The functionalization of Fe 3 O 4/γ-Fe 2 O 3 nanoparticles (NPs) gas sensors with Pd NPs was studied. NPs films were deposited from the mixtures of Fe 3 O 4/γ-Fe 2 O 3 and Pd NPs colloidal solutions by modified Langmuir-Schaefer technique onto Al 2 O 3 substrates, the NP size being 6–7 nm. Samples were composed from 4 Fe 3 O 4/γ-Fe 2 O 3 NP monolayers (MLs), either pure or doped by Pd at the different NPs Pd: Fe 3 O 4/γ-Fe 2 O 3 proportions. NPs and films were studied by DLS, GI XRD, SEM and EDS. Sensors were …