Francesca Gerlin

Palladium on plastic substrates for plasmonic devices.

Innovative chips based on palladium thin films deposited on plastic substrates have been tested in the Kretschmann surface plasmon resonance (SPR) configuration. The new chips combine the advantages of a plastic support that is interesting and commercially appealing and the physical properties of palladium, showing inverted surface plasmon resonance (ISPR). The detection of DNA chains has been selected as the target of the experiment, since it can be applied to several medical early diagnostic tools, such as different biomarkers of cancers or cystic fibrosis. The results are encouraging for the use of palladium in SPR-based sensors of interest for both the advancement of biodevices and the development of hydrogen sensors.

Plasmonic response of different metals for specific applications

Each metal presents different characteristics when used in a surface plasmon resonance (SPR) experiment. These include the shape of the SPR figure, the wavelength of better operation, the tendency to oxidize, the sensitivity to environmental changes, the range of refractive indices detectable and the capability of binding to specific targets or analytes. When choosing the metal for our SPR experiment all of these characteristics have to be taken into account. We investigate the behavior of metals, which are less or have never been used in this kind of application, comparing their characteristics to gold. We deeply investigate both theoretically and experimentally the behavior of palladium. This metal leads to an inverted curve with a maximum of reflected intensity instead of a minimum. In fact, in this case we speak of Inverted Surface Plasmon Resonance (ISPR). Aluminum and copper have also been considered because of their potentiality in specific applications.

Study of optical materials to be used on Multi Element Telescope for Imaging and Spectroscopy instrument

Abstract. The European Space Agency mission Solar Orbiter (SOLO) is dedicated to the study of the solar atmosphere and heliosphere. As a part of the payload, the instrument METIS (Multi Element Telescope for Imaging and Spectroscopy) will provide images of the corona, both in the visible range and at the hydrogen Lyman-α emission line (121.6 nm). The realization of optical coatings, based on Al and MgF2, able to reflect/transmit such spectral components is, therefore, necessary. Since optical characteristics of materials in the vacuum ultraviolet range are not well studied and vary greatly with the realization process, we implemented a study of their properties in different deposition conditions. This is aimed to the realization of a custom designed filter able to transmit the 121.6 nm wavelength while reflecting visible light, and thus separating visible from ultraviolet light paths in the METIS instrument.

Design optimization for quantum communications in a GNSS intersatellite network

We present the results of a feasibility study on the application of optical quantum communication links to a global navigation satellite system (GNSS) network with reference to the Galileo architecture. As a particularly relevant case, we derive specifications for an inter-satellite quantum key distribution (QKD) network and evaluate its expected performance in terms of achievable key lengths.

Graphene-like coatings for biosensors devices

The interest in graphene–like materials involves many research areas, including the development of biosensors devices. We have recently studied the use of graphene/metal bilayer for surface plasmon resonance (SPR) equipment devoted to detection of chemical processes and biomolecules recognition. The dual role of graphene is to protect the metal layer underneath and to enhance the bioaffinity by adsorbing biomolecules with carbon–based ring structures. Depending on the application, it may be necessary laser and chemical treatments of graphene to improve the performances of the whole device. The processing effects will be investigated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The use of synchrotron light is mandatory for NEXAFS analysis since a continuous EUV source of selected polarization is required. The ideas, the analysis and the results are the subjects of this work.

He+ ions damage on optical coatings for solar missions

Single layer thin films have been exposed to low energy alpha particles (4keV). Implanted doses are equivalent to those accumulated in 1, 2, 4 and 6 years of ESA Solar Orbiter mission operation. Two ions fluences have been considered. In order to change the total dose accumulated, for each ion flux the time of exposure was varied. Reflectance in the visible spectral range has been measured prior and after implantation. Results show no significant change in performances in gold and palladium, while a small decrease in performances is observed in iridium. The implantation rate does not seem to affect the experiment.

Radiometric modelling of a space optical instrument: an example of application to PHEBUS

Probing of Hermean Exosphere By Ultraviolet Spectroscopy (PHEBUS) is a dual channels spectrometer working in the Extreme UltraViolet (EUV) and Far UltraViolet (FUV) range. It will be on board of ESA BepiColombo cornerstone mission and it will be devoted to investigate the composition, the dynamic, the formation and the feeding mechanisms of Mercury’s exosphere system. A consistent interpretation of the observational data collected by PHEBUS requires a deeply knowledge of its radiometric behavior. The Mueller’s matrix formalism can be adopted to derive an accurate radiometric model able to takes into account also the polarization state of the source observed by PHEBUS. Moreover, this theoretical model can be further verified and refined during an experimental ground calibration campaign. In this work we present the radiometric model derived for PHEBUS spectrometer together with some results obtained during the Flight Model (FM) ground calibration which is still ongoing. In particular, the obtained results employing this approach show that this is a complete and versatile method to perform the radiometric calibration of a generic space instrument.

Optical and structural properties of noble metal nanoisLAND

Metallic nanostructures are widely studied because of their peculiar optical properties. They possess characteristic absorbance spectra with a peak due to plasmonic resonance. This feature is directly dependent on the nanostructures shape, size, distribution and environment surrounding them. This makes them good candidates for a variety of applications, such as localized surface plasmon resonance sensing (LSPR), surface-enhanced Raman scattering (SERS) and photovoltaics. A well established technique used to create nanoisland on flat substrates is performing a thermal treatment after the deposition of a thin metal film. While the most widely investigated metal in this context is gold, we have extended our investigation to palladium, which is interesting for sensing applications because it has an excellent hydrogen absorption ability. The morphological properties of the nanoisland depend mainly on the starting thickness of the deposited layer and on the annealing parameters, temperature and duration. The deposition and annealing process has been investigated, and the resulting samples has been tested optically and morphologically in order to optimize the structures in view or their application for sensing purposes.

Study of solar wind ions implantation effects in optical coatings in view of Solar Orbiter space mission operation

Low energy ions coming from the quite solar wind are considered among the causes of potential damage of the optical instrumentation and components on board of ESA Solar Orbiter. Predictions of space radiation parameters are available for instruments on board of such mission. Accelerators are commonly used to reproduce the particle irradiation on a spacecraft during its lifetime at the ground level. By selecting energies and equivalent doses it is possible to replicate the damage induced on space components. Implantation of Helium ions has been carried out on different single layer thin films at LEI facility at Forschungszentrum Dresden-Rossendorf varying the total dose. Profile of the implanted samples has been experimentally recovered by SIMS measurements. The change in reflectance performances of such coatings has been experimentally evaluated and modelled. The outcomes have been used to verify the potential impact on the METIS instrument and to drive the optimization of the M0 mirror coating..

Graphene-metal interfaces for biosensors devices

Graphene–metals interfaces are investigated in many subject areas both applicative and speculative. The interest mainly stems from the possibility for CVD synthesis of large area graphene on metals. In this case the metal acts as a catalyst for complete dehydrogenetaion of hydrocarbon precursors that leaves carbon behind at the surface. Such bilayer are also very appealing for surface plasmon resonance devices, since graphene acts both as a protective layer and biorecognition element. Several pairs of graphene–metal interfaces have been studied in terms of SPR performance and physicalchemical properties at the interface. With regard to this last aspect, NEXAFS spectroscopy is a powerful method to study single-, double-, and few- layers graphene and to illustrate any evolution of the electronic states.