Instituto de Tecnología Química CSIC-UPV and Departamento de Química, Avenida De los Naranjos S/N, 46022-Valencia, Spain.
Langmuir. 2012 Feb 7;28(5):2849-57. doi: 10.1021/la204023w. Epub 2012 Jan 24.
Graphene sheets quench the singlet and triplet excited states of a series of six photochemical probes including pyrene, acridine orange, tris(2,2́-bipyridyl)ruthenium(II) dichloride, methylene blue, meso-tetrakis(phenylsulphonate)porphyrin, and 5,10,15,20-tetraphenyl-21H,28H-porphine zinc. It was found that Stern-Volmer fluorescence quenching can fit to one or two different quenching regimes depending on the probe. In addition, the quenching can be either static or dynamic depending on the fluorophore. The occurrence of several quenching regimes has been interpreted considering that quenching arises from the crowding of the fluorophore on both graphene faces, or site isolation on the graphene sheets. Laser flash photolysis has shown that the triplet lifetime of the probes generally decreases due to graphene quenching and that no new transients appear except in the case of methylene blue, where a new absorption spectrum characterized by a continuous absorption band is observed and attributed to graphene radical ion. This spectroscopic evidence suggests that the most general quenching mechanism is energy transfer from the singlet or triplet excited state of the dye to graphene. This raises the issue of determining the energy of the electronic excited states of graphene.
石墨烯片猝灭了一系列六种光化学探针的单重态和三重态激发态，包括芘、吖啶橙、三（2,2′-联吡啶）钌（II）二氯化物、亚甲基蓝、meso-四（苯基磺酸盐）卟啉和 5,10,15,20-四苯基-21H,28H-卟啉锌。结果发现，根据探针的不同，斯特恩-沃尔默荧光猝灭可以拟合一个或两个不同的猝灭区。此外，根据荧光团的不同，猝灭可以是静态的或动态的。考虑到猝灭是由于荧光团在石墨烯两面的拥挤或石墨烯片上的位隔离而产生的，因此出现了几种猝灭区。激光闪光光解表明，由于石墨烯猝灭，探针的三重态寿命通常会降低，并且除了亚甲基蓝之外，不会出现新的瞬变，在亚甲基蓝中，观察到新的吸收光谱，其特征是连续的吸收带，并归因于石墨烯自由基离子。这种光谱证据表明，最常见的猝灭机制是从染料的单重态或三重态激发态向石墨烯转移能量。这就提出了确定石墨烯电子激发态能量的问题。
