Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
FOREST, JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan.
J Phys Chem Lett. 2023 May 25;14(20):4754-4759. doi: 10.1021/acs.jpclett.3c00627. Epub 2023 May 15.
The photoexcited triplet state of dyes can generate highly polarized electron spins for sensing and dynamic nuclear polarization. However, while triplets exhibit long spin-lattice relaxation times () on the microsecond scale in solids, the polarization quickly relaxes on the nanosecond scale in solution due to the rotational motion of chromophores. Here, we report that the immobilization of dye molecules on a solid surface allows molecular contact with a liquid while maintaining high polarization and long as in a solid. By adsorbing anionic porphyrins on cationic mesoporous silica gel, porphyrin triplets exhibit high polarization and long at the solid-liquid interface of silica and toluene. Furthermore, porphyrin triplets on the solid surface can exchange spin polarization with TEMPO radicals in solution. This simple and versatile method using the solid-liquid interface will open the door for utilizing the photoinduced triplet spin polarization in solution, which has been mainly limited to the solid-state.
染料的光激发三重态可以为传感和动态核极化产生高度极化的电子自旋。然而，虽然三重态在固体中以微秒级的自旋晶格弛豫时间（）表现出长寿命，但由于发色团的旋转运动，极化在溶液中很快在纳秒级尺度上弛豫。在这里，我们报告说，染料分子在固体表面上的固定化允许分子与液体接触，同时保持固体中的高极化和长寿命。通过将阴离子卟啉吸附在阳离子介孔硅胶上，卟啉三重态在硅胶和甲苯的固液界面处表现出高极化和长寿命。此外，固体表面上的卟啉三重态可以与溶液中的 TEMPO 自由基交换自旋极化。这种使用固液界面的简单而通用的方法将为利用溶液中的光致三重态自旋极化开辟道路，而这种方法主要局限于固态。
