利用石墨烯-聚甲基丙烯酸甲酯複合材料以溶液製程開發電阻式甲醛氣體感測元件

Abstract

在物聯網的架構下，藉由底層感知層許多的感測器來感知世界，不同感測器所得到之資訊傳遞到應用層，並在不同應用情境中使人們生活更智慧化。其中在智慧居家、環境監控中，氣體感測器都扮演監控人們空氣汙染及品質的重要工具，空氣污染的來源中有機揮發發性氣體尤其甲醛、苯、甲苯、二甲苯、乙苯等，是生活中常見對於人體有害的氣體，甚至一定含量會導致癌症加速死亡，因此要如何開發出更低成本、低能量功耗但又十分可靠的氣體感測器是十分重要的研究。 本研究利用旋轉塗佈法(Spin Coating)將石墨烯(Graphene)材料混合高分子聚甲基丙烯酸甲酯(PMMA,分子量15,000)的溶液沉積在金電極之間通道。在分散劑四氫呋喃(THF)裡，石墨烯與PMMA透過正負電吸引自組裝成導電複合材料，我們也將此複合材料與單純石墨烯相比較兩者對於甲醛氣體感測性質，調配出來的複合材料與甲醛氣體濃度約10ppm~600ppm時，有著電阻變化率 0.5%~30%。所開發的電阻式感測元件都是在室溫環境下操作，而且由不同比例之石墨烯複合材料所組成，感測材料被拿來與其他有機揮發性氣體甲醇、乙醇、丙酮、 苯、甲苯、鄰二甲苯氣體和常見有害氣體一氧化碳、二氧化碳、一氧化氮、及水反應檢測專一特性，實驗結果顯示感測元件對於甲醛氣體有最大的電阻變化率。 除了專一性外，本研究也測試了感測元件之靈敏性、重複性、穩定性、持久性，最後我們也利用貴重儀器掃描式電子顯微鏡、X光繞射儀、紅外線光譜儀、拉曼光譜儀來分析材料性質，並藉由比較材料感測甲醛氣體前後之間差異來推論感測材料與甲醛氣體可能的感測機制。

In bottom layer of Internet of Things(M2M) , there would be a lot of sensors to detect our environment in several applications such as smart home and air monitoring . Air pollution influences human health and can cause a number of diseases.The one of major air pollutiants is volatile organic compounds (VOCs) especially in BTEX and formaldehyde can cause cancer to human beings .Therefore, developing a low cost,low power consumption and reliable gas sensor is very important for sensing technology. In this work ,we demonstrated graphene material blended with Poly(methyl methacrylate,PMMA,M=15,000) composite inks deposited between gold electrode by spin coating method .The deposited graphene composite films with different mixture concentration are sensing materials for VOCs chemiresister gas sensors in room temperature.The sensor response to several VOCs gas including methanol ,ethanol , acetone , benzene ,toluene , o-xylene, formaldehyde and water vapor are investigated. The sensors selectivity ,repeatability and stability,duration are also examined .The graphene material are prepared and selectively blended with PMMA both in dispersant Tetrahydrofuran(THF) to become conductive self-assembly composite materials . We also tested the difference of sensing VOCs characteristics between spin coated pure graphene films and graphene /PMMA composite films. The optional concentration of graphene composite spin coated films show good sensor response to formaldehyde vapor with resistance change about 0.5%~30% after exposing to each vapor concentration(about 10ppm~600ppm) in room temperature .We finally use instruments such as FTIR,SEM,XRD and Raman to analysis materials .We also infer the possible sensing mechanism between the graphene-PMMA composites and the formaldehyde.