This work investigated the properties of bismuth molybdate gas sensors in which the active layers are deposited by pulsed laser deposition (PLD) and by dip-coating techniques. Bismuth molybdate gas sensors fabricated by the PLD technique exhibited good sensitivity for detecting hydrogen. However, the drawback of this technique is the non-stoichiometric deposition of the bismuth molybdates, therefore, the desired pure phases were not formed on the sensors, leading to the difficulty in comparing the gas-sensing properties of the different phases of bismuth molybdates. The dip-coating technique was therefore used since we have shown in our previous work that this technique results in stoichiometric films of bismuth molybdates. However, in the present work, although good and smooth films could be deposited on polished sapphire substrates, the dip-coating technique did not allow us to produce satisfactory coatings on the rough, polycrystalline sensor substrates available to us for the moment. (c) 2005 Elsevier B.V. All rights reserved.