Correlation between Spectroscopic and Mechanical Properties of Gold Nanocrystals under Pressure

The effects of nonhydrostatic pressure on the morphology and stability of gold nanorods (AuNRs) and nanospheres (AuNSs) in 4:1 methanol-ethanol mixtures were studied by optical absorption spectroscopy and transmission electron microscopy at pressures of up to 23 and 30 GPa, respectively. Solvent solidification and associated nonhydrostatic stresses were found to have a negligible effect on the shape and size of AuNSs. On the contrary, while AuNRs maintained their initial morphology in the hydrostatic range, the uniaxial stress component induced under nonhydrostatic conditions had a shearing effect on the AuNRs, breaking them into smaller particles. Interestingly, colloidal stability was maintained in all cases, and the particles showed no sign of aggregation, despite the severe nonhydrostatic conditions to which both AuNR and AuNS colloids were subjected.Financial support from Projects PGC2018-101464−B-I00 (Ministerio de Ciencia, Innovación y Universidades) and MALTA-Consolider Team (RED2018-102612-T) is acknowledged. We acknowledge J. A. Barreda-Argüeso and J. RuizFuertes for support with high-pressure measurements. P.M. thanks the ARC for grant CE170100026. L.M.L.-M. acknowledges grant PID2020-117779R and the Maria de Maeztu Units of Excellence Program (grant MDM-2017-0720) from the Spanish Ministerio de Ciencia e Innovación