Imaging the photoinduced charge injection in CdS/TiO₂ nanoparticles by the sequential fluorescence mapping method

Area of Science:

• Photochemistry
• Materials Science
• Nanotechnology

Background:

• Photocatalytic materials combining sensitizers and TiO2 nanoparticles are crucial in applied photochemistry.
• Charge injection from sensitizers into TiO2 can quench emission, hindering analysis.
• Resazurin dye offers a solution by forming fluorescent resorufin at interfaces via cascade electron transfer.

Purpose of the Study:

• To develop and apply a fluorescence-based method for visualizing and evaluating charge injection efficiency in photocatalytic systems.
• To investigate charge injection in TiO2/CdS and SiO2/TiO2/CdS nanoparticle systems.
• To correlate charge injection efficiency with hydrogen generation performance.

Main Methods:

• Utilizing resazurin as a redox indicator dye.
• Employing total internal reflection fluorescence microscopy (TIRFM) for imaging.
• Analyzing fluorescence changes at nanoparticle interfaces to infer charge injection.

Main Results:

• The method successfully visualized charge injection sites at the interfaces of TiO2/CdS and SiO2/TiO2/CdS nanoparticles.
• Fluorescence enhancement indicated successful cascade electron transfer and formation of resorufin.
• Qualitative evaluation of charge injection efficiency was achieved.

Conclusions:

• Sequential coupling with photoredox dyes like resazurin enables fluorescence-based monitoring of charge injection.
• The developed method provides insights into the differences in photocatalytic activity, such as H2 generation, for various nanoparticle systems.
• This approach offers a valuable tool for optimizing photocatalyst design and performance.