Mono-, multi-layer nanostructured porous films and gas sensors

A simple and flexible strategy is presented for synthesis of mono or multi-layer nanostructured ordered porous films on any desired substrates with flat or even curved surface, based on the fact that polystyrene sphere colloidal monolayer on glass substrate can lift off and floated on some precursor solutions, which can, in turn, be transferred onto any substrates by picking it up. SnO/sub 2/ ordered nanostructured porous films are thus successfully synthesized on the cylindrical surface, the concave surface and the spherical surface, respectively, just by taking the easily acquired SnCl/sub 4/ solution as precursor. More importantly, the mono and multi-layer porous films are also directly synthesized on commercially supplied ceramic or porcelain tubes which are used for the substrate of gas sensors. And hence, the SnO2 ordered nanostructured porous gas-sensor is constructed. Sensitivity of the sensor can be easily controlled by changing the sizes of polystyrene spheres. Such method is universal and suitable for synthesis of many other oxides or doped porous films, mesoporous/macroporous gas sensor films and even the hetero-multi-layer porous films on the curved surfaces just by changing the compositions of the precursors or alternatively repeating this strategy. This strategy provides a good way to construct nanostructured gas-sensors and practical possibility of the nanostructured devices in the near future.