The absorption spectra showed a band edge at 400 nm (3.1 eV) for ZnO which showed a redshift of 20 nm (420 nm ~ 2.9 eV) on being doped by Ce. An increase in intensity (hyperchromic shift) also took place (Fig ). The Kubelka Munk plots showing the bandgaps in congruence with the absorption edges are given in Fig 4b . The band edge for pure ceria was at 370 nm, showing a direct band gap at 3.3 eV (Fig ).