We have further probed the relative energy position of the quantum dots (both undoped and Mn-doped CdS) from where the electron gets injected to the TiO2 conduction band by monitoring the electron injection rate using Photoluminescence spectroscopy as shown in Fig. 5(a). In addition, a blocking layer of Al2O3 on the surface of TiO2 films is introduced to verify the number of the excited electrons of QDs with and without Mn dopant