Abstract:Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl4 with polyphenols from tea extracts, which act as both reducing and capping agents. The obtained AuNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). They act as highly efficient catalysts in the reduction of various aromatic nitro compounds in aqueous solution. The… Show more
“…A study on different amounts of reducing agents and different reaction temperatures was also carried out to select the optimum conditions for the preparation of the Au NPs (electronic supplementary material). The results (electronic supplementary material, figure S1) indicated that excessive amounts of the reducing agents and at high temperatures, the broadening and red shifting of the plasmonic band owing to the increase of particle size was as observed in previous studies [ 57 , 59 ]. Figure 1.…”
This study involves the generation of gold nanoparticles (Au NPs) via a novel natural/non-toxic methodology using tea and orange-peel extracts. These were then embedded into a novel blend composed of a polyethylene oxide and gelatin (PEO-Gel) fibre mat. The scanning electron microscopy results indicated that the addition of both collagen (COL) and ascorbic acid (AA) into the PEO-Gel system (PEO-Gel-AA-COL system) enhances the Au NP incorporation into nanofibres leading to a diameter of 164.60 ± 20.95 and 192.43 ± 39.14 nm in contrast to the spraying observed with the Au PEO-Gel system alone. Releasing studies conducted over 30 min indicated that the PEO-Gel-AA-COL-orange peel Au (OpAu) system accounts for a higher content of Au release than the green tea Au (GtAu) NP system where a maximum release could be attained within 10–30 min depending on the amount of Au NPs that have been incorporated. Moreover, the transdermal diffusion studies conducted using Strat membrane indicated that Au NPs from both formulations (PEO-Gel-AA-COL-GtAu nanofibre, PEO-Gel-AA-COL-OpAu nanofibre) have diffused through the stratum corneum and trapped in the dermis and epidermis indicating its transdermal deliverability. Additionally, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay revealed that nanofibres have similar radical scavenging activity like AA standard. Toxicity evaluation on a zebra fish embryo model confirmed that both GtAu NPs and OpAu NPs do not induce any teratogenic activity and are safe to be used in the range of 1.0–167 µg ml
−1
.
“…A study on different amounts of reducing agents and different reaction temperatures was also carried out to select the optimum conditions for the preparation of the Au NPs (electronic supplementary material). The results (electronic supplementary material, figure S1) indicated that excessive amounts of the reducing agents and at high temperatures, the broadening and red shifting of the plasmonic band owing to the increase of particle size was as observed in previous studies [ 57 , 59 ]. Figure 1.…”
This study involves the generation of gold nanoparticles (Au NPs) via a novel natural/non-toxic methodology using tea and orange-peel extracts. These were then embedded into a novel blend composed of a polyethylene oxide and gelatin (PEO-Gel) fibre mat. The scanning electron microscopy results indicated that the addition of both collagen (COL) and ascorbic acid (AA) into the PEO-Gel system (PEO-Gel-AA-COL system) enhances the Au NP incorporation into nanofibres leading to a diameter of 164.60 ± 20.95 and 192.43 ± 39.14 nm in contrast to the spraying observed with the Au PEO-Gel system alone. Releasing studies conducted over 30 min indicated that the PEO-Gel-AA-COL-orange peel Au (OpAu) system accounts for a higher content of Au release than the green tea Au (GtAu) NP system where a maximum release could be attained within 10–30 min depending on the amount of Au NPs that have been incorporated. Moreover, the transdermal diffusion studies conducted using Strat membrane indicated that Au NPs from both formulations (PEO-Gel-AA-COL-GtAu nanofibre, PEO-Gel-AA-COL-OpAu nanofibre) have diffused through the stratum corneum and trapped in the dermis and epidermis indicating its transdermal deliverability. Additionally, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay revealed that nanofibres have similar radical scavenging activity like AA standard. Toxicity evaluation on a zebra fish embryo model confirmed that both GtAu NPs and OpAu NPs do not induce any teratogenic activity and are safe to be used in the range of 1.0–167 µg ml
−1
.
“…Consequently, enhancement of these compounds found to be related to the total antioxidant capacity, iron reducing power, and free radicals scavenging activity and hence increasing the anticancer activity through lowering growth of the cancer cells. There is a correlation between the percentage of polyphenols consumed and the size of the produced nanoparticles (Alegria et al 2018). Amount of the polyphenol in the extract used during formation of the nano-extract increased when size of the nanoparticles decreased.…”
Background: Moringa oleifera is rich in various active phyto-constituents (tannins, sterols, terpenoids, flavonoids, saponins, anthraquinones, alkaloids, and vitamins) in addition to different minerals in its leaves and seeds. Presence of these constituents is responsible for the antioxidant activity and the ability to protect against oxidative damage. Based on measurements of the cytotoxic activities, M. oleifera leaves were found to be more effective than the plant seeds. Therefore, the plant leaves were selected for preparation of silver plant nano-extract during the present study. Methods: The silver nanoparticles (Ag-NPs) were synthesized then characterized by transmission electron microscope (TEM), ultraviolet-visible (UV-VIS) spectroscopy and dynamic light scattering (DLS) measurements. Moreover, the in vitro antioxidants were assayed in M. oleifera leaves extract before and after incorporating Ag-NPs through measurement of total polyphenolic compounds and scavenging activities against free radicals in addition to the cytotoxic activity against growth of human colon carcinoma. Furthermore, the phenolic compounds were detected by gas chromatography coupled with a mass spectrometer (GC/MS) and fourier transform infrared (FT-IR) spectroscopy. Also, the median lethal dose (LD 50) of the extract and nano-extract was evaluated. Results: It was showed that incorporation of Ag-NPs into the M. oleifera leaves extract enhanced the total antioxidant capacity, concentration of total polyphenolic compounds, reducing power and scavenging activity against attack of free radicals in addition to increasing the cytotoxicity against growth of colon cancer cells. This might be related to increasing the phenolic compounds as a result of incorporation of Ag-NPs and detected by the GC/MS and FT-IR analysis. It was found that there was no wide gap in the LD 50 between M. oleifera leaves extract and silver nano-extract. The LD 50 values of the M. oleifera leaves extract and silver nano-extract were about 14,250 and 13,750 mg/Kg, respectively. Conclusion: The study revealed that incorporation of Ag-NPs into the M. oleifera extract enhanced the in vitro antioxidative efficiency and might be related to increasing the phenolic compounds.
“…Gold nanoparticles are used in catalytic reactions of alkene hydrogenation [7], in chemoselective hydrogenation of crotonaldehyde to crotyl alcohol [8], in chemoselective hydrogenation of nitro compounds [9], and in heterogeneous hydroformylation of olefins [10]. Gold-based nanocatalysts are also used for reduction of nitro compounds [11,12].…”
An experimental study of molecular hydrogen adsorption on single gold nanoparticles of various sizes deposited on the surface of highly oriented pyrolytic graphite (HOPG) was carried out by means of scanning tunneling microscopy and spectroscopy. The effect of size on the HOPG/Au system was established. Hydrogen was dissociatively chemisorbed on the surface of gold nanoparticles with an average size of 5–6 nanometers. An increase in the size of nanoparticles to 10 nm or more led to hydrogen chemisorption being inhibited and unable to be detected.
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