Effect of Probe Ultrasonication, Microwave and Sunlight on Biosynthesis, Bioactivity and Structural Morphology of Punica granatum Peel's Polyphenols-Based Silver Nanoconjugates

Biosynthesis of silver nanoconjugates using agro-waste has drawn the attention of the researchers in recent years due to eco-friendly and low-cost methods. A comparative study on various techniques (sunlight, probe ultrasonication, and microwave irradiation) of silver-bio-nanoconjugate production was carried out using lyophilized pomegranate peel polyphenols. Polyphenols from pomegranate peel extract were identified by LC-MS. The reaction time of each technique for the synthesis of pomegranate peel's polyphenols-based silver nanoconjugates was optimized by UV-visible spectroscopy, dynamic light scattering, and antioxidant activity. Further, they were characterized by FT-IR spectroscopy, XRD, FESEM-EDX, elemental mapping, TEM, and zeta potential. UV-spectroscopy and DLS results showed that the sunlight, probe ultrasonication, and microwave irradiation technique could reduce silver (Ag+) ions to silver nanoparticles (Ag0) at lambda(max) similar to 420 nm with Z-average diameters 51.63-94.76, 40.51-61.47, and 43.40-66.52 nm, respectively. The antioxidant activity was maximum at 50 s of microwave irradiation treatment followed by 15 min of probe ultrasonication and 20 min of sunlight exposer. However, TEM analysis revealed that the probe ultrasonication treated nanoconjugates were spherical, smaller, and less aggregated. FT-IR spectra confirmed the involvement and conjugation of various functional groups from pomegranate peel polyphenols. Probe ultrasonic-assisted-silver nanoconjugates showed good antibacterial activity againstS.aureusandE.colias compared to microwave-assisted silver nanoconjugate. [GRAPHICS] .

Automated summary

The biosynthesis of silver nanoconjugates using agro-waste has become a focus of research due to its eco-friendly and low-cost methods. Different techniques were compared in the production of silver-bio-nanoconjugates using lyophilized pomegranate peel polyphenols. The results showed that the probe ultrasonication technique produced smaller and less aggregated nanoconjugates with good antibacterial activity.