Carbon dioxide is considered a greenhouse gas and is the main cause of global warming. Carbon dioxide (CO2) emissions are increasing each year (420 ppm in 2023 [1]). Therefore, it is important to develop sensors that are capable of detecting these levels of CO2, which have a low cost and that can operate at room temperature (RT). Metal oxide (MOX) semiconductor nanomaterials have generated great expectations as sensitive layers due to their unusual optical, electronic and chemical properties. MOX present a high conductivity and an elevated optical transparency in the ultraviolet (UV), and can be functionalized by rare-earth element doping for optoelectronic applications. In this work we present a system to measure optical and resistive properties of sensors based on these materials simultaneously. An array of tin oxide and zinc oxide nanoparticle sensors doped with terbium has been made in order to explore its performance as an optoelectronic device for environmental applications.