Insights in the Application of Stoichiometric and Non-Stoichiometric Titanium Oxides for the Design of Sensors for the Determination of Gases and VOCs (TiO and TiO vs. TiO).

In this review article, attention is paid towards the formation of various nanostructured stoichiometric titanium dioxide (TiO), non-stoichiometric titanium oxide (TiO) and Magnéli phase (TiO)-based layers, which are suitable for the application in gas and volatile organic compound (VOC) sensors. Some aspects related to variation of sensitivity and selectivity of titanium oxide-based sensors are critically overviewed and discussed. The most promising titanium oxide-based hetero- and nano-structures are outlined. Recent research and many recently available reviews on TiO-based sensors and some TiO synthesis methods are discussed. Some promising directions for the development of TiO-based sensors, especially those that are capable to operate at relatively low temperatures, are outlined. The applicability of non-stoichiometric titanium oxides in the development of gas and VOC sensors is foreseen and transitions between various titanium oxide states are discussed. The presence of non-stoichiometric titanium oxide and Magnéli phase (TiO)-based layers in 'self-heating' sensors is predicted, and the advantages and limitations of 'self-heating' gas and VOC sensors, based on TiO and TiO/TiO heterostructures, are discussed.