吡啶星型分子的双光子上转换荧光特性

摘要

The two-photon absorption and the two-photon-excited fluorescence spectra of a star-shaped pyridine chromophore, 2,5-bis {4-{4-[N,N-bis (4-pyridylethenyl) phenylamino ] styryl } phenyl } -1,3,4-oxadiazole ( PyPASPO), were measured via a femtoseeond Ti: sapphire laser at 800 nm. Its two-photon absorption crosssections obtained by nonlinear transmission method is 412. 5 GM in the solution of CH2Cl2 and 288.8 GM in the solution of THF. The linear absorption, one-photon fluorescence, fluorescence lifetime, and excitationemission-fluorescence intensity 3D spectrum were investigated. When pumped with 800 nm femtosecond laser irradiation, chromophore PyPASPO shows strong two-photon excited green fluorescence at 571 nm in CH2Cl2 and at 525 nm in THF, respectively. In CH2Cl2 the maximum peaks of single-photon-excited fluorescence is at 532 nm and the fluorescence lifetime is 1.24 ns. The electrochemical properties was explored by cyclic voltammetry. The HOMO energy level is - 5.21 eV and the LUMO energy level is - 2. 92 eV. Enhancing the charge transfer extent was adapted to increase the two-photon absorption and upconversion fluorescence emission of the star-shaped pyridine chromophore. Compound PyPASPO having four pyridine and two triphenylamine groups at the oxadiazole core not only shows largest 2PA cross-sections at 800 nm but also has strong the two-photon excited frequency upeonversion emission in the green region. This work opens broad perspectives for new molecular design of 2PA-organic materials.%用飞秒Ti:sapphire激光测定了一种星型吡啶分子2,5-二{4-{4-[N,N-二(4-吡啶乙烯基)苯基氨基]苯乙烯基}苯基}-1,3,4-噁二唑(PyPASPO)的双光子吸收截面及上转换荧光光谱.采用非线性透过率法测得二氯甲烷和四氢呋喃溶液中其双光子吸收截面分别为412.5和288.8 GM.系统研究了吡啶星型分子PyPASPO的线性吸收和透过光谱、单光子荧光、荧光寿命及激发-发射三维荧光谱和前线轨道能级.在800 nm和150 fs钛宝石激光器激发下,PyPASPO在二氯甲烷和四氢呋喃溶液中的双光子上转换荧光发射波长分别为571和 525 nm,在二氯甲烷溶液中单光子荧光峰位于532 nm,荧光寿命为1.24 ns.HOMO和LUMO能级分别为-5.21和-2.92 eV.增大分子内电荷转移有效增强了吡啶星形分子的双光子吸收和双光子上转换荧光发射能力.