Gas-Sensing Properties of Graphene Functionalized with Ternary Cu-Mn Oxides for E-Nose Applications

Abstract

Chemiresistive gas sensors were produced by functionalizing graphene with a ~3 nm layer of mixed oxide xCu2O⸱yMnO using pulsed laser deposition (PLD) from a hopcalite CuMn2O4 target. Sensor response time traces were recorded for strongly oxidizing (NO2, O3) and reducing (NH3, H2S) poisonous gases at ppb and ppm levels, respectively. The morphology of the MOX layer was modified by growth temperature during PLD, resulting in the optimization of the sensor response. Differences in decomposition or oxidation rates on catalytically active metal oxide (MOX) were utilized to achieve partial selectivity for pairs of gases that have similar adsorption and redox properties. The predominant selectivity towards ozone in most samples at different measuring conditions remained difficult to suppress. A distinct selectivity for H2S emerged at higher measurement temperatures (100–150 °C), which was assigned to catalytic oxidation with O2. Several gas–MOX interaction mechanisms were advanced to tentatively explain the sensor behavior, including reversible electron transfer in the simplest case of NO2, decomposition via ionic transients for O3, and complex catalytic oxidative transformations for NH3 and H2S.