Upadhyayula Srigokul, Nuñez Vicente, Espinoza Eli M, Larsen Jillian M, Bao Duoduo, Shi Dewen, Mac Jenny T, Anvari Bahman, Vullev Valentine I
Department of Bioengineering , University of California , Riverside , CA 92521 , USA . Email:
Department of Biochemistry , University of California , Riverside , CA 92521 , USA.
Chem Sci. 2015 Apr 1;6(4):2237-2251. doi: 10.1039/c4sc02881c. Epub 2015 Feb 11.
Cyanine dyes are broadly used for fluorescence imaging and other photonic applications. 3,3'-Diethylthiacyanine (THIA) is a cyanine dye composed of two identical aromatic heterocyclic moieties linked with a single methine, -CH[double bond, length as m-dash]. The torsional degrees of freedom around the methine bonds provide routes for non-radiative decay, responsible for the inherently low fluorescence quantum yields. Using transient absorption spectroscopy, we determined that upon photoexcitation, the excited state relaxes along two parallel pathways producing three excited-state transients that undergo internal conversion to the ground state. The media viscosity impedes the molecular modes of ring rotation and preferentially affects one of the pathways of non-radiative decay, exerting a dominant effect on the emission properties of THIA. Concurrently, the polarity affects the energy of the transients involved in the decay pathways and further modulates the kinetics of non-radiative deactivation.
花青染料广泛应用于荧光成像和其他光子学应用。3,3'-二乙基硫代花青（THIA）是一种花青染料，由两个相同的芳香杂环部分通过一个亚甲基连接而成，即-CH[双键，长度为m破折号]。亚甲基键周围的扭转自由度为非辐射衰变提供了途径，这导致了其固有的低荧光量子产率。通过瞬态吸收光谱，我们确定在光激发后，激发态沿着两条平行的途径弛豫，产生三个激发态瞬态，这些瞬态会发生内转换回到基态。介质粘度阻碍了环旋转的分子模式，并优先影响非辐射衰变的其中一条途径，对THIA的发射特性产生主导作用。同时，极性影响衰变途径中瞬态的能量，并进一步调节非辐射失活的动力学。
