Results
According to Figure 1, the initial sign of silver nanoparticle synthesis is the changeable of the sample color from light yellow to dark brown.
Figure 2 showed the results of UV-Vis spectroscopy. According to reference (26), the presence of silver nanoparticles can be inferred from the absorption peak occurring at a wavelength of 430 nm. This is because silver tends to absorb light within the range of 400-450 nm.
The X-ray diffraction (XRD) pattern displayed in Figure 3 corresponds to the synthesis of silver nanoparticles using the hydroalcoholic extract of the plant. The pattern shows peaks at 2θ values of 23.35°, 27.56°, 32.04°, and 46.00°, which are indicative of the spherical shape of the nanoparticles. Moreover, the XRD pattern matches perfectly with the reference pattern (JCPDS No. 04-0783) for silver nanoparticles. The formula provided can be used to determine the crystallite size of silver nanoparticles:
\begin{equation} D=\ \frac{\text{kλ}}{\text{βcosθ}}\nonumber \\ \end{equation}
In the above relation, K = 0.9 was the form factor, λ The X-ray wavelength is equal to 1.5406 angstroms and β is the full width at half the maximum peak diffraction, θ is the angle corresponding to the diffraction. From this calculation, the size of silver nanoparticles was approximately 29 nm (28.46nm ).
To determine the functional groups responsible for the synthesis of silver nanoparticles in Polygonum aviculare extract, its hydroalcoholic extract was analyzed using FT-IR spectroscopy. Figure 4 presents the FT-IR spectrum of this plant extract, where the broad and intense peak observed at 3416.09 cm-1 represents the stretching vibration of the hydroxyl group (OH) present in water, phenolic compounds, and flavonoids. The peak observed at 2926.40 cm-1 corresponds to the presence of alkyl and CH groups, whereas the peak at 1616.91 cm-1 is associated with the C=O bond of the amide group and the C=C bond of aromatic rings. Additionally, the peaks at 1060.81 cm-1 are related to the presence of ether connections. The FT-IR analysis also revealed the presence of various functional groups, such as hydroxyl, carboxyl, and carbonyl, on the surface of the nanoparticles, which contributed to their negative charge (as shown in Figure 4). The peak at 1604 cm-1 is attributed to the C=C stretching vibration of aromatic rings, and the peak at 1360 cm-1 corresponds to C–H bending. The peaks observed at 1061 cm-1 are related to the C-O tensile vibration bonds in the ester and acid groups, and the bonds at 2839/13 and 2921/88 cm-1 correspond to the C-H tensile bond in alkane compounds. The strong peaks at 3400 cm-1 correspond to -OH tensile due to the presence of phenolic compounds in the Polygonum aviculare L. extract. The intensity of most bands is reduced due to the reduction of silver ions during the synthesis of silver nanoparticles.
Figure 5 showed the FESEM image of the nanometer dimensions of silver particles and shows the spherical shape at all magnifications. According to FESEM images, the cumulative size of nanoparticles varies between 40 and 70 nm .
Figure 6 showed the transmitting electron microscope TEM of silver nanoparticles synthesized with polygonum aviculare L. extract. As can be seen from the pictures, silver nanoparticles were in a darker image and have a spherical shape and a good distribution and around the nanoparticles, a light background is observed, which is related to the solvent, and because the density of the solvent against the passage of light is lower than the density of silver nanoparticles, and therefore silver nanoparticles are darker and solvent lighter in the image.
Figure 7 and Table 1 showed the Results of the antioxidant properties of silver nanoparticles. The synthesized showed that the 50% free radical scavenging (IC50) inhibition rate of the synthesized nanoparticles was calculated to be 15.63mg /L Compared to the standard antioxidant ascorbic acid with IC50 equal to 11.89 mg /L showed excellent antioxidant activity.
Figure 8 showed that synthesized silver nanoparticles by Polygonum aviculare L. extract had more antibacterial properties against Gram-negative E coli. than Gram-positive S. aureus, the highest growth inhibitory zone corresponds to the concentration of 40 (%v/v) of synthesized silver nanoparticles and the lowest growth halo corresponds to the concentration of 10 (%v/v) (Table 2).