Excess dynamic Stokes shift of molecular probes in solution.
Excess dynamic Stokes shift of molecular probes in solution.
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DOI：
10.1021/jp400473n
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发表时间：
2013-06
期刊：
影响因子：
--
通讯作者：
M. Sajadi;N. Ernsting
中科院分区：
文献类型：
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作者：
M. Sajadi;N. Ernsting
利用宽带荧光上转换技术研究了分子探针的溶剂化动力学。测量了S1 → S 0发射带或电子振动线形状随时间变化的位置，分辨率约为80 fs，10 cm（-1）。极性溶质在乙腈和丙酮中，当激发到S1与过量的振动能量，表现出动态斯托克斯位移延伸到红色的准稳态之外。然后通过在10 ps时间尺度上较慢的蓝移达到平衡。在甲醇中，高达~ 14，000 cm（-1）的过量振动能没有显示出这种效应。非极性溶质在极性和非极性溶剂中都表现出过量的发射带红移，即使在电子振动源附近激发时也是如此。所观察到的动力学进行了讨论，在瞬态加热的激发发色团，构象变化，和分子腔尺寸的变化。对于溶剂化研究，光学激发应选择接近带原点。
The solvation dynamics of molecular probes is studied by broad-band fluorescence upconversion. The time-dependent position of the S1 → S0 emission band or of a vibronic line shape is measured with ~80 fs, 10 cm(-1) resolution. Polar solutes in acetonitrile and acetone, when excited into S1 with excess vibrational energy, show a dynamic Stokes shift which extends to the red beyond the quasistationary state. Equilibrium is then reached by a slower blue shift on a 10 ps time scale. In methanol, excess vibrational energy as large as ~14,000 cm(-1) shows no such effect. Nonpolar solutes exhibit an excess red shift of the emission band in both polar and nonpolar solvents even upon excitation near the vibronic origin. The observed dynamics are discussed in terms of transient heating of the excited chromophore, conformational change, and changes of the molecular cavity size. For solvation studies the optical excitation should be chosen close to the band origin.