Silver Nanoparticles Mediated by Costus afer Leaf Extract: Synthesis, Antibacterial, Antioxidant and Electrochemical Properties

Abstract

Synthesis of metallic and semiconductor nanoparticles through physical and chemical routes has been extensively reported. However, green synthesized metal nanoparticles are currently in the limelight due to the simplicity, cost-effectiveness and eco-friendliness of their synthesis. This study explored the use of aqueous leaf extract of Costus afer in the synthesis of silver nanoparticles (CA-AgNPs). The optical and structural properties of the resulting silver nanoparticles were studied using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra–red spectrophotometer (FTIR). TEM images of the silver nanoparticles confirmed the existence of monodispersed spherical nanoparticles with a mean size of 20 nm. The FTIR spectra affirmed the presence of phytochemicals from the Costus afer leaf extract on the surface of the silver nanoparticles. The electrochemical characterization of a CA-AgNPs/multiwalled carbon nanotubes (MWCNT)-modified electrode was carried out to confirm the charge transfer properties of the nanocomposites. The comparative study showed that the CA-AgNPs/MWCNT-modified electrode demonstrated faster charge transport behaviour. The anodic current density of the electrodes in Fe(CN)6]4−/[Fe(CN)6]3− redox probe follows the order: GCE/CA-Ag/MWCNT (550 mA/cm2) > GCE/MWCNT (270 mA/cm2) > GCE (80 mA/cm2) > GCE/CA-Ag (7.93 mA/cm2). The silver nanoparticles were evaluated for their antibacterial properties against Gram negative (Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa) and Gram positive (Bacillus subtilis and Staphylococcus aureus) pathogens. The nanoparticles exhibited better inhibition of the bacterial strains compared to the precursors (leaf extract of Costus afer and silver nitrate). Furthermore, the ability of the nanoparticles to scavenge DPPH radicals at different concentrations was studied using the DPPH radical scavenging assay and compared to that of the leaf extract and ascorbic acid. The nanoparticles were better DPPH scavengers compared to the leaf extract and their antioxidant properties compared favorably the antioxidant results of ascorbic acid. The green approach to nanoparticles synthesis carried out in this research work is simple, non-polluting, inexpensive and non-hazardous.

Green Nanotechnology in Nigeria: The Research Landscape, Challenges and Prospects

“…Spherical AgNPs synthesized byElemike et al (2017c) using leaf extract of Talinum triangulare averaged 13.86 nm in size and scavenged DPPH better than the extract, and with comparable performance with ascorbic acid. Costus afer extract-mediated AgNPs reported byElemike et al (2017d) also scavenged DPPH at different concentrations. The nanoparticles scavenged DPPH better than the leaf extract, while it had comparable action with ascorbic acid.…”

“…Results from cyclic voltammetry experiments revealed that AgNPs-functionalized MWCNT had the best conductivity, which can be deployed for electrocatalysis. Also, CA-AgNPs phytosynthesized by the aqueous extract of C. afer described previously was studied for electrochemical properties (Elemike et al, 2017d). The CA-AgNPs/ MWCNT-modified electrode transfers charge well; a property that can be explored as a sensor in assaying biological and environmental samples.…”

Copper Oxide Nanomaterials Derived from Zanthoxylum armatum DC. and Berberis lyciumRoyle Plant Species: Characterization, Assessment of Free Radical Scavenging and Antibacterial Activity

“…In presence of DPPH, copper oxide nanomaterials have a capacity to transfer an electron density towards the free radical located on nitrogen atom. [57][58][59][60]…”

Biosynthesis of silver nanoparticles using oak leaf extract and their application for electrochemical sensing of hydrogen peroxide

“…Consequently, biomolecules of plant extracts are presently being investigated universally to control dimension, shape and consistency of the nanoparticles. Recently, biosynthesis of Ag NPs has been conducted with Eucalyptus chapmaniana , Thymbra spicata , Arbutus unedo , Artemisia nilagirica , Sesbania grandiflora , Allium sativum , Datura metel , Malva parviflora , Cinnamon zeylanicum , Costus afer , Lippia citriodora , Gliricidia sepium , green tea, Tephrosia purpurea , oak fruit bark, Ocimum tenuiflorum , Manilkara zapota (L.) and Stachys lavandulifolia . The extracts of several plant parts including leaves, roots, seeds, stems and fruits containing antioxidants have been investigated for the biosynthesis of pure Ag NPs.…”