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Item type:Publication, Access status: without files , Exceptional broadband absorption of nanoporous gold explained by plasmonic resonances at dangling ligaments(Optica Publishing Group, 2026-07-13); ; ; ; Nanoporous gold (npAu) has emerged as a potential candidate for many optical applications, exploiting its large surface-to-volume ratio and high broadband absorption. However, the physical origin of its enhanced visible and near infrared absorption remained unclear and was rather explained by simplified phenomenological models. Here, we have employed leveled-wave approximants to simulate the optical response of realistic npAu structures. First, our simulations reproduced well the experimental absorption spectra. Second, we identify multiple resonances in the gaps between dangling ligaments that occur at the top and bottom surfaces of npAu films as the key contribution to the broadband absorption. These resonances at the surface of npAu cannot be captured by bulk effective medium models and should be considered separately as a surface effect. The additional absorption due to dangling ligaments contributes up to 80% to the overall absorption of npAu. Our results provide deeper insights into the absorption behavior of npAu, indicating promising avenues for photocatalysis and sensing applications.Publicationtype: Journal Article13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Bioinspired curved brick-mortar architectures for enhanced mechanical performance: Insights from cuscuta reflexa stem morphologyWe investigated the epidermal morphology, microstructure, and mechanical properties of the stem of Cuscuta reflexa (dodder) to uncover the mechanisms underlying its high mechanical strength. Natural stems and experimentally fabricated bio-inspired models were examined using microscopy, numerical simulations, and mechanical testing. The results show that the stem’s distinctive curved brick-and-mortar architecture plays a critical role in enhancing mechanical performance, providing superior strength compared to conventional stem structures (e.g., those with straight interfaces). This bio-inspired curved configuration produces tensile stress–strain curves shifted to higher stress levels relative to simple (uncurved) brick-and-mortar designs, enabling the structure to withstand greater tensile loads before failure. Furthermore, flexural tests on the bio-inspired models demonstrated a 20% increase in flexural strength for the modified curved brick-and-mortar structure compared to the basic uncurved configuration. Crack propagation in the modified composite is influenced by elevated shear stress at the interfaces, promoting preferential crack growth perpendicular to the loading direction (horizontal) within the hard mortar phase. This behavior enhances fracture toughness through longer crack propagation paths and increased energy dissipation. Additionally, the larger interfacial area and higher mortar volume fraction in the modified structure contribute to more efficient load transfer and improved crack resistance.Publicationtype: Journal Article7 5 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Chemical Interface Damping by Electrochemical Gold Oxidation(American Chemical Society (ACS), 2024-09-19); ; ; ; Chemical interface damping is a change in the effective collision frequency of conduction band electrons in metal originating from a chemical change in the metal interface. In this work, we present in situ ellipsometric measurements that reveal the chemical interface damping effect from the electrochemical oxidation of single-crystal and polycrystalline gold films. We observed an increase in collision frequency of up to 21 meV for single-crystalline gold. To compare with literature results obtained with thiols and metal oxides on gold nanoparticles, we normalize the collision frequency by the electron mean free path to the surface of the structure. We show that electrochemical gold oxidation provides a stronger effect on the collision frequency than these coatings. Similar ellipsometric experiments have previously been conducted to investigate the optical properties of gold oxide but without taking chemical interface damping into account. The change in reflection from the oxidation of gold was solely attributed to the oxide coating. We also show that the chemical interface damping effect saturates at a larger effective oxide thickness, which is attributed to the stabilization of the gold-oxide interface. Our results are important for the design of optoelectronic and photochemical experiments involving nanostructured gold. Electrochemical gold oxidation can be used to significantly change the optical response of such structures and to increase the efficiency of the light-matter interaction.Publicationtype: Journal Article33 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Size-dependent photoemission study by electrochemical coarsening of nanoporous gold(American Chemical Society (ACS), 2024-07-30); ; ; ; The generation and utilization of hot charge carriers in plasmonic materials have emerged as a topic of significant importance with profound implications across multiple disciplines, including optoelectronics, photovoltaics, photocatalysis, and sensing. In this study, we investigate the hot electron transfer from nanoporous gold (npAu) dependent on the structure size, utilizing both the nanoscale feature size and the interconnected nature of this material. We employed photoelectron injection from nanoporous gold into the electrolyte under UV illumination as a test electron transfer process. Nanoporous gold thin films with sub-10 nm initial ligament diameter are stepwise coarsened by potential cycles in a photoelectrochemical setup, thereby allowing us to precisely probe the influence of the ligament diameter on the photocurrent response. The resulting ligament diameter variations are confirmed by scanning electron microscopy (SEM) analysis. As the ligament diameter increased from 8 to 16 nm, there was a corresponding decrease in quantum efficiency proportional to the inverse ligament diameter squared. Such a dependency is expected for electrons excited by surface collisions. For the small ligament diameter of 10 nm, we estimate an emission efficiency of excited 6sp electrons as 3.14%, reaching 23% for the surface-excited electrons.Publicationtype: Journal Article20