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    Electroless-deposited platinum antennas for wireless surface acousticwave sensors
    (Basel : MDPI AG, 2019) Brachmann, E.; Seifert, M.; Neumann, N.; Alshwawreh, N.; Uhlemann, M.; Menzel, S.B.; Acker, J.; Herold, S.; Hoffmann, V.; Gemming, T.
    In an effort to develop a cost-efficient technology for wireless high-temperature surface acoustic wave sensors, this study presents an evaluation of a combined method that integrates physical vapor deposition with electroless deposition for the fabrication of platinum-based planar antennas. The proposed manufacturing process becomes attractive for narrow, thick, and sparse metallizations for antennas in the MHz to GHz frequency range. In detail, narrow platinum-based lines of a width down to 40 μm were electroless-deposited on γ -Al2O3 substrates using different seed layers. At first, the electrolyte chemistry was optimized to obtain the highest deposition rate. Films with various thickness were prepared and the electrical resistivity, microstructure, and chemical composition in the as-prepared state and after annealing at temperatures up to 1100 °C were evaluated. Using these material parameters, the antenna was simulated with an electromagnetic full-wave simulation tool and then fabricated. The electrical parameters, including the S-parameters of the antenna, were measured. The agreement between the simulated and the realized antenna is then discussed.
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    SERS and plasmonic heating efficiency from anisotropic core/satellite superstructures
    (Cambridge : RSC Publ., 2019) Kuttner, Christian; Höller, Roland P. M.; Quintanilla, Marta; Schnepf, Max J.; Dulle, Martin; Fery, Andreas; Liz-Marzán, Luis M.
    The optical properties of nanoparticle assemblies can be tailored via hybridization of plasmon modes. Isotropic core/satellite superstructures made of spherical nanoparticles are known to exhibit coupled modes with a strongly scattering (radiative) character, and provide hot spots yielding high activity in surface-enhanced Raman scattering (SERS). However, to complement this functionality with plasmonic heating, additional absorbing (non-radiative) modes are required. We introduce herein anisotropic superstructures formed by decorating a central nanorod with spherical satellite nanoparticles, which feature two coupled modes that allow application for both SERS and heating. On the basis of diffuse reflectance spectroscopy, small-angle X-ray scattering (SAXS), and electromagnetic simulations, the origin of the coupled modes is disclosed and thus serves as a basis toward alternative designs of functional superstructures. This work represents a proof-of-principle for the combination of high SERS efficiency with efficient plasmonic heating by near-infrared irradiation.