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Microstructural, spectroscopic, and antibacterial properties of silver-based hybrid nanostructures biosynthesized using extracts of coriander leaves and seeds

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ABSTRACT

Coriander leaves and seeds have been highly appreciated since ancient times, not only due to their pleasant flavors but also due to their inhibitory activity on food degradation and their beneficial properties for health, both ascribed to their strong antioxidant activity. Recently, it has been shown that coriander leaf extracts can mediate the synthesis of metallic nanoparticles through oxidation/reduction reactions. In the present study, extracts of coriander leaves and seeds have been used as reaction media for the wet chemical synthesis of ultrafine silver nanoparticles and nanoparticle clusters, with urchin- and tree-like shapes, coated by biomolecules (mainly, proteins and polyphenols). In this greener route of nanostructure preparation, the active biocompounds of coriander simultaneously play the roles of reducing and stabilizing agents. The morphological and microstructural studies of the resulting biosynthesized silver nanostructures revealed that the nanostructures prepared with a small concentration of the precursor Ag salt (AgNO3 =5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO3 =0.5 M) are polydisperse and formation of supramolecular structures occurs. Fourier transform infrared and Raman spectroscopy studies indicated that the bioreduction of the Ag− ions takes place through their interactions with free amines, carboxylate ions, and hydroxyl groups. As a consequence of such interactions, residues of proteins and polyphenols cap the biosynthesized Ag nanoparticles providing them a hybrid core/shell structure. In addition, these biosynthesized Ag nanomaterials exhibited size-dependent plasmon extinction bands and enhanced bactericidal activities against both Gram-positive and Gram-negative bacteria, displaying minimal inhibitory Ag concentrations lower than typical values reported in the literature for Ag nanoparticles, probably due to the synergy of the bactericidal activities of the Ag nanoparticle cores and their capping ligands.

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X-ray diffraction (XRD) patterns of samples S-0.5M and L-0.5M.Notes: Stars and circles indicate the positions of the X-ray diffraction peaks of silver chloride and metallic silver respectively, in agreement with the corresponding JCPDS files. Silver chloride: JCPDS file number 31-1238. Metallic silver: JCPDS file number 04-0783.Abbreviations: JCPDS, Joint Committee on Power Diffraction Standards; L-0.5M, final colloid obtained using coriander leaf extract and 0.5 M AgNO3; S-0.5M, sample obtained using extracts of coriander seeds and 0.5 M AgNO3 solution.
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f1-ijn-11-4787: X-ray diffraction (XRD) patterns of samples S-0.5M and L-0.5M.Notes: Stars and circles indicate the positions of the X-ray diffraction peaks of silver chloride and metallic silver respectively, in agreement with the corresponding JCPDS files. Silver chloride: JCPDS file number 31-1238. Metallic silver: JCPDS file number 04-0783.Abbreviations: JCPDS, Joint Committee on Power Diffraction Standards; L-0.5M, final colloid obtained using coriander leaf extract and 0.5 M AgNO3; S-0.5M, sample obtained using extracts of coriander seeds and 0.5 M AgNO3 solution.

Mentions: Representative X-ray diffraction patterns of samples prepared by using coriander seed and leaf extracts are shown in Figure 1. In these patterns, well-defined diffraction peaks corresponding to the (111), (200), (220), and (311) planes of face-centered cubic (fcc) metallic silver (Joint Committee on Power Diffraction Standards [JCPDS] file number: 04-0783) are clearly observed.14 The mean (± SD) length (L) perpendicular to the (111) planes calculated using the Scherrer equation for the samples L-0.5M and S-0.5M were 18(±2) and 16(±2) nm, respectively. The relative intensities of the Bragg peaks were strikingly different from those observed in the bulk standard reference sample (JCPDS file number: 04-0783), indicating that the (111) Bragg peaks in both biosynthesized samples were more intense than those found in the reference sample. Thus, the relative intensities of the Bragg peaks associated to the (200), (220), and (311) planes with respect to the intensity of the (111) diffraction peak were 10%, 22%, and 15% for the sample L-0.5M and 20%, 22%, and 20% for the sample S-0.5M, respectively, whereas the relative intensities of these peaks in the standard bulk sample were 40%, 25%, and 26%, respectively (JCPDS file number: 04-0783). These features indicate crystalline texture in the biosynthesized nanoparticles where the (111) crystal faces are predominantly exposed, probably promoted by the reduction in the surface energy of the particles since the close-packed (111) surface exhibits the lowest surface energy for the fcc metals.22,23


