Reversible carrier-type transition in alpha-Fe2O3 nanostructure

Metal-oxide sensors are widely used due to their sensitivities to different types of gaseous, and these sensors are suitable for long-term applications, even in the presence of corrosive environments. However, the microscopic mechanisms with quantum effects, which are required to understand the gas-oxide interactions are not well developed despite the oxide sensors potential applications in numerous fields, namely, medicine (breath-sensors), engineering (gas-sensors) and food processing (odor-sensors). Here, we develop a rigorous theoretical strategy based on the ionization energy theory (IET) to unambiguously explain why and how a certain gas molecule intrinsically prefers a particular oxide surface. We make use of the renormalized ionic displacement polarizability functional derived from the IET to show that the gas/surface interaction strength (sensing sensitivity) between an oxide surface and an isolated gas molecule can be predicted from the polarizability of these two systems. Such predictions are extremely important for the development of health monitoring bio-sensors, as well as to select the most suitable oxide to detect a particular gas with optimum sensitivity.