فهرست نشریات علمی دسترسی آزاد ایران

Gold nanoparticles (AuNPs) were prepared successfully as environmentally friendly colloids that contain high purity and no added chemical agents by using pulsed laser ablation in liquid (PLAL) process. Three different types of liquid environments were used for a systematic evaluation in order to assess the physical characteristics: structural, optical, and antibacterial, respectively, of each medium produced by using double-distilled deionized water (DDDW); sodium hydroxide (NaOH); and polyvinylpyrrolidone (PVP). X-ray diffraction (XRD) measurements confirmed that all the prepared AuNPs crystallized in a face-centered cubic (FCC) form, with the smallest crystallite sizes measured for NaOH-synthesized nanoparticles. Transmission electron microscopy (TEM) studies indicated spherical and mostly well spread nanoparticles with average diameters of around 25–39 nm. UV–Visible spectroscopy for optical characterization showed strongly marked surface plasmon resonance (SPR) absorptions of 356–587 nm with significant variation with the synthesis medium. The optical band gap energies, inferred from Tauc plots, were in the range of 3.8 to 4.7 eV, demonstrating robust coupling upon the size and surface electronic structure of nanoparticles. Antibacterial activity of the prepared AuNPs was measured in Gram-negative Escherichia coli and Gram-positive Streptococcus spp. Although green laser irradiation (532 nm, 300 mW) alone resulted in a relatively modest inhibition in bacterial growth, a significantly better antibacterial effect was demonstrated when laser irradiation coupled with AuNP treatment. The synergy behind this effect is due to laser-induced enhancement of bacterial membrane permeability leading to elevated uptake of nanoparticles and subsequent internal cell damage. The dramatically less bacterial viability was also confirmed by ELISA detection at 405 nm, which once again confirmed the drastic reduction in bacterial viability. In general, the results show that AuNPs, formed by PLAL can demonstrate a high antibacterial activity that could be easily enhanced by laser irradiation. The proposed plasmonic nanoparticle–laser synergy showed promise of PLAL-produced AuNPs for applications in photonic and photothermal antibacterial therapy.