Abstract
This work presents a simple green synthesis of gold nanoparticles (AuNPs) by using an aqueous extract of Etlingera elatior (torch ginger). The metabolites present in E. elatior, including sugars, proteins, polyphenols, and flavonoids, were known to play important roles in reducing metal ions and supporting the subsequent stability of nanoparticles. The present work aimed to investigate the ability of the E. elatior extract to synthesise AuNPs via the reduction of gold (III) chloride hydrate and characterise the properties of the nanoparticles produced. The antioxidant properties of the E. elatior extract were evaluated by analysing the total phenolic and total flavonoid contents. To ascertain the formation of AuNPs, the synthesised particles were characterised using the ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) microscopy, and dynamic light scattering (DLS) measurement. The properties of the green synthesised AuNPs were shown to be comparable to the AuNPs produced using a conventional reducing agent, sodium citrate. The UV-Vis measured the surface plasmon resonance of the AuNPs, and a band centered at 529 nm was obtained. The FTIR results proved that the extract contained the O-H functional group that is responsible for capping the nanoparticles. The HRTEM images showed that the green synthesized AuNPs were of various shapes and the average of the nanoparticles’ hydrodynamic diameter was 31.5 ± 0.5 nm. Meanwhile, the zeta potential of −32.0 ± 0.4 mV indicates the high stability and negative charge of the AuNPs. We further successfully demonstrated that using the green synthesised AuNPs as the nanocomposite to modify the working surface of screen-printed carbon electrode (SPCE/Cs/AuNPs) enhanced the rate of electron transfer and provided a sensitive platform for the detection of Cu(II) ions.
Highlights
The application of metallic nanoparticles is gaining traction in various fields due to their unique electrochemical and optical properties
Total phenolic compounds (TPC) in plants are known to act as free radical scavengers and it is believed that the antioxidant activity of the most plant produce is mostly due to the presence of phenolic compounds [13]
Gallic acid (GA) was used as the standard for the calibration curve and TPC was expressed as the gallic acid equivalent (GAE) in mg per 100 g of the sample
Summary
The application of metallic nanoparticles is gaining traction in various fields due to their unique electrochemical and optical properties. These unique properties make them an ideal nanomaterial to be used in biosensor applications. The electrochemical properties of AuNPs can enhance the electrode conductivity by facilitating electron transfer, and improving the sensitivity. The most commonly used stabilising agents reported are sodium citrate (Na3 C6 H5 O7 ), transferrin, sodium borohydride (NaBH4 ), and cetyltrimethylammonium bromide (C19 H42 BrN), which are known as the chemical method that can subsequently produce toxic wastes [5]. Alternative non-toxic reagents are often sought after to improve the biocompatibility of AuNPs
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