Iron Oxides Nanoparticles Langmuir-Schaeffer Multilayers for Chemoresistive Gas Sensing

摘要

Gas sensors based on mixtures of iron oxides nanoparticles (NPs) modified with Pd NPs at the different NPs Pd: Fe_3O_(4/γ)-Fe_2O_3 proportions were prepared and characterized. Nanoparticles diameter was 6-7 nm. NPs films were deposited from the mixtures of Fe_3O_(4/γ)-Fe_2O_3 and Pd NPs colloidal solutions by modified Langmuir-Schaeflfer technique onto alumina substrates. Samples were composed from 4 Fe_3O_(4/γ)-Fe_2O_3 NP monolayers (MLs). Sensors were tested toward acetone vapors and NO_2 at concentration range of 5-200 and 0.5-12 ppm respectively in dry air, and at different working temperatures. Pd-doped Fe_3O_(4/γ)-Fe_2O_3 sensors showed p-type gas response, higher conductance and higher conduction activation energies compared to pure Fe_3O_(4/γ)-Fe_2O_3 sensor that gives n-type gas response. Results were tentatively explained in terms of surface interactions with oxidizing and reducing species, and Nearest Neighbor Hopping conduction model (NNH).