芳杂环推拉型大分子的多光子上转换荧光性质

用Wittig反应和Heck反应制备了2个新的芳杂环推-拉型荧光大分子聚[(2,5-二苯撑-1,3,4-噁二唑)-4,4'-乙烯撑-交替-N,N'-二(4-苯乙烯撑)]苯胺(P1)和聚[(2,5-二苯撑-1,3,4-噁二唑)-4,4'-乙烯撑-交替-N-乙基-3,6-咔唑乙烯撑](P2). P1和P2的分解温度分别为373和412 ℃, 热稳定性良好. 电化学性能用循环伏安法测定. P1和P2的最高占有分子轨道(HOMO)能级分别为-5.39和-5.81 eV, 最低未占有分子轨道(LUMO)能级分别为-2.81和-3.09 eV. 用飞秒Ti:Sapphire激光器测定了P1和P2的三光子和双光子上转换荧光光谱. 在1250 nm波长激发下, 在四氢呋喃溶液中P1和P2的三光子荧光发射峰分别位于510和491 nm. 在800 nm波长激发下, 在四氢呋喃溶液中P1和P2的双光子荧光发射峰分别位于511和495 nm. 在四氢呋喃溶液中大分子P1和P2单光子荧光发射峰分别位于503 和475 nm, P1和P2的荧光量子产率分别为0.80和0.31. 研究了多光子荧光发射过程的溶剂效应. 结果表明, 溶剂极性增大, P1和P2的多光子荧光发射波长明显红移.

Multiphoton Upconversion Fluorescence Properties of Heteroaromatic Push-Pull Polymer

Two novel heteroaromatic push-pull fluorescence polymers poly [(2,5-diphenylene-1,3,4-oxadiazole)-4,4'-vinylene-alt-N,N'-bis(4-phenylenevinylene)-phenylamine] (P1) and poly [(2,5-diphenylene-1,3,4-oxadiazole)-4,4'-vinylene-alt-N-ethyl-3,6-carbazolevinylene] (P2) were synthesized by the Wittig reaction and the Heck reaction. Polymers P1 and P2 have decomposition temperatures of 373 and 412 ℃, respectively, and exhibit good thermal stabilities. Their electrochemical properties were explored by cyclic voltammetry. The highest occupied molecular orbital (HOMO) energy levels of P1 and P2 were -5.39 and -5.81 eV, respectively, and the lowest unoccupied molecular orbital (LUMO ) energylevels of P1 andP2were -2.81and-3.09eV, respectively. Three-photon and two-photon upconversion fluorescence spectra of both polymers were measured using a femtosecond Ti:sapphire that was pumped by a femtosecond laser at 1250 and 800 nm. Strong three-photon upconversion fluorescence with maximumemission wavelengths of 510 nm for P1 and 491 nm for P2 in THF solution were observed. By pumping at 800 nm, strong two-photon upconversion fluorescences at 511 nmfor P1 and 495 nmfor P2 in THF were measured.Maximumpeaks of single-photon fluorescence in THF were at 503 nmfor P1 and at 475 nmfor P2 with fluorescence quantumyields of 0.80 for P1 and 0.31 for P2. The effect of solvent polarity on multi-photon fluorescence was studied. Increased solvent polarity were found to induce a marked red-shift of the emission band in polymers P1 and P2.