Date of Completion


Embargo Period



Nanotechnology, metal-oxide semiconductor, synthesis, Characterization, Chemical Sensor

Major Advisor

Dr. Puxian Gao

Associate Advisor

Dr. Harold D.Brody

Associate Advisor

Dr. George A.Rossetti,Jr.

Field of Study

Materials Science and Engineering


Doctor of Philosophy

Open Access

Open Access


Homogeneous (single material component) nanomaterials generally have limited functional characteristics. Fortunately, with the addition of foreign materials component(s) into (onto) homogeneous nanostructures, potential improvement or multiplication of functions could be achieved. On the other hand, very few functional materials can survive and operate at elevated temperature above 700oC despite the widespread need in automobiles, industrial reactors, and power plants. Thus it demands new design or discovery of functional nanomaterials with good thermal stability and sustained functions at high temperature. In this study, we look to develop a new class of metal oxide-based hybrid nanowires based on ZnO, SnO2, Zn2SnO4, and (La,Sr)CoO3, targeting for designing and understanding new sensing mechanisms and enhancing thermal stability.

Based on Ag2O/Zn2SnO4 hybrid nanowire arrays grown by a unique oxide catalyzed one-step vapor phase growth process, a unique reversible response upon oxygen/ethanol ambient was discovered due to the catalytic effect induced by decorated Ag2O nanoparticles. This instrumental reversible gas sensing mechanism has been found to be generally applied in various binary metal oxide semiconductor nanowires, such as ZnO/Ag2O, SnO2/Ag2O, and ZnO/SnO2/Ag2O hybrid systems.

To enhance the high temperature stability of ZnO nanowires, perovskite (La,Sr)CoO3 (LSCO) nanoshells were coated onto their surfaces using solution or vapor phase process on Si and quartz substrates. The layering of LSCO shell onto ZnO nanowires has successfully enabled significant improvement of the chemical and structure stability in both oxidative and reductive atmospheres at high temperature up to 1000oC compared to the bare ZnO nanowires. A synergistic stabilizing effect between the comprised ZnO core and LSCO shell is proposed to be responsible to this enhancement. A unique photo-responsive humidity sensing mechanism has been demonstrated based on the ZnO/LSCO core-shell semiconductor nanowire arrays. Furthermore, at elevated temperature up to 800oC, improved sensing performance is achieved on the ZnO/LSCO nanowire arrays to various gases including O2, CO and SOx, compared to ZnO nanowire arrays based sensors.