Optimization of biosynthesis of stabilized silver nanoparticles using bitter orange peel by-products and glycerol

TLDR: In this article , the green synthesis of silver nanoparticles using AgNO 3 salt and the peel extract of bitter orange (Citrus aurantium) as a reducing agent was modeled and optimized by central composite design.

Abstract: Nowadays, the biosynthesis of metal nanoparticles (NPs) through eco-friendly, cost-effective, and sustainable methods has drawn considerable attention. In this study, the green synthesis of silver NPs using AgNO 3 salt and the peel extract of bitter orange (Citrus aurantium) as a reducing agent was modeled and optimized by central composite design (CCD). Accordingly, the process parameters including pH (7–11), time (0–4 h), and the ratio of extract/salt solution (0:100–20:80 v/v) were considered to model the responses including the spectrophotometric wavelength of maximum absorbance ( λ max ) and the maximum absorbance value at λ max (A max ), which represented the size and concentration of Ag NPs, respectively. Additionally, the stabilizing effect of glycerol (ratio of glycerol to salt 0–10 g/g) on the optimum treatment was studied using spectrophotometric and SEM analyses. The results showed that the quadratic and linear models were acceptably fitted to the experimental responses of A max and λ max , respectively. The optimization results demonstrated that the optimal reaction parameters to achieve the maximum A max were pH = 10.92, time = 3.5 h and ratio of extract/salt = 17.94:82.06 (v/v). Furthermore, glycerol could favorably play a stabilizer role in the optimum biosynthesized Ag NPs during the reaction and 14 days of storage at room temperature. The ICP-OES and TEM analyses of the stabilized Ag NPs (with 2.5 g/g glycerol) showed the presence of Ag element as nanospheres with ∼20 nm in size. The Ag NPs had great antibacterial properties against Staphylococcus aureus and Escherichia coli . Therefore, the bitter orange peel extract and glycerol could be promisingly used as novel reducing and stabilizing agents, respectively, to synthesize nanosilver via an eco-friendly and economical green approach. • Green synthesis of nanosilver using the bitter orange peel extract was investigated. • Central composite design was used to model and optimize the process parameters. • Glycerol favorably played a stabilizer role in the biosynthesized Ag NPs. • The ICP-OES and TEM analyses showed the presence of 20 nm Ag nanospheres. • These Ag NPs had great antibacterial properties against S. aureus and E. coli.