Synthesis and integration of heterogeneous nanomaterial array based on local thermal energy and sensor application

Abstract

In this Ph. D. Dissertation, we present novel in-situ metal oxide nanostructures synthesis and integration methods, their electrical and mechanical characteristics and photonic and gas sensing applications. This fabrication methods were designed for low-cost and eco-friendly synthesis and fabrication methods. The method is based on a localized hydrothermal synthesis reaction and liquid phase deposition (LPD) and can fabricate various kind of nanomaterial devices including ZnO nanowires, CuO nanospikes, ZnO nanowire/CuO nanospike hybrid structures and TiO2 nanotubes. This methods are applicable to not only rigid substrates but also to flexible substrates. The nanomaterials guaranteed stable and strong electrical and mechanical connection between namomaterial and electrode and the flexible device endured under 6.8 mm radius of bending and 1 % tensile loading conditions. The devices were utilized to photonic sensor and exhibited a sensitive and stable light sensing response under bending and tensile loading conditions. The heterogeneous nanomaterial arrays consisting of $TiO_2$ nanotubes, CuO nanospikes and ZnO nanowires and of ZnO nanowire/CuO nanospike hybrid nanostructures, CuO nanospikes and ZnO nanowires were fabricated combination of sequential localized hydrothermal reaction and LPD method in the microfluidic platform without mixing or contamination of precursor solution. The heterogeneous nanomaterial arrays showed excellent sensing performance of under sub-ppm and several tens of ppm level for $NO_2$ and CO gases, respectively. Moreover, the nanomaterial array device determined the concentrations of $NO_2$ and CO gases in the mixture gas.