Browsing by Author "Krahne, Roman"

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    Dry synthesis of bi-layer nanoporous metal films as plasmonic metamaterial
    (De Gruyter, 2024) Caligiuri, Vincenzo; Kwon, Hyunah; Griesi, Andrea; Ivanov, Yurii P.; Schirato, Andrea; Alabastri, Alessandro; Cuscunà, Massimo; Balestra, Gianluca; Luca, Antonio De; Tapani, Tlek; Lin, Haifeng; Maccaferri, Nicolò; Krahne, Roman; Divitini, Giorgio; Fischer, Peer; Garoli, Denis
    Nanoporous metals are a class of nanostructured materials finding extensive applications in multiple fields thanks to their unique properties attributed to their high surface area and interconnected nanoscale ligaments. They can be prepared following different strategies, but the deposition of an arbitrary pure porous metal is still challenging. Recently, a dry synthesis of nanoporous films based on the plasma treatment of metal thin layers deposited by physical vapour deposition has been demonstrated, as a general route to form pure nanoporous films from a large set of metals. An interesting aspect related to this approach is the possibility to apply the same methodology to deposit the porous films as a multilayer. In this way, it is possible to explore the properties of different porous metals in close contact. As demonstrated in this paper, interesting plasmonic properties emerge in a nanoporous Au–Ag bi-layer. The versatility of the method coupled with the possibility to include many different metals, provides an opportunity to tailor their optical resonances and to exploit the chemical and mechanical properties of components, which is of great interest to applications ranging from sensing, to photochemistry and photocatalysis.
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    Nanoporous Metals: From Plasmonic Properties to Applications in Enhanced Spectroscopy and Photocatalysis
    (American Chemical Society, 2021) Koya, Alemayehu Nana; Zhu, Xiangchao; Ohannesian, Nareg; Yanik, A. Ali; Alabastri, Alessandro; Proietti Zaccaria, Remo; Krahne, Roman; Shih, Wei-Chuan; Garoli, Denis
    The field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has significant implications for ultimate performance of any plasmonic device. Artificially designed nanoporous metals (NPMs) have interesting material properties including large specific surface area, distinctive optical properties, high electrical conductivity, and reduced stiffness, implying their potentials for many applications. This paper reviews the wide range of available nanoporous metals (such as Au, Ag, Cu, Al, Mg, and Pt), mainly focusing on their properties as plasmonic materials. While extensive reports on the use and characterization of NPMs exist, a detailed discussion on their connection with surface plasmons and enhanced spectroscopies as well as photocatalysis is missing. Here, we report on different metals investigated, from the most used nanoporous gold to mixed metal compounds, and discuss each of these plasmonic materials’ suitability for a range of structural design and applications. Finally, we discuss the potentials and limitations of the traditional and alternative plasmonic materials for applications in enhanced spectroscopy and photocatalysis.