Gas sensors have been fabricated using the single-crystalline ${\mathrm{SnO}}_2$ nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and ${\mathrm{NO}}_2,$ as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and $\text{−1550\%}$ for 0.5 ppm ${\mathrm{NO}}_2$ at $\text{400\hspace{0.05em}°}\mathrm{C}.$ The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb.

Three-dimensional (3D) tungsten oxide nanowire networks have been demonstrated as a high-surface area material for building ultrasensitive and highly selective gas sensors. Utilizing the 3D hierarchical structure of the networks, high sensitivity has been obtained towards $\mathrm{N}{\mathrm{O}}_2$ , revealing the capability of the material to detect concentration as low as $50\mathrm{ppb}$ (parts per billion). The distinctive selectivity at different working temperatures is observed for various gases. The results highlight that the nanobelts (nanowires) technology can be adopted for the development of gas sensors with performances suitable for practical applications.