Ανάπτυξη και εφαρμογές υβριδικών νανοϋλικών και νανοδομημένων επιφανειών

The purpose of this PhD thesis is to develop hybrid systems with "smart" and advanced properties, combining micro/nanostructured silicon surfaces with other materials such as graphene, films of polymer blends and zinc oxide nanowires. Silicon microstructures were developed by laser light irradiation (532 and 1064 nm), in SF6 gas environment and the effect of process parameters on the morphology of the microstructures was studied. Irradiation of silicon with laser light of appropriate fluence resulted in large areas of uniformly microstructured silicon surfaces, which were used as substrates for the development of “smart” surfaces with controlled wettability. Also, combining laser processing with soft lithography, microstructured silicon surfaces were used as to microstructure polymeric surfaces. In the first part, the Raman spectrum of graphene integrated in plasmonic laser-nanostructured silicon substrate coated with gold nanoparticles was studied in comparison with the Raman spectrum of graphene integrated in non-plasmonic and/or flat substrates. The nanotopography of silicon platform with gold nanoparticles enhanced the interaction of graphene with electromagnetic radiation and strong SERS (Surface-enhanced Raman Scattering) enhancement was observed in a wide range of excitation wavelengths. In addition, stress and/or doping effects on graphene were observed, due to the process of graphene transfer, but also to the electronic interaction of graphene with the respective substrate. The proposed plasmonic platform can be integrated with graphene, but also with other 2D materials, paving the wave for future real-world applications of large-area 2D devices with complex functionalities in the fields of sensing, photonics, and medical diagnostics etc. In the second part, "smart" organic and inorganic surfaces were developed, showing responsive wettability to the external stimulus of temperature or light. Initially, polymer films of polystyrene blends with thermoresponsive poly(isopropylcrycaloamide) (PNIPAM) and its copolymer, PS-b-PNIPAM, were spin casted on flat silicon substrates. Film morphology varied significantly with the blend ratio and the drying conditions. Upon heating, films of homopolymer blends showed thermoresponsive wetting behavior without transition of their wetting state. Additionally, the thermoresponsive films were casted on laser-microstructured silicon substrates and their thermoresponsivity were enhanced, due to substrate micromorphology, achieving reversibly transition of their wetting state. Last, zinc oxide (ZnO) nanowires were developed on flat and laser-microstructured silicon substrates, creating nanostructured surfaces and surfaces with hierarchical roughness, respectively. Studying the wetting behavior of such surfaces upon light irradiation and dark storage, ZnO nanostructures showed photoresponsive wettability, which was enhanced in case of hierarchical surfaces, achieving reversibly transition of their wetting state. Laser processing is a single-step, maskless, tabletop method to create uniformly micro/nanopatterned surfaces over large areas, which can be used either directly or incombination with other microstructuring techniques, such as soft lithography, in practical applications. Modifying the surface topography in combination with novel materials, such as 2D materials and "smart" materials, develops hybrid systems with new or advanced properties and complex functionalities, which are able to expand SERS-based applications and applications of “smart” surfaces with controlled wettability, but also to improve the traditional applications.