## 3 Results and Discussion  
For titania prepared on stainless steel using the Spray-ILGAR technique, the standard procedure is to use titania (TiO\({}_{2}\)) precursor of titanium diisopropyloxide bis(acetylacetone) in ethanol with a concentration of 6.83 mM, sprayed for 12 min at a temperature of 460 \({}^{\circ}\)C. Using these procedures, the thickness of studied films was determined to be 101 nm. However, this method is usually used for the preparation of solar cells, and not as a photocatalyst. So in order to determine the best condition to prepare a sample with the best photocatalytic activity in the photocatalytic decomposition of air pollutants, the TiO\({}_{2}\) on stainless steel was prepared with different concentrations of TiO\({}_{2}\)-precursor, different heating temperatures, and different durations of spraying time. The thickness of all the samples prepared is presented in Table 1. All of the samples showed similar thickness, in the range of 94-107 nm. Only the sample that had been prepared with 6 min of spraying time showed a lower thickness of only 75 nm, indicating that the spraying time may have been a bit too short for a thicker layer to form. This shows that the thickness of the TiO\({}_{2}\) film on stainless steel was only influenced by the spraying time, and not so much by the concentration of the TiO\({}_{2}\) precursor and heating temperature. This is in accordance with the findings of [PERSON] et al. [8] where they reported that a reasonable time of deposition by ILGAR is needed in order to obtain layers with a maximum thickness of about 100 nm. The SEM image in Figure 1 shows that the TiO\({}_{2}\) prepared by Spray-ILGAR technique using 6.83 mM of TiO\({}_{2}\) precursor, heated at 460 \({}^{\circ}\)C and 12 min of spraying time. The SEM image shows that the TiO\({}_{2}\) was dispersed uniformly on top of the stainless steel. Similar morphology has also been reported for TiO\({}_{2}\) coated on the surface of glass by the same method [10]. The layer of TiO\({}_{2}\) was also very durable, as the attachment was very strong. This was proven by the Scotch tape test, where the layer of TiO\({}_{2}\) remained intact even after removal of the adhesive tapes from the coatings. The concentration of the TiO\({}_{2}\) on the stainless steel can easily be changed by changing the concentration of the TiO\({}_{2}\)-precursor solution (titanium diisopropylopoxide bis(acetylacetone) solution). Higher concentrations will result in a more compact and dense layer (Figure 2a). This was further proven by the SEM image was taken at a higher magnification value (20,000), as shown in Figure 2b. By lowering the concentration of the precursor solution, a less dense layer of TiO\({}_{2}\) was produced (Figure 2c). Some spaces can be seen in between the TiO\({}_{2}\) particles when lower concentrations of TiO\({}_{2}\) precursor were used, as can be clearly seen in the SEM image with higher magnification (Figure 2d). Using different temperatures did not change the distribution of the samples much. When the spraying duration was shortened to 6 min, some parts of the stainless steel were uncoated by the TiO\({}_{2}\) (Figure 3a). This is most probably caused by insufficient spraying time for the layer to form [8]. The thickness measurement also supports this hypothesis. As for the sample prepared by using 24 min of spraying time, a nice dense and compact layer of TiO\({}_{2}\) was formed (Figure 3b).