Supporting information: Ultrafast Interfacial Electron Transfer drives Mn(II) photooxidation on TiO2 Nanoparticles

Preparation of TiO2 NPs. Colloidal solutions containing nanoparticulate TiO2 are prepared through hydrolysis of titanium tetraisopropoxide by following published procedures. For a 500 mg/L solution, 500 mg of Ti(OCH-(CH3)2)4 was dissolved in 20 mL of 2-propanol. A 2 mL aliquot of this solution was slowly injected (microsyringe) into 20 mL of water at pH = 1.5 (adjusted with HCl). The solution was clear since TiO2 does not absorb in the visible spectrum; UV/Vis measurements presented in the Communication show a sharp absorption band beginning at 380 nm, corresponding to a band gap of approximately 3.2 eV.