In this study, bay laurel extract (BLE) used as a reducing and capping agent for the synthesis of silver nanoparticles (AgNPs). The green-prepared AgNPs investigated using UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX) and Transmission electron microscopy (TEM). Formation of AgNPs monitored at ambient temperature by a change in color from the starting solution to dark brown. Green synthesis AgNps were investigated for antimicrobial activity. The microorganisms employed were E. coli, K. pneumoniae, B. cereus, S. aureus, C. lbicans and Aspergillus. The susceptibility of microorganisms against the six AgNPs solutions was determined using the disk diffusion method. The catalytic activity of the prepared AgNPs (sample, d) for basic brown 1 dye was investigated. The results showed the characteristic surface plasmon resonance peak of the AgNPs appeared at approximately 415 - 440 nm. XRD revealed peaks at 38.2, 44.16, 64.24 and 77.22 Ɵ, and the intensity of these peaks enhanced when using microwave curing compared to ambient temperature. SEM and TEM results showed that the silver nano particles have a spherical shape and the particle size for samples is less than 34 nm. FTIR spectroscopy measurements showed the binding of organic compounds on the surface of the silver nanoparticles. Highest antibacterial activity was enhanced with increasing of AgNPs dose and with increasing of extract ration against most of microorganisms except. Removal of basic brown 1 dye by the prepared AgNPs indicated complete dye removal after 8 h.
Metal nanoparticles have unique physical and chemical properties that are mainly different from those of bulk materials, making them a target of study by many researchers in recent years [
The leaves of the bay laurel plant (Laurus nobilis) are widely used as a spice in foods and for production of its essential oil [
The current study was designed for green synthesis of AgNPs from silver nitrate solution using an aqueous extract of bay laurel leaves. In addition, the antimicrobial activity of synthesized AgNPs was examined. The ability of the prepared AgNPs to remove basic brown 1 dye from aqueous solution was studied.
Healthy leaves of bay laurel collected from a local market,
Then, the extract was filtered, and the collected filtrate was stored at 4˚C for further use. AgNO3 99.9% was purchased from Sigma-Aldrich, Cairo, Egypt.
Bacterial strains were isolated from food samples, which included E-Coli and Klebsilla (gram negative); Bacillus Cereus and Staph Aureus (gram positive); Candida (yeast) and Aspirigullus (mold). The strains were kept at 4˚C on agar slant and sub cultured at 37˚C for 24 h on nutrient agar (oxoid UK) before any susceptibility test.
The reduction of silver ions into silver particles monitored by UV-visible spectroscopy (SHIMADZU MODELUV 1800, Japan) at a wavelength of 350 - 700 nm. A diffractometer XRD thin film PANalytical X pert PRO, Cu target, wave length 1.54 Å, 45 kV, 40 mA made in Holland was used for determining the crystallinity of prepared AgNPs. Scanning electron microscopy (SEM) examination was performed using JEOL JSM 6360 DLA, Japan, at 30 kV, and the SEM-EDX analysis was performed by FEI Company, Quanta FEG250, Holland. Transmission electron microscopy image were taken using a Hitachi, H-800 TEM. TEM samples were prepared by placing drops of aqueous dispersion of AgNPs in distilled water on 200 mesh carbon coated copper grids and dried at ambient conditions for 10 to 12 h. The FT-IR spectra of the products recorded on a JASCO Asia Portal-FT/IR-6300 Spectrometer using the KBr pellet method.
The antimicrobial activity of AgNPs was investigated by the disk diffusion method. The pure cultures of each strain were swabbed uniformly on the individual plates using sterile cotton at 35˚C on a rotary shaker at 200 RPM. Three disks were made in each plate, and 10, 20 and 50 µL of the sample of nanoparticle solution were poured using micropipettes onto the disks on all plates. The zones of inhibition (ZoI) around the discs were measured after incubation period.
Code | AgNO3, 5 mM, ml | BLE, ml | Ratio | Temperature |
---|---|---|---|---|
a | 90 | 10 | 10 | ambient |
b | 80 | 20 | 20 | ambient |
c | 70 | 30 | 30 | ambient |
d | 60 | 40 | 40 | ambient |
The catalytic activity of the prepared AgNPs (sample, d) for basic brown 1 (BB1),
Green reduction of Ag+ by BLE was monitored by observing the color of silver solutions that changed from colorless, to yellow, brown and then reddish brown as evidence of silver ion reduction,
The appearance of a strong peak at 437 nm indicated the formation of AgNPs that related to its surface plasmon resonance phenomena [
increased the R-value indicating that the content of silver nanoparticles increased. The organic compounds in the BLE contain numerous functional groups that can interact with silver to form a complex. Furthermore, the cleavage of C―C bonds of organic molecules released electrons required for the reduction of Ag. When the complex compound Ag+−BLE was reduced to Ag0−BLE, the organic molecules endow AgNPs with excellent dispersibility.
