Reactive Oxygen Species in a Non-thermal Plasma Microjet and Water System: Generation, Conversion, and Contributions to Bacteria Inactivation-An Analysis by Electron Spin Resonance Spectroscopy

• Published in: Plasma processes and polymers Vol. 9; no. 4; pp. 417 - 424
• Main Authors: Wu, Haiyan, Sun, Peng, Feng, Hongqing, Zhou, Haixia, Wang, Ruexue, Liang, Yongdong, Lu, Jingfen, Zhu, Weidong, Zhang, Jue, Fang, Jing
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2012; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: electron spin resonance; Exact sciences and technology; non-thermal plasma; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma applications; radicals; reactive oxygen species; Plasma applications; Oxygen; radicals; Singlet state; Non thermal plasma; Inactivation; Concentration measurement; electron spin resonance; Direct current; reactive oxygen species; Bacteria; EPR spectroscopy; non-thermal plasma
• ISSN: 1612-8850; 1612-8869
• DOI: 10.1002/ppap.201100065

Hydroxyl radical (•OH) and singlet oxygen (1O2) were detected by electron spin resonance (ESR) spectroscopy in a direct current He/O2 (2%) non‐thermal plasma microjet‐water system. ^{ \bullet }{\rm O}_{{\rm 2}}^{- } $ is shown to be the precursor of •OH. The concentrations of 1O2 and •OH are evaluated to be around 6 × 10−4 and 1.2 × 10−5 M, respectively. The survival rates of S. aureus exposed to plasma for 20 s in 1 ml H2O, SOD (100 U, for scavenging ^{ \bullet }{\rm O}_{{\rm 2}}^{- } $), D‐Man (0.15 M, for scavenging •OH), and L‐His (0.15 M, for scavenging •OH and 1O2) solutions were 0.7, 1.6, 13.4, and 40.9%, respectively, indicating that 1O2 contributes the most to the inactivation. This paper is characterized by the diagnosis of plasma in aqueous environment by electron spin resonance (ESR) spectrometry, which is the most direct and sensitive method for detecting radicals. By ESR diagnosis, plasma–water reactions can be elucidated, which is meaningful for guiding its clinical application. We specialize in diagnosing three kinds of reactive species, hydroxyl radical (•OH), superoxide anion radical (^{ \bullet }{\rm O}_{{\rm 2}}^{- } $), and singlet oxygen (1O2), and evaluating their relationships, concentrations, and contributions to sterilization.