**4. Photocatalytic activity**

The photocatalytic activity of prepared photo catalyst can be measured by many different test methods [71], which have been accepted at national and international standards. We have used German standard DIN 52980<sup>11</sup> for the determination of photocatalytic activity. This standard method is based on the degradation of organic dye methylene blue (MB) by photo catalyst under UV irradiation. The degradation results are further confirmed by measuring total organic carbon (TOC) of initial dye aqueous solution and degraded dye aqueous solution by TOC analyzer.