The extra peaks near 22.5, 26.2, 29.2 and 32.0 2Ɵ are due to the presence of organic compounds on the surface of AgNPs. The intensity of the characteristic peaks of AgNPs increased with increasing R ratio indicating progression of the reduction process due to the availability of a suitable amount of bio reducer of Ag+. Additionally, the intensities of the characteristic peaks of AgNPs prepared using microwave curing were higher than that prepared at room temperature. These results indicate that using microwave curing enhances the bio-synthesis process of AgNPs. The intensity of the peak at the (111) plane was greater than the other peaks, suggesting that this plane was the predominant one. According to Scherrer’s formula, the average sizes of AgNPs synthesized by leaf extracts at room temperature and using microwave curing are 22 and 28 nm, respectively [
The FTIR spectra of silver nanoparticles prepared with 40:60 (v/v) leaf extract: Ag+ (d) at ambient is shown in
TEM analysis gives actual information about the morphology of the surface of the AgNPs. TEM images of the prepared AgNPs with different magnifications are shown in Figures 6(a)-(c). They clearly show the formation of the best AgNPs with spherical and oval shapes in the size range of 17 - 34 nm. These perfect particle sizes with various shapes of AgNPs may be related to different
components of the plant extract [
Antibacterial activities of the prepared AgNPs using extract of Laurus nobilis against the tested organisms are shown in
The degradation process is dependent on the photocatalytic activity of AgNPs.
Sample | b | c | d | b | c | d | b | c | d | b | c | d | Blank | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dose, µL | 25 | 50 | 100 | 200 | −ve ZOI | +ve ZOI | ||||||||
Micro organism | Zone of inhibition* | |||||||||||||
E. Coli | 0 | 0 | 0 | 11.40 | 17.53 | 16.65 | 22.51 | 22.35 | 18.2 | 26.2 | 28.6 | 32.3 | 0 | 22.75 |
K. Pneumoniae | 11.55 | 12.61 | 13.05 | 22.7 | 20.12 | 21.4 | 22.52 | 16.92 | 20.11 | 34.17 | 23.07 | 25.19 | 0 | 20.61 |
B. Cereus | 0 | 12.37 | 12.61 | 17.72 | 17.26 | 16.25 | 20.34 | 26.64 | 24.93 | 23.34 | 26.86 | 27.17 | 0 | 25.5 |
S. Aureus | 0 | 12.57 | 11.68 | 15.1 | 18.29 | 18.64 | 18.17 | 16.47 | 17.36 | 21.56 | 26.93 | 20.87 | 0 | 27.44 |
C. lbicans | 0 | 0 | 11.05 | 12.34 | 13.11 | 14.11 | 16.39 | 13.14 | 13.83 | 25.48 | 26.69 | 27.95 | 0 | 0 |
Aspergillus | 0 | 0 | 0 | 13.22 | 14.62 | 16.32 | 16.05 | 18.18 | 16.52 | 25.28 | 22.54 | 21.4 | 0 | 0 |
*Values are mean inhibition zone (mm) ± S.D of three replicates.
From the outcomes of this study, we can conclude that silver nano-particles can be prepared using an aqueous extract of bay leaf. The stability of biosynthetic silver nanoparticles was monitored for up to six months. The prepared AgNPs showed antimicrobial activity against and it increased with increasing the dose of plant extract. The prepared AgNPs showed a high potential to degrade BB1 in aqueous media.
Thanks to the help of Deanship of Scientific Research at Al-Baha University, KSA. This work was financial supported by Deanship of Scientific Research at Al-Baha University, Kingdome of Saudi Arabian (48/1438).
The author declares that they have no competing interests.
Al-Ghamdi, A.Y. (2019) Antimicrobial and Catalytic Activities of Green Synthesized Silver Nanoparticles Using Bay Laurel (Laurus nobilis) Leaves Extract. Journal of Biomaterials and Nanobiotechnology, 10, 26-39. https://doi.org/10.4236/jbnb.2019.101003