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Light-induced charge separation and storage in titanium oxide gels
A I Kuznetsov1, O Kameneva, A Alexandrov
1Laboratoire d'Ingénierie des Matériaux et des Hautes Pressions, Centre National de la Recherche Scientifique, Institut Galilée, Université Paris--Nord, 93430 Villetaneuse, France.
Summary
Light irradiation of titanium oxide gels causes charge separation, storing electrons in the gel network and holes in the liquid phase. This creates long-lived trapped electrons responsible for a broad absorption continuum.
Area of Science:
- Materials Science
- Photochemistry
- Nanotechnology
Background:
- Wet gels possess a unique liquid-solid interface, differing from sols and conventional solids.
- Understanding light-matter interactions in these complex media is crucial for novel applications.
Purpose of the Study:
- To investigate the interaction of light with titanium oxide wet gels.
- To characterize charge separation and storage mechanisms under band-gap irradiation.
Main Methods:
- Utilized absorption cross-section measurements of trapped electrons.
- Employed UV-laser irradiation to induce and study charge dynamics.
- Analyzed spectral properties of the resulting absorption continuum.
Main Results:
- Achieved charge separation with a quantum efficiency as high as 46%.
- Electrons are stored as Ti3+ centers in the gel network, while holes reside in the liquid phase.
- Prolonged UV irradiation converted over 14% of Ti4+ to Ti3+ with lifetimes exceeding months.
- Trapped electrons generated a "dark" absorption continuum from 350 nm to 2.5 µm.
Conclusions:
- Titanium oxide wet gels exhibit efficient photogenerated charge separation and long-term storage.
- The observed "dark" absorption is attributed to trapped electrons, indicating potential for optical materials.
- These findings open avenues for developing novel photoactive materials based on wet gel systems.