多巴胺(Dopamine)，是人體中主要的兒茶酚胺神經遞質之一，它影響我們的認知和情緒。此外，當多巴胺濃度太高時，會造成人的情緒亢奮；太低時則會引起帕金森氏症造成身體顫抖及運動障礙。因此，如何設計一個有效偵測多巴胺的感測器為一項很重要的議題。
本研究我將以奈米碳管為主體，設計適用多巴胺感測的材料。其中使用半導體性質的奈米碳管(半導體感測器)和金屬性質的奈米碳管(電化學感測器)作為多巴胺感測器，並且探討在實驗中如何選擇出金屬性質與半導體性質的奈米碳管。首先，在奈米碳管的分離方面，利用半經驗法(PM6)，計算以不同的聚合物纏繞與混合的奈米碳管作用時，奈米碳管與聚合物之間的作用力，並且藉由作用力強弱來判斷聚合物對於奈米碳管的選擇性，以達到分離金屬性質與半導體性質的奈米碳管效果。在此研究中，我發現聚合物PTAA12-alt-PTAA對於 (6,5) 單壁奈米碳管 (SWNT) 有較高的選擇性。
瞭解奈米碳管的分離機制後，我進一步使用密度泛涵理論 (DFT) 計算，研究半導體感測器(Dopamine Semiconducting Sensor)以及電化學感測器(Dopamine Electrochemical Sensor)上偵測多巴胺的機制。我計算多巴胺吸附在不同硼、氮、硼氮摻雜濃度之半導體奈米碳管的吸附結構，並透過態密度(Density of States, DOS)分析，觀察能隙的改變，推算出導電度的變化，發現在0.55%硼-氮摻雜(6,5) SWNT以及2.20%硼-氮摻雜(6,5) SWNT下，多巴胺吸附會導致導電度有明顯的改變。另一方面，我進一步探討金屬性奈米碳管應用在多巴胺電化學感測器的可能性。在此研究中，將氧化態的多巴胺吸附在使用硼或氮摻雜的(5,5) SWNT上，藉由計算的吸附能結果顯示，0.83%硼摻雜 (5,5) SWNT對於第一氧化態和第二氧化態的多巴胺有很好的偵測效果。

Dopamine(DA) is one of the catecholamine neurotransmitters which can cause some nervous system disorders resulting in Parkinson's disease. Thus, the development of dopamine sensor is important for the diagnosis of these disorders. Previous study has reported that carbon nanotube (CNT) based materials could be an electrochemical biosensor for DA detection, including MWNTs and SWNTs. Moreover, separating the specific SWNT is also an important issue since synthesized CNT materials might consist of many kinds of CNTs such as semiconducting and metallic SWNT. In this work, by using semi-empirical calculation, we determined the interactions of polymers wrapped on the different types of SWNTs and found that PTAA12-alt-PTAA has high selectivity for (6,5) SWNT.
After realizing the separation mechanism of SWNTs, we carried out the simulation on DA semiconducting sensor and DA electrochemical sensor by using density functional theory (DFT) calculations. For the DA semiconducting sensor, we observed the large conductivity change on 0.55% B-N codoped (6,5) SWNT and 2.20% B-N codoped (6,5) SWNT after the adsorption of neutral DA. Thus, the calculations indicate that B-N codoped SWNTs illustrated high sensitivity toward to the DA detection. On the other hand, for the DA electrochemical sensor, the 0.83% boron doped (5,5) SWNT showed good performance of the first and second oxidation of DA sensing according to the high adsorption energy.

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