Fitilis Ioannis, Fakis Mihalis, Polyzos Ioannis, Giannetas Vassilis, Persephonis Peter, Mikroyannidis John
Department of Physics, University of Patras, Patras 26504, Greece.
J Phys Chem A. 2008 May 29;112(21):4742-8. doi: 10.1021/jp711896f. Epub 2008 May 7.
Two photon absorption (TPA) and photophysical properties of three new symmetrical chromophores with electron accepting phthalimide edge substituents have been studied. The three chromophores contain fluorene, alcoxy-substituted divinyl benzene, and carbazole moieties as central cores, respectively. The femtosecond time-resolved fluorescence upconversion spectroscopy and two photon excited fluorescence technique have been carried out. The effect of solvent polarity on TPA and on photophysics has also been determined. Ultrafast fluorescence dynamics, with decay times ranging from 1 to 13 ps, are revealed in polar solvents. This is attributed to the relaxation of the chromophores to the intramolecular charge transfer state. The chromophore bearing fluorene central core, being of the type A-pi-A, is the most efficient concerning TPA. Strong TPA, with a cross section value as high as 2100 GM at an excitation wavelength of 770 nm is found in acetophenone which is a solvent of intermediate polarity. The TPA spectra were also reproduced using a sum over states three-state model. A study of the TPA induced photobleaching of the fluorene molecule, doped in a solid poly(methyl-methacrylate) film, has shown that this material is very promising for efficient TPA optical data storage.
研究了三种带有电子接受型邻苯二甲酰亚胺边缘取代基的新型对称发色团的双光子吸收（TPA）和光物理性质。这三种发色团分别以芴、烷氧基取代的二乙烯基苯和咔唑部分作为中心核。采用了飞秒时间分辨荧光上转换光谱和双光子激发荧光技术。还测定了溶剂极性对TPA和光物理性质的影响。在极性溶剂中揭示了超快荧光动力学，其衰减时间范围为1至13皮秒。这归因于发色团弛豫到分子内电荷转移态。具有芴中心核的发色团属于A-π-A型，在TPA方面效率最高。在中等极性的溶剂苯乙酮中，在770 nm激发波长下发现了强TPA，其截面值高达2100 GM。还使用态求和三态模型再现了TPA光谱。对掺杂在固体聚甲基丙烯酸甲酯薄膜中的芴分子的TPA诱导光漂白的研究表明，这种材料在高效TPA光数据存储方面非常有前景。
