工作與腔體氣體成分對電漿水特徵之影響

Effects of the Working gas and Chamber Gas on the Property of Plasma-Activated Water

賴成春(Cheng-Chun Lai)

指導教授 ： 廖英皓

國立交通大學/工學院/機械工程系所/碩士(2019年)

摘要

近年來，非熱平衡電漿在生醫領域應用非常廣泛，因其溫度接近室溫，應用於生物體上佔有非常大之優勢。其中，電漿水(plasma-activated water, PAW) 在殺菌上之研究蓬勃發展。然而，現今之電漿水研究多半是將水置於大氣環境處理，無法有效的區分載體氣體與環境氣體對水之酸鹼值 (pH value) 以及水中化合物濃度之影響。因此，本研究會先將水置於一腔體之中，分別改變腔體內之氣體以及電漿束所用之載體氣體，來探討載體氣體及環境氣體對水質之影響，以及殺菌之效果。實驗結果顯示，經電漿束處理後，水之酸鹼值皆會下降，若所用之氣體內含氮元素，則下降之原因主要為三氧化二氮 (dinitrogen trioxide，N2O3) 分子溶於水產生氫離子，若無氮元素，下降之原因則為氬離子撞擊並分解水分子進而產生氫離子。過氧化氫之濃度與電漿之電子能量有相當程度之關係，水分子分解後產生之羥基 (hydroxyl radical，OH radical)，經覆合反應 (recombination reaction) 產生過氧化氫 (hydrogen peroxide，H2O2)，若所用之氣體內含有氧分子，因其電子親和力很高，電子能量降低，因此過氧化氫之濃度會降低。亞硝酸根 (nitrite，NO2-) 之生成大多為N2O3分子溶於水後產生，此分子則由NO˙自由基經反應後產生。在所用之氣體內含空氣時，氮氧分子經分解後產生氮氧原子，再彼此結合形成NO˙自由基；若所用氣體為氮氣時，氮分子分解後產生氮原子，再與羥基反應形成NO˙自由基。硝酸根 (nitrate，NO3-) 之生成大多與亞硝酸根有關。亞硝酸根在酸性環境中會逐漸轉變為硝酸根，同時，也會與過氧化氫反應形成過氧亞硝基 (peroxynitrite，ONOO-)後，再轉變為硝酸根。此外，經由實驗可得知，以氬氣作為載體氣體及腔體氣體，可產生濃度最高之過氧化氫；以氬氣混入1%空氣作為載體氣體，並且以氬氣為腔體氣體，可產生濃度最高之亞硝酸根；而以氬氣混入1%空氣作為載體氣體，並以空氣為腔體氣體時，可產生濃度最高之硝酸根。抑菌實驗結果顯示，殺菌效果與亞硝酸根之濃度呈現正相關，代表亞硝酸根在殺菌過程裡扮演重要角色。電漿水內之化合物濃度會隨著時間改變，亞硝酸根及過氧化氫濃度會逐漸下降，硝酸根濃度會上升，而水之酸鹼值則較為穩定。

關鍵字

常壓電漿束 ； 電漿水 ； 電漿載體氣體 ； 電漿-液相交互作用

並列摘要

Non-thermal equilibrium plasma has been attractive to many biological and medical applications since under some conditions its temperature can be controlled to be close to the room temperature. In addition to direct application of plasma to biology and medicine, plasma can be used to activate water for similar applications. Plasma-activated water (PAW) has great potential and high effectiveness on sterilization and bacteria inactivation. For activation above liquid, most studies on PAW are performed in open air making it difficult to understand the role of the working gas and the ambient gas on PAW’s property. Therefore, the present study applying a plasma jet to activate water in a sealed chamber is aimed to investigate the effect of gas mixtures on the physicochemical property and the biological effect of PAW. Here, the DI water is activated by plasma jet for 10 minutes and Escherichia coli (E. coli) is used as the microbial model. Results show that a mixture of working/chamber gas have a significant impact on PAW’s physicochemical property and biological effect. The pH value of PAW is observed to decrease after activation. The maximum decrease in solution pH is observed for gas mixtures containing N2 and the pH decrease is attributed to dissolution of N2O3 into water to generate hydrogen ions. In pure argon environment, reactions between metastable argon species and water molecules lead to production of hydrogen ions, resulting in pH decrease. The minimum decrease in solution pH is observed for gas mixtures containing only O2. Formation of hydrogen peroxide (H2O2) is strongly dependent on the electron energy and the mixture of Ar/Ar produces the maximum concentration of H2O2. H2O2 appears to be the major species for most gas mixtures. A gas mixture of Ar + air/Ar produces the maximum concentration of nitrite (NO2-), while Ar + air/air produces the maximum concentration of nitrate (NO3-). Overall, the antibacterial efficacy correlates well with NO2- concentration. Stronger antibacterial efficacy is observed for gas mixtures producing NO2- and NO3- as major species. The role of air in the working gas on antibacterial efficacy is different than that in the chamber gas, i.e. Ar + air/Ar > Ar + air/air > Ar/air > Ar/Ar, mainly due to the difference of electron-impact reactions in the main discharge region and post-discharge region. It is also observed that the solution pH is stable after several days of activation, but concentrations of nitrite and hydrogen peroxide decrease with time, and nitrate concentration increase.

並列關鍵字

atmospheric-pressure plasma jet ； plasma-activated water ； plasma working gas ； plasma-liquid interaction

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