含芳香環側鏈取代之聚苯胺共聚合物之螢光與電子傳遞途徑研究

林敬堯(Jing-Yao Lin)

指導教授 ： 陳益佳

國立清華大學/理學院/化學系/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00612

摘要

本論文研究利用具不同時間解析度之雷射光源，對一系列聚苯胺及其含芳香環側鏈取代基之衍生物進行光激發後衰減機制之探討。以單光子計數系統進行量測得到奈秒級之螢光衰減生命期；從飛秒螢光上轉系統可以得到皮秒級之衰減時間常數。綜合兩套實驗系統的結果，發現以 266 nm 為激發波長、420 nm 處進行偵測時，系列待測化合物皆有四個衰減時間常數，Pan 之 NMP 溶液其四個衰減生命期依序為 2 ps、22 ps、0.6ns 及 2.6 ns。而 Pan-BT、Pan-NPT、Pan-MBT 與 Pan-PYT 等四個聚苯胺衍生物在 NMP 溶液下之衰減常數為 1.7∼3 ps、23∼71 ps、0.5∼0.65 ns 及 2.1∼2.2 ns。因此我們認為稼接的取代基對於螢光衰減生命期並無顯著影響。激發光子將待測分子激發至極高不穩定態後，在短於 400 fs 之時間常數內便躍遷至 S1 能態之較高振動不穩定態。而後分別經由 2 ps 與 22 ps 兩次之振動緩解過程釋放能量至 S1 state 之最低振動能階，最後由該處以放出螢光型式釋放能量回歸基態。以 355 nm 為激發光源時，各化合物之放光位置皆無改變，因此 266 與 355 nm 皆激發至相同能態，而且在時間零點時 355 nm 之非均向性 r 值約為 0.2，代表 355 nm 光源將分子激發至 S1 state 後，在振動緩解之前未經由其他緩解途徑釋出能量。

關鍵字

聚苯胺 ； 飛秒 ； 螢光 ； 能量轉移 ； 生命期

並列摘要

We study the excited state dynamics of polyaniline and its aromatic substituted derivatives using femtosecond and picosecond laser systems combined with techniques time correlated single photon counting and fluorescence up-conversion. Five polymers, polyaniline [Pan(1)], Benzenethiol-polyaniline [Pan-BT(2)], 2-naphthalenethiol-polyaniline [Pan-NPT(3)], 2-mercaptobenzothiazole-polyaniline [Pan-MBT(4)], 2-pyridinethiol-polyaniline [Pan-PYT(5)] are studied. Excitation at wavelength 266 nm and at 355 nm for all the molecules studied we observe four decay components. Using time correlated single photon counting and fluorescence up-conversion techniques we found that upon excitation at 266 nm 1 in NMP solution exhibit four decay processes with fitted time constants 2 ps, 22 ps, 0.6ns and 2.6 ns. The other compounds’ decay time constansts are in the range of 1.7∼3 ps, 23∼71 ps, 0.5∼0.65 ns and 2.1∼2.2 ns. According to the results we conclude that the substituents don’t affect decay lifetimes much. The photons excite the molecules to a highly unstable state followed by transfer to S1 state within 400 fs. And then cool down to the lowest vibrational state by two steps internal vibrational relaxation processes followed by fluorescence emission from S1 state. Upon excitation at 355 nm the emission wavelength is the same with excitation at 266 nm, and this means that the emission states are the same whether the excitation wavelength is 266 or 355 nm. At time zero the anisotropy value r(t＝0) equals to 0.2 means there’s a fast rotational motion within the system response time (TCSPC, 30 ps) after excitation by 355 nm light.