双光子激发二氢卟吩衍生物的光物理特性  

Photophysical Properties of the Chlorophyll Derivative Under Two-photon Excitation

作　　者：赵培德[1] 陈平[1] 汤国庆[1] 姚建忠[2] 傅汝廉[1] 张桂兰[1] 陈文驹[1] 

机构地区：[1]南开大学现代光学研究所 [2]第二军医大学药学院,上海200433

出　　处：《光电子．激光》2005年第7期881-886,共6页Journal of Optoelectronics·Laser

基　　金：天津市科委资助项目(023107611)

摘　　要：用飞秒脉冲激光,研究了二氢卟吩光敏剂CPD3分子在双光子激发(TPE)下的光物理过程。报道了该分子在四氢呋喃(THF)溶剂中的TPE荧光光谱及其寿命,以及在波长800nm处的双光子吸收(TPA)截面,其中,TPE与单光子激发(OPE)的荧光光谱形状一致,具有相同的荧光发射带,荧光寿命分别为5.1ns和5.7ns;在波长800nm处的TPA截面σ2≈12.5×10-22cm4/GW。本文分析表明:在TPE下,该分子跃迁到激发态S2,经历了无辐射弛豫到达OPE的同一荧光能级,呈现激发Q带所产生的正常的荧光发射;该分子具有大的TPA截面是起源于该分子的刚性平面共轭结构所固有的线性吸收特性和TPA共振增强;CPD3作为光动力治疗(PDT)的光敏剂,又具有长波长的荧光发射、ns级的荧光寿命和大的TPA截面特性,这些双重特性使其有可能成为双光子荧光分子探针,借助于双光子荧光显微和成像技术,在分子水平上揭开PDT光敏药物与细胞器的结合特性和作用靶点等深层次问题。Photophysical processes of the chlorophyll derivative photosensitizer CPD3 were investigated under two-photon excitation (TPE) induced by a femtosecond pulse laser. The two-photon excited fluorescence spectra, fluorescence lifetime and two-photon absorption (TPA) cross section of CPD3 at 800 nm are reported for the first time. The fluorescence spectrum is in much correspondence with that induced by one-photon excitation (OPE) at 400 nm (B-band) or at 667 nm (Q-band). The two-photon and one-photon excited fluorescence lifetimes of the molecule are the order of 5.1 ns and 5.7 ns respectively. The TPA cross section at 800 nm is about 12.5 × 10-22 cm4/GW. These results suggest that the excited state S2 populated by TPE or OPE may relax via radiationless process to the fluorescence state induced by OPE of Q band, and then show a normal fluorescence emission behavior. The large TPA cross section may result from the intensive linear absorbance of the molecule due to its conjugate rigid plane structure, and the two-photon resonance excitation condition. These photophysical properties of CPD3, suggest that the chlorophyll derivatives, as the class of new photosensitizers for photodynamic therapy (PDT), may be also the excellent two-photon molecular probes for studying the interaction between the photosensitizer and the inner parts of tumor cell in PDT by means of two-photon fluorescent microscopy and imaging, in order to make it possible to understand the mechanism of PDT on the molecular level.

关 键 词：二氢卟吩光敏剂 双光子激发(TPE)荧光 双光子吸收(TPA)截面 双光子分子探针 

分 类 号：O431.2[机械工程—光学工程]