Modulation of electron injection in CdSe-TiO2 system through medium alkalinity

Charge injection from excited CdSe quantum dots into nanostructured TiO2 film can be modulated by varying solution pH. At increasing solution pH, the conduction band of TiO2 shifts 59 mV/pH unit to a more negative potential, thereby decreasing the driving force and thus decreasing the rate of nonradiative electron transfer from excited CdSe. The emission yield and the average emission lifetime increase with increasing pH, thus providing a way to monitor the variation in medium pH.