以原位聚合法合成導電高分子複合膜 應用於二氧化碳氣體感測器之研究

Abstract

在此研究中，利用快速成膜氧化聚合法合成3,4-乙烯二氧噻吩，並在3,4-乙烯二氧噻吩膜上利用液滴塗布法塗布支鏈型聚乙烯亞胺薄膜，此[3,4-乙烯二氧噻吩]-[支鏈型聚乙烯亞胺]複合膜成膜在黃金指插式電極上，製作成電阻式二氧化碳氣體感測器。在只有3,4-乙烯二氧噻吩薄膜的情形下，感測器對於二氧化碳沒有出現訊號，隨著添加支鏈型聚乙烯亞胺，此感測器對於1000ppm之二氧化碳感測結果，從原來的沒訊號，增加到3.25％，而且訊號大小與添加支鏈型聚乙烯亞胺的量呈現正比關係，此訊號曲線可利用單一指數函數做最適化分析。此感測器在750 ppm到5500 ppm二氧化碳濃度範圍間，其訊號大小與相對應之二氧化碳濃度呈現線性關係；偵測下限經計算約為97 ppm（在訊號/雜訊=3 之標準下）；反應時間(t90)以及恢復時間(t90)分別為1264秒以及接近一小時。在溫度以及溼度效應的實驗中，此感測器在室溫以及高濕度的環境下表現出的訊號最大。在重複使用的測試中，此感測器在重複使用三次後其訊號大小並無明顯的衰退趨勢。最後藉由系統改進，使原本較長的恢復時間（接近一小時）縮短至大約10分鐘。

In this Study, 3,4-ethylenedioxythiophene (EDOT) was oxidatively polymerized via in-situ polymerization and then fabricated a branched polyethylenimine (BPEI) film on PEDOT by drop casting. The PEDOT-BPEI sensing film which deposited on a gold interdigitated electrode was used as a resistive type carbon dioxide gas sensor. There is no response of the sensor when the sensing film is only a PEDOT monolayer. With adding BPEI, the response to expose to 1000 ppm carbon dioxide increased from nearly none to a value of 3.25％ and the response increased with the increasing amount of BPEI. The response curves of PEDOT-BPEI sensing film could be fitted well with single term of exponential expression. The sensor exhibited linear response behavior to carbon dioxide gas at higher concentration (750-5500 ppm). The limit of detection was 97 ppm (signal/noise = 3). The response time (t90) and recovery time (t90) were recorded to be 1264 s and nearly 1 hour, respectively. In the temperature and humidity tests, it could be observed that the optimum operation condition is room temperature and high relative humidity (RH). The reusability test showed that no obvious decay in response for repeatedly (three times) measurements. The long recovery time of nearly 1 hr was shortened to approximately 10 min by heating the sensor during recovery.