The effect of molar ratio on the photo-generated charge activity of ZnO–CdO composites A. Sevik, B. Coskun and M. Soylu Eur. Phys. J. Plus, 135 1 (2020) 65 Published online: 13 January 2020 DOI: 10.1140/epjp/s13360-020-00129-w