外界空氣導入氦氣常壓電漿束增進活性粒子生成及其表面處理與殺菌效果之研究

Abstract

本研究藉導入外界空氣以增加氦氣常壓電漿束內的活性粒子生成，並測試其對聚丙烯高分子膜之表面處理效果與蛀牙菌之殺菌成效。本研究使用流場模擬、紋影法、電漿外貌、電性特性、溫度量測、電子密度量測以及放光光譜儀進行電漿束的觀察與相關特性量測。使用接觸角量測儀、全反射傅立葉紅外線能譜儀、原子力顯微鏡以及X射線光電子能譜儀分析電漿束處理後試片的表面狀況；另外使用殺菌面積大小量測蛀牙菌之殺菌效果。使用階梯狀噴嘴誘導外界空氣進入電漿之放電區，並以電漿束出口直徑來控制外界空氣導入量。流場模擬結果顯示，外界空氣導入量隨著出口直徑的增加而增加。電漿氣體溫量測結果顯示本電漿溫度低於攝氏40度，可應用於絕大多數熱敏感之材料。在電漿放電區的放光光譜量測顯示，藉由導入適量的外界空氣（即本實驗中出口直徑為3 mm的條件），可提高活性粒子之生成，氫氧自由基與氧原子相較於沒有導入外界空氣的電漿束分別增加90%與170%；藉由H-beta之斯塔克譜線增寬分析與估計，該電漿條件亦顯示出產生相對高的電子濃度達4.6*1013 cm-3。於後放電區的放光光譜量測顯示，藉由導入適量的外界空氣，氫氧自由基與氧原子生成量在空氣中、聚丙烯表面與細菌培養基表面，分別增加了約50%與40%、70% 與35%以及50%與800%。本電漿束成功的在二十秒內殺死培養基表面之蛀牙細菌，且從殺菌結果也可看出殺菌面積與活性粒子強度有著雷同的趨勢。根據全反射傅立葉紅外線能譜儀分析結果顯示，電漿處理過的聚丙烯表面多出了許多含氧官能基，如C–O (1543 cm-1)與C=O (1698 cm-1與1647 cm-1)。X射線光電子能譜儀分析亦在電漿處理過的聚丙烯表面發現C-O與C=O官能機，且氧-碳濃度的比值(O/C ratio)結果顯示，其與電漿中活性粒子在聚丙烯表面的強度有著相近的趨勢。這些含氧官能機使聚丙烯經過兩秒鐘的電漿處理，水滴接觸角僅約3度，表面出現超親水的現象。本論文研究顯示，適當的使用外界空氣導入電漿束，能使電漿束產生之化學活性粒子增加，這在設計電漿源時，應將之列入重要考量因素。

A helium atmospheric-pressure plasma jet (APPJ) with various ambient air entrainment conditions was developed and its applications in surface treatment of polypropylene and sterilization of S. mutans were performed. The APPJ was characterized by flow field simulation, Schlieren photography, direct visualization, electrical properties, temperature measurement, electron number density, and optical emission spectroscopy (OES). Surface modification efficacy was evaluated by water contact angle measurement, attenuated total reflection - Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). The sterilization efficacy was evaluated using the magnitude of inactivation area. We used a stepped nozzle to accelerate the gas flow enhancing the ambient air entrainment and controlled the ambient air entrainment by different exit diameters. The results of flow field simulation show that the amount of ambient air entrainment increases with increasing jet exit diameter. Gas temperature of the APPJ is kept below 40°C, which is applicable for most of the heat-sensitive materials. The OES results in discharge region show that with suitable amount of ambient air entrainment using an exit diameter of 3 mm, the chemical reactive species such as hydroxyl radical (309 nm) and atomic oxygen (777 nm) increased up to 90% and 170% higher than that without entrainment, respectively; this entrainment condition also resulted in relatively high electron number density (4.6*1013 cm-3) as estimated by Stark broadening of H-beta line emission. In the post discharge region, the OES analysis of OH/O demonstrated ~50%/40%, ~70%/35% and ~50%/800% enhancement by a favorable amount of ambient air entrainment under free jet condition, at plasma/PP interface and at plasma/agar interface, respectively. This APPJ successfully sterilized S. mutans on agar plate in 20 seconds, and the sterilization efficiency is found to be strongly correlated with the OES intensity of reactive species. The oxygen-containing functional groups such as CO– (1543 cm-1) and C=O (1698 and 1647 cm-1) were found to be incorporated onto the PP surface by ATR-FTIR analysis. The XPS results also reveal that C–O and C=O were incorporated onto the plasma-treated PP surface, and the trend of O/C ratio is in consistent with the OES intensity of reactive species at plasma/PP interface. The oxygen-containing functional groups lead to a super hydrophilic surface with a water contact angle of ~3 degrees after 2 seconds of APPJ treatment. Based on the experimental results in the current study, we can conclude that air entrainment plays an important role in the current design of helium APPJ.