Abstract <p>The purity of gold and silver nanoparticles (NPs) generated through laser ablation in water without the use of surfactants renders them particularly intriguing. Nevertheless, the application of these nanoparticles is still restricted by their long-term stability. The Au@Ag core/shell NPs were synthesized in this study using a Q-switched Nd : YAG laser operating at a wavelength of 532 nm through pulsed laser ablation in distilled water. The monometallic nanoparticles (MNPs) were transformed into bimetallic nanocomposites with a core/shell structure, and the thickness of the shell was adjusted. The structural, morphological, and optical properties of the Au@Ag core-shell nanoparticles were investigated in relation to the number of laser pulses. UV–Vis spectroscopy was employed to investigate the quantum confinement and surface plasmon resonance of the nanostructured particles that had been prepared. The results indicated substantial modifications in color behavior. The surface plasmon resonance of the synthesized nanoparticle solutions was observed at approximately 412 nm for silver nanoparticles and 512 nm for gold nanoparticles. Two surface plasmon resonance peaks were identified at 410 and 517 nm for the Au/Ag in the core-shell structures. The X-ray diffraction analysis revealed that the Au and the Ag NPs possessed a face-centered cubic structure and were crystal-like. The spherical core-shell morphology of the synthesized Au@Ag nanoparticles was plainly demonstrated by transmission electronic microscopic images. The Ag shell became thicker as a result of a greater increase in the laser pulses, which in turn increased the size of the Au@Ag nanoparticles. The particle size was in range from 65 to 350 nm on average.</p>