SrTiO3 powders with various Sr/Ti atomic ratios were synthesized by microwave-assisted
solvothermal reactions of SrCl2 and TiOC3H74 in KOH aqueous solutions. The nanoparticles of perovskite type SrTiO3 structure with the particle size of 30–40 nm were synthesized. The photocatalytic activity was determined by deNOx ability using light emitting diode lamps of various wavelengths such as 627 nm red, 530 nm green, 445 nm blue, and 390 nm UV. The photocatalytic activity significantly changed depending on the Sr/Ti atomic ratio, i.e., the strontium rich sample Sr/Ti atomic ratio1 showed excellent visible light responsive photocatalytic activity for the oxidative destruction of NO.