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Figure 6: XRD Pattern of Silver Nanoparticles: Angle (2 )

The document summarizes the characterization and antimicrobial activity of silver nanoparticles synthesized using the leaf extract of P. glabrum. It reports that the silver nanoparticles formed were spherical in shape and ranged in size from 10 to 35 nm based on SEM analysis. XRD analysis revealed the crystalline nature of the nanoparticles. Gram negative bacteria were found to be more sensitive to the silver nanoparticles than gram positive bacteria, with zones of inhibition up to 12 mm seen against S. typhi. The antimicrobial mechanism is believed to involve disruption of cell membranes and interaction of silver nanoparticles with sulfur and phosphorus containing biomolecules inside bacterial cells.

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38 views2 pages

Figure 6: XRD Pattern of Silver Nanoparticles: Angle (2 )

The document summarizes the characterization and antimicrobial activity of silver nanoparticles synthesized using the leaf extract of P. glabrum. It reports that the silver nanoparticles formed were spherical in shape and ranged in size from 10 to 35 nm based on SEM analysis. XRD analysis revealed the crystalline nature of the nanoparticles. Gram negative bacteria were found to be more sensitive to the silver nanoparticles than gram positive bacteria, with zones of inhibition up to 12 mm seen against S. typhi. The antimicrobial mechanism is believed to involve disruption of cell membranes and interaction of silver nanoparticles with sulfur and phosphorus containing biomolecules inside bacterial cells.

Uploaded by

Afrah M
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Where „D‟ is the mean crystalline size of the particle, K is the shape factor whose value is 1-0.

9, λ is
the wavelength of the X-ray radiation source that is 0.154 nm, β is (π/180) օ full width at half maximum
(FWHM) and „θ‟ is the bragg angle respectively. The sizes of silver nanoparticles of leaf extract of P.glabrum
21.59 nm.
60

50

40

Intesity
30 (111)

(200)
20 (220)

(311)

10

0
30 40 50 60 70 80

Angle (2)

Figure 6: XRD pattern of silver nanoparticles

A representative SEM microphotograph of the silver nanoparticles formed by P. glabrum are shown in
Figure 7. This photograph shows spherical shaped nanoparticles as well as some aggregates. Observation of
such images in an optical microscope, reveals that assembles were found to be aggregates of silver nanoparticles
in the size ranges 10 to 35 nm. The nanoparticles were not in direct contact even within the aggregates
indicating stabilization of the nanoparticles by capping agent. The separation between silver nanoparticles seen
in the SEM images could be due to capping by proteins and would explain the UV-Vis spectroscopy
measurement which is characteristic of well dispersed silver nanoparticles. The above findings corroborates
with the results of previous observation made by 36 in their study on biosynthesis of silver nanoparticles in
Aeromonas species SH10.

Figure 7: SEM images of silver nanoparticles synthesized by leaf extract P. glabrum

Antimicrobial activity
Silver nanoparticles shows good antimicrobial activity against both gram positive and gram negative
bacteria. Gram negative bacteria were more sensitive to silver nanoparticles than the gram positive bacteria.
Silver nanoparticles at different concentration (20, 40, 60, 80 and 100µl) showed different zone of inhibition
(ZOI) with respect to different microorganisms. The gram negative bacteria S. typhi, P. aeruginosa and E. coli
showed maximum zone of inhibition at 12, 8 and 8 mm respectively but, gram positive bacterium S. aurues
showed 6 mm (Figure 8 and table 2). Similar results were found in the fruit extract of Leea indica 37. In the
present investigation S. typhi shows more sensitive towards silver nanoparticles and produces 12 mm ZOI and
least activity was observed in S. aurues. The differential sensitivity of gram negative and gram positive bacteria
towards silver nanoparticles is possibly depends on cell wall structure. The cell wall of gram positive bacteria
composed of a thick peptidoglycan layer, which consisting of linear polysaccharide chains cross linked by short
peptides thus forming more rigid structure leading to difficult penetration of the silver nanoparticles compared
to the gram negative bacteria where the cell wall possesses thinner peptidoglycan layer 38 .The silver
DOI: 10.3109/1040841X.2014.912200 Silver nanoparticles 2

nanoparticles attached to the negatively charged cell wall cause accumulation of protein precursor which
alters membrane permeability results in dissipation of the proton motive force 39. Silver has a greater affinity
towards phosphrous and sulphur containing biomolecules in the cells. Sulphur containing proteins in the cell
membrane and phosphrous containing DNA elements are preferential sites for the silver nanoparticles
binding 40affecting the replication machinery.

Figure 8: Antimicrobial activity of concentrations of silver nanoparticles (20, 40, 60, 80 and 100 µl)

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