Nanostructured photoactive films synthesized by a flame aerosol reactor

A flame aerosol reactor (FLAR) system was used to deposit nanostructured photocatalytic films of titanium dioxide with well controlled morphologies. Nanoparticles were generated in the aerosol phase and then deposited onto a water‐cooled substrate via thermophoresis. Two important parameters that influenced film characteristics were the titanium precursor feed rate and substrate temperature, through their effect on particle sintering dynamics on the substrate. The size of the particles as they arrived at the substrate was controlled by varying the titanium precursor feed rate. When the size was below ∼8 nm, sintering was completed in the time available to obtain films with columnar nanostructures. Larger particle sizes resulted in granular, particulate films. The temperature of the substrate was also an important parameter as it controlled the sintering rate and the resultant crystal phase of the film. The thickness of the films was controlled by varying the precursor feed rate and deposition time. The performance of the as‐synthesized photocatalytic films was established by measuring the resultant photocurrents. Well sintered columnar morphologies and thicker films (in the range of 40–900 nm) resulted in the largest photocurrents.