Berlin 2024 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 8: Interface Controlled Properties, Nanomaterials and Microstructure Design II

MM 8.4: Vortrag

Montag, 18. März 2024, 12:30–12:45, C 230

Reversible mechanical actuation of nanoporous gold modified by electroactive self-assembled monolayers: Impact of the surface stress — •Olga Matts¹, Xinyan Wu², and Nadiia Mameka¹ — ¹Helmholtz-Zentrum Hereon, Geesthacht, Germany — ²Hamburg University of Technology, Hamburg, Germany

Hierarchical nanoporous (hc np) metals made by dealloying present novel opportunities for the development of light-weight, high surface-area materials with diverse functionalities in the fields of catalysis, energy storage, sensing, and actuation. Most hc np metals possess a bimodal pore size distribution, featuring pores of hundreds of nanometers with nanometer-sized pores located within their walls. Understanding the impact of the porous hierarchy on functional behavior of hc np materials is crucial to further enhance their performance. This work reports the actuation in np-Au with single and bimodal size distributions modified by ferrocene-terminated alkanethiol self-assembled molecules (SAMs). For this, in situ dilatometry and cantilever bending are employed in electrolyte under potential control, exploiting the ability of the electroactive molecules to undergo reversible redox reactions. Pronounced variations in the macroscopic length change of the hybrids are revealed in response to the voltage-induced redox transformations. The phenomenon can be explained by a reorientational motion of the alkyl chains and the ferrocene-moiety due to uptake of electrolyte's anions. The steric hindrance and local disorder in the SAM clamped to the gold surface induces the surface stress, that is compensated by the bulk stress, and results in the actuation of the hybrid.

Keywords: hierarchical nanoporous metals; self-assembled molecules; actuation; surface stress; surface functionalization