Picosecond Time Resolved Electron Injection from Excited Cresyl Violet Monomers and Cd₃P₂ Quantum Dots into TiO₂

Abstract

Picosecond time resolved luminescence was employed for monitoring the decay of electronic excited reactants on the surface of oxide semiconductors. Decay of cresyl violet monomers was determined on TiO₂ and on α-Al₂O₃ by measuring decay curves over a wide range of very low coverages. The decay curves showed a characteristic opposite dependence on coverage on the oxide semiconductor with a low conduction band edge, i.e. TiO₂, compared to the oxide semiconductor with a high conduction band edge, i.e. α-Al₂O₃. The dominating time constant for cresyl violet monomer decay was in the range of 280 ps on TiO₂ and 560 ps on α-Al₂O₃. In both cases quenching was attributed to electron transfer.

At room temperature the decay of excited Cd₃P₂ quantum dot luminescence was faster than 1 ps when the dots were attached to TiO₂ colloidal particles in solution. The ultrafast decay was ascribed to electron injection.

Key Words:

• Electron transfer
• picosecond time resolved luminescence
• adsorbed dye molecules
• Cd₃P₂ quantum dots
• TiO₂, α-Al₂O₃