A study published in Nature Communications shows that gold morphology, modified at the nanoscale, can significantly alter its optical and electronic properties. The work, coordinated by Nicolò Maccaferri (Umeå University, Sweden), stems from an international collaboration involving the Istituto Italiano di Tecnologia, the University of Modena and Reggio Emilia and the University of Milano-Bicocca (sample nanofabrication), the Italian National Research Council (cathodoluminescence measurements), and the University of Rome Tor Vergata (Tommaso Giovannini, theoretical rationalization).

The research investigates thin films of nanoporous gold, a metamaterial characterized by pores of variable size, and compares them with continuous gold films. Ultrafast pump-probe experiments reveal that the porous structure absorbs more energy over a broader spectral range, leading to much higher transient electronic temperatures (up to ~3200 K compared to ~800 K in bulk gold) and slower cooling dynamics, with direct implications for hot-carrier generation processes.

This behavior is directly linked to the different Fermi–Dirac distribution in the two materials. In nanoporous gold, the elevated electronic temperature makes electronic states available at lower energies, thereby activating optical transitions over a wider energy range. Atomistic modeling confirms this picture, showing that while intraband transitions largely dominate the optical spectrum of bulk gold, nanoporous gold exhibits a significant interband contribution extending to lower energies. This is also consistent with cathodoluminescence measurements, which show that nanoporous gold supports localized plasmonic resonances spanning a broad region of the visible spectrum.

Overall, the results identify nanoporosity as a new design parameter to control light–matter interaction and hot-carrier generation, with potential implications for nanophotonics and photo-induced processes.

Reference: Nature Communications 17, 829 (2026). DOI: 10.1038/s41467-026-68506-0