A Plasma-Based Decontamination Process Reveals Potential for an in-Process Surface-Sanitation Method

Round 1

Reviewer 1 Report

The manuscript can be published after minor changes.

1.       Line 98: the authors said that the gas temperature was 4000 K. Is it the inserted gas temperature, or the temperature from the inside plasma discharge? Please give an explanation how you’ve inserted hot gas inside the plasma discharge; if it’s not inserted hot gas inside the discharge, please re-formulate the sentence.

2.       Line 105: the authors said that they have used a plasma torch. Please insert this, in the introduction section. By dealing with a plasma torch, the plasma species have a different behavior, than in the case of a cold atmospheric plasma.  

3.       How do you managed to decontaminated the samples, by using a plasma torch, instead a cold atmospheric plasma jet discharge, without destroying the samples?

4.       In the conclusions, the authors said that they used a non-thermal plasma. Please re-evaluate the manuscript, because you have used “plasma torch” in your descriptions, inside the manuscript. Take into account that a plasma torch is commonly used to expressed the existence of a thermal plasma, whereas a non-thermal plasma is a cold plasma, where only the electron temperature dominates.

Author Response

Dear reviewer!

 

Thank you very much for reviewing our manuscript. It helped a lot to take the necessary distance to our own work. Behind that background, I totally agree with your remarks 1 – 3 and I fully followed your advices. My chosen phrases turned out to be misleading in a way highlighted in your advices. 

 

1. The temperature only rises up to 4000 K in a small volume directly connected to the plasma source. Therefore, we conduct an indirect treatment, which is subdivide into two steps. Step one embraces the production/processing of ambient air by a plasma torch and the second step encompasses the sample treatment. Since the sample treatment itself is spatially separated from the place of PPA-production
2. As recommended, we mentioned our type of plasma source in the introduction.
3. As described under 1: We conducted an indirect treatment which offers a heat dissipation of the PPA before it enters the treatment chamber (check also the newly introduced figure 1 of our manuscript)
4. We do not totally agree! It is true that microwave plasmas and equilibrium plasmas (thermal plasmas) share some important properties, especially the high heat output. But the key feature of an equilibrium plasma is an equilibrium between the gas and electron temperature (t_e = t_gas), which is not true for microwave plasmas. Sometimes they referred as quasi-thermal plasmas. For a greater detail please check the publication of Rowuwenhorst et al.¹. However, based on your suggestion, we changed the term non-thermal plasma into quasi-thermal plasma.

 

I hope I was able to contribute to the discussions in plasma on the basis of our publication. Further criticism and comments are highly welcome! Thank you very much for your patience and the interest in our work.

 

Sincerely yours

The authors

Reviewer 2 Report

The manuscript presented an indirect plasma-based decontamination method (Plasma-processed air) to treat different microorganisms. Reduction factors up to several log10-steps were obtained and the influence of experimental conditions was analyzed. This manuscript is well written, and I recommend accepting this manuscript after some minor modifications listed below.

1.      Page 1 line 32, is there a ‘space’ between ‘out’ and ‘coming’?

2.      Page 2 line 72, plasma-processed air (PPA) is defined in the abstract, but the abbreviation needs to be defined again when appearing in the main content for the first time.

3.      Page 2, line 90-91, This sentence ‘’Technological plasmas are………up to 10%” seems to be not necessary because charged particles were less significant in the scope of this manuscript where the authors used indirect treatments. This sentence might cause confusion to readers.

4.      Page 2, line 91-94, regarding the controlled composition of PPA by mass spectroscopy mentioned by the authors, is it from ref [19]? The relative content is not found in this reference

5.      Page 3, line 99, is it dry air or humid air? What is the humidity under experiments?

6.      Page 9, line 311-324, the first paragraph in ‘Discussion’ reads like the start of the conclusion, which is repetitive. It is suggested to shorten this paragraph and remove repetitive information.

 

7.      It is suggested to add a schematic figure of the experimental procedure in the manuscript for the convenience of readers 

Author Response

Dear reviewer.

Thank you very much for reviewing our manuscript. It helped a lot to take the necessary distance to our own work. Behind that background, I totally agree with your remarks 1 – 3 and I fully followed your advices. My chosen phrases turned out to be misleading in a way highlighted in your advices. 

 

1. Page 1 line 32, is there a ‘space’ between ‘out’ and ‘coming’?

Answer: I deleted the space in question.

2. Page 2 line 72, plasma-processed air (PPA) is defined in the abstract, but the abbreviation needs to be defined again when appearing in the main content for the first time.

Answer: I introduced the abbreviation at its first appearance.

3. Page 2, line 90-91, This sentence ‘’Technological plasmas are………up to 10%” seems to be not necessary because charged particles were less significant in the scope of this manuscript where the authors used indirect treatments. This sentence might cause confusion to readers.

Answer: I have deleted that sentence.

4. Page 2, line 91-94, regarding the controlled composition of PPA by mass spectroscopy mentioned by the authors, is it from ref [19]? The relative content is not found in this reference

Answer: I exchanged the citation in question. We mixed up that citation.

5. Page 3, line 99, is it dry air or humid air? What is the humidity under experiments?

Answer: I add the necessary information.

6. Page 9, line 311-324, the first paragraph in ‘Discussion’ reads like the start of the conclusion, which is repetitive. It is suggested to shorten this paragraph and remove repetitive information.

Answer: We completely deleted the first paragraph and double checked the discussion for repetitive information.

7. It is suggested to add a schematic figure of the experimental procedure in the manuscript for the convenience of readers 

Answer: We added such a figure.

I hope I was able to contribute to the discussions in plasma on the basis of our publication. Further criticism and comments are highly welcome! Thank you very much for your patience and the interest in our work.

 

Sincerely yours

The authors

Author Response File: Author Response.docx