Catalytic degradation of Methylene blue dye and Antibacterial study of silver nanoparticles obtained using Murraya Koenigii leaf Extract

Abstract

Introduction: The development of eco-friendly, cost-effective green protocol for the synthesis of nanomaterials is a significant feature of nanobiotechnology connecting synthesis of nanomaterials using microorganisms, including bacteria, viruses, fungi as well as plant and animal based products (1). There is much room of more development in the synthesis of nanoparticles using different biological resources as the source of reducing and stabilizing agents and their potential applications. Silver nanoparticles (AgNPs) are of great interests owing to their optical, electrical, catalytic, and antibacterial properties (1). For waste-water treatment, nanoparticles can exhibit effectiveness in catalytic dye degradation due to the characteristic catalytic properties of nanoparticles (2). In this paper, we have demonstrated an eco-friendly green approach for the room temperature synthesis of biocompatible AgNPs by the reduction of aqueous silver ions using Murraya koenigii (Mk) leaf extract. Methods: The aqueous plant extract was prepared by taking 10 g of pulverized Mk leaves in a 500 mL Erlenmeyer flasks with 60 mL of Milli-Q water and refluxed it for 15 min with constant stirring using magnetic stirrer (2). 9 mL (0.625%) NH3 solution was added to 2 L of 10-3 M aqueous AgNO3 solution followed by the addition of 90 mL of aqueous Mk leaf extract at controlled pH = 7 and homogenized by using a magnetic stirrer. Then the reaction mixture was kept for 5 h at room temperature followed by centrifugation at 6000 rpm for 30 min. The envisaged color change from transparent yellow to dark brownish indicates the formation of AgNPs (2). Results & Discussions: Synthesized AgNPs were well characterized by UV-Visible absorption spectroscopy, FTIR spectroscopy, XRD, DLS, HRTEM and EDX studies. AgNPs would exhibit SPR band at 402 nm. FTIR studies confirmed the presence of different biomolecules responsible for the stabilization as well as formation of AgNPs. Surface morphologies and size distribution of synthesized AgNPs were determined by HRTEM and DLS techniques, respectively. The average particle size was found 20 nm. XRD analysis confirmed the formation of face-centered cubic (FCC) crystalline lattice of AgNPs. EDX studies confirmed the presence of elemental silver (Ag). AgNPs can act as photocatalyst for the degradation of methylene blue (MB) used as a model cationic dye. AgNPs were nontoxic in nature as concluded from cytotoxicity studies and also exhibited substantial antibacterial activities towards gram-positive and gram-negative bacteria. Conclusions: In the present study, stable AgNPs were successfully prepared by a green route using aqueous Murraya koenigii leaf extract in simple, cost-effective, eco-friendly way using less hazardous reagents and solvents, and thereby non-toxic towards both human health and the environment. AgNPs were almost spherical in shape, crystalline in nature, with an average diameter of 20 nm. AgNPs showed catalytic activity for the degradation of a cationic dye MB. AgNPs were nontoxic in nature and can exhibit considerable antibacterial activity towards both gram-positive and gram-negative bacteria. Keywords: Biosynthesis, AgNPs, photocatalysis, methylene blue, antibacterial activity Acknowledgment: UKS would like to acknowledge financial support from the projects funded by the DHESTBT (Department of Higher Education, Science, Technology and Biotechnology), Government of West Bengal (Memo no. 161(sanc)/ST/P/S&T/9G-50/2017.