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.