Abstract
The main antioxidants present in plant extracts—quercetin, β-carotene, gallic acid, ascorbic acid, hydroxybenzoic acid, caffeic acid, catechin and scopoletin—are able to synthesize silver nanoparticles when reacting with a Ag NO3 solution. The UV-visible absorption spectrum recorded with most of the antioxidants shows the characteristic surface plasmon resonance band of silver nanoparticles. Nanoparticles synthesised with ascorbic, hydroxybenzoic, caffeic, and gallic acids and scopoletin are spherical. Nanoparticles synthesised with quercetin are grouped together to form micellar structures. Nanoparticles synthesised by β-carotene, were triangular and polyhedral forms with truncated corners. Pentagonal nanoparticles were synthesized with catechin. We used Fourier-transform infrared spectroscopy to check that the biomolecules coat the synthesised silver nanoparticles. X-ray powder diffractograms showed the presence of silver, AgO, Ag2O, Ag3O4 and Ag2O3. Rod-like structures were obtained with quercetin and gallic acid and cookie-like structures in the nanoparticles obtained with scopoletin, as a consequence of their reactivity with cyanide. This analysis explained the role played by the various agents responsible for the bio-reduction triggered by nanoparticle synthesis in their shape, size and activity. This will facilitate targeted synthesis and the application of biotechnological techniques to optimise the green synthesis of nanoparticles.
Highlights
Nanotechnology, science and technology at the nanoscale of atoms and molecules, will help to address major societal challenges such as climate change, reducing carbon emissions, developing renewable energy, using resources more efficiently and meeting the medical needs of an ageing population [1].In recent years there has been growing interest in the search for new strategies for synthesising nanoparticles to minimise waste and achieve more sustainable and environmentally friendly processes
The antioxidants analysed in this study showed different capacities of synthesis, different shapes and sizes, and different aggregations and presence of capping agents
The micelle-like structures obtained with quercetin, the triangular nanoparticles and polyhedral forms, both with truncated corners synthesized with β-carotene and the pentagonal nanoparticles synthesized with catechin, stood out
Summary
In recent years there has been growing interest in the search for new strategies for synthesising nanoparticles to minimise waste and achieve more sustainable and environmentally friendly processes. The use of substances of biological origin, environmentally friendly solvents and renewable materials has become the key to the development of green synthesis of nanoparticles [2]. Metallic nanoparticles are of great scientific and technological interest because of their specific properties, which differ from those of conventional bulk materials, making them new technical tools [4]. Among the metallic nanoparticles obtained by green synthesis, those of silver stand out with numerous uses in electronics, clothing, paints, cosmetics, bactericides, biofungicides, biomedical applications, in the medical-pharmaceutical and food industries, etc. Silver oxide nanoparticles have great biomedical applications [6]. Silver (I) oxide shows great promise for use in medical polymers and nanodrugs [7]
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