Cedric Boissiere

Nanocrystalline N-doped ceria porous thin films as efficient visible-active photocatalysts

Nanocrystalline porous N-doped ceria films have been prepared by combining sol–gel chemistry, evaporation-induced self-assembly (EISA), flash crystallization and treatment in NH3 gas between 550 and 700 °C at flow rates of 270 and 670 cm3 min−1. The maximum nitrogen uptake is 0.06 moles per Ce, observed for the sample treated at 600 °C and NH3 flow rate of 670 cm3 min−1. Nitrogen bonding to cerium is proved by XPS, through the observation of the characteristic Ce–N feature at ∼397 eV. Microstructural characterization shows that the mesostructure of the films is lost for treatment temperatures in ammonia higher than 550 °C but the porous fraction remains between 35 and 40% after ammonolysis for all the samples. The nitrided films show photocatalytic activity under visible light in the acetaldehyde decomposition, with the best results obtained for the films treated at 550 °C under NH3 flow rate of 670 cm3 min−1.

Mesoporous TiO2 Sensitive Films for Love Wave Humidity Detection: Origins of Stress Release Induced by Sorption

Mesoporous titania-coated acoustic humidity sensors show strongly non-linear responses at high exposure, not fully explained by water condensation. Three possible sources of stresses that alter the film mechanical behavior have been considered in this work: increased swelling, unreleased sol-gel stress, and capillary contraction. If the latter is linked to the film porous nature and cannot be avoided, the two other are mainly side effects of the specific fabrication process developed for the deposition of mesoporous oxides on quartz piezoelectric substrates: partial crystallization and a large pore size distribution.