Size dependent gas sensing properties of spinel iron oxide nanoparticles

Spinel iron oxide nanoparticles of sizes from 12 to 60 nm have been prepared via a hydrothermal synthesis. Thick films of the Fe3−xO4 nanoparticles deposited on interdigital electrodes were applied as resistive gas sensors. The electrical and gas sensing properties were characterized by impedance spectroscopy using multielectrode substrates. The reducing analytes CH4, NO, H2 and NH3 in N2 as a reference were applied in order to investigate the sensor response, the selectivity and the recovery behavior at temperature between 50 °C and 300 °C. The materials exhibit good sensor responses towards NH3 with low cross sensitivities towards H2 and NO at 250 °C. A linearly increasing sensor response towards NH3 and H2 with decreasing particle size was found.