Generation and Transfer of Triplet Electron Spin Polarization at the Solid-Liquid Interface

Area of Science:

• Photophysics
• Spin Chemistry
• Materials Science

Background:

• Photoexcited triplet states of dyes generate polarized electron spins for applications like sensing and dynamic nuclear polarization.
• Triplet spin polarization in solution is rapidly lost due to chromophore rotational motion, unlike in solids where relaxation times (T1) are longer.
• Current methods primarily utilize triplet spin polarization in solid-state systems.

Purpose of the Study:

• To investigate if immobilizing dye molecules on a solid surface can maintain high spin polarization and long relaxation times in a liquid environment.
• To explore the potential for spin polarization transfer between immobilized dye triplets and solution-phase radicals.

Main Methods:

• Adsorption of anionic porphyrins onto cationic mesoporous silica gel.
• Characterization of porphyrin triplet state polarization and spin-lattice relaxation times (T1) at the solid-liquid interface using toluene as the liquid medium.
• Investigation of spin polarization exchange between surface-bound porphyrin triplets and TEMPO radicals in solution.

Main Results:

• Immobilized porphyrins on silica gel maintained high spin polarization and long T1 values, comparable to solid-state systems.
• The solid-liquid interface allowed for efficient spin polarization exchange between the porphyrin triplets and TEMPO radicals in toluene.
• This method successfully bridges the gap between solid-state and solution-phase spin polarization phenomena.

Conclusions:

• Immobilization of dye molecules on solid supports is an effective strategy to preserve photoinduced triplet spin polarization in liquid environments.
• The developed solid-liquid interface method facilitates the use of long-lived triplet spin polarization for solution-based applications.
• This versatile approach expands the utility of triplet spin polarization beyond solid-state limitations, opening new avenues in sensing and polarization techniques.