a b s t r a c t
Gas sensor devices have traditionally comprised thin films of metal
oxides, with tin oxide, zinc oxide and indium oxide being some of
the most common materials employed. With the recent discovery
of novel metal oxide nanostructures, sensors comprising nanoarrays
or single nanostructures have shown improved performance
over the thin films. The improved response of the nanostructures to
different gases has been primarily attributed to the highly single
crystalline surfaces as well as large surface area of the nanostructures.
In this paper the properties of clean and defected quasi
one-dimensional ZnO nanostructures, including hexagonal and triangular
nanowires, nanotubes and facetted nanotubes are reviewed.
The adsorption of atoms and molecules on the ZnO nanostructures
are also reviewed and the findings are compared to studies examining
similar reactions on nanostructured metal oxide surfaces for
sensing purposes. While both experimental and theoretical
approaches have been employed to examine gas sensor reactions,
this review focuses on studies that employ electronic structure calculations,
which primarily concentrate on using density functional
theory. Computational studies have been useful in elucidating the
reaction mechanism, binding strength, charge transfer as well as
other electronic and structural properties of the nanomaterials and
the gas-sensor interaction. Despite these studies there are still significant
areas of research that need to be pursued that will assist in
the link between theoretical and experimental findings, as well as
advancing the current chemical and physical understanding of these
novel materials. A summary and outlook for future directions of this
exciting area of research is also provided.