Related Experiment Video
Updated: Mar 7, 2026
13:39
Optical Trapping of Nanoparticles
Published on: January 15, 2013
23.0K
Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO2 Nanoparticles
Jennifer L Peper1, David J Vinyard1, Gary W Brudvig1
1Department of Chemistry, Yale University , New Haven, Connecticut 06520-8107, United States.
Journal of the American Chemical Society
|February 9, 2017
Summary
Understanding electron traps in titanium dioxide (TiO2) nanoparticles is key for solar energy applications. Researchers found two distinct electron traps that slowly change, suggesting structural modifications in reduced TiO2.
Area of Science:
- Materials Science
- Nanotechnology
- Photochemistry
Background:
- Nanoscale titanium dioxide (TiO2) is crucial for solar energy conversion and photocatalysis.
- Understanding charge carrier behavior in TiO2 is essential for optimizing these applications.
Purpose of the Study:
- To investigate the nature of electron traps in UV-irradiated aqueous TiO2 nanoparticles.
- To characterize the distinct electron trap states and their interconversion dynamics.
Main Methods:
- Electron Paramagnetic Resonance (EPR) spectroscopy
- Optical spectroscopies
- UV-irradiation of colloidal TiO2 nanoparticles in methanol
Main Results:
- Two distinct electron trap types were identified and characterized.
- The relative populations of these traps are temperature-dependent, with a small energy difference (ΔH° = 3.0 ± 0.6 kcal/mol).
- Interconversion between traps occurs slowly (minutes to hours) between 0-50 °C, implying structural or stoichiometric changes.
Conclusions:
- Slow structural modification accompanies changes in trap state occupancy in reduced TiO2 systems.
- This phenomenon is likely general for TiO2 at thermodynamic or photostationary states.
- Consideration of these slow dynamics is important for designing effective TiO2-based devices.
More Related Videos
Related Concept Videos
01:28Atomic Nuclei: Types of Nuclear Relaxation
1.1K
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
1.1K
03:02Colors and Magnetism
14.4K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
14.4K
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
49.3K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
49.3K