Abstract
Gold nanoparticles were synthesized using a water extract of Artemisia capillaris (AC-AuNPs) under different extract concentrations, and their catalytic activity was evaluated in a 4-nitrophenol reduction reaction in the presence of sodium borohydride. The AC-AuNPs showed violet or wine colors with characteristic surface plasmon resonance bands at 534~543 nm that were dependent on the extract concentration. Spherical nanoparticles with an average size of 16.88 ± 5.47~29.93 ± 9.80 nm were observed by transmission electron microscopy. A blue shift in the maximum surface plasmon resonance was observed with increasing extract concentration. The face-centered cubic structure of AC-AuNPs was confirmed by high-resolution X-ray diffraction analysis. Based on phytochemical screening and Fourier transform infrared spectra, flavonoids, phenolic compounds, and amino acids present in the extract contributed to the reduction of Au ions to AC-AuNPs. The average size of the AC-AuNPs decreased as the extract concentration during the synthesis was increased. Higher 4-nitrophenol reduction reaction rate constants were observed for smaller sizes. The extract in the AC-AuNPs was removed by centrifugation to investigate the effect of the extract in the reduction reaction. Interestingly, the removal of extracts greatly enhanced their catalytic activity by up to 50.4 %. The proposed experimental method, which uses simple centrifugation, can be applied to other metallic nanoparticles that are green synthesized with plant extracts to enhance their catalytic activity.
Highlights
With the development of nanotechnology, metallic nanoparticles (MNPs) have attracted considerable attention due to their wide range of applications
An A. capillaris extract was successfully utilized as a reducing agent for the synthesis of AC-AuNPs under different extract concentrations
Phytochemical screening indicated that saponins, amino acids, phenolic compounds, flavonoids, and diterpenes were present in the A. capillaris water extract
Summary
With the development of nanotechnology, metallic nanoparticles (MNPs) have attracted considerable attention due to their wide range of applications. The most common method for synthesizing AuNPs involves chemical reducing agents for the reduction of Au ions to AuNPs. The most common method for synthesizing AuNPs involves chemical reducing agents for the reduction of Au ions to AuNPs These chemical methods employ toxic reagents, and the resulting AuNPs are most likely unsuitable for in vitro and in vivo applications. These applications require processes that are green, environmentally. Our laboratory has reported the synthesis of silver nanoparticles (AgNPs) using A. capillaris extract as a reducing agent [16, 17]. AgNPs synthesized using A. capillaris in the presence of cetyltrimethylammonium bromide exhibited antibacterial properties against methicillin-resistant Staphylococcus aureus [17]. A. capillaris water extract was used as a reducing agent to synthesize AuNPs (hereafter referred to as AC-AuNPs). AuNPs and cf-AC-AuNPs were compared in the reduction reaction of 4-NP to 4-AP
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