Visible LightDriven pType Semiconductor Gas Sensors Based on CaFe2O4 Nanoparticles In this work, we present conductometric gas sensors based on ptype calcium iron oxide (CaFe2O4) nanoparticles. CaFe2O4 is a metal oxide (MOx) with a bandgap around 1.9 eV making it a suitable candidate for visible lightactivated gas sensors. Our gas sensors were tested under a reducing gas (i.e., ethanol) by illuminating them with different lightemitting diode (LED) wavelengths (i.e., 465xe2x80x93640 nm). Regardless of their inferior response compared to the thermally activated counterparts, the developed sensors have shown their ability to detect ethanol down to 100 ppm in a reversible way and solely with the energy provided by an LED. The highest response was reached using a blue LED (465 nm) activation. Despite some responses found even in dark conditions, it was demonstrated that upon illumination the recovery after the ethanol exposure was improved, showing that the energy provided by the LEDs is sufficient to activate the desorption process between the ethanol and the CaFe2O4 surface.

Chemical Gas Sensors Studied at SENSOR Lab, Brescia (Italy): From Conventional to EnergyEfficient and Biocompatible Composite Structures In this paper, we present the investigations on metal oxidebased gas sensors considering the works performed at SENSOR lab, University of Brescia (Italy). We reported the developments in synthesis techniques for the preparation of doped and functionalized lowdimensional metal oxide materials. Furthermore, we discussed our achievements in the fabrication of heterostructures with unique functional features. In particular, we focused on the strategies to improve the sensing performance of metal oxides at relatively low operating temperatures. We presented our studies on surface photoactivation of sensing structures considering the application of biocompatible materials in the architecture of the functional devices as well.