Complex and charge transfer between TiO2 and pyrroloquinoline quinone

Area of Science:

• Materials Science
• Photochemistry
• Nanotechnology

Background:

• Pyrroloquinoline quinone (PQQ) is a redox cofactor.
• Titanium dioxide (TiO2) nanoparticles are widely used photocatalysts.
• Understanding charge transfer dynamics in PQQ-TiO2 systems is crucial for advanced applications.

Purpose of the Study:

• To investigate the complex formation between PQQ and TiO2 nanoparticles.
• To elucidate the charge transfer processes upon photoexcitation of the PQQ-TiO2 complex.
• To evaluate the performance of a PQQ-TiO2/dopamine triad assembly for enhanced charge separation.

Main Methods:

• Complex formation was characterized by determining the association constant (K = 550 M-1 per Ti(IV)surf).
• Low-temperature electron paramagnetic resonance (EPR) spectroscopy was used to identify charges, radicals, and charge-transfer processes.
• Photoexcitation studies were performed on PQQ-TiO2 and PQQ-TiO2/dopamine systems.

Main Results:

• PQQ forms a tridentate complex with unsaturated titanium atoms on TiO2 surfaces.
• Photoexcitation of the PQQ-TiO2 complex leads to electron transfer from TiO2 to PQQ, forming a semiquinone radical.
• The PQQ-TiO2/dopamine triad assembly significantly enhances spatial separation of photogenerated charges, with electrons localizing on PQQ and holes on dopamine.
• PQQ acts as an efficient electron sink in the triad assembly, even at cryogenic temperatures (4 K).

Conclusions:

• PQQ-TiO2 complexes exhibit efficient photoinduced electron transfer.
• The PQQ-TiO2/dopamine triad structure provides a robust platform for charge separation.
• This system demonstrates potential for applications requiring efficient scavenging of photogenerated electrons.