## 5 Conclusions  
In this study, plasma gas species and temperature were varied to evaluate the reactive species produced and the bactericidal effect of plasma. The reactive species produced by the plasma vary greatly depending on the gas species. It was found that a considerable amount of OH radicals were produced in the nitrogen plasma. Varying the plasma gas temperature resulted in a change in the concentration of the generated reactive species. In carbon dioxide plasma, the amount of singlet oxygen produced increased significantly with increasing temperature, and the amount of singlet oxygen produced was more than eight times greater at 90 than at 30 \({}^{\circ}\)C. The bactericidal effects of nitrogen and carbon dioxide plasmas on _Staphylococcus aureus_ in liquids were compared. The bactericidal effect of nitrogen plasma was not significantly affected by the temperature of the plasma gas. In the case of carbon dioxide plasma, the bactericidal effect was significantly improved by increasing the plasma gas temperature. The contribution of the singlet oxygen to the bactericidal effect of carbon dioxide was expected, based on the results of the bactericidal effect and reactive species produced.  
It was also found that the effectiveness of the disinfection process could be improved by properly selecting the plasma gas species and temperature. This result can be attributed to the changes in the type and number of reactive species. Therefore, it is expected that the treatment effect can be improved by changing the plasma gas species and temperature in treatments other than disinfection, such as hemostasis, treatment of plants, and surface treatment. In the case of plasma treatment in air, mixing with ambient air is considered to have a significant effect on the generation of reactive species. To realize a more stable treatment, it is necessary to control the air mixing or to construct a treatment method that does not depend on air. To effectively control plasma gas species and temperature, it is necessary to understand the reactive species that contribute to the effect, and to study the conditions according to the purpose of each treatment. In the future, we will study other plasma applications, such as hemostasis and surface treatments, to improve the treatment effect and clarify the effect mechanism using changes in the plasma gas species and temperature.  
Conceptualization, S.M., T.T. and A.O.; methodology, Y.S., T.A., S.M., Y.M. and A.I.; validation, Y.S. and T.A.; formal analysis, Y.S.; investigation, Y.S., S.M., T.A., T.T. and Y.M.; resources, S.M., Y.M. and A.I.; data curation, Y.S., S.M., T.T. and Y.M.; writing--original draft preparation, Y.S.; writing--review and editing, S.M., T.T., Y.M., A.I. and A.O.; visualization, Y.S. and T.A.; supervision, T.T. and Y.M.; project administration, Y.M., A.I. and A.O.; funding acquisition, A.I. and A.O. All authors have read and agreed to the published version of the manuscript.  
This study was supported by JSPS KAKENHI (Grant Number: 20K07039) and the Cooperative Research Project of the Research Center for Biomedical Engineering, National Cancer Center Research and Development Fund (Grant Number: 31-A-11), TERUMO LIFE SCIENCE FOUNDATION (Grant Number: 18-II106).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author, [PERSON], upon reasonable request.  
The authors would like to thank [PERSON] at Quantum RedOx Chemistry Group, Institute for Quantum Life Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, for providing the measurement equipment for the electron spin resonance method. The authors would like to thank [PERSON] at the Design and Manufacturing Division, Open Facility Center, Tokyo Institute of Technology, for preparing the plasma jet parts.  
The authors declare no conflict of interest.  
References