Penta-twinned gold nanoparticles under pressure: a comprehensive study

We report on the high-pressure optical and mechanical properties of penta-twinned gold nanoparticles (PT-AuNPs) of different geometries: decahedra, rods and bipyramids. Our results show that, unlike single-crystal (SC-AuNPs), PT-AuNPs preserve both their non-cubic crystal structures and their overall morphology up to 30 GPa. This structural integrity under compression is related to an enhanced mechanical resilience of PT-AuNPs, despite exhibiting bulk moduli comparable to those of SC-AuNPs. Notwithstanding, comparable pressure-induced localized surface plasmon resonance redshifts - for all nanoparticle geometries - were observed. Our analysis indicates that these shifts are primarily caused by changes in the refractive index of the surrounding medium, with electron density compression playing a minor role, contrasting with the behavior in SC-AuNPs, where electron density compression has a greater influence.