red Hull of Pistachios

Green synthesis of nanoparticles is more simple, inexpensive, nontoxic, and environmentally friendly than traditional methods. Thus, given the presence of secondary metabolites, the use of plant extracts has attracted much attention in causing metal ion reduction reactions into nanoparticles.

In this study, sampling was conducted from pistachio trees of the same age and from branches of the same diameter with a height of 1.5 meters. Leaves and fruits with green and red hull samples were harvested at a specified time. Besides, biochemical properties of the samples were examined for phenolic compounds, anthocyanins, and flavonoids. Copper nanoparticles were synthesized using 1mM copper sulfate salt at 55 and 80 °C. In addition, the absorption spectrum of the synthesized nanoparticles was analyzed through measuring the UV-Vis spectrum.

The content of phenolic compounds in the leaves showed a significant increase compared to the fruit hull. In addition, red hull fruits had less phenols than green hull ones. Besides, anthocyanin and flavonoid contents were higher in the leaves than in the fruit hull. Unlike the phenolic compounds, the anthocyanin content increased upon fruit development. Nanoparticles were synthesized upon observing the change in the color of the plant extract and the copper sulfate from pale yellow to dark brown. In addition, the peak in the wavelength range of 400- 430 nm confirmed the formation of copper nanoparticles.

The results of this study showed that the phenolic compounds, anthocyanins, and flavonoids exiting in the aqueous extract of the pistachio leaves and hull acted as copper-reducing agents and chemical stabilizers of copper metal ions into copper nanoparticles.