使用大氣電漿製程製作石墨烯超級電容及石墨烯電化學感測器

Abstract

本研究第一部分係利用氮氣直流脈衝常壓噴射電漿來製作一以聚乙烯醇/硫酸(polyvinyl alcohol (PVA)/sulfuric acid (H2SO4))凝膠態電解質構成之可撓性還原氧化石墨烯(rGO, reduced graphene oxide)超級電容，在循環伏安法以掃描速率為2 mV · s−1的測試條件下，測得其面積電容 (Areal capacitance)為47.03 mF · cm−2，且在各種不同之曲率半徑下無明顯之下降，此外，經過1000次循環伏安法測試後，平坦時之電容保持率 (Capacitance retention rate)為100%，而在曲率半徑為0.55公分時之彎矩狀態下為98.6%，證實了本研究所製作出來之可撓性超級電容具有優異的穩定性。 而本研究第二部分係利用一經由常壓噴射電漿處理之還原氧化石墨烯於網印碳電極上的電化學感測器與3D列印微流體通道所整合出的原型裝置進行研究。此原型裝置係用來檢測含有不同濃度多巴胺(DA, dopamine)之磷酸鹽緩衝生理鹽水(PBS, phosphate buffered saline)溶液。在經由常壓噴射電漿鍛燒後之還原氧化石墨烯塗層能夠顯著地增強多巴胺檢測時之電化學信號18倍，顯示出一經由常壓噴射電漿鍛燒之還原氧化石墨烯具有電催化效果。此外，從X光電子頻譜分析(XPS, X-ray photoelectron spectroscopy)結果可知，經由常壓噴射電漿鍛燒之還原氧化石墨烯於網印碳電極上具有更多含量的含氧表面官能基團，因而使其之電化學反應性增強。而在含有干擾物的測試中，當存在著具有相當濃度之尿酸 (UA, uric acid)以及抗壞血酸 (AA, ascorbic acid)等干擾物下，各種濃度之多巴胺溶液的循環伏安曲線以及線性掃描伏安曲線亦能夠明顯地區分出來。

In the first part, we use a nitrogen dc-pulse atmospheric-pressure plasma jet (APPJ) to fabricate a flexible reduced graphene oxide (rGO) supercapacitor with polyvinyl alcohol (PVA)/sulfuric acid (H2SO4) gel electrolyte. An areal capacitance of 47.03 mF · cm−2 (evaluated using cyclic voltammetry (CV) under a potential scan rate of 2 mV · s−1) is achieved. The supercapacitor can be operated without apparent degradation under bending with a bending radius of 0.55 cm. After a 1000 cycle CV stability test, the capacitance retention rate is 100% when flat and is 98.6% under bending (bending radius = 0.55 cm), indicating promising stability of the APPJ-processed flexible supercapacitor. In the second part, we report the prototype investigation of APPJ-processed reduced graphene oxide (rGO) modified carbon electrochemical sensors integrated with 3D-printed microfluidic channels. Dopamine (DA) solutions with various concentrations were used for the model test. The APPJ-calcined rGO coating significantly enhances the electrochemical signal of DA detection by 18 times. X-ray photoelectron spectroscopy (XPS) shows that APPJ-calcined rGO-modified carbon electrodes have more oxygen-containing surface groups, leading to the enhanced electrochemical reactivity. CV curves of various DA concentration solutions are well-distinguishable in the presence of interference agents of uric acid (UA) and ascorbic acid (AA).