Theoretical and experimental study into laser-induced gold nanoparticles for superior surface-enhanced raman spectroscopy applications.

This study presents a comprehensive theoretical and experimental investigation into the fabrication of three-dimensional gold nanostructures with tailored optical properties using a laser-induced method, aimed at enhancing applications based on localized surface plasmon resonance (LSPR) and Surface-Enhanced Raman Spectroscopy (SERS). The effects of the second harmonic (without filtering the fundamental harmonic) of Nd:YAG laser pulses, along with key parameters such as laser fluence and pulse count, are analyzed to achieve precise control over nanoparticle size, shape, and arrangement. Theoretical modeling using Fourier heat equations and the novel Generalized Finite Difference Time Domain (G-FDTD) method provides initial insights into the optical fluences necessary for the formation of surface gold nanoparticles. Experimentally, 100 nm gold thin films are irradiated with different fluences (0.48, 0.12, and 0.053 J/cm2) and pulse numbers (ranging from 1 to 50 pulses) of Nd:YAG laser with a time width of 60 ns. Results demonstrate that manipulating laser parameters significantly influences the localized surface plasmon resonance, offering a scalable and reproducible platform for designing stable, biocompatible, and high-performance nanostructures for applications based on LSPR, like SERS and enhanced fluorescence. Also, the formed gold elliptical NPs are simulated to understand the obtained results and the efficiency of the samples in SERS applications.