釩金屬有機框架應用於可撓性二氧化氮感測器之研製

Abstract

石化燃料的不完全燃燒以及汽機車的排氣是大氣中NO2之主要來源，長期吸入NO2會對人體帶來嚴重且不可逆的為害，故需要開發一種能即時監控NO2濃度的氣體感測器。本研究以釩作為金屬離子，對苯二甲酸(Terephthalic acid, PTA)和均苯四甲酸(Pyromellitic acid, PMA)作為有機配體(Organic ligand)，透過改變水熱法之加熱溫度(120 °C與150°C)，分別製備出四種釩金屬有機框架(Metal organic framework, MOF)作為感測材料，分別為V-MOF120(PTA)、V-MOF150(PTA)、V-MOF120(PMA)和V-MOF150(PMA)。將這些材料塗覆在聚醯亞胺(Polymide, PI)薄膜以CO2雷射誘導石墨烯(Laser-induced graphene, LIG)的指叉電極表面，完成可撓式氣體感測器之開發。將四種感測器在室溫100 ppm的NO2氣體濃度下進行檢測，V-MOF120(PTA)展現794 %的高響應，高於V-MOF150(PTA)的751 %、V-MOF120(PMA)的338 %和V-MOF150(PMA)的424 %。其中，以PTA作為有機配體所製備的感測器，平均響應值為770 %，優於PMA感測器的平均響應值381 %。V-MOF120(PTA)在五次的連續循環下平均響應值為800.8 %，平均響應時間與回復時間則分別為230秒和39.8秒，說明其具有良好的穩定性與重複性，且在1 ppm NO2氣體下仍具有83 %的低LOD響應性能。此外，V-MOF120(PTA)感測器的濕度測試發現，在溼度40-60%的變化時響應值影響不大，而在100 ppm的乙醇、甲醇、和丙酮環境下，響應值則分別僅有–220 %、–200 %和–100%，對比於NO2氣體794 %的響應值，展現其具有不錯的氣體選擇性。最後，對氣體感測機制進行探討，且將本實驗結果與文獻進行比較，證實本研究所製備的V-MOF120(PTA) 在開發實用的室溫型NO2氣體傳感器展現極佳的應用潛力。Incomplete combustion of petrochemical fuels and exhaust emissions from vehicles are the main sources of NO2 in the atmosphere. Prolonged exposure to NO2 can cause severe and irreversible harm to human health. Therefore, there is a need to develop a gas sensor capable of real-time monitoring of NO2 concentrations. In this study, vanadium (V) metal ions were used, with terephthalic acid (PTA) and pyromellitic acid (PMA) as organic ligands, to prepare four types of vanadium metal-organic frameworks (MOFs) as sensing materials. These MOFs, namely V-MOF120(PTA), V-MOF150(PTA), V-MOF120(PMA), and V-MOF150(PMA), were synthesized using a hydrothermal method with different heating temperatures (120°C and 150°C). They were coated on a polyimide (PI) film with laser-induced graphene (LIG) serving as the electrode to create flexible gas sensors.The four sensors were tested under 100 ppm NO2 gas concentration at room temperature. V-MOF120(PTA) exhibited the highest response of 794 %, followed by V-MOF150(PTA) with 751 %, V-MOF120(PMA) with 338 %, and V-MOF150(PMA) with 424 %. Notably, sensors prepared with PTA as the organic ligand showed an average response of 770 %, outperforming those with PMA ligands, which had an average response of 381 %. V-MOF120(PTA) demonstrated good stability and repeatability, with an average response of 800.8% over five consecutive cycles. The average response and recovery times were 230 seconds and 39.8 seconds, respectively. Furthermore, the sensor exhibited a low limit of detection (LOD) of 83% at 1 ppm NO2 concentration. Additionally, in environments containing 100 ppm ethanol, methanol, and acetone, V-MOF120(PTA) showed minimal responses of -220%, -200%, and -100%, respectively, indicating its promising gas selectivity for NO2. Finally, the gas sensing mechanism was investigated, and the experimental results were compared with literature to confirm that V-MOF120(PTA) prepared in this study provides a viable approach for developing practical room-temperature NO2 gas sensors.