Laser Ablation of Tungsten Metal for Au@WO₃ Core-Shell Formation: A Characterizing Study at Different Laser Fluences

This study presents the synthesis and characterization of Au@WO₃ core-shell nanoparticles using a laser ablation in liquid technique. A 1064-nm Nd laser was employed to produce the nanoparticles at varying laser fluences, ranging from 3.18 to 19.10 J/cm². The observed absorption peaks are attributed to the WO3 nanoparticles and the surface plasmon resonance of Au nanoparticles, with wavelengths ranging from 327 to 523 nm, respectively. However, the bandgap energy values decreased from 3.46 to 3.12 eV as a result of increased laser fluence. The photoluminescence (PL) measurements reveal six prominent peaks centered at wavelengths of 357 nm, 359 nm, 361 nm, 362 nm, 363 nm, and 365 nm, which increase in intensity with the thickness of the nanoparticle shells. The XRD analysis confirmed the presence of Au and WO₃ nanoparticles, the diffraction peaks are presented at 2θ= 38.1°, 44.3°, 64.5°, and 77.5°. In the Raman spectrum, the vibrational modes of Au@WO₃ nanoparticles were observed at 716, 948 (cm)⁻¹ which represents the W=O and O-W-O stretching bonds, respectively. These modes indicate the formation of monoclinic tungsten oxide. The EDX spectrum showed an increase in the tungsten weight percentage from 15.74 to 24.45%. It also shows an increase in the oxygen weight percentage from 35.29 to 78.80% due to the increased laser fluence. Additionally, the FE-SEM morphology demonstrated an increase in nanoparticle size from 21.64 to 72.11 nm as the laser fluence is elevated. Finally, the TEM investigation provided a high-resolution image of the core-shell structure of the prepared Au@WO₃ nanoparticles. As the laser fluence increased, the shell thickness also increased, resulting in larger nanoparticles with a thicker shell.