The fabrication methods and the basic properties of the metal-oxide nanostructures referred as nanowires are presented and reviewed in this paper, with particular emphasis to the electrical and optical properties and their useful implementation for chemical and biochemical sensing. The field of chemical sensors has benefited by the wealth of highly crystalline nanostructures produced by physical and chemical methods. Large variation in bulk electrical conductivity, structural stability upon high temperature operation, high degree of crystalline ordering, large impact of point defects and surface states have unveiled the potential for the sensing field and have opened up new perspectives of application and for the realization of novel device architectures. This paper will summarize various techniques for preparation and characterization; then, the growth mechanisms and working principles will be discussed. Finally, the challenges that this field is currently facing are presented to signify the perspectives of expansion.
