A Study on Tin Dioxide Nanoparticles for Gas Sensing

本研究之目的在探討一氧化碳經由不同的二氧化錫奈米顆粒體為感測材料與金梳狀電極為載體之低溫感測器試製與感測特性鑑訂。所建構之氣體偵測器具備歐姆阻抗。利用溶膠-凝膠合成法所製備之二氧化錫奈米顆粒其平均直徑為20nm至50nm。用TEM與XRD檢測感測膜時顯示出二氧化錫奈米顆粒為多晶結構且每個晶粒形狀為矩形，環狀SAD檢測圖形顯示出二氧化錫奈米顆粒體屬於多晶結構。構裝後，實驗所量測輸出之訊號顯示一氧化碳感測訊號靈敏度明顯受操作溫度影響，在350℃時達極大值。平衡輸出訊號與一氧化碳濃度(20-100 ppm）呈線性關係，且由此關係可得一校正曲線。當摻雜鈀(3.5wt %)在二氧化錫奈米顆粒體時，能使感測靈敏度提高約50%，這可能是因為摻雜負電性較錫略高之鈀導致一些缺陷產生在二氧化錫多晶結構上，如此增加更多可用的活位。這些活位能夠與更多氣體分子產生交互作用，因此訊號輸出增加。This thesis reports investigates on CO sensing due to different sizes of SnO2 nanoparticles as probing material. that were coated on a substrate of comb-type Ag electrode. Sol-gel was synthesized to imbed tin-dioxide nanoparticles with average diameter in a range of 20-50 nm. A gas detection instrument system incorporating our sensing element was set-up for performance evaluation based on signal output implementing the ohmic resistance. Transmission electron spectroscope and X-ray diffraction investigations indicated that the SnO2 nanoparticles grown by sol-gel synthesis process formed crystal clustering of rectangle-like. The scattered ring pattern further confirmed that the SnO2 nanoparticles belonged to polycrystalline structure. Performance test showed that the CO sensing signal sensitivity is obviously influenced by operating temperature, and the optimum condition appeared at 350 °C. A linearity output in respond to CO concentration between 20 and 100 ppm was obtained. This shows that it can be served as a calibration curve. Pd (3.5 wt %) doped into SnO2 nanoparticle clusters was shown to increase in sensitivity of approximately 50%. This is presumably duo to the fact that the more electronegative Pd created some defects in SnO2 polycrystals, thus creating more available active sites for CO sensing and enhanced signal condition.誌謝 …ii 摘要 ...iii Abstract ...iv 圖目錄 ...vii 表目錄 ...ix 符號說明 …x 第一章 緒論 1-1 前言 …1 1-2 研究動機與目的 …3 第二章 文獻探討 2-1 分子反應動力學理論 …5 2-2 氣體感測器原理與種類 …13 2-3 奈米材料簡介 …28 2-4 奈米微粒簡介 …31 2-5 奈米顆粒體的製備方法 …32 2-6 二氧化錫的材料性質 …36 2-7 半導體式氣體感測器的工作原理 …38 2-8 影響感測性質之因素 …50 2-9 溶膠-凝膠法 …54 2-10 旋轉塗佈法的原理 …58 2-11 設計方法論 …59 第三章 材料與方法 3-1 實驗藥品 …66 3-2 製備SnO2凝膠 …66 3-3 電極與感測器之製備 …68 3-4 感測電路 …69 3-5 樣品之基本物性分析 …70 3-6 氣體感測實驗 …71 第四章 結果與討論 4-1 溶膠凝膠法-製程 …74 4-2 數據分析 …74 4-3 感測溫度對靈敏度的影響 …77 4-4 氣體濃度對感測度的影響 …78 4-5 催化劑的作用對感測靈敏度之影響 …80 第五章 結論與建議 5-1 結論 …83 5-2 建議 …83 參考文獻 …8