The formation, phase relations, crystal chemistry and physical properties were investigated
for the solid solution deriving from binary clathrate with a solubility limit of 8 Zn atoms per formula unit at
800 °C
( is a vacancy). Single-crystal x-ray data throughout the homogeneity region
confirm the clathrate type I structure with cubic primitive space group type .
Temperature-dependent x-ray spectra as well as heat capacity define a low-lying, almost
localized, phonon branch, whereas neutron spectroscopy indicates a phonon mode with
significant correlations. The transport properties are strongly determined by the
Ge/Zn
ratio in the framework of the structure. Increasing Zn content drives the system towards a
metal-to-insulator transition; for example, shows metallic behaviour at low temperatures, whilst at high temperatures semiconducting
features become obvious. A model based on a gap of the electronic density of states slightly
above the Fermi energy was able to explain the temperature dependences of the transport
properties. The thermal conductivity exhibits a pronounced low-temperature maximum,
dominated by the lattice contribution, while at higher temperatures the electronic part
gains weight. Zn-rich compositions reveal attractive Seebeck coefficients approaching
−180 µV K−1
at 700 K.
This paper describes a new multiplexed label-free biosensor. The detection technology is based on nanostructured gold-polymer surfaces. These surfaces support surface plasmon resonance modes that can be probed by a miniaturized optical setup. The optical characterization of the sensing chip shows the sensitivity and the limit-of-detection to refractive index changes. Moreover, by studying the progressive adhesion of molecular monolayers of polyelectrolytes, the decay of the plasmonic mode electric field above the surface has been reconstructed. A multiplexed label-free biosensing device is then described and characterized in terms of sensitivity, lateral resolution, and sensitivity to a model biological assay. The sensitivity in imaging mode of the device is of the order of 10-6 refractive index units, while the measured lateral resolution is 6.25 μm within a field of view of several tenths of mm2, making the instrument unique in terms of multiplexing capability. Finally, the proof-of-concept application of the technology as a point-of-care diagnostic tool for an inflammatory marker is demonstrated.
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