Citation: Mela Yoro, John David Samson, Japhet Joshua, Patrick Datheh Bello, Joyous Wilson Kitime Jonah (2022). Physicochemical Parameters and Antibacterial Activity of Biosynthesized Silver Nanoparticles from Carica papaya Leaf Extract. Sch Int J Chem Mater Sci, 5(6): 105-110. 105 Scholars International Journal of Chemistry and Material Sciences Abbreviated Key Title: Sch Int J Chem Mater Sci ISSN 2616-8669 (Print) |ISSN 2617-6556 (Online) Scholars Middle East Publishers, Dubai, United Arab Emirates Journal homepage: http://saudijournals.com Original Research Article Physicochemical Parameters and Antibacterial Activity of Biosynthesized Silver Nanoparticles from Carica papaya Leaf Extract Mela Yoro 1* , John David Samson 2 , Japhet Joshua 3 , Patrick Datheh Bello 3 , Joyous Wilson Kitime Jonah 3 1 Department of Chemical Sciences, Faculty of Science, Federal University of Kashere, Gombe, Nigeria 3 Department of Science Laboratory Technology, Federal Polytechnic, Kaltungo, Gombe, Nigeria DOI: 10.36348/sijcms.2022.v05i06.004 | Received: 03.07.2022 | Accepted: 12.08.2022 | Published: 16.08.2022 *Corresponding author: Mela Yoro Department of Chemical Sciences, Faculty of Science, Federal University of Kashere, Gombe, Nigeria Abstract In this research work, Silver nanoparticles were synthesized from Carica papaya leaf extract via green route. The physicochemical parameters including boiling point, color, odor, density, pH as well as the solubility of papaya leaf extract were first determined before proceeding with the synthesis of silver nanoparticles. The formation of Silver Nanoparticles first, was identified by color change from light brown to dark brown after the nucleation of the metal ions indicating that phytoconstituents of Carica papaya resulted in the reduction of Ag + to Ag 0 , a phenomenon that could be attributed to the surface Plasmon absorption. The bio fabricated silver nanoparticles were characterized using UV – Visible and SEM to be certain of its formation before being deployed in the antibacterial studies. The UV-Vis spectral analysis showed maximum absorbance of 1.05 at a corresponding wavelength (λ max) of 400nm reflecting the surface Plasmon resonance of silver NPs from papaya leaves which is characteristic of Silver Nanoparticles. SEM image revealed that, the synthesized silver nanoparticles have a spinel like structure and an average size of about 50nm. The antibacterial studies of Silver nanoparticles were conducted against B. subtilis, K. pneunoniae, P. aeruginosa, E. coli, and S. typhi. Different concentrations of 100, 200, 300, 400 and 500μg/L of Silver nanoparticles were tested against each pathogen. The inhibition zone increases generally with increase in concentrations of silver nanoparticles. At higher concentration of 500μg/L, the zones of inhibition were in the following order; 24.44mm, 17.64mm, 17.52mm, 16.88mm, and 16.00mm for B. subtilis, P. aeruginosa, E. coli, K. pneumoniae and S. typhi respectively. The zone of inhibition for Augmentin was found to be higher compared to silver nanoparticles for each pathogen, except for P. aeruginosa where it is almost the same, an indication of high activity of silver nanoparticles against P. aeruginosa due to the comparability with Augmentin. For each concentration investigated, B. subtilis demonstrated higher zone of inhibition as compared to other pathogens studied in this work, hence, Ag NPs may be a potential antibiotic. Keywords: Physicochemical Parameters, Antibacterial Activity, Biosynthesized, Silver Nanoparticles, Carica papaya, Leaf Extract. Copyright © 2022 The Author(s): This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY-NC 4.0) which permits unrestricted use, distribution, and reproduction in any medium for non-commercial use provided the original author and source are credited. 1. INTRODUCTION Owing to the wide application of silver nanoparticles (Ag NPs) in some disciplines, such as pharmacy, medicine, catalysis, solar energy, and water disinfection, the literature has focused attention on the synthesis of Silver nanoparticles with minimum hazards and maximum advantage. Recently, several studies have shown that plant extracts act as potential originators for the synthesis of the nanomaterials in some ecofriendly ways as they are used successfully in the synthesis of several greener nanoparticles (Fatemeh B, et al., 2017; Mela Y, et al., 2022). This therefore, means Increasing awareness towards green chemistry and other biological processes led to countless interests in fabricating an environmentally friendly approach for the synthesis of nanoparticles(Sharmila B.A, et al.,2018; Bashpa P, et al., 2017; Mahesh and Shivayogeeshwar, 2018; Elisha K, et al., 2020).Quite a number of transition elements (metals) including Silver, Cobalt, Iron, Copper, Gold, Platinum, Nickel, Platinum among others, have over the years, been deployed in the synthesis of plants mediated nanoparticles due to their numerous applications, hence, the reason for their popularity((Flora P.J, et al., 2018; Suriyavathana M, et al., 2018; Mani P, et al., 2016; Ravindra D.K, et al., 2018). In the same vein, these metallic nanoparticles