Synthesis and antibacterial activity of ultrasmall silver nanoparticles by pulsed laser ablation in deionized water

Background: The main objective of this work is the synthesis and evaluation of silver nanoparticles (Ag NPs) by using pulsed laser ablation of a silver (Ag) target in deionized water and examining their antibacterial activity. Methods: Colloidal solutions of silver nanoparticles were prepared with different pulsed laser energies (620, 880, and 1000) mJ of wavelength 1064 nm and frequency 10 Hz. To determine their structure, optical, morphology, elemental composition, and infrared spectra, the synthesized Ag NPs were characterized using various high-throughput analytical techniques such as (UV-Vis) spectroscopy, transmission electron microgram (TEM), electron dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectra, and Zeta potential. Results: The results show that the properties of synthesized Ag NPs depend much more on the laser energy. The laser energy can be used to control the properties of the prepared nanoparticles. Uniform distributions of spherical ultrasmall Ag NPs with an average size of (3) nm were obtained suspended in deionized water, which is the most effective size for antibacterial activity. However, the result indicated that the ablated Ag NPs were stable for 4 months in deionized water. The antibacterial activity of the colloidal solution of synthesized Ag NPs against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria was then examined using the agar-well diffusion method. Conclusion: It was found that the prepared nanoparticles exhibited strong activity against E. coli and S. aureus bacteria growth. The average zones of inhibition of Ag NPs were found to be about (26) m¬¬¬¬¬¬m for E. coli and (32) mm for S. aureus bacteria.