Novel resistive readout CO2 sensor based on receptor -transducer work function coupling and electron affinity - band bending compensation

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The project aims to demonstrate a new approach for CO2 detection by using a combination of receptor and transducer materials based on semiconducting metal oxides. Our main objective is the translation of the changes in the work function of a receptor - determined by CO2 adsorption - into measurable conductance changes in an electrically coupled transducer layer. This is a crucial fact because measuring resistances is straightforward. Adsorption of CO2, an inert molecule in the gas phase, can take place on basic sites on specific metal oxide surfaces (receptors) and in some cases (redistribution of electrical charge between the surface site and the CO2 molecule) determines changes in the electron affinity Δχ. Such effects are difficult to monitor for the changes induced by localised chemisorption processes are not influencing the electrical resistance because they are not affecting the concentration of free charge carriers; to sense such effects one needs work function measurements. We plan to electrically couple the receptor material to another one (transducer) – that should have little or no reactivity towards CO2– and make it possible in this way for the receptor’s changes of the work function - induced by CO2 adsorption - to be translated into resistance changes of the transducer. This should be determined by the control of the electronic properties of the transducer by the pinning/control of its Fermi level by the Fermi level of the receptor (Fermi level coupling of receptor and transducer).