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Abstract
Recently, extensive studies have been accomplished on investigating multifunctional materials and structures with both plasmonic and magnetic properties. For these materials and structures, external magnetic fields can be employed to actively control the optical responses of the systems, and vice versa, the plasmonic effect can be manipulated to optimize the magneto-optical (MO) performance. This kind of system is usually known as magneto-plasmonic (MOP) system and has been normally constructed by combining multi-layers of magnetic materials and noble metals. In this Dissertation, we investigate a novel MOP platform consisting of composite materials and nanostructures, with significantly tunable MOP performances in the visible and near infrared wavelength region.
Metal nano-lattices such as nano-hole arrays and nano-triangle arrays are prototypical plasmonic nanostructures. These two nano-lattices made from Ag-Co composite are created by using a combination of shadow nanosphere lithography and electron beam co-evaporation technique. A systematical study on their MOP properties shows strong MO constant dependences on the Co concentration, and both experimental and numerical results reveal that the MO responses of these MOP systems behave differently, depending on the nature of the plasmon resonance that the system supports. By adjusting the Co content, their MOP performances can be maximized. It is also shown that by using non-normal vapor incident angles for metal co-evaporation, an active Ag-Co composite chiral nano-hole array with a plasmonic-enhanced intrinsic chirality and a large magnetic modulation amplitude can be achieved.
Finally, a Pd80Co20 composite nano-patchy particle array is developed to serve as a hydrogen gas sensor through MO signal readout. Such the Co content and sensor structure are chosen to remarkably increase the hydrogen sorption kinetics at the catalytic Pd sites, while the MO constant of the composite remains significantly strong. By incorporating with appropriate polymer coating, the sensing performances of this sensor platform can be further enhanced to surpass the state-of-the-art optical hydrogen sensors reported the literature, with a sub-0.5-second response time and ppb-level limit of detection. Notably, the results open a promising development of hydrogen based on MOP structures and composite materials such as ternary Ag-Pd-Co composite, with even more impressive sensing metrics.
Metal nano-lattices such as nano-hole arrays and nano-triangle arrays are prototypical plasmonic nanostructures. These two nano-lattices made from Ag-Co composite are created by using a combination of shadow nanosphere lithography and electron beam co-evaporation technique. A systematical study on their MOP properties shows strong MO constant dependences on the Co concentration, and both experimental and numerical results reveal that the MO responses of these MOP systems behave differently, depending on the nature of the plasmon resonance that the system supports. By adjusting the Co content, their MOP performances can be maximized. It is also shown that by using non-normal vapor incident angles for metal co-evaporation, an active Ag-Co composite chiral nano-hole array with a plasmonic-enhanced intrinsic chirality and a large magnetic modulation amplitude can be achieved.
Finally, a Pd80Co20 composite nano-patchy particle array is developed to serve as a hydrogen gas sensor through MO signal readout. Such the Co content and sensor structure are chosen to remarkably increase the hydrogen sorption kinetics at the catalytic Pd sites, while the MO constant of the composite remains significantly strong. By incorporating with appropriate polymer coating, the sensing performances of this sensor platform can be further enhanced to surpass the state-of-the-art optical hydrogen sensors reported the literature, with a sub-0.5-second response time and ppb-level limit of detection. Notably, the results open a promising development of hydrogen based on MOP structures and composite materials such as ternary Ag-Pd-Co composite, with even more impressive sensing metrics.