Synthesis and surface chemistry of Zinc Oxide nanowires for chemical sensor applications

The research work in this dissertation comprises of synthesis and functionalization of high quality ZnO nanowires for highly sensitive and selective p-nitrophenol vapor sensor. High-quality ZnO nanowires were synthesized through a vapor-liquid-solid process in a customized chemical vapor deposition furnace. Scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy were used to characterize morphology, crystal structure and composition. Surface functionalization behavior of pristine ZnO nanowires was tested by oleic acid as a model compound and the surface modification was studied using surface sensitive techniques of Raman and FT-IR spectroscopies. Surface functionalization of ZnO nanowires with optically active 1-pyrenebutyric acid was investigated. A 1-pyrenebutyric acid compound was grafted on a solid-state ZnO nanowires backbone. Optical and electrical properties of this heterostructure were determined through fluorescence and I-V measurements, respectively. Two distinct approaches for device fabrication were tested for integrated system development and validation of sensor operation. A single nanowire device and a multi-nanowire array device were successfully fabricated.