Microstructural, spectroscopic, and antibacterial properties of silver-based hybrid nanostructures biosynthesized using extracts of coriander leaves and seeds
X-ray diffraction (XRD) patterns of samples S-0.5M and L-0.5M.Notes: Stars and circles indicate the positions of the X-ray diffraction peaks of silver chloride and metallic silver respectively, in agreement with the corresponding JCPDS files. Silver chloride: JCPDS file number 31-1238. Metallic silver: JCPDS file number 04-0783.Abbreviations: JCPDS, Joint Committee on Power Diffraction Standards; L-0.5M, final colloid obtained using coriander leaf extract and 0.5 M AgNO3; S-0.5M, sample obtained using extracts of coriander seeds and 0.5 M AgNO3 solution.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036574&req=5

f1-ijn-11-4787: X-ray diffraction (XRD) patterns of samples S-0.5M and L-0.5M.Notes: Stars and circles indicate the positions of the X-ray diffraction peaks of silver chloride and metallic silver respectively, in agreement with the corresponding JCPDS files. Silver chloride: JCPDS file number 31-1238. Metallic silver: JCPDS file number 04-0783.Abbreviations: JCPDS, Joint Committee on Power Diffraction Standards; L-0.5M, final colloid obtained using coriander leaf extract and 0.5 M AgNO3; S-0.5M, sample obtained using extracts of coriander seeds and 0.5 M AgNO3 solution.
Mentions: Representative X-ray diffraction patterns of samples prepared by using coriander seed and leaf extracts are shown in Figure 1. In these patterns, well-defined diffraction peaks corresponding to the (111), (200), (220), and (311) planes of face-centered cubic (fcc) metallic silver (Joint Committee on Power Diffraction Standards [JCPDS] file number: 04-0783) are clearly observed.14 The mean (± SD) length (L) perpendicular to the (111) planes calculated using the Scherrer equation for the samples L-0.5M and S-0.5M were 18(±2) and 16(±2) nm, respectively. The relative intensities of the Bragg peaks were strikingly different from those observed in the bulk standard reference sample (JCPDS file number: 04-0783), indicating that the (111) Bragg peaks in both biosynthesized samples were more intense than those found in the reference sample. Thus, the relative intensities of the Bragg peaks associated to the (200), (220), and (311) planes with respect to the intensity of the (111) diffraction peak were 10%, 22%, and 15% for the sample L-0.5M and 20%, 22%, and 20% for the sample S-0.5M, respectively, whereas the relative intensities of these peaks in the standard bulk sample were 40%, 25%, and 26%, respectively (JCPDS file number: 04-0783). These features indicate crystalline texture in the biosynthesized nanoparticles where the (111) crystal faces are predominantly exposed, probably promoted by the reduction in the surface energy of the particles since the close-packed (111) surface exhibits the lowest surface energy for the fcc metals.22,23

View Article: PubMed Central - PubMed

ABSTRACT

Coriander leaves and seeds have been highly appreciated since ancient times, not only due to their pleasant flavors but also due to their inhibitory activity on food degradation and their beneficial properties for health, both ascribed to their strong antioxidant activity. Recently, it has been shown that coriander leaf extracts can mediate the synthesis of metallic nanoparticles through oxidation/reduction reactions. In the present study, extracts of coriander leaves and seeds have been used as reaction media for the wet chemical synthesis of ultrafine silver nanoparticles and nanoparticle clusters, with urchin- and tree-like shapes, coated by biomolecules (mainly, proteins and polyphenols). In this greener route of nanostructure preparation, the active biocompounds of coriander simultaneously play the roles of reducing and stabilizing agents. The morphological and microstructural studies of the resulting biosynthesized silver nanostructures revealed that the nanostructures prepared with a small concentration of the precursor Ag salt (AgNO3 =5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO3 =0.5 M) are polydisperse and formation of supramolecular structures occurs. Fourier transform infrared and Raman spectroscopy studies indicated that the bioreduction of the Ag− ions takes place through their interactions with free amines, carboxylate ions, and hydroxyl groups. As a consequence of such interactions, residues of proteins and polyphenols cap the biosynthesized Ag nanoparticles providing them a hybrid core/shell structure. In addition, these biosynthesized Ag nanomaterials exhibited size-dependent plasmon extinction bands and enhanced bactericidal activities against both Gram-positive and Gram-negative bacteria, displaying minimal inhibitory Ag concentrations lower than typical values reported in the literature for Ag nanoparticles, probably due to the synergy of the bactericidal activities of the Ag nanoparticle cores and their capping ligands.

No MeSH data available.


Related in: MedlinePlus