Journal of Applied Sciences and Nanotechnology

This study was carried out for the mycosynthesis of silver nanoparticles by Candida albicans supernatant.  All the isolates used in this study were taken from the patients who existed at Al-Elweya children's teaching hospital in Baghdad, Iraq. Mycosynthesized silver nanoparticles were characterized by color visualization, ultraviolet-visible (UV) spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The UV-Vis spectroscopy examination has shown the highest absorbance (λmax) at the wavelength of 429 nanometers, which indicated the creation of silver nanoparticles. Furthermore, the results of the antibacterial potential of AgNO₃ and AgNPs against Klebsiella pneumoniae and Staphylococcus haemolyticus bacteria showed the highest effect of AgNO3 against Staphylococcus haemolyticus when the diameter of the inhibition zone reached (14.00 mm). In contrast, the lowest effect of the AgNO₃ was with the diameter of the inhibition zone that reached (11.66 mm). The highest effect of the AgNO₃ against Klebsiella pneumoniae by the diameter of the inhibition zone was reached (12.66mm), while the lowest effect was (9.00mm). The highest effect of the AgNPs against Klebsiella pneumoniae by the diameter of the inhibition zone reached (16.00mm), while the lowest effect was (13.00mm). The highest effect of the AgNPs against Staphylococcus haemolyticus by the diameter of the inhibition zone was reached (17.33mm). Where the lowest effect by the diameter of the inhibition zone was reached (14.00mm). Interestingly, this revealed that Staphylococcus haemolyticus was more susceptible to silver nitrate (AgNO₃) and silver nanoparticles (AgNPs) than Klebsiella pneumoniae.

Biosynthesis of AgNPs is a new approach in the field of nanotechnology with optimistic implementation in medicine, food control, and pharmacology. In this study, the silver nanoparticles were produced by Lactobacillus gasseri filtrate. The production of AgNPs was confirmed by the color change from yellow to brown. Using UV visible spectrophotometer at 424 nm wavelength, and X-ray diffraction, it was found that the size of the synthesized particles was 58.5 nm after applying Scherrer’s equation. The inhibitory activity of silver nitrate on the growth of some pathogenic isolates was studied Staphylococcus haemolyticus Gram positive, and Klebsiella pneumoniae Gram negative. The highest inhibitory diameter was 14.6 mm at 100% concentration (stock) against Staphylococcus haemolyticus bacteria was followed by that of Klebsiella pneumoniae bacteria with an average inhibition zone diameter reached 13.6 mm at 100% concentration. The highest effect was of AgNPs on the growth of Staphylococcus haemolyticus bacteria, as it found the average diameter of the inhibition zone reached to 29.3 mm, followed by Klebsiella pneumoniae with the average diameter of the inhibiting zone it was 22.6 mm at 100% concentration (stock). This study showed AgNPs have more antibacterial activity against Gram positive bacteria than Gram negative bacteria. The importance of this study lies in testing the effectiveness of by Lactobacillus gasseri bacteria in the biosynthesis of silver nanoparticles and studying their antibacterial activity on pathogenic bacteria.

In this research, raw multiwalled carbon nanotubes (R-MWCNT) was successfully functionalized using sulfuric acid and nitric acid. Then a hybrid (ZnO-MWCNT) synthesized by the sol-gel method where diethylene glycol was used as a solvent and stabilizer that works to prevent the accumulation of nanoparticles and reduces the viscosity of the solution. A group of diagnostic techniques, including XRD, UV-Vis, EDX and microscopy has recognized the structural and optical properties of the prepared nanoparticles. High Resolution Electronic Scanner (FE-SEM) was also used in the investigation. FE-SEM images showed the formation of the hybrid (ZnO-MWCNT) by the growth of spherical clusters on the surface of the cross-linked tubes (MWCNT). In addition, FE-SEM images confirmed the success of a ZnO-MWCNT hybrid. The emergence of spherical shapes deposited on cylindrical tubes and associated with a wrinkled surface was recognized. In addition, the particle size ratio increased. The UV-Vis spectra revealed that all the composites had good absorbency with a shift towards short wavelengths. While it was observed from the analysis of X-ray diffraction (XRD) the formation of a hexagonal wurtzite crystal structure due to zinc oxide with a polycrystalline nature. The average crystal size calculated from the Debye-spark equation increased with the increase in the concentration of the streaked material. Antibacterial activity was studied for all prepared samples against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) at different μg/ml concentrations (500, 750, and 1000). It was observed that the highest inhibition Zone for functionalized multiwalled carbon nanotubes (F-MWCNT) and ZnO-MWCNT hybrid was (17.3, 12.3mm), (22.5, 19mm) for Escherichia coli and Staphylococcus aureus, respectively.