Morphology-dependent plasma behavior analysis in nanoparticle-enhanced laser-induced breakdown spectroscopy based on an intrinsic radiative enhancement framework

Abstract

Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) offers a robust approach for probing strong-field laser–matter interactions and plasmon-assisted energy redistribution at the nanoscale. In this study, Au nanoparticles (AuNPs) with distinct morphologies (nanospheres, nanorods, and nanocages) were deposited on Ti-based substrates to examine morphology-dependent plasma behaviour under nanosecond 1064 nm excitation. Time-resolved emission spectra, combined with Boltzmann-plot temperature diagnostics and Stark-broadening analysis, were employed to evaluate the evolution of electron temperature T_e and electron density n_e. To eliminate the influence of transition probabilities and temperature-dependent population effects, an intrinsic radiative enhancement model, R_s(t), was developed through Boltzmann correction and cross-line geometric averaging, allowing quantitative comparison of radiative efficiencies among different systems. The results indicate that small nanospheres (10 nm) and resonant nanorods substantially increase both T_e and n_e and sustain prolonged radiative persistence, implying efficient energy confinement. In contrast, larger nanospheres (40 nm) and off-resonant nanorods exhibit weak, rapidly decaying enhancement, whereas nanocages (40 nm) show apparent radiative suppression, possibly related to optical shielding or limited carrier transport. The R_s(t) analysis reveals that NELIBS enhancement arises from a morphology-dependent competition between radiative and non-radiative dissipation channels, providing quantitative insight into plasmon–plasma coupling in strongly driven nanostructures.