INTRODUCTION Plasmonic materials, such as gold nanoparticles (AuNPs) are renowned for their strong light-matter interaction, including high extinction and near-field enhancement. These properties arise from localized surface plasmon resonances (LSPRs), which are the collective oscillation of the free electrons of metal nanoparticles when exposed to light. The resonance wavelength of AuNPs can easily be tuned across the visible (VIS) and near-infra-red (NIR) range by varying their size, shape, and surrounding, opening the door for applications in nanoscale (bio)sensing, photocatalysis, and photothermal processes. The near-field enhancement of LSPRs has been utilized to amplify intrinsically weak non-linear responses, such as second-(SHG) and third-harmonic generation (THG). Yet, these performances were achieved by highly engineered nanostructures, which require a demanding fabrication, the use of extremely short pulses, and are not readily scalable.