電壓調控位向之主客化學：單層凹面碗烯分子嵌於具孔洞模版之石墨表面

Abstract

討論有效地調控有機分子在表面的排列方向，對於發展分子電子元件是相當具有挑戰性的議題。調控方式以外界刺激(external stimuli)，如：照光、熱變化、改變電壓，及改變溶劑、濃度為主要途徑。本研究探討於液固界面(溶劑−石墨)下，使用掃描式穿隧顯微術(scanning tunneling microscopy, STM)觀察碗稀分子(Corannulene, COR)崁於均苯三甲酸(Trimesic acid, TMA)孔洞模板內之排列位向。 COR為一結構似碗公狀的立體分子，在不施加外界刺激下，於石墨表面上呈凹面朝上或朝下之位向比例約3:2。本研究結果得知，對COR施加 -4 V於TMA孔洞模板後，能有效調控COR凹面朝上達98.3%；當施加外部電壓愈大，COR凹面朝上的比例愈低，原因推測COR為良好之電子受體，於額外施加負電壓時，能誘導COR與表面接觸面積較多之凹面朝上的位向排列，也因此能說明在施加2 V時，在表面上僅觀察到TMA之孔洞模板。此外，施加分別為 -2、-1、1 V時，COR凹面朝上與朝下的比例近3:2。 為更進一步確認COR能額外施加偏壓調控位向，我們利用位向為凹面朝上之COR能因π−π作用力吸附富勒烯碳七十(Fullerene, C70)之特性，在額外對COR施加 -4 V形成TMA−COR表面後，確認COR凹面朝上的比例達到最高，此時再加入C70進行STM影像觀察。此項結果顯示，在加入C70前，COR朝上的比例與在加入C70後C70吸附於COR的比例近乎一致。透過以上研究，除了能進一步證實COR能受額外偏壓調控位向外，也能表示在主客系統下，我們能再利用客分子的特性探討更多分子間作用力的研究。

In order to research into external stimuli to controllable assembly, we demonstrate that orientation of bowl-shaped corannulene (COR) can be tuned by adjusting variety electric field at liquid/solid interface, procedures are analyzed by scanning tunneling microscopy (STM). Aim to identify the characteristics of COR which can not self-assembly on graphite, trimesic acid (TMA) are employed as the template to accommodate COR, achieving host-guest chemistry on grahite. Without external stimuli, the ratio of bowl-up to bowl-down of COR is close to 3:2. According to results, applying external -4 voltage onto COR, 98.3% of bowl-up COR can be recognized in TMA-COR surface, instead, lower percentage of bowl-up COR are observed while increasing external voltage. By our experience, COR is a better electron acceptor. After applying external negative electrons, COR tends to be bowl-up, which is lager area of molecular geometry that absorbed to the surface. Further to ensure the results above, we add Fullerene, C70, which enable to be attracted by bowl-up COR through π-π interaction. As a result, percentage of C70 stack with COR is close to bowl-up COR applied external -4 voltage on surface. In summary, not only exhibit electric field-induced orientation of COR, but also investigate prospective study of host-guest chemistry.