Nanoscale technologies for plasmon-assisted solar light harvesting and lipid membrane composites

Doctoral thesis, 2016

Techniques for design, manipulation and characterization of nanoscale structures provide the basis for technological advances in areas like optics, electronics and biotechnology. The aim of this thesis is to develop new nanoscale methods and design schemes that extend the applicability of nanoscale devices. In particular the design of plasmonic antennas and formation of composite structures of lipid membranes and graphene oxide (GO) are in the focus of this work. Lipid membranes and lipid vesicles are relevant in the field of biotechnology where they are used to model cell-membranes and as carriers of various functional biological units. The ability to isolate neighboring membranes or to connect them to electrical conductors could prove valuable for future applications. With this in mind the interaction between GO and lipid membranes is studied. Results from quartz crystal microbalance with dissipation monitoring and dual polarization interferometry indicate that flakes of GO, which have negative ζ-potential, bind to lipid membranes with positive ζ-potential. Furthermore, GO induces rupture of immobilized lipid vesicles and together form composite structures in a layer-by-layer fashion. Atomic force microscopy shows that these structures are stable in air. Metal nanoparticles host localized surface plasmon resonances (LSPR) at optical frequencies. These resonances couple to freely propagating light and greatly enhance the optical cross sections of the metal particles. Modifications of particle morphology and materials composition as well as interactions between near-by particles influence the characteristics of the LSPR. Here supported arrays of plasmonic optical antennas are designed with the purpose of light induced heating of the transparent surfaces. The optical properties of these surfaces are studied with optical spectroscopy and a method based on thermal imaging is developed to evaluate the light-to-thermal energy conversion efficiency.